Haas, D. and Grieshaber, M.K.
Institut für Zoophysiologie, Heinrich-Heine-Universität Düsseldorf, Germany
The intertidal zone
characterized by tidal cycles exert a range of environmental stresses
on its inhabitants e.g. Arenicola marina. During ebb the worms
are unable to irrigate their burrows thus the partial pressure of
oxygen (PO2) in the burrow
water declines by 70% after 2 hours (Jones 1955). We determined
maximum sulfide concentrations of 40.2 µmol/l after 5 hours.
These conditions
affect both acid-base parameters of intra- and extracellular
compartments. In field studies we found the blood pH had declined by
0.37 pH units after 5 hours. Acid-base parameters such as intra- and
extracellular pH (pHi, pHe) and non-bicarbonate
buffer capacity (bnb) have been
investigated to elucidate the impact of habitat parameters on
lugworms.
In laboratory
experiments significant changes in pHi were monitored,
whereas in field studies merely a tendency towards acidification was
found. At sulfide concentrations of 52.4 ± 2.5 µmol/l in
hypoxic seawater pHi decreased by 0.27 units whereas in
incubations without sulfide an acidification of 0.23 units was found
after 24 hours. Extracellular pH also declined under these conditions
with a DpH of 0.46 with sulfide and 0.38
without. In resting animals bnb
was 34.2 ± 7 mmol /pH ·
kg wwt.
Jones JD (1955) Observations on the respiratory physiology and on the hemoglobin of the polychaete genus Nephthys with special reference to N. hombergii. J Exp Biol 32:110-125
Hahlbeck, Edda; Pospesel, Mark A.; Felbeck, Horst
Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA
The tubeworm Riftia pachyptila (Vestimentifera) lives at deep sea hydrothermal vent areas along the East Pacific Rise. These habitats are characterized by great variations in temperature, pH and water chemistry over short time periods. High biomass communities live at the interface between sulfide rich hydrothermal water and ambient sea water. R. pachyptila has no gut and relies entirely on its intracellular chemosynthetic bacterial symbionts as carbon source. The bacteria fix carbon by utilizing the oxidation of sulfide as energy source. The host animal has to occupy a region of variable flow in order to ensure a supply of both sulfide from the venting water and oxidants from the ambient sea water. The symbionts respire oxygen as well as nitrate. Because they are located in a tissue remote from the site of gas uptake the transport of respiratory gases and inorganic carbon has long been a topic of interest. Very high nitrate concentrations (>1 mM) in vascular blood of R. pachyptila indicated a novel uptake mechanism. We present evidence that blood serves as a transport medium for nitrate. In dialysis experiments, vascular blood concentrated nitrate up to 2 mM higher than in the surrounding medium. Nitrate concentrations could not be reduced to less than 60% of its original concentration after more than 20h of dialysis in a nitrate-free medium. The majority of nitrate appears to be bound to the protein fraction, which is up to 95 % hemoglobin. The extent to which nitrate is taken up differs markedly between blood samples from different animals indicating an additional binding factor. However, no influence of sulphide or oxygen on the binding was found. To our knowledge Riftia pachyptila is the first animal known to concentrate nitrate in its tissues.
Hedrick, Michael S.
Dept. of Biological Sciences, California State Univ., Hayward, CA 94542.
Nitric oxide (NO) is a free radical gas that has been shown to have important physiological functions in nearly all organisms studied to date. Although NO is abundantly produced in the brain of vertebrates, its role in the central regulation of breathing is unclear. This study examined the role of NO on respiratory-related neural activity (fictive breathing, FB) using an in vitro isolated brainstem preparation from adult North American bullfrogs (R. catesbeiana). FB was recorded as neural activity from the cut efferent ends of cranial nerves V, X and XII during superfusion of the brainstem with oxygenated, isocapnic artificial cerebrospinal fluid (aCSF) at 22°C. Drugs were dissolved in aCSF and perfused at 5-10 ml/min. Sodium nitroprusside (SNP; 0.1-1.0 mM), a NO donor, and L-arginine (L-Arg; 0.01-1.0 mM), the amino acid precursor for NO synthesis, significantly increased FB frequency. The general nitric oxide synthase (NOS) inhibitor, N-nitro-L-arginine (L-NA; 5-10 mM) significantly attenuated or abolished FB. The selective neuronal NOS (nNOS) inhibitor, 7-Nitroindazole (7-NI), was used to test the hypothesis that nNOS is responsible for the central excitatory effects of NO. 7-NI caused a reversible, dose-dependent inhibition of FB frequency at concentrations of 0.1, 0.5 and 1.0 mM. At 1.0 mM, FB was completely and reversibly abolished in every preparation (n=7). There was no significant effect of 7-NI on neural burst duration or amplitude. These data indicate that NO is an excitatory neuromodulator of the respiratory central pattern generator (CPG) in the bullfrog brainstem; the production of NO appears to be mediated by nNOS in this preparation. NO may be important for the transmission of central respiratory drive from the respiratory CPG to motor effectors for breathing in anuran amphibians.
Supported by NIH-MBRS (S06 GMAI48135-04).
Hildebrandt, J.-P.
Department of Zoology II, University of Karlsruhe, Kaiserstrasse 12, D - 76128 Karlsruhe
Initial osmotic stress in marine or potentially marine birds causes characteristic adaptive growth and differentiation responses in their nasal glands. These processes serve to optimize the salt-excretory performance of these organs under conditions of continuous uptake of excess salt during feeding in marine or estuarine environments. In domestic ducklings (Anas platyrhynchos), replacement of the drinking water with a 1 % sodium chloride solution increases the cell number in the gland by a factor of 2 - 3 within 2 days. In addition, morphologically and biochemically defined processes of cell differentiation occur in the secretory cells. These adaptive processes depend on the activation of muscarinic acetylcholine receptors (mAChR) at the surface of the gland cells. Activation of these receptors results in intracellular inositol phosphate and diacylglycerol accumulation and generation of cytosolic calcium signals. In this study, we investigated whether changes in protooncogene expression occur upon salt-stressing animals in vivo or muscarinically activating cultured nasal gland tissue in vitro. Western blot experiments with extracts from freshly isolated glands using polyclonal antisera (Santa Cruz) against Fos- and Jun-proteins revealed an induction of Fos expression after 1 h of osmotic stress in vivo with a maximum between 4 - 6 h. Fos disappeared up to 15 h of osmotic stress while Jun abundance did not change under these conditions. Stimulation of cultured tissue with mAChR-agonists induced Fos expression within 2 h without any changes in Jun expression. Experiments using various activators or inhibitors of intracellular signalling pathways in tissue culture experiments indicated that c-fos induction critically depends on the sustained elevation in the cytosolic calcium concentration and on the activation of the p38 MAP kinase cascade.
Supported by the Deutsche Forschungsgemeinschaft (Hi 448/3 and 4).
Holler, M.; Weber, W.-M.; Clauss, W.
Institute of Animal Physiology, Justus-Liebig-University Giessen, Wartweg 95, D-35392 Giessen, FRG
We investigated electrogenic sodium transport across dorsal skin of Hirudo medicinalis in Ussing chambers. Our previous studies showed that cAMP nearly doubled the short-circuit current (ISC). Because experiments with first messengers gave no convincing results, we investigated the intracellular signal cascade. Neither 2.5 µM forskolin on the basolateral side nor 1µg/ml choleratoxin on the apical or basolateral side, respectively, did elevate ISC. This indicates that leech dorsal integument probably does not possess adenylate cyclase. Next we investigated the role of different proteinkinases. The PKA-inhibitor KT 5720 (0.5 µM), added to the basolateral side, decreased ISC about 1.9 ± 0.6 µA/cm2 which corresponds to about 14%. KT 5720 also reduced the amiloride-sensitive sodium current (4.5 ± 1 µA/cm2 instead of 6 ± 1.4 µA/cm2) significantly. Moreover, the amiloride-insensitive portion of the transepithelial Na+ transport also decreased. Despite the presence of this PKA-inhibitor, cAMP stimulated ISC about 107 ± 33%, indicating the involvement of other signal pathways. Apical application of 160 nM TPA, a PKC-activator, led to inconsistent effects on ISC. Despite this the amiloride-sensitive sodium current decreased on average from 33.5% to 25.6%. Addition of the PKC-inhibitor staurosporine (300 nM) to the apical medium reduced the ISC about 41.2%. Whereas the amiloride-sensitive Na+ current remained uneffected by staurosporine, the total Na+ current was reduced from 21.4 ± 2.2 µA/cm2 to 15.2 ± 0.7 µA/cm2. Apical perfusion with the tyrosine kinase-inhibitor genistein (30 µM) reduced ISC about 16.7 ± 4.6%, and cAMP on the serosal side stimulated the current only about 19%. These results indicate multiple signalling-pathways, and that PKA, PKC and tyrosine kinases may be involved in regulation of electrogenic Na+ transport across this epithelium.
Huebler, Ruediger; Hellmann, Nadja and Decker, Heinz
Institute of Molecular Biophysics, Johannes Gutenberg-University, Mainz, Germany
The molecular
weights of the cheliceratan hemocyanin from Eurypelma californicum
and of the crustacean hemocyanins from Astacus astacus, Cancer
pagurus, Carcinus maenas and Homarus americanus
were redetermined with multiangle laser light scattering (MALLS).
This method does not depend on the size and charge of the molecules
like size exclusion chromatography and is reliable also for large
oligomeric proteins in contrast to gelelectrophoresis. Furthermore it
is a relatively quick and simple method.
The laser light
scattering photometer was connected to an FPLC separation system and
an UV/VIS spectrometer. The concentrations of the samples were
calculated on the basis of their molar extinction coefficient at 278
nm. The values of the latter were taken from the literature
(Nickerson K W and van Holde K E 1971 Comp Biochem Physiol 39: 855,
Herskovits T T et al 1981b Biochemistry 20: 2580) or determined with
the Bradford assay (Bradford M M 1976 Anal Biochem 72: 248).
For the 24-meric
hemocyanin from E. californicum we determined a molecular
weight of 1685 kD which is in good agreement with the molecular
weight based on sequence data and sedimentation runs (Markl J and
Decker H 1992 Adv Comp Environ Physiol 13: 325, Schneider et al 1977
Z Physiol Chem 358: 1133). The molecular weights of the investigated
native 12-meric crustacean hemocyanins are in the range of 911-996
kD. They are comparable to the values calculated on the basis of SDS
gelelectrophoresis for denatured subunits. The molecular weights of
the 12-mers based on these data are in the range of 864-1176 kD
(Markl J et al 1976 Z Physiol Chem 357: 1713, Markl J et al 1979b J
Comp Physiol 133 B: 167, Rochu et al 1978 Comp Biochem Physiol 59 A:
155, Rogala A and Gondko R 1981 Comp Biochem Physiol 68 B: 603).
This work was supported by the DFG, the Stiftung Innovation Rheinland Pfalz and the Naturwissenschaftliches Medizinisches Forschungszentrum Mainz.
Ishimatsu, A.; Aguilar, N. M.; Ogawa, K.; Hishida, Y.; Takeda, T.; Oikawa, S.; Kanda, T. and Khoo, K. H.
Marine Research Institute, Nagasaki University, Nomozaki, Nagasaki 851-0505, Japan
Periophthalmodon
schlosseri inhabits intertidal mudflats of the southeast Asia.
This mudskipper is highly terrestrial, spending most of its time on
the mudflat surface during low tides. It constructs a burrow on the
mudflat, the depth of which often exceeds 1 m. Their burrows are
filled with nearly anoxic water up to the mudflat surface even during
low tides. However, the burrows contain gas whose PO2
can be as high as ambient air. Fish holds a mouthful of air and
transports it into the burrow. During high tides, the mudskipper
appears to stay in the burrow.
As long as air was
accessible, P. schlosseri did not ventilate the gills.
Instead, it regularly gulped air and held it in the buccopharyngeal
cavity for several minutes. The total volume of air held amounted to
15 ml/100 g body weight, and the tidal volume represented 55% of the
total volume. Aerial hypoxia strongly stimulated aerial ventilation,
while aquatic hypoxia had no influence on ventilation.
When the fish was in
normoxic water with free access to air at 30 °C,
the arterial PO2 and SO2
were 3.5-4.5 kPa and 50-70%, respectively. Heart rate
was 60-70 bpm, and arterial blood pressure ca. 3.0 kPa. Total
emersion for 6 h did not affect blood oxygen levels. Blood pH
slightly but significantly increased, and remained high at 2 h of
recovery. Total submersion of the fish in normoxic water induced a
pronounced bradycardia that persisted throughout the submersion
period of 12 h. The first air breath upon emersion instantly elevated
heart rate that was significantly higher than the control rate.
Arterial PO2 instantly
decreased to below 2 kPa and remained at this level until submersion
ended. Arterial PCO2 as well as
total CO2 significantly decreased during the submersion,
but arterial pH was maintained at the control level. Total submersion
elicited continuous gill ventilation at a rate of 45 times/min.
Oxygen uptake was about 2.2 and 3 mmol/h/g during total
submersion and emersion, respectively.
Jaenicke, Elmar; Hellmann, Nadja and Decker, Heinz
Institute for Molecular Biophysics, Johannes Gutenberg University, Mainz, Germany
The
respiratory protein of crustacea (hemocyanin) binds oxygen with high
cooperativity and is modulated by low molecular weight effectors.
This modulation is essential for the animals to adapt to situations
of changing oxygen availability and demand. Besides H+ and
different cations, L-lactate and urate are known to be effectors
(Truchot JP 1980 J Exp Biol 214:205 and Morris S 1985 J Exp Zool
233:135). Lactate and urate increase the oxygen affinity of
hemocyanin (Zeis B 1992 J Exp Biol 168:93 and Nies C 1992 J Exp Biol
168:111).
The aim of our study
was to characterize urate binding to dodecameric hemocyanins of
Astacus leptodactylus, Homarus americanus, Carcinus
maenas and Cancer pagurus with respect to stoichiometry,
dissociation constants (KD) and enthalpy of the binding
(DH). We employed isothermal
microtitrationcalorimetry, which allows the determination of all
three parameters at a given temperature. For the different species
the following number of binding sites per dodecameric hemocyanin were
determined: A. leptodactylus 6.0-8.8, H. americanus
1.8-2.2, C. maenas 3.0-4.3 and C. pagurus 1.9-2.8. The
relatively broad range for the number of binding sites results from
the uncertainty in determining the hemocyanin concentration, due to
the experimental errors of about 10% in both molecular weights and
molecular extinction coefficients. For a given concentration,
however, the error range in determining the stoichiometry is ±0.2.
Values for KD and DH for urate
amount to approx. 20 µM and approx. -14000 cal/mol
for hemocyanins from A. leptodactylus, C. maenas and C.
pagurus at pH 7.5 and 10°C in Tris buffer. For lobster (H.
americanus) hemocyanin a KD of 75 µM and a
DH of -23500 cal/mol were found under
identical conditions. In addition the temperature dependence of KD
and DH for urate binding to C. pagurus
hemocyanin was investigated. KD increases from 11 mM
at 5°C to 70 mM at 30°C,
while DH decreases from -13000 cal/mol
at 5°C to -20000 cal/mol at 30°C.
Our results reveal a
considerable interspecies variability especially concerning the
number of binding sites per dodecameric hemocyanin. The observed
deviations will be discussed.
Financial support was provided by ‘Naturwissenschaftlich medizinisches Forschungszentrum Mainz’ and ‘Stiftung Innovation Rheinland-Pfalz’
Kauschke, E.1; Lange, S.2; Ellisen, R.1; Cooper, E.L.3
1Zoological Institute and Museum, Ernst-Moritz-Arndt-University, J.-S.-Bach-Str. 11/12, 17489 Greifswald, Germany; 2Institute of Molecular Biophysics, Humboldt University Berlin, Germany; 3Department of Neurobiology, University of California Los Angeles, USA
Coelomic fluid (CF)
and coelomocytes of earthworms mediate recognition and immune
processes. In addition to agglutinating,
bacteriostatic/bacteriocidal, and proteolytic activities E. fetida
possesses cytotoxic action. The CF contains three cytolytic proteins
with similar biochemical properties. One of them splits into two
subunits of 18 and 21 kDa under reducing conditions in SDS-PAGE and
has bifunctional character. It is capable of agglutinating and
hemolysing erythrocytes (Eue I et al. 1998 Dev. Comp. Immunol.
22:13). TEM analysis of target membranes revealed ring shaped
structures (pores) with a central channel. The channel complex
consists of six monomers as deduced from the molecular weight of 228
kDa (Lange S et al J. Biol. Chem. 272:20884).
Humoral cytotoxicity is inhibitor controlled (Mohrig W et al 1997 Dev. Comp.
Immunol. 21:116). By using functional tests and Western blotting the
immunological relationship of this inhibitor and vitronectin has been
demonstrated.
Earthworm coelomocytes exert cytotoxic activity against tumor cells.
Coelomocyte target cell killing resembles cytotoxic activity of
natural killer (NK) cells in vertebrates (Cooper E L et al
1996 Cell. Immunol. 166: 113). Coelomocyte lysates significantly
decreased the viability of K562 tumor cells when assayed in the
MTT-test and hemolyzed erythrocytes.
Immunocytochemistry on earthworm coelomocytes with an anti mouse perforin antibody
demonstrated that about 17.5% of coelomocytes with a size of
13.2±1.3nm bind to anti perforin
(P1-8)- antibody (Kawasaki A et al. 1990 Int. Immunol. 2:
677). The anti perforin antibody does not bind to chloragocytes.
These results offer
more evidence of another mechanism in the repertoire of immune
capabilities found in earthworms. Humoral and cellular cytotoxicity
in E. fetida resembles functionally vertebrate pore forming
proteins like poly-C9 and perforin.
The investigations were granted by the Friedrich Naumann Foundation, Königswinter, Germany and the German Academic Exchange Service (DAAD), Bonn, Germany.
The authors like to thank Dr. Okamura for supplying with perforin antibody.
Kleinow, W.; Heggemann, F. & Schmelter, R.
Zoologisches Institut der Universität zu Köln, Weyertal 119, D - 50923 Köln
Ribosomes were
isolated from homogenates of the rotifer Brachionus plicatilis
and characterized by gradient centrifugation, electron microscopy and
by chemical methods.
In general the
properties and composition of the cytoribosomes of Brachionus were
found to be not significantly different to ribosomes of other
eukaryotic organisms. The sedimentation coefficients of the
Brachionus ribosomal subunits seem to be somewhat lower in direct
comparison with Locusta ribosomal subunits. Some peculiarities seem
to exist concerning the influence of ions on dissociation and
solubility. Thus, (1) contrary to other types of cytoribosomes, even
in gradients without Mg2+ a peak in the monosome region is
still observed, beside the peaks for the subunits. It can be only
removed by treatments which obviously destroy also the structure of
the ribosome subunits. (2) The yield of ribosomes from different
homogenate fractions and the efficiency of resuspension of ribosomes
is more effective with buffers containing no Mg2+. (3) On
the other hand when the ribosomes were resuspended in Mg2+
-free buffer the ratio of the absorbencies of 260/280 was not 1.8, as
is typical for purified ribosomes, but about 2.0 (nearly pure RNA).
Some evidence indicates, however, that the resuspension without Mg2+
leads not to heavy losses of ribosomal proteins. The ribosomal
proteins of Brachionus were isolated and were characterized by
two-dimensional gel electrophoresis techniques.
Kloas, W.; Blödt, S.; Levy, G.; Scholpp, S. and Lutz, I.
Department of Zoology II, University of Karlsruhe, Kaiserstr. 12, 76128 Karlsruhe, Germany
Recently several studies showed that environmental chemicals without toxical risks exhibit humoral effects. These so called “endocrine disruptors“ disturb normal endocrine feed back mechanisms and mainly estrogenic effects were observed in all classes of vertebrates causing “feminization“ phenomena. The aim of our present research using amphibians as a model is to study whether environmental water pollution is able to cause feminization phenomena by estrogenic actions, which would also indicate a potential risk for humans. The assessment of estrogenic potencies of environmental chemicals includes several levels of investigation using the amphib Xenopus laevis: (I) binding of environmental chemicals to liver estrogen receptor determined by a radioreceptorassay, (II) biological activity in vitro by assaying induction of vitellogenin-mRNA as well as estrogenreceptor-mRNA in primary cultured hepatocytes using a RT-PCR (reverse transcriptase – polymerase chain reaction) technique, and (III) in vivo effects on intact animals by experiments determining influences on sexual differentiation during larval development. Our results indicate that environmental chemicals are able (I) to bind to estrogenreceptors, (II) to induce vitellogenin and estrogenreceptor syntheses, and (III) to increase female phenotypes during larval development indicating the suitability of all 3 levels of investigation for assessment of estrogenic effects using amphibians as a model.
Supported by Ministry of Environment and Traffic Baden-Württemberg via BW-PLUS (grants 20 9605.02 and 20 9702.02)
Kölsch, Gregor; Kistowski, Kristin von; Braune, Hans Jürgen
Zoological Institute, Dept. of Physiology, University of Kiel, Olshausenstr. 40, 24098 Kiel, Germany
Resistance to submergence has been investigated in some curculionid, chrysomelid and tenebrionid beetles. The results are presented for Agelastica alni (Coleoptera, Chrysomelidae), a univoltine, oligophagous species feeding on deciduous trees of the genus Alnus which typically grow in wet or humid places. After heavy rains or the thawing of snow in springtime, these habitats may be flooded. Since the beetles overwinter close to the trees in the leaf litter or the uppermost soil layer, they are likely to show some degree of resistance to submergence. This resistance was described in the first phase of our research project.
Beetles were experimentally submerged during different seasons and at different temperatures for hours or days. Survival rates and the times elapsed during post-submergence before first and vigorous movements and before full recovery were determined. Resistance increases with decreasing water temperature and is higher in diapausing beetles during overwintering, obviously reflecting the physiological state of the animals. Measurements of O2-uptake in a Warburg apparatus revealed a seasonal pattern of the metabolic rate with a drastic reduction during the state of diapause and a distinct temperature dependence as expected.
The second phase of the project addresses the anaerobic metabolism during submergence, starting with the description of basic parameters. Glycogen reserves have been measured in order to find out whether a reduction of the metabolic rate and lactate formation, which had been shown to occur, alone can explain the survival under anoxia, and if the fuel reserves are the limiting factor. The glycogen store of young adult beetles is built up in summer within the first two weeks of feeding. These reserves are used during submergence. The metabolic rate is spontaneously reduced under anoxic conditions to less than 10% of the normoxic level. (We had been given the opportunity to conduct microcalorimetric measurements in cooperation with K. Jakobi, in the laboratory of Prof. Wegener at the University of Mainz, Germany, which is gratefully acknowledged.) The adenylate energy charge (AEC) as an integrated measure of the physiological condition has been determined before and after submergence. Superimposed on an overall decrease during winter and a large variation in springtime, the AEC values are further reduced during submergence.
Korsmeyer, K.E.; Steffensen, J.F. and Herskin, J.
Marine Biological Laboratory, University of Copenhagen
To determine the metabolic costs of rigid-body, paired-fin swimming, oxygen consumption (MO2) as a function of swimming velocity was measured for parrotfish (Scarus sp.) and triggerfish (Rhinecanthus aculeatus) in a water flume. The parrotfish (23 cm) swam exclusively with the pectoral fins up to 3 body lengths (L)/s. Body-caudal undulations were recruited at maximal velocities (Umax) between 3 and 4 L/s. MO2 ranged from 125 at rest to 670 mgO2/kg/h at Umax. The slope of the semi-log regression of mass-specific MO2 against relative velocity during labriform locomotion was less than in sub-carangiform swimmers, resulting in a very high optimal swimming velocity (Uopt = 2.6 L/s). The triggerfish (18 cm) swam with undulations of the dorsal and anal fin up to 1.5 L/s, recruiting body-caudal fin undulations at greater speeds. Although typically considered adapted for low speed maneuverability, this species of triggerfish was also capable of high prolonged speeds (>4.5 L/s) using sub-carangiform swimming. MO2 ranged from 75 at rest to over 1050 mgO2/kg/h, an aerobic scope of 14-fold. As with the parrotfish, the slope of the semi-log regression of MO2 on velocity was low during balistiform locomotion. However, the slope increased significantly upon switching to body-caudal propulsion, suggesting a greater efficiency for rigid-body swimming.
Krumme, S.; Roces, F.
Theodor-Boveri-Institut, Lehrstuhl für Verhaltensphysiologie und Soziobiologie der Universität Würzburg, 97074 Würzburg, Germany
Ants belonging to the genus Atta sp. live in obligatory symbiosis with a fungus. To supply the fungus with nutrients workers cut semicircular fragments out of leaves. Cutting is in terms of energy expenditure a very expensive activity for the ants. The present study concentrates on the problem whether the costs of cutting influence the behavior of the ants.
For that purpose measurements on metabolic rates were performed with ants cutting Parafilm as a Pseudoleaf at 20 and 25°C. Cutting costs were varied by a change in leaf thickness (one, two and three layers). The effects on the metabolic rate, the cutting speed, the cutting time, and the fragment size were investigated. The increase in leaf thickness had no influence on the metabolic rate of the ants, but it caused a decrease in cutting speed and leaf fragment size. The energy investment per fragment was independent of temperature, because both metabolic rate and cutting speed increased with increasing temperature by a similar factor. As a result no differences in fragment size were expected. At 20°C the amount of energy invested per fragment showed no difference for one, two and three layers of Parafilm, at 25°C it was significantly higher for the more dense leaves because ants cutting thin leafmaterial already reached their maximum possible fragment size which depends on their own size.
Leaf-cutting ants regulate fragment size and therefore cutting time in dependence on their cutting speed, in order to only invest a fixed amount of energy per fragment.
Kuhnen, G.
Physiologisches Institut, Aulweg 129, D-35392 Giessen, Germany
Brain temperature is generally higher than blood temperature. However, artidactyls can cool the brain below the temperature of the arterial blood by a process termed selective brain cooling (SBC). The cooling takes place in the carotid rete, a network of many small arteries, which lies in the cavernous sinus. The cavernous sinus is perfused by cool venous blood draining the nasal mucosa. Carotid rete and cavernous sinus form an internal heat exchanger by which the brain can be cooled. SBC is controlled on the venous side. Cool venous blood can flow via the angularis oculi vein to the cavernous sinus, in which case SBC will ensue. On the other hand, the venous blood can flow via the facial vein directly back to the trunk, in which case the rete heat exchanger is bypassed and no SBC will occur.
The experiments to study the mechanism and function of SBC were performed in conscious goats and have shown that at a blood temperature of 40.5°C brain temperature is about 1.5°C lower in the resting animal. Inspiration of warm air with high humidity is reducing the external heat exchange in the nasal mucosa and was consequently reducing the degree of SBC. Experiments with hypothalamic thermodes in 3 goats have shown that the mechanism of SBC is induced by temperature signals of the hypothalamus. Unilateral warming of the brain in 2 goats induced ipsilateral SBC only. The results demonstrate the precise control of brain temperature by SBC since even unilateral deviations of the brain can be reduced by SBC.
Lewandovski, G.J.; Föll, R. L.; Koch, M.; Paul, R.J.
Institut für Zoophysiologie, Münster, Germany
We used a histochemical assay to measure the increase of reaction-products of succinate-dehydrogenase (SDH) and malat-dehydrogenase (MDH) in 7 µm cryosections of Caenorhabditis elegans (Lojda Z 1965 Folia Morphol 13: 84). During the reaction, images of the sections were recorded with video-technique to reveal the time course of the reactions. We were able to compare the activities of SDH and MDH in different tissues of the nematode by using a computer assisted image processing system. At a surplus of substrates the increase of the histochemical detected reaction products was linear for approx. 15-25 minutes. After this time, the increase declined more and more. The concentration of enzymes can be estimated from the first period of the reaction.
We incubated C. elegans at a temperature of 20 °C in normocapnic anoxia for 6 h. In a second incubation, anoxia lasted 12 h followed by normoxic recovery of 5 h and a further period 6 h anoxia at the same temperature. The enzyme activities were measured in comparison to normoxic incubated animals. The healthy nematodes were parted from Escherichia coli and dead animals by centrifugation in 35% sucrose before and after incubation.
It was found that the activity of metabolic enzymes (SDH, MDH) decreases with the duration of anoxia, especially in the ovary and the developing eggs, but also in the cells of the intestine.
Menze, M.§; Hellmann, N.*; Decker, H.*; Grieshaber, M.K.§
§Institute of Zoophysiology, Heinrich-Heine-Universität Düsseldorf, *Institute for Molecular Biophysics, University of Mainz
Haemocyanins are
extracellular respiratory proteins found in the haemolymph of certain
species of the two phyla Arthropoda and Mollusca [1]. It has been
shown that urate which accumulates in the haemolymph of the lobster
Homarus vulgaris during hypoxia effectively modulates the
haemocyanin oxygen affinity. The analogue caffeine was also reported
as a potential effector of the P50 and a high binding
constant was measured by equilibrium dialysis [2,3].
In order to
determine the thermodynamical properties and stoichiometry of the
binding of urate and caffeine to 12-meric haemocyanin of the lobster
Homarus vulgaris Isothermal Titration Calorimetry (ITC) was
employed. Binding isotherms were determined for fully oxygenated
haemocyanin at pH 8,0. Caffeine binds with a stoichiometry of about
4, an affinity of 35 ± 4 mM-1 and an enthalpy
change of –60 ± 2 kJ/mol at 20°C. In TRIS-buffer a
weak unspecific binding was found however, in HEPES an ideal curve
for n identical binding sites was measured. No positive co-operative
binding effects occurred. We could not determine the stoichiometry of
urate-binding independently due to limits in the solubility of the
effector. However, the urate-binding curves could well be analysed
assuming a binding stoichiometry derived from caffeine-binding.
Although it cannot be totally excluded that urate binds with a
different stoichiometry from caffeine it seems to be reasonable to
assume, considering the similarity of the two substances, that four
binding sites exist for both compounds.
We also investigated
the temperature dependence of urate-binding to haemocyanin in
TRIS-buffer. In the temperature range from 20°C to 10°C the
binding constant increased from 30 ± 15 mM-1 to 60
± 15 mM-1 and the enthalpy change from –16 ±
4 kJ/mol to –43 ± 3 kJ/mol.
[1] Van Holde KE, Miller KE (1995) Adv. Prot. Chem. 47: 1-81
[2] Zeis B, Nies A, Bridges CR, Grieshaber MK (1992) J. Exp. Biol. 168:93-110
[3] Morris S, Bridges CR, Grieshaber MK (1985) J. exp. Zool. 235: 135-139
Milsom, William K.1; Zimmer, M. Beth1 and Harris, Michael B.2
1Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z4 and 2Department of Medicine, University of Calgary, Calgary, Alberta, Canada, T2N 4N1
As mammals enter hibernation, there is a fall in metabolic rate accompanied by proportionate falls in ventilation, heart rate and cardiac output. These are accompanied by large increases in stroke volume and total peripheral resistance. Part of the rise in total peripheral resistance is due to a modest, generalized peripheral vasoconstriction while much is due to large increases in blood viscosity and, in some species, increases in hematocrit. Despite this, blood pressure falls significantly. The increase in peripheral resistance does result in a slow diastolic run off such that, despite the prolonged diastolic interval and fall in systolic blood pressure (40-90 mm Hg), diastolic blood pressures remain relatively high (7-40 mm Hg).
The close correlation between mean heart rate and body temperature during entrance into hibernation results from the introduction of cardiac arrhythmias in the form of skipped beats which progress to periods of more prolonged asystoles. The latter can occur regularly and are often followed by a short tachycardia (i.e. the normal pattern is a regular arrhythmia). Extremely long asystoles can occur and the arrhythmia can be highly irregular with no correlation to other physiological events. These events give way to a uniform heart rate in deep hibernation at low temperatures. Superimposed on these arrhythmias is the normally occurring respiratory-related sinus arrhythmia. Throughout this period, sporadic electrical depolarizations also occur without recorded changes in pulse pressure (or visible contraction in isolated hearts) suggesting that the effective heart rate may be lower than the electrically recorded rate would suggest.
The evidence suggests that as animals enter hibernation the heart is slowed by cyclic parasympathetic activation and sympathetic withdrawal (inducing the skipped beats and asystoles as well as slowing the even beats). Periods of tachycardia result from sympathetic activation when parasympathetic influence is withdrawn. These arrhythmias, due to alternating periods of parasympathetic and sympathetic dominance, may continue throughout hibernation and appear responsible for producing both the regular, orchestrated fall in heart rate as well as periods of highly irregular cardiac activity.
Müller, T.; Steeger, H.-U.; Paul, R.J.
Institut für Zoophysiologie, Westfälische Wilhelms Universität Münster, Hindenburgplatz 55, 48143 Münster, Germany
An indirect effect
of the enhancement of global UV-B radiation as a consequence of the
ozone depletion could be an increase in photooxidative formation of
oxygen radicals and H2O2 in marine systems.
To estimate the role
of UV-B irradiation in the formation of H2O2,
experiments with synthetic seawater, different UV-B intensities (0.24
Wm-2 - 0.52 Wm-2 ) and periods of illumination
(1.7h – several days) were carried out. The fluorimetrically
detected concentrations of H2O2 were not
significantly different from values found in natural seawater (~ 100
nmol l-1).
Hyperoxic conditions
(PO2 300% air saturation), let
to an increase in hydrogen peroxide concentration up to 1 - 1.5 µmol
l-1. Additional UV-B radiation even with the smallest
intensity (0.24 Wm-2) increased the concentration of H2O2
to 2 µmol l-1.
Similar
concentrations of H2O2 were measured in
mud-flat pools during low tide at the German Wadden Sea. Whether this
is primarily due to UV-B or to high oxygen partial pressures produced
by algal photosynthesis is to be discussed.
To estimate the
effects of H2O2 on jung plaice (Pleuronectes
platessa), measurements of ventilation rate and heart rate were
made using video microscopy and digital image analysis. During
instantaneous incubation with hydrogen peroxide concentrations up to
1 mmol l-1 for 30 minutes, no significant irritations of
ventilation rate or heart rate were observed.
Long term incubation
for 10 days with concentrations related to the situation in the mud
flat pools (maximum: 2 µmol l-1) resulted in a
significant difference in the respiratory response to hypoxia between
treated and untreated animals.
Neunaber, Ralf; Achazi, Rudolf K.
Institut für Tierphysiologie, Freie Universität Berlin, Ehrenbergstr. 26-28, 14195 Berlin, FRG.
An endogenous inhibitor of 7-ethoxyresorufin-O-deethylase (EROD) is present in the postmicrosomal cytosolic supernatant (CS) of fish, for example of bream liver homogenates. It inhibits the EROD activity of liver microsomes of different fish species, mammals like marmoset and invertebrates like crayfish. The purified inhibiting substance has no effect on the activity of aryl hydrocarbon hydroxylase (AHH), ethoxycoumarin-O-deethylase (ECOD) and aminopyrine-N-demethylase (APD). It is heat sensitive. Its relative molecular weight was estimated to be 175±35 kDalton using gel filtration on a Sephacryl S 300 HR column. So far it can be characterized as a protein. The inhibitor was partially purified by anion exchange chromatography on DEAE Sephacel followed by anion exchange chromatography on Mono Q to a value of 500 fold. It has a strong tendency to aggregate due to lipophilic interactions of the protein. Following Dixon- and Lineweaver-Burk-plot it has a non-competitive inhibition mode. The inhibitor does not reduce resorufin and the inhibitory activity is not destroyed by the addition of dicumarol. So there is no indication that the inhibitor is a NAD(P)H-quinone reductase (DT-diaphorase). There is also no evidence for suggesting that the inhibitor is some kind of or serine or cysteine dependant protease, because it is not affected by serine – or cysteine protease inhibitors and the inhibitory activity is not increasing over time.
Nicol, S.C. and Andersen, N.A.
Division of Anatomy & Physiology, University of Tasmania, GPO Box 252-24, Hobart, Tasmania, 7001, Australia.
When mammals enter hibernation, the great reduction in metabolic rate is accompanied by a reduction in respiratory requirement, and the breathing pattern changes from continuous to intermittent breathing. Breathing patterns in hibernating mammals closely resemble those of ectothermic vertebrates, suggesting that they may result from a common control mechanism.
The echidna (Tachyglossus aculeatus) is one of the three extant species of monotreme, or egg-laying mammal, and the only one known to enter hibernation. Echidnas may weight up to 8 kg, making them one of the largest hibernating mammals. In Tasmania, all echidnas appear to hibernate, entering hibernation in early autumn. Reproductively active animals emerge from hibernation during winter, often even before the coldest part of the year, while non-reproductive echidnas may not arise from hibernation until late spring. Hibernation in echidnas is broken by periodic arousals, just as it is in eutherian hibernators.
Resting non-hibernating echidnas are characterised by low metabolic rates, but a very low respiratory frequency leading to a low and quite variable respiratory minute volumes, often resulting in low levels of arterial oxygen and high CO2. As the echidna seems to lie at one physiological extreme among the hibernators, in terms of its large size and low metabolism and ventilatory requirement when not hibernating, a study of control of breathing during hibernation in echidnas could provide a useful test of the generality of various models.
We studied breathing patterns, and the control of respiration in 6 echidnas. Echidnas will not hibernate when disturbed and so breathing pattern was measured non-invasively from chamber pressure. Hibernating echidnas showed episodic breathing with long apneas broken by bursts of breathing. A typical burst contained about 30 breaths. Between these main bursts were much smaller bursts of 1 - 4 breaths. Increasing CO2 levels in the inspired air increased the number of breaths in a burst, eventually leading to continuous breathing. Interburst breaths appear to be controlled by the peripheral chemoreceptors: hypoxia increased interburst breaths, and decreased burst length, while hyperoxia increased the apneic period, but increased burst length.
Niederstätter, Harald and Pelster, Bernd
Institute of Zoology and Limnology, University of Innsbruck, A-6020 Innsbruck, Austria
Gas gland cells of the fish swimbladder are specialized for the release of acid. According to pH values down to 6.6-6.8, recorded in blood leaving the gas gland, and according to the observations, that at pH 7.0 about 20% of the total acid release of gas gland cells are not inhibited by removal of extracellular sodium or potassium, and that inhibition of Na+/K+-ATPase also reduces the total acid release to about 20% of control, it is expected that active proton secretion is established in these cells. Determination of ATPase activity revealed presence of an activity that is inhibited by bafilomycin, a specific inhibitor of V-ATPase, and bafilomycin also reduced proton secretion of cultured gas gland cells. There are, however, also cell preparations in which bafilomycin has no effect on proton secretion. Fluorescence microscopy revealed presence of acidic vacuoles in gas gland cells. Using cDNA prepared from gas gland cell polyadenylated RNA and PCR primers for the B-subunit of V-ATPase, we were able to demonstrate the expression of the B-subunit in these cells. Cloning and sequencing of the cDNA so far suggests that gas gland cells express a B-subunit similar to the brain isoform described for human tissues. Exact localization of the enzyme within the cells using specific antibodies may provide more insight into its physiological role in acid secretion.
Supported by Österreichischer Fonds zur Förderung der wissenschaftlichen Forschung (FWF P11837-BIO)
Niggemann, H.; Heldmaier, G.; Schneider, T. and Klingenspor, M.
Dept. Biology, Zoology, Philipps University, D-35043 Marburg
Siberian hamsters reduce energy demands in winter by pronounced seasonal adaptation of energy metabolism, thermoregulation and reproduction. Triggered by short photoperiod (SD) body weight and food intake gradually decrease to a low winter level. Physiological winter adaptation is maintained for ~12 weeks. As hamsters become refractory to SD they spontaneously return to the physiological summer state. The seasonal body weight amplitude is largely generated by altered lipid degradation and deposition. This seasonal model allows to study the reversible transition from the fat to the lean state by manipulation of photoperiod. We are investigating the role of leptin, a cytokine specifically secreted by adipocytes, in the precise adjustment of seasonally ‘appropriate’ body weight in the Siberian hamster. The leptin (Lep) gene and the leptin receptor (Lepr) gene represent two major components of an adipostatic feed back mechanism in mammals. Natural mutations of the leptin gene (Lepob) and the leptin receptor (Leprdb) gene cause imbalanced energy metabolism and obesity in the mouse.
Adipose tissue leptin mRNA and serum leptin levels are elevated in fat summer hamsters (long photoperiod, LD) as compared to lean winter (SD) hamsters. Serum leptin levels are positively correlated with body weight, body fat content and food intake. In SD hamsters leptin injections decrease food intake and body mass. The reduction of body mass is due to body lipid depletion. In food-restricted SD hamsters leptin treatment diminishes the compensatory increase of body mass and food intake during ad libitum refeeding. In LD hamsters leptin treatment has no effect on body weight, food intake, and body lipid content.
We conclude that the leptin adipostatic feed back mechanism controls the seasonal body mass cycle in the Siberian hamster. Taken together, high leptin levels in LD hamsters and their lack of response to leptin injections point to a striking seasonal modulation of leptin sensitivity in this hamster species. In a biological context, tuning the sensitivity of the leptin axis apparently favours survival of food shortage/starvation, when internal energy (fat) depots are minimal.
This study was funded by DFG Kl973/5-1; leptin was supplied by Amgen.
Nikinmaa, Mikko; Salama, Annika & Virkki, Leila V.
Department of Biology, University of Turku, FIN-20014 Turku, Finland
Data on lamprey (1), teleost (2,3) and equine (4) erythrocytes indicate that oxygen tension has pronounced effects on the transport of all major cellular ions. Hypoxia activates the amiloride-sensitive sodium/proton exchange, but inhibits the potassium-chloride cotransport of teleost and equine erythrocytes, the isotonic potassium channel (barium-sensitive channel) and the swelling-activated chloride transport pathway of lamprey erythrocytes. Although it was originally suggested that the effects of oxygen on ion transport would be mediated via the deoxy/oxy conformational changes of haemoglobin molecules, the pronounced effects of oxygen on the erythrocytic ion transport in lamprey, the haemoglobins of which do not show true conformational changes upon oxygenation/deoxygenation indicate that conformational changes of (tetrameric) haemoglobins are not necessarily required for the effects of oxygen on ion transport. The effects of oxygen on the ion transport will tend to stabilize an elevated cell volume and intracellular pH of erythrocytes in hypoxic conditions, and a reduced cell volume and intracellular pH in hyperoxic conditions. These responses favour effective oxygen loading in gills in hypoxic conditions via an increased haemoglobin oxygen affinity and oxygen unloading at high partial pressure of oxygen in well oxygenated conditions via a decreased haemoglobin-oxygen affinity.
1. Virkki, L.V. et
al. (1998) J Exp Biol, in press
2. Motais, R. et al.
(1987) J Gen Physiol 90, 197-207
3. Nielsen, O.B. et
al. (1992) Am J Physiol 263, C1057-C1064
4. Cossins, A.R. &
Gibson, J.S. (1997) J Exp Biol 200, 343-32
Onken, H.
Institut für Tierphysiologie der Freien Universität Berlin, Grunewaldstr. 34, D-12165 Berlin.
To counterbalance passive salt losses in fresh water, Chinese crabs (Eriocheir sinensis) actively absorb NaCl across their posterior gills. Active Na+ absorption proceeds via apical Na+ channels and basolateral Na+/K+ ATPases (Zeiske W et al 1992: Biochim Biophys Acta 1105, 245).
In the present study, split gill lamellae were mounted in a modified Ussing chamber, and active Na+ absorption was measured with a specially constructed low-noise voltage-clamp (modified after the original version by Van Driessche and Lindemann 1978: Rev Sci Instr 49, 52) as positive, amiloride-sensitive (100 µmol/l) short-circuit current (INa) with Cl--free Na+ saline in the external bath (internal: haemolymph-like NaCl saline). Single-channel currents and open channel densities were obtained as described before (Zeiske W et al 1992: see above) by analysing current fluctuations induced by 5 µmol/l amiloride. The influences of internal osmotic perturbations or addition of eyestalk extract on these parameters were monitored.
Reduction of the internal osmolality (from 587 ± 4 to 457 ± 3 mosmol/kg) increased INa from 127 ± 49 to 254 ± 51 µA/cm2 (n=4; ± SEM). The single-channel current was not significantly changed (0.34 ± 0.09 versus 0.35 ± 0.08 pA), whereas the number of open Na+ channels increased from 535 ± 331´106 per cm2 to 905 ± 348´106 per cm2. Increasing the internal osmolality (addition of 100 mmol/l sucrose) reduced INa from 247 ± 74 to 151 ± 50 µA/cm2 (n=4; ± SEM). Again, the single-channel current was not effected (0.41 ± 0.10 versus 0.41 ± 0.07 pA). The open channel density was reduced from 934 ± 474´106 to 436 ± 187´106 per cm2. Addition of eyestalk extract (2 eyestalks/10ml saline) to the internal bathing medium increased INa from 97 ± 23 to 198 ± 33 µA/cm2 (n=8; ± SEM). Single-channel currents seemed to be unaffected (0.38 ± 0.04 versus 0.32 ± 0.05 pA), whereas the number of open sodium channels was increased from 253 ± 48´106 to 709 ± 157´106 per cm2.
From these results it can be concluded that INa modulations by internal osmotic perturbations or by internal addition of eyestalk extract are due to changes in the number of open Na+ channels in the apical membrane.
Ortmann, Ch. and Grieshaber, M.K.
Heinrich-Heine-Universität Düsseldorf, Germany, Universitätsstr. 1 (26.12.00), 40225 Düsseldorf
Today the Asian clam Corbicula fluminea, which was introduced from North America where it is known as a “pest organism“, is one of the most important biomass producers of the river Rhine. Two main characteristics of its life history have led to a successful strategy invading new habitats. First its high fecundity with hundreds of juveniles with two generations a year. Second the development within the gill arches without free-swimming larval stages. Our investigations focused on the mussel's energy metabolism. Therefore, we simultaneously measured heat production (“ThermalActivityMonitor” ThermoMetric, Järfälla, Sweden) and oxygen consumption (Respirometer Cyclobios, Innsbruck, Austria) in a flow-through system under standardized conditions (artificial fresh water at 15°C). Even during normoxia Corbicula shows an intermittent metabolism with long periods (10 to 20 hours) of low standard metabolic rate, which may be correlated with valve closure. Heat dissipation and oxygen consumption dropped to £10% of the values during valve opening. Since the incubation within the calorimeter vessel may cause stress, the natural shell closing behaviour was also investigated in specimens exposed to the natural environment of the river Rhine. With two types of biomonitors (“DreissenaMonitor” Envicontrol, Köln, Germany and “Mosselmonitor” Delta Consult, Kapelle, Netherlands) closing periods from a few minutes up to more than 24h could be confirmed for several specimens. Further experiments must be carried out to determine whether C. fluminea resorts to anaerobic energy provision during their closing periods.
Paul, Rüdiger J.; Pirow, Ralph; Wollinger, Frank; Freitag, Jürgen; Müller, Gabriele; Bäumer, Christopher; Blom, Judith
Institut für Zoophysiologie der Westfälischen Wilhelms-Universität, Hindenburgplatz 55, 48143 Münster
All steps in the cascade of oxygen transport from the ambient to the cell can be imaged and analysed by applying optical methods on transparent organisms. We studied convective or diffusive steps of oxygen transport in limnic, fluvial and marine animals (cladoceres, mayfly larvae, copepods, fish larvae) by applying video microscopy, digital image processing, microspectralphotometry, fluorimetry and phosphorimetry. The access to morphometric data, convective flow rates (ventilation, perfusion), ambient or blood gas values (e.g. oxygen partial pressures, oxygen saturation of haemoglobin, blood pH) or metabolic data (intracellular pH, NADH fluorescence) allows modelling of oxygen transport processes. Both, techniques and physiological results will be discussed to show chances and limits of the new approach.
Colmorgen M, Paul RJ
(1995) Imaging of physiological functions in transparent animals
(Agonus cataphractus, Daphnia magna, Pholcus
phalangioides) by video microscopy and digital image processing.
Comp Biochem Physiol 111A, 4, 583-595
Schneckenburger H,
Gschwend M, Paul RJ, Stepp H, Rick K, Betz V, Strauß W (1995)
Time-gated spectroscopy of intrinsic fluorophores in cells and
tissues. In: Cubeddu R, Marchesini R, Mordon SR, Svanberg K,
Rinneberg HH, Wagnieres G (eds) Optical biopsy and fluorescence
spectroscopy and imaging. Proc SPIE 2324, 187-195
Schneckenburger H,
Gschwend M, Paul RJ, Sailer R, Strauß W (1995) Time-resolved
fluorescence spectroscopy in photobiology and medical diagnosis.
Proceedings of the international conference on Laser’s 94,
567-573
Paul RJ,
Schneckenburger H (1996) Oxygen concentration and the
oxidation-reduction state of yeast: Determination of free/bound NADH
and flavins by time-resolved spectroscopy. Naturwissenschaften 83,
32-35
Paul RJ, Colmorgen
M, Hüller S, Tyroller F, Zinkler D (1997) Circulation and
respiratory control in millimetre-sized animals (Daphnia magna,
Folsomia candida) studied by optical methods. J Comp Physiol B
167, 399-408
Pirow R, Wollinger
F, Paul RJ (1998) Gas exchange and gas transport in a water breather
of millimetre size. Adv Exp Med Biol 428, 193-243
Paul RJ, Pirow R
(1998) The physiological significance of respiratory proteins in
invertebrates. Zoology 100, 319-327
Paul RJ, Colmorgen
M, Pirow R, Chen YH, Tsai MC (1998) Systemic and metabolic responses
in Daphnia magna to anoxia. Comp Biochem Physiol A (im Druck)
Freitag JF, Steeger
HU, Storz UC, Paul RJ (1998) Sub-lethal impairments of respiratory
control in plaice (Pleuronectes platessa) larvae induced by
UV-B radiation determined using a novel biocybernetical approach.
Marine Biology (im Druck)
Paul RJ (1998)
Rotes, grünes, blaues und rosafarbenes Blut: Funktion von
Atmungsproteinen bei wirbellosen Tieren. BIUZ (im Druck)
Pirow R, Wollinger
F, Paul RJ (1998) The importance of the feeding current for oxygen
uptake in the water flea Daphnia magna, assessed by PO2
phosphorimetry, particle fluorimetry and digital image processing. J
Exp Biol (eingereicht)
Müller G, Paul
RJ (1998) Ghosts and liposomes as fluorescent probes to test
physiological reactions in transparent animals. J Exp Biol (in
Vorbereitung)
Perry, S.F.; Schmitz, A.
Institut für Zoologie der Universität Bonn, Poppelsdorfer Schloss, D-53114 Bonn
In insects gas exchange is predicted to take place exclusively at the distal portions of the tracheal system (Wigglesworth. V.B., 1983, Adv. Ins. Physiol. 17, 85-148) and lateral diffusion through the walls of the proximal tracheae is neglected. First instars of C. morosus possess a simple tracheal system, tracheoles do not penetrate the organs and volume-variable air sacs are lacking. In addition, the low metabolic rate of this species suggests that gas exchange through the proximal parts of the tracheal system might be of importance. We employed C. morosus as a model in order to test the hypothesis of lateral diffusion through the walls of the entire tracheal system using stereologic morphometric methods and model calculations.
The morphological diffusing capacity of the tracheal walls for O2 and CO2 was determined in five classes of tracheae according to their inner diameters: class I (tracheoles) < 1 µm; 1 µm < class II < 5 µm; 5 µm < class III < 10 µm; 10 µm < class IV < 20 µm; class V > 20 µm. The O2 diffusing capacity (DO2) is greatest for class I (433 cm3 g-1 h-1 torr-1) and decreases exponentially to class V (DO2 = 0.003 cm3 g-1 h-1 torr-1).
In model calculations we used the O2 consumption rate (median value 0.54 ml h -1 g-1), measured by Warburg manometry and the morphological DO2 of the tracheal classes. Furthermore, we assume an initial DPO2 between the tracheal system (PO2 15-18 kPa) and the tissues (PO2 1-2 kPa) of at least 13 kPa, a value that will reduce over time by lateral diffusion. If we calculate the DPO2 necessary for the entire O2 to diffuse through the walls of each tracheal class, it can be demonstrated that O2 will be able to leave the tracheal system over the walls of tracheal classes I-IV.