Gas fluxes in avian eggs: Driving forces and the pathway for exchange

• 1.1. In this study, we review reported values for fluxes of water vapor and oxygen across the pores in avian eggshells, pore numbers per egg, the changes in O₂ and CO₂ tensions in the air space during development, and the absolute humidity of bird nests in various climates.
• 2.2. With egg mass from 1 to 1500 g as the independent variable we use regression analysis of daily water vapor loss, O₂ uptake at the preinternal pipping (PIP) stage of development, and pore numbers to show that O₂, CO₂ and water vapor fluxes per pore are 68, 50 and 49 μl/day, respectively, independent of egg mass. When these fluxes are divided by the invariant pore conductance previously established by Ar and Rahn (Respir. Physiol. 61, 1–20, 1985), predicted air cell O₂ and CO₂ tensions of ca 100 and 40 Torr just prior to the initiation of lung function are obtained, values which agree well with mean measured gas tensions in 25 species.
• 3.3. Our analysis complements the model proposed by Ar and Rahn, in which pores serve as basic respiratory units for most bird eggs. In this model, pore number per egg is matched to O₂ demand at the PIP stage of development to produce the commonly observed air cell gas tensions. Average, total diffusive water loss in 117 species is 15%, SD 2.6, of initial egg mass. To achieve this value requires the proper combination of pore number, egg temperature and nest water vapor tension; the latter is also a function of nest construction and incubation behavior. Examples of nest absolute humidity are cited for 20 species which incubate in diverse climates with ambient absolute humidities from 4 to 22 Torr. Exceptions to the model are seen in eggs incubated under environmental conditions which are unusual in temperature, humidity, or altitude.

     

Dissociation between several egg parameters in two quail strains genetically selected for resistance or sensitivity to acute hypoxia

• 1.1. Eggs laid by females of two strains of Japanese quail, selected in a divergent way towards survival to an acute normobaric hypoxic challenge, were compared for their mass, the mass and the thickness of their eggshell and their water conductance (g_h2o).
• 2.2. Adults and embryos of the Ls+ strain survive at 70%, whereas those of the Ls-strain survive only at 20% to the acute hypoxia.
• 3.3. While the birds of both sexes of each strain do not statistically differ either by their body masses or by various physiological and biochemical parameters, the eggs laid by the females of these strains differ significantly (0.001 < P < 0.01) in mass, eggshell thickness, egg shell mass and water vapor conductance (g_h2o).
• 4.4. Ls-quail lay lighter eggs with lighter and thinner eggshells and with higher g_h2o than Ls+ quail.
• 5.5. Crossing these two strains gives f₁ hybrids (Ls±) whose females lay eggs that are statistically (0.001 <P <0.05) different from those laid by Ls+ in egg masses and shell masses, and statistically (0.001 <P <0.05) different from those of Ls-in shell masses, shell thicknesses and g_h2o.

     

The effect of water loss upon the urate,urea and ammonia content of the egg of the Japanese quail Coturnix coturnix japonica

• 1.1. The urate, urea and ammonia content of the whole egg of the Japanese quail was measured in late incubation in eggs subject to different rates of water loss.
• 2.2. High rates of water loss substantially increased egg urate content, but had little or no effect on urea or ammonia content.
• 3.3. Allopurinol, an inhibitor of urate synthesis, reduced egg urate content to low levels, but produced no effect on urea content, and a small reduction in ammonia content.
• 4.4. The urea concentration of the embryo was lower than in allantoic fluid.
• 5.5. It is concluded that urate production by the avian embryo is primarily concerned with the modification of allantoic fluid composition.

     

Evidence of an egg-laying factor in the prostatic secretions of Helix aspersa müller

• 1.1. A high percentage (53%) of isolated snails injected with prostate gland homogenates lay eggs.
• 2.2. These egg masses consist of a few eggs which contain many nonviable oocytes.
• 3.3. Preliminary experiments suggest that an egg-laying factor may be present in prostatic secretions.
• 4.4. Snails bred in isolation from hatching, whether injected or not, occasionally lay viable eggs.
• 5.5. This observation shows that self-fertilization or parthenogenesis is, in fact, possible in Helix aspersa Müller.

     

Occurrence of d-alanine in the eggs and the developing embryo of the sea urchin Paracentrotus lividus

• 1.1. d-Alanine has been found in appreciable amounts in the eggs and embryos of the sea urchin Paracentrotus lividus.
• 2.2. The content of d-alanine, expressed as pmol/egg or embryo, is 1.32 in the egg, 0.81 in the blastula, 0.54 in the gastrula and 0.60 in the pluteus.
• 3.3. The percentage of d-alanine with respect to the total alanine (d + l) decreases during embryonic development.
• 4.4. d-Amino acid oxidase, d-alanine transaminase and d-alanine racemase activities were found neither in eggs nor in embryos.
• 5.5. Therefore, it does not appear likely that d-alanine is subject to oxidative metabolism.
• 6.6. The decrease in this d-amino acid during development may be due to its utilization in the synthesis of a more complex molecule.

     

Sea water drinking as a homeostatic response to dehydration in hatchling loggerhead turtles Caretta caretta

• 1.1. Hatching Caretta caretta may lose up to 12% of their initial hatched weight from water loss during emergence from the nest.
• 2.2. After subsequent osmotic and excretory water loss in sea water, hatchlings will drink sea water (166 μl 100 g⁻¹ hr⁻¹) and return to their initial weight within 10–15 days, without feeding.
• 3.3. There were no significant changes in plasma osmolarity or sodium levels over this period.
• 4.4. This osmoregulatory strategy is in marked contrast to that seen in the estuarine crocodile, Crocodylus porosus.

     

Use of a new model to quantify compromises between embryo development and parental self-maintenance in three species of intermittently incubating passerines

• 1.Instead of just times to cool (t_cool) and heat (t_heat), intermittent incubation cycles contain a period (t_equil) when eggs are kept at relatively high equilibrium temperatures after heating.
• 2.Relative allocations favoring parental self-maintenance [when (t_cool+t_heat)>t_equil] versus embryo development [when (t_cool+t_heat)<t_equil] were measured for house wrens (Troglodytes aedon), tree swallows (Tachycineta bicolor) and black-capped chickadees (Poecile atricapillus).
• 3.Wrens showed over-all significant relative allocation to parental self-maintenance, while chickadees and swallows balanced both functions.
• 4.House wrens gradually shifted allocation toward increased average egg temperature as incubation progressed, calling into question how temperature influences development rate.

     

O2-binding by the blood of the landhopper,Arcitalitrus dorrieni (Hunt) (Crustacea: Amphipoda)

• 1.1. The O₂-binding characteristics of the blood of the euterrestrial amphipod (landhopper) Arcitalitrus dorrieni have been studied.
• 2.2. The blood exhibited a low O₂ affinity, with a p₅₀ (at pH = 7.8) of 21.4 torr (10°C). Affinity decreased with an increase in temperature at constant pH (ΔH = − 79.4kJ/mol) but the Bohr factor (ΔlogP₅₀/Δ pH = −0.67) was unaffected.
• 3.3. The O₂-carrying capacity of the blood was moderate (1.51 ml/100 ml)
• 4.4. The results support the hypothesis that the blood of terrestrial amphipods is characterized by having a low affinity pigment.

     

NADPH/NADP ratio could regulate the glyoxylate cycle in Tetrahymena pyriformis

• 1.1. The glyoxylic acid cycle pathway could be regulated through the modulation of the isocitrate dehydrogenase-NADP activity. This enzyme is inhibited by NADPH.
• 2.2. The effect on the glyoxylate cycle flux of variations in the rate of the NADPH-consuming pathways has been studied.
• 3.3. Increase in the rate of NADPH-consuming activity by addition of H₂O₂ produces inhibition of the glyoxylate cycle and decrease in the NADPH/NADP ratio.
• 4.4. These results suggest that the glyoxylate flux in Tetrahymena could be modulated by regulation of NADP-dependent isocitrate dehydrogenase by the NADPH/NADP ratio.

     

Cellular and intracellular localization of catalase and acid phosphatase in the midgut of Lumbricus terrestris L.: A cell fractionation study

• 1.1. Cellular and intracellular localization of catalase and acid phosphomonoesterase in the midgut of Lumbricus terrestris was studied by use of tissue fractionation.
• 2.2. At least 60–70% of the catalase resides in the chloragocyte cytosol and the remaining 30–40% resides in gut epithelium peroxisomes.
• 3.3. One of the main functions of the chloragocyte catalase is probably scavenging for H₂O₂ arising from the interaction between blood heme-protein and oxygen.
• 4.4. A simple method for the histochemical detection of cytosol catalase is proposed.
• 5.5. About 10% of the gut acid phosphatase resides in chloragocyte lysosomes. The chloragosomes contain no acid phosphatase.

     

Decomposition of hydrogen peroxide by metmyoglobin: A cyclic formation of the ferryl intermediate

• 1.1. Metmyoglobin reacted with H₂O₂ to form ferryl-myoglobin, which reverted back spontaneously to the met-form.
• 2.2. Through this cyclic reaction of myoglobin between metMb(III) and ferryl-Mb(IV), we propose that H₂O₂, one of the potent oxidants in vivo, can be decomposed continuously in cardiac and skeletal muscle tissues in the absence of catalase and peroxidase.

     

Purification and characterization of a blue-colored red-fluorescent protein from the silkworm (Bombyx mori L.) larvae

• 1.1. A red-fluorescent blue protein (P600) was purified from the digestive juice of the silkworm (Bombyx mori L.) larvae raised on mulberry leaves.
• 2.2. The purified protein was electrophoretically homogeneous and showed the absorption maxima at 601.5 nm and 278 nm, and the fluorescence maximum at 621 nm.
• 3.3. The molecular weight was estimated to be 540,000 by gel filtration on Sepharose CL-6B. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate suggests that the protein consists of two heterogeneous polypeptide subunits with a mol. wt of 15,000 and 18,000.
• 4.4. The P600 contains excess acidic amino acid residues over basic groups. The polarity and pI were 45.5% and 4.6, respectively.
• 5.5. The production of H₂O₂ was observed in the presence of P600 upon illumination.

     

Probing H2O2-mediated Structural Dynamics of the Human 26S Proteasome Using Quantitative Cross-linking Mass Spectrometry (QXL-MS)

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Highlights

• •Two-step cross-linking coupled with affinity purification to facilitate structural analysis of protein complexes.
• •Integrated QXL-MS workflow for studying condition-dependent structural changes of protein complexes.
• •Mechanistic insights on in vivo H₂O₂-induced conformational dynamics of proteasome complexes.

     

Characteristics of Crassostrea virginica crystalline style chitin digestion

• 1.1. Fundamental chitin digestion characteristics of Crassostrea virginica crystalline style were investigated.
• 2.2. Optimum temperature and pH were 34°C and 4.8. respectively.
• 3.3. The colloidal regenerated chitin (0.56mol/0.5 ml: GlcNAc equivalents) was saturating under all enzyme levels encountered.
• 4.4. There was no evidence of end product inhibition, even after 100 hr incubation.
• 5.5. Calculated K_m for the chitinase complex was 1.19mM when determined using a 30 min assay, but was only 0.70 mM when determined using a 4.6 hr assay.
• 6.6. Both K_m values are lower than reported for similar assays in other molluscs and for most bacteria.
• 7.7. Effect of substrate preparation on the kinetics are discussed.
• 8.8. Eight peaks of chitinase activity were resolved by DEAE-Fractogel ion exchange chromatography.

     

Comparative studies of phosvitin from chicken and salmon egg yolk

• 1.1. A method developed for the isolation of phosvitin from chicken egg yolk was successfully applied to the isolation of phosvitin from salmon eggs.
• 2.2. Salmon roe phosvitin is smaller in molecular size than chicken egg phosvitin.
• 3.3. Circular dichroism spectra of all phosvitins investigated displayed good similarities with spectra showing characteristics of unordered and β-sheet secondary structure.
• 4.4. The main component in the Fourier transform infrared spectra of chicken egg phosvitin is indicative of unordered conformation, whereas the Fourier infrared data of the salmon egg phosvitin are consistent with more of β-sheet structure compared to the chicken egg phosvitin.

     

Factors affecting oxygen consumption in wild-caught yellow-bellied marmots (Marmota flaviventris)

• 1.1. All age groups gained mass during the active season, but mass-gain of adult females was delayed during lactation.
• 2.2. The relationship of body mass to metabolic rate varied widely; when the relationship was significant, R² varied from 10.3 to 72.6%. Body mass affects V_O2 more during lactation than at any other period.
• 3.3. Mean VinO₂ of adult males was higher in June than that of adult, non-lactating females.
• 4.4. V_O2 of reproductive females was significantly higher during lactation than during gestation or postlactation because specific V_O2 varied. Specific V_O2 of non-reproductive females declined over the active season.
• 5.5. Specific V_O2 of all age groups declined between the premolt and postmolt periods. The reduced maintenance costs can contribute 20–46% to daily growth.
• 6.6. Observed V_O2 was lower than the value predicted from intraspecific or interspecific Bm:M regressions.
• 7.7. V_O2 of wild-caught marmots was lower than that of marmots maintained in the laboratory, probably because of dietary differences.
• 8.8. Because basal metabolism is a stage on a food-deprivation curve, we suggest that basal metabolic rate is not an appropriate measure of the metabolic activity of free-ranging animals.

     

Temperature shift-induced changes in the antioxidant enzyme system of Cyanobacterium synechocystis PCC 6803

• 1.1. Effect of controlled up- and down-shifts of growth temperature on the antioxidant enzymes activities and lipid peroxidation were investigated in intact cells of Cyanobacterium synechocystis PCC 6803 acclimated at different growth temperature.
• 2.2. Algal cells grown at 36°C were treated at 20 and 43°C as down- and upward-shifts of growth temperature for 24 hr, respectively. At the down-shift of growth temperature the superoxide dismutase, catalase and glutathione peroxidase were significantly increased with concomitant decrease in protein content.
• 3.3. These parameters showed similar temperature dependencies in the up-shift of growth temperature, they were decreased significantly.
• 4.4. The increased hydroxyl (HO) radical and malonyldialdehyde (MDA) formation, when algal cells exposed to down-shift of growth temperature, supposedly due to stimulated production of superoxide radicals (O₂⁻) and hydrogen peroxide (H₂O₂) at lower temperature.

     

The carotenoids of eggs of wild and farmed cod (Gadus morhua)

• 1.1. Eggs of wild cod, and of farmed cod fed (a) a diet supplemented with astaxanthin and (b) a diet supplemented with both astaxanthin and canthaxanthin, were analysed with respect to carotenoids.
• 2.2. The total carotenoid contents in eggs were 0.7 ppm for wild cod and 0.5 ppm for farmed cod.
• 3.3. Cod, having white flesh, deposit ketocarotenoids in the eggs, preferably astaxanthin.
• 4.4. Canthaxanthin can replace astaxanthin in the eggs, but astaxanthin appears to be deposited preferentially when both carotenoids are present in the diet.
• 5.5. The isomer distribution of (3S, 3′S):(3R, 3′S, meso):(3R, 3′R) astaxanthin in the eggs reflected the isomer composition of the diet.
• 6.6. Echinenone, 4′-hydroxyechinenone, adonixanthin and zeaxanthin encountered in cod eggs may represent reductive metabolites of canthaxanthin and astaxanthin.

     

Kinetic studies of catechol-o-methyltransferase from the brain of the African catfish,Clarias gariepinus

• 1.1. Optimum in vitro conditions, and kinetics of the enzyme catechol-O-methyltransferase from the brain of the male African catfish were studied.
• 2.2. A saturated level for S-adenosylmethionine, as methyldonor, and magnesium as cofactor was reached at 5 μM and 10 mM, respectively.
• 3.3. The addition of ascorbic acid, as an antioxidant, and tranylcypromine, as a MAO inhibitor, was not necessary, during incubations with fore-brain homogenates.
• 4.4. Kinetic analysis of the methylation of catecholestrone, catecholestradiol and dopamine showed K_m values of 1.2, 0.6 and 0.5 μM, respectively.
• 5.5. The affinity of the catecholsubstrates for the enzyme catechol-O-methyltransferase is much higher in the brain of the African catfish than in tissues of mammals.

     

Effects of exercise-stress on ventilation,cardiac output and blood respiratory parameters in the carp,Cyprinus carpio

• 1.1. Carp (Cyprinus carpio) were stressed to exercise by rolling in a respiration chamber. Ventilatory water flow rate, cardiac output and blood respiratory parameters were determined.
• 2.2. During exercise, oxygen uptake increased about 3.5-fold and returned to pre-exercise level within 15 min.
• 3.3. This exercise-stress resulted in no plasma acidosis and in no swelling of the erythrocytes.
• 4.4. Ventilatory water flow rate increased 6-fold, whereas cardiac output increased 2-fold. Hence the ventilation-perfusion ratio increased during exercise.
• 5.5. During exercise, arterial O₂ content (CaO₂) increased due to increases in O₂ tension (PaO₂), O₂ saturation of hemoglobin (SaO₂) and hemoglobin concentration (Hb). On the other hand, Pv̄O₂ and Sv̄O₂ remained at the resting levels but Cv̄O₂ slightly increased due to an increase in Hb.
• 6.6. Arterial-venous O₂ difference (CaO₂-Cv̄O₂) increased by 38%, which was met by a much greater increase in CaO₂ than Cv̄O₂.