Comparative nuclear magnetic resonance studies of diffusional water permeability of red blood cells from different species. V—Rabbit (Oryctolagus Cuniculus)

• 1.1. The diffusional water permeability (P_d) of rabbit red blood cell (RBC) membrane has been monitored by a doping nuclear magnetic resonance (NMR) technique on control cells and following inhibition with p-chloromercuribenzene sulfonate (PCMBS).
• 2.2. The values of P_d were around 6.3 × 10⁻³ cm/sec at 15°C, 7.0 × 10⁻³cm/sec at 20°C, 8.0 × 10⁻³ cm/sec at 25°C, 9.1 × 10⁻³ cm/sec at 30°C and10.7 × 10⁻³ cm/sec at 37°C.
• 3.3. Systematic studies on the effects of PCMBS on water diffusion indicated that the maximal inhibition was reached in 15 min at 37°C with 0.5 mM PCMBS.
• 4.4. The values of maximal inhibition were around 71–74% at all temperatures.
• 5.5. The basal permeability to water was estimated as 1.6 × 10⁻³cm/sec at 15°C, 2.0 × 10⁻³cm/sec at 20°C, 2.4 × 10⁻³cm/sec at 25°C, 2.6 × 10⁻³cm/sec at 30°C, and 3.1× 10^{−3 cm/secat 37°C}.
• 6.6. The activation energy of water diffusion was around 18 kJ/mol and increased to 27 kcal/mol after incubation with PCMBS in conditions of maximal inhibition of water diffusion.
• 7.7. The membrane polypeptide electrophoretic pattern of rabbit RBCs has been compared with its human counterpart.
• 8.8. The rabbit membrane contained a higher amount of spectrin (bands 1 and 2), while the band 6 (glyceraldehyde-3-phosphate dehydrogenase) was markedly less intense.
• 9.9. Considerable differences in the electrophoretic patterns of the two sources of RBC membranes appeared in the bands migrating in the band 4.5 region and in front of band 7, where some polypeptides were apparent in higher amounts in the rabbit RBC membrane.

     

The dynamics of the permeation of an analogue of insect juvenile hormone into nematodes

• 1.1. ¹⁴C-dichlorofarnesoate permeated rapidly into Haemonchus contortus (infective juveniles) and Panagrellus redivivus (mixed cultures) and was strongly bound by hydrophobic association (K_s > 10⁻⁴M).
• 2.2. Uptake rose linearly with increases in temperature (5–38°C) and external concentration (C₀; 0.07–2.15 × 10⁻⁴ M). Within 1 hr the internal concentration, C₁ was >C C₀.
• 3.3. The pH of the medium (6–8) did not affect uptake.
• 4.4. Efflux of dichlorofarnesoate was low: the half-time of release was > 18 hr.
• 5.5. The uptake curve approximated to the expression C₁/C₀ = a(1 − e^−bt) with a and b as constants and t in hr.
• 6.6. These results clarify previous work on the inhibitory action of juvenile hormone on the development of nematodes.

     

Sea-water tolerance in freshwater-resident arctic charr (Salvelinus alpinus)

• 1.1. Freshwater-resident Arctic charr acclimated for 2 months at 8°C, 15% were divided into four experimental groups in July and exposed to 1 and 8°C in 15 and 34% salinity.
• 2.2. Only slight changes in gill Na-K-ATPase activity, blood plasma osmolality and blood plasma concentrations of Cl⁻ and Mg²⁺ were found for the fish exposed to 1 or 8°C in brackish water.
• 3.3. When exposed to sea-water at 8°C, an increase in osmolality and in concentrations of Cl⁻ and Mg²⁺ took place during the first 2–3 days, after which it levelled off.
• 4.4. If exposed to sea-water at 1°C, however, marked increases were found for all parameters measured and all the fish were dead within 5 days of exposure.
• 5.5. These results show that freshwater-resident Arctic charr—if acclimated to brackish water—can survive in sea-water during summer if the environmental temperature is not too low.

     

Solubilization,characterization and photoaffinity labeling of the mitochondrial dihydropyridine receptor from bovine adrenal medulla

• 1.1. The mitochondrial dihydropyridine receptor was solubilized with Chaps at a detergent/ protein ratio of 2.5, during 45 min at 4°C.
• 2.2. From the rate constants of association (8.10 ± 0.25 × 10⁴ M⁻¹ min⁻¹) and dissociation (0.022 ± 0.001 min⁻¹ a K_d of 275 nM was calculated, while from saturation experiments a K_d of 270 ± 30 nM and a density of receptors of 106 ± 9 pmol/mg protein was obtained.
• 3.4. The solubilized receptors are heat-resistant, sensitive to the trypsin and to the reduction of disulfide bonds.
• 4.5. In native membranes, a polypeptide of 50 kDa was specifically photolabelled with [³H]Azidopine.

     

Blood changes in japanese eels,Anguilla japonica,experimentally infected with typical or atypicalAeromonas salmonicida

• 1.1. Changes in the blood and in the rate of oxygen consumption of Japanese eels injected intramuscularly in the head with a lethal dose of typical or atypical Aeromonas salmonicida at 20°C were investigated.
• 2.2. Eels infected with the bacteria became moribund within 4 to 6 days, and then died within 1 day.
• 3.3. The O₂ consumption rate and blood parameters changed markedly with infections. The responses of hosts to infection by the two kinds of bacteria differed with regard to the following four points: blood pH, plasma Cl⁻, lactic acid, and the numbers of granulocytes and lymphocytes.
• 4.4. The responses of eels infected with atypical A. salmonicida were larger and more rapid than those of eels infected with typical A. salmonicida.

     

Thermostability and activation by divalent cations of the membrane-bound inorganic pyrophosphatase of Rhodospirillum rubrum

• 1.1. The activation energy of the membrane bound H⁺-pyrophosphatase is 44.9 k J·mol⁻¹, for the detergent solubilized enzyme is 55.9 kJ·mol⁻¹.
• 2.2. The Arrhenius plots obtained for pyrophosphatases of Rhodospirillum rubrum show no breaks.
• 3.3. At 70°C, the membrane-bound pyrophosphatase is more stable in the presence of either Mg²⁺ or Zn²⁺ than in their absence.
• 4.4. At 65°C, an activator effect of Mg²⁺ or Zn²⁺ was observed. Nevertheless, at 70°C no activation was obtained.
• 5.5. The activator effects of Mg²⁺ or Zn²⁺ were depended of their concentration.

     

The pH dependence of the affinity,kinetics and cooperativity of ligand binding to the root effect haemoglobin of the goldfish Carassius auratus

• 1.1. The binding of O₂ to goldfish haemoglobin showed a strong pH dependence P₅₀=5.5 mmHg; n = 2.4 at pH 8.0 and P₅₀ = 170 mmHg; n = 1.0 at pH 5.5 such that the protein is only 50% saturated in a solution of air equilibrated buffer at pH 5.5.
• 2.2. The binding of CO is cooperative at high pH (n = 2.8; L = 1000; K_R = 0.1 μM; K_T = 4 μM) and non-cooperative (n = 1) at pH 5.5.
• 3.3. The rate of O₂ dissociation is extremely fast and pH dependent; being 30 sec⁻¹ at pH 8.0 and 400 sec⁻¹ at pH 6.0 at 1°C. At 23°C the rate of this process is too fast to obtain accurate data using stopped-flow techniques.
• 4.4. Partial photolysis of the oxyhaemoglobin species leads to homogeneous recombination kinetics at pH 8.0 with an associated rate constant of 4.7 × 10⁷ M⁻¹ sec⁻¹. At pH < 7.5 the recombination process occurs in two steps. One rate is equal to that observed at pH 8.0. The slower process is favoured at low pH.
• 5.5. Photolysis of the CO haemoglobin complex indicates that, at high pH, combination of CO with deoxyhaemoglobin is cooperative, whilst recombination with Hb(CO)₃ is non-cooperative and occurs at a rate of 1.2 × 10⁶ M⁻¹ sec⁻¹.
• 6.6. At neutral pH recombination of CO with partially linganded haemoglobin occurs in a two-step process. The proportion contributed by each of these two steps in pH dependent.
• 7.7. The functioning of this Root effect haemoglobin is discussed in terms of the two state-model of cooperativity in which the αβ chain heterogeneity is minimal

     

Bioelectrical potentials across the mantle epithelium of Achatina fulica

• 1.1. The shell side of the mantle of Achatina fulica is several millivolts positive to the blood side in vitro.
• 2.2. The electrical potential does not depend on Na⁺, Ca²⁺, Mg²⁺, K⁺ or HCO₃⁻ but requires the presence of chloride on the shell side.
• 3.3. The potential difference and short-circuit current ranged from 3.0 to 30.0 mV and 15.0 to 75 μA/cm² with averages at 10m V and 50 μA/cm² respectively.
• 4.4. The electrical gradient is reduced by 2,4-dinitrophenol, thiocyanate and furosemide but not by ouabain, CO₂ or acetozolamide.
• 5.5. It is suggested that the nature and mechanism of electrogenesis in Achatina parallels that of the Helix mantle.

     

Behavioural thermoregulation and critical thermal limits of Macrobrachium acanthurus (Wiegman)

• (1)The preferred temperatures of Macrobrachium acanthurus were determined for prawns acclimated to 20°C, 23°C, 26°C, 29°C and 32°C, and the final preferendum estimate was (29.5°C).
• (2)The critical thermal minima (CTMin) and maxima (CTMax) were 11.0°C, 12.1°C, 13.0°C and 14.8°C, and 34.2°C, 35.0°C, 36.1°C and 39.8°C, respectively.
• (3)The zone of thermal tolerance assessed using the CTMin and CTMax boundaries was 644°C².
• (4)The acclimation response ratio was between 0.33 and 0.62.
• (5)To cultivate this species in the southeastern region of México it should be done in not <15°C (CTMin) during the winter and below 38°C in summer (CTMax).

     

The influence of aerial exposure on gas exchange and cardiac activity in the shore crab,Carcinus maenas (L.)

• 1.1. The cardiovascular physiology of adult Carcinus maenas (L.) emerging into air has been investigated at three different air temperatures.
• 2.2. Transition from seawater to air or vice versa triggered transient increases in cardiac and locomotor activity.
• 3.3. However, crabs became inactive 5–10 min after emerging from seawater (15°C) into air at the same temperature (15°C) or at lower temperatures (12–13°C) and heart rate fell.
• 4.4. At higher air temperatures (18–20°C) heart rate rose but to a lesser extent than predicted from aquatic Q₁₀ heart-rate values.
• 5.5. Crabs were again quiescent in aerial conditions.
• 6.6. Mean arterial oxygen tension (Pa_o2) was ~ 74 mmHg in submerged crabs but fell to ~ 38 mmHg in air while mean arterial carbon dioxide tension (Pa_o2) increased from 1 to 4 mmHg resulting in respiratory acidosis.
• 7.7. A model of gill function is proposed to explain the development of internal hypoxia in air.
• 8.8. The results are discussed in relation to the distribution of adult and juvenile C. maenas in situ.

     

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.

     

Characterization of NaK ATPase from the gills of the freshwater prawn Macrobrachium rosenbergii (de Man)

• 1.1. The specific activity of Na-K ATPase was determined from the microsomal preparation of gills dissected from adult Macrobrachium rosenbergii.
• 2.2. Maximal ATPase activity was achieved at a substrate concentration of 0.5 mM ATP.
• 3.3. Optimal enzyme activity was obtained at pH of 7.5.
• 4.4. The Arrhenius plot of Na-K ATPase activity revealed a marked discontinuity at 30°C. “Mg” ATPase activity did not exhibit a marked discontinuity.
• 5.5. The E_a for Na-K ATPase and “Mg” ATPase was 14.6 kCal/mole and 9.31 kCal/mole respectively. Q₁₀ values for Na-K ATPase was 2.34 and for “Mg” ATPase 1.65.
• 6.6. ATPase activity and gill homogenate protein concentration exhibited a linear relationship up to 130 μg protein/ml.
• 7.7. Na-K ATPase activity was inhibited by 10⁻³ M ouabain. It was equally inhibited by the removal of K⁺ from the reaction medium.

     

Proteolytic cleavage of band 3 protein in relation to anion transport in fish (Oncorhynchus mykiss) red blood cells

• 1.1. The effects of trypsin and chymotrypsin on HCO₃⁻/Cl⁻ exchange through red blood cell membranes of humans and trout were studied.
• 2.2. To measure the anion exchange we used a right-angle light-scattering technique by applying the Jacobs-Stewart cycle in ammonium solution and the osmotiration method at constant cell volume.
• 3.3. The Cl⁻ flux in human red blood cells remained unaltered after treatment with external trypsin and chymotrypsin while in trout red blood cells the flux decreased.
• 4.4. This partial inhibition of anion transport in fish, ranging from 30 to 40%,suggest that one or several of the cleavage sites in band 3 protein, essential for anion transport function, are exposed in fish red blood cells.
• 5.5. In human red blood cells the fragments of band 3 which are affected by proteolytic digestion, retain their tertiary structure because there is no influence on anion transport.

     

The effects of temperature and moisture on survival capacity,cuticular permeability,hemolymph osmoregulation and metabolism in the scorpion,Centruroides hentzi (banks) (scorpiones,buthidae)

• 1.1. The temperature and water relations of Centruroides hentzi females were investigated. At 12 and 72% relative humidity (RH), the lower and upper Lt₅₀ were -4.5 and 43.7°C, and -4.7 and 45.1°C, respectively. When exposed to high temperature stress, survivorship was significantly greater under mesic conditions.
• 2.2. Cuticular water loss was higher under xeric conditions (12% RH), ranging from 0.061 mg/cm²/hr at 30°C to 0.211 at 41°C.
• 3.3. Exposure to dry air (0–5% RH) resulted in a significant increase in hemolymph osmolality: from 441 to 688 mOsm over a 5 day period.
• 4.4. Mean oxygen consumption rates increased from 161.7 mm³/g/hr at 34°C to 541.6 at 44°C. ATPase activity was significantly higher in animals acclimated and tested at 35°C.

     

Purification and properties of a β-1,4-xylanase from a cellulolytic extreme thermophile expressed in Escherichia coli

• 1.1. An endoxylanase (EC 3.2.1.8) was purified from an Escherichia coli strain carrying a xylanase gene from the extreme thermophile “Caldocellum saccharolyticum strain Tp8T6.3.3.1. It was found to have an M_r of 42,000 and an isoelectric point of approx. 5.0.
• 2.2. The enzyme showed optimum activity at pH 5.0–7.7 and had an activation energy of 44 kJ mol⁻¹. It was stable at room temperature at pH 4.5–11.5 in the presence of 0.5 mg ml⁻¹ bovine serum albumin. The half-life of the enzyme at 75°C was 20 min at pH 6.0 in the presence of 0.5 mg ml⁻¹ bovine serum albumin.
• 3.3. The xylanase had highest activity on oat spelts xylan, releasing xylobiose and some xylotriose. The K_m for oat spelts xylan was 0.021% (w/v) at pH6.0.
• 4.4. The enzyme had high activity on sugar cane bagasse hemicelluloses A and B, lower activity on larchwood xylan and also hydrolysed carboxymethylcellulose, 4-methylumbelliferyl β-D-cellobioside and p-nitrophenyl β-D-cellobioside, but could not hydrolyse xylobiose.
• 5.5. It showed transferase activity on p-nitrophenyl β-D-xylopyranoside. Xylose did not inhibit the enzyme.

     

Acid phosphatase in the contents of the oesophagus and stomach of the snail,Helix pomatia L.

• 1.1. In the contents of the oesophagus and stomach, one form of acid phosphatase is found. Its electrophoretic mobility is identical to that of the multiple form 3 of acid phosphatase from the hepatopancreas.
• 2.2. The enzyme is not stimulated by divalent cations. It is inhibited by molybdate, Cu²⁺, Hg²⁺. F⁻ and tartrate L+.
• 3.3. The optimum pH of the enzyme is 4.5. The K_m for paranitrophenylphosphate as substrate amounts to 0.25 mM. The enzyme is stable at a temperature of up to 55°C.

     

Oxygen consumption in the tortoise,Testudo hermanni G., subjected to sudden temperature changes in summer and autumn

• 1.1. A respirometer for long-term measurements of oxygen consumption in terrestrial vertebrates is described.
• 2.2. The tortoise, Testudo hermanni Gmelin, investigated in summer and autumn, presents a day-night rhythm of oxygen consumption at 28 and 18°C but not at 8°C.
• 3.3. The standard metabolic rate presents an important and constant thermal dependence in the range 8-18-28°C.

     

Intracellular localization and characterization of 3-hydroxykynureninase in human liver

• 1.1. 3-hydroxykynureninase in human liver was present in cytosol and mitoehondria.
• 2.2. The cytosolic enzyme and mitochondrial enzyme had the same physiological and enzymic properties.
• 3.3. The enzyme had a mol. wt of 130,000 by gel filtration and isoelectric point of pH 5.9.
• 4.4. The enzyme was active for 3-hydroxykynurenine and kynurenine, and its activity ratio was 15:1. The apparent K_m values of the enzyme were 7.7 × 10⁻⁵M for 3-hydroxykynurenine, 1.0×10⁻³M for kynurenine and 2.5 × 10⁻⁶M for pyridoxal 5'-phosphate with 3-hydroxykynurenine.
• 5.5. Some other properties of purified enzymes are described.

     

Measurement of blood flow to osseous tissue in dogs using the radiolabelled microsphere method

• 1.1. The purpose of this study was to examine bone blood flow in various intra- and extra-oral sites.
• 2.2. The radiolabelled microsphere method was utilized to assess osseous blood flow in the following regions of 10 dogs: rib, long bone, and anterior and posterior regions of the maxilla and mandible.
• 3.3. Samples of cancellous and cortical bone were also obtained from each of these regions with the exception of the maxilla and the anterior mandible.
• 4.4. Mean blood flow ranged from 3.71 ±0.81 (SE) ml min.⁻¹ 100 g⁻¹ in the mandibular posterior cortical bone to 22.7±4.66ml min⁻¹ 100 g⁻¹ in the cancellous rib samples.
• 5.5. Blood flow to the cancellous tissue of the rib was significantly greater (P < 0.05 ) than the other tissues with the exception of maxillary posterior bone and cortical rib.
• 6.6. Results from this study indicate that blood flow to the maxillary posterior bone is relatively high, but blood flow in other intraoral osseous sites is significantly less than that of cancellous rib bone.

     

Determination of temperature preference and the role of the enlarged cheliped in thermoregulation in male sand fiddler crabs,Uca pugilator

• 1.Male Uca pugilator whose major cheliped was immersed in 3 °C water bath experienced a significant drop in T_b. Thus, the enlarged claw of male Uca pugilator may have an unexplored function: thermoregulation.
• 2.Crabs prefer warmer substrates (19–24 and 28–30 °C) over cooler (15–17 °C).
• 3.Mean selected temperature (MST) may not be an accurate reflection of T_b. Crabs in a thermal chamber preferred temperatures between 25 and 30 °C but their average T_b was 23.2 °C.