Electrotonic coupling within a cluster of neurosecretory endogenous oscillators in Lymnaea stagnalis (L.)

• 1.1. Double intracellular and extracellular recordings from cell bodies and axons were made to study the interactions between the neurosecretory “Light Yellow” bursting pacemaker cells (LYC) in the right parietal ganglion of Lymnaea stagnalis.
• 2.2. The LYC are interconnected by low efficiency, non-rectifying electrotonic junctions, transmitting low frequencies only.
• 3.3. Often bursts in different cells coincide; apparently the junctions are responsible for this coherence.
• 4.4. It is inferred that the coupling serves to bring about a pulse-wise release of the cluster's secretory product.

     

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.

     

Some properties of ATPase activity in the intact cells of yeast Saccharomycopsis fibuligera

• 1.1. The properties of ATPase activity were studied with the cells at the early stationary phase of Saccharomycopsis fibuligera.
• 2.2. Optimal pH for the activity was approximately 7.
• 3.3. The activity was stimulated by Mg²⁺.
• 4.4. The activity was inhibited by NaF, DCCD, oligomycin, NaN₃, NaVO₃, or PCMB but not inhibited by ouabain.

     

The effect of temperature on the acid-base status of the blood of the hatching quail (Coturnix c. japonica)

• 1.1. The ambient temperature of embryos of pipped eggs was reduced from 38 to 28°C for a period of 45 min.
• 2.2. The blood P_CO2 was lower and the blood more alkaline at 28°C than at 38°C.
• 3.3. At 28°C plasma [HCO₃⁻] ] was lower than predicted from the blood buffer line determined in vitro.
• 4.4. The plasma concentrations of strong ions and lactate were the same at both temperatures.
• 5.5. After the ambient temperature had been returned to 38°C for a period of 45 min, blood pH was more acidic than before cooling, but there was no difference in blood P_CO2.
• 6.6. The plasma [HCO₃⁻] was the same as that at 28°C and plasma [K⁺] was higher than before cooling.
• 7.7. The results arc discussed in relation to the factors affecting blood pH in embryos at this stage of development.

     

The effect of temperature on oxygen equilibrium curves of trout blood (Salmo gairdnerii)

• 1.1. Oxygen equilibrium curves were measured on trout red blood cell suspensions at pH 7.8 and 8.4 at 15, 20 and 25 C. Normal red cells and red cells that had been depleted of their ATP content were used.
• 2.2. The equilibrium data were fitted to the Adair's model and the enthalpy (ΔH) and entropy (ΔS) changes for the first and fourth steps of oxygenation and for overall oxygenation were calculated from the temperature dependencies of the Adair constants.
• 3.3. For normal red blood cells, the apparent heat for the first oxygenation step, δh₁, is close to zero.
• 4.4. Temperature insensitivity of this step at physiological pH, combined with a large pH dependence, probably denotes a property of Hb4, the Root effect Hb of trout blood.
• 5.5. At pH 7.8, ΔH₄ is about —4kcal/mol, a small value which may be attributed to the large release of Bohr protons that occurs at the last oxygenation step and corresponds to an endothermic process which opposes to the exothermic oxygenation of the haem.
• 6.6. The ΔH₄ value appears to have a large influence on the enthalpy for overall oxygenation.
• 7.7. Results for ATP-free red cells are consistent with a mere increase in the intracellular pH and suggest that ATP has no specific effect at and above pH_i ~ 7.7.
• 8.8. Effects of temperature and pH on trout red blood cell isotherms emphasize the primary importance of the major component of trout blood, namely Hb4, in trout blood functional properties.

     

The effect of aluminum in soft water at low pH on osmoregulation and ionic balance in the dragonfly Libellula julia uhler

• 1.1. To determine the physiological impact of Al on an organism stressed by low pH, the acid tolerant Libellula Julia was exposed to 30 mg/l Al at a pH of 2.3, 0.3 of a pH unit above its 96 hr lc₅₀.
• 2.2. Aluminum at low pH, in comparison to low pH alone, caused highly significant losses of wet and ash weight and of body burdens of Na⁺ and Ca²⁺.
• 3.3. Since at the test pH Al exists as the ion, it would seem that a biological impact can be exerted not only by the ionized and unionized hydroxides, but also by Al³⁺.

     

Effects of temperature and acid stress on hatching,survival capacity,metabolism and postural reflexes in caenid mayflies (ephemeroptera)

• 1.1. Mortality was 100% at pH 3.5 over a temperature range of 10–30°C for embryos and nymphs of Caenis diminuta and C. hilaris.
• 2.2. Hatching success for both species was highest at pH values above 4.5.
• 3.3. Survival capacities were significantly higher at 20°C over a pH range of 4.0-7.2.
• 4.4. Oxygen consumption rates increase as a function of increasing temperature and reduced acidity.
• 5.5. Loss of the nymphal righting response was observed at pH 3.5. This response can be used as a behavioral assay for acid stress.

     

Respiration in the eastern water dragon,Physignathus lesueurii (agamidae)

• 1.1. Some aspects of the gas exchange system of a diving lizard, Physignathus lesuewii were studied.
• 2.2. Breathing patterns were analysed.
• 3.3. Breathing rate increases logarithmically with temperature and Q₁₀ = 1.8. LogBR = −0.237 + 0.0256 T.
• 4.4. Gas tensions in lung air and arterial and venous blood were measured. Arterial pH declines with increasing temperature.
• 5.5. Temperature has a marked effect on oxygen affinity of the blood (ΔH = −10.1 kcal mol⁻). A Bohr effect was also noted.
• 6.6. CO₂ equilibrium curves were drawn.
• 7.7. The results are considered with a view to anticipating the efficiency of the gas exchange system of this species under conditions of variable temperature and during diving.

     

An alkaline phosphatase from Thermus sp strain Rt41A

• 1.1. A thermostable orthophosphoric monoester phosphohydrolase (EC 3.1.3.1) from Thermus sp strain Rt41A has been purified 400-fold to give a specific activity of 25 U/mg at 60°C in IM diethanolamine (pH 11.1).
• 2.2. The enzyme has a M_r of 160,000 and is trimeric.
• 3.3. The half-life of the enzyme is 5 min at 85°C.
• 4.4. The enzyme has a wide specificity for a number of phosphate monoesters.
• 5.5. The H_m of the enzyme is pH dependent, so the pH optimum of the enzyme is affected by the substrate concentration.
• 6.6. The enzyme is inhibited 50% by 20 mM Ca²⁺ or Mg²⁺.
• 7.7. The K_i for phosphate, EDTA-di sodium salt and arsenate (in 1 M diethanolamine, pH 11.1) is approx 1.2, 1.6 and 4mM respectively.
• 8.8. Urea (200 mM) is not inhibitory.

     

Kinetic studies of the transphosphorylation reactions catalyzed by alkaline phosphatase from E. coli: Hydrolysis of p-nitrophenyl phosphate and o-carboxyphenyl phosphate in presence of tris

• 1.1. Transphosphorylation of p-nitrophenyl phosphate and o-carboxyphenyl phosphate to Tris, has been studied at alkaline and acid pH.
• 2.2. The rate of release for all reactions products was Tris-dependent for both substrates, with a slight maximum for phenol at alkaline pH. These dependences have been analyzed from a mechanistic standpoint.
• 3.3. Individual constants of rate of a simple transphosphorylation mechanism have been determined.
• 4.4. At high Tris concentrations (> 1.0 M) a slight competitive inhibition has been observed.
• 5.5. Inhibition in NH₄⁺-NH₃Cl buffer has been found at alkaline pH but not at acid pH. It would therefore seem that the non-protonated NH₂ group of Tris is responsible for inhibition.
• 6.6. The results suggest the formation of complexes between Tris and the enzyme. Other possible alternatives are also analyzed.

     

Lipoxygenase of the thermophilic bacteria thermoactinomyces vulgaris—properties and study on the active site

• 1.1. A lipoxygenase activity was purified from Thermoactinomyces vulgaris and some of its properties were characterized.
• 2.2. The enzyme showed a temperature activity range of 40–55°C with still significant activity over 60°C.
• 3.3. The pH of activity on linoleic acid had a broad range with an optimum at pH 6.0 and a weaker one at pH 11.0.
• 4.4. On arachidonic acid the pattern was narrow bell-shaped with an optimum at pH 6.5.
• 5.5. The purified lipoxygenase from Th. vulgaris showed an apparent K_m of 1 mM and V_max of 0.84 μmol diene/min/mg protein.
• 6.6. It was inhibited by the oxidation products, 9-HPOD and 13-HPOD.
• 7.7. A 160,000 Da molecular weight of the enzyme was determined by molecular filtration. Methionine, tyrosine, tryptophan and cysteine are apparently involved in its activity.

     

Intracellular calcium in the cells of the outer mantle epithelium of Anodonta cygnea

• 1.1. The intracellular concentration of ionized calcium was measured with double-barrelled ion-sensitive microelectrodes under short-circuit conditions in the isolated outer mantle epithelium of Anodonta cygnea.
• 2.2. When the outside baths contained 1 mmol/1 Ca²⁺ the average intracellular Ca²⁺ was 5.42 ± 0.64 mmol/1(N = 41) while the equilibrium concentration estimated from the intracellular potential measured in the same cells was 5.51 ± 0.33 mmol/l.
• 3.3. Bilateral removal of calcium from the external baths induced a fast fall in the intracellular concentration of this ion by almost three orders of magnitude. This effect was similar to that obtained by removing calcium from the bath on the basolateral side.
• 4.4. Removal of calcium from the bath in contact with the apical side of the preparation had little effect on intracellular calcium.

     

Purification and characterization of the endonuclease present in Physalia physalis venom

• 1.1. Physalia physalis nematocyst venom contains a DNase which has a non-specific endonucleolytic action.
• 2.2. This enzyme has an approximate molecular weight of 75,000 daltons.
• 3.3. The enzyme can cleave DNA over a wide pH range with an optimum near neutrality.
• 4.4. The enzyme is thermolabile and its activity can be stimulated by 80 nM NaCl or 10 mM MgCl₂.

     

Structure and bioelectricity of single neurons of Helix pomatia in the intact nervous tissue during epileptic activity: Simultaneous evaluations by confocal microscopy and intracellular recordings of membrane potential changes

• 1.1. Neuronal shape during epileptic activity was studied with confocal laser scanning microscopy and intracellular recording of identified neuronal individuals in the buccal ganglia of Helixpomatia. Simultaneous observations of single Lucifer Yellow stained fibers and epileptic activity of the same neuron were done.
• 2.2. During epileptic activity, the development of several types of morphological changes were observed: local and extended swellings, constrictions, stretching of neuronal processes and release of intracellular material.
• 3.3. Morphological alterations did not only occur with epileptic activity but could also appear due to extended laser exposure of fluorescent neuronal processes.
• 4.4. Phototoxicity is discussed as a limiting factor for a valid interpretation of the morphological changes observed by confocal microscopy.

     

Cardiac responses to stress and activity in the armoured legless lizard Ophisaurus apodus: Comparison with snake and tortoise

• 1.1. Heart rate (HR) was measured during and after stress and activity in the armoured legless lizard Ophisaurus apodus, the snake Natrix natrix and the tortoise Testudo hermanni, at different body temperatures T_b. These are discussed in relation to field T_b, defensive behaviour and published V́O₂.
• 2.2. Ophisaurus apodus used passive defence, including hemipenis or cloacal sac eversion and prolonged immobility after release. This was correlated with a low degree of tachycardia, bradycardia at low T_b, low metabolism and armour.
• 3.3. Defence behaviour was T_b-dependent in wild T. hermanni, with passive withdrawal into the shell at low T_b, and active struggling at high T_b. The degree of tachycardia was lower at low T_b.
• 4.4. Standard and active oxygen pulse OP were insensitive to T_b in O. apodus and N. natrix, and their SOP was lower than tetrapod lizards. Factorial scope of HR was reduced at 35°C, just above the activity T_b range of these species.
• 5.5. Recovery of HR after activity in T. hermanni was much more rapid than in the squamates, and of similar duration to recovery after stress. It is suggested that tortoises do not utilize anaerobic metabolism during activity.

     

Purification and characterization of hatching enzyme of the pike (Esox lucius)

• 1.1. A choriolytic enzyme was isolated from the hatching medium of the pike, Esox lucius.
• 2.2. The enzyme is defined as hatching enzyme.
• 3.3. The molecular weight of the enzyme is 24,000.
• 4.4. The enzyme is a glycoprotein containing 2% carbohydrate.
• 5.5. Its isoelectric point is 6.5.
• 6.6. The pH optimum is around pH 8.
• 7.7. The enzyme molecule contains two disulfide bonds but no free cysteine.
• 8.8. Inhibitor studies and metal analysis show that the enzyme is a zinc-metalloprotease.

     

The regulation of glucose 6-phosphate dehydrogenase from Dicentrarchus labrax (bass) liver

• 1.1. Kinetic constant values of the reaction catalyzed by bass liver glucose 6-phosphate dehydrogenase show to be modified between 10 and 40°C.
• 2.2. The Arrhenius plot between 10 and 50°C shows two slopes with different activation energies.
• 3.3. These results suggest a regulation of this enzyme by environmental temperature.
• 4.4. Kinetics of ATP inhibition were examined between pH 6.2 and 7.8: patterns and K_i values obtained are affected by the pH variation.
• 5.5. NADH is an effective inhibitor of bass glucose 6-phosphate dehydrogenase but this enzyme does not show NAD-linked activity.
• 6.6. Kinetics of pyridoxal 5′-phosphate inhibition have indicated the presence of a lysine in the catalytic site for NADP⁺.

     

S-Adenosyl-l-methionine decarboxylase activities in Mytilus edulis

• 1.1. The activities of S-adenosylmethionine decarboxylase (EC 4.1.1.50) were measured in cell extracts of mantle, hepatopancreas and foot from Mytilus edulis.
• 2.2. The apparent molecular weights of the enzymes estimated by gel filtration chromatography were 65,000 ± 10,000.
• 3.3. The enzymes do not require bivalent cations for catalysis and show optimum pH between 7.0–8.0 in phosphate buffer.
• 4.4. The hepatopancreas enzyme shows different behavior to the other two enzymes against temperature and its activity is strongly inhibited by NH₄⁺.
• 5.5. The apparent K_ms for S-adenosylmethionine were found to be 300, 200 and 250 μM for the hepatopancreas, mantle and foot enzymes, respectively.

     

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.

     

Thrombocyte aggregation in rainbow trout

• 1.1. Thrombocytes from mature rainbow trout (Sahmo gairdneri) aggregated in vitro after addition of ADP, ATP, collagen, epinephrine, 5-hydroxytryptamine or thrombin to thrombocyte-rich plasma.
• 2.2. Thrombocyte aggregation was dose dependent and could be inhibited by preincubating the thrombocyte-rich plasma with adenosine, acetylsalicylic acid or prostaglandin E₁.
• 3.3. Thrombocytes released ADP and ATP when aggregated by 10 μM epinephrine. This release was blocked by 1 mM adenosine.
• 4.4. Electron microscopic observations of thrombocytes revealed them to contain numerous microtubules and electron-dense vesicles. In addition a possible shape change associated with thrombocyte aggregation was noted.