Synaptic transmission at high pressure: Effects of [Ca2+]o

• 1.1. The effects of pressure on synaptic currents were examined in crayfish abdominal muscles.
• 2.2. Helium pressure (10.1 MPa) considerably decreased extracellulariy-recorded excitatory junctional potentials associated with increased short-term facilitation.
• 3.3. These effects could be mimicked by a reduction of [Ca²⁺]_o, and partially compensated by an increase in [Ca²⁺]_o.
• 4.4. Pressure also reduced the amplitude of the extracellular nerve terminal potentials (ENTP) by up to 25%, and significantly increased synaptic delay in a [Ca²⁺]_o-dependent manner.
• 5.5. The interaction between compression and various [Ca²⁺]_o were analysed in terms of an existing model of transmitter release. The results were consistent with the hypothesis that high pressure decreases the maximal Ca²⁺ influx into nerve terminals.
• 6.6. The decreased ENTP and increased synaptic delay suggest that additional processes may be involved in pressure effects on synaptic transmission.

     

The taurine content of avian erythrocytes and its role in osmoregulation

• 1.1. The taurine content of erythrocytes from 15 avian species contained levels of taurine in the range of 20–70 mmol/kg of hemoglobin, about 100-fold that of mammalian red blood cells.
• 2.2. This high taurine content did not appear to be related to the nucleation of these cells as nucleated amphibian erythrocytes and human reticulocytes contained low levels.
• 3.3. The erythrocytes lacked cysteine sulfinic acid decarboxylase, a key enzyme in the synthesis of taurine from cysteine, indicating a probable lack of synthetic capabilities.
• 4.4. The cells were able to accumulate labeled taurine against a concentration gradient. This uptake was inhibited by β-alanine and was Na⁺-dependent.
• 5.5. When incubated in hypotonic medium, the cell volume of pigeon erythrocytes rapidly increased and was followed by a much slower return to normal size. The cell volume reduction was accompanied by a slow efflux of taurine into the medium.
• 6.6. These data suggest that taurine plays a role in cell volume maintenance and osmotic regulation in avian erythrocytes.

     

Amino acid synthesis during hyperosmotic stress in penaeus aztecus postlarvae

• 1.1. Glycine, proline, and taurine are the quantitatively most important amino acid osmolytes in Penaeus aztecus postlarvae.
• 2.2. Taurine dominates the amino acid pool in low salinity, while proline dominates the amino acid pool at higher salinities.
• 3.3. Although not major contributors to the pool, glutamate and alanine are constitutively synthesized from [¹⁴C]glucose and [¹⁴C]glutamate under constant salinity and under hyperosmotic stress treatments.
• 4.4. Proline synthesis from [¹⁴C]-precursors is apparent under constant high (but not low) salinity and is significantly induced by hyperosmotic stress.
• 5.5. No appreciable glycine synthesis was observed from [¹⁴C]glucose or [¹⁴C]glutamate under any experimental conditions.

     

An investigation of gluconeogenesis in marine teleosts,and the effect of long-term exercise on hepatic gluconeogenesis

• 1.1. Gluconeogenesis from ¹⁴C-substrates was measured in liver slices from marine teleosts.
• 2.2. 0.56 to 2.78 μmols of lactate were incorporated/g wet wt/hr with the higher rates corresponding to the active species.
• 3.3. Snapper (Chrysophrys auratus) and bream (Acanthopagrus butcheri) exercised continuously for 14 days showed a substantial increase in the incorporation of lactate; snapper confined for 4 months showed a significant decrease in the incorporation of lactate, compared to freshly caught individuals.
• 4.4. Pyruvate carboxylase and fructose 1,6-diphosphatase were found in red muscle. Some phosphoenolpyruvate carboxykinase may also be present. The three enzymes were present in liver. Possible roles for the enzymes in teleost muscle are discussed.

     

Isolation and characterization of lipoamide dehydrogenase from mackerel dark muscle

• 1.1. Lipoamide dehydrogenase was purified 1500-fold from mackerel dark muscle.
• 2.2. The enzyme was homogeneous as judged by acrylamide gel electrophoresis in the presence and absence of SDS.
• 3.3. Molecular weights of 102,000 and 55,000 were estimated for the native and denatured enzyme, respectively.
• 4.4. Optimal activity for the enzyme was obtained at around pH 5.7 and enhanced with citri acid.
• 5.5. Loss of activity was less than 5% by incubating the enzyme at 70°C for 20 min.
• 6.6. An apparent K_m of 3.1 × 10⁻³ M was obtained for dl-lipoic acid and 1.5 × 10⁻⁵ M for NADH.
• 7.7. The properties of lipoamide dehydrogenase from mackerel dark muscle observed in this investigation were very similar to those reported for the enzyme from other sources.

     

[14C]PEG-4000, chloride,chloride/potassium and sodium spaces as indicators of extracellular phase volume in the tissues of rainbow trout,Salmo gairdneri richardson

• 1.1. Estimates of extracellular phase volume and cellular electrolyte concentrations based on [¹⁴C] PEG-4000, chloride, chloride/potassium and sodium spaces were compared at three epaxial muscle sites and in cardiac muscle, liver, gut, spleen and brain samples of rainbow trout.
• 2.2. [¹⁴C] PEG-4000 appeared to provide realistic estimates of tissue water distribution and cellular ion levels in brain and is suitable for use with epaxial and cardiac muscle, gut and spleen but not liver.
• 3.3. [¹⁴C] PEG-4000, chloride and chloride/potassium spaces were comparable in epaxial muscle, cardiac muscle and gut. Thus, no advantage is associated with use of the former rather than ion-defined estimates of extracellular phase volume in these tissues.
• 4.4. [¹⁴C]PEG-4000 and sodium spaces appear to be preferable to chloride and chloride/potassium spaces as indicators of tissue water distribution in spleen.
• 5.5. Sodium provides unrealistic estimates of extracellular phase volume in tissues other than spleen and liver.

     

In situ phosphorylation of contractile proteins of a molluscan Mytilus edulis catch muscle in different functional states

• 1.1. The incorporation of ³²P into the contractile proteins of the anterior byssus retractor muscle of Mytilus edilus L. was analyzed during the different stages of a contraction-catch-relaxatin cycle.
• 2.2. The experiments were performed with saponin-skinned fibers preincubated with γ-³²P-ATP.
• 3.3. The total amount of ³²P incorporated into the fiber proteins was anlyzed by measuring the label of TCA-insoluble protein in a scintillation counter.
• 4.4. The dose incorporated was about twice as high during Ca²⁺ induced contraction and serotonin induced accelerated relaxation as during test and catch.
• 5.5. The molecular mass of the phosphorylated proteins was analyzed by autoradiography of the proteins separated by SDS-PAGE.
• 6.6. Up to 26 protein spots of different molecular masses were labelled, including such well characterized protein spe+cies as myosin heavy and light chains, paramyosin and tropomyosin.

     

In vitro substrate utilization for lipid synthesis in liver explants from hyperthyroid chickens

• 1.1. Indian River male broiler chickens growing from 7 to 28 days of age were fed diets containing 12, 18, 24 and 30% protein + 0 or 1 mg triiodothyronine (T₃)/kg of diet to study energetic costs of lipogenesis and the use of various substrates for in vitro lipogenesis.
• 2.2. De novo lipid and CO₂ production were determined in the presence of [1-¹⁴C]pyruvate, [2-¹⁴q]pyruvate, [3-¹⁴C]pyruvate, [2-¹⁴C]acetate and [U-¹⁴C]alanine.
• 3.3. Oxygen consumption was determined in mitochondrial preparations to estimate the energetic costs in expiants synthesizing lipid.
• 4.4. Radiolabeled CO₂ derived from [1-¹⁴C]pyruvate was used as an estimate of coenzyme A availability in liver expiants. Lipids derived from [2-¹⁴C]pyruvate, [2-¹⁴C]acetate and [U-¹⁴C]alanine estimate relative substrate efficiency.
• 5.5. Labeled CO₂ production from [1-¹⁴C]pyruvate was greatest in that group fed a 12% protein diet and least in the group fed a 30% protein diet.
• 6.6. In addition, T₃ increased CO₂ production from [1-¹⁴C]pyruvate.
• 7.7. The production of ¹⁴CO₂ from the second carbon of pyruvate or acetate was increased by T₃.
• 8.8. The low-protein diet (12% protein) increased (P <0.05) lipogenesis.
• 9.9. Adding T₃ to the diets decreased carbon flux into lipid from all substrates, but increased CO₂ production from all substrates without changing stage 3 and 4 respiration rates in mitochondrial preparations.
• 10.10. These observations imply that coenzyme A availability may have regulated de novo lipogenesis in the present study.
• 11.11. It was also concluded that previously noted effects of T₃ on intermediary metabolism may involve metabolic pathways that do not involve changes in mitochondrial function.

     

Metabolic roles of carnitine expressed through the carnitine acetyltransferase system in Candida pintolopesii

• 1.1. The carnitine-responsive mutant yeast, Candida pintolopesii ATCC 26014 and the wild type strain (ATCC 22987) were used to investigate the role of carnitine and the carnitine acetyltransferase system.
• 2.2. [³H]l-Carnitine, supplied to the cells, was incorporated into acetylcamitine and [¹⁴C]pantothenate was incorporated into CoA and its derivatives.
• 3.3. Both bioautography and quantitative assays indicated that the relative amounts of CoA and acetylCoA were very different in the mutant and wild type cells.
• 4.4. The wild type yeast maintained an acetylCoA/CoA ratio of 0.33 ± 0.09 indicating that most of the CoA in the cell is in the free CoA form. Carnitine was not required to establish this ratio nor did its presence lower it further.
• 5.5. In contrast, the mutant cells contained a high acetylCoA/CoA ratio (12.8 ± 3.0).
• 6.6. In the mutant cells, carnitine lowered the ratio by decreasing the intracellular acetylCoA concentration and releasing free CoA.
• 7.7. These data indicated that wild type yeast possess an effective mechanism that is not related to the CAT system for regulating the acetylCoA/CoA ratio.
• 8.8. This mechanism appears to be lacking in the mutant. The CAT system decreased the acetylCoA/CoA ratio in the mutant cells but not to the value which is found in the wild type strain.
• 9.9. In both stains of Candida pintolopesii, in the presence of carnitine, an acetylcamitine pool can be created whose concentration exceeds that of acetylCoA.
• 10.10. The intracellular apparent equilibrium constant (K_app) for carnitine acetyltransferase for wild type Candida pintolopesii ATCC 22987 was 0.73 ± 0.12, close to the established value of 0.6, indicating that the CAT system ran close to equilibrium.
• 11.11. The K_app for the CAT system of the carnitine-responsive mutant yeast was 7.7 ± 1.7 indicating that this reaction was not at equilibrium.

     

A study of excitatory efferent fibres in the intestinal nerve of the fowl (Gallus domesticus)

• 1.1. The intestinal nerve of the fowl was studied in vitro.
• 2.2. A significantly larger amplitude spike discharge was recorded in side branches of the nerve which innervate the gut when the aboral end of the main nerve trunk was stimulated than when the oral end was stimulated.
• 3.3. Postganglionic autonomic neurones innervating the smooth muscle of the ileum are not located in the intestinal nerve. Evidence is presented, however, supporting the idea that such neurones innervating the rectum are located in the rectal position of the nerve.
• 4.4. The increase in intraluminal pressure and circular muscle tension in the ileum was greater following aboral nerve stimulation than following oral nerve stimulation.
• 5.5. It is suggested that excitatory efferent nerve fibres ascend the intestinal nerve to innervate the ileum.

     

Cell volume regulation in isolated,perfused heart ventricle of the flounder (Platichthys flesus)

• 1.1. The ventricle cells of the flounder (Platichthys flesus) maintained the cell volume regulation mechanism in vitro, when isolated hearts were submitted to a hyposmotic solution.
• 2.2. The initial osmotic swelling of the cells was followed by a secondary shrinking. A new steady state volume (water content) was established in the course of 6 hr. The water content was 3% above control.
• 3.3. The cellular amount of K⁺ and taurine decreased concomitantly with the decline in cellular water.
• 4.4. The decrement in cellular taurine was explained by leakage of taurine, per se, into the perfusion media.

     

Possible role of prostaglandin F in blastocyst implantation

The synthesis and release of Prostaglandin F (PGF) by the rabbit blastocyst and endometrium were investigated on Day 6 and 7, using radioimmunoassay, autoradiography and conversion experiments. The following results were obtained:

• 1.1) The content of PGF in the blastocyst increased significantly (P < 0.01) form Day 6 and 7.
• 2.2) The content of PGF in the endometrium was significantly higher (P < 0.05) on Day 7 implantation sites compared to the other areas.
• 3.3) The in vitro synthesis and release of PGF by Day 6 balstocysts sharply increased after one and two hours of culture, respectively. Thereafter both values declined with time.
• 4.4) The in vitro synthesis and release of PGF by Day 6 endometria increased continuously with time.
• 5.5) ¹⁴C-arachidonic acid (¹⁴C-AA) was incorporated into Day 6 blastocysts in vitro and converted to PGF_2α. These results suggest that both the endometrium and the blastocyst are the sources of the PGs involved in implantation, and that PGF derived from the blastocysts may act as the trigger of implantation.

     

Purine metabolism in cotyledons and embryonic axes of black gram (Phaseolus mungo L.) Seedlings

• 1.1. The metabolism of purine bases and nucleosides in cotyledons and embryonic axes of black gram (Phaseolus mungo L.) was studied.
• 2.2. A large portion of absorbed [8-¹⁴C]adenine, [8-¹⁴C]guanine and [8-¹⁴C]adenosine was salvaged in nucleotide and nucleic acid synthesis.
• 3.3. Most of the radioactivity of [8-¹⁴C]hypoxanthine and [8-¹⁴C]inosine was incorporated into allantoin and allantoic acid.
• 4.4. Activity of adenine phosphoribosyltransferase in enzyme extracts was much higher than that of hypoxanthme and guanine phosphoribosyltransferase(s).
• 5.5. Apparent activity of adenosine kinase was higher than that of inosine kinase. 6. NAD⁺-dependent xan thine dehydrogenase was detected in both cotyledons and embryonic axes of the seedlings.
• 6.7. The capacity of purine salvage was higher m 24 hr old cotyledons than 24 and 48 hr old embryonic axes. The reverse was observed concerning that of purine degradation.

     

Basis for hyperexcitation symptom caused by high doses of chlordimeform in the American cockroach

• 1.1. Exposure of isolated ventral nerve cords of the American cockroach to chlordimeform was followed by spontaneous and stimulus-induced hyperactivity which different from that induced by dieldrin in the distribution of spike amplitudes, the delay between stimulus and response and the stimulus threshold to induce hyperactivity.
• 2.2. Calcium (20 mM) abolished the impulse-evoked hyper-response of the nerve to chlordimeform but not to dieldrin.
• 3.3. Magnesium (40 mM) abolished the impulse-evoked hyper-responce of the nerve to dieldrin but not to chlordimeform.
• 4.4. Treatment of the insects with reserpine prior to dissection had no effect on the subsequent hyper-response of the isolated nerve to chlordimeform.
• 5.5. The observed action of chlordimeform is probably axonal, and is unrelated to its known aminergic effects.

     

Incorporation of [14C] labelled food into the periostracum of a freshwater mollusc

• 1.1. Freshwater limpets were fed [¹⁴C] labelled food for 24hr, and unlabelled food for 96hr.
• 2.2. Incorporation into the periostracum was on average about 6.8% of total soft body value.
• 3.3. A negative correlation exists between the absolute amount incorporated into the soft body and the per cent incorporation into the periostracum.

     

Taurine regulation of Ca2+ uptake and (Ca2+ + Mg2+)-ATPase in developing chick B-cells

• 1.1. The objective of the present study was to determine the effect of age and taurine on chick B cell calcium uptake and membrane (Ca²⁺ + Mg²⁺)-ATPase activity in 1–4-week-old chicks.
• 2.2. The calcium uptake rate decreased with age (P < 0.05) and was further decreased by taurine (P < 0.05).
• 3.3. (Ca²⁺ + Mg²⁺)-ATPase activity increased with age (P < 0.05) and was stimulated by taurine (P < 0.05).
• 4.4. The data demonstrate that the flux of calcium across the B-cell membrane changes during early post-hatch development, and that taurine regulates both the influx and efflux of calcium in chick B-cells.

     

Glycoprotein effect on the osmotic permeability of liposomes

• 1.1. Proteoliposomes with incorporated α₁-acid glycoprotein were found to be osmotically sensitive to alkali metal salts.
• 2.2. The apparent permeabilities of monovalent metal cations were determined. They were compared with those of pure liposomes in the presence of amphoterecin B.
• 3.3. It was found that proteoliposomes showed a selective permeability to K⁺ in spite of the fact that pure liposomes in the presence of amphotericin B are more permeable to Rb⁺.
• 4.4. It was assumed that this difference arises apparently from the modification of lecithin bilayer in the presence of glycoprotein molecule.

     

Metabolic utilization of leucine in a fat and a lean line of chicken

• 1.1. In vivo incorporation into body lipids and breast muscle proteins from l-[U-¹⁴C]leucine was studied in genetically lean or fat male chickens, fed or starved, 1 or 24 hr after intraperitoneal injection.
• 2.2. Lipogensis and portein synthesis from labelled leucine were significantly higher in fat chickens than in lean birds, particularly in those in the fed state.
• 3.3. Radioactivity in the free amino acid pool was greater in fat birds irrespective of the nutritional state.
• 4.4. However, utilization of injected l-[U-¹⁴C]leucine for lipogenesis was no more than 2%.

     

Effect of pH on metabolism of the glutamine carbon skeleton by renal cortical mitochondria

• 1.1. To determine the effect of altered acid-base homeostasis on the intramitochondrial metabolism of the glutamine carbon skeleton ¹⁴CO₂ production from [U-¹⁴C]glutamine by isolated rat renal cortical mitochondria was measured.
• 2.2. Mitochondria from rats with chronic metabolic acidosis either showed no change or diminished ¹⁴CO₂ production in comparison with pair fed controls.
• 3.3. By contrast, when the pH of the medium incubating mitochondria from normal rats was manipulated (pH 7.0, 7.4, 7.7), ¹⁴CO₂ production was clearly altered, but the direction and magnitude of the change depended on the glutamine concentration used (0.5 or 10.0 mM).
• 4.4. Mitochondria produced significant quantities of ¹⁴CO₂ when [1,4 ¹⁴C]succinate was used as substrate, indicating that ¹⁴CO₂ production from glutamine does not originate solely from the decarboxylation of α KG.
• 5.5. Thus chronic acidosis and pH, per se, affect intramitochondrial glutamine carbon skeleton metabolism in different fashions, but the specific mechanism cannot be elucidated using ¹⁴CO₂ production from [U-¹⁴C]glutamine.
• 6.6. Additional studies directly quantitating the metabolic products of glutamine have confirmed these findings and more precisely defined the sites of metabolic alteration.

     

Synaptic interaction between the giant interneuron and the giant motorneuron in the hermit crab,Pagurus pollicarus

• 1.1. An anatomical and physiological investigation was made of several components in the withdrawal escape response of the hermit crab, Pagurus pollicarus.
• 2.2. In the fused last thoracic-first abdominal ganglion, the giant axon (GA) synapses with the giant motor (GM) neuron which innervates the abdominal flexor muscles.
• 3.3. The synapse is unidirectional, conducting impulses only from the GA to the GM.
• 4.4. The synaptic delay time is less than 0.4 msec.
• 5.5. Concentrations of MgCl₂ and MnCl₂ which normally block chemical synapses were ineffective in interfering with GA-GM transmission.
• 6.6. The GA-GM synapse was reversibly blocked by 0.5 mM DNP.
• 7.7. It is concluded that GA-GM connection is a rectifying electrical synapse.