The pressure tolerance of deep sea amphipods collected at their ambient high pressure

• 1.1. Deep sea benthic amphipods were collected at their normal ambient pressure of 394–442 atm from depths of approximately 4000 m (Parulicella caperesca, Orchomene sp. and other species).
• 2.2. Their activity at their normal pressure and temperature was observed and the responses to a standard pressure test were noted.
• 3.3. Contrary to a prediction derived from the responses of similar animals from lesser depths, the 4000 m amphipods did not convulse at high pressure although they exhibited mild hyperexcitability above 400 atm followed by a progressive inhibition of activity starting at approximately 700 atm.
• 4.4. In failing to convulse at high pressure the amphipods from 4000 m differ radically in their pressure tolerance from those which live at depths down to 2700 m.

     

Comparative studies of sodium transport and its relation to hydrostatic pressure in deep and shallow water gammarid crustaceans from Lake Baikal

• 1.1. Freshwater gammarids from 900–1400 m depths lose Na at 1 atm, 4°C, while related shallow water gammarids are near neutral Na balance.
• 2.2. Na⁺ influx rates are similar at 1 atm, 4°C, for abyssal and shallow water gammarids of similar weight.
• 3.3. Na⁺ efflux is faster for abyssal gammarids than for comparable shallow water gammarids.
• 4.4. Compressing abyssal gammarids to 90–140 atm increases Na⁺ influx rates enough to restore neutral Na balance, while in shallow water crustaceans, compression decreases Na⁺ influx.
• 5.5. Na⁺ influx rates in Baikalian gammarids vary with the 0.55 power of weight.
• 6.6. The equation F_{ma × t} = 1.3 × W^0.55 μEq/hr/animal applies to freshwater crustaceans over the weight range from 0.03 to 35 g.

     

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.

     

Axonal mapping of neurosecretory Helix bursting cells. Functional aspects of peripheral multibranched axons

• 1.1. The peripheral axon distribution from two bursting neurons was investigated using electrophysiological methods. Both of these cells send out a bundle of axon branches which goes via the visceral nerve to the heart and in the uterine nerve.
• 2.2. The relative number of axon branches in the two nerves was determined through double-shock experiments.
• 3.3. The axon bundle takes the visceral nerve and its uterine branch, supplying the effector systems in parallel.
• 4.4. Slight differences in conduction velocity between the axon branches produce an enlargement of the efferent volley.
• 5.5. The number of active axon branches conveying orthodromic or antidromic spikes is controlled by inhibitory potentials converging onto the initial part of the bundle, so that the two bursting cells amount to a pool of 35 to 40 interconnected nerve cells.
• 6.6. The atypical axonal distribution of the two bursting cells might be related to their neurosecretory properties.

     

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.

     

Metabolic capacity,fibre type area and capillarization of rat plantaris muscle. Effects of age,overload and training and relationship with fatigue resistance

• 1.1. The influences of age (5, 13 and 25-month-old rats), overload as obtained by denervation of synergists, and training on the metabolic capacity, relative muscle cross-sectional area occupied by each fibre type, capillarization and fatigue resistance of the rat m. plantaris were investigated.
• 2.2. Creatine kinase, phosphorylase and citrate synthase activities were lower in muscles of 25 than in those of 13-month-old rats (P < 0.001).
• 3.3. Overload resulted in an increased relative area of type I and II a fibres at all ages (P = 0.001).
• 4.4. Capillary density decreased with overload and increasing age (P < 0.001).
• 5.5. Fatigue resistance was higher in muscles of 13 than in those of 5-month-old rats (P < 0.05), and increased with overload (P < 0.05) at all ages.
• 6.6. Fatigue resistance of the whole muscle was not closely related to its oxidative capacity in contrast to what is generally found for single fibres or motor units.

     

Heart rate and its cholinergic control in the sole (Solea vulgaris), acclimatized to different temperatures

• 1.1. The effects of thermal acclimatization at 10 and 24°C on heart rate were investigated on unrestrained soles (Solea vulgaris).
• 2.2. The sensitivity of heart rate to temperature changes induced by temperature acclimatization was higher in cold-acclimatized than in warm-acclimatized soles.
• 3.3. Heart rate of cold-acclimatized fish to temperature changes was not affected by blocking the vagal tone with atropine.
• 4.4. After atropine treatment the ability of heart rate to show thermal compensation decreased in warm-acclimatized soles.
• 5.5. It is suggested that the vagus nerve can function differently at different temperatures.

     

The morphology and physiological properties of nereid giant fibres

• 1.1. The three sets of giant fibres in the nerve cord of Nereis virens are connected by both electrotonic and chemically transmitting junctions.
• 2.2. The paired laterals and paramedials are connected to their partners by electronic junctions. The laterals are also electrically coupled to the median giant fibre.
• 3.3. The laterals are connected to the paramedials by an excitatory chemical synapse, while in the anterior segments the paramedials provide an inhibitory input to the median giant fibre.
• 4.4. Afferent input to the giant fibres through the segmental nerves two and four is excitatory, except that to the median fibre in the caudal segments.
• 5.5. There is no evidence of the segmental origin of the lateral giant fibres, either in the form of macrosynapses or segmental cell bodies.
• 6.6. The median giant fibre originates from two groups of cell bodies in the sub-oesophageal ganglia.

     

Axonal pathways of giant neurons identified in the right parietal and visceral ganglia in the suboesophageal ganglia of an African giant snail (Achatina fulica Férussac)

• 1.1. The axonal pathways of thirteen giant neurons identified in the right parietal and the visceral ganglia, found in the suboesophageal ganglia of an African giant snail (Achatina fulica Férussac), were investigated by intracellular injections of Lucifer Yellow, with regard to their axonal projections into the following six peripheral nerves: lap n (left anterior palliai nerve), lpp n (left posterior palliai nerve), int n (intestinal nerve), anal n (anal nerve), rpp n (right posterior palliai nerve) and rap n (right anterior palliai nerve).
• 2.2. These projections were confirmed by the recording of the axonal responses from the nerves.
• 3.3. On the dorsal surface of the right parietal ganglion, the following four giant neurons were identified: PON (periodically oscillating neuron), TAN (tonically autoactive neuron), RAPN (right anterior palliai neuron), and d-RPLN (dorsal-right parietal large neuron).
• 4.4. The PON axonal pathways projected into int n; those of TAN into all of the nerves examined; those of RAPN into lap n, lpp n, int n, anal n and rap n.; and those of d-RPLN into pd nn (pedal nerves) through the pedal ganglia, lpp n, anal n, rap n and sometimes lap n.
• 5.5. On the dorsal surface of the visceral ganglion, the following four giant neurons were also identified: VIN (visceral intermittently firing neuron), FAN (frequently autoactive neuron), INN (intestinal nerve neuron) and d-VLN (dorsal-visceral large neuron).
• 6.6. The VIN axonal pathways, which had no branch into the six nerves examined, went to both the right and the left pedal ganglia, sending a branch into the cerebro-pleural connective; those of FAN projected into lap n, anal n and rap n, and sometimes into lpp n and rpp n; those of INN into int n; and those of d-VLN into pd nn, lap n, lpp n, anal n and rap n.
• 7.7. On the ventral surface of the right parietal ganglion, v-RPLN (ventral-right parietal large neuron) was identified. The axonal pathways went to pd nn, lap n, lpp n, anal n and rap n.
• 8.8. On the ventral surface of the visceral ganglion, the four giant neurons, v-VNAN (ventral-visceral noisy autoactive neuron), v-VLN (ventral-visceral large neuron), r-VMN (right-visceral multiple spike neuron) and 1-VMN (left-visceral multiple spike neuron) were identified.
• 9.9. The axonal pathway of v-VNAN projected into rpp n and rap n; those of v-VLN into pd nn, lap n, anal n, rap n and sometimes to lpp n; those of r-VMN into int n and rpp n; and those of 1-VMN also into int n and rpp n.
• 10.10. The present morphologial investigations of the giant neurons confirmed well the identifications of the neurons previously studied. The axon of the neurons examined here, except for VIN, projected into some of the peripheral nerves, while the VIN axon extended into the cerebro-pleural connective.
• 11.11. The five neurons, PON, TAN, v-VNAN, r-VMN and 1-VMN, formed fine axonal arborizations terminating at the neuropile, while the arborizations of the other neurons were not clearly observed.
• 12.12. Although the anatomical structures of the portion examined of the suboesophageal ganglia are asymmetrical, three pairs of symmetrically-situated neurons, d-RPLN and d-VLN, v-RPLN and v-VLN, and r-VMN and 1-VMN, were found, indicating the existence of symmetrical components in the ganglia.

     

Effects of feeding,starvation, and refeeding on the fatty acid composition of channel catfish,ICtalurus punctatus,tissues

• 1.1. The effects of feeding, food deprivation (14 and 28 days) and refeeding (starved 14 then fed 14 days) on the fatty acid composition of white muscle, liver and brain of pond-raised channel catfish (Ictalurus punctatus) were investigated.
• 2.2. Levels of n-3 fatty acids were significantly higher (P < 0.05) in white muscle of fish starved 28 days (10.7%) than in fish fed throughout the study (8.0%), due primarily to an increase in 22:6(n-3) docosahexaenoic acid or DHA.
• 3.3. Significantly higher levels of 20:5(n-3) (eicosapentaenoic acid or EPA) were found in livers offish starved 28 days (P < 0.05) compared to fish fed throughout the study.
• 4.4. Results suggest that the fatty acid compositions of channel catfish white muscle and liver are subject to only limited perturbation during periods of starvation and refeeding and that the brain is extremely well protected.

     

Thermal stability of fish myosin

• 1.1. Thermal stability of fish myosin has been studied by using differential scanning calorimetry (DSC) and circular dichroism (CD).
• 2.2. The temperature range of the sharp decrease in α-helical content agreed very closely with that of the endothermic peaks.
• 3.3. There was a high correlation between the enthalpy of denaturation (ΔH) and the decreasing quantity in α-helicity (Δh).
• 4.4. The structure of fish myosins was much more unstable than that of rabbit.
• 5.5. The instability of fish myosins was reflected in its rod moiety.

     

Pigment migration in fish erythrophores is controlled by alpha2-adrenoceptors

• 1.1. The aggregation of erythrosomes within erythrophores of the squirrel fish (Myripristis occidentalis; belonging to the family Holocentridae) was, on pharmacological grounds, shown to be mediated by alpha₂-adrenoceptors.
• 2.2. The erythrophores were shown to be controlled by adrenergic nerves activating the alpha₂-adrenoceptors.
• 3.3. The erythrophores themselves were found to possess a K⁺-sensitive mechanism of aggregation.
• 4.4. Some similarities and differences of the alpha₂-adrenoceptor-mediated chromatosome aggregation in melanophores and erythrophores are also discussed.

     

Pulmonary hypertension and the smooth muscle of the pulmonary arterioles in chickens at high altitude

• 1.1. One-day-old male (m) and female (f) chickens from a population living at 3300m for several generations were raised at 3300 m (HA) and at sea level (SL).
• 2.2. The histology of the pulmonary arterioles was studied in the HA and SL chickens when they were 4 weeks old and the thickness of their muscular coat (MT) determined.
• 3.3. Pulmonary arterial pressure (Ppa), hematocrit (Hct) and the wet and dry weights of the total ventricle, left ventricle, septum and right ventricle (RV) were obtained when the HA and SL birds were 8 weeks old.
• 4.4. Results indicated that chickens have a thick muscular coat in their pulmonary arterioles. MT expressed as a fraction of arteriolar diameter (MT/AD) was 0.113 at SL. Exposure to HA increased this value in the m (0.137, P < 0.01) but not in the f (0.123, P > 0.05).
• 5.5. Ppa, RV and Hct were significantly higher at HA in both sexes. The degree of pulmonary hypertension and right ventricular hypertrophy observed was smaller than that found in earlier generations of these chickens studied several years ago. This probably indicates some degree of adaptation after generations of life at HA.

     

Effect of triton X-100 treatment on the lipid composition,biochemical and functional properties of hake (Merluccius hubbsi) myofibrils purified from pre- and post-spawned fish

• 1.1. The effects of Triton X-100 treatment on the lipid contents and functional properties of hake myofibrils from pre- and post-spawned fish were investigated.
• 2.2. Differences in lipids, biochemical and functional properties of hake myofibrils related to the gonadal condition of fish were observed.
• 3.3. Triton X-100 treatment removed 65% of polar lipids in myofibrils from pre-spawned fish and only 10% in myofibrils from post-spawned fish.
• 4.4. Triton X-100 increased the Hill coefficient to 1.5 in an allosteric type of reaction for the myofibrillar Mg²⁺-ATPase from pre-spawned hake.
• 5.5. The detergent effect observed on the contraction response was greater in myofibrils from prespawned fish than in post-spawned fish.

     

Myo-inositol in the reproductive tract of the female rat

• 1.1. myo-Inositol concentrations in oviduct, ovary and uterus were many-fold those of blood serum during all four stages of the estrous cycle of the female rat.
• 2.2. Inositol concentration was higher in oviduct than in ovary or uterus and was lower in uterine fluid than in uterus.
• 3.3. Estrus uteri had higher inositol concentrations than uteri in other phases of the cycle.
• 4.4. In order to measure dynamic aspects of the distribution of inositol. the distribution of radioactivity among organs of the reproductive tract of mature female rats was measured 45 min after i.p, injection of [2-³H]myo-inositol.
• 5.5. These organs concentrated inositol from the blood, and the tissue radioactivity (expressed as dpm/mg wet wt of tissue) increased in the sequence: vagina < cervix < uterus < ovary < oviduct.
• 6.6. The uterus and ovary concentrated myo-inositol more strongly during proestrus than during metestrus. diestrus or estrus.
• 7.7. The contents of proestrus follicles were more highly radioactive than was the ovary itself, whereas proestrus uterine fluid was less radioactive than the uterine tissue.

     

A comparative study of seafish erythrocytes and agglutinins from seaweeds

• 1.1. To date, only a few authors have assayed the agglutinic activity of marine algae against fish erythrocytes, and in these cases, mainly against freshwater fish.
• 2.2. For the first time, the hemagglutinic activity of 70 seaweeds (29 brown, 37 red and four green algae) against erythrocytes of 16 seaflsh species is reported.
• 3.3. The presence of agglutinins was demonstrated in 100% of algae assayed, against at least one of the different types of erythrocytes tested.
• 4.4. The results obtained confirm the presence of receptors for algae agglutinins on the surface of the erythrocytes of the fish studied.
• 5.5. This could be useful in establishing the origins of fish populations, as these serological differences could distinguish between populations of cultivated and wild fish.

     

Root effect hemoglobins in marine fish

• 1.1. The Root effect was evaluated in hemolysates from 26 species of bony fish and 20 species of cartilaginous fish found on the Brazilian southeastern coast.
• 2.2. Teleost Root shifts, with a single exception, are correlated with the presence of the choroid rete mirabile but not with its counterpart in the swimbladder.
• 3.3. Five ray species displayed weak and moderate Root effects despite the absence of choroid and swimbladder rete.
• 4.4. The presence and intensity of the Root effect is probably primarily related to the high oxygen demand of the retina and with the importance of visual perception in fish.
• 5.5. In marine teleosts the magnitude of the Root effect seems to be associated with the presence and size of both the choroid rete and the pseudobranch.
• 6.6. An antioxidant protection of the fish eyes can be advocated for the pseudobranch.

     

Morphometry and composition of red drum otoliths: Changes associated with temperature,somatic growth rate,and age

• 1.1. Size and composition of sagittal otoliths from red drum, Sciaenops ocellatus (Sciaenidae), reared at various constant temperatures were compared with otoliths from wild-caught fish.
• 2.2. Uncoupling of otolith growth and somatic growth in laboratory-reared fish was evident in otolith length, area, volume, weight, density, and organic fraction.
• 3.3. Fish grown at low temperatures had significantly smaller and less dense otoliths having a greater organic content than fish of the same size grown at higher temperatures.
• 4.4. Changes in inorganic elements were poorly related to temperature in laboratory-reared fish.
• 5.5. The effect of temperature on otolith elemental composition was small relative to the effects of age and its associated physiological changes.

     

Functional maturation of the salt gland of the goose

• 1.1. Experiments were carried out to determine the influence of age on salt gland secretion in the domestic goose.
• 2.2. Oral or i.v. loading of hypertonic NaCl evoked a rapid secretory response in geese 6–14 weeks of age.
• 3.3. A significantly smaller fraction of the salt load was secreted by older birds (2.2 kg and above) than by younger birds (< 2.2 kg).
• 4.4. The maximum volume collected and the maximum sodium concentration during an 80 min observation period did not differ over a range of < 1 kg to > 4 kg in body weight.
• 5.5. The maximum volume and sodium concentration/kg of body weight decreased significantly as the birds aged.
• 6.6. A greater fraction of the administered water load was secreted by the salt gland at any time period compared to the fraction of the salt load secreted, indicating substantial cloacal excretion of the salt load.

     

Laboratory studies on the oxygen consumption of the marine teleost,Lichia amia (Linnaeus, 1758)

• 1.1. The oxygen consumption of the marine teleost, Lichia amia was investigated under controlled laboratory conditions.
• 2.2. The routine oxygen consumption showed a strong circadian rhythm with the fish being mainly active during the light period.
• 3.3. The specific mass exponent (dimension: μg O₂/g/hr) is temperature independent and ranges from 0.27–0.29.
• 4.4. Starving the fish results in a mean decrease in active, routine and standard oxygen consumption of 21%, 24% and 20%, respectively.
• 5.5. Feecling led to an increase in the oxygen consumption of the teleosts, with the mean metabolic rate over the 24 hr that followed, being 58% and 50% higher for fish that had been starved for 162hr and 40 hr, respectively.
• 6.6. Apparent SDA showed some variation and ranged from 6.0 to 35.5%.
• 7.7. The results obtained are generally in agreement with those recorded for other teleosts.