Cardiac responses of larval and adult tiger salamanders to submergence and emergence

• 1.1. The ECG of aquatic Amhystoma tigrinum from the Colorado Rocky Mountains was recorded while the animals submerged and emerged in water. Older larvae and metamorphosed adults were compared.
• 2.2. Free-swimming animals of both types showed slight emergence tachycardia when taking a “gulp” of air.
• 3.3. Preventing access to air for 30 min or more resulted in a slight bradycardia in larvae. Some adults responded with increased, others with decreased, heart rate depending on their level of excitement.
• 4.4. Restraining the animals before forced submergence caused a greater bradycardia than when unrestrained.
• 5.5. Low dissolved oxygen accentuated the cardiac responses of larvae to submergence but not in adults.
• 6.6. Atropine only partially blocked the diving responses of both forms.
• 7.7. The degree of submergence bradycardia seems to be a function of the ability to extract oxygen from water. It probably is not an adaptation to diving in these forms. Instead the submerged heart rate in these predominantly aquatic salamanders may be the “normal” rate with emergence tachycardias for breaths of air.

     

Identification of neurons involved in the earthworm Amynthas hawayanus reflex activity

• 1.1. The medial (MGF), lateral (LGF) and motor (RMS-2) giant neurons were confirmed as neural components in the earthworm Amynthas hawayanus polysynaptic reflex circuit by simultaneous potential recording and dye injection.
• 2.2. The reflex was initiated from the mechanoreceptors when evoked by mechanical stimulation but electrical stimulation also evoked an antidromic response in the motoneuron.
• 3.3. The primary reflex response propagates decrementally along both giant axons but directly evoked action potentials conduct in an all-or-none fashion.
• 4.4. The secondary reflex response continues to propagate after the primary response disappears.
• 5.5. A rhythmically discharging neuron of uncertain function was also identified.

     

Responses of dorsal tricorn-type sensilla on Ligia exotica

• 1.1. In order to investigate the function of the dorsal tricorn-type sensilla on Ligia exotica, the morphology and distribution of the setae and neural responses to certain stimulus modalities were studied.
• 2.2. These foraminate sensilla are found to occur over the body surface, except for several appendages and the ventral carapace (sternite); the dorsal carapace (tergite) is covered by only this type of sensilla.
• 3.3. The tricorn-type sensilla located on the dorsal carapace responded to mechanical, gustatory and olfactory stimulation.
• 4.4. The function of the tricorn-type sensilla on the dorsal carapace was discussed.

     

Two kinds of peripheral afferent neurons in the earthworm reflex arc

• 1.1. Two kinds of neurons were identified in the body-wall longitudinal muscle layer of the earthworm, Amynthas hawayanus, by the simultaneous potential recording and Lucifer Yellow-CH injection method with a single microelectrode.
• 2.2. Both kinds of neurons have their somata, neuntes and longitudinal processes imbedded in the longitudinal muscle layer. Those with two circular processes extending into the third segmental nerve trunk are tentatively named “intra-nerve-trunk” neurons and those with four circular processes extending into four setae shafts are tentatively named “intramural” neurons.
• 3.3. Both kinds of neurons responded to electrical and mechanical stimuli applied in an afferent direction to them.
• 4.4. The “intra-nerve-trunk” neuron decreased its response amplitudes to these stimuli after the third nerve trunk was sectioned in correlation to the response amplitude decrease recorded from the nerve trunk after it was sectioned.
• 5.5. The response amplitude decrease due to denervation implies a nonlinear structure of the earthworm reflex circuits.
• 6.6. The “intramural” neurons are believed to be primary sensory neurons connected to the mechanoreceptors in the setae.

     

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.

     

Action of free radical generating systems upon the biological and immunological properties of caeruloplasmin

• 1.1. Exposure of human caeruloplasmin, an acute phase protein with antioxidant properties, to a mixture of xanthine/hypoxanthine and xanthine oxidase as a source of reactive oxygen intermediates decreased its ferroxidase and ascorbate oxidase activities and its ability to inhibit lipid peroxidation.
• 2.2. Immunological reactivity was also altered.
• 3.3. Exposure to hydrogen peroxide mimicked these effects.
• 4.4. Exposure to low-intensity u.v. irradiation depressed caeruloplasmin's ability to inhibit iron-catalysed hyaluronic acid degradation.
• 5.5. The results may explain the mechanism of the observed inactivation of caeruloplasmin within human rheumatoid synovial fluid.

     

Off-response in frog taste nerve and cell after stimulation of the tongue with bitter solutions

• 1.1. After a Ringer-adapted frog tongue was stimulated with quinine-HCl (Q-HCl), rinsing the tongue with the Ringer produced a large off-response in the glossopharyngeal nerve.
• 2.2. The off-response was caused by the enhancing action of Q-HCl stimulation upon the stimulating effectiveness of an NaCl component of Ringer solution.
• 3.3. Analysis of gustatory neural unit responses showed that following Q-HCl stimulation the enhancement of responses to Ringer of those units which responded to both Q-HCl and Ringer or Ringer alone is related to the generation of the off-response.
• 4.4. A phasic off-depolarization of taste cells elicited by a Ringer rinse following Q-HCl stimulation is thought to be associated with the off-response in the gustatory nerve.

     

Depressed baroreceptor-cardiac reflex sensitivity during simulated diving in ducks

• 1.1. The baroreceptor-cardiac reflex was examined in unanesthetized ducks at rest and during diving. In ducks breathing air an inverse relationship between mean arterial blood pressure and heart rate was observed over the pressure range from 80cm H₂O to 290cm H₂O.
• 2.2. Increases in pressure were obtained by bolus intravenous injection of phenylephrine (PE) while the hypotension was achieved by intravenous acetylcholine (ACh).
• 3.3. The inverse relation of blood pressure and heart rate was also observed in ducks without pharmacologic intervention.
• 4.4. The baroreceptor-cardiac reflex sensitivity was -3.13 beats/min/cm H₂O in non-diving ducks and fell to -0.96 beats/min/cm H₂O with PE and ACh derived data.
• 5.5. During diving the baroreceptor-cardiac reflex sensitivity was further reduced to —0.48beats/ min/cm H₂O.
• 6.6. This finding indicates that even during the pronounced bradycardia of diving baroreceptor stimulation continues to influence heart rate.

     

The response to temperature gradients of scorpions from mesic and xeric habitats

• 1.1. The thermal preference of four scorpion species—two from xeric habitats and two from mesic habitats—was observed in a temperature-gradient.
• 2.2. The two scorpions from mesic habitats responded positively to lower temperatures. The xeric species stayed longer in higher temperatures.
• 3.3. In each pair of scorpion species studied here (the mesic and the xeric species), one of them responded to a more limited temperature range whereas the other to a wider range.
• 4.4. The significance of these findings is discussed in relation to the microclimate in the scorpion's microhabitat and to their dispersal pattern.

     

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.

     

Cyclic AMP stimulation and prostaglandin inhibition of Na transport in freshwater mussels

• 1.1. Pondwater acclimated Carunculina texasensis and Ligumia subrostrata experienced a 230% increase in Na influx when injected with dibutyryl cyclic AMP (0.4mM/l blood).
• 2.2. Theophylline, a phosphodiesterase inhibitor, or indomethacin, an inhibitor of prostaglandin (PG) synthetase, caused a dose dependent stimulation of Na transport.
• 3.3. Prostaglandin E₂ injected into mussels caused an inhibition of Na influx. Arachidonic acid, the precursor of PGE₂, inhibited Na influx or stimulated Na efflux depending on the animal's acclimation conditions.
• 4.4. Chloride transport was unaffected by the drugs used in this study.

     

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.

     

Induction kinetics of immune antibacterial proteins in pupae of Galleria mellonella and Pieris brassicae

• 1.1. Pupae of Galleria mellonella and Pieris brassicae given an injection with live, non-pathogenic Enterobacter cloacae or abiotic foreign molecules induce an acquired immunity that corresponds with the synthesis of haemolymph proteins of antibacterial activity.
• 2.2. This humoral defensive response which persists for several days, differs quantitatively between insect species and between the inducers used, although very different foreign bodies induced the same immune proteins in both lepidopteran insects.
• 3.3. A stronger and longer lasting response was consistently noticed in pupae immunized with non-pathogenic bacterium than after sterile nutrient broth injections.
• 4.4. A demonstrably elevated activity of haemolymph lysozyme and trace activity of cecropins found in pupae of Galleria treated with saline W, a salt solution physiological to moths, disappear soon after 36 hr from injection.
• 5.5. In P. brassicae, however, sterile insect Ringer can give a varying, if present at all, immune response.
• 6.6. A mechanical injury (sterile wounding of insect body) can occasionally induce a similar but much weaker response.
• 7.7. The antibacterial activity was drastically reduced in Pieris or completely depressed in most pupae of Galleria when actinomycin D or cycloheximide was given at an early time post-immunization with E. cloacae.
• 8.8. It is concluded that the de novo synthesis of ribonucleic acid and immune proteins is required for expression of antibacterial activity in pupal haemolymphs.
• 9.9. The synthesis of an immune mRNA was completed about 7 hr after the injection of the immunizing bacteria.

     

Phosphofructokinase from the anterior byssus retractor muscle of Mytilvs edulis: Modification of the enzyme in anoxia and by endogenous protein kinases

• 1.1. Anoxia exposure resulted in a stable modification of the kinetic properties of 6-phosphofructo-1-kinase (PFK) from the anterior byssus retractor muscle (ABRM) of the sea mussel Mytilus edulis L.
• 2.2. Compared to the aerobic enzyme, the anoxic form of PFK. showed a reduced affinity for both substrates, fructose-6-phosphate (F6P) and ATP, and an increased sensitivity to inhibition by phosphoenolpyruvate.
• 3.3. To analyze the involvement of protein kinases in the modification of PFK, extracts from aerobic or anoxic muscle were incubated with ATP and Mg²⁺ plus protein kinase second messengers cyclic 3',5'-adenosine monophosphate (cAMP), cyclic 3',5'-guanosine monophosphate (cGMP) or Ca²⁺ plus phorbol 12-myristate 13-acetate (PMA).
• 4.4. Both forms of the enzyme responded to the presence of cAMP with a strong increase in affinity for F6P.
• 5.5. In response to cGMP affinity of the aerobic enzyme for F6P decreased whereas that of the anoxic enzyme form was not affected (at 0.5 mM ATP) or increased (at 3 mM ATP).
• 6.6. Incubation with Ca²⁺ + PMA had only a limited effect on PFK kinetics but appeared to enhance the response to cGMP when the three compounds were given together.
• 7.7. Treatment of PFK-aerobic with alkaline phosphatase resulted in a strong decrease in enzyme activity and affinity for F6P; subsequent treatment with cAMP reversed the effect on S_0.5 F6P.
• 8.8. The data indicate that PFK activity is altered during the aerobic-anaerobic transition by a change in the phosphorylation state of the enzyme and that cAMP and cGMP act oppositely to regulate PFK activity, and thereby alter glycolytic rate, during this transition.

     

A relationship between circulating natural glucocorticoids and the mechanical responses of the heart in atricial and precocial rodents

• 1.1. A comparison was made of the mechanical performance of heart muscle from mouse, an atricial mammal, with corticosterone as glucocorticoid and spiny mouse (Acomys cahirinus), a precocial mammal, with cortisol as glucocorticoid.
• 2.2. Force-frequency responses were negative in mouse and positive in spiny mouse.
• 3.3. During recovery, there was a gradual increase and an overshoot in the mouse, while in the spiny mouse there was an initial enhanced response, diminishing gradually with time.
• 4.4. High calcium concentration inhibited contractile tension in mouse heart, while it was positively inotropic in spiny mouse heart. Changes in the concentration of calcium did not change the patterns of force-frequency response.
• 5.5. Lowering the experimental temperature increased the time course and amplitude of the tension curve. However, various parameters exhibited different temperature sensitivity.
• 6.6. There was a significant difference in the levels of circulating cortisol between male and female spiny mice.
• 7.7. It is proposed that the differences in the mechanical responses of mouse and spiny mouse hearts may be explained in terms of the effects of the specific glucocorticoid hormone on the development of the sodium-calcium exchanger.

     

Evidence that the 5' end of rabbit globin mRNA is hybridized with its 3' end

• 1.1. A radiopolyadenylated rabbit globin mRNA was treated with different concentrations of ribonuclease V₁ from cobra venom.
• 2.2. The enzymatic digests were chromatographed on an aminophenylboronate-agarose column, which specifically captured the cap structure i.e. n⁷G(5') ppp (5') NmP.
• 3.3. When the capture fragment was chromatographed on a Sephadex G-100 column, its size was smaller than the native molecule and also bore radioactivity, i.e. a poly(A) tail.
• 4.4. These results provide evidence that the 5' end (which encompasses the cap structure) of rabbit globin mRNA is hybridized and in close proximity to its 3' end.
• 5.5. We conclude that this conformation is required for messenger translation efficiency.

     

Ventilatory rate in the butterfish (Pholis gunnellus) as a consequence of temperature and previous emersion

• 1.1. Observation of ventilation in immersed Pholis gunnellus showed a linear relationship between ventilatory rate and temperature between 8 and 20°C.
• 2.2. At 13°C and after 30 min emersion, ventilatory rate was initially lower than prior to emersion, providing evidence of adequate uptake of O₂ for standard metabolism during the emersion period.
• 3.3. This species has a laterally elongate body form with reduced scales and extensive mucus secretion.
• 4.4. During emersion, gaping behaviour probably exposes the gills and extensively vascularised oesophageal regions to air.
• 5.5. These are considered to be morphological and behavioural adaptations by P. gunnellus, to aerial respiration in the intertidal habitats occupied by this species.

     

Electrophysiological and metabolic responses of the isolated teleost retina to changes in po2, and temperature

• 1.1. Comparisons of electrophysiological responses (ERG) were made between two different in vitro preparations of teleost retina.
• 2.2. The ERG was independent of temperature over the normal environmental range.
• 3.3. The Q₁₀ demonstrated temperature independence between 5 and 20°C.
• 4.4. The electrical response of the isolated retina was found to be independent of partial pressures of oxygen at levels above 250 mm Hg.

     

Functional differentiation of crayfish statocyst receptors in sensory adaptation

• 1.1. Response characteristics of tonic- and phasic-type receptors in the crayfish statocyst were investigated with intracellular recording technique.
• 2.2. They were identified to be either tonic- or phasic-type according to their response patterns to the hair deflection performed by water jet stimulation.
• 3.3. Constant depolarizing current applied intracellularly evoked long-lasting spike discharge in the tonic-type neurons and transient discharge in the phasic-type neurons.
• 4.4. These tonic- and phasic-type neurons also showed different patterns of spike discharge to depolarizing pulse stimulus of 50 msec duration.
• 5.5. On the basis of the response patterns to this pulse stimulus, it was shown that the statocyst receptor neurons consist of 46% tonic- and 54% phasic-type neurons.

     

Rank-associated desynchronization of metabolic and activity rhythms of Peromyscus maniculatus in response to social pressure

• 1.1. Saturation level population density conditions drastically affected the level and timing of subordinate males' metabolic rate and locomotor activity and feeding rhythms.
• 2.2. The increased daily metabolic rates of subordinate animals was expressed in the face of depressed locomotor and feeding activity levels.
• 3.3. A phase shift in the metabolic peak of dominant animals occurred at high density, but close synchrony between activity and metabolic rate persisted with no increase in metabolic cost.
• 4.4. Subordinate animals showed desynchronization of activity rhythm at high density; this effect imposed a higher bioenergetic cost upon the subordinate than upon the dominant mice.