Temporal discharge patterns of tectal and medullary neurons chronically recorded during snapping toward prey in toads Bufo bufo spinosus

In freely moving toads, the temporal discharge patterns of tectal and medullary neurons were observed during prey-catching.

1. Tectal T5.2 and T8.1 neurons displayed a premotor warming up firing that in the former was addressed specifically to prey orienting or snapping and in the latter generally to almost any kind of body movement.
2. The temporal discharge patterns of T5.2 neurons during snapping were different from those during orienting toward prey. Snapping started in the peak phase of warming up; firing was immediately terminated during the snap; thereafter some rebound activity was observed. Orienting started after the premotor warming up in the declining phase whilst the neuron kept on firing during orienting and then settled when the orienting movement was completed.
3. In toads which were not motivated to catch prey — comparabl to immobilized ones — the discharge frequency of T5.2 neurons toward a prey stimulus revealed no such warming up.
4. Because it is known that prey-selective T5.2 neurons are controlled by pretectal inhibitory influences, the following experiment was conducted: during recording a T5.2 neuron a pretectal lesion was applied ipsilaterally to the recording site. After a few seconds, the neuron showed a strong premotor wanning up in response to any kind of moving object, followed by prey-catching.
5. In the medulla oblongata, different H-type neurons of the hypoglossal nucleus displayed specific discharge patterns which resembled the tongue protractor and retractor muscle activities; a third type resembled the activity of the genio/sterno-hyoid muscle, which are suggested to stabilize the hyoid bone during snapping.
6. There were medullary M8-type neurons with properties similar to T8.1.
7. Snapping could be triggered by electrical stimulation of the optic tectum in the representation of the frontal visual field, but not by stimulation in the hypoglossal nucleus or the adjacent medial reticular formation.
8. A concept of a neuronal circuit for the coordination of tongue muscle contractions in response to prey is proposed.

     

Physiological and pharmacological properties of responses to GABA and ACh by abdominal motor neurons in Manduca sexta

1. GABA, ACh, and other agents were applied by pressure ejection to the neuropil of the third abdominal ganglion in the isolated nerve cord of Manduca sexta. Intersegmental muscle motor neurons with dendritic arborizations in the same hemiganglion were inhibited by GABA (Fig. 2) and excited by ACh (Fig. 5).
2. Picrotoxin was a potent antagonist of GABA (Fig. 4A). Bicuculline reduced GABA responses in some motor neurons (Fig. 4C), but had no effect on many other motor neurons. Curare reduced ACh responses (Fig. 6A). Bicuculline was an effective ACh antagonist in most motor neurons tested (Fig. 6B).
3. Motor neurons with dendrites across the ganglion from the ejection pipette exhibited different responses to GABA and ACh. Contralateral motor neurons often showed smaller, delayed hyperpolarizing GABA responses (Fig. 7). On two occasions, contralateral motor neurons had excitatory responses (Fig. 8). Contralateral motor neurons were hyperpolarized by ACh (Fig. 9). The inhibitory responses had only slightly longer latencies than ipsilateral excitatory ACh responses (Fig. 10A). The contralateral inhibitory ACh responses, but not the ipsilateral excitatory ACh responses, were eliminated by TTX (Fig. 10B).
4. A model, which includes inhibitory interneurons that cross the ganglionic midline to inhibit their contralateral homologs and motor neurons (Fig. 11), is proposed to account for contralateral responses to GABA and ACh and antagonistic patterns of activity of motor neurons during mechanosensory reflex responses.

     

Response characteristics of wide-field non-habituating non-directional motion detecting neurons in the optic lobe of the locust,Locusta migratoria

1. Extracellular recordings from wide-field nonhabituating non-directional (ND) motion detecting neurons in the second optic chiasma of the locust Locusta migratoria are presented. The responses to various types of stepwise moving spot and bar stimuli were monitored (Fig. 1)
2. Stepwise motion in all directions elicited bursts of spikes. The response is inhibited at stimulus velocities above 5°/s. At velocities above 10°/s the ND neurons are slightly more sensitive to motion in the horizontal direction than to motion in the vertical direction (Fig. 2). The ND cells have a preference for small moving stimuli (Fig. 3).
3. The motion response has two peaks. The latency of the second peak depends on stimulus size and stimulus velocity. Increasing the height from 0.1 to 23.5° of a 5°/s moving bar results in a lowering of this latency time from 176 to 130 ms (Fig. 4). When the velocity from a single 0.1° spot is increased from 1 to 16°/s, the latency decreases from 282 to 180 ms (Figs. 5–6).
4. A change-of-direction sensitivity is displayed. Stepwise motion in one particular direction produces a continuous burst of spike discharges. Reversal or change in direction leads to an inhibition of the response (Fig. 7).
5. It shows that non-directional motion perception of the wide-field ND cells can simply be explained by combining self-and lateral inhibition.

     

Tension field theories for soft tissues

All soft tissues are modeled as either one-dimensionalstrings, two-dimensionalmembranes, or three-dimensionalsolids. Attention is restricted to tissues in which one of the principal stress components is large and positive in comparison with the other negligible components. Results indicate the following:

1. If a deformed string isconstrained to lie on a surface and is free of tangential pressure, the tension is carried by rays which are geodesics of the surface. If a string or membrane isfree to deform in space without normal pressure, the tension rays are straight lines. If a membrane deforms without tangential surface loads, the tension rays are always geodesics on the deformed surface. If a solid deforms without body forces, the tension rays are straight lines.
2. The stress in a string is a constant if the string is free of tangential pressure and has constant cross-sectional area. The stress in flat tension fields free of tangential surface loads decays inversely with distance along a tension ray from the edge of regression. The stress in a spherically symmetric tension field free of body forces decays inversely with the square of the distance from the center of the sphere.
3. Stress singularities can occur in soft tissues, such as at the corners of a closed rectangular hole in a flat membrane strip.
4. The tension rays in the torsion of soft annular membranes are more steeply inclined from the radial direction than the tension rays for hard metals equally displaced.

     

Selective phonotaxis to advertisement calls in the gray treefrog Hyla versicolor: behavioral experiments and neurophysiological correlates

1. The significance of particular acoustic properties of advertisement calls for selective phonotaxis by the gray treefrog, Hyla versicolor (= HV), was studied behaviorally and neurophysiologically. Most stimuli were played back at 85 dB SPL, a level typically measured at 1–2 m from a calling male.
2. Females preferred stimuli with conspecific pulse shapes at 20° and 24°C, but not at 16°C. Tests with normal and time-reversed pulses indicated the preferences were not influenced by the minor differences in the long-term spectra of pulses of different shape.
3. Pulse shape and rate had synergistic or antagonistic effects on female preferences depending on whether the values of one or both of these properties in alternative stimuli were typical of those in HV or heterospecific (H. chrysoscelis = HC) calls.
4. More auditory neurons in the torus semicircularis were temporally selective to synthetic calls (90%) than to sinusoidally AM tones and noise (< 70%).
5. Band-pass neurons were tuned to AM rates of 15–60 Hz. Neurons were more likely to be tuned to HV AM rates ( < 40 Hz) when stimuli had pulses with HV rather than HC shapes.
6. Sharp temporal tuning was uncommon and found only in neurons with band-pass or low-pass characteristics.
7. Many neurons differed significantly in response to HV and HC stimulus sets. Maximum spike rate was more often elicited by an HV stimulus (74%) than by an HC stimulus (24%).
8. Differences in spike rates elicited by HV and HC stimuli were attributable to combinations of differences in the rise times and shapes of the pulses.

     

Encoding of plant odours by receptor neurons in the pine weevil (Hylobius abietis) studied by linked gas chromatography-electrophysiology

Receptor neuron responses to plant volatiles, trapped by head-space procedures, were examined in the pine weevil Hylobius abietis, using gas chromatography linked with electrophysiological recordings from single neurons. Seventy-two receptor neurons were tested 173 times for various plant volatile mixtures, either via a polar or a non-polar column.

1. All responses appeared as increased firing rates which followed the concentration profiles of the GC-eluted compounds.
2. The neurons were classified separately for the two column types in 17 and 19 groups respectively, according to the compounds they responded to. It suggests that the plant odour information is encoded by a large, but limited number of receptor neuron types.
3. Most neurons responded to a limited number of compounds (1–5) and showed a marked best response to one of them, whereas additional responses to several other components which seems to be structurally similar, was recorded for some neurons. It suggests that the plant odour receptor neurons are rather narrowly than broadly tuned, and that each neuron is specialized for receiving information about one or a few related compounds.
4. Most neurons responded to monoterpenes, whereas the other neurons responded to compounds of other categories.
5. Both major and minor plant volatile components activated specifically receptor neurons.

     

Indications de l’imagerie dans l’infertilité masculine (bourses,testicules)

Imaging modalities in the work up of male infertility are almost resumed to Ultrasound with Color Doppler which is quite performant if its indications are well-balanced:

-To look for abnormalities of the seminal tract.

-To evaluate clinical varicoceles (Testis, associated abnormalities).

-To screen the neoscrotal pouchs of ectopic operatively corrected Testis (occult tumor, epididymal abnormalities).

     

The timing of activity in motor neurons that produce radula movements distinguishes ingestion from rejection in Aplysia

1. We have studied the neural circuitry mediating ingestion and rejection in Aplysia using a reduced preparation that produces ingestion-like and rejection-like motor patterns in response to physiological stimuli.
2. We have characterized 3 buccal ganglion motor neurons that produce specific movements of the radula and buccal mass. B8a and B8b act to close the radula. B10 acts to close the jaws and retract the radula.
3. The patterns of activity in these neurons can be used to distinguish the ingestion-like and rejection-like motor patterns. B8a, B8b and B10 are active together during the ingestion-like pattern. Activity in B8a and B8b ends prior to the onset of activity in B10 during the rejection-like pattern.
4. Our data suggest that these neurons undergo similar patterns of activity in vivo. During both feeding-like patterns, the activity and peripheral actions of B8a, B8b, and B10 are consistent with radula movements observed during ingestion and rejection. In addition, the extracellular activity produced by these neurons is consistent with neural activity observed in vivo during ingestion and rejection.
5. Our data suggest that the different activity patterns observed in these motor neurons contribute to the different radula movements that distinguish ingestion from rejection.

     

Protease and Amylase in the digestive tract ofBarbus paludinosus

1. Protease and amylase activity in the digestive system ofBarbus paludinosus Peters (Pisces, Cyprinidae) has been investigated.
2. Chromatographic analysis showed seven amino acids to be present in both the anterior and posterior intestine. Only leucine, phenylalanine, valine, glycine and aspartic acid were positively identified.
3. In the anterior intestine chromatography revealed two sugars, but only one in the posterior intestine which was identified as glucose.
4. The pH of the intestinal fluid was found to be 5.8 and 7.8 for the fore and hind gut respectively, This correlates well with the enzyme pH optima found in in vitro experiments.
5. Protease and amylase activity was found throughout the digestive tract. Maximum proteolytic activity being present in the anterior intestine. Amylase activity is similar in both regions of the gut.
6. Correlation between the digestive enzymes and the fishes diet is briefly discussed.

     

Neurotransmitters of cephalopods

1. ACh, dopamine, noradrenaline, 5-HT,l-glutamate, and GABA are widely distributed in cephalopods and probably all function as neurotransmitters; octopamine also occurs and at one site is known to act as a neuromodulator.
2. Several peptides are also present, as well as nitric oxide synthase.
3. In the brain and sense organs cholinergic, aminergic, serotonergic and glutamatergic systems seem to be the most important.
4. ACh is also active in the gut, vascular system and some body muscles: it is generally inhibitory. The ACh receptors are similar to the vertebrate nicotinic type.
5. The catecholamines are important in the gut and vascular system: they are generally excitatory. The NA receptors are like the α-adrenergic subtype of vertebrates, but the nature of the DA and OA receptors is less certain.
6. 5-HT is important in the gut but is endogenous in some chromatophore nerves and acts on receptors that seem like the vertebrate 5-HT₁ type.
7. l-glutamate is an excitatory transmitter at the chromatophore (and probably at other) nerve-muscle junctions and is an extremely strong candidate for being the excitatory transmitter at the squid giant synapse. There are NMDA receptors on Schwann-cells but the receptors on neurons and muscles are like the vertebrate kainate type.
8. Little is known about the mode of action of cephalopod peptides; nor has it ever been shown that they co-exist with conventional transmitters in these animals.
9. The structure of one (FMRFamide) receptor has been elucidated, but apart from this nothing is known of the molecular biology of receptors in cephalopods.

     

A study on the rate of water transport of the clam katelysia opima in relation to environmental conditions

1. The neutral red technique was employed to study the rate of filtration in Katelysia opima.
2. The weight specific water filtration was found to be greater for younger clams compared to the older ones.
3. The rate of water filtration increased with decreasing salinity.
4. Water filtration was found to increase as temperature increased, reaching a maximum at 35°C. but then sharply decreasing at 39°C.
5. Light had no significant effect on the rate of filtration.
6. Suspended matter was found to affect the rate of water filtration.
7. The rate of filtration was low at high pH and high in low pH.
8. The rate of water filtration was found to be faster during high tide than during low tide.
9. The presence of the parasitic crab, Pennotheris sp., in the mantle cavity of clams had a marked effect on the particle filtration.
10. Accidental cut of the siphon tips had no effect on the rate of filtration.

     

Effects of prenatal cocaine exposure in the prefrontal cortex of the rat

This work was undertaken in order to assess the organization of the prelimbic area of the medial prefrontal cortex of rats exposed prenatally to cocaine. Pregnant Wistar rats were assigned to the following groups:

1. Cocaine—60 mg/kg body wt/d sc, from gestational days 8–22; 0131
2. Saline;
3. Pair-fed; and
4. Nonmanipulated.

Male offspring were perfused on postnatal days 14 and 30. Six brains per group and per age were embedded in celloidin to calculate the volumes of the prelimbic area; sections from the other six brains were embedded in resin and processed for electron microscopy. Using semithin sections (2 μm) of layers II–III and V–VI, the following parameters were calculated:

1. The fraction of the neuropil occupied by neurons (V_V);
2. The packing (N_A) density; and
3. The numerical (N_V) density.

Qualitative alterations consisted of dispersed profiles of degenerated neurons and dendrites in the medial prefrontal cortex. No significant differences were found in the gross morphometric parameters when the cocaine group was compared with the other groups. A high interanimal variation was shown in the prelimbic volumes of postnatal day (PND) 14 cocaine-treated rats, and a decrease in volumes was detected at PND30. Although there are some alterations in the main afferent cortical target area for dopaminergic input, its gross morphometric parameters do not seem to be sufficiently affected to account for the behavioral alterations referred to as being dependent on this brain region.     

Multiple effects of an identified proprioceptor upon gastric pattern generation in spiny lobsters

1. Using deafferented preparations of the stomatogastric nervous system of spiny lobsters (Panulirus interruptus), we stimulated the central soma of the Anterior Gastric Receptor neuron (AGR) and analyzed sensorimotor integration in the gastric central pattern generator during rhythm production.
2. Driving AGR to spike tonically at lower frequencies (10–20 /s) accelerated the gastric rhythm, while higher frequencies (>30 /s) suppressed it.
3. Shorter spike trains in AGR evoked phase-dependent resetting of the gastric rhythm. Repetitive trains could entrain rhythms to both longer and shorter cycle periods. Some pattern-generating effects are consistent with effects upon the lateral gastric neuron, an influential member of the gastric mill network.
4. AGR affected the burst intensity of many of the gastric neurons in specific, complex ways. Some powerstroke motor neurons were excited because AGR activated excitatory, premotor interneurons (E cells). However, AGR also activated parallel, seemingly inhibitory inputs, whose mechanism remains unclear. Still other effects on motor neurons may be mediated partly by synaptic interactions within the network.
5. AGR adjusts the timing, strength and coordination of bursts in the motor innervation of all three teeth of the gastric mill, and may act to optimize the force of chewing to different consistencies of food.

     

Modulation of swimming in Tritonia: excitatory and inhibitory effects of serotonin

1. In the mollusc Tritonia escape swimming is produced by a network of central pattern generator (CPG) neurons. The purpose of this study was to determine which neurotransmitters might be involved in the swim system.
2. Injection of serotonin (5HT) into whole animals elicited swimming followed by a long-lasting inhibition of swimming. In isolated brain preparations, bath-applied 5HT elicited a swim pattern at short latency and also caused a long-lasting inhibition of the swim pattern. The activation of swimming by 5HT was associated with a tonic depolarization of cerebral cell 2 (C2) and the dorsal swim interneurons (DSI) which form part of the swim CPG network.
3. In isolated brain preparations, bath applied glycine, histamine, proctolin, and FMFRamide had no effect on the swim motor pattern elicited by electrical stimulation of a peripheral nerve. Aspartate, carbacol, dopamine, glutamate, octopamine, pilocarpine, and small cardioactive peptide-B (SCP_B) inhibited the activation of swimming by nerve stimulation.
4. The 5HT antagonists cyproheptidine, tryptamine, and 7-methyltryptamine had no effect on swimming, but methysergide and fenfluramine inhibited swimming to both normal sensory stimuli and exogenously applied 5HT.
5. Staining with a polyclonal antibody indicated that one class of CPG neurons, the dorsal swim interneurons (DSI), was immunoreactive for 5HT.
6. Taken together, the data suggest that pattern generator interneurons, particularly the DSIs, use 5HT as a neurotransmitter.

     

Relationship between ecg,eeg and sps responses during arousal in the goldfish (Carassius auratus)

• 1.1. Goldfish (Carassius auratus) were fitted with ECG electrodes and intra-cranial stainless steel electrodes to monitor cardiac, EEG and SPS responses, during minimal restraint, to presentation of environmental stimuli (light-on, moving shadow, tap).
• 2.2. All three stimuli evoked a bradycardia and increases in the EEG frequency; correlates of arousal responses in fish.
• 3.3. EEG frequency changes were most evident in the fore- and midbrain regions; in the hindbrain smaller responses nevertheless showed discrimination between stimuli.
• 4.4. EEG amplitude changes were more site- and stimulus-specific than frequency changes.
• 5.5. SPSs occurred on stimulus presentations which were negative in polarity in the midbrain and positive in the forebrain and hindbrain, though the latter were smaller and less consistent.
• 6.6. Principal components analyses and regression analyses were used to examine detailed associations between peripheral and central physiological changes.
• 7.7. It was found that increases in the EEG frequency of fore- and midbrain regions were related to cardiac deceleration on early stimulus presentations.
• 8.8. This was also shown for the negative SPS of the midbrain to the presentation of the tap stimulus.
• 9.9. Positive SPSs of the forebrain were related to the bradycardia on later stimulus presentation i.e. during habituation of the arousal response.
• 10.10. The results indicate that in fish, as in other vertebrates, negative SPSs in the midbrain are associated with arousal and implicate the forebrain in the modulation of arousal by its habituation.

     

Experimental problems using electronic particle counters

The following scheme lists the problems which have been and will continue to be encountered in grazing experiments on natural particle assemblages. In some cases there are solutions, but many of the problems listed below remain intractable. To solve them will require innovative approaches, most probably combining the use of particle counters with other techniques to approach the problem to be solved from several angles at once. Variance between samples due to

- statistical causes (especially caused by large particles) and

- differences between experimental bottles and between experimentals and controls at start of experiment. Shifts in particle distribution during experiment due to

- increase in small particles

- growth of bacteria and other organisms due to excretion of grazers and

- breakage during handling by grazers into fragments. Processes, independent of grazing, leading to changes in particle size distribution due to

- primary production

- grazing by additional components and

- bacterial growth on detrital particles and the formation of detrital flocs.

     

The use of a continuous assay system to show the stimulation of phosphoenolpyruvate production in intact mitochondria by valinomycin and by Mn2+

1. A method for the direct recording of the PEP efflux from isolated mitochondria is described.
2. This method has been used to show the stimulation of PEP efflux by externally added Mn⁺⁺ ions.
3. Valinomycin, uncoupler and oleate were also shown to stimulate PEP efflux.
4. Valinomycin caused an increase in the internal concentration of both PEP and citrate.
5. The results indicate that the major pathway of PEP synthesis in isolated mitochondria is via PEP carboxykinase and the results do not call for an unknown pathway of metabolism.
6. Two interactions between PEP and citrate are described; competition for the mitochondrial interior and the stimulation of PEP production by citrate.

     

Effet des androgènes sur l’activité sportive

Androgenic hormones seem to be of beneficial effects on sports performance:

- they increase motivation, will, aggressiveness, resistance to the stress and to the fatigue, leading to an increase of the training quantity,

- they increase bone mineralization and probably mechanical resistance,

- they stimulate the bone marrow and so, with the erythropoietin, the erythropoiesis,

- they increase the tendancy to hyperglycemia, but with a decrease of the tolerance to the glucose,

- they stimulate the fatty acids mobilization from the adipose tissue, for their utilization in the muscle during the exercise,

- they participate, for the trained sportmen, to a better gestion of the muscle glycogen storage: their utilization during exercise is decreased,

- they increase the lean body mass, with an increase of the protein synthesis and a decrease of the protein catabolism, leading also to an increase of the muscle force under training. There is no beneficial effect upon the tendons,

- they have an immunomodulation action.

     

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.

     

Seasonal variation in the biochemical composition of Mytilus viridis at Ratnagiri on the West Coast of India

1. The seasonal variation in the water, protein, fat and glycogen contents of the mussel, Mytilus viridis has been studied for the year March, 1974 to March, 1975.
2. The water level increased during the monsoon season and decreased in summer.
3. The level of protein, fat and glycogen showed correlation with the reproductive cycle of the mussel.
4. The protein level was high when the mussels were mature and dropped during the breeding period.
5. During sex change from male to female in May the protein level remained high whereas during sex change from female to male in October and November it was low.
6. The fat level was high in mature mussels and declined on spawning.
7. The glycogen level was at its peak in immature mussels and low in mature.