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.

     

Pathways mediating abdominal phasic flexor muscle activity in crayfish with chronically cut nerve cords

1. Nerve cord transection abolishes the ability of crayfish (Procambarus clarkii) to produce tailflips in response to gradually applied tactile or proprioceptive stimulation of the abdomen, but this ability eventually returns. To determine the time-course of this return and to analyze its underlying neural pathways, we made behavioral observations, electromyographic recordings from abdominal phasic flexor muscles, and intracellular recordings from motoneurons in crayfish with cord lesions between the thorax and the abdomen.
2. Abdominal stimulation activated the phasic flexor muscles in the rostral 5 abdominal segments and their homologs in the 6th segment, the posterior telson flexor muscles. Nearly one-quarter of cord-transected animals responded to the stimuli with phasic flexor muscle activity by one week after the lesion, and almost 90% were responsive by 3 weeks.
3. Regeneration of axons across the lesion played little or no role in the recovery of phasic flexor muscle responsiveness. In addition, the lateral giant axons were not activated by the gradually applied stimuli that triggered phasic flexor muscle contractions. These results suggest that non-giant pathways confined to the abdominal nervous system become functional following chronic cord transection.
4. Retransection of the nerve cord below the original lesion showed that smaller subsets of the abdominal cord, including a single ganglion, could develop the ability to generate phasic flexor muscle contractions in response to gradually applied stimuli.
5. Phasic flexor motoneurons in cord-transected animals could be excited by stimulation of afferents throughout the abdomen. The sensory pathways producing this activation appear to project through the nerve cord without much cross-over between left and right sides.

     

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.

     

Morphological and physiological properties of pheromone-triggered flipflopping descending interneurons of the male silkworm moth,Bombyx mori

1. The morphology of descending interneurons (DNs) which have arborizations in the lateral accessory lobe (LAL) of the protocerebrum, the higher order olfactory center, and have an axon in the ventral nerve cord (VNC), were characterized in the male silkworm moth, Bombyx mori.
2. Two clusters (group I, group II) of DNs which have arborizations mainly in the LALs were morphologically characterized. The axons of these DNs are restricted to the dorsal part of the each connective (Figs. 1–5).
3. Pheromonal responses of the group I and group II DNs were characterized. Flipflopping activity patterns, which have two distinct firing frequencies (high and low) in response to sequential pheromonal stimulation, were usually recorded (Figs.6–10).
4. Two types of flipflopping activity patterns were classified into those that had an antiphasic relationship (called the ‘FF’ type) between the left and right connectives and those with a synchronized relationship (‘ff’ type) (Figs. 8–12). We propose that some group II DNs show ‘FF’ flipflopping activity patterns (Fig. 10).
5. A state transition was usually elicited by less than 10 ng bombykol, the principal pheromone component. Extra impulses were elicited during constant light stimulation (Fig. 9).
6. Our results suggest that the LAL olfactory pathways might be important for producing flipflopping activity patterns (Fig. 11).

     

The optic nerve mediates the circadian pigment migration in the median eyes of the scorpion

• 1.1. The peripheral visual pathway from the median eyes of the scorpion Androctonus australis was interrupted at different points and the effect on the circadian rhythm of median-eye sensitivity was examined.
• 2.2. Any interruption of the visual pathway distal to the supraesophageal ganglion abolishes the circadian sensitivity rhythm in the median eyes. This rhythm is thus controlled by efferents in the optic nerve (very probably via the neurosecretory axons) rather than by way of the hemolymph.
• 3.3. Following transection of the optic nerve, the sensitivity of the median eyes proceeds rapidly to the daytime state. This condition is associated with movement of the screening pigment into the distal ends of the visual cells.
• 4.4. The oscillator system controlling the circadian pigment migration in the median eye cannot be located in the eye itself, but must lie in the CNS, proximal to the first optic ganglion. The oscillator itself need not be connected to both median eyes in order to function normally, as revealed by the continued rhythm in the contralateral eye following unilateral optic nerve section.

     

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.

     

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.

     

Rigorous and extended application of information theory to the afferent visual system of the cat

1. Intracellular recording were obtained from P-cells of the LGN of the cat. The impulse trains of a single presynaptic retinal ganglion cell and the postsynaptic P-cell were separated by band-pass-filtering and subsequent amplitude discrimination.
2. The rates of information and transinformation for the visual channel from the eye to a ganglion cell and to the connected P-cell were calculated. Input signals to the channel were trains of light flashes of different rate, luminance and spatial distribution.
3. Transinformation was calculated without restrictive assumptions for the code.
4. The transient behaviour of the system in response to a flash was fully considered for information calculations. Additionally, it was ensured that the state of the (adaptive) channel was considered correctly.
5. Information theory was applied in an extended way. The time courses of information transfer were calculated for various flash stimuli and compared with each other.

     

Properties of a motor output system involved in the optomotor response in flies

1. The optomotor response of tethered flying houseflies (Musca domestica) has been studied at the level of the neural output which controls the activities of some non-fibrillar flight muscles (N-muscles).-a) During visually induced turning responses in a given direction some N-muscles on the right side of the thorax are synergistically active together with other N-muscles on the left side of the thorax. The same muscles are inactive during turning reactions in the opposite direction while the corresponding antagonists are now active (synopsis in Table 1).-b) The response activities of the N-mussles show a considerable variation during the course of time in spite of constant visual input.-c) There is a strong tendency for N-muscle spikes to be phase-locked with respect to the wingbeat period.-d) The findings obtained fromMusca are in accordance with the corresponding results obtained fromCalliphora (Heide, 1971b).
2. TheN-muscle activities have also been investigated in tethered flying blowflies (Calliphora erythrocephala) which tried to yaw spontaneously with both wings beating. In spontaneous left (right) turn reactions the features of the observed neural output are nearly identical with the features of the motor output showing up during visually induced left (right) turn reactions.-A different motor output pattern has been found in flies with only one wing beating.
3. The wingbeat synchronous rhythm observed in spike trains from activeN-muscles is produced in the thorax without the participation of higher stages of the fly's CNS. On the other hand no distinct rhythms can be found in spike trains fromN-muscles of non-flying flies when their motoneurons are artificially activated by non-rhythmic stimuli. Afferent information from thoracic sense organs seems to be essential for the production of the rhythm observed during flight.
4. The results about the production of the wingbeat synchronous rhythm in spike trains fromN-muscles suggest that the information derived from the motion detectors only acts to gate the output needed to achieve yaw-turn reactions. The strength of the influence of signals from the motion detectors on the output producing system can be modified by the animals “state of excitement”.
5. A model is presented which summarizes some features of information processing in the output systems supplying theN-muscles of flies. Available physiological data are discussed in relation to the model.

     

Sensory and motor innervation of bird intrafusal muscle fibers

• 1.1. Most bird muscle spindles are supplied by only one primary afferent.
• 2.2. Secondary afferents occur irregularly.
• 3.3. Sensory terminals are covered by a basal lamina and a collagenous sheath.
• 4.4. Two types of motor terminal are recognized which can be referred to specific types of intrafusal fiber.
• 5.5. The sensory and motor innervation of bird intrafusal fibers is less understood than that of mammalian intrafusal fibers.

     

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.

     

Role of extralaryngeal muscles in phonation of subhuman primates

1. The electromyographic activity of eight external laryngeal and hyoid muscles was recorded during vocalization in the squirrel monkey (Saimiri sciureus). Calls of different types were elicited by electrical stimulation of the central grey of the midbrain in narcotized animals.
2. Peeping, a short, high-pitched call with minor frequency modulations, is associated with a marked activity in the cricothyroid, a moderate activity in the thyrohyoid, a weak activity in the sternohyoid and no activity in the sternothyroid, omohyoid, mylohyoid and anterior digastric muscles.
3. Chuck, a short, plosive call with a steep frequency descent over several kHz, is associated with a marked activity in the cricothyroid, a moderate activity in the thyrohyoid, sternothyroid and mylohyoid, a weak activity in the sternohyoid and omohyoid, and no or rare activity in the anterior digastric and inferior pharyngeal constrictor, respectively.
4. Cackling, a long and loud call consisting of alternating high- and low-pitched elements which follow each other repetitively in a 12–14 Hz rhythm, is associated with a similar muscular activity pattern as chuck except that the sternohyoid activity is relatively stronger.
5. Cawing, a short low-pitched call with a fundamental frequency of 200–700 Hz, shows a moderate activity in the sternothyroid, an occasional activity in the thyrohyoid and no activity in the cricothyroid, sternohyoid, omohyoid, anterior digastric and inferior pharyngeal constrictor.

     

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.

     

Effects of Environmental Perturbations on Short-Term Phytoplankton Production off Lawson's Bay,A Tropical Coastal Embayment

1. The phytoplankton cycle off Lawson's Bay, Waltair follows a bimodal pattern with a major peak during March–May; a minor peak during October–November months and with a low production during the summer months i.e., June–August.
2. During the summer months of 1957, 1958, 1960 and 1962 dumping of dredged spoil from the entrance channel of the harbour into the sea resulted in a natural enrichment of waters.
3. Following this enrichment, there was a qualitative and quantitative increase in the phytoplankters thus leading to the development of a bloom.
4. Only Thalassiosira subtilis and Chaetoceros curvisetus commonly bloomed during the four years.
5. The increase in gross production which varied from 3–13 fold and the high photosynthesis-respiration ratios 5.1 to 10.5 indicated that the bloom populations were in a healthy state.
6. The decrease of the populations to the initial levels suggests that some unknown factor, other than those investigated must have been operating.
7. Consequences of eutrophication of different origins on stimulation of phytoplankton production are briefly discussed.

     

In vivo buccal nerve activity that distinguishes ingestion from rejection can be used to predict behavioral transitions in Aplysia

1. We are studying the neural basis of consummatory feeding behavior in Aplysia using intact, freely moving animals.
2. Video records show that the timing of radula closure during the radula protraction-retraction cycle constitutes a major difference between ingestion (biting or swallowing) and rejection. During ingestion, the radula is closed as it retracts. During rejection, the radula is closed as it protracts.
3. We observed two patterns of activity in nerves which are likely to mediate these radula movements. Patterns I and II are associated with ingestion and rejection, respectively, and are distinguished by the timing of radula nerve activity with respect to the onset of buccal nerve 2 activity.
4. The association of ingestion with pattern I is maintained when the animal feeds on a polyethylene tube, the same food substrate used to elicit rejection responses. Under these conditions, pattern I is associated with either swallowing or no net tube movement.
5. Most transitions from swallowing to rejection were preceded by one or more occurrences of pattern I in which there was no net tube movement, suggesting that these transitions can be predicted.
6. Our data suggest that these two patterns can be used to distinguish ingestion from rejection.

     

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.

     

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.

     

Properties of the transition from short-term to long-term depression in neurons of Helix pomatia

• 1.1. Synaptic short-term depression could be transferred into long term depression by repetition of series of stimuli.
• 2.2. The transition from short-term depression to long-term depression was blocked by puromycin.
• 3.3. The majority of the transition took place during resting periods between stimulus series.
• 4.4. The initiation of the transition process was 83% completed after 5 min of stimulation.
• 5.5. Short- and long-term depression were quantitatively separated into their two serial sites of origin: afferent axons and synaptic terminals.
• 6.6. Long sequences evoked periods with increased and variable EPSPs not conforming to depression.

     

A study of the relationship between mechanical characteristics and the coastal vegetation among several broad-leaf trees in Miura Peninsula in Japan

The mechanical properties of broad-leaf tree species in a maritime-wind exposed habitat in central Japan were examined. The broad-leaf trees studied were Celtis sinensis var. japonica, Ilex integra, Eurya japonica, Pittosporum tobira, Euonymus japonicus and Cinnamomum japonicum. The results obtained can be summarized briefly as follows:

1. At places with weaker wind, the number of species increased and the height of the canopy increased.
2. The fracture strength σ_m showed no dependence on tree part or branch thickness, but was constant.
3. The order of strength was Celtis sinensis var. japonica > Ilex integra > Eurya japonica > Pittosporum tobira > Euonymus japonicus > Cinnamomum japonicum, and these six species could best adapt to the wind pressure in the study area.
4. Within species, fracture strength varied directly with wind strength.
5. The strain ε_m decreased as the trunk became thicker.
6. Within species, strain energy U_m varied directly with wind strength.