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Biomedical subjects

J Z Young

Publications and source records attributed to J Z Young.

At least 19 recordsLinked to original sources
PubMed1990

The epistellar body and what followed from its discovery.

The sequence of discoveries that has followed the investigation of this small yellow spot shows the value of studies begun out of "mere curiosity". The spot occurs on the stellate ganglion of octopods. It proved to be an enclosed sac, perhaps a gland. The search for it in squids and cuttlefishes led to the discovery of the giant nerve fibres. At first they were thought to be veins but we soon showed that they were nerve fibres concerned with jet propulsion. Their action potentials, membranes and synapses have been used for thousand of studies, including those that led to the Hodkin Huxley equations. They have been the basis of much of modern neuroscience. The epistellar body itself proved not to be a gland but a photoreceptor. Comparable photosensitive vesicles are especially large in the heads of deep-sea squids. In the mesopelagic ones they allow the squid to conceal itself by counterillumination, matching its own light output to the light coming from above. In bathypelagic squids the vesicles are enormous and probably keep the animals in the dark, where they breed. The function of the epistellar body, lying within the mantle of octopods is still unknown. It may act in the transparent larval stage to trigger the ejection of luminous plankton, which would be a hazard.

Animals↗
PubMed1988

Sympathetic innervation of the rectum and bladder of the skate and parallel effects of ATP and adrenalin.

1. Longitudinal muscles of the rectum of the skate are first briefly excited and then inhibited by stimulation of the sympathetic nerve fibres. 2. ATP, adrenalin and noradrenalin also produce inhibition. 3. 5HT is strongly excitatory but acetylcholine is only excitatory above 1 microM. 4. The rectum contracts strongly to mechanical stimulation; the response is not blocked by TTX. 5. The inhibitory actions of sympathetic stimulation or ATP were not blocked by guanethidine, propranalol, antazoline, theophylline or bee venom (apamin). 6. ATP continued to produce inhibition after the nerve response was blocked by TTX. 7. The urinary bladder gives slow rhythmic contractions, which are inhibited by nerve stimulation and by adrenalin but ATP has no action. 8. 5HT is strongly excitatory but acetylcholine has little action.

Adenosine Triphosphate↗
PubMed1988

The effect of peptides on the motility of the stomach, intestine and rectum in the skate (Raja).

1. Pentagastrin (10(-8)-2 X 10(-6) M) was found to increase motor activity in the cardiac stomach and spiral intestine but only occasionally in the pyloric stomach and not at all in the rectum. 2. Substance P increased motor activity in both parts of the stomach and the rectum (10(-8)-5 X 10(-7) M) but had only a slight effect on the spiral intestine. 3. No effect on the activity of any part of the gut was seen with VIP (10(-7) M), neurotensin (2 X 10(-6) M) or bradykinin (2 X 10(-5) M). 4. The responses to pentagastrin or substance P were not abolished by TTX (10(-6) M). 5. The implications of these results for the understanding of the control of gut motility in elasmobranchs is discussed.

Animals↗
PubMed1978

Short-lasting memory in lower nervous centers in Octopus.

Octopuses with the supraesophageal lobes split and the subesophageal centers isolated by cutting the cerebrobrachial connective on one or both sides were trained by food and shock rewards to discriminate between rough and smooth balls. Because there is a greater tendency to take the rough ball, training was done with the smooth ball positive for half the animals, and the rough ball positive for the others. In the animals with the cerebrobrachial connective cut only on one side, the subesophageal lobes showed no capacity to use the information gained by their opposite, intact, half-brains, which learned well. In animals with isolated subesophageal lobes, there was a decrease during each training session in the tendency to take both types of ball; however, this decrease did not persist from day to day. During each training session there were signs of discrimination between the balls by animals with isolated subesophageal lobes, but these also did not survive from day to day. In a series of training sessions spread over seven weeks, there was no change in results in animals with isolated subesophageal lobes when the smooth ball was positive. When the rough was positive the discrimination in its favor was slightly increased at later sessions.

Animals↗
PubMed1976

The nervous system of Loligo. II. Suboesophageal centres.

A well-marked hierarchy of centres can be recognized within the suboesophageal lobes and ganglia of the arms. The inputs and outputs of each lobe are described. There are sets of motoneurons and intermediate motor centres, which can be activated either from the periphery or from above. They mostly do not send fibres up to the optic or higher motor centres. However, there is a large set of fibres running from the magnocellular lobe to all the basal supraoesophageal lobes. The centre for control of the four eye-muscle nerves in the anterior lateral pedal lobe receives many fibres direct from the statocyst and from the peduncle and basal lobes, but none direct from the optic lobe. The posterior lateral pedal is a backward continuation of the oculomotor centre, containing large cells that may be concerned in initiating attacks by the tentacles. An intermediate motor centre in the posterior pedal lobe probably controls steering. It sends fibres to the funned and head retractors, and by both direct and interrupted pathways to the fin lobe. It receives fibres from the crista nerve and basal lobes, but none direct from the optic lobe. The jet control centre of the ventral magnocellular lobe receives fibres from the statocyst and skin and also from the optic and basal lobes. Some of these last also give extensive branches throughout the palliovisceral lobes. The branching patterns of the dendritic collaterals differ in the various lobes. Some estimates are given of the numbers of synaptic points. The dendritic collaterals of the motoneurons spread through large volumes of neuropil and they overlap. The incoming fibres spread widely and each presumably activates many motoneurons either together or serially. Many of the lobes contain numerous microneurons with short trunks restricted to the lobe, but there are none of these cells in the chromatophore lobes or fin lobes. The microneurons have only few dendritic collaterals, in contrast to the numerous ones on the nearby motoneurons.

Animals↗
PubMed1975

The subfrontal lobe and touch learning in the octopus.

Octopuses with the supraoesophageal lobes of the brain divided longitudinally can be taught to discriminate using the arms on either side. If there is no further lesion the two sides behave alike. Lesions limited to one side did not affect the performance of the contralateral, "control" side. Lesions made in the vertical (n=7) lobes led to a slight drop in the quality of performance in training to take a smooth sphere, in discrimination training (rough vs. smooth spheres) and in subsequent extinction and transfer tests. After removal of the median inferior frontal lobe (n = 10) there were somewhat greater effects in the same direction. Much larger effects followed interference with the subfrontal lobe (n = 20). Removal of parts from this always led to a marked loss of capacity for touch learning, broadly dependent on the amount of tissue removed. Removal of the whole of the subfrontal lobe (n = 6) produced animals that showed, at best, only very slight signs of learning. Such animals can adjust their overall level of response as a result of training but they seem incapable of adjusting response levels to two objects independently. These results are discussed in relation to the function of the subfrontal lobe as a memory store.

Animals↗
PubMed1975

Comparison of visual and tactile learning in octopus after lesions to one of the two memory systems.

Sets of animals with lesions to either the vertical lobe or median inferior frontal lobe were trained first visually and then by touch. Lesions of the vertical lobe system did not affect the increase produced by food in tendency to attack a moving figure in the visual field. Any lesion that interrupted the circuit through the vertical lobe greatly impaired the capacity to inhibit attacks on crabs when these attacks resulted in shocks. Removal of the median inferior frontal lobe did not impair this capacity to learn not to attack a crab in the octopus's visual field. The capacity to learn to respond positively to a black disc but to avoid a white one was grossly impaired by an interruption of the vertical lobe circuit. After such operations the animals showed a strong preference for white over black. The capacity to learn to discriminate between black and white was not affected by removal of the median inferior frontal lobe. Animals with interruptions of the vertical lobe circuit could learn to make discrimination between white as a positive figure and black as a negative one, but they made more mistakes than controls. Most mistakes consisted of attacks on the negative (black) figure, but there were also some failures to attack the white. In tactile discrimination between rough and smooth spheres given successively, animals with vertical lobe lesions were, under some circumstances, less accurate than controls. They took more objects than controls. They were less able than controls to reverse the the discrimination. After removal of the median inferior frontal lobe tactile discrimination was greatly impaired. The animals showed a strong preference for rough objects and could not learn to take smooth objects. However, they showed improvement in discrimination when trained with smooth negative and are therefore not wholly incapable of long-term memory storage.

Agonistic Behavior↗