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Biomedical subjects

D J Clarke

Publications and source records attributed to D J Clarke.

At least 127 records · Page 7Linked to original sources
PubMed1988

Psychogenic vomiting among female Asian migrants to the United Kingdom.

Three female Asian migrants to the United Kingdom presented with vomiting which was not of organic origin. Cultural, dynamic and other factors influenced the adoption of vomiting as a manifestation of distress. Non-organic vomiting should be evaluated in terms of its symbolism, gains, and communicatory function for the individual.

Acculturation↗
PubMed1987

Biosensors in process control.

Improvement in bioprocess control will require development of monitors for a wide range of cell-growth and downstream-process parameters. These requirements are examined in terms of the development and application of biosensor devices and physical measurement techniques. Acoustic, dielectric and laser light scattering techniques are discussed primarily as monitors and analysers for biomass parameters. Developments with biosensor devices are discussed in terms of their application in membrane sampling-flow analysis probes and the potential of more direct biosensing principles.

Animals↗
PubMed1987

Cacodemonomania.

The experience of having had intercourse with the devil has in the past been regarded as evidence that the individual is a witch. Those investigating cases of witchcraft were advised to seek the judgment of doctors, and the verdict of physicians became a test for the presence or absence of witchcraft. The woman described in this case study might well have suffered the death penalty in former times. She is unusual because of her belief that she had had intercourse with the Devil, and because the belief was shared by her religious minister. The patient also presents a diagnostic problem.

Adult↗
PubMed1987

Epilepsy and psychosis--ask the family.

Psychotic episodes and epilepsy can occur without mental retardation in tuberous sclerosis. The diagnosis may depend on elucidating the family history since physical signs may not be obvious. Establishing the diagnosis makes genetic counselling possible.

Adult↗
PubMed1986

Grafted septal neurons form cholinergic synaptic connections in the dentate gyrus of behaviorally impaired aged rats.

A group of aged, behaviorally impaired rats received suspension grafts of fetal septal-diagonal band tissue into the otherwise intact hippocampal formation. Three months after grafting, behaviorally recovered rats were studied by immunocytochemistry by using monoclonal antibodies to choline acetyltransferase (ChAT) and electron microscopy. The innervation of the host dentate gyrus by graft-derived ChAT-positive fibres was unmasked by acute removal of the intrinsic septal cholinergic innervation by fimbria-fornix transection 5-7 days before perfusion. The pattern of termination and ultrastructural connectivity were compared with previous results obtained from both young nonoperated control animals and a group of young rats with intrahippocampal septal grafts that had been subjected to denervation of the intrinsic cholinergic input at the time of transplantation. Graft-derived, ChAT-immunoreactive terminals formed abundant synaptic specializations with neuronal elements in the host dentate gyrus. The predominant postsynaptic target (about 65% of all boutons) was dendritic shafts, whereas about 20% of the boutons contacted dendritic spines. Very few synapses onto neuronal perikarya were found in the grafted aged rats. In some of these cases, however, it was possible to identify the target as dentate granule cells. This situation is very similar to that seen in young control rats but significantly different than the distribution observed in the denervated young grafted group, where axosomatic contacts predominated. The results indicate that the graft-induced behavioral improvement seen in the aged rats may depend on the formation of functional cholinergic graft connections with neuronal elements in the host hippocampal formation.

Aging↗
PubMed1986

Ultrastructural organization of choline-acetyltransferase-immunoreactive fibres innervating the neocortex from embryonic ventral forebrain grafts.

Suspension grafts of foetal tissue rich in cholinergic neurones were transplanted into the frontoparietal cortex of rats that had previously undergone deafferentation of the extrinsic cholinergic innervation of the cortex by injection of ibotenic acid into the nucleus basalis magnocellularis. The cortical tissue containing the graft was processed for electron microscopic immunocytochemistry by using a monoclonal antibody to choline acetyltransferase (ChAT) in order to examine the contacts established between cholinergic fibres from the graft and the host neocortex. The density, distribution, and targets of this graft-host innervation were compared with those seen in the intact and deafferented cortex. ChAT-positive fibres in both grafted and control animals formed extensive synaptic connections with various cortical neural elements--those of graft origin being of similar morphology to those in the intact cortex. However, the distribution of postsynaptic cortical targets of the graft-derived ChAT-immunoreactive boutons was abnormal, such that a greater percentage of such terminals formed synaptic contacts with neuronal perikarya, especially layer V pyramidal neurones, than was seen in control brains. It is possible that the formation of new synaptic contacts between the embryonic graft and host frontoparietal cortex may, in part, be necessary for the restoration of functional activity that has been previously reported in these grafted animals.

Animals↗
PubMed1986

Formation of cholinergic synapses by intrahippocampal septal grafts as revealed by choline acetyltransferase immunocytochemistry.

The ultrastructural features of the contacts established by intrahippocampal grafts of foetal septal/diagonal band neurones in the dentate gyrus and the CA1 region of the previously denervated host hippocampus have been analysed with electron microscopic immunocytochemistry using a monoclonal antibody to choline acetyltransferase (ChAT). The results show that the grafted ChAT-positive neurones are capable of forming extensive synaptic contacts with neuronal targets in areas of the dentate gyrus and CA1 which normally receive such innervation. While all types of contacts normally found in association with the granule and pyramidal cell layers were also present in the graft-reinnervated specimens, the quantitative relationship between somatic and dendritic synapses was abnormal. Thus, the ChAT-immunoreactive synapses on cell bodies, which amounted to only a few percent in the normal animal, constituted over 60% in the grafted animals. Conversely, synapses on dendrites which constituted over 90% in the normal dentate were reduced to less than 40% in the grafted animals. The postsynaptic targets of the graft-derived cholinergic synapses included dendrites and cell bodies of dentate granule cells and CA1 pyramidal cells. This supports previous electrophysiological studies and indicates that the septal grafts may be able to modulate host hippocampal function via direct efferent connections onto the granule and pyramidal neurons in the host hippocampal formation.

Animals↗
PubMed1985

Cholinergic innervation of the rat dentate gyrus: an immunocytochemical and electron microscopical study.

Immunocytochemical studies using a monoclonal antibody to choline acetyltransferase (ChAT) were performed on sections of rat dentate gyrus. Light microscopical analysis of the immunoreactivity revealed dense fiber networks and many punctate structures predominantly located at the interface of the granule cell layer and molecular layer. In the electron microscope, the immunostained punctate structures were identified as synaptic boutons which formed mainly symmetrical contacts onto dendritic elements. Few ChAT-immunoreactive boutons formed axosomatic contacts.

Acetylcholinesterase↗
PubMed1985

The development and application of biosensing devices for bioreactor monitoring and control.

Presently, few of the reported (bio)chemical sensor devices have found application in fermentation monitoring and control. Although many devices with desirable selectivities have been reported, few have demonstrated reliability sufficient to encourage significant and widespread application. Chemical sensors (ion-selective electrodes, amperometric detectors, piezoelectric, field-effect transistors, semiconductor, Optrode and optoelectronic sensors), biosensors (based on potentiometric, amperometric, field-effect transistor and conductiometric detectors) and physical detection methods are reviewed with the aim of highlighting the problems of their application in this area. Physical detection principles appear to show promise as reliable and direct monitoring principles. However, even the more reliable discrete (bio)chemical sensor devices require the development of on-line flow sampling and autocalibration methods to demonstrate the necessary reliability. Biosensor devices appear most problematical and it is concluded that continued development of more direct biosensing principles is likely to prove most fruitful.

Biological Products↗
PubMed1983

Uptake of [3H]taurine into medium-size neurons and into identified striatonigral neurons in the rat neostriatum.

Injection of [3H]taurine into the neostriatum of the rat led to accumulation of radioactivity in a distinct population of neurons. Taurine-accumulating neurons had a medium-size cell body, a smooth nucleus and relatively little cytoplasm. Other neuron types, e.g. large neurons with indented nuclei, did not accumulate taurine. Striatonigral neurons, identified by retrograde transport of horseradish peroxidase, were found to take up [3H]taurine. It is suggested that taurine-accumulating neurons in the neostriatum are projection neurons.

Animals↗