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Biomedical subjects

B H Peters

Publications and source records attributed to B H Peters.

At least 19 recordsLinked to original sources
PubMed1988

The tritocerebral commissure 'dwarf' (TCD): a major GABA-immunoreactive descending interneuron in the locust.

The minor branch of the tritocerebral commissure of the locust, Locusta migratoria, contains only two axons which are from interneurons in the brain descending to the ventral cord ganglia. The smaller of these two neurons, the tritocerebral commissure dwarf (TCD), is immunoreactive to GABA, suggesting that it may be an inhibitory interneuron. We have exploited the accessibility of its axon in the commissure, first, to fill it with cobalt to define its morphology, and second, to record its input characteristics. It has a cell body and arborization of fine branches in the deutocerebrum of the brain, its axon passes contralateral through the tritocerebral commissure and it forms bilateral arborizations in the suboesophageal and three thoracic ganglia. It receives mechanosensory input from many regions of the ipsilateral body and head, and it is sensitive to illumination levels, generally showing greater spontaneous activity in the dark. It is one of the largest GABA-immunoreactive descending interneurons in the locust, suggesting it plays a prominent role in behaviour. Since it is easily accessible for physiological recording, its roles in circuits for particular components of behaviour should be amenable to investigation.

Action Potentials↗
PubMed1987

Morphology, ultrastructure and synapse distribution of putative serotonergic salivary neurons in the locust.

Neurons innervating the locust salivary glands have been investigated using the electron microscope. We have examined the projections in the suboesophageal ganglion of two identified salivary neurons by differential double labelling with cobalt ions, followed by silver intensification. Numerous synaptic inputs occur on the arborizations of the salivary neurons, particularly on fine branches and on small spines arising from larger branches. Although a few instances occur of common input to both salivary neurons from a single presynaptic element, many of the appositions between branches seen in the light microscope do not represent functional connections. A few structures resembling presynaptic dense bodies have been observed in salivary neuron profiles, but with few synaptic vesicles. Large dense granules are present in some labelled profiles, but not in the vicinity of synapse-like membrane specializations. We have also examined unidentified neuron profiles within the acini of the salivary glands, which contain large dense granules and small vesicles. There is good evidence that these unidentified terminals correspond to the suboesophageal salivary neurons. The central arborizations of the salivary neurons appear to serve largely as sites of synaptic input, whereas the peripheral terminals are likely sites of transmitter release. The results are considered in the context of the known immunoreactivity of the salivary neurons with antibodies to 5-hydroxytryptamine, and compared with analogous systems in other insect groups.

Animals↗
PubMed1987

Electron microscopy of serotonin-immunoreactive neuron branches and terminals in the locust central nervous system.

Using a pre-embedding peroxidase technique, we have investigated the ultrastructure of elements that react with antibodies to 5-hydroxytryptamine in the central nervous system of the locust. Reactive neuron profiles are widespread, and contain a variety of vesicle types: small lucent vesicles, some of which are stained only on their outer membranes while others are stained internally, and large dense granules that again differ in the staining properties of their cores. Some of the reactive profiles contain synaptic specializations, while others receive synaptic inputs from unlabelled elements. The heterogeneity of reactive profiles makes it impossible to define ultrastructural characteristics of putative serotonergic terminals that might be generally applicable. The differential reactivity both of small vesicles and of large dense granules may indicate functional differences within these categories.

Animals↗
PubMed1986

Spatial segregation of synaptic inputs and outputs in a locust auditory interneurone.

Using intracellular injection of cobalt, processing for electron microscopy, and using on-section silver intensification, we have investigated the distribution of synapses on the metathoracic arborization of the TN1 intersegmental interneurone in the auditory system of the locust. Previous studies have indicated that inputs to this neurone from tympanal afferents are spatially segregated from its outputs to higher-order inhibitory interneurones. Branches in the area of input are characterised by a smooth appearance in Lucifer Yellow preparations, whereas branches in the main output area appear beaded. Sampling different areas of the TN1 arborization, we have found marked differences in the respective densities of input and output synapses. Labelled profiles in areas of beaded branching have an extremely high density of presynaptic sites, with a much smaller number of synaptic inputs. Smooth branches bear many input synapses, but we have found no output synapses on them. Our results indicate a good correlation between branch beading and presynaptic function and between smooth branches and postsynaptic function. These correlations enable us to predict synapse distribution on other insect neurones with a similar division in branch morphology and also extend our knowledge of the functioning of TN1 itself.

Animals↗
PubMed1986

Effects of oral physostigmine and lecithin on memory and attention in closed head-injured patients.

In view of the evidence for the role of the central cholinergic pathways in memory and preliminary studies suggesting alteration of neurotransmitters after severe head injury, we completed a double-blind, placebo-controlled study of combined oral physostigmine and lecithin. Sixteen survivors of moderate to severe closed head injury who had unequivocal memory deficit were studied during the course of inpatient rehabilitation. Although the results generally indicated no difference in the effects of the physostigmine-lecithin combination as compared to lecithin alone, sustained attention on the continuous performance test was more efficient under physostigmine than placebo when the drug condition occurred first in the crossover design. Further investigation of neurotransmitter manipulation is warranted in patients with traumatic brain injury.

Administration, Oral↗
PubMed1985

Synaptic connections between the hindwing stretch receptor and flight motor neurones in the locust revealed by double cobalt labelling for electron microscopy.

Synaptic interactions between sensory and motor neurones in the locust flight system have been investigated by using intracellular labelling with cobalt and nickel for electron microscopy. Simultaneous axonal filling of two neurones with different concentrations of metal ions produces differential labelling, so that contacts between them in the central nervous system can be recognized. We have investigated the connectivity of the hindwing stretch receptor neurone (SR) with a direct hindwing depressor motor neurone (MN 127) known from physiological experiments to receive monosynaptic input from the SR, and an indirect hindwing depressor motor neurone (MN 112/1), for which no monosynaptic connection with the SR has been reported. We have found no direct synapses between the SR and MN 112/1, although some of their branches lie close together in the neuropile. We have, however, found some evidence for polysynaptic connections between them. There are many synapses of conventional dyadic morphology from both the lateral and mediolateral branches of the SR to MN 127; the medial branch was not examined. Those from the lateral branch contact the motor neurone on branches close to the neuropilar segment, while those from the mediolateral branch contact long, thin distal twigs. We estimate that there are about 600 anatomical synapses between these two neurones. Our results suggest that a large number of widely distributed anatomical synapses constitute the physiological synaptic connection between the SR and MN 127. The dyadic arrangement of these synapses provides an anatomical correlate for the physiologically established divergence of SR outputs onto interneurones and motor neurones.

Animals↗
PubMed1979

Biphasic periodic paralysis.

A young man with episodes characteristic of familial normokalemic periodic paralysis was restudied after a change in the nature of his attacks. He now has spontaneously occurring and provokable episodes of both hyperkalemic and hypokalemic periodic paralyses that are superimposed on a persistent myopathy. Hypokalemia seems to be associated with facilitated entry of glucose and potassium into muscles, whereas resistance to glucose and potassium entry accompanies hyperkalemia. The possibility that episodes of both hypokalemic and hyperkalemic weaknesses can occur in one person should be considered in pathogenic postulates regarding periodic paralysis.

Adult↗
PubMed1979

Effects of physostigmine and lecithin on memory in Alzheimer disease.

Because there is evidence that central cholinergic mechanisms are depleted in dementia, we studied the effects of central cholinergic augmentation on the memory of 5 patients with Alzheimer disease. Patients received placebo, lecithin, physostigmine, or lecithin plus physostigmine in a double-blind study using titrated doses of the acetylcholinesterase inhibitor physostigmine. Memory was evaluated with alternate forms of the selective reminding procedure. Compared with lecithin alone, the combination of physostigmine and lecithin consistently enhanced memory storage and retrieval; physostigmine without lecithin produced no memory facilitation. The strategy of combining a cholinergic agonist and precursor holds promise, although a larger clinical trial is needed.

Aged↗
PubMed1977

Memory enhancement after physostigmine treatment in the amnesic syndrome.

Central anticholinergic agents (eg, scopolamine) are known to produce transient memory deficits in human and animal subjects. Damage to the limbic system frequently results from herpes simplex encephalitis (HSE) and produces a memory deficit. If this deficit is due to limbic cholinergic pathway destruction, it might improve with central cholinergic agonists (eg, physostigmine). In a doubleblind study over a three-week period, we compared memory performance on three days after 0.8-mg subcutaneous physostigmine therapy (three sessions) to baseline performance and that obtained in three randomly interspersed control sessions. Serial assessment of memory by the Selective Reminding Test showed reproducible enhancement of long-term storage and retrieval with physostigmine treatment. Performance after control injections did not exceed baseline levels. Our findings encourage the hypothesis that cholinergic mechanisms subserve memory and that their pharmacological potentiation might favorable influence some amnesic conditions.

Adolescent↗
PubMed1977

Neuropathy presenting as prolonged dyspnea. Case report and review of literature.

Polyneuropathy presented as isolated respiratory muscular paralysis. Transdiaphragmatic pressure measurements, nerve conduction studies, electromyography, and biopsy of intercostal muscle confirmed the nature of the process. Patients with unexplained respiratory insufficiency must be carefully evaulated for underlying neuromuscular disease.

Adult↗
PubMed1977

Neurologic and psychologic manifestations of decompression illness in divers.

It has been widely accepted that the neurologic sequelae of decompression illness are confined to the spinal cord. Of 10 divers who gave a history of an episode of decompression illness involving the central nervous system, we found that eight had unequivocal neurologic deficits implicating multiple supraspinal lesions. Seven of these neurologically impaired divers completed a battery of neuropsychologic tests that revealed severe deficits in all cases. The findings show that diffuse and multiple central nervous system lesions result from decompression illness and demonstrate the importance and close correlation of thorough neurologic and neuropsychologic tests in assessment following diving accidents.

Adult↗
PubMed1977

Hyperbaric oxygenation in the treatment of postencephalitic amnesic syndrome.

The efficacy of hyperbaric oxygenation in the treatment of an amnesic disorder was studied in a young woman with a residual memory impairment 2 years after Herpes Simplex Encephalitis. Quantitative testing of memory was performed under controlled conditions before, during, and immediately following treatment. There was no systematic change in storage and retrieval of either verbal or essentially nonverbal information when testing was performed during hyperbaric oxygenation or after termination of four daily treatment sessions. The findings support recent studies which have indicated a lack of therapeutic effects of hyperbaric oxygenation on the mental efficiency of older demented patients.

Adolescent↗
PubMed1976

Pronator syndrome: clinical and electrophysiological features in seven cases.

The clinical and electrophysiological picture of seven patients with the pronator syndrome is contrasted with other causes of median nerve neuropathy. In general, these patients have tenderness over the pronator teres and weakness of flexor pollicis longus as well as abductor pollicis brevis. Conduction velocity of the median nerve in the proximal forearm is usually slow but the distal latency and sensory nerve action potential at the wrist are normal. Injection of corticosteroids into the pronator teres has produced relief of symptoms in a majority of patients.

Adrenal Cortex Hormones↗
PubMed1976

Neuropsychological testing following head injuries: prosopagnosia without visual field defect.

Assessment of residual cerebral dysfunction in the post-traumatic patient poses considerable problems particularly when the neurological examination yields minimal or equivocal findings. The clinical picture is frequently complicated by emotional disturbance not easily differentiated from "post-traumatic neurosis." This report describes such a patient whose disorder was elicidated by neuropsychological testing. Numerous studies have established the validity of neuropsychological tests particularly when they are interpreted by psychologists specifically trained in their use. These procedures are also useful in differentiating patients with neurologic complaints of a nonorganic etiology from patients with similar complaints secondary to confirmed brain lesions. Although the findings reported here pertain to a patient exhibiting a rare neurologic consequence of closed head injury, the methods employed are applicable to subtle behavioral manifestations of diverse etiologies. Neurophyshological findings in a patient unable to recognize faces of familiar persons (prosopagnosia) disclosed a severe impairment of visual perception despite intact visual acuity and fields. The prosopagnosia was also associated with a pervasive memory deficit without dementia. Our results challenge current concepts of prosopagnosia and support the need for neuropsychological evaluation of post-traumatic patients.

Black or African American↗