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Biomedical subjects

P D White

Publications and source records attributed to P D White.

At least 19 recordsLinked to original sources
PubMed1992

Hypothesis: cytokines may be activated to cause depressive illness and chronic fatigue syndrome.

Abnormalities in the regulation of the hypothalamo-pituitary-adrenal (HPA) axis are a well recognised feature of endogenous depression. The mechanism underlying this phenomenon remains obscure although there is strong evidence suggesting excessive CRH activity at the level of the hypothalamus. We propose a novel hypothesis in which we suggest that the aetiological antecent to CRH hyperactivity is cytokine activation in the brain. It is now well established both that interleukins -1 and -6 are produced in a number of central loci and that cytokines are potent stimulators of the HPA axis. Hence, we suggest that activation of IL-1 and IL-6 by specific mechanisms (such as neurotropic viral infection) in combination with the consequent CRH-41 stimulation, may (via their known biological effects) underly many of the features found in major depression and other related disorders, particularly where chronic fatigue is a prominent part of the symptom complex. This theory has considerable heuristic value and suggests a number of experimental stratagems which may employed in order to confirm or reject it.

Cytokines↗
PubMed1991

Human quadriceps strength and fatiguability in patients with post viral fatigue.

Quadriceps isometric strength, activation and fatiguability were measured in 11 patients with symptoms of fatigue three months after glandular fever or a glandular fever-like illness. Predicted normal and lower limits of normal muscle strength were calculated from height and age. These measures and the fatigue index were compared with a group of healthy students of similar age. Two of the patients were unable to activate fully their muscles. After allowing for this inhibition the group mean (SD) strength was 104 (22%) of predicted. Although there was no significant difference in the fatigue index between the patients and the control group, there was a trend for the patients to show less fatigue than controls. There was no difference in the muscle results for those patients who were found to have Epstein-Barr virus infections and those who did not. The feelings of weakness and fatigue experienced by the patients could not be explained by either physiological muscle fatigue or lack of effort.

Adolescent↗
PubMed1990

Melanin-concentrating hormone: a structural and conformational study based on synthesis, biological activity, high-field NMR, and molecular modeling techniques.

A series of Melanin-concentrating hormone (MCH) fragments have been synthesized and their biological activities compared with the parent peptide. The substructural units, 5-14 linear and 5-14 cyclic, have been used as models for MCH-- H-Asp1-Thr-Met-Arg-Cys-Met-Val-Gly-Arg HO-Val17-Glu-Trp-Cys-Pro-Arg-Tyr-Val in 1H-nmr conformational studies. Conformational features predicted by molecular dynamics analyses find support in the nmr experiments.

Amino Acid Sequence↗
PubMed1987

Myoclonus and episodic delirium associated with phenelzine: a case report.

A case of episodic delirium with incapacitating myoclonus associated with therapeutic doses of phenelzine is described. No evidence of epilepsy was found. The delirium and the myoclonus remitted rapidly after phenelzine was stopped and treatment with a benzodiazepine was started. No previous reports of the association of phenelzine with myoclonus and delirium have been found. The possible neurophysiology of the association is explored. Treatment with phenelzine should be reviewed if myoclonus occurs.

Acute Disease↗
PubMed1986

Phaeochromocytoma as a cause of reversible dementia.

The case of a 57 year old man with cognitive impairment, hypertension and insulin dependent diabetes mellitus caused by phaeochromocytoma is reported. One year after removal of the tumour there was a significant improvement with the full scale IQ increasing by 15 points, normotension and minimal glucose intolerance. Possible mechanisms accounting for reversible cognitive impairment in such a situation are discussed. No previous reports of this association have been discovered.

Adrenal Gland Neoplasms↗
PubMed1985

Contrast attenuation characteristics of iris clipped intraocular lens implants in situ.

In this study contrast thresholds were monitored over a wide range of spatial frequencies for patients with iris clipped implants or Fyodorov and Binkhorst types. These results were compared with those of an age matched normal group and attenuation characteristics derived for the implants and media environment alone. These results show that lenticular implants of this type can produce large reductions in contrast with a wide variety of transfer functions, for example, low pass, band reject, and band pass. These findings highlight the potential inadequacies of the assessment of the visual capabilities of these devices by acuity measures alone. We suggest that a more realistic and abbreviated approach should be based upon supplementing acuity assessment with monitoring of threshold sensitivity for a low, medium, and high spatial frequency sinewave grating.

Humans↗
PubMed1983

The reversal by oximes and their de oximinomethyl analogues of neuromuscular block produced by soman.

A series of oximes and related compounds were assessed for their ability to restore soman-induced neuromuscular block in the isolated diaphragm preparation of the rat, guinea-pig and marmoset. In the rat the bispyridinium oximes HS6, HI6 and HS14 were superior to P2S and all other compounds tested. Conversely, in the guinea-pig, most of the compounds tested produced a good reversal of neuromuscular block. In a limited number of experiments in the marmoset, only a partial reversal of neuromuscular block, was obtained with the oximes HI6 and HS6. The restoration of neuromuscular block was due to one or more of the following factors: (i) enzyme reactivation (ii) direct action (iii) adaptation. The results of this study suggest that both the acetylcholine receptor and the rate of 'ageing' of soman inhibited AChE are different in these three species.

Acetylcholinesterase↗
PubMed1979

The reversal by pyridostigmine of neuromuscular block produced by soman.

The effect of pyridostigmine on neuromuscular block produced by soman was studied in the isolated phrenic nerve-diaphragm preparation. In the rat, soman produced an irreversible reduction in tetanic tension and functional acetylcholinesterase (AChE) activity. Pretreatment with pyridostigmine before exposure of the diaphragm to soman, followed by removal of the anticholinesterase from the organ bath, produced a return of tetanic tension and an increase of 5% in functional AChE activity. Similar results were obtained in the guinea-pig. The changes in synaptic AChE activity were verified pharmacologically by showing a decrease in the blocking activity of acetylcholine in preparations pretreated with pyridostigmine in comparison to those given soman alone following removal of the anti-cholinesterase. The blocking dose of carbachol did not change in these two groups indicating that desensitization was not a component of the protective action. A comparison was also made of the results obtained by measuring inhibition of AChE in situ with those obtained from muscle homogenates. The implications of these results are discussed.

Acetylcholine↗