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Biomedical subjects

D Griffiths

Publications and source records attributed to D Griffiths.

At least 91 records · Page 5Linked to original sources
PubMed1985

The pressure within a collapsed tube, with special reference to urethral pressure.

A definition is proposed for tube pressure (the pressure within a collapsible tube in the collapsed state, e.g. the urethral pressure or the pressure in the anal or oesophageal sphincter) which conforms to the common sense view that it is a measure of the ability of the tube to prevent leakage. It is not dependent on the orientation of a measuring probe in the tube. The orientation effects which have previously been reported are due to attempted bending of a stiff measuring catheter by internally and externally applied forces. A satisfactory way of measuring the tube pressure, by slow perfusion through a thin, flexible catheter with an end hole, and of testing whether it is a meaningful concept in a given case, is proposed. It is illustrated by measurements of urethral pressure in 42 continent and incontinent females. No cases of urinary incontinence due to poor urethral sealing ability are observed, indicating that tube pressure is a meaningful concept. The theory of viscosity-limited flow through a compressive zone in a collapsible tube, on which the perfusion method of measuring tube pressure is based, is developed.

Adolescent↗
PubMed1982

Neurosecretory cells of the lamina propria of the appendix and their possible relationship to carcinoids.

Carcinoid tumours of the appendix are generally thought to be derived from enterochromaffin cells; in-situ abnormalities of these cells are, however, rarely observed in the mucosal epithelium. One hundred appendices, removed consecutively at surgery, were stained with an alcian blue-PAS diastase-lead haematoxylin sequence and, in 69, cells were found in the lamina propria with a cellular and architectural morphology identical to those of an archetypal appendiceal carcinoid tumour. These cells appeared to contain neurosecretory granules, were diazo-positive and showed argentaffinity. They were further characterized by the localization of cytoplasmic neurone specific enolase and the presence of neurosecretory granules was confirmed by electron microscopy. These cells are designated subepithelial neurosecretory cells (SNC). It is suggested they are an integral component of the subepithelial nervous plexus and are in progenitors of appendiceal carcinoid tumours. A neuroectodermal origin of the SNC-and hence appendiceal carcinoid tumours-is proposed.

Appendiceal Neoplasms↗
PubMed1980

A factor VII concentrate for therapeutic use.

A concentrate of factor VII suitable for therapeutic use has been prepared from human plasma by a method forming part of a comprehensive scheme of large-scale plasma fractionation. Factor VIII was separated as cryoprecipitate and factors II, IX and X were adsorbed on DEAE-cellulose. Most of the factor VII remained in the supernatant. By batch adsorption on DEAE-Sepharose, followed by elution on a chromatographic column, factor VII was concentrated about 25-fold, and purified about 50-fold compared with original plasma, without the need for further dialysis or concentration steps. Data are presented from 10 batches, each from 80-120 kg plasma. Following doses of factor VII to six congenitally deficient patients, the mean rise in plasma factor VII was 95-100% of theoretical; the half-disappearance time was about 4 h. The treatment of four patients with acquired deficiency of factor VII is also described. No untoward side effects were observed.

Adult↗
PubMed1980

An evaluation of a rehabilitation workshop.

Staff awareness of the steps involved in rehabilitation was assessed before and after a multidisciplinary workshop concerned with the aims, methods and principles of rehabilitation in psychiatry. Results were compared with similar assessments derived from a matched control group which was not exposed to any educational programme. The data suggest severe limitations in staff performance on the rehabilitation problem solving task which was used. Performance was not improved by the workshop, and the limitations of staff opinion as measures of the educational value of the workshop were clearly demonstrated. These results are consistent with other findings, and demonstrate the need to evaluate educational programmes provided in the Health Services.

Evaluation Studies as Topic↗
PubMed1979

Summer and winter cycles in plasma melatonin levels in the elephant seal (Mirounga leonina).

Plasma melatonin concentration of immature male elephant seals was determined by radioimmunoassay. Comparison of concentrations during two 24-h periods, one in midsummer and one in midwinter, showed that there was a marked circadian cycle in winter which was greatly modified during the long day length of summer. It is suggested that in summer there was sufficient ambient lighting during the night hours to depress the nocturnal rise in plasma melatonin. The complexity of pineal cycles in the natural environment is stressed, and in this regard the polar regions are of particular interest due to the extreme seasonal changes in day length there.

Animals↗
PubMed1977

Avoidance-modified generalised distributions and their application to studies of superparasitism.

Given an underlying distribution for the number of encounters between parasites and a host this may be generalised by the distribution of the number of eggs per encounter. If eggs are already present, a parasite may avoid oviposition at subsequent encounters. A class of avoidance-modified generalised distributions is presented to model such situations. The case of a solitary (single egg-laying) parasite and a Poisson distribution for the number of encounters gives rise to a distribution of particular interest. Various properties of this distribution are derived and alternative estimation procedures investigated. Estimators based on the method of mean and zero frequency are shown to have the dual advantages over other estimators that have been proposed of simplicity of computation and increased efficiency. Over a wide range of parameter values there is virtually no loss of efficiency in comparison with maximum likelihood estimation.

Animals↗