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Biomedical subjects

D A Griffiths

Publications and source records attributed to D A Griffiths.

At least 37 records · Page 2Linked to original sources
PubMed1982

Allometry and multivariate growth revisited.

Turner (1978) introduced a class of deterministic models to describe multivariate growth processes along with a least squares fitting procedure. Turner's fitting procedure is shown to be ill founded and the methods of inference associated with it dangerously misleading. An alternative class of stochastic models is introduced; this is largely based on Turner's generalization of allometry and the Lotka-Volterra equations. The associated fitting procedure is the method of maximum likelihood which allows valid inferences to be made. As an example of the superiority of this new class of models in describing multivariate growth processes one of the data sets analysed by Turner is reconsidered here. Some general comments are made on Turner's analysis of the famous lynx and hare data.

Animals↗
PubMed1981

Economic evaluation of health services. Concepts and methodology applied to screening programmes.

This methodological review seeks to explain the different levels of economic analysis, whose nature and use are often ill understood. These include analyses of cost-productivity, cost-effectiveness, and cost-benefit. The types of costs to be considered are then identified and classified into four groups according to whether they are direct or indirect, and visible or invisible. A numerical practical example of the cost-effectiveness of a breast cancer screening programme is used to demonstrate the techniques used in practice, and the types of problems and questions which may occur. The paper concludes that the development of epidemiological and economic models can make a significant contribution to the analysis of the complex interrelationships which prevail in the health services, and to the identification of aspects crucial for research and decision making concerning intervention strategies.

Breast Neoplasms↗
PubMed1980

The significance of certain skin characters of sheep in resistance and susceptibility to fleece-rot and body strike.

Micro-anatomical differences in skin structure associated with resistance and susceptibility of sheep to fleece-rot and body strike were identified, and found to be of similar magnitude in 2 genetically divergent flocks of medium-woolled Merino ewes. Susceptible sheep were characterised by smaller follicle groups, resulting in higher densities of follicle populations with greater concentrations of the primary follicles (and sudoriferous glands) than in the resistant sheep. From these smaller follicle groups of susceptible sheep, thicker wool fibres grew than were found in the resistant sheep. The significance of these findings is discussed in relation to the pathogenesis of fleece-rot and body strike of sheep, and the value of the measured skin characters as a method for identifying resistant sheep.

Animals↗
PubMed1979

Flotation technique for quantitative determination of mite populations in powdered and compacted foodstuffs.

Samples are preheated in 25% aqueous ethanol at 65 degrees C for 5 min. A specially designed flotation flask and solvent mixture of kerosene-tetralin (1+1) is used to form an interface with 25% aqueous ethanol. Mites, insects, and insect fragments are separated from vegetative material by an overflow method. Trials incorporating a known number of mites in samples of pigmeal indicate that at an infestation level of 1000 mites/kg the method always recovered 70% of the population and at 2000 mites/kg, 75%. The method permits collection of mite specimens for microscopic examination as well as allowing differentiation between live and long-dead insects. It does not use highly volatile solvents or corrosive acids. The apparatus has been successfully tested for quantitatively determining mite populations in flour, dried skimmed milk, animal feedstuffs, soya meal, wheat, rape seed, dates, and house dust. It has also been used to estimate insect contamination in packaged dates.

Acari↗
PubMed1978

Behaviour of solute and particle markers in the stomach of sheep given a concentrate diet.

1. Fistulated sheep given a concentrate diet were used to study the behaviour of solute ([51Cr]EDTA) and particle ([103Ru]phenanthroline) markers in the stomach under conditions of continuous feeding. 2. An injection of a mixed dose of [51Cr]EDTA and [103Ru]phenanthroline was given into the rumen and the time course of marker concentrations in the rumen and the abomasum was recorded. The curves were analysed on the assumption that the stomach of the sheep could be represented as two mixing compartments (reticulo-rumen and abomasum) and a time delay (omasum). This model provided a very good description of the data. 3. [103Ru]phenanthroline associated with small particles was retained in the rumen much longer than [Cr]EDTA. Although exchange of [103Ru]phenanthroline occurred between large and small particle fractions, the results suggested that small particles may have been retained somewhat longer in the rumen than solutes. However, it was clear from the results that the mean retention times for particulate matter in the rumen could not be simply obtained using adsorbable markers. 4. Cyclical fluctuations in the concentration of [51Cr]EDTA in the rumen indicated that there were daily variations in net water flux in the rumen. 5. The presence of protozoa was associated with much shorter retention times of both solutes and particles in the rumen. Protozoa were also associated with reduced rumen volumes.

Abomasum↗
PubMed1977

Respiratory disease associated with practolol therapy.

Six patients who had surgical treatment for sclerosing peritonitis caused by practolol now have a respiratory disorder characterised by dyspnoea, extensive fibrotic pleural thickening, and lesions in the lung parenchyma. Respiratory disease appears to be a further feature of the practolol syndrome.

Aged↗
PubMed1977

Sclerosing peritonitis due to practolol: a report on 9 cases and their surgical management.

Nine patients with an unusual and serious intraabdominal complication of the beta-adrenergic blocking agent practolol seen since 1973 are reported. The striking and bizarre peritoneal changes induced by the drug have distinctive features that are not shown by other forms of peritoneal disease. The cases presented with small bowel obstruction, usually chronic in type and often associated with profound weight loss and an abdominal mass. Characteristic radiological features were present. The abnormalities at laparotomy were impressive, with a gross proliferation of the visceral peritoneum which formed a dense white cocoon which encased, constricted and markedly shortened the small bowel, usually from the duodenojejunal flexure to the ileocaecal valve. The obstruction was relieved by mobilizing the small bowel from the ensheathing tissue. Restoration of alimentary function after surgery was delayed but the long term result was satisfactory with full relief of symptoms and the absence of recurrent obstruction during the follow-up period. This complication may arise after treatment with the drug has been stopped, and although long term oral therapy has been discontinued, further cases will almost certainly present for some time to come.

Aged↗
PubMed1976

Single-dose peroperative antibiotic prophylaxis in gastrointestinal surgery.

A single intravenous dose of tobramycin and lincomycin, given at the start of gastrointestinal operations, significantly reduced the incidence of postoperative wound infection from 34% to 5%. The occurrence of both anaerobic and aerobic bacteria was reduced. Therapeutic concentrations of the antibiotics were maintained throughout the operative period in most cases. No toxic effects of the antibiotics were detected, no anaesthetic complication occurred, and resistant strains of bacteria normally sensitive to the antibiotics were not isolated from wounds.

Adolescent↗
PubMed1976

The relationship between the transfer of immunoglobulins, sodium and potassium into mammary secretion of the parturient ewe.

The experiment comprised two sections. First, radiotracer techniques were used to study the metabolism of IgG1 and IgG2 in 5 non-pregnant and 4 pregnant ewes. In the pregnant ewes, the rates of synthesis for IgG1 and IgG2 were similar to the rates observed in non-pregnant animals. However, the irreversible loss of IgG1 was significantly greater than IgG2 in pregnant ewes and IgG1 in non-pregnant ewes. Additionally, it was found that most of the IgG1 and virtually all of the IgG2 in mammary secretion was serum derived. Secondly, the levels of sodium, potassium and lactose and the selective index for IgG1 in mammary secretions of 5 pregnant ewes were monitored over the parturient period. The values of all the measures remained relatively constant until one day before parturition. From one day pre-partum, the levels of potassium and lactose in mammary secretion began to increase and had risen 2-3 fold by 5 days post-partum. Over the same period, the selective index for IgG1 decreased 20 fold, wehreas the level of sodium fell from approximately 32 mmol/l to 18 mmol/l. The concentration of IgG1 in plasma slowly declined from approximately 23 g/l to 15 g/l over the last 10 days of pregnancy. During the parturient period, the decline in plasma IgG1 levels, in comparison with IgG2, without alteration in the rates of synthesis of either immunoglobulin, supports the hypothesis that selective transport of IgG1 into mammary secretion occurs without degradation. The results also indicate that the transport of sodium and potassium into mammary secretions are altered over the parturient period.

Animals↗