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Biomedical subjects

W F Walker

Publications and source records attributed to W F Walker.

At least 55 records · Page 3Linked to original sources
PubMed1982

Nucleotide sequences of 5S ribosomal RNA from four oomycete and chytrid water molds.

The nucleotide sequences of the 5S rRNAs of the oomycete water molds Saprolegnia ferax and Pythium hydnosporum and of the chytrid water molds Blastocladiella simplex and Phlyctochytrium irregulare were determined by chemical and enzymatic partial degradation of 3' and 5' end-labelled molecules, followed by gel sequence analysis. The two oomycete sequences differed in 24 positions and the two chytrid sequences differed in 27 positions. These pairs differed in a mean of 44 positions. The chytrid sequences clearly most resemble the sequence from the zygomycete Phycomyces, while the oomycete sequences appear to be allied with those from protozoa and slime molds.

Base Sequence↗
PubMed1982

Why smoke fewer cigarettes?

Sixteen volunteers were tested when smoking their own brand of cigarettes normally and when smoking half their usual number of cigarettes. While smoking half their usual amount the subjects changed their inhalation behaviour. Over this period the percentages of carboxyhaemoglobin were not significantly different from steady-state values where plasma nicotine concentration rose significantly. With the reduction in cigarettes there were significant falls in haemoglobin concentration, packed cell volume, and red cell count. These findings suggest that the advice given to patients to smoke fewer cigarettes should be accompanied by a warning against increasing inhalation. Patients who say that they have reduced their smoking but who have unaltered carboxyhaemoglobin concentrations should not be discredited.

Adult↗
PubMed1982

In vitro evaluation of U.S. and U.S.S.R. artificial hearts.

This report summarizes the results of the in vitro evaluation of Soviet and American artificial hearts. The devices were tested at the All-Union Institute of Transplantation and Artificial Organs, Moscow, U.S.S.R., and Baylor College of Medicine, Houston, Texas, U.S.A. These studies were designed to standardize procedures to allow comparison of artificial ventricles of different designs. Also, these studies might provide a means for evaluation of other characteristics such as hemolysis, durability, and reliability. Static and dynamic tests were performed, varying preload, afterload, rate, and systolic and diastolic time intervals. All designs demonstrated comparable function curves with capability of taking over the pressure and volume work of the natural heart.

Blood Flow Velocity↗
PubMed1982

The usefulness of naftidrofuryl in severe peripheral ischaemia--a symptomatic assessment using linear analogue scales.

The effect of Naftidrofuryl (Nafronyl) on the symptoms of severe peripheral vascular disease has been studied in 40 hospital inpatients. Assessment of ischaemic symptoms and of symptoms which may occur with any type of chronic pain was made using a linear analogue system. Patients treated with naftidrofuryl showed a significant symptomatic improvement compared to patients treated without vasoactive drug therapy. These results show that this drug has a useful place in the treatment of severe ischaemic symptoms during assessment for vascular reconstruction and in those patients found to be unsuitable for limb-salvage operations.

Aged↗
PubMed1981

Colonic mucosal-submucosal blood flow and the incidence of faecal fistula formation following colostomy closure.

Fistula formation following closure of a colostomy occurs most frequently when closure is carried out within the first few weeks of construction and may be related to an impaired local microcirculation. Using a recently described method for measuring colonic mucosal-submucosal blood flow, the variations in local flow which occur during the first month after colostomy construction were determined in 8 patients. Mean blood flow increased from 6.9 +/- 1.8 ml min-1 100 g-1 (s.d.) at 7 days to 31.1 +/- 12.5 ml min-1 100 g-1 (s.d.) at 28 days. In a further 40 consecutive patients undergoing colostomy closure, blood flow measurements were made before operation. Eight patients developed a faecal fistula, and in 5 of these patients mucosal-submucosal blood flow was found to be less than 15 ml min-1 100 g-1. In every successful colostomy closure blood flow was greater than 15 ml min-1 100 g-1. This study provides evidence that a subnormal blood flow is one of the factors associated with fistula formation following the operation of colostomy closure.

Colon↗
PubMed1981

Changes in human colonic mucosal-submucosal blood flow after body surface cooling.

Mucosal-submucosal blood flow in the human colostomy was measured by a radioisotopic washout technique. Changes in blood flow were recorded in 10 subjects after peripheral vasoconstriction evoked by surface cooling of the body. Accompanying the vasoconstriction was a rise in mucosal-submucosal blood flow of approximately 40%. An interpretation of the blood flow changes and the associated alterations in mean arterial blood pressure provide evidence for vasomotor and local regulatory control in the colostomy microcirculation. We believe, therefore that the colostomy is a suitable preparation for studying the human colonic microcirculation.

Cold Temperature↗
PubMed1981

Amputation of the ischemic limb: selection of the optimum site by thermography.

This report describes the value of infrared thermography in assessing the optimum level of amputation of an ischemic limb. Interpretation of thermograms and the factors that can significantly alter the thermal image of the lower limbs are detailed. Results from 104 patients demonstrate that the thermographic method is a reliable indicator of the level of a major limb amputation. A rationale for the inadequacy of the method when attempting to determine the outcome of a partial foot amputation is considered.

Adult↗
PubMed1980

The measurement of colonic mucosal-submucosal blood flow in man.

1. A method is described for the measurement of colonic mucosal-submucosal blood flow in man, by studying surgically created colostomies. 2. A local radioisotopic clearance technique utilizing a stable preparation of [125I]4-iodoantipyrine is employed. The indicator is injected directly into the colostomy under study and its gamma emission is recorded by a scintillation detector. 3. A radioautographic study was carried out at laparotomy in humans to facilitate the interpretation of the recorded washout curves. This demonstrated that the tracer was cleared from both the mucosa and submucosa throughout the period of study. 4. Mucosal-submucosal blood flow was calculated according to Kety (1949) from the monoexponential clearance curves obtained, and amounted to 31.7 +/- 11 ml./min. 100 g (S.D. of an observation, n = 30). 5. The results from two consecutive measurements in seventeen patients showed that the mean change between first and second readings was not significant (t test). In addition the between-patient variation (12.2) was significantly greater than the within-patient variation (2.6) for consecutive recordings (F test; P less than 0.01). 6. The within-patient between-days variation (12.9; n = 10) was found to be similar to the between-patient variation. 7. It is concluded that the technique permits measurement of local colonic blood flow in man and by consecutive measurements, it may be used to evaluate local changes in blood flow following reflex or pharmacological stimulation.

Autoradiography↗
PubMed1980

Tissue pH electrodes for clinical applications.

The reduction of peripheral blood flow, which occurs during shock or in patients with occlusive arterial disease of the lower limb is accompanied by an increase in hydrogen ion activity in tissue cells. If this change could be measured, it could possibly be used as an indicator of tissue perfusion in such patients. Investigations have been carried out into various pH microelectrode designs in order to construct one which could be used clinically to measure extracellular pH changes in skin. Experiments with antimony and externally insulated glass micro-electrodes demonstrated that these were unsatisfactory for the purpose. The successful design was insulated internally by means of a glass to glass fuse. It was robust, stable, sensitive and had a fast response time. Use of the electrode in normal volunteers produced reproducible skin pH values and demonstrated the feasibility of the system. Preliminary results using the micro-electrodes in patients indicate their possible application to the assessment of peripheral vascular disease, and to the monitoring of patients under intensive care.

Antimony↗
PubMed1979

Measurement of tissue pH in skin by glass microelectrodes.

Alterations in metabolic activity may be used as an indicator of tissue perfusion and haemodynamic status in peripheral ischaemia. A new type of microelectrode was used to measure pH in the skin of patients with vascular disease, and a decrease in pH was demonstrated along the leg, commensurate with the severity of the disease. Measurement of skin pH by this technique is easy and may be useful for assessing tissue perfusion or skin viability in other conditions.

Glass↗
PubMed1979

Micro-electrode measurement of skin pH in humans during ischaemia, hypoxia and local hypothermia.

1. The extracellular pH value in the dermis of human skin (skin pH) was measured in vivo using glass micro-electrodes. They were found to be both reliable and accurate. 2. The mean value of skin pH measured in the legs of forty different volunteers was found to be pH 7.54 +/- 0.09 (S.D.). No difference in skin pH was observed between males and females, or in different regions of the limb. 3. Local reductions in skin surface temperature in ten subjects caused an increase of pH 0.023 +/- 0.007 per degree C fall. 4. A 20 min period of tourniquet ischaemia in twenty volunteers induced a fall in skin pH of 0.13 +/- 0.05 units. 5. Hyperventilation during a 10 min period of breathing 10% O2 in N2 caused an increase of pH 0.04 +/- 0.02 in the skin of healthy subjects. 6. Skin pH fell to a value 0.02 +/- 0.02 units below normal 10 min after the hypoxic period, suggesting the presence of excess lactate. 7. Skin pH results compared well with blood gases and pH values of arterialized samples taken during hypoxia. 8. It was concluded that the system was suitable for clinical trials.

Adult↗