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Biomedical subjects

R J Edwards

Publications and source records attributed to R J Edwards.

154 records · Page 9Linked to original sources
PubMed1976

Effect of heat acclimatization on intravascular responses to acute heat stress in man.

The effects of a 185-min exposure to 48 degrees C db/33 degrees C wb, on intravascular volume and osmolarity and on intravascular electrolyte, aldosterone, and cortisol concentrations have been studied in five male subjects before and after acclimatization to heat. Changes in the hematocrit and plasma protein concentration indicated that a hemodilution occurred during the first 35 min of the heat exposures, and that this was followed by a hemoconcentration. Although these changes in intravascular volume were not affected by acclimatization, the plasma volume after heat acclimatization was 6.7% greater than before. This increase in plasma volume was associated with an elevation in the ratio [Na]/[K]. However, since plasma osmolarity decreased the intravascular expansion could not be explained in terms of elevated electrolyte levels. Plasma aldosterone and cortisol levels were not affected by heat acclimatization, although both were elevated following exercise in the heat. It is concluded that the adrenal cortex is not an important factor in maintaining a state of heat acclimatization once a salt balance has been achieved.

Acclimatization↗
PubMed1976

Measurement of change in plasma volume during heat exposure and exercise.

The application of radio-iodinated human serum albumin (RISA) to the measurement of a continuously changing plasma volume, such as that occurring during heat exposure and exercise, has been considered in terms of the exchange dynamics of albumin between the intravascular and extravascular compartments. In six male subjects resting supine for 2 h in a hot environment, or exercising for 50 min in a thermoneutral or hot environment, there was no statistically significant alteration in the rate of protein efflux from the intravascular space. However, following exercise, protein was added to the circulation at a greater rate than it was lost through the capillary walls. A technique for calculating plasma volume from a single measurement of plasma RISA activity is described. This may be used in conjunction with measurements of changes in haemoglobin concentration of determining plasma volume in situations where alterations in protein exchange dynamics do occur.

Blood Circulation↗
PubMed1975

Distribution of levels of penicillin resistance among freshly isolated strains of N. gonorrhoeae. Application of a novel sensitivity assay.

A novel diffusion zone method of quantitative assay of the antibiotic sensitivity of bacterial strains was tested on freshly isolated gonococci. Smoothly variable estimates of the minimum inhibitory concentration of penicillin for these strains was obtained with sufficient accuracy and precision (coefficient of variation c. 10 per cent.) by means of a simple graphical analysis and without replication. Such estimates were free from the chief sources of error associated with the commonly applied 'incorporation' and 'diffusion' methods. The method revealed that 816 isolates of gonococci obtained in the Bristol area during a 6-month period fell into a large 'sensitive' group (MIC c. 0.02 unit per ml.) and three smaller more resistant groups, and that this pattern occurred in three widely spaced centres within the area. It is suggested that the method is capable of revealing details of distribution that may be masked by the usual techniques and that it is of wide applicability.

England↗
PubMed1975

Effect of exercise and thermal stress on plasma volume.

Six male subjects exercised for 50 min at 25% (light exercise) and 55% (moderate exercise) of their estimated aerobic capacities in environments of 42 degrees C db, 35 degrees C wb and 30 degrees C db, 24 degrees C wb, respectively. Alterations in the hematocrit, hemoglobin, and plasma protein concentrations, and in the activity of an injected aliquot of isotopically labeled albumin were each used to calculate the percentage change in plasma volume occurring during exercise and recovery. Changes in each measure were consistent with a reduction in plasma volume during exercise and a return to preexercise levels during recovery. There was no significant difference between the measures when exercising in the heat, but during the more severe exercise in the cooler environment disproportional changes in protein, hematocrit, and hemoglobin were observed. Disproportional changes were also seen during the recovery phase, when the hematocrit and hemoglobin concentration indicated a more rapid return of the plasma volume to preexercise levels than did either the plasma protein concentration or albumin activity. During moderate exercise and recovery there was a 1% decrease in red cell volume. It is concluded that exercise accelerates the rate of protein movement from extravascular compartments to the intravascular compartment, leading to elevated plasma protein levels during recovery which favor the return of water to the intravascular space. Hemoglobin concentration is considered to be the most reliable measure of plasma volume change during exercise.

Adult↗
PubMedDate not supplied

False elevation of amniotic fluid enzymes of relevance for prenatal diagnosis: creatine kinase measurement in relation to Duchenne muscular dystrophy.

The creatine kinase activity of amniotic fluid was measured in samples collected at fetoscopy. In our first study, the control sample range was 0.25 IU/l, although four samples had activities of 35-85 IU/l. Elevated values did not correlate with the activities in the fetal or maternal circulations. Electrophoresis revealed the presence of the BB isozyme of creatine kinase rather than just the MM form as expected. This suggested that the source of the elevated enzyme activity was from the myometrium, damaged by insertion of the trocar and cannula. In a further series the first 2 ml of amniotic fluid withdrawn yielded a much higher creatine kinase activity than a second aliquot. A control series of such second samples (first 2 ml discarded) gave an activity range of 0-7 IU/l with no spuriously high values. This compares favourably with a series from single samplings taken by amniocentesis. Normal creatine kinase activities were found in the amniotic fluids from 20 pregnancies at risk of Duchenne muscular dystrophy. We conclude that for accurate measurement of amniotic fluid enzyme activity the first portion withdrawn should be discarded. Amniotic fluid creatine kinase activity is of no value for the prenatal diagnosis of Duchenne muscular dystrophy.

Amniocentesis↗
PubMedDate not supplied

Errors in plasma creatine kinase estimations on fetal blood samples resulting from contamination with amniotic fluid and maternal blood: relevance for the prenatal diagnosis of Duchenne muscular dystrophy.

This paper presents a detailed analysis of the calculation of fetal plasma CK activity in fetal blood samples contaminated with amniotic fluid and maternal blood. The seemingly simple formula for this calculation, first presented by Mahoney et al. (1977), is actually more complex than it appears; values for up to nine variables, two of which can only be assumed, are needed. Small variations in certain variables may result in very large errors in the final calculated value of fetal plasma CK activity. Examples of diluted blood samples are considered and the effects of allowing for reasonable errors in the variables is explored. The main source of error is in the measurement of CK activities in the diluted blood sample and in the amniotic fluid. Contamination by blood originating from the maternal circulation can also be a large source of error, especially if the mother is a carrier of DMD and maintains a high level of plasma CK activity during pregnancy. Fetal blood indices have to be assumed; these may be a source of significant error, depending on the difference between the actual and assumed values. The measurement of fetal plasma CK activity by the indirect calculation method is discussed in the context of the prenatal diagnosis of DMD.

Amniocentesis↗
PubMedDate not supplied

Creatine kinase estimation in pure fetal blood samples for the prenatal diagnosis of Duchenne muscular dystrophy.

This paper compares the results of a survey of plasma creatine kinase (CK) activity measured in fetuses at-risk for Duchenne muscular dystrophy (DMD) with a reliable control series. Only pure fetal blood samples obtained by fetoscopy at between 17-24 weeks gestational age were used. Of the at-risk group 19 male pregnancies, mostly at low risk for DMD, proceeded to term with a normal outcome; there was no significant difference between their fetal plasma CK activities and the control group. Another 21 male pregnancies were terminated. This group included the highest risk mothers and hence was expected to contain a significant proportion of affected fetuses. The fetal plasma CK activity range was overlapping but significantly higher than the control group. No grossly elevated CK value was obtained. We conclude that, on average, DMD fetuses at this gestational age have higher plasma CK activity than controls. The problems of applying this finding to the prenatal diagnosis of DMD are discussed.

Creatine Kinase↗
PubMedDate not supplied

Successful limb salvage with prostaglandin infusion: a review of ergotamine toxicity.

OBJECTIVE: A case of severe acute peripheral arterial insufficiency secondary to ergotamine toxicity treated successfully with intravenously administered prostaglandin is presented to highlight the features of this condition and to demonstrate the efficacy of treatment with prostaglandin infusion. CLINICAL FEATURES: A 35-year-old unemployed Caucasian woman with a background of polypharmacy abuse and recurrent migraines presented to St Vincent's Hospital Emergency Department with limb-threatening ischaemia of both legs secondary to chronic ergotamine overuse. INTERVENTION AND OUTCOME: A prostaglandin infusion was started and a dramatic and rapid improvement of her peripheral circulation occurred within six hours. CONCLUSION: Ergotamine toxicity is an uncommon but well documented cause of peripheral vascular insufficiency that should be recognised and treated aggressively because its sequelae can be disastrous. Intravenously administered prostaglandin proved to be successful in this case and is a logical choice as first-line therapy for ergotamine toxicity.

Adult↗