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Biomedical subjects

J Crofton

Publications and source records attributed to J Crofton.

At least 37 records · Page 2Linked to original sources
PubMed1985

Changes in plasma arginine vasopressin during transition from fetus to newborn following minimal trauma delivery of lambs and goats.

Vasopressin in umbilical arterial and venous blood is high at delivery and may be important in the maintenance of arterial pressure and absorption of lung liquid. We used chronically instrumented near-term fetal lambs and goats to investigate the changes in plasma vasopressin that occur during perinatal cardiovascular transition following cesarean section without labor. Plasma arginine vasopressin was more than 5 times greater 15 min following birth than immediately prior to clamping the umbilicus, and it fell progressively over the ensuing 2-5 h to levels not significantly different from before birth. Fifteen min after delivery, neither arterial pressure, blood gases, nor pH appeared to account for the increase.

Animals↗
PubMed1984

The gathering smoke clouds: a worldwide challenge.

Based on the 1983 WHO Expert Report, Smoking control strategies in developing countries, the problem in these countries is briefly reviewed. Many countries are well on the way to adding a formidable epidemic of smoking related diseases to their already overwhelming health problems. Rational policies of prevention are reasonably well understood. But, just as in developed countries, the difficulty is to get them applied. Doctors in the industrialized world could do much to support their colleagues in the threatened countries. All of us should feel a responsibility towards helping to prevent the tragedy.

Asia, Western↗
PubMed1984

Effect of vertebral, carotid and intravenous infusions of lysine vasopressin on plasma vasopressin and cardiovascular function.

The cardiovascular and vasopressin-releasing effects of vertebral artery, carotid artery and intravenous (i.v.) infusions of lysine vasopressin (150 microU/kg X min) were studied in anesthetized dogs. Vertebral and carotid artery infusions of lysine vasopressin led to similar decreases in cardiac output as i.v. infusions. Heart rate, however, decreased to a greater extent with vertebral and carotid artery infusions of lysine vasopressin than i.v. infusions. There were no changes in either mean arterial blood pressure or the plasma vasopressin concentration. The results indicate that peripheral vasopressin: has a central effect to reduce heart rate; has a peripheral effect on the heart to reduce cardiac output, and probably does not feed back to inhibit its own release.

Animals↗
PubMed1982

Morphometric studies of the renomedullary interstitial cells of Dahl hypertension-prone and hypertension-resistant rats.

Two strains of rats, one genetically sensitive (the Dahl S rat) and the other resistant (the Dahl R rat) to the hypertensive effect of a high-salt diet were studied morphometrically for determination of whether any anatomic differences were present in the renomedullary interstitial cells (RICs) that might help explain these strain differences. The rats resistant to the hypertensive effects of sodium chloride had more RIC than those from the sensitive strain. In addition, they were more heavily granulated. These findings may be related to the known antihypertensive function of the RICs and may help explain observed differences in the prostaglandin metabolism of the Dahl S and R rats.

Animals↗
PubMed1980

Removal of immunoreactive arginine vasopressin by the perfused rat liver.

To assess the ability of the liver to remove immunoreactive arginine vasopressin (AVP) from the circulation and to determine the effect of certain metabolic factors on the process, a study was carried out with rat livers perfused at 37 C with an oxygenated albumin--electrolyte solution containing AVP (117 +/- 4.5 muU/ml). In controls, the hepatic clearance of AVP was 795 +/- 120 microliter/min (SEM). The addition of AVP in concentrations up to 9029 microU/ml, perfusion with a glucose-free medium, or perfusion without oxygen did not significantly alter the hepatic clearance of AVP. However, perfusion with cold medium (11 C) significantly altered AVP removal in that initially AVP removal increased, while later on AVP removal became completely inhibited. This phenomenon may possibly be a consequence of a cold-induced increase in hepatic AVP trapping which is rapidly saturated due to a cold-induced depression of AVP transport and degradation. Support for this thesis was provided by finding that high AVP concentrations depressed the cold-endhancing removal phase.

Animals↗
PubMed1979

The handling of immunoreactive vasopressin by the isolated perfused rat kidney.

Using the isolated rat kidney perfused with an artificial medium containing glucose as the sole fuel, we studied the renal handling of immunoreactive arginine vasopressin (AVP) and determined the effect of various factors on the ability of the kidney to remove AVP. In control kidneys perfused with AVP at concentrations below 116 muU/ml, the organ clearance of AVP (OC(AVP)) was 1,145+/-47 (SE) mul/min, whereas glomerular filtration rate (GFR) averaged 515+/-37 mul/min. Filtration could thus account for up to 45% of the OC(AVP), the balance presumably being cleared from the peritubular circulation. Of the AVP filtered, only 38% could be recovered in the urine (urinary clearance AVP averaged 205+/-12 mul/min) suggesting that the balance was taken up by the tubular epithelium and degraded. Fractional excretion of filtered AVP rose significantly in the presence of anoxia and cold (10 degrees C) to 49 and 59%, respectively, but was not affected by ouabain or high levels of AVP (458+/-58 muU/ml). The OC(AVP) was not significantly altered by the absence of glucose in the perfusate, anoxia, or ureteral ligation, maneuvers that were associated with significant reductions in GFR. In these and the control experiments, there was a significant inverse correlation between GFR and peritubular clearance emphasizing the importance of the latter (r = -0.749; P < 0.001). Cold, ouabain, and high concentrations of AVP reduced the clearance of AVP by the kidneys. On the basis of these studies we conclude that the kidney clears AVP from the circulation via two pathways, glomerular clearance and peritubular clearance. This exposes both the luminal and contraluminal surfaces of the tubular cells to the hormone, allowing these cells to remove AVP from the filtrate and the peritubular compartment. Noteworthy is the observation that under several conditions when GFR falls reducing the glomerular clearance of AVP, peritubular clearance increases and the total clearance of AVP by the kidney remains constant.

Albumins↗
PubMed1978

Variations in chemical mediators of hypersensitivity in the sputum of chronic bronchitics: correlation with peak expiratory flow.

Histamine, slow reacting substance of anaphylaxis (S.R.S.-A), IgE, eosinophils, and an eosinophil-associated enzyme, arylsulphatase IIB, were measured in sputum from 11 chronic bronchitics at weekly intervals for 6 weeks. The agents were detected in all patients at some time and in the majority at all times throughout the study period although their concentrations varied. The variations in histamine, S.R.S.-A and IgE gave a highly significant negative correlation with the peak expiratory flow-rate, suggesting that chemical mediators of hypersensitivity may play some role in the pathogenesis of airways obstruction in this disease. Sputum eosinophilia correlated with the arylsulphatase IIB concentration but not with the peak expiratory flow-rate, IgE, histamine, or S.R.S.-A, a finding consistent with the view that eosinophils accumulate at the site of type I reactions after the peak of mediator release.

Bronchitis↗
PubMed1978

Diffuse pulmonary abnormalities: clinical correlations.

The clinical correlations of diffuse pulmonary opacities, visible on the chest X-ray, are reviewed and the main diagnostic investigations outlined. Clinically the patients are classified into those with fever; those with no symptoms; those with cough, malaise and loss of weight, but no fever; and those with dyspnoea as the main symptom. The possible diseases giving rise to each group of manifestations are reviewed and the differential diagnosis discussed.

Body Weight↗