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Biomedical subjects

N Wilson

Publications and source records attributed to N Wilson.

At least 235 records · Page 13Linked to original sources

Plasma vasopressin concentration in the anaesthetized dog before, during and after atrial distension.

Plasma vasopressin (AVP) concentration in dogs anaesthetized with chloralose was measured by radioimmunoassay and was within the range of 2-5 pg/ml. during control periods. Distension of the left atrium led within 2 min to a fall in plasma AVP concentration which reached a steady lower value within 4 min. After cessation of atrial distension the AVP concentration returned to pre-distention values within 4 min. Cooling the cervical vagosympathetic nerves to 8-10 degrees C led to a rise in plasma AVP concentration. Atrial distension during cooling of the vagi resulted in a further increase of plasma AVP concentration.

Animals↗

Reproducibility of histamine challenge tests in asthmatic children.

The measurement of bronchial reactivity by histamine challenge testing is of increasing clinical importance in paediatrics. By means of a simple tidal breathing technique for the measurement of histamine sensitivity (expressed as PC20--the concentration of histamine which produces a 20% fall in peak flow rate) in childhood asthma, the reproducibility of pairs of tests was estimated over one hour and 24-hour intervals in 22 children. Under carefully controlled conditions the 95% confidence limits of PC20 were 0.8-1.25 X baseline PC20 after one hour and 0.36-2.8 X baseline PC20 after 24 hours.

Adolescent↗

Distension of the pulmonary vein - atrial junctions and plasma vasopressin in the chloralose-anaesthetized dog.

The effects of localized distension of the pulmonary vein - left atrial junctions on plasma arginine vasopressin (AVP) have been examined in chloralose anaesthetized dogs. Pulmonary vein distension caused an increase in heart rate and a decrease in plasma AVP concentration. Cooling the vagosympathetic nerves to 10 degrees C caused an increase in arterial pressure and plasma AVP concentration and prevented the changes in heart rate and plasma AVP concentration caused by pulmonary vein distension. Cooling the vagus nerves to 16 degrees C did not change heart rate, arterial pressure, or plasma AVP concentration but significantly reduced the changes in heart rate and plasma AVP concentration caused by pulmonary vein distension. Propranolol (0.5 mg/kg) decreased heart rate and prevented the increase in heart rate associated with pulmonary vein distension but did not abolish the decrease in plasma AVP concentration. It is concluded that distension of the pulmonary vein - left atrial junctions causes a decrease in plasma AVP concentration by stimulating atrial receptors with myelinated afferent fibres. The decrease in plasma AVP concentration is not secondary to the reflex changes in heart rate caused by pulmonary vein distension.

Anesthesia, General↗

Objective test for food sensitivity in asthmatic children: increased bronchial reactivity after cola drinks.

Ten asthmatic children with a history of cough and wheeze after drinking a cola drink performed histamine inhalation tests before and 30 minutes after a drink of Pepsi-Cola, soda water, and water on three separate study days. There was no significant change in baseline peak expiratory flow after any of the three drinks. Sensitivity to histamine was increased after the cola drink (p less than 0.005) but was not significantly different after soda water or water. The detection of change in sensitivity to histamine appears to be a simple and effective method of testing for food sensitivity in asthma.

Adolescent↗

Controlled trial of slow-release aminophylline in childhood asthma: are short-term trials valid?

Slow-release aminophylline, although widely used for the prophylaxis of childhood asthma, has had only limited formal assessment. A four-month double-blind cross-over trial of slow-release aminophylline (14 mg/kg twice daily) was carried out in 24 children with perennial asthma. Satisfactory serum theophylline concentrations were obtained in 17 children, with few side effects. There was a significant improvement in mild daytime and night-time symptoms. The incidence of more severe symptoms was unaffected. Treatment did not improve the mean peak expiratory flow or reduce the incidence of use of bronchodilators. It is concluded that slow-release aminophylline has a place in the prophylaxis of perennial childhood asthma but is unsuitable for children who suffer from severe attacks. The cross-over trial design has severe limitations.

Adolescent↗

Haemodynamic and plasma vasopressin responses with high-dose fentanyl anaesthesia during aorto-coronary bypass operations.

Twelve male patients were given high dose fentanyl (75-100 microgram.kg-1) anaesthesia with oxygen during elective aorto-coronary bypass operations, and their haemodynamic and vasopressin responses were determined during induction, sternotomy, cardiopulmonary bypass, post-bypass and recovery periods. For comparison, a group of 12 male patients were anaesthetized with morphine, halothane 0.5 per cent, nitrous oxide and oxygen, and were similarly studied. Significant alterations in haemodynamics included increased mean arterial pressure after sternotomy in the fentanyl group, increased heart rate in both groups, increased systemic vascular resistance after sternotomy only in the halothane group, and decreased left ventricular stroke work index in both groups following induction, bypass, and during the recovery periods. Plasma vasopressin levels increased significantly in both groups during the bypass period, but returned to baseline levels following bypass. Serum sodium and osmolality did not change significantly, and urinary sodium and potassium excretion rose with the progress of the operation in both groups. A positive correlation was found between mean arterial pressure and vasopressin only in the halothane group. Systemic vascular resistance was correlated to vasopressin levels in both groups. Vasopressin response in both groups was similar, with significant but relatively low increases in levels during cardiopulmonary bypass. Fentanyl-oxygen anaesthesia did not provide haemodynamic stability in eight of 12 patients.

Adult↗

Arginine vasopressin response to anaesthesia produced by halothane, enflurane and isoflurane.

Some of the effects of inhalational anaesthetics may be mediated by beta-endorphins acting on opioid receptors. Stimulation of such receptors has been shown both to promote and to inhibit the release of arginine vasopressin (AVP). Ten rabbits were studied to determine the response of plasma AVP to a predetermined time/concentration "dose" of halothane, enflurane or isoflurane. Abolition of corneal reflex was used as a standard end-point. Plasma samples were obtained from awake animals and after exposure to the anaesthetics, the sequence being randomly assigned. No significant changes in plasma AVP concentrations were observed when predetermined time/concentration "doses" of the agents were administered to the rabbits. Anaesthesia produced by halothane, enflurane or isoflurane, therefore, is not necessarily accompanied by changes in plasma AVP.

Anesthesia, General↗

Antidiuretic effect of acute morphine administration in the conscious rat.

Morphine was administered intravenously to normal and to Brattleboro (genetically deficient in antidiuretic hormone) rats. The injection caused a significant decrease in mean arterial pressure and urine flow in all animals, including those homozygous for diabetes insipidus. It is suggested that the antidiuretic effect of morphine may occur independently of ADH release.

Animals↗

Time course of changes in plasma vasopressin during atrial distension.

Distension of the left atrium in chloralose anaesthetized dogs causes a diuresis and dilution of the urine. It has been reported previously that if distension of the atrium is maintained then urine flow reaches a peak after 50 min and then declines. A radioimmunoassay was used to measure plasma arginine vasopressin (AVP) at 10-min intervals before, during, and after atrial distension for 90 min. Plasma AVP decreased during atrial distension and did not increase until after the atrial distension was removed. Urine volume and free-water clearance increased and urine osmolality decreased, to reach maximum changes after 50 min. Although there was then a decline in some experiments, after reaching the peak changes, the mean values of the group did not show any statistically significant decline. Thus the urinary changes were also present for the 90 min of left atrial distension. The results are consistent with the hypothesis that the diuretic response to left atrial distension is dependent upon decreased release of AVP from the neurohypophysis.

Animals↗

Reducing severe diurnal bruxism in two profoundly retarded females.

Several diurnal audible teeth grinding (bruxism) was found to affect 21.5% of a profoundly retarded population. However, no previous research has treated bruxism in retarded individuals. In the current study a multiple baseline across subjects design was used to assess the effectiveness of contingent "icing," brief contingent tactile applications of ice, as a treatment for bruxism. Three 15-minute treatment periods and two 5-minute generalization periods were conducted 5 days per week. One resident displayed a 95% reduction in the percentage of intervals during which bruxism occurred during treatment periods and a 67% reduction during generalization periods. The other resident displayed a 94% reduction in the percentage of intervals during which bruxism occurred during treatment periods and a 53% reduction during generalization periods.

Adolescent↗

Artifactual complement activation by blood-drawing apparatus. A clinical and investigational caveat.

An increase in the occurrence of false-positive assays for C5a and C3 conversion, combined with hemolytic C assays discrepant between two laboratories, led to the suspicion that serum tubes with silicone separators might activate complement. Plasma incubated with some lots of such tubes showed evidence of complement activation via the alternative pathway, to an extent capable of influencing interpretation of results. The authors recommmend that such tubes not be used for C split-product assays, and be used only with caution for routine hemolytic C assays.

Blood Specimen Collection↗