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Biomedical subjects

S Rowlands

Publications and source records attributed to S Rowlands.

18 recordsLinked to original sources
PubMed1987

Pill-taking routine.

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Contraceptives, Oral↗
PubMed1986

A possible mechanism of action of danazol and an ethinylestradiol/norgestrel combination used as postcoital contraceptive agents.

Twenty-seven women requesting postcoital contraception were randomly allocated to take an ethinylestradiol/dl-norgestrel combination or danazol. Urine specimens were assayed for luteinising hormone (LH) and pregnanediol-3-glucuronide (P3G) levels from the day of the postcoital treatment to the next period. In addition, the urine samples of these recruits and 12 additional women were assayed for the Beta-subunit of human chorionic gonadotropin (B-hCG). A consistent pattern of alteration in urinary steroids was lacking, indicating a heterogeneous effect on ovarian function. There was no evidence of early pregnancy in successfully treated cases. We suggest that the main mechanism of action of these drugs is at the endometrial level.

Chorionic Gonadotropin↗
PubMed1979

Erythrocyte volume and count: a linear relation descriptive of population differences.

In a sample of 215 adult males the mean red cell volume decreases linearly with increasing red cell concentration. The mean corpuscular volume and the red cell count are found uncorrelated with age of subject. Of these subjects 69 are identified as smokers and 114 as nonsmokers. Linear regression analysis shows negative linear relation for the smoking-defined groups, with slopes judged to be no different. When the regression lines are constrained to be parallel the line for smokers is displaced upward by 2.7 fl. No difference is found in mean corpuscular haemoglobin concentration or reticulocyte count. Haematocrit, haemoglobin, mean corpuscular haemoglobin are also reported. Viscosity of blood is greater in smokers. Optical determination of cell volume and area confirms the linear relation of volume and count.

Adolescent↗
PubMed1977

Electronic measurement of red cell flow in micropipettes.

The velocity of human erythrocytes in flow-through tubes of diameter less than 5 mum is measured as a function of driving pressure. The electrical resistance in the lumen of the tube increases when a cell is present, so a pulse can be generated of length inversely proportional to velocity. In the apparatus described the pulses and driving pressure are fed to a computer which derives the correlation between pressure and velocity. Experiments confirm that the resistance to flow of erythrocytes in a narrow tube is substantially the same as that of the suspending medium. The apparatus is being used to study the effects of changes in erythrocyte deformability on flow.

Capillaries↗
PubMed1975

The stages of osmotic haemolysis.

The haemolysis of individual human erythrocytes has been observed using an inverted microscope and cine-camera. 2. With each permeant (glycerol, propylene glycol, ethylene glycol, urea and water) haemolysis is a multistage process. The stages are swelling, popping, reduction in volume possibly accompanied by ion leakage and, finally, haemoglobin leakage. 3. The classical haemolysis time (Th) is made up of a swelling time (Tsw) and a stress time (Tst). Tst is not negligible and with the faster permeants it may occupy more than 75% of the haemolysis time. 4. The stress time can also be divided into two parts: a K+ leak time (TK) during which the cell shrinks and a time (THb) during which haemoglobin is leaving the cell. THb occupies a substantial part of Th, from 25 to 65%, and is relatively longer in fast haemolysis. 5. There is a wide spread in the permeability coefficient to glycerol in a population of erythrocytes. The distribution is compatible with a Gaussian distribution. The mean permeability is 1-79 X 10(-6) cm/sec and the S.D. is +/0 0-45 X 10(-6) cm/sec. 6. The correlation between haemolysis time and swelling time for individual erythrocytes is poor, especially for fast haemolysis. Consequently, a measure of the distribution of haemolysis time does not give a related distribution of the swelling time or of the calculated permeability for individual erythrocytes.

Cell Membrane Permeability↗
PubMed1975

Flow through the bile duct after cholecystectomy.

The human bile duct has no intrinsic motility, but following cholecystectomy, flow through the bile duct is governed by the intraductal pressure generated by the liver, by the resistance to flow through the duct and sphincter at the terminal end of bile duct and by intraduodenal pressure. Pressure-flow experiments were performed upon 50 patients with biliary T-tube drainage following cholecystectomy and choledochostomy; nine patients had also undergone transduodenal sphincterotomy. Saline solution was introduced into the bile duct at controlled pressures, ranging from zero to 30 centimeters of water, while recordings were made of the flow rate of saline solution, intraduodenal pressure and respiratory movements. Although the flow rate of saline solution increased as its perfusion pressure was increased, three types of variation in flow were also recorded: rhythmic arrests of flow, occurring four to eight times per minute, believed to be due sphincteric contractions; nonrhythmic arrests of flow, lasting up to one minute, believed to be due to sphincteric contraction, and variations in flow associated with changes in intraduodenal pressure. The resistance to the flow of saline solution and the variations in flow rate were also similar in the patients who had undergone sphincterotomy. This study supports the view that sphincteric activity is present followingcholecystectomy, that the choledochal sphincter has rhythmic activity which differs from that of duodenal motility and that sphincter probably opens and closes continuously in a rhythmic manner during fasting periods in patients who have undergone cholecystectomy.

Bile Ducts↗