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Biomedical subjects

R I Menzies

Publications and source records attributed to R I Menzies.

9 recordsLinked to original sources
PubMed1994

Levels of active and inactive reninlike enzymes in plasma and reproductive tract of the pregnant wallaby.

Active and total (acid-activated) levels of a reninlike enzyme (hereafter called renin) were measured in plasma, tissues, and yolk sac fluid of pregnant and postpartum wallabies. Plasma active renin generated angiotensin I (ANG I) from sheep angiotensinogen at 14 +/- 1.3 (SE) ng.ml-1.h-1, whereas acid-activated renin generated ANG I at 33.3 +/- 2.5 ng.ml-1.h-1, i.e., 44.2 +/- 3.7% of renin in plasma was active, and 58 +/- 3.7% was inactive. Inactive renin levels were highest in pregnant animals (P = 0.05). Uterine renin was mainly inactive (95%); levels were 5.1 +/- 1.1 times plasma levels. The levels of renin in nonpregnant uteri were the same as those in pregnant uteri from the same animals. Uterine renin levels did not change with gestation. Pooled acid-activated yolk sac fluid generated ANG I at low rates (0.7 and 1.6 ng.ml-1.h-1); the acid-activated supernatant of a homogenate of pooled fetal membranes generated ANG I at 15 ng.g wet wt-1.h-1. Yolk sac fluid was strikingly different in electrolyte composition from maternal plasma. Its lower osmolality suggests that the membranes separating it from maternal plasma have a low permeability to water. Thus, although eutherian and marsupial mammals diverged 136-164 million years ago, the wallaby, like many eutherian mammals, has inactive renin in blood, in the female reproductive tract, and in fetal membranes.

Animals↗
PubMed1993

The effects of a converting enzyme inhibitor (captopril) and angiotensin II on fetal renal function.

1. Renal function was studied in chronically catheterized fetal sheep (119-128 days gestation), before and during treatment of the ewe with the angiotensin converting enzyme (ACE) inhibitor, captopril, which crosses the placenta and blocks the fetal renin angiotensin system. 2. An i.v. dose of 15 mg (about 319 micrograms kg-1) of captopril to salt-replete ewes followed by an infusion to the ewe of 6 mg h-1 (about 128 micrograms kg-1 h-1) caused a fall in fetal arterial pressure (P < 0.01), and a rise in fetal renal blood flow (RBF) from 67.9 +/- 5.6 to 84.9 +/- 8.3 ml min-1 (mean +/- s.e. mean) (P < 0.05). Renal vascular resistance and glomerular filtration rate (GFR) fell (P < 0.01); fetal urine flow (P < 0.01); fetal urine flow (P < 0.01) and sodium excretion declined (P < 0.05). 3. Ewes were treated for the next 2 days with 15 mg captopril twice daily. On the 4th day, 15 mg was given to the ewe and fetal renal function studied for 2 h during the infusion of captopril (6 mg h-1) to the ewe. Of the 9 surviving fetuses, 3 were anuric and 3 had low urine flow rates. When 6 micrograms kg-1 h-1 of angiotensin II was infused directly into the fetus RBF fell from 69 +/- 10.1 ml min-1 to 31 +/- 13.9 ml min-1, GFR rose (P < 0.05) and urine flow (P < 0.01) and sodium excretion increased in all fetuses. 4. It is concluded that the small fall in fetal arterial pressure partly contributed to the fall in fetal GFR but in addition, efferent arteriolar tone fell so that the filtration pressure fell further. Thus maintenance of fetal renal function depends on the integrity of the fetal renin angiotensin system. These findings explain why use of ACE inhibitors in human pregnancy is associated with neonatal anuria.

Angiotensin II↗
PubMed1992

The feasibility of using a double blind experimental cross-over design to study interventions for sick building syndrome.

Methodological problems have limited scientific investigation of the causes of and solutions for sick building syndrome. The feasibility of using an experimental double blind cross-over study to resolve many of these methodological problems was assessed in a pilot study. The experimental intervention was to vary the amount of outdoor air from 10 cubic feet per minute per person (cfmpp) to 20 cfmpp or 50 cfmpp by central manipulation of the building heating, ventilation and air-conditioning (HVAC) system. Over 6 consecutive study weeks, 2 trials of rates were administered in random order. Study subjects and investigators of the study were blinded to intervention sequence. Unblinding, office environment rating and symptom occurrence were measured weekly. Of 305 eligible workers, 254 participated. Problems were encountered in delivering the lowest dose of ventilation due to building leakage. The prevalence of symptoms diminished steadily over the 6 study weeks, time trends which could be controlled by recommended design modifications. Blinding to the intervention was successfully maintained. Weekly non-response did not introduce a response bias but reduced the number of subjects available for analysis by one-third for each trial. We conclude that this design, with certain modifications, is feasible to evaluate many proposed interventions for sick building syndrome.

Adult↗
PubMed1992

Acute effects of captopril, an angiotensin-converting enzyme inhibitor, on the pregnant ewe and fetus.

After control measurements had been made, 15 chronically catheterized pregnant ewes (gestational age 123-141 days) were given 15 mg of captopril intravenously followed by an infusion of 6 mg/h. These doses blocked the pressor responses of both ewes and fetuses to 5 micrograms of angiotensin I. After captopril, maternal mean arterial pressure fell from 94 +/- 3.5 to 88 +/- 3.6 (SE) mmHg (P less than 0.0001) and pulse interval fell (P = 0.008). Maternal flow to the cotyledons fell from 766 +/- 118 to 525 +/- 77 ml/min (P = 0.002), as did flow to the remainder of the maternal placenta, i.e., the caruncles and their underlying myoendometrium (control flow 188 +/- 35 ml/min, flow 10-15 min after captopril 166 +/- 36.1 ml/min; P = 0.021). Flow to the rest of the myometrium did not change. Fetal arterial pressure fell from 46.9 +/- 1.6 to 44.1 +/- 1.6 mmHg (P less than 0.009), and fetal placental blood flow fell from 639.9 +/- 93.2 to 413.1 +/- 53.9 ml/min (P = 0.025). Flow to the fetal membranes declined also, from 53.2 +/- 6.5 to 35.6 +/- 3.3 ml/min (P less than 0.005). Maternal and fetal renal blood flows and fetal adrenal blood flows were unchanged. Fetal arterial PO2 was initially 19.5 +/- 0.8 mmHg; after captopril, it was 17.7 +/- 0.9 mmHg (P = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1991

The relationships between fetal and maternal placental blood flows.

Individual maternal and fetal flows to 706 placental cotyledons obtained from 9 chronically catheterized pregnant ewes and their fetuses (gestation age 123-141 days) were measured. The larger the cotyledon the greater the maternal and fetal blood flow to it. Both fetal and maternal flows to larger cotyledons, however, tended to be lower when corrected for the weight of the cotyledon perfused. Changes in fetal placental flow (dfgc, ml/min/g) occurring within 15 min of administration of 15 mg i.v. of captopril to the ewe were dependent on changes in fetal placental vascular resistance (dcotfr) and maternal flow (dmgc) according to the equation dfgc = 0.123 + 0.185 dmgc - 0.026 dcotfr. Changes in maternal placental flow occurring within 15 min of administration of 15 mg i.v. of captopril to the ewe were dependent on changes in maternal placental vascular resistance (dcotmr) and changes in fetal flow according to the equation dmgc = 0.483 + 0.496 dfgc - 0.0198 dcotmr. The changes in fetal flow over the next 1.5h of treatment with captopril at 6 mg/h were dependent on neither changes in fetal placental vascular resistance nor maternal placental flow. changes in maternal placental flows over the same time were no longer related to changes in fetal flow and depended only to a minimal extent on changes in maternal placental resistance. These analyses suggest that treatment of the pregnant ewe with captopril may have disturbed the normal relationships between maternal and fetal placental circulations.

Animals↗
PubMed1986

Tuberculous peritonitis in Lesotho.

Tuberculous peritonitis, although a common cause of ascites in Africa, previously was rarely diagnosed in Lesotho. We evaluated prospectively 105 consecutive patients admitted with ascites: tuberculosis accounted for 42% of the cases. Clinical differentiation from other causes of ascites proved to be difficult: signs and symptoms commonly associated with this disease were non-specific and often absent. The majority of our patients were elderly, male and alcoholic. Mortality was 26% despite treatment, and was highest among the aged and those who abused alcohol.

Aged↗
PubMed1985

Laparoscopic diagnosis of ascites in Lesotho.

In a prospective study of 98 consecutive patients with undiagnosed ascites examined by laparoscopy a correct immediate diagnosis was made in 76 (78%) and a final diagnosis in 92 (94%) of those who underwent laparoscopy. Visual diagnosis was highly accurate in patients with tuberculous peritonitis but only moderately accurate in those with carcinomatosis and liver disease. When the laparoscopic findings were compared with histological and microbiological results visual diagnosis was found to be the most accurate diagnostic method. Laparoscopy may readily be used in rural hospitals for diagnosing ascites.

Ascites↗