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Biomedical subjects

L Carmichael

Publications and source records attributed to L Carmichael.

70 records · Page 4Linked to original sources
PubMed1981

Effects of synthetic glucocorticoid administration on human fetal breathing movements at 34 to 35 weeks' gestational age.

Fetal breathing movements were measured in six women who had received exogenous glucocorticoids throughout pregnancy and in whom the endogenous circadian rhythm in cortisol was absent or had been suppressed. Studies were performed for 24-hour observation periods while women received prednisone and then one week later on the same women after equivalent doses of dexamethasone. Fetal breathing movements occurred 29.9% +/- 1.9% of the time in the prednisone-treated group and this was not changed in the same fetuses after dexamethasone treatment. There was a significant increase in the percentage of time spent making breathing movements during the second and third hours following breakfast, lunch, and dinner (P less than 0.001). A fourth peak in fetal breathing activity occurred in the late evening and seemed to be related to the time of the evening glucocorticoid medication. These data were compatible with the hypothesis that maternal glucocorticoid concentrations may influence patterns of fetal breathing movements at 34 to 35 weeks' gestational age.

Blood Glucose↗
PubMed1981

Effects of external physical stimulation on fetuses near term.

Measurements were made in 17 healthy pregnant women between 36 and 42 weeks' gestational age 90 minutes before and after a standard physical stimulus. The mean fetal heart rate was 138 +/- 0.4 bpm; the median value of the 5-minute standard deviation of successive heartbeat intervals was 30.3 msec, and the percentage of time spent making gross fetal body movements was 11.1% +/- 0.4%. These measurements did not change following stimulation of fetuses. Fetal breathing movements diminished over the 180-minute observation period but did not appear to be changed by fetal stimulation. During studies, periodic increases separated by periodic decreases in fetal heart rate, fetal heart rate variability, gross fetal body movements, and fetal breathing movements were measured, and these changes did not seem to be related to external stimulation of fetuses. Periodic changes in these measurements may have been related to underlying patterns of fetal behavior but were not usually influenced by external physical stimulation of fetuses.

Female↗
PubMed1980

A definition of human fetal apnea and the distribution of fetal apneic intervals during the last ten weeks of pregnancy.

Fetal breathing movements were studied over 24-hour observation periods for a total of 744 hours in 31 healthy pregnant women at 30 to 39 weeks' gestational age. An analysis of 165,786 breath-to-breath intervals in eight fetuses demonstrated that 97% of breath-to-breath intervals were less than 6 seconds in duration. It was concluded that a breath-to-breath interval of 6 seconds or more is a rational definition of fetal apnea during the last 10 weeks of pregnancy. An analysis of intervals during which time no fetal breathing activity occurred in the 31 fetuses demonstrated that prolonged episodes of apnea were distributed in a similar fashion at different gestational ages. The longest periods of apnea were 65 minutes at 30 to 31 weeks, 105 minutes at 34 to 35 weeks, and 120 minutes at 38 to 39 weeks. No periods of apnea of more than 45 minutes were measured during the second and third hours following maternal meals. A useful strategy for recognition of significant fetal apnea would be to make observations during the second and third hours following maternal meals when apneic lengths greater than 45 minutes were not observed in this highly selected group of normal fetuses.

Apnea↗
PubMed1980

Circadian rhythms in maternal plasma cortisol and estriol concentrations at 30 to 31, 34 to 35, and 38 to 39 weeks' gestational age.

In order to examine the relationship between circadian rhythms in different steroids, cortisol and estriol were measured by radioimmunoassay in maternal venous plasma taken at 30- to 60-minute intervals over 24 hours from nine healthy women at 30 to 31, 11 at 34 to 35, and 10 at 38 to 39 weeks' gestation. Maternal cortisol was maximal at 0730 to 0830 hours and fell significantly to its lowest concentration between 1830 and 0130 hours. At 30 to 31 and 34 to 35 weeks there was a significant circadian rhythm in estriol concentrations which was inversely related to the circadian rhythm in cortisol. At 38 to 39 weeks mean estriol concentrations were significantly higher than those at 30 to 31 and 34 to 35 weeks but there was no significant circadian pattern. We concluded that there is an inverse relationship between maternal cortisol and estriol at 30 to 31 and 34 to 35 weeks, which would be consistent with a maternal effect on fetal adrenal function. The increase in mean concentration and absence of circadian rhythm in maternal plasma estriol at term might suggest an additional positive stimulus to fetal adrenal function. The existence of patterns in maternal estriol concentrations must be taken into account in the u;se of sequential measurements of this hormone during the last 10 weeks of pregnancy.

Circadian Rhythm↗
PubMed1980

Patterns of human fetal breathing during the last 10 weeks of pregnancy.

Continuous measurements of human fetal breathing movements and gross fetal body movements were made with an ultrasonic real-time scanner for periods of 24 houro 31 weeks' gestation, a significant increase in fetal breathing movements occurred during the second and third hours after meals; this pattern apparently followed an increase in maternal plasma glucose concentrations. At 38 to 39 weeks' gestation, fetal breathing movements increased during the second and third hours after breakfast, but the troughs seen before lunch and supper at 30 to 31 weeks' gestation were not present. Fetal breathing movements diminished over the day and reached a minimum between 1900 and 2400 hours. Fetal breathing activity increased in both groups between 0400 and 0700 hours while mothers were asleep; this was not related to an increase in maternal glucose concentrations. Absence of fetal breathing movements was observed for up to 122 minutes in this analysis of 480 hours in 20 patients. These data show that much more information must be obtained on factors that normally influence fetal breathing activity. Only then can research strategies be suggested for clinical evaluation of the usefulness of fetal breathing movements in the assessment of fetal health.

Blood Glucose↗
PubMed1979

Canine viral enteritis. Recent developments.

Two apparently novel viral gastroenteritides of dogs were recognized in 1978: one caused by a parvo-like virus (CPV) and one by a corona-like virus (CCV). A rotavirus has also been tentatively associated with neonatal pup enteritis. Canine viral enteritis is characterized by a sudden onset of vomiting and diarrhea, rapid spread and high morbidity. Treatment is only supportive but must be initiated promptly. Infected animals should be isolated immediately; the extremely contagious nature of these diseases makes them difficult to contain. Feces from infected dogs appear to be the primary means of transmission. Sodium hypochlorite solutions (eg, Clorox) are recommended for disinfection. The development of effective vaccines is an immediate and pressing problem.

Animals↗
PubMed1977

Research in human sexuality education.

Since human sexuality courses are relatively recent additions to most U.S. medical school curricula, there are no established procedures for evaluating the courses. The purpose of this study was to test medical students' attitudes toward concepts in sexuality before and after a 5-day sexuality course using the semantic differential. The concepts students rated were "my sexuality", "masturbation", "homosexuality", and "my role in understanding sexual problems". Post-test scores were subtracted from pre-test scores and analysed by multivariate analysis of variance testing for significant difference from zero. Ninety-six second-year medical students completed the pre- and post-semantic differential tests. The changes between the pre- and post-tests were significant at the 0-001 level for all four concepts with the concept "homosexuality" showing the greatest change. The study suggests the semantic differential may be an effective instrument in assessing attitude changes. It also suggests the teaching techniques used in human sexuality courses may be successfully applied to other areas of medical education.

Adult↗
PubMed1975

Corneal endothelium in viral induced anterior uveitis. Ultrastructural changes following canine adenovirus type 1 infection.

Dogs inoculated intravenously with attenuated canine adenovirus type 1 developed anterior segment inflammation and corneal edema. During the stage of mild anterior uveitis, virus was isolated from the aquious fluid, and by electron microscopy, viral replication was found to occur in corneal endothelial cells. Later, at the stage of severe anterior uveitis with corneal edema, virus was not isolated from the aqueous fluid and cells containing intranuclear (replicating) virus were not found. At this stage, many inflammatory cells had infiltrated the anterior chamber and contained numerous membrane-bound viral aggregates (viral-antibody complexes). Phagocytized viral-antibody complexes were present in the areas of most prominent endothelial cell destruction. Peripheral to the principal lesion sites, inflammatory cells had dissected the endothelium from Descemet membrane. After recovery from the disease, an intact endothelial cell layer was present.

Animals↗
PubMedDate not supplied

Carotid arterial blood flow in the ovine fetus as a continuous measure of cerebral blood flow.

OBJECTIVE: The purpose of this study was to establish a continuous measure of cerebral blood flow in the ovine fetus with a transit time flow probe. METHODS: Seven chronically catheterized fetal sheep were studied near term with placement of a 3R Transonic flow probe on the external carotid artery, just proximal to the internal maxillary artery. Blood flow changes were induced by altering maternal inspired oxygen and carbon dioxide concentrations, with cerebral and extracerebral blood flows also determined by the microsphere technique. RESULTS: Although absolute carotid and cerebral blood flow values were only modestly related under the present study conditions (r = 0.60, P < .05), both the percent change and the actual change in carotid arterial blood flow showed a strong linear correlation with that for cerebral blood flow (r = 0.84, P < .01, and r = 0.72, P < .02) but less so with that for extracerebral blood flow (r = 0.44 and r = 0.28). CONCLUSION: Measurements of carotid blood flow as studied with a transit time flow probe and induced blood gas changes can provide for a continuous assessment of changes in blood flow to the ovine fetal brain.

Animals↗
PubMedDate not supplied

Activation of the fetal hypothalamic-pituitary-adrenal axis with prolonged and graded hypoxemia.

OBJECTIVE: The purpose of this study was to determine whether activation of the hypothalamic-pituitary-adrenal (HPA) axis and uteroplacental prostaglandin (PG) response occur before metabolic deterioration with a progressive decrease in fetal oxygenation. METHODS: Twenty-one chronically catheterized fetal sheep were studied between 126 and 135 days' gestation during a 24-hour normoxic control period and subsequently during 4 experimental days of either prolonged and graded hypoxemia, induced by progressively lowering the maternal inspired oxygen concentration (induced hypoxia, n = 12), or continued study on room air (control, n = 6; spontaneous hypoxia, n = 3). Fetal arterial blood was sampled daily for blood gases and pH, immunoreactive ACTH, cortisol, and PGE2. Placental cotyledons were obtained at the end of the experiment for measurement of prostaglandin-H synthase (PGHS) enzymatic activity. RESULTS: For all hypoxia group measurements, progressive reduction in fetal oxygenation resulted in little change in either plasma ACTH or cortisol until arterial O2 saturation was close to 30% with metabolic acidosis onsetting. This was in keeping with activation of the HPA axis at this time, because ACTH and cortisol values showed a strong linear correlation (r = 0.77, P < .01). Fetal plasma PGE2 concentrations and cotyledonary PGHS enzymatic activity, although somewhat higher in the hypoxia group animals, were not changed significantly. CONCLUSION: In response to prolonged and graded hypoxemia in the ovine fetus, activation of the HPA axis occurs only when the degree of hypoxemia is pronounced and close to that associated with metabolic deterioration, which may limit the time for any uteroplacental response and the ability to initiate labor.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Placental release of corticotrophin-releasing hormone across the umbilical circulation of the human newborn.

This study attempted to determine the placental release of corticotrophin-releasing hormone (CRH) into the umbilical circulation, and the factors which affect it, by measuring venous and arterial levels for CRH across the umbilical circulation in labouring as well as non-labouring elective caesarean section patients. The relationship with measures of fetal oxygenation and acid-base status at birth was investigated also. Forty-eight patients were studied (term labour n = 30, term elective caesarean section n = 12, and preterm labour n = 6) with blood sampling from a clamped segment of cord after delivery of the fetus and from the cord at its insertion into the placenta after delivery of the placenta, with subsequent measurement of blood gases, pH, base excess, and CRH. For all patients, mean plasma CRH levels in the umbilical and placental vein (115+/-13 and 145+/-18 pg/ml) were higher than those from the corresponding artery (85+/-7 and 102+/-8 pg/ml, P<0.01 and P<0.05, respectively), indicating placental release of CRH into the fetal compartment. In addition, placental venous and arterial cord CRH levels were higher than those from the corresponding umbilical levels (P<0.01 and P<0.02, respectively) indicating continued placental release of CRH into blood within the placenta after clamping of the umbilical circulation and delivery of the fetus. While plasma CRH levels from respective cord vessels were all significantly higher in labouring patients at term versus elective caesarean section patients, there were no differences compared with preterm labouring patients. For all patients, CRH as measured in both the umbilical and placental vein showed a modest inverse correlation to base excess as measured in the umbilical artery, -0.31 and -0.33, respectively, both P<0.05. It is concluded that CRH is released by the placenta into the fetal compartment and is increased with both term and preterm labour, and with metabolic acidosis during labour, supporting a role in the endocrine events of labour and/or compensatory changes in uteroplacental blood flow.

Acid-Base Equilibrium↗