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Biomedical subjects

B Richardson

Publications and source records attributed to B Richardson.

155 records · Page 9Linked to original sources
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↗
PubMedDate not supplied

The University of Akron study on air pollution and human health effects I. Methodology, baseline data, and aerometrics.

This study determined the health effects of ambient air pollutants in two grade school populations in Akron, Ohio. One school is adjacent to industry and has elevated levels of sulfur dioxide (SO2) and moderate levels of nitrogen dioxide (NO2), while the other school is 4 km east and unpolluted. This study was designed in this manner for two purposes: (1) to identify and monitor ambient levels of air pollutants in an area proximal to the grade school so that the levels could be accurately assessed, and (2) to determine baseline pulmonary function values and questionnaire responses from the parents indicating any acute and/or chronic respiratory problem in the child. Ninety-five percent of the children enrolled in this study liver within 2 km of the schools and aerometric stations, thus providing for careful control in the study design. The results of this study indicate that SO2 and NO2 levels are significantly higher in the school adjacent to industry. Although pulmonary function data were not significantly different between schools, the frequency of questionnaire responses to acute and chronic pulmonary problems was greater in the children at the school adjacent to industry. The data tend to indicate early pulmonary effects of air pollution in children living adjacent to industry and exposed to elevated levels of SO2 and NO2. We suggest that additional longitudinal work that carefully monitors total suspended particulates, NO2, SO2, and health data should be conducted to confirm these results.

Air↗
PubMedDate not supplied

Disposition of ethanol and its proximate metabolite, acetaldehyde, in the near-term pregnant ewe for short term maternal administration of moderate-dose ethanol.

The effect of short term maternal ethanol administration on the disposition of ethanol in the ovine maternal-fetal unit was determined. Eleven conscious instrumented near-term pregnant ewes (between 125 and 134 days of gestation; term, 147 days) received 1-hr iv infusion of 1 g of ethanol.kg of maternal body weight-1.day-1 for six days (N = 6 ewes) or an equivalent volume of saline for six days (N = 5 ewes). On the seventh day, the ethanol- and saline-pretreated animals were administered 1 g of ethanol.kg of maternal body weight-1. Ethanol and acetaldehyde concentrations were determined by headspace GLC in maternal blood, fetal blood, and amniotic fluid samples obtained at selected times during the 14-hr study. The data demonstrated that short term maternal administration of once-daily moderate dose ethanol did not produce major changes in the disposition of ethanol and its proximate metabolite, acetaldehyde, in the maternal, fetal, and amniotic fluid compartments during near-term ovine pregnancy.

Acetaldehyde↗
PubMedDate not supplied

Utilizing collaborative practice to achieve quality outcomes in gentamicin administration.

An individualized weight-based gentamicin dosing program is used at this community hospital to achieve stable serum drug levels with optimal clinical outcomes. This program requires extensive communication between disciplines and because of its complexity, was identified by the nursing staff as being confusing to initiate and maintain. The authors report the work of an interdisciplinary team to streamline the ordering and administering process and to promote staff satisfaction in using the dosing program.

Adolescent↗