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Biomedical subjects

K C Lowe

Publications and source records attributed to K C Lowe.

102 records · Page 6Linked to original sources
PubMed1980

Comparison of continuous transcutaneous and continuous intravascular PO2 measurement in fetal sheep.

Continuously monitored carotid arterial PO2 (PaO2) and transcutaneous PO2 (tcPO2) from the scalp of fetuses from ewes not in labor have been compared under epidural anesthesia at different levels of fetal oxygenation. A reasonably good correlation existed between the two readings at normal and high PO2 values. In sharp contrast, at low PaO2 levels there was a considerable bias between the two. Since this bias was variable, the failure of tcPO2 to reflect PaO2 accurately at low PaO2 renders the use of the tcPO2 electrode questionable in the very situation for which it was advocated, namely, the prediction of fetal compromise.

Animals↗
PubMed1980

Circulating plasma protein concentrations in the fetal and neonatal sheep.

Fetal and neonatal ovine plasma protein and lactate dehydrogenase concentrations have been measured between 124 and 146 days gestation in th chronically catheterized fetal sheep and in the newborn lamb. Fetal plasma protein concentration ranged from 24.7 to 77.0 mg . ml-1 and increased at a rate of 1.65 mg . ml-1 . day-1. In contrast, in the first 10 days of neonatal life plasma protein concentration fell steadilyu at a rate of 2.64 mg . ml-1 . day-1. Fetal plasma lactate dehydrogenase concentration increased at a rate of 0.014 IU . ml-1 . day-1 during the period of study. The increase correlated significantly with the rise of fetal plasma protein concentration. In contrast, in the newborn lamb no significant change in plasma lactate dehydrogenase concentration was observed during ther first 10 days after birth.

Aging↗
PubMed1980

Time-trend analysis of plasma cortisol concentrations in the fetal sheep in relation to parturition.

Using a cortisol RIA carefully validated for specificity in fetal ovine plasma, we studied plasma cortisol time-trend changes in eight chronically catheterized sheep fetuses in the last 22 days of gestation before the spontaneous onset of labor. Best fit exponential type curves were drawn for each individual fetus to define the time before the onset of labor at which fetal plasma cortisol was rising at different rates. Fetal plasma cortisol increased at a rate of 0.5 ng ml-1 day-1 as early as 17.1 days before labor in one fetus, whereas the mean value for all eight fetuses occurred 11.8 +/- 1.0 (SEM) days before labor. The rate of increase doubled to 1.0 ng cortisol ml-1 day-1 as early as 14.4 days before labor in one fetus, whereas the mean value for all eight fetuses occurred 9.3 +/- 0.9 days before labor. These findings suggest that the regulatory mechanisms responsible for the prelabor increase in fetal cortisol production are activated earlier in gestation than we previously thought.

Animals↗
PubMed1979

Effect of long-term bromocriptine infusion on plasma prolactin and ovine chorionic somatomammotropin in the pregnant ewe and fetal sheep.

It has been shown in previous studies that the continuous infusion of bromocriptine (CB 154) into either the sheep fetus or pregnant ewe was followed by pronounced ultrastructural changes in the binucleate (BN) cells of the ovine chorionic epithelium, which are a likely source of ovine chorionic somatomammotropin (oCS). We have examined ovine fetal and maternal plasma prolactin (PRL) and oCS concentrations following intravascular CB 154 infusion separately into either the fetus (0.03 mg/hour) or ewe (0.2 mg/hour). The CB 154 infusions significantly depressed fetal and maternal plasma radioimmunoassayable PRL concentrations within 24 hours of the commencement of infusion. Maternal plasma radioimmunoassayable oCS concentration was significantly depressed during infusion of CB 154 to the ewe, but the infusion of CB 154 to the fetus did not lower fetal plasma radioimmunoassayable oCS concentration or affect the duration of gestation.

Animals↗
PubMed1979

Continuous variability of fetal PO2 in the chronically catheterized fetal sheep.

A method of continuous monitoring of fetal intravascular PO2 at various sites in the circulation in the chronically catheterized fetal sheep for up to 41 days (mean 11.1 days) has been compared with values obtained in blood samples measured extracorporeally in a standard blood gas analyzer. A double-blind comparison of the two methods showed that there was no bias between the two methods and correlation was 0.94. The stability of the electrodes was superior to that of a conventional blood gas analyzer. In every animal there was continuous variability of fetal vascular PO2. In the period from 105 to 126 days' gestation we noted the presence of slow increases in basal uterine tone that we have called "contractures". The frequency of these contractures was very regular at approximately one per hour. The frequency of these contracutres was very regular at approximately one per hour. There is a statistically significant related fall in fetal vascular PO2 in relation to these contractures. Well-coordinated uterine contractions during labor also produced a fall in fetal vascular PO2 that was related to the uterine activity.

Animals↗
PubMed1979

Comparison of two rapid cortisol radioimmunoassays for use in the fetal sheep.

Cortisol radioimmunoassays (RIA's) utilizing highly specific antisera combined with a simple ethanol protein precipitation procedure (ETOH-PPT) are widely utilized to measure cortisol in human plasma. This same type of RIA has been assumed specific for measurement of cortisol in the plasma of several different species of experimental animals. In order to test this assumption as applied to fetal ovine plasma, we compared an ETOH-PPT cortisol RIA with another rapid cortisol assay which utilizes a dichloromethane extraction (DM-E) step. The DM-E assay in turn was compared with a chromatographic assay previously shown to be highly specific for measurement of fetal plasma cortisol in this species. Fetal ovine plasma cortisol concentrations determined by the DM-E method were nearly identical to the concentrations obtained by the specific chromatographic RIA procedure. On the other hand, the ETOH-PPT RIA grossly overestimated cortisol concentrations when compared with the DM-E RIA. While the rapid DM-E RIA appears to be suitable for use in fetal ovine plasma, the widely used ETOH-PPT RIA yields spuriously high and unpredictable values and must be considered unreliable. These comparisons demonstrate the need for careful reassessment of steroid assays prior to their application in experimental animals even though they have been previously documented as specific in human plasma.

Animals↗
PubMed1979

The effect of prostaglandin E2 infusion in the fetal lamb on fetal plasma ACTH, prolactin and cortisol concentrations.

PGE2 (2 micrograms/min) has been infused for 1h into the fetal jugular vein of 8 chronically catheterized fetuses on 13 occasions from 112 to 138 days gestation. Infusion of ethanol vehicle alone was conducted in fetuses from 111-139 days gestation. PGE2 administration produced a significant increase in fetal plasma cortisol after 30 min. No significant change was observed in fetal plasma prolactin concentration. Fetal plasma ACTH concentration was significantly elevated above resting concentration after 30 min. of PGE2 infusion. Metabolic clearance rate of PGE2 was 860 ml/min or 350 ml/kg/min. Intrauterine pressure was not changes during the infusion at any gestational age.

Adrenocorticotropic Hormone↗
PubMed1979

Ultrastructural changes in the placenta of the ewe after long-term intravascular infusion of 2-bromo-alpha-ergocryptine (CB154) into mother or fetus.

The fine structural appearance of the placenta of the ewe has been examined following long-term infusion of CB154 into either the fetus or the pregnant ewe. Binucleate cells which usually contain aggregations of spherical membrane-bound electron-dense inclusions, are a characteristic component of the chorionic epithelium of the sheep. Following CB154 infusion into either the fetus or ewe at 111 to 137 days of gestation, binucleate cells were partially or completely depleted of the droplets which are present in binucleate cells of control animals at a similar gestational age. No obvious changes in the maternal epithelial syncytium were observed after CB154 administration. Infusion of CB154 into the fetus alone was also followed by degenerative changes in some binucleate cells which ranged from condensation of nuclei to complete cell fragmentation. Either a direct or an indirect action of CB154 on binucleate cells is suggested by these observations. Hypoprolactinaemia followed CB154 infusion in all treated animals; its possible influence on binucleate cell activity is discussed.

Animals↗
PubMedDate not supplied

Effect of Erythrogen on post-thaw recovery of cryopreserved cell suspensions of indica rice (Oryza sativa L.).

This study shows that adding haemoglobin solution (Erythrogen) to post-thaw medium of Indica rice (Oryza sativa L.) cells enhances survival following cryopreservation. Haemoglobin (1:50 - 1:200 v:v) had a beneficial effect on post-thaw viability and subsequent cell growth. A key finding was that the successful recovery from cryopreservation of cell suspensions of the Indica rice cvs. BR26 and Pajam, and their re-establishment in AA2 medium, reflected a requirement for such supplementation of the post-thaw recovery medium with Erythrogen.

Cell Survival↗