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Biomedical subjects

C Armstrong

Publications and source records attributed to C Armstrong.

At least 73 records · Page 4Linked to original sources
PubMed1989

Endothelin is a potent constrictor of the lamb ductus arteriosus.

Endothelin was tested on isolated ductus arteriosus preparations from mature fetal lambs. At low PO2 (18-24 Torr; 1 Torr = 133.3 Pa), the compound constricted the vessel dose-dependently over the range from about 10(-10) to 10(-7) M. The contraction was sustained and did not subside even after an extended period of washing. Endothelin was also effective on tissues (PO2,217-231 Torr; indomethacin, 2.8 X 10(-6) M) that had been completely relaxed with CO (CO/O2 ratio, 0.28). CO treatment interferes with a cytochrome P-450 mechanism, which is considered crucial for the contractile response of the vessel to oxygen. These findings are consistent with a role of endothelin in the closure of the ductus arteriosus at birth.

Animals↗
PubMed1988

Monooxygenase-mediated metabolism and binding of ethylene thiourea to mouse liver microsomal protein.

Ethylenethiourea (ETU), a metabolite and degradation product of the ethylenebisdithiocarbamate fungicides, is a substrate for the flavin-dependent monooxygenase (FMO), a microsomal NADPH requiring enzyme that can oxidize ETU, as well as for the cytochrome P-450 enzyme system. The present study shows that the mouse metabolises ETU preferentially via the FMO system. FMO activity decreases as male, but not female mice, increase in age to 30 weeks. This difference in activity is reflected in decreased overall metabolism of ETU and in a decreased FMO-mediated binding of radiolabelled ETU to mouse liver microsomal protein. The rapid metabolism of ETU by the FMO system may contribute to the lack of acute toxicity and teratogenicity exhibited by the mouse relative to the rat. However, the FMO-mediated binding of ETU metabolites to mouse liver protein is consistent with the chronic hepatotoxicity exhibited by ETU in this species.

Animals↗
PubMed1988

Validation studies for brain blood flow assessment by radioxenon tomography.

A tomographic technique has been used recently for cerebral blood flow measurements with inhaled radioxenon. Based on experiments in a specially developed dynamic phantom and on studies in primates in vivo, we have analyzed the validity of this method for measurements of both regional and total blood flow in the brain. We have also examined the errors introduced into flow computations as a function of changes in such parameters as: rate of xenon input, size of region of interest, magnitude of regional flow rates, and inter-regional flow differences. Our findings indicate a reasonable degree of accuracy for flow measurements in gray matter regions that are 3 cm in diameter or larger, while white matter blood flow is generally overestimated. The accuracy for regional flow assessments degrades as a function of: diminishing region size, increasing inter-regional flow differences, and flow rates in excess of 100 ml/100 g/min. Measurements for brain regions 2 cm or smaller in diameter can be in error by 25-50% as a result of partial volume averaging. Although the technique is not ideal for accurate flow measurements in small regions of the brain, it nevertheless provides a convenient means of assessing perfusion in major vascular territories of the brain in routine clinical applications.

Animals↗
PubMed1987

Role of Enterobius vermicularis in the aetiology of appendicitis.

An evaluation was made of the histological material obtained from all 1529 appendices removed during the last 5 years at Southmead Hospital, Bristol, in order to elucidate possible relationships between the incidence of Enterobius vermicularis and the origin of inflammation in the appendix. In total, 1419 appendices were removed as cases of clinical appendicitis and 110 in the course of another surgical procedure. E. vermicularis was identified in 2.7 per cent of patients with clinical appendicitis and was most commonly seen in appendices with either chronic inflammation or where the appendix was histologically normal. E. vermicularis was rarely associated with histological changes of acute appendicitis. No cases of E. vermicularis infestation occurred in appendices removed during the course of other surgical procedures. The results suggest that, although E. vermicularis may have a causal role in appendicular pain and chronic inflammation, it is rarely related to acute appendicitis.

Animals↗
PubMed1987

Comparison of the efficacy of nicardipine, a new calcium channel blocker, with nifedipine in the treatment of mild to moderate essential hypertension.

Thirty-nine patients with mild to moderate essential hypertension participated in a parallel, single-blind study comparing 6 weeks' treatment of nicardipine hydrochloride (90 mg/day) with nifedipine (40 mg/day). Nicardipine-treated patients commenced therapy with a significantly higher mean supine diastolic blood pressure than the nifedipine-treated patients. There was a statistically significant fall in blood pressure (systolic and diastolic) on both treatments at the 3 and 6 week follow-up visits. On adjusting the results for the baseline inequality, no statistically significant differences were found between treatment groups. Seven patients withdrew from nifedipine therapy and six patients withdrew from nicardipine therapy due to adverse events. The results show that nicardipine hydrochloride at 90 mg/day is an effective anti-hypertensive agent. The incidence and nature of adverse events were similar on the two treatments.

Adult↗
PubMed1987

Maintenance of the normal rat alveolar macrophage cell population. The roles of monocyte influx and alveolar macrophage proliferation in situ.

We investigated the relative importance of monocyte influx and alveolar macrophage proliferation in maintenance of the alveolar macrophage population in normal rats. Two experimental approaches were used. To detect possible monocyte influx, we radiolabeled blood monocytes by a continuous infusion of tritiated thymidine for 7 days and assayed lavaged alveolar macrophages for radiolabel by autoradiography. Although heavily labeled monocytes occurred in the blood, no heavily labeled cells were detectable among lavaged alveolar macrophages by cohort analysis. To evaluate macrophage proliferation in vivo, we injected normal unlabeled rats with colchicine and examined lavaged alveolar macrophages for arrested mitoses. Mitotic figures were observed among lavaged alveolar macrophages, and calculations at serial times after colchicine injection indicated that 1.83% of alveolar macrophages entered mitosis each day. On the basis of these 2 lines of evidence, we conclude that the alveolar macrophage cell population in normal rats is supported mainly by cellular proliferation in situ rather than direct monocyte influx from the blood compartment.

Animals↗
PubMed1975

Spontaneous and chemically induced transformation of rat embryo cell cultures.

The transformation of Wistar rat embryo cells in vitro has been studied in passaged cultures using two criteria for transformation: (1) the ability of cells to form colonies in soft agar and (2) the ability of cells to form tumours in young syngeneic animals. In general there was good correlation between the two criteria. Spontaneous transformation was observed in all untreated cultures by 44 weeks although, by not allowing the cells to become confluent, the tendency was for cultures to transform earlier (i.e. 15-21 weeks). It was noticeable that despite untreated cultures having been in vitro for different lengths of time, most cultures transformed after a similar number of passages (42-50). Treatment of the embryo cells with the alkylating agent nitrosomethylurea (NMU) or benzo(alpha)pyrene (BP) sometimes resulted in transformation after a shorter period in vitro than the controls (minimum 12 weeks) although some treated cultures took longer. Transformed cells produced transplantable fibrosarcomata in syngeneic hosts and those arising from NMU transformed cells were histologically different from those arising from spontaneously transformed cells. The significant of spontaneous transformation in in vitro rat cell transformation systems is discussed.

Animals↗
PubMed1973

The pepsinogens of human gastric mucosa.

Fundic mucosal pepsinogens reveal six major bands of protease activity on gel electrophoresis and four minor bands. Antral mucosa shows two major bands of activity; the four rapidly moving bands found in fundic mucosa are found in lesser activity in the antral mucosa. Duodenal mucosa shows only one slowly moving band of protease activity. There is a significant difference in the pepsinogen pattern when the uninvolved fundic mucosa of gastric ulcer patients is compared with that of cancer patients.A satisfactory method is described for separating the pepsinogens on column chromatography.

Chromatography, DEAE-Cellulose↗
PubMedDate not supplied

Chronic feeding study of deoxynivalenol in B6C3F1 male and female mice.

A 2 year feeding study was conducted with male and female B6C3F1 mice that consumed diets containing 0, 1, 5, or 10 ppm deoxynivalenol (DON). Survivability was good and, while the test animals gained less weight with increasing levels of DON in the diet, there were no consistent toxic manifestations associated with DON consumption. There was some evidence for an increase in serum IgA and IgG in females, and there were sporadic changes noted in the clinical chemistry and hematology parameters conducted at the terminal sacrifice. However, these changes were not considered to be biologically significant. The pathology results provided statistically significant dose-related evidence for a decrease in liver preneoplastic and neoplastic lesions as the dose level of DON increased. This negative trend probably results from the known positive correlation between body weight and the appearance of spontaneous hepatic neoplasms in this strain of mouse.

Analysis of Variance↗