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Biomedical subjects

H Brown

Publications and source records attributed to H Brown.

At least 145 records · Page 8Linked to original sources
PubMed1987

Bicycling performance in Gambian children: effects of supplements of riboflavin or ascorbic acid.

Sixty rural Gambian children between 10 and 14 years of age with normal haematological status but generally poor riboflavin status and some evidence of poor ascorbic acid status were recruited for study at the beginning of the rainy season. Children were allocated to three treatment groups to receive, twice weekly, either a placebo or a supplement of riboflavin or ascorbic acid. Before receiving the supplement, and on two subsequent occasions 6 weeks apart children performed an exercise regimen on a bicycle ergometer during which expired air was collected, heart rate monitored and lactate accumulation measured. A modest but significant improvement in ascorbic acid status occurred in response to supplement and the riboflavin supplement enhanced the overall improvement in riboflavin status observed. There was no measurable change in bicycling performance during the study period in any of the treatment groups.

Adolescent↗
PubMed1986

Determination of aldosterone secretion rate utilizing mixed mode and high performance liquid chromatography.

A simpler method for determining aldosterone secretion rate (ASR) has several applications. High performance liquid chromatography (HPLC) has several advantages over traditional chromatographic methods for purification to constant specific activity of aldosterone liberated from its 18-glucuronide by acid hydrolysis. We found it necessary to introduce several modifications to remove urochromes before HPLC. Two methods for determining ASR were developed. With Method A a more traditional initial procedure was followed, and Sephadex LH-20 chromatography allowed removal of considerable urochromes before HPLC. However, aldosterone recovery was improved with Method B, which employed several bonded phase silica derivatives (Sepralytes) and a PBE 94 column to remove urochromes before HPLC. With this procedure the Sephadex LH-20 chromatography was not required. Aldosterone purification to constant specific activity was achieved by HPLC on a diol column with a normal phase system, and quantification was performed by RIA. ASR determinations were equivalent with both methods. This methodology should be applicable to other steroid secretory rate determinations and to applications involving purification of steroid conjugates.

Aldosterone↗
PubMed1986

Para osteo arthropathy--ectopic ossification of healing tendon about the rodent ankle joint: histologic and type V collagen changes.

Ectopic bone formation, or para osteo arthropathy (POA), is commonly seen in humans following lesions to the central nervous system. The condition also occurs after severe trauma, burns, or tetanus, and, rarely, after poliomyelitis or cauda equina lesions. The lack of a suitable laboratory animal model has hampered study of its etiology and treatment. The lesion occurs just above the rodent ankle joint 7 weeks after repair of the severed achilles tendon. Tendon repair using a single silk suture resulted in ectopic calcification in 22 of 23 animals. Ectopic ossification, with extensive mineralization, occurred in 11 animals, 5 of which showed bone marrow. Ectopic mineralization was moderate in 8 others, minimal in 4, and absent in one. Collagen typing thrice during healing indicated that type V collagen increased by one-third at 10 days, doubled at 20 days, and returned to near normal amounts at 50 days. Since type V collagen is a major component of the nonfibrous collagen of blood vessels, increased amounts of type V collagen are consistent with the presence of many new blood vessels in the granulation tissue at 10 and 20 days. Vascularity is less dense at 50 days when ectopic mineralization and new bone formation are observed. These findings suggest that POA and the degree of maturation of healing tendon may be linked to reduced amounts of type V collagen. It is concluded that the sutured tendon of the rodent ankle joint offers an animal model by which to study ectopic bone formation, or para osteo arthropathy.

Achilles Tendon↗
PubMed1986

Failure of chlordecone (Kepone) to induce behavioral estrus in adult ovariectomized rats.

The effect of chlordecone on behavioral estrus was examined in adult ovariectomized female rats. Chlordecone has been reported to resemble estrogen in altering pituitary secretions, in producing vaginal cornification, in increasing uterine weight and in competing for binding to the estrogen receptor. In the present study, 10, 25, 50 or 75 mg/kg chlordecone was substituted for estrogen in the estrogen-progesterone priming sequence used to facilitate sexual behavior of ovariectomized female rats. Sexual receptivity was measured by the number of lordosis responses exhibited by the female when mounted by a sexually active male. Chlordecone failed to substitute for estradiol in producing lordosis behavior. When female rats were given chlordecone in addition to estrogen plus progesterone, chlordecone reduced the lordosis behavior usually seen in these steroid primed animals. In further studies, chlordecone's effect on the CNS progesterone receptor was examined. Unlike estradiol, chlordecone did not induce progesterone receptors. Furthermore, chlordecone attenuated the increase in progesterone receptors seen after estradiol treatment. These findings suggest that chlordecone fails to mimic, and may actually interfere with, estrogen's facilitative effects on neurally mediated reproductive events.

Animals↗
PubMed1986

Effect of chronic exercise on beta-endorphin receptor levels in rats.

A radioreceptor assay using [3H]2-beta-endorphin (B-EP) was used to examine binding in the brains of rats that had been exercised on a treadmill for 5 months. The binding of [3H]2-beta-EP to brain homogenates gave an average Kd of 0.830 +/- 0.055 nM for the controls and 0.826 + 0.022 nM for the runners, and respective Bmax's of 166 +/- 20 pM and 159 +/- 27 pM.

Animals↗
PubMed1984

Rapid chromatographic purification of urinary steroid glucuronates for determination of aldosterone secretion rate.

Aldosterone secretion rate (ASR) is utilized as a rapid screening procedure to detect subtle forms of hypertension. A rapid and robust chromatographic method has been developed, based on easily prepared, rigid matrices, which permit the flow of urine by suction through sequential purification columns. Both major metabolites, aldosterone glucuronate and tetrahydroaldosterone glucuronate, are isolated in ca. 75% yield. They are hydrolyzed and quantitated by high-performance liquid chromatography-radioimmunoassay (HPLC-RIA) or, for bulk preparation, further purified by preparative chromatofocusing. These two polar conjugates are isolated in nearly pure form by HPLC on a C2 column with a two-step gradient. An ASR determination can be completed in one to two working days; preparative-scale work takes somewhat longer.

Aldosterone↗
PubMed1984

Effect of monensin, estradiol controlled release implants and supplement on performance in grazing steers.

Five trials in five locations in the United States involving 512 steers were conducted to evaluate the effect of monensin [200 mg/d in .9 kg of supplement (Ru mensin )] and estradiol-controlled release implants ( Compudose ) administered alone and in combination on average daily gain (ADG) in steers on pasture. The effect of energy supplementation on rate of gain was also evaluated in these same trials. The initial weight of steers averaged 250 kg and the average duration of the five trials was 124 d. Estradiol-controlled release implants increased ADG by 15.6% (.095 kg/d; P less than .0001) and monensin increased ADG by 8.1% (.054 kg/d; P less than .05). The combination of estradiol-controlled release implant and monensin increased ADG by 27.4% (.168 kg/d). Treatment responses were additive relative to ADG response, with no interaction observed between the treatments. Nine-tenths kilograms of an energy supplement/d increased ADG by 12.4% (.073 kg/d; P less than .01).

Animals↗
PubMed1983

Voluntary regionalization and associated trends in perinatal care: the Nova Scotia Reproductive Care Program.

The Nova Scotia Reproductive Care Program is a system of voluntary regionalization that involves the 37 hospitals in the province that provide obstetric care to a population of 850,000. Between 1971 and 1980, the perinatal mortality rate in the central tertiary care unit for nonreferred patients fell progressively from 12.5 per 1,000 total births to 5.16. For all cases, including high-risk referrals, this rate has fallen from 12.7 to 7.2. During the same interval, the perinatal mortality rate for the province's seven regional hospitals fell from 18.7 to 12.2, and that for the 28 community hospitals fell from 18.4 to 7.0. Analysis of these reductions by fitted trend lines demonstrates statistical significance. Further analysis demonstrates that, with regionalization of perinatal services, it is possible to reduce the perinatal mortality rate in small community hospitals to levels that approximate those of a sophisticated tertiary care hospital.

Female↗
PubMed1983

Aldosterone suppression with dopamine infusion in low-renin hypertension.

A dopaminergic mechanism has been proposed to suppress aldosterone secretion. To assess the possibility that a defect in the dopaminergic mechanism might enhance aldosterone secretion in hypertensive patients, we determined basal and adrenocorticotropic hormone (ACTH)-stimulated plasma aldosterone (PA), cortisol, renin activity, and potassium concentrations before and during dopamine receptor stimulation with dopamine infusion and bromocriptine administration and dopamine receptor blockade with metoclopramide. The patient study groups included: (a) seven patients with low-renin hypertension and abnormal aldosterone suppression with sodium loading and presumed bilateral zona glomerulosa hyperplasia (ZGHP); (b) two patients with aldosterone-producing adenoma; (c) five patients with low-renin hypertension but normal aldosterone suppression with sodium loading; and (d) six patients with normal-renin hypertension. Dopamine infusion in patients with ZGHP caused PA to fall (P less than 0.01) into the normal range, but did not block the enhanced (P less than 0.05) aldosterone response to ACTH that is characteristic of these patients. Dopamine infusion in patients with low-renin hypertension but normal aldosterone suppression also suppressed PA (P less than 0.01), whereas it had no effect upon PA in patients with normal-renin hypertension or aldosterone-producing adenoma and did not blunt the PA response to ACTH in either group. Bromocriptine administration had no effect upon basal or ACTH-stimulated PA. Dopamine infusion in patients with ZGHP also enhanced (P less than 0.05) diuresis and natriuresis in comparison with normal-renin patients. Metoclopramide administration increased (P less than 0.01) PA in all patients. Thus, a dopaminergic mechanism appears to be important in the regulation of aldosterone secretion in patients with ZGHP and in other low-renin hypertensives with normal aldosterone suppression with sodium loading. In contrast, this latter group does not exhibit an enhanced aldosterone response to ACTH. Both of these groups differ from normal-renin hypertensives, who have no PA suppression with dopamine infusion.

Adenoma↗