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Biomedical subjects

G Marshall

Publications and source records attributed to G Marshall.

At least 109 records · Page 6Linked to original sources
PubMed1989

Orchiopexy: an experimental study of the effect of surgical technique on testicular histology.

Orchiopexy was performed in 35 mature Sprague-Dawley rats using absorbable suture, nonabsorbable suture or a classical dartos pouch technique without suture fixation. Examination of the chromic-fixed testes revealed severe acute inflammation of the suture site and most of the parenchyma in 76 per cent, with abscess formation in 65 per cent, complete absence of spermatogenesis in 82 per cent and evidence of tubular necrosis in 88 per cent. Nylon-fixed testes were adherent only at the sutures, with absent spermatogenesis in 29 per cent, moderate to severe tubular necrosis in 29 per cent and tubular atrophy in 58 per cent. Dartos-fixed testes demonstrated complete circumferential adherence, normal spermatogenesis in 94 per cent and minimal focal tubular atrophy in 23 per cent. Contralateral testes appeared normal in all animals.

Animals↗
PubMed1989

The natural history of medication compliance in a drug trial: limitations of pill counts.

To assess medication compliance over time, we prospectively performed pill counts among 121 ambulatory hypertensive subjects for less than or equal to 12 months. Prescribed regimens consisted of pinacidil or hydralazine administered four times a day and of secondary drugs administered up to twice daily. Surreptitious pill counts occurred every 1 to 12 weeks. Among a middle-aged subject group that had been selected for high rates of compliance, we observed mean compliance rates that approximated 100%. We noted marked intrasubject and intersubject variability for any one medication, between medications, and over time. From baseline blood pressures (+/- SE) of 155.5 +/- 1.9/97.3 +/- 1.0 mm Hg, subsequent mean blood pressures varied by compliance subgroup: "hypocompliers" (less than 80%), 151.3/91.0 mm Hg; "hypercompliers" (greater than or equal to 120%), 147.6/91.4 mm Hg; and "eucompliers" (80% to 119%), 143.3/88.5 mm Hg (systolic blood pressure: F1,52 = -220.9, NS; diastolic blood pressure: F1,52 = -121.4, NS). We concluded that weekly pill counts indicated marked intersubject and intrasubject variability, obscured by long-term averages; that compliance lapses appeared to be random; and that excessive medication-taking was the most consistent with "pill dumping."

Antihypertensive Agents↗
PubMed1989

Arrhythmogenic right ventricular dysplasia in a child with congenital enteropeptidase deficiency and hypogammaglobulinaemia.

A case of arrhythmogenic right ventricular dysplasia in a 10 year old girl is described which provides some evidence for an inherited aetiology of this unusual form of heart disease. The parents of this child were first cousins, thus increasing the possibility of inherited disorders in their offspring. She had been known from infancy to have the rare disorder of congenital deficiency of intestinal enteropeptidase, and low serum immunoglobulins G and A. An untyped adenovirus was grown from a myocardial biopsy taken early in the course of her cardiac disease. However, it is unlikely that this virus was a major factor in the aetiology of her cardiac disease. Both the cardiac and intestinal diseases are now commonly believed to result from hereditary factors, and this report provides further support for this view.

Agammaglobulinemia↗
PubMed1989

Royal Naval Medical Staff School--an update.

Four significant changes in the training of RN Medical and Nursing personnel have taken place over the past four years, since training was last outlined in the article commemorating the Branch Centenary namely, the resurrection of MA training with a significantly increased throughput than previously; a relocation from Dophin II to purpose-built accommodation in the grounds of Haslar Hospital; the introduction of the QARNNS Medical Assistant, and also that of the Direct Entry QARNNS Registered General Nurse within the Rating Structure. Current training regimes and constraints are highlighted at all levels to familiarize and update the Branch with the changes and to promote a better understanding of the abilities and capabilities of the Royal Naval Medical and Nursing Services.

Curriculum↗
PubMed1988

Pill count measures of compliance in a drug trial: variability and suitability.

To evaluate pill counts as a compliance measure for drug trials, we followed 121 ambulatory hypertensives selected for good compliance over less than or equal to 12 months. The medication regimens consisted of either pinacidil or hydralazine as monotherapy or with propranolol and/or hydrochlorothiazide. Pill counts for the two primary drugs were obtained at each of the 20 return visits. The population was characterized by chronic uncomplicated hypertension and sociodemographic diversity; mean age was 53 years. Despite excellent average weekly pill counts (overall mean compliance rate [+/- SD] = 96.0 +/- 13.2%), we observed large intersubject and intrasubject variance in weekly pill count assessment: individuals' mean standard deviation = 13.7% (range = 0%-86%) and mean coefficient of variation = 0.138 (range = 0.001-0.410). By pill count, 35% of individuals exhibited greater than 110% compliance on at least 1 visit. We conclude that (a) pill count variability is large, even among highly selected subjects, (b) traditional reports of overall pill counts are suboptimal, and (c) pill counts may unreliably measure medication-taking behavior because "supranormal" compliance by this method is improbable but common.

Antihypertensive Agents↗
PubMed1988

Breastfeeding pattern and the duration of lactational amenorrhea in urban Chilean women.

The influence of the breastfeeding pattern and several clinical variables upon the duration of postpartum amenorrhea was assessed in a group of healthy women selected for having had a normal pregnancy and delivery and being highly motivated for prolonged breastfeeding on demand. 676 women who were fully nursing at the second month postpartum entered the study. Supplements were administered to 11% and 48% of the infants by the end of the 3rd and 6th month, respectively. The first bleeding was experienced before the end of the sixth month postpartum by 57% of the cases. Supplementation had a strong negative influence while nursing frequency had a significant positive influence upon the length of amenorrhea. Notwithstanding, a frequency of 8+ suckling episodes per 24 h could not maintain amenorrhea in around half of the subjects. Age and parity had a moderate negative influence upon the risk of experiencing the first postpartum bleeding. Maternal weight and ponderal index, infant sex, birth weight and growth rate showed no significant influence upon the length of amenorrhea. In this urban population selected for having the highest motivation and best breastfeeding performance, the association of breastfeeding with amenorrhea was weak in comparison with what has been described for other populations. The risk of experiencing the first bleeding was reduced while fully breastfeeding with a high number of nursing episodes per day and night, particularly in older women with higher parity. But even in such situation 25% and 50% of the women had started to cycle by the end of the fifth and eight postpartum month.

Adult↗
PubMed1982

Mode of action of progesterone in the blockade of gonadotropin surges in the rhesus monkey.

The action of progesterone (P) to block estradiol-induced gonadotropin surges in the rhesus monkey requires an intact hypothalamus. The present study was performed to determine whether the blocking action of P is the result of an inhibition in hypothalamic GnRH secretion or of some other mechanism. Ovulatory menstrual cycles were initiated in acyclic rhesus monkeys with intact nervous systems by a pulsatile GnRH replacement regimen previously shown to be effective in sustaining normal ovarian cycles in monkeys with hypothalamic lesions. Whereas unambiguous surges of LH and FSH were elicited by estradiol benzoate during the follicular phase of these cycles, no such gonadotropin discharges were obtained in the presence of luteal phase levels of P generated by sc P-containing Silastic capsules. Because exogenous GnRH replacement was provided throughout these experiments, it is concluded that P blockade of estradiol-induced gonadotropin surges is not the consequence of an interruption in GnRH release. The results suggest, rather, that P may cause the production of an inhibitory factor from the central nervous system which blocks the positive feedback action of estradiol on the pituitary gland.

Animals↗
PubMed1981

Don't be shocked.

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Electric Injuries↗
PubMed1981

Estradiol as a gonadotropin releasing hormone in the rhesus monkey.

The temporal relationship between cessation of GnRH delivery to the pituitary gland and the loss of responsiveness to the stimulatory action of estradiol (E2) was examined in 4 ovariectomized rhesus monkeys whose endogenous GnRH production had been abolished by hypothalamic lesions. Gonadotropin secretion was re-established by the intermittent administration of GnRH. The GnRH-replacement regimen was then discontinued and estradiol benzoate (EB) injected 24, 48, 72 and 96 hours later. Unambiguous gonadotropin discharges were induced when EB was administered 24 or 48 hours after discontinuation of GnRH replacement. We conclude that E2 can initiate gonadotropin discharges in the absence of circulating GnRH. E2 may, therefore, be viewed as a gonadotropin releasing hormone.

Animals↗
PubMed1981

Frequency and amplitude of gonadotropin-releasing hormone stimulation and gonadotropin secretion in the rhesus monkey.

In adult ovariectomized rhesus monkeys bearing hypothalamic lesions which reduced circulating LH and FSH to undetectable levels, sustained elevated gonadotropin concentrations were reestablished by the intermittent administration of gonadotropin-releasing hormone (GnRH) at the rate of 1 microgram/min for 6 min once every hour. The effects of varying either the frequency or the amplitude of these GnRH pulses on gonadotropin secretion were examined in such animals. Increasing the frequency of GnRH administration from the physiological one pulse per h to two, three, or five pulses h while maintaining a constant infusion rate and pulse duration resulted in gradual declines in plasma gonadotropin concentrations. These declines were most profound at the highest frequencies and the consequence of reduced pituitary responses to individual GnRH pulses. Decreasing the frequency of GnRH pulses from one per h to one every 3 h led to variable declines in plasma LH levels, but circulating FSH invariably rose. Reducing the GnRH infusion rate from 1 to 0.1 mg/min while maintaining constant frequency and pulse duration resulted in abrupt declines in plasma LH and FSH to immeasurable levels, although pulsatile increments in circulating GnRH concentrations without a concomitant reduction in plasma LH concentrations, which remained unchanged. An infusion rate of 0.5 microgram/min resulted in unstable plasma LH and FSH levels. These results demonstrate that changes in the frequency or amplitude of hypophysiotropic stimulation have profound effects on plasma gonadotropin levels as well as on FSH to LH ratios in the circulation. The physiological implications of these observations are discussed.

Animals↗
PubMed1981

On the site of action of progesterone in the blockade of the estradiol-induced gonadotropin discharge in the rhesus monkey.

The site of action of progesterone (P) in the blockade of estradiol-induced gonadotropin discharges was examined in rhesus monkeys bearing hypothalamic lesions which abolish endogenous GnRH production. Normal ovulatory menstrual cycles were re-established in these animals by the pulsatile, hourly administration of GnRH. In the follicular phase of these induced menstrual cycles, P-containing Silastic capsules were implanted sc yielding luteal phase plasma P concentrations which normally block estradiol-induced gonadotropin surges. P failed to block estradiol-induced surges in lesioned animals on GnRH replacement. In such animals, however, P advanced the initiation of these surges. While estradiol acts on the pituitary to cause gonadotropin discharges, P appears to block this effect by acting on the central nervous system. On the other hand, the results also suggest that the site of facilitatory action of P on gonadotropin release is at the level of the pituitary gland.

Animals↗
PubMed1980

Control of the rhesus monkey menstrual cycle: permissive role of hypothalamic gonadotropin-releasing hormone.

In rhesus monkeys with hypothalamic lesions (which appear to abolish the endogenous production of gonadotropin-releasing hormone), normal ovulatory mestrual cycles were reestablished by an unvarying, long-term replacement regimen consisting of one intravenous pulse of synthetic gonadotropic-releasing hormone per hour. This finding is in accord with the hypothesis that the pattern of pituitary gonadotropin secretion throughout the menstrual cycle (basal secretion interrupted, once every 28 days on the average, by a preovulatory surge) is not directed by alterations in hypothalamic gonadotropin-releasing hormone secretion but by the ebb and flow of ovarian estrogens acting directly on the pituitary gland.

Animals↗