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Biomedical subjects

M C White

Publications and source records attributed to M C White.

At least 91 records · Page 5Linked to original sources
PubMed1993

Mortality associated with nosocomial infections: analysis of multiple cause-of-death data.

Nosocomial infection mortality is an important problem, with estimates of magnitude placing it among the 10 leading causes of death in the United States. This is a preliminary study to determine the potential usefulness of death certificate data in providing information about the frequency of nosocomial infections and their association with other conditions listed as underlying or contributing causes of death. Multiple cause-of-death data were examined for 1988, to identify the number and characteristics of persons dying with nosocomial infections. The mortality rate associated with nosocomial infections found on death certificates was 3.83 per 100,000 person-years. This method needs to be validated by further work. Because nosocomial infections are a contributing rather than an underlying cause of death, multiple-cause mortality data may provide another way to estimate the magnitude of this problem.

Aged↗
PubMed1993

The anti-estrogen tamoxifen blocks the stimulatory effects of interleukin-6 on 17 beta-hydroxysteroid dehydrogenase activity in MCF-7 cells.

Previous studies have revealed that human breast fibroblasts secrete the cytokine, interleukin-6 (IL-6) which stimulates the ability of MCF-7 human breast carcinoma cells to convert estrone (E1) to the biologically more active 17 beta-estradiol (E2). This is mediated by an increase in reductive 17 beta-hydroxysteroid dehydrogenase (17-HSD) activity. In the studies described here, we have extended our observations using the anti-estrogen, tamoxifen, to demonstrate that in a steady state, endogenous intracellular concentrations of E2 have no effects on reductive 17-HSD activity (E1-->E2), but are already maximally inhibitory for the oxidative reaction (E2-->E1). Increasing intracellular concentrations of E2, however, stimulated the reductive 17-HSD in a dose-dependent manner. IL-6 stimulated the reductive pathway and was synergistic with E2. IL-6 is most likely acting through an E2-dependent mechanism, since tamoxifen completely reversed the effects of E2 and IL-6 separately and in combination. These observations suggest that tamoxifen may reduce intratissular levels of E2 by directly increasing oxidative 17-HSD activity and by blocking the actions of paracrine factors such as IL-6 which increase reductive 17-HSD activity.

17-Hydroxysteroid Dehydrogenases↗
PubMed1993

Interactive effects of interleukin-6, 17 beta-estradiol and progesterone on growth and 17 beta-hydroxysteroid dehydrogenase activity in human breast carcinoma cells.

It has been demonstrated that reductive 17 beta-hydroxysteroid dehydrogenase activity (17-HSD) in the human breast cancer cell line MCF-7 can be stimulated by 17 beta-estradiol (E2), progesterone (P) and interleukin-6 (IL-6). We have examined the interactive effects of these factors on growth and reductive 17-HSD activity of MCF-7 cells cultured under defined conditions in phenol red-free medium. E2 stimulated growth of MCF-7 cells in a dose-dependent manner, while IL-6 had a growth inhibitory effect and in combination with E2, it reduced or abolished the stimulatory effects of the steroid. Both E2 and IL-6 stimulated 17-HSD activity by a maximum of 2- to 5-fold, but, in combination, the stimulatory effects ranged from 7- to 10-fold, indicating a strong synergism between the 2 factors. P had growth stimulatory effects on MCF-7, but when combined with IL-6 had no further positive or negative growth effects. Both factors stimulated reductive 17-HSD activity and simultaneous treatment with P and IL-6 indicated a synergy between the 2 factors. These results provide evidence of powerful interactive effects between steroidal and paracrine control of human breast epithelial cells in vitro.

17-Hydroxysteroid Dehydrogenases↗
PubMed1993

Relationship between markers of endothelial dysfunction, oxidant injury and tubular damage in patients with insulin-dependent diabetes mellitus.

1. Diabetic nephropathy is a serious microvascular complication in patients with insulin-dependent diabetes mellitus, resulting in end-stage renal disease in 30-45% of such patients. Despite intensive investigation, the pathophysiology of diabetic renal disease has not been fully elucidated. However, several clinical and experimental studies have suggested that endothelial dysfunction and free-radical activity may be important factors. 2. Forty normotensive patients with insulin-dependent diabetes mellitus of between 10 and 20 years duration with persistent normoalbuminuria (albumin excretion < 30 mg/day) and normal renal function were investigated for markers of endothelial dysfunction (plasma von Willebrand factor, soluble thrombomodulin and angiotensin-converting enzyme activity), free oxygen radical generation (erythrocytic superoxide dismutase and glutathione peroxidase) and oxidant injury (serum malondialdehyde). Glomerular proteinuria (albuminuria, transferrinuria), tubular proteinuria (retinol-binding protein) and tubular enzymuria (N-acetyl glucosaminidase and leucine aminopeptidase) were also measured. 3. Patients were divided into two groups. Group 1 comprised 21 patients with elevated markers of endothelial dysfunction, and group 2 comprised 19 patients with normal levels of plasma von Willebrand factor, soluble thrombomodulin and angiotensin-converting enzyme activity. Thirty-eight healthy subjects matched for age and sex acted as controls. 4. Groups 1 and 2 were similar in age, sex, body weight, duration of diabetes mellitus and recent glycaemic control. Serum cholesterol, serum creatinine and glomerular proteinuria were similar in the three groups. Group 1 patients had significantly increased oxidant injury, tubular enzymuria and proteinuria compared with group 2 patients and control subjects (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Pituitary apoplexy and sudden blindness following the administration of gonadotrophin releasing hormone.

Pituitary apoplexy has been reported as a rare complication of combined tests and of TRH administration in prolactinomas. A 54-year-old man with a pituitary macroadenoma had a single injection of 100 micrograms GnRH. Twenty minutes later he complained of increasing headache and vomited. These symptoms settled spontaneously and were attributed to the pharmacological effects of GnRH. Five hours later he was found to be blind and disorientated without spontaneous complaint. Emergency CT showed a large adenoma with central necrosis, consistent with pituitary apoplexy. An urgent surgical decompression was carried out and necrotic haemorrhagic debris removed. Baseline bloods revealed non-pulsatile FSH of 40 U/l with LH 0.3 U/l with no hormonal response to GnRH administration, but the sequence of events strongly suggests a causal relationship between this and pituitary apoplexy. To our knowledge this is the first time that GnRH administration has been associated with pituitary apoplexy of a glycoprotein secreting pituitary adenoma.

Adenoma↗
PubMed1993

Basic fibroblastic growth factor stimulates prolactin secretion from human anterior pituitary adenomas without affecting adenoma cell proliferation.

The effects of human recombinant basic fibroblastic growth factor (bFGF) on the secretion and/or proliferation of 26 human anterior pituitary adenomas secreting PRL alone (6 tumors), PRL and GH (18 tumors), or GH alone (2 tumors) were examined. Secretory studies were performed over 4 h, 4 days, and 21 days, and proliferation studies over 4 days. The acute effect of bFGF on secretion over 4 h was examined in 10 tumors. bFGF (10 nmol/L) increased PRL compared to that in controls (100%) in 2 tumors (126% and 290%; P < 0.05) and PRL and GH in a third tumor (183% and 133%, respectively; P < 0.05), whereas 7 tumors remained unaffected. Fourteen tumors were studied over 4 days. bFGF (10 nmol/L) increased PRL secretion in 9 of 11 tumors (117-525%; P < 0.05) cosecreting PRL and GH and in all 3 tumors secreting PRL alone (156%, 183%, and 691%; P < 0.01). Dose-response curves with 0.1, 1, and 10 nmol/L bFGF in 2 of these tumors cosecreting GH and PRL showed that stimulation was achieved with all 3 concentrations. bFGF (10 nmol/L) stimulated GH secretion in 2 of 11 mixed tumors (159% and 196%, respectively; P < 0.05). In 2 tumors studied over 3 weeks, 5 nmol/L bFGF stimulated PRL secretion progressively without affecting GH secretion (106% and 207%; P < 0.05). Tissue proliferation was determined by double immunostaining after bromodeoxyuridine incorporation for 1 h in 7 tumors after 4 days. The labeling index did not exceed 1.2% in any tumor, and there was no effect of 10 nmol/L bFGF on the proliferation of adenoma cells. These results suggest that bFGF may have a paracrine role in the stimulatory regulation of PRL secretion in human pituitary adenomas, and these effects are most likely due to increased hormonal synthesis. An in vitro cell culture system can be used to study proliferative potential. However, bFGF is not mitogenic for human anterior pituitary adenomas secreting PRL and PRL plus GH in vitro.

Adenoma↗
PubMed1993

Differential effects of insulin-like growth factor 1 on the hormonal product and proliferation of glycoprotein-secreting human pituitary adenomas.

The effects of human recombinant insulin-like growth factor 1 (IGF-1) on the secretion, viability, and proliferation of dispersed human anterior pituitary adenomas secreting FSH, LH, and alpha-subunit (alpha-su) were examined in vitro over 4 h and 4 days. The acute effect of IGF-1 on secretion over 4 h was examined in four tumors secreting FSH, LH, and alpha-su. IGF-1 (100 nmol/L) reduced LH compared to control (100%) in one tumor (61%, P < 0.01), and three tumors remained unaffected. FSH and alpha-su secretion were insufficient to measure over 4 h. Nine tumors were studied over 4 days; relative to control, IGF-1 (100 nmol/L) increased FSH secretion in all seven tumors secreting FSH (28-266%, P < 0.05) and increased alpha-su secretion in all four tumors studied (36%, 63%, 91%, and 121%, P < 0.05). IGF-1 reduced LH secretion in four/nine tumors (13%, 23%, 32%, and 50%, P < 0.05). Dose response curves (1-100 nmol/L IGF-1) were performed on three tumors cosecreting FSH and LH. Stimulation of FSH was achieved with either 1 or 10 nmol/L IGF-1, a single tumor in which alpha-su was measured showed maximal stimulation at 10 nmol/L IGF-1, and one of three tumors showed LH inhibition with 100 nmol/L IGF-1. In situ viability of attached cells was assessed with fluorescein and propidium iodide in seven tumors. After 4 days' exposure to 100 nmol/L IGF-1, in situ viability was increased in five tumors (range 12-19%, 15 +/- 1.3% SEM, P < 0.05). The effects of IGF-1 on the adenoma cell proliferative S-phase fraction was determined in six tumors after 4 days of treatment using double immunostaining with bromodeoxyuridine incorporation for 1 h. In four/six adenomas that stained positive for bromodeoxyuridine in the controls (1-5.6%), the S-phase fraction was increased by 100 nmol/L IGF-1 [(range 2.1-10.6%, increase 90-220%) (P < 0.05)]. These results show that IGF-1 has differential effects on gonadotropins from human pituitary adenomas, stimulating intact FSH and alpha-su, inhibiting or being without effect on intact LH in vitro, and increasing both viability and number of tumorous glycoprotein-secreting cells entering into the S-phase of proliferation.

Adenoma↗
PubMed1993

Home health care: occupational health issues.

1. Although much work has been done to identify occupational risks to health care workers in institutions, little has been done to describe such risks in the growing home care industry. Changes in the nature of home care suggest the risks may be equivalent, with additional risks from the variable environment of the home. 2. Directors of home care agencies in Northern California were surveyed with respect to the nature of home care, workers, characteristics of occupational programs, and common illnesses and injuries. Musculoskeletal injuries were the most common occupational injuries reported. 3. Despite legislation and accreditation standards, occupational programs in home care agencies are incomplete. Further work is needed to determine the relationship between the presence of occupational health programs and home health care outcomes.

California↗
PubMed1992

Infections and infection risks in home care settings.

OBJECTIVES: To describe the characteristics of home healthcare clients with respect to infection risks and the presence of infections. DESIGN: Descriptive survey of client charts using a point prevalence design. SETTING: A private San Francisco, California, Bay area home care agency. PARTICIPANTS: A random sample of 175 clients (28%) was taken from the active client list for a single day; demographic data and clinical data from the last visit prior to the selection day were collected from each chart. RESULTS: The clients were predominantly elderly (mean = 68.6) with an average of 3.6 co-morbid conditions; 12% had an invasive device. Over 20% had an infection on the day surveyed. Five percent had an infection that occurred during home care delivery. CONCLUSIONS: A substantial proportion of home health clients have infections, and they represent persons with a number of the risks associated with infections. Guidelines for defining and monitoring infections in home care need to be developed. Hospital-based surveillance methods are not altogether appropriate in this setting; redesigning methods such as targeted surveillance, monitoring rehospitalization, or immunization practices are discussed as potential ways to measure quality of care in the home setting.

Aged↗
PubMed1992

Alterations in the microbial flora and in the incidence of bacteremia at a university hospital after adoption of amikacin as the sole formulary aminoglycoside.

Because of the rapid emergence of resistance to gentamicin and tobramycin among isolates of aerobic and facultative gram-negative bacteria at our university hospital, we designed a prospective study to track aminoglycoside resistance, bacteremic episodes, and bacteremia-associated deaths before and after the institution of amikacin as the sole formulary aminoglycoside. From June 1984 through June 1987 (immediately before this policy change), amikacin accounted for only 20% of patient-days of aminoglycoside therapy, and rates of resistance to gentamicin, tobramycin, and amikacin among aerobic and facultative gram-negative bacterial isolates were 12.8%, 10.8%, and 5.9%, respectively. During the next 30 months (immediately after the change in policy), amikacin accounted for 98% of patient-days of aminoglycoside therapy, and rates of resistance to gentamicin, tobramycin, and amikacin were 6.3%, 5.0%, and 3.3%, respectively. Furthermore, during the latter 30 months, the incidence of both bacteremia and bacteremia-associated death decreased significantly. Hospitals at which resistance to gentamicin or tobramycin is increasing among the gram-negative flora may benefit from the use of amikacin as the principal aminoglycoside.

Amikacin↗
PubMed1992

Investigation of adrenal function in women with oligomenorrhoea and hirsutism (clinical PCOS) from the north-east of England using an adrenal stimulation test.

OBJECTIVE: To determine the prevalence of adrenal enzyme dysfunction in women presenting with oligomenorrhoea and hirsutism, two clinical features of polycystic ovary syndrome (PCOS). DESIGN: A prospective study of women attending outpatient clinics with these complaints. Androstenedione, dehydroepiandrosterone (DHEA), 17-hydroxyprogesterone (17-OHP), 11-deoxycortisol and cortisol were measured before and after overnight dexamethasone suppression and at 60 minutes after adrenal stimulation by ACTH injection. SUBJECTS: Fifty women with clinical features of PCOS and 37 control women with regular cycles and normal hair distribution from the catchment area of the Royal Victoria Infirmary which includes Newcastle upon Tyne, Co. Durham, Cleveland, Cumbria and Northumberland. MEASUREMENTS: Number of women with steroid responses to ACTH beyond the normal range, as defined by the responses of the control group and in previous studies. RESULTS: Nineteen women (38%) were found to have some abnormality. One woman (2%) was identified with 21-hydroxylase (21-OHase) deficiency and a second (2%) had an increase in 17-OHP compatible with the heterozygote state for 21-OHase deficiency. Four women (8%) had isolated elevations in the DHEA response consistent with minimal 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) deficiency. Thirteen women (26%) showed increases in both androstenedione and DHEA, or androstenedione alone, compatible with enhanced 17-20 lyase activity. CONCLUSIONS: Twelve per cent of the group showed evidence consistent with an adrenal enzyme deficiency; 26% had results in keeping with increased adrenal androgen production without an enzyme deficiency. These findings may be of relevance both in the pathogenesis of the features of PCOS and in determining appropriate treatment for individual patients.

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Gonadotrophin secretion in vitro by cells of a pituitary tumour from a patient with multiple endocrine neoplasia type I.

OBJECTIVE: The aim was to investigate the hormone secretory products of a pituitary tumour from a patient with multiple endocrine neoplasia type I (MEN I) utilizing cell culture and immunoassay techniques. DESIGN: Adenoma tissue was enzymically dispersed and established in cell culture. Medium was collected for hormone measurement after 2 days, and also after 24-hour periods during long-term culture. In addition, tissue fixed at surgery was analysed by immunocytochemistry and electron microscopy. PATIENT: The subject was a 59-year-old male with a clinical history characteristic of familial MEN I syndrome. MEASUREMENTS: Pituitary hormones in serum and culture medium were measured by fully characterized radioimmunoassays. RESULTS: Preoperative serum LH and FSH levels were normal, or slightly elevated, and there was a progressively blunted gonadotrophin response to GnRH throughout the 8 years prior to adenomectomy. TRH induced a small, paradoxical increase in serum gonadotrophin levels 2 weeks preoperatively. Post-operative pituitary hormone responses to standard stimulation tests showed an active normal pituitary. In vitro, the pituitary tumour cells secreted only gonadotrophins and glycoprotein hormone alpha-subunit. The fixed tumour tissue immunostained for alpha-subunit alone, and electron microscopy confirmed the presence of secretory granules with diameters of 100-280 nm. Gonadotrophin secretion continued throughout 77 days in long-term culture, but whilst LH was released at a steady rate, that of FSH transiently increased between days 29 and 48 in vitro. CONCLUSIONS: These data demonstrate that a pituitary tumour associated with the MEN I syndrome secreted gonadotrophins in vitro.

Adenoma, Chromophobe↗
PubMed1992

A comparison of octreotide delivered by continuous subcutaneous infusion with intermittent injection in the treatment of acromegaly.

This study was undertaken to evaluate GH, IGF1 and drug levels during incremental continuous subcutaneous infusion of octreotide and compare these parameters following long-term treatment of 300 micrograms 24 h-1 by intermittent injection in a group of acromegalic patients. Ten patients were treated by continuous subcutaneous infusion in increasing dose from 200 micrograms 24 h-1 to 1600 micrograms 24 h-1; this resulted in consistent 24-h growth hormone suppression (less than 5.0 mU l-1), and normalisation of IGF1; the optimum dose was 400 micrograms 24 h-1, the maximum dose was tolerated without any untoward effects. There was no deterioration in carbohydrate tolerance despite a marked decrease in fasting and stimulated insulin levels. After 1 year of maintenance treatment, 300 micrograms 24 h-1 by intermittent injection, patients were re-evaluated; GH levels were not so consistently suppressed over the 24-h period and carbohydrate tolerance had deteriorated. A sub-group of patients with sub-optimal GH suppression on this regimen were identified and reassessed after 6 weeks treatment with an increased dose, 600 micrograms 24 h-1 by intermittent injection; both mean GH suppression and carbohydrate tolerance improved. The dose of drug and method of administration is best adjusted for each patient to achieve optimum GH suppression, thereby minimise compensatory hyperinsuliaemia and hopefully reduce morbidity and mortality. Alterations in pituitary tumour size and acquisition of gallstones during treatment have been observed which substantiate the need to re-evaluate these parameters on routine follow-up of acromegalic patients on long-term octreotide.

Acromegaly↗
PubMed1991

Autocrine control of human meningioma proliferation: secretion of platelet-derived growth-factor-like molecules.

We have used cell-culture techniques to investigate growth-factor production by human meningioma cells. Meningioma tissue was dispersed with collagenase and the cells grown to high density in tissue-culture flasks. The cultures were used to generate conditioned medium (MEN-CM), which was used to cultivate IMR32 cells (a human neuroblastoma line) and freshly dispersed primary meningioma cells. MEN-CM profoundly stimulated the in vitro growth of both IMR32 and meningioma cells. In addition, H3-thymidine uptake by cultured meningioma cells was increased in a dose-dependent manner by varying concentrations of MEN-CM. A neutralizing anti-body against platelet-derived growth factor (PDGF) completely abolished the stimulatory effects of MEN-CM, whereas an antibody against TGF-alpha was without effect. The mitogenic activity of MEN-CM, as assayed by promotion of H3-thymidine uptake by cultured meningioma cells, eluted from a Sephadex G-100 column in 3 peaks corresponding to molecular weights of greater than or equal to 150, 56 and 28 kDa. Our results show that proliferation of human meningiomas may be under autocrine control via secretion of PDGF-like molecules.

Cell Division↗
PubMed1991

Human insulin and awareness of acute hypoglycaemic symptoms in insulin-dependent diabetes.

Some insulin-dependent diabetic patients who have clear symptoms of hypoglycaemia during animal insulin treatment have reported loss of these symptoms when human insulin preparations are introduced. A survey of Mersey Region, UK, identified eleven patients whose awareness of hypoglycaemia was lost after introduction of human insulin but returned with animal insulin treatment; seven took part in the study. Acute hypoglycaemia was induced in these patients on two occasions by intravenous infusion of porcine or human soluble insulin (2.5 mU.kg-1, min-1) in random order. There was no significant difference between porcine and soluble insulin in the plasma glucose profile; mean (SEM) plasma glucose fell from 7.1 (0.4) mmol/l to a nadir of 1.5 (0.1) mmol/l with porcine insulin and from 7.1 (0.5) mmol/l to 1.6 (0.2) mmol/l with human insulin. An acute autonomic reaction occurred in all seven patients, at a similar plasma glucose concentration (1.9 [0.1] mmol/l with porcine insulin; 2.0 [0.2] mmol/l with human insulin). There were no significant differences in the frequency of symptoms or signs of hypoglycaemia between the two insulin species, nor any consistent differences in plasma glucagon, cortisol, growth hormone, adrenaline, or noradrenaline responses to hypoglycaemia. Symptomatic and hormonal responses to acute hypoglycaemia induced by porcine and human soluble insulins therefore seem to be almost indistinguishable, even in patients carefully selected for their apparent loss of hypoglycaemia awareness with human insulin.

Acute Disease↗