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Biomedical subjects

A M Walker

Publications and source records attributed to A M Walker.

At least 235 records · Page 13Linked to original sources
PubMed1987

Treatment of intrathyroidal papillary carcinoma of the thyroid.

Among 237 patients with grossly noninvasive (intrathyroidal) papillary carcinoma of the thyroid treated by surgery at the Massachusetts General Hospital and followed for a median of 14 years, no patient had tumor recurrence either in the thyroid bed or opposite lobe. There were 12 metastatic recurrences with risks of recurrence 4.0% and 6.9% at 10 years and 20 years respectively. Eight of these recurrences were restricted to cervical lymph nodes and did not herald the development of more serious recurrent disease. The remaining recurrences were lung metastases in four patients, two of whom died, accounting for the only deaths from thyroid carcinoma in this series. Factors that influenced the risk of recurrence included lymph node metastases at initial surgery, large tumor size, and to a lesser extent, male sex. The majority of patients (176) had subtotal thyroidectomies, mostly lobectomy (131 patients). There was no evidence that the 61 patients who underwent total thyroidectomy fared better than those with similar patient and tumor characteristics on whom subtotal procedures were performed. The overall findings of this study strongly support the concept that intrathyroidal thyroid carcinoma can be successfully treated by conservative surgery.

Adolescent↗
PubMed1987

Non-steroidal anti-inflammatory drugs and hospital admission for perforated peptic ulcer.

The frequency of hospital admission for perforated ulcer was not measurably affected by concurrent use of non-steroidal anti-inflammatory drugs (NSAID) during nearly 30 million person-days of NSAID use at Group Health Cooperative of Puget Sound. Whether patients had ever used cimetidine or antacids, drugs which indicate the presence of ulcer disease or symptoms, was strongly predictive of perforation in the same population (rate ratio 5.1; 95% CI 2.6-10.0). Perforation rates increased sharply with age but were similar for men and women.

Adolescent↗
PubMed1987

A case-control study of risk factors in open angle glaucoma.

In a case-control study using an exploratory health questionnaire, we examined the relationship between primary open angle glaucoma (POAG) and a variety of personal characteristics and potential toxic exposures in patients in a general eye service. There were 83 patients with definite POAG, 121 POAG suspects, and 237 controls. Using multiple logistic regression analysis for simultaneous evaluation of potential risk factors, we found that black race (rate ratio = 6.8; 95% confidence interval [CI] = 2.8 to 16.0) and untreated systolic hypertension (rate ratio = 5.8; 95% CI = 2.2 to 15) were the most important risk factors. Current cigarette smoking was also associated with glaucoma (rate ratio = 2.9; 95% CI = 1.3 to 6.6). Suggestive associations were found with family history of glaucoma, definite or borderline diabetes, and myopia. The effects of many of these personal characteristics and exposures as risk factors were also noted for the glaucoma suspect group, though not as strongly as for the definite glaucoma cases.

Alcohol Drinking↗
PubMed1987

Origins and regional distribution of blood flow to the respiratory muscles in conscious sheep.

The blood flow to the portions of the diaphragm (sternal, costal, and crural) and to the external and internal intercostal muscles was measured, using radio-labelled microspheres, in 12 young sheep breathing quietly. We calculated total blood flow and oxygen uptake of the diaphragm (VO2di). We also determined the proportion of diaphragmatic and intercostal muscle blood flow that arose from the descending aorta. Diaphragmatic blood flow (Qdi) was 0.62 +/- 0.04% of cardiac output (mean +/- SEM). VO2di was 1.53 +/- 0.15 ml X min-1 X 100 g-1, and was linearly related to Qdi. When standardized for weight Qdi was 28.3 +/- 1.5 ml X min-1 X 100 g-1, significantly greater than both external intercostal muscle blood flow (18.9 +/- 2.6 ml X min-1 X 100 g-1; P less than 0.05), and internal intercostal muscle blood flow (11.4 +/- 1.4 ml X min-1 X 100 g-1; P less than 0.01). Blood flow to the costal portion of the diaphragm was significantly less than blood flow to the crural portions. There was no difference between flow to these portions and to the sternal portion of the diaphragm. The blood supplying the dorsal-most regions of the diaphragm arose predominantly from the descending aorta. The results suggest that the crural portions work at a higher rate than the costal portions under resting conditions.

Animals↗
PubMed1987

The age curve of nervous system tumour incidence in adults: common shape but changing levels by sex, race and geographical location.

A multiplicative model was fitted to incidence rates of nervous system tumours cross-tabulated for each sex by five-year age groups between ages 35-64 and 51 populations in which at least ten cases had been observed and 60% of cases histologically verified. There was no significant departure from a model in which the age curve was assumed to have the same shape but a different level in each population. On log-log scale this shape was a straight line with identical slope (2.6) for males and females. Population-specific multipliers were highest in Israel and lowest in Asia. Within the US, rates were significantly lower among blacks, Hispanics, Chinese and Japanese compared to whites. A model for both sexes combined showed that sex ratios were rarely below unity but varied significantly between populations. Exposure (or susceptibility) to as yet unidentified aetiological factors appears to be higher in males and whites than in females and non-whites.

Adult↗
PubMed1987

Age dependence of cohort phenomena in breast cancer mortality in the United States.

Breast cancer mortality has increased in most parts of the world, and many explanations have been postulated. In this paper, the authors examined the evolution of mortality rates for white and nonwhite females in the United States from 1950-1979. Using both graphic techniques and Poisson regression models, they found that there has been strong modification of apparent cohort effects by age. For both white and nonwhite females, they observed an increase in mortality rates limited to the postmenopausal ages.

Adult↗
PubMed1987

Diphtheria-tetanus-pertussis immunization and sudden infant death syndrome.

We compared the recency of diphtheria-tetanus-pertussis (DTP) immunization in healthy children with birthweights greater than 2500 gms who died of sudden infant death syndrome (SIDS) to that of age-matched reference children, using a modified case-control analysis. Focusing on very narrow time intervals following immunization, we found the SIDS mortality rate in the period zero to three days following DTP to be 7.3 times that in the period beginning 30 days after immunization (95 per cent confidence interval, 1.7 to 31). The mortality rate of non-immunized infants was 6.5 times that of immunized infants of the same age (95 per cent CI, 2.2 to 19). The latter result and to some extent the former appear to be ascribable to known risk factors for SIDS. Although the mortality ratios for SIDS following DTP, as estimated from this study, are high the period of apparently elevated risk was very short, so that only a small proportion of SIDS cases in infants with birthweights greater than 2500 gms could be associated with DTP.

Birth Weight↗
PubMed1987

The effects of bupivacaine on the umbilical circulation and placental gas exchange in the fetal lamb.

Seven chronically catheterized fetal sheep at 125-140 days gestation were studied in 12 experiments to determine the direct effects of the local anesthetic bupivacaine (infused intravenously to the fetus) on the umbilical circulation and placental gas exchange. Electrocortical activity, umbilical blood flow, heart rate, and umbilical arterial and venous pressures were continuously monitored in experiments comprising a baseline period, a drug infusion period and a recovery period, each of 2 hr duration. Samples of umbilical arterial and venous blood were taken for blood gas analysis, and for bupivacaine assay using high pressure liquid chromatography technique. Fetal plasma bupivacaine levels were 1.3 +/- 0.3 microgram/ml (mean +/- SEM) between 60-120 min of infusion. Heart rate and umbilical blood flow decreased significantly to 89 and 94% of control, respectively, (P less than 0.05) during the infusion and returned to control levels by 2 hr afterwards. Mean umbilical arterial and venous pressures were not significantly altered, and no significant rise in umbilical vascular resistance occurred. No changes occurred in umbilical arterial or venous pH, PO2, or PCO2. In summary, bupivacaine reversibly depressed fetal heart rate and umbilical blood flow without detrimental changes in fetal blood gas or acid-base status.

Animals↗
PubMed1987

Nonsteroidal anti-inflammatory drugs and hospitalization for gastroesophageal bleeding in the elderly.

Hospitalization because of bleeding from the stomach or esophagus occurred 4.8 times per million person-days among persons over 64 years of age who filled a prescription for nonsteroidal anti-inflammatory drugs (NSAIDs) within 90 days of hospitalization, and 3.4 times per million person-days among nonusers of NSAIDs over 64 years of age at the Group Health Cooperative of Puget Sound, Seattle. The NSAID users included those who had used these drugs on a long-term basis as well as those who were recent users only. The observed difference in rates (1.3 hospitalizations per million person-days; 95% confidence interval, -0.2 to 3.4 hospitalizations per million person-days) is incompatible with any major increase in the frequency of hospitalization for gastroesophageal bleeding in the elderly. No single NSAID appeared to carry an exceptional risk. Both chance and uncontrollable selection factors could provide plausible explanations for the small rate differences observed between users and nonusers.

Aged↗
PubMed1987

Mortality among oral contraceptive users.

The occurrence of fatal conditions was substantially similar in a large population of recent, healthy oral contraceptive users and comparable nonusers at Group Health Cooperative of Puget Sound during the years 1977-1981. There were no deaths from cardiovascular disease among those who were oral contraceptive users at the onset of their cardiovascular illness; there was one death from liver cancer, probably attributable to oral contraceptive use; and there were no deaths from complications of pregnancy among either users or nonusers. Newer formulations of oral contraceptives and greater care in prescribing oral contraceptives to the healthiest younger women may have substantially lessened the risks identified with earlier preparations and prescription practices.

Adolescent↗
PubMed1986

A double-masked comparison of betaxolol vs timolol in the treatment of open-angle glaucoma.

We conducted a six-month prospective, double-masked randomized trial comparing betaxolol with timolol at 0.25% and 0.5% concentrations in the treatment of primary open-angle glaucoma in 38 patients. To qualify, patients had to demonstrate an average intraocular pressure in at least one eye of greater than or equal to 26 mm Hg without treatment. The median intraocular pressure was consistently lower in the timolol group than in the betaxolol group (after four weeks of therapy, it was 20.2 mm Hg for timolol vs 22.5 mm Hg for betaxolol; P less than .04). Adjunctive therapy was required in eight patients in the betaxolol group compared to one in the timolol group (P less than .05). Betaxolol appears to be a clinically effective and safe agent in the treatment of open-angle glaucoma. However, the magnitude of the decrease in intraocular pressure with it may not be as great as that with timolol and there may be a greater need for adjunctive therapy with it than with timolol.

Adult↗
PubMed1986

Phosphorylation of prolactin.

Rat prolactin exhibits microheterogeneity when examined in electrophoretic systems, running as three isoforms having the same molecular weight but different net charges (prolactins 1, 2, and 3 with isoform 3 being the most acidic). As there is precedent for the phosphorylation of a pituitary hormone and phosphorylation is a common cause of microheterogeneity, we examined the possibility that rat prolactin existed in differentially phosphorylated forms. The investigation included examinations of rat prolactin phosphorylation both in vitro and in vivo. For the in vitro studies, purified rat prolactin was incubated with [gamma-32P]ATP and low levels of each of five purified protein kinases. Phosphorylated rat prolactin was identified by autoradiography of silver-stained one- and two-dimensional gels. For the in vivo studies, rat anterior pituitary cells in primary culture were incubated in the presence of H3 32PO4 for 2 or 12 h, after which time the proteins were extracted from the cells, cold acetone-precipitated, or immunoprecipitated and run on two-dimensional gels. We report the in vitro phosphorylation of rat prolactin by cAMP-dependent protein kinase, casein kinase I, protease-activated kinase I, and the calcium/phospholipid-dependent kinase, that phosphorylation with these kinases results in phosphate incorporation only into isoforms 2 and 3, and the phosphorylation of prolactin in rat pituitary cells in primary culture.

Animals↗
PubMed1986

Increased dietary leucine changes the rhythm of prolactin secretion.

As we have recently shown that prolactin secretion in vitro is regulated by extracellular leucine, we wanted to determine whether leucine had a similar regulatory action on prolactin secretion in the intact animal. Leucine was administered to cycling female rats by way of their drinking water (0.5%) for a period of 24 days. At daily intervals during this time, six control and six leucine-treated rats were killed and their trunk blood subsequently assayed for prolactin content. On days 7, 14, and 21 during this period, pituitaries from the sacrificed rats were fixed and processed for electron microscopy. Leucine treatment resulted in an alteration in the normal four-day cyclicity in serum prolactin levels and a stimulation of prolactin synthesis as evidenced by ultrastructural changes in the pituitary mammotrophs. In a parallel set of experiments, daily vaginal smears were taken from nonsynchronized animals for 24 days before and 24 days during leucine administration. Leucine treatment resulted in variable alterations in the estrus cycle depending upon the stage of the cycle when the leucine was first administered. The changes in serum prolactin and the disturbances of the estrus cycle in the leucine-treated animals persisted for approximately 20 of the 24 days. In a shorter control experiment (seven days), alanine treatment (0.5%) was found to have no effect on prolactin levels. It is concluded that a mild elevation in dietary leucine can affect prolactin synthesis and release and the normal progression of the estrus cycle.

Animals↗
PubMed1986

Phasic respiratory activity in the fetal lamb during late gestation and labour.

We quantified the respiratory activity of 9 fetal lambs using computer-analysis of the diaphragmatic electromyogram (EMG) obtained during 2 h recording sessions interspersed over the last 13 days of gestation. The fetuses delivered unassisted at an average gestational age of 145 days (term = 147 days). During the last 2 h of labour the number of phasic EMG bursts (breaths) averaged 3% of the peak recorded earlier in the study. This decline in breathing began at least 2 days before labour and resulted predominantly from the fetus spending an increasing proportion of time in apnoea. Respiratory rate within epochs of breathing also fell significantly 1 day before labour, and the proportion of time spent in the low voltage electrocortical state declined once labour commenced. No significant change occurred in arterial PO2, PCO2 or pH over the study period. We conclude that fetal respiratory activity falls well before the onset of labour, largely as a result of increased apnoea, and that the decline does not result from the development of a progressive hypoxaemia associated with labour.

Animals↗
PubMed1986

Specific and reversible degranulation of pituitary mammotrophs.

When dissociated anterior pituitary cells were cultured over a layer of gelatin, electron microscopic observation showed the mammotrophs in the culture to be essentially degranulated and to have massively dilated rough endoplasmic reticulum (RER) and Golgi apparatus (GA), while there were no discernible effects on any of the other cell types. PRL synthesis in the gelatin-cultured cells occurred at twice the rate of that in the control cells and the gelatin-cultured cells contained 3% of the normal amount of PRL. Transfer of the cells to a more traditional culture situation reversed most of the morphological changes within 24 h. The mammotrophs were responsive to thyrotropin-releasing hormone (10(-7) M) both immediately after gelatin culture (3-fold control) and after reversal (5-fold control). As placement of the gelatin-cultured cells into traditional culture synchronizes the onset of granulation, we conclude that mammotrophs cultured in this fashion will be useful in the further study of PRL synthesis, packaging, storage and degradation.

Animals↗
PubMed1986

Vitamin measurements in pooled blood samples.

From 610 blood samples collected in September 1983 in an intervention trial in Huixian, Henan Province, People's Republic of China, which were individually analyzed for retinol, beta-carotene, and alpha-tocopherol levels, 10 pools were formed from 50 individual samples, and the vitamin levels in the merged pools were also measured. Oxidation losses by repeated thawing and refreezing render the absolute levels measured in the pools smaller than the corresponding means of the individual measurements. A very good relative agreement was found between pool levels of retinol and beta-carotene and the respective means. The pooling technique could be a valuable tool in large correlation studies and has possible further applications in case-control studies.

Adult↗