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Biomedical subjects

A H Smith

Publications and source records attributed to A H Smith.

At least 19 recordsLinked to original sources
PubMed1992

Long-term followup of infants with gross vesicoureteral reflux.

The majority of children (1 year old or less) with gross vesicoureteral reflux already have renal damage at the time of presentation or reflux nephropathy develops during the first few years of life. We report the long-term followup of 31 patients (16 boys) presenting in infancy with gross vesicoureteral reflux (Rolleston classification) between 1952 and 1970. They had a total of 44 grossly refluxing ureters (13 bilateral, 18 unilateral) and presented between ages 1 day and 48 weeks (mean 15.3 weeks). Of the 31 infants 5 died within the first year of life, 4 were followed for up to 11 years before being lost to followup and 1 was killed in a motor vehicle accident after 19.5 years of followup. The remaining 21 patients have been followed for 16 to 37 years (mean 23.9 years); 4 have normal kidneys, and 13 have unilateral and 4 have bilateral reflux nephropathy. Of those patients with unilateral reflux nephropathy proteinuria, hypertension and renal failure developed in 1 born with a single kidney and he is now on hemodialysis, while 2 others have a diastolic blood pressure of 90 mm. Hg or greater. Of the 4 patients with bilateral reflux nephropathy 2 have proteinuria and renal insufficiency, with 1 progressing towards end stage renal failure. Infants who present with gross vesicoureteral reflux within the first year of life appear to do well if free of severe bilateral reflux nephropathy at presentation. Patients with reflux nephropathy should remain under regular nephrological supervision with particular attention given to proteinuria, renal function and blood pressure.

Female↗
PubMed1992

Confidence limit analyses should replace power calculations in the interpretation of epidemiologic studies.

Frequently, after an epidemiologic study is completed, statistical power to detect a relative risk of interest is recalculated using data obtained during the course of the study. A negative study may then be dismissed on the grounds that its power was too low. However, post hoc power calculations ignore the actual relative estimate and its variance, which are by then known. We present evidence that post-study power calculations have little value and should be replaced by a more informative method using the upper (1 - alpha)% confidence limit of the point estimate that touches the value of the relative risk of interest.

Confidence Intervals↗
PubMed1992

Cancer risks from arsenic in drinking water.

Ingestion of arsenic, both from water supplies and medicinal preparations, is known to cause skin cancer. The evidence assessed here indicates that arsenic can also cause liver, lung, kidney, and bladder cancer and that the population cancer risks due to arsenic in U.S. water supplies may be comparable to those from environmental tobacco smoke and radon in homes. Large population studies in an area of Taiwan with high arsenic levels in well water (170-800 micrograms/L) were used to establish dose-response relationships between cancer risks and the concentration of inorganic arsenic naturally present in water supplies. It was estimated that at the current EPA standard of 50 micrograms/L, the lifetime risk of dying from cancer of the liver, lung, kidney, or bladder from drinking 1 L/day of water could be as high as 13 per 1000 persons. It has been estimated that more than 350,000 people in the United States may be supplied with water containing more than 50 micrograms/L arsenic, and more than 2.5 million people may be supplied with water with levels above 25 micrograms/L. For average arsenic levels and water consumption patterns in the United States, the risk estimate was around 1/1000. Although further research is needed to validate these findings, measures to reduce arsenic levels in water supplies should be considered.

Animals↗
PubMed1979

Multi-element analysis of the living body by neutron activation analysis-application to critically ill patients receiving intravenous nutrition.

Neutron activation analysis has been used to determine the total content in the body of N, K, Na, Cl, P and Ca in 25 critically ill surgical patients before and after a 14-day course of intravenous nutrition. Muscle elemental composition was also determined in these patients at the same time as the total body analysis. Over the 14-day period of intravenous feeding the total body contents of all the measured elements increased (2-9.7 per cent) but only the increase in K was statistically significant. Muscle chemistry suggested an intracellular K depletion which was corrected over the study period. The results of the total body multi-element analysis were interpreted to show a mean gain of 1.25 l of extracellular fluid and 0.51 l of intracellular fluid and direct measurement of total body water suggested that this interpretation was probably valid. The first application of the technique to patients with nutritional and metabolic problems has quantified the weight gained by two body compartments during a 2-week period of intravenous nutrition. Its further application should help to solve a number of nutritional and metabolic problems in clinical surgery.

Adult↗
PubMed1979

Psychiatric aspects of sterilization: a prospective survey.

Patients consecutively referred for sterilization were examined at the time of referral, two months and one year after operation. Twenty-five per cent of the sample were identified as psychiatric cases at the time of referral, and rates of disturbance were even higher in some subgroups of women. The rate of disturbance fell in all these groups by one year after operation. New psychiatric disturbance following sterilization was similar in amount to that found in the community and was not related to any groups of women said in the literature to be at risk apart from those divorced or separated at the time of referral. Many experienced improvement in their marital and sexual relationships and only 3 per cent expressed feelings of regret.

Adult↗
PubMed1979

Murine T-cell heterogeneity.

Immunoregulatory lymphoid cells that mature under the influence of the thymus gland (T cells) have been implicated to a major extent in the induction or at least the perpetuation of malignant neoplasms in man. Those T cells are thought to inactivate, suppress, or neutralize the normally occurring tumoricidal effector cells and thereby facilitate the unchecked growth of the neoplasm; the term "suppressor T cells" is therefore used to denote their individual activity. This concept implies that there is a balance between the effector cells and the suppressor cells in healthy subjects and that perhaps enrichment and activation of those cells involved in the defense against neoplastic growth, and specific depletion and elimination of those cells involved in suppression or inactivation of the former in patients with malignant diseases, may provide new modalities in cancer immunotherapy. Most of the studies that form the basis of this concept have been derived in animal models, particularly the mouse. The existence of cell-surface markers which have been used as phenotypic tools has provided the knowledge that distinct subpopulations of lymphoid cells do exist. The phenotypic characterization of lymphoid cells involved in functionally dinstinct immunologic events has been the object of intensive investigation. Therefore, the purpose of this paper is to briefly document our current knowledge of the functional heterogeneity that exists in murine T cells based on the differential expression of these cell-surface markers.

Animals↗
PubMed1979

Characterization of the immunosuppressive state during Schistosoma mansoni infection.

Analysis of a murine model of schistosomiasis revealed that both the thymus (T)- and bursa (B)-derived compartments of the immune system are modified during acute infection. The functional capacity of T and B lymphocytes to respond to mitogenic stimuli and the humoral response to thymus-dependent (SRBC) and thymus-independent (DNP-Ficoll) antigens are severely depressed. In addition, it was found that suppressor cells capable of inhibiting the response of normal lymphocytes to SRBC arise during acute infection. Although the splenic frequency of T (theta) and B (Ig+) cells remained constant during chronic infection, quantitative changes were detected in each population. In the T cell pool there was a decrease in the percentage of Ly-1+ cells and a concomitant increase in Ly-1+, 2+, 3+, cells, whereas the B cell pool showed a progressive loss of complement receptor-bearing lymphocytes, which apparently was the result of inactivation of surface complement receptor by a serum factor specifically found in infected mice. Characterization of the serum factor strongly suggests it is an immune complex. Thus, it appears that both suppressor cells and immune complexes contribute to changes noted in the immune system during acute schistosomiasis. Additional studies carried out in mice after unisexual infection revealed that egg production is not a necessary prerequisite for several of the immunologic phenomena associated with acute schistosomiasis.

Animals↗
PubMed1979

Tolerance of domestic fowl to high sustained +Gz.

A system is described for the acceleration treatment of domestic fowl. A reasonable endpoint for acceleration tolerance is provided by a bradycardia which occurs fairly close to the lethal limit. In a group of 61 male Rhode Island Red chickens exposed to 6 Gz, the mean tolerance (+/- S.D.) was 11.1 +/- 10.6 min. Among individuals, the acceleration tolerance is inversely related to both body size and age, and positively to pre-treatment heart rate.

Acceleration↗
PubMed1979

Responses of domestic fowl to repeated +Gz acceleration.

The responses of domestic fowl to repeated exposures of 4 min to +6Gz (8 times daily, 5 d weekly) are reported. Survivorship curves for the test group of 48 birds divided into three response categories: mode I, highly susceptible, with all individuals dying on the first day; mode II, more tolerant, with mortality occurring within the first 20 d of treatment; and mode III, highly tolerant, with mortality occurring only after 20 d of treatment. Observations of lymphocyte frequency, an index of systemic stress, and postmortem observations indicate that this heterogeniety has a biological basis.

Acceleration↗
PubMed1979

Effects of brief exposure of domestic fowl to very intense acceleration fields.

Since biological responses to high sustained Gz (HSGz) are determined largely by field intensity and duration of exposure, a series of experiments was arranged to emphasize the effects of field intensity. Male Rhode Island Red chickens were given a single standard exposure of 1 min to a field, which increased from 5-18 +Gz for the series. Acceleration-induced changes were observed in heart rate during and after the treatment, and in lymphocyte frequency and body mass maintenance subsequently. Generally, there was an increasing bradycardia and lymphopenia, which was proportional to field strength. Above 13 G, normal growth and even the maintenance of a pre-treatment body mass were impaired.

Acceleration↗
PubMed1978

A new method for the rapid measurement of body composition in critically ill surgical patients.

A rapid, non-invasive method for the measurement of absolute amounts of fat, protein, minerals and water in the body has been developed which is applicable to very ill patients. The patient is weighed and skinfold thickness is measured with calipers. The body contents of potassium, nitrogen, sodium, chlorine, calcium and phosphorus are measured in a whole-body radiation counter after irradiation with fast neutrons. From these values absolute amounts of body fat, protein, minerals and water are calculated. The procedure, which takes about 40 min, is carried out with the patient lying supine on a couch. The errors in the absolute measurement of the components expressed as percentages of body weight are: for fat, 4.5 per cent; for protein, 1.6 per cent; for minerals, 0.8 per cent; and for water, 4.9 per cent. The radiation dose is equivalent to that of a chest radiograph (50 mrem). We have used this technique (a) to determine the tissue composition of the weight lost in 16 patients after excision of the rectum; (b) to establish that the weight gained by 16 patients receiving intravenous nutrition was mainly water; and (c) to show that in 10 patients who received a simple solution of amino acids for 2 weeks after rectal excision body protein was preserved as efficiently as in 10 similar patients who received a full course of intravenous nutrition. This is the first time body weights of living persons have been broken down into terms of fat, protein, minerals and water, and the method should help to solve a number of metabolic and nutritional problems in clinical surgery.

Adipose Tissue↗
PubMed1978

The assessment of patient prognosis using an interactive computer program.

The use of chronic disease probabilistic models to calculate patient prognosis is presented. The method relies on the calculation of transition probabilities between discrete disease states from a patient data bank. Maximum likelihood estimates are used for each age and unwanted fluctuations are removed by a moving average. An interactive computer program was written and the method applied to the calculation of the probability of stroke and myocardial infarction for male patients on antihypertensive therapy. A clinician could obtain the prognostic information for a patient in less than one minute. Applications in medical student education are also discussed.

Cerebrovascular Disorders↗
PubMed1978

Body mass, composition, and food intake in rabbits during altered acceleration fields.

The effects of gravitational loading and unloading on body mass, body composition, and food intake were investigated in chronically accelerated adult male rabbits. The intensity of the acceleration field was increased by 0.25-G increments at intervals that permitted stabilization of body mass and food intake to a maximal field of 2.5 G. Control rabbits of the same age were maintained at Earth gravity under the same conditions of light and temperature. A negative rectilinear relationship was observed between body mass and the intensity of acceleration field. In spite of this, the decreased body mass appeared to be regulated, since centrifuged animals readily regained their lost body mass upon realimentation after a 3-day fast. At acceleration intensities above 1.75 G, ad libitum food intakes as well as maintenance food requirements increased with increasing acceleration fields despite a corresponding reduction in body mass. Analysis of body composition indicated a significant decrease in body fat and an increase in body water in animals adapted to a 2.5-G environment. Within 6 wk after the animals were returned from 2.5 G to Earth gravity, body mass and food intakes returned to the precentrifuged levels of corresponding control animals.

Adaptation, Physiological↗