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PubMed1990

Prevalence of anisometropia in volunteer laboratory and school screening populations.

For 10 years our laboratory has conducted, a longitudinal study of focusing and motor behavior of a volunteer population of 686 subjects aged 3 months to 9 years. Its purpose is to characterize normal refractive development in infants and children and to relate refractive anomalies to subsequent visual problems. Using age-related criteria for anisometropia adjusted to detect the most unusual 5% of the refractions on a test battery, we have found 19 nonstrabismic, anisometropic subjects (2.8% of total subject population). Of these, eight were either seen once or their anisometropia appeared at their last visit. Of the remaining 11 subjects, all had a reduction of their anisometropia to within normal limits on subsequent visits. Thus our current best estimate of persistent infant anisometropia is 0%, a startling result. By comparison, we found ten strabismic subjects (1.46%), two of whom had persistent anisometropia. Although we did not believe that anisometropic subjects could self-select and not participate in the study, it was possible that the volunteer laboratory population had characteristics atypical of the county at large. Thus we conducted a screening of 374 Head Start and first-grade pupils throughout the county, using the same methods. We found virtually no difference in the average refractive conditions between the laboratory and school populations and no significant difference in the prevalence of visual disorders. The very low prevalence of anisometropia in infants and young children in both populations has important implications for the etiology of anisometropic amblyopia.

Anisometropia↗

PubMed1990

Natural childbirth--the Johannesburg Hospital experience, 1983-1989.

The Johannesburg Hospital Active Birth Unit (ABU), the only one of its kind in southern Africa to date, has provided an alternative to conventional labour practices since 1983. In a retrospective study of the results achieved in this unit the intrapartum records of 492 patients admitted to the ABU between 1 March 1983 and 30 June 1989 were analysed. During the 6.3-year study period 364 patients (74%) successfully laboured and delivered within the unit. These figures included 50 underwater deliveries. One hundred and twenty-eight patients required intrapartum transfer to the conventional labour ward and of these 44 achieved spontaneous vaginal delivery. Thirty-four patients (7%) 'self-selecting' for natural childbirth ultimately required caesarean section delivery. Primiparous patients were more likely than their multiparous counterparts to require intrapartum transfer to the labour ward (38% v. 13%). Birth outcome results achieved in the Johannesburg Hospital ABU compare favourably with those for 6 other ABUs reported in the literature.

Female↗

PubMed1990

Occupational stress and well-being: do seafarers harbor more health problems than people on the shore?

The popular image of life at sea is one of stress: often difficult physical conditions, dislocation, isolation and less than ideal personal habits. In order to determine whether this stressful way of life is manifested when seamen's health status is assessed by standard measurements, we studied 144 sea captains and marine chief engineers as compared with a group of ordinarily employed men. The referent men were matched for age, ethnic origin, and level of education with the seamen. Outcome measures included a wide spectrum of physiological, psychological and behavioral indices. The comparisons revealed only mild differences between the two groups. Captains and chief engineers tend to harbor slightly higher levels of certain biochemical or physiological parameters (risk factors), such as serum cholesterol and uric acid, hemoglobin level and leukocyte count. Certain behavioral risk factors were more dominant among the seamen than among the control group (smoking level, alcohol consumption and lack of leisure-time physical activity). The study group did not exhibit a greater prevalence of overt disease or a higher degree of psychological symptoms. It is suggested that the group under study represents a self-selected group of persons well adjusted to their job and their special way of life.

Adult↗

PubMed1990

Physiologic and perceptual responses during treadmill running with ankle weights.

This study examined the effects of ankle weighting on physiologic and perceptual responses during treadmill running in seven healthy, female recreational runners with a mean maximal aerobic power of 48.4 +/- 4.0 ml/kg/min. Each subject completed four experimental one-mile runs at individually selected treadmill running speeds with 0, 1.6, 3.2 and 4.8 kg weights on their ankles. The subjects selected a speed at which they would run (train) if their objectives were to significantly improve cardiovascular function and induce weight loss. Metabolic and cardiovascular responses were continuously monitored, and ratings of perceived exertion were recorded near the end of the activity. During the unweighted run, the subjects selected a running speed of 6.87 +/- 0.63 mph which resulted in a net energy expenditure of 0.153 kcal/kg/min or 1.34 +/- 0.16 kcal/kg/mile. This corresponded to a training intensity of 76.3% +/- 5.1% of maximum oxygen consumption or 88.1% +/- 9.7% of maximum heart rate. Addition of weight to the ankles caused a significant decrease (p less than .05) in the running speed selected and, therefore, did not result in any significant changes (p greater than .05) in the rate of oxygen consumption, heart rate or ratings of perceived exertion when compared to the unweighted condition. These observations are in contrast to previous studies on ankle weighting which were conducted at fixed treadmill running speeds. However, the use of ankle weights did have a tendency to increase gross and net energy expenditure of running when values were expressed in kcal/mile because of slower self-selected running speeds under these conditions. This increase in energy expenditure could be of physiologic significance if running with ankle weights was performed on a regular basis at a fixed distance.

Adult↗

PubMed1990

dl-fenfluramine challenge to nutrient-specific textural preference conditioned by concurrent presentation of two diets.

Effects of the ingestion of protein and carbohydrate conditioned a preference for one size of chow particle over another, which was triggered by need for a specific nutrient. This learned elicitation of nutrient-specific dietary selection was not changed by injection of dl-fenfluramine HCl (2.5 mg/kg). This indicates that previously observed effects of fenfluramine on differential intakes of dextrin- and casein-rich diets do not depend on nutrient-specific self-selection.

Animals↗

PubMed1990

Ankle-foot orthoses: effect on energy expenditure of gait in spastic diplegic children.

This study examined the effect of conventional plastic bilateral ankle-foot orthoses (AFOs) on the energy expenditure of ambulation in spastic diplegic cerebral palsy patients. Eighteen subjects (aged 8.3 +/- 2.83 years) ambulated five minutes at freely chosen velocities with and without their AFOs. Heart rate (beats per minute) and distance (meters) ambulated were recorded for each minute. A physiologic cost index was calculated by determining the ratio of walking heart rate to velocity [(HRamb-HRrest) divided by meters per minute]. The mean physiologic cost indexes for the last three minutes of ambulation with and without orthoses were 1.34 +/- 0.69 beats per meter and 1.51 +/- 0.79 beats per meter, respectively (p less than 0.05). Ambulation heart rate, velocity and total distance traveled were not statistically different between the two trials. The results indicated that energy expenditure of ambulation at self-selected speeds in spastic diplegic children was reduced by the application of conventional AFOs. However, each child should be evaluated on a single-case basis because of individual differences.

Adolescent↗

PubMed1990

The effect of exercise on energy intake and body composition in overweight women.

Twelve moderately overweight women with mild obesity were studied to determine the effect of exercise on nutrient intake and body composition. The women, 16 to 42 percent above desired body weight (BW) and 30 to 41 percent body fat, rotated through three 18-day treatment periods: no exercise (NO-EX), moderate duration exercise (M-EX), and long duration exercise (L-EX). Daily exercise was prescribed to increase energy expenditure by 12.5 (M-EX) or 25 percent (L-EX) of energy intake required for BW maintenance during baseline. Diets were self-selected from a variety of conventional foods, and intake was monitored. Exercise did not affect quantity of energy intake or macronutrient composition of diets during the treatment periods. Energy and carbohydrate intakes tended to be higher in response to M-EX and L-EX compared to NO-EX during the last 5-day interval of the treatment periods, but these trends were not statistically significant. Exercise did affect BW and fat-free mass (FFM); mean FFM values were 49.3, 49.7 and 50.8 kg at the end of NO-EX, M-EX and L-EX, respectively (P = 0.017). Body fat mass (FM) was not consistently affected by exercise. It appears that exercise affects FFM but has no consistent effect on nutrient intake in mildly obese women who are choosing food intake from a variety of foods.

Adipose Tissue↗

PubMed1990

Patient selection and outcomes for out-of-hospital births in one family practice.

This paper reports a study of the pregnancies followed to delivery in one family medicine group practice that offered a choice of childbirth settings. Those choosing out-of-hospital birth (OHB) were a self-selected group of highly motivated couples interested in natural childbirth or desiring to minimize the cost of pregnancy care. Of 790 singleton pregnancies followed to term, 71 (9.0%) planned home births, 510 (64.6%) planned clinic births, and 209 (26.5%) planned hospital births. Of those planning clinic or home birth, 73% gave birth outside the hospital as planned (44 at home and 379 in the clinic), 81 (14%) changed plans prenatally and gave birth in a local hospital, 46 (8%) were transferred to the local hospital intrapartum, and 29 (5%) were referred to tertiary care. Primiparas who initially chose OHB were more likely than multiparas to give birth in a hospital (46% vs 16%). Controlling retrospectively for obstetric risk and parity, there were few differences in outcome between local hospital and out-of-hospital births. The observed rates of serious complications for OHB were low, but overall, 27% of those initially considered candidates for birth outside the hospital required a change to a higher level of care. For primiparas initially planning clinic or home birth, discriminant analysis revealed five variables that together might have improved the prediction of the eventual decision for hospital delivery in 46%. Clinical pelvimetry was the most powerful variable, in keeping with the finding that most intrapartum transfers were for arrests of labor. The results also suggest that financial factors and other features of the physician-patient relationship influenced clinical decision making.

Adult↗

PubMed1990

Control of body mass transfer as a function of speed of ascent in sit-to-stand.

The purpose of this study was to test the hypothesis that a progressive variation in the speed of ascent would result in differences in the horizontal and vertical motions of the body center of mass (CM) and in the governing impulse-momentum relationship. A motion analysis system and two force platforms were used to examine the STS task among 10 healthy adults at each of three self-selected speeds. As the speed of ascent became faster, a progressively earlier time to the maximum vertical linear momentum and an increase in its magnitude occurred. In contrast, a relatively constant time to the maximum linear momentum, which was also the time when the propulsive impulse became the braking impulse, was found in the horizontal direction, and the propulsive impulse showed a disproportionately (1:3) smaller increase from slow to fast speeds than its vertical counterpart. The relative invariance in the horizontal motion suggested that different neuromuscular control strategies may have been employed in the horizontal and vertical directions to accomplish the different tasks of balance control in one direction and changing the gravitational potential energy in the other direction.

Adult↗

PubMed1990

Oxygen uptake and heart rate responses to treadmill and water running.

The relationship between heart rate (HR) and oxygen uptake (VO2) was assessed during treadmill running and during running-like motions in water without ground support. Athletes self-selected easy, moderate and hard efforts during water running. While there was a linear relationship between HR and VO2 in both exercise conditions, there was considerable between-subject variability of the slope and intercept of the linear regressions. These data are taken to indicate that HR for a given VO2 during water compared to land running is influenced in large part by the skill of the athlete in the water running activity.

Adult↗

PubMed1990

Influence of concentric resistance training on concentric and eccentric strength.

This study investigated the effects of isokinetic concentric training on isokinetic concentric and eccentric torque outputs. Sixteen female subjects (mean age in years +/- SE = 21 +/- 1) were randomly assigned to either a training or a control group. Concentric and eccentric torques of the right knee extensors were assessed at 1.05rad.s-1 using a KinCom isokinetic dynamometer system. Each test consisted of a set of four maximal concentric and four maximal eccentric contractions of the knee extensors. The peak and average torques for each contraction were calculated using the computer software supplied by the KinCom manufacturer. On a separate day, after abstaining from heavy exercise for at least 12 hours, a single cross-sectional image of the thigh at midfemur was obtained using computer tomography (CT) scanning. From this image, cross-sectional area of the quadriceps femoris group was calculated using the computer software associated with the General Electric 9800 CT Scanning System. Training group subjects trained three days weekly for six weeks on a Cybex II+ isokinetic dynamometer, completing five sets of ten maximal effort knee extensions at an angular velocity of 1.05rad.s-1. Each set of exercise was separated by two minutes of self-selected recovery. Torque outputs were monitored daily to ensure that adequate recovery was provided between sets of exercise, and to document changes in strength as the program progressed. Significant (p less than .01) increases in peak and average concentric torque (11% and 12%, respectively), peak and average eccentric torque (18% and 21%, respectively), and muscle cross-sectional area (3.2%) were observed for training group subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1989

A circadian rhythm of population behavior in Gonyaulax polyedra.

Like other flagellates, Gonyaulax polyedra exhibits diurnal vertical migration and pattern formation. Shape and size of the aggregations depend on container type, light intensity, and cell density. In Petri dishes, cells form oval "swarms"; within these, cells move downward in the highly dense center and rise up at the periphery. We have investigated the daily rhythm of this swarming activity in Petri dishes illuminated from the side, using time-lapse video recordings. At night, a "lawn" of cells forms at the bottom of the dish toward the light source (independent of light intensity). Before dawn, cells rise toward the surface and aggregate in swarms. The daily vertical migration occurs independent of light direction and intensity. The diurnal swarms, however, form every day at the same location within the dish, at a distance from the light that depends on light intensity, indicating a self-selection of light intensity. In constant light and temperature and with negligible vertical nutrient differences, all aspects of the rhythm continue to oscillate for up to 3 weeks, when the rhythm of the population becomes desynchronized. Under cycles of bright white-dim red light (WR), cell entrain to WR 10:10 but free run in WR 8:8 and shorter cycles, showing relative coordination (von Holst, 1939) to the driving light cycle. They also entrain to the 24-hr multiple of WR 6:6. Under nonentrained conditions, swarming activity is still influenced by light changes, and in spite of the apparent free run, the phasing of the averaged activity varies systematically with different T-cycle frequencies.

Animals↗

PubMed1989

Evidence for spread of the human immunodeficiency virus epidemic into low prevalence areas of the United States.

Reports of an increased proportion of AIDS cases occurring in small and medium-sized cities suggest that the HIV epidemic may be spreading into locations that were previously characterized by their low HIV antibody prevalences. Studying the question of the geographic spread of the HIV infection epidemic (rather than the AIDS epidemic) has been difficult largely because most serial seroprevalence data have been gathered from cohorts of high risk individuals (e.g., homosexual/bisexual cohorts) in New York City, San Francisco, and other geographically circumscribed areas. The U.S. military applicant HIV screening data were used in the current report to examine rates and 24 month temporal trends in geographic areas characterized by their HIV endemicities. The data examined concern the seven most populous states and four hyperendemic metropolitan areas located within those states (New York City, Miami, Houston, and San Francisco). In the nonepidemic regions, seroprevalence rates increased among black and white applicants. In the four epidemic urban areas, only young black applicants had higher HIV seroprevalence rates during the second 12 month period. Six of the seven nonepidemic regions had positive HIV seroprevalence trends, and these trends were significant in Florida, California, Texas, Illinois, and Ohio. The increases in these regions were greater for young blacks (30% excess for year 2 vs. year 1) compared to young whites (12% excess for year 2 vs. year 1). These data provide evidence of birth year specific increases in seroprevalence over time occurring in presumed low HIV prevalence areas. These increases cannot be due to, but are observed in spite of, biases associated with increasing self-selection over time.

Acquired Immunodeficiency Syndrome↗

PubMed1979

Potential effect of demographic and other variables in studies comparing morbidity of breast-fed and bottle-fed infants.

Comparing the morbidity of breast-fed and bottle-fed infants is confounded by inherent differences in breast-feeding and bottle-feeding mothers and their infants. Self-selection introduces complex variables encompassing much more than milk source used for infant feeding. Reasons for selecting breast or bottle feeding relate to demographic, socioeconomic, educational, ethnic, cultural, and psychological factors, as well as maternal and infant physical and emotional health. Many of the differences in the maternal populations may affect infant care practices, access to medical care, and infant health status. Studies published to date have not quantified these confounding effects and other potential biases in comparing morbidity to breast- and bottle-fed infants and the relationship between milk source and incidence of infantile disease remains in question. There is need for more cautious use of the available data and investigators must seek ways to design future studies to take into account the differences between breast-feeding and bottle-feeding mothers that affect both reported and actual infant morbidity.

Bottle Feeding↗

PubMedDate not supplied

[Treatment of the sick elderly in households accommodating several generations].

Multigenerational households with widowed persons aged 70 and more have been studied in order to determine the relationship between the following two groups of variables: (a) variables in the aged person describing the existence and degree of an organic mental impairment due to a dementive process and of other signs of physical illnesses. (b) variables in her daughter or daughter in law consisting of selfratings of psychosomatic complaints and of attitude-scales. Results were as follows: (a) If there were indications of personality changes due to an organic brain syndrom the relatives had a lower degree of life-satisfaction and more frequently suffered from psychosomatic symptoms and interpersonal stress than those, whose old relatives showed an unaltered personality. (b) A great number of comparisons failed to show any statistical differences. Especially severe physical illness, organic brain syndrome and the need for physical care were not related to life satisfaction, psychosomatic complaints, stress due to emotional involvement and the attitude towards home-care. Our attempt to explain the missing correlations led to the following factors: the small size of the sample, self-selection of the sample and possibly inappropriate operationalisation and measurement of variables. In respect to these results the ongoing study will be modified in some details: There will be a qualitative analysis of transcribed semi-structured interviews. The proportion of families with severely demented relatives will be increased. In an additional step we shall examine families, who have decided to transfer their old member into an institution.

Aged↗

PubMed1978

The effect of energy and nitrogen intake upon urea production in children with uremia and undernutrition.

Children with severe uremia who had anorexia were observed in a clinical study center where dietary energy and nitrogen intake could be compared with urea nitrogen production (UNPr). The children received a supplement of dextrose and amino acids at night, ate a self-selected diet and were encouraged to use carbohydrate supplements. Energy intake varied from 22 to 110 kcal/kg/day and nitrogen intake from 105 to 323 mg/kg/day. UNPr was reciprocally related to energy intake. Nitrogen intake minus UNPr, an index of nitrogen balance, was positively related to energy intake. UNPr was not related to nitrogen intake. Nitrogen intake (NI) and NI-UNPr were correlated and the slope of the regression was 1.15. We inferred from the data that low energy intakes (less than 60 kcal/kg/day) were associated with catabolic losses of body protein. Intakes above that level were associated with a low and stable rate of UNPr. The level of energy and nitrogen intake within the range observed limited the rate of nitrogen retention. Once maintenance requirements for energy and nitrogen were satisfied, the efficiency with which nitrogen was used for net protein synthesis was very high.

Adolescent↗

PubMed1979

Gastric secretory and humoral responses to anticipated feeding in five men.

It is believed that humans anticipate appetizing meals by increasing vagally mediated gastric acid secretion. Studies were conducted on 5 normal male volunteers to characterize further the secretory response to anticipated meals. Plasma gastrin and glucose levels were monitored to assess the possibility that these humoral factors participated in the observed secretory changes. Subjects were not fed for 22 hr and were intubated at 10 AM. Basal gastric collections were begun, and at 1 PM on different days, subjects either (a) selected meals of choice prepared in their presence for 1 hr before nasogastric tube withdrawal and meal ingestion or (b) were not food-teased or fed. Gastric collections were obtained every 10 min during the "test" hour (1-2 PM) during both (a) and (b) studies and titrated for gastric acid. Blood samples for plasma glucose and RIA gastrin were obtained during basal and test hours every 10 min. Pentagastrin-stimulated maximal acid output studies were conducted on all subjects on separate days. Results showed a progressive and statistically significant rise in gastric acid secretion when an appetizing, self-selected meal was anticipated. The magnitude of this rise was 55% of the mean pentagastrin-induced acid response. This acid response did not correlate with changes in plasma glucose or gastrin. The study demonstrated that pure psychic stimulation may be as effective an acid stimulant as sham feeding.

Adult↗

PubMed1977

Enrollment choice in a mutli-HMO setting:the roles of health risk, financial vulnerability, and access to care.

Results of an analysis of enrollment decisions in HMO-type plans are reported. Previous studies concern dual-choice situations; this paper deals with a quadruple-choice situation involving one open- and two closed-panel HMO-type plans as well as Blue Cross/Blue Shield (BC/BS). The risk-vulnerability hypothesis is disaggregated into its components and the results show that there is no adverse health risk self-selection in an employed population. The hypothesis of economic vulnerability is maintained when tested in terms of per capita income rather than the previously used measure of family income. It is shown that those who enroll in any HMO-type plan are younger and have younger and larger families and lower per capita income than those who do not. No meaningful differences in terms of health status, health concerns, or prior utilization are found. Of the few differences found between those who enroll in closed- and open-panel HMO-type plans, having a private physician as the usual source of care is the most significant: those with an established physician relationship who join any HMO-type plan tend to follow their physician into the open-panel plan. The results should not be generalized to situations involving premium differences since the premium cost to subscribers in any of the plans considered here was fully paid by the employer. The validity of the results in terms of nonfinancial factors, on the other hand, is enhanced by the removal of cost considerations.

Adolescent↗