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Biomedical subjects

A Kristal

Publications and source records attributed to A Kristal.

At least 19 recordsLinked to original sources
PubMed2006

Real-time patient-specific finite element analysis of internal stresses in the soft tissues of a residual limb: a new tool for prosthetic fitting.

Fitting of a prosthetic socket is a critical stage in the process of rehabilitation of a trans-tibial amputation (TTA) patient, since a misfit may cause pressure ulcers or a deep tissue injury (DTI: necrosis of the muscle flap under intact skin) in the residual limb. To date, prosthetic fitting typically depends on the subjective skills of the prosthetist, and is not supported by biomedical instrumentation that allows evaluation of the quality of fitting. Specifically, no technology is presently available to provide real-time continuous information on the internal distribution of mechanical stresses in the residual limb during fitting of the prosthesis, or while using it and this severely limits patient evaluations. In this study, a simplified yet clinically oriented patient-specific finite element (FE) model of the residual limb was developed for real-time stress analysis. For this purpose we employed a custom-made FE code that continuously calculates internal stresses in the residual limb, based on boundary conditions acquired in real-time from force sensors, located at the limb-prosthesis interface. Validation of the modeling system was accomplished by means of a synthetic phantom of the residual limb, which allowed simultaneous measurements of interface pressures and internal stresses. Human studies were conducted subsequently in five TTA patients. The dimensions of bones and soft tissues were obtained from X-rays of the residual limb of each patient. An indentation test was performed in order to obtain the effective elastic modulus of the soft tissues of the residual limb. Seven force sensors were placed between the residual limb and the prosthetic liner, and subjects walked on a treadmill during analysis. Generally, stresses under the shinbones were approximately threefold higher than stresses at the soft tissues behind the bones. Usage of a thigh corset decreased the stresses in the residual limb during gait by approximately 80%. Also, the stresses calculated during the trial of a subject who complained about pain and discomfort were the highest, confirming that his socket was not adequately fitted. We conclude that real-time patient-specific FE analysis of internal stresses in deep soft tissues of the residual limb in TTA patients is feasible. This method is promising for improving the fitting of prostheses in the clinical setting and for protecting the residual limb from pressure ulcers and DTI.

Amputees↗
PubMed2001

Genetic taste responses to 6-n-propylthiouracil among adults: a screening tool for epidemiological studies.

Genetically mediated taste responsiveness to 6-n-propylthiouracil (PROP) has been linked to reduced acceptance of some bitter foods. In this community-based study male (n = 364) and female (n = 378) adults enrolled in a self-help dietary intervention trial were screened for PROP taster status. Respondents, aged 18--70 years, were mailed filter papers impregnated with PROP or with aspartame solutions. They received instructions to rate taste intensity and hedonic preference using nine point category scales. Women rated PROP as more bitter than did men. Both sweetness and bitterness ratings were lower for older adults. Taste responsiveness to PROP was unrelated to body mass index in women or men. Higher bitterness ratings for PROP were weakly associated with higher sweetness ratings for aspartame, but were unrelated to sweet taste preferences. Successful administration of PROP filter papers by mail suggests new avenues for the screening of taste phenotypes in epidemiological studies.

Adolescent↗
PubMed1996

Constitutional factors and sun exposure in relation to nevi: a population-based cross-sectional study.

A survey of benign melanocytic nevi (moles), suspected precursors or markers for melanoma, was conducted in Washington State among 717 randomly selected 18- to 50-year-old white adults who participated in a telephone interview in 1990-1991. Participants were questioned about constitutional factors, time spent in the sun, and severe sunburns over three time periods and were asked to count the raised nevi on both their arms. Logistic regression was used to examine the risk for 2+ nevi compared with none. An odds ratio (OR) of 2.0 (95% confidence interval (CI) 1.3-3.1) was seen for current freckling. Skin color, tendency to burn, and inability to tan were important risk factors but were not independent of each other. Individuals with a history of severe sunburns had an increased risk of nevi: OR = 1.9 (95% CI 0.9-3.9) for 3+ severe sunburns compared with none in the last 5 years; OR = 2.0 (95% CI 1.2-3.1) for 4+ severe teenage sunburns; and OR = 3.1 (95% CI 1.7-5.3) for 4+ severe childhood sunburns. Furthermore, childhood sunburns were related to nevi independently of sun sensitivity and teenage and recent sunburns: OR = 2.0 (95% CI 1.0-4.0) for 4+ severe sunburns. These data suggest that childhood sunburns are important in the etiology of nevi. This study supports prior studies of the relation between melanoma and early sun exposure.

Adolescent↗
PubMed1996

Nevi and migration within the United States and Canada: a population-based cross-sectional study.

A survey to ascertain factors associated with benign melanocytic nevi or moles was conducted among randomly-selected White adults (aged 18 to 50 years) in Washington State (United States). Participants of the telephone interview in 1990-91 were questioned about lifetime places of residence and constitutional factors. Subjects counted raised nevi on their arms at the end of the survey. Logistic regression was used to examine the risk for two or more nevi compared with no nevi. Individuals who resided in warmer areas and lower latitudes than Washington State were at higher risk of having multiple nevi. This association held for residence at birth, during childhood, adolescence, and over lifetime: an odds ratio (OR) of 2.3 (95 percent confidence interval = 1.2-4.3) for lifetime average daily maximum temperature of > or = 64 degrees F compared with 58.9 degrees F, and similar ORs of 2.1 for adolescence and 1.8 for childhood. These associations remained significant after adjusting for potential confounding effects of constitutional factors and for childhood sunburns as a potential mechanism. Risk of multiple nevi was reduced for both early age at migration and longer duration of stay in Washington. These data are consistent with the importance of childhood and adolescent sun exposure in the etiology of nevi, but also suggest an effect of lifetime sun exposure.

Adolescent↗
PubMed1996

The Women's Health Trial Feasibility Study in Minority Populations: design and baseline descriptions.

The Women's Health Trial: Feasibility Study in Minority Populations (WHT:FSMP), a randomized trial of 2208 women, was conducted to investigate three questions. First, can women from minority and low-socioeconomic-status populations be recruited in numbers sufficient to evaluate a dietary intervention designed to lower fat intake. Second, the efficacy of a low fat, increased fruit/vegetable/ grain product intervention for reducing fat consumption. Third, will participation in the intervention lower plasma cholesterol and estradiol levels relative to the controls. The baseline results showed that an adequate number of minority and low SES women could be recruited to test the study hypotheses. A diverse study population of postmenopausal women consuming a high fat diet was recruited: 28% of participants were Black, 16% were Hispanic, 11% had less than a high school level of education, and 15.5% had household incomes of < $15,000.

Aged↗
PubMed1995

Evaluating community-based nutrition programs: comparing grocery store and individual-level survey measures of program impact.

BACKGROUND: This paper examines whether an "environmental indicator"--a survey of grocery store product displays--can provide a realistic alternative to individual-level telephone surveys for the evaluation of community-based nutrition programs. METHODS: Telephone and grocery store measures were used separately to evaluate three community-level dietary interventions that were part of the Kaiser Family Foundation Community Health Promotion Grants Program (CHPGP). Both surveys were conducted in the three intervention and seven control communities at three points in time: 1988, 1990, and 1992. The grocery store survey recorded the relative availability of low-fat and high-fiber products and the amount of store-provided health-education information. Self-reported dietary intake of residents was obtained in the same communities using a telephone survey. RESULTS: In the one community in which the intervention seemed to have contributed to reduced fat consumption, the grocery store and telephone surveys showed very similar relative changes for the only variable they had in common, low-fat milk consumption. In another community, both survey approaches indicated that there was no change or perhaps a slight worsening in the treatment relative to the controls. The third community produced the only contradictory results: the telephone survey suggested no change or perhaps a worsening, while the grocery store results were generally positive, though not statistically significant. CONCLUSION: These results, combined with the much lower cost of the grocery store survey, justify further pursuit of environmental indicators as an evaluation tool.

Diet↗
PubMed1995

Obesity, alcohol, and tobacco as risk factors for cancers of the esophagus and gastric cardia: adenocarcinoma versus squamous cell carcinoma.

Adenocarcinomas of the esophagus and gastric cardia were once rare. However, for unknown reasons, their incidence has been increasing rapidly over the past 15 years in the United States and parts of Western Europe. In contrast, the incidence of esophageal squamous cell carcinomas has remained relatively constant. To investigate possible reasons for these diverging incidence rates we analyzed data from two population-based case-control studies of cancers of the esophagus and gastric cardia that were conducted among male and female residents of western Washington between 1983 and 1990. Information on body mass index, cigarette use, alcohol intake, and other possible risk factors was collected via personal interviews with 404 cases or their next of kin (including 298 adenocarcinomas and 106 squamous cell carcinomas) and 724 controls identified by random digit dialing. Use of alcohol and cigarettes were significant risk factors for both histological types. The increase in risk for current smokers of 80 or more pack-years compared to nonsmokers was substantially higher for squamous cell cancer [odds ratio (OR) = 16.9; 95% confidence interval (CI) = 4.1-69.1] than for adenocarcinoma (OR = 3.4; 95% CI = 1.4-8.0), as was the increase for persons who typically drank 21 or more drinks/week compared to those who drank <7/week (OR = 9.5; 95% CI = 4.1-22.3 versus OR = 1.8; 95% CI = 1.1-3.1). For squamous cell carcinoma, body mass index was inversely associated with risk, whereas for adenocarcinoma, the highest risk was observed among persons who were in the highest decile of body mass index (OR = 1.9; 95% CI = 1.1-3.2).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1993

Can measures of the grocery store environment be used to track community-level dietary changes?

BACKGROUND: This article examines whether an in-store unobtrusive survey of grocery store product displays can be used to track community-level dietary behavior. METHODS: The survey was conducted in 12 western communities two different times to measure two aspects of the grocery store environment: (a) the relative availability of low-fat and high-fiber products and (b) the amount of store-provided health-education information. Self-reported dietary intake of residents was obtained in the same 12 communities using a telephone survey. We compared the individual and store-level measures both cross-sectionally and over time. RESULTS: We found positive and statistically significant correlations between the availability of healthful products in stores and the reported healthfulness of individual diets in cross-sectional analyses, but correlations between changes over time in the two measures were weaker and not statistically significant. The variance of the grocery store measures was nonetheless sufficiently small that a grocery store survey of 15 stores in each of 8 communities (n = 120 surveys) had power comparable to that of a telephone survey of 200 individuals/community (n = 1,600) surveys, at a fraction of the cost. CONCLUSION: Although the results provide further validation of cross-sectional measures of the grocery store environment, additional efforts are required to establish the validity of the grocery store survey as a method of measuring dietary change.

Advertising↗
PubMed1991

Community-level comparisons between the grocery store environment and individual dietary practices.

BACKGROUND: This article examines the relationship at the community level between individual dietary practice and the grocery store environment. METHODS: Individual dietary practice was measured in 12 communities using a telephone survey to obtain self-reported diet. A protocol was developed to measure two aspects of the grocery store environment in these same 12 communities: the relative availability of healthful (low-fat and high-fiber) products, and the amount of health-education information provided. Comparisons were made between individual and store-level measures at two levels of geographic aggregation: community (typically a county) and zip code within community (n = 34). RESULTS: We found positive and statistically significant correlations at both the community and the zip code level between the availability of healthful products in stores and the reported healthfulness of individual diets. Positive correlations were also found between measures of the amount of health-education material provided by stores and the healthfulness of individual diets, but these correlations did not reach statistical significance. CONCLUSIONS: The results provide support for including measures of the grocery store environment as part of a community-level assessment of dietary behavior.

Adult↗
PubMed1990

Maternal cigarette smoking during pregnancy, adiposity, social class, and perinatal outcome in Cardiff, Wales, 1965-1977.

There have been several reports in which maternal nutritional status has been implicated as either a mediating or moderating factor in the relationship between maternal cigarette smoking and birthweight and perinatal survival. Also, there is evidence that the effects of maternal cigarette smoking on both intrauterine growth and fetal viability are more intense among women of lower social status. The well-maintained data set of the Cardiff Births Survey from 1965-1977 afforded an opportunity to review these issues among over 50,000 births in south Wales (the survey took place in Cardiff City through 1973 and subsequently included suburban areas of South Glamorgan). The major findings were: (1) Smoking was much more common with descending maternal social status; (2) among upper status women, smokers had similar or slightly greater mean Quetelet's indices (kg/m2) than nonsmokers. Among lower status women, smokers were considerably thinner than nonsmokers; (3) the greater the adiposity of the mother, the less the association between cigarette smoking and depressed birthweight; (4) perinatal mortality was significantly higher among heavy smokers (10 or more cigarettes a day) than among nonsmokers; and (5) neither the decrease in birthweight nor the excess mortality associated with smoking was greater among those of lower rather than upper social status, except among class I women, among whom smoking was only minimally associated with depressed birthweight. With the inclusion of the South Glamorgan suburban population in the survey after 1974, the excess mortality associated with heavy smoking dropped from 53 to 16%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

The effects of maternal cigarette smoking on placental morphology, histomorphometry, and biochemistry.

We related cigarette smoking during pregnancy to the macroscopic and microscopic morphology, histomorphometry, and biochemistry of the placenta among participants in The Prenatal Project, a randomized, controlled trial of nutritional supplementation during pregnancy. The aim was to ascertain if the harmful effects of cigarette smoking on the fetus were reflected, and possibly mediated, by changes in the placenta, and whether such changes might be modified by the nutritional supplements, parallel to the nutritional reversal of birthweight depression among heavy smokers. Maternal smoking was associated with increased alkaline ribonuclease (RNase) levels, possibly resulting in disturbed protein synthesis. More smokers had placentas with villous hyperplasia on histologic examination. This was accompanied by biochemical evidence of significantly increased cellularity (increased DNA/gm of placental mass and decreased protein/DNA ratios) and (nonsignificant) trends to reduced syncytial villous cell size on histomorphometry. There were joint effects of cigarette smoking and use of either form of nutritional supplementation on the fibrin and stoma components of the villi, but such changes are not necessarily pathologic. The significant reduction in pathology of the stem villi among smokers was confined to those who were nutritionally supplemented, particularly heavy smokers. This change may thus have reflected the protective effects of supplementation on the birthweight of the offspring of these heavy smokers.

Cell Division↗
PubMed1984

The effects of dietary supplementation during pregnancy on placental morphology, pathology, and histomorphometry.

We related the macroscopic and microscopic morphology and the histomorphometry of the placenta to prenatal nutritional supplementation. In the Prenatal Project, a controlled clinical trial, three dietary treatments (supplement, a high-protein beverage; complement, a balanced protein-calorie beverage, or routine vitamin and mineral tablets) were randomly allocated to poor Black pregnant women, and the outcome was assessed. Herein we report the effects on placental morphology and histomorphometry. There were significantly fewer preterm deliveries in the complement group, and this was reflected by an increase in the size of decidual cells, an index associated with placental aging. Several other characteristics of the placentas of the complement group may have been more directly associated with improved perinatal outcome: decreased intervillous fibrin, lower incidence of gross surface infarct, and smaller (and presumably less edematous) cells of the villous stroma, may have mediated increased placental perfusion. There was no evidence of any placental change associated with the increase in very preterm delivery and the highly significant depressed birth weight among preterm deliveries in the supplement group. The significantly lower incidence of meconium staining of Wharton's jelly among controls seems likely to have been a chance finding. While there were several other indices that reflected placental aging, the significantly increased chorioamnionitis, acute funisitis , and acute decidual inflammation among placentas of those who delivered prematurely [the former two associated with very early delivery (less than 35 wk gestation)] were likely to have been involved as causes of premature delivery.

Clinical Trials as Topic↗
PubMedDate not supplied

Environmental indicators: a tool for evaluating community-based health-promotion programs.

We propose using a class of community-level measures--environmental indicators--as part of the evaluation of community-based health-promotion programs. Community-level measures of health-related behavior can be divided into three conceptual categories. The first two categories comprise statistical aggregates (e.g., means, sums, percentages) of measurements made on individuals, distinguished by whether individual-level covariates are also available. Individual-disaggregated measures include covariates, such as a comprehensive survey of health-risk behavior, including demographic information; individual-aggregated measures, such as sales data, do not. Our main focus is on the third category, environmental indicators, derived from observations of the community environment. Environmental indicators measures aspects of the physical, legal, social, and economic environment in a community that reflect, and likely influence, the attitudes and behavior of individual community members. They also measure an important intermediate step in community-based health-promotion interventions, namely environmental factors that programs target to modify individual attitudes and behavior. We present examples of environmental indicators for tobacco use and diet.

Attitude to Health↗