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Biomedical subjects

J Baxter

Publications and source records attributed to J Baxter.

At least 55 records · Page 3Linked to original sources
PubMed1993

Ethnic differences in risk factors associated with the prevalence of non-insulin-dependent diabetes mellitus. The San Luis Valley Diabetes Study.

Non-insulin-dependent diabetes mellitus is 2-5 times more common in Hispanics than in non-Hispanic whites in the United States. The authors conducted this case-control study in two Colorado counties from 1984 to 1986 to determine whether known risk factors for non-insulin-dependent diabetes mellitus explained the excess incidence in Hispanics. There were 279 subjects with prevalent diabetes and 488 subjects with normal glucose tolerance who were eligible for this analysis. After adjustment for age and sex, results showed that Hispanics were 3.5 times more likely than non-Hispanic whites to have non-insulin-dependent diabetes mellitus (95% confidence interval 2.4-4.9). The excess risks of diabetes associated with body mass index, subscapular and triceps skinfold thickness, family history of diabetes, and income were similar in Hispanics and non-Hispanic whites, after adjustment for age and sex. However, 1-unit increases in subscapular/triceps skinfold ratio and waist/hip ratio were associated with greater increases in risk among non-Hispanic whites than among Hispanics. When risk factors were entered into logistic regression models simultaneously, higher subscapular skinfolds, a higher waist/hip ratio, family history of diabetes, older age, male sex, and lower income were independently associated with non-insulin-dependent diabetes mellitus in both ethnic groups. No association was found with skin reflectance, a marker for Amerindian admixture. While the excess risk of diabetes in Hispanics was reduced, a significant 1.9-fold excess risk in Hispanics remained. Further studies are needed to understand factors contributing to the excess prevalence of diabetes in Hispanic Americans.

Adult↗
PubMed1993

The effects of electronic mail on communication in two health sciences institutions.

A study was done during 1991-1992 to determine the perceived impact of electronic mail (E-mail) relative to other forms of communication in health sciences institutions. E-mail subscribers at two major health sciences institutions were sent 2919 surveys, and 823 (28%) completed survey instruments were returned. A significant positive impact of E-mail was found relative to other forms of communication (e.g., paper, phone) with regard to E-mail messaging, response rates, influence, value, formality, perceptions, errors in communication, cost-effectiveness, communication style, and other factors. Areas where no differences were found between communication mechanisms were also revealing. Technical problems, maintenance, and confidentiality of E-mail messaging were not found to be significant problems. Trends, value, and impact of E-mail use in health sciences institutions are also discussed.

Academic Medical Centers↗
PubMed1993

Sequencing of double-stranded polymerase chain reaction products for mutation analysis.

This report describes a reproducible, straightforward approach to sequencing double-stranded DNA products from the polymerase chain reaction (PCR) for analysis of mutations. The sequencing protocol is a modification of that published by Kretz (Kretz et al., 1989) and has been successful in the hands of a number of investigators working on diverse projects. Following this procedure, PCR DNA products generated from bacterial sources (including pBR322 and F' derivatives), as well as cDNA and genomic DNA from both hamster and human cell lines, have been sequenced with equal success. Close attention to the molar ratio of nucleotides to double-stranded DNA template present during the labeling reaction ensures best results.

Animals↗
PubMed1993

Worrying about waste: living close to solid waste disposal facilities in southern Ontario.

As a complement to an epidemiological survey, depth interviews were used to discover the individual level impacts of living close to waste disposal facilities in southern Ontario. The paper begins by describing the nature of the sites and reporting some of the survey findings, which the depth interviews explored. Sample selection and data analysis methods are described. A by-code analysis of the material is presented, emphasizing both within- and between-site differences in type and concern (or impact). Concern varied according to type of exposure and site context. The paper ends with a discussion which relates the study's findings on non-toxic facilities to other research on psychosocial effects, lay reasoning and risk perceptions and assessments.

Adaptation, Psychological↗
PubMed1993

Excision repair reduces doxorubicin-induced genotoxicity.

LacI mutations induced by doxorubicin in a wild-type, uvr(A)BC repair-proficient E. coli strain were analyzed by DNA sequencing. These mutations were contrasted with mutations previously recovered from doxorubicin-treated uvrB- organisms in order to assess the role of excision repair in doxorubicin-induced genotoxicity. After a 30-min exposure of wild-type E. coli to 330 microM doxorubicin, survival was 34% and the overall lacI mutation frequency increased 1.8-fold to 340 x 10(-8). The distribution of doxorubicin-induced mutants among subclasses of mutation involving the i-d and lac operator regions differed significantly between repair-proficient and -deficient strains. Distributional differences appeared to result both from a decrease in deletions involving the lac operator and an increase in base substitutions involving the i-d region in repair proficient organisms. However, elements of the doxorubicin-induced mutation spectrum in uvrB- E. coli are still discernable in wild-type organisms. These elements include the remarkable shift of 3'-deletion endpoints to palindromic sequence within the lac operator and the recovery of multiple isolates of T:A-->A:T transversions at position 96 in doxorubicin-treated cultures. These observations suggest that components of the uvr(A)BC nucleotide excision repair system function through a general mechanism prior to fixation of mutations to reduce, but not completely eliminate, the genotoxic effects of doxorubicin.

Base Sequence↗
PubMed1993

Waist-hip ratio measurement location influences associations with measures of glucose and lipid metabolism. The San Luis Valley Diabetes Study.

The ratio of waist to hip circumference is widely used to characterize fat distribution patterns but the locations for measurement are not standardized. Between 1986 and 1988, we measured two waist and two hip circumferences on 616 Hispanic and non-Hispanic white subjects, aged 30 to 74 years. Intraclass correlation coefficients, based on repeat measurements of 38 subjects, showed that minimum waist and maximum hip circumferences attained or exceeded the level of repeatability seen with the landmark-based circumference measures. Sex-specific partial correlation coefficients, adjusted for age and body mass index, indicated wide variation in the magnitudes of associations of the two waist-hip ratios with measures of insulin, high-density-lipoprotein cholesterol, triglycerides, and diastolic blood pressure. Models with simple waist circumference generally produced partial correlation coefficients of equal or greater magnitude compared to the coefficients seen with the waist-hip ratio.

Adult↗
PubMed1993

Reproductive history, glucose tolerance, and NIDDM in Hispanic and non-Hispanic white women. The San Luis Valley Diabetes Study.

OBJECTIVE: To ascertain whether childbearing would decrease oral glucose-stimulated insulin and C-peptide levels and increase the risk of NIDDM and impaired glucose tolerance in a population of Hispanic and non-Hispanic white women residing in the San Luis Valley of Colorado. Several investigators have related childbearing to subsequent abnormal glucose tolerance. RESEARCH DESIGN AND METHODS: In a population-based case-control epidemiological study, diabetic patients 20-74 yr of age (n = 196) and randomly sampled control women subjects (n = 735) underwent a glucose tolerance test, a physical examination, and an in-person standardized interview. The relations between the live-birth number and fasting and oral glucose stimulated glucose, insulin and C-peptide concentrations, and NIDDM and impaired glucose tolerance were estimated using linear or logistic regression to adjust for extraneous variables. RESULTS: In women selected as control subjects, the live-birth number was related to a significant decrease in the sum of 1- and 2-h C-peptide concentrations (coefficient = -0.077, P < 0.001) and the logarithm of the sum of 1- and 2-h insulin concentrations (coefficient = -0.014, P = 0.02). After adjustment for subscapular skin-fold thickness, the relative odds of NIDDM for the live-birth number, which was small and of borderline significance, diminished (odds ratio = 1.04 for one birth, P = 0.18). Findings were similar for impaired glucose tolerance. CONCLUSIONS: Childbearing was related to lower C-peptide and insulin levels in Hispanic and non-Hispanic women of the San Luis Valley. It had little apparent effect on later risk of NIDDM or impaired glucose tolerance.

Adult↗
PubMed1993

Excess incidence of known non-insulin-dependent diabetes mellitus (NIDDM) in Hispanics compared with non-Hispanic whites in the San Luis Valley, Colorado.

Non-insulin-dependent diabetes mellitus is between two and five times more prevalent among Hispanic Americans than among non-Hispanic whites (NHW). Incidence data for Hispanic populations will help to determine whether this excess prevalence is due to increased incidence, survivorship, or other factors. Incident cases were identified through concurrent surveillance of all local medical practices from 1983 to 1988 in two southern Colorado counties in which the population was 46% Hispanic. All identified subjects were invited for an oral glucose tolerance test. Among the subjects who attended clinic, 83% were confirmed as having diabetes, using WHO criteria. The standardized average annual incidence rates per 1000 for confirmed non-insulin-dependent diabetes, accounting for nonresponse, were 3.7 and 1.6 for Hispanic and NHW males, and 4.5 and 1.2 for Hispanic and NHW females, respectively. The age and nonresponse adjusted rate ratio comparing Hispanics to NHWs was 3.1 (95% CI: 2.3-4.2), indicating a significant excess risk of diabetes incidence for the Hispanic population in southern Colorado. Peak age-specific incidence among Hispanics occurred in persons 50 to 59 years old, a decade earlier than among NHWs. These results are consistent with data from the Mexican-American population in Texas and suggest that the previously observed excess in diabetes prevalence is due to higher incidence rates. The earlier age-specific peak in incidence has also been observed in Mexican-American and American Indian populations, suggesting that risk factors may operate at earlier ages.

Adult↗
PubMed1993

Is the risk of coronary heart disease lower in Hispanics than in non-Hispanic whites? The San Luis Valley Diabetes Study.

A less favorable cardiovascular risk factor profile, but paradoxically lower coronary heart disease mortality and prevalence have been reported for Hispanic men compared to non-Hispanic white men. Since mortality and prevalence data are susceptible to bias, the patterns of coronary heart disease incidence, as well as prevalence and mortality, were investigated in a biethnic Hispanic and non-Hispanic white population of the San Luis Valley in Colorado. Little evidence was found for lower incidence, prevalence, or mortality due to coronary heart disease among Colorado Hispanics without diabetes. The risk of coronary heart disease among diabetic Hispanics appeared, however, to be approximately 50% lower than among non-Hispanic whites, especially in men. Adjustment for selected cardiovascular risk factors (age, gender, diabetes, hypertension, cigarette smoking, body mass index, and high-density lipoprotein cholesterol and triglycerides levels) did not change this ethnic pattern. The plausible explanations of a lower coronary heart disease risk among diabetic Hispanics, compared to non-Hispanic whites, include both biologic mechanisms and artifacts due to deficiencies of mortality classification or differential access to health care. The existing evidence is insufficient to conclude that the risk of coronary heart disease in the general population differs between Hispanics and non-Hispanic whites. The ethnic patterns of coronary heart disease incidence should be investigated further through population-based incidence studies.

Adult↗
PubMed1992

The roles of insulin, obesity, and fat distribution in the elevation of cardiovascular risk factors in impaired glucose tolerance. The San Luis Valley Diabetes Study.

The objective of this study was to determine whether a less favorable risk factor pattern for cardiovascular disease among persons with impaired glucose tolerance could be explained by fasting insulin, obesity, and/or a central distribution of body fat. Between 1984 and 1988, cardiovascular risk factors were examined cross-sectionally in Hispanic and non-Hispanic white participants in the San Luis Valley Diabetes Study who had either impaired (n = 173) or normal (n = 1,107) glucose tolerance. Sex-specific analysis of covariance models were constructed to adjust risk factor levels for age, age and insulin, and age, insulin, body mass index, and centrality index. Both males and females with impaired glucose tolerance had higher age-adjusted mean diastolic blood pressures, heart rates, uric acid levels, and triglyceride levels and lower levels of high density lipoprotein (HDL) cholesterol and HDL3 cholesterol than normal subjects; differences were significant for all risk factors except HDL cholesterol and HDL3 cholesterol in males. Differences in diastolic blood pressure in males, and differences in heart rate and triglyceride in both sexes, remained significant after adjustment for all covariates. However, differences in uric acid in males and differences in diastolic blood pressure and HDL3 cholesterol in females were attenuated to borderline significance levels. Differences in uric acid and HDL cholesterol in females were diminished to nonsignificant levels, especially after adjustment for obesity-related measures. With few exceptions, fasting insulin did not appear to play a major role in accounting for differences in these risk factors. With adjustment, ethnic differences (Hispanic vs. non-Hispanic white) were smaller and were statistically significant less often than differences observed between impaired and normal glucose tolerant groups. The authors concluded that hyperinsulinemia, obesity, and a central body fat distribution accounted for some, but usually not all, of the less favorable cardiovascular risk factor pattern found in subjects with impaired glucose tolerance.

Adult↗
PubMed1992

Prevalence of coronary heart disease in subjects with normal and impaired glucose tolerance and non-insulin-dependent diabetes mellitus in a biethnic Colorado population. The San Luis Valley Diabetes Study.

The prevalence of coronary heart disease was studied in 1984-1988 in 1,092 individuals with normal glucose tolerance, 173 individuals with impaired glucose tolerance, and 429 individuals with non-insulin-dependent diabetes mellitus, who were age 25-74 years and were from a biethnic community in the San Luis Valley, Colorado. Glucose tolerance was classified using the World Health Organization criteria, and coronary heart disease prevalence was assessed using the Rose Questionnaire and a resting electrocardiogram. Compared with normal glucose tolerance, coronary heart disease was significantly more prevalent in diabetic non-Hispanic white women (odds ratio (OR) for all end points combined = 3.2, 95% confidence interval (Cl) 1.8-5.5) and men (OR = 1.9, 95% Cl 1.1-3.3) and in diabetic Hispanic women (OR = 1.7, 95% Cl 1.1-2.5), but not men (OR = 1.0, 95% Cl 0.6-1.7). Among diabetic men, the prevalence of possible myocardial infarction was lower in Hispanics than in non-Hispanic whites (OR = 0.4, 95% Cl 0.2-0.7). Similar patterns of coronary heart disease were observed in individuals with impaired glucose tolerance. The paradoxically low prevalence of coronary heart disease in Hispanics with non-insulin-dependent diabetes mellitus, especially men, may be due to unknown protective factors, increased case fatality, or competing mortality in this group.

Adult↗
PubMed1992

Purification and characterization of human truncated prorenin.

Posttranslational processing of enzymatically inactive prorenin to an active form participates in the control of the activity of a key system involved in blood pressure regulation, growth, and other important functions. The issue is complicated because renin can be produced by a number of tissues throughout the body, in addition to the kidney, but the mechanism by which they process prorenin to renin is unknown and difficult to determine because of the small amounts of renin present. In the juxtaglomerular cell of the kidney, a 43 amino acid prosegment is cleaved from the amino terminus of prorenin to generate renin of molecular weight 44,000 [Do, Y. S., Shinagawa, T., Tam, H., Inagami, T., & Hsueh, W. A. (1987) J. Biol. Chem. 262, 1037-1043]. Using human uterine lining or a recombinant human prorenin system, we employed the same approach as that used in kidney, ammonium sulfate precipitation at pH 3.1 followed by pepstatin and H-77 affinity chromatography or gel filtration, to purify to homogeneity a 45,500-MW totally active renin. The specific activity of the active truncated prorenin was 850 Goldblatt units (GU)/mg of protein for chorion-decidua renin and 946 GU/mg of protein for recombinant renin, both similar to that reported for pure human renal renin. Both forms of renin cross-reacted with an antibody generated against 44,00-MW pure human renal renin and with an antibody generated against a peptide identical to the carboxy-terminal one-third of the prosegment.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Morbidity from congestive and hypertrophic cardiomyopathy in the Minneapolis-St. Paul metropolitan area: 1979-1984.

In order to develop an epidemiologic profile of congestive and hypertrophic cardiomyopathy, we reviewed hospital discharge diagnosis data for the Minneapolis-St. Paul metropolitan area from 1979 to 1984. For congestive cardiomyopathy, we found statistically significant increases in the age-adjusted hospital discharge diagnosis rate for both men (from 63 to 125/100,000 population/year) and women (from 35 to 58/100,000 population/year). We also found that the age-specific rates increased significantly among older men (55-64 years of age, from 86 to 198/100,000 population/year; 65-74 years of age, from 182 to 322/100,000 population/year) and older women (65-74 years of age, from 106 to 196/100,000 population/year). The rates increased with advancing age for both genders. Men had greater rates than women. For hypertrophic cardiomyopathy, no temporal trends could be discerned. Women were observed to have greater age-specific rates than men; the age-adjusted rates were, however, approximately the same for men and women. The hospital discharge diagnosis rate increased with advancing age among both men and women. The possible reasons for these observed patterns, including the major impact of improvements in diagnosis during the observation period, are discussed. Additional research into these disorders is needed.

Adult↗
PubMed1992

Process evaluation of a home-based program to reduce diet-related cancer risk: the "WIN at Home Series".

A random mailed survey (response N = 226; 75.3%) of participants in diet-related home-based learning evaluated exposure to recruitment channels and impact on salience, utility, level of participation, sharing the course with others, knowledge, and performing recommended behaviors. A post-only design, the study was conducted in a small Minnesota city (population = 20,000), part of the Cancer and Diet Intervention (CANDI) project. About 18.5% of residents (3,711) enrolled during an 8-week media campaign; women, college graduates, and those over 44 years old were overrepresented. Participants learned about the program through mass media (97%); small media (41.9%); and interpersonal sources (50%). Women were more likely to learn about the course through interpersonal sources. In analysis of variance (ANOVA) modeling, salience and utility predicted level of participation in course activities. Level of participation in turn predicted nutrition knowledge and with salience predicted performance of recommended behaviors. Although the course appealed to individuals who needed it less, there was evidence of diffusion to the unenrolled. About 57% of responding participants reported sharing it with spouses; about 67% reported sharing it with someone outside their households.

Adult↗
PubMed1991

High-fat, low-carbohydrate diet and the etiology of non-insulin-dependent diabetes mellitus: the San Luis Valley Diabetes Study.

Diet has long been believed to be an important risk factor for non-insulin-dependent diabetes. Animal studies generally support a relation between high-fat diets and development of insulin resistance. However, conclusive epidemiologic evidence is lacking. To further investigate the role of dietary fat and carbohydrate as potential risk factors for the onset of non-insulin-dependent diabetes mellitus, current diet was assessed among a geographically based group of 1,317 subjects without a prior diagnosis of diabetes who were seen in the period from 1984 to 1988 in two countries in southern Colorado. In this study, 24-hour diet recalls were reported prior to an oral glucose tolerance test. Persons with previously undiagnosed diabetes (n = 70) and impaired glucose tolerance (n = 171) were each compared with confirmed normal controls (n = 1,076). The adjusted odds ratios relating a 40-g/day increase in fat intake to non-insulin-dependent diabetes mellitus and impaired glucose tolerance were 1.51 (95% confidence interval 0.85-2.67) and 1.62 (95% confidence interval 1.09-2.41), respectively. Restricting cases to diabetic persons with fasting glucose greater than 140 mg/dl and persons with impaired glucose tolerance confirmed on follow-up, the odds ratios increased to 3.03 (95% confidence interval 1.07-8.62) and 2.67 (95% confidence interval 1.33-5.36), respectively. The findings support the hypothesis that high-fat, low-carbohydrate diets are associated with the onset of non-insulin-dependent diabetes mellitus in humans.

Adult↗
PubMed1991

DNA sequence specificity of doxorubicin-induced mutational damage in uvrB- Escherichia coli.

In the absence of excision repair, doxorubicin caused a striking (41-fold) increase in the frequency of large deletion mutations extending from the lac operator (lacO) into the lac repressor gene (lacI) of Escherichia coli. In contrast, there was only a 2-fold increase in the frequency of small deletions despite a 3-fold increase in overall mutation frequency. The 5'-endpoints of doxorubicin-induced lacO and lacI/lacO deletions occurred at the DNA sequence 5'-pyTAA or 5'-AATpy (where py is pyrmidine) (16%), at runs of purines or pyrimidines (41%) and adjacent to 5'-dGdC or 5'-dCdG doublets (34%). Ninety % (27 of 30) of the doxorubicin-induced deletions involving the region of the lacO palindrome had 3'-endpoints within the palindrome sequence as compared with 40% (4 of 10) spontaneous deletions in an untreated set. Doxorubicin-induced single base substitutions were highly focused at one site (4 of 6) in the i-d region of lacI, in contrast to the spontaneous distribution of point mutations, where 16 mutants were recovered at 12 different sites. An increased frequency (3-fold) of highly focused base substitutions was also observed at 2 sites in the lac operator region (at lacO +6, which is a transition "hotspot" in the spontaneous spectra of both wild type and uvrB- organisms and at the adjacent +5 site). Notably, the frequency of 1- and 2-base frameshifts did not increase in the doxorubicin-induced spectrum, relative to the spontaneous mutation spectrum. These in vivo observations in E. coli suggest that in the absence of excision repair, doxorubicin causes highly focused deletions and base substitutions. These mutations occur adjacent to DNA sequences identified in previous in vitro studies as preferential sites of doxorubicin binding.

Base Sequence↗
PubMed1991

Physical-activity-assessment measures compared in a biethnic rural population: the San Luis Valley Diabetes Study.

We evaluated the consistency of three questionnaire methods of assessing work and leisure activity in the rural biethnic population of the San Luis Valley Diabetes Study. A 7-d physical activity recall (PAR), a ranking of usual activity, and a history of usual participation in vigorous activity were used. Energy expenditure (kJ.kg-1.wk-1) (EE) was estimated from PAR. Subjects were 503 adults [49% non-Hispanic white (NHW), 51% Hispanic]. Physical activity at work rather than leisure-time activity largely determined total energy expenditure. Average EE at work increased with work rank for all subjects combined [mean EE (SEE) for rank 1 (low) = 324.2 (24.4), rank 4 (high) = 874.0 (102.1)] and within sex, ethnic, and occupational subgroups. Leisure EE increased with leisure rank only for NHW men and employed women. Similar patterns were observed in comparisons of PAR data with history of vigorous activity. Further development and validation of instruments appropriate for use across population subgroups are needed.

Adult↗