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Biomedical subjects

G Maldonado

Publications and source records attributed to G Maldonado.

At least 19 recordsLinked to original sources
PubMed1998

Interaction of murine macrophage-membrane proteins with components of the pathogenic fungus Histoplasma capsulatum.

The interaction of macrophage-membrane proteins and histoplasmin, a crude antigen of the pathogenic fungus Histoplasma capsulatum, was studied using murine peritoneal macrophages. Membrane proteins were purified via membrane attachment to polycationic beads and solubilized in Tris-HCl/SDS/DTT/glycerol for protein extraction; afterwards they were adsorbed or not with H. capsulatum yeast or lectin binding-enriched by affinity chromatography. Membrane proteins and histoplasmin interactions were detected by ELISA and immunoblotting assays using anti-H. capsulatum human or mouse serum and biotinylated goat anti-human or anti-mouse IgG/streptavidin-peroxidase system to reveal the interaction. Results indicate that macrophage-membrane proteins and histoplasmin components interact in a dose-dependent reaction, and adsorption of macrophage-membrane proteins by yeast cells induces a critical decrease in the interaction. Macrophage-membrane glycoproteins with terminal D-galactosyl residues, purified by chromatography with Abrus precatorius lectin, bound to histoplasmin; and two bands of 68kD and 180kD of transferred membrane protein samples interacted with histoplasmin components, as revealed by immunoblot assays. Specificity for beta-galactoside residues on the macrophage-membrane was confirmed by galactose inhibition of the interaction between macrophage-membrane proteins and histoplasmin components, in competitive ELISA using sugars, as well as by enzymatic cleavage of the galactoside residues.

Animals↗
PubMed1998

Do vouchers improve breast cancer screening rates? Results from a randomized trial.

OBJECTIVE: To determine the effect of a voucher for free mammography on compliance with recommended mammography screening guidelines. STUDY DESIGN: Vouchers for free mammography distributed to a random sample of women over the age of 50 in two rural southern Minnesota counties. The vouchers were good for one year. Baseline and follow-up data were collected and rates of compliance with current mammography guidelines were observed for the voucher group and a control group of women living in the same counties. METHODS: Logistic regression models were used to estimate the effect of the voucher on compliance with mammography guidelines and the impact of factors potentially influencing the effectiveness of the voucher. PRINCIPAL FINDINGS: The voucher improved mammography rates primarily through increasing screening among women who were out of compliance at baseline. CONCLUSIONS: Vouchers, even when distributed randomly within a population of rural Midwestern women, can significantly improve compliance rates. Vouchers are no less effective a means of increasing screening among vulnerable women than among other women.

Adult↗
PubMed1998

Factoring vs linear modeling in rate estimation: a simulation study of relative accuracy.

A common strategy for modeling dose-response in epidemiology is to transform ordered exposures and covariates into sets of dichotomous indicator variables (that is, to factor the variables). Factoring tends to increase estimation variance, but it also tends to decrease bias and thus may increase or decrease total accuracy. We conducted a simulation study to examine the impact of factoring on the accuracy of rate estimation. Factored and unfactored Poisson regression models were fit to follow-up study datasets that were randomly generated from 37,500 population model forms that ranged from subadditive to supramultiplicative. In the situations we examined, factoring sometimes substantially improved accuracy relative to fitting the corresponding unfactored model, sometimes substantially decreased accuracy, and sometimes made little difference. The difference in accuracy between factored and unfactored models depended in a complicated fashion on the difference between the true and fitted model forms, the strength of exposure and covariate effects in the population, and the study size. It may be difficult in practice to predict when factoring is increasing or decreasing accuracy. We recommend, therefore, that the strategy of factoring variables be supplemented with other strategies for modeling dose-response.

Bias↗
PubMed1997

Participation of a sialic acid-specific lectin from freshwater prawn Macrobrachium rosenbergii hemocytes in the recognition of non-self cells.

Phagocytic activity of circulating hemocytes from freshwater prawns is mediated by a small group of granulocytes. Recognition of nonself cells by these cells seems to be mediated by two independent mechanisms: specific, via O-acetylsialic acid, as well as N-acetylated sugars on recognized cells and a nonspecific one. Both mechanisms show differences in their optimal temperature and time differences for activity. Hemocytes with phagocytic activity interact positively with rabbit IgG raised against the serum lectin. Attempts to elucidate the nature of the membrane-lectin on hemocytes performed by electroimmunotransfer blot assays on cell lysates indicates the presence of two major proteins with a molecular weight of 68-72 kDa. Electron microscopy revealed a regular distribution of lectin on hemocyte plasma membranes. Our results suggest the active participation of a membrane lectin in the recognition of nonself.

Animals↗
PubMed1997

Alternative approaches to analytical designs in occupational injury epidemiology.

In this paper, we discuss the theoretical framework upon which observational studies of occupational injuries are based. Following a general description of how causal effects are estimated, the challenges faced by researchers working in this area are outlined, with an emphasis on case-control studies. These challenges include defining the at-risk period for workers whose tasks change over time and whose hazard period may be very brief, evaluating the underreporting of both exposures and injuries, and considering the effects of multiple injuries per individual on study design and data analysis. We review both the theoretical and practical considerations in the design and conduct of traditional case-control studies, based on the collection of individual level data, as well as other approaches, such as using information culled from administrative and descriptive databases, and case-control studies in which the plant or work site is the unit of analysis. The case-crossover design is also reviewed and its utility for reducing confounding due to differences between individuals by self-matching is highlighted. While this design has not yet been applied to the work setting, its potential for increasing our understanding of the causes of acute-onset occupational injuries seems promising. Finally, a variety of hybrid designs are discussed, including combinations of case-control, case-crossover, and cohort designs.

Accidents, Occupational↗
PubMed1997

Injury from dairy cattle activities.

Animals have been implicated as an important source of injury for farm household members. Little is known, however, about the specific activities associated with the animal/livestock operations that place a person at increased or decreased risk for injuries. The primary aim of this case-control study was to identify which dairy cattle operation activities (that is, milking, feeding, cleaning barns, trimming and treating feet, dehorning, assisting with difficult calvings, and doing treatments) were associated with an increased or decreased risk of injury. We found milking to have the greatest increase in risk for injury. The ratios for increasing hours per week spent at milking (0, 1-10, 11-20, 21-30, 31-63) were 1.0, 2.3, 5.5, 10.9, and 20.6, respectively. We also found an increased rate ratio associated with trimming or treating hooves (rate ratio = 4.2).

Adolescent↗
PubMed1997

Risk factors for work-related violent victimization.

This case-control study used the National Crime Victimization Survey database (a national sample of housing addresses) to examine sociodemographic risk factors for becoming a victim of work-related robbery and assault. Cases (N = 267) reported having been violently victimized in the previous 6 months. Controls (N = 1,783) were chosen from all nonvictims of violent crime at the end of the 6-month period. Risk factors varied by type of victimization, and differences were evident between men and women. Men less than 45 years of age had an increased risk for assault [odds ratio (OR) = 2.0-2.7], compared with those 55 years of age and older; and those with a family income of less than $40,000 had an increased risk for assault (OR = 1.7-1.9), compared with those having a family income of $50,000 or more. We found a decreased risk for those with a high school education (OR = 0.6), compared with those with some college education. For women, an increased risk was seen for ages 16-18 years (OR = 3.3) and 25-34 years (OR = 2.3), compared with those 55 years of age or older. Women who were divorced or separated (OR = 4.4) and never-married (OR = 2.1) were at higher risk than women who were married. We found a decreased risk for nonwhites (OR = 0.5), compared with whites.

Adolescent↗
PubMed1997

Lower respiratory illness, recurrent wheezing, and day care attendance.

We prospectively assessed the relations between various characteristics of day care and lower respiratory illness (LRI) in a cohort of 1,268 Minnesotan children, born between October 1989 and January 1991 and followed to 2 yr of age. Information on LRI was abstracted from medical records and data on day care use, respiratory symptoms, and physician diagnosis of asthma were obtained from questionnaires. We identified a subgroup of 60 children with recurrent wheezing illnesses. The LRI rate ratio for day care attendance was 2.0 (95% confidence interval = 1.7, 2.2). Rate ratios were similar regardless of the day care setting, number of other children present, or the number of hours spent in day care. A parental history of asthma further increased the rate ratio for day care attendance. Day care attendance was associated with a threefold risk of having recurrent wheezing illnesses. We conclude that day care attendance is an important risk factor for LRI in young children, and for recurrent wheezing illnesses.

Child Day Care Centers↗
PubMed1996

Worker exposures to inhalable and total aerosol during nickel alloy production.

This paper describes a study that was carried out at a North American nickel alloy production facility to compare the levels of personal exposures to inhalable and total nickel-containing aerosols. It is part of a large body of work aimed at assessing the impact of introducing new personal sampling instrumentation with performance consistent with the latest criteria proposed by the International Standards Organization (ISO), the Comité Européen Normalisation (CEN) and the American Conference of Governmental Industrial Hygienists (ACGIH). Side-by-side sampling using the 37-mm filter holder (for total aerosol) and the so-called IOM inhalable aerosol sampler was conducted for the personal exposures of workers in a range of workplaces throughout the facility. The results showed that inhalable aerosol exposure levels-for both overall aerosol and for total nickel-were consistently and significantly higher than the corresponding total aerosol levels. Weighted least-squares linear regression yielded factors ranging from about 1.3 to 2.4 for overall dust and from about 1.5 to 3.5 for nickel. Inspection of the statistical distribution of the exposures for the whole plant suggested that it was log-normal.

Aerosols↗
PubMed1996

Impact of model-form selection on the accuracy of rate estimation.

A key assumption underlying the use of model-based estimates in epidemiology is that the structural-model form is an adequate mathematical description of the dependence of disease occurrence on exposures and covariates (that is, the model form is correctly specified). If this assumption is violated, model-based point estimators and variance estimators may be biased, standard confidence intervals may be invalid, and inferences derived from these estimators may be incorrect. In practice, the true structural-model form is usually unknown, and investigators frequently use their data to help select a model form. We conducted a simulation study to examine the impact of model-form selection on the accuracy of rate estimation in cohort-study situations resembling those found in environmental and occupational epidemiology. For the situations we examined, the increase in variance produced by using model-form selection was often more than offset by the corresponding reduction in bias, sometimes resulting in a dramatic increase in accuracy. Model-form selection was observed to be most beneficial relative to no selection when effects were stronger, the sample size was larger, and the candidate model forms included the true model form or allowed the model to more closely approximate the true model form. It was least beneficial when effects were weak and the sample size was small, even if the candidate model forms included the true model form.

Cohort Studies↗
PubMed1996

The indoor air and children's health study: methods and incidence rates.

The Indoor Air and Children's Health Study is a prospective cohort study of the relation between indoor air pollution and lower respiratory illness (LRI) during the first 2 years of life. Information on family and household characteristics was obtained from a health maintenance organization for 1,424 infants enrolled at birth. Data on LRI were abstracted from medical records. The incidence of all LRI was 48.4 per 100 child-years. Wheezing-associated respiratory illness (WARI)/asthma was the most common specific LRI, with an incidence of 11.5 per 100 child-years. Total LRI incidence was lowest during the first 6 months of life. Girls had lower incidence than boys [rate ratio (RR) = 0.8; 95% confidence interval (CI) = 0.7-0.8)]. With the exception of croup, all LRI were most common during February and March. These results are comparable with those of other prospective studies. Consistent with other studies, self-reported maternal smoking demonstrated an RR of 1.5 (95% CI = 1.2-1.8) for total LRI, but the association varied for specific LRIs from 2.3 (95% CI = 1.5-3.0) for WARI/asthma to 1.0 (95% CI = 0.7-1.6) for bronchitis.

Air Pollution, Indoor↗
PubMed1996

The state of the literature on primary care specialty choice: where do we go from here?

A large body of research on medical students' choice of primary care specialties has been published. However, the literature is difficult to interpret because of multiple biases, design weaknesses, small numbers of subjects, inconsistencies in both dependent and independent variables, and conflicting results. These weaknesses have been noted by authors who have reviewed the work in this area, but the authors have given little direction for ways to improve and build upon the current state of the literature. This paper provides a quantitative description of the content of the specialty choice literature. As part of a larger project that included an exhaustive literature analysis, all research on primary care specialty choice published between 1987 and 1993 was collected and summarized according to study questions, designs, data sources, samples, theory, and outcome variables. Portions of this information were used to rate the quality of each study, yielding a score from zero to 100 that indicated the trustworthiness of the study's conclusions. Overall, the studies examined were found to use predominantly cross-sectional designs and to lack theoretical basis. Special curricular tracks, student personality, and self-reported influences were the most frequently studied determinants of primary care specialty choices. The results confirm previous qualitative descriptions of the state of the literature on specialty choice, and lead to recommendations for approaches to improve the quality of further work in this area. The research agenda that emerged from the larger project is also presented.

Career Choice↗
PubMed1996

[Comparative study of HELISAL T.M. RAPID BLOOD and ELISA, JATROX and pathologic anatomy in the diagnosis of Helicobacter pylori infection].

OBJECTIVES: To assess the usefulness of HELISAL in the diagnosis of Helicobacter pylori infection by comparing it with ELISA, JATROX and histopathologic findings. EXPERIMENTAL DESIGN: Randomized prospective study. PATIENTS: Sixty-one patients, thirty-three males and twenty-eight females, 18-73 years old, submitted to esophagogastroduodenoscopy. RESULTS: The sensitivity of HELISAL when compared to ELISA test was 60.8%, the specificity 73.3%, the positive predictive value 87.5%, the negative predictive value 37.9%, and the kappa index 0.26. When compared to histopathologic test: sensitivity 60.9%, specificity 65%, positive predictive value 78.1%, negative predictive value 44.7%, kappa 0.28. When compared to JATROX, sensitivity 57.7%, specificity 62.5%, positive predictive value 81.2%, negative predictive value 34.4%, kappa 0.21. CONCLUSION: The sensitivity of HELISAL test is lower than that of other compared tests, and the negative predictive value is very low. The specificity and the positive predictive value are higher than the sensitivity. The kappa index shows a very low concordance.

Adult↗
PubMed1995

Determinants of primary care specialty choice: a non-statistical meta-analysis of the literature.

This paper analyzes and synthesizes the literature on primary care specialty choice from 1987 through 1993. To improve the validity and usefulness of the conclusions drawn from the literature, the authors developed a model of medical student specialty choice to guide the synthesis, and used only high-quality research (a final total of 73 articles). They found that students predominantly enter medical school with a preference for primary care careers, but that this preference diminishes over time (particularly over the clinical clerkship years). Student characteristics associated with primary care career choice are: being female, older, and married; having a broad undergraduate background; having non-physician parents; having relatively low income expectations; being interested in diverse patients and health problems; and having less interest in prestige, high technology, and surgery. Other traits, such as value orientation, personality, or life situation, yet to be reliably measured, may actually be responsible for some of these associations. Two curricular experiences are associated with increases in the numbers of students choosing primary care: required family practice clerkships and longitudinal primary care experiences. Overall, the number of required weeks in family practice shows the strongest association. Students are influenced by the cultures of the institutions in which they train, and an important factor in this influence is the relative representation of academically credible, full-time primary care faculty within each institution's governance and everyday operation. In turn, the institutional culture and faculty composition are largely determined by each school's mission and funding sources--explaining, perhaps, the strong and consistent association frequently found between public schools and a greater output of primary care physicians. Factors that do not influence primary care specialty choice include early exposure to family practice faculty or to family practitioners in their own clinics, having a high family medicine faculty-to-student ratio, and student debt level, unless exceptionally high. Also, students view a lack of understanding of the specialties as a major impediment to their career decisions, and it appears they acquire distorted images of the primary care specialties as they learn within major academic settings. Strikingly few schools produce a majority of primary care graduates who enter family practice, general internal medicine, or general practice residencies or who actually practice as generalists. Even specially designed tracks seldom produce more than 60% primary care graduates. Twelve recommendations for strategies to increase the proportion of primary care physicians are provided.

Age Distribution↗
PubMed1995

A systematic approach to conducting a non-statistical meta-analysis of research literature.

Literature analyses and syntheses are becoming increasingly important as a means of periodically bringing coherence to a research area, contributing new knowledge revealed by integrating single studies, and quickly informing scientists of the state of the field. As a result, there is a need for approaches that can provide replicable, reliable, and trustworthy results. Over the last decade many researchers have begun using the statistical meta-analysis approach to integrate studies. However, the single studies conducted in many areas are not of the type amenable to statistical meta-analysis but are more appropriate for non-statistical analysis and synthesis. The present paper describes (1) a rigorous approach to conducting a non-statistical meta-analysis of research literature and (2) an example of how this approach was applied to the literature of determinants of primary care specialty choice published between 1987 and 1993. This approach includes model development, literature retrieval, literature coding, rating references for quality, annotating high-quality references, and synthesizing only the subset of the literature found of sufficient quality to be considered. Also, the basic results of each included study are reported in the synthesis so that readers have before them all the "data points" used in the synthesis. Thus, readers can draw their own interpretations without having to re-collect the data, just as they would be able to do in any single study that presents original data as well as conclusions and discussion.

Meta-Analysis as Topic↗