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Biomedical subjects

S L Stewart

Publications and source records attributed to S L Stewart.

At least 19 recordsLinked to original sources
PubMed2002

Preliminary assessment of intrahemispheric QEEG measures in bipolar mood disorders.

OBJECTIVE: This study assessed the quantitative electroenchephalographic (QEEG) absolute power and coherence differences between a group of patients with bipolar I mood disorder (BMD I) and a group of patients with schizophrenia. We also examined the correlation between QEEG measures and family history of BMD. METHOD: Using the National Institutes of Mental Health (NIMH) Global Rating Scale, we rated 18 adult inpatients with a DSM-III-R diagnosis of BMD I for the severity of the current episode. We also collected data on the family history of the illness. This group was then matched for age, sex, and handedness with an equal number of inpatients with a DSM-III-R diagnosis of schizophrenia. QEEG absolute power and coherence was calculated for the alpha bandwidth (8.0 to 12.0 Hz), assessed at 18 pairs of electrodes in both hemispheres during resting, eyes-closed condition in all the patients. RESULTS: The patients with schizophrenia showed significantly higher coherence (P = 0.047) at 6 pairs of electrodes on the right side. The group with BMD showed significantly higher power (P = 0.042) at 2 pairs of electrodes on the right side. Correlational analysis showed that QEEG measures were significantly correlated (P = 0.01) with positive family history of BMD. CONCLUSION: These findings suggest that the patients with BMD are more disorganized in the right anterior hemisphere and that there is a significant positive correlation between the QEEG measures and the presence of family history of BMD. Further studies in a larger sample are required to confirm these preliminary findings.

Adult↗
PubMed2001

Phytoestrogen consumption and breast cancer risk in a multiethnic population: the Bay Area Breast Cancer Study.

Research on the relation between phytoestrogens and breast cancer risk has been limited in scope. Most epidemiologic studies have involved Asian women and have examined the effects of traditional soy foods (e.g., tofu), soy protein, or urinary excretion of phytoestrogens. The present study extends this research by examining the effects of a spectrum of phytoestrogenic compounds on breast cancer risk in non-Asian US women. African-American, Latina, and White women aged 35-79 years, who were diagnosed with breast cancer between 1995 and 1998, were compared with women selected from the general population via random digit dialing. Interviews were conducted with 1,326 cases and 1,657 controls. Usual intake of specific phytoestrogenic compounds was assessed via a food frequency questionnaire and a newly developed nutrient database. Phytoestrogen intake was not associated with breast cancer risk (odds ratio = 1.0, 95% confidence interval: 0.80, 1.3 for the highest vs. lowest quartile). Results were similar for pre- and postmenopausal women, for women in each ethnic group, and for all seven phytoestrogenic compounds studied. Phytoestrogens appear to have little effect on breast cancer risk at the levels commonly consumed by non-Asian US women: an average intake equivalent to less than one serving of tofu per week.

Adult↗
PubMed2001

Sources of support and the physical and mental well-being of young women with breast cancer.

Women following the stress resulting from the diagnosis and treatment for breast cancer draw resources from their network of friends and relatives. These resources include both emotional support and instrumental resources such as getting a ride to a medical appointment. Emotional support buffers the effects of the stresses they face and improves their mental well-being while the existence, rather than the use, of instrumental supports is positively related to physical well-being. These hypotheses are tested on a population-based cohort of 336 women in the United States, diagnosed and treated for breast cancer when aged 50 or less. Most are married (65%), work (75%), have dependent children (63%), are white (70%), and had a mastectomy (51%). Results of the multi-variate analyses indicate that consistent with predictions, controlling for socio-demographic and treatment-related variables, the size of the social network was related to greater emotional and instrumental support, and greater emotional support was related to better mental well-being. Contrary to predictions, greater use of instrumental resources was related to poorer physical well-being. The results indicate the importance of social resources on well-being following life-threatening illness.

Adaptation, Psychological↗
PubMed2001

Identification of the Arg1086His mutation in the alpha subunit of the voltage-dependent calcium channel (CACNA1S) in a North American family with malignant hyperthermia.

Individuals from a large North American population were screened for the presence of the mutation in the alpha1 subunit of the voltage-dependent calcium channel (CACNA1S) that has recently been associated with malignant hyperthermia (MH). This Arg1086His mutation was screened for in 154 MH normal (MHN) individuals and 112 MH susceptible (MHS) individuals, who were diagnosed by the North American protocol of the in vitro contracture test. PCR and restriction enzyme analysis was used to test for the mutation. The Arg1086His mutation in the CACNA1S was not found in any of the MHN individuals. In contrast, two related individuals (grandfather and grandson, father and son of the MH proband) among the MHS group exhibited this mutation. However, a third MHS individual in the same family (granddaughter, cousin of the grandson) did not exhibit this mutation. These results indicate that this mutation may be associated with MH in this family. Genetic alterations in the CACNA1S associated with MH are present in approximately 1% of this North American MHS population.

Animals↗
PubMed2001

Quality of data in multiethnic health surveys.

OBJECTIVE: There has been insufficient research on the influence of ethno-cultural and language differences in public health surveys. Using data from three independent studies, the authors examine methods to assess data quality and to identify causes of problematic survey questions. METHODS: Qualitative and quantitative methods were used in this exploratory study, including secondary analyses of data from three baseline surveys (conducted in English, Spanish, Cantonese, Mandarin, and Vietnamese). Collection of additional data included interviews with investigators and interviewers; observations of item development; focus groups; think-aloud interviews; a test-retest assessment survey; and a pilot test of alternatively worded questions. RESULTS: The authors identify underlying causes for the 12 most problematic variables in three multiethnic surveys and describe them in terms of ethnic differences in reliability, validity, and cognitive processes (interpretation, memory retrieval, judgment formation, and response editing), and differences with regard to cultural appropriateness and translation problems. CONCLUSIONS: Multiple complex elements affect measurement in a multiethnic survey, many of which are neither readily observed nor understood through standard tests of data quality. Multiethnic survey questions are best evaluated using a variety of quantitative and qualitative methods that reveal different types and causes of problems.

Black or African American↗
PubMed2001

Cancer screening in public health clinics: the importance of clinic utilization.

OBJECTIVES: To determine how screening for breast and cervical cancer in public health clinics was associated with overall clinic utilization. METHODS: Evidence of screening and clinic visits between June 1989 and May 1992 was obtained by medical record audit for a random sample of 1825 women aged 40 to 75 attending eight public health clinics in the San Francisco Bay Area. RESULTS: With an average number of visits (4 per year), women who did not receive a physical examination were much less likely than those who did to obtain a clinical breast examination (OR = 0.03), mammography referral (OR = 0.1), or a mammogram (OR = 0.4) within 2 years, or a Papanicolaou smear (OR = 0.1) within 3 years. Without a physical examination, the odds of screening or referral increased with the first visit (OR = 1.2 for referral, breast examination, and Pap; 1.3 for mammography), but with a decreasing marginal effect of each additional visit (ratio of successive one-visit OR values = 0.992 for referral and breast examination; 0.995 for Pap; 0.98 for mammography). With a physical exam, visits were associated with mammography only (first visit OR = 1.2; OR ratio = 0.992). CONCLUSIONS: In public health clinics, screening is associated either with receipt of routine care or repeated visits for treatment. Women who fall through the cracks are those who come to the clinic with a medical problem but otherwise receive few services. Interventions in public health clinics need to facilitate the provider's ability to use medically related visits as opportunities to increase adherence to screening recommendations.

Adult↗
PubMed2001

Iodine and thyroid cancer risk among women in a multiethnic population: the Bay Area Thyroid Cancer Study.

Research on the relationship between iodine exposure and thyroid cancer risk is limited, and the findings are inconclusive. In most studies, fish/shellfish consumption has been used as a proxy measure of iodine exposure. The present study extends this research by quantifying dietary iodine exposure as well as incorporating a biomarker of long-term (1 year) exposure, i.e., from toenail clippings. This study is conducted in a multiethnic population with a wide variation in thyroid cancer incidence rates and substantial diversity in exposure. Women, ages 20-74, residing in the San Francisco Bay Area and diagnosed with thyroid cancer between 1995 and 1998 (1992-1998 for Asian women) were compared with women selected from the general population via random digit dialing. Interviews were conducted in six languages with 608 cases and 558 controls. The established risk factors for thyroid cancer were found to increase risk in this population: radiation to the head/neck [odds ratio (OR), 2.3; 95% confidence interval (CI), 0.97-5.5]; history of goiter/nodules (OR, 3.7; 95% CI, 2.5-5.6); and a family history of proliferative thyroid disease (OR, 2.5; 95% CI, 1.6-3.8). Contrary to our hypothesis, increased dietary iodine, most likely related to the use of multivitamin pills, was associated with a reduced risk of papillary thyroid cancer. This risk reduction was observed in "low-risk" women (i.e., women without any of the three established risk factors noted above; OR, 0.53; 95% CI, 0.33-0.85) but not in "high-risk" women, among whom a slight elevation in risk was seen (OR, 1.4; 95% CI, 0.56-3.4). However, no association with risk was observed in either group when the biomarker of exposure was evaluated. In addition, no ethnic differences in risk were observed. The authors conclude that iodine exposure appears to have, at most, a weak effect on the risk of papillary thyroid cancer.

Adult↗
PubMed2001

Abnormal Pap smear follow-up in a high-risk population.

Low-income women are at high risk of developing cervical cancer attributable not only to the higher prevalence of risk factors in this population but also to the lack of timely follow-up of abnormal Pap smears. This study evaluates the efficacy of an aggressive follow-up strategy. Women with abnormal Pap smear results after screening in a public hospital emergency department were randomly assigned to follow-up either by a case-managed approach using computerized tracking and universal colposcopy or by traditional care. The main outcome was the proportion of women receiving follow-up in 6 months. A secondary outcome was the proportion of women receiving follow-up by 6 months and diagnostic resolution in 18 months. Of 54 women in the intervention group, 65% kept at least one follow-up appointment in 6 months compared with 41% of the 54 women in the control group (P = 0.012). Half the women in the intervention group versus 19% of women in the control group had follow-up in 6 months and diagnostic resolution in 18 months (P = 0.001). After adjusting for age, initial Pap smear result, and race/ethnicity, the odds of having follow-up in 6 months were four times greater for women in the intervention group (odds ratio = 4.0; 95% confidence interval, 1.6-9.7), and the odds of having both follow-up in 6 months and diagnostic resolution in 18 months were more than six times greater (odds ratio = 6.5; 95% confidence interval, 2.4-17.8). This study demonstrates that an aggressive follow-up strategy significantly improves the rate of both initial follow-up and diagnostic resolution of abnormal Pap smears among low-income women with atypical squamous cells of undetermined significance and atypical glandular cells of undetermined significance when compared with traditional care.

Adolescent↗
PubMed1999

Comparison of methods for classifying Hispanic ethnicity in a population-based cancer registry.

The accuracy of ethnic classification can substantially affect ethnic-specific cancer statistics. In the Greater Bay Area Cancer Registry, which is part of the Surveillance, Epidemiology, and End Results (SEER) Program and of the statewide California Cancer Registry, Hispanic ethnicity is determined by medical record review and by matching to surname lists. This study compared these classification methods with self-report. Ethnic self-identification was obtained by surveying 1,154 area residents aged 20-89 years who were diagnosed with cancer in 1990 and were reported to the registry as being Hispanic or White non-Hispanic. Predictive value positive, sensitivity, and relative bias were used to assess the accuracy of Hispanic classification by medical record and surname. Among those persons classified as Hispanic by either or both of these sources, only two-thirds agreed (predictive value positive = 66%), and many self-identified Hispanics were classified incorrectly (sensitivity = 68%). Classification based on either medical record or surname alone had a lower sensitivity (59% and 61%, respectively) but a higher predictive value positive (77% and 70%, respectively). Ethnic classification by medical record alone resulted in an underestimate of Hispanic cancer cases and incidence rates. Bias was reduced when medical records and surnames were used together to classify cancer cases as Hispanic.

California↗
PubMed1999

ATX II, a sodium channel toxin, sensitizes skeletal muscle to halothane, caffeine, and ryanodine.

BACKGROUND: The function or expression of subtypes of the sodium ion (Na+) channel is altered in biopsies or cultures of skeletal muscle from many persons who are susceptible to malignant hyperthermia (MH). ATX II, a specific Na+ channel toxin from a sea anemone, causes delayed inactivation of the channel similar to that seen in cell cultures of MH muscle. ATX II was added to skeletal muscle to determine whether altered Na+ channel function could increase the sensitivity of normal skeletal muscle to agents (halothane, caffeine, ryanodine) to which MH muscle is hypersensitive. METHODS: Studies were performed of fiber bundles from the vastus lateralis muscle of persons who were deemed not MH susceptible (MH-) or MH susceptible (MH+) according to the MH diagnostic test and of strips of diaphragm muscle from rats. Preparations in a tissue bath containing Krebs solution were connected to a force transducer. ATX II was introduced 5 min before halothane, caffeine, or ryanodine. RESULTS: ATX II increased the magnitude of contracture to halothane in preparations from most MH-, but not MH+, human participants. After ATX II treatment, preparations from 9 of 24 MH- participants generated contractures to halothane, 3%, that were of the same magnitude as those from MH+ participants. Preparations from four of six ATX II-treated healthy participants also gave responses of the same magnitude as those of MH-susceptible participants to a graded halothane challenge (0.5-3%). The contractures to bolus doses of halothane in specimens from male participants were more than three times larger than the contractures in specimens from female participants. In rat muscle, ATX II increased the magnitude of contracture to caffeine (2 mM) and decreased the time to produce a 1-g contracture to ryanodine (1 microM). CONCLUSIONS: ATX II, which causes delayed inactivation of the Na+ channel in cell cultures similar to that reported in cultures of MH+ skeletal muscle, increased the sensitivity of normal muscle to three agents to which MH+ muscle is hypersensitive. The increased sensitivity to halothane, 3%, occurred in most (79%), but not all, MH- participants, and this effect was most evident in male participants. Therefore, abnormal function of the Na+ channel, even if it is a secondary event in MH, may contribute to a positive contracture test result for MH.

Animals↗
PubMed1998

Increased RB1 abnormalities in human primary prostate cancer following combined androgen blockade.

BACKGROUND: The RB1 proliferation control pathway is a critical determinant of cell cycle progression. Abnormalities of RB1 are found in a variety of cancers, and the association with human prostate cancer (CaP) was examined here. METHODS: RNA expression levels of RB1 in CaPs were examined by RT-PCR. RNA integrity was assessed by evaluating expression of an endogenous gene standard. RESULTS: Abnormally low RB1 mRNA expression was found in 12/33 (36%) of CaPs from patients who had received combined androgen blockade (CAB) treatment. In contrast, 6/48 (13%) untreated CaPs showed abnormally low expression. This difference was statistically significant (P = 0.015). In the samples from untreated patients, a higher frequency of abnormal RB1 was found in specimens with a higher Gleason grade (P = 0.038). In addition, one untreated stage C, grade 9 specimen was found to express RB1 transcripts lacking exon 22, as determined by sequencing of DNA from the truncated transcripts. CONCLUSIONS: These findings suggest that abnormalities of RB1 may contribute to hormone-withdrawal-related survival of CaP cells.

Androgen Antagonists↗
PubMed1998

Racial differences in clinically localized prostate cancers of black and white men.

PURPOSE: Tumor grade, deoxyribonucleic acid (DNA) ploidy, proliferation, p53 and bcl-2 expression were examined in clinically localized prostate cancers of black and white American men to learn whether these features showed racial differences. MATERIALS AND METHODS: A total of 117 prostate cancers (43 black and 74 white patients) obtained at radical prostatectomy for clinically localized disease were assigned Gleason scores by a single pathologist. Enzymatically dissociated nuclei from archival prostate cancers were examined by DNA flow cytometry using propidium iodide staining and the multicycle program to remove debris and sliced nuclei and to perform cell cycle analysis. For immunostaining after microwave antigen retrieval we used a DO-1/DO-7 monoclonal antibody cocktail for p53 and the clone 124 antibody for bcl-2. RESULTS: Significantly more black than white men had Gleason score 7 tumors. The DNA ploidy distribution of Gleason 6 or less tumors was similar for both races. As anticipated, the ploidy distribution of higher grade prostate cancer in white men was more abnormal but, unexpectedly, this was not found for higher grade prostate cancer in black men. No significant racial differences were found in S phase fractions, p53 or bcl-2 immunopositivity. However, for prostate cancer in black men there was a significant association between bcl-2 immunopositivity and higher S-phase fractions. CONCLUSIONS: The aggressive prostate cancers of black men may be characterized by the 2 features of high proliferation and a block to programmed cell death.

Apoptosis↗
PubMed1998

Failure to identify the ryanodine receptor G1021A mutation in a large North American population with malignant hyperthermia.

Anesthesia-induced malignant hyperthermia (MH) is a rare inherited disorder of skeletal muscle. Several mutations in the ryanodine receptor (RYR1) have been found to be causative of MH. The G1021A mutation in the RYR1 is one of the most frequently occurring mutations in European populations. MH normal (165) and MH susceptible (114) North American patients were screened for the presence of the G1021A mutation. This mutation was not found in any of the patients tested. These studies support the absence of this mutation in the normal population. Furthermore, these findings emphasize the importance of viewing the distribution of MH mutations as variable gene pools with frequencies dependent on the geographical location of the population examined.

DNA↗
PubMed1998

Child-rearing attitudes and behavioral inhibition in Chinese and Canadian toddlers: a cross-cultural study.

Behavioral inhibition data were collected from samples of 2-year-olds from the People's Republic of China and Canada. Information on child-rearing attitudes and beliefs was obtained from mothers of the children. Chinese toddlers were significantly more inhibited than their Canadian counterparts. Inhibition was associated positively with mothers' punishment orientation and negatively with mothers' acceptance and encouragement of achievement in the Canadian sample. However, the directions of the relations were opposite in the Chinese sample; child inhibition was associated positively with mothers' warm and accepting attitudes and negatively with rejection and punishment orientation. The results indicated different adaptational meanings of behavioral inhibition across cultures.

Canada↗
PubMed1998

Adjustment of cancer incidence rates for ethnic misclassification.

Although ethnic population counts measured by the United States Census are based on self-identification, the same is not necessarily true of cases reported to cancer registries. The use of different ethnic classification methods for numerators and denominators may therefore lead to biased estimates of cancer incidence rates. The extent of such misclassification may be assessed by conducting an ethnicity survey of cancer patients and estimating the proportion misclassified using double sampling models that account for sample stratification. For two ethnic categories, logistic regression may be used to model self-identified ethnicity as a function of demographic variables and the fallible classification method. Incidence rates then may be adjusted for misclassification using regression results to estimate the number of cancer cases of a given age, sex, and site in each self-identified ethnic group. An example is given using this method to estimate ethnic misclassification of San Francisco Bay area Hispanic cancer patients diagnosed in 1990. Results suggest that the number of cancer cases reported as Hispanic is an underestimate of the number of cases self-identified as Hispanic, resulting in an underestimate of Hispanic cancer rates.

Data Interpretation, Statistical↗
PubMed1998

Accuracy of racial classification of Vietnamese patients in a population-based cancer registry.

Racial classification of Asian subgroups is increasingly important for health statistics, given the growing Asian-American populations. This study reports the reliability of racial classification of Vietnamese in population-based cancer registry data from northern California. From the Greater Bay Area Cancer Registry, we selected 2240 persons diagnosed with cancer in 1989-1992 and whom the registry considered Vietnamese by birthplace and/or registry race and/or surname, or who were Southeast Asian or Chinese by race. One thousand ninety persons (49%) were interviewed. Sensitivity and predictive value positive, and cancer incidence rates, were calculated using different combinations of the classification factors (birthplace, registry race, and name). By registry-reported race alone, 74% of those the registry classified as Vietnamese agreed with this classification on interview, while 90% of those identifying themselves as Vietnamese were so classified. With classification based on 2 of 3 factors, 78% of those classified as Vietnamese agreed, and 91% of self-reported Vietnamese were correctly classified. Misclassification was associated with age, sex, year of immigration, education, and language use. Registry-based annual age-adjusted all-site cancer incidence rates per 100,000 for Vietnamese were 287.7 for males and 221.3 for females. Rates adjusted for self-reported ethnicity were 242.8 (male) and 213.7 (female). Registry classification of Vietnamese is currently problematic. Approximately 20% of cancer cases classified as Vietnamese are probably not Vietnamese. The higher incidence rates for Vietnamese in the United States than in Vietnam partly may reflect such classification error.

Adult↗
PubMed1997

Epstein-Barr virus-associated Hodgkin's disease: epidemiologic characteristics in international data.

Hodgkin's disease (HD) has long been suspected to have an infectious precursor, and indirect evidence has implicated Epstein-Barr virus (EBV), a ubiquitous herpesvirus, as a causal agent. Recent molecular studies using EBER in situ hybridization or latency membrane protein-I (LMP-I) immunohistochemistry have identified EBV latent infection in up to 50% of HD tumors. However, the epidemiologic features of these cases have not been examined in detail. To explore the epidemiology of EBV-positive HD so as to understand the role of EBV in HD etiology more clearly, this project accumulated patient data from 14 studies that had applied these EBV assays to HD tumors. With information on age at diagnosis, sex, ethnicity, histologic subtype, country of residence, clinical stage and EBV tumor status from 1,546 HD patients, we examined risk for EBV-positive disease using logistic regression. Forty percent of subjects had EBV-positive tumors, and EBV prevalence varied significantly across groups defined by the study variables. Odds ratios (OR) for EBV-associated HD were significantly elevated for Hispanics vs. whites (OR = 4.1), mixed cellularity vs. nodular sclerosis histologic subtypes (OR = 7.3, 13.4, 4.9 for ages 0-14, 15-49, 50+ years), children from economically less-developed vs. more-developed regions and young adult males vs. females (OR = 2.5). These findings suggest that age, sex, ethnicity and the physiologic effects of poverty may represent biologic modifiers of the EBV association and confirm that this association is strongly but variably linked to histologic subtype. The data augment biologic evidence that EBV is actively involved in HD pathogenesis in some cases but describe epidemiologic complexity in this process.

Adolescent↗