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C Callahan

Publications and source records attributed to C Callahan.

14 recordsLinked to original sources
PubMed1995

Anticipation and instability of IT-15 (CAG)n repeats in parent-offspring pairs with Huntington disease.

Huntington disease (HD) is an autosomal dominant degenerative disorder caused by an expanded and unstable trinucleotide repeat (CAG)n in a gene (IT-15) on chromosome 4. HD exhibits genetic anticipation--earlier onset in successive generations within a pedigree. From a population-based clinical sample, we ascertained parent-offspring pairs with expanded alleles, to examine the intergenerational behavior of the trinucleotide repeat and its relationship to anticipation. We find that the change in repeat length with paternal transmission is significantly correlated with the change in age at onset between the father and offspring. When expanded triplet repeats of affected parents are separated by median repeat length, we find that the longer paternal and maternal repeats are both more unstable on transmission. However, unlike in paternal transmission, in which longer expanded repeats display greater net expansion than do shorter expanded repeats, in maternal transmission there is no mean change in repeat length for either longer or shorter expanded repeats. We also confirmed the inverse relationship between repeat length and age at onset, the higher frequency of juvenile-onset cases arising from paternal transmission, anticipation as a phenomenon of paternal transmission, and greater expansion of the trinucleotide repeat with paternal transmission. Stepwise multiple regression indicates that, in addition to repeat length of offspring, age at onset of affected parent and sex of affected parent contribute significantly to the variance in age at onset of the offspring. Thus, in addition to triplet repeat length, other factors, which could act as environmental factors, genetic factors, or both, contribute to age at onset. Our data establish that further expansion of paternal repeats within the affected range provides a biological basis of anticipation in HD.

Age of Onset↗
PubMed1994

Cocaine exposure during pregnancy: improving assessment with radioimmunoassay of maternal hair.

OBJECTIVE: To compare radioimmunoassay of postpartum maternal hair samples with a structured maternal interview for the detection of cocaine use during pregnancy. METHODS: Radioimmunoassay of hair samples obtained postpartum was compared with self-report of cocaine use obtained by confidential, structured interviews of 405 postpartum women. RESULTS: Cocaine or benzoylecgonine was detected in the hair samples of 129 of the 148 women (87%) who reported using cocaine at least once during pregnancy. Thirty-six of 257 women (14%) who reported that they had used no cocaine during pregnancy had positive hair tests. Positive hair assay with negative self-report was significantly more common among women who were unmarried (P = .001), African-American (P < .001), and multiparous (P = .035). CONCLUSIONS: Hair analysis is a valuable complement to maternal self-report by interview. The methods used together provide a useful clinical and research technique yielding a comprehensive estimate of gestational cocaine exposure. Either method alone may result in misclassification of gestational cocaine exposure.

Adult↗
PubMed1992

The Jefferson-Penn State B.S.-M.D. program: a 26-year experience.

Since the 1960s a number of physicians have completed both their baccalaureate and their M.D. degrees in six or fewer years. In this longitudinal study the authors track the academic performances, clinical ratings, and career follow-up data of 659 students in one of these accelerated programs, the Jefferson Medical College-Pennsylvania State University B.S.-M.D. program, from entering years 1964 through 1989. The medical school performances, clinical performances in residencies, and rates of board certification and faculty appointment of the accelerated students compared favorably with those of a control group of medical students with similar high school credentials who had followed a four-year baccalaureate program. The authors conclude that a carefully chosen group of students can achieve high academic standards in an accelerated medical school program, graduate as younger physicians able to perform well in postgraduate training, and go on to highly productive careers in medicine.

Achievement↗
PubMed1991

Drake Chemical Workers' Health Registry Study: I. Notification and medical surveillance of a group of workers at high risk of developing bladder cancer.

A medical surveillance program and epidemiologic study of 408 former workers of the Drake Chemical Company (now a Superfund waste site) was established in 1986. The Drake Health Registry Study was initiated because these workers had probable past exposures to beta-naphthylamine (BNA), a potent bladder carcinogen. The registry is widely viewed as a model for notification of workers at high risk of disease due to past occupational exposures. By the 40th month, 90% of the 366 living workers had been notified of the existence of the registry; 262 had been enrolled in the annual or semi-annual screening for bladder cancer. Among these, 27 persons have had abnormal screening results indicating moderate to high risk of bladder cancer and have been made eligible for further diagnostic tests. While no invasive bladder tumors were found among 18 persons completing the extended diagnostic evaluation, two diagnoses of moderate to severe dysplasia have been made. The registry has also identified three living and three deceased cases of bladder cancer in the cohort; a mortality analysis showed a 20- to 30-fold excess of bladder cancer. An incidence projection, based on the six identified cases, reveals that between six and ten new bladder cancer cases are likely to occur among the Drake cohort over the next 20 year period.

2-Naphthylamine↗
PubMed1991

A field study of the safety and efficacy of two candidate rotavirus vaccines in a Native American population.

A double-blind, randomized, placebo-controlled trial was conducted to evaluate the safety and efficacy of a rhesus rotavirus vaccine and RIT 4237, a bovine rotavirus vaccine, in a Navajo population. Infants aged 2-5 months were randomized to receive one dose of either 10(4) pfu of the rhesus rotavirus vaccine or 10(8) pfu of the RIT 4237 vaccine or placebo. Eleven (10.2%) of 108 infants in the rhesus vaccine group, 11 (10.4%) of 106 in the RIT 4237 group, and 9 (8.4%) of 107 in the placebo group experienced rotavirus diarrhea during the follow-up period of 17 months. Thus, in this population, neither vaccine was efficacious in preventing rotavirus diarrhea.

Diarrhea, Infantile↗
PubMed1991

Drake Chemical Workers' Health Registry: coping with community tension over toxic exposures.

BACKGROUND: Programs to communicate health risk information and to protect the health of groups exposed to toxic substances need to tailor interventions to the political, economic, and cultural situation of the at-risk group. In particular, such programs must often cope with exceptional community tension and conflict over these exposures. METHODS: This article uses interviews and written materials to document and describe the state of affairs that led up to community tension over an occupational exposure to a bladder carcinogen. The article describes the planning and design of a program to provide medical surveillance to workers, which also alleviated community concern. RESULTS: The Drake Chemical Workers' Health Registry coped successfully with community conflict and obtained a high participation rate. CONCLUSIONS: General recommendations include the following: avoid identification with extraneous agendas; know the community and maintain communication; and match the intervention to the evolution of the community conflict.

2-Naphthylamine↗
PubMed1990

A protocol for bladder cancer screening and medical surveillance among high-risk groups: the Drake Health Registry experience.

In 1986, the Drake Health Registry Study initiated bladder cancer screening for 366 persons at high risk because of occupational exposure to beta-naphthylamine. The Drake Health Registry Study screening protocol consists of urinalysis, Papanicolaou cytology, and quantitative fluorescence image analysis. A positive screening test qualifies participants for a full diagnostic evaluation. The screening protocol has been modified during the first 3 years of the program's existence to address unexpected patterns of test results and to incorporate advances in screening technology. The current protocol, which has a two-tiered screening schedule, has been utilized successfully for 15 months. Of the 26 positive results to date most have been based on abnormal Papanicolaou cytology and/or quantitative fluorescence image analysis. Bladder abnormalities were cited among most of the 18 study members who underwent diagnostic evaluation, including chronic cystitis, inflammation, hyperplasia, and dysplasia. We conclude that the screening program is detecting very early changes in a relatively young cohort and that these persons must be monitored over a number of years to ensure adequate medical surveillance.

2-Naphthylamine↗
PubMed1988

Direct methods of obtaining information on cigarette smoking in occupational studies.

Many occupational epidemiology studies require complete and accurate information on tobacco use to control for confounding by smoking and to assess interactions of smoking with workplace exposures. This paper reviews and evaluates the availability, reliability, validity, and efficiency of the various data sources and techniques for obtaining individual smoking data, including existing records, biological markers, and surveys. Emphasis is placed on the highly problematic issue of obtaining retrospective smoking histories. In general, the survey technique is currently deemed the most feasible approach for obtaining lifetime smoking histories. Both theoretical and practical aspects of smoking surveys are discussed in detail and are illustrated with a review of the recent literature and with data from two recent retrospective cohort studies conducted at the University of Pittsburgh. Several recommendations involving both the use of smoking data and areas for future methodologic research are presented. These include (1) justification for collecting smoking data in occupational studies based primarily on the potential for smoking to act as an effect modifier rather than solely as a confounder, (2) checks for reliability and validity in all studies which involve the collection of smoking data, (3) more methodologic research to better understand the impact that missing, unreliable, and invalid smoking data may have on the ability to detect and quantify important smoking-exposure interactions, and (4) an assessment of the correlation between biological markers and cigarette carcinogen exposure.

Epidemiologic Methods↗
PubMed1987

Characteristics of nurse anesthetists working with and without anesthesiologists.

All professionally active certified registered nurse anesthetists (CRNAs) in four geographically representative states were surveyed by mail and telephone in 1981, and response rate of greater than or equal to 70% was obtained for each state. CRNAs who worked with anesthesiologists (Group I) were compared with those who worked in hospitals with no anesthesiologists (Group II). More than 75% of both groups were employed by hospitals, but Group II CRNAs (15.5% of respondents) were nearly five times as likely to practice on an independent, fee-for-service basis. Members of Group II worked predominantly in hospitals in small or rural communities and, compared with those in Group I, were more likely to be male and older, less likely to hold a baccalaureate degree, and less likely to use invasive monitoring techniques. Nearly 50% of Group II had no standing consulting relationship with an anesthesiologist. A consultation network supported by telecommunications deserves consideration as a means of providing CRNAs who work independently in small rural hospitals with a cost-effective team approach to anesthesia care.

Adult↗
PubMed1986

Chlamydial infections in pregnancy.

Chlamydia trachomatis is recognized as a common sexually transmitted cervical pathogen that may be transmitted to the neonate at delivery. Neonatal infection may be manifested as conjunctivitis, pneumonitis or both. Additionally, cervical infection may be related to premature rupture of the membranes and premature delivery. Women registering for prenatal care in the first half of pregnancy were cultured for Chlamydia to further define its role as a cause of perinatal complications and to evaluate a method of preventing transmission to the neonate. Positive cultures were obtained in 33 of 221 women evaluated (14.9%). No significant differences were found in pregnancy or neonatal complications between the groups with positive and negative cultures. Women with positive cultures were treated at 36 weeks' gestation with erythromycin; 18 received an adequate course of therapy. Of these 18, 16 returned with their infants four to eight weeks postpartum. No symptoms of conjunctivitis or pneumonitis were noted at that time, and cultures of the conjunctiva and nasopharynx were negative in all the infants. Thus, surveillance for Chlamydia and treatment late in pregnancy appear to have no adverse impact on pregnancy and effectively block vertical transmission of the organism.

Chlamydia Infections↗