Binding properties of newly identified Xenopus proteins containing dsRNA-binding motifs.

BACKGROUND: Although most RNA-binding proteins recognize a complex set of structural motifs in their RNA target, the double-stranded (ds) RNA-binding proteins are limited to interactions with double helices. Recently, it has been discovered that some dsRNA-binding proteins share regions of amino-acid similarity known as dsRNA-binding motifs. RESULTS: A Xenopus ovary cDNA expression library was screened with radiolabeled dsRNA to identify previously uncharacterized dsRNA-binding proteins. The analysis of an incomplete cDNA identified during the screen led to the discovery of two longer cDNAs of related sequence. The proteins encoded by these cDNAs each contained two dsRNA-binding motifs, in glycine. The nucleic-acid-binding properties of a fusion protein containing the two dsRNA-binding motifs and the auxiliary domain were analyzed using a gel mobility shift assay. The fusion protein bound dsRNA of a variety of different sequences, and exhibited a preference for binding to dsRNA and RNA-DNA hybrids over other nucleic acids. Appropriate mRNAs, corresponding to each cDNA, were detected in polyadenylated RNA isolated from Xenopus stage VI oocytes, but translation of one of the mRNAs appeared to be masked until meiotic maturation. CONCLUSION: dsRNA-binding motifs are often found in proteins that bind dsRNA, and our results show that they can be associated with auxiliary domains rich in arginine and glycine. These motifs can confer very tight binding to dsRNA. Binding can also occur to RNA-DNA hybrids, suggesting recognition of some aspect of the A-form helical structure that is adopted by both dsRNA and RNA-DNA hybrids.

Coordinating DNA replication to produce one copy of the genome requires genes that act in ubiquitin metabolism.

We have developed a genetic screen of the yeast Saccharomyces cerevisiae to identify genes that act to coordinate DNA replication so that each part of the genome is copied exactly once per cell cycle. A mutant was recovered in this screen that accumulates aberrantly high DNA contents but does not complete a second round of synthesis. The mutation principally responsible for this phenotype is in the DOA4 gene, which encodes a ubiquitin hydrolase, one of several yeast genes that encode enzymes that can remove the signalling polypeptide ubiquitin hydrolase, one of several yeast genes that encode enzymes that can remove the signaling polypeptide ubiquitin from its covalently linked conjugated forms. DOA4 is nonessential, and deleting this gene causes uncoordinated replication. Overreplication does not occur in cells with limiting amounts of Cdc7 protein kinase, suggesting that entry into S phase is required for this phenotype. The DNA formed in doa4 mutants is not highly unusual in the sense that mitotic recombination rates are normal, implying that a high level of repair is not induced. The temperature sensitivity of doa4 mutations is partially suppressed by extra copies of the polyubiquitin gene UB14, but overreplication still occurs in the presence of this suppressor. Mutations in DOA4 cause loss of the free ubiquitin pool in cells under heat stress conditions, and extra copies of UB14 restore this pool without restoring coordination of replication. We conclude that a ubiquitin-mediated signaling event directly involving the ubiquitin hydrolase encoded by DOA4 is needed in S. cerevisiae to prevent uncoordinated DNA replication.

In vivo analysis of the Saccharomyces cerevisiae HO nuclease recognition site by site-directed mutagenesis.

HO nuclease introduces a specific double-strand break in the mating-type locus (MAT) of Saccharomyces cerevisiae, initiating mating-type interconversion. To define the sequence recognized by HO nuclease, random mutations were produced in a 30-base-pair region homologous to either MAT alpha or MATa by a chemical synthesis procedure. The mutant sites were introduced into S. cerevisiae on a shuttle vector and tested for the ability to stimulate recombination in an assay that mimics mating-type interconversion. The results suggest that a core of 8 noncontiguous bases near the Y-Z junction of MAT is essential for HO nuclease to bind and cleave its recognition site. Other contacts must be required because substrates that contain several mutations outside an intact core reduce or eliminate cleavage in vivo. The results show that HO site recognition is a complex phenomenon, similar to promoter-polymerase interactions.

Double-strand breaks stimulate alternative mechanisms of recombination repair.

To test the double-strand break repair model, we used HO nuclease to introduce double-strand breaks at several sites along a yeast chromosome containing duplicated DNA. Depending on the configuration of the double-strand break and recombining markers, different spectra of recombinant products were observed. Different repair kinetics and recombinant products were observed when a double-strand break was introduced in unique or duplicated DNA. The results of this study suggest that double-strand breaks in yeast stimulate recombination by several mechanisms, and we propose an alternative mechanism for double-strand break-induced gene conversion that does not depend on direct participation of the broken ends.

Medical care use and expenditure among children and youth in the United States: analysis of a national probability sample.

Good access to health care for all US children and youth remains an important social policy goal. Recent patterns of access as reflected in the presence of regular care sources, health care use, health insurance coverage, and expenditures for medical care are described and analyzed using the subsample of all children 0 to 18 years of age from the 1980 National Medical Care Utilization and Expenditure Survey. Data from the survey indicate that in 1980, 92% of US children and youth had a regular care source and the same percentage were covered for the full year or part of the year by some form of public or private health insurance. However, use rates and patterns of expenditure continued to differ dramatically according to family background factors, particularly race, ethnicity, poverty status, and location of residence. These differences are analyzed and comparative data are presented for groups of children from various sociodemographic groups. Minority-group and near-poor children were found to be at highest risk for limited utilization of services and inadequate insurance coverage.

Health insurance coverage and physician use among children with disabilities: findings from probability samples in five metropolitan areas.

The effect of insurance coverage on physician use for children in the United States who have been identified as disabled by their schools under the provisions of the Education for All Handicapped Children Act (PL 94-142) is examined. The research is based on identically drawn stratified random samples of children from the elementary school special education populations of five large metropolitan school systems. It was found that health insurance coverage was a predictor of whether a disabled child had seen a doctor in the past year even after adjustment for site, family background characteristics, type and severity of childhood disability, and structural access factors (adjusted odds ratio, 1.76, P less than .05); Hispanic children with disabilities were more likely than white children to be without any health insurance (adjusted odds ratio, 3.63; P less than .001), but there was no similar statistically significant difference between blacks and whites; and wide variations persist in scope of insurance payment for care, such that parents of publicly insured children paid out of pocket for only 5% of all physician visits as compared to 30% of visits for the privately insured. Even for children with various low-prevalence disabilities, when privately insured, parents paid out of pocket for 23% of all physician visits. These data help clarify the extent of health insurance coverage among children with disabilities and indicate that insurance remains an important predictor of physician use even though it continues to pay for only certain elements of care.

Providing therapeutic services to children in special educational placements: an analysis of the related services provisions of Public Law 94-142 in five urban school districts.

Using the sample of 1726 special education students from the Collaborative Study of Children With Special Needs, the authors describe the related services being provided to the children and then analyze the relationship between service provision and class placement. Related services are provided in all settings, with a concentration in special schools and special classes. For even the most severely involved children the trade-off with academics is no more than 1 hour per day. It is argued that schools now are major sites of therapeutic service provision for children with special needs.

Technology's children: report of a statewide census of children dependent on medical supports.

In April 1987, a census of children dependent on medical technology was carried out in Massachusetts to determine the one-month point prevalence. All medical and educational providers in the state who were likely to interact with such children were contacted and asked to complete a two-sided data form on youngsters (aged 3 months to 18 years) with tracheostomies, supplementary oxygen, respirators, suctioning, gastric feeding, central venous lines, ostomies, ureteral diversion, urethral catheterization and dialysis. Nearly 1250 children were found meeting these criteria. Capture-recapture analysis set the lower bound for technology dependence at 0.08% of the state's children. An analysis of the organ systems involved showed that 57% of the children had neurologic involvement--13% multisystem, 7% gastrointestinal-metabolic, 4% renal-genitourinary, and 3% musculoskeletal. Less than 1% of the children were reported as having immunologic or "other" disorders. Review of putative etiologies indicated that 45% of the children had congenital anomalies, 33% chronic medical diseases, 9% perinatal conditions, 7% hereditary-genetic disorders, 5% injuries, 2% infections, and 3% "other." The substantial prevalence of technology dependency among children creates challenges at the social, economic, and policy-making levels. It will be important to carry out systematic reporting and monitoring activities throughout time and across sites. This census is an example of one such statewide effort.

Investigating onset, cessation, relapse, and recovery: why you should, and how you can, use discrete-time survival analysis to examine event occurrence.

In this article, we show how discrete-time survival analysis can address questions about onset, cessation, relapse, and recovery. Using data on the onset of suicide ideation and depression and relapse into cocaine use, we introduce key concepts underpinning the method, describe the action of the discrete-time hazard model, and discuss several types of main effects and interactions that can be included as predictors. We also comment on practical issues of data analysis and strategies for interpretation and presentation.

Mixed messages about primary care in the culture of U.S. medical schools.

PURPOSE: To examine the contributions of school-level variables associated with primary care career choice to students' enthusiasm for and perceived encouragement toward primary care. METHOD: Multilevel analysis of 264 fourth-year students and 500 clinical faculty members at 59 medical schools using data obtained in 1993 to 1994 from telephone interviews of a national stratified probability sample of students (response rate 90%) and faculty (response rate 81%). RESULTS: On average, students reported slightly positive regard for primary care and felt neither supported nor unsupported in their interests in primary care. Students' reports of encouragement toward primary care showed some consistency within schools (intraclass correlation = .08); their regard for primary care did not (intraclass correlation = .02). Regard for primary care was associated with students' intended specialty choices (p < .001), with students who planned to enter primary care careers reporting more positive attitudes. Students' perceptions of encouragement toward primary care careers were unrelated to their intended specialty choices, but significantly related to their schools' historical primary care production (p < .0001), federal research funding (p < .01), and school ownership (p < .01). CONCLUSION: Schools that have primary care missions and have historically produced more generalists transmit higher levels of encouragement to their students about primary care. However, even at schools with strong primary care missions, students hold unenthusiastic attitudes about primary care practice.

The effect of medical education on primary care orientation: results of two national surveys of students' and residents' perspectives.

PURPOSE: To examine changes among a nationally representative sample of students and residents in their orientations toward primary care as reflected in their attitudes toward the psychosocial and technical aspects of medicine and their perceptions of the academic environment for primary care. METHOD: Confidential telephone interviews of stratified national probability samples of first- and fourth-year medical students and residents were conducted in 1994 and 1997. The 1997 survey included 219 students and 241 residents who had also been interviewed in 1994. Participants were asked about their attitudes toward addressing psychosocial issues in medicine and their perceptions of faculty and peer attitudes toward primary care. Responses were compared over time and across groups. RESULTS: Between the first and fourth years of medical school, there was a decline over time in students' reported orientations to socioemotional aspects of patient care (61.6% versus 42.7%, p =.001) and their perceptions that working with psychosocial issues of patients made primary care more attractive (56.3% versus 43.5%, p =.01). This pattern continued for 1997 residents (PGY-3), who were even less likely to say that addressing psychosocial issues made primary care more attractive (26.9%). For fourth-year students in 1994 who became PGY-3 residents in 1997, there was an increased perception that non-primary-care house officers and specialty faculty had positive attitudes toward primary care (20.8% versus 33.0%, p =.005; 28.3% versus 45.7%, p <.0001; respectively). CONCLUSIONS: Between 1994 and 1997 students and residents perceived a positive shift in the attitudes of peers and faculty toward primary care. During the course of their education and training, however, the students experienced an erosion of their orientations to primary care as they progressed through medical school into residency.

Job experiences over time, multiple roles, and women's mental health: a longitudinal study.

Are changes over time in the quality of a woman's job associated with changes in her psychological distress? Do family roles moderate these relationships? We addressed these questions using longitudinal data from a 2-year 3-wave study of a stratified random sample of 403 employed women who varied in occupation, race, partnership, and parental status. After estimating individual rates of change for each woman on each of the predictors and the outcome, we modeled the relationships between family role occupancy and change in job-role quality on the one hand, and change in psychological distress on the other. Among single women and women without children, as job-role quality declined, levels of psychological distress increased. Among partnered women and women with children, change in job-role quality was unrelated to change in psychological distress.

Early child-care selection: variation by geographic location, maternal characteristics, and family structure.

More than half of all U.S. infants and toddlers spend at least 20 hr per week in the care of a nonparent adult. This article uses survival analysis to identify which families are most likely to place their child in care and the ages when these choices are made, using data from a national probability sample of 2,614 households. Median age at first placement is 33 months, but age varies by geographic region, mother's employment status during pregnancy, mother's education level, and family structure (1 vs. 2 parents, mother's age at 1st birth, and number of siblings). Controlling for these effects, differences by race and ethnicity are small. Implications for studies of child-care selection and evaluations of early childhood programs are discussed.

Health and special education: a study of new developments for handicapped children in five metropolitan communities.

Since the implementation in 1977 of the Education for All Handicapped Children Act (Public Law 94-142), public school systems have provided special education and related services to students with a wide range of handicapping conditions, including some children served previously in hospitals or other institutions. Although the Federal law does not require physician participation in the special education process, it does imply an active new role for the medical care community, both public and private, in helping schools to identify and diagnose children with disabilities and in ensuring that those children have adequate access to health services. This study explores the experience of five nationally dispersed urban school systems in implementing P.L. 94-142, with particular reference to the interaction of physicians and the schools. The findings highlight continued problems with early identification of certain types of childhood handicaps, classification of children's functional disorders, and adequate participation of practicing physicians in the program, especially with regard to developmental and behavioral issues. In addition, inequities in community health services are documented for a substantial number of the children studied. Improved collaboration between the health and education sectors is needed to address these concerns in order to fulfill the intent of national special education policy and to maximize the potentialities of these children and their families.

Physician familiarity with the educational programs of their special needs patients.

As part of an analysis of health care for children in special education programs, physician familiarity with the educational status and program enrollment of their disabled patients was examined. Telephone interviews were performed with a random sample of 411 of the children's physicians. The majority (70%) of the physicians interviewed professed no knowledge of their patients' current special educational program. Certain physician, child, and family characteristics were associated with physician awareness of the children's programs. These were physician specialty, physician gender, child's disability, and severity of the child's problem. This study suggests that, although some physicians of very involved patients do familiarize themselves with their patients' day-to-day school life, many other physicians are poorly informed about the school activities and functional status of their young patients with disabilities. Better mechanisms are needed to ensure physicians' understanding of these aspects of child health.

Mainstreaming children with handicaps: implications for pediatricians.

The judicial precedents and legislative mandates passed during the past two decades to ensure full appropriate public education for all children have resulted in a movement toward mainstreaming children with a wide range of physical and developmental disabilities into regular education classroom settings. Although some child development and pediatric literature has addressed the effects of these initiatives on the children with handicaps, less attention has been paid to the effect that mainstreaming has on their nondisabled peers in the classroom. As knowledgeable community advocates, pediatricians should be informed about the specifics of the mainstreaming movement. This paper outlines the movement's historical underpinnings, discusses current definitions of "mainstreaming", and briefly reviews the literature on the effects of this policy on classrooms, teachers, and students with and without disabilities. The impact of mainstreaming children with handicaps in regular classroom settings is equivocal, with many studies lacking methodological sophistication to yield reliable and valid data. Results of the few well-designed studies do show, however, that academic and social outcomes for both the handicapped child and for his/her nondisabled peers are consistently better in mainstreamed classrooms where adequate resources have been made available to the child and teacher than in more segregated settings. Furthermore, the literature consistently points out the key role both regular and special education teachers play in successful mainstreamed classrooms. Pediatricians can help families with children with disabilities negotiate the educational system in order to achieve the appropriate classroom placement.

Patterns of response in families of chronically disabled children: an assessment in five metropolitan school districts.

Interviews with parents of 1,726 special education students yielded reports of stress that varied significantly by type of disability and by maternal education level; family involvement in the special education process also varied significantly by level of education. Clinically important differences in family perceptions and coping mechanisms are described and the need for better child care provisions and involvement of low-income parents in the education process is highlighted.