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Biomedical subjects

N Johnson

Publications and source records attributed to N Johnson.

At least 109 records · Page 6Linked to original sources
PubMed1999

Bacterial contamination rates during bone allograft retrieval.

A retrospective study of allograft bone retrieved from 401 donors between January 1987 and March 1996 was performed to determine the incidence of bacterial contamination. Contamination according to type of donor (live, multiorgan, cadaveric) was also determined. Live donors donating a femoral head demonstrated a contamination rate of 13%; multiorgan donors, 24%; and cadaveric donors, 35%. Donor contamination by type of bone (hemipelvis, femur, tibia) showed no significant difference in the multiorgan donors. In cadaveric donors, there was a significant increase in contamination of the hemipelves as compared to the femur and tibias. Recommendations for contamination control in allograft retrieval are given. Our findings are of great significance for musculoskeletal banks that do not secondarily irradiate and rely on screening of allograft bone for contamination alone.

Bacteria↗
PubMed1999

Violence prevention and young adolescents' participation in community youth service.

PURPOSE: To examine whether participation in a school-sponsored community youth service program reduces self-reported violent behaviors among young urban adolescents. METHODS: A total of 972 seventh- and eighth-grade students at two large, urban, public middle schools were surveyed at baseline and at 6-month follow-up. One school was assigned to interventions and the other served as a control. All students at the intervention school received the Reach for Health classroom curriculum that included a 10-lesson unit focusing on violence prevention. In addition, approximately half the students were randomly assigned by classroom to participate in the Reach for Health Community Youth Service program (CYS). Under the guidance of teachers and community nurses, these students spent several hours each week providing service in local health care agencies. Regression analyses were used to assess the influence of treatment condition on violent behavior outcomes. RESULTS: Comparing students in the curriculum-only and curriculum-plus-CYS interventions to the control group, there is a statistically significant interaction (p < .03) among grade, CYS participation, and violence at follow-up. Eighth-grade CYS students reported significantly less violence at follow-up than students in the control school, taking into account baseline level of risk behavior, gender, ethnicity, and social desirability (p < .04). There was no significant difference between controls and students in the curriculum-only condition. Comparing students in the CYS intervention to the curriculum-only condition within the intervention school, the grade by intervention interaction again is significant (p < .05). Eighth-grade CYS students-who received the broadest CYS experience-reported less violence at follow-up than their curriculum-only counterparts. CONCLUSION: When delivered with sufficient intensity, school programs which couple community service with classroom health instruction can have a measurable impact on violent behaviors of a population of young adolescents at high risk for being both the perpetrators and victims of peer violence. Community service programs may be an effective supplement to curricular interventions and a valuable part of multicomponent violence prevention programs.

Adolescent↗
PubMed1999

The mitochondrial permeability transition pore.

This chapter reviews recent advances in the identification of the structural elements of the permeability transition pore. The discovery that cyclosporin A (CsA) inhibits the pore proved instrumental. Various approaches indicate that CsA blocks the pore by binding to cyclophilin (CyP)-D. In particular, covalent labelling of CyP-D in situ by a photoactive CsA derivative has shown that pore ligands have the same effects on the degree to which CsA both blocks the pore and binds to CyP-D. The recognition that CyP-D is a key component has enabled the other constituents to be resolved. Use of a CyP-D fusion protein as affinity matrix has revealed that CyP-D binds very strongly to 1:1 complexes of the voltage-dependent anion channel (from the outer membrane) and adenine nucleotide translocase (inner membrane). Our current model envisages that the pore arises as a complex between these three components at contact sites between the mitochondrial inner and outer membranes. This is in line with recent reconstitutions of pore activity from protein fractions containing these proteins. The strength of interaction between these proteins suggests that it may be a permanent feature rather than assembled only under pathological conditions. Calcium, the key activator of the pore, does not appear to affect pore assembly; rather, an allosteric action allowing pore flicker into an open state is indicated. CsA inhibits pore flicker and lowers the binding affinity for calcium. Whether adenine nucleotide translocase or the voltage-dependent anion channel (via inner membrane insertion) provides the inner membrane pore has not been settled, and data relevant to this issue are also documented.

Animals↗
PubMed1999

Import and processing of heart mitochondrial cyclophilin D.

Cyclophilins are a family of cyclosporin-A-binding proteins which catalyse rotation about prolyl peptide bonds. A mitochondrial isoform in mammalian cells, cyclophilin D, is a component of the permeability transition pore that is formed by the adenine nucleotide translocase and the voltage-dependent anion channel at contact sites between the inner and outer membrane. This study investigated the submitochondrial location of cyclophilin D by following the fate of radiolabelled protein following import. Precursor [(35)S]cyclophilin D was expressed in vitro from a PCR-generated cDNA. The precursor was imported by rat heart mitochondria and processed in a single step to a 21-kDa protein that was identical (SDS/PAGE) to an in vitro expressed mature protein and a cyclophilin D purified from rat heart mitochondria. No further modification of the mature protein could be demonstrated. Fractionation of mitochondria following import established that cyclophilin D locates only to the matrix. It is concluded that cyclophilin D binding to the permeability transition pore must occur at the inner face of the mitochondrial inner membrane.

Animals↗
PubMed1999

The Academic Support Program at the University of Michigan School of Medicine.

The University of Michigan has a support program aimed at early identification, remedial plans, and appropriate academic accommodations for at-risk students in under-graduate colleges and graduate and professional schools. Since 1994, the medical school has formally taken part in this program. Medical students at risk for academic failure (e.g., repeated failure in academic course work, licensure examinations, clinical examinations) are automatically referred to their academic counselors in the Student Programs Office of the medical school. Once a referral is made, the student is evaluated at the Office of Services for Students with Disabilities to identify problem areas. The office makes appropriate recommendations for interventions or accommodation. Tutoring, academic assistance, and other services are available through the medical school, specific divisions of the medical center, and the community. The Student Programs Office acts as a liaison between community and university assistance programs and between the student and the medical school. During the first four years of the program, 28 medical students were identified through it; of these, 24 (86%) were underrepresented minorities. Most (21) were referred during the first and third years of the curriculum. After a range of services for a variety of problems, 26 (93%) of the 28 students either graduated or continued to progress in their studies; the other two left the medical school for academic reasons.

Adult↗
PubMed1999

The epidemiology of lip cancer: a review of global incidence and aetiology.

Lip cancer (140 ICD-9) is a form of oral cancer that has a distinctive global epidemiology. This review summarises global incidence rates for male and female lip cancer with the aid of cancer atlases. High male lip cancer rates are reported for regions of North America (12.7 per 100 000 per annum), Europe (12.0 per 100 000 per annum) and Oceania (13.5 per 100 000 per annum), while it is virtually unknown in parts of Asia. Factors commonly cited as important in the aetiology of lip cancer include solar radiation, tobacco smoking and viruses. An attempt is made to summarise the evidence for factors that may be important in lip carcinogenesis. While incidence rates are generally stable or falling among males worldwide, they are rising in many female populations. The aetiology of the disease is far from established and much information regarding its pathogenesis is based on anecdotal rather than case-controlled epidemiological evidence. The epidemiology of lip cancer supports the proposal that the lip should be considered as a distinct cancer site, rather than being included with other forms of intraoral cancer.

Asia↗
PubMed1999

The effectiveness of the Reach for Health Community Youth Service learning program in reducing early and unprotected sex among urban middle school students.

OBJECTIVES: This study evaluated the effectiveness of a community youth service (CYS) program in reducing sexual risk behaviors among African American and Latino urban young adolescents. METHODS: A total of 1061 students at 2 urban middle schools were surveyed at baseline and 6-month follow-up. Students at one school were randomly assigned by classroom to receive either the Reach for Health CYS program or the Reach for Health classroom curriculum only. Students at the other school served as controls. RESULTS: At follow-up. CYS participants reported significantly less recent sexual activity (P < .05) and scored lower on a sexual activity index than those in the control condition (P < .03). The greatest effect was among eighth graders, who received the most intensive service program (P < .03). The benefit of the curriculum-only intervention appeared greatest among students in special education classes. CONCLUSIONS: Well-organized CYS that couples community involvement with classroom health instruction can have a positive impact on the sexual behaviors of young adolescents at risk for HIV, sexually transmitted diseases, and unintended pregnancy. This study also suggests the importance of including students in special education classes in health education programs.

Adolescent↗
PubMed1999

Community learning: the Reach for Health Nursing Program-Middle School Collaboration.

Nursing faculty and students have a vital role to play in promoting adolescent health at the community level. However, few nursing education programs have developed programs which provide nursing students with the skills and hands-on experiences they need to work with adolescents in community settings. A successful model for integrating community-based adolescent health promotion into nursing education is described in this article. Developed by nursing faculty from Medgar Evers College Department of Nursing, teachers and staff from a large middle school in Brooklyn, New York serving economically disadvantaged Black and Hispanic youth, and Education Development Center, Inc., the Reach for Health (RFH) Nursing Program-Middle School Collaboration has two mutually reinforcing components: (a) classroom-based health instruction taught by teachers with assistance from nursing students and faculty, and (b) community youth service in which middle school students spend approximately 3 hours per week providing assistance in health-related facilities under the guidance of nursing faculty and student nurse mentors. As part of an evaluation study, the authors conducted focus groups with nursing students involved in this program and administered an identical survey before and after intervention to assess potential benefits of participation. Compared to a control group of nursing students, those who participated in the RFH program reported increased skills and comfort working in school and community settings and with young adolescents, their teachers, and their parents. An example of other benefits was a greater understanding of the health and developmental needs of adolescents. At the same time they provided a service to the community, nursing students gained the skills and experience needed to be effective in community health promotion efforts.

Adolescent↗
PubMed1999

Feminizing genitoplasty for congenital adrenal hyperplasia: what happens at puberty?

PURPOSE: We document the postpubertal outcome of feminizing genitoplasty. MATERIALS AND METHODS: A total of 14 girls, mean age 13.1 years, with congenital adrenal hyperplasia were assessed under anesthesia by a pediatric urologist, plastic/reconstructive surgeon and gynecologist. Of these patients 13 had previously undergone feminizing genitoplasty in early childhood at 4 different specialist centers in the United Kingdom. RESULTS: The outcome of clitoral surgery was unsatisfactory (clitoral atrophy or prominent glans) in 6 girls, including 3 whose genitoplasty had been performed by 3 different specialist pediatric urologists. Additional vaginal surgery was necessary for normal comfortable intercourse in 13 patients. Fibrosis and scarring were most evident in those who had undergone aggressive attempts at vaginal reconstruction in infancy. CONCLUSIONS: These disappointing results, even in the hands of specialists, highlight the importance of late followup and challenge the prevailing assumption that total correction can be achieved with a single stage operation in infancy. Although simple exteriorization of a low vagina can reasonably be combined with cosmetic correction of virilized external genitalia in infancy, we now believe that in some cases it may be best to defer definitive reconstruction of the intermediate or high vagina until after puberty. The psychological issues surrounding sexuality in these patients are inadequately researched and poorly understood.

Adolescent↗
PubMed1998

Induction of retinoblastoma gene expression during terminal growth arrest of a conditionally immortalized fetal rat lung epithelial cell line and during fetal lung maturation.

The process by which fetal lung epithelial cells differentiate into type 1 and type 2 cell is largely unknown. In order to study lung epithelial cell proliferation and differentiation we have infected 20-day fetal lung epithelial cells with a retrovirus carrying a temperature-sensitive SV40 T antigen (T Ag) and isolated several immortalized fetal epithelial cell lines. Cell line 20-3 has characteristics of lung epithelial cells including the presence of distinct lamellar bodies, tight junctions, keratin 8 and 18 mRNA, HFH8, and T1 alpha mRNA and low levels of surfactant protein A mRNA. At 33 degrees C 20-3 grows with a doubling time of 21 h. At 40 degrees C the majority of cells cease to proliferate. Growth arrest is accompanied by significant morphological changes including an increase in cell size, transition to a squamous phenotype that resembles type 1 cells, and an increase in the number of multinucleated cells within the population. Greater than 95% of the cells incorporate [3H]thymidine into DNA at 33 degrees C whereas at 40 degrees C label incorporation drops to less than 20%. When shifted down to 33 degrees C 40% of the cells remain terminally growth arrested. In addition, cells plated at 40 degrees C have a reduced ability to form colonies when replated at 33 degrees C. Treatment with TGF-beta increases the percentage of cells that terminally growth arrest to greater than 80%. Growth arrest is accompanied by an increase in the levels of c-jun, jun D, cyclin D1, C/EBP-beta, transglutaminase type II, and retinoblastoma (Rb) mRNA and an induction of p105, the hypophosphorylated, growth regulatory form of Rb. Evaluation of Rb mRNA in fetal lung indicates that it is induced 2.5-fold between 17 and 21 days of gestation. These studies indicate that 20-3 terminally growth arrests in culture at the nonpermissive temperature and that it may be useful in studying changes in gene expression that accompany terminal growth arrest during lung development.

Animals↗
PubMed1998

Prevalence of human papillomavirus infection in premalignant and malignant lesions of the oral cavity in U.K. subjects: a novel method of detection.

To evaluate the possible role of human papillomavirus (HPV) in oral neoplasms, 28 oral squamous cell carcinomas (SCC) and 12 potentially malignant lesions were analysed for the presence of HPV DNA. A nested polymerase chain reaction (PCR) approach, using two sets of HPV consensus primers to the L1 region, was used, which was able to detect a broad spectrum of HPV types. HPV DNA was detected in 14/28 (50%) carcinomas and 4/12 (33%) precancerous lesions. A novel approach based on labelling the PCR products with 32P and the separation of radioactively labelled products on an 8% polyacrylamide gel increased the sensitivity of the detection and enabled the identification of the HPV types. The typing of HPV was subsequently confirmed by direct DNA sequencing. HPV 6 and HPV 16 were the only HPV types detected and seven tumours harboured both types. Our results suggest that HPVs may be an important aetiological factor in the development of oral cancer. The detection procedure ensured sensitivity and consistency of the detection of low copy numbers of the virus DNA. The presence of HPV in 33% of premalignant tissues suggests that HPV infection may be an early event in the malignant transformation of oral SCC. There was no statistically significant association between viral infection and tumour grade or stage.

Adult↗
PubMed1998

Anti-retroviral therapy reverses HIV-associated abnormalities in lymphocyte apoptosis.

The objective of this study was to assess the role of anti-retroviral therapy (ART) on the susceptibility of peripheral blood lymphocytes (PBL) from HIV-1-infected individuals to activation-induced apoptosis and in comparison with changes in CD4 lymphocyte counts. Eleven symptomatic HIV+ patients were studied. Ex vivo apoptosis was measured in phytohaemagglutinin (PHA)-stimulated PBL and CD4 subsets by flow cytometry, at baseline and after 1 month (4-6 weeks) and 2/3 months of ART. Six patients had extended studies of the effects of therapy to a maximum of 21 months. Lymphocyte apoptosis was significantly elevated in HIV+ patients at baseline (median 22% compared with 7.5% in HIV- risk-matched controls; P < 0.05). This decreased to control levels on ART (7.4% at 4-6 weeks, P < 0.01, and 6.2% at 8-12 weeks, P < 0.05, compared with baseline). Similar changes occurred in the CD4+ subpopulation. The decrease in apoptosis was maintained for several months, but the effect was rapidly lost if ART was discontinued. CD4 counts showed a reciprocal relationship to changes in apoptosis. The association of changes in apoptosis with those in CD4 counts suggests a link between programmed cell death and lymphocyte depletion. Apoptosis reduced in some individuals without any reduction in viral load, suggesting apoptosis may be influenced by factors in addition to the overall extent of HIV replication.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Heterotopic pregnancy complicating in vitro fertilization.

A review was undertaken of the cases of heterotopic pregnancy resulting from in vitro fertilization/embryo transfer (IVF/ET) and frozen embryo replacement (FER) in a 6-year cohort of women at National Women's Hospital in Auckland. The incidence of heterotopic pregnancy was 2.9% (5 cases) in 173 clinical pregnancies resulting from 901 embryo replacements. Of the 5 women with heterotopic pregnancy, 1 had unilateral tubal patency and 4 had bilateral tubal blockage; 3 had 'high responder' peak serum oestradiol levels (greater than 9,000 pmol/L) prior to oocyte pick-up (OPU); 3 had a serum human chorionic gonadotrophin beta subunit (beta-HCG) level greater than 600 IU/L on Day 14 following embryo transfer (ET) in the absence of a multiple intrauterine gestation on subsequent ultrasound scan. In the 4 women in whom unequivocal diagnosis of heterotopic pregnancy was not made on the initial ultrasound scan, there was delay in appropriate management, in 1 for more than 5 months. In conclusion, early IVF pregnancies require a transvaginal ultrasound scan performed by a sonographer experienced in the diagnosis of ectopic pregnancy and management of early pregnancy complications by clinicians in close consultation with the IVF centre itself. No single risk factor, laboratory test or combination of these is sensitive or specific enough to predict the occurrence of heterotopic pregnancy. The first-line surgical treatment of heterotopic pregnancy should be laparoscopic salpingectomy with excision of all except the intramural portion of the affected Fallopian tube.

Adult↗
PubMed1998

Dopamine agonists reorient visual exploration away from the neglected hemispace.

OBJECTIVE: To study the effects of bromocriptine, a dopamine agonist, on visual search. BACKGROUND: The anatomic substrate of spatial attention takes the form of a distributed network with interconnected cortical (frontal, parietal, and cingulate) and subcortical (striatal and thalamic) components. Dopamine appears to exert a modulatory effect on the function of this network. METHODS: Seven consecutive right-handed subjects with right-sided cerebral lesions were studied using a computerized target search paradigm. Eye movements were recorded. RESULTS: Bromocriptine caused the subjects to spend more time exploring the ipsilesional hemispace and therefore increased the relative neglect of the contralesional left hemispace. However, target detection accuracy did not change. Bromocriptine thus had a differential impact on the exploratory-motor versus sensory-perceptual components of directed attention. CONCLUSIONS: Our results show that bromocriptine may worsen some aspects of hemispatial neglect in patients with lesions that include the postsynaptic components of ascending dopaminergic pathways.

Adult↗