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Biomedical subjects

J C Leonard

Publications and source records attributed to J C Leonard.

At least 19 recordsLinked to original sources
PubMed2001

Hirschsprung disease in an infant with a contiguous gene syndrome of chromosome 13.

Hirschsprung disease is a developmental disorder resulting from the arrest of the craniocaudal migration of enteric neurons from the neural crest along gastrointestinal segments of variable length; see Behrman [Nelson textbook of pediatrics, 1992:954-956]. It is a heterogeneous disorder in which familial cases map to at least three loci whose function is necessary for normal neural crest-derived cell development. Homozygous mutations in the endothelin-B receptor gene (EDNRB) on 13q22 have been identified in humans and mice with Hirschsprung disease type 2 (HSCR2). The auditory pigmentary disorder, Waardenburg-Shah syndrome, comprises Waardenburg syndrome and Hirschsprung disease and has also been mapped to the EDNRB locus. Hirschsprung disease, malrotation, isochromia, a profound sensorineural hearing loss, and several other anomalies were found in an infant with an interstitial deletion of 13q, suggesting the existence of a contiguous gene syndrome involving developmental genes necessary for the normal growth of the neural crest derivatives of the eye, inner ear, and colon. We report on an additional patient with a deletion in 13q and Hirschsprung disease. Congenital anomalies associated with deletions of the distal long arm of chromosome 13 are sufficiently consistent to suggest a clinical syndrome.

Chromosome Banding↗
PubMed1999

Regional mapping panels for human chromosomes 1, 2, and 7.

The NIGMS Human Genetic Cell Repository has assembled regional mapping panels for human chromosomes 1, 2, and 7 from human rodent somatic cell hybrids submitted to the collection by researchers from 14 different laboratories. All hybrids were characterized initially by the submitters and verified by the Repository. Each hybrid carries a stable defined human segment as a derivative or deletion chromosome. These panels define 8-10 intervals for each chromosome. The panel for chromosome 2 is a new resource. The panels for chromosomes 1 and 7 complement previously published panels. The Repository distributes these regional mapping panels as cell cultures or as DNA. Information about these panels as well as for panels for chromosomes 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 21, 22, 22, and X may be viewed in the NIGMS Repository electronic catalog (http://locus.umdnj.edu/nigms).

Animals↗
PubMed1998

Complete replication of human sperm genome in egg extracts from Xenopus laevis.

To examine the ability of Xenopus egg extracts to support a complete replication cycle of human sperm genome, demembranated human spermatozoa were incubated with the extract from activated Xenopus laevis eggs. Most sperm heads were decondensed within 15 min. The heads became round within 30 min with diameters of 10-30 microns. The process of DNA replication in the pronuclei was monitored by two methods, bromodeoxyuridine incorporation and flow cytometry. The results indicate that DNA replication was initiated approximately 1.5 h after membrane structure formation and that it lasted up to 9 h. The amounts of DNA in most pronuclei were doubled by 4-9 h, depending on which donor toad was the source of the egg extract. Inclusion of the protein synthesis inhibitor, cycloheximide (100 micrograms/ml), had no obvious effect on human sperm DNA replication but appeared to prevent the pronuclei from degradation after a prolonged period (> 6 h) of incubation. After storage in liquid nitrogen for > 1.5 mo, the efficiency of the egg extracts in supporting sperm head decondensation and DNA replication was reduced for human sperm but not for Xenopus sperm. Possible applications of the use of Xenopus egg extract for human sperm activation and DNA replication are discussed.

Animals↗
PubMed1998

Idiopathic thrombocytopenic purpura presenting in a high school football player: a case report.

OBJECTIVE: To alert athletic trainers to the signs and symptoms of idiopathic thrombocytopenic purpura and its clinical presentation in order to facilitate immediate intervention. BACKGROUND: Idiopathic thrombocytopenic purpura (ITP), also known as immune thrombocytopenic purpura, is a hemorrhagic disorder that is primarily immunologic in origin but is sometimes triggered by viral infection in children. It has also been associated with heroin and quinine drug use. A reduced platelet count can result in mucosal or deep tissue bleeding, or both, and most importantly, intracranial bleeding. Because football is a collision sport, it is imperative that any player presenting with ITP-type symptoms be removed immediately from all contact and referred to a physician. DIFFERENTIAL DIAGNOSIS: Leukemia, aplastic anemia, drug side effects, vitamin deficiency, kidney failure, infection, multiple contusions. TREATMENT: The traditional first-line treatment consists of corticosteroid medication and time and removal from all physical activities until the blood platelet count is normal and controlled. In quinine-induced ITP, discontinuation of the drug and bedrest are recommended to reduce the risk of major hemorrhage for a 12-to 14-hour period in order to allow the quinine to clear the system and the platelet count to return to normal. UNIQUENESS: ITP's presentation needs to be differentiated from other disorders. Incorrect diagnosis could seriously jeopardize the athlete, who could develop intracranial and internal bleeding. CONCLUSIONS: Recognition of the signs and symptoms associated with ITP is essential to prevent further participation by the athlete. Immediate intervention is needed to determine the severity and to institute appropriate treatment.

Journal Article↗
PubMed1997

Regional mapping panels for chromosomes 3, 4, 5, 11, 15, 17, 18, and X.

The NIGMS Human Genetic Mutant Cell Repository collects and distributes well-characterized human/rodent somatic cell hybrid regional mapping panels for human chromosomes 3, 4, 5, 11, 15, 17, 18, and X. Each regional mapping panel consists of 4 to 11 hybrids that divide the chromosome into 5 to 11 intervals. These panels have been extensively characterized by the submitters and the NIGMS Repository.

Animals↗
PubMed1997

Adeno-associated virus vectors for vascular gene delivery.

A variety of delivery systems have been used to genetically modify vascular endothelial cells and smooth muscle cells (SMCs), but currently available systems suffer from either inefficient in vivo gene transfer, transient episomal vector expression, or significant immune responses and inflammation. In the present study, we evaluated an alternate vector system, recombinant adeno-associated virus (rAAV) for transduction of vascular cells in culture and in vivo. Primary cultures of rabbit, monkey, and human SMCs; macaque and human microvascular endothelial cells; and human umbilical vein endothelial cells were efficiently transduced at a dose of 100 to 1000 DNase-resistant particles per cell. rAAV-mediated transduction of the vasculature in vivo was observed after intraluminal gene delivery or after intra-adventitial injection in carotid arteries of atherosclerotic cynomolgus monkeys. Whether vector delivery was intraluminal or adventitial, transduction was observed in the adventitia, particularly within microvessels (vasa vasorum) but not in cells of the intima or media. Transduction of adventitial microvessels was enhanced by balloon injury 4 days before gene transfer. This was particularly true for adventitial delivery. We have previously shown that adventitial cell proliferation increases significantly 4 days after balloon injury (45%) in this animal model. Together, these data suggest that cell proliferation may enhance AAV transduction in vivo in the vasculature. AAV vectors exhibited a tropism in vivo for the microvascular endothelium at the doses used in the present study, which may provide the opportunity for targeting gene delivery. In summary, we have demonstrated the utility of rAAV vectors for ex vivo vascular cell gene delivery and present an initial experience with rAAV for in vivo vascular gene delivery. This alternate vector system may overcome some of the limitations hampering the development of gene therapy for vascular disorders.

Animals↗
PubMed1996

[Congenital tarsal synostosis].

Tarsal coalition results from the fusion of at least two tarsal bones. The clinical and radiological pictures depend on the anatomic location of the coalition. Calcaneonavicular and talonavicular coalitions are the most frequent features which may result in peroneal spastic flat foot; however they are symptomless in most cases. Tarsal coalitions are usually evident on plain X-ray films using appropriate incidences. In selected cases, partial talocalcaneal coalition requires CT scan or MRI. No treatment is needed for asymptomatic conditions. Painful spastic flat foot must be treated conservatively by limiting sport activity as a first step treatment. In case of persistent symptoms, cast with correction of deformities under general anesthaesia is recommended. Surgery is needed only in case of failure of previous treatment, requiring resection of the bony bridge and sometimes triple foot arthrodesis.

Child↗
PubMed1996

Gender and interest in academic careers among first- and third-year residents.

BACKGROUND: While increasing proportions of medical students and residents are women, the proportion of women in the advanced ranks of medicine remains small. This study describes gender differences among residents concerning interest in academic medicine and related influences. METHOD: A survey instrument was mailed to all 308 first- and third-year residents at the University of Washington School of Medicine in the late summer of 1993. The survey assessed interest in academic careers, values, psychological traits, exposure to mentoring, and perceived role stress. Frequency analysis and chi-square analysis were performed to compare the distribution responses by gender within the entire respondent group and within the first-year and third-year subgroups. RESULTS: A total of 180 (58%) of all first- and third-year residents responded; 99 (55%) were men. Although the level of interest in academic careers was similar among first-year male and female residents, the level of interest was greater among third-year men than among third-year women. Women overall were less likely to consider it personally important to achieve national recognition. Women in the third (but not the first) year of residency were significantly less likely than men to agree that leading others was personally important to them. Women reported feeling less confident, were less likely to have identified a faculty member who had successfully balanced career and personal life, and were significantly more likely to feel under stress and to have interrupted their careers for childbearing. CONCLUSION: The interest in academic careers appeared to be lower among third-year female residents than among third-year male residents, despite the similar interests in academic medicine among male and female first-year residents. Increasing role stress among women in training may explain the reduced interest in leadership and academic careers among women at more advanced levels of training.

Attitude of Health Personnel↗
PubMed1996

Ready, set, go! Sports medicine on and off the field.

Team and event physicians can play an important role in ensuring the medical safety of a sports event by several actions: analyzing common injuries particular to a sport and planning accordingly in terms of equipment and procedures, establishing a hierarchy of the team's staff (ie, who has the authority to take a player out of the game), organizing medical equipment, establishing communication among the support personnel, considering crowd-control techniques for large events, arranging accessible transportation to a nearby medical facility, and being alert to possible dangerous weather conditions. Athletes will be safer, physicians more secure, and sports events more successful if these precautions are primary.

Emergencies↗
PubMed1996

[Latex allergy and orthopedic surgery].

PURPOSE OF THE STUDY: Latex allergy is becoming a subject of extreme concern, especially in patients who have undergone multiple operations and/or have after effects of myelodysplasia. Presenting their data, the authors wish to make it aware to orthopaedic surgeons focusing on different risk groups, and at the same time advising on medical examinations, of the various measures to take. MATERIAL AND METHODS: Twenty patients were tested (17 with spina bifida and 3 with cerebral palsy) for latex and ethylene oxide allergy, and with certain fruits known for their cross-reactivity. Atopic history has also been researched. The immunologic examination had been carried out by means of skin-tests with evidence of specific IgE antibodies being found. RESULTS: Out of the twenty patients tested, eight had clinical signs of a latex allergy while the twelve others were classified as being at risk. The results show that 11 out of 20 are allergic to latex, 4 of them have an allergy to ethylene oxide, and 7 have food allergies: banana (2), kiwi (1), chestnut (1), hazelnut (3). DISCUSSION: We confirm: 1) the increased risk of a latex allergy among patients with spina bifida: 47 per cent in our study; 2) the association of an ethylene oxide allergy, practically the only product used in the sterilisation of medical equipment; 3) a more and more frequent association to food allergies, in particular to fruits: 7 out of 11 patients in our study compared to 50 per cent in other published studies. The classical subject of atopy is not found here. CONCLUSION: Against the increase of latex allergy, it is necessary to propose a strategy: firstly to determine the groups at risk: patients who have undergone multiple operations, atopic persons, isolated cases of food allergies, spina bifida cases. Then, to test them and if necessary, taking draconian measures concerning their medical environment; to identify them; to provide them with auto-injectable epinephrine; to give premedication, though with no success guarantee in case of anticipated surgical procedure. Finally, we recommend to manufacturers that all equipment and products should be free of latex.

Adolescent↗