Search PubMed⌕ Search

Biomedical subjects

J Kaplan

Publications and source records attributed to J Kaplan.

At least 163 records · Page 9Linked to original sources
PubMed1996

Complementation of the beige mutation in cultured cells by episomally replicating murine yeast artificial chromosomes.

Chédiak-Higashi syndrome in man and the beige mutation of mice are phenotypically similar disorders that have profound effects upon lysosome and melanosome morphology and function. We isolated two murine yeast artificial chromosomes (YACs) that, when introduced into beige mouse fibroblasts, complement the beige mutation. The complementing YACs exist as extrachromosomal elements that are amplified in high concentrations of G418. When YAC-complemented beige cells were fused to human Chédiak-Higashi syndrome or Aleutian mink fibroblasts, complementation of the mutant phenotype also occurred. These results localize the beige gene to a 500-kb interval and demonstrate that the same or homologous genes are defective in mice, minks, and humans.

Animals↗
PubMed1996

Evidence of genetic heterogeneity of Leber's congenital amaurosis (LCA) and mapping of LCA1 to chromosome 17p13.

Leber's congenital amaurosis (LCA) is an autosomal recessive disease responsible for congenital blindness. It is the earliest and most severe inherited retinal dystrophy in human and its genetic heterogeneity has long been recognised. We have recently reported on the first localisation of a disease gene (LCA1) to the short arm of chromosome 17 by homozygosity mapping in five families of North African origin. Here, we refine the genetic mapping of LCA1 to chromosome 17p13 between loci D17S938 and D17S1353 and provide strong support for the genetic heterogeneity of this condition (maximum likelihood for heterogeneity, 17.20 in InL; heterogeneity versus homogeneity, P = 0.0002, heterogeneity versus no linkage, P < 0.0001)

Blindness↗
PubMed1996

Retinitis punctata albescens associated with the Arg135Trp mutation in the rhodopsin gene.

PURPOSE: To screen for mutations in the rhodopsin, peripherin/RDS, and ROM1 genes in a family affected with retinitis punctata albescens. Because clinical heterogeneity was observed in this family, with some members affected with retinitis punctata albescens and one member affected with features typical of retinitis pigmentosa, we analyzed the apolipoprotein E gene to elucidate this unusual intrafamilial heterogeneity. METHODS: The coding sequences of these genes were analyzed with a combination of single-strand conformation polymorphism and direct sequence analysis. Haplotypes of the apolipoprotein E gene were analyzed by polymerase chain reaction and enzymatic digestion. RESULTS: The Arg135Trp mutation in the rhodopsin gene was observed in all affected members of this family, but no mutation was detected in the peripherin/RDS or ROM1 genes. The e4 allele of the apolipoprotein E gene apparently cosegregated with the albescens phenotype in this family. CONCLUSIONS: The albescent phenotype in retinal dystrophy appears to not be caused exclusively by a peripherin/RDS gene mutation, and we suggest that the apolipoprotein E gene may play a role in the albescent phenotype.

Adolescent↗
PubMed1996

Identification of the murine beige gene by YAC complementation and positional cloning.

The beige mutation is a murine autosomal recessive disorder, resulting in hypopigmentation, bleeding and immune cell dysfunction. The gene defective in beige is thought to be a homologue of the gene for the human disorder Chediak-Higashi syndrome. We have identified the murine beige gene by in vitro complementation and positional cloning, and confirmed its identification by defining mutations in two independent mutant alleles. The sequence of the beige gene message shows strong nucleotide homology to multiple human ESTs, one or more of which may be associated with the Chediak-Higashi syndrome gene. The amino acid sequence of the Beige protein revealed a novel protein with significant amino acid homology to orphan proteins identified in Saccharomyces cerevisiae, Caenorhabditis elegans and humans.

Amino Acid Sequence↗
PubMed1996

Retinal-specific guanylate cyclase gene mutations in Leber's congenital amaurosis.

Leber's congenital amaurosis (LCA, MIM 204,000), the earliest and most severe form of inherited retinopathy, accounts for at least 5% of all inherited retinal dystrophies. This autosomal recessive condition is usually recognized at birth or during the first months of life in an infant with total blindness or greatly impaired vision, normal fundus and extinguished electroretinogram (ERG). Nystagmus (pendular type) and characteristic eye poking are frequently observed in the first months of life (digito-ocular sign of Franceschetti). Hypermetropia and keratoconus frequently develop in the course of the disease. The observation by Waardenburg of normal children born to affected parents supports the genetic heterogeneity of LCA. Until now, however, little was known about the pathophysiology of the disease, but LCA is usually regarded as the consequence of either impaired development of photoreceptors or extremely early degeneration of cells that have developed normally. We have recently mapped a gene for LCA to chromosome 17p13.1 (LCA1) by homozygosity mapping in consanguineous families of North African origin and provided evidence of genetic heterogeneity in our sample, as LCA1 accounted for 8/15 LCA families in our series. Here, we report two missense mutations (F589S) and two frameshift mutations (nt 460 del C, nt 693 del C) of the retinal guanylate cyclase (RETGC, GDB symbol GUC2D) gene in four unrelated LCA1 probands of North African ancestry and ascribe LCA1 to an impaired production of cGMP in the retina, with permanent closure of cGMP-gated cation channels.

Blindness↗
PubMed1996

A multidimensional approach to the study of the structure of coping with stress.

This article described a study in which the responses of 199 respondents to measures of coping with stress were submitted to multidimensional scaling. The three-dimensional solution suggests that respondents' perceptions of coping with stress are best explained along the following dimensions: (a) active coping versus denial/escape, (b) turning to interpersonal support versus seeking religious comfort, and (c) instrumental/cognitive disengagement versus affective/spiritual engagement.

Adaptation, Psychological↗
PubMed1996

Linkage of scapuloperoneal spinal muscular atrophy to chromosome 12q24.1-q24.31.

Scapuloperoneal (SP) syndromes are heterogeneous neuromuscular disorders which are characterized by weakness in the distribution of shoulder girdle and peroneal muscles. SP syndromes can resemble facioscapulohumeral muscular dystrophy (FSH) due to scapular weakness or Charcot-Marie-Tooth disease (CMT) due to atrophy of peroneal muscles. Both neurogenic and myopathic SP syndromes have been described. Locus for the myopathic form of SP syndrome (scapuloperoneal muscular dystrophy, SPMD) has recently been assigned to chromosome 12q. We previously described a large New England kindred exhibiting an autosomal dominant neurogenic SP syndrome (scapuloperoneal spinal muscular atrophy, SPSMA). Disease expression was more severe and progressive in successive generations, which suggested genetic anticipation. We performed genetic linkage analysis of this family with microsatellite markers and excluded the loci for FSH, CMT, SPMD and SMA (spinal muscular atrophy) in our family. Linkage in our SPSMA family (lod score > 3) was established to seven microsatellite markers that map to chromosome 12q24.1-q24.31. The highest lod score with two-point linkage analysis was 6.67 (theta = 0.00) with marker D12S353. Multipoint analysis gave maximum lod scores of 7.38 between D12S354 and D12S79, and also 7.38 between D12S369 and NOS1 (neuronal nitric oxide synthase). The gene for SPSMA lies within the 19 cM interval between D12S338 and D12S366. This report establishes a locus for the neurogenic form of SP syndrome approximately 20 cM telomeric to the one described for the myopathic form of SP syndrome.

Chromosome Mapping↗
PubMed1996

Elevated transforming growth factor-beta concentration correlates with posttrauma immunosuppression.

OBJECTIVE: To determine whether trauma induces an increase in the concentration of circulating transforming growth factor-beta (TGF-beta), and whether there is a temporal correlation between plasma TGF-beta concentration and the development of posttrauma cellular immunosuppression. MATERIALS AND METHODS: Male Sprague-Dawley rats were anesthetized, subjected to bilateral femur fractures or sham injury, and killed 1, 3, or 5 days later. Plasma TGF-beta levels, splenocyte phenotypes, mitogen-induced proliferation, interleukin-2 (IL-2) production, and IL-2 receptor (IL-2R) expression were determined at each time point. MEASUREMENTS AND MAIN RESULTS: Splenocyte proliferation increased on day 1 postinjury without corresponding change in IL-2 or plasma TGF-beta levels. Splenocyte proliferation and IL-2 production were suppressed on day 3 postinjury, while plasma TGF-beta levels peaked. No differences were observed between trauma and control groups on day 5. Splenocyte phenotypes and IL-2R expression were similar in injured and control rats at all times. CONCLUSIONS: Suppression of lymphocyte proliferation and IL-2 production after trauma occurs concomitantly with a rise in plasma TGF-beta. The immune response is restored with normalization of TGF-beta concentration. These observations suggest that TGF-beta may contribute to posttrauma immunosuppression.

Animals↗
PubMed1996

Molecular biology of iron acquisition in Saccharomyces cerevisiae.

In recent years, significant advances have been made in our understanding of the mechanism and regulation of elemental iron transport in the eukaryote Saccharomyces cerevisiae. This organism employs two distinct iron-transport systems, depending on the bioavailability of the metal. In iron-replete environments, a low-affinity transport system (K(m) = 30 microM) is used to acquire iron. This system may also be used to acquire other metals including cobalt and cadmium. When environmental iron is limiting, a high-affinity (K(m) = 0.15 microM) iron-transport system is induced. Genetic studies in S. cerevisiae have identified multiple genes involved in both iron-transport systems. Cell-surface reductases, FRE1 and FRE2, provide ferrous iron for both systems. A non-ATP-dependent transmembrane transporter (FET4) has been identified as the main component of low-affinity transport. One gene identified to date as part of the high-affinity transport system is FET3, which shows high sequence and functional homology to multicopper oxidases. Accessory genes required for the functioning of this transport system include a plasma-membrane copper transporter (CTR1), an intracellular copper transporter (CCC2), and a putative transcription factor (AFT1). The mechanism by which these genes act in concert to ensure iron accumulation in S. cerevisiae presents an intriguing picture, drawing parallels with observations made in the human system almost 40 years ago.

Biological Transport↗
PubMed1996

The late chlamydial inclusion membrane is not derived from the endocytic pathway and is relatively deficient in host proteins.

Chlamydiae are obligate intracellular parasites which multiply within infected cells in a membrane-bound structure termed an inclusion. Newly internalized bacteria are surrounded by host plasma membrane; however, the source of membrane for the expansion of the inclusion is unknown. To determine if the membrane for the mature inclusion was derived by fusion with cellular organelles, we stained infected cells with fluorescent or electron-dense markers specific for organelles and examined inclusions for those markers. We observed no evidence for the presence of endoplasmic reticulum, Golgi, late endosomal, or lysosomal proteins in the inclusion. These data suggest that the expansion of the inclusion membrane, beginning 24 h postinoculation, does not occur by the addition of host proteins resulting from either de novo host synthesis or by fusion with preexisting membranes. To determine the source of the expanding inclusion membrane, antibodies were produced against isolated membranes from Chlamydia-infected mouse cells. The antibodies were demonstrated to be solely against Chlamydia-specified proteins by both immunoprecipitation of [35S]methionine-labeled extracts and Western blotting (immunoblotting). Techniques were used to semipermeabilize Chlamydia-infected cells without disrupting the permeability of the inclusion, allowing antibodies access to the outer surface of the inclusion membrane. Immunofluorescent staining demonstrated a ring-like fluorescence around inclusions in semipermeabilized cells, whereas Triton X-100-permeabilized cells showed staining throughout the inclusion. These studies demonstrate that the inclusion membrane is made up, in part, of Chlamydia-specified proteins and not of existing host membrane proteins.

3T3 Cells↗
PubMed1996

Evidence for a fourth locus in Usher syndrome type I.

Usher syndrome type I (US1) is an autosomal recessive condition in which three different genes have been already localised (USH1A, USH1B, and USH1C on chromosomes 14q32, 11q13, and 11p15 respectively). The genetic heterogeneity of US1 has been confirmed in a previous study by linkage analysis of 20 French pedigrees. Here, we report the genetic exclusion of the three previously reported loci in two large multiplex families of Moroccan and Pakistani origin, suggesting the existence of at least a fourth locus in Usher syndrome type I.

Abnormalities, Multiple↗
PubMed1996

Molecular mechanisms of iron uptake in eukaryotes.

Iron serves essential functions in both prokaryotes and eukaryotes, and cells have highly specialized mechanisms for acquiring and handling this metal. The primary mechanism by which the concentration of iron in biologic systems is controlled is through the regulation of iron uptake. Although the role of transferrin in mammalian iron homeostasis has been well characterized, the study of genetic disorders of iron metabolism has revealed other, transferrin-independent, mechanisms by which cells can acquire iron. In an attempt to understand how eukaryotic systems take up this essential element, investigators have begun studying the simple eukaryote Saccharomyces cerevisiae. Several genes have been identified and cloned that act in concert to allow iron acquisition from the environment. Some of these genes appear to have functional homologues in human systems. This review focuses on the recent developments in understanding eukaryotic iron uptake with an emphasis on the genetic and molecular characterization of these systems in both cultured mammalian cells and S. cerevisiae. An unexpected connection between iron and copper homeostasis has been revealed by recent genetic studies, which confirm biologic observations made several decades ago.

Animals↗
PubMed1996

Predictors of carbon monoxide and hydrogen cyanide exposure in smoke inhalation patients.

OBJECTIVE: A prospective study of civilian (nonfirefighter) smoke inhalation patients was carried out to test the hypotheses that: 1) absorption of carbon monoxide and hydrogen cyanide from smoke can be predicted by clinical examination and historical data; and, more specifically 2) a history of exposure to burning synthetic polymers is an important predictor of systemic cyanide levels. METHODS: The study was conducted over a three-year period at six urban hospitals. Patients with or without burns who were exposed to smoke within five hours of hospital arrival were sampled for carboxyhemoglobin, whole blood cyanide, urine cotinine and urine creatinine. Controls consisted of a smaller group of smoking status-matched, nonsmoke-exposed burn patients. ANALYSIS: Historical information was obtained on SMOKING status, FIRETYPE (structural vs other), MATERIAL burned (natural vs synthetic) and LAGTIME (from exposure to sampling). A smoke inhalation SCORE (0-10) was assigned to each case, based on physical examination findings and changes on chest X ray, and carboxyhemoglobin and cyanide levels were entered into various multivariate linear regression models. RESULTS: A total of 40 cases and 9 controls were recruited, ranging in age from 15 to 92 years. Thirty-four cases were discharged alive and six expired in-hospital. Observed carboxyhemoglobin levels ranged from 1.2% to 41.6% in cases (mean 8.6%), and from 0.5 to 7.3% in controls (mean 2.9%). Observed cyanide levels ranged from nondetectable (< 0.05 micrograms/mL) to 2.79 micrograms/mL in cases (mean 0.25 micrograms/mL), and from nondetectable to 0.11 micrograms/mL in controls (mean 0.03 micrograms/mL). Among cases, linear regression models explained up to 35% of the observed variance in carboxyhemoglobin levels (p < 0.001) and up to 48% of the variance in cyanide levels (p = 0.0001). CONCLUSIONS: SCORE was the strongest predictor of both carboxyhemoglobin and cyanide levels; LAGTIME also explained significant variance for [log-transformed] carboxyhemoglobin. Historical factors, such as FIRETYPE, MATERIAL, and SMOKING status, did not explain significant variance in most of the statistical models employed.

Adolescent↗
PubMed1996

Susceptibility of human cytomegalovirus to two-drug combinations in vitro.

Human cytomegalovirus (HCMV) is a major cause of morbidity and mortality for immunocompromised hosts. We sought to determine the in vitro susceptibility of HCMV reference laboratory strains, clinical isolates and strains with known resistance to currently available anticytomegaloviral drugs to two-drug combinations of the following compounds: ganciclovir, foscarnet, cidofovir and its cyclic congener, cyclic HPMPC (cHPMPC), and lobucavir. Cytotoxicity was determined by Trypan Blue exclusion of cells exposed both when proliferating (non-confluent) and once confluent. Antiviral effect was determined by a plaque-reduction assay in MRC-5 human embryonic lung cells. Drug interactions were determined by median-dose effect analysis with the combination index calculated at 50, 75, 90 and 95% inhibitory concentrations. No drug, either alone or in combination, reached a 50% cytotoxicity concentration in the dose ranges tested. Overall, 252/280 (90.0%) of the two-drug combinations demonstrated additive or synergistic interactive effects towards the panel of HCMV isolates tested. No combination demonstrated antagonism at all inhibitory concentrations to more than one isolate. Interestingly, the clinical isolate tested demonstrated the highest frequency of antagonistic combinations (3/10), as well as marked differences from pan-susceptible laboratory strains. The combinations of ganciclovir + foscarnet and cHPMPC + foscarnet demonstrated additive to synergistic effects against all isolates tested. In vitro combination drug studies could help in the rational choice of therapeutic regimens for use in clinical trials, potentially resulting in decreased toxicity, increased efficacy and delayed onset of drug resistance.

Antiviral Agents↗
PubMed1996

[Rapid demonstration of mutations previously identified in parents at risk of patients with autosomic dominant retinitis pigmentosa].

PURPOSE: We have previously identified rhodopsin gene mutations in France in autosomal dominant (ADRP) retinitis pigmentosa in France, using a combination of SSCP (single-strand conformation polymorphism) and direct sequence analysis. The aim of this study was to perform a more rapid tool to identify a mutation in a ADRP family, when this mutation has been identified for one affected member of this family. METHODS: We looked for a restriction site, created or abolished by a mutation in the rhodopsin gene. We performed in vitro DNA amplification using PCR (polymerase chain reaction), enzymatic digestion, and migration on agarose gel. RESULTS: Abnormal patterns of migration were observed for affected ADRP members. DISCUSSION: This technique is useful and rapid (less than 5 hours) to recognize a previously identified mutation. However, previous precise identification of the mutation in one member of the family is needed.

DNA Restriction Enzymes↗