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Biomedical subjects

M Schmid

Publications and source records attributed to M Schmid.

At least 253 records · Page 14Linked to original sources
PubMed1996

The chicken beta 2-microglobulin gene is located on a non-major histocompatibility complex microchromosome: a small, G+C-rich gene with X and Y boxes in the promoter.

beta 2-Microglobulin is an essential subunit of major histocompatibility complex (Mhc) class I molecules, which present antigenic peptides to T lymphocytes. We sequenced a number of cDNAs and two genomic clones corresponding to chicken beta 2-microglobulin. The chicken beta 2-microglobulin gene has a similar genomic organization but smaller introns and higher G+C content than mammalian beta 2-microglobulin genes. The promoter region is particularly G+C-rich and contains, in addition to interferon regulatory elements, potential S/W, X, and Y boxes that were originally described for mammalian class II but not class I alpha or beta 2-microglobulin genes. There is a single chicken beta 2-microglobulin gene that has little polymorphism in the coding region. Restriction fragment length polymorphisms from Mhc homozygous lines, Mhc congenic lines, and backcross families, as well as in situ hybridization, show that the beta 2-microglobulin gene is located on a microchromosome different from the one that contains the chicken Mhc. We propose that the structural similarities between the beta 2-microglobulin and Mhc genes in the chicken are due to their presence on microchromosomes and suggest that these features and the microchromosomes appeared by deletion of DNA in the lineage leading to the birds.

Amino Acid Sequence↗
PubMed1996

Detection and typing of human papillomavirus in biopsy and cytological specimens by polymerase chain reaction and restriction enzyme analysis: a method suitable for semiautomation.

Screening for high-risk human papillomavirus (HPV) types allows the detection of women at a high risk of cervical squamous carcinomas, thereby defining a subset of patients targeted for more intensive screening and follow-up. Thirty-four cervical biopsy specimens and isolated cells from cervical smears of normal women or women diagnosed with high-grade intraepithelial lesion (HGSIL) were screened for the presence of HPV by in situ hybridization (ISH) and/or by polymerase chain reaction (PCR). The exact HPV type was determined using a novel restriction typing method. The detection of HPV was facilitated greatly by the use of a PCR-enzyme-linked immunosorbent assay (ELISA)-based method. HPV was detected by PCR in 32% of the biopsy specimens, whereas only 23% had a positive staining by ISH. In one case, a double infection was detected by ISH as well as by PCR. In two cases, the presence of HPV was detected by both methods but the exact type was different. Analyzing cells isolated from cervical smears by the PCR-ELISA technique or by PCR followed by agarose gel electrophoresis, HPV was detected only in patients with HGSIL and not in the control group. The PCR system is more sensitive than conventional ISH, and the PCR-ELISA system presented in this study is efficient in screening large series of cytological samples. Furthermore, this system allows exact HPV typing on the microtiter plate. These innovations may allow the application of HPV detection and typing as a routine screening method to identify patients with a high risk of developing cervical neoplasia.

Automation↗
PubMed1996

Clustered organization and conservation of the Xiphophorus maculatus D locus, which includes two distinct gene sequences.

Genomic organization and chromosomal localization of a previously uncharacterized D (Donor) locus in Xiphophorus and Poecilia species was investigated using fluorescence in situ hybridization (FISH) and Southern blot analysis. Part of this region is thought to be involved in the recombination event leading to formation of the Xmrk oncogene and it has recently been shown that this locus includes two different genes, one with high homology to a zinc finger protein of the Krüppel type, and the other an unknown gene with high similarity to a Caenorhabditis elegans gene. FISH to Xiphophorus chromosomes revealed that these two unrelated genes are closely linked and clustered at a unique chromosomal site. Southern blot hybridization patterns suggest that these genes exist in the genome as multiple copies. Furthermore, similar genomic organization profiles seem to prevail among other related fish. In particular, our FISH experiments reveal the existence of a conserved homologous chromosomal segment harboring the zinc finger protein sequence in several poeciliid fish.

Animals↗
PubMed1996

Yeast artificial chromosome mapping of the cystinosis locus on chromosome 17p by fluorescence in situ hybridization.

The gene locus for cystinosis has been mapped between markers D17S1583 and D17S1584 on the short arm of chromosome 17. Using markers encompassing the cystinosis region, we assigned different yeast artificial chromosome (YAC) clones previously identified by sequence tagged site (STS) screening to 17p13.3. Three of the clones hybridized to the target 17p gene region; one of these was chimeric, hybridizing both to chromosomes 3p and 5q; two of the YACs did not contain sequences of 17p13.3. Our physical mapping has identified candidate YACs as a first step towards a positional cloning approach.

Amino Acid Sequence↗
PubMed1996

Fixed versus titrated interferon-alpha 2B in chronic hepatitis C. A randomized controlled multicenter trial. The Swiss Association for the Study of the Liver.

BACKGROUND/AIM: Interferon has become the mainstay of treatment of chronic hepatitis C; however, duration of treatment and dose remain unresolved questions. The present study aimed to compare standard dose interferon with a titrated dose regimen carried out for 1 year. METHODS: This was a randomized, controlled multicenter trial. Patients with chronic hepatitis C were randomly allocated to a control group (n = 30), to a fixed dose group (n = 31) where interferon-alpha 2b 3 MU thrice weekly was given for 1 year or a titrated group (n = 34) where interferon was titrated starting at 5 MU thrice weekly to the lowest dose keeping the patient in remission as assessed by a normal ALT value. Liver biopsies were obtained before and at the end of treatment; in addition, galactose elimination capacity was measured as a measure of cytosolic function. RESULTS: In the control, fixed and titrated groups a complete response was achieved in 2/29, 10/28 and 15/31, respectively (p < 0.001 in favor of treatment, p = n.s. for the two treatments). The corresponding figure for sustained response was 1/29, 5/28 and 6/ 31 (p = n.s). In the titrated group, a complete (sustained) response was achieved with 5 MU in 2 (2), with 4 MU in 1 (0), with 3 MU in 4 (0), with 2 MU in 3 (0) and with 1 MU in 5 (4). Liver biopsy score and galactose elimination capacity improved significantly in responders but not in treatment failures. CONCLUSIONS: Both fixed and titrated dosing of interferon given for 1 year induced virus clearance in only a minority of treated patients. However, in a small number of patients, a complete and sustained response can be achieved with low doses of interferon. Dose titration could be an interesting approach to decreasing the cost and side effects in the treatment of chronic hepatitis C.

Adult↗
PubMed1996

The human gene of a protein that modifies Na(+)-D-glucose co-transport.

Recently, a cDNA (pRS1) was cloned from pig kidney cortex that encodes a membrane-associated protein involved in Na(+)-coupled sugar transport. pRS1 alters sugar transport by SGLT1 from rabbit intestine or by SMIT from dog kidney which is homologous to SGLT1. In contrast, pRS1 does not influence transporters from other genetic families. We report the cloning of the intronless human gene hRS1 (6,743 bp), which encodes a 617-amino-acid protein with 74% amino acid identity to pRS1. By fluorescence in situ hybridization, hRS1 was localized to chromosome 1p36.1. The localization to one chromosome and Southern blot analysis of restricted genomic DNA suggest that there is only one RS1-homologous gene in humans. Functionality of hRS1 was demonstrated by co-expression experiments of hRS1 and SGLT1 from human intestine in oocytes from Xenopus laevis. They show that hRS1-protein inhibits Na(+)-D-glucose co-transport expressed by human SGLT1 by decreasing both the Vmax and the apparent Km value of the transporter. The analysis of the 5'-noncoding sequence of hRS1 revealed different enhancer consensus sequences that are absent in the SGLT1 gene, e.g., several consensus sequences for steroid-binding proteins.

Animals↗
PubMed1996

Are there genetic risks associated with microassisted reproduction?

Of all the techniques available for microassisted reproduction, the direct injection of individual sperm cells or spermatids into the cytoplasm of the oocyte (ICSI) is the most invasive, through which any possible selection against sperm cells with genomic defects would be excluded. It has, however, been shown that such a possible selection is present neither in the female genital tract nor at the zona pellucida. Selection against genetic-based defects occurs after the fertilization of the oocyte, during both embryonic and fetal development. Based on the data to date, it can be assumed that ICSI would not result in either a significant increase in genetic-based diseases, or in an increase in the number of infertile males. If, however, mutations of X-chromosomal or Y-chromosomal genes should play a major role in male fertility disorders, one could expect, over generations, an increase, though probably very slight, in the number of males with such disorders.

Animals↗
PubMed1996

Interphase chromosome arrangement in Sertoli cells of adult mice.

Sertoli cells of adult male laboratory mice were examined with a number of banding techniques and by nonradioactive in situ hybridization applying different repetitive DNA probes. All banding methods revealed the typical features of mouse Sertoli cells, i.e., a central nucleolus, usually with two chromocenters associated at diametrically opposed sides in which the centromeric regions of the chromosomes are clustered. Silver staining as well as in situ hydridization with rDNA labeled part of the chromocenters and the nucleolus, indicating transcriptional activity of at least some of the nucleolus organizer regions. In situ hybridization with X- and Y-specific DNA probes showed both sex chromosomes to be undercondensed in Sertoli cells This decondensation suggests expression of sex chromosomal genes in Sertoli cells. While the X chromosome appeared to occupy a central position near one of the chromocenters, the Y chromosome was found at the periphery of the nucleus in the majority of cells. Hybridization with telomeric sequences resulted in strong labeling of the chromocenters and dispersed signals at the nuclear periphery.

Animals↗
PubMed1996

The association between self-reported symptoms of asthma and allergic rhinitis and self-reported traffic density on street of residence in adolescents.

We examined the association between self-reported symptoms of asthma and allergic rhinitis and self-reported exposure to motor vehicle traffic in adolescents in Münster, Germany. A total of 3,703 German students age 12-15 years completed a written and video questionnaire in 1994-1995. We found positive associations between both wheezing and symptoms of allergic rhinitis during the past 12 months and self-reported frequency of truck traffic. The sex- and age-adjusted prevalence odds ratios and 95% confidence intervals (CI) for truck traffic, contrasting the categories "frequent" and "constant" against "never," were, for wheezing obtained by written questionnaire: 1.53 (95% CI = 1.15-2.05) and 2.15 (95% CI = 1.44-3.21); for wheezing obtained by video questionnaire: 1.61 (95% CI = 1.26-2.07) and 2.47 (95% CI = 1.74-3.52); and for symptoms of allergic rhinitis: 1.71 (95% CI = 1.36-2.15) and 1.96 (95% CI = 1.40-2.76), respectively. We found a similar positive association with self-reports on traffic noise. Putative confounding variables, including indicators of socio-economic status, smoking, etc, did not alter these associations substantially. The results correspond closely with findings of a survey carried out in 1991 in Bochum, Germany. Our results support the hypothesis that exposure to motor vehicle traffic is related to symptoms of asthma and allergic rhinitis in children, but we cannot rule out misclassification due to self-reports of traffic exposure.

Adolescent↗
PubMed1996

Detection of t(11;22)(q24;q12) translocation breakpoint in paraffin-embedded tissue of the Ewing's sarcoma family by nested reverse transcription-polymerase chain reaction.

Tumors of the Ewing's sarcoma family often present a major diagnostic challenge for the pathologist. In recent years, significant progress has been made in identifying characteristic chromosomal rearrangements associated with certain solid tumors. More than 85% of Ewing's sarcoma and related tumors present a specific t(11;22) (q24;q12) balanced translocation, which generates a fusion transcript of the EWS gene and the FLI-1 gene. The cloning of the t(11;22)(q24;q12) breakpoint has raised the possibility of using a reverse transcription-polymerase chain reaction (RT-PCR) based assay as a diagnostic tool. We report an improvement of the established method, which currently depends on fresh or snap-frozen tissue, so that it is possible to use formalin-fixed, paraffin-embedded tissue as a source of RNA. The described nested RT-PCR assay enables the pathologist to investigate retrospectively archival tumor samples or to confirm the diagnosis in cases where no fresh or frozen material is available.

Adult↗
PubMed1996

The Xmrk oncogene promoter is derived from a novel amplified locus of unusual organization.

Hereditary melanoma in Xiphophorus hybrids is caused by the receptor tyrosine kinase Xmrk. Tumor formation is initiated by overexpression of the Xmrk gene, apparently because of insufficient transcriptional control in the melanocytic lineage of hybrid fish. The oncogenic Xmrk resulted from gene duplication and nonhomologous recombination of the corresponding Xmrk proto-oncogene during evolution. By this event Xmrk was translocated downstream of the promoter of another gene, D (for Donor). This raised the question whether both the Xmrk oncogene and D share similar transcriptional control elements. Studies on the genomic organization of D showed that this gene is amplified in the Xiphophorus genome, presumably with all copies clustered on a single chromosome. Surprisingly, at least two completely different, tightly linked genes are included in the amplified segment. We find a ubiquitously expressed zinc finger gene of the krüppel type, followed by a previously unknown gene, which was the partner of the Xmrk proto-oncogene in the recombination generating the Xmrk oncogene. The nucleotide sequence predicts a gene product with very high amino acid similarity to a hypothetical Caenorhabditis elegans protein. The expression pattern is unrelated to that of the Xmrk oncogene suggesting that despite extended sequence homology a new type of promoter was created by this rearrangement.

Amino Acid Sequence↗
PubMed1996

Population and colony structure of the carpenter ant Camponotus floridanus.

The colony and population structure of the carpenter ant, Camponotus floridanus, were investigated by multilocus DNA fingerprinting using simple repeat motifs as probes [e.g. (GATA)4]. The mating frequency of 15 queens was determined by comparing the fingerprint patterns of the queen and 17-33 of her progeny workers. C. floridanus queens are most probably singly mated, i.e. this species is monandrous and monogynous (one queen per colony). C. floridanus occurs in all counties of mainland Florida and also inhabits most of the Key islands in the southern part of Florida. We tested whether the two mainland populations and the island populations are genetically isolated. Wright's FST and Nei's D-value of genetic distance were calculated from intercolonial bandsharing-coefficients. The population of C. floridanus is substructured (FST = 0.19 +/- 0.09) and the highest degree of genetic distance was found between one of the mainland populations and the island populations (D = 0.35). Our fingerprinting technique could successfully be transferred to 12 other Camponotus species and here also revealed sufficient variability to analyse the genetic structure. In three of these species (C. ligniperdus, C. herculeanus and C. gigas) we could determine the mating frequency of the queen in one or two colonies, respectively.

Animals↗
PubMed1996

[Virus titre and histological inflammation activity in chronic hepatitis C].

We determine the correlation between viremia in serum specimens, transaminase activity (ALT and AST) and histological grading in 37 patients with chronic hepatitis C. In addition we compared two PCR methods for hepatitis C virus (HCV)-RNA in serum specimens. For the histological grading we used a modified Knodell score. For detection and quantification we measured the viremia (HCV-RNA titer) with a standardized "nested primer" PCR (end-point dilution method) and the commercially available Amplicor HCV Monitor. The mean HCV-RNA and AST level was significantly higher in patients with a histologically active inflammation. In the individual patient we could not conclude from the titer of HCV-RNA on the histologic grading because of the wide range of the results. We did not find a significant difference in ALT in patients having varying histological gradings. HCV-RNA titer and transaminases (ALT and AST) did not correlate significantly. The HCV-RNA titer was significantly marked in older patients (above 40 years) and patients having sporadic hepatitis than in younger patients and patients with chronic hepatitis after drug abuse. The "nested primer" PCR (end-point dilution method) was more sensitive for detection of HCV-RNA in serum specimens than Amplicor HCV Monitor. The lack of HCV-RNA with Amplicor HCV Monitor in 12 of 37 patients (32%) did not rule out viremia. We conclude that in patients with a chronic hepatitis C marked viremia points to a histologically active inflammation. In the individual patient we could not conclude from the titer of HCV-RNA on the histological grading. Because of the lower sensitivity of Amplicor HCV Monitor it is necessary to confirm negative results with a "nested primer" PCR.

Adult↗
PubMed1996

Polymorphism within the second intron of the IL-1 receptor antagonist gene in patients with hematopoietic malignancies.

Alleles of the IL-1 genes are associated with several autoimmune and inflammatory diseases, where they tend to have a role in the severity of the disease rather than in susceptibility to the disease itself. Allele 2 of the variable number tandem repeat (VNTR) polymorphism in the IL-1 receptor antagonist (IL-1ra) gene was the first marker of the IL-1 cluster to be associated in this way with severity of chronic, systemic and local inflammatory diseases. Because of the role that IL-1 also plays in the pathobiology of certain hematopoietic disorders, we aimed at examining the allelic distribution of the IL-1ra VNTR in leukemias, lymphomas and related malignancies. While in patients with chronic lymphocytic leukemia (CLL), hairy cell leukemia (HCL), multiple myeloma (MM) and related disorders, primary acute myeloid leukemia (AML), chronic myeloid leukemia (CML), and Hodgkin's disease (HD), the allelic distribution of IL-1RN was comparable to that seen in healthy control subjects, in a small group of patients with secondary AML the frequency of the IL-1RN*4 allele appeared to be significantly increased.

Alleles↗