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J Ott

Publications and source records attributed to J Ott.

At least 163 records · Page 9Linked to original sources
PubMed1990

Localizing multiple X chromosome-linked retinitis pigmentosa loci using multilocus homogeneity tests.

Multilocus linkage analysis of 62 family pedigrees with X chromosome-linked retinitis pigmentosa (XLRP) was undertaken to determine the presence of possible multiple disease loci and to reliably estimate their map location. Multilocus homogeneity tests furnished convincing evidence for the presence of two XLRP loci, the likelihood ratio being 6.4 x 10(9):1 in favor of two versus a single XLRP locus and gave accurate estimates for their map location. In 60-75% of the families, location of an XLRP gene was estimated at 1 centimorgan distal to OTC, and in 25-40% of the families, an XLRP locus was located halfway between DXS14 (p58-1) and DXZ1 (Xcen), with an estimated recombination fraction of 25% between the two XLRP loci. There is also good evidence for a third XLRP locus, midway between DXS28 (C7) and DXS164 (pERT87), supported by a likelihood ratio of 293:1 for three versus two XLRP loci.

Chromosome Mapping↗
PubMed1990

Report of a workshop on genetic linkage studies in schizophrenia.

A workshop on genetic linkage studies in schizophrenia was held at Columbia University's Arden House Conference Center in October 1989. This report summarizes the contents of invited talks by Drs. Arno Motulsky and T. Conrad Gilliam and the discussions at the five workshop sessions. Topics of the workshop sessions were (1) diagnostic boundaries and hierarchies in schizophrenia, (2) genetic models and linkage parameters, (3) selection and ascertainment of pedigrees, (4) future extensions of molecular genetics strategies, and (5) possibilities for future collaboration.

Genetic Linkage↗
PubMed1990

The impact of phenotypic variation on genetic analysis: application to X-linkage in manic-depressive illness.

Genetic linkage studies have opened new vistas for behavioral and psychiatric genetics. However, phenotypic diversity and diagnostic uncertainties can lead to spurious linkage findings. A method of analysis is proposed that takes these factors into account. When applied to manic-depressive disease, the results indicate that previous evidence for a major gene localized on the distal long arm of the X-chromosome cannot be ascribed to phenotypic uncertainties and misclassifications, i.e., a type I error. Although the lod score (the logarithm of odds) favoring linkage is reduced with the more restrictive clinical definitions of the phenotype, it remains significant nonetheless. Thus, the linkage finding is robust over a range of phenotypic patterns and presumed phenocopy frequencies. The results also suggest that the X-linked phenotype is a particularly severe form of manic depression characterized by early onset, high familial prevalence of the bipolar form, and high recurrence rate of major depression. These findings may have important implications for the design and interpretation of genetic linkage studies and for refining diagnostic techniques in mental disorders.

Adolescent↗
PubMed1990

Genetic linkage in mental illness. Limitations and prospects.

Advances in genetic linkage strategies, including techniques of molecular genetics, augur well for the discovery of disease-related genes in mental disorders. Recent studies showing linkage of chromosomal loci to bipolar affective illness and schizophrenia attest to the potential in the 'new genetics'. However, the failure to replicate some of the early findings has led to calls for re-evaluation of the methodology in psychiatric research. Problems in studying complex (psychiatric) disorders include diagnostic uncertainties, unclear mode of transmission, aetiological heterogeneity, cohort effects, and assortative mating. Knowing the potential pitfalls in linkage analysis of mental illness should avert spurious findings and will increase the prospects of success.

Genetic Linkage↗
PubMed1990

A54145 a new lipopeptide antibiotic complex: microbiological evaluation.

A54145 complex is made up of eight factors; A, A1, B, B1, C, D, E, and F which were active in vitro (MIC 0.25 approximately greater than 32 micrograms/ml) against Gram-positive aerobic organisms. The complex, factor B and B1 were found to be active against two strains of Clostridium perfringens. A calcium dependence study on some of the factors showed that their in vitro antibacterial activity was greatly enhanced by the presence of calcium (50 mg/liter) in the media. Resistance build-up was seen when Staphylococcus sp. and Streptococcus sp. were passed seven times in the presence of sublethal concentrations of A54145 antibiotics. This resistance disappeared immediately when the resistant organisms were passed in the absence of the antibiotics. Factor A was very effective against Staphylococcus aureus and Streptococcus pyogenes infections in mice (sc ED50s of 3.3 approximately 2.4 mg/kg x 2, respectively). Factor B was more active against S. pyogenes in vivo (sc ED50, 0.9 mg/kg x 2). Acute mouse toxicities were determined with these antibiotics. Semisynthetic derivatives were evaluated.

Amino Acid Sequence↗
PubMed1990

A80915, a new antibiotic complex produced by Streptomyces aculeolatus. Discovery, taxonomy, fermentation, isolation, characterization, and antibacterial evaluation.

New semi-naphthaquinone antibiotics A80915A, B, C, and D were isolated from the fermented broth of Streptomyces aculeolatus A80915 (NRRL 18422). Factors A and C, present in both the broth filtrate and mycelial methanol extract, and factors B and D, found predominantly in the broth filtrate, were recovered by extraction with ethyl acetate. Purification of the individual factors was accomplished by preparative reverse phase high performance liquid chromatograph on C18 bonded silica supports. Factors A through D show antimicrobial activity against Gram-positive aerobic and anaerobic organisms in vitro. Mechanism of action studies demonstrated nearly complete inhibition of macromolecular biosynthesis (protein, RNA, DNA, and cell wall) by A80915 factors A through D. A less highly cyclized semi-naphthaquinone, A80915 factor G, was isolated from the broth of the strain fermented in an alternate medium.

Animals↗
PubMed1990

Huntington disease in Finland: linkage disequilibrium of chromosome 4 RFLP haplotypes and exclusion of a tight linkage between the disease and D4S43 locus.

The question about heterogeneity of Huntington disease (HD) at the DNA level can be approached by analyzing the RFLP haplotypes formed by several RFLP loci of the diseased chromosome in different populations. In genetically isolated populations such as Finland, it is further possible to use this approach to test the hypothesis of a single mutation enriched in this population demonstrating an exceptionally low prevalence of HD. In this study covering 70% of all diagnosed HD cases in Finland, linkage disequilibrium of RFLP haplotypes of D4S10 and D4S43 loci polymorphisms was found. This phenomenon, not so far reported in any other population, could support the hypothesis of one ancestor HD mutation in the Finnish population. Despite the lower heterozygosity obtained with some RFLP markers, the proportion of individuals receiving informative DNA test results did not significantly differ from that reported in more mixed populations. In one HD family we established a recombination event between HD and the D4S43 locus, an event which can be highly useful in the more precise mapping of the HD gene.

Chromosome Mapping↗
PubMed1989

Predisposition to familial osteoarthrosis linked to type II collagen gene.

The genetic background of two families, in whom a predisposition to primary osteoarthrosis is inherited as a dominant trait, was investigated. Use of restriction fragment length polymorphisms within and around the type II collagen gene on chromosome 12 revealed a linkage between this cartilage-specific gene and primary osteoarthrosis.

Adult↗
PubMed1989

Linkage of a prion protein missense variant to Gerstmann-Sträussler syndrome.

Gerstmann-Sträussler syndrome is a rare familial neurodegenerative condition that is vertically transmitted, in an apparently autosomal dominant way. It can also be horizontally transmitted to non-human primates and rodents through intracerebral inoculation of brain homogenates from patients with the disease. The exact incidence of the syndrome is unknown but is estimated to be between one and ten per hundred million. Patients initially suffer from ataxia or dementia and deteriorate until they die, in one to ten years. Protease-resistant prion protein (PrP) and PrP-immunoreactive amyloid plaques with characteristic morphology accumulate in the brains of these patients. Current diagnostic criteria for Gerstmann-Sträussler syndrome incorporate clinical and neuropathological features, as animal transmission studies can be unreliable. PrP is implicated in the pathogenesis and transmission of the condition and in scrapie, an equivalent animal disease. It was discovered by enriching scrapie-infected hamster brain fractions for infectivity. Because there is compelling evidence that the scrapie isoform of PrP is a necessary component of the infectious particle, it seemed possible that the PrP gene on the short arm of human chromosome 20 in Gerstmann-Sträussler syndrome might be abnormal. We show here that PrP codon 102 is linked to the putative gene for the syndrome in two pedigrees, providing the best evidence to date that this familial condition is inherited despite also being infectious, and that substitution of leucine for proline at PrP codon 102 may lead to the development of Gerstmann-Sträussler syndrome.

Chromosome Mapping↗
PubMed1989

Statistical properties of the haplotype relative risk.

In the haplotype relative risk (HRR) statistic (Rubinstein et al.: Human Immunol 3:384 [abstract], 1981), a disease sample is constructed along with its own internal control by comparing those marker alleles passed from the parents to an affected child with the other parental marker alleles not transmitted. Based on the conditional parental genotype distribution given that they have an affected child, statistical properties of the HRR statistic are derived. It is shown that the HRR is different from 1 only when allelic association is present and the recombination fraction is different from 1/2. Transmitted and nontransmitted marker alleles are shown to be statistically independent only in the absence of either allelic association or recombination.

Genetic Diseases, Inborn↗
PubMed1989

Affective disorders: evaluation of a three-allele model accounting for clinical heterogeneity.

The group of major affective disorders is clinically heterogeneous. In the genetic linkage study of the Old Order Amish [Egeland et al., 1987] the same disease gene appears to be responsible for the occurrence in one family of several clinically variant forms of affective disorders. Apparently other genetic or environmental factors determine the clinical presentation of this disease gene. We evaluated a three-allele model where the clinical expression of the disease allele is determined by the other allele at the same locus. In the presence of a proposed modifying allele the disease allele is expressed as major depression, in the presence of the normal (neutral) allele as bipolar disorder (I or II). We applied this model in our analysis of the Old Order Amish data. In analysis of linkage between the locus for affective disorders and two DNA markers on chromosome 11p, we obtained considerably higher likelihood values under the three-allele model than under a comparable two-allele model. Also, lodscores were higher under the three-allele model, with differences in lodscores between both models ranging from 0.95 to 1.34.

Alleles↗
PubMed1989

Haplotype and multipoint linkage analysis in Finnish choroideremia families.

Multipoint linkage analysis of choroideremia (TCD) and seven X chromosomal restriction fragment length polymorphisms (RFLPs) was carried out in 18 Finnish TCD families. The data place TCD distal to PGK and DXS72, very close to DXYS1 and DXYS5 (Zmax = 24 at theta = 0) and proximal to DXYS4 and DXYS12. This agrees with the data obtained from other linkage studies and from physical mapping. All the TCD males and carrier females studied have the same DXYS1 allele in coupling with TCD. In Northeastern Finland, 66/69 chromosomes carrying TCD had the same haplotype at loci DXS72, DXYS1, DXYS4, and DXYS12. The same haplotype is seen in only 15/99 chromosomes not carrying TCD. Moreover, in 71/104 non-TCD chromosomes, the haplotype at six marker loci is different from those seen in any of the 76 TCD chromosomes. This supports the previously described hypothesis that the large Northern Finnish choroideremia pedigrees, comprising a total of over 80 living patients representing more than a fifth of all TCD patients described worldwide, carry the same mutation. These linkage and haplotype data provide improved opportunities for prenatal diagnosis based on RFLP studies.

Choroideremia↗
PubMed1989

Determining informativity of marker typing for genetic counseling in a pedigree.

For the situation of a Mendelian disease linked to a genetic marker, a new method is described that allows evaluating for genetic counseling the information potentially available from the linked marker before the marker data are actually obtained, that is, prior to drawing blood for marker typing. For a consultand in a family pedigree, the method determines the risk distribution (small families) or an approximation to it (larger families) and calculates the probability that the risk will deviate beyond certain limits from its a priori value, which exists without marker data, for example, that the risk will be smaller than 0.10 or larger than 0.90. The method was applied here to a pedigree of 15 individuals for which analytical calculations would be difficult to carry out.

Computer Simulation↗
PubMed1989

Computer-simulation methods in human linkage analysis.

In human linkage analysis, many statistical problems without analytical solution could be solved by ad hoc Monte Carlo procedures were efficient computer-simulation methods available for members of family pedigrees. In this paper, a general method is described for randomly generating genotypes at one or more marker loci, given observed phenotypes at loci linked among themselves and with the markers. The method is based on a well-known expansion of the multivariate probability of genotypes, given phenotypes, into a product of conditional univariate probabilities that may be viewed as corresponding to conditionally independent univariate random variables. This representation allows a recursive evaluation of the univariate probabilities that can be implemented in a surprisingly simple manner by carrying out successive "risk calculations" with respect to marker genotypes, given observed phenotypes and marker genotypes already generated. Potential applications to various unresolved problems are discussed. The method is applied to 28 published families analyzed for genetic linkage between hereditary motor and sensory neuropathy I and the Duffy (FY) blood group locus and confirms heterogeneity of hereditary motor and sensory neuropathy I. An implementation of the simulation methods developed in the LINKAGE program package will be available later in 1989.

Chromosomes, Human↗