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Biomedical subjects

M C King

Publications and source records attributed to M C King.

At least 19 recordsLinked to original sources
PubMed1992

The gene for an inherited form of deafness maps to chromosome 5q31.

Primary--i.e., nonsyndromal-postlingual deafness is inherited as an autosomal dominant phenotype in a large kindred in Costa Rica. Genetically susceptible individuals begin to lose hearing at low frequencies at about age 10 years, after language and speaking are learned. Deafness inevitably progresses by age 30 years to bilateral hearing loss of all frequencies. Intelligence, fertility, and life expectancy are normal. The family traces its ancestry to an affected founder born in Costa Rica in 1754. We have mapped the gene for deafness in this kindred to chromosome 5q31, between the markers IL9 and GRL, by linkage analysis involving 99 informative relatives.

Base Sequence↗
PubMed1992

Identifying individuals by sequencing mitochondrial DNA from teeth.

Mitochondrial DNA (mtDNA) was extracted from teeth stored from 3 months to 20 years, including teeth from the semi-skeletonized remains of a murder victim which had been buried for 10 months. Tooth donors and/or their maternal relatives provided blood or buccal cells, from which mtDNA was also extracted. Enzymatic amplification and direct sequencing of roughly 650 nucleotides from two highly polymorphic regions of mtDNA yielded identical sequences for each comparison of tooth and fresh DNA. Our results suggest that teeth provide an excellent source for high molecular weight mtDNA that can be valuable for extending the time in which decomposed human remains can be genetically identified.

Base Sequence↗
PubMed1992

Genetic risk factors for perinatally acquired HIV-1 infection.

This study evaluates genetic influence on susceptibility to perinatal HIV-1 infection among 106 Black infants from New York and San Francisco born to mothers infected with HIV-1. Genes tested by molecular techniques are HLA class II loci DRB1, DPB1 and DQA1; HLA class III loci complement C4A and C4B; alpha and beta interferons; and the constant region of the T-cell receptor beta chain. Of the 106 infants analysed, 54 are infected with HIV and 52 remain uninfected at age 15 months and older. Genotypes in the HLA region appear to influence risk of HIV infection. Specifically, infants with the amino acid sequence -asp-glu-ala-val- at DPB1 positions #84-87 are more likely to be infected (P = 0.001) and infants with the allele DQA1*0102 are less likely to be infected (P = 0.031). Combinations of these two risk factors show a strong dose response (P = 0.0005). HLA DPB1 and DQA1 may play a direct role in immune response associated with HIV-1 infection, or the critical region may be located between these two genes. Characterisation of other class II HLA genes in these infants will allow more precise determination of the role of HLA loci in susceptibility to HIV-1 infection.

Alleles↗
PubMed1992

The influence of social and political violence on the risk of pregnancy complications.

BACKGROUND: Events in Chile provided an opportunity to evaluate health effects associated with exposure to high levels of social and political violence. METHODS: Neighborhoods in Santiago, Chile, were mapped for occurrences of sociopolitical violence during 1985-86, such as bomb threats, military presence, undercover surveillance, and political demonstrations. Six health centers providing prenatal care were then chosen at random: three from "high-violence" and three from "low-violence" neighborhoods. The 161 healthy, pregnant women due to deliver between August 1 and September 7, 1986, who attended these health centers were interviewed twice about their living conditions. Pregnancy complications and labor/delivery information were subsequently obtained from clinic and hospital records. RESULTS: Women living in the high-violence neighborhoods were significantly more likely to experience pregnancy complications than women living in lower violence neighborhoods (OR = 5.0; 95% CI = 1.9-12.6; p less than 0.01). Residence in a high-violence neighborhood was the strongest risk factor observed; results persisted after controlling for several sets of potential confounders. CONCLUSION: Living in areas of high social and political violence increased the risk of pregnancy complications among otherwise healthy women.

Adult↗
PubMed1992

Heterogeneity analysis of breast cancer families by using age at onset as a covariate.

An extension of the usual mixture model of heterogeneity (two family types, one with and one without linkage) is proposed by introducing age at onset as a covariate. The extended model defines age-dependent penetrances where the exact parametrization of age-at-onset distributions depends on the given genotype and family type (linked or unlinked). This extension was applied to breast cancer families. We postulated that the mean age at onset in individuals affected by the linked gene was lower than the mean age at onset in all other affected individuals. Linkage heterogeneity for breast cancer families was detected at a significance level of .003.

Adult↗
PubMed1992

Linkage of familial breast cancer to chromosome 17q21 may not be restricted to early-onset disease.

Lod scores for linkage between familial breast and ovarian cancer and markers on chromosome 17q21 are more frequently positive among families with disease diagnosed at younger ages than they are among older-onset families, suggesting that linkage is restricted to early-onset disease. However, for late-onset cases, the relative probability of sporadic rather than inherited disease is higher than previously suggested. If this correction is made, then later-onset families are much less informative; linkage heterogeneity based on age at onset is no longer significant; and for the sample of families as a whole, linkage is significant at a recombination fraction since demonstrated to be close to the correct local. There is probably more than one gene for inherited breast cancer, but heterogeneity may not be due to age at disease onset.

Adult↗
PubMed1992

Closing in on a breast cancer gene on chromosome 17q.

Linkage of early-onset familial breast and ovarian cancer to 11 markers on chromosome 17q12-q21 defines an 8-cM region which is very likely to include the disease gene BRCA 1. The most closely linked marker is D17S579, a highly informative CA repeat polymorphism. D17S579 has no recombinants with inherited breast or ovarian cancer in 79 informative meioses in the seven families with early-onset disease (lod score 9.12 at zero recombination). There is no evidence for linkage heterogeneity in the families with early-onset disease. The proportion of older-onset breast cancer attributable to BRCA 1 is not yet determinable, because both inherited and sporadic cases occur in older-onset families.

Base Sequence↗
PubMed1991

Chromosome 1 Charcot-Marie-Tooth disease (CMT1B) locus in the Fc gamma receptor gene region.

The Charcot-Marie-Tooth disease (hereditary motor and sensory neuropathy) loci have been reported to be on at least three chromosomes: 1 (CMT1B, HMSN1B), 17 (CMT1A), and X (CMTX). In this study multipoint linkage analysis of two Duffy-linked families given a combined LOD score of 8.65 to establish that the Duffy-linked CMT1B gene exists in the 18 centimorgan region between the antithrombin III gene and the Duffy/sodium-potassium ATPase loci. The simultaneous segregation of polymorphisms near the CMT1A locus on chromosome 17 excludes linkage to this chromosome region in both families. Polymorphic sites that flank the CMT1B gene have been subchromosomally localized to the proximal chromosome-1 long arm (1q21.2----1q25) by spot blot analysis of sorted chromosomes, polymorphic deletion analysis, in situ hybridization, and multipoint linkage analysis.

Antigens, Differentiation↗
PubMed1991

Complex segregation analysis of primary hepatocellular carcinoma in Chinese families: interaction of inherited susceptibility and hepatitis B viral infection.

Primary hepatocellular carcinoma (PHC) is extremely common in eastern China, where it is both associated with chronic infection with hepatitis B virus (HBV) and often familial. Complex segregation analysis of 490 extended families was undertaken with liability classes defined by age, sex, and HBV infection status. The maximum-likelihood model suggests that a recessive allele with population frequency approximately .25 yields lifetime risk of PHC, in the presence of both HBV infection and genetic susceptibility, of .84 for males and .46 for females. The model further predicts that, in the absence of genetic susceptibility, lifetime risk of PHC is .09 for HBV-infected males and .01 for HBV-infected females and that, regardless of genotype, it is virtually zero for uninfected persons. Complex segregation analysis therefore provides evidence for the interaction of genotype, environmental exposure, sex and age in determining the occurrence of PHC in this population.

Carcinoma, Hepatocellular↗
PubMed1979

Laterality of breast cancer in families.

A new method for analyzing concordance for a binary variable in extended pedigrees was developed to study tumor laterality in families with high incidence of breast cancer. It was found that related breast cancer patients in 15 high-risk Midwestern US families did not have their tumors on the same side more frequently than would be expected by chance. This finding is in contrast to previous studies in London and Denmark that reported a significant concordance for tumor laterality in related breast cancer patients. This result may reflect an increasing incidence of sporadic breast cancer in genetically susceptible families or, alternatively, independent determination of cancer susceptibility and tumor laterality.

Adult↗
PubMed1978

Cholecystokinin cholecystography in the diagnosis of acalculous extrahepatic biliary tract disorders.

Cholecystokinin cholecystography represents a study designed to identify patients with acalculous extrahepatic biliary tract disorders. In this study, a positive cholecystokinin cholecystogram (CCK-GB) was defined as both reproduction of the patient's biliary tract-type pain plus one or more of various roentgen abnormalities. Using these criteria, 20 patients had a positive CCK-GB. After failure of medical management, 19 of these patients came to surgery. Seventeen of 18 available for follow-up were cured of their biliary tract pain by surgery. Follow-up of this group of patients has ranged from one month to 60 months. In view of our findings plus those in other reported series, we conclude that CCK-GB provides a reliable study for the diagnosis of acalculous extrahepatic biliary tract disorders.

Adolescent↗
PubMed1977

Genetic markers and cancer epidemiology.

The study of potential associations between genetic markers and various cancers has a long history in cancer epidemiology. Such investigations are subject to serious problems of statistical significance and the choice of appropriate control populations. A promising future for the use of human population genetics in cancer epidemiology may be in the investigation of genetic markers (such as the HL-A complex) which code for proteins of potential immunological or physiological importance in susceptibility or resistance to cancer. The cerumen gentic marker has played a central part in a hypothesis formulated in our laboratory for the etiology of breast cancer. A second new development in this field is likely to be the investigation of genetic markers in families with high incidence of cancer. Such families permit the simultaneous study of genetic hypotheses of cancer inheritance and the association of marker genotypes with cancer through segregation and linkage analysis.

ABO Blood-Group System↗
PubMed1977

Classifying intergral stimuli.

Two reported experiments support holistic, as opposed to analytic, processing models for integral stimuli. Speeded classification data from different information-processing tasks (univariate and correlated) were predicted by distance between stimuli in similarity space but not by redundancy. The results of the filtering and condensation tasks and the notion of configural stimuli are also explicable in these terms. It is shown that some operational definitions commonly used to define integral stimuli are usually confounded with stimulus similarity. The assumption of independence between the attributes that combine to form multidimensional stimuli is not always met and is always an empirical question. When these attributes are not independent, physical and psychological spaces are not necessarily the same. Similarity structure is a crucial concern if inferences of cognitive processing are to be based on information-processing task results.

Association↗
PubMed1977

New data on glucose-6-phosphate dehydrogenase deficiency in Saudi Arabia. G6PD variants, and the association between enzyme deficiency and hemoglobins S.

67/369 male Saudi subjects (18%) were found to be G6PD deficient on screening, and electrophoresis of blood samples stored on filter paper strips revealed B-like variants with intermediate enzyme activityin 11%, presumed Mediterranean variant in 13%, Gd + (A+) in 2%, Gd--(A--7) in 0.8%, and indeterminate enzyme status in 6% of the subjects tested. A significant association between G6PD deficiency and hemoglobin S correlated with previous studies on similar samples from the general population.

Adolescent↗