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Biomedical subjects

D F Roberts

Publications and source records attributed to D F Roberts.

At least 19 recordsLinked to original sources
PubMed2000

Media and youth: access, exposure, and privatization.

PURPOSE: To describe U.S. youth's access and exposure to the full array of media, as well as the social contexts in which media exposure occurs. METHODS: A cross-sectional national random sample of 2065 adolescents aged 8 through 18 years, including oversamples of African-American and Hispanic youth, completed questionnaires about use of television, videotapes, movies, computers, video games, radio, compact discs, tape players, books, newspapers, and magazines. RESULTS: U.S. youngsters are immersed in media. Most households contain most media (computers and video game systems are the exception); the majority of youth have their own personal media. The average youth devotes 6 3/4 h to media; simultaneous use of multiple media increases exposure to 8 h of media messages daily. Overall, media exposure and exposure to individual media vary as a function of age, gender, race/ethnicity, and family socioeconomic level. Television remains the dominant medium. About one-half of the youth sampled uses a computer daily. A substantial proportion of children's and adolescents' media use occurs in the absence of parents. CONCLUSIONS: American youth devote more time to media than to any other waking activity, as much as one-third of each day. This demands increased parental attention and research into the effects of such extensive exposure.

Adolescent↗
PubMed1997

The founding mitochondrial DNA lineages of Tristan da Cunha Islanders.

Genealogical histories show that the inhabitants of Tristan da Cunha are derived from a known number of founders. Using the transmission of mitochondrial DNA (mtDNA) from mother to offspring pairs, we traced the mtDNA types found in 161 extant individuals to five female founders. Although the historical data claimed that two pairs of sisters were among the founding females, mtDNA data showed support for only one pair of sisters. We also studied the fidelity of mtDNA transmission in conjunction with the genealogical data. We did not detect any mutations from 698 base pairs of sequence data from 75 individuals, which together accounted for 108 independent transmissions of mtDNA from mother to offspring. Based on this observation, we estimate that the mtDNA mutation rate is no more than one new mutation every 36 transmissions. These results indicate a high fidelity of maternal mtDNA transmission and support the utility of mtDNA in evolutionary and forensic studies.

DNA, Mitochondrial↗
PubMed1997

Application of HLA class II polymorphism analysis to the study of the population structure of the Island of Krk, Croatia.

The population structure of the northern Adriatic island of Krk, Croatia, was studied using PCR methodology and nonradioactive oligonucleotide hybridization for the analysis of HLA-DRB1, DRB3, DRB4, DRB5, DQA1, and DQB1 polymorphisms. Allele frequencies, genetic kinship (R), and genetic distances (E2) were computed, and correlations between distance (genetic, linguistic, geographic) and kinship (migration) matrices were examined. The results, reflecting past (micro-) evolutionary processes, indicate that ethnohistorical and sociocultural events rather than geographic distances are the primary determinants of today's population structure of the island.

Adult↗
PubMed1996

Reduced expression of HLA-B35 in schizophrenia.

The frequencies of HLA class I (HLA-A, B, C) and class II (HLA-DR, DQ) antigens were measured in 107 unrelated schizophrenic subjects and the results compared with 264 controls from south-east Scotland and a second control group of 133 individuals from north-east England. The expression of HLA-B35 was significantly reduced in the schizophrenic population compared to both control populations and these differences remained significant after correction for multiple testing. Linkage of schizophrenia and the major histocompatibility complex region of chromosome 6p was, however, excluded in a group of 17 families multiply affected with schizophrenia. Linkage was also excluded with several red cell antigens, red cell enzymes and plasma proteins. A negative association between the frequency of an HLA antigen and schizophrenia suggests that immune mechanisms may contribute to the aetiology of the disease in some subjects.

Adolescent↗
PubMed1994

Age at menarche.

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Age Factors↗
PubMed1994

Serogenetic analysis in the study of the population structure of the eastern Adriatic (Croatia).

The anthropogenetic structure of six island and peninsular populations (Brac, Hvar, Korcula, Peljesac, Silba, and Olib) of the eastern Adriatic, Croatia, is analyzed on the basis of the study of four different erythrocyte antigen systems or groups (ABO, Rhesus, Kell-Celano, P) and two erythrocyte isoenzyme systems (ACP, ESD). The average sample size was 555 individuals. Allele frequencies, genetic distances, and gene diversity values were computed. The results indicate that all the populations in question have preserved their separate characteristics over the course of their (micro)evolution to the present day; this is especially noticeable for the island populations of Korcula and Olib, as these are distinguished from the other four populations by a greater degree of isolation. Today's genetic structure of the six populations can be explained through the existing historical and cultural data for the region in question, which indicate that over the course of their ethnohistory they were all influenced by significant waves of immigration and selective emigrations that must have greatly shaped their present-day population structure.

Alleles↗
PubMed1993

Menarcheal age in University of Warwick young women.

Data from the final 16 years of a 28-year ongoing survey of menarcheal age are reported. From 1971 onwards, recalled aged at menarche was recorded for all young women entering the University of Warwick. These data show that mean menarcheal age is increasing, a trend which is independent of father's occupation, family size, position of girl in the family, and physique. This continues a similar upward tendency noted in a preceding study in Swansea. It appears that the downward trend to earlier age at menarche of the earlier decades of this century has been replaced by one in the opposite direction.

Adolescent↗
PubMed1992

Social class and diachronic trends in physique in young university women.

In a large sample of female students admitted to the University of Warwick in the period 1971-86, physique as measured by height, weight and ponderal index was examined in relation to family variables and socioeconomic class. Stature and weight both show a secular tendency to increase, and there is no indication of any slowing of rate. The different social classes do not participate equally in these trends, in a way that is difficult to reconcile with the attribution of the diachronic changes to simple improvement in environmental conditions. Maternal competence is suggested as a possible factor in the pattern of class difference.

Adolescent↗
PubMed1992

P blood group phenotype, proteus antibody titres, and rheumatoid arthritis.

The interrelationships between P blood group phenotype, proteus antibodies and rheumatoid arthritis (RA) were investigated in 140 patients with RA and 114 of their siblings who did not have RA. In the group with RA P2 subjects had significantly higher titres of proteus antibodies than P1 patients. This was not observed in the group without RA, or for antibodies to Escherichia coli. Although C reactive protein was the best predictor of proteus antibodies in the group with RA, the P blood group had an independent and significant influence. These observations suggest a testable model in which asymptomatic carriage of proteus in the urinary tract may lead to antibody production, which in turn may be important in the pathogenesis of RA.

Acute Disease↗
PubMed1992

Contribution of inherited factors to rheumatoid arthritis.

A total of 231 sibships of the same sex (186 female, 45 male), in which the proband had classical or definite rheumatoid arthritis (RA) have been selected from rheumatology clinics. Each sibship member was questioned about symptomatic joints, which were then examined. Hospital records, radiographs, and rheumatoid factor measurements allowed each sibling to be classified as having classical, definite, probable, or no RA. Each sibling was typed for HLA-A and B and was classified as sharing two, one, or zero HLA haplotypes with the proband. Concordance rates for classical and definite RA were three times greater in sibships of women than of men (9.3 v 3.0%). Concordance rates in HLA identical sibships were twice those in hemi- and non-identical sibships (15.5, 7.1, and 5.2%, respectively). Probable RA was more common in male and HLA hemi- and non-identical sibships. These results suggest that female sex and the two inherited HLA haplotypes are important for the presence and expression of RA. Although environmental factors may be shared more in twins than siblings, a concordance rate of 20.5% in seropositive HLA identical sibships of the same sex compared with 30% in monozygotic twins suggests that sex and HLA type account for about two thirds of the inherited risk of RA.

Arthritis, Rheumatoid↗
PubMed1992

Effect of disease severity on rheumatoid arthritis concordance in same sexed siblings.

To assess the factors in a proband with rheumatoid arthritis (RA) that might predict the occurrence of the disease in siblings, 240 same sexed sibships (190 female, 50 male) in which the proband had classical or definite RA were clinically and immunologically documented. Sibship concordance rates were consistently higher for features of severe disease in the proband, reaching statistical significance for a clinical score of disease severity (the SS index). This trend for increasing disease severity to be associated with increasing sibship concordance rates could not be accounted for by age or disease duration of the proband. These results suggest that siblings of probands with severe RA are at greater risk of developing RA than those of probands with mild disease.

Age Factors↗
PubMed1991

Population variation in molecular polymorphisms of the short arm of the human X chromosome.

Five DNA probes (RC8, 754, XJ 1-1, pert 87.8, and L1.28) from the short arm of the human X chromosome were investigated in samples from five populations (English, Nigerian, Chinese, Muslim, and Hindu from India). The variation in the allele frequencies of several probes between different groups was significant. The average heterozygosity in females of the five populations ranged from 32% to 51%. The genetic distance between the five groups was compatible with that using traditional polymorphic systems. There is an interesting suggestion of longitudinal cline for allele *2 (9 kb) detected with probe L1.28. The X-linked RFLPs are useful genetic markers for anthropological studies.

Alleles↗
PubMed1991

Consanguinity and multiple sclerosis in Orkney.

For all patients with multiple sclerosis in Orkney who were alive in 1974 or who had died during 1958 to 1974, pedigree data were analysed. The relationship between their parents, expressed by kinship coefficients, was compared with that between parents of matched controls. The closer relationship between parents of patients suggests that it is the genes that are shared by a patient's parents, and that he inherits from both, that influence his susceptibility to multiple sclerosis.

Consanguinity↗
PubMed1991

Genetic epidemiology of Down's syndrome in Shetland.

Pedigrees of all known cases, on Shetland, of Down's syndrome, cytogenetically confirmed as trisomy 21, and of a control for each patient matched by birth date, sex and birth place, were traced over a minimum of eight generations. Mean kinship coefficients in all pairs of Down's syndrome patients and in all pairs of controls were similar. The kinship between the father and mother of each case shows that the parents are more closely related than the general level of relationship in the population, suggesting some recessive element in the etiology. It is argued that the effect of the resulting increased homozygosity would be to prevent the loss of the conceptus that occurs in the majority of trisomy 21 conceptions.

Adult↗
PubMed1991

Factor B (BF) allotypes and multiple sclerosis in north-east England.

A significant decrease in the frequency of BF*F allele and an increase of BF*F1 allele was found in 101 clinically definite multiple sclerosis patients compared to 270 normal controls from North-East England. In Dw2 types 41 patients and 60 controls, only the rare allele BF*F1 showed a significant increase in the patients group. For the common BF*S allele a significant increase was found in Dw2+ patients compared to the Dw2- patients, but a slight similar increase observed in Dw2+ controls did not attain significance. This increase in the patient group is attributed to a strong linkage disequilibrium between BF*S and Dw2 alleles. No such linkage disequilibrium exists in the normal controls. There is a suggestion that the BF*S and Dw2+ alleles are more prevalent in chronic progressive patients, implying that in Dw2+ patients BF may influence the progression of the disease.

Alleles↗
PubMed1991

Autosomal dominant inheritance of autoantibodies to thyroid peroxidase and thyroglobulin--studies in families not selected for autoimmune thyroid disease.

Recently the tendency to produce autoantibodies to thyroid peroxidase (TPO Ab) and thyroglobulin (Tg Ab) was shown to be inherited as an autosomal dominant characteristic in women but not in men. Because of potential bias in this study which was carried out in families with autoimmune thyroid disease (AITD), the inheritance of thyroid autoantibodies has been evaluated in 49 families unselected for autoimmune thyroid disease. Among these families (24 with facioscapulohumeral disease, 10 with Friedreich's ataxia, and 15 with schizophrenia) the prevalences of TPO Ab and Tg Ab were 27.8% and 26.7%, respectively, in women and 9.2% and 11.7%, respectively, in men. In 40 families where one or more individual had TPO Ab and/or Tg Ab, segregation analysis showed that the tendency to make antibodies was consistent with a Mendelian dominant trait in women but not in men. In young women, however, the prevalence of both TPO Ab and Tg Ab increased with age, rising from 14% and 10%, respectively, at age 15-24 to 35% and 40% at age 35-44. As this is inconsistent with a simple dominant hypothesis, a further segregation analysis by age was carried out in the families unselected for thyroid disease together with 16 pedigrees with AITD previously studied and two additional large AITD families. The results of the combined analysis provided strong support for the hypothesis of dominant inheritance but also showed significant reduction in gene expression among women aged 15-24 yr.

Adolescent↗