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Biomedical subjects

J H Roger

Publications and source records attributed to J H Roger.

15 recordsLinked to original sources
PubMed1997

Small sample inference for fixed effects from restricted maximum likelihood.

Restricted maximum likelihood (REML) is now well established as a method for estimating the parameters of the general Gaussian linear model with a structured covariance matrix, in particular for mixed linear models. Conventionally, estimates of precision and inference for fixed effects are based on their asymptotic distribution, which is known to be inadequate for some small-sample problems. In this paper, we present a scaled Wald statistic, together with an F approximation to its sampling distribution, that is shown to perform well in a range of small sample settings. The statistic uses an adjusted estimator of the covariance matrix that has reduced small sample bias. This approach has the advantage that it reproduces both the statistics and F distributions in those settings where the latter is exact, namely for Hotelling T2 type statistics and for analysis of variance F-ratios. The performance of the modified statistics is assessed through simulation studies of four different REML analyses and the methods are illustrated using three examples.

Analysis of Variance↗
PubMed1981

The major histocompatibility complex of rhesus monkeys. XIV. A family study of DR and other RhLA-linked cell membrane antigens.

The segregation of B-cell specific (Ia) determinants was studied in a large number of rhesus families. As expected, on the basis of results of a recent population study, the eight serologically defined DR antigens segregated as alleles of a single locus within RhLA. Two or three antigens not controlled by DR remained candidates for a second Ia series closely linked to DR. The 162 identifiable haplotypes provided interesting information regarding positive associations among antigens of two, three or even four sets of RhLA loci. Further, a new series of antigens closely linked to the RhLA-A locus could be postulated. Data obtained from 8 recombinant offspring permitted a better definition of the mapping position of all known loci of RhLA.

Animals↗
PubMed1980

The major histocompatibility complex of rhesus monkeys. XIII. Current knowledge of DR and other B-cell specific antigens.

Results of a population study with all currently available B-cell specific alloantisera indicate that eight antigens controlled by the RhLA-linked DR locus can now be identified. This leaves a gene frequency of about 0.15 for unidentified or "blank" antigens of that locus. Of the nine identifiable Ia antigens which are not controlled by the DR locus, three or four may form the basis of a second series which is probably also controlled by the RhLA region.

Animals↗
PubMed1979

A two-locus model for the inheritance of a familial disease.

A model for the inheritance of a disease involving genes at just two linked loci is presented and discussed. One of the two pairs of opposite double homozygotes is assumed to lead to the disease and death. The other genotypes are assumed to be less fit than the double heterozygote. The cause of this reduced fitness may or may not be due to the disease. Conditions for the existence of a stable equilibrium are presented. The model has a sound biological basis and could be used to explain a wide range of disease frequencies and patterns of inheritance. Mutation is not required to explain why the disease persists in the population. Recurrence risks for sibs and twin concordance rates are derived and the consequences of the relaxation of selection against those with the disease are predicted. The effects of a selection model of the kind described on the amount of linkage disequilibrium in the population and on the estimation of the frequency of recombination are discussed.

Chromosome Mapping↗
PubMed1978

The major histocompatibility complex of Rhesus monkeys IX. Current concepts of serology and genetics of Ia antigens.

Eleven Ia or B-cell specificities of rhesus monkeys have been serologically identified. They are probably all controlled by the RhLa complex, but, according to results of a large population and family study, only five or six can be placed in a segregant series, designated as Ia1. Data from recombinant offspring in two rhesus families place the Ia1 locus in the close vicinity of the D or major MLC locus within RhLA. The genetic control of the Ia antigens not defined by the Ia1 locus has not yet been clarified.

Animals↗
PubMed1978

The major histocompatibility complex of chimpanzees: identification of several new antigens controlled by the A and B loci of ChLa.

The serology and genetics of 17 serologically defined tissue antigens of chimpanzees is described. Analysis of their distribution in 200 unrelated chimpanzees and their segregation in a large number of chimp families suggests that 14 of the antigens are controlled by two closely linked loci: seven by the A and seven by the B locus of ChLA. Typing of chimpanzees with human alloantisera revealed that several of those A and B locus antigens of ChLA are the chimp's serological counterparts of A and B locus antigens of the human HLA system, respectively. One of the newly discovered chimp antigens may be defined by a "third series" of ChLA, most likely the chimp's analogue of the human HLA-C series. The probable existence of a ChLA-linked D locus of chimpanzees and similarities between D-locus and Ia-locus (DRw) antigens of chimpanzee and man, are also briefly discussed.

Animals↗
PubMed1977

Differential kidney graft survival associated with interaction between recipient ABO group and pretransplant blood transfusion.

In 1973 we reported significantly superior survival of kidneys transplanted to blood group O recipients compared with recipients of those from blood groups A, B, and AB taken together. In this extended series, the difference between these categories was less prominent and no longer significant. In the present study, blood transfusion significantly improved the survival of kidney grafts in patients of blood group O, but not of combined A, B. and AB groups. The difference between the graft protecting effect of transfusion in group O and combined groups A, B, and AB recipients was also significant. This suggests that the improvement in subsequent graft survival after transfusion is either confined to blood group O recipients, or is much stronger in them than in recipients of other groups. Our previous policy of restriction of blood transfusion is seen as one of the causes of the reduced superiority of group O over other groups in this extended series in comparison with our 1973 series. It seems that transfusion of group O recipients can markedly improve the prognosis of a subsequent first kidney graft.

ABO Blood-Group System↗
PubMed1977

The major histocompatibility complex of rhesus monkeys, RhL--A. VII. Identification of five new serologically defined antigens.

Five new serologically defined (SD) tissue antigens of rhesus monkeys are described. Results of a population study and a segregation analysis in families were consistent with their control by the major histocompatibility complex (MHC), as alleles of the two previously established SD loci of RhL--A. The number of identifiable SD specificities of the rhesus monkeys' MHC is now twenty-five, thirteen controlled by the SD1 locus and twelve by SD2. The recombination frequency between SD1 and SD2 is estimated to be 0.3%. No evidence of a third SD series, as analogue of the human HLA--C locus, has yet been found.

Animals↗
PubMed1977

Parallel studies of HLA antigens in patients with rheumatic heart disease and scleritis: comparisons with three control populations.

Parallel studies were carried out on HLA antigens in patients with rheumatic heart disease and scleritis. Comparison with one control population showed a significant excess of BW15 in both disease samples, while a comparison with two other control populations, showed the excess not to be significant. Possible reasons for this discrepancy are discussed, together with the effect on statistical significance of a small percentage of false antigen assignments in one of the samples. A small systematic serological false assignment of an antigen can, by itself, produce a significant result more easily if the frequency of the antigen being detected is low than if it is high. It is suggested that this effect may contribute to the discrepant significant results obtained by different workers in some HLA and disease studies.

Eye Diseases↗
PubMed1976

HL-A antigens in patients with guttate psoriasis.

Tissue typing was performed on lymphocytes of sixty-two patients with guttate psoriasis, in forty-four of whom this was the first manifestations of the disease. In 84% of cases, the guttate psoriasis was preceded by a clinical infection. A highly significant excess of antigen W17 (HLA-BW17) was found in patients when compared with healthy population. In common with some other studies antigens HL-A13 (HLA-B13), W15 (HLA-BW15) and W21 (HLA-BW21) were found in excess but these became non-significant after correction for the number of antigens studied. 68% of patients who had guttate psoriasis de novo, subsequently developed persistent plaque psoriasis.

HLA Antigens↗
PubMed1976

The major histocompatibility complex of rhesus monkeys. VI. Serology and genetics of Ia-like antigens.

The serology and genetics of11 new cell surface alloantigens of rhesus monkeys are described: They are controlled by the mamor histocompatibility complex but are distinct from the conventional serologically defined (SD) antigens ofRhL-A. The new specifications are termed "Ia-like" because ofserological, immunocytological and other characteristics reminiscent of Ia-antigens of the mouse. Population and family analyses led to the postulation of two segregant series controlling eight of the 11 Ia-like specificities of the monkey. Strong linkage disequilibria with SD2 antigens and genetic mapping on the basis of segregation studies in recombinant offspring in the monkey families, places at least one of the two loci in the vicinity of the SD2 locus of RhL-A, not in the region of the major MLC or LD1 locus. For this and other reasons, the new B-cell alloantigens of rhesus monkeys are not believed to be similar to or associated with the stimulator antigens of LD1. The biological function(s) of the Ia-like antigens of primates are as yet unknown.

Alleles↗