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Biomedical subjects

T Reich

Publications and source records attributed to T Reich.

At least 163 records · Page 9Linked to original sources
PubMed1980

An ultrapure germanium detector array for quantitating three-dimensional distribution of a radionuclide: a study of phantoms.

A new stationary 200-element ultrapure germanium (HPGe) array has been tested for accuracy and sensitivity in quantitating the distributed concentration of single-gamma-emitting radionuclides in phantoms approximating the size of the human brain. The phantoms consisted of 42 blocks of 39.1 cm3 average volume. Fourteen different permutations were studied. The concentrations in the blocks varied from 0i to 4.64 muCi/cm3. This first-generation instrument makes it possible to reconstruct the distributed concentration with a mean relative error of 8.3% at 200,000 counts per sample (1,000 counts/detector), and has sensitivities of 6,200 and 12,000 cps, respectively, for 1 muCi/cm3 of Xe-133 and Tc-99. The reconstruction algorithm is based on the conjugate gradient method of solving the set of linear equations that account for geometric, attenuation, and scatter factors. The results have implications for measuring the distribution of the partition coefficients, blood flow, blood volume, and concentration of tracers emitting single gamma photons in 42 anatomic subvolumes (30 cm3 average) of the entire brain simultaneously.

Cadmium↗
PubMed1979

The management of patients with undiagnosed psychiatric illness.

The results of using formal diagnostic criteria on a series of newly admitted inpatients are presented. Several strategies were employed in the management of the undiagnosed patients. The percent of undiagnosed patients significantly decreased with time during the course of hospitalization.

Alcoholism↗
PubMed1979

The use of multiple thresholds and segregation analysis in analyzing the phenotypic heterogeneity of multifactorial traits.

(1) Three models based on multifactorial inheritance are introduced to account for phenotypic heterogeneities. These models are used to determine whether subforms of a triat are: (a) different degrees of the same process, (b) non-familial environmental variants of the same process, and (c) independently transmitted processes. (2) The parameters of each model consist of two population prevalences and either one, two, or three correlation coefficients which reflect the three hypotheses given above. The models are formulated so that a likelihood ratio test may be performed to discriminate between them. (3) The following types of analyses are described: (a) analysis of prevalence data with separate population prevalence estimates, (b) analysis of prevalence data with the proband a parent with specified spouse, (c) analysis of prevalence data with the proband an offspring with specified parents, and (d) the full segregation distribution of families using Complex Segregation Analysis. (4) When compared with the Analysis of Prevalences, Complex Segregation Analysis has the following advantages: (a) the number of degrees of freedom for parameter estimates is greater and separate estimates of the population prevalences are not necessary, (b) standard errors of the parameters are smaller, and (c) the power to discriminate models is increased. (5) Phenotypic heterogeneities such as age of onset, severity, and sex effect can be more completely understood by the methods of analyses described above. The nosology of familial disorders can also be clarified, and environments relevant to the transmission of the trait can be detected. This approach is particularly suitable for the analysis for behavioural traits since it does not require the assumption that environmental effects common to relatives be ignored. (6) Finally, our experience indicates that incorporating both prevalence and pedigree data into a single analysis decreases the time required to perform the analysis.

Environment↗
PubMed1979

Variability in sib pair genetic identity.

Using a realistic model of meiotic crossing over the variability in full sib genetic identity is estimated by simulating 200 independent pairs of sibs. The standard deviation of the percentage of the autosomal genome identical by descent (IBD) was found to be about 0.056. Simulations of sibships larger than size two revealed that the average within sibship standard deviation is between 0.054 and 0.056, thus indicating that sib pair variability is insensitive to the nonindependence structure present when considering all possible sib pairs contained in a large sibship.

Chromosomes, Human↗
PubMed1979

Is juvenile diabetes determined by a single gene closely linked to HLA?

The transmission behavior of insulin-dependent juvenile diabetes mellitus (JDM) has been studied with respect to its frequency in the relatives of JDM probands and its possible linkage to the HLA complex. Mathematical analysis shows that under a single locus hypothesis a very restricted range of incidence rates is possible in the full siblings of probands once the concordance rate in monozygotic (MZ) twins is specified. Specifically, for a given population prevalence of the disease, high concordance rates in MZ twins require high incidence rates in siblings, and low rates require low incidence rates, if a single locus model is th be valid. Moreover, if these rates do conform to a single locus model, then they give additional information about possible linkage between the purported JDM susceptibility gene and the HLA complex. By using observations on the identity by descent scores at the HLA locus of sibling pairs, both of whom are affected with JDM, it is shown that tight linkage of a disease susceptibility locus is possible only when the MZ twin and sibling incidence rates are low, whereas high rates support loose linkage. If the single locus model is rejected, then an alternative hypothesis, involving epistasis between a JDM susceptibility locus and genes in (or close to) the HLA complex can be suggested as a mechanism whereby JDM would appear to be linked to HLA within families while maintaining an association with HLA at the population level.

Diabetes Mellitus, Type 1↗
PubMed1979

Multifactorial inheritance with cultural transmission and assortative mating. II. a general model of combined polygenic and cultural inheritance.

A general linear model of combined polygenic-cultural inheritance is described. The model allows for phenotypic assortative mating, common environment, maternal and paternal effects, and genic-cultural correlation. General formulae for phenotypic correlation between family members in extended pedigrees are given for both primary and secondary assortative mating. A FORTRAN program BETA, available upon request, is used to provide maximum likelihood estimates of the parameters from reported correlations. American data about IQ and Burks' culture index are analyzed. Both cultural and genetic components of phenotypic variance are observed to make significant and substantial contributions to familial resemblance in IQ. The correlation between the environments of DZ twins is found to equal that of singleton sibs, not that of MZ twins. Burks' culture index is found to be an imperfect measure of midparent IQ rather than an index of home environment as previously assumed. Conditions under which the parameters of the model may be uniquely and precisely estimated are discussed. Interpretation of variance components in the presence of assortative mating and genic-cultural covariance is reviewed. A conservative, but robust, approach to the use of environmental indices is described.

Computers↗
PubMed1979

The natural history of acute organic mental syndrome after bilateral electroconvulsive therapy.

Thirty-one patients undergoing electroconvulsive therapy (ECT) were followed prospectively for the development of acute organic mental syndrome (AOMS); 15 patients (48.4%) developed AOMS during ECT. For these 15 patients, the average number of ECTs before development of AOMS was 5.5 with average duration of AOMS being 20.1 days. Comparison of these 15 patients to the 16 patients who did not develop AOMS for diagnoses, demographic data, pre-ECT laboratory data, and medications, differed only in exposure to psychoactive medications and prior presence of major medical illness.

Acute Disease↗
PubMed1979

Multifactorial inheritance with cultural transmission and assortative mating. III. Family structure and the analysis of separation experiments.

Demographic data about family composition or structure in the United States is reviewed. About 25% of white children and a majority of black children are reared in either broken or extended families, and this must be taken into consideration for valid studies of cultural inheritance. Atypical family structures are described including those in which parents include: biological parents, stepparents, grandparents, uncles, aunts, sibs, foster parents, and their spouses. General formulae for a wide variety of kinship correlations are derived using path analysis. The multifactorial model presented allows for cultural inheritance, polygenic inheritance, correlated sibling environments, and phenotypic assortative mating (as previously described for intact families) plus extensions necessary for the analysis of separation experiments. These extensions allow for variable family structure and differences in parental influence due to separation, age or stage of development of the child, birth order, or type of relationship. Family structure is observed to have a marked effect on familial resemblance. Computer simulation studies demonstrate marked heterogeneity among phenotypic correlations for kinships of the same degree of genetic relationship arising in different family structures. Analyses of multiple types of sibs and other relatives in variable family structures offer great promise for the study of cultural inheritance.

Adolescent↗
PubMed1978

Implications of sex differences in the prevalences of antisocial personality, alcoholism, and criminality for familial transmission.

We describe three multifactorial models of disease transmission in which the prevalences of a disease differ in men and women. These models demonstrate explicitly how such sex differences may be caused by genetic factors, home environment, sociocultural, or other nonfamilial factors. Independent sets of family data about antisocial personality and alcoholism in the United States and criminality in Danish twins are analyzed according to these quantitative models. Relevant clinical and adoption data about these disorders are reviewed. The sex differences observed in the development of antisocial personality and of crime appear to be due to familial factors whereas the differences between male and female alcoholics are due to nonfamilial factors. The models and results are discussed in terms of their general implications for testing hypotheses about gender-related differences.

Adolescent↗
PubMed1978

The generalized sib pair IBD distribution: its use in the detection of linkage.

General expression for the distribution of identity by descent (IBD) scores at a marker locus have been derived given neither, one or both sibs affected with a disorder determined by a linked trait locus with arbitrary gene frequency and penetrance vector. It is shown that the distirbution of IBD scores depends only on the additive and dominance variances and the population prevalence of the disorder. A one-sided test is suggested as an appropriate means of statistically testing the hypothesis that the recombination fraction is significantly less than 1/2. This sib pair approach is designed primarily to detect the presence of a critical disease susceptibility locus but when the assumptions of the incompletely penetrant single locus model are correct the methodology proposed here results in consistent estimates of the recombination fraction. The affected sib pair methodology seems especially suited to traits determined by single loci with non-Mendelian transmission.

Alleles↗
PubMed1978

A note on the essential parameters of the two-allele autosomal locus model.

A resolution of the parameter problem for the two-allele autosomal locus (TAAL) model has been presented. It was shown that three are four essential parameters which describe the model, by examination of the joint probability for sibs with specified parental phenotypes. This equation together with previously derived prevalence relationships uniquely specifices all parameters of the model except for the singular case VA = 0.

Alleles↗
PubMed1978

A robust method for the detection of linkage in familial disease.

A nonparametric method for the detection of critical genes associated with familial disease was presented. The method involves the detection of deviations from expected identity by descent distributions at polymorphic marker loci for affected sib pairs. The method thus avoids the difficulties arising from incomplete penetrance, variable age of onset and other complications present in other forms of linkage analysis. The theoretical properties of method were worked out in detail for two important cases -- that of an incompletely penetrant recessive or incompletely penetrant dominant critical autosomal gene linked to a codominant marker locus. An easily implementable decision rule for the detection of linkage was proposed, and its operating characteristics for a variety of alternative hypothesis were obtained.

Genes, Dominant↗