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At least 253 records · Page 14Linked to original sources
PubMed2001

Oligodendrogliomas: clinical and genetic correlations.

Oligodendrogliomas, once obscure, are now recognized as a relatively common form of primary brain tumour, and are among the most chemosensitive of all solid human malignancies. New histopathological, molecular, and genetic information has, for the first time, allowed the distinction of several subtypes of human glioma with predictable biological and clinical behaviour. Genetic markers are emerging as useful not only for the diagnosis of oligodendroglioma, but also as specific predictors of both the response to treatment and prolonged survival. This review will focus upon the past year of advances in the area of clinical-molecular genetic predictors of glioma behaviour and highlight the importance of these advances in everyday clinical practice.

Antineoplastic Agents↗
PubMed1996

[Charcot-Marie-Tooth syndrome. Clinico-genetic correlation in an affected family].

Hereditary motor and sensory neuropathy (HMSN) is one of the most frequently inherited causes of peripheral neurological disability. To date, the classification has been based on clinical, histological and genetic grounds. Due to increased genetic knowledge at the molecular level in recent years, diagnosis of the different subtypes has been considerably improved and their relationship clarified. We describe three generations of a family with HMSN IA (Charcot-Marie-Tooth disease IA = CMT 1A) with a genetic defect mapped to chromosome 17 and show the importance of genetic testing. Even in benign and clinically non-manifested causes of the disease, an early and non-invasive diagnosis should be made by genetic testing to identify affected persons; thus, nerve biopsy can be abandoned. Operations of pes cavus, which are not indicated and are often complicated by delayed healing, may be avoided. Instead, patients should undergo early physiotherapy and be counselled about their professional careers and family planning.

Adult↗
PubMed1999

Genetic correlations in mutation processes.

We study the role of phylogenetic trees on correlations in mutation processes. Generally, correlations decay exponentially with the generation number. We find that two distinct regimes of behavior exist. For mutation rates smaller than a critical rate, the underlying tree morphology is almost irrelevant, while mutation rates higher than this critical rate lead to strong tree-dependent correlations. We show analytically that identical critical behavior underlies all multiple point correlations. This behavior generally characterizes branching processes undergoing mutation.

Genetics↗
PubMed1982

The inheritance and genetic correlation of tyrosine hydroxylase activities in the substantia nigra and corpus striatum in the C x B recombinant inbred mouse strains.

In mouse, strain differences in the activity of tyrosine hydroxylase (TH) in ventral midbrain dopamine systems of substantia nigra-A10 (SN) region of mouse brain and in a terminal field, the striatum (CS), can be entirely attributed to variations in the number of dopaminergic neurons2. To obtain further information about the complexity of the genetic systems influencing phenotypes for regional TH activity, we examined TH activity in the SN and CS of 7 recombinant inbred (RI) mouse strains, their progenitor strains (BALB/cBy and C57BL/6By), their reciprocal F1 hybrids and a CB6F2 segregating generation. Genetic analysis indicated that TH activity in both brain regions seems unlikely to be controlled by single gene effects. However, the mode of inheritance is presumably not very complex. Estimates of the degree of genetic determination for TH activity in SN and CS were relatively high with significant and positive correlations with respect to either the RI lines (r = 0.82) or the CB6F2 generation (r = 0.53). These positive correlations suggest that some of the genes of two gene sets influencing TH activities in the SN and CS are the same. However, additional non-shared genes may also be present. Assuming that our two measures reflect the number of dopaminergic neurons in SN-A10 area and density of their processes in corpus striatum, our results lead us to the hypothesis that the number of dopaminergic neurons and the axonal arborization of these neurons in the nigrostriatal system are in part under a common genetic control but that other genes may contribute to branching of SN neurons.

Animals↗
PubMed2003

The devil in the details of life-history evolution: instability and reversal of genetic correlations during selection on Drosophila development.

The evolutionary relationships between three major components of Darwinian fitness, development rate, growth rate and preadult survival, were estimated using a comparison of 55 distinct populations of Drosophila melanogaster variously selected for age-specific fertility, environmental-stress tolerance and accelerated development. Development rate displayed a strong net negative evolutionary correlation with weight at eclosion across all selection treatments, consistent with the existence of a size-versus-time tradeoff between these characters. However, within the data set, the magnitude of the evolutionary correlation depended upon the particular selection treatments contrasted. A previously proposed tradeoff between preadult viability and growth rate was apparent only under weak selection for juvenile fitness components. Direct selection for rapid development led to sharp reductions in both growth rates and viability. These data add to the mounting results from experimental evolution that illustrate the sensitivity of evolutionary correlations to (i) genotype-by-environment (G x E) interaction, (ii) complex functional-trait interactions, and (iii) character definition. Instability, disappearance and reversal of patterns of genetic covariation often occur over short evolutionary time frames and as the direct product of selection, rather than some stochastic process. We suggest that the functional architecture of fitness is a rapidly evolving matrix with reticulate properties, a matrix that we understand only poorly.

Animals↗
PubMed1996

Frequency of migrants and migratory activity are genetically correlated in a bird population: evolutionary implications.

Most migratory bird populations are composed of individuals that migrate and individuals that remain resident. While the role of ecological factors in maintaining this behavioral dimorphism has received much attention, the importance of genetic constraints on the evolution of avian migration has not yet been considered. Drawing on the recorded migratory activities of 775 blackcaps (Sylvia atricapilla) from a partially migratory population in southern France, we tested two alternative genetic models about the relationship between incidence and amount of migratory activity. The amount of migratory activity could be the continuous variable "underlying" the phenotypic expression of migratory urge, or, alternatively, the expression of both traits could be controlled by two separate genetic systems. The distributions of migratory activities in five different cohorts and the inheritance pattern derived from selective breeding experiments both indicate that incidence and amount of migratory activity are two aspects of one trait. Thus, all birds without measurable activity have activity levels at the low end of a continuous distribution, below the limit of expression or detection. The phenotypic dichotomy "migrant-nonmigrant" is caused by a threshold which may not be fixed but influenced both genetically and environmentally. This finding has profound implications for the evolution of migration: the transition from migratoriness to residency should not only be driven by selection favoring resident birds but also by selection for lower migratory activity. This potential for selection on two aspects, residency and migration distance, of the same trait may enable extremely rapid evolutionary changes to occur in migratory behavior.

Animals↗
PubMed2005

Genetic relationship between milk score and litter weight for Targhee, Columbia, Rambouillet, and Polypay sheep.

This study was conducted to evaluate the relationship between milk score (MS) and litter weight at 70 d (LW) for four sheep breeds in the United States. Milk score is a subjective measure of milk production used to assess milk production of range ewes when milk yield cannot be quantitatively determined. Variance components for MS and LW were estimated for each of Targhee, Columbia, Rambouillet, and Polypay breeds. Data collected from 1990 through 2000 at the U.S. Sheep Exp. Stn. in Dubois, ID, were analyzed with an animal model using REML. There were 13,900 records of MS and LW for 5,807 ewes. Records were grouped according to parity as first, second, and greater (mature), and all records (lifetime). Estimates of heritability for MS were in the range of 0.05 to 0.18 for first, 0.01 to 0.27 for second, 0.05 to 0.10 for mature, and 0.08 to 0.13 for all lifetime parity groups. Estimates of genetic correlation between MS at first and second parities ranged from 0.74 to 1.00. Similarly, mature MS was highly correlated genetically with MS at first (0.83 to 1.00) and at second (0.60 to 1.00) parities, suggesting that additive genetic value for milking ability at maturity could be evaluated as early as at first parity. Heritability estimates for LW ranged from 0.00 to 0.18 over all breeds and parity groupings. The genetic correlation between LW at first and second parity groups ranged from 0.43 to 1.00. Estimates of genetic correlation between LW at first or second parity with mature LW were mostly high and positive, except for Targhee (-0.10) and Polypay (0.14) at first parity. Litter weight for mature ewes could be improved by selection at first or second parity. Estimates of genetic correlation at first parity between MS and LW were high (1.00) for Rambouillet and Polypay, and near zero for Columbia and Targhee. At second parity, estimates of genetic correlation between MS and LW were positive and moderate for Rambouillet and Polypay but more variable for Columbia and Targhee. Estimates of genetic correlation between MS and LW were mostly positive and may be favorable with smaller estimates of standard errors using all lifetime records rather than first or second parity records. Although estimates are variable, the average of the estimates of the genetic correlation suggests that LW can be improved by selecting ewes for favorable MS.

Analysis of Variance↗
PubMed2003

Genetic correlation of exercise with heart rate and respiratory sinus arrhythmia.

PURPOSE: A twin design was used to test whether the association between exercise behavior and heart rate and the association between exercise behavior and respiratory sinus arrhythmia (RSA) derive from a common genetic factor. METHODS: Data were available from 157 adolescent (aged 13-22) and 208 middle-aged twin pairs (aged 35-62), divided into five sex by zygosity groups (male and female monozygotic twin pairs, and dizygotic twin pairs of same or opposite sex). Exercise behavior was assessed as the average weekly METs spent on sports activities or other vigorous activities in leisure time (sportMETS) in the last 3 months. RSA and heart period (HP) were assessed in the time domain from the combined ECG and respiration signals. RESULTS: Heritability estimates were 16% and 29% for RSA, 64% and 68% for HP, and 79% and 41% for sportMETS in young and middle-aged twins, respectively. A significant association was found between RSA and sportMETS (0.17) in the adolescent twins that derived entirely from a common genetic factor. No association was found between sportMETS and RSA in the older twins. A significant association was found between HP and sportMETS in both adolescent (0.35) and middle-aged (0.18) twins. A large contribution of common genetic factors to these associations was found amounting to 84% and 88% in the young and middle-aged twins, respectively. CONCLUSIONS: Although the results of this study do not preclude causal effects of exercise on RSA and heart rate, they show that the association between exercise and these cardiovascular risk factors largely derives from a common genetic factor.

Adolescent↗