Exaggerated response to isotonic saline loading in genetically hypertension-prone rats.
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Animals↗
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[Does phenylalanine load disclose genetic variants?].
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Female↗
Recent approaches into the genetic basis of inbreeding depression in plants.
Predictions for the evolution of mating systems and genetic load vary, depending on the genetic basis of inbreeding depression (dominance versus overdominance, epistasis and the relative frequencies of genes of large and small effect). A distinction between the dominance and overdominance hypotheses is that deleterious recessive mutations should be purged in inbreeding populations. Comparative studies of populations differing in their level of inbreeding and experimental approaches that allow selection among inbred lines support this prediction. More direct biometric approaches provide strong support for the importance of partly recessive deleterious alleles. Investigators using molecular markers to study quantitative trait loci (QTL) often find support for overdominance, though pseudo-overdominance (deleterious alleles linked in repulsion) may bias this perception. QTL and biometric studies of inbred lines often find evidence for epistasis, which may also contribute to the perception of overdominance, though this may be because of the divergent lines initially crossed in QTL studies. Studies of marker segregation distortion commonly uncover genes of major effect on viability, but these have only minor contributions to inbreeding depression. Although considerable progress has been made in understanding the genetic basis of inbreeding depression, we feel that all three aspects merit more study in natural plant populations.
Epistasis, Genetic↗
The evolution of intratetrad mating rates.
Intratetrad mating, the fusion of gametes formed in a single meiosis, has unusual consequences for genetic diversity, especially in genome regions linked to mating type loci. Here we investigate the fate of modifier alleles that alter the rate of intratetrad mating, under models of heterozygote advantage and of genetic load resulting from recurrent mutation. In both cases, intratetrad mating is favored if the recombination rate between the selected locus and mating type is less than the frequency of lethal recessive alleles at that locus in the population. Positive feedback often accelerates the invasion of modifiers to the intratetrad mating rate. Recombination rate and intratetrad mating rate exert indirect selection on one another, resulting in a cascading decline in outcrossing, even in the absence of any cost of sex. However, under recurrent mutation, alleles for obligate intratetrad mating invade only very slowly, perhaps explaining why outcrossing can persist at low frequencies in a largely intratetrad mating population.
Biological Evolution↗
Chemokines (RANTES and MCP-1) and chemokine-receptors (CCR2 and CCR5) gene polymorphisms in Alzheimer's and Parkinson's disease.
Parkinson's disease (PD) is a complex disorder characterized by the progressive degeneration of dopaminergic neurons in the midbrain. Late-onset Alzheimer's disease (LOAD) is the most common cause of dementia in the elderly, affecting about 5% of the population older than 65 years. Several works have demonstrated the involvement of inflammation in the pathogenesis of both, PD and LOAD. Genetic susceptibility to develop PD and LOAD has also been widely recognised. Thus, functional polymorphisms at the genes encoding inflammatory proteins could influence the overall risk of developing these neurodegenerative disorders. We examined whether DNA-polymorphisms at the genes encoding chemokines MCP-1 (-2518 A/G) and RANTES (-403 A/G), and chemokine receptors 5 (CCR5, Delta32) and 2 (CCR2,V64I), were associated with the risk and/or the clinical outcome of LOAD and PD. A total of 200 PD, 326 LOAD, and 370 healthy controls were genotyped for the four polymorphisms, and genotype frequencies statistically compared. We did not find significant differences in the frequencies of the different genotypes between both groups of patients and controls. We conclude that the four DNA polymorphisms, which have been associated with several immuno-modulated diseases, did not contribute to the risk of PD or LOAD.
Aged↗
[Analysis of diversity of autosomal-recessive diseases in Russian populations].
The diversity of autosomal recessive (AR) diseases was studied in six Russian regions: the Kirov, Kostroma, and Bryansk oblasts; Adygea Republic; Krasnodar krai, and Marii El Republic (in the latter region, the Mari and Russian ethnic groups were studied separately). In total, more than 1.5 million people were studied. The spectrum of the AR diseases included 101 nosological forms; the total number of the affected subjects was 942. For all diseases, the prevalence rate in the region where they were found and the mean prevalence rate in the total population studied were calculated. Only seven AR diseases had prevalence rates of 1:50,000 or higher; however, this group contained about 50% of the patients. About half of the AR diseases (66) had an extremely low prevalence rate (1:877,483). Eleven diseases exhibit local accumulation. Accumulation of some or other diseases was only observed in four out of seven populations studied (Marii El, Adygea, and the Kirov and Bryansk oblasts). To determine the cause of the local accumulation of some diseases in populations, correlation analysis of the dependence of accumulation of hereditary diseases on the genetic structure of the populations studied was performed. The accumulation coefficients for AR and autosomal dominant (AD) diseases and the mean values of random inbreeding (Fst) in individual districts were calculated for all populations studied. The coefficients of the Spearman rank correlation between the accumulation coefficient and random inbreeding (Fst) were 0.68 and 0.86 for the AD and AR diseases, respectively. The correlation between the accumulation of AD and AR diseases was 0.86. The relationships found indicate that the diversity of AD and AR diseases, as well as the genetic load, distinctly depended on the population genetic structure and were largely determined by genetic drift.
Genes, Recessive↗
The heritability of melatonin secretion and sensitivity to bright nocturnal light in twins.
The super-sensitivity of the neurohormone melatonin to light in patients with bipolar disorder provides evidence of the circadian nature of the disorder. This response has been proposed as an endophenotype for identifying people at risk of the disorder and guiding investigations of molecular genetic targets. However, before this response is used as an endophenotypic marker, the heritable nature of melatonin sensitivity in the normal population must be established. The aim of this study was to investigate the heritability of nocturnal melatonin secretion and sensitivity to light in monozygotic and dizygotic twins with no psychiatric history. This study investigated overall melatonin levels (between 2000 and 2400 h) and suppression by 500 lx of light (between 2400 and 0100 h) in 20 pairs of twins (nine monozygotic, 11 dizygotic). The results indicate that melatonin secretion is highly heritable with secretion in one twin being a significant predictor of secretion in their twin in both monozygotic and dizygotic pairs. In relation to light sensitivity, genetic loading appears to play a significant role with the greatest concordance between monozygotic twins, followed by dizygotic twins and finally low concordance in unrelated individuals. This provides additional support for the usefulness of melatonin sensitivity to light as a potential endophenotypic marker of bipolar affective disorder.
Adolescent↗
Genomic analysis of xerophyte Salweenia species provides insights into the alpine dry-warm valleys divergence and survival history.
Salweenia species are evergreen shrubs capable of preventing desertification and maintaining the health of alpine dry-warm ecosystems in the Hengduan Mountains. However, both the narrowly distributed S. bouffordiana and its more widespread close relative S. wardii are endemic and endangered. Furthermore, their small population sizes render each of these species at risk of extinction. To infer how past climate changes have shaped the evolutionary history of these species, we developed a chromosome-level S. bouffordiana genome (788 Mb) and compared the two species' evolutionary histories, genetic loads and the genomic adaptions to local environmental conditions using whole-genome resequencing data. Our findings reveal a sharp population decline from the Pliocene to the Quaternary. However, populations of S. bouffordiana then started to recover before declining further, while S. wardii populations continued to decline until recently. Abundant homozygous-derived variants accumulated in the two species, particularly in S. bouffordiana, while the species with the most heterozygous variants was S. wardii. Accumulated extensive inbreeding effects but possessed few LOF mutations and few highly deleterious variants in the S. bouffordiana that have experienced the most severe demographic bottlenecks, most likely because of purging effects. This accelerating decline cascade will likely be detrimental to the consequences for the species' future viability and adaptive potential. Overall, this study improves our understanding of the evolutionary history of Salweenia shrubs tolerant to extreme environments and offers a genetic resource for future breeding and conservation efforts.
Genome, Plant↗
Do multiple families alter estimates of risk for age-related cataract in a population-based study? The Beaver Dam Eye Study.
We sought to determine the effect of "genetic" load on the strengths of risk factors for age-related cataracts in the population-based Beaver Dam Eye Study. Of the 4,926 participants in the baseline examination in 1988 to 1990, 2,338 were members of 594 family groups. There were no important differences in the risks due to pack-years smoked, systolic and diastolic blood pressures, body mass index, current smoking, hypertension or hormone replacement therapy for either the whole population or subgroups created by omitting siblings or any family relation. There were some differences when the analyses were limited to only a randomly selected family member or a randomly selected sibling. These latter findings may relate to the older average age of those in sibships or in families compared to those not in families. We conclude that for the associations we explored, the relatively large number of families in our population had little effect on the strengths of the risk factors, and that limiting analyses to only those not in families may distort risk factor associations by altering the age structure in this population.
Adult↗
Subtypes of alcohol-dependent men: a typology based on relative genetic and environmental loading.
Using scales that distinguish between relative genetic and environmental loading, cluster analysis was used to identify three subtypes of alcohol dependence in Caucasian men from the Epidemiologic Catchment Area study (n = 911). Although all subjects met DSM-III criteria for alcohol dependence, only the severe subtype showed evidence of substantial genetic influence. When compared on a range of clinical characteristics, the mild subtype (53% of the sample) was typically least adversely affected and the severe subtype (17%) most affected, with the dyssocial subtype (30%) falling between. Severe subtype subjects had significantly greater comorbid drug dependence and were at least four times more likely than mild subjects to have sought treatment for alcohol problems. Ratio of genetic scale score to total symptom count (genetic ratio) was highest for the severe subtype (mean = 0.37), and negatively correlated with age of first alcohol problem (rs = -0.16) and years between first intoxication and first problem (rs = 0.19). No significant correlations were found between these clinical features and genetic ratio for the mild or dyssocial subtypes. Use of these scales and subtypes may improve our ability to detect specific gene effects in genetic linkage studies and to identify environmental influences in behavioral and epidemiological studies.
Adult↗
[ADHD and alcohol dependence: a common genetic predisposition?].
INTRODUCTION: Nearly 50 % of subjects with continuing symptoms of attention-deficit hyperactivity disorder (ADHD) in adulthood show a comorbid substance use disorder. Both, ADHD and alcohol dependence have a high genetic load and might even share overlapping sources of genetic liability. METHOD: We investigated phenotype and 5-HTT/5-HT2c allelic characteristics in 314 alcoholics of German descent. RESULT: 21 % of the alcoholics fulfilled DSM-IV-criteria of ADHD with ongoing symptoms in adulthood. There was no significant difference in 5-HTT- or 5-HT2c-allele distribution between alcoholics and matched controls or between alcoholics with or without ADHD. CONCLUSION: In our sample the functional relevant 5-HTT-promoter and the 5-HT2c-receptor Cys23Ser polymorphism do not contribute to the supposed common genetic predisposition of ADHD and alcohol dependence.
Adolescent↗
Comorbidity of alcohol dependence with attention-deficit hyperactivity disorder: differences in phenotype with increased severity of the substance disorder, but not in genotype (serotonin transporter and 5-hydroxytryptamine-2c receptor).
BACKGROUND: Nearly 50% of subjects with continuing symptoms of attention-deficit hyperactivity disorder (ADHD) in adulthood have been reported to show a comorbid substance use disorder. Both ADHD and alcohol dependence have a high genetic load and might even share overlapping sources of genetic liability. Recently, the functional relevant polymorphism within the promoter region of the serotonin transporter gene (5-HTT) and the 5-hydroxytryptamine-2c (5-HT2c) receptor Cys23Ser have been proposed as candidate genes for both entities. METHODS: We investigated phenotype and 5-HTT/5-HT2c genotype characteristics in 314 alcoholics of German descent. RESULTS: There was no significant difference in 5-HTT genotype or 5-HT2c allele distribution between alcoholics and matched controls. Sixty-seven alcoholics fulfilled DSM-IV criteria of ADHD with ongoing symptoms in adulthood and had a Wender Utah Rating Scale score greater than 90. Thirty had ADHD plus antisocial personality disorder. The subgroup of alcoholics with ADHD (ADHD+) showed a significantly higher daily and record ethanol intake per month, an earlier age at onset of alcohol dependence, and a higher frequency of suicidal ideation, court proceedings, and antisocial personality disorder. In our sample, more than 50% of type 2 alcoholics according to Cloninger consist of the ADHD+ and/or antisocial personality disorder-positive subjects. There were no differences in 5-HTT genotype or 5-HT2c allele distribution between the ADHD+ subgroups and alcoholics without comorbidity and matched controls, respectively. CONCLUSIONS: Comorbidity of alcoholism and ADHD forms a distinct phenotype that shows an increased severity of the substance disorder. This phenotype contributes substantially to the so-called type 2 alcoholics according to Cloninger. In our sample, the functional relevant 5-HTT promoter and the 5-HT2c receptor Cys23Ser polymorphism do not contribute to the supposed common genetic predisposition of ADHD and alcohol dependence.
Adolescent↗
Antibiotic multiresistance plasmid pRSB101 isolated from a wastewater treatment plant is related to plasmids residing in phytopathogenic bacteria and carries eight different resistance determinants including a multidrug transport system.
Ten different antibiotic resistance plasmids conferring high-level erythromycin resistance were isolated from an activated sludge bacterial community of a wastewater treatment plant by applying a transformation-based approach. One of these plasmids, designated pRSB101, mediates resistance to tetracycline, erythromycin, roxythromycin, sulfonamides, cephalosporins, spectinomycin, streptomycin, trimethoprim, nalidixic acid and low concentrations of norfloxacin. Plasmid pRSB101 was completely sequenced and annotated. Its size is 47 829 bp. Conserved synteny exists between the pRSB101 replication/partition (rep/par) module and the pXAC33-replicon from the phytopathogen Xanthomonas axonopodis pv. citri. The second pRSB101 backbone module encodes a three-Mob-protein type mobilization (mob) system with homology to that of IncQ-like plasmids. Plasmid pRSB101 is mobilizable with the help of the IncP-1alpha plasmid RP4 providing transfer functions in trans. A 20 kb resistance region on pRSB101 is located within an integron-containing Tn402-like transposon. The variable region of the class 1 integron carries the genes dhfr1 for a dihydrofolate reductase, aadA2 for a spectinomycin/streptomycin adenylyltransferase and bla(TLA-2) for a so far unknown Ambler class A extended spectrum beta-lactamase. The integron-specific 3'-segment (qacEDelta1-sul1-orf5Delta) is connected to a macrolide resistance operon consisting of the genes mph(A) (macrolide 2'-phosphotransferase I), mrx (hydrophobic protein of unknown function) and mphR(A) (regulatory protein). Finally, a putative mobile element with the tetracycline resistance genes tetA (tetracycline efflux pump) and tetR was identified upstream of the Tn402-specific transposase gene tniA. The second 'genetic load' region on pRSB101 harbours four distinct mobile genetic elements, another integron belonging to a new class and footprints of two more transposable elements. A tripartite multidrug (MDR) transporter consisting of an ATP-binding-cassette (ABC)-type ATPase and permease, and an efflux membrane fusion protein (MFP) of the RND-family is encoded between the replication/partition and the mobilization module. Homologues of the macrolide resistance genes mph(A), mrx and mphR(A) were detected on eight other erythromycin resistance-plasmids isolated from activated sludge bacteria. Plasmid pRSB101-like repA amplicons were also obtained from plasmid-DNA preparations of the final effluents of the wastewater treatment plant indicating that pRSB101-like plasmids are released with the final effluents into the environment.
ATP Binding Cassette Transporter, Subfamily B↗
Mechanisms of variability of vertebrate virus populations.
A number of factors favouring the persistence and accumulation of mutant virus particles are active in virus populations with a complicated genetic structure. The latter circumstance permits to apply the concept of genetic load to these virus populations. Complication of the genetic structure permits a virus population to make a qualitative leap in the struggle for existence.
Arboviruses↗
[Correction for the estimated load of hereditary diseases in the population of the Krasnodarsk district].
Medico-genetical examination of children from 6 invalid houses, 2 asylum houses, 3 internate schools and 1 house for deaf and feeble-hearing children as well as from the internate school for children with poor vision was undertaken in Krasnodar district. 10.6% of the children were found to have chromosomal abnormality, 26.5%--multifactorial pathology and 62.9% of children were affected by monogenic diseases. The spectrum of diseases covers 20 forms, 8 of them being autosomal-dominant, 10--autosomal-recessive and 2--X-linked forms. A "selective" method presented in this article for revealing patients affected by genetical diseases in specialised institutions permitted to evaluate a portion of the patients having been not identified when using the "survey" expeditional method of population--epidemiological study of the district population. This portion constitutes 19%. The more accurate values of genetic load in populations of Krasnodar district were obtained, being 1.06-0.06 for autosomal-dominant, 0.78-0.05 for autosomal-recessive and 0.38-0.05 for X-linked diseases per thousand.
Child↗
Refractory depression in children and adolescents.
Refractory or treatments resistant depression in child and adolescent populations is a difficult construct to operationalize currently. To date, only one of the small number of completed double-blind placebo-controlled treatment investigations have not demonstrated a significant effect of antidepressants in comparison to placebo. However, it has been established that child and adolescent MDD is a serious disorder that appears to have clinical continuity with adult affective disorders and is generally of long duration with high rates of recurrence and eventual progression to mania, substance abuse, or other serious psychopathology. In addition, families of children with affective disorders evidence substantial genetic loading with high rates of affective disorders contributing both genetic vulnerability and potential environmental risk as well. There have been no empirically identified treatments that alter the long-term course of the illness. Thus treatment resistance is a significant issue for this population. This review will focus on controlled treatment trials and will examine the potential relevance of psychosocial impairment, genetic-familial risk, and neuromorphometric brain differences to treatment resistance in children and adolescents with major depression.
Adolescent↗
Personality traits in subtypes of alcoholics.
Earlier studies have identified at least two distinct subgroups of alcoholics: Type II with early onset and high genetic loading and Type I with late onset in which genetic factors seem to be of minor importance. In the present study, type I and type II alcoholics are compared on stable personality traits determined by the Karolinska Scales of Personality. Both groups were found to have high scores on scales that measured somatic anxiety, psychic anxiety, muscular tension, impulsiveness, detachment, psychastenia, suspicion, guilt and inhibition of aggression. Both groups had low scores on the scale that measured socialization. Type II alcoholics had significantly higher scores than type I alcoholics on Somatic Anxiety and Verbal Aggression scales and significantly lower scores on Socialization and Inhibition of Aggression scales. On the Impulsive Sensation-Seeking Psychopathy factor (Impulsiveness + Monotony Avoidance - Socialization), type II alcoholics were significantly differentiated from both type I alcoholics and healthy volunteers. Results of this study were consistent with those of other studies indicating that alcoholism accompanied by antisocial behavior should be kept separate from alcoholism that is unrelated to antisocial behavior.
Adult↗
[Influence of urbanization level on the lethal load and on the intensity of natural selection in the Turkmen population].
Dynamics of genetic load in aboriginal population of the Turkmen SSR was studied using two approaches to calculate "lethal" equivalents. Intensity and structure of natural selection were measured using the Crow's index and its components. All statistics indicated were determined using the data obtained in Ashkhabad city and in two rural populations of Ashkhabad region (Yasman and Nokhur) within the time interval prior to 60s and after 70s. The results obtained made it possible to subdivide the populations under study into three different groups according to different stages of demographic process: 1) urbanized population; 2) rural (transient) population; 3) "relict" rural population.
Genes, Lethal↗