Brother-sister Pairs Research Articles

The trend of correlation changes of macronutrient intakes among different familial pairs: a prospective study among participants of Tehran Lipid and Glucose Study

Background/AimFamilial resemblance in dietary patterns has been a subject of interest, with both genetic and environmental factors playing crucial roles. This study aims to investigate trends in macronutrient intake correlations over a 9-year period among different familial pairs, including parent-offspring, siblings, and spouses, using data from the Tehran Lipid and Glucose Study (TLGS).MethodsThis longitudinal study, conducted within the framework of the TLGS, analyzed data from 1,814 families over a 9-year period. Dietary intakes were assessed using a validated 168-item food frequency questionnaire. Macronutrient intakes were calculated and adjusted for age. Familial correlations were estimated using intraclass correlation coefficients for various familial pairs (parent-offspring, siblings, and spouses) across four consecutive surveys. Changes in correlations were analyzed over 3-year, 6-year, and 9-year intervals, as well as across all four surveys, to determine overall trends in macronutrient intake correlations.ResultsThe results revealed diverse trends in intake correlations for carbohydrates, proteins, fats, and specific fatty acids across familial relationships. Parent-offspring dyads exhibited varied patterns, with some nutrients showing regression to the mean. Sister-sister pairs demonstrated strengthening correlations for energy, carbohydrates, fats, and saturated fatty acids over time. Conversely, brother-sister pairs displayed weakening correlations for most macronutrients, particularly energy, proteins, cholesterol, and fiber. Spouse correlations tended towards regression to the mean for energy, carbohydrates, and fats, and fiber.ConclusionsThe present study illuminates the dynamic nature of familial dietary correlations over time. The contrasting trends between sister-sister and brother-sister dyads suggest a significant influence of gender on shared dietary patterns. These findings underscore the complex interplay of genetic and environmental factors in shaping family dietary behaviors and highlight the importance of considering both gender and relationship type when examining familial nutritional habits.

Contrasting Patterns of Movement across Life Stages in an Insular Iguana Population

West Indian rock iguanas (genus Cyclura) represent the most endangered group of lizards in the world, with most taxa restricted to few or single islands. In addition to distribution and availability of resources, factors influencing optimal use of insular space in these large vertebrates may include a combination of social, ontogenetic, and long-term demographic factors. Life stage-specific dispersal and habitat use patterns have previously been characterized in Cyclura, but assessments across the lifespan are lacking. This study evaluates shifting patterns of movement in a single taxon, Cyclura nubila caymanensis. We used mark–recapture and radio tracking simultaneously to assess age- and sex-dependent variation in spatial ecology. Evidence for prolonged site fidelity among adults was consistent with territoriality-modulating space use in this long-lived taxon. Over 5–10 yr, some females were never resighted or recaptured outside of an 80-m perimeter. A notable exception was that gravid females migrated 1.17 ± 0.91 km to utilize coastal areas during the nesting season. In contrast, neonates dispersed farther (2.32 ± 2.26 km) and their trajectories were often nonlinear. Radio-tracked brother–sister pairs exhibited no tendency to disperse together during their first 4 wk, settling into final known locations at pairwise distances of 2.16 ± 1.74 km. Annual net displacement remained high over the first 1–3 yr of life. Our data are consistent with studies of related taxa wherein individual spatial requirements vary with population density and island size. Notably, panmixis of small island iguana populations appears largely driven by pre-reproductive movements.

Change and Stability in Sibling Physical Fitness: The Portuguese Sibling Study.

This study aims to 1) describe mean changes in muscular and motor fitness components in sibships over 2 yr, 2) analyze individual tracking of fitness within sibships, 3) investigate sibling resemblance in fitness over time, and 4) examine the joint influence of biological, behavioral, and familial characteristics on fitness. The sample comprises 166 Portuguese biological sibling pairs (brother-brother, sister-sister, brother-sister) age 9-17 yr assessed at baseline and 2 yr later. Physical fitness components were measured with standardized tests. Percentage body fat and biological maturation were assessed, and physical activity, diet, screen time, and familial characteristics were obtained by questionnaires. Multilevel models were used to analyze the clustered longitudinal data. Crude results showed that, on average, all sib-types increased their muscular and motor fitness components from baseline to follow-up (except sister-sister pairs in standing long jump and shuttle run). When adjusted for covariates, the mean changes were no longer significant. Individual tracking was moderate to high for the muscular component but low to moderate for the motor component. Consistency in sibling resemblance was higher in sister-sister pairs than in brother-brother and brother-sister pairs. More mature sibs were fitter in both components, whereas siblings with higher body fat percentage were less fit. Screen time, physical activity, and parental occupation were not associated with fitness components. Biological characteristics were more strongly associated with fitness components than individual behaviors and familial characteristics. Furthermore, the muscular component tracked better than the motor component. Sister-sister pairs had greater resemblance in fitness over time compared with brother-brother or sister-brother pairs.

Resemblance in physical activity levels: The Portuguese sibling study on growth, fitness, lifestyle, and health.

To investigate the relationships of biological, behavioral, familial, and environmental characteristics with siblings´ physical activity (PA) levels as well as the intrapair resemblance in PA. The sample comprises 834 (390 females) biological siblings [brother-brother (BB), sister-sister (SS), brother-sister (BS)] aged 9 to 20 years. Total PA index (TPAI) was estimated by questionnaire. Information on potential behavioral, familial, and environmental correlates was obtained by self-report; body mass index (BMI), biological maturation, and physical fitness were measured. Multilevel models were used to analyze siblings´ clustered data, and sibling resemblance was estimated with the intraclass correlation (ρ). On average, younger sibs, those more physically fit, and those with more parental support had greater TPAI. Further, BB pairs had higher TPAI levels than SS or BS pairs, but also had greater within-pair variance. When adjusted for all covariates, SS pairs demonstrated greater resemblance in TPAI (ρ = 0.53, 95%CI = 0.38-0.68) than BS (ρ = 0.26, 95%CI = 0.14-0.43) or BB pairs (ρ = 0.18, 95%CI = 0.06-0.44). Age, physical fitness, and parental support were the best predictors of TPAI levels. A moderate level of resemblance in TPAI was observed in SS pairs, while lower resemblance was found for BS and BB pairs. These findings may be due to differences in the roles of shared genetic factors, familial, and environmental characteristics across different sibling types.

A multilevel analysis of health-related physical fitness. The Portuguese sibling study on growth, fitness, lifestyle and health

This study investigates biological, behavioural and sociodemographic correlates of intra-pair similarities, and estimates sibling resemblance in health-related physical fitness (PF). The sample comprises 1101 biological siblings (525 females) aged 9–20 years. PF components and markers were: morphological [waist circumference (WC) and %body fat (%BF)], muscular [handgrip strength (GS) and standing long jump (SLJ)], motor [50-yard dash (50YD) and shuttle run (SR)], and cardiorespiratory (1-mile run). Biological maturation was assessed; physical activity (PA), TV viewing and socioeconomic status (SES) information was obtained. On average, older and more mature subjects are better performers in all PF components; PA was negatively associated with SR, while SES was negatively associated with SLJ and SR. A pattern was observed in the intraclass correlations (ρ) wherein same sex siblings demonstrate greater resemblance for most PF components (sister-sister: 0.35≤ ρ≤0.55; brother-brother: (0.25≤ρ≤0.60) than brother-sister pairs (BS) (0≤ρ≤0.15), except for %BF (ρBB>ρSS>ρBS), and the 1-mile run (ρSS>ρBS>ρBB). In conclusion, behavioural and sociodemographic correlates play different roles in siblings PF expression. Further, a significant familial PF resemblance was observed with different trends in different sibling types, probably due to variations in shared genetic factors and sociodemographic conditions.

Multilevel modelling of somatotype components: the Portuguese sibling study on growth, fitness, lifestyle and health

Background: Somatotype is a complex trait influenced by different genetic and environmental factors as well as by other covariates whose effects are still unclear.Aims: To (1) estimate siblings’ resemblance in their general somatotype; (2) identify sib-pair (brother–brother (BB), sister–sister (SS), brother–sister (BS)) similarities in individual somatotype components; (3) examine the degree to which between and within variances differ among sib-ships; and (4) investigate the effects of physical activity (PA) and family socioeconomic status (SES) on these relationships.Subjects and methods: The sample comprises 1058 Portuguese siblings (538 females) aged 9–20 years. Somatotype was calculated using the Health-Carter method, while PA and SES information was obtained by questionnaire. Multi-level modelling was done in SuperMix software.Results: Older subjects showed the lowest values for endomorphy and mesomorphy, but the highest values for ectomorphy; and more physically active subjects showed the highest values for mesomorphy. In general, the familiality of somatotype was moderate (ρ = 0.35). Same-sex siblings had the strongest resemblance (endomorphy: ρSS > ρBB > ρBS; mesomorphy: ρBB = ρSS > ρBS; ectomorphy: ρBB > ρSS > ρBS). For the ectomorphy and mesomorphy components, BS pairs showed the highest between sib-ship variance, but the lowest within sib-ship variance; while for endomorphy BS showed the lowest between and within sib-ship variances.Conclusions: These results highlight the significant familial effects on somatotype and the complexity of the role of familial resemblance in explaining variance in somatotypes.

The Effects of Differential Parenting on Sibling Differences in Self-Control and Delinquency Among Brother–Sister Pairs

Gottfredson and Hirschi acknowledge that there are sex differences in levels of self-control, with males exhibiting lower levels of self-control compared to females. There remains a gap in the empirical literature, however, as to whether differential parental treatment can explain differences in levels of self-control across the sexes. Using siblings of opposite sex from the Add Health study ( N = 356, brother–sister pairs) and following a within-family research design, the current study examines whether differences in parenting behaviors within the home are associated with sex differences in self-control between siblings and whether these differences in self-control explained sex differences in delinquency. The results revealed that differential maternal attachment and differential maternal rejection were significantly related to sex differences in self-control. Sex differences in self-control, in turn, were significantly associated with sex differences in delinquency. The findings also showed that sex differences in self-control mediated the association between differential maternal rejection and delinquency, but that differential maternal attachment was indirectly associated with higher levels of delinquency for boys via lower levels of self-control. The impact of nonshared environmental factors on behavioral differences in opposite-sex siblings within the home is discussed.

Lipoprotein(a) concentration does not differ between sexes in healthy offspring of patients with premature myocardial infarction

Although a family history of coronary artery disease (CAD) is an established factor influencing lipoprotein(a) [Lp(a)] levels, the effect of sex on Lp(a) concentration remains unclear. A potential cause of the conflicting findings regarding the effect of sex on this novel CAD risk factor is the limited ability of the studies, to date, to adequately control for the potential confounding effect of CAD familial predisposition. Our purpose was to evaluate the influence of sex on Lp(a) concentration in healthy young individuals by controlling for family history of CAD. In order to achieve our goal, we compared Lp(a) levels in pairs of brothers and sisters with a positive parental history of premature myocardial infarction (PHPMI). We measured Lp(a) concentration in 77 healthy brother-sister pairs with PHPMI (mean age: brothers: 18.4 ± 6.2 years and sisters: 18.1 ± 5.8 years). Total cholesterol, low-density lipoprotein (LDL)-cholesterol and high-density lipoprotein (HDL)-cholesterol, triglycerides, apolipoprotein (Apo) A-I and B were also measured. Lp(a) levels did not differ between siblings of different sex (male vs. female sex: 0.994 ± 1.29 vs. 0.860 ± 0.82 μmol/l, P = 0.940); moreover, the prevalence of elevated (>1.071 μmol/l) Lp(a) concentrations between sexes was the same (29.9%). As expected, compared to female sex, male sex showed higher total/HDL-cholesterol ratio (3.642 ± 0.99 vs. 3.329 ± 0.89, P = 0.017) and lower HDL-cholesterol (1.221 ± 0.24 vs. 1.343 ± 0.28 mmol/l, P = 0.001), Apo A-I (1.390 ± 0.20 vs. 1.474 ± 0.23 g/l, P = 0.003) concentrations and Apo A-I/Apo B ratio (1.632 ± 0.49 vs. 1.830 ± 0.66, P = 0.016). Our results show that healthy young men with PHPMI have a similar Lp(a) levels but worse lipid profile than women.

Homozygosity mapping in outbred families with mental retardation

Autosomal recessive mental retardation (AR-MR) may account for up to 25% of genetic mental retardation (MR). So far, mapping of AR-MR genes in consanguineous families has resulted in six nonsyndromic genes, whereas more than 2000 genes might contribute to AR-MR. We propose to use outbred families with multiple affected siblings for AR-MR gene identification. Homozygosity mapping in ten outbred families with affected brother-sister pairs using a 250 K single nucleotide polymorphism array revealed on average 57 homozygous regions over 1 Mb in size per affected individual (range 20-74). Of these, 21 homozygous regions were shared between siblings on average (range 8-36). None of the shared regions of homozygosity (SROHs) overlapped with the nonsyndromic genes. A total of 13 SROHs had an overlap with previously reported loci for AR-MR, namely with MRT8, MRT9, MRT10 and MRT11. Among these was the longest observed SROH of 11.0 Mb in family ARMR1 on chromosome 19q13, which had 2.9 Mb (98 genes) in common with the 5.4 Mb MRT11 locus (195 genes). These data support that homozygosity mapping in outbred families may contribute to identification of novel AR-MR genes.

Kin recognition and adjustment of reproductive effort in zebra finches

The differential allocation theory predicts that females should invest more in offspring produced with attractive partners, and a number of studies support this prediction in birds. Females have been shown to increase reproductive investment when mated to males showing elaborated sexual traits. However, mate attractiveness might also depend on the interaction between male and female genotypes. Accordingly, females should invest more in offspring sired by individuals that are genetically dissimilar or carry superior alleles. Here, we show in zebra finches (Taeniopygia guttata) that pairs of unfamiliar genetic brothers and sisters are less likely to reproduce in comparison with randomly mated pairs. Among the brother-sister pairs, those that attempted to breed laid smaller clutches and of lower total clutch mass. Our results provide the first experimental evidence that females adjust their reproductive effort in response to the genetic similarity of their partners. Importantly, these results imply a female ability to assess relatedness of a social mate without prior association.

Sibling resemblance in natal dispersal distance and direction in the Ortolan Bunting Emberiza hortulana

Natal dispersal distance and direction determine the likelihood that siblings will settle close together and hence the risk of inbreeding. Several studies have shown a sibling resemblance in dispersal distance, but few studies have analysed sibling resemblance in dispersal direction or the distance between siblings after dispersal at the landscape level. I studied the entire Norwegian population of Ortolan Buntings Emberiza hortulana, which is patchily distributed in an area covering c. 500 km2. Males and females did not differ in dispersal distance (overall median 3.7 km), but directions were different. Natal dispersal distances and directions were positively related within sibling pairs, but comparisons with control individuals suggested that any effects were due to spatial effects of configuration of habitat patches in the study area. Brother–sister pairs (n = 16) were at least as similar as brother–brother pairs (n = 18). Distance between siblings after natal dispersal increased with dispersal distance, but even so, five of 35 sibling pairs settled < 1 km apart, despite dispersal distances of 8.3–9.9 km for two of these pairs. Including movements later in life, eight sibling pairs were < 1 km apart at some time (four pairs of brothers and four brother–sister pairs), and in one case a brother mated with its sister. Another case of mating between close relatives (father and daughter) involved short female natal dispersal. These data indicate that female‐biased natal dispersal and long‐distance dispersal may reduce, but do not exclude, the possibility of inbreeding.

Multifactorial analysis of a mixed-longitudinal sample of Indian siblings: Age and sex effects on heritability

The aim of the present study was to examine the heritability of 11 traits in a mixed-longitudinal sample of Indian siblings, and to determine whether heritability estimates vary during the growth period and whether they are influenced by sex. The sample consisted of 245 brothers and 213 sisters from 138 nuclear families living in a semi-urban area in Kolkata, India. The age ranged between 5 and 19 years. The traits were standardised for age and sex using standard deviation scores (SDS) produced by the LMS method (Cole, T.J., 1988. Fitting smoothed centile curves to reference data. J. R. Stat. Soc. A 151, 385–418). The standard deviation scores were analysed by PCA. The two factors with eigenvalues above 1 explained 77.3% of the variance; they showed a high level of pleiotropism present among the studied traits and represented body lengths (PC1) and body weight and breadths (PC2). The heritability between all types of siblings (irrespective of sex) for the PC1 and PC2 was estimated. The heritability between various pairs of siblings showed variations along the whole ontogenetic period studied. During the childhood and pre-pubertal period, heritability between brothers, brother–sister pairs and any sibling pairs was mostly constant, with small and non-significant variations. All the pairs showed the lowest degree of heritability during puberty for PC1 but not for PC2, with significant changes of heritability estimates between adolescence and adulthood, in most of the analysed sibling pairs and in both PC factors. The highest heritability was generally observed at the end of the examined growth period in all pairs. A significant effect of sex on heritability was only detected for PC2 at 11 years of age.

Inbreeding avoidance under different null models of random mating in the great tit

1. In populations where inbreeding causes a substantial decrease in fitness, selection is expected to favour the evolution of inbreeding avoidance behaviours. Elsewhere we have documented substantial inbreeding depression and the importance of dispersal in avoiding inbreeding in a long-term population study of the great tit Parus major in Wytham (UK). In this study, we ask whether individuals from this population actively avoid mating with kin. 2. We generated four contrasting models of random mate choice that assumed varying levels of mate availability in each year of the data set. This allowed us to compare observed and simulated distributions and frequencies of inbreeding coefficients from 41 years of breeding data. 3. We found no evidence that birds avoid mating with related partners. Our results show that birds breed more often with relatives than expected under null models of mate choice that lack population structure, but not when compared to scenarios where birds were mated with their nearest neighbours. Pedigree-derived F(IS) values were positive for all scenarios of random mating, confirming the lack of inbreeding avoidance in this population. 4. These results imply the existence of spatial genetic structure where related individuals occur closer together than nonrelated individuals while breeding, and suggest that the relatedness between breeding individuals of the opposite sex decreases with distance. Thus, while dispersal from the natal site decreases the number of relatives around an individual, it does not completely homogenize genetic structure. 5. We show that brother-sister pairs are observed more often than under any scenario of random mating, suggesting that not only birds do not avoid mating with kin, but also that the apparently maladaptive choice of mating with a sibling is made more often than expected. 6. Our results provide no evidence to suggest that individuals actively avoid kin. In fact, some types of inbreeding occur more often than expected, despite the substantial fitness costs. The observed lack of inbreeding avoidance is in agreement with other studies of non-cooperatively breeding passerine birds, although the higher than expected frequency of sibling mating remains a puzzling result.

Heritability of parturition timing: an extended twin design analysis

The objective of the study was to assess relative maternal and paternal genetic influences on birth timing. Utilizing The Netherlands Twin Registry, we examined the correlation in birth timing of infants born to monozygotic (MZ) twins and their first-degree relatives (dizygotic twins and siblings of twins). Genetic models estimated the relative influence of genetic and common environmental factors through model fitting of additive genetic (A), common environmental (C), individual-specific environmental factors, and combinations thereof. We evaluated birth timing correlation among the infants of 1390 twins and their 644 siblings. The correlation in MZ female twins (r = 0.330) was greater than MZ male twins (r = -0.096). Positive correlation were also found in sister-sister pairs (r = 0.223) but not in brother-brother (r = -0.045) or brother-sister pairs (r = -0.038). The most parsimonious AE model indicated a significant maternal contribution of genetic and individual-specific environmental factors to birth timing, but no paternal heritability was demonstrated. Heritability of birth timing in women was 34%; and the remaining variance (66%) was caused by individual-specific environmental factors. Our data implicate a significant contribution of maternal but not paternal genetic influences on birth timing.

Heritability of elevated factor VIII antigen levels in factor V Leiden families with thrombophilia

Factor VIII activity (factor VIII:C) and factor VIII antigen (factor VIII:Ag) levels above 150 IU/dl are associated with a five- to sixfold increased risk of venous thrombosis compared with levels < 100 IU/dl. These high levels are present in 25% of patients with a first episode of deep-vein thrombosis and in 11% of healthy controls. von Willebrand factor (VWF) and blood group are important determinants of the factor VIII level in plasma and therefore contribute to thrombotic risk, while factor VIII appears to be the final effector. Previously, we found familial clustering of factor VIII:C levels in women, which remained after adjustment for VWF and blood group. In the present study, we analysed the familial influence on factor VIII:Ag levels exceeding 150 IU/dl in 12 large families with thrombophilia in which high factor VIII:Ag levels contribute to thrombotic risk. As expected, blood group was a main determinant of the plasma factor VIII level: 58 relatives (32%) had factor VIII levels above 150 IU/dl and 50 (86%) of these had blood group non-O. After adjustment for blood group and age, we found an association between factor VIII:Ag levels in sister pairs (0.35, P = 0.003), brother pairs (0.35, P = 0.003), brother-sister pairs (0.35, P < 0.001) and in mother-son pairs (0.45, P = 0.02), but not in father-daughter or father-son pairs. The familial aggregation test was strongly positive for factor VIII:Ag levels (P < 0.001) and remained so after adjustment for the influence of blood group. We conclude that high factor VIII:Ag levels are a highly prevalent risk factor for venous thrombosis and contribute to risk in families with thrombophilia, and that these high levels are likely to be genetically determined by factors other than just blood group.

Heritability of anxiety sensitivity: a twin study.

In attempting to explain the familial predisposition to panic disorder, most studies have focused on the heritability of physiologic characteristics (e.g., CO2 sensitivity). A heretofore unexplored possibility is that a psychological characteristic that predisposes to panic-anxiety sensitivity-might be inherited. In this study, the authors examined the heritability of anxiety sensitivity through use of a twin group. Scores on the Anxiety Sensitivity Index were examined in a group of 179 monozygotic and 158 dizygotic twin pairs. Biometrical model fitting was conducted through use of standard statistical methods. Broad heritability estimate of the Anxiety Sensitivity Index as a unifactorial construct was 45%. Additive genetic effects and unique environmental effects emerged as the primary influences on anxiety sensitivity. There was no evidence of genetic discontinuity between normal and extreme scores on the Anxiety Sensitivity Index. This study suggests that one psychological risk factor for the development of panic disorder-anxiety sensitivity-may have a heritable component. As such, anxiety sensitivity should be considered in future research on the heritability of panic disorder.

Daily Energy Expenditure of Male and Female Marsh Harrier Nestlings

We used the doubly labeled water (DLW) method to measure daily energy expenditure (DEE) in eight brother-sister pairs of free-living Marsh Harrier (Circus aerugi- nosus) nestlings. We calculated metabolizable energy intake (ME) from DEE and body-mass change. In each pair, males had lower body mass, DEE, and ME than their female siblings. On average, male body mass was 20%, DEE 19%, and ME 20% lower than that of female siblings. Thus, energy turnover was proportional to body mass. Because the average sex ratio at fledging in Marsh Harriers is 55% male, and the energy requirement of sons is 45% of the son-daughter pair, this sex ratio matches exactly that predicted by Fisher's theory (1930). A literature review revealed that DEE (kJ/ day) measured by DLW when nestlings were ap- proximately 95% of asymptotic or fledging mass scaled as 4.58 M 0-76 (where M = body mass in g) in 11 species of altricial nestlings, including the Marsh Harrier. Received 14 November 1996, accepted 3 December 1997.

Demographic anthropology in the study of matrimonial exchanges in a Dogon isolate

The Dogon population of Boni lives in the south-Sahelian bush of Mali, on several abrupt mountains. It forms a community within which each of its members finds a spouse. This criterion of membership is based on a concept of population taken in the “genetic sense”. This population is small (5000 persons approximately) and it forms a genetic isolate. Matrimonial exchanges are very important in the process of evolution of populations thus it can be useful to construct explanatory models. Different analysis levels allow to better describe a phenomenon resulting from a complex system of interdependent factors. -the global analysis is quantitative and shows the high endogamic level observed within each village and each mountain, -the qualitative analysis, motivated by a genetic study associated to criteria of choice of the spouse. -an anthropological analysis will be presented as a third possible level in the matrimonial market analysis. It consists of investigating alliance cycles based on the study of brother-sister pairs and implying three marriages. The high frequency of the type of cycle raises questions and incites to researching a coherent interpretation.

Dde I restriction fragment length polymorphism of the ??2-adrenoceptor gene does not correlate with blood pressure in the F2 generation obtained from crossing stroke-prone spontaneously hypertensive rats and Wistar???Kyoto rats

A pathogenetic role of altered alpha 2-adrenoceptors in essential hypertension has been suggested, based on studies in humans and animals. To examine the role of the alpha 2-adrenoceptor in genetically hypertensive rats, we compared the alpha 2-adrenoceptor genes of stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto (WKY) rats by restriction fragment length polymorphism analysis using human alpha 2-adrenoceptor probes (alpha 2-C10) and Dde I restriction endonuclease, and conducted a genetic cosegregation study. Five female WKY rats were bred with five male SHRSP. Eight pairs of F1 rats were mated in brother-sister pairs to yield an F2 population of 84 rats. Systolic blood pressure was determined by tail-cuff sphygmomanometry. Direct arterial blood pressure was taken under ether anaesthesia just before the rats were killed. Southern blots were performed using alpha 2C10 as a probe and the DNA from the F2 generation. A restriction fragment length polymorphism of the SHRSP allele of a 1.6-kb fragment and a WKY rat allele of a 0.9-kb fragment with a common band of 1.3 kb in SHRSP and WKY rats was found, as reported previously. The distribution of the genotype based on restriction fragment length polymorphism conformed to a 1:2:1 ratio in F2 rats, as expected for a Mendelian trait. There was no significant difference in the blood pressure of F2 rats with respect to alpha 2-adrenoceptor genotype. This study demonstrated that the alpha 2-adrenoceptor gene restriction fragment length polymorphism distribution is a Mendelian trait in the F2 rats of crossed SHRSP and WKY rats, but failed to show genetic cosegregation of this restriction fragment length polymorphism with blood pressure in this generation.

Familial psychosis and vulnerability to tardive dyskinesia.

The demography, course of illness, cognitive dysfunction and neurological consequences of long term treatment of 11 family pairs with long history of chronic schizophrenic illness were studied. There was concordance for the presence of tardive dyskinesia in 6 pairs; each of 2 brother-brother pairs; 3 brother-sister pairs and one of mother-daughter pair. There was concordance for the absence of tardive dyskinesia in 5 pairs, each of 3 father-son pairs and 2 brother-sister pairs. In schizophrenic patients the presence or absence of tardive dyskinesia in one member of the family is a risk factor for the development of the syndrome in another member with the same psychotic illness. Those pairs with tardive dyskinesia were characterized by negative symptoms of schizophrenia and evidence of intellectual deterioration.