Interspersed repeats in the horse (Equus caballus); spatial correlations highlight conserved chromosomal domains.

The interspersed repeat content of mammalian genomes has been best characterized in human, mouse and cow. In this study, we carried out de novo identification of repeated elements in the equine genome and identified previously unknown elements present at low copy number. The equine genome contains typical eutherian mammal repeats, but also has a significant number of hybrid repeats in addition to clade-specific Long Interspersed Nuclear Elements (LINE). Equus caballus clade specific LINE 1 (L1) repeats can be classified into approximately five subfamilies, three of which have undergone significant expansion. There are 1115 full-length copies of these equine L1, but of the 103 presumptive active copies, 93 fall within a single subfamily, indicating a rapid recent expansion of this subfamily. We also analysed both interspersed and simple sequence repeats (SSR) genome-wide, finding that some repeat classes are spatially correlated with each other as well as with G+C content and gene density. Based on these spatial correlations, we have confirmed that recently-described ancestral vs. clade-specific genome territories can be defined by their repeat content. The clade-specific Short Interspersed Nuclear Element correlations were scattered over the genome and appear to have been extensively remodelled. In contrast, territories enriched for ancestral repeats tended to be contiguous domains. To determine if the latter territories were evolutionarily conserved, we compared these results with a similar analysis of the human genome, and observed similar ancestral repeat enriched domains. These results indicate that ancestral, evolutionarily conserved mammalian genome territories can be identified on the basis of repeat content alone. Interspersed repeats of different ages appear to be analogous to geologic strata, allowing identification of ancient vs. newly remodelled regions of mammalian genomes.

Genome sequence, comparative analysis, and population genetics of the domestic horse.

We report a high-quality draft sequence of the genome of the horse (Equus caballus). The genome is relatively repetitive but has little segmental duplication. Chromosomes appear to have undergone few historical rearrangements: 53% of equine chromosomes show conserved synteny to a single human chromosome. Equine chromosome 11 is shown to have an evolutionary new centromere devoid of centromeric satellite DNA, suggesting that centromeric function may arise before satellite repeat accumulation. Linkage disequilibrium, showing the influences of early domestication of large herds of female horses, is intermediate in length between dog and human, and there is long-range haplotype sharing among breeds.

Sex-dependence of body fat distribution in patients with obesity and hypertension.

The relationship of body fat distribution with blood pressure, fat cell weight and extracellular fluid volume was studied and compared in 20 obese hypertensive men and 20 obese hypertensive women of similar age, degree of overweight and blood pressure level. Body fat distribution, as reflected by the ratio between waist and hip circumference (W/H ratio), was significantly higher in male than in female obese patients. The W/H ratio was positively and independently correlated with systolic arterial pressure both in males and females. However, for the same W/H ratio, systolic arterial pressure was higher in females. The W/H ratio was positively correlated with gluteal fat cell weight only in males and not in females. Both in males and females, the W/H ratio was positively correlated with extracellular fluid volume, independently of the level of blood pressure level and/or the degree of obesity. The study provided evidence that the relationship between body weight and blood pressure in obese hypertensives is affected by the sex-dependence of body fat distribution with possible interferences on fat cell weight and extracellular fluid volume. Several epidemiological studies have emphasized the positive correlation observed between body weight and blood pressure in many. Many investigations have documented the association of blood pressure with body weight, weight to height, overweight or other indices of fatness such as skinfold thickness. However, the correlation coefficients of these different relationships were found constantly small, indicating that the relationship between overweight and blood pressure is somewhat complex. In patients with hypertension, body weight was shown to be strongly related with the levels of both blood pressure and extracellular fluid volume. On the other hand, patients with overweight and hypertension were found to be principally affected by hypertrophic obesity, as shown by the evaluation of fat cell weight. However these findings were exclusively observed in males. No solid data were reported in females. The relationships between body weight and extracellular fluid on one hand, and between body weight and fat cell weight on the other hand, are certainly different in males and in females. First, in females, extracellular fluid volume is submitted to cyclic changes in sodium balance involving the effect of sex steroid hormones. Second, body fat distribution, a parameter which is weakly correlated to blood pressure, is different in males and females. In males, body fat predominates in the upper part of the body while, in females, adiposity is mainly observed in the lower part of the body.(ABSTRACT TRUNCATED AT 400 WORDS)

Forearm haemodynamics in obese normotensive and hypertensive subjects.

Forearm haemodynamics using pulsed Doppler flowmetry were studied in 83 men: 15 non-obese and eight obese normotensive subjects; 30 non-obese and 30 obese hypertensive patients. Mean ages were similar in the four subgroups. The blood pressure of normotensives and hypertensives was identical in obese and non-obese subjects. Blood flow, expressed in ml/min, was significantly higher in obese subjects, whether normotensive or hypertensive. However, when blood flow was expressed per unit litre of forearm volume, it was similar in the four subgroups. Forearm vascular resistance, whether expressed as absolute or normalized values, was significantly higher (P less than 0.001) in non-obese hypertensives. When obese and non-obese hypertensives were compared, the former were characterized by higher values of blood flow velocity and blood flow, and lower values of vascular resistance, whether absolute or normalized values were used. This study shows firstly that forearm vascular resistance in hypertensives is increased exclusively in non-obese subjects, and secondly that obese hypertensives, when compared with non-obese hypertensives, are characterized by a hyperkinetic forearm circulation.