Kashin-Beck disease and iodine deficiency in Tibet.
(9/210)
We evaluated iodine and selenium status in 575 children between 5 and 15 years with Kashin-Beck disease from endemic and non-endemic areas. Of these 267 (46%) children had goiter. The proportion of subjects with goiter was higher in the villages with Kashin-Beck disease than in the control village. In the villages with Kashin-Beck disease, 105 (23%) of the subjects had a serum thyrotropin greater than 10 mU/l as compared with 3 (4%) in the control village. The percentages of low serum thyroxine values and low serum tri-iodothyronine were greater in the villages where Kashin-Beck disease was endemic than in the control village. The percentages of low urinary iodine concentration were significantly greater in the subjects with Kashin-Beck disease. The results suggest that in areas where severe selenium deficiency is endemic, iodine deficiency is a risk factor for Kashin-Beck disease. (+info)
Kashin-Beck disease and drinking water in Central Tibet.
(10/210)
A cross-sectional survey was carried out in order to study the relationship between Kashin-Beck disease and drinking water. The average volume of the water containers was larger in families unaffected by the disease. Organic material was measured by ultraviolet (UV) spectroscopy. The UV absorbency was significantly lower in drinking water of unaffected families. Thus, the organic material in drinking water may play a role in the pathogenesis of Kashin-Beck disease. (+info)
Ethno-agricultural approach to the rural environment in the prevention of Kashin-Beck disease.
(11/210)
Kashin-Beck disease occurs in several villages of Tibet; however, its local importance varies greatly. The ecoclimatological as well as the phytogeographical framework of the studied area are presented. An ecological approach based upon the ethno-ecosystem concept was carried out in the vicinity of each village. This study identifies 18 vegetation units on a structural basis; they were named for the dominant plants of each unit. Half of them belonged to the aquatic milieu. The different factors controlling their distribution were also identified. Particular attention will be paid to the links between man and the environment, particularly regarding alternative food intakes and water supply access. (+info)
Epidemiological support for a multifactorial aetiology of Kashin-Beck disease in Tibet.
(12/210)
We carried out a cross-sectional study in 12 rural villages in order to identify the risk factors for Kashin-Beck disease in Tibet. Children aged 5-15 years (n=575) were examined and their corresponding houses were visited. Samples were collected in order to study fungal contamination of stored grain and the organic matter content of drinking water. Multivariate analysis was performed using logistic regression and population attributable fractions were computed to estimate the impact of each factor. The following variables were independently associated with the disease: age, gender, low socio-economic status, indicators of a poorly diversified diet, iodine deficiency and small water container size (with higher organic matter levels in small containers). Selenium deficiency was severe in all study subjects. The degree of fungal contamination of barley grain was related to the highest percentage of cases (65%) in a sample of the study population. Higher urinary iodine levels were not associated with decreasing prevalence rates when Alternaria sp. was isolated. The data that we report supports the hypothesis that Kashin-Beck disease occurs as a consequence of oxidative damage to cartilage and bone cells when associated with decreased antioxidant defence. Another mechanism that may coexist is bone remodelling stimulated by thyroid hormones whose actions can be blocked by certain mycotoxins. (+info)
Effects of physical therapy on patients with Kashin-Beck disease in Tibet.
(13/210)
A clinical trial of physical therapy treatment for patients suffering from Kashin-Beck disease (KBD) has been carried out in Tibet. One-hundred and thirty-five patients with Kashin-Beck disease were allocated to either physical therapy (72 patients) or prescription of multivitamins (63 patients). The patients were followed for 4 years. This study suggested a beneficial effect of physical treatment. (+info)
Genetic composition and diploid hybrid speciation of a high mountain pine, Pinus densata, native to the Tibetan plateau.
(14/210)
Pinus densata has been suggested to have originated from hybridization events involving P. tabulaeformis and P. yunnanensis. In this study, allozyme differentiation at 12 loci was studied in 14 populations of P. tabulaeformis, P. densata, and P. yunnanensis from China. The observed genetic composition of P. densata supported the hybrid hypothesis and showed varying degrees of contribution from P. yunnanensis and P. tabulaeformis among its populations. These data, together with previous chloroplast DNA results, indicated different evolutionary histories among P. densata populations. To examine the possibility of ongoing hybridization among the three species, we analyzed patterns of linkage disequilibria between allozyme loci in ovule, pollen, and zygote pools. None of these tests suggested that there is significant ongoing gene exchange, implying that populations of P. densata have a stabilized hybrid nature. The normal fertility and high fecundity of P. densata indicate that this hybrid is maintained through sexual reproduction. P. densata represents an example of diploid hybrid speciation in an extreme ecological habitat that is both spatially and ecologically separated from that of its parents. (+info)
Muscle tissue adaptations to hypoxia.
(15/210)
This review reports on the effects of hypoxia on human skeletal muscle tissue. It was hypothesized in early reports that chronic hypoxia, as the main physiological stress during exposure to altitude, per se might positively affect muscle oxidative capacity and capillarity. However, it is now established that sustained exposure to severe hypoxia has detrimental effects on muscle structure. Short-term effects on skeletal muscle structure can readily be observed after 2 months of acute exposure of lowlanders to severe hypoxia, e.g. during typical mountaineering expeditions to the Himalayas. The full range of phenotypic malleability of muscle tissue is demonstrated in people living permanently at high altitude (e.g. at La Paz, 3600-4000 m). In addition, there is some evidence for genetic adaptations to hypoxia in high-altitude populations such as Tibetans and Quechuas, who have been exposed to altitudes in excess of 3500 m for thousands of generations. The hallmark of muscle adaptation to hypoxia in all these cases is a decrease in muscle oxidative capacity concomitant with a decrease in aerobic work capacity. It is thought that local tissue hypoxia is an important adaptive stress for muscle tissue in exercise training, so these results seem contra-intuitive. Studies have therefore been conducted in which subjects were exposed to hypoxia only during exercise sessions. In this situation, the potentially negative effects of permanent hypoxic exposure and other confounding variables related to exposure to high altitude could be avoided. Training in hypoxia results, at the molecular level, in an upregulation of the regulatory subunit of hypoxia-inducible factor-1 (HIF-1). Possibly as a consequence of this upregulation of HIF-1, the levels mRNAs for myoglobin, for vascular endothelial growth factor and for glycolytic enzymes, such as phosphofructokinase, together with mitochondrial and capillary densities, increased in a hypoxia-dependent manner. Functional analyses revealed positive effects on V(O(2)max) (when measured at altitude) on maximal power output and on lean body mass. In addition to the positive effects of hypoxia training on athletic performance, there is some recent indication that hypoxia training has a positive effect on the risk factors for cardiovascular disease. (+info)
Angiotensin-converting enzyme gene polymorphism and its association with essential hypertension in a Tibetan population.
(16/210)
There is strong evidence to support the idea that the renin-angiotensin system (RAS) plays an important role in the pathogenesis of essential hypertension (EH) and its complications. However, existing data about the association of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism with blood pressure is conflicting, mainly due to racial differences and environmental exposure status. We therefore conducted a case control study to observe the relationship between ACE I/D polymorphism and EH in a Tibetan population who live in relatively isolated areas and are genetically homogeneous. The study was conducted at stable residential communities in the urban district of Lhasa, the capital of the Tibet autonomous region, China, and 106 unrelated EH patients and 135 normotensIve subjects were recruited. PCR, PCR/RFLP and PCR-SSCP were carried out to study the association between RAS genes and EH. Frequencies for the DD, ID and II genotypes were 27, 47 and 29 in hypertensive subjects, and 15, 60 and 48 in normotensive subjects, respectively. Derived allele frequencies for the I and D alleles were 0.51 and 0.49 in hypertensive subjects and 0.64 and 0.36 in normotensive subjects. There were significant differences in genotype distribution and derived allele frequency between these two groups. The genotype and allele frequencies of the ACE gene differed significantly between hypertensive and normotensive females (p>0.05), but there were no differences in males. In females, the DBP and MAP level were significantly higher for the DD than for the ID and II genotype, and SBP was significantly higher for the DD than for the II genotype. But in males, there were no significant differences in blood pressure among ACE genotypes. The results showed a significant association between the D allele of the ACE gene and hypertension in Tibetan women but not in Tibetan men. (+info)