The Effect of Chronic Long-Term Intermittent Hypobaric Hypoxia on Bone Mineral Density in Rats: Role of Nitric Oxide

Intermittent hypoxia is the most common pattern of hypoxic exposure in humans. The effect of chronic long-term intermittent hypobaric hypoxia (CLTIHH) on bone metabolism is not investigated. We examined the effect of CLTIHH on bone metabolism and the role of nitric oxide (NO) in this process. The rats were divided into three groups in this study. The animals in groups I and II have been exposed to CLTIHH. The animals in group II were also treated with nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester. To obtain CLTIHH, rats were placed in a hypobaric chamber (430 mm Hg; 5 h/day, 5 days/week, 5 weeks). The group III (control) rats breathed room air in the same environment. At the begining of the experiments, bone mineral density (BMD) of the animals were measured, and blood samples were collected from the tail vein. After the 5-week CLTIHH period, the same measurements were repeated. Parathyroid hormone, calcium, phosphate, bone alkaline phosphatase (b-ALP), NO, interleukin 1 beta, interleukin 6, and tumor necrosis factor alpha levels were determined. The cytokines, NO levels, and BMD in CLTIHH-induced rats were higher compared with baseline and control values. The cytokines, b-ALP, and BMD increased while NO levels decreased in the group II compared with baseline values. BMD values of group II were lower than group I but higher than control group. Our results suggested that CLTIHH has positive effects on bone density. Intermittent hypoxia protocols may be developed for treatment and prevention of osteopenia and osteoporosis.     

Bone metabolism in ovariectomized rats with induced hyperthyroidism: the effect of estrogen replacement

We aimed to investigate whether or not the estrogen is playing any role in the effect of thyroid hormones on bone metabolism. The rats were divided into five groups. In the first group L-thyroxine-induced hyperthyroid rats were ovariectomized (OVX) while the OVX rats were administered L-thyroxine in the second group. 17beta-Estradiol (E2) was replaced in OVX rats in Group III. L-thyroxine and E2 were simultaneously administered to OVX rats in Group IV. The fifth group received sham operation. Blood samples taken from the tail vein of rats were analyzed for plasma T3, T4, TSH and serum interleukin (IL)-1beta, IL-6, tumor necrosis factor (TNF)alpha, calcium (Ca), phosphorous (P), parathyroid [corrected] hormone (PTH), alkaline phosphatase (t-ALP), bone-specific alkaline phosphatase (b-ALP) and E2. The levels of cytokines, t-ALP and b-ALP increased but PTH decreased, while there was no change in Ca and P levels in L-thyroxine-administrated rats. However, the levels of cytokines, Ca, P, PTH, t-ALP and b-ALP did not change in L-thyroxine-administered OVX rats. In OVX rats, the cytokines, t-ALP and b-ALP increased while Ca, P remained the same, but PTH decreased. L-thyroxine administration to OVX rats did not change the cytokines, Ca, P, PTH, t-ALP and b-ALP levels. The replacement of E2 in OVX rats decreased the cytokines, t-ALP and b-ALP values, increased PTH levels while there was no change in Ca and P. L-thyroxine and E2 administration to OVX rats increased the cytokines, t-ALP and b-ALP levels and decreased PTH, but Ca and P remained the same. In sham-operated rats, there was no change in all parameters compared to initial values. This study suggests that estrogen may play a role in the effects of thyroid hormones on bone metabolism.     

Gaucher disease and brucella: just a mere coincidence?

Gaucher disease type I and brucellosis are chronic diseases with similar symptoms and physical signs though the former is the most common lysosomal storage disease and the latter is an infectious disease. The similarities between these diseases make differential diagnosis difficult. Immunodeficiency is a feature of Gaucher disease type I and increases the susceptibility towards infections. A Gaucher disease type I patient with brucellosis is presented with improvement after treatment of brucellosis.     

Cytosolic phospholipase A2alpha is targeted to the p47phox-PX domain of the assembled NADPH oxidase via a novel binding site in its C2 domain

We have previously demonstrated a physical interaction between cytosolic phospholipase A2alpha (cPLA2) and the assembled NADPH oxidase on plasma membranes following neutrophil stimulation. The aim of the present study was to define the exact binding sites between these two enzymes. Here we show, based on blot overlay experiments, F?rster resonance energy transfer analysis and studies in neutrophils from patients with chronic granulomatous disease deficient in p67phox or p47phox, that cPLA2 specifically binds to p47phox and that p47phox is sufficient to anchor cPLA2 to the assembled oxidase on the plasma membranes upon stimulation. Blot overlay and affinity binding experiments using subfragments of cPLA2 and p47phox demonstrated that the cPLA2-C2 domain and the p47phox-PX domain interact to form a complex that is resistant to high salt. Computational docking was used to identify hydrophobic peptides within these two domains that inhibited the association between the two enzymes and NADPH oxidase activity in electro-permeabilized neutrophils. These results were used in new docking computations that produced an interaction model. Based on this model, cPLA2-C2 domain mutations were designed to explore its interaction p47phox in neutrophil lysates. The triple mutant F35A/M38A/L39A of the cPLA2-C2 domain caused a slight inhibition of the affinity binding to p47phox, whereas the single mutant I67A was highly effective. The double mutant M59A/H115A of the p47phox-PX domain caused a significant inhibition of the affinity binding to cPLA2. Thus, Ile67 of the cPLA2-C2 domain is identified as a critical, centrally positioned residue in a hydrophobic interaction in the p47phox-PX domain.     

Osteoporotic cytokines and bone metabolism on rats with induced hyperthyroidism; changes as a result of reversal to euthyroidism

Hyperthyroidism is characterized by increased bone turnover and resorptive activity. Raised levels of serum osteoporotic cytokines, such as interleukin (IL) -1beta, IL-6 and tumor necrosis factor (TNF)-alpha have been demonstrated previously in hyperthyroidism. These elevations are controversial and it is difficult to differentiate the contribution of thyroid hormones to the elevation of cytokines from that of the autoimmune inflammation in Graves' disease (GD) and follicular cell damage in thyroiditis. Therefore, we investigated the effect of thyroid hormones on serum IL-1beta, IL-6, TNF-alpha levels and bone metabolism on L-thyroxine induced hyperthyroid rats and changes in cytokine levels and bone metabolism on the same rats after reversal to euthyroidism. Rats were treated with L-thyroxine for 5 weeks (0.4 mg/ 100 g food). Plasma T3, T4, TSH and serum IL-1beta, IL-6, TNFalpha, Calcium (Ca), phosphorous (P), parathyroid hormone (PTH), alkaline phosphatase (ALP), bone alkaline phosphatase (B-ALP) levels were measured and differential leucocyte counts were made initially, at the 5th week of the experiment (hyperthyroid state) and 5 weeks after quitting the administration of L-thyroxine (euthyroid state). Significant rises in serum IL-1beta, IL-6 and TNFalpha were noted in hyperthyroidism (P < 0.001). In euthyroid state, IL-15, IL-6 and TNFalpha decreased significantly, but IL-beta and TNFalpha were significantly higher than the baseline values (P < 0.05) while IL-6 levels turned back to the baseline values. Plasma T3 and T4 levels were significantly correlated with serum cytokines in hyperthyroid state while there was no correlation in euthyroid states. Ca and P levels did not differ significantly while PTH levels declined significantly in the hyperthyroid state (P < 0.05). After the reversal to the euthyroidism, there was no significant change in Ca, P and PTH levels. ALP and B-ALP increased significantly in hyperthyroidism (P < 0.001, P < 0.01) and they did not decrease in euthyroid state. The lymphocyte number and ratio in differentials increased significantly in the hyperthyroid state (P < 0.001). In euthyroidism they decreased significantly (P < 0.001) but it was significantly higher than the baseline value (P < 0.05). Our findings showed that the deleterious effect on bone metabolism in hyperthyroidism might be mediated by cytokines and the increased bone turnover in hyperthyroidism failed to decrease despite euthyroidism.     

The role of peripheral chemoreceptor activity on the respiratory responses to hypoxia and hypercapnia in anaesthetised rabbits with induced hypothyroidism

The purpose of this study was to investigate the role of peripheral chemoreceptor activity on the hypoxic and hypercapnic ventilatory drives in rabbits with induced hypothyroidism. Experiments were carried out in control and hypothyroid rabbits. Hypothyroidism was induced by an administration of an iodide-blocker, methimazole in food (75 mg/100 g food) for ten weeks. At the end of the tenth week, triiodothyronine (T3) and thyroxine (T4) levels significantly decreased (P<0.001) while thyroid stimulating hormone (TSH) increased (P<0.001). Tidal volume (VT), respiratory frequency (f/min), ventilation minute volume (VE) and systemic arterial blood pressure (BP) were recorded during the breathing of the normoxic, hypoxic (8% O2-92% N2) and hypercapnic (6% CO2-Air) gas mixtures, in the anaesthetised rabbits of both groups. At the end of each experimental phase, PaO2, PaCO2, and pHa were measured. The same experimental procedure was repeated after peripheral chemoreceptor denervation in both groups. VT significantly decreased in some of the rabbits with hypothyroidism during the breathing of the hypoxic gas mixture (nonresponsive subgroup) (P<0.05). After chemodenervation, a decrease in VT was observed in this nonresponsive subgroup during normoxia (P<0.05). The percent decrease in VT in nonresponsive subgroup of hypothyroid rabbits after chemodenervation was lower than that of the chemodenervated control animals (P<0.01). When these rabbits with hypothyroidism were allowed to breath the hypercapnic gas mixtures, increases in VT and VE were not significant. In conclusion, although there is a decrease in peripheral chemoreceptor activity in hypothyroidism, it does not seem to be the only cause of decrease in ventilatory drive during hypoxia and hypercapnia.     

Antlers and parasites

Development of ornamental characters exposed to directional selection may be particularly sensitive to the effect of parasitic infections. Antlers are ornamental characters of importance in intraspecific interactions, and are in reindeer (Rangifer) developed by both males and females. By antihelmintic treatment of naturally infected female reindeer we show that parasite intensities affect development of antler asymmetry, but not antler length. These results suggest that asymmetry in antlers may reflect parasite intensities and thus be of importance in intraspecific assessment of genetic resistance towards infectious organisms.     

No Spillover Effect of the Foreclosure Crisis on Weight Change: The Diabetes Study of Northern California (DISTANCE)

The emerging body of research suggests the unprecedented increase in housing foreclosures and unemployment between 2007 and 2009 had detrimental effects on health. Using data from electronic health records of 105,919 patients with diabetes in Northern California, this study examined how increases in foreclosure rates from 2006 to 2010 affected weight change. We anticipated that two of the pathways that explain how the spike in foreclosure rates affects weight gain—increasing stress and declining salutary health behaviors- would be acute in a population with diabetes because of metabolic sensitivity to stressors and health behaviors. Controlling for unemployment, housing prices, temporal trends, and time-invariant confounders with individual fixed effects, we found no evidence of an association between the foreclosure rate in each patient''s census block of residence and body mass index. Our results suggest, although more than half of the population was exposed to at least one foreclosure within their census block, the foreclosure crisis did not independently impact weight change.     

The role of nitric oxide on bone metabolism in ovariectomized rats following chronic ethanol intake

This experimental study was designed to examine the effect of nitric oxide (NO) on bone metabolism in ovariectomized rats following chronic ethanol treatment. Chronic ethanol intake was produced by gradual substitution (within 3 weeks) of tap water in diet with 5,10,15 and finally 20% of ethanol. Thereafter, the rats were maintained under these conditions for a duration of 4 months. The rats were divided into two groups. The first group received sham operation (SHAM) and the rats in Group II were ovariectomized (OVX). Five weeks after the SHAM and ovariectomy, the rats were treated with ethanol for 4 months. After this period of ethanol administration, the NOS inhibitor N(W)-nitro-L-arginine methyl ester (L-NAME) was given for three weeks along with ethanol to the same rats. Serum interleukin (IL)-1beta, IL-6, tumor necrosis factor (TNF)-alpha, NO, calcium (Ca), phosphorous (P), parathyroid hormone (PTH), 25 HydroxyvitaminD3 [25(OH)D3], alkaline phosphatase (ALP), bone alkaline phosphatase (b-ALP), alanine amino transferase (ALT), aspartate amino transferase (AST), gamma-glutamyltransferase (GGT) levels were measured in different stages of the experiment. IL-1beta, IL-6, TNFalpha and NO levels increased after ethanol administration in SHAM and OVX rats.The decrease in serum Ca was significant while the changes in P, PTH and 25 (OH)D3 levels were not. ALP and b-ALP levels were significantly decreased; ALT, AST and GGT levels were significantly increased. In ovariectomized and SHAM rats, administration of L-NAME together with ethanol, produced a significant increase in IL-1beta, IL-6 and TNFalpha levels. In this group, Ca and P levels were significantly increased, PTH and 25 (OH)D3 levels were significantly decreased. Also, there was a significant decrease in ALT, AST, ALP, b-ALP, and GGT levels. NO increase due to alcohol intake may function as a protective mechanism preventing bone resorption in cases of estrogen insufficiency.