Endothelin-1 blockade prevents COX2 induction and TXA2 production in the fructose hypertensive rat

Feeding rats with a high fructose diet results in insulin resistance and hypertension. Fructose-hypertensive rats (FHR) have increased vascular levels of endothelin-1 (ET-1) and thromboxane (TXA2). We have previously shown that chronic treatment with either the dual endothelin receptor blocker, bosentan, or the thromboxane synthase inhibitor, dazmegrel, prevented fructose-induced increases in blood pressure, suggesting that both ET-1 and TXA2 play important roles in the development of hyperinsulinemia/insulin resistance-associated hypertension. In this study, we investigated the potential interrelationship between ET-1 and TXA2 in the development of fructose-induced hypertension in vivo. Male Wistar rats were fed on a high fructose diet for 9 weeks. Either bosentan or dazmegrel treatment (daily by oral gavage) was initiated 3 weeks after the start of fructose feeding for a total duration of 6 weeks. At the end of drug treatment, blood and aorta were collected from each animal. Plasma thromboxane B2 (TXB2), a stable TXA2 metabolite, increased significantly in FHR and was reduced to control level by both chronic bosentan and dazmegrel treatment. Protein expression of cyclooxygenase 2 (COX2) was elevated significantly in FHR aortas and treatment with bosentan and dazmegrel corrected these changes. These results indicate that the actions of ET-1 in the aorta of FHR may be mediated through COX2-derived TXA2. Bosentan may prevent the development of hypertension in fructose-fed rats through inhibition of COX2 induction and subsequently the reduction in plasma TXA2.     

An Approaching Motor Boat Induces Stress-Related Behaviors in Proboscis Monkeys (Nasalis larvatus) Living in a Riparian Area

International Journal of Primatology - Primate ecotourism is a fast-growing tourism sector that may have a negative effect on wildlife. In riparian areas, tourists can conveniently reach primates...     

Isoprenylcysteine carboxy methylation is essential for development in Dictyostelium discoideum

Members of the Ras superfamily of small GTPases and the heterotrimeric G protein gamma subunit are methylated on their carboxy-terminal cysteine residues by isoprenylcysteine methyltransferase. In Dictyostelium discoideum, small GTPase methylation occurs seconds after stimulation of starving cells by cAMP and returns quickly to basal levels, suggesting an important role in cAMP-dependent signaling. Deleting the isoprenylcysteine methyltransferase-encoding gene causes dramatic defects. Starving mutant cells do not propagate cAMP waves in a sustained manner, and they do not aggregate. Motility is rescued when cells are pulsed with exogenous cAMP, or coplated with wild-type cells, but the rescued cells exhibit altered polarity. cAMP-pulsed methyltransferase-deficient cells that have aggregated fail to differentiate, but mutant cells plated in a wild-type background are able to do so. Localization of and signaling by RasG is altered in the mutant. Localization of the heterotrimeric Ggamma protein subunit was normal, but signaling was altered in mutant cells. These data indicate that isoprenylcysteine methylation is required for intercellular signaling and development in Dictyostelium.     

Immunoregulatory effects of regulated, lung-targeted expression of IL-10 in vivo

Regulation of pulmonary inflammation involves an intricate balance of both pro- and anti-inflammatory mediators. Acute lung injury can result from direct pulmonary insults that activate alveolar macrophages to respond with increased cytokine expression. Such cytokine gene expression is mediated in part via NF-kappaB. IL-10 has been previously identified as an important endogenous anti-inflammatory cytokine in vivo on the basis of inhibiting NF-kappaB activation; however, the mechanism of this inhibition remains incompletely defined. We hypothesized that IL-10 regulated NF-kappaB activation in vivo via IkappaK inhibition. A bitransgenic mouse that allowed for externally regulated, lung-specific human IL-10 overexpression was generated. In the bitransgenic mice, introduction of doxycycline induced lung-specific, human IL-10 overexpression. Acute induction of IL-10 resulted in significant decreases in bronchoalveolar lavage fluid neutrophils (48%, P = 0.03) and TNF (62%, P < 0.01) following intratracheal LPS compared with bitransgenic negative mice. In vitro kinase assays showed this decrease to correlate to diminished lung IkappaK activity. Furthermore, we also examined the effect of chronic IL-10 overexpression in these transgenic mice. Results show that IL-10 overexpression in lungs of mature mice increased the number of intrapulmonary cells the phenotype of which was skewed toward increased B220+/CD45+ B cells and CD4+ T cells and was associated with increased CC chemokine expression. Thus regulated, lung-specific IL-10 overexpression may have a variety of complex immunologic effects depending on the timing and duration of expression.     

Prenatal exposure to thyroid hormone is necessary for normal postnatal development of murine heart and lungs

Maternal hypothyroxinemia during early pregnancy poses an increased risk for poor neuropsychological development of the fetus. We tested the hypothesis that maternal hypothyroidism before the onset of fetal thyroid function also affects postnatal development of heart and lungs. This question was addressed in transgenic mice that express herpes simplex virus thymidine kinase in their thyroidal follicle cells. Treatment with ganciclovir rendered these mice severely hypothyroid because viral thymidine kinase converts ganciclovir into a cytotoxic nucleoside analog. Since ganciclovir crosses the placenta, it also destroyed the thyroid of transgenic embryos while leaving the thyroids of nontransgenic littermates unaffected. Hypothyroidism of both mother and fetus did not affect prenatal heart and lung development. However, the postnatal switch from beta- to alpha-myosin heavy chain (beta- and alpha-MHC, respectively) gene expression and the increase of SERCA-2a mRNA expression did not occur in the ventricular myocardium of either the transgenic (thyroid destroyed) or nontransgenic (intact thyroid) offspring of hypothyroid mothers. Similarly, postnatal animals of the latter two groups retained elevated surfactant protein (SP) A, B, and C mRNA levels in their alveolar epithelium. In hypothyroid pups from hypothyroid mothers, these changes were accompanied by decreased alveolar septation. Our study shows that these effects of maternal hypothyroidism become manifest after birth and are aggravated by the concomitant existence of neonatal hypothyroidism.     

Serum-free organ culture of suckling rat jejunum: Effect of regulatory hormones

Summary To facilitate the study of regulators of differentiation and proliferation of small intestinal epithelium in the suckling rat we have developed a serum-free organ culture system and used it to examine epithelial responsiveness to various regulatory hormones. These hormones included the insulin-like growth factors (IGFs) whose action can be blocked by binding proteins in serum. Jejunal explants from 5-day-old suckling rats maintained better brush border enzyme activity and better histology when cultured under hyperbaric conditions for 24 h in serum-free Dulbecco’s modified Eagle’s medium/F12 medium than in RPMI 1640 plus 10% fetal bovine serum. Tissue responsiveness to various regulatory hormones was then tested in the serum-free medium. Insulin had no significant effect on morphology, proliferation rate, or enzyme activity in 5-day explants after 24 h in culture. However, insulin did increase lactase activity and induce the early appearance of sucrase in 10- and 12-day explants after 48 h culture. Dexamethasone increased specific activities of alkaline phosphatase (30%,P<0.001) and lactase (15%,P<0.001), and reduced shedding of alkaline phosphatase into the medium (P<0.001), in explants of 5-day-old rats cultured over 24 h. Dexamethasone combined with insulin had no obvious effect on the rate of protein or DNA synthesis but did increase villus height (P=0.04) and crypt depth (P=0.001) and acted synergistically to further increase lactase activity above levels obtained by either alone. IGF-I and IGF-II, des-(1–3)IGF-I, fibroblast growth factor (FGF), and growth hormone (GH) had no effect on morphology or biochemical activity of explants after 24 or 48 h culture. In conclusion, histology, enzyme activity, protein, and DNA synthesis of suckling rat jejunal explants were equivalent or better in serum-free than in serum-containing organ culture systems. Furthermore, biological responsiveness was demonstrated by dexamethasone and insulin altering the explants morphologically or biochemically. None of the IGFs or GH had any biological effects, raising doubts about their direct biological action on the developing intestinal epithelium.     

Modulation of the amino acid control of hepatic protein degradation by caloric deprivation. Two modes of alanine co-regulation

Intracellular protein degradation in perfused livers of fed rats has been shown to be directly regulated by 7 amino acids (Leu, Tyr, Gln, Pro, Met, His, and Trp) and co-regulated by alanine. Responses to graded increases of regulatory amino acids (individually or combined) are multiphasic and include (a) an initial inhibition at 0.5 times normal plasma concentrations, (b) a localized, zonal loss of inhibition at normal levels, and (c) suppression to basal rates at 4 times normal concentrations or greater; the zonal loss of inhibition is prevented by 0.5 mM (normal) alanine. In further perfusion studies carried out at the usual time (1100 h), we have occasionally observed a sharp decrease in proteolytic responsiveness at normal amino acid concentrations. The decrease, which occurred spontaneously in normal fed rats, was attributed to a nearly 90% loss in the sensitivity of alanine co-regulation. In all instances, alanine sensitivity was restored after 4 to 24 h of starvation. The cause of the insensitivity and the mechanism of its reversal by caloric deprivation are not presently known. Starvation for 24 h also appeared to alter the individual inhibitory effectiveness of Leu, Tyr, and Gln. On the other hand, inhibition by the full regulatory group at 4 times normal plasma levels was unchanged when compared with the complete plasma mixture except for a concentration shift in the peak zonal loss of proteolytic inhibition from 1.25 to 0.6 times plasma levels. Since the shift paralleled known changes in portal vein regulatory amino acids, it may have been adaptive in nature. As with fed animals, the zonal loss in starvation was abolished by 0.5 mM alanine, but not with high levels of lactate and pyruvate (10 mM), a finding consistent with the view that co-regulation is mediated by the recognition of alanine per se rather than its metabolism.     

Kinetic study of the irreversible thermal denaturation of Bacillus licheniformis alpha-amylase.

The irreversible thermal inactivation of Bacillus licheniformis alpha-amylase was studied. A two-step behaviour in the irreversible denaturation process was found. Our experimental results are consistent only with the two-step model and rule out the two-isoenzyme one. They suggest that the deactivation mechanism involves the existence of a temperature-dependent intermediate form. Therefore the enzyme could exist in a great number of active conformational states. We have shown that Ca2+ is necessary for the structural integrity of alpha-amylase. Indeed, dialysis against chelating agents leads to a reversible enzyme inactivation, though molecular sieving has no effect. Further, the key role of Ca2+ in the alpha-amylase thermostability is reported. The stabilizing effect of Ca2+ is reflected by the decrease of the denaturation constants of both the native and the intermediate forms. Below 75 degrees C, in the presence of 5 mM-CaCl2, alpha-amylase is completely thermostable. Neither other metal ions nor substrate have a positive effect on enzyme thermostability. The effect of temperature on the native enzyme and on one intermediate form was studied. Both forms exhibit the same optimum temperature. Identical activation parameters for the hydrolytic reaction catalysed by these two forms were found.