Prevalence and Association of Obesity with Self-Reported Comorbidity: A Cross-Sectional Study of 1321 Adult Participants in Lasbela, Balochistan

Association of fatness with chronic metabolic diseases is a well-established fact, and a high prevalence of risk factors for these disorders has increasingly been reported in the third world. In order to incorporate any preventive strategies for such risk factors into clinical practice, decision-makers require objective evidence about the associated burden of disease. A cross-sectional study of 1321 adults from one of the districts of Balochistan, among the most economically challenged areas of Pakistan, was carried out for the measures of fatness and self-reported comorbidities. Body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR) were measured and demographic information and self-reported comorbidities were documented. The prevalence of obesity was 4.8% (95% CI: [3.8, 6.1]) and 21.7% (95% CI: [19.5, 24.0]), as defined by the World Health Organization (WHO) international and Asia/Asia-Pacific BMI cut-offs, respectively. The proportion exhibiting comorbidity increased with increasing levels of fatness in a dose-response relationship (p value < .001). An interaction of weight status with gender was observed to produce a significantly (p = .033) higher comorbidity among overweight women (odds ratio (OR) = 6.1 [1.2, 31.7]) compared with overweight men (OR = 1.1 [0.48, 2.75], p = .762).

The effect of mycobacterial virulence and viability on MAP kinase signalling and TNF alpha production by human monocytes

SETTING

The success of Mycobacterium tuberculosis as a human pathogen depends on its ability to tolerate and perhaps manipulate host defense mechanisms.

OBJECTIVE

To determine the induction of tumour necrosis factor-alpha (TNF alpha), a central mediator of immunity, by human monocytes infected with virulent M. tuberculosis, M. leprae and attenuated M. bovis BCG.

DESIGN

Mycobacteria-induced cellular activation pathways of TNF alpha production was investigated using an inhibitor of protein tyrosine kinase (PTKs) and an inhibitor of mitogen-activated protein (MAP) kinases.

RESULTS

TNF alpha production was significantly lower during infection with virulent M. tuberculosis than with BCG and this differential response was independent of mycobacterial viability. TNF alpha production involved the PTK and MAP kinase pathways. Reduced TNF alpha induction by M. tuberculosis was associated with a reduction in the extent and duration of phosphorylation of extracellular-signal regulated kinases (ERK 1/2). Infection with M. leprae triggered low and transient ERK 1/2 activation as well as low TNF alpha production.

CONCLUSION

Maintenance of the differential response in both live and heat-killed preparations suggests that the reduced TNF alpha response associated with virulent mycobacteria is due to differences in the presence of components capable of triggering host pattern recognition receptors, rather than events associated with phagosome trafficking or the active release of intracellular modulators.

Molecular mechanisms involved in human platelet aggregation by synergistic interaction of platelet-activating factor and 5-hydroxytryptamine

Our recent studies have shown that co-activation of Gq and Gi proteins by 5-hydroxytryptamine (5-HT) and adrenaline show synergism in human platelet aggregation. This study was conducted to examine the mechanism(s) of synergistic interaction of 5-HT and platelet activating factor (PAF) in human platelets. We show that PAF, but not 5-HT, increased platelet aggregation in a concentration-dependent manner. However, low concentrations of 5-HT (2 microM) potentiated platelet aggregation induced by subthreshold concentration of PAF (40 nM) indicating a synergistic interaction between the two agonists and this synergism was blocked by receptor antagonists to either 5-HT or PAF. 5-HT also potentiated the effect of PAF on thromboxane A2 (TXA2) formation and phosphorylation of extracellularly regulated mitogen-activated protein kinases (ERK1/2). The synergism of 5-HT and PAF in platelet aggregation was inhibited by calcium (Ca2+) channel blockers, verapamil and diltiazem, phospholipase C (PLC) inhibitor, U73122, cyclooxygenase (COX) inhibitor, indomethacin, and MEK inhibitor, PD98059. These data suggest that synergistic effect of 5-HT and PAF on human platelet aggregation involves activation of PLC/Ca2+, COX and MAP kinase pathways.

Agonist-induced signaling, desensitization, and internalization of a phosphorylation-deficient AT1A angiotensin receptor

An analysis of the functional role of a diacidic motif (Asp236-Asp237) in the third intracellular loop of the AT1A angiotensin II (Ang II) receptor (AT1-R) revealed that substitution of both amino acids with alanine (DD-AA) or asparagine (DD-NN) residues diminished Ang II-induced receptor phosphorylation in COS-7 cells. However, Ang II-stimulated inositol phosphate production, mitogen-activated protein kinase, and AT1 receptor desensitization and internalization were not significantly impaired. Overexpression of dominant negative G protein-coupled receptor kinase 2 (GRK2)K220M decreased agonist-induced receptor phosphorylation by approximately 40%, but did not further reduce the impaired phosphorylation of DD-AA and DD-NN receptors. Inhibition of protein kinase C by bisindolylmaleimide reduced the phosphorylation of both the wild-type and the DD mutant receptors by approximately 30%. The inhibitory effects of GRK2K220M expression and protein kinase C inhibition by bisindolylmaleimide on agonist-induced phosphorylation were additive for the wild-type AT1-R, but not for the DD mutant receptor. Agonist-induced internalization of the wild-type and DD mutant receptors was similar and was unaltered by coexpression of GRK2K220M. These findings demonstrate that an acidic motif at position 236/237 in the third intracellular loop of the AT1-R is required for optimal Ang II-induced phosphorylation of its carboxyl-terminal tail by GRKs. Furthermore, the properties of the DD mutant receptor suggest that not only Ang II-induced signaling, but also receptor desensitization and internalization, are independent of agonist-induced GRK-mediated phosphorylation of the AT1 receptor.

Wortmannin inhibits platelet aggregation produced by interaction of gamma-aminobutyric acid and the calcium tonophore, A23187

Platelet aggregation by gamma-aminobutyric acid (GABA) agonists combined with a calcium ionophore was studied. GABA, baclofen and mucimol markedly amplified aggregatory responses to a subthreshold concentration of the ionophore, A23187. This effect was inhibited by wortmannin, a blocker of phosphoinositide 3-kinase. However, several antagonists of GABA receptors had no effect on the response, and benzodiazepines inhibited aggregation. These results suggest that the GABA effect is not mediated by traditional neuronal GABA receptors. We propose that wortmannin inhibits aggregation at a nexus downstream from membrane mechanisms triggered by the GABA-A23187 interaction.

Synergistic interaction of adrenaline and histamine in human platelet aggregation is mediated through activation of phospholipase, map kinase and cyclo-oxygenase pathways

This study was conducted to examine the mechanism(s) of synergistic interaction of histamine- and adrenaline-mediated human platelet aggregation. We found that platelet aggregation mediated by subthreshold concentrations of histamine (1-4 microm) plus adrenaline (0.5-2 microm) is inhibited by both an alpha(2)-adrenoceptor blocker (yohimbine) and a histamine (H1) receptor antagonist (diphenhydramine). In examining the role of the downstream signalling pathway, we found that such an interaction is inhibited by the calcium channel blockers verapamil and diltiazem. However, platelet aggregation by adrenaline plus histamine was inhibited by very low concentrations of the phospholipase C (PLC) inhibitor, U73122 (IC(50)= 1.2 microm), the MEK inhibitor, PD98059 (IC(50)= 1.1 microm) and the cyclo-oxygenase (COX) inhibitor, indomethacin (IC(50)= 7 microm). However the inhibition of receptor tyrosine kinase, protein kinase C and phosphatidylinositol 3-kinase by genistien, chelerythrine and wortmannin, respectively, had no significant effect on aggregation. Similarly the nitric oxide donor (SNAP) had no effect on this synergism. These data suggest that the synergistic effect of histamine and adrenaline during human platelet aggregation is receptor mediated and involves activation of PLC, COX and MAP kinase signalling pathways.

Studies on antihypertensive and antispasmodic activities of methanol extract of Acacia nilotica pods

A methanol extract of Acacia nilotica pods (AN) caused a dose-dependent (3-30 mg/kg) fall in arterial blood pressure. Treatment of animals with atropine abolished the vasodilator response of acetylcholine (ACh), whereas the antihypertensive effect of the plant extract remained unaltered. Phentolamine (an alpha-adrenergic blocker) abolished the vasoconstrictor effect of norepinephrine (NE), whereas pretreatment of the animal with AN, did not modify the NE response. These results indicate that the antihypertensive effect of plant extract is independent of muscarinic receptor stimulation or adrenoceptor blockade. In the in vitro studies, AN produced a dose-dependent (0.3-3.0 mg/mL) inhibitory effect on force and rate of spontaneous contractions in guinea-pig paired atria. Similarly, it inhibited the spontaneous contraction of rabbit jejunum in a concentration-dependent (0.1-3.0 mg/mL) manner. AN also inhibited K(+)-induced contractions in rabbit jejunum at a similar concentration range, which suggests that the antispasmodic action of AN is mediated through calcium channel blockade, and this may also be responsible for the blood pressure lowering effect of AN, observed in the in vivo studies.

Inhibitory effect of curcumin, a food spice from turmeric, on platelet-activating factor- and arachidonic acid-mediated platelet aggregation through inhibition of thromboxane formation and Ca2+ signaling

Curcumin, a dietary spice from turmeric, is known to be anti-inflammatory, anticarcinogenic, and antithrombotic. Here, we studied the mechanism of the antiplatelet action of curcumin. We show that curcumin inhibited platelet aggregation mediated by the platelet agonists epinephrine (200 microM), ADP (4 microM), platelet-activating factor (PAF; 800 nM), collagen (20 microg/mL), and arachidonic acid (AA: 0.75 mM). Curcumin preferentially inhibited PAF- and AA-induced aggregation (IC50; 25-20 microM), whereas much higher concentrations of curcumin were required to inhibit aggregation induced by other platelet agonists. Pretreatment of platelets with curcumin resulted in inhibition of platelet aggregation induced by calcium ionophore A-23187 (IC50; 100 microM), but curcumin up to 250 microM had no inhibitory effect on aggregation induced by the protein kinase C (PKC) activator phorbol myrsitate acetate (1 microM). Curcumin (100 microM) inhibited the A-23187-induced mobilization of intracellular Ca2+ as determined by using fura-2 acetoxymethyl ester. Curcumin also inhibited the formation of thromboxane A2 (TXA2) by platelets (IC50; 70 microM). These results suggest that the curcumin-mediated preferential inhibition of PAF- and AA-induced platelet aggregation involves inhibitory effects on TXA2 synthesis and Ca2+ signaling, but without the involvement of PKC.

Cholera toxin mediated regulation of the expression of Gq alpha and G11 alpha GTP binding proteins

Previously it has been shown that persistent activation of the stimulatory adenylyl cyclase pathway with cholera toxin (CT) downregulates the Gs alpha polypeptide (80%) in a cAMP-independent manner in C6 glioma cells (Shah, 1997). This study was conducted to examine the short and long term effects of CT on the regulation of pertussis toxin-sensitive and -insensitive G proteins and their transcripts in C6 glioma cells. Treatment of C6 cells with CT (100 ng/ml) up to 16 h had no effect on either Gi or Gq/11 alpha proteins. However, prolonged exposure (24-48 h) caused increased expression of Gi (20-30%) and Gq/11 alpha proteins (40%). Urea gradient gels, which can separate Gq alpha and G11 alpha proteins, revealed that prolonged CT treatment increased the expression of both of these G proteins. The CT-mediated enhanced expression of Gq alpha and G11 alpha proteins was accompanied by increased mRNA levels of these proteins as determined by RT/PCR. Cyclic-AMP elevating agents like forskolin (10 microM) and db-cAMP (1 mM) mimicked the effect of CT on Gi but not Gq/11 alpha proteins. These studies show long term cAMP-dependent regulation of Gi and cAMP-independent expression of Gq/11 alpha proteins in C6 glioma cells.

Co-activation of Gi and Gq proteins exerts synergistic effect on human platelet aggregation through activation of phospholipase C and Ca2+ signalling pathways

Our previous studies have shown that subthreshold concentrations of two platelet agonists exert synergistic effects on platelet aggregation. Here we studied the mechanism of synergistic interaction of 5-hydroxytryptamine (5-HT) and epinephrine mediated platelet aggregation. We show that 5-HT had no or little effect on aggregation but it did potentiate the aggregation response of epinephrine. The synergistic interaction of 5-HT (1-5 microM) and epinephrine (0.5-2 microM) was inhibited by alpha2-adrenoceptor blocker (yohimbine; IC50= 0.4 microM), calcium channel blockers (verapamil and diltiazem with IC50 of 10 and 48 mM, respectively), PLC inhibitor (U73122; IC50=6 microM) and nitric oxide (NO) donor, SNAP (IC50=1.6 microM)). The data suggest that synergistic effects of platelet agonists are receptor-mediated and occur through multiple signalling pathways including the activation PLC/Ca2+ signalling cascades.

Dual effects of nimesulide, a COX-2 inhibitor, in human platelets

Nimesulide (CAS 51803-78-2) has been shown to exert marked anti-inflammatory effect in several in vivo models of inflammation. Since nimesulide is considered to be a selective inhibitor of COX-2, it has not been studied in detail in relation to its mechanistic effects on platelets, which express COX-1. This study was conducted to investigate the effects of nimesulide in platelet aggregation. We show that nimesulide (1-100 microM) inhibited platelet aggregation induced by adrenaline (20-200 microM). It also inhibited thromboxane A2 (TXA2) formation by platelets at low concentration (IC50; 1 microM). However, much lower concentrations of nimesulide (0.01-0.1 microM) potentiated the aggregatory response of subthreshold concentrations of adrenaline (0.2-2 microM). Such an effect was blocked by Ca2+-channel blockers, verapamil and diltiazem (IC50: 7 and 46 microM, respectively), nitric oxide donor, SNAP (IC50; 2 microM) and cinchonine (10 nM) but not by genistein (up to 10 microM). These results are indicative of the concentration-dependent dual effects of nimesulide on human platelet aggregation. The synergistic effect of low doses of nimesulide and adrenaline seems to be mediated through inhibition of multiple signalling pathways.

The inhibitory effect of cinchonine on human platelet aggregation due to blockade of calcium influx

The Cinchona bark contains alkaloids like quinine, quinidine, cinchonine and cinchonidine. These agents are effective antimalarial drugs and have been used clinically in malaria caused by Plasmodium falciparum. Previous studies show that quinine and quinidine exert effects on cardiovascular system. This study was conducted to examine the effect of cinchonine on human platelet aggregation. The results show that cinchonine inhibited platelet aggregation mediated by platelet agonists, epinephrine (200 microM), ADP (4.3 microM), platelet activating factor (PAF; 800 nM) and collagen (638 nM) but had no effect on arachidonic acid (AA; 0.75 mM). Cinchonine was most effective in inhibiting aggregation induced by platelet activating factor and epinephrine with IC50 values of 125 and 180 microM respectively, however, higher concentrations of cinchonine were required to inhibit aggregation mediated by ADP or collagen (IC50; 300 microM). Pretreatment of platelets with cinchonine inhibited aggregation caused by Ca2+ ionophore, A-23187 (6 microM), in a dose-dependent manner (IC50; 300 microM) indicating an inhibitory effect on Ca2+-signaling cascade. This was supported by measuring [Ca2+]i in platelets loaded with Fura-2AM where cinchonine inhibited the rise in cytosolic Ca2+ mediated by A-23187 (6 microM) or collagen (638 nM). Results show that cinchonine (20 microM) also inhibited aggregation when platelets were pretreated with protein kinase C (PKC) activator, phorbol myristate acetate (PMA; 0.1 microM) in combination with low doses of platelet activating factor (80 nM). Cinchonine, however, had no effect on AA-induced platelet aggregation and thromboxane A2 (TXA2) synthesis in platelets. These results suggest that antiplatelet effects of cinchonine are mediated mainly through inhibition of Ca2+-influx and protein kinase C pathways in platelets.

Esculetin prevents liver damage induced by paracetamol and CCL4

Esculetin, a phenolic compound found in Cichorium intybus and Bougainvllra spectabillis was investigated for its possible protective effect against paracetamol and CCl4-induced hepatic damage. Paracetamol produced 100% mortality at the dose of 1 g kg-1 in mice while pre-treatment of animals with esculetin (6 mg kg-1) reduced the death rate to 40%. Oral administration of paracetamol (640 mg kg-1) produced liver damage in rats as manifested by the rise in serum enzyme levels of alkaline phosphatase (ALP) and aminotransferases (AST and ALT). Pre-treatment of rats with esculetin (6 mg kg-1) prevented the paracetamol-induced rise in serum enzymes. The hepatotoxic dose of CCl4 (1.5 ml kg-1; orally) also raised serum ALP, AST and ALT levels. The same dose of esculetin (6 mg kg-1) was able to prevent the CCl4-induced rise in serum enzymes. Esculetin also prevented CCl4-induced prolongation in pentobarbital sleeping time confirming hepatoprotectivity. These results indicate that esculetin possesses anti-hepatotoxic activity and the presence of this compound in Cichorium intybus and Bougainvllra spectabillis may explain the folkloric use of these plants in liver damage.

Perinatal exposure to morphine disrupts brain norepinephrine, ovarian cyclicity, and sexual receptivity in rats

The effect of perinatal exposure to morphine on the development of catecholaminergic and reproductive function in female rats was investigated. Adult rats received morphine intraperitoneally daily for 40 days. The dose of morphine was progressively increased at 10-day intervals from 5, 7.5, 10 to 15 mg/kg body weight until day 40. The rats were mated between days 38 and 45. Administration of morphine at dose rates of 20 and 30 mg/kg continued during pregnancy. The dose was increased to 40 mg/kg for 10 days postpartum. Results showed that morphine disrupted ovarian cyclicity in 52% of the females. Amongst the remaining females, 43% became pregnant when mated. In the female offspring born to such dams, sexual maturation was delayed and body weight was reduced until weaning. At adulthood, lordosis behavior was inhibited when the female offspring were tested against stimulus males. Plasma estradiol and ovarian estradiol and progesterone levels were reduced. Norepinephrine concentration in the hypothalamus was reduced, whereas it remained unchanged in the amygdala. Dopamine concentrations in both hypothalamus and amygdala were not influenced by perinatal morphine exposure. These results suggest that chronic morphine treatment during perinatal life selectively influences the development of noradrenergic mechanisms in the rat brain and this may in turn be responsible for reduced reproductive activity.

The antiplatelet aggregatory activity of Acacia nilotica is due to blockade of calcium influx through membrane calcium channels

1. The extract of Acacia nilotica (A. nilotica) blocked platelet aggregation mediated by platelet agonists, arachidonic acid (0.75 mM), ADP (4.3 microM), platelet activating factor (800 nM) and collagen (638 nM) in a dose-dependent manner. 2. The extract (0.21-1.4 mg/ml) blocked the platelet aggregation induced by Ca2+ ionophore, A-23187 (6 microM), in a dose-dependent manner, indicating that the Ca2+ influx is involved in aggregation. 3. The plant extract also inhibited aggregation in platelets pretreated with phorbol, 12-myristate, 13-acetate (196 nM) alone or in combination with ADP (4.3 microM), indicating an effect on protein kinase C. 4. These results indicate that the antiplatelet aggregatory activity of the extract of A. nilotica is mainly due to blockade of Ca2+ channels, although evidence also suggests the involvement of protein kinase C.

Anti-thrombotic and anti-inflammatory activities of protopine

The effects of protopine on human platelet aggregation and arachidonic acid (AA) metabolism via cyclooxygenase (COX) and lipoxygenase (LOP) enzymes were examined. Platelet aggregation induced by various platelet agonists (AA, ADP, collagen and PAF) was strongly inhibited by protopine in a concentration-related manner. The IC50 values (microM) of protopine (mean +/- SEM) against: AA; 12 +/- 2: ADP; 9 +/- 2: collagen; 16 +/- 2 and PAF; 11 +/- 1, were much less than those observed for aspirin. In addition, protopine selectively inhibited the synthesis of thromboxane A2 (TXA2) via COX pathway and had no effect on the LOP pathway in platelets. In vivo, pretreatment with protopine (50-100 mg kg-1) protected rabbits from the lethal effects of AA (2 mg kg-1) or PAF (11 micrograms kg-1) in dose-dependent fashion. Protopine (50-100 mg kg-1) also inhibited carrageenan-induced rat paw oedema with a potency of three-fold as compared to aspirin. These results are suggestive that protopine acts as a potent inhibitor of thromboxane synthesis and PAF with anti-inflammatory properties.

Causal role for jun protein in the stimulation of choline acetyltransferase by insulin in embryonic chick retina

Previous work showed that the availability of insulin to the embryonic chick retina at a critical developmental stage stimulated the activity of the acetylcholine synthetic enzyme, choline acetyltransferase (ChAT) (R. E. Hausman et al., 1991, Dev. Brain Res. 59, 31-37). Here we show that a 2- to 5-min exposure to insulin results in a greater than 24 hr elevation in ChAT protein. Immediately following exposure to insulin there is a transient increase in the level of jun protein followed by an increase in ChAT. The stimulation of ChAT protein is not the result of an overall stimulation of protein synthesis as other proteins are not affected. Exposure of the cells to antisense oligonucleotide to jun, but not to sense oligonucleotide, reduces the increase in both jun and ChAT. These and previous results suggest that insulin is necessary for the characteristic increase in ChAT protein during retina development and that this increase requires the transient synthesis of jun.

Effects of lipoproteins on cyclo-oxygenase and lipoxygenase pathways in human platelets

The products of arachidonic acid (AA) metabolism in platelets play an important role in platelet shape change, adhesion and aggregation which may participate in the pathogenesis of ischemic heart disease and thrombosis. Since lipoproteins are also involved in the pathogenesis of thrombo-embolic disorders, the effect of human lipoproteins (HDL, LDL, VLDL) on AA metabolism in human platelets was investigated. Lipoproteins were separated by density gradient zonal ultracentrifugation. The effects of lipoproteins on production of AA metabolites in human platelets i.e., thromboxane A2 (TXA2) and hydroxy-eicosatetraenoic acids (HETEs) were examined using radiometric thin layer chromatography coupled with automated data integrator system. In human platelets, HDL inhibited 12-HETE and TXA2 formation in a concentration-dependent manner. LDL had a strong inhibitory effect on TXA2 production and a weak inhibitory effect on 12-HETE production. VLDL had no effect on platelet AA metabolism. These findings point to a new facet of lipoproteins action and suggest that lipoproteins may have a physiological role in the regulation of AA metabolism in platelets.

Neonatal androgen manipulation differentially affects the development of monoamine systems in rat cerebral cortex, amygdala and hypothalamus

Neural tissue during perinatal life is sufficiently plastic to respond to the presence of testicular androgens. Here we studied the effect of neonatal androgen manipulation (castration of male and androgenization of female rats) on monoamine neurotransmitter systems in the cerebral cortex and sexually dimorphic regions of brain (hypothalamus and amygdala). Norepinephrine (NE) and dopamine (DA) concentrations in cortex, amygdala and hypothalamus of rats were assayed by HPLC at days 25, 60, 120, 180, 240 and 300. Results show that NE levels in all groups of rats at day 25 were higher in the hypothalamus (5-9 ng/mg protein) compared to the amygdala (0.5-3 ng/mg protein) and the cortex (0.5-1 ng/mg protein). Levels of DA at day 25 in the hypothalamus and the amygdala were comparable (up to 3.5 ng/mg) but higher than in the cortex (1.25-1.75 ng/mg protein). NE and DA concentrations in sham-castrated male and androgen-treated females were higher at day 25 compared to castrated male and control females in both amygdala and hypothalamus; however, levels of NE and DA remained unchanged in the cortex. Pattern of NE concentrations started reversing with increase in age, i.e., NE levels in control females and castrated males increased almost 4-fold in amygdala and 2-fold in hypothalamus by day 300, but there was no significant change in the cortex. Compared to that, NE levels decreased in sham-castrated male (2-fold) and androgen-treated females (3-fold) in amygdala as well as in the hypothalamus (2-fold) in both these groups. A similar pattern of reversal of DA levels was found in both amygdala and hypothalamus, however, at day 300 DA levels were comparable in all the four groups. These studies suggest that androgen manipulation (castration or androgen administration) induces age-dependent short- and long-term effects on the development of noradrenergic and dopaminergic systems in the sexually dimorphic regions of brain, amygdala and hypothalamus, without a significant change in the cerebral cortex.

Enhanced degradation of stimulatory G-protein (Gs alpha) by cholera toxin is mediated by ADP-ribosylation of Gs alpha protein but not by increased cyclic AMP levels

Cholera toxin (CT) catalyses ADP-ribosylation of the alpha-subunit of stimulatory protein (Gs) leading to stimulation of adenylyl cyclase and elevated intracellular cAMP. Persistent treatment (24-48 h) of C6 glioma cells with cholera toxin (100 ng/ml) caused marked downregulation of Gs alpha (75-80%) which could not be mimicked by dibutyryl cAMP (1 mM) and forskolin (10 microM) over the same time periods suggesting that CT-mediated Gs alpha downregulation is independent of cAMP production. However, CT increased the expression of Gq/11 alpha proteins at 24 and 48 h of treatment. The increase in mRNA levels of Gq/11 alpha proteins preceded the increase in Gq/11 proteins. Such stimulatory effects of CT were mimicked by forskolin and dibutyryl-cAMP. These results suggest that CT-mediated downregulation of Gs alpha is independent of cAMP but CT upregulates the expression of Gq/11 alpha proteins in a cAMP-dependent manner.

Protein kinase C inhibitor, chelerythrine, potentiates the adrenaline-mediated aggregation of human platelets through calcium influx

The role of protein kinase C (PKC) using its selective inhibitor, chelerythrine, in agonist mediated platelet aggregation was studied. Chelerythrine had no effect on the aggregation induced by adrenaline, PAF, collagen and ADP at the maximum doses of these agonists. However, it potentiated the aggregatory response of low doses of adrenaline (0.4-1 microM). Such an effect was blocked by Ca(++)-channel blockers, verapamil and diltiazem indicating the likely involvement of Ca++ influx in the platelet aggregation during the cascade.

Phosphatidylinositol 3-kinase inhibitor, wortmannin, inhibits 5-hydroxytryptamine-mediated potentiation of platelet aggregation induced by epinephrine

The role of phosphatidylinositol 3-kinase (PI 3-kinase) was investigated in human platelets exposed to varying doses of 5-hydroxytryptamine (5-HT) and subthreshold doses of epinephrine. The synergistic effect of 5-HT on epinephrine-induced aggregation was blocked by a specific inhibitor of PI 3-kinase, wortmannin, in a dose-dependent manner. However, there was no effect of inhibitors of protein kinase A (PKA) or protein kinase C (PKC). These studies suggest a role of PI 3-kinase in the 5-HT induced potentiation of epinephrine-mediated platelet aggregation.

Expression of the human beta 2-adrenoceptor in NCB20 cells results in agonist activation of adenylyl cyclase and agonist-mediated selective down-regulation of Gs alpha

Murine neuroblastoma x embryonic Chinese hamster brain NCB20 cells were transfected with a construct containing the human beta 2-adrenoceptor under the control of a beta-actin promoter. Two clones were selected for detailed analysis: D1, which expressed some 12.7 pmol/mg of membrane protein, and L9, which expressed 1.2 pmol/mg of membrane protein of the receptor. Incubation with the beta-adrenoceptor agonist isoprenaline resulted in stimulation of adenylyl cyclase activity in both of the clones, whereas no such activation was observed in wild-type NCB20 cells. The EC50 for isoprenaline stimulation of adenylyl cyclase activity in membranes of clone D1 (0.8 nM) was significantly lower, however, than in membranes of clone L9 (10.4 nM). Although the maximal adenylyl cyclase stimulation by isoprenaline was similar in both clones, D1 had a higher basal activity. Immunoblotting studies with specific antipeptide antisera directed against various G protein alpha subunits showed that treatment of the cells with isoprenaline resulted in a 35% reduction in the membrane-associated levels of Gs alpha in membranes of clone L9 cells and a 50% reduction in Gs alpha levels in membranes prepared from clone D1. Isoprenaline treatment had no effect on the levels of Gs alpha in wild-type NCB20 cells, and such treatment had no effect on the levels of other G protein alpha subunits such as Gq/G11 and Gi2 in any of the cell lines investigated. Time course analysis revealed that half-maximal loss of Gs alpha in clone D1 was achieved within 1-2 h of addition of agonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Gonadotrophin-releasing hormone receptor agonist-mediated down-regulation of Gq alpha/G11 alpha (pertussis toxin-insensitive) G proteins in alpha T3-1 gonadotroph cells reflects increased G protein turnover but not alterations in mRNA levels

Prolonged exposure of alpha T3-1 pituitary gonadotrophs to a gonadotrophin-releasing hormone receptor agonist results in marked down-regulation of the pertussis toxin-insensitive G proteins Gq alpha and G11 alpha. The turnover of Gq alpha/G11 alpha was substantially accelerated in the presence of agonist. By contrast, the rate of degradation of the G protein Gi2 alpha was unaffected by agonist treatment. Analysis of Gq alpha/G11 alpha mRNA levels by reverse transcription-PCR demonstrated no detectable differences between control and agonist-treated cells. These studies indicate that gonadotrophin-releasing hormone receptor agonist-mediated down-regulation of Gq alpha/G11 alpha is a reflection of enhanced proteolysis of the activated G proteins.

Biochemical approaches to examine the specificity of interactions between receptors and guanine nuclotide binding proteins

It is now appreciated both that G-protein-linked receptors and signal transducing heterotrimeric G-proteins consist of large multi-member superfamilies and that regulation of a signal transduction cascade can be produced by a variety of means following activation of a G-protein by a receptor. To begin to unravel the complexities of this regulation it is clearly important to be able to define the molecular identity of the G-protein or G-proteins activated by a receptor and to assess the quantitative importance of such interactions for the integration of signals produced by a receptor agonist. Substantial progress has been made towards these goals in recent years and the purpose of this short review will be to discuss the use and potential limitations of some of the currently most widely used approaches.

The gonadotrophin-releasing hormone receptor of alpha T3-1 pituitary cells regulates cellular levels of both of the phosphoinositidase C-linked G proteins, Gq alpha and G11 alpha, equally

The alpha T3-1 cell line, an immortalized gonadotroph cell line, expresses high levels of the gonadotrophin-releasing hormone (GnRH) receptor. Sustained exposure of these cells to the GnRH receptor agonist des-Gly10-[D-Ala6]luteinizing hormone-releasing hormone ethylamide resulted in a substantial down-regulation of cellular levels of a combination of the alpha subunits of the phospholipase C-beta 1-linked G proteins Gq and G11, as assessed by immunoblotting with an antiserum able to identify these two proteins equally. This effect was dependent upon the concentration of agonist used (EC50 = 4 nM) and on the time of the treatment (t1/2 = 6 hr) when a maximally effective concentration of agonist (1 microM) was used. Comparison of agonist regulation of inositol phosphate generation and Gq alpha/G11 alpha down-regulation demonstrated that effects on inositol phosphate production were approximately 3-fold more potent. In contrast to Gq alpha/G11 alpha, membrane-associated levels of Gs alpha and G12 alpha, the G proteins that transduce stimulatory and inhibitory regulation, respectively, of adenylyl cyclase, were not altered by agonist treatment. Analysis of mRNA by reverse transcriptase/polymerase chain reaction indicated the coexpression by alpha T3-1 cells of mRNA corresponding to both Gq alpha and G11 alpha. Immunoblotting with antisera selective for either Gq alpha or G11 alpha confirmed their coexpression. Resolution of membranes from untreated and agonist-treated alpha T3-1 cells under sodium dodecyl sulfate-polyacrylamide gel electrophoresis conditions able to separate Gq alpha from G11 alpha indicated that G11 alpha was more prevalent than Gq alpha at steady state but that agonist treatment regulated cellular levels of both of these G proteins in a nonselective manner. Sustained activation of protein kinase C with phorbol myristate acetate was unable to mimic agonist regulation of cellular Gq alpha/G11 alpha levels, as was treatment of alpha T3-1 cells with the selective protein kinase C inhibitor chelerythrine. These data suggest that the GnRH receptor is able to interact functionally with both Gq alpha and G11 alpha in alpha T3-1 cells and that sustained exposure to a GnRH receptor agonist selectively regulates the cellular levels of the G proteins that interact with the receptor.

Effects of cell signaling on the development of GABA receptors in chick retina neurons

R-cognin, a cell recognition molecule, and insulin are known to play significant roles in GABAergic differentiation in the developing chick retina. In the present study, the effects of insulin and R-cognin on post-synaptic (GABAceptive) differentiation were investigated. In ovo binding of [3H]GABA and [3H]flunitrazepam ([3H]Flu) to the GABA and benzodiazepine (BZD) receptors, respectively, remained at low levels during early embryogenesis but increased sharply from mid-embryogenesis through hatching, increases which also occur in cultured neurons from early-embryonic (E7) and mid-embryonic (E11) chick retina. E7 neurons respond to insulin treatment (100 ng/ml) with increased [3H]Flu binding but no change in [3H]GABA binding. Cognin antibody (10 micrograms/ml) treatment of E7 neurons caused no significant inhibition of the developmental increases in binding of either radioligand. Insulin in E11 cultures led to greater developmental increases in binding sites for both radioligands, but exposure to cognin antibody was without significant effect. These data, along with previous studies, indicate that GABAergic differentiation in developing chick retina is regulated, in part, by insulin and cognin-mediated cell signaling. Insulin also regulates post-synaptic (GABAceptive) differentiation whereas cognin-mediated interactions are relatively insignificant.

Effect of insulin on GABAergic development in the embryonic chick retina

We investigated the role of insulin in GABAergic differentiation in the embryonic chick retina at different embryonic ages using glutamate decarboxylase (GAD) and high-affinity GABA uptake as developmental markers. Both these GABAergic markers exhibit developmentally programmed increases in activity during retinogenesis that also occur in culture. Insulin stimulated GABA uptake in retina neurons at all embryonic ages in a dose-dependent manner and GAD activity by 30% in embryonic retina neurons after 11 days of development. The stimulation of GABA uptake by insulin was blocked by addition of ouabain suggesting a role for the Na+,K+ ATPase. The same concentration of insulin caused a 76% stimulation of protein synthesis in these retinal cells, and previous work demonstrated that insulin also stimulates cholinergic differentiation in the chick retina (Hausman et al., Dev. Brain. Res. 59, (1991) 31-37). Thus, there was no selective stimulation of GABAergic differentiation by insulin but likely a neurotrophic effect. The increase in GAD activity in neurons from post-11-day embryonic neurons contrasts with our previous findings at embryonic days 6-7 where there is little change in GAD activity after addition of insulin. It is possible that the failure of insulin to stimulate GAD activity during early retina development is due to the increased accumulation of GABA in the presence of insulin. GABA levels were increased more than two-fold by 100 ng/ml insulin.

Role of the cell recognition molecule, cognin, in GABAergic differentiation in chick retina

Previous work showed that GABAergic differentiation in developing chick retina depends on insulin and cell interactions. Here, we investigated whether it depended on cell signaling mediated by retina cognin, a 50 kDa cell recognition molecule. Cognin mediates cell adhesion in vitro and occurs on retinal neurons that become both GABAergic and cholinergic. We investigated two markers of GABAergic differentiation: glutamate decarboxylase (GAD) activity and high-affinity GABA uptake. Both increase during differentiation of retinal neurons in culture and can be easily measured. We blocked cognin-mediated cell signaling with cognin antibody and found a reduction of the developmental increase in GAD activity in cultures of retinal neurons from 7 and 11 day chick embryos. There was no reduction of high-affinity GABA uptake. This suggested that cognin-mediated signaling was necessary for the normal developmental increase in GAD but not for high-affinity GABA uptake. These results contrasted with our previous observations on cholinergic differentiation in cultured retinal neurons. We found that cognin antibody blocked the normal developmental increase in choline acetyltransferase (ChAT) only if the cells were exposed before embryonic day 7. Thus, while both GAD and ChAT activity appear to be controlled by cell signaling involving cognin, the periods of developmental sensitivity for the two differentiation markers are different. Antibodies to other adhesion molecules, Ng-CAM, and N-cadherin, did not similarly affect GAD activity. Antibodies to laminin at a 10-fold higher concentration inhibited GAD activity only in early embryonic retina. Tests for protein synthesis and "housekeeping" enzyme activity demonstrated that the cognin antibody effect was selective for neuronal differentiation pathways.(ABSTRACT TRUNCATED AT 250 WORDS)

Initial cholinergic differentiation in embryonic chick retina is responsive to insulin and cell-cell interactions

Previous work [Kyriakis et al., Proc. Natl. Acad. Sci. U.S.A., 84 (1987) 7463-7467] had shown that insulin, when added during a window of binding from embryonic days 9-11, stimulates the normal developmental increase in choline acetyltransferase (ChAT) activity (a marker for cholinergic differentiation) in cultured embryonic chick retinal neurons. Here, we investigated the effect of insulin and IGF 1 on embryonic chick retinal neurons at the stage of development (embryonic day 6) when ChAT activity is first expressed. We investigated insulin peptide effects in retinal tissue developing in vitro as well as in cultures of retinal cells. We show that insulin also stimulated the initial embryonic increase in ChAT activity but had no stimulatory effect on glutamic acid decarboxylase activity (a marker for GABAergic differentiation), an enzyme whose activity also increases developmentally in the same retinal neurons. In fact, insulin inhibited the expression of GAD activity in the retina. The insulin-mediated increase in ChAT activity was independent of normal cell-cell interactions but could not replace them. Insulin also stimulated choline uptake but only after a two day delay, suggesting that the normal program for cholinergic differentiation in the chick retina was induced by insulin. IGF 1 did not have any effect on either cholinergic or GABAergic differentiation. We conclude that cholinergic differentiation in chick embryo retinal neurons is dependent on both insulin- and cell contact-mediated signals.

Effect of chronic administration of aspirin, phenobarbitone and oxytetracycline on the plasma levels of vitamin A in albino rats

Effect of chronic administration of aspirin, phenobarbitone and oxytetracycline under therapeutic doses on the bioavailability of vitamin A was determined in different groups of albino rats. The rats treated with phenobarbitone (group C) showed significantly decreased vitamin A level in plasma whereas the other two groups (B and D) treated with aspirin and oxytetracycline respectively did not exhibit any significant difference as compared to control group (A).

Flu like syndrome with rifampicin pulse therapy

Flu like syndrome was found in a patient of BT leprosy taking Rifampicin in pulse therapy. This side effect was absent when the dose of Rifampicin was decreased. Details of this case is given with a review of literature.

Use of Benzathine Pencillin in Impectigo in Children

One hundred and fifty children having impetigo were investigated bacteriologically. Pure growth of staphylococcus aureus was found in 92 children, Streptococcus pyogenes in 39 children and both organisms were isolated in 19 children. Forty four per cent Staphylococcus aureus and 82% Streptococcus pyogenes were sensitive to penicillin. One hundred children were treated with injection benzathine penicillin and fifty cases treated with oral tablet sulfamoxole. Benzathine pencillin was effective in 92.3% cases irrespective of whether the staphylococci and streptococci isolated were sensitive to penicillin or not. Sulfamoxole therapy was effective in 64% children.

Tetanus in a case of lepromatous leprosy

A patient of Lepromatous Leprosy had neuropathic plantar ulcer of 6 months duration. He developed "Tetanus". We are reporting this case with review of literature, as there is dearth of published literature on this association of Leprosy and Tetanus.