The effect of sildenafil on the elasticity of erythrocytes in homozygous sickle cell disease.

Purpose: One of the features of homozygous sickle cell disease (HbSS) is the impaired elasticity of the erythrocyte membrane that could impede microcirculatory blood flow and cause hypoxia and tissue damage. We investigated the effect of sildenafil, a phosphodiesterase 5 (PDE5) inhibitor that inhibits the breakdown of cyclic guanosine monophosphate (cGMP) resulting in vasodilatation, on the elasticity of HbSS erythrocyte. Materials and Methods: Blood samples from ten HbSS patients in steady state was exposed to different doses (5, 10, 20, and 40 μg/mL) of sildenafil and the elasticity of the erythrocytes measured at native hematocrit with the BioProfiler. An equal number of subjects with normal hemoglobin (HbAA) served as the control group. Results: There was a marginal increase in elasticity with 5 μg/mL of the drug and this became significant (P < 0.05) with the 10 μg/mL dose. Thereafter, gradual nonsignificant decreases were observed with the 20 and 40 μg/mL doses. A similar trend was observed for the control group. The elasticity values for the HbSS subjects at native hematocrit were significantly (P < 0.05) less when compared with the corresponding concentrations for the HbAA controls. This was reversed at a corrected hematocrit of 45%. Conclusion: The result of this study shows that sildenafil caused an initial increase in erythrocyte membrane elasticity in both HbSS and HbAA subjects, and this later decreased with increasing concentration of the drug possibly due to the dual effect of cyclic adenosine monophosphate (cAMP).

Primary pigmented nodular adrenocortical disease and Cushing's syndrome

Primary pigmented nodular adrenocortical disease (PPNAD) is a form of bilateral adrenocortical hyperplasia that is often associated with corticotrophin (ACTH)-independent Cushing's syndrome (CS) and is characterized by small to normal-sized adrenal glands containing multiple small cortical pigmented nodules (1,2). PPNAD may occur in an isolated form or associated with a multiple neoplasia syndrome, the complex of spotty skin pigmentation, myxomas, and endocrine overactivity, or Carney complex, in which Cushing's syndrome is the most common endocrine manifestation (3). Molecular studies have led to the identification of several genes, defects in which may predispose PPNAD formation; all of these molecules play important role for the cAMP signaling pathway. This review intends to present the most recent knowledge of the pathology and molecular genetics of the benign bilateral adrenocortical lesions, as well as to discuss the modern tools for diagnostics and treatment of this condition.

A doença adrenocortical nodular pigmentada primária (PPNAD) é uma forma de hiperplasia adrenocortical bilateral que está freqüentemente associada com a síndrome de Cushing (SC) ACTH-independente, sendo caracterizada por glândulas adrenais de tamanho pequeno ou normal contendo múltiplos nódulos corticais pigmentados pequenos. PPNAD pode ocorrer de forma isolada ou associada com uma síndrome de neoplasia múltipla, o complexo de manchas pigmentadas na pele (lentigíneas), mixomas e hiperatividade endócrina, ou complexo de Carney, no qual a SC é a manifestação endócrina mais comum. Estudos moleculares levaram à identificação de vários genes que, quando mutados, podem predispor à formação da PPNAD; todas essas moléculas têm um papel importante na via de sinalização do AMPc. Esta revisão pretende apresentar os conhecimentos mais recentes sobre a patologia e a genética molecular das lesões adrenocorticais benignas bilaterais e discutir os modernos instrumentos para diagnóstico e tratamento dessa condição.

Effect of chronic vibration on the immune state of albino rats.

A study was undertaken to investigate the effects of whole body chronic vibration on the immune system. Albino rats were exposed to whole body horizontal vibration acceleration 5.0 g, frequency 20 Hz for 3 hours per day for 3 months and changes were observed in plasma corticosterone level, total leucocyte count and differential leucocyte count. Neutrophil functions were accessed by candida phagocytosis and Nitroblue tetrazolium reduction test. The total leucocyte count was significantly decreased. A marked lymphopenia was observed in the differential count of the leucocytes. A significant increase in the plasma corticosterone level, candida phagocytosis and Nitroblue tetrazolium reduction was observed, indicating chronic whole body vibration to be a potent stressor in albino rats.

Cyclic AMP-mediated control of oocyte maturation in the catfish, Clarias batrachus (Bloch): effects of 17 alpha,20 beta-dihydroxy-4-pregnen-3-one and phosphodiesterase inhibitors.

An increase in the percentage of germinal vesicle breakdown (GVBD) with a corresponding decrease in cAMP was found in the oocytes which were incubated for 36 hr with different concentrations of 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-DP). At its highest concentration (1 microgram/ml), 17 alpha,20 beta-DP induced 91.9 +/- 2.3% GVBD and decreased cAMP level to 0.8 +/- 0.1 pmol/oocyte from 2.9 +/- 0.2 pmol/oocyte (control). The two different known inhibitors of phosphodiesterase viz. 3-isobutyl-1-methyl-xanthine (IBMX) and theophylline inhibited GVBD in vitro and promoted the accumulation of cAMP in a dose-dependent manner irrespective of whether the oocytes were treated for a short duration (2 hr) or for a long duration (36 hr). Evaluation of time course response to 1 mM IBMX or 1 mM theophylline revealed that cAMP levels increased at all the time points when compared with their respective controls and blocked maturation. In contrast, 1 microgram/ml 17 alpha,20 beta-DP not only induced oocyte maturation but also caused an immediate decrease in cAMP within the first 2 hr (from 3.2 +/- 1.3 to 1.3 +/- 0.1 pmol/oocyte) of incubation which was maintained till the end of experiment (36 hr). Likewise, a significant inhibition of GVBD and accumulation of cAMP was recorded even in oocytes pre-stimulated with 1 microgram/ml 17 alpha,20 beta-DP for 6 hr and then treated with different concentrations of IBMX or theophylline. Taken together, these data strongly suggest that in C. batrachus a decrease of oocyte cAMP concentration is a prerequisite for the induction of oocyte maturation, and its increase is associated with the maintenance of meiotic arrest.

Mechanism of cAMP-induced H(+)-efflux of Dictyostelium cells: a role for fatty acids.

Aggregating Dictyostelium cells release protons when stimulated with cAMP. To find out whether the protons are generated by acidic vesicles or in the cytosol, we permeabilized the cells and found that this did not alter the cAMP-response. Proton efflux in intact cells was inhibited by preincubation with the V-type H(+) ATPase inhibitor concanamycin A and with the plasma membrane H(+) ATPase blocker miconazole. Surprisingly, miconazole also inhibited efflux in permeabilized cells, indicating that this type of H(+) ATPase is present on intracellular vesicles as well. Vesicular acidification was inhibited by miconazole and by concanamycin A, suggesting that the acidic vesicles contain both V-type and P-type H(+) ATPases. Moreover, concanamycin A and miconazole acted in concert, both in intact cells and in vesicles. The mechanism of cAMP-induced Ca2(+)-fluxes involves phospholipase A2 activity. Fatty acids circumvent the plasma membrane and stimulate vesicular Ca2(+)-efflux. Here we show that arachidonic acid elicited H(+)-efflux not only from intact cells but also from acidic vesicles. The target of regulation by arachidonic acid seemed to be the vesicular Ca2(+)-release channel.

Fosfodiesterasas de nucleótidos cíclicos: diversidad, clasificación, estructura y función / Cyclic nucleotide phosphodiesterases: diversity, classification, structure and function

During the last years there have been major advances in the knowledge of cyclic nucleotide phosphodiesterases. Particularly, referred to the presence of multiple different isozymes. Seven different phosphodiesterase gene families, have been described in mammalian tissues, containing several distinct genes, most of them expressed in different tissues as functionally unique splice variants. This article includes various aspects of the currently accepted nomenclature, structure and function of each family of phosphodiesterases. Finally, a brief discussion of the presence and role of these enzymes in the cell proliferation and differentiation processes, in parasites of the Trypanosmatidae family, is provided

Chemical reception in vertebrate olfaction: evidence for multiple transduction pathways

Odorant detection takes place at the receptor neurons of the olfactory epithelium and odorant discrimination relies in an important degree on these chemosensory cells. Here we review the evidence for the participation of multiple transduction pathways in the mechanisms of odor recognition in olfactory neurons

Role of messenger system in orthodontic tooth movement.

Various in vivo and in vitro studies have established that arachidonic acid metabolites i.e., prostaglandins and leukotriens play a key role in the conversion of orthodontic pressure stimuli into a cell mediated response. However, considering the different response of osteoblasts and osteoclasts to the same chemical stimuli that leads to the deposition of bone on tension side and resorption on pressure side it has been suggested that it is the messenger system that modulates the behaviour of cells. The messenger system translates a wide array of external stimuli (first messenger) in to a narrow range of internal signals (second messengers). The role of Cyclic-AMP (C-AMP), Inositol phosphate (IP3), and Diacyleglycerol (DAG) as second messengers in the mediation of orthodontic tooth movement have been discussed in this article.

Cellular adaptation of the rat medullary thick ascending limb to chronic renal failure

Chronic renal failure (CRF) is accompanied by adaptive changes in renal and extrarrenal epithelial ionic transport. Fluid reabsorption in the thick ascending limb of Henle is increased and the capacity to lower the urine osmolality in water diuresis is preserved. To study the cellular mechanism of this adaptation, we measured intracellular cAMP in microdissected medullary thick ascending limb (mTAL) segments in rats with CRF. mTAL exhibited in CRF nephrons an increase of basal cAMP from 6.0 +/- 1.5 in controls to 47.0 + 10.3 fmol. mm-1 tubule in CRF (P < 0.05). Maximally stimulated cAMP levels (10(-3) M IBMX plus 10(-5) M Forskolin) were different from basal levels in controls (6.0 + 1.5 vs 63.1 +/- 18.8, P < 0.05) but not from basal levels in CRF (47.0 +/- 10.3 vs 63.0 +/- 16.0, P = N.S.). Preincubation with the adenylate cyclase inhibitor 2'5' -dideoxyadenosine (DDA) 10(-4) M produced no changes in cAMP in controls (93.7 +/- 10.3 percent of DDA untreated samples) whereas it decreased to 76.2 +/- 8.8 percent (24 percent inhibition) in CRF (P < 0.05). No differences between controls and CRF groups were found in basal and stimulated cAMP in red blood cells and distal colon. The data would suggest that the cAMP pathway is an intracellular signal for mTAL adaptation in epithelial transport and that the adenylate-cyclase system is specifically activated in CRF.

Further studies on the influence of dibutyryl cAMP, theophylline and prostaglandin E1 on composition and biosynthesis of phospholipids in Microsporum gypseum.

Exogenous supplementation of dibutyryl cAMP and cAMP modulators like theophylline and prostaglandin E1 in the growth medium of Microsporum gypseum lead to increase in the levels of phosphatidylcholine and lysophosphatidylcholine and thereby in total phospholipid content. These observations were further confirmed by the increased incorporation of [32P]orthophosphoric acid into total phospholipid and [14C]choline into phosphatidylcholine and lysophosphatidylcholine. The activity of sn-glycerol-3-phosphate acyltransferase, the enzyme involved in phospholipid synthesis, was stimulated in the presence of dibutyryl cAMP, theophylline and PGE1 supporting the increased synthesis of phospholipids.

Effect of actions on the action of cyclic amp on the metabolism of adipose tissue

The aim of the present work is to study the effect of cyclic AMP on the metabolism of adipose tissue as well as the effect of cations on the action of cyclic AMP. The epididymal fat pads isolated from the male albino rats were used for this experimental work. The epididymal fat pads were incubated under different condition according to the 8 Schedule presented in table. According to the results obtained in this work, it is apparant that: 1. Addition of cyclic AMP in a dose of 0.2 mM to the incubation medium resulted in a significant antilipolytic effect as well as insignificant changes in glucose uptake and cyclic AMP content in adipose tissue. 2. Addition of Ca[2+] inos to the incubation medium was found to has a non significant changes in glucose uptake by adipose tissue as well as marked antilipolyptic effect. The antilipolytic effect is attributed to the inhibitory effect of Ca[2+] ions on adenyl cyclase enzyme as well as phosphodiesterase enzyme. Ca[2+] ions stimulate the adipose tissue phosphatase enzyme with subsequent inactivation of adipose tissue lipase enzyme. 3. Addition of Mg[2+] ions to the incubation medium, led to a marked antilipolytic effect. This effect was attributed to the presence of; Mg[2+] ions which responsible for the normal function of adenyl cyclase as well as phosphodiesterase enzymes. On the other hand, addition of Mg[2+] ions to the incubation medium resultad in a significant increase in glucose uptake by adipose tissue. This effect may be attributed to the stimulatory effect of Mg[2+] ions on phosphofructok-inase as well as pyruvate kinase enzymes. 4. Addition of K+ inos to the incubation medium led to a significant lipolytic effect. This effect may be attributed to stimulation of adenyl cyclase by K+ ions with subsequent increase in cyclic AMP content in adipose tissue. On the other hand, K+ ions led to a non significant decrease in glucose uptake by adipose tissue. 5. Addition of 0.2mM cyclic AMP to the incubation medium devoid of either Ca[2+] or K+ led to a significant increase in glucose uptake by adipose tissue as well as a mrked lipolytic effect. These effects may be attributed to the fact that Omission of these cations from the incubation medium permits the enterance of cyclic AMP to the adipocytes. It can be concluded from the present work that some cations modulates the effect of cyclic AMP in adipose tissue metabolism. In the presence of Ca[2+] and Mg ions in the incubation medium cyclic AMP has antilipolyic effect. This effect may be due to its conversion to metabolites which inhibit endogenous adenyl cyclase. On the other hand it was found that the addition of K+ ions to the incubation medium led to a significant increase in the rate of lipolysis. This lipolytic effect may be attributed to the associated increase in cyclic AMP content in adipose tissue