Effect of Interaction of Heavy Metals on (Na+-K+) ATPase and the Uptake of 3H-DA and 3H-NA in Rat Brain Synaptosomes

Abstract: The effect of interaction of Mn²⁺, Pb²⁺ and Cd²⁺ on (Na⁺-K⁺) ATPase and uptake of labelled dopamine (³H-DA) and labelled noradrenaline (³H-NA) were studied in vitro in rat brain synaptosomes. The inhibition of (Na⁺-K⁺) ATPase by Pb²⁺ and Cd²⁺ alone was concentration dependent, however, Mn²⁺ had almost no effect on the activity of this enzyme. Interaction of Cd²⁺ with either Pb²⁺ or Mn²⁺ was most powerful in inhibiting the activity of synaptosomal transport ATPase. Lower concentrations of Pb²⁺ increased while higher concentrations inhibited synaptosomal uptake of ³H-DA and ³H-NA. Lower concentrations of Cd²⁺ increased the uptake of ³H-DA while at concentrations of 100 μM, the uptake was inhibited, this metal had strong inhibitory effect on the uptake of ³H-NA. Mn²⁺ had inhibited the uptake of labelled amines. Interaction of Mn²⁺ with Pb²⁺ or Cd²⁺ produced inhibition on the uptake of ³H-DA and ³H-NA. The results of the uptake of biogenic amines in the presence of metal ions apparently had no correlation with the activity of (Na⁺-K⁺) ATPase which is involved in the active transport of cations across cell membranes.     

Primary malignant fibrous histiocytoma of the maxilla.

A case of a primary malignant fibrous histiocytoma of the maxilla in a 14-year-old girl is presented. A search of the literature has revealed only one previous case. Primary malignant fibrous histiocytoma is a rare tumour of the jaws which is locally aggressive with little tendency to metastasize, although there have been reports of distant spread. There is no effective treatment but surgery might increase the survival time. The tumour does not respond to radiotherapy or chemotherapy. Recurrence is common, being about 73 per cent. In the present case in spite of early diagnosis and prompt treatment the patient survived for only 10 months.     

Investigation on physicochemical and biological differences of cefpodoxime proxetil enantiomers.

Cefpodoxime proxetil (CP) is a prodrug of cefpodoxime acid (CA), and is supplied as racemic mixture of R- and S-enantiomers. CP has only 50% absolute bioavailability, and the reasons responsible for low bioavailability remain poorly understood. The present work ascertains physicochemical and biological properties of individual isomers of CP and explores their capacity to optimize delivery of CP. Both isomers showed similar pH stability behavior, but R-isomer was more susceptible to enzymatic metabolism compared to S-isomer, when incubated with enzymes collected from various segments of GIT. Based on the in vitro and in vivo results, use of S-isomer for development of a dosage form such as gastro-retentive dosage form can improve oral bioavailability of CP.     

Dopaminergic modulation of arginine mediated growth hormone and prolactin release in man

The mechanism of arginine (ARG) induced growth hormone (GH) and prolactin (PRL) release is poorly understood. Though dopamine (DA) is known to inhibit a number of GH and PRL secretagogues, it has been reported not to affect arginine mediated GH release. Our study was undertaken to study the interaction of DA and ARG further. Six healthy male volunteers received DA (4μg/kg/min) or saline from 0–240 min on two separate days. ARG (30 gms) was given 150–180 min on both days (Protocol I). In Protocol II 5 subjects received ARG on different days 30–60 min into a DA or saline infusion. On a third day only DA was given. Arginine alone was given in 2 separate infusions spaced 135 minutes apart to 5 volunteers (Protocol III). In Protocol I when ARG was given at 150 min, the maximal GH peak of 11.1 ± 1.3 ng/ml, which occurred 45 min later, was blunted by DA treatment (5.3 ± 1.1 ng/ml, p < 0.005). On the DA day prior to ARG, there was also a GH peak at 75 min of 8.1 ± 1.9 ng/ml. In Protocol II, when the ARG and DA responses coincided, the mean maximal GH response to both stimuli was 20.5 ± 3.3 ng/ml which was greater than to either DA (7.7 ± 2.2 ng/ml, p < 0.01) or ARG alone (14.6 ± 3.0 ng/ml, N.S.). Moreover, the area under the curve for DA and ARG together (1196 ± 186 ng/ml/150 min) was greater than for DA (484 ± 160 ng/ml/150 min, p < 0.001) or ARG separately (544 + 70 ng/ml/150 min, p < 0.05). During the double arginine, which mirrored temporally the pattern of GH release observed in Protocol I, the peak GH responses after each infusion were similar (9.0 ± 2.1 and 8.8 ± 2.1 ng/ml). The maximal PRL responses to ARG were 11.1 ± 3.8 ng/ml and 15.7 ± 4.8 ng/ml in Protocol I and II respectively, but these responses were abolished by the DA infusion in both studies. Our data, therefore, provide further evidence to support a dual role of DA in GH release. DA stimulates basal GH secretion and this effect is additive to that of ARG. However, when ARG administration is delayed, the GH response is now blunted. The inhibitory action of DA is not mediated by its prior release of GH, since the GH responses are similar after sequential ARG infusions. Consequently, the role of DA is directly related to the degree of secretion. This duality is not seen with PRL secretion, where DA is always inhibitory.     

Extended B cell phenotype in patients with myalgic encephalomyelitis/chronic fatigue syndrome: a cross‐sectional study

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a heterogeneous condition of unknown aetiology characterized by multiple symptoms including fatigue, post‐exertional malaise and cognitive impairment, lasting for at least 6 months. Recently, two clinical trials of B cell depletion therapy with rituximab (anti‐CD20) reported convincing improvement in symptoms. A possible but undefined role for B cells has therefore been proposed. Studies of the relative percentages of B cell subsets in patients with ME/CFS have not revealed any reproducible differences from healthy controls (HC). In order to explore whether more subtle alterations in B cell subsets related to B cell differentiation exist in ME/CFS patients we used flow cytometry to immunophenotype CD19⁺ B cells. The panel utilized immunoglobulin (Ig)D, CD27 and CD38 (classical B cell subsets) together with additional markers. A total of 38 patients fulfilling Canadian, Centre for Disease Control and Fukuda ME/CFS criteria and 32 age‐ and sex‐matched HC were included. We found no difference in percentages of classical subsets between ME/CFS patients and HC. However, we observed an increase in frequency (P < 0·01) and expression (MFI; P = 0·03) of CD24 on total B cells, confined to IgD⁺ subsets. Within memory subsets, a higher frequency of CD21⁺CD38^– B cells (>20%) was associated with the presence of ME/CFS [odds ratio: 3·47 (1·15–10·46); P = 0·03] compared with HC, and there was a negative correlation with disease duration. In conclusion, we identified possible changes in B cell phenotype in patients with ME/CFS. These may reflect altered B cell function and, if confirmed in other patient cohorts, could provide a platform for studies based on clinical course or responsiveness to rituximab therapy.     

Pulmonary Hypertension,Right Ventricular Failure,and Kidney: Different from Left Ventricular Failure?

In this article, the pathophysiology of left ventricular failure is reviewed. By contrast, the paucity of information about pulmonary arterial hypertension and right ventricular failure is acknowledged. The potential mechanisms whereby renal sodium and water retention in right ventricular failure secondary to pulmonary arterial hypertension can occur, despite normal left ventricular function, are discussed. With right ventricular failure as the primary cause of death in patients with pulmonary hypertension, more information about the mechanisms of renal sodium and water retention in these patients is direly needed. Specifically, studies to examine the activation of the neurohumoral axis at various stages of pulmonary arterial hypertension and right ventricular failure, including inhibition of mineralocorticoid and V2 vasopressin receptors, are indicated.The renal sodium and water retention that occurs with advanced left ventricular failure is associated with substantial morbidity and mortality. This sodium and water retention, which can lead to pulmonary edema, pleural effusion, and peripheral edema, occurs despite an increase in total blood volume. In normal individuals, a rise in total blood volume increases renal sodium and water excretion. The kidney is intrinsically intact with left ventricular failure, because the renal sodium and water retention does not persist after a successful heart transplant.This seeming paradox of increased blood volume yet renal sodium and water retention in cardiac failure has been explained by the body fluid volume regulation hypothesis (1–3). This hypothesis proposes that the kidney does not respond to changes in total blood volume but rather responds to what has been termed effective arterial blood volume. In general terms, approximately 85% of circulating blood volume is in the low-pressure venous side of the circulation, whereas only 15% is in the high-pressure arterial circulation. The integrity of the arterial circulation depends on cardiac output and systemic vascular resistance and is modulated by arterial stretch baroreceptors in the carotid sinus, aortic arch, and afferent arteriole of the glomerulus (4). Thus, despite an increase in total blood volume, arterial underfilling can occur secondary to a decrease in cardiac output in low-output heart failure or decreased systemic vascular resistance in high-output heart failure. With arterial underfilling secondary to either condition, arterial baroreceptor–mediated activation of the neurohumoral axis occurs. The resultant increase in renin-angiotensin-aldosterone system (RAAS) leads to sodium retention, and the increase in the nonosmotic release of arginine vasopressin (AVP) is associated with water retention and hyponatremia in advanced left ventricular failure, a known risk factor for increased mortality (5). This water retention is due to AVP activation of the V2 vasopressin receptors on the basolateral surface of the principal cells of the collecting duct, which increases aquaporin 2 water channel expression and trafficking to the apical membrane of the collecting duct (6–8).There is also evidence that increased plasma AVP concentration with left ventricular failure stimulates V1 vasopressin receptors on blood vessels, which contributes, along with angiotensin II and the sympathetic nervous system, to increasing systemic vascular resistance in low-cardiac output failure (9). This arterial baroreceptor–mediated neurohumoral activation maintains arterial pressure but at the expense of renal vasoconstriction and sodium and water retention. The pathophysiology of left ventricular cardiac failure is shown in Figure 1.These arterial baroreceptor pathways seem to override any of the low-pressure reflexes in the atria during left ventricular failure. An increase in transmural atrial pressure normally suppresses AVP and stimulates atrial natriuretic peptide (ANP), which leads to increased sodium and water excretion (10). With advanced left ventricular failure, however, left atrial pressure rises, yet sodium and water retention occurs. This suggests that activation of the arterial stretch receptors in cardiac failure predominates over any atrial pressure receptor reflex. There is also evidence that these normal atrial reflexes are blunted in patients with left ventricular failure (11).An increase in the ventricular synthesis of brain natriuretic peptide (BNP) and, thus, circulatory BNP concentration also occurs in left ventricular failure and may attenuate the degree of renal sodium and water retention. BNP may decrease the edema formation by both suppressing the RAAS and inhibiting tubular sodium reabsorption (12).     

LC-UV-PDA and LC-MS studies to characterize degradation products of glimepiride

Degradation products of glimepiride formed under different forced conditions have been characterized through LC-UV-PDA and LC-MS studies. Glimepiride was subjected to forced decomposition under the conditions of hydrolysis, oxidation, dry heat and photolysis, in accordance with the ICH guideline Q1A(R2). The reaction solutions were chromatographed on reversed phase C8 (150 mm x 4.6mm i.d., 5 microm) analytical column. In total, five degradation products (I-V) were formed under various conditions. The drug degraded to products II and V under acid and neutral hydrolytic conditions while products I, III and IV were formed under the alkaline conditions. The products II and V were also observed on exposure of drug to peroxide. No additional degradation product was shown up under photolytic conditions. All the products, except I, could be characterized through LC-PDA analyses and study of MS fragmentation pattern in both +ESI and -ESI modes. Product I could not be identified, as it did not ionize under MS conditions. The products II, III and V matched, respectively, to impurity B (glimepiride sulfonamide), impurity J and impurity C (glimepiride urethane) listed in European Pharmacopoeia. The product IV was a new degradation product, characterized as [[4-[2-(N-carbamoyl)aminoethyl]phenyl]sulfonyl]-3-trans-(4-methylcyclohexyl) urea. The degradation pathway of the drug to products II-V is proposed, which is yet unreported.