Importance of timing of magnesium administration: a study on the isolated ischemic-reperfused rat heart

The present study attempted to explore the antioxidant potential of magnesium (2 and 10 mM) in the postischemic isolated rat heart. Magnesium demonstrated a significant antioxidant effect, as deduced by thiobarbituric acid reactive material and glutathione levels. However, this effect was evident only when magnesium was administered prior to ischemia but not when administered during reperfusion. On the other hand, attenuation of calcium accumulation following reperfusion was noted in both treatment schedules and showed dose dependency when administered during reperfusion. Thus, the results of this study strongly suggests an antioxidant effect of magnesium which is distinct from its calcium antagonising effects and it also stresses the critical role played by the time of administration of magnesium.

Protein kinase C in platelets of depressed patients

BACKGROUND

We studied the role of protein kinase C (PKC), a major regulatory enzyme and an important component of the phosphoinositide signaling system, in depression.

METHODS

PKC was determined using [3H]phorbol dibutyrate (PDBu) as the radioligand in the membranal and cytosolic fractions of platelets obtained from hospitalized drug-free depressed patients during a baseline period and from drug-free normal control subjects.

RESULTS

We observed that the [3H]PDBu binding was significantly higher in the cytosolic fraction obtained from platelets of depressed patients compared to normal control subjects.

CONCLUSIONS

Our studies indicate increased formation of PKC in platelets of depressed patients. The significance and mechanisms involved in increased PKC in the cytosolic fraction of platelets are unclear, but they suggest that increased PKC may be associated with the pathophysiology of depressive illness.

Alterations in the vasoreactivity of hypertensive rat aortic rings: role of nitric oxide and superoxide radicals

OBJECTIVES

Present study was undertaken to investigate involvement of nitric oxide (NO) and superoxide radicals in the modulation of vasoreactivity in a model of renal hypertension.

METHOD

Hypertension was induced in the male Sprague Dawley rats by aortic banding just above the left kidney. Relaxation or contraction following cumulative addition of acetylcholine (Ach, 1 x 10(-8) to 1 x 10(-5) M) or phenylephrine (PE, 1 x 10(-8) to 1 x 10(-5) mol/l) was studied in the aortic rings obtained from sham operated normotensive, hypertensive and captopril pretreated rats. Ach and PE responses were taken in the presence or absence of NO synthase inhibitor (L-NAME; 1 x 10(-5) and 1 x 10(-4) mol/l). Spontaneous release of NO from the aortic rings was evaluated by studying the inhibition of adenosine diphosphate stimulated platelet aggregation, while superoxide radicals were estimated by cytochrome c reduction method.

RESULTS

Ach induced vasorelaxation in PE precontracted rings was impaired following 8 wk after aortic banding, while spontaneous release of NO remained unaffected. Captopril pretreatment restored the aortic ring responsiveness to Ach. An increase in the superoxide radical generation and PE induced contraction following L-NAME treatment in the hypertensive rat aortic rings was observed.

CONCLUSION

Attenuation in the Ach induced NO release and augmentation in the superoxide radical generation seems to play an important role in the modulation of vasoreactivity following renal hypertension in rats.

Susceptibility status of malaria vectors to insecticides in India

The use of chemical insecticides for control of malaria vector populations continues to be the mainstay of malaria control strategy in India. Monitoring vector susceptibility to chemical insecticides is an important activity under the National Malaria Eradication Programme to ensure judicious and effective use of chemical Insecticides. 72 entomological zones were established under NMEP in 1977 for undertaking entomological studies in the malaria problematic areas. These zones have been generating insecticide susceptibility data in respect of the various malaria vectors. In this paper the insecticide susceptibility data, in respect of major vectors of malaria as on 1997, is presented.

Inhibition of platelet aggregation by a protein factor present in rat peripheral polymorphonuclear leukocyte supernatant

In the present investigation, effect of rat peripheral polymorphonuclear leukocyte (PMNL) supernatant was investigated on platelet aggregation. Rat PMNLs suspended in Hanks balanced salt solution (HBSS, pH 7.4) were incubated at 37 degrees C for different time intervals and cell-free supernatant was obtained by centrifugation. Supernatant was found to inhibit adenosine diphosphate (ADP), arachidonic acid (AA), and calcium ionophore-induced platelet aggregation. The inhibitory effect of PMNL supernatant on platelet aggregation was not blocked by methylene blue (10 microM) or adenosine deaminase (5 U ml(-1)) pretreatment, suggesting that the inhibitory effect of the supernatant on aggregation was not mediated by nitric oxide (NO) or ecto-ADPase. The effect of PMNL supernatant on platelet aggregation was abolished by preheating the supernatant at 95 degrees C for 5 minutes. Pretreatment of the supernatant with protease inhibitors abolished the inhibitory effect of supernatant on platelet aggregation suggesting that the factor may be a protein or peptide with protease activity. Partial purification of biologically active factor by fine particle liquid chromatography (FPLC) by using Superose 6B column yielded a peak with a molecular weight of approximately 30 kDa having antiaggregatory activity. The results obtained suggest that rat peripheral PMNLs release yet another factor(s) that inhibits platelet aggregation. The factor is a heat labile protein with a molecular weight of approximately 30 kDa.

Alterations in the free radical generation and nitric oxide release from rat peripheral polymorphonuclear leukocytes following thrombosis

The present investigation was undertaken to study the alterations in free radical generation and release of nitric oxide (NO) from polymorphonuclear leukocytes (PMNLs) following thrombosis. Thrombosis was induced in rats by intravenous injection of collagen and adrenaline. PMNLs were separated from rat blood by using dextran sedimentation and Ficoll-Hypaque. Arachidonic acid (AA), formyl methionine leucine phenylalanine (FMLP) and opsonized zymosan (OZ) induced free radical generation was estimated as luminol (LCL) and Lucigenin (LUCDCL) dependent chemiluminescence. PMNLs nitric oxide synthase (NOS) activity and NO release were measured by using [14C] L-Arginine (L-Arg) and oxy-hemoglobin respectively. LCL and LUCDCL responses in rat PMNLs were significantly attenuated following thrombosis. There was no change in the release of myeloperoxidase enzyme (MPO) from PMNLs obtained following thrombosis. PMNLs NOS activity and NO release were also found to be increased after thrombosis. Pretreatment of rat PMNLs with 10 mM L-NAME (NO precursor) or 100 microM sodium nitroprusside (NO donor), resulted in significant reduction of AA induced LCL response. Results obtained indicate that NO release form PMNLs was augmented while free radical generation response was attenuated after the induction of thrombosis.

Interaction of nitric oxide synthase inhibitors and their D-enantiomers with rat neutrophil luminol dependent chemiluminescence response

1. Formyl-methionyl-leucyl-phenylalanine (FMLP) or arachidonic acid (AA) induced luminol dependent chemiluminescence (LCL) response of rat polymorphonuclear leukocytes (PMNLs) was found to be inhibited by nitric oxide synthease inhibitors and their D-enantiomers. 2. Rat PMNLs LCL response was inhibited by NG-nitro-L-arginine methyl ester (L-NAME), D-NAME, NG-monomethyl-L-arginine (L-NMMA) or D-NMMA, in a concentration- and time-dependent manner. 3. It was observed that both L- and D-enantiomers of the arginine analogues (1000 microM) did not inhibit AA induced lucigenin-dependent chemiluminescence (LUCDCL) response and cytochrome c reduction, used for estimating the NADPH-oxidase activity in the cells and in the cell free system, respectively. 4. None of the L- and D-enantiomers had any effect on either rat basal PMNLs or AA-induced oxygen consumption. 5. In addition, neither the L nor D-enantiomers of NAME altered either AA-induced release or the activity of myeloperoxidase from rat PMNLs azurophilic granules. 6. The results obtained indicate that the attenuation of the LCL response by L- and D-enantiomers of arginine analogues, is a non-specific effect as there was no inhibition of NADPH-oxidase and MPO activity, MPO release or oxygen consumption. Therefore, the data obtained indicate that these agents should be used with caution to analyse the role of nitric oxide in rat PMNLs LCL response.

Involvement of bioantioxidants in thrombosis in mice

An involvement of free radicals in thrombosis has been suggested previously. In order to further explore the role of free radicals and antioxidants in thrombosis, we have measured preventive (enzymes of the glutathione redox cycle) and chain-breaking antioxidants (vitamin E and C) in whole blood, platelets, neutrophils (PMNLs), heart and lung following collagen and adrenaline induced thrombosis in mice. A significant decrease in platelet glutathione (GSH) level (54%) and glutathione reductase activity was observed after thrombosis. In addition, GSH content in whole blood was also found to be reduced. In PMNLs, an increase in glutathione peroxidase activity and a four-fold elevation in vitamin C content was observed following thrombosis. However, levels of vitamin E and total thiol groups remained unchanged in both the cells and tissues. The results further suggest involvement of free radicals and PMNLs in thrombosis.

Motor neurone disease like picture in hyperthyroidism

Five patients of hyperthyroidism with Motor Neurone Disease like picture seen over a span of five years are described. The illness was of over 3 years duration and all patients were males. One patient had even the diagnosis of "MND'. It took 1 to 3 months for disappearance of MND picture with antithyroid drugs. In MND like disease every effort should be made to exclude hyperthyroidism.

Effect of platelet activating factor antagonists in different models of thrombosis

Effect of three specific PAF antagonists, SR-27417, BN-50739 and ginkgolide derivative BN-52021 have been evaluated in models of thrombosis in the mouse, rat and cat. Thrombosis in the mouse was induced by intravenous infusion of collagen and adrenaline. In rats it was induced by inserting a metallic wire into the inferior vena cava. In the cat, thrombus formation was assessed in the extracorporeal shunt. All the antagonists offered a dose-dependent protection against pulmonary thromboembolism in mice (1, 3 and 10 mg/kg) and the thrombosis monitored in the extracorporeal shunt in cats (0.3, 1 and 3 mg/kg). In rats, no significant protection was observed with these antagonists even at the highest dose used.

Alterations in the bioantioxidants following thrombosis

The role of free radicals in rat thrombosis has been demonstrated by studying its scavenging enzyme system. Changes in the bio-antioxidants (GSH-redox cycle, total thiol groups, vitamins E and C) that also offer protection against the free radicals, have, however, not been studied so far. This investigation was undertaken to understand the involvement of these antioxidants during thrombosis. The tissues investigated following thrombosis were blood, platelets, polymorphonuclear leukocytes (PMNLs), heart, and lung. Glutathione (GSH) content in the platelets was observed to be depleted. However, oxidized glutathione (GSSG) contents in the platelets, PMNLs, and blood remain unaltered. In addition, in the whole blood GSH levels were increased significantly, whereas there was no change in the GSSG level. Activity of glutathione reductase (GR) was decreased significantly in platelets and lungs with an increase in the total thiol groups in the lung homogenate. Activity of Glutathione peroxidase (Gpx) remained unaltered in all the tissues studied. In addition, 24% and 15% decrease in the alpha-tocopherol concentration was observed in thrombocytes and PMNLs, respectively, with no change in the ascorbate levels in these cells. Results of this investigation suggest alterations in the GSH-redox cycle in blood, platelets, and lung after thrombosis in the rat.

Modulation of rat peripheral polymorphonuclear leukocyte response by nitric oxide and arginine

The effect of nitric oxide (NO) on the luminol-dependent chemiluminescence (LCL) response of rat polymorphonuclear leukocytes (PMNLs) was analyzed by using sodium nitroprusside (SNP), a NO donor, and L-arginine (L-arg), a NO precursor. A significant reduction in the LCL intensity was observed in presence of SNP (100 mumol/L) or L-arg (5 or 10 mmol/L) in arachidonic acid (AA) phorbol ester (PMA) and formyl-methionyl-leucyl-phenylalanine stimulated PMNLs. However, opsonized zymosan-induced LCL was not attenuated significantly. Reduction in hydroxyl radical and superoxide generation was also observed in SNP- or L-arg-pretreated cells. D-Arg (10 mmol/L) pretreatment did not inhibit PMNLs' LCL response. Furthermore, methylene blue (5 mumol/L) and L-NG-mono methyl-L-arginine (100 or 300 mumol/L) significantly attenuated the LCL response, as induced by various agonists. Cyclic GMP did not alter the reactive oxygen species generation from rat PMNLs. In addition, AA-induced release of myeloperoxidase, a marker of azurophilic granules, was found to be enhanced in L-arg- (10 mmol/L) pretreated PMNLs. The results suggest that NO inhibits free radical generation from rat PMNLs.

Resting and biting habits of Anopheles sundaicus in Car Nicobar Island

Resting and biting habits of An. sundaicus were studied in Car Nicobar Island. Results of resting behaviour revealed that although substantial numbers of An. sundaicus rest outdoor, still the species prefer to rest indoors, and much less in human dwellings. High parity rate (73.38%) in An. sundaicus and close contact with man were the factors responsible for high transmission in Car Nicobar. An. sundaicus population in Car Nicobar is susceptible to DDT. Indoor man-biting of An. sundaicus was significantly higher than outdoors and the species showed bimodal biting activity with first peak between 2130 to 2230 hrs and second between 0130 to 0230 hrs. An. sundaicus preferred to feed on people's legs and hands. Due to complex behaviour of An. sundaicus, an integrated approach comprising (i) chemical, (ii) bioenvironmental control, and (iii) personal protection methods was suggested to interrupt malaria transmission in Car Nicobar Island.

Feeding preferences of Anopheles sundaicus in Car Nicobar Island

Host feeding behaviour of An. sundaicus population in Car Nicobar Island was studied by bloodmeal analysis and bait collection. Results indicated the zoophagic nature of the species in different resting sites. However, a human blood index of 0.18 was observed in specimens collected from human dwellings. The highest proportion of females was found positive for porcine antigen. Bait collections also indicated a similar feeding pattern.

Pulmonary thromboembolism-induced alterations in nitric oxide release from rat circulating neutrophils

We have earlier reported that neutrophils play an important role in pulmonary thromboembolism. The effect of circulating polymorphonuclear leukocytes (PMNL) isolated from normal and thrombotic rats was, therefore, studied on platelet aggregation in platelet-rich plasma. PMNL inhibited the platelet aggregation in a concentration- and time-dependent manner at 37 degrees C. The platelet aggregation inhibitory response of PMNL was more pronounced in the presence of superoxide dismutase and was abolished by hemoglobin and methylene blue. These observations suggested that the inhibitory effect of PMNL on platelets was mediated by neutrophil-derived relaxing factor. PMNL, obtained after thromboembolism, inhibited the platelet aggregation response more strongly due to an increased release of nitric oxide from them. It is suggested that PMNL play an important role in the regulation of hemostasis.

Serum enzyme abnormalities in protein energy malnutrition

Six serum enzymes, alkaline phosphatase, cholinesterase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase and gamma-glutamyl transpeptidase were studied in 30 cases of protein energy malnutrition (PEM). The mean serum values of alkaline phosphatase, cholinesterase and lactate dehydrogenase in cases of PEM were significantly lower than the controls, lowering being maximum in PEM Grade IV. The mean serum values of aspartate aminotransferase and alanine aminotransferase in patients with PEM were significantly higher than the controls. The mean serum values of gamma-glutamyl transpeptidase showed similar significant rise in all but PEM Grade IV. The degree of increase in the serum values of these three enzymes were maximum in cases with PEM Grade I. These findings suggest that abnormalities in blood levels of these enzymes occur in any form of PEM and these are related to the severity of the disease.

Free radical scavenging mechanisms during pulmonary thromboembolism in rats

In the present investigation alterations in the free radical generating and scavenging enzymes in platelets, neutrophils (PMNLs), heart and lung homogenates following rat pulmonary thromboembolism have been studied. Thrombosis was induced by intravenous infusion of collagen and adrenaline. Levels of malonaldehyde (MDA) were elevated in the PMNLs after thrombosis. Activities of superoxide dismutase (SOD) and catalase (CAT) were found to increase in platelets and PMNLs respectively. However, there was no significant alteration in the lactate dehydrogenase (LDH), lysozyme (LYS), ratio of xanthine oxidase to dehydrogenase (XO/XH) and PMNLs O2- generation before and after thrombosis. Migration of PMNLs following thrombosis was indicated by increased activity of myeloperoxidase (MPO) in the heart. In addition, pretreatment with allopurinol, a xanthine oxidase inhibitor and indomethacin, a cyclooxygenase inhibitor offered protection against thromboembolism induced death/paralysis. Results suggest the involvement of free radicals in thrombosis.

Acanthamoeba keratitis--a report of two cases

Two cases of unilateral corneal ulcers caused by Acanthamoeba are reported. Neither of the patients had contact lenses at any time. The diagnosis was confirmed by Giemsa stain and cultures of the corneal scrapings.

Effect of pulmonary thromboembolism on circulating neutrophils in mice

The role of free radical generation and its scavenging enzymes in circulating mice polymorphonuclear leukocytes (PMNLs) has been studied following pulmonary thromboembolism. Levels of malonaldehyde (MDA), 02- radical generation, activity of superoxide dismutase (SOD), catalase (CAT), lactate dehydrogenase (LDH), myeloperoxidase (MPO) and lysozyme were estimated in lysed neutrophil preparations. Activities of SOD and CAT were increased in neutrophils, while animals showed 60 +/- 4% thrombocytopenia. Levels of MDA in PMNLs were also elevated significantly following thrombosis. However, there was no significant change in superoxide radical generation, after thrombotic challenge, in mice neutrophils. The present study provides evidence for the involvement of free radicals in mice pulmonary thromboembolism.

The effect of etch-time on the bond strength of a sealant and on the etch-pattern in primary and permanent enamel: an evaluation

This study was undertaken to establish laboratory evidence of minimum etch-time for primary enamel, for effective retention of occlusal sealants. The effect on enamel of contamination by oral fluid for different exposure times was also evaluated. Here it is shown that a short etch-time of 15 sec is satisfactory for primary enamel, and is also sufficient to produce the required etch-pattern for the strong binding of sealants.