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A K Grover

Publications and source records attributed to A K Grover.

At least 37 records · Page 2Linked to original sources
PubMed1999

ET(B)-mediated contraction differs between left descending coronary artery and its next branch.

Pig left descending coronary artery (main artery) and its next branch (branch arteries) differ in many properties. Here we report on the receptor types and the Ca2+ pools utilized for endothelin (ET) contraction in 3 mm long de-endothelialized rings of the main (weight 7.38 +/- 0.38 mg) and the branch (1.07 +/- 0.03 mg) arteries. KCl (60 mM) contracted the main and the branch arteries with force of 41.8 +/- 3.1 and 16.9 +/- 1.0 mN (millinewton), respectively. Force of contraction for all the other agents was normalized taking the KCl value as 100%. We determined the total ET-induced responses using ET-1 and those mediated by ET(B) using IRL1620. In Ca2+-containing solutions, ET-1 contracted the main arteries with pEC50 = 8.2 +/- 0.1 and a maximum force of 98 +/- 5%. The branch arteries also gave similar values of pEC50 (8.4 +/- 0.1) and maximum force (99 +/- 14%). IRL1620 contracted the main and the branch arteries with pEC50 = 7.9 +/- 0.1 but the maximum force was significantly higher in the branch arteries (44 +/- 3%) than in the main (15 +/- 2%). In Ca2+-free solutions, the pEC50 values for ET-1 or IRL-1620 did not change but the maximum force of contraction was diminished considerably in both main and branch arteries. Thus, the left coronary artery and its next branch differ in that the role of ET(B) receptors is greater in the latter.

Animals↗
PubMed1999

Granulocytic sarcoma of orbit preceding acute myeloid leukaemia: a case report.

A rare case of granulocytic sarcoma of orbit preceding the onset of acute meyloblastic leukaemia is presented. A 7-year-old boy presented with proptosis and no other systemic complaints. The appearance of an enlarged muscle in initial tomographic imaging with a normal peripheral blood picture caused a diagnostic problem. Biopsy suggested a diagnosis of granulocytic sarcoma. Subsequent bone marrow study revealed the diagnosis of acute myeloid leukaemia.

Child↗
PubMed1999

Sarco/endoplasmic reticulum Ca2+ (SERCA)-pumps: link to heart beats and calcium waves.

Mobilization of endoplasmic reticulum Ca2+ is pivotal to the ability of a cell to send or respond to stimuli. Ca(2+)-Mg(2+)-ATPases, termed SERCA pumps, sequester Ca2+ into the sarco/endoplasmic reticulum. There are several SERCA protein isoforms encoded by three genes. This paper summarizes the structure, function, tissue and subcellular distribution, and regulation of various SERCA isoforms. Then it attempts to link divergence in the signal transduction processes of cells to the types and levels of SERCA proteins they express and to how the cells regulate their SERCA pump activity. The paper examines possible linkages between SERCA pumps and receptor-activated Ca2+ entry, SERCA isoform localization and Ca(2+)-waves, and the role of SERCA pumps in nuclear Ca2+ in cell proliferation and apoptosis. Then it uses available information on cardiac function and chronic stimulation of the fast-twitch muscle to answer a series of basic questions on the regulation of SERCA activity and expression and their linkage to signal transduction. Finally, it discusses the possibility that neurons exhibit complex Ca(2+)-waves whose interactions have the potential to explain the operational basis of neural networks. A series of unanswered questions emerge based on this synthesis, including the unsettling issue of whether all the isoforms are needed to achieve the divergence in signal transduction or if there is a degree of redundancy in the system.

Animals↗
PubMed1998

Effects of peroxide on endothelial nitric oxide synthase in coronary arteries.

Reactive oxygen species (ROS) are produced in ischemia and reperfusion. Since endothelial nitric oxide synthase (eNOS) is key to the endothelium-dependent vasodilation, we examined the effects of peroxide on this enzyme. We treated cells cultured from pig coronary artery endothelium with different concentrations of hydrogen peroxide, washed them, solubilized them and measured NOS activity by arginine to citrulline conversion. Hydrogen peroxide inhibited the eNOS activity with an IC50 value of 0.85 +/- 0.39 mM. In another experiment, we perfused arteries with solutions containing 0 or 1 mM hydrogen peroxide, washed them, removed the endothelium using a cotton swab, centrifuged and solubilized the endothelium and monitored its NOS activity. Hydrogen peroxide (1 mM) did not affect the NOS activity significantly (p > 0.05) in this assay. We conclude that the inactivation of eNOS by hydrogen peroxide does not play a major role in the ischemia-reperfusion damage because the peroxide concentrations attained during ischemia-perfusion are much lower than those affecting the eNOS activity.

Animals↗
PubMed1998

Effects of peroxide on the fluorescence of the Ca2+ probe Fluo 3 and the pH probe BCECF.

Fluorescence probes are invaluable tools in monitoring intracellular ion concentrations. They have also been used for studying how reactive oxygen species alter these concentrations and yet there are no studies indicating how reactive oxygen species directly affect the characteristics of the probes. Our concern was that if reactive oxygen were to affect characteristics of these probes, these measurements would be inconsequential. Therefore, we examined the effects of peroxide on the Ca2+-sensitive dye Fluo 3 and the pH sensitive dye BCECF. Peroxide concentrations below 10 mM did not alter fluorescence or binding characteristics of either dye. Since the concentrations of peroxide used in most pathophysiological experiments are in the micromolar range, we conclude that these probes are appropriate for monitoring the effects of peroxide on intracellular ion concentrations.

Aniline Compounds↗
PubMed1998

Medical management of orbital myocysticercosis: a pilot study.

PURPOSE: To evaluate the efficacy of albendazole in the management of orbital myocysticercosis. METHOD: Twenty-one consecutive patients diagnosed as having orbital myocysticercosis by ultrasonography, supported by computed tomography (CT)/magnetic resonance imaging (MRI), were included in the study. All patients received oral albendazole at a dosage of 30 mg/kg for 15 days with a low-dose steroid cover (5-10 mg per day). The patients were followed on day 2 at 2 weeks, 1 month, 3 months, 6 months and 9 months, and finally at 1 year. Orbital sonography was performed at 2 weeks, 3 months, 6 months, 9 months and 1 year. CT scan was performed at 6 months and 1 year. RESULTS: Orbital sonography revealed a well-defined cystic lesion with clear contents and a hyperechoic area suggestive of a scolex in all the patients. CT or MRI provided additional supportive evidence. The size of the cysts measured before treatment ranged from 6.2 to 13.4 mm (mean 11.4 mm). Medial rectus was involved in 10 cases, superior rectus in 7 cases and lateral rectus in 4 cases. Serial ultrasonography revealed a gradual reduction in the cyst size in 20 patients. A mild obscuration of the cyst wall, followed by collapse of the cyst cavity and obscuration of the scolex, were progressively seen as the cyst reduced in size. Complete resolution of the cyst was seen in all cases at 6 months. A CT scan performed at 1 year supported the ultrasonographic findings. No systemic side effects were noted. CONCLUSION: Oral albendazole appears to be highly efficacious in the management of orbital myocysticercosis.

Adolescent↗
PubMed1997

Sarco(endo)plasmic reticulum Ca2+ pump isoform SERCA3 is more resistant than SERCA2b to peroxide.

Sarco(endo)plasmic reticulum Ca2+ pumps are encoded by genes SERCA1, SERCA2, and SERCA3. Most tissues express SERCA2 Ca2+ pumps (splice SERCA2b) which are inactivated by reactive oxygen. In contrast, SERCA3 is expressed in tissues such as tracheal epithelium, mast cells, lymphoid cells, and aortic endothelium, which are frequently exposed to oxidative stress. Therefore, we compared SERCA3 and SERCA2b proteins for their sensitivity to oxidation. We isolated microsomes from HEK-293 cells overexpressing SERCA3 or SERCA2b. We incubated the microsomes with different concentrations of hydrogen peroxide and then determined Ca2+ pump activities in them in the following three assay systems: ATP-dependent oxalate-stimulated azide-insensitive 45Ca2+ uptake by the microsomal vesicles, Ca(2+)-Mg(2+)-ATPase, and Ca(2+)-dependent acylphosphate formation. Peroxide inhibited the pump activities in microsomes with half-maximal inhibitory concentration (IC50) values of 69 +/- 14, 66 +/- 13, and 84 +/- 15 microM for the 45Ca2+ uptake, Ca(2+)-Mg(2+)-ATPase, and the acylphosphate formation reactions, respectively. However, for microsomes from SERCA3-expressing cells, the corresponding values of IC50 for peroxide were 274 +/- 47, 857 +/- 110, and 746 +/- 40 microM. Thus, in each assay system, the resistance to inactivation by peroxide was significantly (P < 0.05) higher for the SERCA3 protein than for SERCA2b. The SERCA3 resistance to oxidants may aid the cells expressing it to function during exposure to oxidative stress.

Animals↗
PubMed1997

Peroxide resistance of ER Ca2+ pump in endothelium: implications to coronary artery function.

We examined the effects of peroxide on the sarco(endo)plasmic reticulum Ca2+ (SERCA) pump in pig coronary artery endothelium and smooth muscle at three organizational levels: Ca2+ transport in permeabilized cells, cytosolic Ca2+ concentration in intact cells, and contractile function of artery rings. We monitored the ATP-dependent, azide-insensitive, oxalate-stimulated 45Ca2+ uptake by saponin-permeabilized cultured cells. Low concentrations of peroxide inhibited the uptake less effectively in endothelium than in smooth muscle whether we added the peroxide directly to the Ca2+ uptake solution or treated intact cells with peroxide and washed them before the permeabilization. An acylphosphate formation assay confirmed the greater resistance of the SERCA pump in endothelial cells than in smooth muscle cells. Pretreating smooth muscle cells with 300 microM peroxide inhibited (by 77 +/- 2%) the cyclopiazonic acid (CPA)-induced increase in cytosolic Ca2+ concentration in a Ca2+-free solution, but it did not affect the endothelial cells. Peroxide pretreatment inhibited the CPA-induced contraction in deendothelialized arteries with a 50% inhibitory concentration of 97 +/- 13 microM, but up to 500 microM peroxide did not affect the endothelium-dependent, CPA-induced relaxation. Similarly, 500 microM peroxide inhibited the angiotensin-induced contractions in deendothelialized arteries by 93 +/- 2%, but it inhibited the bradykinin-induced, endothelium-dependent relaxation by only 40 +/- 13%. The greater resistance of the endothelium to reactive oxygen may be important during ischemia-reperfusion or in the postinfection immune response.

Animals↗
PubMed1997

Endothelin contraction in pig coronary artery: receptor types and Ca(2+)-mobilization.

Endothelin is one of the most potent vasoconstrictors known. It plays an important role in the regulation of vascular tone and in the development of many cardiovascular diseases. This study focuses on the receptor types and the Ca2+ mobilization responsible for endothelin-1 (ET-1) contraction in de-endothelialized pig coronary artery rings. ET-1 contracted the artery rings with an EC50 = 6.5 +/- 1 nM and a maximum contraction which was 98.6 +/- 9% of the contraction produced by 60 mM KCl. BQ123 (5 microM), an ETA antagonist, reversed 78 +/- 3% of the ET-1 contraction (50 nM). IRL1620, a selective ETB agonist, produced 23 +/- 3% of the total ET-1 contraction with an EC50 = 12.7 +/- 2 nM. More than 85% of the contraction due to 100 nM IRL 1620 was inhibited by 200 nMBQ788, an ETB antagonist. Therefore, approximately 80% of the ET-1 contraction in this artery occurred via ETA receptors, and the other 20% was mediated by ETB receptors. To assess the Ca2+ pools utilized during the ET-1 response, ET-1 contraction was also examined in medium containing an L-type Ca2+ channel blocker nitrendipine, and in Ca2+ free medium containing 0.2 mM EGTA. In Ca2+ containing medium the contraction elicited by ET-1 was 98.6 +/- 9% of the KCl contraction, however, in the presence 10 microM nitrendipine the ET-1 induced contraction was 54 +/- 7% of the KCl contraction, and in Ca(2+)-free medium it was 13 +/- 2%. Similarly, the IRL 1620 contractions in Ca2+ containing medium, in the presence of nitrendipine and in Ca(2+)-free medium were 22.4 +/- 3%, 12 +/- 3% and 11 +/- 2% of the KCl response respectively. Thus, both ETA and ETB contractions utilize extracellular Ca2+ pools via L-type Ca2+ channels and other undefined route(s), as well as intracellular Ca2+ pools. In the pig coronary artery smooth muscle, ET-1 contractions occur predominantly via ETA receptors, with ETB receptors using similar Ca2+ mobilization pathways, but the ETB receptors appear to use the intracellular Ca2+ stores to a greater extent.

Animals↗
PubMed1996

Sarcoplasmic reticulum Ca(2+)-pump density is higher in distal than in proximal segments of porcine left coronary artery.

Densities of sarcoplasmic reticulum (SR) Ca(2+)-pump were compared in proximal and distal segments of pig left coronary artery using two biochemical methods: acylphosphate formation and immunoreactivity in Western blots, and a functional assay based on contraction to SR Ca(2+)-pump inhibitors. In the microsomes prepared from smooth muscle, the level of the 115 kDa SR Ca(2+)-pump acylphosphate was 7.1 +/- 0.3 -fold greater in distal than in proximal segments. Similarly in Western blots using these microsomes, the reactivity of the 115 kDa band to an anti-SR Ca(2+)-pump antibody was 5.3 +/- 0.8 -fold greater in distal than in proximal segments. Endothelium free coronary artery rings contracted to the SR Ca(2+)-pump inhibitors Cyclopiazonic acid (CPA, EC50 = 0.19 +/- 0.06 microM) and thapsigargin (EC50 = 0.0095 +/- 0.0035 microM). With 10 microM CPA, the force of contraction per tissue wet weight was 4.2 +/- 0.5 -fold greater in distal than in proximal rings, and with 1 microM thapsigargin it was 4.0 +/- 1.0 -fold greater. The contractions produced by 60 mM KCl were used as a control. In contrast to the CPA and thapsigargin, the force per mg tissue weight produced by 60 mM KCl did not differ significantly between the proximal and distal segments. Thus, the results from the two biochemical methods and those from the contractility data were all consistent with the smooth muscle in the distal segments of the coronary artery containing a higher density of the SR Ca(2+)-pump than the proximal segments.

Animals↗
PubMed1996

Sarcoplasmic reticulum Ca2+ pump in pig coronary artery smooth muscle is regulated by a novel pathway.

Coronary artery smooth muscle expresses an alternative splice (SERCA2b) of the sarcoplasmic reticulum (SR) Ca2+ pump gene SERCA2, which is also expressed in cardiac muscle (SERCA2a), but how the activity of this transporter is regulated in the coronary artery is not known. SERCA2a in the cardiac muscle can be regulated via phospholamban or, as recently reported, by a direct phosphorylation of this protein by calmodulin kinase (Xu, A., C. Hawkins, and N. Narayanan. J.Biol. Chem. 268:8394-8397, 1993). Because both SERCA2a and SERCA2b contain this calmodulin kinase phosphorylation site, we examined the effect of endogenous calmodulin kinase phosphorylation of the SR Ca2+ pump in the coronary artery. SR-enriched membranes were isolated from coronary artery smooth muscle and washed in ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid to remove bound calmodulin. When these membranes were incubated with MgATP2- in the presence of Ca2+/calmodulin, a 115-kDa protein was phosphorylated. This phosphorylated 115-kDa protein was identified as SERCA2b in Western blots and by immunoprecipitation using a SERCA2-selective antibody. Preincubating the membranes in MgATP2- in the presence of Ca2+/calmodulin stimulated the subsequent Ca2+ uptake in the presence of oxalate plus MgATP2- and azide. The stimulation of Ca2+ uptake was inhibited by including the SR Ca2+ pump inhibitors thapsigargin and cyclopiazonic acid in the Ca2+ uptake medium or by including the calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide or the calmodulin kinase II peptide fragment 290-309 in the phosphorylation solution. Thus an endogenous calmodulin-dependent kinase phosphorylated SERCA2b and activated it. Phospholamban could not be detected in these membranes in Western blots. Therefore, the regulation of the SR Ca2+ pump activity in coronary artery smooth muscle may involve a direct phosphorylation of the pump protein by an endogenous calmodulin-dependent kinase.

Alternative Splicing↗
PubMed1996

SR Ca2+ pump heterogeneity in coronary artery: free radicals and IP3-sensitive and -insensitive pools.

Reactive oxygen species are known to decrease the action of agents that mobilize Ca2+ from sarcoplasmic reticulum (SR) in pig coronary artery smooth muscle. Potentially, this may be due to damage to the SR Ca2+ pump or to the myo-inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release channels. Here we report on the effects of peroxide and superoxide on the SR Ca2+ pump and the subsequent IP3-induced Ca2+ release. Smooth muscle cells cultured from pig left coronary arteries were permeabilized using saponin and then loaded with 45Ca2+ in the presence of an ATP-regenerating system and the mitochondrial Ca2+ uptake inhibitor sodium azide. IP3 caused a release of up to 65% of the loaded 45Ca2+, whereas the Ca2+ ionophore A-23187 caused a release of > 95%. The nature of the IP3-insensitive component of the Ca2+ uptake is not known. The IP3-induced Ca2+ release occurred at 0 or 37 degrees C and was complete in < 30 s. The 50% effective concentration for IP3 was 2.7 +/- 1.0 microM at pH 6.8 and 37 degrees C. At pH 7.4 the IP3-induced Ca2+ release was slightly lower than at pH 6.4-6.8. The IP3-induced release was also inhibited by Ca2+ concentration in the release medium. To investigate the effects of peroxide or superoxide, the cells were treated with these agents, washed, skinned, and then used to examine the IP3-sensitive and -insensitive Ca2+ pools under the conditions in which the IP3-sensitive pool was 60-65% of the total. Peroxide pretreatment was equipotent in inhibiting loading into the IP3-sensitive and -insensitive Ca2+ pools. In contrast, superoxide pretreatment inhibited loading into the IP3-sensitive pool but not into the IP3-insensitive pool. These data are consistent with a model in which the SR Ca2+ pumps are heterogeneous: those required to pump Ca2+ into the IP3-sensitive pool are inhibited by peroxide and superoxide, but those loading the IP3-insensitive pool are inhibited by peroxide only.

Animals↗
PubMed1995

Properties of the sarcoplasmic reticulum Ca(2+)-pump in coronary artery skinned smooth muscle.

Pig coronary artery cultured smooth muscle cells were skinned using saponin. In the presence of an ATP-regenerating system and oxalate, the skinned cells showed an ATP-dependent azide insensitive Ca(2+)-uptake which increased linearly with time for > 1 h. The Ca(2+)-uptake occurred with Km values of 0.20 +/- 0.03 microM for Ca2+ and 400 +/- 34 microM for MgATP2-. Thapsigargin and cyclopiazonic acid inhibited this uptake with IC50 values of 0.13 +/- 0.02 and 0.56 +/- 0.04 microM, respectively. These properties of SR Ca(2+)-pump are similar to those reported for membrane fractions isolated from fresh smooth muscle of coronary artery and other arteries. However, optimum pH of the uptake in the skinned cells (6.2) was lower than that reported previously using isolated membranes (6.4-6.8).

Actins↗
PubMed1995

Effects of peroxide and superoxide on coronary artery: ANG II response and sarcoplasmic reticulum Ca2+ pump.

The sarcoplasmic reticulum (SR) Ca2+ pump in membranes isolated from arterial smooth muscle is damaged by reactive oxygen species (ROS). Because angiotensin II (ANG II) contracts arterial smooth muscle by mobilizing intracellular Ca2+ concentrations ([Ca2+])i, we determined the effects of ROS pretreatment on ANG II-induced contractions in coronary artery rings and [Ca2+]i transients in smooth muscle cells (SMC) cultured from them. This experimental design eliminates direct ROS interference in assay solutions, thus monitoring only the tissue damage. Pretreating the arteries with peroxide inhibited the ANG II contractions with the concentration for half-maximal activation (K0.5) = 74 +/- 5 microM. Peroxide (250 microM) inhibited the contractions to ANG II and cyclopiazonic acid (CPA, SR Ca(2+)-pump inhibitor) by 78.3 +/- 5.1 and 67.4 +/- 6.3%, respectively, but did not significantly affect the contractions by 60 mM KCl. Pretreating SMC with peroxide inhibited the ANG II-induced increase in [Ca2+]i with K0.5 = 24 +/- 3 microM for peroxide. Peroxide (100 microM) inhibited the increase in [Ca2+]i in response to ANG II and CPA by 78.9 +/- 5.1 and 38.3 +/- 4.9%, respectively. The SR Ca(2+)-pump activity was also measured as the Ca(2+)-dependent formation of 115-kDa acylphosphate. Pretreating SMC with 100 microM peroxide inhibited the acylphosphate levels by 36.3 +/- 3.2%. Peroxide (100 microM) pretreatment of SMC did not significantly affect their ANG II binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Acylation↗
PubMed1994

Angiotensin II contractions in coronary artery. Nature of receptors and calcium pools.

Pig coronary artery rings denuded of endothelium contract to the vasoactive hormone angiotensin II (Ang II). The nature of Ang II receptors and their Ca(2+)-pool utilization were examined for contraction of the artery rings and for increase in ultracellular [Ca2+] ([Ca2+]i) in smooth muscle cells cultured from them. Ang II contracted the arteries (EC50 = 7 +/- 4 nM) but with a lower maximal force (1.4 +/- 0.25 N/g tissue) than the contraction with 60 mM K+ (6.11 +/- 0.63 N/g tissue). In the cultured cells it caused a transient increase in [Ca2+]i with an EC50 value of 11 +/- 4 nM. The cells bound Ang II with a dissociation constant (Kd) of 7 +/- 2 nM. Based on the effects of the Ang II antagonists saralasin, DuPont 753, dithiothreitol and PD123319, the Ang II receptors responsible for contraction, increase in [Ca2+]i and Ang II binding to coronary artery smooth muscle were of type AT1. The contraction to Ang II was abolished by EGTA but not by nitrendipine. The sarcoplasmic Ca2+ pump inhibitors cyclopiazonic acid (10 microM CPA) and thapsigargin (1 microM) produced contractions of 4.35 +/- 0.73 and 2.07 +/- 0.54 N/g, respectively. Ang II contractions in the control arteries were nearly abolished upon pretreatment with CPA and thapsigargin. CPA and thapsigargin induced contractions were abolished by exposure to EGTA for 1 h but short exposure of the cells to EGTA only modulated the CPA or thapsigargin induced increase in [Ca2+]i; Ang II induced increase in [Ca2+]i was not inhibited by 1 microM nitrendipine but was reduced significantly by a 30-60 sec exposure to EGTA.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗