Glutamate receptor signaling interplay modulates stress-sensitive mitogen-activated protein kinases and neuronal cell death

Glutamate receptors modulate multiple signaling pathways, several of which involve mitogen-activated protein (MAP) kinases, with subsequent physiological or pathological consequences. Here we report that stimulation of the N-methyl-D-aspartate (NMDA) receptor, using platelet-activating factor (PAF) as a messenger, activates MAP kinases, including c-Jun NH2-terminal kinase, p38, and extracellular signal-regulated kinase, in primary cultures of hippocampal neurons. Activation of the metabotropic glutamate receptor (mGluR) blocks this NMDA-signaling through PAF and MAP kinases, and the resultant cell death. Recombinant PAF-acetylhydrolase degrades PAF generated by NMDA-receptor activation; the hetrazepine BN50730 (an intracellular PAF receptor antagonist) also inhibits both NMDA-stimulated MAP kinases and neuronal cell death. The finding that the NMDA receptor-PAF-MAP kinase signaling pathway is attenuated by mGluR activation highlights the exquisite interplay between glutamate receptors in the decision making process between neuronal survival and death.

Studies on the antibacterial potential of Cryptostegia grandiflora R. Br. (Asclepiadaceae) extract

Different extracts of Cryptostegia grandiflora (Roxb) Rbr. leaves were investigated for their antibacterial potential against Pseudomonus cepacia NCIM-2106, Bacillus megatorium NCIM-2087, Staphylococcus aureus NCIM-2492, Escherichia coli NCIM-2345, Bacillus subtilis NCIM-2349 and Bacillus coagulans NCIM 2323. Almost all the extracts produced significant antibacterial activity against all the microorganisms being tested and the effect so produced was comparable to the standard antibiotic, tetracycline hydrochloride. The petroleum ether (60 degrees-80 degrees C) extract showed maximum efficacy.

Platelet-activating factor is a downstream messenger of kainate-induced activation of mitogen-activated protein kinases in primary hippocampal neurons

Excitatory amino acids transduce physiological and pathological signals to neurons. Similarly, the neuroactive lipid platelet-activating factor (PAF) has been implicated in modulating long-term potentiation and neuronal survival. Excitatory amino acids and PAF have been shown to increase mitogen-activated protein (MAP) kinases in different cell types. Here, we have investigated the similarities and differences between PAF and kainate in activating MAP kinases in primary hippocampal neurons in vitro. Extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 kinases were activated by kainate or PAF in hippocampal neurons. This activation was blocked by the receptor antagonists CNQX and BN 50730 for kainate and PAF, respectively. The PAF receptor antagonist BN 50730 also blocked kainate activation. CNQX had no effect on PAF activation of the kinases, indicating that PAF is downstream of kainate activation. Coapplication of submaximal concentrations of PAF and kainate resulted in a less than additive activation, suggesting similar routes of activation by the two agonists. Both CNQX and BN 50730 blocked kainate-induced neurotoxicity. These results indicate that PAF and kainate activate similar kinase pathways. Therefore, PAF acts downstream of the kainate subtype of glutamate receptors, and when excessive receptor activation takes place, this bioactive lipid may contribute to neuronal cell death.

Purified arginine permease of Candida albicans is functionally active in a reconstituted system

We have for the first time purified arginine permease from a pathogenic yeast, Candida albicans, to homogeneity by affinity chromatography using L-arginine-linked agarose matrix as affinity column. The purified protein (PP) was of 66 kDa with no subunit structure. Two kinetically distinct binding affinities of PP were evident where high affinity binding (S1) revealed a dependence on acidic pH while pH did not have dramatic effect on low affinity (S2) binding. The specificity of L-arginine binding to PP with regard to other amino acids, structural analogues and inhibitors, was essentially similar to arginine transport observed in the intact cells of C. albicans (Rao et al., 1986). The purified arginine permease was reconstituted into proteoliposomes and its functionality was tested by imposing a valinomycin-induced membrane potential. All the characteristic features of L-arginine transport displayed by the reconstituted system were similar to those observed in intact cells. Thus homogeneous purified arginine permease was also functionally active.

Screening of anti-diarrhoeal profile of some plant extracts of a specific region of West Bengal, India

Ethanol extract of four different plants of the Khatra region of the Bankura district of West Bengal, India were evaluated for anti-diarrhoeal activity against different experimental models of diarrhoea in rats. The extracts of Ficus bengalensis Linn. (hanging roots), Eugenia jambolana Lam. (bark), Ficus racemosa Linn. (bark) and Leucas lavandulaefolia Rees (aerial parts) showed significant inhibitory activity against castor oil induced diarrhoea and PGE2 induced enteropooling in rats. These extracts also showed a significant reduction in gastrointestinal motility in charcoal meal tests in rats. The results obtained establish the efficacy of all these plant materials as anti-diarrhoeal agents.

Effect of Nelumbo nucifera rhizome extract on blood sugar level in rats

Oral administration of the ethanolic extract of rhizomes of Nelumbo nucifera markedly reduced the blood sugar level of normal, glucose-fed hyperglycemic and streptozotocin-induced diabetic rats, when compared with control animals. The extract improved glucose tolerance and potentiated the action of exogenously injected insulin in normal rats. When compared with tolbutamide, the extract exhibited activity of 73 and 67% of that of tolbutamide in normal and diabetic rats, respectively.

Experimental models and their use in studies of diabetic retinal microangiopathy

Diabetes produces dramatic changes in retinal microvasculature, triggering endothelial cell proliferation and microaneurysms. Capillaries become weakened, releasing blood into vitreal and retinal spaces. Photoreceptors become occluded and separated from the choriocapillaris, resulting in visual acuity decline, detachment and cell death. Several models have been developed that have proved useful for the study of this disease, resulting in a better understanding of the processes involved. Streptozotocin treatment affects the pancreatic beta cells, rapidly reducing them until insulin is no longer synthesized in sufficient amounts. The galactosemic model shifts metabolism away from glucose, increasing aldose reductase and retinal polyol metabolism. Finally, two weeks of cycled oxygen from high to low tension every 24 hours, followed by return to room air, triggers microangiogenesis in developing retinas. Use of these models, separately or in combination, as well as electroretinographic analysis, has begun to reveal the events taking place as diabetic retinopathy progresses. Endothelial cells become separated from pericytes as basement membranes thicken, and vascular endothelial growth factor increases, triggering their proliferation. Finally, early changes occurring within photoreceptors can now be studied.

Studies on the anti-inflammatory activity of rhizomes of Nelumbo nucifera

The anti-inflammatory activity of the methanol extract of Nelumbo nucifera rhizome as well as of betulinic acid, a steroidal triterpenoid isolated from it, were evaluated on carrageenin and serotonin induced rat paw edema. Methanol extract at doses of 200 and 400 mg/kg and betulinic acid at doses of 50 mg/kg and 100 mg/kg p.o., showed significant anti-inflammatory activity in both the models of inflammation in rats. The effects produced were comparable to that of phenylbutazone and dexamethasone, two prototype anti-inflammatory drugs.

Studies on in vivo antitussive activity of Leucas lavandulaefolia using a cough model induced by sulfur dioxide gas in mice

The methanol extract of Leucas lavandulaefolia was investigated for its effects on a cough model induced by sulfur dioxide gas in mice. It exhibited significant antitussive activity when compared with control in a dose-dependent manner. The antitussive activity of the extract was comparable to that of codeine phosphate (10 mg/kg), a prototype antitussive agent. The Leucas lavandulaefolia extract at 100, 200, and 400 mg/kg. p.o. showed inhibition of cough by 35.0, 51.9, and 56.5% within 1 h of performing the experiment.

Wound healing activity of Leucas lavandulaefolia Rees

Leucas lavandulaefolia Rees (Labiatae), commonly known as Halkusha, is a well-known plant in Indian traditional medicine. On the basis of its traditional use and literature references, this plant was selected for evaluation of its wound healing potential. A methanol extract of L. lavandulaefolia was examined for its wound healing activity both in the form of an ointment as well as an injection in two types of wound model in rats: (i) the excision wound model and (ii) the incision wound model. Both the injection and the ointment of the methanol extract of the plant material produced a significant response in both of the wound types tested. The results were also comparable to those of a standard drug, nitrofurazone, in terms of wound contracting ability, wound closure time, tensile strength and regeneration of tissues at the wound site.

Studies on antitussive activity of Drymaria cordata Willd. (Caryophyllaceae)

The methanol extract of Drymaria cordata Willd. was investigated for its effect on a cough model induced by sulfur dioxide gas in mice. It exhibited significant antitussive activity when compared with the control in a dose-dependent manner. The antitussive activity of the extract was comparable to that of codeine phosphate, a prototype antitussive agent. The D. cordata extract (100, 200, 400 mg/kg) showed 11.6%, 31.6% and 51.5% inhibition of cough with respect to the control group.

Studies on psychopharmacological effects of Nelumbo nucifera Gaertn. rhizome extract

Methanolic extract of rhizomes of Nelumbo nucifera (NNRE) was investigated for different psychopharmacological actions in rats and mice. The extract was found to cause reduction in spontaneous activity, decrease in exploratory behavioural pattern by the head dip and Y-maze test, reduction in muscle relaxant activity by rotarod, 30 degrees inclined screen and traction test and potentiated the pentobarbitone induced sleeping time in mice significantly.

Antipyretic activity of Nelumbo nucifera rhizome extract

Antipyretic activity of methanolic extract of rhizome of N. nucifera was studied on normal body temperature and yeast induced pyrexia in rats. Yeast suspension (10 ml/kg, s.c.) increased rectal temperature after 19 hr of administration. The extract, in doses of 200, 300 or 400 mg/kg (po) produced significant dose dependent lowering of normal body temperature and yeast provoked elevation of body temperature in rats. The effect produced was comparable with the standard antipyretic drug, paracetamol (150 mg/kg, i.p.).

Diagnosis of malignant neoplasms of male breast by fine needle aspiration cytology

Fine needle aspiration cytology (FNAC) is now an established procedure for the evaluation of breast masses in women. But there are only occasional reports of aspiration cytology of rare malignant neoplasms of male breast. During the past 8 years the authors detected 12 malignant neoplasms of male breast by FNAC out of total 167 cases of aspirates of male breast lesions. There were eight infiltrating ductal carcinomas, two leiomyosarcomas and two metestatic carcinomas. The cytologic features with short review of literature of male breast carcinomas are presented. Due to high diagnostic accuracy, FNAC should be routinely practiced as a quick and safe diagnostic procedure in all outpatients department.

Platelet-activating factor and retinoic acid synergistically activate the inducible prostaglandin synthase gene

Platelet-activating factor (PAF), a potent lipid mediator generated in cell injury and in the inflammatory and immune responses, promotes transcriptional activation of several primary response genes. TIS10/PGS-2 is a primary response gene encoding the inducible form of prostaglandin synthase. The inductive effects of PAF and retinoic acid (RA), alone and in combination, were studied with the regulatory region of TIS10/PGS-2 transfected into an exponentially growing glioblastoma-neuroblastoma NG108-15 hybrid in the human SH-SY5Y neuroblastoma or in the NIH 3T3 cell. RA alone exhibited only a small inductive effect. However, in the presence of RA (100 nM), a PAF-dependent (1-50 nM) synergistic activation of luciferase reporter constructs driven by regulatory regions of the TIS10/PGS-2 gene was found. The hetrazepine BN-50730, an antagonist selective for intracellular PAF binding sites, inhibited PAF and RA induction of luciferase from the TIS10/PGS-2 promoter. Thus, the intracellular PAF binding site is involved in TIS10/PGS-2 expression. Induction is rapid, suggesting that the combination of PAF and RA activates a preexisting latent transcription factor(s). Deletion studies restrict the major PAF and RA cis-acting response element of the TIS10/PGS-2 gene to a 70-nucleotide sequence as an intracellular inducer of TIS10/PGS-2 expression. The synergistic effect of RA and PAF represents an unusual convergence of nuclear signaling pathways by which, through the modulation of preexisting transcription factors, specific gene expression can be upregulated. PAF-dependent induction of TIS10/PGS-2 expression may play a role in cell injury, differentiation, inflammation, and immune responses.