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Biomedical subjects

S Srikanth

Publications and source records attributed to S Srikanth.

At least 19 recordsLinked to original sources

Neuropsychiatric symptoms in dementia-frequency, relationship to dementia severity and comparison in Alzheimer's disease, vascular dementia and frontotemporal dementia.

Noncognitive behavioral and psychiatric disturbances are common in dementia and help in the clinical differentiation of the various subtypes. We studied the frequency of neuropsychiatric disturbances, their relationship to dementia severity and compared these disturbances in Alzheimer's disease (AD), vascular dementia (VaD) and frontotemporal dementia (FTD) using the 12-item Neuropsychiatric Inventory (NPI). A total of 98 patients (AD-44, VaD-31, FTD-23) were evaluated. All subjects were community dwelling at the time of evaluation. The three groups were comparable on global dementia severity and functional ability. All patients had clinically significant scores on the NPI with apathy, irritability and agitation being very common (>90% of patients). AD and VaD patients in Clinical Dementia Rating (CDR) stage 2 had significantly higher scores on the total NPI, agitation and disinhibition subscales compared to those in CDR stage 1. Mean scores in the domains of aberrant motor behavior, disinhibition and appetite/eating behavior differentiated FTD from AD and VaD. Neuropsychiatric disturbances in dementia appear to be universal with agitation, disinhibition and irritability being more frequent in the later stages. In this cohort disinhibition, aberrant motor behavior and appetite/eating disturbances could reliably differentiate AD and VaD from FTD. There were no significant differences between the neuropsychiatric profiles of AD and VaD.

Aged↗

A prospective study of reversible dementias: frequency, causes, clinical profile and results of treatment.

BACKGROUND: Dementia due to potentially reversible etiologies is an important group of dementias to be identified not only because of the number of such Patients encountered but also due to the potential for substantial improvement with treatment. AIMS: To prospectively investigate the frequency and causes of dementias with potentially reversible etiologies; to examine the clinical features of this subgroup with a view to identifying a signature profile and to determine if this potential reversibility translates into actual reversibility with appropriate treatment. SETTING AND DESIGN: A prospective longitudinal study of patients with dementia presenting to the outpatient services of a tertiary referral hospital. METHODS: All Patients above 40 years referred for evaluation of cognitive complaints were serially enrolled and underwent clinical examination, various laboratory tests and neuroimaging. Patients were followed-up for one year. STATISTICAL ANALYSIS: One way analysis of variance for continuous variables followed by post hoc comparisons using Scheffe's procedure. RESULTS: A total of 129 patients met Diagnostic and Statistical Manual of Mental Disorders edition 4 (DSM IV) criteria for dementia and qualified for inclusion into the study. Twenty-four patients (18%), all with moderately severe cognitive [mean mini mental state examination (MMSE) score +/- SD = 17.9 +/- 4.8] and neuropsychiatric [mean neuropsychiatric inventory (NPI) score +/- SD = 30.7 +/- 8.7] dysfunction were diagnosed to have reversible causes - neuroinfections in 11 patients, normal pressure hydrocephalus in 8 patients and vitamin B12 deficiency in 5 patients. The majority of these patients had gait and urinary dysfunction reminiscent of subcortical dementias. These reversible causes were clinically suspected in only 58% of patients. In 20/24 patients in whom follow up was possible mean MMSE score had improved to 22.2 and mean NPI score had improved to 8.0, following 6 months of treatment. CONCLUSIONS: Reversible causes, especially neuroinfections and vitamin B12 deficiency accounted for 18% all dementias in this study. The majority of these conditions was not clinically suspected though resulting in moderate to severe cognitive and psychiatric dysfunction. Most of these patients had a subcortical pattern of dementia and showed substantial improvement with treatment.

Adult↗

Developing peptide inhibitors to thrombin activation of platelets from bradykinin analogs.

Investigations identified peptide, platelet-selective thrombin inhibitors. Three peptides (MAP4-RPPGF, RGKWC and RGDWC) were relatively selective inhibitors of thrombin-induced platelet activation and calcium mobilization. MAP4-RPPGF at 35.5+/-0.03 microM inhibits gamma-thrombin-induced platelet aggregation 100% and alpha-thrombin-induced calcium mobilization in fibroblasts 84%. RGKWC at 800+/-400 microM inhibits gamma-thrombin-induced platelet aggregation 100% and calcium mobilization 63%. RGDWC at 140+/-100 microM inhibits gamma-thrombin-induced platelet aggregation 100% and calcium mobilization 32%. RGDWC also inhibits ADP-induced platelet aggregation, whereas MAP4-RPPGF and RGKWC do not. RGKWC prolongs the activated partial thromboplastin time (APTT) but not the prothrombin time (PT) or thrombin clotting time (TCT). RGKWC uniquely inhibits alpha-thrombin activation of human factor XI. Single amino acid substitutions in peptide pentamers result in differences in potency and mechanism(s) of inhibition of platelet and fibroblast activation by thrombin.

Adenosine Diphosphate↗

Hemostatic/fibrinolytic protein changes in C3H/HeN mice infected with Rickettsia conorii--a model for Rocky Mountain spotted fever.

Changes in plasma hemostatic and fibrinolytic proteins were determined during courses of a murine model of fatal and non-fatal Rocky Mountain spotted fever. C3H/HeN mice were infected with Rickettsia conorii and coagulation and histopathologic studies were performed at prescribed periods of time. A significant decrease in plasma factor VIII activity and rise in plasma factor V procoagulant activity correlated with a fatal infection. Factor VII levels were unchanged; factor XI levels dropped early in the course in the lethally infected animals, but returned to normal. Factor XII, high molecular weight kininogen, and prekallikrein levels were unchanged by the sublethal infection. Prekallikrein levels fell during the lethal infection. Antithrombin concentrations were decreased significantly in all animals, but plasma plasminogen levels did not change in either group of animals. Nonocclusive thrombi were microscopically observed rarely and only in animals surviving a sublethal infection. A fall in tissue plasminogen activator activity and a rise in plasminogen activator inhibitor activity highly correlated with a lethal outcome. Lethal infection with R. conorii is associated with primary endothelial cell injury resulting in decreased tissue plasminogen activator and increased plasminogen activator inhibitor.

Animals↗

Alkaptonuric ochronosis presenting as palmoplantar pigmentation.

We describe a 37-year-old woman who presented with palmoplantar pigmentation, thickening and pitting of 4 years duration. Bluish pigmented patches were seen over the sclera of her eyes. Her lumbar spine showed typical calcification of the intervertebral discs. Addition of Benedict's reagent to a urine sample of the patient gave rise to greenish brown precipitate and brownish black supernatant. Alkalinization of urine turned it black. A biopsy of the palmar lesion demonstrated irregular breaking up, swelling and homogenization of collagen bundles in the reticular dermis. Yellow-brown (ochre coloured) pigment was seen lying within the collagen bundles and also freely in the deeper dermis confirming our clinical diagnosis of alkaptonuric ochronosis. To the best of our knowledge this is probably the second report of alkaptonuria presenting with palmoplantar pigmentation.

Adult↗

Human DU145 prostate cancer cells overexpressing mitogen-activated protein kinase phosphatase-1 are resistant to Fas ligand-induced mitochondrial perturbations and cellular apoptosis.

Recent studies have suggested that MAP kinase phosphatase 1 (MKP-1) is overexpressed in prostate cancer. To evaluate the role of MKP-1 in regulating cell death and tumor growth in prostate cancer, MKP-1 was conditionally overexpressed in the human prostate cancer cell line DU145. Overexpression of MKP-1 in DU145 cells blocked activation of stress-activated protein kinase (SAPK/JNK). MKP-1 overexpression in DU-145 cells was also found to inhibit Fas ligand (FasL)-induced apoptosis, as well as block the activation of caspases by Fas engagement. In addition, MKP-1 blocked the activation of apoptosis by transfected MEKK-1 and ASK-1, presumably through its inhibition of the SAPK/JNK family of enzymes. MKP-1 blocked the ability of FasL to induce loss of mitochondrial transmembrane potential (delta Psi(m)), suggesting that MKP-1 acts upstream of mitochondrial pro-apoptotic events induced by FasL and that the SAPK/JNK pathway may form the signaling link between Fas receptor and mitochondrial dysfunction. Thus, MKP-1 overexpression in prostate cancer may play a role in promoting prostate carcinogenesis by inhibiting FasL-induced cell death.

Apoptosis↗

Adenovirus-mediated expression of Fas ligand induces apoptosis of human prostate cancer cells.

Several laboratories have reported on the apoptotic potentials of human prostate cancer (PC) cell lines in response to crosslinking of Fas (CD95/APO-1) with agonistic anti-Fas antibodies. We have re-evaluated the apoptotic potentials of seven human PC cell lines using the natural Fas ligand (FasL) in place of agonistic antibody. First, PC cell lines were tested in a standard cytotoxicity assay with a transfected cell line that stably expresses human FasL. Next, we developed an adenoviral expression system employing 293 cells that stably express crmA, a poxvirus inhibitor of apoptosis, to analyze the effects of FasL when expressed internally by the PC cell lines. Our data suggest that the apoptotic potentials of these cell lines were greatly underestimated in previous studies utilizing agonistic anti-Fas antibodies. Lastly, adenoviral-mediated expression of FasL prevented growth and induced regression of two human PC cell lines in immunodeficient mice. These preliminary in vivo results suggest a potential use for adenovirus encoding FasL as a gene therapy for PC.

Adenoviridae↗

Thrombostatin inhibits induced canine coronary thrombosis.

Thrombostatin (RPPGF), an angiotensin converting enzyme metabolite of bradykinin, is an inhibitor of alpha-thrombin's ability to activate platelets. We examined the in vivo pharmacokinetics and pharmacodynamics of thrombostatin in rabbits and its ability to inhibit coronary thrombosis induced by electrolytic injury in dogs. Plasma half-life of thrombostatin had a t1/2alpha of 2.6 min and a t1/2beta of 24 min in rabbits. Ligating the renal arteries did not prolong clearance (t1/2alpha = 2.4 min; t1/2beta = 12 min). Thrombostatin produced a prolonged in vivo antiplatelet effect. At 30 min after a single intravenous administration in rabbits, thrombostatin's plasma concentration was <8.7 microM (5 microg/ml). However, ex vivo 20 and 40 nM gamma-thrombin-induced platelet aggregation of these rabbits' platelets was inhibited 40% for 2.75 and 1 h, respectively. In vitro, flow cytometry studies revealed that thrombostatin specifically bound to human platelets and washed human platelets treated with thrombostatin were less responsive to gamma-thrombin than control platelets. Using electrolytic injury to induce coronary artery thrombosis, dogs treated with thrombostatin, aspirin, or combined thrombostatin and aspirin occluded in 62+/-25 (mean +/- SD), 62+/-36, or 89+/-32 min versus untreated animals which occluded at 39+/-27 min, (p<0.01, p<0.01 and p<0.001, respectively). These studies show that thrombostatin binds to platelets and can delay coronary occlusion in vivo.

Amino Acid Sequence↗

Fibrinogen activates NF-kappa B transcription factors in mononuclear phagocytes.

Adhesion to extracellular matrices is known to modulate leukocyte activation, although the mechanisms are not fully understood. Mononuclear phagocytes are exposed to fibrinous provisional matrix throughout migration into inflammatory foci, so this study was undertaken to determine whether fibrinogen triggers activation of NF-kappa B transcription factors. U937 cells differentiated with PMA in nonadherent culture were shown to express two fibrinogen-binding integrins, predominately CD11b/CD18, and to a lesser extent, CD11c/CD18. Cells stimulated with fibrinogen (10-100 microg/ml)/Mn2+ (50 microM) for 2 h were examined by electrophoretic mobility shift assay. NF-kappa B activation, minimal in unstimulated cells, was substantially up-regulated by fibrinogen. Fibrinogen also caused activation of AP-1, but not SP1 or cAMP response element-binding protein (CREB) factors. Blocking mAbs against CD18 and CD11b abrogated fibrinogen-induced NF-kappa B activation. To determine the effects on transcriptional regulation, U937 cells were transfected with a plasmid containing the HIV-1 enhancer (bearing two NF-kappa B sites) coupled to a chloramphenicol acetyltransferase (CAT) reporter. Cells were subsequently stimulated with 1) PMA for 24 h, inducing CAT activity by 2.6-fold, 2) fibrinogen/Mn2+ for 2 h, inducing CAT activity by 3.2-fold, or 3) costimulation with fibrinogen and PMA, inducing 5.7-fold the CAT activity induced by PMA alone. We conclude that contact with fibrinogen-derived proteins may contribute to mononuclear phagocyte activation by signaling through CD11b/CD18, resulting in selective activation of transcriptional regulatory factors, including NF-kappa B.

Adjuvants, Immunologic↗

PU.1 regulates the expression of the human neutrophil elastase gene.

PU.1 is a transcription factor present in B-cells and macrophages. Here, we report our studies on the role of PU.1 in myelopoiesis using human neutrophil elastase (HNE) as a model. HNE, a component of the primary granules of mature granulocytes, is a serine protease which is transcriptionally restricted to the late promyelocytic stage of granulocytic maturation. The first 200 bp of the HNE promoter directs myeloid specific expression of a reporter gene and a 30-bp element within this region was been identified as the major determinant of myeloid specific expression [S. Srikanth, T. Rado, A 30-bp element is responsible for the myeloid specific activity of the human neutrophil elastase promoter, J. Biol. Chem. 269 (1994) 32626-32632.]. We now show that the B-cell and macrophage specific transcription factor, PU.1, binds to the PU.1 consensus site within the 30-bp element to activate transcription. Substitution mutations within this recognition sequence results in the loss of PU.1 binding and in a 90% decrease in promoter activity in myeloid cells. Cotransfection of PU.1 and a reporter gene controlled by the HNE promoter into non-myeloid HeLa cells resulted in activation of reporter gene transcription.

Amino Acid Substitution↗

Conditional expression of mitogen-activated protein kinase phosphatase-1, MKP-1, is cytoprotective against UV-induced apoptosis.

UV irradiation induces apoptosis in U937 human leukemic cells that is accompanied by the activation of both the stress-activated protein kinase (SAPK) and p38 mitogen-activated protein kinase (MAPK) signal transduction pathways. The MAPK phosphatase, MKP-1, is capable of inactivating both SAPK and p38 MAPK in vivo. To determine whether MKP-1-mediated inhibition of SAPK and/or p38 MAPK activity provided cytoprotection against UV-induced apoptosis, a U937 cell line conditionally expressing MKP-1 from the human metallothionein IIa promoter was established. Conditional expression of MKP-1 was found to abolish UV-induced SAPK and p38 MAPK activity, and inhibit UV-induced apoptosis as judged by both morphological criteria and DNA fragmentation. MKP-1 was also found to inhibit other biochemical events associated with apoptosis, including activation of caspase-3 and the proteolytic cleavage of the caspase-3 substrate, poly(ADP ribose) polymerase. These findings demonstrate that MKP-1 acts at a site upstream of caspase activation within the apoptotic program. The cytoprotective properties of MKP-1 do not appear to be mediated by its ability to inhibit p38 MAPK because the p38 MAPK specific inhibitor SB203580 had no effect on UV-induced apoptosis in U937 cells. Furthermore, by titrating the level of MKP-1 expression it was found that MKP-1 inhibited UV-induced SAPK activity, DNA fragmentation, and caspase-3 activation in a similar dose-dependent manner. The dual-specificity phosphatase, PAC1, which does not inhibit UV-induced activation of SAPK, did not provide a similar cytoprotection against UV-induced apoptosis. These results are consistent with a model whereby MKP-1 provides cytoprotection against UV-induced apoptosis by inhibiting UV-induced SAPK activity.

Apoptosis↗

Inhibition of caspases by cytokine response modifier A blocks androgen ablation-mediated prostate cancer cell death in vivo.

Androgen withdrawal is a major therapeutic modality in the treatment of prostate cancer. Although tumors initially respond, they subsequently relapse, and these recurring tumors are androgen independent. To examine possible mechanisms to explain the androgen independence of prostate cancer, we have expressed cytokine response modifier A (CrmA), a competitive inhibitor of caspases, interleukin 1beta-converting enzyme-like proteases, which mediate apoptotic cell death, in the human androgen-dependent prostate cancer cell line LNCaP. LNCaP cells require androgens for continuous growth in culture and to form tumors in nude mice. The expression of CrmA in LNCaP cells prevented the decreased growth rate induced by androgen withdrawal in tissue culture. When CrmA-expressing LNCaP (LNCaP-CrmA) cells were implanted s.c. in nude mice, the tumors grew six times faster than parental cells. Androgen ablation by castration before tumor implantation suppressed the ability of control LNCaP cells expressing nonfunctional CrmA mutant (R291T) to form tumors, but LNCaP-CrmA cells formed tumors similar in size to those formed in normal mice. When orchiectomy was performed 10 days after tumor implantation, control LNCaP cells expressing a nonfunctional CrmA mutant (R291T) regressed, but LNCaP-CrmA tumors continued to grow. Thus, inhibition of caspases prevents androgen withdrawal-induced prostate cancer cell death, suggesting that caspase activation is normally an important part of this process.

Androgens↗

Multifunctional cytokine expression by human mast cells: regulation by T cell membrane contact and glucocorticoids.

Human mast cells readily release a variety of mediators, including cytokines, in response to IgE receptor crosslinking, but the mechanisms governing the expression of cytokines are still unclear. Using a human mast cell line, HMC-1, we show expression of cytokine transcripts as early as 2 h after activation with ionomycin and phorbol myristate acetate (PMA). Resting HMC-1 cells expressed transcripts for interleukin-1 receptor antagonist (IL-1RA), IL-2, IL-4, IL-5, GM-CSF, and weakly for IL-8, and stimulation with ionomycin and PMA induced additional transcripts for IL-6 and IL-13 and upregulated expression of IL-8 transcripts. HMC-1 cells secreted IL-4, IL-8, and GM-CSF protein after activation and dexamethasone significantly inhibited the production of these cytokines. Of significance is the finding that the addition of membranes purified from activated T cells to mast cell cultures induced transcripts selectively for IL-8 and none for other proinflammatory cytokines. Flow cytometry revealed that resting HMC-1 cells express CD40, a molecule involved in contact-dependent signaling of monocytes and B cells by T cells. However, activation of HMC-1 by anti-CD40 antibody did not induce IL-8 gene expression or protein production. This study demonstrates that human mast cells are capable of expressing multiple cytokines that can be inhibited by glucocorticoids. It also raises the possibility that T cells may activate mast cell cytokine synthesis by novel contact-dependent mechanisms. This phenomenon of T cell regulation of mast cell function requires further study.

Anti-Inflammatory Agents↗

Lymphoblastoid interferon-alpha inhibits T cell proliferation and expression of eosinophil-activating cytokines.

T cell-derived cytokines, such as interleukin-5 (IL-5) and granulocyte-macrophage colony-stimulating factor (GM-CSF) activate eosinophils, whereas other cytokines, such as tumor necrosis factor (TNF)-alpha and IL-13, determine eosinophil recruitment. Interferon-alpha (IFN-alpha), a leukocyte-derived cytokine, has been shown to have beneficial effects in eosinophil-mediated disorders, such as the hypereosinophilic syndrome and a murine model of allergic asthma, where it inhibited eosinophil recruitment. We tested the hypothesis that IFN-alpha acted in eosinophil-mediated disorders by modulating T cell cytokine expression. Peripheral blood mononuclear cells (PBMC) or human ragweed-specific TH1 (2B8) and TH2 (2D2) T cell clones were cultured in the presence of 5 micrograms/ml of phytohemagglutinin (PHA) or 25 micrograms/ml of antigen Amb a 1 (short ragweed allergen), respectively, and lymphoblastoid IFN-alpha (varying from 0 to 10,000 U/ml). We assessed T cell proliferation by [3H]thymidine incorporation and production of IL-5 and GM-CSF by ELISA. Expression of cytokine transcripts was analyzed by the reverse transcription-polymerase chain reaction technique (RT-PCR). IFN-alpha induced a dose-dependent suppression of T cell proliferation of both PBMC (p < 0.001) and the T cell clones (p < 0.001). IFN-alpha inhibited gene expression of IL-5, GM-CSF, TNF-alpha, and IL-13 in PBMC. Furthermore, IFN-alpha significantly inhibited mitogen-induced and antigen-induced production of IL-5 and GM-CSF. IFN-alpha may benefit eosinophil-mediated disorders by inhibiting T cell function and production of cytokines active on human eosinophils.

Adult↗

Effect of interferon alpha on HLA-DR expression by human buccal epithelial cells.

/We have studied the effect of interferon alpha (IFN-alpha) on MHC class II expression by human buccal epithelial cells (BEC), and mRNA expression by BEC and mucosal-associated mononuclear cells (MAMC). In 6 experiments, freshly collected BEC were suspended at a concentration of 1.0 x 10(5)/ml in RPMI 1640 and incubated in the presence of 0-10,000 IU/ml of human lymphoblastoid IFN-alpha (HuIFN-alpha). Zero and six hour samples were analyzed by single color flow cytometry using FITC-labeled murine IgG1 monoclonal antibody to HLA-DR. Preparations were also analyzed for expression of cytokine transcripts (IL-2, IL-4, IL-5, IL-6, IL-8, IFN-gamma, GM-CSF) by reverse transcriptase polymerase chain reaction (RT-PCR). Increasing concentrations of IFN-alpha resulted in proportionate increases in the percentage of HLA-DR + BEC (r = 0.7897, p = 0.0627) and in the percentage of HLA-DR+ staining at higher intensities (10(1) to 10(2) log fluorescence intensity) (LFI) (r = 0.4010, p = 0.0424). The percentage of HLA-DR + BEC rose from a mean of 1.5% with no IFN-alpha to 7% with 10,000 IU/ml IFN-alpha (p < 0.05). The percentage of HLA-DR + BEC staining at 10(1) to 10(2) LFI rose from a mean of 8.3% with no added IFN-alpha to 19.2% with 10,000 IU/ml IFN-alpha (p < 0.05). Unstimulated BEC constitutively expressed IL-8 and GM-CSF. IFN-alpha stimulated preparations also expressed IFN-gamma, possibly due to the presence of MAMC, which comprised 2-9% of the total cell population. These data indicated that HuIFN-alpha upregulates MHC class II expression by human BEC, possibly by enhancing IFN-gamma production by MAMC present in the culture preparations.

Cells, Cultured↗

A 30-base pair element is responsible for the myeloid-specific activity of the human neutrophil elastase promoter.

Human neutrophil elastase (HNE), a serine protease, is expressed only in the promyelocytic stages of granulocyte maturation. We examined several regions of the promoter for transcriptional activity and report that a 30-base pair (bp) element located between -76 and -106 in the 5'-flanking region of HNE is sufficient for myeloid-specific expression of HNE. Gel shift assays using nuclear extracts from myeloid and non-myeloid cells reveal several myeloid-specific complexes binding to the 30-bp element. Examination of DNA-protein interactions shows that at least two myeloid-specific proteins of 38 and 55 kDa bind to this element. DNase I protection analysis reveals two distinct footprints between -80 to -91 and -94 to -104 within this element. Transient expression studies using deletion constructs of the HNE 5'-flanking region show that the 30-bp element is active in myeloid cells K 562 and U 937 but not in HeLa cells. Internal deletion of this element results in a 60-85% loss of promoter activity in myeloid cells. Additional functional studies also show that a 19-bp region between -112 and -131 contributes to transcriptional activity of the elastase promoter as well.

Base Composition↗

Viral antibodies in recent onset, nonorganic psychoses: correspondence with symptomatic severity.

A parallel of generalized viral infection with psychiatric symptoms has been reported in nonorganic psychotic disorders. The patients concerned had been ill for long periods and some of them had been readmitted. In order to determine the presence of viral infection at the very onset of the psychosis, antibodies in blood and cerebrospinal fluid (CSF) to six viruses [cytomegalovirus (CMV), herpes simplex (HSV) Type 1, mumps, measles, varicella zoster virus (VZV), and Japanese encephalitis virus (JEV)] were assayed in 35 psychotic patients [14 schizophrenics; 13 manic patients; and 8 patients with psychosis not otherwise specified (NOS)] within 1 month of onset of illness. Ten (28.6%) patients had a diagnostic (fourfold) change in the antibody titer in the paired serum and/or CSF samples (drawn at 2-week intervals) and another 10 had high titers (above 2 SDs from the mean in 35 control subjects). The striking temporal correlation with the initial severity and resolution of psychopathology by 2 weeks on the Brief Psychiatric Rating Scale (BPRS) suggests a causally significant, currently active viral infection in these 20 cases.

Acute Disease↗