PubMed Health⌕ Search

Biomedical subjects

Ajit Kumar

Publications and source records attributed to Ajit Kumar.

36 records · Page 2Linked to original sources
PubMed2003

Nursing care of patients with late-stage Parkinson's disease.

Patients in the late stages of Parkinson's disease may be significantly disabled for many years, often because of their increasing inability to tolerate therapeutic doses of antiparkinson drugs. Their status and management have been overlooked in the literature. Few current healthcare professionals have cared for patients with Parkinson's disease in the prelevodopa era and do not understand how severe and protracted the illness can be without effective treatment. This article describes a practical approach to the nursing management of severely affected patients (i.e., Hoehn and Yahr Stage 4-5) who no longer derive consistent, therapeutic benefit from their drugs. Specific problems these patients face are adverse drug reactions such as postural hypotension, psychosis, and confusion, as well as difficulties with nutrition, elimination, mobility and falling, communication, sexuality, memory, and mood. Nursing interventions can help minimize the effect of these problems on the patient.

Activities of Daily Living↗
PubMed2003

Restriction of human immunodeficiency virus type 1 Rev function in murine A9 cells involves the Rev C-terminal domain.

The human immunodeficiency virus type 1 (HIV-1) Rev and human T-cell leukemia virus type 1 (HTLV-1) Rex proteins are essential for the expression of viral structural proteins and productive infection. Both contain a nuclear export signal (NES) in their C-terminal domain and a nuclear localization signal (NLS) in their N-terminal domain. The NES and NLS are necessary for shuttling between nucleus and cytoplasm and are therefore indispensable for the transport of unspliced and singly spliced viral transcripts. HIV-1 Rev function is restricted in A9 cells, a murine fibroblast cell line, whereas HTLV-1 Rex is functional in these cells. Immunofluorescence studies with RevGFP fusion protein demonstrate normal import and export of Rev in A9 cells. To ascertain which domains of Rev are necessary for the restriction of Rev function in A9 cells, we studied a chimeric construct in which the NES domain of Rev was exchanged with Rex C-terminal amino acids 79 to 95, the Rev1-79/Rex79-95 chimera, which restored Rev function in A9 cells. In addition, overexpression of a truncated Rev containing the Rev C-terminal domain in the presence of wild-type Rev, led to restoration of Rev function in A9 cells. These results suggest that the C-terminal domain of HIV-1 Rev plays an important role in restricting Rev function in murine cells.

Animals↗
PubMed2003

Chromatin remodeling and modification during HIV-1 Tat-activated transcription.

Human immunodeficiency virus type 1 (HIV-1) is the etiologic agent of AIDS. Following entry into the host cell, the viral RNA is reverse transcribed into DNA and subsequently integrated into the host genome as a chromatin template. Chromatin structure may be responsible for silencing retroviral gene expression. Transcriptional activation occurs after ATP-dependent chromatin remodeling complexes alter chromatin structure and positioning of nucleosomes. Histone acetyltransferases (HATs), histone deacetylases (HDACs), kinases, and methyltransferases (HMTs), covalently modify nucleosomes by adding or removing chemical moieties in the N-terminal tails of histones. Recent advances have indicated that HIV-1 encoded proteins interact with chromatin remodeling complexes and histone modifying enzymes, implying that chromatin remodeling plays an important role in the HIV-1 life cycle. Nucleosomes are positioned on the HIV-1 LTR and are barriers to transcription. Following cellular activation, these nucleosomes are modified and repositioned allowing for activation of viral gene expression. Tat recruits various HATs to the HIV-1 promoter region and can also be acetylated by some of these enzymes. Unmodified Tat is involved in binding to the CBP/p300 and cdk9/cyclin T complexes and facilitates transcription initiation. Acetylated Tat dissociates from the TAR RNA structure and recruits bromodomain-containing chromatin modifying complexes such as p/CAF and SWI/SNF to facilitate transcription elongation. This review summarizes our current knowledge and understanding of chromatin remodeling complexes and their regulation of HIV-1 replication, and highlights the important contributions HIV-1 research has made to further our understanding of the transcription process.

Chromatin↗
PubMed2002

Protein phosphatase-1 dephosphorylates the C-terminal domain of RNA polymerase-II.

Transcription by RNA polymerase-II (RNAPII) is controlled by multisite phosphorylation of the heptapeptide repeats in the C-terminal domain (CTD) of the largest subunit. Phosphorylation of CTD is mediated by the cyclin-dependent protein kinases Cdk7 and Cdk9, whereas protein serine/threonine phosphatase FCP1 dephosphorylates CTD. We have recently reported that human immunodeficiency virus-1 (HIV-1) transcription is positively regulated by protein phosphatase-1 (PP1) and that PP1 dephosphorylates recombinant CTD. Here, we provide further evidence that PP1 can dephosphorylate RNAPII CTD. In vitro, PP1 dephosphorylated recombinant CTD as well as purified RNAPII CTD. HeLa nuclear extracts were found to contain a species of PP1 that dephosphorylates both serine 2 and serine 5 of the heptapeptide repeats. In nuclear extracts, PP1 and FCP1 contributed roughly equally to the dephosphorylation of serine 2. PP1 co-purified with RNAPII by gel filtration and associated with RNAPII on immunoaffinity columns prepared with anti-CTD antibodies. In cultured cells treated with CTD kinase inhibitors, the dephosphorylation of RNAPII on serine 2 was inhibited by 45% by preincubation with okadaic acid, which inhibits phosphatases of PPP family, including PP1 but not FCP1. Our data demonstrate that RNAPII CTD is dephosphorylated by PP1 in vitro and by PPP-type phosphatase, distinct from FCP1, in vivo.

Animals↗
PubMed2002

HIV-1 Tat-associated RNA polymerase C-terminal domain kinase, CDK2, phosphorylates CDK7 and stimulates Tat-mediated transcription.

HIV-1 gene expression is regulated by a viral transactivator protein (Tat) which induces transcriptional elongation of HIV-1 long tandem repeat (LTR). This induction requires hyperphosphorylation of the C-terminal domain (CTD) repeats of RNA polymerase II (Pol II). To achieve CTD hyperphosphorylation, Tat stimulates CTD kinases associated with general transcription factors of the promoter complex, specifically TFIIH-associated CDK7 and positive transcription factor b-associated CDK9 (cyclin-dependent kinase 9). Other studies indicate that Tat may bind an additional CTD kinase that regulates the target-specific phosphorylation of RNA Pol II CTD. We previously reported that Tat-associated T-cell-derived kinase (TTK), purified from human primary T-cells, stimulates Tat-dependent transcription of HIV-1 LTR in vivo [Nekhai, Shukla, Fernandez, Kumar and Lamb (2000) Virology 266, 246-256]. In the work presented here, we characterized the components of TTK by biochemical fractionation and the function of TTK in transcription assays in vitro. TTK uniquely co-purified with CDK2 and not with either CDK9 or CDK7. Tat induced the TTK-associated CDK2 kinase to phosphorylate CTD, specifically at Ser-2 residues. The TTK fraction restored Tat-mediated transcription activation of HIV-1 LTR in a HeLa nuclear extract immunodepleted of CDK9, but not in the HeLa nuclear extract double-depleted of CDK9 and CDK7. Direct microinjection of the TTK fraction augmented Tat transactivation of HIV-1 LTR in human primary HS68 fibroblasts. The results argue that TTK-associated CDK2 may function to maintain target-specific phosphorylation of RNA Pol II that is essential for Tat transactivation of HIV-1 promoter. They are also consistent with the observed cell-cycle-specific induction of viral gene transactivation.

CDC2-CDC28 Kinases↗
PubMed2002

Nuclear factor 90 mediates activation of the cellular antiviral expression cascade.

Viral infection triggers a cascade of interferon response genes, but the mechanisms that prime such innate antiviral defenses are poorly understood. Among candidate cellular mediators of the antiviral response are the double-stranded RNA (dsRNA)-binding proteins. Here we show that a C-terminal variant of the ubiquitous dsRNA-binding protein, nuclear factor 90 (NF90ctv), can activate the interferon response genes in the absence of viral infection. NF90ctv-expressing cells were infected with the syncytium-inducing HIV-1 strain NL4-3 and were shown to inhibit viral replication. To gain insight into this mechanism of protection, we analyzed the expression profiles of NF90ctv-positive cells as compared with parental cells transduced with the empty vector. Of the 5600 genes represented on the expression arrays, 90 displayed significant (4-fold or more) changes in mRNA levels in NF90-expressing cells. About 50% are known interferon alpha/beta-stimulated genes. The microarray expression data were confirmed by quantitative reverse transcriptase-polymerase chain reaction analysis of six representative interferon-inducible genes. Electrophoretic mobility shift assays showed that the biological response is mediated by the activation of transcription factors in NF90ctv-expressing cells. Functional significance of the activated transcription complex was evaluated by transfection assays with luciferase reporter constructs driven by the interferon-inducible promoter from the 2'-5'-oligoadenylate synthetase (p69) gene. Resistance to HIV-1, caused by the expression of NF90ctv in the cell culture system, appears to be mediated in part by the induction of interferon response genes. This leads to a hypothesis as to the mechanism of action of NF90 in mediating endogenous antiviral responses.

Amino Acid Sequence↗
PubMed2002

A protein phosphatase from human T cells augments tat transactivation of the human immunodeficiency virus type 1 long-terminal repeat.

HIV-1 Tat protein regulates viral gene expression by modulating the activity and association of cellular transcription factors with RNA polymerase II (RNAPII). Possible mechanisms include Tat-associated protein kinase(s) and phosphatase(s) that regulate phosphorylation of the C-terminal domain (CTD) of the large subunit of RNAPII. Hypophosphorylated RNAPII (RNAPIIa) is recruited to promoters during formation of a preinitiation complex, whereas hyperphosphorylated RNAPII (RNAPIIo) is associated with the elongation complex. The role of phosphatases in maintaining the equilibrium between the two phosphorylated states of RNAPII, which is required for sustained transcriptional activation from the HIV-1 LTR, is not clear. In this study, we discuss the properties of a Tat-associated CTD phosphatase fractionated from Jurkat T cells. The Tat-associated protein phosphatase (TAPP) is related to the serine/threonine, type 1, protein phosphatase (PP1) family. TAPP dephosphorylates the hyperphosphorylated form of recombinant CTD specifically on serine 2, and augments Tat-mediated transcriptional transactivation of HIV-1 LTR in an in vitro transcription reaction. TAPP is associated with the transcription complex during the early initiation steps, and its release from the HIV-1 promoter coincides with the Tat-specific activation of CDK9. The results suggest a unique role of the Tat-associated phosphatase which regulates viral transcription by target-specific dephosphorylation of RNAPII during the early stages of elongation.

Gene Products, tat↗
PubMed2002

Gene expression profiling in DQA1*0501+ children with untreated dermatomyositis: a novel model of pathogenesis.

Juvenile dermatomyositis (JDM), the most common pediatric inflammatory myopathy, is a systemic vasculopathy affecting young children. Epidemiology studies documenting an antecedent illness in the 3 mo before the first definite symptom (rash and/or weakness) of JDM are supported by immunologic data that suggest that the disease pathophysiology is Ag driven. The purpose of this study was to compare the gene expression profiles in muscle biopsies of four untreated DQA1*0501(+) JDM children with profiles from children with a known necrotizing myopathy (Duchenne muscular dystrophy), as well as an in vitro antiviral model (NF90), and healthy pediatric controls. Nearly half (47%) of the dysregulated genes in JDM were associated with the immune response. In particular, increased expression of IFN-alphabeta-inducible genes 6-16, myxovirus resistance protein p78, latent cytosolic transcription factor, LMP2, and TAP1 was observed. This profile is consistent with an IFN-alphabeta transcription cascade seen in the in vitro viral resistance model. The IFN-alphabeta-inducible profile was superimposed on transcription profiles reflective of myofiber necrosis and regeneration shared with Duchenne muscular dystrophy. Expressed genes were confirmed by quantitative real-time PCR (6-16), immunofluorescence (thrombospondin 4), and immunolocalization (IFN-gamma, p21). We hypothesize that these data support a model of Ag (?viral) induction of an apparent autoimmune disease based on dynamic interaction between the muscle, vascular, and immune systems in the genetically susceptible (DQA1*0501(+)) child.

Adolescent↗
PubMed2002

Mechanism of biochemical action of substituted 4-methylbenzopyran-2-ones. Part 9: comparison of acetoxy 4-methylcoumarins and other polyphenolic acetates reveal the specificity to acetoxy drug: protein transacetylase for pyran carbonyl group in proximity to the oxygen heteroatom.

The evidences for the possible enzymatic transfer of acetyl groups (catalyzed by a transacetylase localized in microsomes) from an acetylated compound (acetoxy-4-methylcoumarins) to enzyme proteins leading to profound modulation of their catalytic activities was cited in our earlier publications in this series. The investigations on the specificity for transacetylase (TA) with respect to the number and positions of acetoxy groups on the benzenoid ring of coumarin molecule revealed that acetoxy groups in proximity to the oxygen heteroatom (at C-7 and C-8 positions) demonstrate a high degree of specificity to TA. These studies were extended to the action of TA on acetates of other polyphenols, such as flavonoids and catechin with a view to establish the importance of pyran carbonyl group for the catalytic activity. The absolute requirement of the carbonyl group in the pyran ring of the substrate for TA to function was established by the observation that TA activity was hardly discernible when catechin pentacetate and 7-acetoxy-3,4-dihydro-2,2-dimethylbenzopyran (both lacking pyran ring carbonyl group) were used as the substrates. Further, the TA activity with flavonoid acetates was remarkably lower than that with acetoxycoumarins, thus suggesting the specificity for pyran carbonyl group in proximity to the oxygen heteroatom. The biochemical properties of flavonoid acetates, such as irreversible activation of NADPH cytochrome C reductase and microsome-catalyzed aflatoxin B(1) binding to DNA in vitro were found to be in tune with their specificity to TA.

Acetates↗
PubMed2002

Xanthones as inhibitors of microsomal lipid peroxidation and TNF-alpha induced ICAM-1 expression on human umbilical vein endothelial cells (HUVECs).

Xanthones bearing different functionalities, namely 1-hydroxyxanthone (1), 3-hydroxyxanthone (2), 1,4-dihydroxyxanthone (3), 2,6-dihydroxyxanthone (4), 1,2-diacetoxyxanthone (5), 2,6-diacetoxyxanthone (6), 3-methoxyxanthone (7), 1,3,7-trimethoxyxanthone (8) and 1,5-dihydroxy-6-methoxyxanthone (9) were synthesised and examined for their effect on nicotinamide adenine dinucleotide phosphate (NADPH)-catalysed liver microsomal lipid peroxidation and on tumour necrosis factor-alpha (TNF-alpha) induced expression of intercellular adhesion moledule-1 (ICAM-1) on endothelial cells, with a view to establish structure-activity relationship. Hydroxy- and acetoxyxanthones showed potent inhibitory effects on NADPH-catalysed lipid peroxidation and TNF-alpha induced expression of ICAM-1 on endothelial cells.

Animals↗
PubMed2002

Movement disorders in the tropics.

The spectrum of movement disorders in the tropics is different from that seen in the industrialized nations of the west. This is not surprising given the unique combination of environmental and population characteristics in the tropics. Infections seldom encountered in the west such as tuberculous meningitis, typhoid fever, Japanese encephalitis, malaria, trypanosomiasis or cysticercosis are often seen in the tropics and with global patterns of travel and immigration these conditions are becoming more common worldwide. Movement disorders associated with these infections, HIV, slow virus and prion disease are discussed. Taking into account the diverse etiologies of movement disorders in the tropics, movement disorders with a nutritional basis such as the infantile tremor syndrome, seasonal ataxia and tropical ataxic neuropathy, and manganese neurotoxicity are also reviewed. Finally, certain special characteristics of ubiquitous disorders such as Parkinson's disease, and disorders with a genetic basis such as Wilson's disease and spinocerebellar degeneration are described.

Animals↗
PubMed2002

Ca(2+) activation and tension cost in myofilaments from mouse hearts ectopically expressing enteric gamma-actin.

To determine the significance of actin isoforms in chemomechanical coupling, we compared tension and ATPase rate in heart myofilaments from nontransgenic (NTG) and transgenic (TG) mice in which enteric gamma-actin replaced >95% of the cardiac alpha-actin. Enteric gamma-actin was expressed against three backgrounds: mice expressing cardiac alpha-actin, heterozygous null cardiac alpha-actin mice, and homozygous null cardiac alpha-actin mice. There were no differences in maximum Ca(2+) activated tension or maximum rate of tension redevelopment after a quick release and rapid restretch protocol between TG and NTG skinned fiber bundles. However, compared with NTG controls, Ca(2+) sensitivity of tension was significantly decreased and economy of tension development was significantly increased in myofilaments from all TG hearts. Shifts in myosin isoform population could not fully account for this increase in the economy of force production of TG myofilaments. Our results indicate that an exchange of cardiac alpha-actin with an actin isoform differing in only five amino acids has a significant impact on both Ca(2+) regulation of cardiac myofilaments and the cross-bridge cycling rate.

Actin Cytoskeleton↗
PubMedDate not supplied

Cytologic diagnosis of pancreatic tuberculosis in immunocompetent and immunocompromised patients: a report of 2 cases.

BACKGROUND: Pancreatic tuberculosis (PT) is a very rare occurrence in the setting of extrapulmonary tuberculosis. It usually occurs as a complication of miliary tuberculosis in immunodeficient individuals, particularly with HIV infections, but isolated involvement in an immunocompetent patient is extremely rare. Pancreatic involvement by tuberculosis in immunocompromised states, such as AIDS, and isolated involvement in immunocompetent patients require a high index of suspicion. Fine needle aspiration cytology under imaging guidance is highly conclusive. CASES: A patient presented with diabetes mellitus and a pancreatic mass clinically diagnosed as pancreatic carcinoma. A second patient, who was HIV seropositive, presented with generalized lymphadenopathy and a pancreatic mass, clinically diagnosed as lymphoma. These were conclusively diagnosed by fine needle aspiration cytology (FNAC) as PT under imaging guidance. After antituberculous therapy the first patient showed a dramatic improvement, whereas the second died; an autopsy was performed. Because of the atypical presentation of PT in immunocompromised and immunocompetent patients, FNAC can be used as a first-line diagnostic intervention. FNAC under imaging guidance is sensitive, specific, rapid and inexpensive. It resolves the diagnostic dilemma and thus avoids major surgery for a clinically diagnosed neoplasm.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Results of Savary-Gilliard dilatation in the management of cervical web of esophagus.

BACKGROUND/AIMS: Cervical web is predominantly a disease of middle-aged females. Sixteen patients with cervical web of esophagus were studied. Dysphagia is mostly for solids, intermittent, non-progressive and was present for many months before they presented. METHODOLOGY: Treatment consisted of forceful dilatation with Savary-Gilliard bougies of 15 or 17 mm diameter after initial rupture of the web by endoscope or 11 mm dilator. RESULTS: Single session of dilatation was adequate in all patients (100%) and there was no recurrence of web during follow-up of 22.8 +/- 18.9 months. CONCLUSIONS: Endoscopic dilatation is a simple outpatient procedure having least morbidity and is suggested as the treatment modality of choice in the management of cervical web of the esophagus.

Adolescent↗
PubMedDate not supplied

Clinical and aetiological profile of hepatoma at a tertiary care centre.

Hepatocellular carcinoma (HCC) is one of the most common cancers in the world. Infection with the hepatitis B virus (HBV) is one of the high-risk factors for the development of HCC, particularly in Asia and Africa. Other risk factors include hepatitis C virus (HCV) infection and, to a certain extent, exposure to a liver-specific carcinogen such as aflatoxin B, and alcohol consumption. In the present retrospective study, we analysed the clinical profile and aetiological role of HBV and HCV in HCC. A total of 40 cases of HCC (33 males and 7 females, age range 22-80 years) were seen from January 1999 to June 2001 at our institute. A detailed history of age, sex, past history of liver disease, clinical symptoms and presenting complaints was recorded. The most common presenting complaints were abdominal distention, pedal oedema and pain abdomen. Underlying cirrhosis of the liver was seen in 30 cases (75%), Child's A in 6, Child's B in 11 and Child's C in 13 cases. A history of alcoholism was present in 6 patients. All the patients were tested for HBsAg and anti-HCV by ELISA. HBsAg and anti-HCV was positive in 19 (47.5%) and 8 patients (20%), respectively. The diagnosis in the majority of cases was derived by FNAC and in a few by imaging techniques plus alfa-fetoprotein (AFP) evaluation. The diagnosis was confirmed by FNAC in 34, CT scan and AFP in 2, and ultrasound abdomen and AFP in 4 cases. We conclude that viral infection (HBV > HCV) is still a major aetiological factor and the incidence of HCV infection appears to be increasing. The majority of the cases of HCC studied had a cirrhotic background.

Adult↗
PubMedDate not supplied

Dengue fever presenting with acute colitis.

Gastrointestinal manifestations of dengue fever are mainly in the form of bleeding or liver function abnormalities. Dengue fever presenting as acute colitis-like picture is not reported to date. We report a 50-year-old man with dengue fever presenting with lower gastrointestinal bleeding and colonoscopic features of acute inflammatory colitis.

Acute Disease↗