Biomedical subjects

C D'Souza

Publications and source records attributed to C D'Souza.

At least 19 recordsLinked to original sources

PubMed2003

Management of psychosis in Parkinson's disease.

Psychosis is one of the most disabling complications associated with Parkinson's disease (PD) and occurs in up to 30% of PD patients treated chronically with antiparkinsonian drugs. Visual hallucinations, with or without delirium and paranoid delusions, are the most frequent symptoms. Psychosis complicating PD can be more disabling than the motor symptoms of PD; it frequently poses a serious threat to the patient's ability to maintain independence and is the single greatest risk factor for nursing home placement. Choosing an antipsychotic drug for a PD patient is a common clinical dilemma. The conventional antipsychotic drugs are poorly tolerated in PD because of their predictable and at times profound worsening in parkinsonian motor symptoms. The recent availability of atypical antipsychotic drugs that can control psychotic symptoms without compromising motor function has led to significant advances in therapeutic strategies in the management of PD psychosis in the community. This article reviews data on the use of atypical antipsychotics in patients with PD and the current recommendations on their use in the management of PD psychosis.

Antipsychotic Agents↗

PubMed2001

Humoral hypercalcemia of malignancy: severe combined immunodeficient/beige mouse model of adult T-cell lymphoma independent of human T-cell lymphotropic virus type-1 tax expression.

The majority of patients with adult T-cell leukemia/lymphoma (ATL) resulting from human T-cell lymphotropic virus type-1 (HTLV-1) infection develop humoral hypercalcemia of malignancy (HHM). We used an animal model using severe combined immunodeficient (SCID)/beige mice to study the pathogenesis of HHM. SCID/beige mice were inoculated intraperitoneally with a human ATL line (RV-ATL) and were euthanized 20 to 32 days after inoculation. SCID/beige mice with engrafted RV-ATL cells developed lymphoma in the mesentery, liver, thymus, lungs, and spleen. The lymphomas stained positively for human CD45RO surface receptor and normal mouse lymphocytes stained negatively confirming the human origin of the tumors. The ATL cells were immunohistochemically positive for parathyroid hormone-related protein (PTHrP). In addition, PTHrP mRNA was highly expressed in lymphomas when compared to MT-2 cells (HTLV-1-positive cell line). Mice with lymphoma developed severe hypercalcemia. Plasma PTHrP concentrations were markedly increased in mice with hypercalcemia, and correlated with the increase in plasma calcium concentrations. Bone densitometry and histomorphometry in lymphoma-bearing mice revealed significant bone loss because of a marked increase in osteoclastic bone resorption. RV-ATL cells contained 1.5 HTLV-1 proviral copies of the tax gene as determined by quantitative real-time polymerase chain reaction (PCR). However, tax expression was not detected by Western blot or reverse transcriptase (RT)-PCR in RV-ATL cells, which suggests that factors other than Tax are modulators of PTHrP gene expression. The SCID/beige mouse model mimics HHM as it occurs in ATL patients, and will be useful to investigate the regulation of PTHrP expression by ATL cells in vivo.

Animals↗

PubMed2001

Treatment of aneurysmal subarachnoid haemorrhage in elderly patients.

Spontaneous subarachnoid haemorrhage (SAH) due to ruptured saccular aneurysm is the fourth most frequent cerebrovascular disorder following atherosclerosis, embolism, and primary intracerebral haemorrhage (1). SAH is a common and often devastating condition, which is a significant cause of world-wide morbidity and mortality (2). The aim of this article is to review the epidemiology, pathophysiology and current management of SAH.

Age Factors↗

PubMed2001

Role of glutamine synthetase in nitrogen metabolite repression in Aspergillus nidulans.

Glutamine synthetase (GS), EC 6.3.1.2, is a central enzyme in the assimilation of nitrogen and the biosynthesis of glutamine. We have isolated the Aspergillus nidulans glnA gene encoding GS and have shown that glnA encodes a highly expressed but not highly regulated mRNA. Inactivation of glnA results in an absolute glutamine requirement, indicating that GS is responsible for the synthesis of this essential amino acid. Even when supplemented with high levels of glutamine, strains lacking a functional glnA gene have an inhibited morphology, and a wide range of compounds have been shown to interfere with repair of the glutamine auxotrophy. Heterologous expression of the prokaryotic Anabaena glnA gene from the A. nidulans alcA promoter allowed full complementation of the A. nidulans glnADelta mutation. However, the A. nidulans fluG gene, which encodes a protein with similarity to prokaryotic GS, did not replace A. nidulans glnA function when similarly expressed. Our studies with the glnADelta mutant confirm that glutamine, and not GS, is the key effector of nitrogen metabolite repression. Additionally, ammonium and its immediate product glutamate may also act directly to signal nitrogen sufficiency.

Amino Acid Sequence↗

PubMed2000

In vitro and in vivo functional analysis of human T cell lymphotropic virus type 1 pX open reading frames I and II.

Human T lymphotropic virus type 1 (HTLV-1) is a complex retrovirus containing regulatory and accessory genes encoded in four open reading frames (ORF I-IV) of the pX region. It is not clear what role pX ORFs I and II-encoded proteins have in the pathogenesis of the lymphoproliferative diseases associated with HTLV-1 infection. The conserved ORF I encodes for a hydrophobic 12-kDa protein, p12, (I) that contains four SH3 binding motifs (PXXP) that localizes to cellular endomembranes when overexpressed in cultured cells. Differential splicing of pX ORF II results in the production of two nuclear proteins, p13(II) and p30(II). p13(II) also localizes to mitochondria. p30(II) shares homology with the POU family of transcription factors. We have identified functional roles of pX ORF I and ORF II in establishment and maintenance of infection in a rabbit model. To functionally study p12(I) we have tested a proviral clone with selective ablation of ORF I (ACH.p12(I)) for its ability to infect quiescent peripheral blood mononuclear cells (PBMC). Our data indicate that T cells infected with the wild-type clone of HTLV-1 (ACH) are more efficient than ACH.p12(I) in infecting quiescent PBMC. These findings parallel our animal model data and suggest a role for p12(I) in the activation of quiescent lymphocytes, a prerequisite for effective viral replication in vivo. To test the ability of p30(II) to function as a transcription factor we have constructed p30(II) as a Gal4-fusion protein. When transfected with Gal4-driven luciferase reporter genes, the p30(II)-Gal4-fusion protein induces transcriptional activity up to 50-fold in both 293 and HeLa-Tat cells. These systems will be useful to identify molecular mechanisms that explain the functional role of pX ORF I and ORF II-encoded proteins in HTLV-1 replication.

Animals↗

PubMed1999

Comparison of four components of sensory gating in schizophrenia and normal subjects: a preliminary report.

Dysfunction of sensory gating has been implicated in the pathophysiology of schizophrenia. The goal of this study was to provide evidence that sensory gating dysfunction in schizophrenia patients is a compounded problem with difficulty in filtering out irrelevant input and filtering in relevant input at both an early-preattentive stage and a later, early-attentive stage of information processing. Four components of sensory gating were examined in 12 medicated, stable schizophrenia patients and 12 age- and sex-matched normal control subjects. Evoked potential paradigms designed to examine the effects of stimulus repetition and stimulus change were utilized. Attenuation of the amplitude of the P50 and the N100 evoked potentials with stimulus repetition was significantly decreased in schizophrenia patients as compared to normal control subjects. The presentation of deviant stimuli caused the degree of attenuation to decrease in normal subjects. This effect was much decreased (and at times reversed) in schizophrenia subjects. These data suggest that schizophrenia patients have difficulty inhibiting incoming, irrelevant stimuli and responding to incoming, significant input as measured by preattentive EPs (P50). The data also suggest that similar abnormalities can be demonstrated at a slightly later phase of information processing (i.e. early-attentive phase) using the N100 EP.

Adult↗

PubMed1999

No evidence of altered in vivo benzodiazepine receptor binding in schizophrenia.

Deficits in gamma-amino-butyric acid (GABA) neurotransmitter systems have been implicated in the pathophysiology of schizophrenia for more than two decades. Previous postmortem and in vivo studies of benzodiazepine (BDZ) receptor density have reported alterations in several brain regions of schizophrenic patients. The goal of this study was to better characterize possible alterations of the in vivo regional distribution volume (VT) of BDZ receptors in schizoprenia, using the selective BDZ antagonist [123I]iomazenil and single photon emission computerized tomography (SPECT). Regional BDZ VT was measured under sustained radiotracer equilibrium conditions. The reproducibility and reliability of this measurement was established in four healthy volunteers. No differences in regional BDZ VT were observed between 16 male schizophrenic patients and 16 matched controls. No relationships were observed between BDZ VT and severity of psychotic symptoms in any of the regions examined. In conclusion, this study failed to identify alterations of BDZ receptors density in schizoprenia. If this illness is associated with deficits in GABA transmission, these deficits do not substantially involve BDZ receptor expression or regulation.

Adult↗

PubMed1999

Proliferation response to interleukin-2 and Jak/Stat activation of T cells immortalized by human T-cell lymphotropic virus type 1 is independent of open reading frame I expression.

Human T-cell lymphotropic virus type 1 (HTLV-1), a complex retrovirus, encodes a hydrophobic 12-kD protein from pX open reading frame (ORF) I that localizes to cellular endomembranes and contains four minimal SH3 binding motifs (PXXP). We have demonstrated the importance of ORF I expression in the establishment of infection and hypothesize that p12(I) has a role in T-cell activation. In this study, we tested interleukin-2 (IL-2) receptor expression, IL-2-mediated proliferation, and Jak/Stat activation in T-cell lines immortalized with either wild-type or ORF I mutant clones of HTLV-1. All cell lines exhibited typical patterns of T-cell markers and maintained mutation fidelity. No significant differences between cell lines were observed in IL-2 receptor chain (alpha, beta, or gamma(c)) expression, in IL-2-mediated proliferation, or in IL-2-induced phosphorylated forms of Stat3, Stat5, Jak1, or Jak3. The expression of ORF I is more likely to play a role in early HTLV-1 infection, such as in the activation of quiescent T cells in vivo.

Cell Line, Transformed↗

PubMed1999

CSF monoamine metabolite and beta endorphin levels in recently detoxified alcoholics and healthy controls: prediction of alcohol cue-induced craving?

BACKGROUND: Abnormalities in central neurotransmitter systems have been described in alcohol-dependent individuals and may contribute to alcohol craving. This study compared cerebrospinal fluid (CSF) levels of monoamine metabolites and beta endorphin levels in samples from early-onset alcohol-dependent patients (n = 20), late-onset alcohol-dependent patients (n = 14), and healthy controls (n = 23). It also evaluated whether these CSF measures levels predicted the degree of craving experienced in response to an alcohol cue. METHODS: Individuals meeting DSM-III and -IV R-criteria for alcohol dependence, 1 to 3 months postdetoxification, and healthy controls underwent a lumbar puncture. Patients also completed a cue exposure test day between 3 and 15 days later. RESULTS: Alcohol-dependent patients had lower CSF levels of the norepinephrine metabolite MHPG compared with the healthy subjects, but this difference disappeared when differences in age between the groups were accounted for. No other group comparisons between patients and healthy subjects reached significance. CSF levels of the dopamine metabolite HVA were significantly higher in the early-onset patients compared with the late-onset patients and controls. The CSF measures did not predict the precue levels of craving, or the increase in craving after alcohol cue exposure. CONCLUSIONS: These results are inconclusive about the role of monoaminergic dysregulation in recovering alcoholics. They also question the utility of these CSF measures to predict alcohol cue reactivity in patients who have been sober at least 1 month.

Adult↗

PubMed1998

Evaluation of new vaccines in the mouse and guinea pig model of tuberculosis.

The results of this study provide the first evidence that two completely separate vaccine approaches, one based on a subunit vaccine consisting of a mild adjuvant admixed with purified culture filtrate proteins and enhanced by the cytokine interleukin-2 and the second based on immunization with DNA encoding the Ag85A protein secreted by Mycobacterium tuberculosis, could both prevent the onset of caseating disease, which is the hallmark of the guinea pig aerogenic infection model. In both cases, however, the survival of vaccinated guinea pigs was shorter than that conferred by Mycobacterium bovis BCG, with observed mortality of these animals probably due to consolidation of lung tissues by lymphocytic granulomas. An additional characteristic of these approaches was that neither induced skin test reactivity to commercial tuberculin. These data thus provide optimism that development of nonliving vaccines which can generate long-lived immunity approaching that conferred by the BCG vaccine is a feasible goal.

Acyltransferases↗

PubMed1997

The course of Mycobacterium tuberculosis infection in the lungs of mice lacking expression of either perforin- or granzyme-mediated cytolytic mechanisms.

CD8 T cells have been shown to be protective against Mycobacterium tuberculosis infections in the mouse. These cells have been shown to be cytolytic toward M. tuberculosis-infected cells and have also been shown to release the protective cytokine gamma interferon in response to mycobacterial antigen. It has therefore been unclear how these cells mediate their protective response. To dissect this problem, we compared the courses of M. tuberculosis infections in control, perforin gene-knockout, and granzyme gene-knockout mice exposed by the realistic pulmonary route. The inability to express either of these molecules limits the expression of the major lytic pathway but does not appear to influence the course of the infection or result in any discernible histologic differences. These data seem to rule against a lytic role for CD8 T cells in the lungs and hence tend to suggest instead that another type of mechanism, such as cytokine secretion by these cells, is their primary mode of action.

Animals↗

PubMed1996

Immunogenicity and protective efficacy of a tuberculosis DNA vaccine.

Tuberculosis is the most widespread and lethal infectious disease affecting humans. Immunization of mice with plasmid DNA constructs encoding one of the secreted components of Mycobacterium tuberculosis, antigen 85 (Ag85), induced substantial humoral and cell-mediated immune responses and conferred significant protection against challenge with live M. tuberculosis and M. bovis bacille Calmette-Guérin (BCG). These results indicate that immunization with DNA encoding a mycobacterial antigen provides an efficient and simple method for generating protective immunity and that this technique may be useful for defining the protective antigens of M. tuberculosis, leading to the development of a more effective vaccine.

Animals↗

PubMed1995

Translation of the open reading frame encoded by comS, a gene of the srf operon, is necessary for the development of genetic competence, but not surfactin biosynthesis, in Bacillus subtilis.

A small open reading frame, comS of the srf operon, is the site of mutations that impair competence development in Bacillus subtilis. comS open reading frame translation was required for competence, as was confirmed by the suppression of a comS amber mutation [comS(Am)] by the nonsense suppressor sup-3. comS(Am), when introduced into the srf operon, eliminated late competence gene expression but had no significant effect on surfactin production.

Amino Acid Sequence↗

PubMed1994

Identification of comS, a gene of the srfA operon that regulates the establishment of genetic competence in Bacillus subtilis.

Genetic competence (the ability to internalize exogenous DNA) in Bacillus subtilis is dependent on a regulatory pathway that activates the expression of a battery of competence-specific genes. The srfA operon, encoding the subunits of surfactin synthetase, which catalyzes the nonribosomal synthesis of the peptide antibiotic surfactin, also functions in the competence regulatory pathway. The DNA encoding only one of the seven amino acid-activating domains of surfactin synthetase, the valine-activating domain (srfAB1), is necessary for competence. Deletion analysis revealed that a 569-bp fragment of srfAB1, fused to the srfA promoter, complements a srfA deletion mutation (delta srfA) with respect to competence. This fragment contains an open reading frame consisting of 46 amino acids (orf46), which is out of frame with srfAB1. A frameshift mutation in srfAB upstream of orf46 has no effect on competence but a frameshift and nonsense mutation in orf46 resulted in failure to complement the delt srfA mutation. These results indicate that orf46 encodes the srfA-associated competence regulatory factor. Computer-aided analysis of the putative orf46 product (ComS) shows similarity to the homeodomain of the POU domain class of eukaryotic transcriptional regulators.

Amino Acid Sequence↗

PubMed1993

Analysis of a mutant amino acid-activating domain of surfactin synthetase bearing a serine-to-alanine substitution at the site of carboxylthioester formation.

The reactive serine of the TGGHSL thioester binding motif of the first amino acid-activating domain of surfactin synthetase was replaced by alanine using site-directed mutagenesis. The multienzyme from cells of the resulting mutant lost its ability for thioester formation with L-Glu and was therefore inactive in surfactin production. The thiolation reactions catalyzed by the other amino acid-activating domains of surfactin synthetase were not affected by the mutation. The results show that L-Glu is activated at the first domain of surfactin synthetase, and give further evidence that a serine residue is essential for substrate amino acid activation at the reaction centers of peptide synthetases.

Alanine↗

PubMed1993

Nucleotide sequence of 5' portion of srfA that contains the region required for competence establishment in Bacillus subtilus.

The nucleotide sequence of the 20,535 base pairs of the 5' end of the srfA operon, containing the region required for competence development, was determined. This included the srfA promoter region, the first open reading frame, srfAA, encoding surfactin synthetase I and part of the second open reading frame, srfAB, encoding surfactin synthetase II. Three amino acid-activating domains characteristic of those found in peptide synthetases could be discerned in both srfAA (activating Glu, Leu and D-Leu) and srfAB (activating Val, Asp, and D-Leu). The presence of a conserved spacer motif in the amino-terminal end of srfAA suggests that the srfAA product may not initiate surfactin synthesis. The portion of srfA that contains the region required for competence is composed of srfAA and the first amino acid-activating domain of srfAB.

Amino Acid Sequence↗

PubMed1993

Amino-acylation site mutations in amino acid-activating domains of surfactin synthetase: effects on surfactin production and competence development in Bacillus subtilis.

The part of the srfA operon of Bacillus subtilis that contains the region required for competence development is composed of the first four amino acid-activating domains which are responsible for the incorporation of Glu, Leu, D-Leu, and Val into the peptide moiety of the lipopeptide surfactin. Ser-to-Ala substitutions were made in the amino-acylation site of each domain, and their effects on surfactin production and competence development were examined. All of the mutations conferred a surfactin-negative phenotype, supporting the finding that the conserved Ser in the amino-acylation site is required for peptide synthesis. However, none of the mutations affected significantly competence development or the expression of a lacZ fusion to the late competence operon comG. This, coupled with recent findings that only the fourth, Val-activating, domain is required for competence, suggests that some activity, other than amino-acylation and perhaps unrelated to peptide synthesis, possessed by the fourth domain is involved in the role of srfA in regulating competence development.

Amino Acids↗

PubMed1992

Biosynthesis of lipid-linked oligosaccharides. I. Preparation of lipid-linked oligosaccharide substrates.

In order to purify the glycosyltransferases involved in the assembly of lipid-linked oligosaccharides and to be able to study the acceptor substrate specificity of these enzymes, methods were developed to prepare and purify a variety of lipid-linked oligosaccharides, differing in the structure of the oligosaccharide moiety. Thus, Man9 (GlcNAc)2-pyrophosphoryl-dolichol was prepared by isolation and enzymatic synthesis using porcine pancreatic microsomes, while Glc3Man9(GlcNAc)2-PP-dolichol was isolated from Madin-Darby canine kidney cells. Treatment of these oligosaccharide lipids with a series of selected glycosidases led to the preparation of Man alpha 1,2Man alpha 1,2Man alpha 1,3[Man alpha 1,6(Man alpha 1,3)Man alpha 1,6]Man beta 1,4GlcNAc beta 1,4GlcNAc-PP-dolichol; Man alpha 1,2Man alpha 1,2Man alpha 1,3[Man alpha 1,6]Man beta 1,4GlcNAc beta 1, 4GlcNac-PP-dolichol; and Man alpha 1,6(Man alpha 1,3)Man alpha 1, 6[Man alpha 1,3]Man beta 1,4GlcNAc-beta 1,4GlcNAc-PP-dolichol. The preparation, isolation, and characterization of each of these lipid-linked oligosaccharide substrates are described.

Animals↗