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Biomedical subjects

S Paul

Publications and source records attributed to S Paul.

At least 73 records · Page 4Linked to original sources
PubMed2000

The Dopamine/D1 receptor mediates the phosphorylation and inactivation of the protein tyrosine phosphatase STEP via a PKA-dependent pathway.

The striatal-enriched protein tyrosine phosphatase (STEP) family is expressed within dopaminoceptive neurons of the CNS and is particularly enriched within the basal ganglia and related structures. Alternative splicing produces several isoforms that are found in a number of subcellular compartments, including postsynaptic densities of medium spiny neurons. The variants include STEP(61), a membrane-associated protein, and STEP(46), a cytosolic protein. The C terminals of these two isoforms are identical, whereas the N-terminal domain of STEP(61) contains a novel 172 amino acid sequence that includes several structural motifs not present in STEP(46). Amino acid sequencing revealed a number of potential phosphorylation sites in both STEP isoforms. Therefore, we investigated the role of phosphorylation in regulating STEP activity. Both STEP(61) and STEP(46) are phosphorylated on seryl residues by a cAMP-dependent protein kinase (PKA)-mediated pathway in striatal homogenates. The specific residues phosphorylated in STEP(61) were identified by site-directed mutagenesis and tryptic phosphopeptide mapping as Ser160 and Ser221, whereas the major site of phosphorylation in STEP(46) was shown to be Ser49. Ser160 is located within the unique N terminal of STEP(61). Ser221 and Ser49 are equivalent residues present in STEP(61) and STEP(46), respectively, and are located at the center of the kinase-interacting motif that has been implicated in protein-protein interactions. Phosphorylation at this site decreases the activity of STEP in vitro by reducing its affinity for its substrate. In vivo studies using striatal slices demonstrated that the neurotransmitter dopamine leads to the phosphorylation of STEP via activation of D1 receptors and PKA.

Adenosine Triphosphate↗
PubMed2000

Targeted macrophage cytotoxicity using a nonreplicative live vector expressing a tumor-specific single-chain variable region fragment.

Antigen-specific recognition and subsequent destruction of tumor cells is the goal of vaccine-based immunotherapy of cancer. Often, however, tumor antigen-specific cytotoxic T lymphocytes (CTLs) are either not available or in a state of anergy. In addition, MHCI expression on tumor cells is often downregulated. Either or both of these situations can allow tumor growth to proceed unchecked by CTL control. We have shown previously that tumor antigen-specific monoclonal antibodies can be expressed in vaccinia virus and that activated macrophages infected with this virus acquire the ability to kill tumor cells expressing that antigen. Here we show that a membrane-anchored form of the scFv portion of the MUC1 tumor antigen-specific monoclonal antibody, SM3, can be expressed on activated macrophages with the highly attenuated poxvirus, modified vaccinia Ankara (MVA), as a gene transfer vector. Cells infected with the MVA-scFv construct were shown to express the membrane-bound scFv by Western blot and FACS analysis. That cells expressing the membrane-anchored scFv specifically bind antigen was shown by FACS and by BIAcore analysis. GM-CSF-activated macrophages were infected with the construct and shown to recognize specifically MUC1-expressing tumor cells as measured by IL-12 release. Furthermore, activated macrophages expressing the membrane-bound scFv specifically lyse target cells expressing the MUC1 antigen but not cells that do not express MUC1.

Animals↗
PubMed2000

Monoclonal antibody light chain with prothrombinase activity.

Prothrombin is the precursor of thrombin, a central enzyme in coagulation. Autoantibodies to prothrombin are associated with thromboembolism, but the mechanisms by which the antibodies modulate the coagulation processes are not understood. We screened a panel of 34 monoclonal antibody light chains isolated from patients with multiple myeloma for prothrombinase activity by an electrophoresis method. Two light chains with the activity were identified, and one of the light chains was characterized further. The prothrombinase activity eluted from a gel-filtration column run in denaturing solvent (6 M guanidine hydrochloride) at the characteristic positions of the light chain dimer and monomer. A constant level of catalytic activity was observed across the width of the light chain monomer peak, assessed as the cleavage of IEGR-methylcoumarinamide, a peptide substrate corresponding to residues 268-271 of prothrombin. Hydrolysis of this peptide by the light chain was saturable and consistent with Michaelis-Menten-Henri kinetics (K(m) 103 microM; k(cat) of 2.62 x 10(-)(2)/min). Four cleavage sites in prothrombin were identified by N-terminal sequencing of the fragments: Arg(155)-Ser(156), Arg(271)-Thr(272), Arg(284)-Thr(285), and Arg(393)-Ser(394). The light chain did not cleave radiolabeled albumin, thyroglobulin, and annexin V under conditions that readily permitted detectable prothrombin cleavage. Two prothrombin fragments (M(r) 55 000 and 38 000), were isolated by anion-exchange chromatography and were observed to cleave a thrombin substrate, tosyl-GPR-nitroanilide. Conversion of fibrinogen to fibrin was accelerated by the prothrombin fragments generated by the light chain. These finding suggest a novel mechanism whereby antibodies can induce a procoagulant state, i.e., prothrombin activation via cleavage of the molecule.

Antibodies, Monoclonal↗
PubMed2000

"The scarlet E": the presentation of epilepsy in the English language print media.

OBJECTIVE: To examine the coverage of epilepsy in English language newspapers and magazines to determine how they portray the medical risks associated with epilepsy, whether they report research and treatment advances accurately, whether stigmatizing biases toward persons with epilepsy persist, and to examine the sources of errors in reporting about epilepsy. BACKGROUND: The print media reflect and shape current views about epilepsy and other neurologic conditions. They also have the potential to further misconceptions about neurologic issues and particular brain disorders. Persistent myths about epilepsy, such as the ancient belief that it is a demonic disorder, can result in discrimination, emotional difficulties, and reluctance to seek effective treatment. METHODS: A large commercial database was used to search for stories about epilepsy from approximately 2,000 English language newspapers and popular magazines. Two epileptologists independently classified story themes and main sources, and screened for the presence of gross errors in 210 stories about epilepsy or seizures. The authors analyzed the metaphors and terminology used to describe seizures and epilepsy. RESULTS: The majority of English language print stories about epilepsy were accurate depictions of social and medical issues regarding the disorder, most commonly depictions of persons overcoming epilepsy and announcements of new therapies and reports of scientific advances. Thirty-one percent of the stories, however, contained gross errors, most commonly scientific inaccuracy, exaggerated treatment claims, and overestimates of the risks of dying during a seizure. New drug therapies were often described inaccurately by physicians and pharmaceutical spokespersons as curative and without side effects. Patients and their families frequently overemphasized the risk of dying during a seizure and misstated medical issues. Most celebrities with recurring seizures denied having epilepsy. Seizures were described with demonic imagery in 6% of stories. United States epilepsy associations discourage labeling patients as "epileptics"; however, the term was used in 45% of stories. CONCLUSION: Physicians and reporters should be aware of both professional and popular biases that influence the print media's presentation of the causes and consequences of epilepsy.

Anticonvulsants↗
PubMed2000

A mutation in PRKAG3 associated with excess glycogen content in pig skeletal muscle.

A high proportion of purebred Hampshire pigs carries the dominant RN- mutation, which causes high glycogen content in skeletal muscle. The mutation has beneficial effects on meat content but detrimental effects on processing yield. Here, it is shown that the mutation is a nonconservative substitution (R200Q) in the PRKAG3 gene, which encodes a muscle-specific isoform of the regulatory gamma subunit of adenosine monophosphate-activated protein kinase (AMPK). Loss-of-function mutations in the homologous gene in yeast (SNF4) cause defects in glucose metabolism, including glycogen storage. Further analysis of the PRKAG3 signaling pathway may provide insights into muscle physiology as well as the pathogenesis of noninsulin-dependent diabetes mellitus in humans, a metabolic disorder associated with impaired glycogen synthesis.

AMP-Activated Protein Kinases↗
PubMed2000

Augmentation of blood circulation to the fingers by warming distant body areas.

Future activities in space will require greater periods of time in extreme environments in which the body periphery will be vulnerable to chilling. Maintaining the hands and fingers in comfortable conditions enhances finger flexibility and dexterity, and thus effects better work performance. We have evaluated the efficacy of promoting heat transfer and release by the extremities by increasing the blood flow to the periphery from more distant parts of the body. The experimental garment paradigm developed by the investigators was used to manipulate the temperature of different body areas. Six subjects, two females and four males, were evaluated in a stage-1 baseline condition, with the inlet temperature of the circulating water in the liquid cooling/warming garment (LCWG) at 33 degrees C. At stage 2 the total LCWG water inlet temperature was cooled to 8 degrees C, and at stage 3 the inlet water temperature in specific segments of the LCWG was warmed (according to protocol) to 45 degrees C, while the inlet temperature in the rest of the LCWG was maintained at 8 degrees C. The following four body-area-warming conditions were studied in separate sessions: (1) head, (2) upper torso/arm, (3) upper torso/arm/head, and (4) legs/feet. Skin temperature, heat flux and blood perfusion of the fingers, and subjective perception of thermal sensations and overall physical comfort were assessed. Finger temperature (T(fing)) analyses showed a statistically significant condition x stage interaction. Post-hoc comparisons (T(fing)) indicated that at stage 3, the upper torso/arm/head warming condition was significantly different from the head, upper torso/arm and legs/feet conditions, showing an increase in T(fing). There was a significant increase in blood perfusion in the fingers at stage 3 in all conditions. Subjective perception of hand warmth, and overall physical comfort level significantly increased in the stage 3 upper torso/arm/head condition. The findings indicate that physiological methods to enhance heat transfer by the blood to the periphery within protective clothing provide an additional tool for increasing total and local human comfort in extreme environments.

Adult↗
PubMed2000

Congenital hepatoportal arteriovenous fistula: report of a case.

Fistulae between the hepatic artery and portal vein, known as hepatoportal arteriovenous fistula (HPAVF), most commonly occur secondary to trauma or malignancy. Congenital HPAVF is an extremely rare anomaly and only 11 pediatric cases have been documented to date HPAVF causes portal hypertension with the reversal of flow in the portal circulation, leading to hyperemia and congestion of the bowel, causing severe ascites, gastrointestinal bleeding, anemia, and malabsorption. The diagnosis is first made by Doppler sonography, then confirmed by angiography. HPAVF is most effectively treated by performing either ligation of the hepatic artery or percutaneous transcatheter embolization. We describe herein the case of an 8-month-old boy diagnosed to have congenital HPAVF by duplex Doppler sonography and confirmed by digital subtraction angiography, who was successfully managed by percutaneous transcatheter embolization of the feeding right hepatic artery. A review of the previously reported 11 cases of infants with this unusual anomaly, examining presentation, management, and outcome, is also presented.

Arteriovenous Fistula↗
PubMed2000

Coinfection of fibroblasts with Coxiella burnetti and Toxoplasma gondii: to each their own.

Intracellular pathogens have evolved distinct strategies to subvert host cell defenses. At diametrically opposed ends of the spectrum with regard to the host endosomal/lysosomal defenses are the obligate intracellular protozoan Toxoplasma gondii and the bacterium Coxiella burnetti. While the intracellular replication of T. gondii requires complete avoidance of the host endocytic cascade, C. burnetti actively subverts it. This results in these organisms establishing and growing in very different vacuolar compartments. In this study we examined the potential interaction between these distinct compartments following coinfection of mammalian fibroblasts. When present within the same cell, these organisms exhibit minimal interaction with each other. Colocalization of T. gondii and C. burnetti within the same vacuole occurs at a low frequency in doubly infected cells. In such instances only one of the organisms appears to be replication competent, emphasizing the different requirements for survival and/or intracellular growth. The potential basis for both the lack of interaction between these distinct pathogen-containing compartments, and the mechanisms to address their low frequency of colocalization are discussed in the context of our understanding of the biology of the organisms and membrane traffic in eukaryotic cells.

Animals↗
PubMed2000

Germline transformation of the silkworm Bombyx mori L. using a piggyBac transposon-derived vector.

We have developed a system for stable germline transformation in the silkworm Bombyx mori L. using piggyBac, a transposon discovered in the lepidopteran Trichoplusia ni. The transformation constructs consist of the piggyBac inverted terminal repeats flanking a fusion of the B. mori cytoplasmic actin gene BmA3 promoter and the green fluorescent protein (GFP). A nonautonomous helper plasmid encodes the piggyBac transposase. The reporter gene construct was coinjected into preblastoderm eggs of two strains of B. mori. Approximately 2% of the individuals in the G1 broods expressed GFP. DNA analyses of GFP-positive G1 silkworms revealed that multiple independent insertions occurred frequently. The transgene was stably transferred to the next generation through normal Mendelian inheritance. The presence of the inverted terminal repeats of piggyBac and the characteristic TTAA sequence at the borders of all the analyzed inserts confirmed that transformation resulted from precise transposition events. This efficient method of stable gene transfer in a lepidopteran insect opens the way for promising basic research and biotechnological applications.

Actins↗
PubMed2000

Redirected cellular cytotoxicity by infection of effector cells with a recombinant vaccinia virus encoding a tumor-specific monoclonal antibody.

Cytotoxicity is an important function of the immune system that results in the destruction of cellular targets by humoral and/or cellular mechanisms. We wanted to assess the possibility of targeting the lytic function of immune cells toward cancer cells, which express the gene coding for a known tumor antigen (Ag) (GA733-2/epithelial cell adhesion molecule), using a viral vector encoding a monoclonal antibody (mAb) specific for said tumor Ag (CO17-1A). To this end, we have constructed recombinant vaccinia viruses expressing the sequences corresponding to mAb CO17-1A, which recognizes a specific Ag (GA733-2) that is present on the surface of most gastrointestinal carcinomas. The recombinant vectors encoding either a secreted or membrane-anchored form of CO17-1A mAb were used to infect effector cells, which were subsequently assessed for their cytotoxic activity. The recombinant viruses were able to infect both granulocyte-macrophage colony-stimulating factor-activated human macrophages and Ag-stimulated murine cytotoxic T lymphocytes. Infected granulocyte-macrophage colony-stimulating factor-activated macrophages were found to be able to kill GA733-2-expressing tumor cells. Likewise, infected cytotoxic T lymphocytes, although conserving their original alloreactivity, gained the capability of killing GA733-2-expressing cancer cells.

Animals↗
PubMed2000

Proteolytic components of serum IgG preparations.

Chemical catalysis, an effector mechanism utilized by fully assembled antibodies, can also be mediated by the isolated antibody subunits. Because trace amounts of free light chains (L chains) are present in IgG preparations, a detailed study was undertaken to identify the constituents responsible for the polyreactive proteolytic activity of IgG purified from human sera, determined as the extent of cleavage of the model peptide substrate Pro-Phe-Arg-methylcoumarinamide. Two proteolytic species with approximate mass of 50 kD and 150 kD were separated by repetitive gel filtration in a denaturing solvent (6 M guanidine hydrochloride). The activity of the renatured 50-kD fraction (in fluorescence units/microg protein) was more than 45-fold greater than of the 150-kD fraction. Both fractions lost the activity following immunoadsorption on immobilized anti-IgG antibody. Fab fragments prepared from the 150-kD IgG fraction retained the activity. Reducing and non-reducing SDS-electrophoresis suggested the 50-kD fraction isolated from the IgG preparations to be a mixture of heavy chain (H chain) monomers and disulphide bonded L chain dimers. Electrophoretically homogeneous monomers of 50-kD H chains and 25-kD L chains were prepared by gel filtration of reduced and alkylated IgG from seven human subjects. Each of the alkylated L chain preparations displayed the proteolytic activity. The activity in alkylated H chains was undetectable or only marginally greater than the background values. L chain dimers appear to be the major species responsible for the polyreactive proteolytic activity of serum IgG preparations, with a smaller contribution furnished by tetrameric IgG.

Antibodies, Catalytic↗
PubMed2000

Construction of a genetic linkage map for Camellia sinensis (tea).

Genetic maps are a vital tool in cultivar improvement programmes for woody perennial tree crops such as tea (Camellia sinensis). A population thought to be derived from two known, noninbred parents was scored for RAPD and AFLP markers, in order to develop a linkage map. However, a very high proportion of the markers exhibited unexpected segregation ratios in the light of their configurations in the parents, and an exploratory statistical analysis revealed patterns in the marker scores which can most easily be explained by the hypothesis of three male parents contributing pollen to this cross. We discuss the evidence for this and the subsequent analysis required to assemble the markers from the female parent into the first linkage map for tea. The map has 15 linkage groups of three or more markers, agreeing with the haploid chromosome number of tea. The statistical methods that revealed the subpopulations are easy to apply routinely, and may prove a useful diagnostic tool for the analysis of noninbred mapping populations.

Chromosome Mapping↗
PubMed2000

Human immunodeficiency virus (HIV) subtype surveillance of African-born persons at risk for group O and group N HIV infections in the United States.

A population-based surveillance registry was used to identify human immunodeficiency virus (HIV)-infected persons in the United States at increased risk for group O and group N infections (those born in or near African countries where group O infection has been reported). Of 155 eligible subjects, 37 gave samples. By phylogenetic and serologic analysis, 32 were infected with group M (16 with subtype A, 5 with B, 7 with C, and 1 each with subtypes D, F2, G, and recombinant A/J) and 2 with group O but none with group N virus. For 3, samples could not be typed by serology or amplified by polymerase chain reaction using group M-, O-, or N-specific primers. In the United States, group O HIV infection is uncommon; no case of group N infection was found. African-born persons may have HIV strains typical of their birth country. Ongoing subtype surveillance may allow early identification of novel or emerging HIV strains.

Adult↗