PubMed Health⌕ Search

Biomedical subjects

J Nguyen

Publications and source records attributed to J Nguyen.

At least 55 records · Page 3Linked to original sources
PubMed1994

Spectroscopic characterization of conformational differences between PrPC and PrPSc: an alpha-helix to beta-sheet transition.

Although no chemical modifications have been found to distinguish the cellular prion protein PrPC from its infectious analogue PrPSc, spectroscopic methods such as Fourier transform infrared (FTIR) spectroscopy reveal a major conformational difference. PrPC is rich in alpha-helix but is devoid of beta-sheet, whereas PrPSc is high in beta-sheet. N-terminal truncation of PrPSc by limited proteolysis does not destroy infectivity but it increases the beta-sheet content and shifts the FTIR absorption to lower frequencies, typical of the cross beta-pleated sheets of amyloids. Thus the formation of PrPSc from PrPC involves a conformational transition in which one or more alpha-helical regions of the protein is converted to beta-sheet. This transition is mimicked by synthetic peptides, allowing predictions of domains of PrP involved in prion diseases.

Amino Acid Sequence↗
PubMed1994

Heat-inducible proteins that react with antibodies to chaperonin60 are localized in the nucleus of a fish cell line.

We report in the present paper that proteins which react with a polyclonal antibody (pAb) raised against the heat-shock protein chaperonin60 (cpn60) were revealed by indirect immunofluorescence in the nucleus of a fish (fathead minnow, Pimephales promelas) cell line after heat-shock. This immunoreactive cpn60 associated with the nucleolus and with discrete foci. An increased abundance of two nuclear proteins of approx. 57 and 42 kDa, present in approximately equal amounts, was detected by Western blotting using an anti-cpn60 pAb as a probe during the same time period that cpn60 was revealed in the nucleus. These proteins also reacted with a monoclonal antibody (mAb) against human cpn60 but did not react with an mAb against the cytoplasmic chaperonin, TCP1. The kinetics of translocation and pattern of nuclear localization of this immunoreactive cpn60 differed from that of stress70, another major family of heatshock proteins. We suggest that these nuclear immunoreactive cpn60 proteins are members of the cpn60 family and that they play a chaperone role in folding and assembly of proteins in the nucleus which is distinct from that of stress70.

Animals↗
PubMed1994

The interaction of substituted 2-phenylquinoline intercalators with poly(A).poly(U): classical and threading intercalation modes with RNA.

The interaction of a series of 2-phenylquinoline derivatives with RNA was investigated by means of viscometric, pKa, spectroscopic, binding, Tm, and kinetic methods. Compounds 1, 2, and 3 have a piperazyl substituent at the para, meta, or ortho position, respectively, while 4 has an unsubstituted phenyl ring. The pKa results suggest that 1 has three charges, 2 and 3 have more than two charges, and 4 has two charges at pH 6.2. Spectroscopic and Tm results indicate that 1 binds more strongly to RNA than 2-4. Kinetic and modeling results indicate that 1 is a threading intercalator while 2 and 4 are classical intercalators. All experimental results indicate that 3, which has a large twist between the phenyl and quinoline rings, binds weakly with RNA.

Antiviral Agents↗
PubMed1994

Secondary solid malignant tumors occurring after bone marrow transplantation for severe aplastic anemia given thoraco-abdominal irradiation.

PURPOSE: We have evaluated irradiation doses received at location of secondary solid tumors occurring after bone marrow transplantation (BMT) in five of 147 patients grafted for severe aplastic anaemia. RESULTS: All 5 tumors occurred within the radiation field penumbra. The estimated received dose varied from 6 Gy for one inner field secondary tumor, to 2.5 Gy for the remaining secondary tumors. CONCLUSION: Tumors may arise in the zone where the delivered radiation dose drops dramatically. Irradiation, with associated cofactors, may promote the development of epidermoid carcinoma in irradiated patients for BMT.

Abdomen↗
PubMed1994

Protein and lipid composition of radial component-enriched CNS myelin.

The radial component is a junctional complex that is believed to stabilize the apposition of myelin membranes in the internode of CNS myelin. Based on our previous finding that the radial component of compact myelin retains its structure in tissue treated with the detergent Triton X-100, we have attempted to isolate the junctional complex from spinal cord myelin treated with this detergent. Using 0.5% Triton X-100, our procedures yielded a fraction of isolated myelin that was enriched in well-preserved radial component. This fraction that contained morphologically well-defined radial component was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting, and TLC, and was found to be significantly and consistently enriched in the 21.5-kDa and 17-kDa isoforms of myelin basic protein, and in cerebrosides, hydroxy sulfatide, and sphingomyelin. In addition, the myelin-associated enzyme 2',3'-cyclic nucleotide 3'-phosphodiesterase, tubulin, and actin tended to be resistant to Triton extraction. The fraction of isolated myelin that contained radial component was deficient in proteolipid protein and DM-20, the 18.5- and 14-kDa isoforms of myelin basic proteins, and in the major phospholipids, phosphatidylethanolamine, phosphatidylcholine, and phosphatidylserine. Our data indicate that the radial component can be isolated and that certain myelin and cytoskeletal proteins and lipids are closely associated with it.

Animals↗
PubMed1994

The Bacillus subtilis nucleoid-associated protein HPB12 strongly compacts DNA.

The HPB12 protein from the nucleoid of Bacillus subtilis was previously described, and its DNA binding properties have been reported previously (V. Salti, F. Le Hégarat, and L. Hirschbein, Biochim. Biophys. Acta 1009:161-167, 1989). The DNA-HPB12 complexes were examined by electron microscopy. They appeared as short, slightly curved rods whereas naked DNA showed no compaction. Since only a small number of complexes with an intermediate degree of folding were observed, it appears that the nucleoid-associated protein HPB12 binds cooperatively to DNA, confirming Salti et al. (V. Salti, F. Le Hégarat, and L. Hirschbein, Biochim. Biophys. Acta 1009:161-167, 1989), and gives rise to a tightly compacted DNA-protein complex. N-terminal sequencing of purified HPB12 showed that all but one of the first 26 amino acids were identical to those of the L24 ribosomal protein.

Amino Acid Sequence↗
PubMed1993

Conversion of alpha-helices into beta-sheets features in the formation of the scrapie prion proteins.

Prions are composed largely, if not entirely, of prion protein (PrPSc in the case of scrapie). Although the formation of PrPSc from the cellular prion protein (PrPC) is a post-translational process, no candidate chemical modification was identified, suggesting that a conformational change features in PrPSc synthesis. To assess this possibility, we purified both PrPC and PrPSc by using nondenaturing procedures and determined the secondary structure of each. Fourier-transform infrared (FTIR) spectroscopy demonstrated that PrPC has a high alpha-helix content (42%) and no beta-sheet (3%), findings that were confirmed by circular dichroism measurements. In contrast, the beta-sheet content of PrPSc was 43% and the alpha-helix 30% as measured by FTIR. As determined in earlier studies, N-terminally truncated PrPSc derived by limited proteolysis, designated PrP 27-30, has an even higher beta-sheet content (54%) and a lower alpha-helix content (21%). Neither PrPC nor PrPSc formed aggregates detectable by electron microscopy, while PrP 27-30 polymerized into rod-shaped amyloids. While the foregoing findings argue that the conversion of alpha-helices into beta-sheets underlies the formation of PrPSc, we cannot eliminate the possibility that an undetected chemical modification of a small fraction of PrPSc initiates this process. Since PrPSc seems to be the only component of the "infectious" prion particle, it is likely that this conformational transition is a fundamental event in the propagation of prions.

Animals↗
PubMed1993

Inhibition of nerve- and agrin-induced acetylcholine receptor clustering on Xenopus muscle cells in culture.

During an early stage of neuromuscular junction formation the nerve induces acetylcholine (ACh) receptors to accumulate at the contact area. To elucidate the induction process we tested various glycosaminoglycans for their ability to inhibit nerve-induced receptor accumulation. The potency sequence was found as follows: fucyoidin > dextran sulfate > heparin = heparan sulfate > chondroitin sulfate type A and B. This sequence is similar to that for agrin-induced receptor clustering in chick myotubes [J. Neurosci., 10 (1990) 3576-3582], suggesting that agrin-like molecules are involved in nerve-induced receptor accumulation in the Xenopus system. We further tested whether agrin in the culture medium competes with the endogenous inducing substance and found that agrin partially inhibited nerve-induced receptor accumulation. We compared nerve- and agrin-induced receptor accumulation under various experimental conditions. Generally, they behaved similarly except in the presence of heparin. Heparin in the culture medium partially blocked nerve-induced receptor accumulation, whereas it totally inhibited agrin-induced receptor clustering. Our observations are consistent with the hypothesis that an agrin-like molecule released by the nerve is the induction signal for receptor accumulation in the Xenopus system.

Agrin↗
PubMed1993

Establishment of a new replicon generated from an integrational plasmid and a cryptic pUB110 origin-like region in Bacillus subtilis.

A Bacillus subtilis integrational plasmid pVG4 (7.3 kb) was constructed. It was composed of a part of pBR322 (Ap, OriC), a part of pUB110 (Nm), and a part of the spoOA gene. The origin region of pUB110 had been deleted over 1.4 kb. Surprisingly, the replicative plasmids (8 kb) were generated by transformation of B. subtilis BG83 with pVG4 on selection with Nm. Analysis of the total DNA indicated the presence of repeated DNA and that pVG4 did not appear to integrate at the spoOA locus. The new replicon termed pYV exhibited a quite different restriction pattern from pVG4 due to dramatic DNA rearrangements. Although some components initially present in pVG4 were either present in pYV (Ap, oriC, and Nm) or lost (spoOA), other ones were newly gained such as a chromosomal fragment and a pUB110-type origin-like region. The latter was identified by restriction sites mapping and limited sequence analyses. By PCR amplification, the origin region of pYV was shown to be present as a cryptic sequence in the chromosome of strain BG83. The chromosomal fragment integrated into pYV was at least 0.25 kb long and located in a 19-kb SfiI fragment mapping at 106 degrees. We propose that the establishment of the new replicon pYV is the result of a genetic recombination between the pUB110 part present in the integrational plasmid pVG4 and the cryptic origin region of pUB110 harbored in the chromosome of the recipient strain BG83 in relation with a particular role of neomycin selection.

Bacillus subtilis↗
PubMed1991

Morphology and antibody recognition of synthetic beta-amyloid peptides.

To elucidate the relationship between amyloid fibril formation in Alzheimer disease (AD) and the primary structure of the beta-amyloid protein (beta-AP), we investigated the ability of peptides sharing sequences with beta-AP to form fibrils in vitro and to recognize anti-beta-amyloid antisera. The peptides, which were synthesized using a FMOC solid phase procedure and purified by HPLC, consisted of residues 6-25 from the putative aqueous domain, residues 22-35, which overlaps the putative aqueous and transmembrane domains, and residues 1-38 and 1-40 representing nearly the full length of beta-AP. Electron microscopy of negative-stained or thin-sectioned preparations revealed that the peptides assembled into fibrils having different morphologies, some of which resembled in situ AD amyloid. Peptide 6-25 fibrils had diameters of 50-80 A and occasionally showed a central groove suggestive of constituent filaments. Cross sections of the fibril showed a penta- or hexameric arrangement of globular subunits with diameters of 25-30 A. Peptide 22-35 fibrils were helical, with a pitch of 1,100 A and a width of 120 A at its greatest and 50-60 A at its narrowest. The fibrils formed by peptides 1-38 and 1-40 were 70-90 A in diameter. When the peptide assemblies were singly oriented by sedimentation or doubly oriented in a magnetic field, their X-ray diffraction patterns all showed reflections typical of a cross-beta pleated sheet conformation. The patterns differed mainly in their small-angle equatorial intensity, which arises from the packing of fibrils having different widths. Antiserum raised to either native amyloid or to synthetic peptide beta-(1-28) was highly reactive in an inhibition-ELISA assay to beta-(6-25) and beta-(1-38), but not to beta-(22-35), and immunostained beta-(1-40) on Western blots. These studies show that the beta-(6-25), beta-(1-38) and beta-(1-40) peptides can assemble into cross-beta fibrils that retain epitopes characteristic of AD amyloid.

Amino Acid Sequence↗
PubMed1991

Genetic linkage analysis and homology relationships of genes located on human chromosome 11q.

We have used DNA polymorphisms detected by probes for 11q to order 16 genes and to determine the genetic distances between them. Our map includes the genes for CD20, tyrosinase, progesterone receptor, stromelysin, collagenase, N-CAM, dopamine-D2 receptor, apolipoproteins AI-CIII-AIV, CD3-epsilon, -delta, and -gamma, porphobilinogen deaminase, thy-1, and ets-1. These genes have previously been sequenced as well as placed on the 11q cytogenetic map, which now makes them anchor points between the cytogenetic, genetic, and physical maps of this region. The ordering and distances between these genes are of immediate use in testing hypotheses of candidate genes for human genetic diseases associated with chromosome 11q. A comparison between our genetic map and similar maps from other species defines regions of homologous synteny that may be useful in mapping human genetic disease genes localized to the 11q region. Analysis of such homology provides additional bases for speculation of the evolutionary histories of gene families in this region.

Animals↗
PubMed1991

An outbreak of pneumococcal pneumonia in two men's shelters.

We report a retrospective study of 39 homeless men hospitalized for acute pneumonia from April 1988 to March 1989. All of them had recently stayed in one of two shelters. A Streptococcus pneumoniae serotype 1, resistant to cotrimoxazole, was isolated in 29 patients (74 percent). Blood cultures were positive in 24 (61 percent). The patients were relatively young; none was over 70 years old. Thirty-five (90 percent) were heavy smokers; 32 (82 percent) were alcoholics. The radiologic pattern was atypical in 14 cases (36 percent). The only fatal case was linked to the adult respiratory distress syndrome. It is likely that the rate of outbreaks of pneumococcal pneumonia is underestimated. The homeless are at high risk for pneumococcal pneumonia. In addition, the closeness existing in shelters favors the occurrence of outbreaks. Consequently, we suggest that shelter residents would benefit from pneumococcal vaccination.

Alcoholism↗
PubMed1991

Lobular carcinoma in situ within a fibroadenoma.

The entity of lobular carcinoma in situ within a fibroadenoma is being increasingly recognized. Clinical examination, mammography, and fine-needle aspiration are the cornerstones in managing breast masses. A patient is presented with three lumps in the left breast. Although the workup was completely negative, pathological examination revealed lobular carcinoma in situ within one of the fibroadenomas.

Adenofibroma↗
PubMed1991

[Infantile acropustolosis: unusual manifestation of scabies in the infant?].

Three pediatric cases of vesiculopustules persisting for several months or years after eradication of Sarcoptes scabiei are reported. This particular course of scabies in infants is underrecognized although probably common. Its clinical manifestations, natural history and histologic features are identical to those seen in infantile acropustulosis, a recently individualized syndrome whose pathogenesis is unelucidated. In the light of these cases and a review of the literature, the possible relationship between scabies and infantile acropustulosis is discussed.

Acrodermatitis↗