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Biomedical subjects

C Roy

Publications and source records attributed to C Roy.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Importance of MRI in hydronephrosis caused by acute or chronic ureteral obstruct. Prospective study].

Magnetic resonance imaging (MRI) of the normal kidney shows in T1 weighted sequence a spontaneous corticomedullary differentiation. In case of ureteral obstruction the corticomedullary differentiation tends to disappear, the medullary signal intensity in T1 weighted sequence is lower and the whole kidney signal intensity in T2 weighted sequence is greater in acute phase. 16 patients with lithiasis ureteral obstruction were evaluated in MRI study. A T1 weighted S.E. 500/28 sequence in axial and frontal planes (7 mm thick-section) and a T2 weighted E.G. 2000/40 sequence in axial plane were used to study the hydronephrotic kidney and to compare it with contralateral normal kidney. Ultrasounds and intravenous pyelography (IVP) were performed to assess the renal dysfunction. MRI realize a morphologic study of the kidney which can be compared with ultrasounds and IVP. MRI assess renal function by the signal intensity but the time of obstruction and the time of medical treatment before MRI are of interest.

Acute Disease↗
PubMed1991

Involvement of gap junctions in tumorigenesis: transfection of tumor cells with connexin 32 cDNA retards growth in vivo.

Gap junction channels provide a pathway for exchange of ions and small molecules between coupled cells, and this exchange is believed to be critical for normal tissue growth and development. As a test for a role of gap junction-mediated intercellular communication in control of cell growth, we have compared growth rates of communication-deficient human tumor cells (SKHep1) with clones stably transfected with cDNA encoding the rat liver gap junction protein connexin 32. In culture, growth rates for parental and transfected clones were similar. However, when sizes of tumors were evaluated following injection of these clones into athymic nude mice, growth rates for two well-coupled clones were significantly lower than for communication-deficient or poorly coupled clones. This study demonstrates that growth rate of these tumor cells in situ is negatively correlated with strength of intercellular communication.

Animals↗
PubMed1991

Sequences of three genes specifying xylanases in Streptomyces lividans.

The entire nucleotide (nt) sequences of three genes (xlnA, xlnB and xlnC) of Streptomyces lividans encoding three distinct xylanases (Xln) have been determined. The nt sequences were confirmed by comparing the deduced amino acid (aa) sequences with the ones derived from the N-terminal aa sequences of the mature purified proteins. The N-terminus of the XlnA showed some homology with either the N-termini or the C-termini of eight other Xln and of two exo-glucanases. The N-terminus of XlnB is homologous to that of XlnC and to Xln of seven other microorganisms.

Amino Acid Sequence↗
PubMed1991

[Characterization of Haemophilus influenzae's resistance to ampicillin].

BACKGROUND: The resistance of Haemophilus influenzae to ampicillin is nearly always dependent on plasmid-mediated betalactamase production. The betalactamase type most frequently identified was TEM-1; type ROB has occasionally been identified. The presence of plasmid-mediated betalactamase has been studied in H. influenzae strains moderately susceptible or resistant to ampicillin. METHODS: The test used in the detection of the presence of betalactamase was nitrocefin hydrolysis; the enzyme type was identified by analytic isoelectric focusing; the codifying gene of this betalactamase was identified by hybridisation with a TEM-1 probe labeled with digoxigenine. Strains studied were 110, obtained during the period 1987 to 1989 and isolated from four Hospitals of the Vallés area of Barcelona. RESULTS: Enzyme production was detected in 105 of 110 strains studied; TEM-1 type betalactamase was identified in 108 and positive hybridisation was obtained in these strains with the TEM-1 probe. CONCLUSIONS: Nitrocefin hydrolysis is a reliable test for the detection of betalactamase production, although it may be unable to detect it (falses negatives) when the production is low. The only betalactamase type identified was TEM-1. The frequency of the strains with non-enzymatic resistance was 1.8%.

Adult↗
PubMed1991

DNA protein interactions at the interferon-responsive promoter elements: potential for an H-DNA conformation.

The regions of several genes (IFI-56K, HLA-A3, HLA-DR and 6-16) containing the (putative) ISRE (Interferon Stimulatable Response Element) were tested for their ability to be recognized by HeLa cells nuclear extract proteins. In a band shift assay, all probes yielded two B1 and B2 DNA-protein complexes of similar mobilities. Unexpectedly the titration of the B1 complex with a synthetic ISRE core (OL1), promoted the formation of B2. Both the probe and OL1 were recovered in B2. For each probe, the possibility of the part of the sequence involved in B1 complex to form a H-DNA structure with the part of the sequence involved in B2 exists. Such a structure was favored by the colinearity of the pairing regions and requires ATP. Although probes seemed to have a secondary structure, the formal existence of a H-DNA structure has not been demonstrated. Such a model could be extended to other interferon inducible gene promoters and may account for their binding properties and differential inducibility after 5' deletion or point mutations.

2',5'-Oligoadenylate Synthetase↗
PubMed1991

Taxol protects the microtubules of concanavalin A-activated lymphocytes from disassembly by methylmercury, but DNA synthesis is still inhibited.

We have shown previously that there is a good correlation between the degree of microtubule disassembly by methylmercury (MeHg) and the extent of inhibition of DNA replication in Concanavalin A (Con A)-stimulated mouse splenic lymphocytes. The purpose of this study was to determine if these two events are causally related and to examine the effects of MeHg-induced microtubule disassembly on earlier events of the stimulation process. We show that early steps constituting the activation pathway, such as the Con A-induced increase in Ca2+ influx and the expression of interleukin 2 receptor, are not inhibited by concentrations of MeHg that disassemble microtubules. RNA synthesis is not affected by short-term (3 h) treatment with MeHg, but longer treatment (24 h) inhibits RNA synthesis. In contrast, DNA synthesis is effectively inhibited by a 3-h treatment with MeHg. In lymphocytes treated with taxol, microtubules are not disassembled by MeHg; however, the inhibition of RNA and DNA synthesis persists. We conclude that the inhibition of nucleic acid synthesis by MeHg is not causally related to MeHg-induced microtubule disassembly.

Alkaloids↗
PubMed1991

Biophysical properties of gap junctions between freshly dispersed pairs of mouse pancreatic beta cells.

Coupling between beta cells through gap junctions has been postulated as a principal mechanism of electrical synchronization of glucose-induced activity throughout the islet of Langerhans. We characterized junctional conductance between isolated pairs of mouse pancreatic beta cells by whole-cell recording with two independent patch-clamp circuits. Most pairs were coupled (67%, n = 155), although the mean junctional conductance (gj) (215 +/- 110 pS) was lower than reported in other tissues. Coupling could be recorded for long periods, up to 40 min. Voltage imposed across the junctional or nonjunctional membranes had no effect on gj. Up to several hours of treatment to increase intracellular cAMP levels did not affect gj. Electrically coupled pairs did not show transfer of the dye Lucifer yellow. Octanol (2 mM) reversibly decreased gj. Lower concentrations of octanol (0.5 mM) and heptanol (0.5 mM) than required to uncouple beta cells decreased voltage-dependent K+ and Ca2+ currents in nonjunctional membranes. Although gj recorded in these experiments would be expected to be provided by current flowing through only a few channels of the unitary conductance previously reported for other gap junctions, no unitary junctional currents were observed even during reversible suppression of gj by octanol. This result suggests either that the single channel conductance of gap junction channels between beta cells is smaller than in other tissues (less than 20 pS) or that the small mean conductance is due to transitions between open and closed states that are too rapid or too slow to be resolved.

Animals↗
PubMed1991

Low-molecular-weight xylanase from Trichoderma viride.

An endo-1,4-beta-xylanase (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) has been isolated from a commercial preparation of Trichoderma viride. The molecular weight was 22,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the pI value was 9.3. The xylanase was a true xylanase without cellulase activity. When the N-terminal amino acid sequence of the first 50 residues was compared with that of a xylanase from Schizophyllum commune, strong evidence for homology was found, with more than 50% amino acid identity. T. viride xylanase also possessed extensive identity with a proposed amino-terminal consensus sequence of xylanases from bacteria.

Amino Acid Sequence↗
PubMed1991

[Localized cancer of the prostate. Correlation between MRI and anatomo-pathological results after radical prostatectomy].

Magnetic Resonance Imaging of 20 patients with local prostatic carcinoma was correlated with pathological findings after radical prostatectomy. The tumor was always seen with an hyposignal, associated in 6 cases with benign prostatic hyperplasia. Extracapsular extension was correctly evaluated (17 cases/20). There were 6 false positive diagnosis of seminal vesicles extension among 40 cases because of an hyposignal in intact vesicles and one false negative diagnosis. Magnetic Resonance Imaging is a good exam to appreciate loco-regional extension of prostatic carcinoma.

Humans↗
PubMed1991

Red cell distribution width, free erythrocyte protoporphyrin, and England-Fraser index in the differential diagnosis of microcytosis due to iron deficiency or beta-thalassemia trait. A study of 200 cases of microcytic anemia.

Microcytic anemias are often encountered in clinical practice. In most cases they are due to iron deficiency, but in some geographical areas other diagnoses, such as that of beta-thalassemia trait, must be considered. In some cases, the hematological data presented by the automated hemogram may be very similar in both entities, showing moderate anemia, microcytosis, and increased red blood cells. From a practical point of view, it may be important to make an "at-first sight" diagnosis using simple parameters that may readily be obtained from the hemogram or from the laboratory. We have assessed the usefulness of RDW (red cell distribution width), of the England-Fraser index and of free erythrocyte protoporphyrin determination in predicting iron deficiency anemia or beta-thalassemia trait. Our results suggest that the most accurate of these parameters is the England-Fraser index, but that a presumptive diagnosis of beta-thalassemia trait can correctly be made if RDW and FEP values are near normality.

Adolescent↗
PubMed1990

An analytical study of the dimerization of in vitro generated RNA of Moloney murine leukemia virus MoMuLV.

The genome of Moloney murine leukemia virus(MoMuLV) is composed of two identical RNA molecules joined at their 5' ends by the dimer linkage structure (DLS). Recently it was shown that in vitro generated MuLV RNA formed dimeric molecules and that dimerization sequences are located within the Psi encapsidation domain between positions 215 and 420. Conditions for the spontaneous dimerization of a MuLV RNA fragment encompassing the Psi domain have been investigated. The rate of spontaneous MuLV RNA dimer formation is dependent upon RNA, NaCl and MgCl2 concentrations as well as temperature. Thermal denaturation of in vitro generated dimer RNA of 350 nt, from positions 215 to 565, gave a Tm of about 58 degrees C in 100 mM NaCl. This Tm value is very close to that found for RNA corresponding to the 5' 755 nt and to the genomic 70 S RNA isolated from virions. According to thrermodynamic parameters derived from denaturation curves of MuLV dimer RNA generated in vitro, the dimer linkage structure probably involves short sequences.

Animals↗
PubMed1990

DNA-protein interactions at the interferon-responsive promoter: evidences for an involvement of phosphorylation.

Several alpha beta and gamma interferons (IFN) induced genes are regulated transcriptionally via a 29 bp cis acting regulatory element (ICS, Interferon Consensus Sequence). The ICS binding capacity of HeLa cell nuclear extracts was strictly dependent on the presence of nucleoside triphosphate and Mg2+. It increased upon alpha beta or gamma IFN treatment of the cells. Three 50 mer synthetic oligonucleotides containing the ICS or putative ISRE (Interferon Stimulatable Response Element), representing portions of genes inducible by alpha beta IFN (HLA-A3 and IFI-56K) or by gamma (HLA-DR) were used as probes to titrate nuclear factors interacting with the ICS. All three probes were retarded in a mobility shift assay in two bands. Phosphorylation conditions were crucial for demonstrating their existence and/or their relative amounts. A factor whose activity and/or amount was modulated upon IFN treatment, appeared to be involved in phosphorylation dependent post-translational modification(s) of the ISRE binding proteins responsible for altered binding properties.

Adenosine Triphosphate↗
PubMed1990

cis elements and trans-acting factors involved in dimer formation of murine leukemia virus RNA.

The genetic material of all retroviruses examined so far consists of two identical RNA molecules joined at their 5' ends by the dimer linkage structure (DLS). Since the precise location of the DLS as well as the mechanism and role(s) of RNA dimerization remain unclear, we analyzed the dimerization process of Moloney murine leukemia virus (MoMuLV) genomic RNA. For this purpose we derived an in vitro model for RNA dimerization. By using this model, murine leukemia virus RNA was shown to form dimeric molecules. Deletion mutagenesis in the 620-nucleotide leader of MoMuLV RNA showed that the dimer promoting sequences are located within the encapsidation element Psi between positions 215 and 420. Furthermore, hybridization assays in which DNA oligomers were used to probe monomer and dimer forms of MoMuLV RNA indicated that the DLS probably maps between positions 280 and 330 from the RNA 5' end. Also, retroviral nucleocapsid protein was shown to catalyze dimerization of MoMuLV RNA and to be tightly bound to genomic dimer RNA in virions. These results suggest that MoMuLV RNA dimerization and encapsidation are probably controlled by the same cis element, Psi, and trans-acting factor, nucleocapsid protein, and thus might be linked during virion formation.

Avian Sarcoma Viruses↗
PubMed1990

[Rendu Osler disease revealed by ruptured cerebral arterial aneurysm in an infant].

A 6 week-old boy whose mother and sister present with hereditary hemorrhagic telangiectasia (HHT) presented suddenly with listlessness, hypotonia, and acute anemia. Cerebrospinal fluid was grossly hemorrhagic. Brain CT scan was compatible with subarachnoid and intracerebral hemorrhage. Operative investigation diagnosed a ruptured aneurysm of one branch of the right middle cerebral artery. A large clot was removed from the right frontal lobe. The ruptured artery was clipped. Further cerebral and abdominal angiographies did not show other aneurysms. The infant died 18 days later, with bilateral subdural hematoma. The family history and review of the literature suggest that the rupture of a cerebral aneurysm in this infant may have been an early manifestation of HHT. Brain CT scan study seems mandatory in every infant born to a mother with HHT.

Cerebral Hemorrhage↗