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Biomedical subjects

M Salas

Publications and source records attributed to M Salas.

At least 217 records · Page 12Linked to original sources
PubMed1988

Transition from initiation to elongation in protein-primed phi 29 DNA replication: salt-dependent stimulation by the viral protein p6.

The transition step from the p3-dAMP initiation complex to the first elongated products, p3-(dAMP)2 and p3-(dAMP)3, requires a dATP concentration higher than that needed for the initiation reaction or for the further elongation of the p3-(dAMP)3 complex. The elongation in phi 29 DNA-protein p3 replication in vitro was strongly inhibited by salt. Under inhibitory salt concentration, the viral protein p6 greatly stimulated phi 29 DNA-protein p3 replication. The effect of protein p6 was not on the rate of elongation but on the amount of elongated product, stimulating the transition from initiation to formation of the first elongation products.

Bacteriophages↗
PubMed1988

Treatment of upper ureteral stones.

From September 1984 to March 1986, 70 patients with upper ureteral stones were treated in our institution. 43 patients underwent endoscopic procedures including retrograde ureterorenoscopy, antegrade ureterorenoscopy and percutaneous surgery. A second group of 27 patients was treated by extracorporeal shock wave lithotripsy (ESWL). The overall success rate was 74.5 and 85% for the endoscopic and the ESWL groups, respectively. Obstruction and dilatation of the renal collecting system seemed to play a major role in the failure of either endoscopic or ESWL treatment.

Adult↗
PubMed1987

Structural and functional relationships between prokaryotic and eukaryotic DNA polymerases.

The Bacillus subtilis phage luminal diameter 29 DNA polymerase, involved in protein-primed viral DNA replication, was inhibited by phosphonoacetic acid (PAA), a known inhibitor of alpha-like DNA polymerases, by decreasing the rate of elongation. Three highly conserved regions of amino acid homology, found in several viral alpha-like DNA polymerases and in the luminal diameter 29 DNA polymerase, one of them proposed to be the PAA binding site, were also found in the T4 DNA polymerase. This prokaryotic enzyme was highly sensitive to the drugs aphidicolin and the nucleotide analogues butylanilino dATP (BuAdATP) and butylphenyl dGTP (BuPdGTP), known to be specific inhibitors of eukaryotic alpha-like DNA polymerases. Two potential DNA polymerases from the linear plasmid pGKL1 from yeast and the S1 mitochondrial DNA from maize have been identified, based on the fact that they contain the three conserved regions of amino acid homology. Comparison of DNA polymerases from prokaryotic and eukaryotic origin showed extensive amino acid homology in addition to highly conserved domains. These findings reflect evolutionary relationships between hypothetically unrelated DNA polymerases.

Amino Acid Sequence↗
PubMed1987

Purification in an active form of the phage phi 29 protein p4 that controls the viral late transcription.

The phage phi 29 protein p4, that controls viral late transcription, was highly purified from Escherichia coli cells harbouring a gene 4-containing plasmid. This protein, representing about 6% of the total cellular protein, was obtained in a highly purified form. The protein was characterized as p4 by amino acid analysis and NH2-terminal sequence determination. The purified protein was active in an in vitro transcription assay, allowing specific initiation of transcription at the phi 29 A3 late promoter in the presence of Bacillus subtilis sigma 43-RNA polymerase holoenzyme.

Amino Acids↗
PubMed1987

Fibrinogen Barcelona I. Congenital dysfibrinogenemia characterized by defective release of fibrinopeptide A and fibrinogen degradation products.

A congenital dysfibrinogenemia, fibrinogen Barcelona I, was detected in a 28 year-old woman with no prior history of bleeding. The thrombin induced clotting of plasma and purified fibrinogen was much prolonged. Fibrin monomer aggregation was impaired. The abnormal fibrinogen polymerized in the presence of calcium and can be further cross-linked by factor XIIIa. The turbidity of fibrin gels obtained from fibrinogen Barcelona was much lower than normal fibrinogen. The kinetic constant Km for fibrinogen Barcelona plus normal fibrinogen gelation was similar to normal fibrinogen gelation. The release rate of fibrinopeptide A by thrombin was slower than that of normal fibrinogen. However, two mol of fibrinopeptide A was released per mol of fibrinogen in 30 min. SDS-PAGE of abnormal and normal fibrinogens and of reduced fibrinogens showed identical patterns. Sialic acid content was markedly decreased in fibrinogen Barcelona. Plasmin digestion of two fibrinogens showed identical patterns in SDS-PAGE as regards X fragment formation. The kinetics of fibrinogen degradation showed a decrease in the formation rate of D and E fragments. The fact that the patient was in threat of abortion and developing a haemorrhagic syndrome may indicate that the defect in the fibrinogen was important in the pathogenesis of haemorrhage in this patient.

Adult↗
PubMed1987

Induction of interferon-gamma in human leukocyte cultures stimulated by Zn2+.

Our studies have confirmed previous reports that Zn2+ has a mitogenic effect on human lymphocytes. Furthermore, we have tested the ability of Zn2+ to induce interferon production in human leukocyte cultures. Peripheral blood mononuclear cells were stimulated with ZnCl2 at different concentrations. Interferon was detected in the supernatants of cultures stimulated with concentrations ranging from 5 X 10(-4) to 5 X 10(-5) M. Interferon was produced only in the presence of accessory cells. The type of interferon induced by Zn2+ was interferon-gamma, as proven by the use of specific antisera.

Cells, Cultured↗
PubMed1987

A set of expression plasmids for the synthesis of fused and unfused polypeptides in Escherichia coli.

A set of plasmid expression vectors for cloning of DNA fragments containing open reading frames has been obtained. The plasmids carry the strong leftward promoter of bacteriophage lambda and the translation initiation signals from either the gene ner of bacteriophage Mu or the gene 4 of bacteriophage phi 29. The vectors could overexpress the cloned sequences as fusion peptides at the N terminus with the N-terminal segment of the phi 29 protein p4 or at the C terminus with the Escherichia coli beta-galactosidase from its 8th residue, or both. Alternatively, the cloned sequences could be directed to overproduce proteins in an unfused form. DNA fragments of the hemagglutinin gene from human influenza A virus, have been cloned in one of the plasmid vectors and some potential antigenic determinants have been characterized using monoclonal antibodies.

Base Sequence↗
PubMed1987

A Bacillus subtilis phage phi 29 transcription terminator is efficiently recognized in Streptomyces lividans.

A DNA fragment from the Bacillus subtilis phage phi 29, containing the bidirectional transcription terminator TD1, where the right early transcription and late viral transcription terminate, has been inserted in one orientation between the aminoglycoside phosphotransferase (APH) gene (neo) and the phi 29 main early and late promoters present in derivative constructs of the Streptomyces promoter-probe plasmid pIJ486. The TD1 terminator is efficiently recognized in S. lividans and ends the transcription, started in vivo at the phi 29 promoters, at the same point as the B. subtilis RNA polymerase, resulting in a considerable reduction of the level of the APHII enzyme synthesized under the control of the phage promoters.

Bacillus subtilis↗
PubMed1987

Structure-activity relationships among di- and tetramine disulfides related to benextramine.

The synthesis and irreversible alpha-blocking activity in the rat vas deferens of a series of tetra- and diamine disulfides 2-38, structural analogues of benextramine (BHC), are described. All compounds containing a central cystamine moiety displayed an irreversible alpha-adrenergic blockade at concentrations ranging from 10(-4) to 6 X 10(-6)M. Potency was increased in cystamines N,N'-disubstituted with 6-aminohexyl groups, especially when the outer nitrogen atoms bear arylalkyl substituents or are enclosed in a ring. However, N,N,N',N'-tetrasubstituted cystamines were poor blockers. Structural specificity in the outer portion of the tetramine disulfide is low, since many types of substituents gave rise to potent alpha-blockers. Even replacement of the outer amines with nonbasic ethers or amides was observed to maintain irreversible alpha-blockade.

Adrenergic alpha-Antagonists↗
PubMed1987

Effect of NH4+ ions on phi 29 DNA-protein p3 replication: formation of a complex between the terminal protein and the DNA polymerase.

Ammonium ions stimulated the formation of the phi diameter 29 protein p3-dAMP initiation complex by decreasing the Km value for dATP in a purified system containing the viral terminal protein p3, the viral DNA polymerase p2, and the phi 29 DNA-protein p3 complex as a template. In addition, NH4+ ions stimulated the amount of p3-dAMP complex elongation and increased by about twofold the rate of elongation. The stimulatory effect of NH4+ ions on in vitro phi 29 DNA replication is probably related to the formation of a stable complex between the terminal protein and the DNA polymerase, which was detected only in the presence of NH4+ ions.

Ammonium Sulfate↗
PubMed1987

In vivo transcription of bacteriophage phi 29 DNA: transcription termination.

The main early and late transcription termination sites in vivo in bacteriophage phi 29 DNA were determined by nuclease S1 mapping. Transcription of the phi 29 early genes located at the left end of the viral genome terminated at the very end of the DNA molecule and within the HindIII G fragment of the viral DNA. Transcription termination of the early genes located at the right end of the genome and that of the late viral genes overlapped in a specific region of the phi 29 DNA within the EcoRI D fragment. Stem-loop structures followed by uridine-rich tails could be derived close to the 3' ends of early and late mRNAs, suggesting Rho-independent transcription termination in phi 29 DNA.

Bacteriophages↗
PubMed1987

[Endoscopic treatment of vesico-ureteral reflux].

Submucosal injection of Teflon for treatment of vesicoureteral reflux (the sting of O'Donnell) was used in 43 patients (66 ureters-21 bilateral cases). 14 patients were on dialysis and reflux was diagnosed at medical evaluation during pretransplantation work-up; correction of reflux was indicated as a preparation for renal transplantation. In another group of 24 patients with normal renal function reflux appeared as a simple congenital abnormality. 5 patients had reflux secondary to TUR or ureteral reimplantation. The procedure was performed under general or epidural anesthesia. Ultrasound examination of kidneys was performed 24 hours after the procedure, cystography and UIV was performed after 30, 100 days and one year. No ureteral obstruction were observed. In the first group of patients (on dialysis) correction of reflux was effective in 40% of cases. In the second group (congenital vesicoureteral reflux) correction was observed in 85% of cases (30/35 controlled cases). In the third group correction of reflux was observed in 83% of cases (5/6). Results in the first group of patients may be due to technical difficulties while injecting of Teflon in small, thickened sclerotic bladders. Though longterm results are still to be evaluated. The sting may be beneficial in patients on dialysis waiting for a renal transplant as it obviates the need for bilateral nephrectomy. In simple congenital reflux short and middle term results are excellent.

Adult↗
PubMed1986

In vivo transcription of bacteriophage phi 29 DNA early and late promoter sequences.

The in vivo transcription initiation sites of eight putative phi 29 promoters have been accurately determined: seven of them correspond to early promoters, including the four main ones, and the other corresponds to the only late promoter found in vivo. Comparison of the phi 29 promoter sequences with the consensus sequence for the Bacillus subtilis sigma 43 RNA polymerase suggests that the sigma 43 enzyme is involved in the recognition of the viral early promoters, whereas the late promoter sequences share homology with the consensus sequence only at its -10 region.

Bacillus subtilis↗
PubMed1986

In vitro transcription of bacteriophage phi 29 DNA. Correlation between in vitro and in vivo promoters.

The phi 29 DNA in vitro transcription initiation sites have been accurately mapped by S1 protection experiments. The results obtained indicated that the B. subtilis RNA polymerase containing the sigma 43 subunit basically recognized the same set of phi 29 promoters in vitro as those used in vivo. In addition, the sequence of the phi 29 early A2a promoter used both in vitro and in vivo has been determined as well as the precise nucleotide where initiation of transcription from the C2 promoter occurs in vitro.

Bacillus subtilis↗
PubMed1986

Replication of phage phi 29 DNA in vitro: role of the viral protein p6 in initiation and elongation.

The phi 29 protein p6 stimulates the formation of the protein p3-dAMP initiation complex when added to a minimal system containing the terminal protein p3, the phi 29 DNA polymerase p2 and phi 29 DNA-protein p3 complex, by decreasing about 5 fold the Km value for dATP. In addition, protein p6 stimulates elongation of the p3-dAMP initiation complex. Whereas the effect of protein p6 on initiation is similar with protein p3-containing fragments from the right or left phi 29 DNA ends, the stimulation of elongation is higher with the right than with the left phi 29 DNA terminal fragment, suggesting DNA sequence specificity. The stimulation by protein p6 of the initiation and elongation steps of phi 29 DNA replication does not require the presence of the parental protein p3 at the phi 29 DNA ends. No effect of protein p6 was obtained on the elongation of the template-primer poly(dT)-(dA) 12-18 by the phi 29 DNA polymerase.

Bacillus subtilis↗