Biomedical subjects

M Vicente

Publications and source records attributed to M Vicente.

At least 55 records · Page 3Linked to original sources

PubMed1992

An amino-proximal domain required for the localization of FtsQ in the cytoplasmic membrane, and for its biological function in Escherichia coli.

The location of FtsQ, an Escherichia coli protein essential for cell division, is, under physiological conditions, in the cytoplasmic membrane facing towards the periplasmic space. An amino-proximal hydrophobic domain is required for FtsQ to reach its location and for its activity in the cell. Overexpression of modified forms of FtsQ is deleterious for the cell.

Bacterial Proteins↗

PubMed1992

[Detection of respiratory syncytial and adenovirus in nasopharyngeal aspirates: comparison of cellular cultures and immunofluorescence].

Respiratory syncytial and adenovirus are 2 of the most important pathogens for respiratory infection in infancy. We compared the results of cellular cultures and immunofluorescence in the detection of these agents in nasopharyngeal exudates from hospitalized infants. Evidence for respiratory syncytial virus was searched in 776 samples. Immunofluorescence was much more sensitive, detecting 303 positive results, compared to only 142 for cell culture. Compared to immunofluorescence, the sensitivity and specificity of cell culture was 44% and 98%, respectively. Adenoviruses were investigated in 498 samples by both techniques. 88 positive results were identified by cell culture and only 30 by immunofluorescence. The sensitivity of immunofluorescence, compared to cell culture, was 31%, with a specificity of 99%. Thus, immunofluorescence is the technique of choice for detection of respiratory syncytial virus, while cell culture is preferable for adenovirus.

Adenoviridae Infections↗

PubMed1991

Preferential cytoplasmic location of FtsZ, a protein essential for Escherichia coli septation.

An ftsZ thermonull mutant has been constructed in which the ftsZ gene has been deleted from the Escherichia coli chromosome while maintaining a wild-type copy of the gene in a thermosensitive plasmid. Under conditions in which the ftsZ+ allele is unable to be replicated at the same pace as the chromosome, the cells become non-viable and grow as filaments, indicating that, contrary to other reports, FtsZ performs a function essential for cell survival. Antibodies raised against FtsZ have been used to detect the cellular location of FtsZ and its contents per cell. Fractionation experiments indicate that most of the total FtsZ present in the cell stays in the cytoplasm.

Bacterial Proteins↗

PubMed1991

The role of the 'gearbox' in the transcription of essential genes.

Regulation of transcription occurs at different levels, one being in the presence of sequences specifically recognized by different forms of RNA polymerase, i.e. the promoters. Three different kinds of promoter are defined according, among other things, to their dependence on the growth rate of the cell: the 'house-keeper' promoter of many metabolic genes, the stringent promoter found at several rRNA and ribosomal protein genes, and the 'gearbox' at genes whose products are required at higher relative amounts at lower growth rates. The identified gearbox promoters of Escherichia coli share specific homologies in the -10, -35 and upstream regions. Although there may be different types of gearbox promoters, the -10 sequence of one of these promoters has been found to be essential for functioning as a gearbox. This suggests the existence of specific sigma factors for its transcription. RpoS (KatF) is a likely candidate for being one of these sigma factors. Computer simulation allows us to predict that such sigma factors should, in turn, be expressed following a gearbox mode, which would then imply the existence of self-regulated loops contributing to the expression of some genes of bacterial division.

Base Sequence↗

PubMed1990

Cloning vectors, derived from a naturally occurring plasmid of Pseudomonas savastanoi, specifically tailored for genetic manipulations in Pseudomonas.

A minimal replicon of 1.8 kb isolated from a 10-kb plasmid of Pseudomonas savastanoi, pPS10, has been used to obtain a collection of small vectors specific for Pseudomonas (P. savastanoi, P. aeruginosa and P.putida). In addition, shuttle vectors that can be established both in Pseudomonas and Escherichia coli have been constructed by adding a pMB9 replicon. The vectors permit cloning of DNA fragments generated by a variety of restriction enzymes using different antibiotic resistance markers for selection and offer the possibility to screen recombinants by insertional inactivation. This cloning system can be used to establish recombinant plasmids in Pseudomonas either at low or high copy number. pPS10 derivatives are compatible with other Pseudomonas vectors derived from broad-host-range replicons of the incompatibility groups P1, P4/Q and W. Introduction and expression of the iaaMH operon in a P. savastanoi mutant deficient in the production of indoleacetic acid has been achieved using one of these vectors.

Cloning, Molecular↗

PubMed1990

Division genes in Escherichia coli are expressed coordinately to cell septum requirements by gearbox promoters.

The cell division ftsQAZ cluster and the ftsZ-dependent bolA morphogene of Escherichia coli are found to be driven by gearboxes, a distinct class of promoters characterized by showing an activity that is inversely dependent on growth rate. These promoters contain specific sequences upstream from the mRNA start point, and their -10 region is essential for the inverse growth rate dependence. Gearbox promoters are essential for driving ftsQAZ and bolA gene expression so that the encoded products are synthesized at constant amounts per cell independently of cell size. This mode of regulation would be expected for the expression of proteins that either play a regulatory role in cell division or form a stoichiometric component of the septum, a structure that, independently of cell size and growth rate, is produced once per cell cycle.

Base Sequence↗

PubMed1990

Antiviral activity of S-adenosylhomocysteine hydrolase inhibitors against plant viruses.

Three SAH hydrolase inhibitors, (RS)-3-adenin-9-yl-2-hydroxypropanoic acid (isobutyl ester) [(RS)-AHPA]; (RS)-9-(2,3-dihydroxypropyl)adenine [(RS)-DHPA] and the carbocyclic analog of 3-deazaadenosine (C-c3Ado) were evaluated for their inhibitory activity against tobacco mosaic virus (TMV) and potato virus X (PVX). Using the local lesion assay and ELISA, we demonstrated that all three compounds inhibit the replication of TMV and PVX. Whereas the three compounds proved about equally active against PVX, (RS)-AHPA was the most effective against TMV. (RS)-AHPA and C-c3Ado induced chlorosis in Nicotiana tabacum leaf discs. They also caused a substantial reduction in the growth of the main root of Phaseolus vulgaris. (RS)-DHPA was less phytotoxic than its two congeners.

Adenine↗

PubMed1990

The native form of FtsA, a septal protein of Escherichia coli, is located in the cytoplasmic membrane.

Antisera able to recognize FtsA, one of the septal proteins of Escherichia coli, have been obtained and used to show that native FtsA, when expressed at levels ranging from physiological to induced from lambda pR, is located in the inner membrane. Experiments of trypsin accessibility to FtsA in membranes, spheroplasts, and vesicles indicated that FtsA is located such that it faces the cytoplasm. This location is consistent with current knowledge about the participation of FtsA in a molecular complex active in cell division called septator.

Bacterial Proteins↗

PubMed1989

Induction of a growth-phase-dependent promoter triggers transcription of bolA, an Escherichia coli morphogene.

The bolA gene, which is involved in the morphogenetic pathways of Escherichia coli, was sequenced and two potential promoters were identified. Expression from promoter P1, proximal to the bolA structural gene is specifically induced during the transition to the stationary phase of growth. This promoter contains an unusual--10 region (CGGCTAGTA), which defines a new class of E. coli promoters necessary for the dramatic increase in the rate of synthesis of a large set of proteins during the cessation of logarithmic growth. This conclusion was confirmed by identifying two additional E. coli promoters and one plasmid promoter, which also were induced during the transition to the stationary phase of growth. Analysis of proteins produced during the exponential and stationary phases of growth in a bolA null mutant suggest a possible role for the BolA protein in the induction of the expression of penicillin-binding protein 6 (PBP6) in the transition to the stationary phase. Supporting this hypothesis is the presence of a putative DNA-binding domain within the bolA coding sequence.

Amino Acid Sequence↗

PubMed1989

[Lipoprotein Lp(a) in patients with chronic renal insufficiency on hemodialysis].

An increased concentration of lipoprotein Lp(a) is considered a risk factor for coronary artery disease. In the present study, the plasma levels of Lp(a), total cholesterol, cholesterol bound to high density lipoproteins (C-HDL), and triglycerides (TG) were measured in 50 patients with chronic renal failure treated with hemodialysis (HD). The results were compared with those from a control group constituted by 46 individuals. Hypertriglyceridemia was detected in 34% of the HD patients and in none of the controls (p less than 0.001); also, a significant reduction of C-HDL level was found in the HD group as compared with controls (p less than 0.001). These two results are in agreement with previously reported data. The outstanding result of our study was the higher prevalence of positive Lp(a) (greater than 30 mg/dl) in the HD group as compared with controls (p less than 0.05). As the increase in Lp(a) is a risk factor for coronary artery disease, we suggest that its measurement may be helpful to delineate the serum lipid profile of these patients.

Adolescent↗

PubMed1988

Identification, cloning, and expression of bolA, an ftsZ-dependent morphogene of Escherichia coli.

A newly found morphogene of Escherichia coli, bolA, mapping at min 10 of the genetic map, was cloned in a 7.2-kilobase BamHI fragment and identified by its ability to produce osmotically stable spherical cells when overexpressed. This gene codes for a polypeptide of 13 kilodaltons. Overexpression of bolA+ was achieved in low-copy-number vectors with operon fusions to the tet and lac promoters, indicating a clockwise direction of transcription. While no modification of any of the penicillin-binding proteins was observed, morphological effects due to overexpression of bolA+ were shown to be dependent on the presence of an active ftsZ gene product. Our results suggest the existence of a mechanism mediated by FtsZ for modifying the conformation of nascent murein in the early steps of septum formation.

Cell Division↗

PubMed1987

Antiviral effects of dihydroxypropyladenine [RS)-DHPA) and bromovinyldeoxyuridine (BVDU) on plant viruses.

Two established antiviral agents, dihydroxypropyladenine (RS)-DHPA and bromovinyldeoxyuridine (BVDU) were evaluated for their inhibitory effects on 4 plant viruses: Tobacco mosaic virus, potato virus X (PVX), eggplant mosaic virus (EMV) and a potyvirus isolated from Solanum palinacanthum (Poty-Sp). Using the leaf disc incubation test, BVDU proved virtually inactive while (RS)-DHPA efficiently inhibited EMV and Poty-Sp when applied at concentrations as low as 5 mg/l. TMV was less susceptible to the chemical while PVX could be inhibited at drug concentrations of 100 mg/l. To achieve a similar inhibitory effect in the leaf spray test, concentrations up to 250 and 500 mg/l were required. Using these tests no phytotoxicity was observed with (RS)-DHPA at any of the concentrations used.

Adenine↗

PubMed1987

Structural inhibition and reactivation of Escherichia coli septation by elements of the SOS and TER pathways.

The inhibition of cell division caused by induction of the SOS pathway in Escherichia coli structurally blocks septation, as deduced from two sets of results. Potential septation sites active at the time of SOS induction became inactivated, while those initiated during the following doubling time were active. Penicillin resistance increased in wild-type UV light-irradiated cells, a behavior similar to that observed in mutants in which structural blocks were introduced by inactivation of FtsA. Potential septation sites that have been structurally blocked by either the SOS division inhibitor, furazlocillin inhibition of PBP3, or inactivation of a TER pathway component, FtsA3, could be reactivated one doubling time after removal of the inhibitory agent in the presence of an active lon gene product. Reactivation of potential septation sites blocked by the presence of an inactivated FtsA3 was significantly lower when the lon protease was not active, suggesting that Lon plays a role in the removal of inactivated TER pathway products from the blocked potential septation sites.

ATP-Dependent Proteases↗

PubMed1986

Interaction of FtsA and PBP3 proteins in the Escherichia coli septum.

Mutations in the ftsA gene of Escherichia coli conferred a higher resistance to lysis induced by penicillin or by a combination of cefsulodin and furazlocillin. The ftsA2 allele codes for an FtsA protein which is inactive at 42 degrees C but is able to regain its activity once it is transferred back to 30 degrees C; ftsA2 filaments formed at 42 degrees C in the presence of penicillin divided once the penicillin was removed and the temperature was lowered to 30 degrees C. Potential septation sites in the filaments of wild-type cells treated in the same way remained inactive. The binding of a radioactively labeled derivative of ampicillin to penicillin-binding protein 3 (PBP3) was significantly decreased in strain D-3, containing the mutant allele ftsA3, when the binding assay was performed at the restrictive temperature. A molecular species able to cross-react with an anti-PBP3 serum was nevertheless found to be present in the envelope of D-3 cells. These observations suggested that the FtsA protein, a protein with a structural and regulatory role in septation, and PBP3, a protein enzymatically active in the synthesis of murein for septation, interact with each other.

Alleles↗

PubMed1985

The ftsA gene product: a possible connection between DNA replication and septation in Escherichia coli.

The study of Escherichia coli strain D-2, which harbours the ftsA2(ts) allele, has shown that temperature-induced filaments of this strain can divide, at 30 degrees C, in the absence of DNA replication and translation. Strain D-2 is thermosensitive during a period coincident with that in which the termination protein should be synthesized and exert its action. The ftsA gene product, which participates in the structure of the septum, needs for its synthesis a short period of DNA replication. The FtsA protein could be involved in a mechanism that coordinates chromosome replication and cell division by a pathway different from and independent of the SOS-induced response.

Cell Division↗

PubMed1985

Cell length in a wee dnaA mutant of Escherichia coli.

The cell length of the short siblings of dividing pairs formed in the absence of replication by two strains of Escherichia coli, OV-25-9 [dnaA46 wee(Am)] and OV-25-10 [dnaA46 wee(AM) supF] was measured. In the presence of Wee, the length of these cells increased to those values expected for newborn wild-type cells growing under similar conditions. In its absence, cell length remained at values near the minimum unit length possible for newborn cells. Our results show that both cell elongation and the action of Wee are independent of DNA replication, being compatible with the role proposed for Wee in coordination between cell elongation and division.

Bacterial Proteins↗

PubMed1985

Coupling between DNA replication and cell division mediated by the FtsA protein in Escherichia coli: a pathway independent of the SOS response, the "TER" pathway.

Inhibition of DNA synthesis prevented the recovery of cell division in filaments of D-3R [ftsA3(Ts) recA56] returned to the permissive temperature. The FtsA protein may be a signal involved in the "TER" pathway, a series of events that coordinate cell division with DNA replication, that is independent of the SOS pathway.

Bacterial Proteins↗

PubMed1984

Effect of tiazofurin on tomato plants infected with tomato spotted wilt virus.

Tiazofurin (2-beta-D-ribofuranosylthiazole-4-carboxamide) was examined for its activity against tomato-spotted wilt virus (TSWV) in tomato plants. Solutions containing 50, 100, 200, 400 and 800 mg/l of the drug were sprayed onto the leaves. The results showed that 100 and 200 mg/l were the most efficient concentrations to suppress TSWV infection, thereby delaying the appearance of systemic symptoms. The drug was more effective in controlling TSWV infection when applied after than before virus inoculation. The results suggest that tiazofurin can be used as an efficient antiviral drug in the treatment of TSWV-infected tomato plants.

Antiviral Agents↗