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Biomedical subjects

M Vicente

Publications and source records attributed to M Vicente.

At least 19 recordsLinked 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

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↗
PubMed1978

Inhibitory effect of virazole (ribavirin) on the replication of tomato white necrosis virus (VNBT).

Tomato plants (Lycopersicon esculentum Mill.) inoculated with tomato white necrosis virus (VNBT) and treated with Virazole (1-beta-D-ribofuranosyl--1, 2, 4-triazole-3-carboxamide) at a concentration of 500 mg/l developed systemic virus symptoms in only 40 per cent of the plants in which a remarkable reduction in virus concentration was also observed. From inoculated and Virazole-treated plants which had produced no symptoms, no virus could be recovered. This result suggests that Virazole may inhibit replication of VNBT in tomato.

Plant Viruses↗
PubMed1978

Cell growth and length distribution in Escherichia coli.

The length growth rate of an exponentially growing population of Escherichia coli B/r was calculated from the population length and birth length distributions. Cell elongation took place at a constant rate that doubled at a certain length. This change in rate was responsible for a sudden drop in the frequency of classes of cells longer than that length. Asymmetry in cell partition was able to generate cells both shorter and longer than the expected twofold range, but did not greatly modify the length distribution in between.

Computers↗
PubMed1976

Cell length, cell growth and cell division.

When cells of E. coli reach a certain critical length, which is constant in all growth conditions and eqqal to twice the minimum cell length, they abruptly increase their rate of elongation and divide about 20 min later. Chromosome replication terminates at about this same cell length but is not the signal for the change in rate of cell elongation.

Cell Division↗
PubMed1975

The uptake of glucose and gluconate by Pseudomonas putida.

The uptake of glucose and gluconate is under inductive control in Pseudomonas putida. Glucose, gluconate, and 2-ketogluconate were each good nutritional inducers of these transport abilities. Glucose and gluconate uptake obeyed saturation kinetics: the apparent Km for glucose was 6 mM and that for gluconate was 0.5 mM. Therefore, transport of both substrates appears to be mediated by enzyme-like carriers. Glucose and gluconate are parallel inhibitors for their uptake9 Strains selected for their inability totransport glucose were found to be deficient in gluconate uptake. The reverse was alsotrue: mutations affecting gluconate entry also blocked the uptake of glucose. These results demonstrate that a common carrier is involved in the uptake of both glucose and gluconate by P. putida cells.

Biological Transport↗
PubMed1975

The uptake of fructose by Pseudomonas putida.

Fructose transport was not apparently affected in a number of Pseudomonas putida strains with deranged activity of a common glucose-gluconate uptake system, indicating the existence of an independent fructose uptake system. Fructose uptake by glucose-gluconate uptake mutants was induced by fructose and obeyed saturation kinetics (apparent Km equal 0.3 mM). The fructose uptake system serves to transport glucose in addition to fructose. The entry of fructose into P.putida cells appears to be mediated also by the glucose-gluconate uptake system, as shown by the ability to accumulate fructose of wild type cells grown on glucose, a substrate that induces the glucose-gluconate uptake system but not the fructose uptake system. In addition, fructose was found to be an inducer of the glucose-gluconate uptake system. The physiological significance of these observations is not clear because the fructose uptake system can provide the cell with a high enough internal concentration of fructose to support maximum growth rate on this hexose, as shown by following the growth course of a glucose-gluconate uptake mutants on fructose.

Biological Transport↗
PubMedDate not supplied

On the chronology and topography of bacterial cell division.

Gene products that play a role in the formation of cell septum should be expected to be endowed with a set of specific properties. In principle, septal proteins should be located at the cell envelope. The expression of division genes should ensure the synthesis of septal proteins at levels commensurate with the needs of cell division at different rates of cell duplication. We have results indicating that some fts genes located within the 2.5-min cluster in the Escherichia coli chromosome conform to these predictions.

Bacterial Proteins↗
PubMedDate not supplied

[Etiology of lower respiratory infections in hospitalized infants].

As a contribution to knowledge about the etiology of lower respiratory tract infections (LRI) in infants, 235 patients aged one year or less admitted to a children's hospital at northern metropolitan area of Santiago, Chile along years 1987 throughout 1989 with radiologically confirmed diagnosis were studied. Infants were eligible only if their symptoms lasted for not more than five days and their hospital stay was less than two days. Controls consisted on 74 healthy infants. A search for presumptive etiology was done by means of usual bacteriological procedures (pharyngeal swabs and blood cultures), plus latex test for type b Haemophilus influenzae (Hib) and Streptococcus pneumoniae (SP) in concentrated urine specimens; indirect immunofluorescence (IF) for specific Chlamydia trachomatis (CT) IgM; serological tests, isolation and IF in pharyngeal aspirates for syncytial respiratory virus (SRV), influenza, parainfluenzae and adenoviruses were also used. Evidence of viral infection was detected from 135/235 (57.5%) of cases and 21/74 (28.3%) controls, SRV being the most common. From 18/119 and 2/119 studied patients Hib and SP antigens were respectively detected, but urinary antigens were also present in 6/24 controls, raising questions about this test's specificity. IF titers of 1:32 or higher for CT were found in 5/80 patients, all younger than 5 months. It was possible to perform the whole set of available methods in 80 patients, in 70% of which some evidence of a known etiologic agent was found. Serology alone gave etiological clues in only 30% of these cases and usual microbiological cultures of throat swabs and blood from none of them. No combinations of age, fever, respiratory rate, apnea, bronchial obstructive syndrome, white blood cell counts over 15,000 or of band forms over 500 per cu mm, erythrocyte sedimentation rates, reactive C protein and x-ray findings allowed differential diagnosis between presumptive bacterial or viral etiology, except in one case of an infant presenting with pleural effusion and positive antigenuria for Hib.

Bronchopneumonia↗
PubMedDate not supplied

[Hospital acute respiratory infections].

To study the incidence of nosocomial respiratory tract infection along the first week after admission, 31 children under 2 years of age admitted to the pediatric wards of a general hospital at Metropolitan Santiago, Chile, with the diagnosis of lower respiratory tract infection, were studied for viral agents by immunofluorescence tests, viral isolation from pharyngeal aspirates, paired serum viral antibodies and bacterial cultures, all of them performed at admission and 4 to 5 days later from May through August 1988. In 13 out of 31 patients admitted because of acute lower respiratory tract infection at least one new virus (to a total of 18 viral isolates) was detected in the second sample, which could have been nosocomially acquired, as follows: adenovirus from 8 cases, respiratory syncytial virus from 5 patients and cytomegalovirus from 5 patients, in different combinations. No significant changes in bacterial cultures were found.

Acute Disease↗