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Biomedical subjects

F Moreno

Publications and source records attributed to F Moreno.

At least 307 records · Page 17Linked to original sources
PubMed1977

Development of bacteriophage phi29 in sporulating and non-sporulating cells of bacillus subtilis 168.

Infection by bacteriophage phi29 of Bacillus subtilis 168 and of its asporogenous mutant spoOA-3NA has been studied in exponential and stationary phases. As first observed with phage phie infections, the burst-size decreases during the stationary phase much more rapidly in wild type than in mutant cells. In addition, the two strains are shown to differ even during growth in their response to phage phi29 infection. During a short period in the exponential phase, no phage production occurs when infected bacteria (whether spo+ or spo-) are incubated in their growth medium, but phage is produced when incubation takes place after transfer to fresh medium. From these and other unexpected findings it is concluded that any causal relation between sporulation and phage development must be considered with caution. Phage infection of spo+ cells at the end of the growth period does not affect the time required for mature spore formation.

Bacillus subtilis↗
PubMed1976

Bacillus subtilis phage phi29. Characterization of gene products and functions.

A total of 22 phi29-induced proteins have been resolved by slab gel electrophoresis; two of these proteins are the precursor and product fragment, respectively, in the synthesis of the neck appendage protein of the phage. The protein products of 10 out of the 17 cistrons detected in the genome of phage phi29 have been identified. Mutants in two other cistrons fail to synthesize two proteins. Mutants in six genes do not synthesize phage DNA. A cistron, probably involved in the final lysis of the infected bacteria, has been found. Mutants in this gene give place, under restrictive conditions, to delayed lysis and produce, after artificial lysis, a burst size similar or higher than that obtained after wild-type phage infection.

Bacillus subtilis↗
PubMed1976

Genetic analysis of bacteriophage phi 29 of Bacillus subtilis: integration and mapping of reference mutants of two collections.

Reference mutants of Bacillus subtilis phage phi 29 of the Madrid and Minneapolis collections were employed to construct a genetic map. Suppressor-sensitive and temperature-sensitive mutants were assigned to 17 cistrons by quantitative complementation. Three-factor crosses were used to assign an unambiguous order for the 17 cistrons. Recombination frequencies determined by two-factor crosses were used to construct a linear genetic map of 24.4 recombination units. The genes were numbered sequentially from left to right (1 to 17) according to their relative map position.

Bacillus subtilis↗
PubMed1976

Mitral atresia with normal aortic valve: a study of eighteen cases and a review of the literature.

Eighteen cases of mitral atresia with normal aortic valve plus 68 cases from the literature are analyzed. A new classification based on anatomical findings is proposed. Pulmonary stenosis or atresia is frequent in the type with transposition of the great arteries. The rare instances of normal or large left ventricle are due to a large ventricular septal defect, or to straddling or displaced tricuspid valve. The clinical, radiologic and electrocardiographic findings have been summarized and correlated with the different physiopathological situations. In our catheterized cases an oxygen saturation step-up was found in the right atrium together with left atrial hypertension. In seven cases mitral atresia was demonstrated by selective left atrial contrast injection. The average age at death was six months. Among the cases surviving one year or more, the association of atrial septal defects or pulmonary stenosis was frequent. Enlargement of the interatrial communication, accompanied by other palliative measures, is the only available surgical procedure.

Angiocardiography↗
PubMed1976

Rates of synthesis of polyadenylated messenger RNA and ribosomal RNA during the cell cycle of Schizosaccharomyces pombe. With an appendix: calculation of the pattern of protein accumulation from observed changes in the rate of messenger RNA synthesis.

The rates of polyadenylated messenger RNA and ribosomal RNA synthesis were measured in synchronously dividing cultures of fission yeast (Schizosaccharomyces pombe). Control asynchronous cultures, which had been exposed to the conditions used for preparing synchronous cultures, were investigated to check for effects of the synchronization procedure itself on RNA synthesis. After each period of DNA synthesis in synchronous culture, the rates of messenger and ribosomal RNA synthesis doubled, suggesting that gene number controls the rate of messenger and ribosomal RNA synthesis. This was confirmed by experiments with asynchronous, exponential-phase cultures in which DNA synthesis was inhibited by hydroxyurea. Both synchronous culture and hydroxyurea experiments suggested that there is a delay of 15 min (0-1 of the cell generation time) between replication of the DNA and transcription of both gene copies. A pattern of protein accumulation was calculated from changes in the rate of polyadenylated messenger RNA synthesis during synchronous culture. The simulated pattern indicates that protein is accumulated linearly, with a doubling in the rate of accumulation once per cell cycle. The simulated pattern of protein accumulation is very similar to measurements previously reported by other workers of changes in activities of 3 enzymes in synchronous cultures. It is suggested that the doubling of the rate of messenger RNA synthesis, as a consequence of the replication of the DNA once per cycle, provides the basis of a mechanism for control of the doubling of other cellular constituents during the cell cycle.

Adenine↗
PubMed1975

Molecular forms of yeast invertase.

The molecular forms of yeast invertase have been studied. It is shown that by gel filtration on Sephadex G-200 it is possible to demonstrate the presence not only of a light, carbohydrate-free, invertase, and a heavy invertase containing 50% carbohydrate, but also of a continuous spectrum of molecular forms that probably represent the sequential addition of mannose to the light form during the secretion process, which culminates in the formation on the heavy enzyme that is found outside the cytoplasmic membrane. The elution volume-void volume ratio in Sephadex G-200 varies from 1.75 of the light to 1.05 of the heavy invertase. The separation of invertase has also been achieved by ion-exchange chromatography and by isoelectric focusing and is facilitated by removal of the heavy form by ammonium sulphate precipitation. During the protoplasting process the removal of the cell wall is accompanied by the loss of most of the heavy form. Thintermediate forms are exclusively detected inside the protoplast, together with the light invertase and a small amount of heavy invertase. The effect of 2-deoxy-D-glucose and cycloheximide on the biosynthesis and distribution of molecular forms of yeast invertase has also been studied. In the presence of 10 mM glucose Saccharomyces 303-67 repressed cells readily synthesize invertase during the two-hour incubation period. Upon the addition of 2-deoxy-D-glucose, at a concentration of 75 mu g/ml, the observed inhibition in the cells is 60%, but if the activity is measured after breaking the cells, only a 31% inhibition is found, revealing an accumulation of invertase inside the protoplast. 2-Deoxy-D-glucose originates a pile-up of the light and intermediate forms at the expense of the formation of the heavy enzyme, showing that the inhibition of the glycosilation and, therefore, the secretion process, has taken place. In the absence of de novo invertase synthesis originated by cycloheximide, the glycosilation process still takes place as indicated by the accumulation of the heavy form at the expense of the light, carbohydrate-free, enzyme.

Cell Wall↗