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Biomedical subjects

P Lopez

Publications and source records attributed to P Lopez.

At least 127 records · Page 7Linked to original sources
PubMed1986

Varix of the vortex vein ampulla.

Varix of the vortex vein ampulla is a bulging of the vein and overlying retina into the vitreous. It is of uncertain etiology. The lesion is lightly pigmented and ranges in size from one to three disc diameters. It has a dynamic nature and can be flattened by applying pressure to the globe. Viewing the varix is greatly enhanced with red-free light. Three cases are presented as incidental findings during routine examination, and one as a referral. Varices are a benign condition requiring no treatment.

Adult↗
PubMed1985

Binding of transforming DNA to protoplasts isolated from competent Bacillus subtilis.

Transforming 3H-labelled DNA binds specifically to protoplasts isolated from competent cultures of Bacillus subtilis. The bound DNA is fully accessible to added DNase I, indicating that protoplasts bind, but do not process donor DNA. A bi-phasic pattern of competition for binding with increasing amounts of unlabelled and labelled DNA was found. In these conditions, two levels of saturation appeared which correspond to two kinds of DNA receptor sites. Homologous DNA binds preferentially to the first kind of receptor (specific) and only at higher concentrations would bind to the second (unspecific) binding sites. Bound DNA forms a rather stable complex with some constituent(s) of the protoplasts.

Bacillus subtilis↗
PubMed1985

[X-ray computed tomography and recent injuries of the abdomen].

Computed tomography was performed in 38 patients with a recent abdominal trauma. Results of this procedure are presented in lesions of the spleen (4 cases), liver (15 cases), pancreas (6 cases), gastrointestinal tract (2 cases), kidney (15 cases). Indications of computed tomography in emergency are only limited by the small number of units. Computed tomography should play an important role in the management of patients with a severe abdominal trauma.

Abdominal Injuries↗
PubMed1985

[Bone x-ray computed tomographic densitometry by the dual energy technic in a single rotation. Initial results].

Computed tomography is one of the most promising methods for the non-invasive measurement of the bone mass. A review of the theoretical bases of the double energy technique developed by the authors' experimental study on tubes containing defined calcium concentrations and on cadaver vertebrae, demonstrates the value of this investigation in this field. The theoretical study also reveals the limitations of the technique, in particular the decrease in the values induced by fat. The value of this new technique has been confirmed by the preliminary clinical results obtained in non-osteoporotic control women and in women with confirmed osteoporosis, which obviously need to be confirmed by larger series.

Adipose Tissue↗
PubMed1984

Intracellular effects of phage phi W-14 DNA on transformation of Bacillus subtilis.

Uptake of transforming DNA by competent Bacillus subtilis cells in the presence of phage phi W-14 DNA (in which half the thymine residues are replaced by alpha-putrescinyl-thymine) is accompanied by a decrease in the amount of trichloracetic acid-precipitable label of the former retained by recipient cells during subsequent incubation. Fractionation of lysates of cells incubated for 0.5 min at 37 degrees C after DNA uptake at 30 degrees C in the presence of low concentrations of phi W-14 DNA (0.1 microgram/ml) demonstrated the presence of single-stranded transforming DNA molecules, typical for DNA taken up by B. subtilis. The intracellular effect of phi W-14 DNA was enhanced by an increase in its concentration (to 0.5-1 microgram/ml), or by increasing the temperature of uptake (to 37 degrees C). With either of these treatments transforming DNA taken up was found in the form of a broad asymmetric band, indicative of degradation, and partially located at the density characteristic for single-stranded molecules. Fractionation of lysates of cells treated (0.1 microgram/ml) or untreated with phi W-14 DNA, and incubated for 20 min at 37 degrees C after DNA uptake, showed disappearance of the single-stranded band. Donor DNA label was then found exclusively in the recipient DNA band, its amount being lower in samples treated with phi W-14 DNA. The influence of a high concentration of phi W-14 DNA on retention of transforming DNA label was correlated with its effect on transformation.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacillus subtilis↗
PubMed1984

Physical structure and genetic expression of the sulfonamide-resistance plasmid pLS80 and its derivatives in Streptococcus pneumoniae and Bacillus subtilis.

The 10-kb chromosomal fragment of Streptococcus pneumoniae cloned in pLS80 contains the sul-d allele of the pneumococcal gene for dihydropteroate synthase. As a single copy in the chromosome this allele confers resistance to sulfanilamide at 0.2 mg/ml; in the multicopy plasmid it confers resistance to 2.0 mg/ml. The sul-d mutation was mapped by restriction analysis to a 0.4-kb region. By the mechanism of chromosomal facilitation, in which the chromosome restores information to an entering plasmid fragment, a BamHI fragment missing the sul-d region of pLS80 established the full-sized plasmid, but with the sul-s allele of the recipient chromosome. A spontaneous deletion beginning approximately 1.5 kb to the right of the sul-d mutation prevented gene function, possibly by removing a promoter. This region could be restored by chromosomal facilitation and be demonstrated in the plasmid by selection for sulfonamide resistance. Under selection for a vector marker, tetracycline resistance, only the deleted plasmid was detectable, apparently as a result of plasmid segregation and the advantageous growth rates of cells with smaller plasmids. When such cells were selected for sulfonamide resistance, the deleted region returned to the plasmid, presumably by equilibration between the chromosome and the plasmid pool, to give a low frequency (approximately 10(-3) of cells resistant to sulfanilamide at 2.0 mg/ml. Models for the mechanisms of chromosomal facilitation and equilibration are proposed. Several derivatives of pLS80 could be transferred to Bacillus subtilis, where they conferred resistance to sulfanilamide at 2 mg/ml, thereby demonstrating cross-species expression of the pneumococcal gene.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacillus subtilis↗
PubMed1984

Biochemical functionality and recovery of hepatocytes after deep freezing storage.

The present study was undertaken to define the conditions for optimal cryopreservation of hepatocytes. Two different freezing procedures were analyzed: a slow freezing rate (SFR) (-2 degrees C/min down to -30 degrees C and then quick freezing to -196 degrees C) and a fast freezing rate (FFR) (direct freezing of tubes to -196 degrees C: -39 degrees C/min). Cells were frozen in fetal bovine serum containing 10% Dimethyl sulfoxide (DMSO). After rapid thawing at 37 degrees C, followed by dilution and removal of the cryoprotectant, cells were plated and several parameters were followed as criteria for optimal cryopreservation of cells. The FFR cells showed no apparent ultrastructural damage after 24 h of culture. Plating efficiency and spreading were similar as controls. Gluconeogenesis from pyruvate and fructose, tyrosine amino transferase induction by glucagon and dexamethasone, urea production, and plasma protein synthesis of FFR cells were similar to those found in control cultures. The FFR procedure, in comparison to the SFR method, seemed to render the best preserved hepatocytes.

Animals↗
PubMed1984

[Value of the lateral chest x-ray in the diagnosis of traumatic pleural effusions].

Forty patients were admitted to a hospital emergency department after closed chest injury. Chest X-rays, a-p and lateral, with low and high voltage, were performed in a supine position. The aim of the study was to show the interest of lateral films in the diagnosis of post-traumatic pneumo- and hemothoraces. A special technique, using a double-drawer plate holder, gave a good quality radiograph in emergency conditions without danger for patients with severe trauma. In 30 of the patients, chest radiographs confirmed pleural gas or blood collection. In ten of these, the diagnosis could only be made after radiographic examination. In nine other cases, radiographs showed an absence of hemo- or pneumothorax. Lateral views were very important in confirming a hemothorax and appreciating its volume, as well as in showing up partial pneumothoraces which could not be seen on a-p views. The interest of performing a lateral film in all the cases of chest injury is pointed out.

Adolescent↗
PubMed1984

[An improvement in the performance of emergency frontal- and lateral-view thoracic radiography].

A special technique giving good quality front and lateral chest roentgenograms in emergencies with no danger for the critically ill patient is described. The system consisted of a double-drawer plate-holder: one was passed at the back of the thorax, the other then being perpendicular to it. Placing the patient on an X-ray transparent stretcher made the technique easier. Several people were required to gently move the patient while the plate-holder was put in place.

Emergencies↗
PubMed1984

Generation of deletions in pneumococcal mal genes cloned in Bacillus subtilis.

The pneumococcal recombinant plasmid pLS70, which contains two strong promoters for transcription of the malM and malX genes, is unstable when transferred to Bacillus subtilis, and it gives rise to deleted derivatives. Analysis of proteins produced by the deleted plasmids and restriction mapping of 29 different deletions showed that stabilization in B. subtilis was accompanied by deletions affecting both promoters. Plasmids containing even a single strong promoter were at a selective disadvantage. Nucleotide sequences surrounding the deletions in 10 plasmids were determined. Six different deletions occurred between directly repeated sequences of 3-13 base pairs in length, presumably by a recombination mechanism involving short homologies. Four deletions occurred between sites not contained within repeated sequences. A weak but significant similarity of an 11-base sequence was found surrounding these deletions and the corresponding points of junction in the progenitor plasmids. It is suggested that this sequence may be the recognition site for a topoisomerase-like enzyme that can produce deletions.

Bacillus subtilis↗
PubMed1983

Influence of temperature-induced competence in the genetic transformation of Bacillus subtilis.

Competence of Bacillus subtilis can be induced or repressed by decreasing or raising the temperature of incubation from 42 degrees C to 37 degrees C or vice-versa. Concomitantly with changes in transformability of the cultures, changes in the cell ability to bind 3H-transforming DNA and to degrade the donor DNA was discovered. These alterations reflect changes in the processing of donor DNA rather than at the level of integration of the transforming DNA, since phage SPP1 DNA transfection was affected to the same extent as transformation. Induction of competence development by temperature shift from 42 degrees C to 37 degrees C requires continuous synthesis of protein(s) involved in the binding of donor DNA to the competent cells, whereas the nucleolytic activity related to DNA entry into the cells is already synthesized at the moment of the induction of competence.

Bacillus subtilis↗
PubMed1982

Uptake and fate of bacteriophage phi W-14 DNA in competent Bacillus subtilis.

Phage phi W-14 DNA (in which one-half of the thymine residues are replaced by alpha-putrescinyl thymine) was taken up by competent Bacillus subtilis cells at a rate threefold higher than the rate of homologous DNA uptake. In contrast to other types of heterologous DNA, the amount of phi W-14 DNA taken up in 15 min exceeded the amount of homologous DNA taken up by a factor of two to three, as measured in terms of acid-precipitable material. The amount of phi W-14 DNA taken up was even greater than this analysis indicated if allowance was made for the fact that phi W-14 DNA was degraded more rapidly after uptake than homologous DNA. Competition experiments showed that the affinity of phi W-14 DNA for homologous DNA receptors was lower than the affinity of homologous DNA and was similar to the affinities of other types of heterologous DNA. The more rapid and more extensive uptake of phi W-14 DNA appeared to occur via receptors other than the receptors for homologous DNA, and these receptors (like those for homologous DNA) were an intrinsic property of competent cells. Uptake of phi W-14 DNA was affected by temperature, azide, EDTA, and chloramphenicol, as was uptake of homologous DNA. This was consistent with entry of both DNAs by means of active transport. After uptake, undegraded phi W-14 [3H]DNA was found in the cells in a single-stranded form, whereas a portion of the label was associated with recipient DNA, presumably as a result of incorporation of monomers resulting from degradation. Acetylation of the amino groups of the putrescine side chains in phi W-14 DNA decreased the affinity of this DNA for its receptors without affecting its ability to compete with homologous DNA.

Azides↗
PubMed1982

Facilitation of plasmid transfer in Streptococcus pneumoniae by chromosomal homology.

The frequency of plasmid establishment in the transformation of Streptococcus pneumoniae by plasmid DNA was increased more than 10-fold when the plasmid carried DNA homologous to the host chromosome. Perfect homology was not necessary for such facilitation; small additions or deletions were tolerated, but extensive deletions in the homologous segment of either plasmid or chromosome reduced or eliminated facilitation. The facilitated plasmid transfer showed a linear dependence on monomeric plasmid concentration rather than the quadratic dependence found in the absence of homology, which indicated that entering plasmid fragments interacted with the chromosome rather than with each other to establish a plasmid replicon. Restriction enzyme cleavage of the plasmid in the nonhomologous segment destroyed its activity, but cleavage in the homologous segment or even enzymatic removal of part of that segment did not prevent plasmid transfer, and plasmids of the original size were established. In facilitated transfer, chromosomal markers (additions and deletions as well as single-site mutations) entered the plasmid with a frequency ranging from 10 to 90% depending on the marker location. Several possible mechanisms for the establishment of plasmids in the presence of chromosomal homology and for the transfer of chromosomal information are considered. They depend on synapsis of the newly entered single-strand plasmid fragment with the host chromosome and subsequent copying of, donation from, or integration into the homologous chromosomal segment. After plasmid establishment, equilibration of donor and chromosomal markers between the chromosome and the plasmid pool, presumably by homologous recombination events, was observed.

Alleles↗
PubMed1981

Cloning of chromosomal genes in Streptococcus pneumoniae.

A system for molecular cloning in Streptococcus pneumoniae was developed. The multicopy plasmids pMV158 (5.4 kilobases) and pLS1 (4.3 kilobases), which confer tetracycline resistance, were used as vectors to clone chromosomal genes of S. pneumoniae in host cells of this species. A 3.3-kilobase restriction fragment containing the malM gene, which codes for amylomaltase, was cloned in a deletion mutant lacking chromosomal homology with the fragment. The recombinant plasmid pLS70, could transform over 50% of a recipient population to maltose utilization. Amylomaltase constituted up to 10% of the protein of cells containing pLS70. A derivative with a deletion, pLS69, appeared to gain a selective advantage by producing less enzyme. A 10-kilobase restriction fragment containing the sul-d gene for sulfonamide resistance was cloned in the presence of the homologous chromosomal gene. De novo establishment of a recombinant plasmid was just as frequent as transformation in an endogenous plasmid. Despite the processing of DNA during uptake in the transformation of S. pneumoniae, recombinant plasmids can be introduced. Models for the reconstruction of recombinant DNA in cells of S. pneumoniae and Bacillus subtilis are considered and compared.

Chromosomes, Bacterial↗