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Biomedical subjects

A Díaz

Publications and source records attributed to A Díaz.

16 recordsLinked to original sources
PubMed1992

The 5' to 3' exonuclease activity of DNA polymerase I is essential for Streptococcus pneumoniae.

Three different mutations were introduced in the polA gene of Streptococcus pneumoniae by chromosomal transformation. One mutant gene encodes a truncated protein that possesses 5' to 3' exonuclease but has lost polymerase activity. This mutation does not affect cell viability. Other mutated forms of polA that encode proteins with only polymerase activity or with no enzymatic activity could not substitute for the wild-type polA gene in the chromosome unless the 5' to 3' exonuclease domain was encoded elsewhere in the chromosome. Thus, it appears that the 5' to 3' exonuclease activity of the DNA polymerase I is essential for cell viability in S. pneumoniae. Absence of the polymerase domain of DNA polymerase I slightly diminished the ability of S. pneumoniae to repair DNA lesions after ultraviolet irradiation. However, the polymerase domain of the pneumococcal DNA polymerase I gave almost complete complementation of the polA5 mutation in Escherichia coli with respect to resistance to ultraviolet irradiation.

DNA Mutational Analysis↗
PubMed1992

Erythropoietin treatment in allogeneic BMT accelerates erythroid reconstitution: results of a prospective controlled randomized trial.

Twenty-eight allogeneic BMT patients (16 with acute leukemia, 12 with chronic myeloid leukemia) were included in a single center, prospective, randomized, controlled trial to assess the value of recombinant human erythropoietin (rh-Epo) in this setting. rh-Epo was administered through a central venous catheter as a single bolus injection (days 0-7: 100 U/kg/d; days 7-30: 150 U/kg/d). No secondary effects to rh-Epo treatment were detected. An earlier appearance of reticulocytes and a diminished need of red blood cells (RBCs) transfusions were observed in patients who were treated with rh-Epo (4 units vs 12 units; p < 0.05). The time to unsupported platelets above 25 x 10(9)/l was less in patients treated with rh-Epo than in control patients (19 days vs 31; p < 0.05), and they received significantly fewer platelet transfusions (36 units vs 138.5; p < 0.05). Our results show that rh-Epo treatment is capable of accelerating the erythroid reconstitution and decreasing the need for RBC transfusions. A beneficial effect on platelet reconstitution is also suggested, but further studies are necessary to confirm this point.

Adolescent↗
PubMed1992

[The cardiology consultation in a health-service area hospital. The clinical aspects and the demand for diagnostic procedures].

Four consecutive years (1987-1990) outpatients attendance at a cardiology clinic was recorded in a district hospital with a catchment area of 200,000 inhabitants. The aim being to identify and evaluate the demand for cardiology consultations. A system for recording diagnoses was developed, based on the WONCA. The total number of consultations was 26,273, 27% being new patients, 78% of whom were referred by family doctors and health centers. Of the total, 57% were male. The most common age groups being from 60 to 69 (25%) and from 50 to 59 (23%); 22% were over 69. In 13.7% of the consultations, the find diagnosis was of "healthy hearts", in 16.7% valvular heart disease, in 31.5% ischaemic heart disease, in 15.1% arrhythmias, in 8.4% hypertension, and the remainder were other diseases. We carried out 4,406 echocardiograms, 1,408 exercise tests and 511 Holter monitoring traces. There were 322 direct hospital admissions, and 6,094 discharges in the four years period. We consider this type of records to be useful organizing cardiology outpatients clinics, analyzing the demand, and planning the use of health care resources, as well as estimating future needs and assessing quality of care.

Age Factors↗
PubMed1991

Regionally specific age-dependent decline in alpha 2-adrenoceptors: an autoradiographic study in human brain.

The effect of sex, postmortem delay and aging on alpha 2-adrenoceptor binding was studied in tissue sections from several representative regions of the human brain from 21 subjects using [3H]UK-14304 as a ligand. Sex and postmortem delay did not influence the density of alpha 2-receptors. Aging resulted in clear decreases in most forebrain areas examined (n. basalis greater than basal ganglia greater than hypothalamus greater than fronto-temporal cortex greater than hippocampus greater than visual cortex), whereas alpha 2-receptors did not significantly change with age in the amygdala and several infratentorial areas. We conclude that age-related, regionally specific decreases in the density of alpha 2-receptors occur in the human brain. The implications of these findings for age-dependent noradrenergic degeneration are discussed.

Adrenergic alpha-Agonists↗
PubMed1991

The polymerase domain of Streptococcus pneumoniae DNA polymerase I. High expression, purification and characterization.

The 3'-terminal two-thirds of the Streptococcus pneumoniae polA gene was cloned in an Escherichia coli genefusion vector with inducible expression. The resulting recombinant plasmid (pSM10) directs the hyperproduction of a polypeptide of 70.6 kDa corresponding to the C-terminal fragment of pneumococcal DNA polymerase I. Induced cells synthesized catalytically active protein to the extent of 7% of the total soluble protein in the cells. The polymerase fragment was purified to greater than 90% homogeneity with a yield of 1.5 mg pure protein/l culture. The protein has DNA polymerase activity, but no exonuclease activity. The enzyme requires a divalent cation (MgCl2 or MnCl2) for polymerization of DNA. Comparison of the mutant and wild-type pneumococcal polymerases shows that the construction did not affect the enzymatic affinity for the various substrates. The mutant protein, like its parent DNA polymerase I, exhibited an intermediate level of activity with primed single-stranded DNA. At high molar ratio of enzyme/DNA substrate, the polymerase fragment catalyzes strand displacement and switching after completing the replication of a primed single-stranded M13 DNA molecule.

Amino Acid Sequence↗
PubMed1991

Metabolic responses of isolated hepatocytes to adenosine; dependence on external calcium.

The role of cyclic-adenosine monophosphate (cAMP) and calcium (Ca2+) in the metabolic responses to adenosine was studied in isolated hepatocytes from fed rats. In the presence of 1.2 mM Ca but not in the absence of Ca2+, adenosine stimulated ureagenesis without increasing cAMP. Adenosine inhibited the glucagon mediated increase in cAMP. Adenosine increased free cytoplasmic Ca2+ provided that cells were incubated in the presence of external Ca2+. In the absence of added Ca2+ adenosine did not stimulate ureagenesis or the movements of Ca2+. It is suggested that, in the liver cell, Ca2+ may be a second messenger for adenosine.

Adenosine↗
PubMed1991

Community- and hospital-acquired respiratory syncytial virus infections in Chile.

Nasopharyngeal aspirates were obtained on admission from 614 patients younger than 2 years of age who were hospitalized in a ward for acute respiratory infections from June 1988 through October, 1989, in Santiago, Chile. Patients in two rooms were followed during the cold seasons by sampling aspirates every other day during the child's entire hospital stay. Clinical features were recorded daily. Indirect monoclonal immunofluorescent assay and isolation in HEp-2 were used for respiratory syncytial virus (RSV) diagnosis. The mean RSV detection rate was 39% at the time of admission, ranging from 8% in April, 1989, to 62% in July, 1988. During the cold months 43 of 288 (15%) nosocomial RSV cases were detected. Pneumonia and wheezing bronchitis were the principal diagnoses of both groups admitted, whether they were shedding RSV or not. It is concluded that RSV plays a major role in admissions for acute respiratory infections, as well as in nosocomial infections, in Santiago. Because clinical features do not allow one to differentiate viral from bacterial acute respiratory infections, the importance of rapid viral diagnosis is emphasized.

Chile↗
PubMed1976

[Purification of kininogen II (LMW) from human plasma].

Plasma supernatant in which kallikrein has been activated and removed by glass powder whilst kininogen I (HMW) has been consumed by the activated kallikrein, was used for the preparation of kininogen II. It was purified by chromatography on DEAE-cellulose followed by gel filtration on G-200 Sephadex. The purification of kininogen II was assessed from determinations of the amount of kinin released (expressed as bradykinin) as measured on the isolated guinea pig ileum, using samples incubated with human salivary kallikrein or trypsin. A preparation of kininogen II containing an activity equivalent to 8 microgram Br/mg protein, was obtained. Salivary kallikrein released approximately three times more kinin from the substrate as compared to trypsin.

Chromatography, DEAE-Cellulose↗
PubMed1976

[Purification and enzyme study of kininogens I and II from human plasma].

Kininogens I (HMW) and II (LMW) were isolated and partially purified from human plasma. The disappearance of kininogen I was prevented by the use of hexadimethrine bromide, which inhibits the activation of plasma prekallikrein. The two kininogens were separated by chromatography on DEAE-cellulose. Further purification of kininogen I and II was achieved by separate chromatographic steps of the partially purified kininogens on SP-Sephadex. The purification of the kininogens was controlled by incubation of the respective samples with different kininogenases: human plasma kallikrein, human salivary kallikrein and trypsin. As determined by gel filtration, a molecular weight of 250 000 daltons was found for kininogen I (HMW) and 48 000 daltons for kininogen II (LMW).

Clinical Enzyme Tests↗
PubMedDate not supplied

[Primary adenocarcinoma of the duodenum: a report of 2 cases and a review of the world literature].

We presented two cases of adenocarcinoma of the duodenum diagnosed at the Gastroenterology Unit of the General Hospital of Lidice Dr. Jesús Yerena and reviewed retrospectively the pathology cases from 1980-1990. We review the world literature and found that the most common clinical presentation was as obstructive type. In our cases perforation and jaundice were the presentation.

Adenocarcinoma↗
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

[Recurrent obstructive bronchitis in infants].

The study comprised 458 infants complaining of recurrent obstructive bronchitis from the clinical, chest X-rays and gastroesophageal reflux investigation view points. Spontaneous radiological reflux was found in 49.1% of the patients, although a history of vomiting was present only in 26.6%. In infants with positive radiological reflux, manometrics showed a shorter gastroesophageal sphincter and with lesser pressures than a group of normal infants. With medical treatment of the reflux, remission of the respiratory symptoms was seen in 63.5% of the patients. In a group of infants treated, control X-rays, and manometrics were practiced at the end of the medical treatment showing significant improvement of pressure and length of the gastroesophageal sphincter. The long-term follow-up in infants showing failure of the medical treatment, bronchial asthma appeared in 56.6%.

Bronchitis↗
PubMedDate not supplied

[Bronchiolitis].

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Age Factors↗