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Biomedical subjects

G Romero

Publications and source records attributed to G Romero.

At least 109 records · Page 6Linked to original sources
PubMed1981

Kinetic studies on the interactions of Escherichia coli K12 elongation factor Tu with GDP and elongation factor Ts.

The kinetic parameters describing the dissociation of GDP from the elongation factor Tu (EF-Tu) . GDP complex in the absence and presence of elongation factor Ts (EF-Ts) have been characterized using an equilibrium isotope exchange technique. The rate constant for dissociation of GDP from EF-tu was found to be 1.7 x 10(-3) s-1. Since this dissociation rate is greatly enhanced by EF-Ts, it follows that the dissociation of GDP in the presence of EF-Ts proceeds via the formation of a ternary EF-Tu . GDP . EF-Ts complex as represented below: EF-Tu . GDP + EF-Ts in equilibrium EF-Tu . GDP . EF-Ts in equilibrium EF-Tu . EF-Ts + GDP. Analysis of the exchange kinetics according to this reaction scheme yields a rate constant for the dissociation of GDP from the ternary complex of greater than or equal to 1270 s-1. The equilibrium association constants for GDP and EF-Ts to form the ternary complex was found to be 6.4 x 10(4) M-1 and 1.8 x 10(5) M-1, respectively. These results demonstrate that the dissociation of GDP from EF-Tu in the presence of EF-Ts is not the rate-limiting process in protein synthesis.

Bacterial Proteins↗
PubMed1980

Kinetic studies on the dissociation of adenosine cyclic 3',5'-monophosphate from the regulatory subunit of protein kinase from rabbit skeletal muscle.

The exchange rate of unlabeled adenosine 3',5'-monophosphate (cAMP) with labeled [3H]cAMP in the dimeric regulatory subunit-cAMP complex of cAMP-dependent protein kinase, type I, purified from rabbit skeletal muscle is described by using the equilibrium isotope exchange technique. Results indicate that the rate of exchange carried out in the absence of the catalytic subunit (C) is rather slow with a half-life of approximately 870 s. This slow exchange rate is not affected by the presence of MgATP (50 microM). However, when both MgATP (50 microM) and C (1-13 NM) are present, the rate of isotope exchange is observed to increase markedly. Furthermore, less than stoichiometric amounts of C are required for the increase in the rate of cAMP exchange, indicating that the effect of C on the rate enhancement is a catalytic process. These results indicate that in the presence of MgATP, a ternary complex between C and regulatory subunit-cAMP complex must be formed, and a dynamic equilibrium between the eternary complex and its dissociable species must be reached within seconds. On the basis of our kinetic data, it is proposed that the formation of this ternary complex intermediate allows the rapid activation or the inactivation of cAMP-dependent protein kinase following changes in the cellular cAMP levels.

Animals↗
PubMed1979

Inhibitory activity of alpha 1-antitrypsin in infants with idiopathic respiratory distress syndrome.

In two groups of neonates serum concentrations of alpha-1-antitrypsin (1-AT) were determined by means of radial immunodiffusion, and 1-AT inhibitory capacity determinations were made using benzoyl-1-arginine-p-nitroanilide as a substrate. There were 66 children in the first group of neonates with idiopathic respiratory distress syndrome (IRDS), and 82 healthy children in the second group with birth weight and gestational and post natal ages similar to those of neonates with IRDS. In the latter, 1-AT concentration and inhibitory activity levels were lower than those found in healthy children; these differences were statistically significant. These findings explain both the retardation in the lysis of the hyaline membrane and the fact that a decrease in serum 1-AT levels elicits lung tissue damage by the action of proteolytic enzymes contained in leucocytes.

Birth Weight↗
PubMed1977

[Pharmacodynamics of alcoholic and aqueous extracts from the Casimiroa edulis seed].

The hypnotic properties of leaves and seed of Casimiroa edulis (zapote blanco) a tropical fruit, are well known. In the present investigation, pharmacological studies on aqueous and alcoholic extracts were carried out in dogs, cats, rabbits and guinea pigs, using different experimental models. The action of the extracts upon blood pressure, cardiac activity, respiration rate, muscular tone, electroencephalographic activity, sleep and other parameters were studied too. In addition to, studies upon isolated human, cat, rabbit and guinea pig tissues gave information about the extracts effect on smooth muscle activity. It was found that both aqueous and alcoholic extract of the seed of zapote blanco produced marked hypotension in all animal species, which was followed by a sleep-like stage. Also a definitive oxitocic effect in vivo and in vitro was demonstrated suggesting the presence of a potent uterus constricting substance.

Animals↗
PubMed1976

Ambient temperature of hypoxia: a differential study of liver catalase and cytochrome oxidase in guinea pig.

The activities of liver catalase and cytochrome oxidase have been determined in sea-level and high-altitude native guinea pigs exposed to different ambient temperatures. The activities of both of these enzymatic systems have been found to increase as ambient temperature is reduced, and this occurs in the sea-level and the high-altitude animals. At equal temperatures, cytochrome oxidase activity is identical in the liver of guinea pigs from sea-level and high-altitude. Catalase activity is approximately 50% lower in the high-altitude animals than in the sea-level ones maintained at the same ambient temperature. It is necessary to reassess current data on hypoxia-induced enzymatic and hormonal changes measured under conditions where the ambient temperature was not controlled, especially in those cases involving volunteer human subjects.

Altitude↗
PubMed1976

Human semen ribonuclease. Location, properties and inhibition by sodium dodecyl sulfate, zinc sulfate and EDTA.

Optimal conditions were established for RNase activity measurement. The enzyme was measured in human seminal plasma as well as in spermatozoa. Results suggest that sperm enzyme may come from seminal plasma contamination and that RNase may be used as a marker enzyme for seminal plasma contamination. Sodium dodecylsulfate, a reagent utilized to produce the solubilization of the spermatozoa, produced a very strong inhibition of the RNase at low concentrations (530 muM). Zinc sulfate and EDTA also produced inhibition of the RNase activity. Such inhibition may be very useful in future studies of RNA metabolism in human spermatozoa.

Dithiothreitol↗
PubMed1967

Catalysis of ester hydrolysis by mixed micelles containing N-alpha-myristoyl-L-histidine.

Model compounds are described for the study of the properties of amino acid side chains in the surface of micelles. Mixed micelles of N-(alpha)- mnyristoyl-L- histidine and cetyltrimethylammonium bromide catalyze the hydrolyses of p-nitrophenyl acetate and p-nitrophenyl caprylate at much higher rates than imidazole or histidinie do. The reaction shows a kinetic behavior similar to that of surface-catalyzed reactions.

Bromine↗
PubMedDate not supplied

Anoxic cardiac arrest: Its effect on myocardial mitochondrial metabolism.

Forty eight healthy dogs are subjects to cardiopulmonary bypass and divide into two groups according to whether the perfusion is performed in normothermia or moderate hypothermia (30 degrees C). The effects on oxidative phosphorylation and mitochondrial respiration, produced by increasing periods of myocardial anoxia from aortic cross clamping, are studied. A clear correlation is found between the disturbances of mitochondrial metabolism and the future cardiac recovery. Hypothermia shows a protective effect on the anoxic myocardium. It is concluded that the period of absolute safety in cardiac anoxia, as far as mitochondrial function is concerned, is 15 minutes in normal thermic perfusion and 90 minutes in moderately hypothermic ones.

Animals↗
PubMedDate not supplied

[Comparative study on the protective effect of two immunization schemes using a hepatitis B recombinant vaccine in vulnerable health science students].

OBJECTIVE: Demonstrate the protective effect of hepatitis B in vaccine vulnerable health sciences students, under 30 years with three schemes the vaccination, two of them are conventional three doses and another one with two doses. HYPOTHESIS: Three schedules of vaccination dosage schemes hepatitis B produce antibody response over 10 IU/ml. DESIGN: Analytical, experimental, longitudinal., prospective and concurrent cohort study. MATERIALS AND METHOD: 100 vulnerable female and male students of the Medical Technology Faculty of the UNMSM Medical School were enrolled at first. 89 students completed the final analysis due to the inclusion and exclusion criteria in accordance with the study purpose. A vaccine dosage of 20 ug of surface antigen in 1 mL through three dosage schemes was administered: month 0, 1, 6; month 0, 1, 2; and month 0, 1. Blood samples were taken before and 1, 2, 6, and 7 months after the first dosage administration to determine the anti-HBs level. Anti-HBs approximately 10 mIU/mL was defined as seroprotective value. RESULTS: 89 students under 30 years (average age: 23.5 years). 46 (51.7%) male individuals, and 43 (48.3%) female individuals.12.4% of students reached protection within 30 days from the first dosage; 98.8% reached protection within 30 days from the second dosage; and 100% reached protection 180 days later. After the second dosage, the three groups reached protection values, and at the end of the study, the average antibody levels were between 532.7 mIU/mL and 1237.2 mIU/mL. CONCLUSIONS: This study showed an equivalent protective effect 7 months after the first dosage. An equivalent protective effect for hepatitis B was reached through three different vaccination schemes: conventional three dose scheme (month 0, 1, 6); two dose brief scheme (month 0, 1); and three dose brief scheme (month 0, 1, 2). A two dose scheme is suggested for individuals under 30 years, which would imply a higher compliance rate, lower cost, and a similar protection benefit.

Adult↗
PubMedDate not supplied

[Modular diet and parenteral support in persistent diarrhea].

Eleven infants with protracted diarrhea were treated with modular diet and short-term parenteral nutrition. Mean age at admission was 3.7 months with males predominating. Enteropathogenic E. coli, classic serotypes, were isolated from 7 patients and rotavirus from one. A child with combined, severe immunodeficiency died. Milk protein intolerance was diagnosed in another patient. Balance studies and peroral biopsies were performed. Malnutrition was more frequent and hospital stay was longer in those infants who developed nosocomial infections. Even though this treatment shortened the duration of the hospitalization, the negative nutritional impact persisted: Weight/Age (NCHS) decreased from 84% to 61%, with rapid recovery after discharge. Fecal lactic acid excretion was increased on admission to 1,296 mg x day and disaccharidase activity was decreased. The modular diet decreased both fecal volume and lactic acid excretion.

Diarrhea, Infantile↗
PubMedDate not supplied

[Refractory diarrhea].

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Diarrhea, Infantile↗