Search PubMed⌕ Search

Biomedical subjects

M Orozco

Publications and source records attributed to M Orozco.

At least 73 records · Page 4Linked to original sources
PubMed1989

Theoretical study of the protonation and tautomerization of adenosine, formycin, and their 2-NH2 and 2-F derivatives: functional implications in the mechanism of reaction of adenosine deaminase.

A quantum chemical study of adenosine, formycin, and their 2-NH2 and 2-F derivatives is performed. The tautomerism of neutral and protonated species as well as the protonation of adenosine, formycin, and their derivatives are theoretically studied using semiempirical MNDO and AM1, as well as ab initio STO-3G methods. Calculations have been performed on a reduced model, in which the ribose moiety has been substituted by a hydroxy-methyl group. Results indicate that adenosine is mainly protonated at the N1 atom, whereas formycin can be protonated on N1 or N3, depending on the tautomeric form (N8-H or N7-H). The quantum chemical study of the N1-protonated molecules shows that a second protonation of adenosine is mainly on the N3 atom, whereas formycin can be protonated on N8 or N3, depending on the tautomeric form. On the other hand, results indicate that the protonation of formycin and its derivatives at the N1 atom leads to a change in their tautomeric preference from N7-H to N8-H. The importance of both tautomerism and protonation reactions in the mechanism of action of adenosine deaminase is studied by means of a quantitative structure activity relationships strategy. Significant correlations were found between several electronic parameters and the logarithm of the maximum rate of deamination (log Vm) of the studied compounds. For formycin and its derivatives, it was necessary to consider their N8-H tautomeric forms. The electronic parameters giving good correlations were as follows: energy of the minimum of the ab initio molecular electrostatic potential on N1, net charge over purine (pyrazolo-pyrimidine) and pyrimidine rings, and the N1 protonation energy. It must be noted that all these parameters are informative in relation to a proton attack. Adenosine and purine ribosides have been studied largely because of their high biological relevance. They are constituents of nucleic acids, intermediates in secondary metabolism, neuromodulators, and neurohormones. Their analogues have been extensively used because of their wide range of pharmacological effects (1). Formycin A (Fig. 1) is one of the most studied analogues of adenosine. It is a natural product extracted from Nocardia interforma (2) with proven antiviral (3-5), antibiotic (2), immunodepressant (6), antitumor (6), and antimetabolic (5) activities.

Adenosine↗
PubMed1988

POEMS: program for outliers elimination in multidimensional space.

A Program for Outliers Elimination in Multidimensional Space (POEMS), which allows the user to eliminate outliers from training spaces as a prior step to any statistical study, is presented. Even though the program can be applied to any scientific field, the characteristics of POEMS makes it particularly suitable for 'series design' on Quantitative Structure-Activity Relationships studies.

Algorithms↗
PubMed1984

[Use of chigo seed (Campsiandra comosa, Benth) in human nutrition. I. Antecedents, nutritional potential, and characteristics of the plant and seed].

A review of the information in the literature in regard to the utilization of the seed of the "chigo" (Campsiandra comosa, Benth) as human food in Venezuela, is presented. The seed of the "chigo" is used as food by inhabitants in areas of the Orinoco basin. Several types of products are prepared from its flour. The nutritional potential of the seed and some of its characteristics, as well as those of the tree from which it is obtained, are also presented. Based on the carbohydrate and protein content of the seed, and on its amino acid composition, it is considered of interest to proceed with a more detailed study in order to determine its potential for human nutrition and, at the same time, analyze the processing conditions of the seed so as to increase its yield and quality as a food.

Amino Acids, Essential↗
PubMed1984

[Use of chigo seed (Campsiandra comosa, Benth) in human nutrition. II. Process of non-industrial manufacture of chiga].

A quantitative study of the traditional process for making "chiga" flour was performed. The "chiga" flour is obtained from the seed of the "chigo" (Campsiandra comosa, Benth) and is utilized as a human food in areas of Venezuela in the Orinoco basin, especially in the State of Apure and in the Territorio Federal Amazonas. The block diagram with the description of the traditional process is presented, together with labor and time requirement studies of the different stages of the process. The yields as well as the requirements for raw materials are also discussed. This research work was carried out to study and provide quantitative information that may allow the duplication of the process, in order to improve the efficiency and yield of the product.

Diet↗
PubMed1983

Bicompartmental analysis of cerebrospinal fluid circulation. Theory and clinical applications.

A new model for cerebrospinal fluid (CSF) circulation is proposed. Specific activity/time curves for CSF kinetics determined after intraventricular injection of a radiotracer were produced by fitting a biexponential function to data points and developing a two-compartmental model. Calculation of kinetic parameters of the model provides quantitative data about CSF dynamics. The study of each compartment separately and of the intercompartmental relationship is possible with this model. Sequential scan images and graphic plots of the variations of radioactivity in both compartments, derived from this model, add supplementary information in the evaluation of patients. Ventriculography was performed in 80 patients, who fell into four groups: those with normal CSF circulation, hydrocephalus, infantile hydrocephalus, and functioning ventricular shunts. Normal and hydrocephalic patients showed significant differences between the two groups in the means of some numerical parameters calculated from the new model. An increase of intraventricular radioactivity at 24 hours (p less than 10(-4)) and of the volume of Compartment 1 (p less than 0.01) with decreased volume of Compartment 2 (p less than 10(-4)) and total flow outside the system (p less than 10(-3)) were found in patients with hydrocephalus. The limiting values for normal patients were also estimated. Communicating and obstructive hydrocephalus could be differentiated by this method; however, no differences in mean values were found relating to the etiology or clinical course of the hydrocephalus. Normal-pressure hydrocephalus and cerebral atrophy produced significantly different mean values for the volume of Compartment 2 (p less than 0.01), flow out of the system (p less than 0.01), and intercompartmental flow (p less than 0.01).

Cerebral Ventriculography↗
PubMed1978

[Metabolic studies in brothers affected by alcaptonuria (ochronosis)].

The case of two brothers affected by alcaptonurie is reported. The activity of the homogenthisycasa enzyme has been determined by the material obtained through percutaneous biopsy. Concentrations of the aminoacids producing fenilalanina and thiroxina in their parents' blood have been investigated, the tests showing lack of liver enzyme and normal concentration of the amount of aminoacids in blood. Some aspects of skin lesion have been briefly reported and methods for treatment presented.

Adult↗
PubMed1978

Intracranial aneurysms in early childhood.

A case of an aneurysm of the middle cerebral artery in a 17-month-old child has been presented and the literature on the problem reviewed. A total of 27 aneurysms in young children (under two years of age) has been found. The characteristics that define this group of patients are: a greater proportion of aneurysms of the middle cerebral artery and its branches and of the vertebrobasilar system; greater size of the aneurysms; and frequent pseudotumor syndromes. The surgical prognosis in this group of patients is excellent. The physical and pathophysiological characteristics of these aneurysms appearing in early childhood are described.

Cerebral Angiography↗
PubMed1975

Spontaneous extradural haematomas.

Spontaneous extradural haemorrhage may be due to neighbourhood infections, vascular malformations of the dura mater, and disorders of blood coagulation. Two cases are described here: in one, infection was present; in the other, there was a berry aneurysm of the middle meningeal artery with a small parietal dural angioma. Operation was successful in both patients.

Adolescent↗
PubMedDate not supplied

A theoretical investigation on the effect of remote amino groups in hydrogen bonding of nucleic acids.

The effect of remote amino groups in the H-bonding of complementary bases of duplex and triplex DNA has been investigated in the gas phase by means of density functional theory. It is found that amino groups incorporated in regions of the purine that are distant from the H-bonding sites might have a notable influence on the stability of H-bonded dimers. The results show that, in addition to primary and secondary interactions, polarization effects can be relevant for the determination of hydrogen bonding in nucleobases.

Amines↗
PubMedDate not supplied

Selective diaphragmatic mitochondrial abnormalities in a patient with marked air flow obstruction.

There is increasing evidence that exercise overload induces changes in skeletal muscle structure and function. Recent studies suggest that muscle mitochondria could be involved either as the result or the origin of these changes. This study describes a case of a patient with marked air flow obstruction related to chronic obstructive pulmonary disease, in which large aggregates of mitochondria were found in diaphragm muscle fibers. Many of the mitochondria contained paracrystalline rectangular inclusions. Latissimus dorsi and intercostal muscles were also available for ultrastructural examination that showed, respectively, normal and moderately increased number of mitochondria with normal mitochondrial structure. This is the first known report of paracrystalline rectangular inclusions in respiratory skeletal muscle from a patient with chronic obstructive pulmonary disease.

Carcinoma, Squamous Cell↗