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Biomedical subjects

G López

Publications and source records attributed to G López.

At least 37 records · Page 2Linked to original sources

Personal-computer-based system for three-dimensional anatomic-physiological correlations during stereotactic and functional neurosurgery.

This paper describes the automatic three-dimensional (3D) graphic possibilities that are supplied by the Neurosurgical Deep Recording System (NDRS) to facilitate anatomic-physiological targeting during stereotactic and functional neurosurgery using depth recording. This software has been developed to substitute the complex electronic equipment ordinarily used for deep brain electrical recording, display and processing by a personal computer. It may also help to improve on-line graphic analysis, automatic management of the recorded information and flexibility to implement different forms of signal analysis. It can automatically show a 2D or 3D representation of the electrode track, with the electrophysiological findings superimposed as well as the corresponding sagittal, coronal and axial views of a brain atlas using automatic scaling. The NDRS has already successfully been applied during more than 300 neurosurgeries in Spain and Cuba, enabling improved targeting accuracy and safety.

Brain Mapping↗

Crystallization and preliminary X-ray diffraction studies of Streptococcus pyogenes plasmid pSM19035-encoded omega transcriptional repressor.

The transcriptional repressor, omega protein, from the Streptococcus pyogenes broad-host-range plasmid pSM19035 was crystallized at pH 7. 5 and 8.5 by the vapour-diffusion method using PEG 4000 as precipitant. Two crystal forms were obtained; the first belongs to the tetragonal space group P4(1)2(1)2 or P4(3)2(1)2 and the second to the hexagonal space group P6(1) or P6(5). The crystals are most likely to contain one omega protein in the asymmetric unit, with V(m) values of 3.2 and 3.5 A(3) Da(-1), respectively. The crystals diffract X-rays to 2.4 and 2.9 A resolution for the tetragonal and hexagonal systems, -respectively.

Bacterial Proteins↗

[Heat treatment and dietary fiber effect on protein quality of artichoke and its sub-product].

Blanched (95 degrees C, 5 min), autoclaved (100 degrees C, 5 min) artichoke hearts and their by-product (external leaves and distal portion of stem) were analysed for amino acid composition, "in-vitro" protein digestibility (DIVP), and dietary fiber. Amino acid score of the three samples was in a good agreement with FAO/WHO recommendations including sulphur amino acids. Dietary fiber content was high in all samples, decreasing in autoclaved artichokes that might be relate with the improvement of DIVP. By-product was consider a potential food source because it showed a good amino acid profile and the highest levels of DIVP (76.4%), but fibrouness was also too high (51.6%).

Amino Acids↗

[Iron bioavailability in food].

The nutritional need for iron in living organisms is derived from the central role that it plays in the energy metabolism of living cells. However, iron exists in almost exclusively in the less soluble oxidised state (Fe III). This has greatly reduce its accessibility. Iron in foods exist in two main forms: haem iron and non-haem iron, which are absorbed by different pathways with different degrees of efficiency depending upon dietary and physiological factors. All these factors increase or reduce the proportion of the total iron in a food or diet that is utilised for metabolism, that is iron bioavailability. Iron deficiency leads to anaemia, one of the most common nutritional deficiency disorders in the world both in industrialised and developing countries. Preventing this illness is based on a gradual growth in our understanding of iron nutrition.

Absorption↗

[Iron, zinc and copper content of foods commonly consumed in Mexico].

Nutrient composition in foods is necessary for the determination of nutrient intake. Food composition tables used for dietary studies in Mexico do not have information of zinc, iron and copper; when present the values have been extrapolated from laboratory analysis carried out with foods in other countries and regions of the world. In this study zinc, iron, and copper content of 104 plant foods and 32 animal foods was determined. The procedure used was atomic absorption spectrophotometry for the minerals. Foods were grouped into cereals, vegetables, fruits, legumes and animal foods. Zinc content ranged from 0.018 mg/100 g for strawberry to 9.193 mg/100 g for beef. Iron content ranged from 0.113 mg/100 g for yogurt to 19.82 mg/100 g for a commercial cereal which had minerals added during processing. In some foods copper was not found and the highest content was 3.371 mg/100 g in beef liver. This study has provided information on zinc, iron and copper content of the most commonly consumed foods in Mexico.

Animals↗

B-mode, utero-ovarian and intratumoural transvaginal colour Doppler ultrasonography for differential diagnosis of ovarian tumours.

OBJECTIVES: The aim of this study was to evaluate and compare the use of B-mode transvaginal, utero-ovarian Doppler and intratumoural colour Doppler imaging in the diagnosis of ovarian tumours in order to establish whether they are organic or functional, and malignant or benign in nature prior to surgery. STUDY DESIGN: A series of 213 women between the ages of 15 and 87 presenting ovarian tumours were examined with pulsed and colour Doppler and the functional state of the ovary at the time of the exploration was also established. Size and morphology were evaluated through a new scoring system called sonographic index. This score is calculated as the sum of the points corresponding to tumoural volume (< or = 8 ml = 1 point; > 8 ml and < or = 100 ml = 2 points; > 100 ml = 3 points) and the points corresponding to morphological characteristics (negative echogenicity = 1 point; mixed echogenicity = 2 points; multilocular morphology = 3 points; complex morphology = 4 points; positive echogenicity = 5 points) varying between 2 and 8 points. The flow velocity waveform (FVW) of the utero-ovarian and intratumoural arteries were obtained and analyzed after assessing their resistance indices. Other parameters studied were the presence and location of the colour signal in the intratumoural arteries. RESULTS: Of the total, 84 of the tumours were found to be functional and had disappeared by the time later examinations took place. Surgery was performed in 129 of the patients, and posterior histopathological studies permitted classifying the tumours as benign in 107 cases and malignant in 22. The sonographic index was significantly higher in the organic (4.9 +/- 1.5) and malignant (6.9 +/- 1.0) tumours than in the functional (3.6 +/- 1.5) and the benign (4.1 +/- 1.2) tumours. The utero-ovarian and intratumoural blood flow RIs in the malignant tumours (0.48 +/- 0.12 and 0.43 +/- 0.08, respectively) was significantly lower than in the benign tumours (0.83 +/- 0.12 and 0.58 +/- 0.15, respectively). There were no significant differences in the utero-ovarian and intratumoural blood flow RIs when organic and functional tumours were compared. In all of the malignant tumours a colour signal was identified; it was centrally located in 90% of the cases. A colour signal was observed in 83% of the functional tumours, and in 52% of the organic benign tumours. In the benign tumours the colour signal was peripherally located in 98% of the cases. The variables for sensitivity, specificity, positive predictive value, negative predictive value and precision when organic tumours were diagnosed were 82.9, 65.5, 78.7, 71.4 and 76.1 for a sonographic index where the score was > or = 4; the values for the utero-ovarian RI were 48.4, 90.4, 88.4, 53.6 and 65.1 (cut-off 0.55 > or = RI > or = 0.90); the values for the intratumoural RI were 56.5, 68.6, 54.2, 70.6 and 63.8 (cut-off < or = 0.55). When malignancy was diagnosed these variables were 95.5, 82.2, 38.2, 99.4 and 83.6 for the sonographic index (score > or = 6); 90.9, 98.9, 90.0, 98.9 and 98.1 for the utero-ovarian RI (cut-off < or = 0.55) and 80.0, 66.7, 33.3, 94.1 and 69.0 for the intratumoural RI (cut-off < or = 0.50). The number of false positives diagnosed on the basis of the intratumoural RI decreased when cases that had been evaluated during the luteal phase were excluded from the study. Notwithstanding, the phase of the cycle does not seem to interfere with the diagnosis when utero-ovarian Doppler imaging is used. CONCLUSIONS: B-mode transvaginal ultrasonography and utero-ovarian Doppler velocimetry seem to complement each other to aid in differentiating between organic and functional ovarian tumours. Transvaginal ultrasonography and Doppler imaging provide good results for the diagnosis of malignancy, although the utero-ovarian RI reduces the number of false positives that occur with ultrasonography. Our group, therefore, believes that the combined use of these techniques is beneficial in the clinical d

Adolescent↗

Naltrexone effects on insulin sensitivity and insulin secretion in hyperandrogenic women.

A total of 12 women (24.2 +/- 1.6 years old, BMI 36.7 +/- 1.5 Kg/m2) with hyperandrogenism (HA) and with normal glucose tolerance test were studied to evaluate the involvement of endogenous opioids in the pathophysiology of insulin secretion and insulin sensitivity in HA by administering naltrexone, an oral opioid receptor antagonist. Six patients received naltrexone orally (75 mg daily) and another six received placebo for 12 weeks (double-blind study). Before and after therapy a frequently sampled intravenous glucose tolerance test (FSIVGTT) was performed. The insulin sensitivity index (SI) was determined by Bergman's program. SHBG, DHEAS, testosterone, free androgen index (FAI) and plasma concentrations of IGF-I and IGFBP-1 were determined in 3 basal samples, before and after therapy. Treatment with naltrexone in hyperandrogenic patients resulted in a decrease in fasting insulin concentrations of 40% and C-peptide concentrations of 50% (p < 0.05). Insulin and C-peptide from the FSIVGTT displayed a similar pattern with a fall in the area under the curve under naltrexone treatment of 34% for insulin and 35% for C-peptide. Insulin sensitivity did not change under naltrexone (1.26 +/- 0.19 vs 1.32 +/- 0.32 10(-4) x min(-1)/(uU/ml)) or placebo (0.95 +/- 0.19 vs 1.12 +/- 0.28 10(-4) x min(-1)/(uU/ml)) administration. However, glucose effectiveness increased significantly with naltrexone (2.231 +/- 0.002 vs 3.354 +/- 0.006 x 10(-2) min(-1)). Glucose (fasting and area under the curve) was not modified significantly after naltrexone administration. Baseline hormone levels were similar in the two groups, and they did not change after long-term treatment with naltrexone or placebo. In conclusion, these results support the hypothesis of elevated opioid tonus and increased insulin secretion as a possible mechanism of hyperinsulinism in a group of hyperandrogenic women of ovarian origin. This alteration could act as an additional factor in the pathogenesis of insulin resistance found in an important proportion of these patients.

Adolescent↗

Dietary protein level regulates expression of the mitochondrial branched-chain aminotransferase in rats.

The first step in the degradation of branched-chain amino acids (BCAA) is transamination catalyzed by the branched-chain aminotransferase (BCAT), which is located in extrahepatic tissues. Studies of the effect of dietary protein on BCAT activity have given contradictory results. Therefore, we established the levels of BCAT activity and mitochondrial BCAT (BCATm) mRNA expression in different organs and tissues of rats. We then determined the effect of different levels of dietary protein in well-nourished rats, the effect of feeding a 0.5% casein diet for 5 wk (protein-malnourished rats) and nutritional rehabilitation of these rats with different levels of dietary protein on BCAT activity and BCATm mRNA expression in selected tissues. Finally, the response of tissue BCAT activity and BCATm mRNA levels in rats fed a 10% casein diet and injected with glucagon (4 d) or hydrocortisone (7 d) was determined. The highest concentration of BCATm mRNA was found in stomach, followed by kidney, heart, muscle, brain, skin and lung. Low levels were found in intestine, and no BCATm mRNA was detectable in liver. Although BCAT activity was significantly higher in muscle, kidney and brain from rats adapted to consume a 50% casein diet for 7 h/d for 10 d than in rats fed 6, 18 or 35% casein diets, only muscle had significantly higher levels of BCATm mRNA. In protein-malnourished rats, BCAT activity and BCATm mRNA expression in kidney, muscle and heart were not different from those of rats with free access to an 18% casein diet. Nutritional rehabilitation of the protein-malnourished rats with 50% casein for 21 d significantly increased the BCAT activity and BCATm mRNA expression in muscle. Neither hydrocortisone nor glucagon injection affected BCAT activity or BCATm mRNA concentrations in rat kidney, muscle or heart. We conclude that the nutritional regulation of BCATm is extrahepatic, tissue specific and may involve transcriptional and post-translational mechanisms.

Animals↗

Influence on the selenium concentration and selenium intake of infants of infants of ingredients in Spanish homogenised infant beikosts.

Selenium (Se) concentration in 13 homogenised beikosts ("any additional food used in infant nutrition different from human milk and formulas") was investigated, as well as the influence of ingredients on Se concentration in three beikost types (meat, vegetables and fish). Levels of Se varied widely, ranging from 20 micrograms/kg d.w. for mixed vegetables to 258 micrograms/kg d.w. for hake with rice. These values increased as high-protein ingredients (meat or fish) were included. Fish-based beikosts showed the highest contribution of Se, covering more than 50% of the RDA in the USA for infants from 6 to 12 months old. The best Se sources were meat and fish, and their contributions to Se concentrations in the final products were 85.3% for chicken with rice and 75% for hake and vegetables.

Animals↗

[Nutritional importance of selenium].

Selenium is an important trace element that was considered toxic for humans and animals for a long time. The best known biochemical role of selenium is, as a selenocysteine residue, to be a part of the active site of the enzyme glutathione peroxidase (GSH-Px). The highest values of selenium have been found in protein foods (meat and fish); although selenium from vegetables sources are more available than from the other foods. Nowadays are not known exactly the recommended dietary allowances for humans, mainly for children. The selenium intake in Spain is 221 micrograms/person/day and the plasmatic values of Spanish people (87 +/- 14 micrograms/L) are within the European average (85 micrograms/L).

Animals↗

[Biochemical markers and methods to assess insulin resistance in normal, obese and hyperandrogenic women].

BACKGROUND: Euglycemic or hyperglycemic clamp and the frequently sampled i.v. glucose tolerance test are the most frequently used methods to assess insulin resistance. However, both are expensive and cumbersome. AIM: To evaluate the relative or discriminatory usefulness of sex hormone binding globulin (SHBG), dehydroepiandrosterone sulphate (DHEAS) and insulin like growth factor binding protein 1 (IGFBP-1) as markers of insulin resistance and to estimate the tissue sensitivity to insulin by means of the insulin tolerance test (ITT) and the frequently sampled i.v. glucose tolerance test (IVGTT) in normal, obese and hyperandrogenic women. SUBJECTS AND METHODS: Six normal, 6 obese and 12 hyperandrogenic women of similar ages, were studied. In two consecutive days, the ITT and the IVGTT were performed and a basal blood sample was obtained to measure SHBG, DHEAS and IGFBP-1. Insulin sensitivity was calculated as the blood glucose slope in the ITT and with the minimal model of Bergman in the IVGTT. RESULTS: Insulin sensitivity, measured with ITT was 0.58 (0.53-0.63) in normal, 0.38 (0.05-0.59) in obese and 0.20 (0.0-0.36) in hyperandrogenic women. The figures for the IVGTT were 7.97 (4.1-15.4), 2.41 (0.81-4.89) and 1.1 (0.46-1.88), respectively. Both methods had a positive correlation coefficient of 0.792 (p < 0.001). SHBG was 87.0 m 37.9 and 18.3 nmol/l in normal, obese and hyperandrogenic women, respectively (p < 0.09). IGFBP-1 values were 3.0, 2.1 and 1.6 ng/ml respectively (p < 0.05). DHEAS values were 132, 190 and 206 ug/dl, respectively (ND). CONCLUSIONS: ITT is a simple and reliable method to assess insulin sensitivity. SHBG discriminates subjects with different levels of insulin sensitivity. Since it is easy to measure, it could be used as a marker on insulin sensitivity.

Adult↗

[Effects of metformin on insulin resistance in obese and hyperandrogenic women].

BACKGROUND: Metformin is a biguanide often used in obese diabetics that improves tissue sensitivity to insulin. AIM: To assess the effects of metformin on tissue insulin sensitivity in obese and hyperandrogenic women. PATIENTS AND METHODS: Eight obese and eight obese and hyperandrogenic women received metformin 850 mg orally during 12 weeks. Before and at the end of the treatment period, an insulin tolerance test to measure insulin sensitivity was performed and blood was drawn to measure sex hormone binding globulin (SHBG), dehydroepiandrosterone sulphate (DHEAS), testosterone, triglycerides, total and HDL cholesterol. The free androgen index was calculated for each sample. RESULTS: After metformin treatment, the insulin sensitivity index improved from 0.38 (0.05-0.5) to 0.43 (0.25-0.59) in obese women and from 0.2 (0-0.36) to 0.3 (0.06-0.4) in obese and hyperandrogenic women. SHBG increased and total cholesterol and triglycerides decreased significantly in both groups. No other significant changes were observed. CONCLUSIONS: Metformin has a favorable effect on tissue sensitivity to insulin, SHBG and serum lipids in obese and hyperandrogenic women.

Adult↗

[Functional properties of dietary fiber. Mechanisms of action in the gastrointestinal tract].

Physiological effects of dietary fiber (DF) are the result of complex interacting mechanisms between the components of food which is not digested by the endogenous enzymes of the digestive tract and the conditions of gastrointestinal environment, such as pH, ionic strength and other food components. Chemical nature and structure of each component of DF are two factor that determine their behaviour in lumen intestinal. This article report the main functional properties of DF and explain how these are responsible of physiological effects developed by DF in gastrointestinal tract.

Dietary Fiber↗

[Detection of HIV antibodies in pooled sera].

The use of sera mixtures for the detection of HIV antibodies was studied in a population of low prevalence (0.006%), using the diagnosis systems of national production: Recombinant HIV UMELISA and RECHIV 1 + 2. The systems were evaluated with individual samples and mixtures of 5 and 10 sera from healthy blood donors and from HIV-1 and/or HIV-2 positive and undetermined persons. It was observed that the utilization of mixtures of 10 sera is not feasible; however, the use of mixtures of 5 affects neither the specificity nor the sensitivity of the systems studied.

AIDS Serodiagnosis↗

One of the lowest validated incidence rates of insulin dependent diabetes mellitus in the Americas: Santiago, Chile.

The goal of this study was to estimate the average annual incidence rate of insulin-dependent diabetes mellitus (IDDM) in Santiago as part of a Multinational Project in Childhood Diabetes (Diabetes Mondiale or DiaMond). Incidence was calculated among subjects under 15 years of age, through a retrospective search and confirmation method from 1 January 1986 to 31 December 1992. Hospitals and private offices of endocrinologists and specialists in diabetes were surveyed. A total of 252 registered cases, 118 boys and 134 girls, for an annual incidences of 2.36/100,000 hab.year. which is one of the lowest validated rates in the Americas.

Adolescent↗