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Biomedical subjects

S Paredes

Publications and source records attributed to S Paredes.

At least 19 recordsLinked to original sources
PubMed2004

Orally administered tryptophan and experimental type 2 diabetes.

There is a link between diabetes and oxidative stress. Hyperglycaemia leads to free radical generation and alterations of endogenous antioxidants. Our aim is to study the effect of orally administered L-tryptophan (TRP), the melatonin precursor, an endogenous antioxidant, on circulating levels of glycaemia, insulin and melatonin, and on the superoxide dismutase and catalase antioxidant systems in non-diabetic (ND) and type 2 diabetic (n5-STZ) male Wistar rats. At 19:30 every day for 15 days, TRP (125 mg/kg body weight) was administered orally. At 09:00 every two days the glycaemia was measured and every day the intake of food and water was recorded. At the beginning and end of treatment (at 09:00; 21:00; 02:00) plasma insulin and melatonin levels were measured, and (at 09:00) the enzymatic activities of catalase and superoxide dismutase (SOD) in erythrocytes were also measured. Glycaemia values were greater (p < 0.01) in n5-STZ rats than in ND rats, while insulin levels were lower (p < 0.05) at all times studied and these parameters were not altered by the TRP administration. Melatonin levels at 02:00 were lower in n5-STZ than in ND rats (p < 0.05). The TRP administration did not modify the circulating melatonin levels in ND rats, but raised (p < 0.01) the levels at 02:00 in the treated n5-STZ group. In ND rats after TRP administration there was a decline in catalase activity (p < 0.05), while in n5-STZ rats there was a rise (p < 0.01) at the end of treatment. However, there were no significant changes in SOD activity. There was increased food intake (g/day) in the treated n5-STZ group (p < 0.01). In conclusion, the oral administration of TRP did not modify glycaemia or insulinaemia levels, but raised melatonin levels in diabetic rats at 02:00, lowered catalase activity in ND rats but raised it in n5-STZ rats, and increased food intake in n5-STZ rats.

Administration, Oral↗
PubMed2001

Elevated levels of small, low-density lipoprotein with high affinity for arterial matrix components in patients with rheumatoid arthritis: possible contribution of phospholipase A2 to this atherogenic profile.

OBJECTIVE: This work studied the presence of inflammatory and atherogenic lipoprotein markers that could explain the high incidence of cardiovascular disease (CVD) reported in rheumatoid arthritis (RA) patients. METHODS: Inflammatory markers were 1) soluble adhesion molecules (intercellular adhesion molecule [ICAM] and vascular cell adhesion molecule [VCAM]), 2) C-reactive protein (CRP), 3) fibrinogen (Fb), 4) cytokines (interferon-gamma [IFNgamma], tumor necrosis factor alpha [TNFalpha]), and 5) secretory group IIA phospholipase A2 (sPLA2-IIA). Atherogenic lipoprotein markers were 1) the size distribution of plasma lipoprotein subclasses, and 2) the binding affinity of low-density lipoprotein (LDL) to chondroitin 6-sulfate glycosaminoglycan (GAG). RESULTS: RA patients (n = 31) and matched controls (n = 28) had similar plasma concentrations of total cholesterol, triglycerides, Apo B, Apo A-I, very low-density lipoprotein, intermediate-density lipoprotein, and high-density lipoprotein (HDL). RA patients had significantly higher plasma levels of sPLA2-IIA, ICAM, CRP, Fb, TNFalpha, and IFNgamma compared with controls. RA patients also had significantly higher levels of small, dense LDL-1 (P < 0.05) and lower levels of small HDL-2 particles (P < 0.001) compared with controls. In addition, LDL from RA patients had a significantly higher binding affinity (Kd) to GAG (mean +/- SD Kd 204+/-22.4 nM Apo B) than did LDL from control subjects (Kd 312+/-36 nM Apo B) (P < 0.05). This Kd value showed a significant negative correlation with the plasma levels of LDL-1 (r = -0.566, P < or = 0.004). In RA patients, a significant positive correlation was obtained between sPLA2-IIA and CRP, ICAM, and LDL-1. HDL-2 showed a negative correlation with sPLA2-IIA. CONCLUSION: These atherogenic lipoprotein factors combined with the presence of chronic inflammation may contribute to the high CVD-related mortality in RA patients.

Adult↗
PubMed2001

Enhancing conversation skills in children with autism via video technology. Which is better, "self" or "other" as a model?

The present study was designed to compare the efficacy of "self" versus "other" video-modeling interventions. Five children with autism ranging in age from 4 to 11 were taught to answer a series of conversation questions in both self and other video-modeled conditions. Results were evaluated using a combination of a multiple baseline and alternating treatments design. Three out of the five participants performed at levels of 100% accuracy at posttreatment. Results indicated no overall difference in rate of task acquisition between the two conditions, implying that children who were successful at learning from video in general, learned equally as well via both treatment approaches. Anecdotal evidence suggested that participants who were successful with video treatment had higher visual learning skills than children who were unsuccessful with this approach. Results are discussed in terms of a visual learning model for children with autism.

Autistic Disorder↗
PubMed2000

Criteria for selecting and using non-steroidal anti-inflammatory drugs in primary health care.

BACKGROUND: Numerous non-steroidal anti-inflammatory drugs (NSAIDs) are commercially available in Spain. This makes proper selection and use of these drugs difficult for GPs. OBJECTIVE: To find out the criteria which GPs use to choose among the drugs in this group and to evaluate other criteria related to the clinical management of NSAIDs. METHOD: A survey questionnaire was distributed among all the GPs of the reformed network in the health area of Tarragona (Spain). RESULTS: The doctors questioned chose a limited number of NSAIDs. Major preferences were diclofenac and piroxicam. The main criteria for selection were: efficacy and safety of the drug; previous and/or current gastrointestinal pathology of the patient; the difference between acute and chronic use; and the type of inflammatory process. There were a large number of combinations of routes of administration. The histamine H2 antagonists were the prophylactic drugs which were used most for gastropathy. CONCLUSION: Sometimes the main criteria for choosing between the drugs in this study do not reflect the drugs that are used in clinical practice. Some of the criteria used by GPs for selecting and using NSAIDs should be reviewed.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1996

Fluorimetric determination of tin and organotin compounds in hydroorganic and micellar media in the presence of 8-hydroxyquinoline-5-sulfonic acid.

The fluorescence of tin(IV) complexed by 8-hydroxyquinoline-5-sulfonic acid (8-HQSA) has been studied in both aqueous and hydroorganic (acetate buffer and dimethylsulfoxide) media. Several experimental parameters such as pH, DMSO/water ratio and reactant concentration have been investigated to increase the fluorescence of the tin(IV)-8-HQSA complex. A linear relationship between tin(IV) concentration and fluorescence intensity was observed between 1.7 and 20 microM). Mechanistic and quantitative studies in the presence of surfactants have been performed. Judiciously selected micellar media permitted solubilisation and quantitation of tin(IV) as well as dibutyltin compounds. A linear relationship between concentration and fluorescence intensity was found for mono-, di- and tributyltin with detection limits of 0.1 microM, 0.7 microM and 1 microM, respectively.

Dentifrices↗
PubMed1995

Social cost of land mines in four countries: Afghanistan, Bosnia, Cambodia, and Mozambique.

OBJECTIVES: To document the effects of land mines on the health and social conditions of communities in four affected countries. DESIGN: A cross design of cluster survey and rapid appraisal methods including a household questionnaire and qualitative data from key informants, institutional reviews, and focus groups of survivors of land mines from the same communities. SETTING: 206 communities, 37 in Afghanistan, 66 in Bosnia, 38 in Cambodia, and 65 in Mozambique. SUBJECTS: 174,489 people living in 32,904 households in the selected communities. MAIN OUTCOME MEASURES: Effects of land mines on food security, residence, livestock, and land use; risk factors: extent of individual land mine injuries; physical, psychological, social, and economic costs of injuries during medical care and rehabilitation. RESULTS: Between 25% and 87% of households had daily activities affected by land mines. Based on expected production without the mines, agricultural production could increase by 88-200% in different regions of Afghanistan, 11% in Bosnia, 135% in Cambodia, and 3.6% in Mozambique. A total of 54,554 animals was lost because of land mines, with a minimum cash value of $6.5m, or nearly $200 per household. Overall, 6% of households (1964) reported a land mine victim; a third of victims died in the blast. One in 10 of the victims was a child. The most frequent activities associated with land mine incidents were agricultural or pastoral, except in Bosnia where more than half resulted from military activities, usually during patrols. Incidences have more than doubled between 1980-3 and 1990-3, excluding the incidents in Bosnia. Some 22% of victims (455/2100) were from households reporting attempts to remove land mines; in these households there was a greatly increased risk of injury (odds ratio 4.2 and risk difference 19% across the four countries). Lethality of the mines varied; in Bosnia each blast killed an average of 0.54 people and injured 1.4, whereas in Mozambique each blast killed 1.45 people and wounded 1.27. Households with a land mine victim were 40% more likely to experience difficulty in providing food for the family. Family relationships were affected for around one in every four victims and relationships with colleagues in 40%. CONCLUSIONS: Land mines seriously undermine the economy and food security in affected countries; they kill and maim civilians at an increasing rate. The expense of medical care and rehabilitation add economic disability to the physical burden. Awareness of land mines can be targeted at high risk attitudes, such as those associated with tampering with mines.

Adolescent↗
PubMed1994

Migraine, polycythemia and chronic mountain sickness.

In the epidemiological study among 379 adult men with permanent residence at 4300 meters (14,200 feet), we found 32.2% with migraine (mostly migraine with aura), 15.2% with tension-type headache (episodic more than chronic), and 7.2% with other headaches. The frequency of migraine increased with age from 30.1% in the 20-29 year age group to 36.8% in the 50-59 year group. Episodic tension-type headaches also showed this trend. We found an age-specific increase in the frequency of high hemoglobin (Hb > 213 milligrams), low oxygen saturation (O2 saturation < 81.5%) and high chronic mountain sickness scores. Male migraineurs and those with more than two headaches per month had the highest hemoglobin levels and chronic mountain sickness scores when compared with high altitude men without headaches.

Adult↗
PubMed1993

Photodynamic action of endogenously synthesized porphyrins from aminolevulinic acid, using a new model for assaying the effectiveness of tumoral cell killing.

1. The effectiveness of the photodynamic action of porphyrins, was studied by means of the tissue explant culture technique. A murine tumor tissue explant was incubated in a medium containing 0.6 mM of ALA for periods of 1 and 2 hr; total porphyrins synthesized under these conditions were of the same level as those found in our previous in vivo experiments. The explants were then irradiated for 30 min with He-Ne laser of 3.5 mW output power placed at a distance of 10 cm. Controls of non-irradiated tumor tissue slices incubated with and without ALA were performed. Immediately after irradiation, inocula of exactly 1 mm3 of the irradiated and non-irradiated tissue were subcutaneously injected under the right and left flanks of the same animal, respectively. The growth of the tumor was measured 15, 20 and 25 days after implantation. 2. Results obtained showed that the explants that were incubated for 1 hr with ALA and irradiated, reaching a concentration of 2.8 micrograms porphyrins/g tissue, produced a reduction of 50-70% of tumor size as compared with the non-irradiated controls incubated with ALA. Explants incubated for 2 hr, reaching a concentration of 4.6 micrograms porphyrins/g tissue, produced from 60% to complete lack of tumor growth. The effectiveness index (EI) of photoirradiation was calculated on the basis of the tumor growth in irradiated and non-irradiated tumors. EI was nearly 100% showing almost complete tumor cell destruction for tumor irradiated for 2 hr with 0.6 mM ALA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1992

Tumour-localizing properties of porphyrins. In vivo studies using free and liposome encapsulated aminolevulinic acid.

1. Using different doses of free and liposome encapsulated aminolevulinic acid (ALA) (between 2 and 8 mg/animal), given i.p., s.c. and intra-tumoural (i.t.), in vivo porphyrin synthesis by tumour, red blood cells (RBC) and different organs from tumour-bearing mice (TBM) and normal mice (NM) at different times, up to 24 hr after ALA administration, was examined. 2. It was found that by giving entrapped ALA, at a dose of 6 mg/animal (or 200 mg/kg wt), after 10 hr, a high level of porphyrin accumulation in the tumour was produced (7 micrograms/g tissue). Low synthesis occurred in muscle, lung, brain, RBC and skin; in spleen, kidney and liver synthesis is significant after 10 hr, but after 24 hr returned to normal values in the spleen and to about 2-3 micrograms/g tissue in the kidney and liver. 3. The tumour/skin porphyrin concentration ratio after 10 hr was nearly 30, the highest so far reported. 4. These results support our previous in vitro findings, indicating that free or encapsulated ALA might be used for early diagnosis of cancer and in photodynamic therapy.

Aminolevulinic Acid↗
PubMed1990

Kinetics of purple membrane dark-adaptation in the presence of Triton X-100.

The kinetics of purple membrane dark adaptation were studied at pH 5 and 7, in the presence and absence of the nonionic detergent Triton X-100. The effect of both sublytic and lytic surfactant concentrations has been considered. Our results show that: (a) dark adaptation is faster at pH 5 than at pH 7, (b) dark adaptation is slower, and of smaller amplitude, in the presence than in the absence of Triton X-100. The data may be interpreted in terms of a simple first-order kinetic model, according to which light-dark adaptation would depend basically on the equilibrium between the 13-cis- and the all-trans-isomers. The experiments also suggest that at pH 5, but not at pH 7, solubilizing surfactant concentrations produce a considerable increase in the velocity of the dark adaptation reaction, perhaps through changes in the microenvironment of a protonable group.

Bacteriorhodopsins↗
PubMed1990

Detergent solubilization of phospholipid vesicle. Effect of electric charge.

In order to explore the effect of electric charge on detergent solubilization of phospholipid bilayers, the interaction of nine electrically charged surfactants with neutral or electrically charged liposomes has been examined. The detergents belonged to the alkyl pyridinium, alkyl trimethylammonium or alkyl sulphate families. Large unilamellar liposomes formed by egg phosphatidylcholine plus or minus stearylamine or dicetyl phosphate were used. Solubilization was assessed as a decrease in light-scattering of the liposome suspensions. The results suggest that electrostatic forces do not play a significant role in the formation of mixed micelles and that hydrophobic interactions are by far the main forces involved in solubilization. In addition, from the study of thirty different liposome-surfactant systems, we have derived a series of empirical rules that may be useful in predicting the behaviour of untested surfactants: (i) the detergent concentration producing the onset of solubilization (Don) decreases as the alkyl chain length increases; the decrease follows a semi-logarithmic pattern in the case of alkyl pyridinium compounds; (ii) for surfactants with critical micellar concentrations (cmc) less than 6 x 10(-3) M, Don. is independent of the nature of the detergent and the bilayer composition; for detergents having cmc greater than 6 x 10(-3) M, Don. increases linearly with the cmc; and (iii) Don. varies linearly with the surfactant concentration that produces maximum solubilization.

Chemical Phenomena↗
PubMed1990

Mutual effect of glucose and glutamine on their utilization by tumour cells.

Interactions between glucose and glutamine metabolisms have been studied in a line of Ehrlich ascites tumour cells and the results obtained are compared with those recently published for ascites Lettré cells. In contrast with Lettré cells, in the less malignant line used in this work, glucose did not modify glutaminolytic flux and glutamine changed the rate of glucose consumption. It is concluded that the biochemical behaviour of the cells could be correlated to the degree of malignancy.

Animals↗
PubMed1989

Tumor-localizing properties of porphyrins. In vitro studies using the porphyrin precursor, aminolevulinic acid, in free and liposome encapsulated forms.

Tumor, liver, skin and brain explants from tumor-bearing mice were cultured for 6, 12 and 22 hours in the presence of 0.06, 0.1 and 0.2 mM aminolevulinic acid (ALA). It was found that in all organs, synthesis of porphyrins increased with time and ALA concentration. The synthesising activity of tumor was high, of the same order as that of liver, and nearly twice that of skin and brain. The tissue/tumor porphyrin concentration ratios were lower than 0.5 at longer times and higher ALA concentration. In the case of skin/tumor the lowest ratio was about 0.2 and was obtained with 0.2 mM ALA. Chromatographic analysis of individual porphyrins showed that the whole heme pathway was functional in all organs studied, including tumor. Porphyrin synthesis by different organs from tumor bearing and normal mice was comparatively investigated using free and liposome encapsulated ALA. After 22 hours of incubation with 0.4 mM ALA, porphyrin formation was greater when encapsulated ALA was used. Accumulation of porphyrins in tumor was very high. The levels of activity were the same in each pair of organs in either the tumor-bearing mice or the control. These results indicate that free or encapsulated ALA may be used for the detection of tumors and in photodynamic therapy.

Adenocarcinoma↗
PubMed1976

Investigation of ribonuclease-catalysed kinetics by a micro-calorimetric method.

A rapid micro-calorimetric method for the simultaneous determination of the Michaelis-Menten parameters and the enthalpy of enzymic reactions is developed. The hydrolysis of 2': 3'-cyclic CMP by ribonuclease A is studied to test the proposed method; values obtained are in good agreement with already published data. Enzymic hydrolysis of yeast RNA, unlike that of cyclic phosphates, is shown to be endothermic. This result is explained by the two-step mechanism of this reaction.

Calorimetry↗
PubMed1975

The use of computed activity coefficients in Raoult's reference system, for n-alcohol/water mixtures, and their application to the study of proteins.

Activity coefficients of alcohols in Raoult's reference system have been calculated. Using data from papers dealing with transition temperatures in the presence of n-alcohols, lipase deactivation and competitive inhibition by n-alcohols of pepsin and alpha-chymotrypsin, it is shown that the conversion of concentrations into activities (using Pierotti's equation) profoundly affects the original data. Within experimental error, if inhibition constants by alcohols keep the same value, lupase deactivation becomes independent of the length of the alcohol chain, and except for butanol, transition temperature is no longer dependent on the number of methylene groups. Interpretations which take into account the thermodynamic reference system and final environment are related to the fact that alcohol molecules bind to some inner parts of the proteins.

Alcohols↗