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Biomedical subjects

M Casas

Publications and source records attributed to M Casas.

At least 37 records · Page 2Linked to original sources
PubMed1999

Rotational behavior in dopamine nigrostriatal denervated rats: effects of a wide range of time intervals between apomorphine administrations.

Previous studies using the turning behavior animal model have shown both increases and decreases in rotational behavior following successive administrations of dopamine agonists. To clarify the results obtained with this model, we studied the variability of rotational behavior after repeated challenges with low doses of apomorphine (0.05 mg/kg) at different time intervals ranging between 2 h and 14 days. Results show a decrease in the total number of turns with time intervals of 2, 6, and 12 h between administrations, and an increase in the total number of turns when apomorphine was administered once every 24 h. In contrast, when animals were tested at 7- and 14-day intervals, a stable number of turns in successive challenges was obtained. These results suggest that when successive injections of dopamine agonists are administered at sufficiently long intervals of time, the neuroadaptations that take place due to repeated drug exposure may not be apparent. These findings are relevant for the design of future experiments using this model.

Animals↗
PubMed1999

Repeated co-administration of caffeine and bromocriptine prevents tolerance to the effects of caffeine in the turning behavior animal model.

The present study examined the effects of repeated co-administrations of caffeine and bromocriptine for 9 consecutive days on contralateral turning in unilateral nigrostriatal 6-hydroxydopamine denervated rats. In agreement with previous data, our results showed that on the first administration, both caffeine and bromocriptine injected plus saline produced a significant increase in contralateral rotational behavior as compared to saline-saline injections. However, with repeated administrations, tolerance was observed to caffeine, but not to bromocriptine. The combination of different doses of bromocriptine (0.1, 0.2, 0.4 and 0.8 mg/kg) with caffeine (40 mg/kg) significantly enhanced the effects of either drug injected with saline on rotational behavior, and no tolerance was observed with repeated treatment. The continuous co-administration of both substances was necessary to maintain elevated levels of rotational behavior, since withdrawing one or the other drug led to decreased contralateral turning. These results demonstrate that when caffeine is administered repeatedly in combination with bromocriptine, tolerance to its psychostimulant effects is not observed, suggesting that caffeine could be used as an adjunctive therapeutic agent with dopamine agonists for the treatment of Parkinson's disease.

Adrenergic Agents↗
PubMed1999

Intermittent hypobaric hypoxia stimulates erythropoiesis and improves aerobic capacity.

PURPOSE: The purpose of the study was to examine the effect of a very short intermittent exposure to moderate hypoxia in a hypobaric chamber on aerobic performance capacity at sea level and the erythropoietic response. The effects of hypobaric hypoxia alone and combined with low-intensity exercise were also compared. METHODS: Seventeen members of three high-altitude expeditions were exposed to intermittent hypoxia in a hypobaric chamber over 9 d at simulated altitude, which was progressively increased from 4000 to 5500 m in sessions ranging from 3 to 5 h x d(-1). One group (N = 7; HE group) combined passive exposure to hypoxia with low-intensity exercise on a cycle ergometer. Another group (N = 10; H group) was only exposed to passive hypoxia. Before and after the exposure to hypoxia, medical status, performance capacity, and complete hematological and hemorheological profile of subjects were evaluated. RESULTS: No significant differences were observed between the two groups (HE vs H) in any of the parameters studied, indicating that hypoxia alone was responsible for the changes. After the acclimation period, a significant increase in exercise time (mean difference: +3.9%; P < 0.01), and maximal pulmonary ventilation (+5.5%; P < 0.05) was observed during the maximal incremental test at sea level. Individual lactate-velocity curves significantly shifted to the right (P < 0.05), thus revealing an improvement of aerobic endurance. A significant increase was found in PCV (42.1-45.1%; P < 0.0001), RBC count (5.16 to 5.79 x 10(6) x mm(-3); P < 0.0001), reticulocytes (0.5 to 1.1%; P < 0.0001) and hemoglobin (Hb) concentration (14.2 to 16.7 g x dL(-1); P < 0.002). CONCLUSIONS: It was concluded that short-term hypobaric hypoxia can activate the erythropoietic response and improve the aerobic performance capacity in healthy subjects.

Acclimatization↗
PubMed1999

Regional cerebral blood flow changes in chronic alcoholic patients induced by naltrexone challenge during detoxification.

UNLABELLED: The recent introduction of the opioid antagonist naltrexone for alcohol-dependence therapy has been mainly based on behavioral animal models that provide evidence of the involvement of the endogenous opioid system in alcohol drinking and dependence. However, the neurophysiological mechanisms of the effect of naltrexone in alcoholic patients remain unknown. This study investigates the effects of a naltrexone challenge on regional cerebral blood flow (rCBF) in chronic alcoholic patients during detoxification. METHODS: Sixteen alcoholic inpatients underwent two 99mTc-hexamethyl propyleneamine oxime (HMPAO) brain SPECTs: a basal SPECT on day 10 of abstinence and a second SPECT on day 12 of abstinence after oral administration of 150 mg naltrexone. Region-to-cerebellar ratios were obtained for the orbitary frontal, prefrontal, lateral temporal and mesial temporal regions, basal ganglia and thalamus in each hemisphere. A percentage of rCBF change between both SPECTs was calculated for each region as 100 x (naltrexone - baseline)/ baseline. Values from 13 brain SPECTs of age-matched normal volunteers including test-retest measurements were used for statistical comparison. RESULTS: In baseline conditions, alcoholics showed lower rCBF than controls in left orbitofrontal cortex (84.0+/-5.1 versus 89.8+/-5.0, P < 0.01) and prefrontal cortex (left hemisphere: 87.4+/-5.2 versus 96.2+/-3.6, P < 0.001; right hemisphere: 87.0+/-4.9 versus 95.8+/-4.2, P< 0.001). After naltrexone, a significant rCBF decrease was found versus test-retest values in left basal ganglia (-3.3%+/-4.0% versus 1.5%+/-4.1%, P< 0.05), right basal ganglia (-4.2%+/-4.9% versus 0.6%+/-2.7%, P < 0.01) and left mesial temporal region (-4.5%+/-6.8% versus 2.2%+/-2.9%, P < 0.01). CONCLUSION: The rCBF decrease detected by SPECT after naltrexone challenge in structures rich in opioid receptors, such as the basal ganglia and the left mesial temporal region, may reflect a naltrexone-induced decreased metabolic activity in these areas. These results support the involvement of the opioid system in alcohol dependence. Furthermore, the localization of naltrexone-induced rCBF changes in mesial temporal structures and in basal ganglia supports the implication of emotional memory and obsessive-compulsive phenomena in craving.

Adult↗
PubMed1998

Molecular organisation of amphotericin B at the air-water interface in the presence of sterols: a monolayer study.

Using the monolayer technique to study the surface behaviour of systems consisting of amphotericin B (AmB) and various sterols, the components were found to interact with each other. The interactions observed are accounted for by postulating that, at low surface pressures, AmB and different sterols form mixed films where the former lies parallel and the latter normal to the air-water interface in such a way that the polar groups in both components establish hydrogen bonds that lead to the formation of an AmB-sterol 'complex' of 2:1 stoichiometry at the interface. At high surface pressures, AmB molecules rearrange themselves normal to the interface; this gives rise to the Van der Waals interactions between non-polar chains of both components that vary with the nature and composition of the system. The occurrence of these hydrophobic interactions prevents the desorption of AmB into the subphase, which is consistent with the positive excess areas of mixing obtained under these surface pressure conditions. Among the four sterols studied, ergosterol exhibits the strongest interaction with AmB and beta-sitosterol the weakest. Cholesterol and stigmasterol show intermediate behaviour.

Amphotericin B↗
PubMed1998

Selective and conventional house-spraying of DDT and bendiocarb against Anopheles pseudopunctipennis in southern Mexico.

Indoor feeding behaviors and mortalities of Anopheles pseudopunctipennis females were evaluated following contact with selective (bands covering mosquitoes' preferred resting areas) and full applications of DDT and bendiocarb on indoor sprayable surfaces. The DDT residues provoked strong avoidance behavior. To a lesser degree, mosquitoes were also repelled by bendiocarb-sprayed surfaces. Because of strong irritancy/repellency, unfed mosquitoes were driven outdoors in proportionally higher numbers. The resting time on selectively or fully DDT-sprayed huts was greatly reduced in comparison to bendiocarb-sprayed huts. Although unfed mosquitoes tended to rest on non-DDT-sprayed surfaces in the selectively treated hut, the man-biting rate was similar with both types of treatments. Unfed mosquitoes were repelled less from selectively bendiocarb-treated surfaces. Similar reductions in postfed resting times were observed on all surfaces suggesting that once fed, mosquitoes rested on sprayed surfaces for shorter intervals of time. Engorged mosquitoes had normal resting behavior (pre- and postspray) within the range of preferred resting heights in both DDT- and bendiocarb-sprayed huts, but the proportion of mosquitoes fed in the DDT-treated huts was lower. Selective spraying of walls was as effective as spraying the complete walls with both insecticides, but DDT was more effective in reducing mosquito-human contact. These studies show that by more effectively targeting vector behavior, a cost-effective alternative to traditional control techniques can be achieved.

Animals↗
PubMed1997

Processes of change assessment in heroin addicts following the Prochaska and DiClemente transtheoretical model.

The processes of change dimension of Prochaska and DiClemente's transtheoretical model of change is tested in a sample of opiate addicts for the first time. A self-report (The Processes of Change Inventory for Opiate Addicts, PCI-OA) designed to assess the frequency of processes of change was administered in a sample of 178 heroin addicts in order to study its reliability, validity and discriminative efficiency. An alpha-reliability coefficient of 0.87 was obtained. A principal component analysis of the measure revealed a three-component solution which accounted for 34% of the variance: 'contemplation and preparation processes', 'processes of action', and 'processes of the final part of the action phase and maintenance'. Comparisons between abstinent and non-abstinent subjects revealed significant differences (P < 0.0001) in two of the ten processes considered: counterconditioning and stimulus control. A stepwise discriminant analysis yielded a linear combination of eight processes that correctly identified 78% of the total sample. Theoretical and clinical implications of the results are discussed, suggesting that the PCI-OA can be considered as a useful self-report instrument for identifying which processes of change are being used by a specific opiate-dependent patient.

Adult↗
PubMed1997

Study of pi-A Curves for Mixed Monolayers of Cyclosporin and Poly(dl-Lactic Acid-co-Glycolic Acid) Spread at the Air/Water Interface

Mixed monolayers of CyA and poly(dl-lactic acid-co-glycolic acid) spread at the air/water interface were studied by measuring surface pressure (pi) as a function of the area per residue (A). The pi-A curves suggest that the components are miscible below surface pressures of 10 mN/m. Also, the diagrams obtained by plotting the mean area per residue as a function of molar fraction show positive deviations from ideal, which indicate the existence of interactions between both components in the mixed films. The nature of these interactions was influenced by the pH and temperature of the subphase; however, it was not dependent on the molecular size of the polymer. Above pi = 10 mN/m mixed monolayers showed immiscible behavior with no interactions between their components. This was manifested by the obedience to the mean area additivity rule and the same value of collapse pressure present for all mixed monolayers studied.

Journal Article↗
PubMed1997

Cocaine use immediately prior to entry in an inpatient heroin detoxification unit as a predictor of discharges against medical advice.

Detection of benzyolecgonine, the major metabolite of cocaine, in the urinalysis conducted on the first day of an inpatient heroin detoxification treatment program was studied as a predictor of discharge against medical advice (AMA). With this aim, we conducted a chart-review procedure of 275 heroin dependents (DSM-III-R) who received methadone or dextropropoxyphene chlorhydrate to treat Opioid Withdrawal Syndrome. Data were analyzed following a case-control design. The 49 (17.8%) patients who did not complete the treatment due to discharged AMA were characterized by having achieved total heroin abstinence during fewer months from the time they began consumption of this substance to the time of hospitalization (p = .001). Moreover, those patients who requested discharge AMA were characterized by more frequent detection of benzoylecgonine in their urine on the day of admission (p = .004). The value of the odds ratio of this association was 3.81 (95% CI; 1.30 to 11.04). Lastly, noncompleters due to discharge AMA were more likely to be single than ever married (p = .037). The logistic regression model confirmed that there is a significant relationship between an AMA event and the presence of benzoylecgonine in urine upon beginning detoxification and to a shorter duration of the period of total heroin abstinence. In the discussion, the influence that recent interruption of cocaine consumption has on the decision to drop out of a detoxification program AMA is considered.

Analgesics, Opioid↗
PubMed1996

[Internal medicine in a group of 52 Spanish hospitals. Analysis of a case series and efficiency].

BACKGROUND: To analyze the case-mix and efficiency in a group of Services of Internal Medicine (IM) from 52 Spanish hospitals with routinary clinical information system. METHODS: From a total amount of 566,726 discharges during 1992, we studied the 71,430 corresponding to IM, analyzing the Minimum Basic Data Set and the Diagnosis-Related Groups (DRG). The hospitals were classified as level A (< 250 beds), B (251-599) and C (600 or over). We analyzed: Major Diagnostic Category (MDC); DRG, raw average length of stay (ALOS); outliers, trimmed ALOS; mortality; case-mix index; performance index; ajusted ALOS (by standard performance and case-mix); associated complications; number of diagnoses per discharge. A Chi-square test was used for qualitative variables and a mean-comparison test (independent data) for the quantitative ones. RESULTS: Among the Internal Medicine Departments, IM was the Service that cared most patients, even more in the small-size hospitals. The most frequent DRG were: chronic obstructive pulmonary disease (COPD) 6.5% (DRG 088); simple pneumonia & pleuresy 6.1% (DRGs 089-090); heart failure 5.9% (DRG 127); stroke 4.5% (DRG 014); and angor pectoris 2.4% (DRG 140). The ALOS was shorter in the A-level hospitals (10.1 days) vs. B-level (11.6) and C-level (14.4). However, the trimmed ALOS was more homogeneous (A 8.8; B 9.9; C 11.7). The complexity indexes increased with the hospital level although the performance index also increased. CONCLUSIONS: The IM services provide care for a high percentage of hospital patients, especially in the small-size centers. In these, less complex patients are seen, with decreased comorbidity, complications and mortality and they solve their patients with shorter ALOS than the IM services in the large-size hospitals.

Adolescent↗
PubMed1995

The apomorphine test in heroin addicts.

Chronic administration of opiates to laboratory animals induces supersensitivity of the dopamine receptors in the cerebral areas innervated by the mesotelencephalic dopamine pathways. In humans, the in vivo study of the sensitivity of the dopamine neurotransmitter system in Parkinson's patients can be done by means of the apomorphine test, which consists of measuring the number of yawns induced by the subcutaneous administration of low doses of apomorphine (0.005 mg/kg). If chronic opiate use in humans, as in experimental animals, results in supersensitivity of the dopamine systems, the apomorphine test could differentiate between heroin addicts and healthy volunteers, with the former showing greater number of yawns. In order to test this hypothesis we carried out the apomorphine test in two groups of subjects: a group of male heroin addicts attending our Addiction Treatment Centre for detoxification and the other group consisting of healthy volunteer male university students. Results showed that subcutaneous apomorphine administration induced a greater number of yawns (p < 0.05) in the group of heroin addicts as compared with the group of healthy volunteers, suggesting that heroin addicts present an enhanced sensitivity of the dopamine nuerotransmitter system.

Adolescent↗
PubMed1994

Lessons from Sharing Hospital MBDS in the CAMISE project: need for further standardization.

Hospital MBDS is a powerful tool for improving the knowledge on hospital performance. Within CAMISE, a BIOMED research, a databank of about 4,000,000 discharges from 420 hospitals in 12 countries has been collected, and a lot of effort has been devoted to make them comparable and therefore useful for research purposes. Results from CAMISE shows important opportunities from cooperation of European level. It points out the need for making them available to researchers under the suitable conditions of confidentiality, security and control.

Data Collection↗
PubMed1994

Intradomicillary pre- and postfeeding behavior of Anopheles pseudopunctipennis of southern Mexico: implications for malaria control.

The intradomicillary pre- and postfeed resting behavior of Anopheles pseudopunctipennis was studied in an experimental house in southern Mexico. During resting periods (both pre-/postfeed) mosquitos had greater contact (landings) with the inner roof than with the walls and other surfaces. A comparison of mean landing frequency and overall resting time (pre-/postfeed) showed that a greater periodic and prolonged contact occurred prefeed, probably as a result of disturbed activity associated with host movements. Pre-/postfeed resting patterns on walls were limited to a 0.6-0.5-m-wide band, nearly 1 m from the floor, and to a narrower band on the roof, 0.3-0.2 m wide, approximately 2.3 m from the floor, respectively. We calculated that with a band width of 0.8 m on the walls and another band 0.8 m wide on the roof, 87.2% of the mosquitoes had at least one contact with either the wall, the roof, or with both surfaces, along with an overall mean resting time (pre-/postfeed) of 8.1 min/landing. These findings suggest that a high potential for control can be achieved by spraying preferred wall and roof resting sites in this region where the intradomicillary application of residual insecticide is the primary malaria control measure.

Animals↗