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Biomedical subjects

J Riba

Publications and source records attributed to J Riba.

At least 19 recordsLinked to original sources
PubMed2006

Influence of individual differences in the Behavioral Inhibition System and stimulus content (fear versus blood-disgust) on affective startle reflex modulation.

Inconsistencies among affective startle reflex modulation studies may be due to differences in the startle potentiation produced by the specific content of the images used, to individual differences in sensitivity to negative stimuli, or to the interaction of both factors. To explore this interaction, 52 undergraduates obtaining extreme scores on a self-report measure of the Behavioral Inhibition System (BIS) participated in an affective startle reflex modulation paradigm. A significant interaction between BIS group (high versus low) and image content emerged from the MANOVA. Comparing startle magnitude between fear and pleasant images, low BIS participants did not seem to show startle potentiation, whereas high BIS participants did. Both groups displayed potentiated startle during blood-disgust images. The present results suggest the importance of considering personality variables and their interaction with image content in the affective startle modulation paradigm.

Adult↗
PubMed2006

Quantifying drug-drug interactions in pharmaco-EEG.

A drug interaction refers to an event in which the usual pharmacological effect of a drug is modified by other factors, most frequently additional drugs. When two drugs are administered simultaneously, or within a short time of each other, an interaction can occur that may increase or decrease the intended magnitude or duration of the effect of one or both drugs. Drugs may interact on a pharmaceutical, pharmacokinetic or pharmacodynamic basis. Pharmacodynamic interactions arise when the alteration of the effects occurs at the site of action. This is a wide field where not only interactions between different drugs are considered but also drug and metabolites (midazolam/alpha-hydroxy-midazolam), enantiomers (ketamine), as well as phenomena such as tolerance (nordiazepam) and sensitization (diazepam). Pharmacodynamic interactions can result in antagonism or synergism and can originate at a receptor level (antagonism, partial agonism, down-regulation, up-regulation), at an intraneuronal level (transduction, uptake), or at an interneuronal level (physiological pathways). Alternatively, psychotropic drug interactions assessed through quantitative pharmaco-EEG can be viewed according to the broad underlying objective of the study: safety-oriented (ketoprofen/theophylline, lorazepam/diphenhydramine, granisetron/haloperidol), strictly pharmacologically-oriented (benzodiazepine receptors), or broadly neuro-physiologically-oriented (diazepam/buspirone). Methodological issues are stressed, particularly drug plasma concentrations, dose-response relationships and time-course of effects (fluoxetine/buspirone), and unsolved questions are addressed (yohimbine/caffeine, hydroxizyne/alcohol).

Brain↗
PubMed2005

Effects of tobacco smoking on the kinetics of the pupillary light reflex: a comparison between smokers and non-smokers.

BACKGROUND: The time course of the pupillary light reflex (PLR) is determined by the successive activation of parasympathetic and sympathetic innervations of the iris, latency and amplitude reflecting parasympathetic activity and recovery time showing mainly sympathetic activity. OBJECTIVE: To determine the effects of tobacco cigarette smoking on the PLR in smokers after an abstinence period of at least 12 h. METHODS: Ten smokers (mean 15.7 cigarettes/day) and 10 non-smokers participated in a randomised, non-intervention controlled, cross-over study that included a parallel control group. Smokers underwent two sessions with a time interval between 3 and 8 days; two recordings were taken at each session, separated by 20 min: session 1, without smoking, and session 2, smoking 3 cigarettes within a 30-min period. Non-smokers underwent one session; two recordings were taken separated by 20 min. At each recording, in both groups, PLR was elicited with four light flashes of increasing luminance. RESULTS: The relationship between PLR parameters and light intensity was linear in each subject. The slope of the regression line for relative amplitude increase versus intensity was significantly flatter in abstinent smokers than in non-smokers (p=0.033); the slope returned significantly after smoking (p=0.043). No other significant effects were obtained. CONCLUSIONS: Kinetic parameters of PLR provide a sensitive pharmacological test to detect cholinergic neurotransmission manipulation effects, as they seem to detect changes in moderate smokers after 12 h of abstinence, and their reversal on return to smoking. These results suggest an enhancement in the suppression of the parasympathetic oculomotor reflex arc rather than a facilitation of the sympathetic drive to the iris.

Adult↗
PubMed2003

Immunocytochemical evidence on the effects of glucocorticoids on type I collagen synthesis in human osteoblastic cells.

The effects of glucocorticoids on DNA synthesis and cellular function were assessed in cultures of human osteoblastic cells by using indirect immunoperoxidase staining with a type I antiprocollagen antibody and by measuring procollagen type I N and C propeptides (PINP, PICP) in the culture medium by radiometric methods. Likewise, we analyzed the correlation between intracellular immunostaining and procollagen propeptides released into the culture medium, as well as the correlation between PINP and PICP. Human osteoblasts were cultured with and without addition of dexamethasone (DEX) at two supraphysiological concentrations, 10(-6) M and 10(-7) M, for 24 and 48 h. Treatment with DEX at 10(-6) M was associated with a significant decrease in the percentage of cells showing intracellular type I procollagen immunoreactivity at 24 and 48 h ( P < 0.05). Similar effects were observed with 10(-7) M DEX. Dexamethasone 10(-6) M and 10(-7) M also induced significant decreases in PINP and PICP values after 24 and 48 h of treatment ( P < 0.05). The decrease in intracellular procollagen immunoreactivity and propeptide secretion was not associated with a reduction in DNA synthesis. A highly significant correlation was observed between the values of PINP and PICP in the culture medium as well as between the values of intracellular immunostaining and PINP and PICP ( P < 0.001). In conclusion, our results suggest that supraphysiological doses of glucocorticoids produce a direct inhibition on osteoblastic function through their effect on type I procollagen synthesis. Immunoperoxidase detection of type I intracellular procollagen as well as the quantification of PINP and PICP in the culture medium are reliable methods of assessing osteoblast function.

Alkaline Phosphatase↗
PubMed2003

Presumptive infection of a total hip prosthesis by Mycobacterium tuberculosis: a case report.

Infection of a total hip prosthesis by Mycobacterium tuberculosis (MT) is an uncommon complication. We report a patient with septic loosening of a total hip prosthesis with a presumptive diagnosis of MT infection. His previous history was negative to any form of tuberculosis, and there was no evidence of a primary focus on the radiological study of the chest. He was diagnosed initially as presenting aseptic loosening and revision surgery was performed. Six months after surgery, septic loosening was diagnosed. The prosthesis was then removed. The histological study showed caseum granulomas and acid-fast bacilli, and routine cultures of the synovial fluid were negative. Since only a positive Löwenstein culture would have confirmed the diagnosis with certainty, a presumptive diagnosis of MR infection was made based on the findings in the histological study. Tuberculostatic treatment was administered for 9 months. At six years follow-up no signs of infection are present, neither by clinical or radiological criteria.

Aged↗
PubMed2002

Basics of PK-PD using QEEG: acute/repetitive administration, interactions. Focus on anxiolytics with different neurochemical mechanisms as examples.

Utilizing computer-assisted quantitative analysis of the electroencephalogram (EEG) in combination with certain statistical procedures and under specific design conditions, it is possible to objectively evaluate the functional bioavailability of psychotropic substances in the target organ: the human brain. Specifically, one may determine whether a drug is active in the central nervous system (CNS) compared with placebo in humans, the dose effect (including nonmonotonic drug effects along the continuum range of concentrations) and the time effect (including time-dependent pharmacodynamic phenomena as tolerance and sensitization), as well as its activity in relation to the formulation and route of application. Methodological aspects are introduced, discussing the usefulness of evaluating different treatments, doses, time points, states, target variables, electrodes and even different groups. Several issues are raised in relation to acute vs. repetitive administration, particularly those dealing with statistical comparisons when making conclusions about acute, repetitive or superimposed effects, and in relation to human psychotropic interactions, such as mechanistic drug-drug interaction descriptions, drug metabolites and enantiomers, as well as the importance of acquiring drug plasma concentrations, elapse of time and topographic distributions to accurately identify its occurrence. PK-PD modeling is introduced as a tool to enlarge the scope of inferences that can be derived when using pharmaco-EEG. The examples presented in order to develop the arguments are mainly focused on anxiolytic compounds belonging to the different neurochemical groups, benzodiazepines and azaspirones. Questions that have yet to been resolved are also addressed.

Anti-Anxiety Agents↗
PubMed2001

Psychometric assessment of the Hallucinogen Rating Scale.

Reliability and convergent-discriminant validity of a Spanish version of the Hallucinogen Rating Scale (HRS) were assessed in two differentiated populations of hallucinogen users involving the retrospective assessment of drug effects. In Study 1 (immediate assessment), 75 European users of the South American hallucinogenic drink ayahuasca answered the HRS 4 h after drug intake in their habitual setting. In Study 2 (delayed assessment), 56 adult polydrug users answered the HRS and a short form of the Addiction Research Center Inventory (ARCI) recalling the effects they experienced when they last took a hallucinogen, in order to test the convergent-discriminant validity of HRS with the scales of the standard questionnaire used in most studies involving psychoactive drugs. The HRS scales showed increases after both the immediate and delayed retrospective assessment of drug effects. Reliability data indicated that four of the six scales show an acceptable level of internal consistency. Significant but limited correlations were found between the Perception and Somaesthesia scales and the ARCI LSD scale, pointing out the questionnaire's construct validity. Thus, the HRS was sensitive to hallucinogenic drug effects other than those elicited by intravenous N,N-dimethyltryptamine (DMT), for which it was originally designed, and showed reasonable reliability and convergent validity. Results suggest its usefulness in the evaluation of subjective effects elicited by psychoactive drugs with hallucinogenic properties, and constitute a preliminary approach to the effects of ayahuasca in European subjects.

Adolescent↗
PubMed2001

Subjective effects and tolerability of the South American psychoactive beverage Ayahuasca in healthy volunteers.

RATIONALE: Ayahuasca is a South American psychoactive beverage that contains the naturally occurring psychedelic agent N,N-dimethyltryptamine (DMT). This "tea" has been used for centuries in religious and medicinal contexts in the rain forest areas of South America and is presently gaining the attention of psychedelic users in North America and Europe. OBJECTIVES: In the present study, the psychological effects and tolerability of ayvahuasca were assessed. METHODS: Three increasing doses of encapsulated freeze-dried ayahuasca (0.5, 0.75, and 1.0 mg DMT/kg body weight) were administered to six healthy male volunteers with prior experience in the use of this tea, in a single-blind crossover placebo-controlled clinical trial. RESULTS: Ayahuasca produced significant dose-dependent increases in five of the six subscales of the Hallucinogen Rating Scale, in the LSD, MBG, and A scales of the Addiction Research Center Inventory, and in the "liking", "good effects" and "high" visual analogue scales. Psychological effects were first noted after 30-60 min, peaked between 60-120 min, and were resolved by 240 min. The tea was well tolerated from a cardiovascular point of view, with a trend toward increase for systolic blood pressure. Modified physical sensations and nausea were the most frequently reported somatic-dysphoric effects. The overall experience was regarded as pleasant and satisfactory by five of the six volunteers, while one volunteer experienced an intensely dysphoric reaction with transient disorientation and anxiety at the medium dose and voluntarily withdrew from the study. CONCLUSIONS: Ayahuasca can be described as inducing changes in the perceptual, affective, cognitive, and somatic spheres, with a combination of stimulatory and visual psychoactive effects of longer duration and milder intensity than those previously reported for intravenously administered DMT.

Adult↗
PubMed2001

Differential effects of alprazolam on the baseline and fear-potentiated startle reflex in humans: a dose-response study.

RATIONALE: The "fear-potentiated startle" paradigm has been extensively used in animal studies, and more recently in human experimental psychopharmacology to evaluate the effects of anxiogenic and anxiety-relieving drugs. Previous human studies have shown that both the baseline and the fear-potentiated responses can be inhibited by anxiety-relieving drugs, suggesting drug activity on two different emotional states, the former reflecting a resting condition and the latter more akin to pathological anxiety. OBJECTIVES: To examine to which extent the reductions induced by a benzodiazepine on the basic and the fear-potentiated startle responses are of equal intensity, and whether or not the drug shows a predominant, i.e., selective, effect on either. METHODS: The effects of three increasing doses of the benzodiazepine alprazolam (0.25, 0.5, and 1.0 mg) were assessed on the human baseline and fear-potentiated startle responses. Twelve healthy volunteers attended the laboratory on four experimental days and received either alprazolam or placebo according to a double-blind crossover balanced design. Startle recordings were undertaken 2 h after drug intake. Fear potentiation was implemented by means of an electric-shock-anticipation experimental procedure. Additionally, subjective self-reports of sedation and anxiety and psychomotor performance were obtained at 2 and 3 h, respectively, after drug administration. RESULTS: Alprazolam dose-dependently impaired psychomotor performance and produced increases in subjective anxiolytic activity and sedation, although the latter did not reach statistical significance. Additionally, the drug reduced the magnitude of the startle response both in the absence and in the presence of a threat-related cue, although a differentially greater inhibitory effect was seen on the fear-potentiated response as the dose increased. CONCLUSIONS: Alprazolam showed a greater inhibitory effect on the fear-potentiated startle than on the baseline reflex, suggesting a more selective action of the drug on those structures mediating potentiation of the behavioral response by anxiety.

Acoustic Stimulation↗
PubMed2001

The use of proximal femoral allografts in revision total hip arthroplasty.

The implant of a proximal femoral structural allograft is one of the possibilities to restore circumferential defects of multiply revised total hip arthroplasties. A review of 7 patients who underwent proximal femoral reconstruction with an allograft-prosthesis composite to restore bone loss in revision hip replacements is presented. The average follow-up period was 50.2 months. Two patients developed an infection and in one case an instability of the prosthesis appeared. Incorporation in the remaining 5 cases was/achieved in an average period of 8.2 months. Neither fractures nor high rate of resorption appeared in our series. The majority of patients have improved in the functional assessment. Despite the rate of complications, structural femoral allografts can be used with success in this difficult challenge of reconstructing major segmental bone loss of the proximal femur in revision hip surgery.

Arthroplasty, Replacement, Hip↗
PubMed2000

Abnormalities of the acoustic startle reflex and reaction time in gilles de la tourette syndrome.

OBJECTIVE: To study the startle reflex and the effect of the startle reflex stimulus over reaction time (start-react effect) in Gilles de la Tourette syndrome (GTS). METHOD: Ten GTS patients and ten matched healthy volunteers underwent a simple RT paradigm (4 blocks of 50 trials). Forty acoustic startle reflex stimuli (110 dB) were randomly delivered with a 20% occurrence probability and presented unexpectedly at the same time as the imperative stimuli of the RT. Variables of interest were: amplitude, onset latency, degree of spread and rate of habituation of the startle response, and RT and the start-react effect caused by the startle stimuli. RESULTS: GTS patients showed a significantly higher amplitude, a major degree of spread and fewer habituation phenomena of the startle reflex. GTS patients showed poorer non statistically significant RT performance compared to controls, with a significant correlation between RT and severity of the disease. The start-react effect was significantly less pronounced in GTS patients. CONCLUSIONS: The present study confirms that GTS has an exaggerated startle reflex response and extend the spectrum of abnormalities to the start-react effect. A state of dopaminergic hyperactivity may have contributed to these results.

Adolescent↗
PubMed2000

Effect of cisapride on intestinal bacterial overgrowth and bacterial translocation in cirrhosis.

Deranged intestinal motility, which occurs in cirrhosis, may facilitate the development of intestinal bacterial overgrowth (IBO), which can lead to bacterial translocation (BT). To assess the effect of cisapride on IBO and BT in cirrhosis, cirrhotic rats received cisapride or a placebo for 7 days, and measurements of jejunal bacterial content and BT studies were performed. In addition, jejunal fluid from 46 cirrhotic patients was obtained for quantitative bacterial culture. Those patients in whom gram-negative IBO was detected were randomized to receive or not to receive cisapride (20 mg twice per day) for 1 week. Cisapride significantly reduced IBO in cirrhotic rats. In addition, no BT was documented in treated animals, whereas it occurred in 40% in nontreated cirrhotic rats. Total IBO was documented in 23 of 46 cirrhotic patients, which was caused by gram-negative organisms in 10 cases. Orocecal transit time (OCT) significantly decreased after cisapride therapy, and was associated with the abolishment of bacterial overgrowth caused by gram-negative organisms in 4 out of 5 treated patients, whereas it persisted in nontreated cases. Cisapride administration to cirrhotic rats resulted in a reduction of the IBO, which is associated with a marked decrease in BT. On the other hand, cisapride facilitates the abolition of IBO caused by gram-negative organisms in cirrhotic patients.

Adolescent↗
PubMed1999

Effects of alprazolam on the acoustic startle response in humans.

In the present study, we assessed the effects of the potent benzodiazepine alprazolam on the human acoustic startle response in healthy volunteers. Eight undergraduate students received single oral doses of placebo and alprazolam 2 mg on 2 separate days, according to a double-blind balanced crossover design. Electromyographic activity of the orbicularis oculi muscle was recorded 5, 7 and 11 h after drug administration. At each recording time, subjects received 21 acoustic stimuli (1 KHz, 116 dB, 50 ms duration) separated by variable intervals (8-30 s, mean 16.5 s). Consistent with previous results obtained for diazepam in humans, alprazolam significantly reduced the amplitude of the startle reflex. A patent increase in onset latency was also observed, this being a novel effect not previously described for benzodiazepines in human studies. Both effects were maximum at 5 h after dosing, the startle response experiencing a recovery as the drug disappeared from systemic circulation. These results indicate a potent inhibitory effect of alprazolam on baseline startle at the dose used, with a robust time-dependent recovery of initial values effectively counteracting between-session habituation.

Adult↗
PubMed1999

[Radio-guided surgery with MIBG in a case of abdominal neuroblastoma].

Radio-guided surgery is a new technique which can provide benefits for pediatric oncology, as in our patient with neuroblastoma in stage IV, that after a chemotherapy, surgical, radiotherapy and autologous bone marrow transplant treatment kept showing, at 2 years, residual tumoral fragments and increase of catecholamines. Radio-guided surgery allowed an easy and exact location. This technique decreases surgery time and let us find residual tumoral tissue no matter how small. With radio-guided surgery we can obtain higher survival and even cure the patient.

3-Iodobenzylguanidine↗
PubMed1998

[Transmyocardial revascularization with laser].

Patients with severe angina pectoris, refractory to medical treatment, in which conventional revascularization (PTCA or bypass surgery) is not possible because they present advanced coronary artery disease with a poor distal bed, account for an important clinical problem due to an increasing incidence, combined with poor quality of life, an elevated risk of severe complications, repeated hospital admissions and high mortality rate. Laser transmyocardial revascularization provides a new therapeutic alternative for these patients. Although up to now there are only a few published series, with a small number of patients, the results obtained in the two ongoing multicentric studies in Europe and the United States (including more than 500 patients at present) are quite promising. It is a simple surgical procedure, but its associated mortality is not to be dismissed (in the beginning 12% and currently 5%), because patients are in an advanced evolutionary stage. In Spain this procedure has been available since April 1996 and the results have been encouraging. In our small series we have noted a significant symptomatic improvement and better quality of life.

Aged↗
PubMed1998

[Obtaining myo-cardial perfusion images synchronized with the ECG (gated-SPEC) after injecting MIBI during exertion: comparative study with echocardiography in 95 patients for the assessment of left ventricular function].

Technical innovation has recently resulted in the routine use of gated-SPECT in myocardial perfusion imaging. In the present work we compare estimates of left ventricular function (LV cavity) by gated-SPECT with those of conventional echocardiography in a group of 95 ischemic patients, 49 of whom had previous myocardial infarction. Kappa analysis showed correlation coefficients of 0.67 for global function in the whole group and of 0.68 in patients with MI, as well as of 0.56 in the anterior wall, and 0.55 in the inferior wall. With these data, we believe that the technique is useful and it adds to the conventional perfusion SPECT imaging. Also, it is conveniently validated against echocardiography in our hands.

Adult↗
PubMed1998

[Painful tibial swelling in a young patient. Findings of radiology and radionuclide scanning. Anatomopathological correlation].

We report on the case of a young man with a longstanding tumor in the left proximal tibia, in whom we had the opportunity to correlate both radiologic (plain films plus MRI) and bone scintigraphic findings with those of biopsy and clinical follow-up. The final diagnosis was bone fibrous dysplasia. The correlation between noninvasive diagnostic findings is discussed, and the convenience of using such test combination is also stressed in order to endorse a noninvasive approach to such patients, given the low malignant potential, the exception being those patients in whom there is a definite fractures risk.

Adult↗