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Biomedical subjects

Miguel A Rubio

Publications and source records attributed to Miguel A Rubio.

9 recordsLinked to original sources
PubMed2004

Abnormal activity patterns in premotor cortex during sequence learning in autistic patients.

BACKGROUND: Evidence for frontal abnormality in autism has accumulated in recent years. Our own studies have shown abnormal activation in prefrontal cortex during finger tapping and visuomotor coordination. Studies in healthy adults suggest reduced premotor and increased prefrontal activity during advanced learning stages. We examined hemodynamic changes during visuomotor learning in autistic patients. METHODS: We studied eight high-functioning autistic patients and eight control subjects during learning of an 8-digit sequence over a period of 8 min, using functional magnetic resonance imaging. RESULTS: Autistic patients showed overall less prefrontal activation during late visuomotor learning; however, the main finding was a complementary one of enhanced activation in right pericentral and premotor cortex. In the autism group, Brodmann areas 3, 4, and 6 of the right hemisphere became more involved during late learning stages (trials 25-48), compared with early stages (trials 1-24). This effect was not seen in the control group. CONCLUSIONS: Our findings suggests that in autistic patients 1) primary sensorimotor and premotor cortex, which is normally predominant in early stages of visuomotor learning, plays an atypical role in later stages, even when learning is evident; and 2) handedness and side of execution interact with asymmetry of visuomotor learning activations, contrary to what is seen in normal adults.

Adult↗
PubMed2004

Telomere length mediates the effects of telomerase on the cellular response to genotoxic stress.

Telomerase inhibition may be a novel anti-cancer strategy that can be used in combination with conventional therapies, such as DNA damaging agents. There are conflicting reports as to whether and to what extent telomerase and telomere length influence the sensitivity of cells to genotoxins. To understand the relationship between telomere length, telomerase expression, and sensitivity to genotoxic stress, we expressed the catalytic subunit of telomerase, hTERT, in human fibroblasts having different telomere lengths. We show that telomerase confers resistance to ionizing radiation, bleomycin, hydrogen peroxide, and etoposide only in cells with short, presumably near-dysfunctional, telomeres. This resistance depended on the ability of telomerase to elongate the short telomeres, and telomerase did not protect cells with long telomeres. Interestingly, although long telomeres had no effect on sensitivity to etoposide and bleomycin, they exacerbated sensitivity to hydrogen peroxide, supporting the idea that, compared to other types of DNA damage, telomeres are particularly vulnerable to oxidative damage. Our findings identify a mechanism and conditions under which telomerase and telomeres affect the response of human cells to genotoxic agents and may have important implications for anti-cancer interventions.

Antineoplastic Agents↗
PubMed2003

Microstructure evolution in magnetorheological suspensions governed by Mason number.

The spatiotemporal evolution of field-induced structures in very dilute polarizable colloidal suspensions subject to rotating magnetic fields has been experimentally studied using video microscopy. We found that there is a crossover Mason number (ratio of viscous to magnetic forces) above which the rotation of the field prevents the particle aggregation to form chains. Therefore, at these high Mason numbers, more isotropic clusters and isolated particles appear. The same behavior was also found in recent scattering dichroism experiments developed in more concentrated suspensions, which seems to indicate that the dynamics does not depend on the volume fraction. Scattering dichroism experiments have been used to study the role played by the volume fraction in suspensions with low concentration. As expected, we found that the crossover Mason number does not depend on the volume fraction. Brownian particle dynamics simulations are also reported, showing good agreement with the experiments.

Anisotropy↗
PubMed2003

Comparison of free amino acids profile in honey from three Argentinian regions.

The physical chemistry characteristics of honey are directly related to floral origin and, as a result, to the production region. There are some available methods that can determine the botanical or geographical origin of honey such as the free amino acids profile analysis. This paper reports data on the free amino acid composition, determined by reversed-phase high-performance liquid chromatography UV detection on 56 honey samples from three different Argentine regions, with characteristic apiarian flora. To evaluate if the quantified amino acid could be used to verify the geographical or botanical origin of honey, statistical analyses were performed. The cluster analysis showed that samples were grouped in clusters related to sampling regions and more strictly to apiarian flora around apiaries. Each cluster appears associated, in accordance with the principal component analysis, to high or low concentrations of different amino acids.

Amino Acids↗
PubMed2002

Reversible manipulation of telomerase expression and telomere length. Implications for the ionizing radiation response and replicative senescence of human cells.

Most human cells do not express telomerase and irreversibly arrest proliferation after a finite number of divisions (replicative senescence). Several lines of evidence suggest that replicative senescence is caused by short dysfunctional telomeres, which arise when DNA is replicated in the absence of adequate telomerase activity. We describe a method to reversibly bypass replicative senescence and generate mass cultures that have different average telomere lengths. A retrovirus carrying hTERT flanked by excision sites for Cre recombinase rendered normal human fibroblasts telomerase-positive and replicatively immortal. Superinfection with retroviruses carrying wild-type or mutant forms of TIN2, a negative regulator of telomere length, created telomerase-positive, immortal populations with varying average telomere lengths. Subsequent infection with a Cre-expressing retrovirus abolished telomerase activity, creating mortal cells with varying telomere lengths. Using these cell populations, we show that, after hTERT excision, cells senesce with shorter telomeres than parental cells. Moreover, long telomeres, but not telomerase, protected cells from the loss of division potential caused by ionizing radiation. Finally, although telomerase-negative cells with short telomeres senesced after fewer doublings than those with long telomeres, telomere length per se did not correlate with senescence. Our results support a role for telomere structure, rather than length, in replicative senescence.

Blotting, Western↗
PubMed2002

Polarizable particle aggregation under rotating magnetic fields using scattering dichroism.

We used scattering dichroism to study the dynamics of dipolar chains induced in magnetorheological suspensions under rotating magnetic fields. Both the dichroism (proportional to the total number of aggregated particles) and the phase lag show different behavior below and above a cross-over frequency. The cross-over frequency depends linearly on both the square of the magnetization and the inverse of the viscosity. The Mason number (ratio of viscous to magnetic forces) governs the dynamics. Therefore, there is a cross-over Mason number below which the dichroism remains almost constant and above which the rotation of the field prevents the particle aggregation process from taking place. Our experimental results have been compared with particle dynamics simulations showing good agreement.

Journal Article↗
PubMed2002

Gastric surgery and restraint from food as triggering factors of eating disorders in morbid obesity.

UNLABELLED: Obese patients may share some clinical features with anorexia nervosa patients because they risk developing an eating disorder when they diet. Methods and Results Some common etiological, psychological, and social factors have been proposed for both disorders. We present two cases of patients suffering from morbid obesity who, after weight loss, presented an intense fear of regaining weight and developed anorexic-like symptoms. In the first case, the symptoms appeared after gastric reduction surgery. In the second case, a strict diet was the triggering factor. DISCUSSION: This paper stresses the need for psychiatric evaluation of all patients with morbid obesity who seek treatment in clinical settings, in order to identify the factors that may lead to psychiatric complications.

Adult↗
PubMed2002

Psychopathological status and interpersonal functioning following weight loss in morbidly obese patients undergoing bariatric surgery.

BACKGROUND: We questioned whether differences in psychopathological status and interpersonal relations exist in a group of morbidly obese patients 18 months after bariatric surgery, as related to extent of weight loss. METHODS: The study group consisted of 100 morbidly obese patients (85 female, 15 male) who had undergone surgical treatment (vertical banded gastroplasty) for weight reduction. Each patient completed the Lancashire Quality of Life Profile European version, the Eating Disorder Inventory, the Symptom Check List-90-Revised, and the Millon Clinical Multiaxial Inventory-II. The sample was divided into 2 groups according to the percentage of excess weight loss 18 months after surgery: a greater weight loss group (weight loss > 30%) and a lesser weight loss group (weight loss < 30%). RESULTS: Significant differences were found between the 2 groups in percentage of weight loss (P < 0.0001), negative self-esteem (P < 0.001), drive for thinness (P < 0.001), body dissatisfaction (P < 0.001), global EDI (P < 0.002), anxiety (P < 0.003), GSI (P < 0.002), avoidant (P < 0.001), borderline (P < 0.0001), and passive-aggressive (P < 0.002). CONCLUSION: Greater weight loss strongly correlates with improved quality of life, less disturbed eating behavior, and lower psychopathology. These results justify the clinical use of surgical procedures and demonstrate that weight loss has powerful psychological and psychosocial implications.

Adult↗