Biomedical subjects

Alejandro Peña

Publications and source records attributed to Alejandro Peña.

4 recordsLinked to original sources

PubMed2006

Hexose-specificity of hexokinase and ADP-dependence of pyruvate kinase play important roles in the control of monosaccharide utilization in freshly diluted boar spermatozoa.

Incubation of boar sperm from fresh ejaculates in a minimal medium with 10 mM glucose induced a fast and intense activation of glycolysis, as indicated by the observed increases in the intracellular levels of glucose 6-phosphate (G 6-P) and ATP and the rate of formation of extracellular L-lactate. The effect of glucose was much more intense than that induced by fructose, sorbitol, and mannose. The greater utilization of glucose was related to a much greater sensitivity to hexokinase when compared with the other monosaccharides. Thus, the presence of 0.5 mM glucose induced total hexokinase activity in supernatants from sperm extracts of 1.7 +/- 0.1 mIU/mg protein, while the same concentration of both fructose, mannose, and sorbitol induced total hexokinase activity from 0.3 +/- 0.1 mIU/mg protein to 0.60 +/- 1 mIU/mg protein. Kinetic analysis of the total pyruvate kinase activity indicated that this activity was greatly dependent on the presence of ADP and also showed a great affinity for PEP, with an estimated Km in supernatants of 0.15-0.20 mM. Immunological location of proteins closely related to glycolysis, like GLUT-3 hexose transporter and hexokinase-I, indicated that these proteins showed the trend to be distributed around or in the cellular membranes of both head and midpiece in a grouped manner. We conclude that glycolysis is regulated by both the specific availability of a concrete sugar and the internal equilibrium between ATP and ADP levels. Furthermore, localization of proteins involved in the control of monosaccharide uptake and phosphorylation suggests that glycolysis starts at concrete points in the boar-sperm surface.

Adenosine Diphosphate↗

PubMed2006

Delay in the initiation of HAART, poorer virological response, and higher mortality among HIV-infected injecting drug users in Spain.

Differences in the uptake and time to initiation of highly active antiretroviral therapy (HAART), the virological response to HAART, and survival from AIDS by transmission category were analyzed. A multicenter hospital-based cohort of HIV-infected patients attending 10 hospitals in Spain from January 1997 to December 2003 was used. Cross-checks with the National AIDS Registry were performed. Cox proportional hazard models were used to assess the impact of transmission category on time to HAART initiation, viral suppression (defined by first HIV-1 RNA viral load measurement <500 copies/ml after HAART), and survival from AIDS. Of 4643 patients, 73% were men and 56% were injecting drug users (IDUs). A statistically significant interaction was found between transmission category and previous non-HAART antiretroviral treatment (ART) (p < 0.05). Among ART naive patients, IDUs had a 33% lower risk of initiating HAART compared to men who have sex with men (MSM) [HR 0.67 (95% CI 0.57-0.79)]. No differences by transmission categories were seen among patients with prior non-HAART ART. IDUs had poorer viral load (VL) suppression than MSM [HR 0.86 (95% CI 0.74-0.99)] adjusting by baseline VL, AIDS diagnosis, and prior ART. Mortality from AIDS was two and a half times higher in IDUs than MSM [HR 2.51 (95% CI 1.03-6.1)]. Among patients who access the hospital network, IDUs have a lower uptake of HAART, have worse virological suppression, and have higher mortality after AIDS diagnosis. There is a need to extend the programs in order to enhance access and adherence of IDUs to HAART and consider the treatment of drug addiction as an integral part of the treatment for HIV infection.

Adult↗

PubMed2004

Using emulsion inversion in industrial processes.

Emulsion inversion is a complex phenomenon, often perceived as an instability that is essentially uncontrollable, although many industrial processes make use of it. A research effort that started 2 decades ago has provided the two-dimensional and three-dimensional description, the categorization and the theoretical interpretation of the different kinds of emulsion inversion. A clear-cut phenomenological approach is currently available for understanding its characteristics, the factors that influence it and control it, the importance of fine-tuning the emulsification protocol, and the crucial occurrence of organized structures such as liquid crystals or multiple emulsions. The current know-how is used to analyze some industrial processes involving emulsion inversion, e.g. the attainment of a fine nutrient or cosmetic emulsion by temperature or formulation-induced transitional inversion, the preparation of a silicone oil emulsion by catastrophic phase inversion, the manufacture of a viscous polymer latex by combined inversion and the spontaneous but enigmatic inversion of emulsions used in metal working operations such as lathing or lamination.

Journal Article↗

PubMed2003

Glucose- and fructose-induced dog-sperm glycogen synthesis shows specific changes in the location of the sperm glycogen deposition.

Immunocytochemistry of glycogen deposition in dog sperm from fresh ejaculates showed that 53.7% of the population had glycogen at the midpiece, whereas 27.3% of the whole population accumulated glycogen only in the post-acrosomal region of the head. A similar distribution was observed when glycogen synthase, the enzyme which controls glycogen deposition, was studied. Incubation of spermatozoa with fructose increases the intracellular glycogen levels in a time- and concentration-dependent manner. Moreover, after incubation with 2 mM fructose for 30 min, 47.3% of the spermatozoa had glycogen located in both the midpiece and post-acrosomal zone, 25.4% of the population showed the polysaccharide only in the midpiece, and 24.7% of the spermatozoa showed a uniform distribution of glycogen all over the cell. Similar results were observed after incubation with 10-mM fructose. The distribution of glycogen synthase followed a similar pattern to that of glycogen. Incubation with glucose also induced a time- and concentration-dependent increase of glycogen content, whereas incubation with 2 mM glucose for 30 min showed that the majority of the population (81.2%) had the glycogen distributed throughout either the midpiece or the midpiece and the post-acrosomal zones together. There were practically no cells with a uniform glycogen distribution. Similar results were obtained after incubation with 10-mM glucose, whereas glycogen synthase suffered a similar glucose-induced distribution change. These results indicate that dog-sperm glycogen metabolism is modulated by changes in the activity of their controlling enzymes and also by changes in the specific location places where glycogen synthesis is produced.

Acrosome↗