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R Blanco

Publications and source records attributed to R Blanco.

At least 163 records · Page 9Linked to original sources
PubMed1989

Role of association on protein adsorption isotherms. Beta-lactoglobulin A adsorbed on a weakly hydrophobic surface.

This paper explores the role of association on the adsorption isotherms of beta-lactoglobulin A on a weakly hydrophobic stationary phase at 4 degrees C and mobile phases of 0.85 M and 1 M ammonium sulfate, pH 4.5. The isotherms, obtained by frontal analysis, show an S-shape and the corresponding Scatchard plots indicate positive cooperativity. The slopes and intercepts of the Scatchard plots at low solute concentration are analyzed in terms of two species--a promoter and a higher order stronger adsorbing species. An explicit equation of the isotherm is developed based on this model, and this expression is shown to reproduce the isotherm shape using the appropriate derived parameters. It is further shown from this equation that a Langmuir-shaped adsorption isotherm can be obtained if the higher order associate or aggregate binds weaker to the support than the promoter. These results indicate that protein-protein interactions and the formation of associates can play a significant role on the shape of the isotherm and ultimately on the behavior of the species in preparative scale chromatography.

Adsorption↗
PubMed1989

Protein aggregation in high-performance liquid chromatography: hydrophobic interaction chromatography of beta-lactoglobulin A.

Aggregation of beta-lactoglobulin A under acidic buffer conditions was studied in hydrophobic interaction chromatography. At high ammonium sulfate concentrations, pH 4.5 and 4 degrees C, UV chromatograms revealed a maximum of three peaks for beta-lactoglobulin A concentrations greater than 5 mg/mL, suggesting three distinct aggregate species. The size of the smallest aggregate (tetramer) and its stoichiometric relationship to the other two aggregates (octamer and dodecamer) were determined from the chromatographic data and a simple mass balance model. These stoichiometries agreed with those determined in a separate study by on-line low-angle laser light scattering. In addition, the association constants describing the formation of octamer from two tetramer molecules and the formation of dodecamer from the octameric and tetrameric species were found to be (2.4 +/- 0.5) X 10(4) M-1 and (3.3 +/- 0.8) X 10(3) M-1, respectively. Analysis of the beta-lactoglobulin A system is based on a model in which aggregates form in solution upon injection before adsorbing to the column matrix. The column retains those species formed in solution and induces little change in the relative amounts of each species. These results illustrate another example by which multiple peaks can arise in high-performance liquid chromatography, beyond the previously described studies of protein conformational changes during chromatography.

Chromatography, High Pressure Liquid↗
PubMed1989

[Variations in arch and tooth size in the upper jaw of cleft palate patients].

The size of the upper dental arch and of the upper permanent teeth in a group of cleft lip/palate patients of both sexes, 12 years of age and older were compared to a control group of normal patients. Our results showed a significant size reduction in all of the longitudinal arch dimensions in cleft lip/palate patients. It was also seen a significant reduction of the intercanine and intermolar width dimensions. Mesiodistal and buccolingual teeth diameter reductions were observed in patients with left unilateral cleft lip and cleft palate, being this feature remarkable in the central and lateral incisors. Differences in size between antimeric teeth were only observed in upper lateral incisors in patients with left unilateral clefts. The relative influence of genetic and environmental factors on our patients was not determined with the results obtained in the present investigation.

Adolescent↗
PubMed1988

Antagonism of behavioral effects of bromocriptine by prolactin in female cats.

The effects of the dopaminergic agonist bromocriptine (BC) and exogenously administered prolactin (PRL) on the spontaneous behavior of female cats were investigated. The objective was to test whether BC-induced behavioral effects may be antagonized by PRL. BC (6 mg/kg ip) administration induced abnormal behaviors such as limb flicks, abortive grooms, head/body shakes, and hallucinatory-like behavior/escape as well as excessive grooming. PRL (5 mg/kg ip) administration induced biphasic changes in grooming. The first change was an increase in grooming frequency averaging 256% of baseline control values and lasting for 1 h. This change was followed by reductions in grooming of 75 and 82.5% below baseline during Hours 2 and 3 postinjection, respectively. Combined BC and PRL treatment antagonized the frequency of BC-induced motor effects such as limb flicks, abortive grooms, and head/body shakes. Limb flicks occurred nine times more often 2 h after BC alone than after BC and PRL. The combined treatment also antagonized the excessive grooming observed after separate administrations of BC and PRL. The observed interactions between PRL and BC behavioral effects support the notion that PRL may be an important modulator of dopamine-dependent motor behavior in female cats.

Animals↗
PubMed1988

Cholinergic neurotransmission in human corpus cavernosum. I. Responses of isolated tissue.

To investigate the role of cholinergic neurotransmission in erection, human penile corpus cavernosum tissue was studied. Electrical stimulation of strips of corpus cavernosum suspended in an organ chamber induced contractions and relaxations that were blocked by tetrodotoxin. The contractions also were blocked by bretylium and prazosin. Norepinephrine and phenylephrine contracted the isolated strips and this response was prevented by prazosin. Electrical stimulation-induced relaxations were enhanced by bretylium and physostigmine and partially blocked by atropine. The effect of atropine, but not that of physostigmine, was prevented by bretylium. Corporal strips contracted with norepinephrine relaxed to acetylcholine; this effect was blocked by atropine and enhanced by physostigmine. Strips lacking endothelium contracted normally with norepinephrine, but the relaxation caused by acetylcholine was virtually abolished. Thus endothelium lining the lacunar spaces within human corpus cavernosum is required for the relaxation caused by exogenous acetylcholine. There may be three neurotransmitter effector systems that control corpus cavernosum smooth muscle tone: adrenergic (excitatory), cholinergic (inhibitory), and nonadrenergic noncholinergic (inhibitory). Cholinergic nerves do not dilate or constrict directly the smooth muscle but may modulate other neuroeffector systems and/or the endothelium.

Acetylcholine↗
PubMed1988

Cholinergic neurotransmission in human corpus cavernosum. II. Acetylcholine synthesis.

Physiological and histochemical evidence indicates that cholinergic nerves may participate in mediating penile erection. Acetylcholine synthesis and release was studied in isolated human corporal tissue. Human corpus cavernosum incubated with [3H )choline accumulated [3H]choline and synthesized [3H]acetylcholine in a concentration-dependent manner. [3H]Acetylcholine accumulation by the tissue was inhibited by hemicholinium-3, a specific antagonist of the high-affinity choline transport in cholinergic nerves. Transmural electrical field stimulation caused release of [3H]acetylcholine which was significantly diminished by inhibiting neurotransmission with calcium-free physiological salt solution or tetrodotoxin. These observations provide biochemical and physiological evidence for the existence of cholinergic innervation in human corpus cavernosum.

Acetylcholine↗