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P Rodríguez

Publications and source records attributed to P Rodríguez.

At least 73 records · Page 4Linked to original sources
PubMed1990

Characterization of a protein:glucosyltransferase activity in human platelets.

Human platelets exhibited significant glucosyltransferase activity, that transfer [14C]glucose from UDP-Glc to an endogenous protein acceptor. The enzyme protein:glucosyltransferase responsible for the catalysis was characterized and compared with glycogen:glucosyltransferase. We describe a partial separation of both activities, the ratio of protein:glucosyltransferase/glycogen:glucosyltransferase varied from 7:1 in a crude homogenate of platelets to 36:1 in the Sephadex G-100 column. This procedure failed to separate the protein:glucosyltransferase from its endogenous acceptor. Glucosylation of protein demonstrated dependence with respect to time and both protein and UDP-Glc concentration, and was saturated by very low concentration of donor and acceptor substrates. It was inhibited 76% by 5 mM Mn2+ concentration and was activated 23 and 11% by 5 mM concentrations of Ca2+ and Mg2+, respectively. With respect to glycogen:glucosyltransferase, when the effect of time, protein, and substrate concentration were determined under identical conditions, it did not show the same dependence. At 5 mM concentration, Mn2+, Ca2+, and Mg2+ were activators of the enzyme 43, 80, and 200%, respectively. On the basis of these characteristics, we conclude that the synthesis of glucoprotein and glycogen are catalyzed by two distinct enzymes. Addition of exogenous glycogen (range 0.002-1%) inhibited the protein:glucosyltransferase, whereas at 0.001-0.007% concentration it was acceptor substrate for glycogen:glucosyltransferase activity. At higher concentrations this activity was strongly inhibited. The concentration of glycogen in platelets could play a regulatory role in forming the glucoprotein and the glycogen molecules.

Blood Glucose↗
PubMed1990

Squamous cell carcinoma of the penis.

Squamous cell carcinoma of the penis (CA Penis) is not a rare disease in P.R. We have reviewed all cases of CA penis diagnosed in our institution from Jan. 79-Jan. 89. Pathology and hospital records were audited. The survival data on all patients was updated via telephone or record review up to May 89. A total of 18 pts were seen in the last decade. Of these 11. (61%) were seen in the last four years. Four of 18 patients were excluded from analysis due to lack of staging and therapy data. The median age 54.9 y (range 23-82y). The following risk factors were identified: phimosis 12/14 (86%) p = .05, leukoplakia 8/14 (57%); prior venereal disease 1/14 (7%). The primary lesion appeared in the prepuce 8/14 (57%) and glans 6/14 (43%). TNM staging was done in all pts. Most pts presented with T3 or T4 disease 10/14 (71%) and palpable regional adenopathy (N1-N3) 9/14 (64%). Of the nine pts with palpable adenopathy, in 5 (56%) microscopic malignant disease was confirmed. A correlation between T3 or T4 disease and the presence of palpable adenopathy was seen (80%). The Stage at diagnosis of the 14 pts: I: 0/14 (29%), II: 5/14 (7%), III: 3/14 (21%), IV: 6/14; (43%). All pts were treated with partial penectomy and 7/14 had unilateral or bilateral inguinal lymphadenectomy. Long term survivors (LTS), greater than 12 mo., were seen 3/4 pts with Stage II disease, 1/3 Stage III, and 2/5 in Stage IV. The most important prognostic factor for LTS was malignant involvement of regional lymph nodes with 0/5 in this group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Urachal cyst. Current status of the problem].

Attention is focussed on urachal cysts, an uncommon disease entity recognized in 1 out of 5,000 autopsies performed in children. Two male patients, aged 47 and 30 years are described herein. Ultrasonography is considered to be necessary for diagnosing this disease. Treatment by complete removal of the cyst is advocated while others suggest the possibility of a more aggressive approach: removal combined with resection of a bladder anuria to avoid recurrence or development of a carcinoma.

Adult↗
PubMed1988

Galactosylation of endogenous proteins from human platelets.

Human platelets have been shown to contain the enzyme glycoprotein:galactosyltransferase that catalyzes the transfer of galactose to an endogenous protein acceptor present in the platelet. Galactosylation of added ovalbumin also occurs. The activity was extracted with 30 mM Tris buffer (pH 7.5). The endogenous activity was enriched 1.4-fold (compared with the crude homogenate) in the fraction, 105,000 g pellet, and the exogenous enzyme was retained in the respective supernatant. The two galactosyltransferase activities showed proportionality to time, protein, and substrate concentration, and were identical in pH dependence and Mn+2 requirement. The effect of Triton X-100 (range 0-1.5%) in the assay system appeared to be different for both activities: with the optimum concentration of detergent (0.15%) the endogenous activity increased by 50% whereas the exogenous activity was augmented 5-fold. From a number of sugar nucleotides tested as glycosyl donor into the endogenous proteins, the optimum substrate was UDP-Glc (100%), followed by UDP-Gal (80%), GDP-Man (24%), UDP-Glc-NAc (21%), UDP-Xyl (19%), and ADP-Glc (5%). An appropriate exogenous acceptor for UDP-Glc as donor was not found. The different solubilization of galactosyl- and glucosyltransferase activities by Triton X-100 suggests that they are distinct enzymes. In addition, the exogenous galactosyltransferase activity achieved after the treatment was much higher (940%) than the endogenous (26%). It is suggested that these differences on both galactosyltransferases could reflect changes in the accessibility of the exogenous substrate to the enzyme.

Blood Platelets↗
PubMed1987

Glycoprotein biosynthesis by human normal platelets.

Incorporation of radioactive Man, Gal, Fuc, Glc-N, and NANA into washed human normal platelets and endogenous glycoproteins has been found. Both parameters were time dependent. Analysis of hydrolyzed labeled glycoproteins by paper chromatography revealed that the radioactive monosaccharide incubated with the platelets had not been converted into other sugars. Acid hydrolysis demonstrates the presence of a glycosidic linkage. All the effort directed to the demonstration of the existence of a lipid-sugar intermediate in intact human platelets yielded negative results for Man and Glc-N used as precursors. The incorporation of these sugars into glycoproteins is insensitive to bacitracin, suggesting no involvement of lipid-linked saccharides in the synthesis of glycoproteins in human blood platelets. The absence of inhibition of the glycosylation process in the presence of cycloheximide suggests that the sugars are added to proteins present in the intact platelets. These results support the contention that glycoprotein biosynthesis in human blood platelets observed under our experimental conditions is effected through direct sugar nucleotide glycosylation.

Bacitracin↗
PubMed1987

Effects of discrete medial preoptic hypothalamic lesions on the androgen gonadotropin feedback system in the male rat.

The effect of discrete lesions of the Anterior Medial Preoptic Area of the Hypothalamus (MPOA) in the control of pituitary gonadotropins in the adult male Wistar rat has been studied. Electrolytic lesions were made by passing an anodal current through tungsten electrodes. Electrodes were oriented stereotaxically into the MPOA and lesion placement was histologically checked. In sham controls, electrodes were lowered into the MPOA but no current was applied. Serum LH and FSH were measured by RIA. MPOA lesioned animals showed significantly lower plasma LH (p less than 0.01) in comparison to sham lesioned group. Plasma FSH remained unaltered. To test whether these results were related to an alteration in the negative feedback system, the response to administration of Testosterone Propionate (TP) and the secretion patterns of LH and FSH after castration were analyzed. Administration of TP revealed similar LH and FSH 24 and 48 h decrements and the pattern of LH and FSH secretion after gonadectomy was not significantly different in lesioned and sham lesioned animals. Responsiveness to exogenous LHRH was not impaired by MPOA lesions. The results suggest that neural elements within the MPOA are functionally related to pituitary LH secretion in the male rat. The LH control alteration in lesioned animals is not associated with modifications in negative feedback of androgens and pituitary sensitivity to LHRH remains unaltered.

Animals↗
PubMed1986

Enzymatic dephosphorylation of retinyl monophosphate by rat liver.

Rat liver has been shown to contain an enzyme that catalyzes the dephosphorylation of retinyl monophosphate. This activity was extracted with 0.1 M Tris buffer (pH 7.5). Maximum reaction rate was observed at a pH range of 7.0-7.5. It did not require metal ions for activity and was sensitive to fluoride ion. The retinyl monophosphate phosphatase activity was proportional to time and protein and substrate concentration. Triton X-100 (range of 0.05-0.10%) increased the activity 100%, whereas other detergents (Tween 80, cholate, and deoxycholate) did not activate the enzyme. A number of phosphorylated compounds tested as inhibitors of retinyl monophosphatase activity, such as glucose 6-phosphate (20 mM), glycerophosphate (20 mM), phosphatidic acid (8 mM), and dolichyl phosphate (3 mM), did not compete with retinyl monophosphate as substrate. However, at 20 mM concentration, ATP, ADP, 5'-AMP, and pyrophosphate were inhibitors of the enzyme. It is not possible at present to give further details about the specificity of the phosphatase activity. The enzyme described could play a regulatory role in retinol-mediated glycosylations, by altering the endogenous level of retinyl monophosphate.

Animals↗