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Biomedical subjects

P Ramos

Publications and source records attributed to P Ramos.

At least 73 records · Page 4Linked to original sources
PubMed1994

A new transgenic mouse model of chronic hyperglycemia.

Expression under the control of the mouse transferrin promoter of a transgene encoding a soluble secreted derivative of the ectodomain of the human insulin receptor in transgenic mice results in the accumulation of this high-affinity insulin-binding protein in the plasma. Alterations of glucose homeostasis are observed including postabsorptive hyperglycemia concomitant with increased hepatic glucose production and hyperinsulinemia. Thus, this is the first transgenic animal model of chronic hyperglycemia with alterations in glucose homeostasis that are produced without a targeted alteration of pancreatic function. These mice provide a new experimental model to follow the progression and long-term consequences of chronic hyperglycemia.

Animals↗
PubMed1994

Methotrexate treatment in the management of giant cell arteritis.

Eleven newly-diagnosed GCA patients were included in a prospective open study and treated with high initial prednisone doses, a quick-tapering CS schedule and weekly oral MTX for two years. It took a mean of 14 weeks to reach a 10 mg/day dose of prednisone and 29.8 weeks until steroid withdrawal. The mean cumulative dose of prednisone was 3.4 g. Two patients relapsed and five developed CS side effects. No serious MTX side effects were observed. Our results suggest that MTX is safe and could be useful in the therapy of GCA.

Aged↗
PubMed1994

Carbohydrate-lipid interactions during gestation and their control by insulin.

1. During the first two thirds of gestation, coinciding with a minimal accretion by the conceptus, the mother is in an anabolic state which is supported by her hyperphagia and the more efficient conservation of exogenous nutrients when she eats. During this phase maternal fat deposits are accumulated thanks to the enhancement in adipose tissue lipogenic and glycerologenic activity. In contrast, in the latter part of gestation, the rapid fetal growth is sustained by the intense transfer of nutrients from maternal circulation. 2. Glucose is quantitatively the most abundant of the several substrates that cross the placenta and despite increased maternal gluconeogenesis this transfer is responsible for the maternal tendency to hypoglycemia. This causes a switch to a net catabolic state which is especially evident in the net breakdown of fat depots. 3. Enhanced release of adipose tissue lipolytic products, free fatty acids (FFA) and glycerol, facilitates the liver synthesis of triglycerides and their later release into circulation associated to very low-density lipoprotein (VLDL). Glycerol is also used as an important gluconeogenic substrate and FFAs are broken down through beta-oxidation for ketone body synthesis. Flow through these pathways becomes increased when food is withheld and this actively contributes to the availability of fuels to the fetus which becomes partially preserved from maternal metabolic insult. Increased liver production of VLDL-triglycerides and decreased extrahepatic lipoprotein lipase contribute to exaggerated maternal hypertriglyceridemia which, besides being a floating metabolic reserve for emergency conditions such as starvation, constitutes an essential substrate for milk synthesis around parturition in preparation for lactation. 4. While the maternal anabolic tendencies found during the first two-thirds of gestation seem to be facilitated by hyperinsulinemia in the presence of a normal responsiveness to the hormone, it is proposed that most of the metabolic changes taking place during the last third of gestation seem to be caused by the insulin-resistant state which is consistently present at this stage, since its reversion caused by sustained exaggerated hyperinsulinemia also reverts several of these metabolic adaptations.

Adipose Tissue↗
PubMed1992

An assessment of human insulin receptor phosphorylation and exogenous kinase activity following deletion of 69 residues from the carboxyl-terminus of the receptor beta-subunit.

A mutant human insulin receptor with a carboxyl-terminal deletion of 69 amino acids (proreceptor residues 1287-1355) is expressed as a stable protein in transiently transfected COS cells. We find that in intact cells this mutant is phosphorylated in an insulin-dependent manner on core tyrosines 1158, 1163 and 1163. As expected, the carboxyl-terminal beta-subunit phosphorylation sites (serines 1305/6, tyrosines 1328/34 and threonine 1348) are absent from this mutant. However, the two major insulin-stimulated serine phosphopeptides remain. In intact cells, insulin stimulates exogenous substrate phosphorylation by the truncated receptor only approximately 1.9-fold (cf. approximately 9-fold for the wild-type receptor in these cells), a consequence of a approximately 4.8-fold elevation in basal insulin-independent kinase activity.

Amino Acid Sequence↗
PubMed1990

Structure of an exocellular polysaccharide produced by Streptococcus thermophilus.

Streptococcus thermophilus strains grown on skimmed milk produced a viscosifying, exocellular, and water-soluble polysaccharide which contains D-glucose, D-galactose, and N-acetyl-D-galactosamine in the ratio of 1:2:1. Methylation analysis identified the glycosidic linkages in the tetrasaccharidic repeating-unit, and Smith degradation and nitrous deamination after N-deacetylation gave the sequence of monosaccharides in the repeating-unit. The anomeric configurations of the sugar residues were determined by oxidation of the peracetylated polysaccharide with chromium trioxide and by 1H- and 13C-n.m.r. spectroscopy. The following structure was assigned to the repeating unit of the polysaccharide,----3)-beta-D-Galp-(1----3)-[alpha-D-Galp-(1----6)]-beta- D- Glcp-(1----3)-alpha-D-GalpNAc-(1----.

Acetylation↗
PubMed1989

Expression in heterologous cells of the unusual cytoplasmic domain of rat brain 5B4/NCAM-ld.

Monoclonal antibody 5B4 recognizes a carboxy-terminal epitope common to large (approximately 180 kDa) and short (approximately 140 kDa) forms of neural cell adhesion molecules (NCAM-ld and NCAM-sd, respectively). The deduced primary sequence of rat brain 5B4/NCAM-ld predicts a large cytoplasmic domain (390 amino acids, Mr 39,284) of striking amino acid composition (52% proline, alanine, serine and threonine) and little predicted alpha or beta secondary structure: its function is unknown. To directly test the deduced topology of the protein, and especially the solubility and stability of its unusual cytoplasmic domain, we have constructed a cDNA expression vector designed to express this domain independently as a soluble protein (designated 5B4cyt) in a heterologous cell system (simian Cos cells). 5B4cyt is indeed soluble, but migrates anomalously on SDS-PAGE under denaturing and reducing conditions as two species of approximately 77 and approximately 80 kDa. In pulse chase experiments, the approximately 77 kDa band chases into the approximately 80 kDa band with a t1/2 of approximately 1 h. The difference in mobility is apparently a consequence of the rapid phosphorylation of the approximately 77 kDa species. The approximately 88 kDa phospho-form is reasonably stable with a t1/2 of approximately 6 h. These results are consistent with the deduced topology of 5B4/NCAM-ld, and demonstrate the feasibility of this experimental approach for exploring the biochemistry and structure of its unusual cytoplasmic domain.

Animals↗
PubMed1989

Isolation and sequence of lambda gt11 cDNA clones encoding the 5B4 antigen expressed on sprouting neurons.

Monoclonal antibody (mAb) 5B4 recognizes a developmentally regulated membrane glycoprotein (Mr approximately 185,000-255,000) expressed on sprouting neurons. The amino acid sequence deduced from lambda gt11 cDNA clones encoding the transmembrane and cytoplasmic domains of the 5B4 antigen is co-linear with that of chick NCAM-ld. The significant level of overall sequence identity (75%) demonstrates that the 5B4 antigen is rat brain NCAM. The 5B4 epitope maps to the carboxy-terminus common to both NCAM-ld and NCAM-sd.

Amino Acid Sequence↗
PubMed1989

[Heterosexual transmission of HIV infection, Madrid 1987].

Seven males of 132 (5%) and 9 females of 85 (10%) out of 217 heterosexual individuals without addiction to drugs or previous blood transfusion who attended a STD clinic in Madrid because they had high risk sexual partners were found to have antiHIV antibodies by ELISA and immunofluorescence (CNMVIS). However, when variables such as sex, promiscuity and sexual habits were correlated with HIV infection, significant differences were not found between seropositive and seronegative individuals (kappa 2, p greater than 0.05). Among the factors statistically linked with the infection (kappa 2, p less than 0.05) there were the previous STD and the sustained sexual intercourse with proven HIV seropositive individuals: there 8 infected individuals out of 40 with such type of partners (relative risk 4.4). On the other hand, the partners of individuals with unknown serological findings had the following results: 4 seropositive individuals out of 71 partners of parenteral drug abusers, 3 of 82 users of prostitutes, and 1 infected individual out of the 24 remaining ones (partners of bisexual individuals or combinations) (relative risk of each of them less than 1). These results show the importance of heterosexual, not mediated by blood, HIV transmission in couples of high risk persons, and they suggest that the infection is highly likely if sexual intercourse is maintained with infected individuals irrespective of their sex.

Adult↗
PubMed1989

Peritoneal functional parameters after five years on continuous ambulatory peritoneal dialysis (CAPD): the effect of late peritonitis.

Functional stability of the peritoneum is essential for patients on long-term continuous ambulatory peritoneal dialysis (CAPD) treatment. Sixteen patients on CAPD treatment for at least 4 years were studied. Their mean age was 47 +/- 15 years, 5 were males, and none were diabetic. Residual creatinine clearance at the beginning was 2.1 +/- 2.6 mL/min. Once yearly since starting CAPD, we have evaluated their peritoneal ultrafiltration (UF) and diffusion capacities by calculating the peritoneal mass transfer coefficient (MTC, mL/min) for urea and creatinine. Patients were categorized so that we could distinguish the effect of peritonitis, betablockers, and hypertension. For all patients the average initial and final MTCs and UF values were not different. Early episodes of peritonitis (those occurring less than 36 months after starting CAPD) did not influence long-term function. However, late peritonitis (occurring greater than 36 months since initiation) induced a decrease in urea-MTC (22.3 +/- 6 to 15.8 +/- 3.9, p less than 0.05), creatinine-MTC (9.4 +/- 3.1 to 7.4 +/- 2.5, p less than 0.05), and a corresponding increase in UF (1.25 +/- 0.4 to 1.4 +/- 0.3, mL/min, p less than 0.05). Age, sex, betablockers and hypertension did not influence the peritoneal parameters followed. After 5 years on CAPD, functional stability of the peritoneum is evident, except for patients who suffer late episodes of peritonitis. We speculate that the peritoneum in patients who have been on long-term CAPD are more susceptible to injuries, such as peritonitis, and that this results in functional deterioration.

Adrenergic beta-Antagonists↗
PubMed1989

Induced changes of the peritoneal diffusion capacity by smoking, intraabdominal hypertension and omentectomy.

UNLABELLED: Peritoneal membrane suffers in some CAPD patients changes which modify its functionalism. In order to know whether these changes could be expected or appropriate, it is necessary to explore the general and particular conditions which can alter peritoneal physiology. Three aspects, smoking, intraabdominal hyperpressure and and omentectomy are situations which have not been included in the studies of peritoneal physiology. PATIENTS: The control group was constituted by 23 patients. Diabetics were studied as a separate group, with their own 10 patient controls. Smokers (1-20 cigarettes per day): 15 were non-diabetic patients, 9 were females. Diabetic smokers: 7 patients. Intraabdominal hyperpressure was determined by two big polycycstic kidneys (PCKD) in 8 patients, none diabetic. Omentectomy was performed in 6 non-diabetic and 9 diabetic patients. In all cases the procedure was prescribed because of an early catheter entrapment. Smoker patients show significant higher MTCs values for urea and creatinine than controls, but the slightly lower ultrafiltration value did not reached significant difference. Polycystic kidney patients showed lower MTCs values in respect to controls. Ultrafiltration capacity was similar. Omentectomized patients did not show any differences in respect to controls. In the diabetic patients group, neither ultrafiltration nor MTCs values presented significant differences between the established subgroups. So, smoking did not seem to induce higher MTC values as in the non-diabetic group. In conclusion, and according to the present results, two more situations should be taken into account in the evaluation of the peritoneal membrane dialyzing capacities: smoking, which increases diffusion capacity except for diabetics and PCKD with tow big kidneys, which decreases this capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1988

Efficient expression in insect cells of a soluble, active human insulin receptor protein-tyrosine kinase domain by use of a baculovirus vector.

The human insulin receptor (IR) is a transmembrane glycoprotein, whose cytoplasmic domain contains an insulin-activated protein-tyrosine kinase (EC 2.7.1.112). By the use of an appropriately engineered baculovirus expression vector, a soluble cytoplasmic derivative of this domain was expressed in the insect cell line Spodoptera frugiperda (Sf9). At 24 to 48 h after Sf9 cells were infected with recombinant virus, a protein of the size expected for this domain (approximately 48 kilodaltons) constituted a major band when total cell lysates of metabolically labeled cells were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. This protein (designated AchIRPTK) was immunoprecipitated by three monoclonal antibodies, each of which recognizes a distinct antigenic site of the IR cytoplasmic domain and requires the native structure of the protein for recognition and one of which binds at or near the physiologically relevant site(s) of IR autophosphorylation. In vivo, AchIRPTK was phosphorylated on both tyrosine and serine residues. When affinity purified, the kinase was active in vitro; it autophosphorylated exclusively on tyrosine residues, and phosphorylated the exogenous substrates histone H2b and poly(Glu-Tyr). The expression of an active IR protein-tyrosine kinase molecule in this heterologous cell system provides an efficient experimental method for producing this domain in quantity for enzymatic and structural studies.

Animals↗
PubMed1986

Mutagenicity of nickel sulphate in Drosophila melanogaster.

Nickel sulphate was injected into Drosophila melanogaster males at different concentrations in order to test the chemical for the induction of SLRL and SCL in germ cells. Nickel sulphate induced SLRL at concentrations tested, with the peak of activity at premeiotic and postmeiotic stages. It failed to produce SCL except at the highest concentration tested, where induction of XO males was significant for the pooled data.

Animals↗
PubMed1985

Sanfilippo disease, type A with some features of ceroid lipofuscinosis.

Light microscopic, histochemical and electron-microscopic studies were made on the brain of a case (No. 1) with Sanfilippo disease, type A. In this case pigment preparations of the isocortex have been demonstrated. Ultrastructural investigations of the skin biopsies (his two male siblings) were also studied (cases 2, 3). Our three siblings of MPS III A, have demonstrated ceroid lipofuscin storage in the brain (case No. 1) and skin biopsies (cases No. 2 and 3) in addition to histological features of MPS. The biochemical studies (enzymatic identification) were made in the cultures of fibroblasts. Also, urine quantitative studies for MPS and N-sulfonate to hexosamino ratio were performed.

Adult↗
PubMed1978

Ovarian arteriovenous fistula. An unusual cause of abdominal pain.

Arteriovenous fistulae of the ovarian artery may develop after gynecologic surgery. A case that occurred 9 years after hysterectomy with bilateral oophorectomy is presented and discussed. It illustrates an unusual cause of left lower quadrant abdominal pain. Surgical removal of the ovarian arteriovenous fistula resulted in complete relief of the patient's symptoms. This uncommon entity must be considered when dealing with lower quadrant pain and a past history of hysterectomy.

Abdomen↗