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Biomedical subjects

R Torres

Publications and source records attributed to R Torres.

At least 127 records · Page 7Linked to original sources
PubMed1989

Serum tartrate-resistant acid phosphatase and bone mineral content in postmenopausal osteoporosis.

Serum tartrate-resistant acid phosphatase (sTr-AcP) and bone mineral content (BMC) were measured in 29 women with postmenopausal osteoporosis and in 12 control women. Serum Tr-AcP was higher in osteoporotic patients than in controls and a negative linear correlation was found between sTr-AcP and BMC in osteoporotic women. These results suggest that sTr-AcP could be a useful marker for bone loss and consequently, for the measure of bone resorption rate in postmenopausal women.

Acid Phosphatase↗
PubMed1989

Ventricular vulnerability in diabetes and myocardial norepinephrine release.

Previously the authors have observed a reduction of the ventricular fibrillation threshold (VFT) in a mild diabetic model. This investigation examines the role of more severe hyperglycemia in altering the ventricular fibrillation threshold and how the sympathetic nervous system modulates the response. Alloxan diabetes was induced in eight male mongrel dogs 3-5 years of age (Group 2), for comparison with matched controls (Group 1). Hemoglobin A1c rose from 2.9 +/- .4-7.8 +/- .3% and body weight was maintained with daily insulin. After 1 year, anesthesia was induced with chloralose and an electrode catheter placed at the right ventricular apex. VFT was 41.7 +/- 1.8 ma in Group 1 and 27.8 +/- 2.1 ma in the diabetics of Group 2 (p less than .001). There was significantly greater decline of VFT in response to epinephrine infusion in Group 2. The threshold in diabetics rose to normal levels after infusion of the beta-blocking agent, esmolol. Subsequently, the response of the cardiac sympathetic system was assessed during ventricular pacing at 200 beats/minute. Serial paired blood samples were taken from catheters in the aorta and coronary sinus for catecholamine assay by HPLC. Both groups had similar coronary blood flow responses by the thermal method, as well as changes in arterial pressure. While no change occurred in Group 1, a progressive rise of norepinephrine (NE) concentration was observed in coronary venous effluent of Group 2 (p less than .01). The basal arterial-coronary sinus difference was-123 +/- 52 pg/ml, which rose during pacing in Group 2 to a peak of -376 +/- 9.3 pg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Osteocalcin and bone remodelling in Paget's disease of bone, primary hyperparathyroidism, hypercalcaemia of malignancy and involutional osteoporosis.

We have measured classic markers of bone turnover, serum alkaline phosphatase (sAP), urinary hydroxyproline/creatinine ratio (uOH-Prol/creatinine) and osteocalcin (sBGP), in two bone disorders characterized by an increase in bone remodelling, namely Paget's disease of bone and primary hyperparathyroidism (PHPT) and in two other bone diseases characterized by an increase in bone resorption without the concomitant increase in bone formation, hypercalcaemia of malignancy (HM) and involutional osteoporosis (IO). Serum BGP was increased in patients with Paget's disease of bone (6.7 +/- 3.1; n = 25; p less than 0.01) and in PHPT patients (8.3 +/- 5.3; n = 20; p less than 0.005) with respect to control patients (4.2 +/- 1.2 ng/ml; n = 12). Two subgroups of patients with high and normal levels of sBGP were found in both pathologies. Serum BGP was decreased in HM patients (2.1 +/- 1.7; n = 9; p less than 0.01) and in IO patients (1.9 +/- 1.4; n = 31; p less than 0.001). Two subgroups of patients with normal and low sBGP values were found in these two last disorders. A positive linear correlation was found between sBGP and sAP (y = 14.6x + 73.7; r = 0.44; p less than 0.05) and between sBGP and uOH-Prol/creatinine (y = 0.008x + 0.007; r = 0.67; p less than 0.001) in Paget's disease of bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Effects of diabetes on myocardial perfusion in the atherosclerotic monkey.

We examined the influence of diabetes on the severity of coronary atherosclerosis, as judged by coronary morphometric and blood flow studies. Cynomolgus monkeys were fed a coconut-peanut oil mixture plus cholesterol to induce the plaque lesions of atherosclerosis in nondiabetic (group 2) and diabetic monkeys (group 3). Group 1 consisted of chow-fed controls. After 18 months of hypercholesterolemia, the animals were anesthetized to assess myocardial blood flow, by use of radioactive microspheres. Transmural and inner/outer wall flow ratios were normal in the two lipid-fed groups in the basal state. Vasodilation after adenosine (0.45 mg/kg/min IV) elicited a more than threefold rise of transmural blood flow in group 1, and a significantly reduced increment in groups 2 and 3. The blood flow ratio was not different from unity in group 1 but declined to 0.69 +/- 0.03 in group 2 and 0.69 +/- 0.06 in group 3, with similar decrements of heart rate and aortic pressure. In contrast to results in group 1, left ventricular filling pressure rose and velocity of contractile elements declined to a similar extent in groups 2 and 3 after adenosine, consistent with myocardial ischemia. Morphometric measurements as well as chemical analyses were performed on the three major coronary arteries. The degree of intimal thickening and increase of cholesterol and collagen content were comparable in groups 2 and 3. Thus, in this model the plaque lesions of atherosclerosis did not appear to be intensified by diabetes. Moreover, the responses to adenosine in terms of myocardial underperfusion and mechanical dysfunction were comparable in the two experimental groups.

Adenosine↗
PubMed1988

Complex structure of the ribosomal DNA spacer of Cucumis sativus (cucumber).

The nuclear 18 S, 5.8 S and 25 S ribosomal RNA genes (rDNA) of Cucumis sativus (cucumber) occur in at least four different repeat types of 10.2, 10.5, 11.5, and 12.5 kb in length. The intergenic spacer of these repeats has been cloned and characterized with respect to sequence organization. The spacer structure is very unusual compared to those of other eukaryotes. Duplicated regions of 197 bp and 311 bp containing part of the 3'end of the 25 S rRNA coding region and approximately 470 bp of 25 S rRNA flanking sequences occur in the intergenic spacer. The data from sequence analysis suggest that these duplications originate from recombination events in which DNA sequences of the original rDNA spacer were paired with sequences of the 25 S rRNA coding region. The duplicated 3'ends of the 25 S rRNA are separated from each other mostly by a tandemly repeated 30 bp element showing a high GC-content of 87.5%. In addition, another tandemly repeated sequence of 90 bp was found downstream of the 3'flanking sequences of the 25 S rRNA coding region. These results suggest that rRNA coding sequences can be involved in the generation of rDNA spacer sequences by unequal crossing over.

Base Sequence↗
PubMed1987

Expression of the human B-cell surface protein CD20: alteration by phorbol 12-myristate 13-acetate.

The monoclonal antibody 1F5 recognizes human B-cell surface protein CD20 and can activate resting B cells; with this antibody we found CD20 to be a 35/37-kDa non-disulfide-linked protein. The protein has a pI of 7.5-8.0 and is phosphorylated in B-cell lines, tonsillar B cells, and peripheral blood B cells. Both CD20 surface expression and phosphorylation are increased on buoyant tonsillar B cells activated in vivo. Because phorbol 12-myristate 13-acetate (PMA) supports the activation signal initiated by monoclonal antibody 1F5, we studied the effect of PMA on CD20 expression. After brief incubation with mitogenic levels of PMA, the number of dense tonsillar B cells positive for CD20 protein transiently decreased. Paradoxically, the cells remaining positive had more surface CD20 than did control cells, and these remaining surface CD20 molecules were hyperphosphorylated. Furthermore, PMA not only induced phosphorylation of CD20 protein on Raji cells but also increased the internalization of CD20 molecules; both phosphorylation and internalization of CD20 molecules were decreased with the protein kinase C inhibitor palmitoyl carnitine. Conditions that increase CD20 phosphorylation are shown also to increase surface mobility of the molecule, suggesting that CD20 protein internalization may be a critical early event for B-cell entry into the G1 phase of the cell cycle.

Antibodies, Monoclonal↗
PubMed1987

Base sequence effects in double helical DNA. I. Potential energy estimates of local base morphology.

A series of potential energy calculations have been carried out to estimate base sequence dependent structural differences in B-DNA. Attention has been focused on the simplest dimeric fragments that can be used to build long chains, computing the energy as a function of the orientation and displacement of the 16 possible base pair combinations within the double helix. Calculations have been performed, for simplicity, on free base pairs rather than complete nucleotide units. Conformational preferences and relative flexibilities are reported for various combinations of the roll, tilt, twist, lateral displacement, and propeller twist of individual residues. The predictions are compared with relevant experimental measures of conformation and flexibility, where available. The energy surfaces are found to fit into two distinct categories, some dimer duplexes preferring to bend in a symmetric fashion and others in a skewed manner. The effects of common chemical substitutions (uracil for thymine, 5-methyl cytosine for cytosine, and hypoxanthine for guanine) on the preferred arrangements of neighboring residues are also examined, and the interactions of the sugar-phosphate backbone are included in selected cases. As a first approximation, long range interactions between more distant neighbors, which may affect the local chain configuration, are ignored. A rotational isomeric state scheme is developed to describe the average configurations of individual dimers and is used to develop a static picture of overall double helical structure. The ability of the energetic scheme to account for documented examples of intrinsic B-DNA curvature is presented, and some new predictions of sequence directed chain bending are offered.

Base Composition↗
PubMed1986

Arrhythmia susceptibility and myocardial composition in diabetes. Influence of physical conditioning.

Abnormal myocardial composition in diabetes mellitus has been described, but the effects on ventricular vulnerability have not been defined. We have assessed the susceptibility to arrhythmias in a canine model after 1 yr of mild diabetes induced by alloxan. Since physical conditioning can affect metabolic abnormalities in diabetes, this intervention has also been evaluated. Group 1 served as controls and groups 3 and 4 were diabetic. Animals in the latter group as well as nondiabetic controls of group 2 were exercised on a treadmill for the last 8 mo of the experiment. After 1 yr, anesthesia was induced with chloralose for vulnerability studies. The ventricular fibrillation threshold of 24.4 +/- 1.9 mA in group 3 was significantly less than in normals (45.1 +/- 2.2). Spontaneous arrhythmias were also more prevalent in diabetics during acute ischemia (group 3-A). Increased ventricular vulnerability after epinephrine infusion was present in the sedentary diabetes despite normal ventricular function responsiveness. In a superfused preparation of myocardium, resting membrane potential and action potential amplitude were normal in diabetics, and beta-adrenergic stimulation shortened repolarization more than in controls. Myocardial collagen concentrations, which included an interfibrillar distribution on morphologic examination, were increased in group 3. In the trained diabetics of group 4 the basal vulnerability thresholds and responses to epinephrine were normal. While myocardial collagen levels were normal, cholesterol and triglyceride increments persisted. Thus, in mild experimental diabetes, enhanced susceptibility to arrhythmias exists; this susceptibility may be based on a combination of nonhomogenous collagen accumulation affecting local conduction and increased electrophysiologic sensitivity to catecholamines.

Action Potentials↗
PubMed1985

Interaction of chronic cigarette and ethanol use on myocardium.

Chronic cigarette use is common in persons who habitually use other cardioactive agents that have been causally associated with heart disease. This study was undertaken to determine if cigarette use intensifies the abnormalities of myocardial function and composition observed in experimental alcoholism over an 18-month period. Young adult male beagles with tracheostomy were divided into four groups. There were 10 controls (group 1); 9 smoked seven cigarettes per day (group 2); 7 were fed ethanol as 20% of calories (group 3), and 6 received both ethanol and cigarettes (group 4). After a period of 18 months, left ventricular function was assessed under anesthesia. Heart rate, left ventricular end-diastolic pressures, and volumes (indicator dilution) did not differ in the four groups. An index of contractility derived by normalizing peak dP/dt for pre- and afterload was reduced significantly below the level of 2.41 +/- 0.7 cm/s in controls to 1.41 +/- 0.35 in group 2, 1.19 +/- 0.38 in group 3, and 1.28 +/- 0.17 in the ethanol cigarette group (each p less than 0.002). Arterial pressures were moderately elevated above group 1 in all three experimental groups without evidence of left ventricular hypertrophy. In contrast to smoking, which elicited no abnormalities of myocardial cation composition, ethanol reduced myocardial potassium and sodium in group 3 without a gain of water content. In group 4, no further decline of tissue cations was observed. Thus, cigarette use when combined with ethanol over a relatively long period produced no greater myocardial abnormalities than ethanol alone and may not be essential to the genesis of cardiomyopathy in alcoholics.

Alcohol Drinking↗
PubMed1983

Evidence of the existence of a factor that induces C3 receptors on bone marrow cells.

The existence of a molecule responsible for the induction of C3R receptors (C3R) on murine bone marrow cells (C3R inducer, C3RI) is demonstrated in lung conditioned media. The inducer of Fc receptors on murine bone marrow cells (FcRI) and the colony-forming factor MGI (macrophage and granulocyte inducer) are also identified from the same source. The three inducing factors are shown by molecular sieving chromatography and by isoelectric focusing in granulated gel to be three different molecules. The molecular weights estimated were of 35,000, 22,000, and 10,500 for C3RI, MGI, and FcRI, respectively, with isoelectric pH values of 3.9, 6.6, and 7.6 for the same molecules. The C3RI is assumed to be of protein nature, because the molecule lost its biologic activity after trypsin or heat treatment. In the two techniques used, the three peaks of activity were completely separated, suggesting that the induction of C3 or Fc receptors and colony formation are mediated by different molecules and thus regulated independently at the cellular level.

Ampholyte Mixtures↗