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Biomedical subjects

R Torres

Publications and source records attributed to R Torres.

At least 19 recordsLinked to original sources
PubMed1993

Antibodies to murine CD40 stimulate normal B lymphocytes but inhibit proliferation of B lymphoma cells.

A rat anti-mouse CD40 antiserum has been prepared by hyperimmunisation of Lewis rats with a highly purified preparation of the recombinant extracellular domain of murine CD40. This antiserum specifically binds CD40-expressing L cell transfectants, but not untransfected L cells, and induces vigorous proliferation of highly purified small dense B cells obtained from the spleens of unstimulated mice. Anti-CD40-induced B cell proliferation can be augmented by the addition of IL-4 and is inhibited by purified recombinant soluble mouse CD40. Interestingly the same anti-CD40 antiserum specifically inhibits the in vitro growth of A.20 murine B lymphoma cells. The specificity of this inhibition can be demonstrated by reversing the effect with purified recombinant soluble mouse CD40. These data implicate CD40 as a possible target for therapeutic intervention in the treatment of B lymphomas.

Animals↗
PubMed1993

Evaluation of penicillin acylase production by two strains of Bacillus megaterium.

Penicillin acylase is a key enzyme for the production of semisynthetic beta-lactam antibiotics. The intracellular enzyme from Escherichia coli has been thoroughly studied and characterized. The extracellular enzyme from Bacillus megaterium, despite its potential advantages, has received less attention in the recent scientific literature. A comparative study is presented for the production of penicillin acylase with two strains of Bacillus megaterium in batch fermentation in previously optimized complex and defined media. The enzyme produced by the selected strain has been recovered, partially purified and its kinetic behaviour determined.

Bacillus megaterium↗
PubMed1992

Genomic structure and chromosomal mapping of the murine CD40 gene.

The B cell-associated surface molecule, CD40, is likely to play a central role in the expansion of Ag-stimulated B cells, and their interaction with activated Th cells. In our study we have isolated genomic clones of murine CD40 from a mouse liver genomic DNA library. Comparison with the murine CD40 cDNA sequence revealed the presence of nine exons that together contain the entire murine CD40 coding region, and span approximately 16.3 kb of genomic DNA. The intron/exon structure of the CD40 gene resembles that of the low affinity nerve growth factor receptor gene, a close homolog of both human and murine CD40. In both cases the functional domains of the receptor molecules are separated onto different exons throughout the genes. Southern blot analysis demonstrated that murine CD40 is a single copy gene that maps in the distal region of mouse chromosome 2.

Amino Acid Sequence↗
PubMed1992

Baboon T cell lymphomas expressing the B cell-associated surface proteins CD40 and Bgp95.

Papio hamadryas baboons in the Sukhumi colony develop enzootic outbreaks of malignant lymphomas with an incidence of about 1.5% per year among adults of the high-risk stock. We investigated the surface phenotypes of cells from normal and lymphomatous animals using antibodies against human lymphocyte antigens. We found that more than 80% of the lymphomas that developed during the last 3 years were characterized histologically to be of the peripheral T cell type. Generally, the lymphomatous cells also expressed high levels of MHC class II DR protein, CD18 (LFA-1 beta chain), and CD45RO. Surprisingly, these cells also expressed on their surface two proteins previously characterized as being relatively B cell-restricted: CD40 and Bgp95. These proteins were never found on the peripheral blood T cells from normal animals. The expression of these two gene products was confirmed by RNA blotting and immunoprecipitation. In most cases, the two B cell-associated proteins were expressed on the predominant T cell subsets; we found both B cell proteins on CD4+, CD8+ as well as on the CD4/8 double-positive cells when these subsets were expressed at high levels. About 90% of these animals are seropositive for Herpesvirus papio and human T cell leukemia virus-1 (HTLV-1) before developing outright lymphomas. In all of the lymphoma samples, HTLV-1 tax DNA sequences were detected by PCR amplification. Whether or not HTLV-1 or the Herpesvirus papio gene products influence the surface expression of CD40 and Bgp95 remains to be determined.

Animals↗
PubMed1992

Myocardial inositol and sodium in diabetes.

Although inhibition of Na(+)-K+ ATPase has been described in the diabetic heart, K+ loss from myocardium has not been observed in a canine model of mild diabetes. The finding of tissue Na+ accumulation and a potential relation to alteration of left ventricular inositol as observed in other tissues in diabetes form the basis of this investigation. Diabetes was induced with alloxan in three groups of male mongrel dogs who were studied after 1 yr. In the initial experiment the tissue compartment volumes, determined with intravenous 51Cr EDTA as a marker, were found to be normal. Calculated cell sodium was increased to 32.8 +/- 2.6 mEq/kg cell H2O vs 18.7 +/- 1.1 in controls (p < 0.01). Cell potassium in diabetes was normal. In the second group, myocardial polyols were analyzed by gas-liquid chromatography. Inositol was diminished in diabetes to 0.61 +/- 23 microM/g of left ventricle, vs the respective control levels of 1.9 +/- 0.57 microM/g (p < 0.02). Sorbitol concentration was unaltered. Left ventricular sodium increments were not associated with altered tissue calcium. In group III the hypothesis that inhibition of Na(+)-K+ ATPase in diabetes might not elicit the expected alteration of K+ transport was assessed during intracoronary infusion of acetyl strophanthidin. No difference in cation responses from control was observed. It is postulated that a change in the conformation of Na(+)-K+ ATPase, with high affinity sodium binding sites facing the intracellular compartment, may render sodium less releasable from cell membrane.

Animals↗
PubMed1992

Myc and Max: a putative transcriptional complex in search of a cellular target.

Biochemical and genetic observations have supported the hypothesis that Myc family proteins function to regulate genes important in cellular growth and differentiation. The recent findings that Myc proteins can associate with other cellular proteins, possess sequence-specific DNA-binding activity and may directly transactivate transcription of several candidate genes have provided an experimental framework in which to test the transcription factor model. Based on principles established for several well characterized viral oncoproteins, a model is presented in which the regulation of Myc function is controlled by specific cellular protein interactions that serve to activate or repress transactivation activity or deny access of the Myc complex to its target sequences.

Animals↗
PubMed1992

Characterization of large-conductance chloride channels in rabbit colonic smooth muscle.

1. A large-conductance Cl- channel was characterized in cell-free membrane patches from the rabbit longitudinal colonic smooth muscle using the patch clamp technique. In addition, the regulation of these channels by neurokinin-1 (NK-1) receptor agonists and G proteins was studied. 2. No spontaneous channel activity was observed in cell-attached patches at the cell resting potential, or in excised patches at pipette potentials (Vp) between -20 and 20 mV. In excised patches, channel activity could be induced in thirty-six out of ninety-six patches by holding the patch at Vp values more negative than -60 mV or more positive than 60 mV. Once induced, the channel showed a bell-shaped voltage activation curve in high symmetric [Cl-], with maximal open probability between 20 and -5 mV. Varying cytosolic calcium concentration ([Ca2+]) between 5 x 10(-8) M and 1.0 mM had no effect on the voltage activation of the channel. 3. In inside-out and outside-out patches, when pipette and bath solutions contained equal [Cl-] (130 mM), the anion channel showed a linear current-voltage (I-V) relationship between -60 and 60 mV with a slope conductance of 309 +/- 20 pS (n = 13). Reversal potential measurements indicated that the channel was selective for Cl- over Na+ and K+ (PCl/PNa = 6:1). 4. Channel openings from the closed state to the full open state as well as transitions through smaller conductance states were observed. The smallest detectable substate had a conductance of 15.6 pS. Based on the similarities in selectivity and linearity of the I-V curve of the smaller conductances with the full open state, and kinetic analysis of channel activity, it is concluded that the large conductance channel is composed of multiple substates which can either open and close independently, or simultaneously via a main gate. 5. The stilbene derivative diiso-thiocyanato-stilbene-disulphonic acid (DIDS) and the diphenylamine-2-carboxylate analogue 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) caused a dose-dependent, reversible flicker block of the small conductance and significantly reduced the macroscopic current flow through the channel. 6. In quiescent outside-out patches, when the pipette contained a 140 mM-CsCl solution with 10(-6) M-CaCl2, 1.2 mM-MgCl2 and 1 mM-GTP, and the bath contained Ringer solution, addition of the NK-1 receptor antagonists substance P methylester resulted in activation of the full conductance state and of smaller substates.(ABSTRACT TRUNCATED AT 400 WORDS)

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1992

[Fasciola hepatica infestation. Biopathology and new diagnostic and therapeutic aspects].

We present here 6 patients with Fasciola hepatica infection, all from rural origin, and with the risk factors of eating wild watercress. The more common symptoms were: fever (83%), abdominal pain (100%), weight loss (83%) and generalized myalgia and joint pain (67%). All patients presented with an absolute eosinophil count above 1,000 cell/mm3. The diagnosis was established in five cases by means of serologic techniques (haemagglutination) and with direct visualization of adult worms while surgery in one case. A CT abdominal scan was performed in five patients, revealing specific lesions of tissue infiltration in four of them. Praziquantel was used in four patients, achieving clinical cure in three cases. In two patients, bithionol was used, with clinical cure in both cases. We review also some newer diagnostic and therapeutic approaches to this parasitic disease.

Adult↗
PubMed1991

The glucocorticoid hormone signal transduction pathway in mice homozygous for chromosomal deletions causing failure of cell type-specific inducible gene expression.

Wild-type newborn mice are characterized by the ability of certain liver-specific genes encoding various enzymes and mapping on different chromosomes to respond to glucocorticoid induction. Newborn mice homozygous for deletions at and around the albino locus on chromosome 7 fail to develop this competence for hormone-inducible gene expression even through they do show normal constitutive expression of the same genes. Studies of the glucocorticoid hormone signal transduction pathway reported here show identical expression of glucocorticoid receptor mRNA and protein in deletion homozygotes and normal littermates. Furthermore, the receptor interacts normally with the 90-kDa heat shock protein hsp90. Elevated glucocorticoid hormone levels in newborn deletion homozygotes, most likely resulting from their stressed condition, provide an explanation for the reduced binding activities of receptors reported previously. The elimination of receptors and hormones as direct targets of the chromosomal deletion effects suggests that the failure of inducible gene expression might reside in defective competence of the affected structural genes to respond to the hormonal stimulus.

Animals↗
PubMed1991

[Septic thrombophlebitis of the great vessels of the neck. A severe complication of central venous catheters].

Septic thrombophlebitis of the large veins of the neck is an uncommon, but extremely severe, complication in carriers of central venous catheters. Treatment of these cases is difficult and, generally, the clinical condition does not permit surgical approach. Four patients with septic central vein thrombophlebitis are reported. They were treated with conservative measures including catheter removal and high-dose parenteral antibiotics for at least four weeks, with excellent results in all. The relevant literature and the therapeutic alternatives are reviewed.

Adult↗
PubMed1991

Cellular immunodeficiency in Paget's disease of bone: changes induced by treatment with elcatonin.

We have found a cellular immune defect (low CD4 T lymphocyte count, high CD8 T lymphocyte count and a low CD4/CD8 ratio) in 39 PDB patients. This finding is not correlated with the bone metabolic activity of the disease. There was an improvement in the cellular immune defect in fifteen patients after treatment with elcatonin. These changes could be related to the improvement in the metabolic derangement or else could be the consequence of an effect on altered immunity.

Aged↗
PubMed1991

Clinical usefulness of serum tartrate-resistant acid phosphatase in Paget's disease of bone: correlation with other biochemical markers of bone remodelling.

Tartrate resistant acid phosphatase (TRAP) has been proposed as a new biochemical marker for bone resorption. We have compared this new marker, TRAP, with the classical biochemical markers of bone remodelling, serum alkaline phosphatase (sAP), serum osteocalcin (sBGP), and with the urinary hydroxyproline/creatinine ratio (uOHProl/creatinine), a routine marker of bone resorption. Serum TRAP was significantly higher in pagetic patients (n = 43) than in control subjects (n = 12) (13.02 +/- 4.7 vs 5.48 +/- 1.31 IU/L, P less than 0.001) and a significantly positive linear correlation was found between the sTRAP and uOHProl/creatinine ratio (y = 0.0051x - 0.0069, r = 0.82, P less than 0.001), between sTRAP and sAP (y = 19.3x - 85.0, r = 0.71, P less than 0.001) and also between sTRAP and sBGP (y = 0.02x + 2.23, r = 0.52, P less than 0.01). Serum TRAP levels were higher than the upper limit of normality in all our pagetic patients except for two, whose uOHProl/creatinine levels were in the normal range. We conclude that (1) sTRAP could be a parameter as sensitive as uOHProl/creatinine in the diagnosis of Paget's disease; (2) sTRAP and uOHProl/creatinine are both good markers of bone resorption; (3) the correlation found between sTRAP and formation markers (sAP and sBGP) makes sTRAP a marker of disease activity in Paget's disease of bone; (4) the assay of sTRAP is easier, faster, and of lower cost than the urinary hydroxyproline determination. We suggest that sTRAP determination could be used as a routine marker of bone resorption in Paget's disease of bone, as is the case with uOHProl determination.

Acid Phosphatase↗
PubMed1991

Binding of serum osteocalcin to hydroxyapatite in Paget's disease of bone.

Serum osteocalcin (serum bone Gla protein, sBGP) is elevated in diseases characterized by an enhanced bone turnover. However, in Paget's disease of bone there is a discrepancy between the low increase of sBGP and the high increase of bone remodelling assessed by serum alkaline phosphatase and urinary hydroxyproline. It is possible that the relatively low levels of sBGP reflect an abnormal binding of the molecule to the bone due to an alteration of the BGP molecule and/or of the pagetic mineral phase of bone. Another possibility would be a disregulation of BGP synthesis. In the present work we studied the binding of pagetic sBGP to an experimental model of mineral phase of bone (HPLC hydroxyapatite column). Serum of 14 patients with Paget's disease of bone (sBGP = 7.8 +/- 3.5 ng/ml) and of 14 control subjects (sBGP = 3.3 +/- 0.9 ng/ml) was purified through a Sephadex G-50 medium column (2.6 x 100 cm, 5 mM NH4CO3H). The BGP peak was lyophilized and resuspended in 1 mM KH2PO4, 1 mM CaCl2, 0.02% NaN3, pH 8.4, and then injected into an HPLC gradient system (Waters 660), from 1 to 300 mM KH2PO4 through a hydroxyapatite column (BioGel HPHT, Bio-Rad, 0.78 x 10 cm). A single peak of sBGP was obtained with a retention time of 12 min in control and pagetic patients. From these results we conclude that BGP binding to hydroxyapatite is similar in pagetic patients and in control subjects, suggesting that an alteration in BGP molecule is not responsible for an abnormal binding to the bone. In order to validate our system, the binding of serum BGP from warfarin-treated rats to the hydroxyapatite HPLC column was also studied and compared to binding of serum BGP from normal rats.

Aged↗
PubMed1991

Correlation between serum osteocalcin and 24,25-dihydroxyvitamin D levels in Paget's disease of bone.

We have studied the possible correlation between serum 24,25-dihydroxyvitamin D [24,25-(OH)2D] and osteocalcin levels (sBGP) in Paget's disease of bone. We measured serum calcium, phosphate, PTH, 25-hydroxyvitamin D, 1,25-(OH)2D, 24,25-(OH)2D, alkaline phosphatase (sAP), and the urinary hydroxyproline/creatinine ratio (UOH prol/creat) in 19 patients with Paget's disease of bone and 16 age- and sex-matched controls. As expected, sAP, UOH prol/creat, and sBGP levels were significantly elevated, and there was a tendency to a decrease in serum levels of 24,25-(OH)2D in Pagetic patients with respect to the control group. There was no significant difference between patients and controls in serum calcium, phosphate, PTH, 25-hydroxyvitamin D, and 1,25-(OH)2D. The Pagetic patients were subdivided into two subgroups; subgroup A had normal sBGP levels (less than 5 ng/mL), and subgroup B had increased sBGP levels (greater than 5 ng/mL). Serum 24,25-(OH)2D levels in subgroup B were significantly lower than those in controls, while subgroup A showed levels similar to those in the control group. We also found a positive linear correlation between sAP and sBGP and between sAP and UOH prol/creat as well as a negative linear correlation between sBGP and 24,25-(OH)2D and between 24,25-(OH)2D and UOH prol/creat in Pagetic patients. These results point to a possible role of 24,25-(OH)2D in disease activity.

24,25-Dihydroxyvitamin D 3↗
PubMed1991

[Endocarditis caused cy Erysipelothrix rhusiopathiae. Study of 2 cases and review of the literature].

Endocarditis produced by E. rhusiopathiae is a uncommon disease. Most of the infected persons (90%) work in environments with frequent exposure to E. rhusiopathiae (butchers, fisherman). Although the clinical picture of endocarditis produced by E. rhusiopathiae is indistinguishable from other forms of subacute endocarditis, this infection has a mortality rate of 40% and a high morbidity. Microbiological diagnosis should consider the possibility of making a mistake considering that isolation of a gram-positive bacillus may represent contamination by an agent without clinical relevance. Treatment with penicillin G during 4 weeks is commonly sufficient to cure the disease.

Adult↗