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Biomedical subjects

J Rodriguez

Publications and source records attributed to J Rodriguez.

At least 199 records · Page 11Linked to original sources
PubMed1991

A comparative study of histamine and K+ effects on (Ca(2+)-Mg2+)-ATPase activity in synaptosomes.

Histamine (10(-4) M) and 60 mM K+, but not 60 mM Na+ or 60 mM choline+, increased the maximal synaptosomal (Ca(2+)-Mg2+)-ATPase activity by 15 and 36% respectively and decreased the extrasynaptosomal Ca2+ concentration necessary to reach it. Histamine and K+ enhanced the synaptosomal (Ca(2+)-Mg2+)-ATPase activity in a concentration-dependent manner. In synaptic plasma membranes histamine (10(-4) M) and 60 mM choline+ were not able to alter the enzymatic activity, however 60 mM K+ and 60 mM Na+ elevated (Ca(2+)-Mg2+)-ATPase activity by 20 and 15%, respectively, without altering the affinity for Ca2+. Histamine effects in synaptosomes were mediated by H2 receptor stimulation. 3-Isobutyl-1-methyl-xanthine (10(-4) M) potentiated (15%) the maximal histamine effect. The slow Ca2+ channel antagonists verapamil and diltiazem, both at 10(-6) M, completely inhibited K+ effects in synaptosomes, however histamine effects were only blocked by verapamil. The data suggest that K+ and histamine effects on synaptosomal (Ca(2+)-Mg2+)-ATPase activity are mediated by increases of intrasynaptosomal Ca2+ levels. Moreover, histamine effects on synaptosomal enzyme activity were mediated by cAMP.

1-Methyl-3-isobutylxanthine↗
PubMed1991

Results of radiation therapy in carcinoma of the base of the tongue. The Curie Institute experience with about 166 cases.

Between 1960 and 1980, 166 patients with squamous cell carcinoma of the base of the tongue were treated with primary irradiation at the Curie Institute (Paris, France). Distribution according to the TNM system 1978 International Union Against Cancer (UICC) was the following: 22 T1 lesions, 47 T2 lesions, 64 T3 lesions, and 33 T4 lesions. Regional nodes were not palpable in 50 cases, 35 had N1 nodes, 12 had N2 nodes, and 69 had N3 nodes. All patients received external beam radiation. The 2-year, 3-year, and 5-year overall survival rates for all patients were, respectively, 45%, 37%, and 27%. Local control was significantly related to the initial status of the primary, to the tumor regression at the end of the radiation therapy, and to the histologic differentiation. The 2-year local control was 96% for T1 lesions, 57% for T2 lesions, 45% for T3 lesions, and 23% for T4 lesions. Local control was 70% if the tumor regression was complete at the end of the treatment and 27% if the tumor regression was partial. No significant differences were found in primary local control with respect to degree of infiltration, age, and dose of radiation therapy over a dose of 60 Gy in 6 weeks. The 3-year regional control was 86% for N0, 78% for N1, and 60% for N2 and N3. Among the tumor characteristics analyzed, the most useful ones for predicting local control and survival were clinical tumor staging parameters and tumor radiation-induced regression. A new therapeutic approach based on the evaluation of the tumor regression at 50/55 Gy is under discussion.

Adult↗
PubMed1991

Comparative study of the fatty acid composition of sponges of the genus Ircinia. Identification of the new 23-methyl-5,9-tetracosadienoic acid.

1. The phospholipid fatty acid compositions of the sponges Ircinia strobilina, Ircinia felix, Ircinia campana, Ircinia sp., Spongia tubulifera and Dysidea etherea were studied, revealing the presence, besides other common fatty acids, of considerable amounts (2-5%) of the novel 23-methyl-5,9-tetracosadienoic acid (1). 2. The demospongic acids 5,9-tetracosadienoic acid, 23-methyl-5,9-tetracosadienoic acid (1), and 5,9-pentacosadienoic acid, were particularly abundant in sponges of the genus Ircinia, in contrast to the most common 5,9-hexacosadienoic acid found in other species. These findings are discussed in terms of the taxonomy of the Dictyoceratida. 3. The complete characterization of the novel phospholipid fatty acid 23-methyl-5,9-tetracosadienoic acid (1) is presented.

Animals↗
PubMed1991

Differential regulation of cerebellar granule neurons by two types of quisqualate receptors.

Stimulation of the quisqualate (QA) subtype of glutamate receptor increased the expression of phosphate activated glutaminase (needed for neurotransmitter glutamate synthesis) and the ability to release neurotransmitter glutamate in cultures of glutamatergic cerebellar granule neurons. In contrast, QA had no significant effects on the lactate dehydrogenase activity and amount of protein. The QA-mediated elevation in glutaminase activity was blocked by the ionotropic QA receptor antagonist CNQX and mimicked by the ionotropic QA receptor agonist AMPA, but not by the metatropic QA receptor agonist t-ACPD. The increase in Ca2+ influx essentially through activation of L-type channels, and not the mobilization of internal Ca2+ stores, was responsible for these QA receptor-mediated long-term changes in cerebellar granule neurons.

2-Amino-5-phosphonovalerate↗
PubMed1991

Highly efficient expression of proteins encoded by recombinant vaccinia virus in lymphocytes.

Using a recombinant vaccinia virus (VV) that expresses E. coli beta galactosidase (beta-Gal) to infect lymphocytes, we show that enzymometrically or immunologically detectable beta-Gal expression is less pronounced among T cells than among B cells. VV infection caused growth inhibition of B cells, but barely affected T-cell proliferation in vitro. Moreover, the production of infectious viral particles was less pronounced in T lymphocytes. Kinetic studies revealed that after an initial dose-dependent growth inhibition, T cells continued to proliferate without the doubling time being affected by VV infection. Nonetheless, the T cells do express proteins encoded by recombinant VV, such as beta-Gal, or secrete soluble proteins such as interleukin-4, though at a lower efficiency at the per cell level than B lymphocytes. In conclusion, the physiology of T cells appears to be less perturbed by VV than that of B cells, although the virus is capable of directing expression of recombinant genes to T lymphocytes.

Animals↗
PubMed1991

Calcium effects on the solubilization of membrane-bound histidine decarboxylase in the rat brain.

In a previous work we have shown that histidine decarboxylase (HD) activity is found in a soluble and a membrane-bound form. A major part (82%) of the membrane-bound HD activity in the crude mitochondrial fraction (P2) was present in the synaptic plasma membrane-containing subfraction. Physiological concentrations of Ca2+ had no direct effect on HD activity but caused a solubilization of approximately 50% of membrane-bound HD in the P2 fraction. Mg2+ had similar but lower effects (20% solubilization) than Ca2+. Incubation with depolarizing concentrations of K+ in the presence of 1 mM CaCl2 caused a significant (30%) solubilization of HD.

Animals↗
PubMed1991

Individualising gentamicin dosage regimens. A comparative review of selected models, data fitting methods and monitoring strategies.

The various components required for individualising clinical drug dosage regimens are reviewed, including a study of 3 types of fitting procedures, 2 types of gentamicin pharmacokinetic model and the utility of D-optimal times for obtaining serum gentamicin concentrations. The combination of the current Bayesian fitting procedure, the kslope pharmacokinetic model [in which the elimination rate constant (kel) can change from dose to dose with changing creatinine clearance] and the explicit measurement of the assay error pattern yielded predictions of future serum gentamicin concentrations which were (a) slightly better than those found using weighted nonlinear least squares; (b) somewhat better than those found with Bayesian fitting and a fixed-kel model; (c) better than those found using the traditional linear regression fitting procedure and a fixed kel model. D-Optimally timed pairs of concentrations also predicted future concentrations at least as well, and more cost effectively.

Data Interpretation, Statistical↗
PubMed1990

Automatic definition of recurrent local structure motifs in proteins.

An automatic procedure for defining recurrent folding motifs in proteins of known structure is described. These motifs are formed by short polypeptide fragments of equal size containing between four and seven residues. The method applies a classical clustering algorithm that operates on distances between selected backbone atoms. In one application, we use it to cluster all protein fragments into only four structural classes. This classification is rough considering the observed diversity of local structures, but comparable in homogeneity to the four classes of secondary structure (alpha-helix, beta-strand, turn and coil). Yet, it discriminates between extended and curved coil and distinguishes beta-bulges from beta-strands. In a second application, the clustering procedure is combined with assignment of backbone dihedral angles to allowed regions in the Ramachandran map. This produces an exhaustive repertoire of highly homogeneous families of structural motifs that contains all the beta-hairpins, beta alpha- and alpha beta-loops previously defined by manual procedures, and new structural families of which two examples, a beta alpha-loop and an alpha-helix beginning, are analyzed in detail. The described automatic procedures should be useful in categorizing structure information in proteins, thereby increasing our ability to analyze relations between structure and sequence.

Amino Acid Sequence↗
PubMed1990

Relations between protein sequence and structure and their significance.

The relation between amino acid sequence and local structure in proteins is investigated. The local structures considered are either the four classes of secondary structure (H, E, T and C) or four classes of local conformations defined using measures of conformational similarity based on distances between C alpha atoms. The classes are obtained by applying an automatic clustering procedure to short polypeptide fragments of uniform length from a database of 75 known protein structures. The thrust of our investigation consists of systematically searching the database for simple amino acid patterns of the type Gly-X-Ala-X-X-Val, where X denotes an arbitrary residue. Patterns that are nearly always associated with the same structure are retained. Finding many such associations, we then evaluate by a statistical approach how many among them are non-random and compare the results for different definitions of local structure. A similar comparison is made for the predictive value of retained associations, which is assessed using an internal test based on dividing the database into "learning" and "test" subsets. While we find that local structures defined by conformational similarity are not superior to secondary structure for prediction purposes, they help us gain insight into the factors that influence the predictive value of derived associations. A major conclusion is that the number of retained associations is in large excess over the number expected from a random correlation between sequence and structure, irrespective of how local conformation is defined. However, only a very small number of these associations can be earmarked as reliable using statistical criteria, due to the limited size of the database. We find, for instance, that the pattern Ala-Ala-X-X-Lys reliably characterizes helix, and the pattern Val-X-Val-X-X-X-Ala reliably characterizes extended structure and beta-strand. The possibility is discussed that these and other reliable associations correspond to regions of the polypeptide chain whose conformations are locally determined and that these regions may play a role in folding.

Amino Acid Sequence↗
PubMed1990

Histamine increases ornithine decarboxylase activity in primary cultures of cerebellar granule cells.

The effect of histamine on the activity of ornithine decarboxylase (ODC) of cerebellar granule neurons was studied using primary cultures grown both in serum-containing medium and in chemically defined medium. In comparison with granule neurons grown in chemically defined medium, the activity of ODC was about twice as great in the neurons grown in serum-containing medium. Treatment of cultured cerebellar neurons with histamine caused a dose-dependent increase in ODC activity. The maximum elevation was observed at 500 nM of histamine, when the increase in ODC activity was about 50% and 120% over controls in granule cells grown in serum-containing medium and in chemically defined medium, respectively. Histamine had no significant effect on the activity of lactate dehydrogenase in these cultures. The present findings provided direct evidence for the involvement of histamine in the regulation of ODC-related non-mitotic growth of granule neurons in the cerebellum.

Animals↗
PubMed1990

Purification and properties of a beta-glucosidase from Penicillium oxalicum autolysates.

A beta-glucosidase from the medium of an autolyzed culture of Penicillium oxalicum has been purified by tannic acid precipitation, sephacryl S-200, DEAE-Biogel, CM-Biogel and Mono Q successively. The purification process produced a homogeneous band in the SDS-PAGE that correspond to a Mr of 133,500. The enzyme had a pl of 4, and the active optima were found at pH 5.5 and 55 degrees C. The enzyme hydrolyzed different substrates showing maximum affinity against p-nitrophenyl-beta-D-glucoside with a Km value of 0.37 mM. The beta-glucosidase was inhibited by Glucono-D-lactone but not by glucose in the concentration range of 1 to 10 mM. The enzyme was adsorbed by Concanavalin-A-Sepharose.

Glucosidases↗
PubMed1990

Cardiopulmonary resuscitation with simultaneous chest and abdominal compression: comparative study in humans.

To assess the efficacy of the simultaneous application of chest and abdominal compression (SCAC) in cardiopulmonary resuscitation (CPR), we performed a prospective study on 18 patients shortly after cardiac arrest. Three different CPR procedures were carried out consecutively: (1) Standard CPR; (2) CPR interposed with abdominal compression (IAC-CPR); and (3) SCAC-CPR. Standard CPR was repeated at the end of each sequence. Thoracic aortic and right atrial pressures were recorded during maneuvers and no vasoactive drugs were administered. Systolic aortic pressures were 39.02 +/- 21 mmHg, 63.6 +/- 21 mmHg and 94.04 +/- 21 mmHg during standard CPR, IAC-CPR and SCAC-CPR, respectively (P less than 0.001). There was no evidence of intra-abdominal injury in the eight autopsies performed. We have reached the conclusion that the use of SCAC-CPR on humans does produce greater intravascular pressure and we recommend this technique as a possible alternative to standard CPR.

Aged↗
PubMed1990

Definitive control of mortality from severe pelvic fracture.

Within a group of 271 patients with pelvic fracture, 69 patients met criteria for severe hemorrhage. Sixty consecutive patients were treated by a combined multispecialty musculoskeletal trauma service using a protocol designed to control bleeding, rapidly diagnose and control associated injuries, as well as to prepare the patient for open reduction of the pelvic fracture, if appropriate. The pneumatic antishock garment, external fixation, and angiography were selectively used to control bleeding. Abdominal injuries were diagnosed using clinical examination and diagnostic peritoneal lavage. When lavage aspirate was grossly bloody, patients had no negative explorations. Microscopically positive lavages were associated with a 50% false-negative rate. Using the protocol, the mortality rate was 5%. Overall mortality rate was 10%. The combination of a trauma team approach and a specifically designed protocol reduces the number of deaths from pelvic fracture.

Adult↗