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Biomedical subjects

E García

Publications and source records attributed to E García.

At least 145 records · Page 8Linked to original sources
PubMed1996

Adenine nucleotides and intracellular Ca2+ regulate a voltage-dependent and glucose-sensitive potassium channel in neurosecretory cells.

Effects of membrane potential, intracellular Ca2+ and adenine nucleotides on glucose-sensitive channels from X organ (XO) neurons of the crayfish were studied in excised inside-out patches. Glucose- sensitive channels were selective to K+ ions; the unitary conductance was 112 pS in symmetrical K+, and the K+ permeability (PK) was 1.3 x 10(-13) cm x s(-1). An inward rectification was observed when intracellular K+ was reduced. Using a quasi-physiological K+ gradient, a non-linear K+ current/voltage relationship was found showing an outward rectification and a slope conductance of 51 pS. The open-state probability (Po) increased with membrane depolarization as a result of an enhancement of the mean open time and a shortening of the longer period of closures. In quasi-physio- logical K+ concentrations, the channel was activated from a threshold of about -60 mV, and the activation midpoint was -2 mV. Po decreased noticeably at 50 microM internal adenosine 5'-triphosphate (ATP), and single-channel activity was totally abolished at 1 mM ATP. Hill analysis shows that this inhibition was the result of simultaneous binding of two ATP molecules to the channel, and the half-blocking concentration of ATP was 174 microM. Internal application of 5'-adenylylimidodiphosphate (AMP-PNP) as well as glibenclamide also decreased Po. By contrast, the application of internal ADP (0.1 to 2 mM) activated this channel. An optimal range of internal free Ca2+ ions (0.1 to 10 microM) was required for the activation of this channel. The glucose--sensitive K+ channel of XO neurons could be considered as a subtype of ATP-sensitive K+ channel, contributing substantially to macroscopic outward current.

Adenine Nucleotides↗
PubMed1996

Demonstration of UDP-glucose dehydrogenase activity in cell extracts of Escherichia coli expressing the pneumococcal cap3A gene required for the synthesis of type 3 capsular polysaccharide.

The gene cluster of Streptococcus pneumoniae coding for the type 3 capsular polysaccharide contains four genes (cap3ABCD). A DNA fragment containing the cap3A gene was amplified by PCR and cloned under the control of a T7 RNA polymerase-dependent promoter. Overexpression of this gene in Escherichia coli resulted both in a 47-kDa protein in the cytoplasm of isopropyl-beta-D-thiogalactopyranoside-induced bacteria and in high levels of UDP-glucose dehydrogenase activity. These data demonstrate, in a direct experimental way, that cap3A encodes the UDP-glucose dehydrogenase of pneumococcus type 3.

Bacterial Capsules↗
PubMed1996

Quinine specifically inhibits the proteolipid subunit of the F0F1 H+ -ATPase of Streptococcus pneumoniae.

Streptococcus pneumoniae is uniquely sensitive to quinine and its derivatives, but only those alkaloids having antimalarial properties, i.e., those in the erythro configuration, also possess antipneumococcal activity. Quinine and related compounds inhibit the pneumococcal H+ -ATPase. Quinine- and optochin-resistant pneumococci showed mutations that change amino acid residues located in one of the two transmembrane alpha-helices of the c subunit of the F0F1, H+ -ATPase.

Amino Acid Sequence↗
PubMed1996

[LDL apheresis using a double filtration technique. Results after a 6-to-12 month follow-up in patients with refractory hyperlipemia and ischemic heart disease].

METHODS: Five patients with a family history of hypercholesterolemia were treated for one year with double filtered technique of LDL-apheresis: heterozygotic in four patient and homozygotic in one. All patients presented documented cardiovascular disease and had been treated unsuccessfully with lipid lowering drugs. RESULTS: Plasmatic cholesterol was significantly reduced from 463.8 +/- 60.9 mg/dl to 326.36 +/- 36 mg/dl at 6 months after treatment and 347.56 +/- 68.1 mg/dl at 12 months (p < 0.05). LDL was also reduced from 407.92 +/- 69.39 mg/dl to 294.04 +/- 62.02 mg/dl and 296.6 +/- 82.42 mg/dl respectively (p < 0.05) and Apo B was reduced from 291.84 +/- 28.97 mg/dl to 224.5 +/- 47.11 mg/dl at 6 and 12 months respectively, without significant modifications of other lipidic parameters and without adverse events. CONCLUSIONS: LDL-apheresis is a therapeutic approach effective in the reduction of total plasmatic cholesterol, in conjunction with to LDL and APO B in patients refractory to lipid lowering agents.

Adult↗
PubMed1996

Morphometry of uremic rat growth plate.

Growth retardation is a common manifestation of chronic renal failure in children. To gain insight into the alterations of bone growth plate of chronic uremia, a morphometric study of tibia proximal growth plate was performed in 5/6 nephrectomized rats (NX, n = 4) and sham animals (SHAM, n = 4). Toluidine blue stained sagittal sections (5-6 microns) from ethanol-fixed and methylmethacrylate-embedded tibias were analyzed. Widths (X +/- SEM) of growth plate (GPW), proliferative (PZW) and hypertrophic zones (HZW) were calculated. Results were as follows: [table: see text] Growth plate modifications in uremia are rather due to alterations in the hypertrophic than proliferative zone. This is consistent with an abnormal metabolism of condrocytes as shown by a lower mean area of extracellular matrix (EMA) per cell in the hypertrophic zone of the NX rats (0.23 vs. 0.58 microns 2).

Animals↗
PubMed1996

[Wiktor stent in de novo lesions: immediate results in 100 consecutive patients].

BACKGROUND: Randomized trials which compare different stents are lacking and the studies to test the behavior of the Wiktor stent in de novo lesions have not been substantiated by large numbers and with consistent results. METHODS: The lesions were predilated with a conventional balloon 1/2 mm smaller in diameter than the stent to be used. The overdilation was done with the same balloon in which the stent comes mounted. The quantitative coronary analysis was "off line" by the automatic edge detection method with the CMS system by Medis. The post implantation treatment was aspirin and ticlopidine in most of the patients and they were discharged 24-48 hours after the procedure. RESULTS: In one hundred consecutive patients 112 Wiktor stents were attempted to treat 106 de novo lesions. All stents but one were successfully implanted. The quantitative coronary analysis of the treated lesions showed a pre-procedure minimal luminal diameter of 0.85 +/- 0.65 mm for a reference diameter of 3.18 +/- 0.49 mm. The minimal luminal diameter after stent implantation was 2.97 +/- 0.39 mm for a reference diameter of 3.42 +/- 0.46 mm. The diameter stenosis changed from 73 +/- 18% pre-procedure to 13 +/- 9% after stent implantation. One patient was sent to emergency surgery. Another patient was referred for a semiselective bypass surgery. There was no mortality. One patient suffered a non Q wave myocardial infarction. There were no important bleeding complications. There were no cases of subacute thrombosis. All the patients were contacted by telephone one month after the procedure. CONCLUSIONS: In this study we have demonstrated that Wiktor stent implantation is associated with excellent immediate results. The new model makes stent implantation a rapid, safe and relatively easy procedure. If the angiographic result is good, there is no need for an stringent anticoagulation regimen. We have to wait for long term clinical and angiographic results to determine the role of Wiktor stent in novo lesions.

Coronary Disease↗
PubMed1996

[Renal hemangiopericytoma and secondary hypertension].

OBJECTIVES: Tumors arising from pericytes are rare; even more so are those located in the kidney. A case of renal hemangiopericytoma is described herein. The literature is reviewed with special reference to the unclear prognosis of the foregoing condition and the therapeutic approach. METHODS: A 51-year-old male with renal hemangiopericytoma who underwent radical nephrectomy is described. RESULTS/CONCLUSIONS: The arterial hypertension that had led to the diagnosis of this neoplasm remitted after surgery and can be considered to be a paraneoplastic manifestation.

Hemangiopericytoma↗
PubMed1996

[Registry of activities at the Section of Hemodynamics and Interventional Cardiology in 1995].

The results of the Spanish Registry of Hemodynamic and Interventional Cardiology are presented. Eighty hospitals have collaborated, which represent 100% of the cardiac catheterization laboratories. Seventy-two of which performed cardiac catheterization in adults and eight laboratories which exclusively performed pediatric cardiac catheterizations. We have studied 57,773 diagnostic procedures which were performed, which represents an increase of 11% from 1994. In addition, 12,359 angioplasties were performed, representing an increase of 18%. This represents 312 PTCAs per million people. PTCA success (91%) and global complications (3.2%) were similar to those of 1994. There was an increase in stent implantation: 3,418 procedures with 4,321 stents. This represents 1.26 stent per procedure. Sixty-four per cent of them were done electively and with a marked reduction in complications rate: subacute thrombosis, 1.6%, MI, 1.8% and a mortality of 1.1%. The number of mitral valvuloplasties decreases 16% and the pediatric interventional procedures (464) were similar to those of last year.

Adult↗
PubMed1995

Sequence and transcriptional analysis of a DNA region involved in the production of capsular polysaccharide in Streptococcus pneumoniae type 3.

The nucleotide (nt) sequence of a 9704-bp EcoRI fragment of Streptococcus pneumoniae (Sp) type-3 DNA has been determined and found to contain one partial and five complete open reading frames (ORFs). One of these ORFs corresponds to the cap3 A gene coding for the UDP-glucose (UDPGlc) dehydrogenase which is directly responsible for the transformation of some unencapsulated serotype-3 Sp mutants to the encapsulated phenotype [Arrecubieta et al., J. Bacteriol. 176 (1994) 6375-6383]. The two ORFs downstream from this gene (cap3B and cap3C) encode proteins with molecular masses of 49 and 34 kDa. Analysis of the deduced amino acid (aa) sequences of Cap3B and Cap3C shows homology to polysaccharide synthases and UDPG1c pyrophosphorylases, respectively. Furthermore, genetic complementation analysis showed that cap3C restored the galU defect of an Escherichia coli mutant. Northern blots have shown that cap3A, cap3B and cap3C constitute a single transcriptional unit, and primer extension analysis has revealed that the transcription start point is preceded by a nt sequence identical to the sigma 70 consensus promoter sequence of E. coli. The sequence upstream from this cluster also has a high degree of similarity with genes postulated to be essential for capsular production in several Gram+ bacteria. However, Northern blot analysis and insertion-duplication mutagenesis indicated that genes located in this region are not necessary for type-3 capsule production in the Sp strain 406.

Amino Acid Sequence↗
PubMed1995

Streptococcus pneumoniae type 3 encodes a protein highly similar to the human glutamate decarboxylase (GAD65).

A 2.5-kb ScaI fragment of the type 3 pneumococcal strain 406 DNA containing a 1425-nucleotide open reading frame (gadA) and encoding a 475-amino acid protein (M(r) 54,427) was characterised. The gene gadA was expressed in Salmonella typhimurium. Pulsed-field gel electrophoresis and Southern blotting analysis of DNAs prepared from several pneumococcal serotypes showed that only those clinical isolates belonging to serotype 3 harbour the gadA gene. Sequence comparison of GadA with proteins included in the data banks revealed the highest similarity with human glutamate decarboxylase (GAD65) (59% similarity, 28% identity). Auto-antibodies to GAD65 have been associated with the onset of insulin-dependent diabetes mellitus. Interestingly, several epitopes of GAD65 that have been identified as immunodominant are particularly well conserved in the pneumococcal GadA.

Amino Acid Sequence↗
PubMed1995

Expression of the human complex-forming glycoprotein HC (alpha 1-microglobulin) in Escherichia coli.

The mature form of human protein HC, or alpha 1-microglobulin, has been expressed in Escherichia coli. Protein HC is a member of the lipocalin superfamily of hydrophobic ligand-binding proteins, and carries a heterogeneous chromophore linked covalently by a reduction-resistant bond. Protein HC was first overexpressed as a C-LytA/HC fusion protein containing the C-terminal moiety of the pneumococcal lytic amidase (LytA). Recombinant C-LytA/HC was found to be an insoluble aggregate that was solubilized with 6 M guanidinium chloride and renatured by the addition of thiol reagents in the presence of L-arginine. Recombinant protein HC (rHC) was released from C-LytA/HC by trypsin digestion and purified by size-exclusion chromatography. rHC protein possesses an N-terminal amino-acid sequence identical to that of human protein HC, and a slightly lower molecular mass as determined by SDS-PAGE. Both C-LytA/HC and rHC reacted with polyclonal antibodies raised against native protein HC. A photodiode array detection system on-line with a HPLC system has allowed the identification of a chromophore associated to rHC protein displaying significant absorption in the visible region of the spectrum in resemblance to that found in the natural form of human protein HC.

Alpha-Globulins↗
PubMed1995

Hypoxia-selective agents derived from quinoxaline 1,4-di-N-oxides.

Hypoxic cells, which are a common feature of solid tumors, but not normal tissues, are resistant to both anticancer drugs and radiation therapy. Thus the identification of drugs with selective toxicity toward hypoxic cells is an important objective in anticancer chemotherapy. The benzotriazine di-N-oxide (SR 4233, Tirapazamine) has been shown to be an efficient and selective cytotoxin for hypoxic cells. Since the bioreductive activation of Tirapazamine is thought to be due to the presence of the 1,4-di-N-oxide moiety, a series of 3-aminoquinoxaline-2-carbonitrile 1,4-di-N-oxides with a range of electron-donating and -withdrawing substitutents in the 6- and/or 7- positions has been synthesized and evaluated for toxicity to hypoxic cells. Electrochemical studies of the quinoxaline di-N-oxides and Tirapazamine showed that as the electron-withdrawing nature of the 6(7)-substituent increases, the reduction potential becomes more positive and the compound is more readily reduced. Apart from the unsubstituted 6a and the 6,7-dimethyl derivative 6c, the quinoxaline di-N-oxides have reduction potentials significantly more positive than Tirapazamine (Epc -0.90 V). The most potent cytotoxins to cells in culture were the 6,7-dichloro and 6,7-difluoro derivatives 6i and 6l, which were 30-fold more potent than Tirapazamine. The 6(7)-fluoro and 6(7)-chloro compounds, 6e and 6h, showed the greatest hypoxia selectivity. Four of the compounds, 63, 6f, 6h and 6i, killed the inner cells of multicellular tumor spheroids in vitro. In vivo Balb/c mice tolerated a dose of these four compounds twice the size of that of Tirapazamine. This study demonstrates that quinoxaline 1,4-di-N-oxides could provide useful hypoxia-selective therapeutic agents.

Animals↗
PubMed1995

Postnatal handling reduces emotionality ratings and accelerates two-way active avoidance in female rats.

The present study evaluated whether postnatal handling (PH; administered daily during the first 21 days of life) could reduce anxiety or emotional reactivity in tasks of either spontaneous or conditioned fear-related behavior. To this purpose control nonhandled and postnatally handled female rats were submitted to three different behavioral tests: an emotionality rating (ER) followed by an elevated plus-maze test of anxiety in one experiment, and an acquisition of two-way active (shuttlebox) avoidance under two different training conditions in a separate experiment. Significant effects of PH treatment appeared in the three testing situations, clearly indicating an important and enduring reduction of emotionality/anxiety in PH-treated rats. Of special interest were the results of shuttlebox training: by shortening the conditioned stimulus (CS) and the intertrial interval (ITI) duration, avoidance acquisition was impaired as expected but the improving effects of PH were even more marked. The results are discussed in relation to previous studies reporting controversial results in the same (or similar) testing situations.

Animals↗
PubMed1995

[Alveolar lipoproteinosis treated by bronchopulmonary lavage].

Alveolar lipoproteinosis is a rare disease, a review of the Spanish Medical Index for 1971 to June 1994 showing only 9 reported cases. The intra-alveolar deposit of lipoprotein-type matter produces severe hypoxemia and favors infection by opportunistic germs. Treatment with massive bronchial lavage (MBL) removes the matter from the alveolar space, improves gas exchange and decreases the risk of infection. We report a case of primary alveolar lipoproteinosis treated with MBL in which the patient developed infections by Aspergillus fumigatus before lavage and after starting steroid treatment. The procedure was performed without complications, with significant clinical and gasometric improvement. The natural evolution of this disease is poorly understood. Spontaneous remissions have been observed, and as MBL is not a risk-free procedures, its use in treatment is controversial. We believe that when severe hypoxemia is present, MBL should be used early, when the risk is slight; MBL improves gas exchange and probably reduces the risk of opportunistic infection.

Adult↗