Search PubMed⌕ Search

Biomedical subjects

R Reyes

Publications and source records attributed to R Reyes.

At least 55 records · Page 3Linked to original sources
PubMed1998

Effects of alendronate on gastric and duodenal mucosa.

OBJECTIVES: This single-center, double-blind, randomized study assessed the effect of alendronate 5 and 10 mg on the gastroduodenal mucosa. METHODS: Overall, 95 postmenopausal women without a recent history of major upper gastrointestinal (GI) disease and not taking gastric-irritant drugs, were screened with an upper GI endoscopy. Fourteen women (15% of the total) were found to have baseline endoscopic gastric and/or duodenal abnormalities, including mucosal hemorrhages (n = 4), erosions (n = 11), and ulcers (n = 3). Two additional women had baseline esophageal abnormalities. Thus, 79 postmenopausal women (mean age 51 yr, range 41-64 yr), free of esophageal, gastric and/or duodenal erosions or ulcer, were enrolled. Subjects received placebo, alendronate 5 mg/day or 10 mg/day, or aspirin 650 mg q.i.d. for 14 days. Endoscopy was repeated on Day 8 and on Day 15. Gastric and duodenal mucosae were graded separately using a 5-point scale for erosive mucosal injury. RESULTS: The proportions of subjects with a gastric or duodenal erosion score > or = 2 (presence of at least one mucosal erosion) on either Day 8 or 15 were four of 22 (18.2%) in the placebo group; four of 22 (18.2%) in the alendronate 5 mg group; five of 21 (23.8%) in the alendronate 10 mg group; and 14 of 14 (100.0%) in the aspirin group. Thirty-five of 76 (46%) subjects were H. pylori-positive (Pyloritek test), and were equally distributed across treatment groups. CONCLUSIONS: Alendronate 5 and 10 mg/day for 2 wk was associated with a lower incidence of gastric erosions than aspirin. The incidence of gastric erosions in the alendronate groups did not differ significantly from the placebo group. In this study, unlike aspirin, alendronate did not induce gastric erosions.

Adult↗
PubMed1998

Expression of TWIK-1, a novel weakly inward rectifying potassium channel in rat kidney.

Several K+ conductances have been identified in the kidney, with specific properties and localization in distinct cell types and membrane domains. On the other hand, several K+ channels have been characterized at the molecular level. By immunolocalization, we show that a new inward rectifying K+ channel, TWIK-1, is specifically expressed in distinct tubular segments and cell types of the rat kidney. In the proximal tubule, TWIK-1 prevails in the initial portions (convoluted part), where it is restricted to the apical (brush-border) membrane. In the collecting duct, immunofluorescence was intracellular or confined to the apical membrane and restricted to intercalated cells, i.e., in cells lacking aquaporin-2, as shown by double immunofluorescence. TWIK was also expressed in medullary and cortical parts of the thick limb of the loop of Henle, identified with an anti-Tamm-Horsfall protein antibody (double immunofluorescence). The intensity of TWIK-1 immunolabeling was unchanged in rats fed a low-Na+ or a low-K+ diet. Because TWIK-1 shares common properties with the low-conductance apical K+ channel of the collecting duct, we propose that it could play a role in K+ secretion, complementary to ROMK, another recently characterized K+ channel located in principal cells of the cortical collecting duct and in the loop of Henle.

Animals↗
PubMed1998

[Endovascular treatment of abdominal aorta aneurysms using bifurcated endoprosthesis].

OBJECTIVE: To obtain an initial assessment of the implantation technique of bifurcated vascular endoprothesis in the treatment of abdominal aorta aneurysms (AAA). METHODS: Eleven Vanguard type endoprostheses were implanted in eleven patients with infra-renal aortic aneurysm. The technique was performed with surgical approach in one femoral artery, and percutaneously in the other. The procedure was performed with epidural anesthesia. RESULTS: A technical success--i.e., the exclusion of the aneurysm--was obtained in all cases. No technical complications occurred during the procedure. Three patients had low degree contrast leak in the angiographic control immediately after the procedure. Eight patients had low grade fever in the immediate follow-up which resolved with medical therapy, two patients had hematomas in the approach sites, one renal infarction, one ileus for two days, another one for five days, and three patients had lymphatic effusion. During follow-up the patients with leak had to undergo co-axial endoprosthesis implantation. CONCLUSIONS: It is our view that bifurcated vascular endoprostheses offer a valid alternative in the treatment of AAA. The procedure can be performed with epidural anesthesia and sedation, with a low rate of complications. The long term follow-up and the perfecting of the approach and resection systems will ultimately dictate their usefulness in this and other vascular conditions.

Aged↗
PubMed1998

[Percutaneous extraction of a foreign body from the right ventricle. Clinical case].

Percutaneous retrieval of intravascular foreign bodies has emerged as a standard method of treatment, which audits major surgery. This procedure was performed in a patient with a fragment of a broken introducer sheath located in the right ventricle with risk of arrhythmias. Extraction was difficult because the sheath was trapped in the tendinous cords. The foreign body was embolized to the pulmonary artery and extraction was performed. No clinically significant complications occurred.

Adolescent↗
PubMed1997

TASK, a human background K+ channel to sense external pH variations near physiological pH.

TASK is a new member of the recently recognized TWIK K+ channel family. This 395 amino acid polypeptide has four transmembrane segments and two P domains. In adult human, TASK transcripts are found in pancreas<placenta<brain<lung, prostate<heart, kidney<uterus, small intestine and colon. Electrophysiological properties of TASK were determined after expression in Xenopus oocytes and COS cells. TASK currents are K+-selective, instantaneous and non-inactivating. They show an outward rectification when external [K+] is low ([K+]out = 2 mM) which is not observed for high [K+]out (98 mM). The rectification can be approximated by the Goldman-Hodgkin-Katz current equation that predicts a curvature of the current-voltage plot in asymmetric K+ conditions. This strongly suggests that TASK lacks intrinsic voltage sensitivity. The absence of activation and inactivation kinetics as well as voltage independence are characteristic of conductances referred to as leak or background conductances. For this reason, TASK is designated as a background K+ channel. TASK is very sensitive to variations of extracellular pH in a narrow physiological range; as much as 90% of the maximum current is recorded at pH 7.7 and only 10% at pH 6.7. This property is probably essential for its physiological function, and suggests that small pH variations may serve a communication role in the nervous system.

Amino Acid Sequence↗
PubMed1997

Dichlorodiphenyltrichloroethane serum levels and breast cancer risk: a case-control study from Mexico.

Some, but not all, epidemiological studies have suggested that dichlorodiphenyltrichloroethane (DDT) may play a role in the development of breast cancer. These investigations have been conducted in countries where this substance has been banned for at least 20 years. We conducted a study in Mexico, a country in which DDT is still being used to control malaria. In a hospital-based case-control study, we compared 141 histologically confirmed cases of breast cancer with 141 age-matched controls (+/-3 years). All subjects were identified at three referral hospitals of Mexico City between March 1994 and April 1996. Reproductive histories and other variables were obtained by structured interviews, DDT/DDE levels were determined in serum by gas-liquid chromatography. The arithmetic mean of serum DDE in lipid basis was 562.48 +/- 676.18 ppb (range, 10.24-4661.44) for the cases and 505.46 +/- 567.22 ppb (range, 0.004 to 4361.75) for the controls, but this difference was not statistically significant. The age-adjusted odds ratios for breast cancer regarding the serum level of DDE were 0.69 (95% confidence interval, 0.38-1.24) and 0.97 (confidence interval, 0.55-1.70) for the contrasts between tertile 1 (lowest level) and tertiles 2 and 3, respectively. These estimates were unaffected by adjustment for body mass, accumulated time of breast-feeding and menopause, and other breast cancer risk factors. These results do not lend support to the hypothesis that DDT is causally related to breast cancer at the body-burden levels found in our study population but do not exclude the possibility that higher levels of exposure could still play a role in the etiology of this tumor.

Adult↗
PubMed1997

The structure, function and distribution of the mouse TWIK-1 K+ channel.

The two P domain K+ channel mTWIK-1 has been cloned from mouse brain. In Xenopus oocytes, mTWIK-1 currents are K+-selective, instantaneous, and weakly inward rectifying. These currents are blocked by Ba2+ and quinine, decreased by protein kinase C and increased by internal acidification. The apparent molecular weight of mTWIK-1 in brain is 81 kDa. A 40 kDa form is revealed after treatment with a reducing agent, strongly suggesting that native mTWIK-1 subunits dimerize via a disulfide bridge. TWIK-1 mRNA is expressed abundantly in brain and at lower levels in lung, kidney, and skeletal muscle. In situ hybridization shows that mTWIK-1 expression is restricted to a few brain regions, with the highest levels in cerebellar granule cells, brainstem, hippocampus and cerebral cortex.

Amino Acid Sequence↗
PubMed1996

Cloning, functional expression and brain localization of a novel unconventional outward rectifier K+ channel.

Human TWIK-1, which has been cloned recently, is a new structural type of weak inward rectifier K+ channel. Here we report the structural and functional properties of TREK-1, a mammalian TWIK-1-related K+ channel. Despite a low amino acid identity between TWIK-1 and TREK-1 (approximately 28%), both channel proteins share the same overall structural arrangement consisting of two pore-forming domains and four transmembrane segments (TMS). This structural similarity does not give rise to a functional analogy. K+ currents generated by TWIK-1 are inwardly rectifying while K+ currents generated by TREK-1 are outwardly rectifying. These channels have a conductance of 14 pS. TREK-1 currents are insensitive to pharmacological agents that block TWIK-1 activity such as quinine and quinidine. Extensive inhibitions of TREK-1 activity are observed after activation of protein kinases A and C. TREK-1 currents are sensitive to extracellular K+ and Na+. TREK-1 mRNA is expressed in most tissues and is particularly abundant in the lung and in the brain. Its localization in this latter tissue has been studied by in situ hybridization. TREK-1 expression is high in the olfactory bulb, hippocampus and cerebellum. These results provide the first evidence for the existence of a K+ channel family with four TMS and two pore domains in the nervous system of mammals. They also show that different members in this structural family can have totally different functional properties.

Amino Acid Sequence↗
PubMed1996

Dimerization of TWIK-1 K+ channel subunits via a disulfide bridge.

TWIK-1 is a new type of K+ channel with two P domains and is abundantly expressed in human heart and brain. Here we show that TWIK-1 subunits can self-associate to give dimers containing an interchain disulfide bridge. This assembly involves a 34 amino acid domain that is localized to the extracellular M1P1 linker loop. Cysteine 69 which is part of this interacting domain is implicated in the formation of the disulfide bond. Replacing this cysteine with a serine residue results in the loss of functional K+ channel expression. This is the first example of a covalent association of functional subunits in voltage-sensitive channels via a disulfide bridge.

Amino Acid Sequence↗
PubMed1996

Functional muscarinic receptors in cultured skeletal muscle.

We studied the influence of muscarinic and nicotinic stimulation on both phosphoinositide metabolism and intracellular calcium levels in rat skeletal muscle primary cultures. Both nicotine and muscarine induced an increase in cytosolic calcium measured by fluo 3 fluorescence in confocal microscopy. The mass of inositol (1,4,5)trisphosphate measured by radioreceptor assay rose 2- to 3.5-fold upon carbachol, nicotine, or muscarine stimulation. The muscarine effect was mimicked by oxotremorine-M; pirenzepine prevented the muscarine-induced inositol (1,4,5)trisphosphate increase, whereas 4-diphenylacetoxy-N-methyl piperidine methiodide was ineffective. A relatively small (40 fmol/mg protein) high-affinity 3-quinuclidinylbenzilate binding to rat myotube microsomes was consistent with the muscarinic effect found. On the other hand, the effect of nicotine on the mass of inositol (1,4,5)trisphosphate was totally suppressed in sodium-free medium. Expression of Ml muscarinic receptors coupled to phospholipase C and to internal calcium stores in cultured skeletal muscle is proposed; nicotinic receptors could be acting via ion fluxes and membrane depolarization.

Animals↗
PubMed1996

Transjugular intrahepatic portosystemic shunt versus sclerotherapy in the elective treatment of variceal hemorrhage.

BACKGROUND & AIMS: Uncontrolled studies suggest that placement of a transjugular intrahepatic portosystemic shunt (TIPS) could be useful in the treatment of variceal bleeding. The aim of this study was to evaluate the efficacy and safety of TIPS in the elective treatment of hemorrhage from esophageal varices in a randomized controlled study that compared the effects of TIPS with those of endoscopic sclerotherapy (ES). METHODS: Sixty-three consecutive cirrhotic patients with hemorrhage from esophageal varices were included. Thirty-two patients were randomly allocated to ES and 31 to TIPS groups. RESULTS: One patient in each group died before the therapeutic procedure could be performed. During a mean follow-up period of 15 months, variceal rebleeding occurred in 51.6% of the patients in the ES group and 23% of those in the TIPS group. Uncontrolled rebleeding occurred in 10 of 31 patients in the ES group, whereas rebleeding did not occur in any patient of the TIPS group. Hepatic encephalopathy was more frequent in TIPS patients (33.3%) than in those treated by ES (13%). However, mortality was similar in both treatment groups. CONCLUSIONS: These preliminary results suggest that TIPS is more effective than ES in the prevention of variceal rebleeding in cirrhotic patients, even though no difference in survival was observed.

Adult↗
PubMed1995

Mus spretus LINE-1 sequences detected in the Mus musculus inbred strain C57BL/6J using LINE-1 DNA probes.

The inbred mouse strain, C57BL/6J, was derived from mice of the Mus musculus complex. C57BL/6J can be crossed in the laboratory with a closely related mouse species, M. spretus to produce fertile offspring; however there has been no previous evidence of gene flow between M. spretus and M. musculus in nature. Analysis of the repetitive sequence LINE-1, using both direct sequence analysis and genomic Southern blot hybridization to species-specific LINE-1 hybridization probes, demonstrates the presence of LINE-1 elements in C57BL/6J that were derived from the species M. spretus. These spretus-like LINE-1 elements in C57BL/6J reveal a cross to M. spretus somewhere in the history of C57BL/6J. It is unclear if the spretus-like LINE-1 elements are still embedded in flanking DNA derived from M. spretus or if they have transposed to new sites. The number of spretus-like elements detected suggests a maximum of 6.5% of the C57BL/6J genome may be derived from M. spretus.

Animals↗
PubMed1995

Distal foot coverage with a reverse dorsalis pedis flap.

A reverse dorsalis pedis flap based on the proximal communicating branch of the dorsalis pedis artery was successfully used to close distal forefoot defects in two patients. The skin paddle was oriented transversely across the ankle crease, allowing for direct closure of the flap donor site. Both patients maintained full active ankle motion without bowstringing of the dorsal foot tendons and did not require special footwear. Both flaps maintained sensation to light touch and pinprick. We believe that this flap offers a viable alternative when faced with the challenge of a small soft-tissue defect requiring flap reconstruction in the distal foot.

Adult↗
PubMed1993

Construction of shuttle plasmids which can be efficiently mobilized from Escherichia coli into the chromatically adapting cyanobacterium, Fremyella diplosiphon.

In some strains of cyanobacteria the composition of the light-harvesting antennae is determined by the color of available light. The mechanism of this chromatic adaptation involves the regulation of gene expression by red and green light and has been most studied in Fremyella diplosiphon (Calothrix sp. PCC 7601), a filamentous cyanobacterium for which there has been no reported means of genetic manipulation. We have constructed shuttle plasmids which can be efficiently mobilized by RP4 from Escherichia coli into F. diplosiphon and which can be recovered from transconjugant F. diplosiphon and returned to E. coli by transformation. The ability of these plasmids to replicate in F. diplosiphon is conferred by an 8.0-kb DNA fragment isolated from pFDA, a plasmid native to F. diplosiphon. To create these shuttle plasmids the 8.0-kb fragment was cloned into pJCF22, a mobilizable plasmid constructed from oriV and bom from pBR322, cat from pACYC184 and aphA from pACYC177.pJCF22 lacks sites for the restriction enzymes FdiI and II. Transconjugant F. diplosiphon containing shuttle plasmid pJCF62 are resistant to chloramphenicol and highly resistant to the aminoglycosides, G418 and neomycin. When aadA from the omega interposon was incorporated into a shuttle plasmid transconjugant F. diplosiphon could also be selected with streptomycin or spectinomycin. In F. diplosiphon shuttle plasmid pJCF62 replicates with a minimum copy number of seven. The oriV for replication in F. diplosiphon was localized to a 2.8-kb region within the cyanobacterial part of pJCF62. The presence on a shuttle plasmid of a single recognition site for FdiI reduced the efficiency of mobilization into F. diplosiphon by 5- to 10-fold. Restriction at this site was prevented when the E. coli donor strain in the mating contained the enzyme Eco47II methylase.

Conjugation, Genetic↗
PubMed1993

Transjugular intrahepatic portosystemic shunt: early experience with a flexible trocar/catheter system.

OBJECTIVE: The purpose of this study was to determine the feasibility of using a flexible trocar/catheter system to create a transjugular intrahepatic portosystemic shunt (TIPS). SUBJECTS AND METHODS: A flexible needle/trocar was used to connect the hepatic vein to the portal vein in 23 patients with portal hypertension and a history of bleeding gastroesophageal varices. Five patients had signs and symptoms of encephalopathy before shunting; in four, the disease was classified as Child's class C and in one, as Child's class B. Nine-millimeter self-expandable metallic stents were used in all patients. RESULTS: The procedure was technically successful in all patients. The mean portosystemic pressure gradient decreased from 26 to 16 mm Hg (range, 7-23 mm Hg). Eight patients have died. One patient in a hepatic coma with hepatorenal failure survived percutaneous portosystemic shunting, but died 2 days after the TIPS procedure was done. After creation of the shunt, three other patients died of unrelated disease without recurrence of bleeding from gastroesophageal varices. Two patients died of massive bleeding from esophageal varices, one 24 hr after shunting and one of disseminated intravascular coagulation after a second attempt to establish a shunt. One patient died of sepsis associated with infected ascitic fluid 2 months after the TIPS procedure was done, and one died of unknown causes 4 months after the procedure was done. The mean follow-up time in the surviving 15 patients was 12 months. Seven patients had recurrence of gastrointestinal bleeding; the recurrence was due to a thrombosed shunt in two, to hepatic vein stenosis in four, and to a high portosystemic pressure gradient (22 mm Hg) after creation of the shunt in one. Hepatic vein stenosis was noted on portal venograms in another three otherwise asymptomatic patients. In four of five patients, encephalopathy was adequately controlled after shunting. The fifth patient with encephalopathy (Child's class C) and an additional patient in whom encephalopathy (Child's class C) developed after the TIPS procedure have had two additional hospital admissions because of difficulty in controlling the encephalopathy. The amount of ascitic fluid decreased or totally disappeared after treatment in all cases. No severe complications associated with creation of a TIPS were observed. CONCLUSION: Use of a flexible trocar/catheter system to create a TIPS is a simple, safe, and moderately reliable means of decompressing the portal vein in patients with portal hypertension.

Adult↗
PubMed1992

Intraparenchymal anesthesia infiltration during transjugular intrahepatic portosystemic shunting.

The authors describe a technique for administration of anesthetic to the area of the transparenchymal tract during transjugular percutaneous transhepatic portosystemic shunting. Seven of the eight patients in whom the technique was used did not experience pain during balloon dilation of the tract, and one patient experienced only minimal pain. The technique allows good pain control in patients with severe liver failure and resultant inability of the liver to metabolize pharmaceuticals.

Aged↗