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Biomedical subjects

R Reyes

Publications and source records attributed to R Reyes.

At least 37 records · Page 2Linked to original sources
PubMed2000

An endoscopic comparison of the effects of alendronate and risedronate on upper gastrointestinal mucosae.

OBJECTIVES: The nitrogen-containing bisphosphonates alendronate and risedronate have been reported to have upper gastrointestinal (GI) safety and tolerability profiles comparable to those of placebo. Nevertheless, both agents have demonstrated similar potential for irritation of gastric mucosa at high doses in preclinical studies. The present study compared the potential for alendronate and risedronate to produce endoscopic upper GI mucosal irritation using the highest approved dosage regimens for the two agents. METHODS: This was a multicenter, randomized, parallel-group, double-blind, placebo-controlled trial in which a total of 235 patients (men or postmenopausal women, aged 45-80 yr) with normal upper GI endoscopy at baseline received 28-day treatments with the following: alendronate 40 mg/day (N = 90), risedronate 30 mg/day (N = 89), placebo (N = 36), or placebo with aspirin 650 mg q.i.d. for the last 7 days (N = 20). Endoscopy was repeated on day 29 using standardized scoring scales. RESULTS: After 28 days of treatment, the alendronate and risedronate groups had comparable mean gastric and duodenal erosion scores that were significantly lower than those of the aspirin group. Esophageal scores were comparable in all groups. Gastric ulcers and/or large numbers of gastric erosions occurred in approximately 3% of alendronate and risedronate patients versus 60% with aspirin. Both bisphosphonates were clinically well tolerated. CONCLUSIONS: The potential for gastroduodenal irritation is similar for alendronate and risedronate and is markedly less than for aspirin. The findings of this study, together with the large placebo-controlled clinical trial experience with both agents and extensive epidemiological data for alendronate, suggest that the risk for clinically important gastric irritation with these bisphosphonates is very low, even at the highest available doses.

Aged↗
PubMed2000

IP(3) receptors, IP(3) transients, and nucleus-associated Ca(2+) signals in cultured skeletal muscle.

Inositol 1,4,5-trisphosphate (IP(3)) receptors (IP(3)R) and ryanodine receptors (RyR) were localized in cultured rodent muscle fractions by binding of radiolabeled ligands (IP(3) and ryanodine), and IP(3)R were visualized in situ by fluorescence immunocytological techniques. Also explored was the effect of K(+) depolarization on IP(3) mass and Ca(2+) transients studied using a radio-receptor displacement assay and fluorescence imaging of intracellular fluo 3. RyR were located in a microsomal fraction; IP(3)R were preferentially found in the nuclear fraction. Fluorescence associated with anti-IP(3)R antibody was found in the region of the nuclear envelope and in a striated pattern in the sarcoplasmic areas. An increase in external K(+) affected membrane potential and produced an IP(3) transient. Rat myotubes displayed a fast-propagating Ca(2+) signal, corresponding to the excitation-contraction coupling transient and a much slower Ca(2+) wave. Both signals were triggered by high external K(+) and were independent of external Ca(2+). Slow waves were associated with cell nuclei and were propagated leaving "glowing" nuclei behind. Different roles are proposed for at least two types of Ca(2+) release channels, each mediating an intracellular signal in cultured skeletal muscle.

Amino Acid Sequence↗
PubMed2000

The risks of clinical practice.

The hospital workplace is changing dramatically, moulded in part by the need to protect medical staff from the increasing physical and mental risks of medical practice today. This article examines the risks and look to the future.

Aggression↗
PubMed2000

Survival of HIV-1 in syringes: effects of temperature during storage.

In a previous paper we demonstrated that HIV-1 survival in syringes was strongly associated with the volume of blood remaining and with the duration of storage at room temperature. The current study was performed to determine the effects of storage temperature upon the survival of HIV-1 inside syringes. At 4 degrees C, 50% of all syringes contained viable HIV-1 at 42 days of storage, the longest storage duration tested. At room temperature (20 degrees C), the last day that syringes with 2 microL of infected blood were positive was Day 21, and viable HIV-1 was recovered from 8% of syringes. The last day on which syringes with 20 microL were positive was Day 42, and viable HIV-1 was recovered from 8% of syringes. Above room temperature (27, 32, and 37 degrees C), the likelihood of encountering syringes with viable HIV-1 when periods of storage exceeded 1 week decreased to less than 1%. The temperatures at which drug injectors are likely to store their used syringes will vary according to climate, season, and circumstances faced by the injector. The survival of HIV-1 in contaminated syringes varied over a range of temperatures, and this may be a factor influencing the syringe-borne transmission of HIV-1.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Conditionally immortalized mouse hepatocytes for use in liver gene therapy.

BACKGROUND AND AIMS: The use of hepatocytes for gene therapy is limited by the difficulty of maintaining and altering primary liver cells in culture. A conditionally immortalized mouse hepatocyte cell line has been developed which can be passaged indefinitely at the permissive temperature (33 degrees C), but fails to proliferate and dies at the non-permissive temperature (39 degrees C) in vitro. METHODS: Hepatocytes were harvested from a 6 week-old male transgenic mouse ('immortomouse') carrying a thermolabile SV40 Large T gene, using a modified two-step collagenase perfusion method, and serially passaged at 33 degrees C for more than 1 year. To assess the ability of immortohepatocytes to engraft and populate mouse liver, cells were infused into partially hepatectomized congenic mice via the portal vein (n = 10) or the spleen with (n = 2) and without (n = 2) partial hepatectomy. The ability to transfect immortohepatocytes was assessed using the reporter gene enhanced green fluorescent protein (EGFP). RESULTS: All immortohepatocytes in culture stained positive by immunohistochemistry for the hepatocyte markers albumin, AFP, CK8 and CK18. In early cultures a proportion of cells also stained strongly for the biliary epithelial markers CK7 and CK19. Late cell cultures were negative for M2PK and CK7 and stained variably with anti-CK19 antibodies. Cells transferred to the non-permissive temperature of 39 degrees C ceased proliferation and died within 1 week in vitro. Large T DNA was detected in the liver of all postoperative mice up to 2 weeks post-hepatocellular transplantation via PCR and Southern blot analysis. The immortohepatocytes were easily transfected with a reporter gene. CONCLUSIONS: Immortohepatocytes can survive in vivo after transfer to liver, and will be useful as a model for hepatic gene therapy.

Animals↗
PubMed1999

Copper levels are increased in the cerebral cortex and liver of APP and APLP2 knockout mice.

The pathological process in Alzheimer's disease (AD) involves amyloid beta (Abeta) deposition and neuronal cell degeneration. The neurotoxic Abeta peptide is derived from the amyloid precursor protein (APP), a member of a larger gene family including the amyloid precursor-like proteins, APLP1 and APLP2. The APP and APLP2 molecules contain metal binding sites for copper and zinc. The zinc binding domain (ZnBD) is believed to have a structural rather than a catalytic role. The activity of the copper binding domain (CuBD) is unknown, however, APP reduces copper (II) to copper (I) and this activity could promote copper-mediated neurotoxicity. The expression of APP and APLP2 in the brain suggests they could have an important direct or indirect role in neuronal metal homeostasis. To examine this, we measured copper, zinc and iron levels in the cerebral cortex, cerebellum and selected non-neuronal tissues from APP (APP(-/-)) and APLP2 (APLP2(-/-)) knockout mice using atomic absorption spectrophotometry. Compared with matched wild-type (WT) mice, copper levels were significantly elevated in both APP(-/-) and APLP2(-/-) cerebral cortex (40% and 16%, respectively) and liver (80% and 36%, respectively). Copper levels were not significantly different between knockout and WT cerebellum, spleen or serum samples. There were no significant differences observed between APP(-/-), APLP2(-/-) and WT mice zinc or iron levels in any tissue examined. These findings indicate APP and APLP2 expression specifically modulates copper homeostasis in the liver and cerebral cortex, the latter being a region of the brain particularly involved in AD. Perturbations to APP metabolism and in particular, its secretion or release from neurons may alter copper homeostasis resulting in increased Abeta accumulation and free radical generation. These data support a novel mechanism in the APP/Abeta pathway which leads to AD.

Alzheimer Disease↗
PubMed1999

Cloning of a new mouse two-P domain channel subunit and a human homologue with a unique pore structure.

Mouse KCNK6 is a new subunit belonging to the TWIK channel family. This 335-amino acid polypeptide has four transmembrane segments, two pore-forming domains, and a Ca2+-binding EF-hand motif. Expression of KCNK6 transcripts is principally observed in eyes, lung, stomach and embryo. In the eyes, immunohistochemistry reveals protein expression only in some of the retina neurons. Although KCNK6 is able to dimerize as other functional two-P domain K+ channels when it is expressed in COS-7 cells, it remains in the endoplasmic reticulum and is unable to generate ionic channel activity. Deletions, mutations, and chimera constructions suggest that KCNK6 is not an intracellular channel but rather a subunit that needs to associate with a partner, which remains to be discovered, in order to reach the plasma membrane. A closely related human KCNK7-A subunit has been cloned. KCNK7 displays an intriguing GLE sequence in its filter region instead of the G(Y/F/L)G sequence, which is considered to be the K+ channel signature. This subunit is alternatively spliced and gives rise to the shorter forms KCNK7-B and -C. None of the KCNK7 structures can generate channel activity by itself. The KCNK7 gene is situated on chromosome 11, in the q13 region, where several candidate diseases have been identified.

Amino Acid Sequence↗
PubMed1999

Effects of a purified fraction from Echeveria gibbiflora aqueous crude extract on guinea-pig spermatozoa.

Guinea-pig spermatozoa in the presence of a purified fraction from Echeveria gibbiflora aqueous crude extract suffer a hypotonic-like effect. The phenomena exhibited included a distension of the plasma membrane over the acrosome region, inducing the formation of a huge 'head-bubble'. The agglutination effect was so enhanced that instead of inducing sperm clusters, it produced cane-like 'stalk' structures. The immobilizing activity was induced instantaneously after the addition of the purified fraction. At electron microscope level it was possible to observe a heavy amount of electron dense material of the purified fraction embedded or intercalated along the plasma membrane. It was also possible to corroborate the dispersion of the acrosomal content and the disappearance of the external acrosome membrane. The purified fraction induced loosening of the plasma membrane all along the sperm cell, however, the distension of the membrane was only produced in the apical portion of the sperm head and not in the post equatorial region. The results suggest that the plant may yield a compound suitable for use as a vaginal barrier or male contraceptive agent.

Acrosome↗
PubMed1999

CO2 as a contrast medium in endoluminal treatment of high flow vascular malformations.

PURPOSE: To evaluate the diagnostic usefulness of CO2 as a radiologic contrast medium in pre and post-embolization of hemodynamically active vascular malformations. MATERIAL AND METHODS: Eight pre-and post-embolization angiographies were performed on five patients with hemodynamically active vascular malformations. In all cases sequentially iodinated contrast medium and CO2 were used. Procedures were performed using Philips Integris V equipped with specific software to process images obtained with CO2 as contrast medium and with a purpose-built gas injector pump. The images were assessed by three interventional radiologists who evaluated the findings by consensus. They were asked whether uptake of the malformations were better, worse or the same with iodinated contrast and CO2. The images were judged according to the following characteristics; quality, the filling in of the contrast in afferent artery of the HAVM, caliber and number of vessels and existence of pathologic communications in HAVM. These characteristics were assessed in all the patients of the study, both before and after embolization. RESULTS: The CO2 angiographic results were compared to those obtained using iodinated contrast material. Iodinated contrast provided superior image quality in all performed studies. The filling of arterial afference of HAVM was well defined with both contrast media. In all performed cases with CO2, the malformations showed more vessels. No inmediate nor subsequent complications developed with CO2 injections, except in one female patient, who presented an intense sensation of cramps in the lower limbs. CONCLUSION: CO2 is a useful diagnostic and assessment tool before and especially during the embolization of hemodynamically active vascular malformations. It improves quantification and uptake of the malformation's vascular architecture, detecting collateral circulation and arteriovenous shunts. It also detects residual post-embolization disease when iodinated contrast agent is unsuccessful.

Adolescent↗
PubMed1999

Immunoreactive neurotensin in gonadotrophs and thyrotrophs is regulated by sex steroid hormones in the female rat.

In addition to regulating anterior pituitary function by being released from the median eminence, mammalian neurotensin (NT) may also exert an autocrine or a paracrine action within the anterior pituitary. In this study, using double immunostaining with elution restaining, we identified the specific anterior pituitary cells which express NT immunoreactivity (NT-IR) during the rat oestrous cycle. In the normal cycling rat, NT-IR was present in both gonadotrophs and thyrotrophs and displayed plastic changes along the oestrous cycle. Both the number of TSH-NT positive cells and the intensity of immunological reaction were elevated during dioestrus, and decreased through pro-oestrus and early oestrus. NT-IR was also high in both follicle stimulating hormone (FSH)- or luteinizing hormone (LH)-positive cells during early pro-oestrus, and decreased during late pro-oestrus. Treatment of intact rats with either the anti-oestrogens Tamoxifen or LY117018, or the anti-progestagen RU486 prevented the normal expression of NT-IR in thyroid-stimulating hormone (TSH)-, FSH-, and LH-positive cells during pro-oestrus. Bilateral ovariectomy induced a dramatic reduction in the number of NT-IR cells. This effect was completely prevented by treatment of ovariectomized rats with oestradiol and progesterone, and was unaffected by the concurrent administration of a GnRH antagonist. Furthermore, administration of an anti-oestrogen together with an anti-progestagen to ovariectomized-oestrogen, progesterone-treated rats, blocked the stimulatory effect of ovarian hormones on NT-IR in anterior pituitary cells. These findings demonstrate that, in female rats, NT is specifically localized in gonadotrophs or thyrotrophs. In addition, they strongly suggest that changes in circulating concentrations of ovarian steroids may control both NT synthesis in, and release from, these cells.

Animals↗
PubMed1999

Diagnosis and percutaneous treatment of gastrointestinal hemorrhage. Long-term experience.

OBJECTIVE: to report our experience in the diagnosis and treatment of gastrointestinal hemorrhage. METHOD: from April 1987 to April 1997, 196 patients with gastrointestinal hemorrhage (134 men and 62 women) were studied. 165 (84%) were diagnosed as presenting upper gastrointestinal hemorrhage, and 31 (16%) presented lower gastrointestinal hemorrhage. The patients were studied with endoscopy and arteriography, and embolization was prescribed in 131 (67%). Patients with bleeding from esophageal varices were excluded from this study. RESULTS: a bleeding point was identified angiographically in 33% (n = 65) patients. 131 (67%) patients were treated with therapeutic embolization, which was successful in 89% (n = 116) patients. The bleeding was resolved in 80% (n = 93) of the patients. Complications included arterial spasm (n = 12), pain (n = 24), coil migration (n = 8), allergic reaction (n = 2) and celiac trunk dissection (n = 2). During follow-up 16 patients presented rebleeding that stopped after reembolization in 9 cases, whereas in 7 cases surgery was needed. CONCLUSIONS: in our experience, diagnostic angiography and percutaneous therapeutic embolization are effective, less aggressive methods that lead to few complications. Both methods have become indispensable tools in managing patients with gastrointestinal hemorrhage that does not respond to conservative therapy. Even in patients with no evidence of angiographic bleeding, embolization in selected patients is successful.

Adult↗
PubMed1998

Cloning and expression of a novel pH-sensitive two pore domain K+ channel from human kidney.

A complementary DNA encoding a novel K+ channel, called TASK-2, was isolated from human kidney and its gene was mapped to chromosome 6p21. TASK-2 has a low sequence similarity to other two pore domain K+ channels, such as TWIK-1, TREK-1, TASK-1, and TRAAK (18-22% of amino acid identity), but a similar topology consisting of four potential membrane-spanning domains. In transfected cells, TASK-2 produces noninactivating, outwardly rectifying K+ currents with activation potential thresholds that closely follow the K+ equilibrium potential. As for the related TASK-1 and TRAAK channels, the outward rectification is lost at high external K+ concentration. The conductance of TASK-2 was estimated to be 14.5 picosiemens in physiological conditions and 59.9 picosiemens in symmetrical conditions with 155 mM K+. TASK-2 currents are blocked by quinine (IC50 = 22 microM) and quinidine (65% of inhibition at 100 microM) but not by the other classical K+ channel blockers tetraethylammonium, 4-aminopyridine, and Cs+. They are only slightly sensitive to Ba2+, with less than 17% of inhibition at 1 mM. As TASK-1, TASK-2 is highly sensitive to external pH in the physiological range. 10% of the maximum current was recorded at pH 6. 5 and 90% at pH 8.8. Unlike all other cloned channels with two pore-forming domains, TASK-2 is essentially absent in the brain. In human and mouse, TASK-2 is mainly expressed in the kidney, where in situ hybridization shows that it is localized in cortical distal tubules and collecting ducts. This localization, as well as its functional properties, suggest that TASK-2 could play an important role in renal K+ transport.

Amino Acid Sequence↗
PubMed1998

A neuronal two P domain K+ channel stimulated by arachidonic acid and polyunsaturated fatty acids.

TWIK-1, TREK-1 and TASK K+ channels comprise a class of pore-forming subunits with four membrane-spanning segments and two P domains. Here we report the cloning of TRAAK, a 398 amino acid protein which is a new member of this mammalian class of K+ channels. Unlike TWIK-1, TREK-1 and TASK which are widely distributed in many different mouse tissues, TRAAK is present exclusively in brain, spinal cord and retina. Expression of TRAAK in Xenopus oocytes and COS cells induces instantaneous and non-inactivating currents that are not gated by voltage. These currents are only partially inhibited by Ba2+ at high concentrations and are insensitive to the other classical K+ channel blockers tetraethylammonium, 4-aminopyridine and Cs+. A particularly salient feature of TRAAK is that they can be stimulated by arachidonic acid (AA) and other unsaturated fatty acids but not by saturated fatty acids. These channels probably correspond to the functional class of fatty acid-stimulated K+ currents that recently were identified in native neuronal cells but have not yet been cloned. These TRAAK channels might be essential in normal physiological processes in which AA is known to play an important role, such as synaptic transmission, and also in pathophysiological processes such as brain ischemia. TRAAK channels are stimulated by the neuroprotective drug riluzole.

Amino Acid Sequence↗
PubMed1998

[Treatment of dysphagia of malignant origin with the endoprosthesis of Strecker].

OBJECTIVE: To evaluate the effectiveness of metallic Strecker stents for palliation of malignant dysphagia. PATIENTS AND METHODS: From June 1992 to August 1995, 66 Strecker stents were inserted in 55 consecutive patients, 50 male and 5 female, with a mean age of 62 years (range 25-83). The cause of dysphagia was incurable malignant obstruction of the esophagus. Three patients presented with dysphagia grade I, 8 grade II, 27 grade III and 17 grade IV. All the procedures were performed under fluoroscopic control. RESULTS: Exact positioning of the stent was technically feasible in all patients. No procedure-related mortalities or major complications occurred. Immediate complications were transient chest pain (n = 11), blood stain sputum (n = 8) and gastroesophageal reflux (n = 8). During follow-up, 7 patients (12.7%) had recurrent dysphagia due to tumor ingrowth or overgrowth. In these patients an additional overlapping stent was successfully placed in six cases and balloon dilatation in one. Latest evaluation revealed dysphagia grade O in five patients (9%), 10 dysphagia grade I (18%), 14 grade II (25%), 13 grade III (23.6%) and seven grade IV. CONCLUSIONS: Implantation of Strecker stents is an effective and safe method of palliating severe malignant dysphagia. Placement of the stents was feasible without major procedure complications.

Adult↗
PubMed1998

Comparison of thrombolytic therapy of lower-extremity acute, subacute, and chronic arterial occlusions.

Our purpose was to study the effectiveness of thrombolytic therapy in treating acute, subacute, and chronic arterial occlusions in a multicenter retrospective study. Intraarterial urokinase infusion was performed in 235 patients for occluded native arteries. There were 70 (30%) with acute and 26 (5%) with subacute occlusions, and 141 (59%) with chronic symptoms for longer than 3 mo. Complete thrombolysis was achieved in 60 (86%) of the acute, 20 (77%) of the subacute, and 106 (75%) of the chronic occlusions. Adjunctive interventional procedures were performed as needed. Long-term follow-up revealed a primary patency of 87%, 85%, and 76% for the acute, subacute, and chronic occlusion groups, respectively. We conclude that the rate of complete thrombolysis of chronic occlusions proved slightly more efficient for acute and virtually the same for subacute occlusions. Long-term follow-up demonstrated a higher failure rate with chronic than with acute occlusions, probably due to worsened peripheral vascular runoff.

Acute Disease↗
PubMed1998

Transcatheter embolization of symptomatic hepatic venous malformations.

The aim of this study was to evaluate our results in treatment and management of symptomatic hepatic venous malformations using transcatheter embolization therapy. From 1991 to 1997 five venous malformations were embolized in one man and four women ranging in age from 31 to 50 years. All patients presented nonspecific abdominal pain and were assessed in the general surgery unit. Percutaneous embolization was recommended. In all cases polyvinyl alcohol was used to embolize the afferent arterioles. Clinical and echographic control follow-up was carried out on an outpatient basis in our Vascular and Interventional Radiology Unit. Embolization was possible in all cases. No complications developed during the procedure, except in one case where the subject suffered a spasm of the hepatic artery. Mean follow-up time was 42 months (6-73 months). Four patients remained asymptomatic during the entire follow-up period, whereas one patient required reembolization. In our experience, transcatheter embolization of hepatic venous malformations is a noninvasive technique which requires few admissions and presents few complications. With further use, it could become the treatment of choice in symptomatic hepatic venous malformations as an alternative to surgery.

Adult↗
PubMed1998

Intramuscular low flow vascular malformations: treatment by means of direct percutaneous embolization.

PURPOSE: Intramuscular hemodynamically inactive vascular malformations are infrequent entities whose surgical treatment is often impossible, crippling, or inefficient. We describe a nonsurgical therapeutic approach consisting on embolization by direct puncture with sclerosant substances. METHODS: Four patients have been treated from April to November 1994, three female and one male, ranging in age from 13 to 31 years. Three vascular malformations were located in the quadriceps and one in the deltoid muscle. The point of access was determined with information provided by MR. The skin was cleaned with an antiseptic solution and puncture was performed with a 22 gauge Chiva needle. Blood flow inside the malformation was slow in all cases and no afference to the normal venous system was detected. We embolized with 5-15 cc (mean 7.5 cc) of a mixture of ethibloc and ethanol. RESULTS: The mean follow-up period was 17 months (range 14-21). All patients remain asymptomatic and have resumed normal daily life activities. There were no complications. CONCLUSION: Percutaneous embolization by direct puncture of intramuscular vascular malformations is a feasible and simple procedure. Our preliminary results are promising, although more extensive studies need to be to performed in order to reach definite conclusions.

Adolescent↗