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J Rueda

Publications and source records attributed to J Rueda.

At least 37 records · Page 2Linked to original sources
PubMed2001

Structural compatibility between the putative voltage sensor of voltage-gated K+ channels and the prokaryotic KcsA channel.

Sequence similarity among and electrophysiological studies of known potassium channels, along with the three-dimensional structure of the Streptomyces lividans K(+) channel (KcsA), support the tenet that voltage-gated K(+) channels (Kv channels) consist of two distinct modules: the "voltage sensor" module comprising the N-terminal portion of the channel up to and including the S4 transmembrane segment and the "pore" module encompassing the C-terminal portion from the S5 transmembrane segment onward. To substantiate this modular design, we investigated whether the pore module of Kv channels may be replaced with the pore module of the prokaryotic KcsA channel. Biochemical and immunocytochemical studies showed that chimeric channels were expressed on the cell surface of Xenopus oocytes, demonstrating that they were properly synthesized, glycosylated, folded, assembled, and delivered to the plasma membrane. Unexpectedly, surface-expressed homomeric chimeras did not exhibit detectable voltage-dependent channel activity upon both hyperpolarization and depolarization regardless of the expression system used. Chimeras were, however, strongly dominant-negative when coexpressed with wild-type Kv channels, as evidenced by the complete suppression of wild-type channel activity. Notably, the dominant-negative phenotype correlated well with the formation of stable, glycosylated, nonfunctional, heteromeric channels. Collectively, these findings imply a structural compatibility between the prokaryotic pore module and the eukaryotic voltage sensor domain that leads to the biogenesis of non-responsive channels. Our results lend support to the notion that voltage-dependent channel gating depends on the precise coupling between both protein domains, probably through a localized interaction surface.

Animals↗
PubMed2000

The prevalence of human herpesvirus-7 in renal transplant recipients is unaffected by oral or intravenous ganciclovir.

The purpose of this study was to compare the prevalence of human herpesvirus (HHV)-7 and cytomegalovirus (CMV) viremia and the effects of oral and intravenous (iv) ganciclovir in renal transplant recipients at risk for CMV. Stored lysates from peripheral blood leukocytes from 92 patients, who had been previously analyzed for CMV viremia by polymerase chain reaction (PCR) for 12 weeks after transplantation, were analyzed for HHV-7 viremia. Baseline and peak prevalences of HHV-7 viremia were 22% and 54%, respectively (P<. 0001). Eighty-two (89%) of 92 patients had at least 1 positive PCR for HHV-7. Oral ganciclovir and treatment with iv ganciclovir had no effect on the prevalence of HHV-7 viremia. In contrast, CMV was almost completely suppressed in patients who received oral ganciclovir, and when present, CMV responded to iv therapy. These results indicate that HHV-7 is resistant to ganciclovir at levels that were effective for prevention and treatment of CMV.

Administration, Oral↗
PubMed2000

Study of the olivocochlear neurons using two different tracers, fast blue and cholera toxin, in hypothyroid rats.

Congenital hypothyroidism results in deafness that is caused by changes in the auditory receptor, including scanty development of the outer hair cells and a lack of synaptogenesis between these cells and the efferent system. although the afferent population is present. The normal efferent innervation of the cochlea originates in the superior olivary complex, arising from efferent neurons belonging to the lateral or to the medial olivocochlear system. In the rat, the former is constituted by neurons located in the lateral superior olivary nucleus, that project to the inner hair cells, while the later originates in the ventral nuclei of the trapezoid body and project to the outer hair cells. The aim of this work is to study the localization, number and morphology of the olivochochlear neurons in congenital hypothyroid animals by means of the injections of the retrograde tracers, either fast blue or cholera toxin, in the cochlea. The mean total number of labeled olivocochlear neurons after injection of fast blue in hypothyroid animals was 1,016, and in control ones was 1,027. Using cholera toxin, the mean total number of labeled olivocochlear neurons was slightly lower: 863 in hypothyroid animals versus 910 in control ones. Although both tracers showed no significant differences between groups, when the somatic area of the labeled olivocochlear neurons is considered, the size of all of the three different population of cells (lateral olivocochlear neurons, medial olivocochlear neurons and shell neurons) was significantly lower in the hypothyroid rats. This is the first study of the olivocochlear neurons in hypothyroid animals. The conclusion from this work is that in hypothyroid rats the labeled olivocochlear neurons are significantly smaller but that there is not any modification in the localization and number of the labeled olivocochlear neurons, suggesting that thyroid hormones are necessary for the neuronal growth. However, most of the medial olivocochlear neurons do not make contact with their target, so their maintenance suggests that the axons are in contact with other structures of the cochlea.

Abnormalities, Drug-Induced↗
PubMed2000

The F-actin cytoskeleton modulates slow secretory components rather than readily releasable vesicle pools in bovine chromaffin cells.

Adrenal chromaffin cells were used to test the role of the peripheral cytoskeleton of F-actin in controlling different vesicle pools. Phorbol 12-myristate 13-acetate and calyculin A, two substances affecting phosphorylation-dephosphorylation cycles, produced different degrees of F-actin reorganization, inducing the partial and the almost total disassembly of this structure, respectively, as visualized using rhodamine-phalloidin staining. Consequently, electron microscopy studies revealed the higher efficiency of calyculin-A over phorbol 12-myristate 13-acetate in promoting vesicle access to the plasmalemma boundary. Surprisingly, only the phorbol ester enhanced fast kinetics and the population of rapidly releasable vesicle pools as studied by single-cell amperometry, whereas both agents, as well as the F-actin severing compound, Latrunculin A, promoted an increase in the population of vesicles recruited in response to prolonged or repetitive stimulations. Taken together, our data support the notion that the F-actin peripheral barrier controls primary granule recruitment from reserve vesicle pools, whereas the phorbol ester effect on the rapidly releasable pools might be related to the alteration of late secretory stage through protein kinase C-dependent phosphorylation of an unidentified target.

Actins↗
PubMed2000

Is the prognosis poorer in heart transplanted patients who develop a right bundle branch block?

BACKGROUND: Currently studies conflict on the impact on mortality of right bundle branch block development after transplantation. Most studies conclude that right bundle branch block does not affect patient survival. However, no distinction is made between patients in whom right bundle branch block progresses and those in whom it remains unchanged during follow-up. The objective of this study is to assess clinical or survival differences between patients who develop right bundle branch block and those who do not, and also to analyze these differences depending on progression of this conduction abnormality. MATERIALS AND METHODS: Ninety-seven consecutive heart transplant recipients with more than 1 year's survival were analyzed. Twelve-lead standard ECGs were performed during the first week after transplantation, which allowed for classification of patients depending on the presence or absence of right bundle branch block. Subsequently, throughout the first year, 2 groups were identified, depending on increase of the conduction defect. The groups were compared and factors determining the presence of right bundle branch block and progression of the conduction defect were found. Survival curves for the conduction defect were also compared. RESULTS: Fifty percent of the patients developed right bundle branch block after transplantation; it was progressive in 10. Progressive right bundle branch block was related to greater renal dysfunction (odds ration [OR] = 10.8; confidence interval [CI] = 2-58; p = 0.006), a larger number of rejections (p = 0.01), and a greater death rate (OR = 12.8; CI = 2.5-64; p = 0.002). The presence of progressive right bundle branch block was an independent predictor of long-term mortality (OR = 27.9; CI = 4.2-186.3; p = 0.0006). CONCLUSIONS: The development of right bundle branch block after transplantation is related to intraoperative factors and to a greater number of rejections. The presence of this conduction disorder, particularly if it progresses during the first year, identifies a sub-group of patients with a poorer long-term prognosis.

Adult↗
PubMed1999

Specific staining of nonpyramidal cell populations of the cerebral cortex by lectin cytochemistry on semithin sections.

The pattern of lectin labeling in the cerebral cortex of the cat was studied using semithin sections. The labeling produced by some lectins (Concanavalin A, Lens culinaris, Phaseolus vulgaris-L, Phaseolus vulgaris-E, Pisum sativum, wheat germ agglutinin, and succynilated-wheat germ) appeared inside every neuron as small cytoplasmic granules, probably corresponding to cisterns of endoplasmic reticulum and/or the Golgi complex. Lectins with affinity for alpha-mannosyl residues (Pisum sativum, Lens culinaris, and Concanavalin A) stained the cell surface of a subset of cortical neurons. The labeled cells were round or polygonal, medium to large neurons present in layers II-VI, exhibiting the morphological features of nonpyramidal cells. Previous lectin studies of perineuronal nets have shown that these extracellular specializations contain N-acetylgalactosamine and N-acetylglucosamine. Our results show that mannose is also a component of perineuronal nets and that lectins specific for alpha-mannose can be used as tools for the cytochemical detection of a separate class of cortical neurons, which have not yet been fully characterized. In addition, some lectins (Bandeiraea simplicifolia, Concanavalin A, Lens culinaris, Phaseolus vulgaris-L, Phaseolus vulgaris-E, Pisum sativum, and succynilated-wheat germ agglutinin) specifically labeled a population of a type of microglia-related cells known as perivascular cells. The data presented here report for the first time the selective staining of perivascular cells and further support the hypothesis that they are different from typical microglial cells.

Animals↗
PubMed1999

[The measurement of jet width at its origin in assessing mitral prosthetic regurgitation. The effect of the spatial disposition of the jet].

INTRODUCTION AND OBJECTIVES: The study was performed to test the influence of the jet spatial disposition on the correlation degree between the measurement of the jet width at its origin and the severity of mitral prosthetic regurgitation by transesophageal Doppler color flow imaging. MATERIAL AND METHODS: In 165 patients with mitral valve prosthesis which were submitted for transesophageal echocardiography examination due to suspected prosthetic dysfunction, we studied 126 with pathological mitral regurgitation. On these patients, studies of jet spatial disposition, maximum width in its origin and severity quantification by means of maximum regurgitation area were performed. RESULTS: For the free jet group of patients (90), jet width at its origin correlated with maximal regurgitation area (r = 0.75); whereas for the wall jet group (36), the correlation degree was 0.59. We observed a relationship (p < 0.05) between severe mitral regurgitation assessed by maximal regurgitant jet size and jet width > or = 5 mm in both groups: the sensitivity and specificity of 72.7% and 95% respectively for free jets, and 70.7% and 64.4% for wall jets. CONCLUSIONS: The correlation between the area measurement and the width in its origin is better for free jets than for wall jets. A statistically significant relationship between the presence of severe mitral regurgitation and width in its origin > or = 5 mm could be observed, independently of the jet spatial disposition.

Adult↗
PubMed1997

A peptide that mimics the C-terminal sequence of SNAP-25 inhibits secretory vesicle docking in chromaffin cells.

Excitation-secretion uncoupling peptides (ESUPs) are inhibitors of Ca2+-dependent exocytosis in neural and endocrine cells. Their mechanism of action, however, remains elusive. We report that ESUP-A, a 20-mer peptide patterned after the C terminus of SNAP-25 (synaptosomal associated protein of 25 kDa) and containing the cleavage sequence for botulinum neurotoxin A (BoNT A), abrogates the slow, ATP-dependent component of the exocytotic pathway, without affecting the fast, ATP-independent, Ca2+-mediated fusion event. Ultrastructural analysis indicates that ESUP-A induces a drastic accumulation of dense-core vesicles near the plasma membrane, mimicking the effect of BoNT A. Together, these findings argue in favor of the notion that ESUP-A inhibits ATP-primed exocytosis by blocking vesicle docking. Identification of blocking peptides which mimic sequences that bind to complementary partner domains on interacting proteins of the exocytotic machinery provides new pharmacological tools to dissect the molecular and mechanistic details of neurosecretion. Our findings may assist in developing ESUPs as substitute drugs to BoNTs for the treatment of spasmodic disorders.

Adrenal Medulla↗
PubMed1996

Tectorial membrane-organ of Corti relationship during cochlear development.

The development of stereociliary attachment to the tectorial membrane was investigated in the mouse cochlea using transmission and scanning electron microscopy. At the 18th gestational day, only the major tectorial membrane can be identified covering the greater epithelial ridge and the inner hair cells in all turns. At the 19th gestational day, the minor tectorial membrane was first seen in the basal turn, over the outer hair cells. During early stages of development, the stereocilia of hair cells were surrounded by a loose fibrillar material underneath the tectorial membrane. After the 10th postnatal day, the outer hair cells' stereocilia were attached to Kimura's (or Hardesty's) membrane, while inner hair cells' stereociliary bundles were attached to the undersurface of the tectorial membrane near the Hensen's stripe. Between the 10th and the 14th postnatal days, the space between the inner hair cells and the first row of outer hair cells widened by virtue of the growth of the heads of pillar cells, and the inner hair cells' stereocilia were displaced towards the Hensen's stripe. After the 14th postnatal day, the inner hair cells' stereociliary bundles detached from the tectorial membrane, while the outer hair cells' stereocilia remained attached to it. The tip-link system, which connects the tips of the stereocilia to the next tallest stereocilia, is present at birth in the outer hair cells. The marginal pillar, that anchored the tectorial membrane to the underlying organ of Corti during development, first appeared on the 6th postnatal day and disappeared on the 14th-15th postnatal day. The present data together with other reports support the idea that although some structures, such as hair cells' stereocilia and innervation, are already formed early during development, the cochlear microarchitecture is not fully developed morphologically and ready to function normally until the end of the second postnatal week in the mouse.

Animals↗
PubMed1996

Development of vestibular function: biochemical, morphological and electronystagmographical assessment in the rat.

Glutamate decarboxylase and choline acetyltransferase were measured in homogenated ampullar cristae of rats during development from postnatal day 13 to 60 to determine changes in levels of these enzymes during early postnatal development. Afferent and efferent innervation of the hair cells of the developing cristae were studied using electron microscopy. In parallel, groups of rats, postrotatory nystagmus were used to assess the development of semicircular canal function during the same time interval. The level of glutamate decarboxylase was high on postnatal day 15 and did not change notably over the remaining days to day 60. Activity of choline acetyltransferase was nearly absent at day 15, but reached levels seen in mature animals by day 17, and remained almost unchanged thereafter. In contrast, as revealed by electronmicroscopy, afferent and efferent innervation appeared to be mature by day 8. Postrotatory nystagmus presented the adult-like features from day 19 onward. According to these results, a role for glutamate decarboxylase in afferent transmission is suggested by the parallel development of levels of glutamate decarboxylase and afferent innervation of the ampullary cristae. The finding of a similar time course of development of choline acetyltransferase levels and postrotatory nystagmus suggests that a cholinergic efferent innervation is involved in the onset of vestibular-ocular function.

Animals↗
PubMed1996

[Coronary involvement in Takayasu's arteritis].

Takayasu's arteritis is a chronic inflammatory disease that primarily affects young women. Cardiac involvement is infrequent and it includes aortic regurgitation, pericarditis, angor pectoris or myocardial infarction due to coronary narrowing and cardiac heart failure due to coronary involvement and/or high blood pressure. A patient with Takayasu's aortitis and angina pectoris due to severe narrowing of the left coronary arterial ostia is described.

Adult↗
PubMed1995

Distal deletion of chromosome 13 in a child with the "opitz" GBBB syndrome.

We describe a patient who had craniofacial and genitourinary abnormalities, swallowing difficulties, esophageal dysfunction, hypotonia and moderate developmental delay, and who also had a terminal deletion of chromosome 13 (q32.3qter). This MCA pattern strongly suggests the Opitz GBBB syndrome. The deletion of chromosome 13 was interpreted as terminal with a breakpoint at 12q32.3. Coagulation factors VII and X located in 13q34, were markedly reduced in the propositus. Although there is some clinical overlap between patients with terminal deletion of 13q and those with the Opitz GBBB syndrome, our patient manifests a whole pattern of abnormalities characteristics of the latter disorder. The concurrence of the Opitz GBBB syndrome and the chromosome abnormality in our patient could be due to chance or, be because a gene for the Opitz GBBB syndrome is located at the tip of 13q.

Abnormalities, Multiple↗