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C Morera

Publications and source records attributed to C Morera.

At least 19 recordsLinked to original sources
PubMed1997

Genetic evidence for 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) as a negative effector of cytochrome terminal oxidase cbb3 production in Rhizobium etli.

A Rhizobium etli Tn5mob-induced mutant (CFN035) exhibits an enhanced capacity to oxidize N,N,N',N', tetramethyl-p -phenylenediamine (TMPD), a presumptive indicator of elevated cytochrome c terminal oxidase activity. Sequencing of the mutated gene in CFN035 revealed that it codes for the amidophosphoribosyl transferase enzyme (PurF) that catalyzes the first step in the purine biosynthetic pathway. Two c-type cytochromes with molecular weights of 32 and 27 kDa were produced in strain CFN035, which also produced a novel CO-reactive cytochrome (absorbance trough at 553 nm), in contrast to strain CE3 which produced a single 32 kDa c-type protein and did not produce the 553 nm CO-reactive cytochrome. A wild-type R. etli strain that expresses the Bradyrhizobium japonicum fixNOQP genes, which code for the symbiotic cytochrome terminal oxidase cbb3, produced similar absorbance spectra (a trough at 553 nm in CO-difference spectra) and two c-type proteins similar in size to those of strain CFN035, suggesting that CFN035 also produces the cbb3 terminal oxidase. The expression of a R. etli fixN-lacZ gene fusion was measured in several R. etli mutants affected in different steps of the purine biosynthetic pathway. Our analysis showed that purF, purD, purQ, purL, purY, purK and purE mutants expressed three-fold higher levels of the fixNOQP operon than the wild-type strain. The derepressed expression of fixN was not observed in a purH mutant. The purH gene product catalyzes the conversion of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) to 5-form-aminoimidazole-4-carboxamide ribonucleotide (FAICAR) and inosine. Supplementation with AICA riboside lowered the levels of fixN expression in the purF mutants. These data are consistent with the possibility that AICAR, or a closely related metabolite, is a negative effector of the production of the symbiotic terminal oxidase cbb3 in R. etli.

Amidophosphoribosyltransferase↗
PubMed1997

Modification of Christensen urease test as an inexpensive tool for detection of Helicobacter pylori.

About half the world population is infected with Helicobacter pylori. Most live in developing countries where clinical studies face the constraints of high costs of imported rapid diagnostic tests. In this work, we describe and validate a simple local urease test (LUT) to determine the presence of the bacterium in gastric biopsies, and report the incidence of infection among symptomatic patients in Caracas, Venezuela. Statistical comparison of LUT and CLOtest (Delta West, Bentley, Australia) (N = 216 patients) showed that the probability of 95% agreement between the two test was 0.936. Overall incidence of infection determined by the LUT was 65% (N = 229), and it was higher in patients from public (72%; N = 153) than from private (50%; N = 76) hospitals (p = .001). Therefore, the incidence of infection differs in two socioeconomic groups that coexist in the same city. LUT may represent an affordable tool in clinical studies needed to identify social factors that increase the risk of infection by H. pylori.

Adolescent↗
PubMed1997

Expression of thiamin biosynthetic genes (thiCOGE) and production of symbiotic terminal oxidase cbb3 in Rhizobium etli.

In this paper we report the cloning and sequence analysis of four genes, located on plasmid pb, which are involved in the synthesis of thiamin in Rhizobium etli (thiC, thiO, thiG, and thiE). Two precursors, 4-methyl-5-(beta-hydroxyethyl)thiazole monophosphate and 4-amino-5-hydroxymethylpyrimidine pyrophosphate, are coupled to form thiamin monophosphate, which is then phosphorylated to make thiamin pyrophosphate. The first open reading frame (ORF) product, of 610 residues, has significant homology (69% identity) with the product of thiC from Escherichia coli, which is involved in the synthesis of hydroxymethylpyrimidine. The second ORF product, of 327 residues, is the product of a novel gene denoted thiO. A protein motif involved in flavin adenine dinucleotide binding was found in the amino-terminal part of ThiO; also, residues involved in the catalytic site of D-amino acid oxidases are conserved in ThiO, suggesting that it catalyzes the oxidative deamination of some intermediate of thiamin biosynthesis. The third ORF product, of 323 residues, has significant homology (38% identity) with ThiG from E. coli, which is involved in the synthesis of the thiazole. The fourth ORF product, of 204 residues, has significant homology (47% identity) with the product of thiE from E. coli, which is involved in the condensation of hydroxymethylpyrimidine and thiazole. Strain CFN037 is an R. etli mutant induced by a single Tn5mob insertion in the promoter region of the thiCOGE gene cluster. The Tn5mob insertion in CFN037 occurred within a 39-bp region which is highly conserved in all of the thiC promoters analyzed and promotes constitutive expression of thiC. Primer extension analysis showed that thiC transcription in strain CFN037 originates within the Tn5 element. Analysis of c-type protein content and expression of the fixNOQP operon, which codes for the symbiotic terminal oxidase cbb3, revealed that CFN037 produces the cbb3 terminal oxidase. These data show a direct relationship between expression of thiC and production of the cbb3 terminal oxidase. This is consistent with the proposition that a purine-related metabolite, 5-aminoimidazole-4-carboxamide ribonucleotide, is a negative effector of the production of the symbiotic terminal oxidase cbb3 in R. etli.

Amino Acid Sequence↗
PubMed1997

Immunohistochemical expression of Bcl-2 oncoprotein in EBV-associated nasopharyngeal carcinoma correlated to histological type and survival.

Expression of Bcl-2 is associated with inhibition of apoptosis and extension of cell survival. In vitro Bcl-2 protein expression is up-regulated by the EBV-latency associated antigen latent membrane protein (LMP-1). We have investigated the relationship between the presence of EBV-DNA screened by means of sensitive nested-PCR, nasopharyngeal carcinoma (NPC) histological types according to two different schemata (WHO and Micheau classifications) and Bcl-2-124 immunohistochemical expression in 55 biopsy samples of NPC. EBV genome was detected in 100% of samples with sufficient DNA quality to support the previous view that all types of NPC are variants of EBV-infected neoplasia. Bcl-2 was observed in the basal layer of normal nasopharyngeal mucosa and also at cytoplasmic level in 42 of 55 (76.4%) NPC cases. Mitotic neoplastic cells usually showed strong cytoplasmic and chromosomal staining, a finding not well referred to previously. Bcl-2 expression was significantly associated (p<0.05) to undifferentiated NPC (UNPC) when a histological classification with only two major microscopical types was applied. No close correlations were found between the presence of EBV-DNA, NPC location, clinical stage and age or sex of the patients in relation to Bcl-2 positive expression. However, when comparing Bcl-2 expression and known survival mean of the patients, significant differences were observed (p<0.001) so that mean survivals were 31.1, 24.4, 52.2 and 54.1 months respectively for NPC patients with -, +, ++ and Bcl-2 immunoreactivity. Nevertheless this better clinical outcome in Bcl-2 NPC positive cases may depend on the histological type due to close relationship with UNPC. Only studies of larger series with long-term follow-up and multivariate analyses may document whether Bcl-2 expression is an independent prognostic marker in the evolution of NPC patients.

Adolescent↗
PubMed1996

[Vascular anomalies presenting as middle ear mass].

We study several cases of patients who presented clinical symptoms indicating the presence of a middle ear mass (tinnitus, hearing loss, otorrhea, otorrhagia...). We had to rule out the presence of an expanding tumour (either in the form of a cholesteatoma or a glomus tumor) and the existence of vascular anomalies of the middle ear (enlarged jugular bulb or jugular megabulb deformity). Due to the possibility of a different treatment in each particular case (radiotherapy, radical surgery, jugular vein ligation or even no treatment at all), the relative value of various imaging techniques and/or a possible surgical approach before arriving to a conclusive diagnosis, is discussed.

Adolescent↗
PubMed1996

[Surgery of the cochlear implant: complications].

From 1991 to 1994 13 patients underwent cochlear implant in our Department. The surgical results and complications in this group of patients are reviewed. In all cases the cochlear implant was successful and no major complications were recorded. The most common problems was transient dizziness or imbalance. Other complications were minor facial nerve stimulation during the programming of the device, dehiscence of the suture in the tragal region, problems in the insertion of the electrodes in the scala tympani and a case that needed reimplantation due to technical problems with the device. We consider that a proper selection of cases and a precise surgical technique are essential in order to achieve the adaptation of the cochlear implant and avoid pitfalls.

Adolescent↗
PubMed1995

Circulating auto-antibodies in Ménière's disease.

In the last years, it has been claimed that patients suffering from Menière's disease exhibit Circulating Immune Complexes, as well as free antibodies specifically directed against type II collagen, a component of the mammal inner ear. Furthermore, by means of repeated injections of type II collagen to the guinea-pig. Menière's disease has been reproduced. Taken together, all these features strongly suggest that Menière's disease fulfills most of the postulates that Witebsky established for the classification of auto-immune diseases. However, in spite of being a very well known marker of auto-immune conditions, non organ nor species specific Circulating Auto-Antibodies (CAA) have not been reported, to our knowledge, in Meniere's disease. Based upon this fact, Anti-Nuclear, Anti-Mitochondrial, Anti-Smooth Muscle, Anti-LKM and Anti-Parietal Gastric Cells Auto-Antibodies have been investigated in 49 patients diagnosed as having Meniere's disease according to the criteria of the AAOO. All of them were asymptomatic at the time of the study. Seventy eight serum samples from Normal Healthy Subjects (NHS) constituted the control group. CAA were tested by indirect immunofluorescence on rat organs according to the method described by Coons. Additionally, the seric levels of C3, and C4 as well as the haemolytic capacity (CH-50) of the serum samples were tested. Furthermore, Circulating Immune Complexes (CIC) as well as the Complement-Mediated Mechanisms involved in the clearance of CIC (Complement-Mediated Solubilization and Inhibition of the Immune Precipitation) were investigated in parallel.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[Osteoma of the middle ear].

Osteomas of the middle ear are extremely rare. Those of the mastoid process being most frequent encountered als the tympanic sitting. Extracanalicular osteomas of the temporal bone are scarce. Bibliography about this particular subject account for 60 communications, only 9 with reference to the middle ear. The AA. report the case of an osteoma of the left incus in an 17-years-old boy, suffering a progressive deafness dating from 3 years term. The otoscopy showed a reddish mass protruding in the tympanum. TC and MNR provided evidence of a mass involving de auditory ossicula. Through an exploratory tympanotomy could be removed the anomaly. Histopathology make sure the diagnosis of osteoma. The AA. remark some clinical and surgical features of the piece compared with the other 10 cases reported in the literature reviewed.

Adolescent↗
PubMed1993

[Deafness in patients with osteogenesis imperfecta].

This study deals with 8 cases of progressive deafness in patients with abnormalities in growth and skeletal disease, suffering from Osteogenesis imperfecta (5 of them are a familial case). The work is both and audiological and radiological research of the temporal bone, done in order to uncover the reasons of the patient's deafness. This curses just like otosclerosis with a conductive component (fixation of the stapes) and a sensitive one (cochlear demineralization), starting up in adolescence as bilateral and symmetric process. Because of its progressive nature the AA, recommend as treatment the ear prostheses and refuse the surgery of the stapes.

Adolescent↗
PubMed1993

[ENT emergencies in a tertiary hospital. Study of frequency and etiology].

We have reviewed 19,061 emergencies attended in the ENT Department of our Hospital, over a period of 3 years. And analyzed the aetiologic distribution and the frequency of the cases, finding out the most frequent pathology were the external otitis followed by epistaxis. In the paper are also considered their relation with other parameters such as sex (no differences), age (25-35 years) and seriousness, this latter not being of gravity. Finally, we've studied the amount and degree of appropriteness of the visits attended and found out that near half of the cases could be attended in a less specializated centers.

Adult↗
PubMed1991

[Oculographic findings in the Arnold-Chiari malformation type I].

The paper deals with 5 adults carriers of this syndrome diagnosed by means of nuclear magnetic resonance (NMR). Neither the conventional radiography nor the plain computerized tomography showed indicative clues of the deformity. However electronystagmography prove in all cases a vertical down beating nystagmus. In one instance the nystagmus become rotatory at lateral glance. In all cases appeared an altered smooth pursuit and a lack of suppression fixation of the vestibular nystagmus. The AA. emphasize the diagnostic value of the electronystagmography (which tracings could spare several other, sometimes expensive, examinations) and suggest a prompt MRI.

Adult↗
PubMed1984

The commissural neurons of the inferior colliculus of the rat.

During systematic observation of the cellular subnuclei of the inferior colliculus of adult rats, it was noted that in the zone of the intercollicular commissure, numerous neuronal perikaria appear intermingled between the commissural fibers. The neurons were studied using Golgi and TEM methods and classified according to their dendritic pattern in the isodendritic (15%), allodendritic (19%) and intermediate forms (66%) of neurons. A fourth neuronal group, situated between the commissure and the upper periventricular zone, is also in relation with the commissural fibers. The constancy of these neurons and their frequently axodendritic and axosomatic synapses suggest that they play an important role in the whole function of the commissure which, at present, is not well understood in spite of the number and distinct origin of their afferents.

Animals↗
PubMed1984

Experimental contribution to the origin of brain-stem potentials.

The origin of the different BSP waves is open to discussion. In this work we analyze the response curves with surface and intranuclear electrodes in cats, both before and after inducing electrolytic lesions in acute and chronic phase, in order to study the subsequent alterations. We found that waves whose origins are attributed to specific regions of the acoustic pathway when carried out with surface electrodes, fail to correspond with the results obtained by intranuclear electrodes. On the other hand, although the lesions to the lowest part of the acoustic pathway (cochlear nuclei) cause important alterations in the recordings, these alterations become smaller as the lesions are induced higher up the pathway. Thus, we believe that the origin of the different BSP waves is due to the sum of potentials of different zones of neuron activation, and not to specific locations of the acoustic pathway; this is more evident in the delayed waves.

Animals↗