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J Mora

Publications and source records attributed to J Mora.

At least 163 records · Page 9Linked to original sources
PubMed1977

Neurospora crassa glutamine synthetase. Role of enzyme synthesis and degradation on the regulation of enzyme concentration during exponential growth.

The specific activity of Neurospora crassa glutamine synthetase varies according to the nitrogen source in which the organism is grown. In a poor nitrogen source such as glutamate, the specific activity of the enzyme is higher than that found in good nitrogen sources such as ammonium or glutamine. These differences in specific enzyme activity correspond to differences in enzyme concentration. The relative rates of glutamine synthetase synthesis and degradation were measured in exponential cultures grown in different nitrogen sources. The differences in enzyme concentration are explained by differences in the relative rate of enzyme synthesis.

Ammonia↗
PubMed1977

Nitrogen regulation of arginase in Neurospora crassa.

The final products of the arginine catabolism that can be utilized as a nitrogen source in Neurospora crassa are ammonium, glutamic acid, and glutamine. The effect of these compounds on arginase induction by arginine was studied. In wild-type strain 74-A, induction by arginine was almost completely repressed by glutamic acid plus ammonium, whereas ammonium or glutamic acid alone had only moderate effects. Arginine products of catabolism also repressed arginase induction. A mutant, ure-1, which lacks urease activity, hyperinduced its arginase with arginine as a nitrogen source. The addition of either ammonium or glutamine produced effects similar to those in the wild-type strain. The effect of ammonium on arginase induction is mediated through its conversion into glutamine. This was demonstrated in mutant am-1, which lacks L-glutamate dehydrogenase activity. In this mutant, the effect of glutamic acid was reduced, and, with ammonium, it was completely lost. The addition of glutamine or glutamic acid plus ammonium to this strain decreased by threefold the induction of arginase by arginine. Proline, a final product of arginine catabolism, competitively inhibited arginase activity. This effect and the repression of arginase by glutamine are examples of negative modulation of the first enzyme in a catabolic pathway by its final products.

Ammonia↗
PubMed1972

Regulation of arginase activity by intermediates of the arginine biosynthetic pathway in Neurospora crassa.

It has been found that, in Neurospora crassa, arginine synthesized from exogenous citrulline was not as effectively hydrolyzed as exogenous arginine. This was explained by the observed inhibition of arginase in vitro and in vivo by citrulline. The high arginine pool formed from exogenous citrulline feedback inhibits the arginine pathway. These two factors allow exogenous citrulline to be used adventitiously and efficiently as an arginine source. Finally, it was found that ornithine was a strong inhibitor of arginase. This suggests that the characteristically high ornithine pool of minimal cultures of Neurospora may act to control a potentially wasteful catabolism of endogenous arginine by arginase.

Arginase↗
PubMed1972

Interactions between amino acid transport systems in Neurospora crassa.

Mutants of Neurospora crassa, selected as resistant to l-canavanine and l-thialysine, are partially deficient in the uptake of basic amino acids. Neutral amino acids completely inhibit uptake of basic amino acids, and this inhibition is dependent on the activity of a neutral amino acid permease. In contradistinction, mutants resistant to 4-methyl-dl-tryptophan are partially deficient in the uptake of neutral amino acids. Basic amino acids completely inhibit neutral amino acid uptake, and this inhibition is dependent on the activity of a basic amino acid permease. It is proposed that these specific transport systems compete with a general amino acid permease for some common element. The general permease is also regulated by ammonia, the amino acid pool, or both. The activity of the general permease can be eliminated phenotypically by a high concentration of glycerol or a high temperature. It is also shown that l-citrulline is transported by the neutral amino acid permease and by the general amino acid permease.

Amino Acids↗
PubMed1968

Mutants of Neurospora crassa deficient in ornithine-delta-transmainase.

The arg-12(s) mutation of Neurospora causes a partial block in the ornithine transcarbamylase (OTC) reaction. Strains carrying this mutation will use endogenous ornithine, but not exogenous ornithine, as a precursor of arginine. Certain strains carrying arg-12(s) may be used for direct selection of variants able to use exogenous ornithine as an arginine precursor. Among eight such derivatives, six lacked the catabolic enzyme ornithine transaminase (OTA). All six mutations were alleles of a single gene, designated ota, on linkage group III. No mutation affected arginase, the first enzyme in the catabolic pathway with OTA. Strains carrying ota mutations alone are vigorous prototrophs, but, unlike wild-type Neurospora, fail to use ornithine efficiently as a sole nitrogen source. The selection method by which ota mutants arose suggests that OTA is severely competitive with OTC for exogeneous ornithine.

Arginase↗
PubMed1965

Characteristics of arginases from ureotelic and non-ureotelic animals.

1. Livers of ureotelic and uricotelic animals possess the capacity, to a varying extent, of hydrolysing l-arginine and other guanidino compounds. 2. Three different enzymes responsible for such activity have been separated and partially characterized. They are the ;ureotelic' arginase, the ;uricotelic' arginase (both of them specific for l-arginine) and the guanidinobutyrate ureohydrolase (able to hydrolyse beta-guanidinopropionate, gamma-guanidinobutyrate and d-arginine but not l-arginine or guanidinoacetate). 3. The implication of the advent of a ;ureotelic' arginase in the integration of the Krebs-Henseleit cycle is discussed.

Acetates↗
PubMedDate not supplied

[CEA and Cyfra 21.1 study pre-treatment in 252 patients with head and neck carcinomas].

INTRODUCTION: Squamous cell carcinoma is the most frequent malignant tumor in the head and neck. As in most malignant tumors, the earlier the diagnosis, is made the longer the survivalis. Several molecules, including CEA and Cyfra 21.1, have been evaluated in an attempt to improve diagnosis and follow-up. OBJECTIVE: To investigate whether CEA and Cyfra 21.1 present pathological increased values prior to treatment, and to correlate tumor and patient characteristics with CEA and Cyfra 21.1 levels. MATERIAL AND METHODS: CEA and Cyfra 21.1 were measured pre-treatment in sera of 252 patients treated for head and neck tumors from1999 to 2003. RESULTS: Increases of CEA were detected in 23.6%, and increases of Cyfra 21.1 in 19.1% of patients. Significative differences were found between the concentrations of Cyfra 21.1 related to the tumor stage, local extension, histological grade, and an increasing relation with age. No differences were found in relation to the primary tumor site. Regarding CEA, the only finding was an increased relation between concentrations of this marker and cigarette and alcohol habits. CONCLUSIONS: Cyfra 21.1 does not appear to be a good marker for tumoral screening of head and neck carcinomas. However, a good correlation was observed between sera concentrations of Cyfra 21.1, tumoral burden, and histological grade of the tumor, but this was not the case with CEA.

Adult↗
PubMedDate not supplied

[Neurological explorations in Nuclear Medicine. A Spanish survey].

A representative Nuclear Medicine Service in Spain has two or three gammacameras. It performs neurologic studies one or two days at week wich account 2,1% of total workload. Brain Perfusion SPECT, specially in cognitive disorders, is the most frequent application. Neurooncology has a lower but established relevance. Neuroreceptors imaging are increasing in the last months. Emission tomography is obtained using a double-headed camera fitted with high-resolution parallel hole collimators and a half an hour total acquisition time. Datasets are reconstructed by filtered backprojection with Butterworth or Metz filtres. Images are visually interpreted with comparison to MRI and/or CT findings.

Brain Neoplasms↗
PubMedDate not supplied

[First diagnostic choice in patients with high clinical suspicion of pulmonary thromboembolism: helical CT or ventilation/perfusion pulmonary scintigraphy?].

AIM: Comparative analysis about helical CT (ThC) vs ventilation-perfusion pulmonary scintigraphy (V/P Sc) diagnosis effectiveness, as a first diagnosis technique in patients with high clinical suspicion of pulmonary thromboembolism (PT). MATERIALS AND METHODS: Prospective study of 30 patients with high clinical suspicion and high Dimer-D levels (> 250 microg/l). The diagnosis was defined as anticoagulant therapeutic prescription and posterior clinical evolution. V/P Sc were performed to each patient within the next 48 h (an average of 14.8 h) after TCh, without anticoagulant treatment. We classified the scintigrams according to the PIOPED criteria and hTC images as positive, negative and indeterminated. RESULTS: In sixteen patients final diagnosis was PT: in 9 both techniques were positive; in 5 scintigraphy was positive with normal hTC and in 1, hTC was normal with negative scintigraphy. The last case was an indeterminated hTC with negative scintigraphy. In fourteen patients, final diagnosis was non-PT: in 6 both techniques were negative; in 7 scintigraphy was negative with positive hTC and in 1, both results were indeterminated. The sensitivity, specificity, positive predictive value, negative predictive value and efficiency were respectively 87.5, 100, 100, 87.5 and 93 % for V/P Sc and 62, 50, 58.8, 53.8 and 53 % for TCh. CONCLUSION: V/P Sc has better PT diagnosis reliability. It is recommended to do V/P Sc in all patients with high clinical suspicion of PT.

Adult↗
PubMedDate not supplied

The enhancement of ammonium assimilation in Rhizobium etli prevents nodulation of Phaseolus vulgaris.

The modification of the ammonium assimilation pathway of Rhizobium etli (GS-GOGAT) by adding an additional ammonium assimilation enzyme, GDH, strongly affects its symbiotic interaction with beans. The plasmid pAM1a, based in the stable vector pTR101 (M. Weinstein, R. C. Roberts, and D. R. Helsinki, J. Bacteriol. 174,7486-7489, 1992), containing the Escherichia coli gdhA gene flanked by two transcription-translation terminators was constructed. The expression of GDH in both, the wild type (CFN42/pAM1a) and a ntrC- mutant (CFN2012/pAM1a) R. etli strains, gave a similar metabolic effect, i.e., high GDH and reduced GOGAT activities, and an increased synthesis and excretion of several amino acids. The total inhibition of bean nodulation was observed when the minimum optimal inoculum of R. etli CFN42/pAM1a was used; however, an effective symbiosis occurred with the CFN2012/pAM1a mutant strain. While a total inhibition of the induction of the nodA gene by bean root exudate or by naringenin was observed in the CFN42/pAM1a strain, at 10 mM ammonium, the CFN2012/pAM1a showed an optimal nodA gene induction. A correlation between nodA gene induction, Nod factor production, and nodulation was observed. We conclude that in R. etli, there is a down-regulation of nod gene expression and nodulation when a high internal nitrogen content is built up by the presence of a functional GDH and that NtrC is involved in such regulation. An instability of the plasmid harboring the gdhA gene was observed during symbiosis, indicating a strong selection against cells containing this plasmid.

Down-Regulation↗
PubMedDate not supplied

[Clinical utility of fused 67Ga SPECT/CT scan images in patients with lymphoma].

AIM: The aim of this work is to show the clinical utility of the fused SPECT 67Ga/CT images in patients with lymphoma. MATERIAL AND METHOD: 44 patients (22 male) with lymphoma have been studied. 22 with Hodgkin's disease and 22 with non Hodgkin lymphoma. 59 studies were performed (33 thorax-cervical [T], 24 abdomen [A] and 2 skull-cervical area [SC]) with an hybrid gammacamera Millenium VG. We acquire consecutively a whole body scan, a SPECT and a CT, for its fusion with the SPECT, of the affects areas. The images were evaluated by two experts blinded, who classify the contribution of the fusion of images respect to the SPECT like: non changes, it improves the location or changes the extension of the injuries and it changes the staging. Final lesion location was confirmed by a high resolution CT performed within one month. RESULTS: 32/59 studies did not change the location or extension of the injuries (20T, 12A), 23/59 studies changed the location or extension of the injuries (12T, 9A and 2 SC) and on 4/59 the change of location induced a change of staging respect to showed by the SPECT. CONCLUSION: To make fused SPECT 67Ga/CT images in patients with lymphoma allows improving the diagnostic precision in a 46% of the cases, mainly in the abdominal, bone and of the diaphragmatic area studies.

Abdominal Neoplasms↗