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J M Romero

Publications and source records attributed to J M Romero.

14 recordsLinked to original sources
PubMed1990

floricaula: a homeotic gene required for flower development in antirrhinum majus.

Plants carrying the floricaula (flo) mutation cannot make the transition from inflorescence to floral meristems and have indeterminate shoots in place of flowers. The flo-613 allele carries a Tam3 transposon insertion, which allowed the isolation of the flo locus. The flo gene encodes a putative protein (FLO) containing a proline-rich N-terminus and a highly acidic region. In situ hybridization shows that the flo gene is transiently expressed in the very early stages of flower development. The earliest expression seen is in bract primordia, followed by sepal, petal, and carpel primordia, but no expression is detected in stamen primordia. This pattern of expression has implications for how flo affects phyllotaxis, organ identity, and determinacy. We propose that flo interacts in a sequential manner with other homeotic genes affecting floral organ identity.

Amino Acid Sequence↗
PubMed1989

Determination of intracellular nitrate.

A sensitive procedure has been developed for the determination of intracellular nitrate. The method includes: (i) preparation of cell lysates in 2 M-H3PO4 after separation of cells from the outer medium by rapid centrifugation through a layer of silicone oil, and (ii) subsequent nitrate analysis by ion-exchange h.p.l.c. with, as mobile phase, a solution containing 50 mM-H3PO4 and 2% (v/v) tetrahydrofuran, adjusted to pH 1.9 with NaOH. The determination of nitrate is subjected to interference by chloride and sulphate when present in the samples at high concentrations. Nitrite also interferes, but it is easily eliminated by treatment of the samples with sulphamic acid. The method has been successfully applied to the study of nitrate transport in the unicellular cyanobacterium Anacystis nidulans.

Biological Transport↗
PubMed1989

Relationship between a 47-kDa cytoplasmic membrane polypeptide and nitrate transport in Anacystis nidulans.

The polypeptide composition of cytoplasmic membranes of the cyanobacterium Anacystis nidulans changes in response to variations in the nitrogen source available to the cells, differing specifically in the amount of a polypeptide of 47-kDa molecular mass. Synthesis of the polypeptide and expression of nitrate transport activity are repressed by ammonium. Transfer of ammonium-grown cells to a medium containing nitrate as the sole nitrogen source results in parallel development of the 47-kDa polypeptide and nitrate transport activity of the cells. These results suggest the involvement of the 47-kDa cytoplasmic membrane polypeptide in nitrate transport by A. nidulans.

Carrier Proteins↗
PubMed1987

Modulation of nitrate uptake in Anacystis nidulans by the balance between ammonium assimilation and CO2 fixation.

Gradual inhibition of ammonium assimilation in Anacystis nidulans cells by increasing concentrations of 5-hydroxylysine resulted in a progressive enhancement of nitrate uptake. For 5-hydroxylysine-treated cells, the magnitude of the inhibition of nitrate uptake promoted by added ammonium was dependent on the ammonium assimilation capacity. In cells with a moderate ammonium assimilation activity, acceleration of CO2 fixation induced by bicarbonate addition antagonized the negative effect of ammonium, allowing full nitrate uptake activity. The results support the contention that nitrate utilization is under the feed-back control exerted by products of its own assimilation via ammonium, the inhibitory effect being potentiated by ammonium addition and alleviated by enhanced CO2 fixation. Results of amino acid analysis in cells exhibiting different capacities to utilize nitrate speak against these compounds as direct effectors of nitrate uptake.

Amino Acids↗
PubMed1987

Regulated nitrate transport in the cyanobacterium Anacystis nidulans.

Intracellular accumulation of nitrate, indicative of the operation of an active nitrate transport system, has been measured in intact cells of the cyanobacterium Anacystis nidulans. The ability of the cells to accumulate nitrate was effectively hindered by either ammonium addition or selective inhibition of CO2 fixation by DL-glyceraldehyde, with the effect of either compound being prevented by previously blocking ammonium assimilation. The results support the contention that nitrate utilization in cyanobacteria is regulated at the level of nitrate transport through the concerted action of ammonium assimilation and CO2 fixation.

Ammonia↗
PubMed1985

Inhibition of nitrate utilization by amino acids in intact Anacystis nidulans cells.

In an attempt to establish the nature of the ammonium-assimilation products which mediate the inhibition by ammonium of nitrate uptake in cyanobacteria, the effect of different amino acids on nitrate utilization by intact Anacystis nidulans cells has been assayed. To exclude an indirect inhibition of nitrate uptake through the ammonium which the amino acids might release, the cells were pretreated with L-methionine-D,L-sulfoximine (MSX), a potent inactivator of glutamine synthetase. Under these conditions, several L-amino acids, but not the corresponding D-isomers, affected nitrate utilization to a variable extent, causing inhibitions ranging between 20 and 80% when added at 20 mM concentration. For most of the inhibitory amino acids, including L-isoleucine, L-leucine and L-valine, a correlation was found between their ability to act as amino group donors to alpha-ketoglutarate, in reactions catalyzed by A. nidulans cell-free extracts, and their inhibitory effect on nitrate utilization. L-Glutamine, L-asparagine and glycine, being effective inhibitors of nitrate utilization, were poor substrates for the transaminating activity to alpha-ketoglutarate, however. The possible role of the latter amino acids as mediators in the ammonium-promoted inhibition of nitrate uptake is discussed.

Amino Acids↗
PubMed1985

Dependence of nitrate utilization upon active CO2 fixation in Anacystis nidulans: a regulatory aspect of the interaction between photosynthetic carbon and nitrogen metabolism.

Specific inhibition of photosynthetic CO2 fixation in Anacystis nidulans cells by D,L-glyceraldehyde resulted in the simultaneous inhibition of nitrate utilization, indicating a dependence of the latter process upon the provision of CO2-fixation products. This dependence was lost in cells treated with L-methionine-D,L-sulfoximine or azaserine, effective inhibitors of ammonium assimilation. In these cells, nitrate uptake could proceed at rates similar to those in control cells even if CO2 fixation was severely inhibited by D,L-glyceraldehyde. The results support the contention that CO2-fixation products participate in the control of nitrate uptake in A. nidulans by preventing the accumulation of certain ammonium derivatives which are negative effectors of nitrate uptake.

Ammonia↗
PubMed1983

Bioelectrical tissue resistance during various methods of myocardial preservation.

Twenty-one mongrel dogs underwent cardiopulmonary bypass (CPB) and ischemic cardiac arrest for 60 minutes. The bioelectrical tissue impedance, water content, and ultrastructure of the myocardium were studied and correlated with various types of myocardial protection applied. The animals were divided into three groups according to the myocardial protection applied: Group 1, moderate general hypothermia; Group 2, moderate general and local hypothermia; Group 3, moderate general hypothermia and crystalloid cardioplegia. The hearts from 3 normal dogs served as controls. After 35 minutes of ischemic arrest, the difference in bioelectrical impedance of the myocardium of the left ventricle between Groups 1 and 2 was highly significant (p less than 0.001); in Groups 2 and 3, a significant difference was observed after 50 minutes. The heart water content in all three groups increased over that found in the hearts of the control animals, but there was no significant difference between Groups 2 and 3. There was evidence by ultramicroscopic study of ischemic damage to the myocardium in all of the experimental groups. Damage was less evident in Groups 2 and 3. We conclude that measurement of myocardial bioelectrical tissue resistance is a sensitive indicator of myocardial damage due to ischemia and may be useful clinically in determining the need for and type of cardiac resuscitation, particularly following CPB.

Animals↗
PubMed1980

[Comparative evaluation of prostate size by transabdominal echography, urethral profile and radiology (author's transl)].

Disappointed by the approximate assessment of prostate size given by traditional methods (rectal examination, endovesical filling defect produced by the hypertrophic organ in the secretory cystogram, length of the prostatic urethra by micturating urethrography), the authors carried out a prospective study in 100 patients undergoing surgery for benign prostatic hypertrophy which compared traditional data with those provided by transabdominal prostatic echography and the measurement of urethral manometric profile. Determination of the maximum dimensions of the adenoma was used to calculate its volume and weight. Ultrasound studies gave the most accurate information : 95% correct results. This was followed by the measurement of urethral profile with 81% of accurate results (but this is an instrumental procedure which has certain disadvantages). Radiology takes 3rd place, with 59% accurate results and rectal examination immediately after with 58%.

Abdomen↗
PubMed1969

[Conization].

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Adult↗