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P Candau

Publications and source records attributed to P Candau.

At least 19 recordsLinked to original sources
PubMed1995

Existence of two ferredoxin-glutamate synthases in the cyanobacterium Synechocystis sp. PCC 6803. Isolation and insertional inactivation of gltB and gltS genes.

The first two genes of ferredoxin-dependent glutamate synthase (Fd-GOGAT) from a prokaryotic organism, the cyanobacterium Synechocystis sp. PCC 6803, were cloned in Escherichia coli. Partial sequencing of the cloned genomic DNA, of the 6.3 kb Hind III and 9.3 kb Cla I fragments, confirmed the existence of two different genes coding for glutamate synthases, named gltB and gltS. The gltB gene was completely sequenced and encodes for a polypeptide of 1550 amino acid residues (M(r) 168,964). Comparative analysis of the gltB deduced amino acid sequence against other glutamate synthases shows a higher identity with the alfalfa NADH-GOGAT (55.2%) than with the corresponding Fd-GOGAT from the higher plants maize and spinach (about 43%), the red alga Antithamnion sp. (42%) or with the NADPH-GOGAT of bacterial source, such as Escherichia coli (41%) and Azospirillum brasilense (45%). The detailed analysis of Synechocystis gltB deduced amino acid sequence shows strongly conserved regions that have been assigned to the 3Fe-4S cluster (CX5CHX3C), the FMN-binding domain and the glutamine-amide transferase domain. Insertional inactivation of gltB and gltS genes revealed that both genes code for ferredoxin-dependent glutamate synthases which were nonessential for Synechocystis growth, as shown by the ferredoxin-dependent glutamate synthase activity and western-blot analysis of the mutant strains.

Amino Acid Oxidoreductases↗
PubMed1995

The NADP-glutamate dehydrogenase of the cyanobacterium Synechocystis 6803: cloning, transcriptional analysis and disruption of the gdhA gene.

The gdhA gene of Synechocystis PCC 6803, which encodes an NADP-dependent glutamate dehydrogenase (NADP-GDH), has been cloned by complementation of an Escherichia coli glutamate auxotroph. This gene was found to code for a polypeptide of 428 amino acid residues, whose sequence shows high identity with those of archaebacteria (42-47%), some Gram-positive bacteria (40-44%) and mammals (37%). The minimal fragment of Synechocystis DNA required for complementation (2kb) carries the gdhA gene preceded by an open reading frame (ORF2) encoding a polypeptide of 130 amino acids. ORF2 and gdhA are co-transcribed as a 1.9 kb mRNA, but shorter transcripts including only gdhA were also detected. Two promoter regions were identified upon transcriptional fusion to the cat reporter gene of a promoter probe plasmid. Transcription from the promoter upstream of ORF2 was found to be regulated depending on the growth phase of Synechocystis, in parallel to NADP-GDH activity. This promoter is expressed in Escherichia coli too, in contrast to the second promoter, located between ORF2 and gdhA, which was silent in E. coli and did not respond to the stage of growth in Synechocystis. Disruption of the cyanobacterial gdhA gene with a chloramphenicol resistance cassette yielded a mutant strain totally lacking NADP-GDH activity, demonstrating that this gene is not essential to Synechocystis 6803 under our laboratory conditions.

Amino Acid Sequence↗
PubMed1992

Purification and characterization of the ferredoxin-glutamate synthase from the unicellular cyanobacterium Synechococcus sp. PCC 6301.

Ferredoxin-glutamate synthase from the unicellular cyanobacterium Synechococcus sp. PCC 6301 has been purified using, as main steps, ethanol fractionation in the presence of high ionic strength, ion-exchange chromatography and ferredoxin-Sepharose affinity chromatography. The overall process yielded an homogeneous enzyme with a specific activity of 30 U/mg protein, after a purification of 2800-fold with a recovery of 43%. The molecular mass of the native protein was 156 kDa, as calculated from its Stokes radius (rS, 4.32 nm) and sedimentation coefficient (S20,w, 8.46 S). The size was also estimated by SDS/PAGE as 160 kDa, indicating that the native protein was a monomer. The enzyme exhibited absorption maxima at 279, 370 and 438 nm and a A279/A438 absorbance ratio of 11. One molecule of FMN, but not FAD, was found/molecule native protein. The addition of dithionite resulted in the loss of the absorption peak at 438 nm, which was restored by the addition of 2-oxoglutarate, thus indicating that the prosthetic group is functional in catalysis. Classical hyperbolic kinetics with substrate inhibition was seen for 2-oxoglutarate. The Km values determined for glutamine and ferredoxin were 0.7 mM and 7 microM, respectively, and the apparent Km for 2-oxoglutarate was estimated to be 1.7 mM. Azaserine and 6-diazo-5-oxo-L-norleucine were potent inhibitors of the activity, while pyridoxal 5-phosphate, known to react with Lys residues, partially inactivated the enzyme. This ferredoxin-dependent glutamate synthase is, as far as we know, the first purified from prokaryotic organisms and resembles its counterpart from chloroplasts, suggesting that cyanobacterial glutamate synthase may have been the ancestor of ferredoxin-glutamate synthase in plants.

Amino Acid Oxidoreductases↗
PubMed1992

[Exposure of the facial recess through the ear canal. Value in posterosuperior retraction pockets (initial results)].

19 patients had surgery for progressive [17] and/or symptomatic [2] posterior attic retraction pockets involving the facial recess. Exposition of the suprapyramidal region was obtained after endaural incision by thinning the posterior wall of the ear canal and removing the posterior-superior portion of the tympanic sulcus. This technique is less complicated than intact canal wall tympanoplasty with mastoidectomy. Yet gives similar functional results. After a mean follow-up of 20.3 months, we have observed no residual cholesteatoma and no recurrent retraction pockets. Unlike posterior tympanoplasty, this technique makes it possible to meticulously remove the osteitic bone invariably found in the facial recess when there is infection of the retraction pocket.

Adolescent↗
PubMed1991

In vitro reactivation of in vivo ammonium-inactivated glutamine synthetase from Synechocystis sp. PCC 6803.

Glutamine synthetase from Synechocystis sp. strain PCC 6803 is inactivated by ammonium addition to cells growing with nitrate as the nitrogen source. The enzyme can be reactivated in vitro by different methods such as alkaline phosphatase treatment, but not phosphodiesterase, by raising the pH of the crude extract to values higher than 8, by increasing the ionic strength of the cell-free extract, or by preincubation with organic solvents, such as 2-propanol and ethanol. These results suggest that the loss of glutamine synthetase activity promoted by ammonium involves the non-covalent binding of a phosphorylated compound to the enzyme and support previous results that rule out the existence of an adenylylation/deadenylylation system functioning in the regulation of cyanobacterial glutamine synthetase.

Alkaline Phosphatase↗
PubMed1991

An NAD-specific glutamate dehydrogenase from cyanobacteria. Identification and properties.

The unicellular cyanobacterium Synechocystis sp. PCC 6803 presents a hexameric NAD-specific glutamate dehydrogenase with a molecular mass of 295 kDa. The enzyme differs from the NADP-glutamate dehydrogenase found in the same strain and is coded by a different gene. NAD-glutamate dehydrogenase shows a high coenzyme specificity, catalyzes preferentially glutamate formation and presents Km values for ammonium, NADH and 2-oxoglutarate of 4.5 mM, 50 microM and 1.8 mM respectively. An animating role for the enzyme is discussed.

Ammonia↗
PubMed1991

Regulation of glutamine synthetase activity in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 by the nitrogen source: effect of ammonium.

Glutamine synthetase activity from Synechocystis sp. strain PCC 6803 is regulated as a function of the nitrogen source available in the medium. Addition of 0.25 mM NH4Cl to nitrate-grown cells promotes a clear short-term inactivation of glutamine synthetase, whose enzyme activity decreases to 5 to 10% of the initial value in 25 min. The intracellular levels of glutamine, determined under various conditions, taken together with the results obtained with azaserine (an inhibitor of transamidases), rule out the possibility that glutamine per se is responsible for glutamine synthetase inactivation. Nitrogen starvation attenuates the ammonium-mediated glutamine synthetase inactivation, indicating that glutamine synthetase regulation is modulated through the internal balance between carbon-nitrogen compounds and carbon compounds. The parallelism observed between the glutamine synthetase activity and the internal concentration of alpha-ketoglutarate suggests that this metabolite could play a role as a positive effector of glutamine synthetase activity in Synechocystis sp. Despite the similarities of this physiological system to that described for enterobacteria, the lack of in vivo 32P labeling of glutamine synthetase during the inactivation process excludes the existence of an adenylylation-deadenylylation system in this cyanobacterium.

Ammonia↗
PubMed1991

[Role of emergency subtotal colectomy in neoplastic obstructions of the left colon].

From 1984 to 1990, 60 patients underwent emergent surgery for a neoplastic obstruction of the left colon. We performed 19 colostomies without initial exeresis and 41 immediate tumoral resections. In the latter group, five subtotal colectomies (S.T.C.) were performed, including four with immediate mechanical anastomosis. Two patients had synchronous cancers and three had pre-perforating cecal lesions. Three patients had an associated general peritonitis. Three of the patients treated with STC died. These were these patients with general peritonitis, two of whom also had hepatic metastases. The data found in the literature on neoplastic obstructions of the left colon treated with STC with immediate anastomosis (227 cases are published) show an overall mortality rate of 8.4% with 24% morbidity, a complication of the anastomosis occurring in 4.5% of all cases.

Aged↗
PubMed1990

Purification and properties of glutamine synthetases from the cyanobacteria Synechocystis sp. strain PCC 6803 and Calothrix sp. strain PCC 7601.

Glutamine synthetases (GSs) from two cyanobacteria, one unicellular (Synechocystis sp. strain PCC 6803) and the other filamentous (Calothrix sp. strain PCC 7601 [Fremyella diplosiphon]), were purified to homogeneity. The biosynthetic activities of both enzymes were strongly inhibited by ADP, indicating that the energy charge of the cell might regulate the GS activity. Both cyanobacteria exhibited an ammonium-mediated repression of GS synthesis. In addition, the Synechocystis sp. showed an inactivation of GS promoted by ammonium that had not been demonstrated previously in cyanobacteria.

Adenosine Diphosphate↗
PubMed1989

[Cholesteatoma of the ear].

Cholesteatoma of the ear is characterized by the presence of a keratinizing squamous epithelium in the cavities of the middle ear. The epithelium invades the ear either by direct migration or by retraction of the eardrum. Owing to is potentials for migration, desquamation, bone erosion and infection, it is for most of the complications of chronic otitis and fully justifies the adjective "dangerous" applied to chronic cholesteatomatous otitis. The clinical diagnosis rests on microscope otoscopy. Audiometry informs on the degree of hearing loss and on the state of the contralateral ear. Standard radiography and computerized tomography of the petrous bone evaluate the extent of the lesion. Treatment is purely surgical: it consists of excision of the entire epithelium that has entered the middle ear and, secondarily, conservation or improvement of hearing. Whatever the surgical technique used, the frequency of recurrences calls for long-term follow-up.

Cholesteatoma↗
PubMed1989

Ammonia assimilating enzymes from cyanobacteria: in situ and in vitro assay using high-performance liquid chromatography.

Assay systems for ammonia assimilating enzymes in cyanobacteria are reported. Glutamine synthetase, glutamate synthase, and glutamate dehydrogenase can be easily assayed in situ, after the cells are made permeable to the reagents, or in vitro. The method is based upon the quantitation of glutamine or glutamate after the separation, when needed, of their o-phthaldialdehyde derivatives by reverse-phase high-performance liquid chromatography on a C18 column. The isocratic elution and the fluorometric detection of the amino acid derivatives make the method fast, simple, sensitive, and free of the assay artifacts which can be produced in coupled assays or when spectrophotometric measurements are carried out in the turbid samples employed for in situ assays.

Ammonia↗
PubMed1987

[Refractory cancer pain. Subarachnoid or epidural administration of morphine].

Spinal analgesia, a new method for relieving refractory cancer pain, was tested in 19 patients. A catheter was installed in the subarachnoid (17 cases) or peridural (2 cases) space and connected to a subcutaneous site of injection. The success rate at 10 days was 68%. In 11 patients pain was relieved throughout the course of the malignant disease, with doses that did not exceed 6 mg in 7 patients and 10 mg in the remaining 4 patients. The most severe complications were leakage of the cerebrospinal fluid in 1 case, meningitis after 18 months of injection in 1 case and displacement of the catheter in 3 cases.

Adult↗
PubMed1985

[Vascular malformations of the digestive tract: a cause of severe digestive hemorrhage. Apropos of 2 cases].

We report on two cases of angiodysplasia of the digestive tract complicated by serious acute bleeding. The preoperative diagnoses were made by angiography. One case concerned a voluminous jejunal lesion which was macroscopically visible; the other concerned a punctiform lesion detected only by angiography and not found on the pathology specimen. The authors insist on the potential gravity of these angiodysplastic lesions, the necessity to perform an emergency celio-mesenteric angiogram when confronted with a serious digestive tract hemorrhage non-explained by conventional methods of exploration when they can be performed.

Adult↗
PubMed1985

[Early diffuse hypertrophic osteitis recurrence. Unexpected and consternating development after a large évidement cavity. Apropos of 15 cases].

The authors report 15 cases collected over a period of 13 years (1972 - 1984) of a particularly serious eventuality affecting certain evacuation cavities: Early recurrence of diffuse hypertrophic osteitis (E.R.D.H.O.). This is a rare complication, occurring in 1.5% of cases of chronic otitis. However, the fact of having operated upon 7 cases in 1984 alone, whilst during the previous 12 years, only 8 had been seen, raised the alarm. The classical pattern of this complication occurs in 3 stages, each involving surgical operation: at the outset, chronic otitis with cholesteatoma or osteitis, most often mixed, for which an "inadequate" surgical procedure is performed. then, after a variable period which may exceed 10 years, a very large evacuation cavity was created by the authors. finally, 3rd and final stage: within 6 months, this cavity filled progressively and, at operation, the authors discovered a cavity virtually completely filled with a "fantastic" "moist sugar" osteitis, requiring a new evacuation cavity, even larger than that created before. In all cases, a successful result was obtained within a varying period, sometimes accompanied by spectacular improvement in general condition. The most plausible etiopathogenic hypothesis advanced to attempt to explain this phenomenon is that of secondary infection by a varied microbial flora, including, on the one hand, aerobic organisms usually discovered in such cases (pseudomonas pyocyaneus, proteus mirabilis) and, secondly, this being of essential importance, "anaerobic" bacteria, the bacteriological diagnosis of which requires application of a strict protocol. The authors have taken three decisions following their bibliographic investigations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

[Involvement of the tympanic bone in chronic otitis (44 cases)].

44 cases of tympanic involvement in the context of chronic otitis are described. 34 occurred during active chronic otitis. This is a rare possibility (approximately 4% of our own cases of chronic otitis). The following may be mentioned amongst them: 21 cases of osteitis, for which the following concepts should be borne in mind: the extreme severity of the chronic otitis responsible, in most instances, ears which had undergone multiple surgery (17/21), lesions exclusively of osteitis, but very extensive in 2/3 of cases (14/21). 7 cases of osteolytic disease, occurring severe or atypical cholesteatomatous chronic otitis and quite often involving associated osteolysis affecting the main VII, the promontory, the bulb of the internal jugular vein, or even the carotid canal. 4 cases of diffuse sub-obstructive osteomatous disease of the walls of the E.A.M., "progressive" development of which over several months was noted in 3 cases. Finally, 2 cases of mixed disease: (osteitis--osteomatoma and osteitis--osteolysis). 8 cases occurred following myringoplasty: this is a rare eventuality (approximately 1%), 1 case only of osteolysis due to iatrogenic cholesteatoma, 7 cases of osteitis, either highly localized and not preventing further myringoplasty (4 cases), or very extensive, finally resulting in a vast evacuation cavity. In 2 cases, a malformation is the origin of involvement of the tympanic at the origin of chronic otitis was felt probable, without it being possible to reach any definite conclusion concerning auriculobranchial fistula or Huschke foramen.

Adolescent↗
PubMed1985

[Changes in bone conduction in the surgery of chronic otitis and its sequelae (evaluation of 800 operations)].

The authors undertook a study of changes in bone conduction (BC) during 800 operations carried out over a 5 years period (1979-1984) for chronic otitis or sequelae of chronic otitis. After elimination of ears with deafness (47) and cases unsuitable for evaluation (39), they finally included 714 records in the study. Only comparison of free and post-operative BC was made and using 4 conversational frequencies, not taking into account a deviation of 5 DB for each of these 4 frequencies. The study involved 317 myringoplasties: In 271 (i.e. 85,5%) there was no change in BC. Amongst them, 37 patients nevertheless showed a transient fall in BC. Of particular importance is the fact that almost 1/3 (11 to be exact) recovered only during the 2nd semester following surgery, a period which was even exceeded in the other 5 cases. 46 (i.e. 14.5%) were classified as "permanent" falls in BC. Amongst these in only 17 (i.e. 5%) were there "only" the three standard aggression factors for the I.O.: aspiration--scraping--manipulation of the tympano-ossicular system, without it being possible to attribute a predominant role to one more than the other. With regard to reaming of the E.A.M., those cases in which this could be considered responsible appeared to be infinitesimal. Furthermore, there was no statistically significant difference (reduced deviation test--"chi"2 test) between the number of falls in BC seen following myringoplasty with or without reaming. 83 tympanoplasties by Piston-Malleus, study of which led to the same conclusions as for myringoplasties. 118 masto-atticotomies, including 23 with posterior tympanotomy. Despite peri-labyrinthine and peri-ossicular scraping, results were essentially identical. 196 evacuation cavities (227-31 deafness) of which somewhat less than half only (46%) were ears undergoing surgery for the first time. Percentage of unchanged BC was here much more unfavourable, with 49 "permanent" falls in BC, i.e. 25%, of which, it must be said, 5 were minimal falls, and with, in 25 cases, a follow-up of less than 3 months.

Bone Conduction↗
PubMed1983

[Use of a severity index in 8 multidisciplinary resuscitation centers].

A universal severity index for acutely ill patients was applied to 794 acute patients treated in eight medical and surgical French intensive care units located in teaching or community hospitals either in Paris or in provincial towns. Measured on the first day in hospital from objective numerical data, the index proved reliable and correlated well with hospital mortality and the sustained therapeutic efforts of the first 24 hours. It could be used in multicentre studies to compare outcomes and evaluate new treatments.

Disease↗