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Biomedical subjects

R Fournier

Publications and source records attributed to R Fournier.

At least 55 records · Page 3Linked to original sources
PubMed1996

Secondary structure of the yeast Saccharomyces cerevisiae pre-U3A snoRNA and its implication for splicing efficiency.

The Saccharomyces cerevisiae U3 snoRNA genes contain long spliceosomal introns with noncanonical branch site sequences. By using chemical and enzymatic methods to probe the RNA secondary structure and site-directed mutagenesis, we established the complete secondary structure of the U3A snoRNA precursor. This is the first determination of the complete secondary structure of an RNA spliced in a spliceosome. The peculiar cruciform structure of the U3A snoRNA 3'-terminal region is formed in the precursor RNA and the conserved Boxes B and C are accessible for binding the U3 snoRNP proteins. The intron forms a highly folded structure with a long central stem-loop structure that brings the 5' box and the branch site together. This is in agreement with the idea that secondary structure interactions are necessary for efficient splicing of long introns in yeast. The 3' splice site is in a bulged loop and the branch site sequence is single-stranded. Surprisingly, the 5' splice site is involved in a 6-base pair interaction. We used in vitro splicing experiments to show that, despite a noncanonical branch site sequence and a base paired 5' splice site, transcripts that mimic the authentic pre-U3A snoRNA are spliced very efficiently in vitro. Sequestering the 5' splice site in a more stable structure had a negative effect on splicing, which was partially compensated by converting the branch site sequence into a canonical sequence. Analysis of spliceosomal complex formation revealed a cumulative negative effect of a base pair interaction at the 5' splice site and of a deviation to the consensus sequence at the branch site on the efficiency of spliceosome formation in vitro.

Base Composition↗
PubMed1995

[Bilateral tumors of the testis: the role of the diagnosis of carcinoma in situ in early detection].

In a series of 540 patients with testicular germ cell tumors, the diagnosis of bilateral tumor was observed nine times. Two patients presented a simultaneous bilateral tumor and for seven others a second tumor occurred after an interval varying from 1 to 16 years. The often late discovery of the contralateral cancer sometimes requires a prolonged follow up for patients with unilateral testicular malignancy. Incidence, risk factors and therapy are discussed, in particular the anomalies in testicular migration, hypofertility, testicular atrophy and carcinoma in situ. Prevention of bilateral consecutive tumors depends on the research of carcinoma in situ thanks to testicular biopsy. A slight radiotherapy allows eradication of this tumor, whose evolution towards invading cancer is particularly high. A rigorous watch of these patients can be considered. With the absence of early detection, the treatment of the simultaneous tumor needs taking into consideration the treatment of the initial tumor. In case of a diagnosis at stage 1, observation after orchidectomy is possible without further treatment.

Adult↗
PubMed1994

[Intestinal intussusception in adults: contribution of ultrasonography].

After observing a benign tumour of the small bowel which led to ileo-ileal invagination in an adult we recalled the main data on the epidemiology, aetiology and diagnosis. In infants, the diagnosis is usually made but in adults, the situation is much rarer and the clinical and radiographic signs are not specific. Echotomography of the abdomen is the most reliable examination. In the adult, surgery is always indicated because invagination is caused by an organic cause in 9 out of 10 cases.

Abdomen, Acute↗
PubMed1991

Short leader sequences may be transferred from small RNAs to pre-mature mRNAs by trans-splicing in Euglena.

Very closely related short sequences are present at the 5' end of cytoplasmic mRNAs in Euglena as evidenced by comparison of cDNA sequences and hybrid-arrested translation experiments. By cloning Euglena gracilis nuclear DNA and isolating the rbcS gene (encoding the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase), we have shown that the short leader sequence does not flank the nuclear gene sequence. The leader sequences were found to constitute the 5' extremities of a family of small RNAs. Sequencing six members of this family revealed a striking similarity to vertebrate U snRNAs. We propose that a trans-splicing mechanism transfers the spliced leader (SL) sequence from these small RNAs (SL RNAs) to pre-mature mRNAs. Transfer of leader sequences to mRNAs by trans-splicing has been shown only in trypanosomes where cis-splicing is unknown, and in nematodes where not more than 10% of the mRNAs have leader sequences. Our results strongly suggest that Euglena is a unique organism in which both a widespread trans-splicing and a cis-splicing mechanism co-exist.

Animals↗
PubMed1986

Effects of diets high in refined carbohydrates on renal ammonium excretion in rats.

Ammonium excretion was investigated in spontaneously hypertensive rats (SHR) and normotensive control rats (WKY) ingesting different diets. SHR and WKY on low protein-high sucrose diets surprisingly showed the same ammonium excretion as rats ingesting a higher protein-lower sucrose diet. This was unexpected, because ammonium excretion correlates positively with protein intake. The relatively high ammonium excretion despite low protein intake (approximately 40% of control) was not associated with acidosis, hypokalemia, hypocalcemia, and/or hypomagnesemia. In a follow-up study, where diets were high in refined carbohydrates (sucrose, glucose, and starch) but more equal in protein content compared with a diet high in carbohydrates of a more complex form (grains), ammonium excretion increased significantly. When we examined the factors known to influence ammonium excretion, the only significant positive correlations found were between norepinephrine, epinephrine, dopamine, and ammonium excretion. These correlations still remained significant when only the data from the rats on the diets high in refined carbohydrates, i.e., rats on the same dietary intake of minerals and proteins, were compared. In vitro, we corroborated that catecholamines significantly increased ammoniagenesis from kidney slices. Our data show that diets high in refined carbohydrates augment both ammonium and catecholamine excretion and suggest that these two events may be interrelated.

Ammonia↗
PubMed1986

[Septic arthritis caused by Campylobacter fetus].

The ten published cases of septic arthritis due to Campylobacter fetus and two more recent cases, one of which was a delayed septic complication of a total hip replacement, are discussed. In 83% of cases, febrile monoarthritis occurred which in 7 out of the 12 cases involved an already diseased joint in a subject over 70 years of age (half of the patients), who was frequently alcoholic and presented either cancer or hepatic cirrhosis and/or diabetes. Hyperleukocytosis of the blood was variable (55% of cases). The joint fluid, which contained a high level of deteriorated polynuclear cells, was routinely cultured on an enriched medium in an anaerobic or microerophilic atmosphere and in 10 out of 12 cases Campylobacter fetus was isolated within 15 days, even in the absence of previous antibiotic therapy. The arthritis, which showed little sign radiographically of destructiveness, was cured, leaving no sequellae in most cases. Treatment usually involved ampicillin or the tetracyclines, either alone or in association with the aminoglycosides.

Aged↗
PubMed1983

[Adenomatous lesions of the papilla in familial adenomatous rectocolic polyposis. Value of duodenoscopy].

When compared to the general population, individuals with Gardner's syndrome may have a 100- to 200-fold increased risk of developing periampullary carcinoma. This prospective work was undertaken in order to study the endoscopic aspects and to perform biopsies of the papilla in 9 patients (7 males, 2 females, aged 18-65 years) with familial polyposis coli or Gardner syndrome. In 4 cases the papilla was endoscopically grossly polypoid and biopsies showed adenomatous lesions. In 5 cases, the papilla appeared endoscopically normal; in 2 cases, the papilla appeared endoscopically normal; in 2 of these cases biopsies showed adenomatous proliferation; in the 3 other cases, the biopsies were normal. In 5 cases, there were adenomatous duodenal lesions outside the papilla. These results suggest that: a) adenomatous lesions of the papilla are frequent in familial polyposis coli and Gardner's syndrome; b) the endoscopic gross aspect of the papilla may be normal even when there are adenomatous lesions; c) adenomatous lesions of the papilla may be associated or not with adenomatous lesions of the 2nd duodenum; d) as the natural history of these lesions is not known and because of the risk of cancer of Vater's ampulla, it seems reasonable to perform routine duodenoscopies with biopsies in order to ensure early diagnosis of cancer.

Adenoma↗
PubMed1983

[Morphological aspect and chemical composition of Skeletonema costatum (Bacillariophyceae) growing in natural nutritive media with the aid of a culture system of dialysing fibers].

The growth of Skeletonema costatum, under natural nutriment conditions, was studied using a bulk culture fiber dialyzing apparatus. The diatom displayed normal development of chain length (average cell number per chain) which coincided with the culture growth stages; that is, the cell number per colony increased during the active division period and decreased thereafter with the beginning of the prestationary phase. This morphological behaviour showed that the alga cells were not affected by such physical shocks as collision or tension occurring during repeated cell transfers from growth chambers to the dialyzing apparatus or at the time of their passage through the fiber fascicles. Measured at different growth stages, the cell contents in carbon, nitrogen, and chlorophyll confirmed the above results and showed for S. costatum a biological productivity comparable with that obtained in smaller dialyzing containers (dialyzing bags). Through a comparison between the dialyzing culture and a static culture grown in an enriched medium, certain characteristics were determined.

Culture Media↗
PubMed1978

[Coralliform urolithiasis. A report of 56 case histories (author's transl)].

Analysis of 56 cases of coralliform urolithiasis has shown, among other things, the normally poor symptomology. This is in contrast to the poor prognosis which, in the absence of treatment, almost always ends in the destruction of the kidney. Besides ten immediate nephrectomies, 52 conservative operations were performed on forty patients. These conservative operations are difficult, long and meticulous. They are greatly facilitated by using an endocavitary lighting source of cold light. The use of contact X-ray is indispensable. Removal of stones must be absolutely complete. The number and extent of the nephrotomies must be reduced to a strict minimum. One must avoid the big, destructive nephrotomies--except, perhaps, in children. With the help of all these precautions, the results are encouraging; no secondary nephrectomies until present time, only two real relapses, and three small previously-undetected calculi. Yet, thanks to the systemic use of the cold light and of the contact X-rays, there were no more "undetected" calculi for the last 4 1/2 years.

Adolescent↗
PubMed1977

[Endoscopic resection in the treatment of non-invasive excreto-urinary carcinomas of the bladder 146 endoscopic resections carried out in 53 patients].

The authors divided their cases of excreto-urinary tumours of the bladder using the classification of Chome and Algazi. The diagnosis was made in 8 cases out of 10 on the basis of the cystogram obtained by IV pyelography. The upper urinary tract was free of disease in all cases. All patients were treated by endoscopic resection with or without the addition of intravesical instillations of triaziridinyl phosphine sulphide. The effectiveness of such instillations would not appear to have been conclusively demonstrated at the present time. Recurrences of intravesical tumours are extremely common (33/53 patients), but were always at the initial stage: i.e. highly differentiated non-invasive carcinoma. Up to the present none of these 53 patients (maximum follow-up 10 years) has died of an invasive carcinoma of the bladder.

Adult↗