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Biomedical subjects

R Fournier

Publications and source records attributed to R Fournier.

At least 37 records · Page 2Linked to original sources

U3 snoRNA genes with and without intron in the Kluyveromyces genus: yeasts can accommodate great variations of the U3 snoRNA 3'-terminal domain.

The U3 snoRNA coding sequences from the genomic DNAs of Kluyveromyces delphensis and four variants of the Kluyveromyces marxianus species were cloned by PCR amplification. Nucleotide sequence analysis of the amplification products revealed a unique U3 snoRNA gene sequence in all the strains studied, except for K. marxianus var. fragilis. The K. marxianus U3 genes were intronless, whereas an intron similar to those of the Saccharomyces cerevisiae U3 genes was found in K. delphensis. Hence, U3 genes with and without intron are found in yeasts of the Saccharomycetoideae subfamily. The secondary structure of the K. delphensis pre-U3 snoRNA and of the K. marxianus mature snoRNAs were studied experimentally. They revealed a strong conservation in yeasts of (1) the architecture of U3 snoRNA introns, (2) the 5'-terminal domain of the mature snoRNA, and (3) the protein-anchoring regions of the U3 snoRNA 3' domain. In contrast, stem-loop structures 2, 3, and 4 of the 3' domain showed great variations in size, sequence, and structure. Using a genetic test, we show that, in spite of these variations, the Kluyveromyces U3 snoRNAs are functional in S. cerevisiae. We also show that S. cerevisiae U3A snoRNAs lacking the stem-loop structure 2 or 4 are functional. Hence, U3 snoRNA function can accommodate great variations of the RNA 3'-terminal domain.

Base Sequence↗

[Value of detection of carcinoma in situ in conservative surgery of germ cell tumors of the testis].

OBJECTIVE: It is currently proposed to perform tumour enucleation in mono-orchid patients presenting with a small germ cell tumour, in order to preserve physiological endocrine function. However, this conservative surgery must be accompanied by treatment of any carcinoma in situ lesions present in the remaining testicular parenchyma. MATERIAL AND METHODS: The presence of carcinoma in situ was investigated in 35 patients with germ cell tumour of the testis on samples obtained from the presumably healthy pulp of the orchidectomy specimen, adjacent to and away from the tumour. Samples away from the tumour were performed according to principle of surgical testicular biopsy. Histological examination also concerned the tissue situated in contact with the tumour. RESULTS: 25 patients (74.22%) presented intratubular germ cell dysplasia in the testicular parenchyma presumed to be healthy. These lesions were always concomitantly observed on samples performed adjacent to and away from the tumour. It was observed more frequently in seminomas, but was also observed in other histological forms. CONCLUSION: Because of the diffuse nature of carcinoma in situ in germ cell tumours of the testis, pulp samples adjacent to the tumour are sufficient to ensure the diagnosis during conservative surgery. Carcinoma in situ is currently treated by local radiotherapy.

Adolescent↗

An in vivo and in vitro structure-function analysis of the Saccharomyces cerevisiae U3A snoRNP: protein-RNA contacts and base-pair interaction with the pre-ribosomal RNA.

The structure and accessibility of the S. cerevisiae U3A snoRNA was studied in semi-purified U3A snoRNPs using both chemical and enzymatic probes and in vivo using DMS as the probe. The results obtained show that S. cerevisiae U3A snoRNA is composed of a short 5' domain with two stem-loop structures containing the phylogenetically conserved boxes A' and A and a large cruciform 3' domain containing boxes B, C, C' and D. A precise identification of RNA-protein contacts is provided. Protection by proteins in the snoRNP and in vivo are nearly identical and were exclusively found in the 3' domain. There are two distinct protein anchoring sites: (i), box C' and its surrounding region, this site probably includes box D, (ii) the boxes B and C pair and the bases of stem-loop 2 and 4. Box C' is wrapped by the proteins. RNA-protein interactions are more loose at the level of boxes C and D and a box C and D interaction is preserved in the snoRNP. In accord with this location of the protein binding sites, an in vivo mutational analysis showed that box C' is important for U3A snoRNA accumulation, whereas mutations in the 5' domain have little effect on RNA stability. Our in vivo probing experiments strongly suggest that, in exponentially growing cells, most of the U3A snoRNA molecules are involved in the 10-bp interaction with the 5'-ETS region and in two of the interactions recently proposed with 18S rRNA sequences. Our experimental study leads to a slightly revised version of the model of interaction proposed by J. Hughes. Single-stranded segments linking the heterologous helices are highly sensitive to DMS in vivo and their functional importance was tested by a mutational analysis.

Animals↗

Glucose kinetics of the Virginia opossum: possible implications for predicting glucose turnover in mammals.

Primed continuous infusions of 6-3H-glucose, respirometry and measurements of nitrogen excretion were carried out in adult Virginia opossums (Didelphis virginiana). Our goals were to determine resting glucose turnover rate, to establish the relative importance of this oxidative fuel in the energy budget of this species, to assess whether metabolic rate is a better predictor of glucose turnover rate than body mass and to demonstrate that glucose kinetics can be measured in the opossum for future use of this animal model in studies of mammalian glucoregulation. Results show that the resting glucose turnover rate of opossums averages 17.5 +/- 0.9 mumol/kg.min (n = 9), that 31% of total glucose flux is oxidized and that glucose oxidation represents 9% of their metabolic rate. An allometric equation predicting glucose turnover rate from body mass for placental mammals overestimates the measured turnover rate of this marsupial by 30%, suggesting that turnover rate is better predicted from metabolic rate than from body mass. Finally, this study demonstrates that the Virginia opossum is a convenient model to study glucose metabolism in vivo, and we propose that the very rapid aging characteristics of this species should be exploited to investigate the effects of aging on glucose homeostasis.

Aging↗

Persistent efficacy of topical moxidectin against Dictyocaulus viviparus and Ostertagia ostertagi.

The persistent activity of moxidectin topically administered at the dose rate of 0.5 mg kg-1 bodyweight was evaluated against experimental nematode infection in 30 calves randomly allocated to six groups. Five groups were treated on days -42, -35, -28, -21 and -14. The 6th group remained untreated as a control. On Day 0, the calves were infected experimentally with 1000 Dictyocaulus viviparus and 50,000 Ostertagia ostertagi larvae and killed 3 weeks later. The formulation of moxidectin showed excellent activity against both parasites for up to 5 weeks (> 99%). Six weeks after treatment the reduction in the number of D. viviparus was still high (> 90%). No adverse reactions to moxidectin were observed in any of the animals.

Administration, Topical↗

[Role of testicular biopsy in the investigation of a carcinoma in situ].

Carcinoma in situ (CIS) of the testis is recognized to be a precursor of cancer. Radiological examinations are not sufficient to improve the diagnosis. So the diagnosis is made by testicular biopsy. The indications are controlateral testis biopsy in man with testicular cancer and risk factors (cryptorchidism, dysgenetic gonads...) and extragonadic germ cell tumors. The authors review the risk factors. Chemotherapy is not sufficient to eradicate the CIS. A dose of 16 Gy of localized radiation is curative, excludes bilateral orchidectomy and preserves androgen function and azoospermic patient.

Biopsy↗

[The incidence of the variability of the free PSA/total PSA ratio on the early diagnosis of prostate cancer].

INTRODUCTION: In patients with moderate elevation of total PSA, the use of the Free PSA/Total PSa ratio (F+T PSA) has been shown to be useful in the diagnosis of impalpable prostatic cancer. However, the cut-off values proposed in the literature vary from study to study and according to the immunoassay kit used. Our prospective study was designed to compare 3 different kits (Tandem, Cis Bio and Immunocorp) on the same series of patients in order to determine on the basis of these results and a review of the literature, the optimal ratio for which prostatic biopsies should be indicated in the presence of an isolated elevation of Total PSA. MATERIAL AND METHODS: Serum samples from 141 patients (43 cancers and 98 cases of histologically confirmed BPH) were included. Assays were performed concomitantly with histological examination of the prostate, using Tandem, Cis Bio and Immunocorp kits. RESULTS: In the overall patient population, Total PSA and Free PSA assays were statistically different for the 3 kits (p < 0.001). The F/T PSA ratio was always statistically different between the cancer and benign prostatic hyperplasia groups (p < 0.002). The cut-off values defined by a sensitivity of 90% were of 0.22 for Tandem (specificity: 27.5%), 0.34 for Cis Bio (specificity: 19.4%) and 0.26 for Immunocorp (specificity: 26.5%). When the total PSA level was between 4.0 and 10.0 ng/ml, these cut-off values also differed: 0.23 for Tandem (specificity: 26.6%), 0.35 for Cis Bio (specificity: 17.2%) and 0.25 for Immunocorp (specificity: 29.7%). In patients with a non-suspicious digital rectal examination and a F/T PSA ratio less than 0.10, the cancer detection rate (number of biopsies required to diagnose 1 cancer) was 1.66 for Tandem, 1 for Cis Bio and 1.87 for Immunocorp versus 7.7 while, when the F/T PSA ratio was greater than 0.22, the cancer detection rate was infinity (no cancer beyond this limit), 12.5 and 23, respectively. CONCLUSION: The F/T PSA ratio increases the specificity of prostatic cancer detection in patients with a total PSA between 4 and 10.0 ng/ml with a non-suspicious digital rectal examination, therefore resulting in a reduction of the useless biopsy rate and defining more relevant indications for biopsies in the case of periodic follow-up. The systematic indication of this ratio in the screening context cannot be recommended, but it can be useful to demonstrate stage TIC tumours in order to avoid numerous useless biopsies.

Aged↗

[Late diagnosis of the avulsion of the pyelo-ureteral junction treated by ureterocalicostomy].

The authors report an exceptional case of delayed diagnosis of avulsion of the ureteropelvic junction in a 27-year-old man. Organization of the urohaematoma prevented ureteropelvic anastomosis and the kidney could only be preserved by performing ureterocalicostomy. This technique, generally used for tuberculous retracted renal pelvis, or failure of pyelotomy or ureteropelvic junction repair in horseshoe kidneys or kidneys with retracted renal pelvis, allowed renal preservation in this case.

Accidents, Traffic↗

[Subperitoneal rupture of the bladder due to pelvic fractures. Apropos of 3 cases].

Three different approaches to the diagnostic and therapeutic management of bladder trauma were adopted in 3 patients. Haematuria was discovered on bladder catheterization. Emergency cystography remains the best diagnostic examination. CT has the same limitations as intravenous urography. There are two schools of thought concerning the treatment of the bladder lesion: surgical repair and healing by simple drainage. The indications depend on the size of the rupture and the severity of haematuria: intravesical clots and the need for continuous irrigation constitute contraindications to simple drainage. Emergency surgery must be combined with treatment of the bone lesions. Apart from external fixation, posterior osteosynthesis, when possible, is also indicated in unstable fractures.

Adolescent↗

Efficacy of moxidectin as a 1% injectable solution and a 0.1% oral drench against nasal bots, pulmonary and gastrointestinal nematodes in sheep.

Thirty ewes, 3-10 years old, known to be naturally infected with internal parasites, were allocated to three homogeneous groups of ten ewes each based on faecal nematode egg counts. The following experimental treatments were administered on Day 0: (A) moxidectin 1% injectable solution at 0.2 mg kg-1 body weight; (B) moxidectin 0.1% oral drench solution at 0.2 mg kg-1 liveweight; (C) untreated control. Faecal samples were taken on Days -7, 0, 1, 2, 3, 7, 14, 21, 28 and 35 to obtain counts of nematode eggs. One-half of the ewes in each treatment group were slaughtered 14 days after dosing, while the remainder were slaughtered 35 days after treatment to count the numbers of nasal bots, pulmonary nematodes and gastrointestinal nematodes. Moxidectin 1% injectable solution and moxidectin 0.1% oral drench solution were highly effective against gastrointestinal nematodes and against a variable infection of Dictyocaulus filiaria. Moxidectin 1% injectable solution was effective against first stage larvae of Oestrus ovis, whereas moxidectin 0.1% oral drench was ineffective.

Abomasum↗

[Posterior trans-anal-sphincter approach in the management of urethro-prostate-rectal fistula].

Uretroprostatorectal fistulas occur rarely, often due to trauma or iatrogenic causes. We observed a case caused by a gun wound and present our surgical route for treatment. The deep situation of these fistulae explains the difficulty in surgical access. Several routes have been described. We used the posterior transanosphincter route proposed by York Mason. This technique has the advantage of direct access for the fistula. Success rate is high and morbidity is limited. No fecal incontinence has been reported in the literature.

Adult↗

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↗

[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↗

[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↗

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↗