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Biomedical subjects

J F Charles

Publications and source records attributed to J F Charles.

At least 19 recordsLinked to original sources
PubMed1998

The Polo-related kinase Cdc5 activates and is destroyed by the mitotic cyclin destruction machinery in S. cerevisiae.

BACKGROUND: Following chromosome segregation in anaphase, ubiquitin-dependent degradation of mitotic cyclins contributes to the exit from mitosis. A key step in this process is catalyzed by a ubiquitin-protein ligase known as the anaphase-promoting complex (APC), the regulation of which is poorly understood. The Polo-related protein kinase Cdc5 in Saccharomyces cerevisiae might encode a regulator of the APC, because cdc5 mutant cells arrest with a late mitotic phenotype similar to that observed in cells with defective cyclin destruction. RESULTS: We investigated the role of Cdc5 in the regulation of mitotic cyclin degradation. In cdc5-1 mutant cells, we observed a defect in the destruction of cyclins and a reduction in the cyclin-ubiquitin ligase activity of the APC. Overexpression of CDC5 resulted in increased APC activity and mitotic cyclin destruction in asynchronous cells or in cells arrested in metaphase. CDC5 mutation or overexpression did not affect the degradation of the APC substrate Pds 1, which is normally degraded at the metaphase-to-anaphase transition. Cyclin-specific APC activity in cells overexpressing CDC5 was reduced in the absence of the APC regulatory proteins Hct 1 and Cdc20. In G1, Cdc5 itself was degraded by an APC-dependent and Hct1-dependent mechanism. CONCLUSIONS: We conclude that Cdc5 is a positive regulator of cyclin-specific APC activity in late mitosis. Degradation of Cdc5 in G1 might provide a feedback mechanism by which the APC destroys its activator at the onset of the next cell cycle.

Adenomatous Polyposis Coli Protein↗
PubMed1997

Binding of the 51- and 42-kDa individual components from the Bacillus sphaericus crystal toxin to mosquito larval midgut membranes from Culex and Anopheles sp. (Diptera: Culicidae).

Individual components (P51 and P42) from the crystal toxin (Bin) of Bacillus sphaericus were used for in vitro binding competition experiments with brush border membranes (BBMFs) from Culex pipiens and Anopheles gambiae larval midguts. P51 competed for the Bin binding site with a similar affinity to the Bin toxin, on both BBMFs. For C. pipiens, P42 bound non-specifically until P51 was added with maximum binding of P42 at a molar ratio of each component. The binding of P42 was much greater on A. gambiae BBMFs and the presence of either P51 or P42 enhanced the binding of the other component, with highest binding when a mole ratio of each protein was supplied.

Animals↗
PubMed1997

Binding kinetics of Bacillus sphaericus binary toxin to midgut brush-border membranes of Anopheles and Culex sp. mosquito larvae.

Direct-binding assays and homologous-competition assays were used to identify specific binding between the radiolabelled toxin of Bacillus sphaericus and brush-border membrane fractions (BBMF) from Anopheles gambiae and Anopheles stephensi, obtained from whole larvae preparations. In both species, the toxin bound to a single class of receptors. BBMF of A. gambiae had the highest binding affinity for the toxin of the species tested, with a dissociation constant (Kd) of 30 +/- 15 nM and a maximum receptor concentration of 5 +/- 1 pmol/mg. Toxin binding to A. gambiae BBMF was compared with that to BBMF from B. sphaericus-susceptible (IP) and B. sphaericus-resistant (SPHAE) Culex pipiens populations. BBMF toxin binding was slower in A. gambiae than in the C. pipiens populations. The BBMF of the B. sphaericus-resistant population of C. pipiens had an association profile that was similar to the susceptible population, despite of the lack of susceptibility in vivo. No relationship between toxicity and irreversibility of toxin binding was detected. On the contrary, toxin dissociation from BBMF was fast and almost complete in BBMF of all species studied.

Animals↗
PubMed1997

Resistance to Bacillus sphaericus involves different mechanisms in Culex pipiens (Diptera:Culicidae) larvae.

Field Culex pipiens pipiens (L.) mosquitoes that were collected after a control failure with Spherimos in southern France developed high resistance (> 10,000-fold) to Bacillus sphaericus crystal toxin after < 8 generations of laboratory selection. We show that this resistance is encoded by a single major recessive gene on linkage group I at 22.1 recombination units from the sex locus, and that it is not associated with any loss of binding affinity between brush border membrane fractions and the B. sphaericus radiolabeled toxin. Thus, in Southern France, resistance differs from the high B. sphaericus resistance developed after laboratory selection of Californian C. p. quinquefasciatus. This demonstrates that at least 2 different mechanisms may confer high levels of resistance to B. sphaericus crystal toxin in mosquitoes of the C. pipiens complex. These results have important implications for mosquito control strategies.

Animals↗
PubMed1996

[Complications of colostomies. Follow-up study of 500 colostomized patients].

The complications of colostomies may constitute a handicap for patients: their prevalence severity and methods of treatment remain poorly known. 500 colostomy patients, with a mean age of 66 +/- 14 years, were retrospectively reviewed. The mean follow-up of the study was 6 +/- 5 years. Colorectal cancers represented 65% of the initial diseases. 59.5% of colostomies were terminal. They were performed for resection of the colon and or rectum in 56.5% of cases. 30.5% of patients (n = 152) presented complications (n = 235). The early complications (n = 147) observed in 29.5% of patients were mostly benign (20 required emergency operations). The late complications (n = 88), observed in 22.5% of 391 patients with a follow-up of more than one year required another operation in 1/3 of cases (11 cases of stenosis, 9 incisional hernias and 8 prolapses). Complications of colostomies remain frequent (one out of every 4 stomies ends in a complication) and the reoperation rate is situated between 13 and 33%. The therapeutic success rate of late reoperation is between 63 and 74%. When a reoperation is necessary, it should be ideally radical via a midline incision. The transposition technique gives better results than the repositioning technique via a local approach.

Abscess↗
PubMed1995

In vitro binding of Bacillus thuringiensis var. israelensis individual toxins to midgut cells of Anopheles gambiae larvae (Diptera: Culicidae).

Midguts from Anopheles gambiae fourth instars were dissected and processed for immuno-light microscopy. Cloned insecticidal crystal proteins (ICPs) from Bacillus thuringiensis var. israelensis (Bti) were individually expressed in crystal-negative strains of Bacillus thuringiensis. Tissue sections of A. gambiae were incubated in vitro with each solubilized and trypsin-activated ICP. Immunodetection of CryIVA, CryIVB, CryIVD and CytA toxins on sections was performed using purified rabbit IgG directed against Bti ICPs, in combination with an anti-rabbit IgG/peroxidase. CryIVA, CryIVB, CryIVD and CytA toxins were detected on the apical brush border of midgut cells, in the gastric caecae and posterior stomach. CytA was also detected, to a lesser extent, on microvilli of anterior stomach cells.

Animals↗
PubMed1995

Resistance in a laboratory population of Culex quinquefasciatus (Diptera: Culicidae) to Bacillus sphaericus binary toxin is due to a change in the receptor on midgut brush-border membranes.

Direct binding experiments with isolated brush border membrane fractions (BBMF) from larvae of a susceptible laboratory strain of Culex quinquefasciatus Say, indicated the presence of a single class of Bacillus sphaericus binary toxin receptors. The dissociation constant (Kd) was approximately 11 nM and the maximum binding capacity (Bmax) approximately 8 pmol/mg BBMF protein. Similar binding experiments with a field population of C. quinquefasciatus that had been selected in the laboratory to more than 100,000-fold resistance to B. sphaericus binary toxin failed to reveal the presence of any specific binding. Thus this resistant strain had lost the functional receptor for B. sphaericus toxin. The binding characteristics of BBMF from the F1 larval progeny (susceptible females x resistant males) were very close to those of the parental susceptible strain, consistent with the resistance being recessive.

Animals↗
PubMed1995

Comparison of toxin overlay and solid-phase binding assays to identify diverse CryIA(c) toxin-binding proteins in Heliothis virescens midgut.

The binding proteins, or receptors, for insecticidal Bacillus thuringiensis subsp. kurstaki delta-endotoxins are located in the brush border membranes of susceptible insect midguts. The interaction of one of these toxins, CryIA(c), with proteins isolated from Heliothis virescens larval midguts was investigated. To facilitate the identification of solubilized putative toxin-binding proteins, a solid-phase binding assay was developed and compared with toxin overlay assays. The overlay assays demonstrated that a number of proteins of 170, 140, 120, 90, 75, 60, and 50 kDa bound the radiolabeled CryIA(c) toxin. Anion-exchange fractionation allowed the separation of these proteins into three toxin binding fractions, or pools. Toxin overlay assays demonstrated that although the three pools had distinct protein profiles, similar-size proteins could be detected in these three pools. However, determination of toxin affinity by using the solid-phase binding assay showed that only one of the three pools contained high-affinity binding proteins. The Kd obtained, 0.65 nM, is similar to that of the unsolubilized brush border membrane vesicles. Thus, the solid-phase binding assay in combination with the toxin overlay assay facilitates the identification and purification of high-affinity B. thuringiensis toxin-binding proteins from the insect midgut.

Animals↗
PubMed1994

[Value of colonic irrigation. Long-term followed-up in 432 colostomized patients].

OBJECTIVES: Irrigating colostomies allows patients to achieve nearly complete fecal continence using a simple technique. We assessed long-term results in our series of 432 patients. METHODS: From 1979 to 1992, we followed 432 patients who had undergone definitive colostomy surgery (mean follow-up = 8.4 years). RESULTS: Colonic irrigation was impossible in 281 cases mainly due to retarded patient information (42%) or patient incapacity (31%). It was possible in 151 patients (globally 31%). In patients with abdominoperineal amputations the rate was 63%, for Hartmann procedures 17% and for derivations 6%. Most of the derivations were supraombilical colostomies (n = 51) including 6 who used colonic irrigation. No complications related to the technique were observed and minor incidents (usually problems with the cannula and/or pain) occurred in 61 patients. Thirteen patients (9%) abandoned the technique including 5 who complained of incontinence. CONCLUSIONS: Based on these observations, we conclude that colonic irrigation is not used enough. The key to success is a quality stomy and early patient information and training. This technique is particularly adapted for active patients. It is performed every 48 hours and lasts about 35 minutes.

Adult↗
PubMed1994

[Cavernous hemangioma of the spleen: values and limitations of ultrasonic and computed tomographic diagnosis].

A case of a cavernous haemangioma associated with an hepatic haemangioma is reported. It presented in the form of a hyperechogenic mass on ultrasound imaging. On the Computed Tomography scan with contrast, the splenic tumour became progressively hyperdense: this last characteristic is observed in 6 out of 9 cases reported in the literature. MR imaging seems to allow an accurate preoperative diagnosis; nevertheless, splenectomy is often indicated because of the risk of rupture, in which case histological examination removes any doubt concerning an exceptional malignant form.

Female↗
PubMed1993

TP53 gene mutation profile in esophageal squamous cell carcinomas.

Esophageal squamous cell carcinoma is a form of cancer occurring most commonly in males, particularly those living in some areas of Asia, Africa, and western Europe. In some of these tumors, a sequence alteration has been identified in the coding region of the TP53 gene which is known to inactivate the tumor suppressor function of its product. Using a GC clamp (i.e., a GC rich domain) denaturing gradient gel electrophoresis assay we have been able to identify sequence modifications in 27 of the 32 tumor samples analyzed (84%). Most of the mutations occur in exon 6, a region of the gene which has not previously been reported as being a hot spot for the mutations of other cancers. Twelve of the mutations reported here have not been described in other types of tumors and these consist mostly of frameshift or splice mutations. The distribution of mutations [transitions (45%), transversions (34%), and frameshift (21%)] suggests that the etiological contribution of genotoxic factors might be complex and might associate different exogenous and endogenous mutagen exposures.

Adult↗
PubMed1993

Clostridium bifermentans serovar malaysia: characterization of putative mosquito larvicidal proteins.

The toxicity of Clostridium bifermentans serovar malaysia to mosquito larvae is due to protein toxins, belonging to a novel class of insecticidal toxins. Toxic extracts contains three major proteins of 66, 18 and 16 kDa. The 18-kDa and 16-kDa proteins are probably involved in toxicity. They are synthesised during sporulation, concomitant with activity. They are absent from non-toxic strains of C. bifermentans and are present at very low levels in non-toxic C. bifermentans serovar malaysia cultures produced at 42 degrees C. The 66-kDa protein is present throughout the growth phases of C. bifermentans serovar malaysia, and an immunologically related 66-kDa protein is present in non-toxic C. bifermentans strains.

Animals↗
PubMed1993

[Postoperative obstructions].

The intestinal obstructions after a laparotomy in adult may be caused by an inflammatory or a mechanic pathology; the incidence of the bowel obstruction in the early postoperative period is about 0.5 to 2% of all surgical procedures; these obstructions are often related to the degree of contamination or infection; contrary to postoperative paralytic ileus, they result in a reoperation, so as a peritonitis may be associated. In the later postoperative period intestinal obstructions may be caused by adhesions, internal strangulation or fibrosis bridles; these obstructions are frequent and they affect especially the small intestine (5% of laparotomies will be complicated by small bowel obstruction). The intestine volvulus due to bridles or adhesions is observed in approximately 10% of cases and the diagnosis must be conjured up in principle because it necessities an operation immediately; it's the same for the strangulation by incarceration. The absence of classic indicators of gangrene permits a non-operative treatment using a naso-gastric tube decompression during 24 to 48 hours: generally the causes of obstruction are small bowel adhesions, nevertheless it's important to eliminate a colonic obstruction. The management of chronic postoperative adherences is a difficult problem because the iterative operations increase the risk of intestinal obstructions; the video-laparoscopic surgery seems to be a promising technique to prevent and to treat (laparoscopic adhesiolysis) the post-operative adherences; its results are not evaluated.

Humans↗
PubMed1993

Respective role of the 42- and 51-kDa components of the Bacillus sphaericus toxin overexpressed in Bacillus thuringiensis.

The 42- and 51-kDa protein genes of Bacillus sphaericus 1593 have been subcloned independently downstream from the cytA gene promoter of Bacillus thuringiensis serovar israelensis and introduced into a non-mosquitocidal strain of Bacillus thuringiensis. Consequently, each protein was overproduced and accumulated as inclusion bodies which were purified. For the first time, the 42-kDa protein inclusions alone were found to be toxic to Culex pipiens larvae (LC50 at 48 h 300 ng ml-1); in contrast, the 51-kDa protein inclusions were not. Moreover, a synergistic effect between these two components was observed.

Animals↗