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Biomedical subjects

R Boivin

Publications and source records attributed to R Boivin.

At least 37 records · Page 2Linked to original sources
PubMed1991

Enhancement of the Potential To Utilize Octopine in the Nonfluorescent Pseudomonas sp. Strain 92.

The nonfluorescent Pseudomonas sp. strain 92 requires the presence of a supplementary carbon source for growth on octopine, whereas the spontaneous mutant RB100 has acquired the capacity to utilize this opine as the sole carbon and nitrogen source. Insertional mutagenesis of RB100 with transposon Tn5 generated mutants which were unable to grow on octopine and others which grew slowly on this substrate. Both types of mutants yielded revertants that had regained the ability to utilize octopine. Some of the revertants had lost the transposon, whereas in others the transposon was retained but with rearrangements of the insertion site. Genes of octopine catabolism from strain 92 were cloned on a cosmid vector to generate pK3. The clone pK3 conferred the ability to utilize octopine as the sole carbon and nitrogen source on the host Pseudomonas putida KT2440. Although they conferred an equivalent growth phenotype, the mutant genes carried by RB100 and the cloned genes on pK3 differed in their regulation. Utilization of [C]octopine was inducible by octopine in RB100 and was constitutive in KT2440(pK3).

Journal Article↗
PubMed1990

Evidence for two types of cytotoxic necrotizing factor in human and animal clinical isolates of Escherichia coli.

We have characterized the in vitro and in vivo toxic properties of cell sonic extracts from 22 animal and human clinical isolates of Escherichia coli that caused both necrosis in the rabbit skin and multinucleation in tissue cultures, two toxic properties previously reported as being specific for E. coli cytotoxic necrotizing factor (CNF). Two distinct toxic phenotypes were observed. Type 1, which was displayed by originally described CNF strains, was characterized by extensive multinucleation and rounding of cells in HeLa cell culture assays, moderate necrosis in the rabbit skin test, and absence of necrosis in the mouse footpad test. Type 2, which has recently been shown to be associated with E. coli Vir plasmid, was characterized by moderate multinucleation, by polymorphism and elongation of HeLa cells, and by an intense necrotic response in both the rabbit skin test and the mouse footpad test. The distinction between the two cytotoxins accounting for these effects (CNF 1 and CNF 2), together with their partial relatedness, was confirmed by seroneutralization studies of both cytopathic effects and necrosis in the rabbit skin test. In addition, type 2 extracts were more lethal in the mouse intraperitoneal test and induced a moderate, although not totally repetitive, fluid accumulation in the ileal loop test. The original toxic properties of these recently recognized categories of E. coli strains, together with their association with enteritis and septicemia, suggest that these strains may play a significant role in pathology.

Animals↗
PubMed1990

Urea recycling from the renal pelvis in sheep: a study with [14C]urea.

To test the hypothesis that urea can be recycled from the renal pelvis, [14C]urea diluted in native urine (1 microCi/ml) was perfused (0.5 ml/min) into one of the pelvises of sheep fed either normal (NP) or low (LP)-protein diets. Blood samples were obtained from the ipsilateral renal vein and from the carotid artery throughout the perfusions. 14C activity determinations in urine and plasma demonstrated a flux of [14C]urea from the pelvis to renal vein blood (40,000 in NP and 130,000 disintegrations/min in LP sheep, P less than 0.01). The corresponding flux of native urea was only 1.5 times higher in NP than in LP sheep (6.8 +/- 1.1 vs. 4.7 +/- 2.9 mumol/min, not significant) despite their 8 times higher urinary concentration of urea. The fraction of filtered urea that was reabsorbed in the pelvis was larger in LP sheep (7.5 +/- 3.7 vs. 1.9 +/- 0.7% in NP sheep, P less than 0.05). A fraction of urea is thus actually recycled from the renal pelvis in sheep, and this pelvic retention is enhanced in LP animals. The importance of this phenomenon in the nitrogen economy is discussed.

Absorption↗
PubMed1990

[Diffusion of elements of glass ionomer cements placed in a dentin cavity: influence on pulp pressure].

The biocompatibility of glass ionomer cement with silver and titanium ions is studied in vivo on dog's canine. Class V cavities, side by side the pulp, are prepared and Ketak Silver cement is placed inside. Variation of pulp pressure are recorded before and after the cement's applying, after which the crowns are cut and broken at the filling level, the different components part diffusion through the dentin are placed in prominent position by means of a microanalysis and a cartography of the sample is obtained by colorimetric picture. The pulp's haemodynamic responses to Ketak Silver are in harmony with the metallic ions diffusion and specially with silver.

Animals↗
PubMed1990

[Experimental study of the effect of a photopolymerizable glass ionomer cavity liner on pulp pressure and temperature].

The biocompatibility of a light curing glass ionomer cement was studied for its pulpal effect when used as a capping agent in a dentin cavity. Pulpal pressure and temperature were recorded in 14 dog canines after placement of the glass ionomer cement. No increase was observed in 12 specimens on 14 samples. These results indicate that no pulpal effect can be demonstrated when using Vitrabond as a dentin capping agent.

Animals↗
PubMed1990

[Diuresis, renal plasma flow and glomerular filtration in conscious and anesthetized sheep: the effects of a diet deficient in proteins].

Determinations of renal plasma flow (RPF), glomerular filtration rate (GFR) and urine flow in sheep fed low protein diets have yielded controversial data. In the present experiment, 8 sheep were fed a regular diet and another 6 received a low protein ration. Water intake and urine output were measured over 10 days. RPF and GFR were determined on 2 consecutive days. The latter determinations were repeated on 5 anaesthetized animals (sodium thiopental) in each group. An important increase in water intake (58%) and urine output (98%) was observed in the sheep on the low protein diet. In these animals, blood urea averaged 0.1 g/l. Urine output was greater (with a lower osmolarity) when the blood urea level was the lowest. RPF and GFR were significantly lower in the sheep on the low protein diet (RPF: 13.5 versus 28.1 ml/min/kg in the control animals; GFR: 1.61 versus 4.01 ml/min/kg); no relationship could be established with the blood urea level. The only effect of the anaesthesia was a reduction in RPF, of the same magnitude in both groups of sheep (about 35%). In conclusion, when sheep are fed a low protein diet, the volume of plasma processed through the kidney is decreased. In the present experiment, the increased urine flow and the lowered urinary osmolarity indicate an impaired renal concentrating ability. Barbiturate anaesthesia does not affect this phenomenon.

Anesthesia↗
PubMed1990

[Renal extraction of para-aminohippurate and inulin from sheep on low-protein diets].

In sheep fed low-protein diets, renal PAH and inulin extractions are not affected by the fall in plasma urea level or in the renal plasma flow itself. The noted reduction in glomerular filtration rate is not due to a preglomerular shunt of arterial blood since the filtration fraction does not vary by comparison to sheep on regular diets. Thus, the reduction in renal plasma flow (PAH clearance), induced by low protein rations, is not dependent on any change in PAH extraction. This reduction is probably responsible for the simultaneous decrease of glomerular filtration.

Aminohippuric Acids↗
PubMed1989

Cytotoxic effect of multinucleation in HeLa cell cultures associated with the presence of Vir plasmid in Escherichia coli strains.

Escherichia coli strain S5 possesses a virulent plasmid termed Vir, which codes for a lethal toxin and a surface antigen. This strain and two trans-conjugant strains, which have received the Vir plasmid from S5, produced a specific and thermolabile cytopathic effect of multinucleation in an HeLa cell cultures assay, whereas isogenic Vir- strains did not. Moreover sonicates of two epidemiologically unrelated Vir+ strains, exerted the same type of cytotoxicity. This effect, together with lethality for chicken, was specifically neutralized by a rabbit antiserum prepared against Vir+ sonicates. The Vir cytopathic effect appeared morphologically distinct from the one caused by the cytotoxic necrotizing factor of E. coli, which was partially related immunologically. We therefore propose to call this type of toxin 'Vir cytotoxin'.

Antigens, Surface↗
PubMed1989

An in vivo assay for the detection of cytotoxic strains of Escherichia coli.

We have examined the local and systemic responses produced in mice by the inoculation of the footpad with cell-free sonicates from cytotoxic and non-cytotoxic strains of Escherichia coli. The cytotoxic strains, previously characterized in HeLa cell culture assay, produced one of the following cytotoxins: (1) cytotoxic necrotizing factor (CNF; 5 strains); (2) a cytotoxin that induced polynucleation of cells but was serologically distinct from CNF (4 strains); (3) Shiga-like toxin (3 strains). Whereas extracts from non-cytotoxic strains induced only a slight and transitory local edema, those from cytotoxic strains produced a marked local inflammatory response. This response, specific for the type of cytotoxin, was measured by increase in footpad thickness, persistence of inflammation and occurrence of necrosis of the leg extremity. Type 1 and 2 extracts produced persistent inflammatory lesions with, in the case of type 2 extracts only, necrosis of the leg extremity. Conversely, type 3 activity was characterized by a transient local infiltration with no apparent residual lesions. The mouse footpad test therefore provides an in vivo assay for the differential diagnosis of cytotoxic strains of E. coli.

Animals↗
PubMed1988

Construction of a Tn5 derivative encoding bioluminescence and its introduction in Pseudomonas, Agrobacterium and Rhizobium.

A simple method based upon the use of a Tn5 derivative, Tn5-Lux, has been devised for the introduction and stable expression of the character of bioluminescence in a variety of gram-negative bacteria. In Tn5-Lux, the luxAB genes of Vibrio harveyi encoding luciferase are inserted on a SalI--BglII fragment between the kanamycin resistance (Kmr) gene and the right insertion sequence. The transposon derivative was placed on a transposition suicide vehicle by in situ recombination with the Tn5 suicide vector pGS9, to yield pDB30. Mating between Escherichia coli WA803 (pDB30) and a strain from our laboratory, Pseudomonas sp. RB100C, gave a Kmr transfer frequency of 10(-6) per recipient, a value 10 times lower than that obtained with the original suicide vehicle pGS9. Tn5-Lux was also introduced by insertion mutagenesis in other strains of gram-negative soil bacteria. The bioluminescence marker was expressed in the presence of n-decanal, and was monitored as chemiluminescence in a liquid scintillation counter. The recorded light intensities were fairly comparable among the strains, and ranged between 0.2 to 1.8 x 10(6) cpm for a cell density of 10(3) colony forming units/ml. Nodules initiated by bioluminescent strains of Rhizobium leguminosarum on two different hosts were compared for intensity of the bioluminescence they produced.

DNA Transposable Elements↗
PubMed1987

Cytotoxins in non-enterotoxigenic strains of Escherichia coli isolated from feces of diarrheic calves.

We have examined the cytotoxic responses produced in HeLa and Vero cell cultures by sonicates from 15 non-enterotoxigenic (STa-, LT-) strains of E. coli, highly lethal for mice parenterally LD50 less than 3 X 10(7) CFU), which had been isolated from feces of diarrheic calves. Three types of cytotoxic responses were observed. Type 1 (five strains) consisted of enlargement, rounding and polynucleation of HeLa cells, an effect previously reported with cytotoxic necrotizing factor (CNF) in E. coli from infant and piglet enteritis. Type 2 toxicity (three strains and the control Vir strain S5) was also characterized by enlargement and polynucleation of HeLa cells, but in contrast to Type 2 effect, cells were elongated. Sonicates from the latter strains were lethal for chickens, producing the lesions previously described with Vir strains. Type 3 toxicity (two strains and the control VT strain H19), produced an extensive destruction of both Vero and HeLa cell cultures. Cytotoxic effects were completely abolished upon heating for 1 h at 60 degrees C for Type 1 and 2 extracts and at 80 degrees C for Type 3 extracts. Seroneutralization assays showed that cytotoxins of the same type were closely related antigenically. In addition, a slight cross-neutralization was observed between Type 1 (CNF) and Type 2 (Vir) toxins.

Animals↗
PubMed1986

[Urea feeding of sheep on a diet rich in proteins: effects on urinary secretion].

Ten ewes kept on a high protein level diet were fed water solutions of urea (0.25 g/kg). Blood urea, urine volume and renal urea excretion were determined thereafter. A long lasting increment of blood urea level was observed as well as an increased urine volume with a lowered urinary osmotic pressure. Moreover, urea clearance was significantly decreased in spite of the increased amount of urea excreted by the kidney. A negative correlation between urea clearance and blood urea level could be demonstrated when the latter was higher than 0.5 g/l.

Animal Nutritional Physiological Phenomena↗
PubMed1985

[Characteristics of esophageal antiperistaltic activity in sheep].

Oesophageal motility was investigated in standing conscious sheep. A manometric method was used in four animals; two sheep, fitted with permanent electrodes at four levels, were used for oesophageal electromyography. The occurrence of retrograde peristalsis (mean speed 71,5 cm.s-1) at the beginning of every rumination cycle is reasserted. The characteristics of this activity are pointed out, with reference to normal peristalsis during the deglutition of saliva. Different types of stimulation have been compared. Retrograde peristalsis (mean speed 66 cm.s-1) can be triggered readily in non-ruminating animals by the association of two stimulations. One being oesophageal distension and the other injection of a solution prepared with some physical or chemical components of the rumen liquid. No specialized sensitive area could be demonstrated. However, facilitation is evident during reticular contractions. Retrograde waves of contraction always start from the terminal part of the thoracic oesophagus, whatever the level of stimulation.

Animals↗