Biomedical subjects

R Boivin

Publications and source records attributed to R Boivin.

At least 19 recordsLinked to original sources

PubMed2006

Determination of parotid sulfate secretion in sheep by means of ultrasonic flow probes.

The bilateral output of sulfate in parotid saliva, the relationship with its plasma level and with parotid flow, and its variation according to feeding behavior were determined in ad libitum, normal-sulfate (0.28% DM)-fed sheep (n = 6) using a transit time ultrasonic flow meter system to measure salivary flow. Ultrasonic flow meter probes were bilaterally implanted, under general anesthesia, around parotid ducts previously fitted through their oral ends with nonobstructive sampling catheters. Salivary flows were continuously recorded during 24 h, and saliva and blood samples for sulfate determinations were obtained hourly. Jaw movements were monitored with the submandibular balloon technique. The sulfate concentration in parotid saliva (mean of the group = 4.9 +/- 3.7 microg/mL) showed high variability between sheep (individual means from 0.4 +/- 0.3 to 9.3 +/- 5.9 microg/mL) and averaged 12.3% of the more stable plasma level (41.2 +/- 8.1 microg/mL). Pronounced intraindividual variations were also evident (0.1 to 26.3 microg of sulphate/mL of parotid saliva), in strong association with the fluctuations of salivary output. In 4 sheep, a decreasing exponential relationship was observed between parotid sulfate concentration and salivary secretion rate (r2 = 0.36, P < 0.01). This fact and the absence of a relationship between sulfate levels in plasma and in saliva suggest a sulfate secretory process during the passage of primary saliva through the ductal tree of the gland. The greatest rates of bilateral salivary sulfate output were observed during feeding (14.1 +/- 14.0 microg/min) and rumination (12.7 +/- 11.0 microg/min). Nevertheless, 49% of the sulfate output in parotid saliva was present during rest, as a result of the length of the resting times. The contribution of parotid sulfate to the ruminal S pool was highly variable and averaged 13.2 mg/d, representing less than 1% of the S intake. In conclusion, the accurate, reliable, nonobstructive, and bilateral salivary flow monitoring, using a previously characterized ultrasonic flow meter technique, allowed a detailed determination of the secretory dynamics of sulfate in parotid saliva, without disturbing the animal's routine or altering the physiological regulation of salivary output. The results indicated that, in the absence of S deficiency, the recycling of sulfate via saliva seems not to be a major factor in sheep nutrition.

Animals↗

PubMed2001

Cytokine gene expression in lymph node and spleen of sheep in response to Salmonella infection by two serotypes displaying different host specificity.

In order to investigate the determinism of the host specificity and to better understand the host resistance mechanisms, infections of sheep were performed with either S. abortusovis, serotype specific for ovine species, or with S. dublin, serotype adapted to cattle and accidentally transmissible to human. Following a subcutaneous challenge, S. dublin disseminated more rapidly towards lymphoid tissues than S. abortusovis. However, S. abortusovis tended to persist in spleen more efficiently than S. dublin. Using a quantitative RT-PCR method, the expression level of ovine cytokines genes was measured in the draining lymph node and in the spleen, in the course of infection. Inflammatory cytokine response was characterised by an early and strong increase of IL-1beta and TNFalpha mRNA in both lymphoid organs following S. dublin infection, while S. abortusovis challenge only induced IL-1beta mRNA increase in the spleen at day 3 post-inoculation. Likewise, S. dublin infection provoked a marked increase of IL-12 mRNA and a slight up-regulation of IFNgamma gene transcription in the local lymphoid site, in contrast to S. abortusovis infection. Elsewhere, both serotypes induced a strong and early IL-10 mRNA production and had no effect on IL-4 gene expression. Finally, taken together, these data suggest that the intensity of inflammatory and anti-infectious cytokine responses, but not the type 2 cytokine response, is serotype-dependent. They also suggest that the host-specific serotype, by limiting the host cytokine-mediated defence, could favour its persistence within lymphoid organs.

Animals↗

PubMed2000

Extrarenal renin-angiotensin systems are unable to maintain blood pressure in sheep.

1. The present study was designed to assess the participation of extrarenal tissue renin-angiotensin systems (RAS) in pressure homeostasis in sheep. 2. The effect of the administration of an angiotensin II type 1 receptor antagonist (losartan; 30 mg/kg, i.v.) on mean arterial blood pressure (MABP) was investigated in eight intact (controls) and 10 binephrectomized sheep haemodialysed every 2 days for 10 days. 3. In control sheep, losartan decreased blood pressure and this decrease was significantly more marked after furosemide-induced water and salt depletion. After nephrectomy and throughout the anephric period, losartan lost its hypotensive effect, while the plasma renin concentration fell to undetectable levels. Baseline MABP became significantly lower than at the beginning of the anephric period after 7 days. The inability to maintain blood pressure after several volume-depleting haemodialysis sessions proved that an efficient system for blood pressure regulation was lacking after nephrectomy. 4. Renin gene expression measured by reverse transcription-polymerase chain reaction was found in liver, adrenal and arterial wall tissue. Neither nephrectomy nor sodium depletion enhanced this tissue renin gene expression. 5. In conclusion, the present work allows us to exclude an active role of extrarenal RAS in the maintenance of blood pressure. In addition, haemodialysis technology in nephrectomized sheep can be used as a good model for the study of extrarenal control of blood pressure.

Angiotensin Receptor Antagonists↗

PubMed2000

Comparative study of the cardiovascular effects of losartan in normal and in water- and salt-depleted sheep.

The cardiovascular effects of losartan, a non-peptidic angiotensin II (ANG II) receptor antagonist, were studied in sheep. Eight normotensive, conscious sheep were tested twice: first under normal conditions and second when subjected to water and electrolytic depletion (furosemide 5 mg/kg twice a day for 3 days). Intravenous injection of 30 mg/kg losartan lowered the mean arterial blood pressure (MABP) in both control and water- and electrolyte-depleted sheep alike. The maximal decrease in MABP was significantly greater in diuretic-treated sheep than in controls (20.0 +/- 2.7 vs 9.3 +/- 1.1 mmHg) and occurred earlier (8.0 +/- 3.3 min vs 12.1 +/- 2.9 min). The decrease in blood pressure was associated with tachycardia in both controls and diuretic-treated sheep (+5.5 +/- 1.8 vs +11.3 +/- 3.9 beats/min). The vasopressor response to 0.1 microg/kg ANG II administered 30 min after losartan was completely antagonized. Two hours after losartan administration, MABP was on the increase in all animals and ANG II receptor blockade was partially obliterated in control sheep. The more marked cardiovascular effects recorded in diuretic-treated sheep as compared to control animals were associated with an increased activation of the renin-angiotensin system (plasma renin concentration: 6.51 +/- 1.33 vs 1.42 +/- 0.37 ng angiotensin I/ml/hr).

Angiotensin II↗

PubMed2000

Determination of parotid urea secretion in sheep by means of ultrasonic flow probes and a multifactorial regression analysis.

For determination of the dynamics of parotid urea secretion in conscious sheep, a previously standardized transit time ultrasonic flow metering system was used to measure bilateral parotid flow. Six ewes fed for ad libitum consumption were prepared under halothane anesthesia with ultrasonic probes around both parotid ducts; these ducts were also cannulated orally. After probe encapsulation (8 d), parotid flows were recorded during 24 h, and samples of saliva and blood for urea determination were obtained hourly. Jaw movements were recorded by means of a submandibular balloon to monitor feeding behavior. Urea concentration in parotid saliva was 60 to 74% of that in plasma (a positive linear correlation existed) and was poorly influenced by the parotid flow. The amount of urea secreted with parotid saliva was directly related to the salivation rate. To calculate the urea secretion in parotid saliva, a multiple linear regression model was developed from computer-calculated parotid flows over 1-min periods and plasma urea concentration. The model was accurate because the plot of calculated vs measured values was not significantly different from the line of identity. The daily parotid urea N varied from .35 to 1.02 g among ewes. The higher urea secretion rate found during rumination and eating (1.32+/-.42 and .98 +/-.33 mg/min, respectively) vs. during rest (.60+/-.39 mg/ min, P<.05) was due to higher salivation rates (5.17 +/-1.46, 3.56+/-.90, and 2.04+/-.52 mL/min, respectively, P<.05) rather than to changes in saliva urea concentrations (saliva:plasma urea ratio = .65+/-.04, .67+/-.04, and .68+/-.03, respectively). Of the daily parotid urea output, 40.8% was secreted during rest. The contribution of parotid urea N to the ruminal N pool was relatively small (1.2 to 3.7% of the N intake, which was 23.0 to 33.6 g/d). These techniques allowed direct and precise measurements of parotid urea secretion without disturbing the animal or altering the physiological regulation of salivary secretion.

Animals↗

PubMed1999

The relaxant effects of parathyroid hormone(1-34) and parathyroid hormone-related protein(1-34) on ovine reticulo-ruminal smooth muscle in vivo.

The motility of the reticulo-rumen has been measured in trained, conscious sheep using inflated balloons temporarily introduced to selected regions of that forestomach. The frequency and amplitude of the contractions of the reticulum and both the A and B waves of contraction of the rumen were measured under the same conditions before, during and after the administration of an i.v. bolus of either parathyroid hormone (PTH(1-34)) or PTH-related protein (PTHrP(1-34)) followed by its i.v. infusion. These two peptides are known to share a common receptor in other organs, e.g. the kidney. In this study they both showed an inhibitory effect on reticulo-ruminal motility. The effect of PTHrP(1-34) on the rate of ruminal blood flow was also examined and a significant reduction observed, after a transient increase. The secretion of endogenous PTH(1-34) was stimulated by a 32% reduction in the plasma calcium ion concentration induced by an i.v. infusion of sodium citrate. Associated with this were significant reductions in reticulo-ruminal motility, e.g. the reduction in the mean amplitude of the reticular contractions reflected the reduction in plasma calcium ion concentration. When the PTH(1-34)/PTHrP(1-34) receptor was blocked with [Asn10,Leu11,D-Trp12]PTHrP(7-34) before and during the induction of hypocalcaemia, all but one of the parameters of reticulo-ruminal motility were normalized. Indeed, by the day following the administration of this blocking agent, all these parameters had returned to their normal range. It is concluded that stimulation of the PTH(1-34)/PTHrP(1-34) receptor in reticulo-ruminal smooth muscle reduces the motility of this tissue and may play a role in the depression of motility of the digestive tract which is characteristic of clinical milk fever in the dairy cow.

Animals↗

PubMed1998

Comparative pharmacokinetics of sulfamethazine in plasma and parotid saliva of sheep.

Salivary output in sheep is large enough to be considered a physiologic body fluid compartment. The hypothesis for this work was that pharmacokinetics of sulfamethazine in saliva was similar to that in plasma. A reliable technique was developed to measure parotid salivary output. Mean output of saliva was 3.18 +/- 1.04 L from a single parotid gland per day with a mean flow of 2.21 +/- 0.43 mL/min. Using concentrations of sulfamethazine in parotid saliva made it possible to calculate the total passage of sulfamethazine to parotid saliva, which was calculated to be 3.5% of the total dose. Pharmacokinetic variables obtained for sulfamethazine in plasma and in saliva were closely related (AUC 1408 micrograms.h/mL and AUC 1484 micrograms.h/mL; Vdarea 0.434 L/kg and Vdarea 0.374 L/kg; t 1/2 beta 4.30 h and 3.46 h, respectively) and no substantial differences were observed. The convenience of using salivary concentrations of sulfamethazine for drug monitoring is discussed.

Animals↗

PubMed1997

Structural and evolutionary relationships among chitinases of flowering plants.

The analysis of nuclear-encoded chitinase sequences from various angiosperms has allowed the categorization of the chitinases into discrete classes. Nucleotide sequences of their catalytic domains were compared in this study to investigate the evolutionary relationships between chitinase classes. The functionally distinct class III chitinases appear to be more closely related to fungal enzymes involved in morphogenesis than to other plant chitinases. The ordering of other plant chitinases into additional classes mainly relied on the presence of auxiliary domains-namely, a chitin-binding domain and a carboxy-terminal extension-flanking the main catalytic domain. The results of our phylogenetic analyses showed that classes I and IV form discrete and well-supported monophyletic groups derived from a common ancestral sequence that predates the divergence of dicots and monocots. In contrast, other sequences included in classes I* and II, lacking one or both types of auxiliary domains, were nested within class I sequences, indicating that they have a polyphyletic origin. According to phylogenetic analyses and the calculation of evolutionary rates, these chitinases probably arose from different class I lineages by relatively recent deletion events. The occurrence of such evolutionary trends in cultivated plants and their potential involvement in host-pathogen interactions are discussed.

Amino Acid Sequence↗

PubMed1997

Parotid secretion daily patterns and measurement with ultrasonic flow probes in conscious sheep.

Five sheep under halothane anesthesia were prepared with bilateral transit time ultrasonic flow probes around the parotid ducts. The ducts were fitted with non-obstructive sampling catheters through their oral ends. After probe encapsulation (8 days), salivary flows were continuously recorded (4-5 days, dual-channel ultrasonic flowmeter). For rumination, eating, resting and drinking periods, respectively, the parotid daily outputs recorded were 1.96 +/- 0.57, 0.97 +/- 0.34, 2.84 +/- 0.41 and < 0.041 and bilateral flow rates were 6.76 +/- 0.70, 5.63 +/- 1.42, 2.50 +/- 0.58 and 1.69 +/- 0.88 ml min-1. An ipsilateral secretory reflex was evident when the sheep changed chewing side during rumination (4.44 +/- 0.96 ml min-1 ipsilateral vs 2.63 +/- 0.90 ml min-1 contralateral flow, P < 0.01). Secretory patterns are described in detail during rest, eating, drinking and rumination periods. The pH of parotid saliva (8.36 +/- 0.14) and the osmolality (273.8 +/- 9.9 mosmol kg-1) were independent of secretory rates. In situ probe calibration showed high accuracy (0-9%). The main advantages of the technique are its accuracy and good tolerance, duct integrity and maintenance of nervous supply, minimal surgery, uninterrupted salivary flow, simultaneous bilateral measurements and precise flow monitoring, permitting detailed observations.

Animals↗

PubMed1996

Phylogenetic inferences from chloroplast chlB gene sequences of Nephrolepis exaltata (Filicopsida), Ephedra altissima (Gnetopsida), and diverse land plants.

The chloroplast chlB gene, involved in light-independent protochlorophyllide reduction, has been reported present in algae, in one bryophyte and some gymnosperms, but absent from various angiosperms. In this study, the complete or nearly complete chlB gene sequences from the fern Nephrolepis exaltata and the seed plant Ephedra altissima were determined. Comparison of five available land plant chlB sequences with a similar set of rbcL sequences, encoding the large subunit of ribulose 1,5-bisphosphate carboxylase, showed that the chlB rate of nonsynonymous substitution was about fourfold higher than for rbcL, while the chlB phylogeny resulted in a better resolution of the clades surveyed. The presence of chlB in other lineages of land plants was determined by amplification and sequencing of a chlB internal fragment, which was recovered from all the nonangiosperm taxa surveyed except Psilotum and Gnetum. The phylogenies derived from 23 land plant chlB sequences were largely congruent with the relationships inferred from other analyses. Neighbor-joining analysis supported the view that bryophytes are paraphyletic, with mosses as sister group to vascular plants. Within lycopodiophytes, Selaginella clustered with Lycopodium, but Isoetes was located basally to the other land plants. The various ferns surveyed were found to form a coherent group which derived after horsetails and which was sister group to seed plants. Our results strongly supported monophyly of the conifers-Ginkgo-cycads clade, where conifers were sister group to Ginkgo and cycads. The various phylogenies suggested an early divergence of the seed plant lineage leading to Ephedra.

Algal Proteins↗

PubMed1994

Stage-specific transcription of the homebox gene Bnhd1 in young tissues and flowers of Brassica napus.

The Bnhd1 cDNA, only distantly related to published homebox gene sequences, was isolated from Brassica napus by the polymerase chain reaction. The Bnhd1 transcript was detected in all organs of young seedlings, but only in the youngest leaves and flowers of mature plants. A 4- and 7-fold increase in transcription levels was observed after wounding of young roots and leaves, respectively.

Amino Acid Sequence↗

PubMed1994

Novel narrow-host-range vectors for direct cloning of foreign DNA in Pseudomonas.

Narrow-host-range vectors, based on an indigenous replicon and containing a multiple cloning site, have been constructed in a Pseudomonas host capable of growth on unusual substrates. The new cloning vectors yield sufficient amounts of DNA for preparative purposes and belong to an incompatibility group different from that of the incP and incQ broad-host-range vectors. One of these vectors, named pDB47F, was used to clone, directly in Pseudomonas, DNA fragments from Agrobacterium, Pseudomonas, and Rhizobium. A clone containing Agrobacterium and KmR gene sequences was transformed with a higher efficiency than an RSF1010-derived vector (by as much as 1250-fold) in four out of five Pseudomonas strains tested. The considerable efficiency obtained with this system makes possible the direct cloning and phenotypic selection of foreign DNA in Pseudomonas.

Base Sequence↗

PubMed1994

Detection of Escherichia coli strains producing cytotoxic necrotizing factor type two (CNF2) by enzyme-linked immunosorbent assay.

Sheep and rabbit antisera were produced against lysates of E. coli strain 711 (pVir). This K-12 strain carries the Vir plasmid which codes for Cytotoxic Necrotizing Factor type 2 (CNF2). Immunoglobulin G (IgG) fractions of both immune sera were subsequently purified by a two-step precipitation method. To increase the specificity for CNF2, the sheep IgG preparation was extensively adsorbed against both a sonicated extract of isogenic K-12 strain 711 and intact phenol-treated cells of vaccine strain 711 (pVir). An enzyme-linked immunosorbent assay (ELISA) was developed to detect clinical isolates of E. coli producing CNF2, using the final preparations of rabbit and sheep IgG in a double sandwich technique. The results obtained with this CNF2-ELISA were compared to those obtained with the conventional HeLa cell cytotoxicity assay. The testing of 133 E. coli strains (49 CNF2 positive strains and 84 negative strains) resulted in no false-negative and no false-positive. Therefore, the CNF2-ELISA offers a good alternative to the HeLa cell culture assay for the detection of CNF2-producing strains where facilities for and experience with cell cultures is lacking.

Bacterial Toxins↗

PubMed1994

Effects of glucagon on diuresis, renal plasma flow and glomerular filtration in sheep.

The effects of intravenous infusion of glucagon (100 ng.kg-1.min-1) on diuresis, renal plasma flow and glomerular filtration rate were studied in conscious sheep. Diuresis began to decrease upon initiation of glucagon infusion, down to 50% of its baseline value at the end of glucagon infusion. Glomerular filtration rate was also decreased by 75%. With regard to renal plasma flow, the decrease started at the beginning of glucagon infusion, but remained restricted. It was not possible, from these results, to explain the reduced diuresis by a decrease in renal plasma flow; the observed anti-diuretic effect could be the consequence of a modification of either the filtration coefficient or water tubular reabsorption.

Animals↗

PubMed1993

Isolation of Lhcb3 sequences from Brassica napus: evidence for conserved genes encoding LHCII type III chlorophyll a/b binding proteins.

Three closely related sequences were isolated from Brassica napus genomic DNA and were identified as Lhcb3 (genes encoding type III chlorophyll a/b binding proteins of LHCII, the major light-harvesting complex of photosystem II). These genes, as was observed for a tomato Lhcb3, contain two introns and yield both divergent and conserved predicted amino acid segments as compared with type I and type II polypeptides. One of the B. napus genes, designated Lhcb3*1, is transcribed in vivo, since it is identical to corresponding sequences in a cDNA clone. The protein deduced from another sequence, Lhcb3*2, appears as the most divergent type III so far characterized. The partial sequence of a third gene, Lhcb3*3, was also recovered. The 5' noncoding sequences of Lhcb3*1 and Lhcb3*2, in the far upstream region, are characterized by an extremely high AT content and extensive direct repeats. In the near upstream region, two long Lhcb3*2 segments are very similar to a segment proposed as containing regulatory signals in Lhcb3*1. Specific binding of nuclear proteins to Lhcb3*1 promoter fragments was detected by electrophoretic mobility-shift assays. The evolutionary relationship between genes for type III polypeptides and the other types present in LHCII is discussed.

Amino Acid Sequence↗

PubMed1991

Promoter for a Brassica napus ribulose bisphosphate carboxylase/oxygenase small subunit gene binds multiple nuclear factors and contains a negative-strand open reading frame encoding a putative transmembrane protein.

Using a fractionated genomic bank, we have cloned and characterized a Brassica napus gene (rbcSF1) encoding the small sub-unit of ribulose 1,5-bisphosphate carboxylase. The promoter of this gene contains a 29 bp direct repeat capable of forming a single or a double hairpin loop, and three elements that are recognized by leaf nuclear proteins in vitro. The most upstream are the S-box, a small A/T-rich sequence between -516 and -512, and the F-box between -492 and -475. Finally, we have also observed binding to the G-box, a regulatory element common to numerous plant promoters. The promoter of rbcSF1 also has a 113 amino acids open reading frame (ORF113) in the non-coding strand. When used to probe a northern blot of leaf RNA, this ORF hybridizes to a 1.5 kb transcript. The protein encoded by ORF113 contains a transmembrane domain.

Amino Acid Sequence↗

PubMed1991

A novel approach to the rapid isolation and nucleotide sequencing of genomic clones.

In this study, a genomic library subdivided into fractions was rapidly screened by a Southern detection technique. Deletion libraries were obtained from recovered genomic clones by single random cuts with nuclease S1. These deletion libraries proved useful for localizing genes in the inserts and yielded, after size fractionation, nested deletions suitable for nucleotide sequencing. An heterologous vector (pDB21) carried the insert used as probe for all hybridizations involved in the process of genomic clones isolation and characterization.

Base Sequence↗

PubMed1991

Dentinal permeability of the dog canine after exposure of a cervical cavity to the beam of a CO2 laser.

The dentinal permeability of the axial wall of a class V cavities in the canine of the dog was analyzed before and after its laser CO2 irradiation at two energy levels: 285 J per cm2 and 570 J per cm2. The sealing of the exposed dentin was verified by means of a pellet of cotton wool placed in contact with the axial wall and on which 20 microliters of a 50 mg per ml solution of noradrenaline was injected with a micrometric syringe. The transdentinal passage of noradrenaline induces a vasoconstriction of the pulp which is attested by a drop in its blood pressure. The absence of any variation in the pulpal pressure is an indication of the sealing to noradrenaline of the dentinal wall irradiated with an energy level of 570 J per cm2. This experimentation illustrates that it is possible to obtain dentinal sealing by means of laser irradiation without affecting the underlying pulp. The quality of this reduction in permeability is dependent upon the different factors which define the energy level.

Animals↗