Search PubMed⌕ Search

Biomedical subjects

A Petit

Publications and source records attributed to A Petit.

At least 145 records · Page 8Linked to original sources
PubMed1987

Biosynthesis and degradation of nodule-specific Rhizobium loti compounds in Lotus nodules.

Two nodule-specific Rhizobium loti compounds were identified in Lotus tenuis and Lotus pedunculatus nodules induced by strain NZP2037. One, a silver nitrate-positive cation called rhizolotine, has been characterized as the riboside of a novel alpha-hydroxyimino acid containing a 1,4,5,6-tetrahydropyrimidine ring (G. J. Shaw, R. D. Wilson, G. A. Lane, L. D. Kennedy, D. B. Scott, and G. J. Gainsford, J. Chem. Soc. Chem. Commun., p. 180-181, 1986), and the other, yellow-1, stains yellow with ninhydrin. Both compounds were degraded by R. loti NZP2037 but not by strains of Rhizobium meliloti, Rhizobium trifolii, or Agrobacterium tumefaciens. Under the conditions tested neither compound was able to serve as a sole source of C or N for growth of R. loti NZP2037. Rhizolotine and yellow-1 were found in nodules from a range of different legumes inoculated with NZP2037, suggesting that the Rhizobium and not the host plant determines their synthesis. Neither compound was found in nodulelike structures of L. pedunculatus induced by transposon Tn5-induced noninfectious (Inf-) mutants of NZP2037 or in similar structures induced by a transconjugant of NZP2037 containing the symbiotic (Sym) cointegrate plasmid pPN1 of R. trifolii. Both compounds were also absent in the ineffective nodules induced by the bacterial-release-negative (Bar-) mutant, strain PN239. However, both compounds were present in nodules induced by the fixation-negative (Fix-) mutant PN235 and in Fix+ nodules formed by a plasmid-cured derivative of NZP2037. These results would suggest that infection and bacterial release from the infection thread are necessary for nodule (symbiotic) synthesis of these compounds.

Bacterial Proteins↗
PubMed1987

Intestinal absorption of macromolecules during viral enteritis: an experimental study on rotavirus-infected conventional and germ-free mice.

Epithelial transport and degradation of horseradish peroxidase (HRP), a macromolecular tracer, was studied in conventional and germ-free suckling mice following an experimental infection with rotavirus. Conventional and germ-free mice developed diarrhea from days 2 to 8 postinfection (pi), with growth failure. In mucosal homogenates, infectious virus detected by immunofluorescence on MA 104 cells was present from day 2 through day 8 pi in germ-free mice, but persisted longer (day 13 pi) in conventional mice. Only mild histological lesions were observed during diarrhea, but obvious macrovacuolation of epithelial cells and increased cellular density occurred during the convalescence period (days 9 to 13 pi). Intact and degraded HRP fluxes from mucosa to serosa were measured in vitro on segments of jejunum mounted in Ussing chambers. Both groups of mice developed increased HRP permeability during the experimental period, but at different times after inoculation: during the diarrheal period (days 2 and 3 pi) conventional mouse epithelium absorbed five times more HRP than noninfected controls and during the convalescence period (days 9 to 13 pi) HRP absorption in germ-free mice rose 10-fold as compared to its level before infection. In both cases, this increase in HRP permeability was entirely due to an increase in intact HRP absorption, probably via a transcellular route, and occurred without any alteration in degraded HRP transport. These results indicate that in mice, rotavirus infection causes a transient rise in gut permeability to undegraded proteins. The intestinal microflora seems to affect the timing, magnitude, and duration of this increased permeability.

Animals↗
PubMed1986

Agrobacterium Ti and Ri plasmids specify enzymic lactonization of mannopine to agropine.

A novel enzymic activity, responsible for the conversion of mannopine to agropine by lactonization, has been identified in Agrobacterium strains. This activity is encoded by octopine-type and agropine-type Ti or Ri plasmids, and is inducible by mannopine and agropine. In crude extracts it is stable for long periods and can be used for preparative synthesis of agropine from mannopine. The physiological role of this activity is not understood. However, it is probably involved in degradation of opines of the agropine family since it is always associated with agropine utilization in wild-type strains.

Chemical Phenomena↗
PubMed1986

Arginine catabolism in Agrobacterium strains: role of the Ti plasmid.

We present a study of the enzymatic activities involved in the pathway for arginine catabolism by Agrobacterium tumefaciens. Nitrogen from arginine is recovered through the arginase-urease pathway; the genes for these two activities are probably chromosomally born. Arginase was found to be inducible during growth in the presence of arginine or ornithine. Urease was constitutively expressed. Ornithine, resulting from the action of arginase on arginine, could be used as a nitrogen source via transamination to delta 1-pyrroline-5-carboxylate and reduction of the latter compound to proline by a reductase (both enzymatic activities are probably chromosomally encoded). Ornithine could also be used as a carbon source. Thus, we identified an ornithine cyclase activity that was responsible for direct conversion of ornithine to proline. This activity was found to be Ti plasmid encoded and inducible by growth in medium containing octopine or nopaline. The same activity was also chromosomally encoded in some Agrobacterium strains. In such strains, this activity was inducible during growth in arginine-containing medium.

Ammonia-Lyases↗
PubMed1986

[Interruption of the aortic arch without patent ductus arteriosus. Apropos of a case associated with partial atrioventricular canal].

The authors report a case of type A interruption of the aortic arch with the subclavian arteries arising from the descending aorta which was of special interest because of the absence of a patent ductus arteriosus. Therefore, the systemic circulation was assured from the carotid arteries which perfused the vertebral arteries retrogradely via the circle of Willis. The association of a partial endocardial cushion defect and hypoplasia of the ventricle explained the surgical failure. A review of the literature of interruption of the aortic arch without a ductus confirmed that this was a rare condition and, paradoxically, well tolerated in the absence of associated malformations. On the other hand, the left ventricular lesions, usually present in the classical forms with patent ductus arteriosus, operated in the neonatal period, increase the operative risk.

Aorta, Thoracic↗
PubMed1986

[Congenital paravertebral arteriovenous fistulae in children and adolescents].

These arteriovenous fistulae (AVF) situated in the paravertebral area present as a murmur which explains their cardiological orientation. They are characterised by the presence of one or more afferent paravertebral arteries giving rise to collateral vessels irrigating the bone marrow. The aim of this study of 13 cases was to study the diagnostic and therapeutic problems, and the evolution of this particular localisation of AVF. Two groups of paravertebral AVF were individualised: - Cervical AVF in which the vertebral artery was always involved (7 cases). Four were simple (only one fistula) and three were complex, having several afferent arteries. Two presented as a rapidly growing vascular tumour. Two caused an asymptomatic angiographic vertebral steal syndrome. Two simple forms were obturated by a detachable balloon and one by surgical excision. Two complex forms were treated by embolisation and surgery. Total closure of the AVF was obtained in all cases without complications. - Dorso-lumbar AVF (6 cases). The afferent vessels are the intercostal (D6 to D8) or lumbar (L2 to L4) arteries. Anatomically, these are extra-medullary fistulae with an extra or intra-vertebral venous drainage. Enlargement in an adjacent conjugating foramen forms a tumour which may narrow the spinal canal (1 case diagnosed by CAT) or erode the vertebral body, so compromising the spinal support. Spontaneous closure of the AVF was observed in 1 case. Three cases were treated surgically with good results; two patients are waiting for embolisation. A review of the literature provides complementary information on the long-term evolution of these AVF and confirms the need for systematic therapy as demonstrated in our study.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

[Unruptured aneurysms of the sinus of Valsalva disclosed by syncopal disorders of cardiac excitability. Apropos of 2 cases].

Aneurysms of the sinus of Valsalva are rarely diagnosed before rupture into the cardiac cavities which usually leads to the appearance of a continuous murmur and cardiac failure. In the two cases described, the presenting symptom of the aneurysm was syncope due to cardiac hyperexcitability: ventricular tachycardia in the first and paroxysmal tachyarrhythmia in the second case. The presenting symptoms of unruptured aneurysms of the sinus of Valsalva were analysed. In general, they are: uncontinuous cardiac murmurs: either diastolic murmurs of aortic regurgitation, systolic murmurs of mitral or tricuspid regurgitation, or, as in our first case, of obstruction to right ventricular ejection; arrhythmias: the commonest are conduction defects, which can be syncopal; hyperexcitability (especially ventricular) seems to be very care. Echocardiography is a valuable tool for the diagnosis of sinus of Valsalva aneurysms. The appearances of unruptured aneurysms in our two patients are described. The presence of syncopal cardiac hyperexcitability, possibly associated with one of the preceding auscultatory abnormalities is an indication for echocardiography which may lead to the diagnosis of this condition.

Aged↗
PubMed1986

Analysis of the cytosolic proteins of chick embryo gonads by two-dimensional gel electrophoresis.

Gonads and mesonephros dissected from normal chick embryos, as well as a blood sample, were labelled in vitro with [35S]methionine and [14C]leucine. The patterns of cytosolic protein synthesis of the different tissues were analysed using two-dimensional (2-D) polyacrylamide gel electrophoresis. Three developmental stages, i.e. 8, 12 and 17 days of incubation, were investigated. Five sex-specific proteins were detected in the male and two in the female. In the testis, only one protein is already present at the 8-day stage. In the ovary, one protein exists since the 8-day stage, but it is also synthesized in the mesonephros. The second ovary-specific protein appeared only at the 12-day stage.

Animals↗
PubMed1985

Inactivation of human placental aromatase by 6 alpha- and 6 beta-hydroperoxyandrostenedione.

The epimeric 6 alpha- and 6 beta-hydroperoxy derivatives of androstendione caused irreversible inactivation of human placental aromatase. Microsomes from term-placentae were first preincubated in the presence of increasing concentrations of the hydroperoxides. The microsomes were then washed free of steroids and its residual aromatase activity was assayed by the tritium-exchange method to [3H]water. Aromatase activity decreased in a time-, and concentration-dependent manner; the axial, beta-hydroperoxy epimer was the slightly stronger inactivator. Less inactivation occurred when during the preincubation stage the natural aromatase substrate, androstenedione, or the anti-oxidant, dithiothreitol, was added. The sulfhydryl reagent, p-hydroxy-mercuribenzoate, decreased this protective effect. The inactivation is not dependent on the presence of NADPH. Both steroids induced a Type I difference spectrum with a Ks of 0.167 microM and 0.163 microM for the 6 alpha-, and the 6 beta-hydroperoxyandrostenedione, respectively. We suggest that these 6-hydroperoxyandrogens may function as active-site directed inhibitors and inactivators of estrogen synthetase through oxidation of cysteine residues.

Androstenedione↗
PubMed1985

Murine intestinal intraepithelial lymphocytes I. Relationship of a novel Thy-1-,Lyt-1-,Lyt-2+, granulated subpopulation to natural killer cells and mast cells.

Highly purified populations of intraepithelial lymphocytes (IEL) were obtained from the murine small intestine. We found that 84% of IEL expressed Lyt-2 and that 45-55% possessed the unique phenotype, Thy-1-,Lyt-1-,Lyt-2+. Sixty percent of IEL had granules in their cytoplasm and thus resembled the large granulated lymphocytes associated with natural killer (NK) activity. However, less than 15% of IEL had NK activity in a 6-h assay. This activity resided in a subpopulation of Lyt-2- lymphocytes, leaving a large population of Thy-1-,Lyt-1-,Lyt-2+ granulated cells (45-55% of IEL) with unknown function. Sensitive radioenzymic assays for histamine showed that IEL from healthy CBA mice do not contain this amine. IgE-binding assays revealed that IEL, unlike mast cells, do not carry high-affinity receptors for IgE. Thus, only a small percentage of granulated IEL (less than 15%) possess NK activity, whereas 45-55% of IEL have granules, lack typical characteristics of mast cells, express the unique antigenic phenotype, Thy-1-,Lyt-1-,Lyt-2+ and have unknown function.

Animals↗
PubMed1985

Murine intestinal intraepithelial lymphocytes II. Comparison of freshly isolated and cultured intraepithelial lymphocytes.

Highly enriched preparations of intraepithelial lymphocytes (IEL) containing a large subpopulation of granulated cells were isolated from the murine small intestinal mucosa. We cultured IEL in media containing interleukin 2 (growth media conditioned with 20% concanavalin A supernatant; Con A CM) or mast cell growth factor(s) (growth media conditioned with 40% WEHI-3 supernatant; WEHI CM) and compared the physical and functional properties of the cultured cells to freshly isolated IEL. IEL cultured in Con A CM developed enhanced cytotoxicity against YAC-1, compared to freshly isolated IEL, and spontaneous cytotoxicity for P815 targets. Most of these cultured cells were Thy-1+ Lyt-1- Lyt-2+, and contained cytoplasmic granules similar to those seen in electron photomicrographs of other cytotoxic cell populations. IEL cultured in WEHI CM gave rise to cells that morphologically resembled mast cells. Unlike freshly isolated IEL, the cells stained metachromatically, contained 200-450 ng of histamine/10(6) cells and expressed high-affinity receptors for IgE. Our data clearly show that, although IEL do not themselves have physical characteristics of mast cells, they do contain mast cell precursors. In addition, IEL grown in the presence of T cell growth factors give rise to an activated cytotoxic cell population which is mostly granulated and Thy-1+ Lyt-1- Lyt-2+.

Animals↗
PubMed1984

Histochemistry of mucosubstances in the frog respiratory epithelium.

The histochemical nature of the mucosubstances of the respiratory epithelium of the frog palate was studied. 3 main types of epithelial cells were identified: Goblet cells which contained some glycogen, some neutral mucins and a mixture of sialidase-resistant and sialidase-labile sialomucins, non ciliated columnar cells with a secretory activity restricted to their apical pole. These cells contained abundant glycogen, some neutral mucins and sialidase-resistant sialomucins, ciliated cells with no secretory activity. The surface mucous blanket was composed of a mixture of predominant sialomucins and some neutral mucins. The histochemistry of mucosubstances in the respiratory epithelium of the frog palate differed from that of human and most respiratory systems by the presence of glycogen and the absence of sulphated mucins.

Animals↗
PubMed1984

[Systemic arterial hypertension caused by discharge of catecholamines following ligation of ductus arteriosus].

A case of severe systemic hypertension due to catecholamines discharge after ligation of a large patent ductus arteriosus in an 8 months old child is reported. The blood pressure was corrected by the association of alpha- and betablocker drugs which were withdrawn on the 15th post-operative day without recurrence. Transient increases in blood pressure are quite common after closure of a patent ductus arteriosus with a large shunt. Persistent hypertension greater than 160/110 mmHg is rare. It always regresses but may sometimes cause complications. Hyperactivity of the sympathetic nervous system has already been suggested as a possible cause. Massive discharge of catecholamines and the spectacular effect of the association of alpha- and betablocker therapy, reported here apparently for the first time, provide additional evidence in favour of this hypothesis.

Catecholamines↗
PubMed1984

Fine structure of the frog palate mucociliary epithelium.

The mucociliary epithelium (MCE) of the frog palate is a pseudostratified columnar respiratory epithelium supported by connective tissue with no submucosal glands. Morphologically different types of cells have been identified using scanning and transmission electron microscopy: ciliated cells, mucous and serous cells, intermediate cells, basal cells, and patches of vomero-nasal epithelium with sensory receptors and supporting cells. The cilia of the MCE of the frog palate are 5 to 7 microns long and a cluster of 3 to 7 projections forms a ciliary crown at their tips. Using cationized ferritin, anionic charges are identified on their whole outer surface. The mucus discharged by the secretory cells forms a continuous blanket which lies at the tips of the cilia.

Animals↗
PubMed1983

[Right coronary-cardiac fistulae. Anatomic and clinical study, course and therapy. Apropos of 3 new cases].

Three cases of coronary-cardiac fistulae diagnosed in the Cardiologic Unit of the Dijon University Hospital are reported. With reference to these cases current knowledge on this rare condition is reviewed. Symptomatology is variable, with sometimes only a systolic and diastolic murmur on the sternal border, usually with good functional tolerance. A thorough investigation, including left angiography, ascertains diagnosis and shows the exact nature of the lesions. Surgery is almost always advocated as it often ensures good results and avoids delayed complications, which are mainly heart failure by coronary insufficiency, and infectious endocarditis.

Adult↗
PubMed1983

The frog palate for studying mucus transport velocity and mucociliary frequency.

The palate of the frog possess a pseudostratified epithelium with mucus secreting cells and numerous ciliated cells covered with a continuous mucus blanket of 4 to 8 micron thickness. This palate can be used as a simple model for studying mucus transport and giving rapid information on the transportability of pathological bronchial secretion by the ciliary mechanism. The analysis of the relationship between the rheological properties of sputum an their transport rates on the frog palate showed that the highest transport rates were obtained with sputum samples characterized by a high spinability (Sp greater than 70 mm) and an intermediate range of viscosity (25-180 P) and elasticity (SR = 4-12 units). The mucociliary frequency (Fm) of the frog palate was measured by a photoelectric method and analyzed as a distribution function of the ciliary frequencies by the Fast Fourier Transform method. Fm decreased significantly after mucus depletion and was restored when adding a drop of frog mucus collected on a freshly excised frog palate. On the other hand, it remained about 20% lower than the original predepleted value, when adding purulent sputum collected in patients with chronic bronchitis and cystic fibrosis. The frog palate appears as a valuable model for analyzing the mucociliary transport rate and also for studying the effect of pathological secretions on the ciliary beating frequency.

Animals↗