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Biomedical subjects

A Petit

Publications and source records attributed to A Petit.

At least 127 records · Page 7Linked to original sources
PubMed1989

Multiplicity of TEM-derived beta-lactamases from Klebsiella pneumoniae strains isolated at the same hospital and relationships between the responsible plasmids.

Five plasmid-mediated beta-lactamases conferring high-level resistance to ceftazidime were isolated from Klebsiella pneumoniae strains in the same hospital. These enzymes had isoelectric points ranging from 5.3 to 6.5 (CAZ-1, 5.55; CAZ-2, 6.0; CAZ-3, 5.3; CAZ-6, 6.5; and CAZ-7, 6.3). All isolates and their Escherichia coli transconjugants were highly resistant to amoxicillin (MICs, greater than 4,096 micrograms/ml), piperacillin (64 to 256 micrograms/ml), cephalothin (32 to 256 micrograms/ml), and ceftazidime (32 to 512 micrograms/ml) but remained moderately susceptible to cefotaxime (0.5 to 8 micrograms/ml). Only CAZ-6- and CAZ-7-producing strains were highly resistant to aztreonam (64 to 128 micrograms/ml). All the isolates remained susceptible to moxalactam and imipenem. The reduced activity of piperacillin, cefotaxime, ceftazidime, or aztreonam was restored by 2 micrograms of clavulanate, sulbactam, tazobactam, or brobactam per ml for E. coli producing CAZ-2, CAZ-3, and CAZ-7. Sulbactam had a lower protective effect than other inhibitors for E. coli harboring CAZ-1 and especially CAZ-6. Except for CAZ-1, which was mediated by a 150-kilobase (kb) plasmid (pCFF14), the other ceftazidimases were mediated by plasmids of 85 kb with EcoRI digestion patterns similar to that of pCFF04 encoding CTX-1 beta-lactamase. A TEM probe hybridized with a 19-kb EcoRI fragment of all these closely related plasmids.

Conjugation, Genetic↗
PubMed1989

Ti plasmid-controlled chromosome transfer in Agrobacterium tumefaciens.

In octopine-type A. tumefaciens R10, transfer of chromosomal arginine degradation genes (arc genes) was observed under conditions in which Ti plasmid transfer took place. However, transconjugants that had acquired the arc genes but not the Ti plasmid were recovered. During this process, several other chromosomal genes, such as genes encoding phage resistances or genes complementing a galactose utilization mutation or a glycine-serine auxotrophy, were transferred from strain R10 to the recipient.

Arginine↗
PubMed1989

Multiple subcutaneous abscesses due to Mycobacterium tuberculosis in an immunocompetent host.

A 58-year-old immunocompetent man presented with a 9-month history of several disseminated subcutaneous ulcerative nodules, fever and weight loss. Histopathological changes were not specific. X-ray of the chest disclosed a large right hilar density highly suggestive of a lung carcinoma. All these manifestations eventually proved to be caused by Mycobacterium tuberculosis, which grew from sputum and skin. We report this case because of its striking clinical features.

Abscess↗
PubMed1989

Ca2+, but not membrane lipid hydrolysis, mediates human chorionic gonadotropin production by luteinizing hormone-releasing hormone in human term placenta.

We postulated a role for lipid metabolism and Ca2+ in the LHRH-induced release of hCG by human placentas. Term placental cells in suspension prelabeled with [3H]myoinositol were stimulated without or with increasing concentrations of LHRH in the presence of 10 mM LiCl, and total inositol phosphate (IP) was measured by ion exchange chromatography; a nonsignificant 0.9 +/- 0.08-fold increase over the control value was observed. In contrast, placental cells stimulated with equimolar concentrations of angiotensin II (AII) induced a 4.6 +/- 0.9-fold increase in total IP (P less than 0.01), while rat pituitary cells showed 1.9 +/- 0.2- and a 2.4 +/- 0.07-fold increases in total IP production after stimulation with LHRH or AII, respectively (P less than 0.05). These increases were blocked by coincubation with specific LHRH and AII antagonists. When 1 x 10(6) placental cells were incubated with 45Ca2+ without and with increasing doses of LHRH for 0-75 s and then filtered under negative pressure, we observed significant incorporation of 45Ca2+. This influx was linear with incubation time, significantly more pronounced in cells exposed to LHRH than in control cells, and showed a dose-response curve to LHRH that reached maximal influx rates of 3.6 +/- 0.3 nM/min.1 x 10(6) cells with 10(-5) M LHRH. This response was completely blocked by coincubation with 10(-5) M LHRH antagonists; cobalt chloride and verapamil reduced it by 60% and 80%, respectively. Compared to placental cells stimulated with LHRH alone, those coincubated with LHRH and specific LHRH or Ca2+ antagonists released from 10-100% less hCG. We conclude that Ca2+ participates in the LHRH action in human placentas, but uncoupled to PI turnover.

Angiotensin II↗
PubMed1989

Angiotensin II stimulates both inositol phosphate production and human placental lactogen release from human trophoblastic cells.

We studied the functional significance of the binding of angiotensin-II (AII) to human placentas. Human trophoblastic cell suspensions were prepared by trypsin digestion of minced tissue. Cell incubations with increasing doses of [125I](SAR1)AII, ranging from 0.01-2.5 nmol/L, were carried out for 20 min at 37 C. The results indicated the presence of specific low capacity [4300 +/- 1300 (+/- SE) sites/cell], high affinity (Kd = 0.38 +/- 0.06 nmol/L) binding sites for [125I](Sar1)AII. This binding was specific for AII analogs. When placental cells were preloaded with 40 microCi/mL [3H]myoinositol for 2 h at 37 C, AII stimulation resulted in a dose-dependent increase in inositol phosphate (InsP) production [EC50 = 1.4 +/- 0.4 (+/- SE) nmol/L], as measured by ion exchange chromatography. (Sar1)AII also stimulated InsP production, with an EC50 of 0.3 +/- 0.2 nmol/L. AII-stimulated production of InsP was completely blocked by the antagonist (Sar1,Ala8)AII. AII also stimulated human placental lactogen release from trophoblastic cells in a dose-dependent fashion. The EC50 was 18 +/- 9 pmol/L, and the stimulation was blocked by (Sar1,Ala8)AII, as found for AII-stimulated InsP production. These results suggest that stimulation of human placental lactogen release by AII may be mediated by activation of phospholipase-C, which, in turn, produces phosphoinositide breakdown. The results, therefore, provide evidence of a physiological role for the renin-angiotensin system within the human placenta.

Angiotensin II↗
PubMed1988

Sex-specific proteins in normal chick embryo gonads and testis feminized by oestrogen treatment: a two-dimensional gel electrophoresis investigation.

Gonads dissected from 17-day-old normal chick embryos, as well as testes feminized by oestrogen treatment, were labelled in vitro with [35S]methionine and [14C]leucine. The patterns of cytosolic protein synthesis by the gonads were analysed using two-dimensional (2-D) polyacrylamide gel electrophoresis. In the feminized testis, two female-specific proteins appeared, the rate of synthesis of four testis-specific proteins was decreased, and quantitative variations of other synthesized proteins in relation to sex were detected. This altered protein synthesis indicates that the protein synthesis of the testis feminized by oestrogen treatment has in part become similar to that of a normal ovary. The synthesis of female-specific proteins in the feminized testis raises the question of their role in normal ovarian differentiation.

Animals↗
PubMed1988

Hairy roots are more sensitive to auxin than normal roots.

Responses to auxin of Lotus corniculatus root tips or protoplasts transformed by Agrobacterium rhizogenes strains 15834 and 8196 were compared to those of their normal counterparts. Three different types of experiments were performed, involving long-term, medium-term, or short-term responses to a synthetic auxin, 1-naphthaleneacetic acid. Root tip elongation, proton excretion by root tips, and transmembrane electrical potential difference of root protoplasts were measured as a function of exogenous auxin concentration. The sensitivity of hairy root tips or protoplasts to exogenous auxin was found to be 100-1000 times higher than that of untransformed material.

Journal Article↗
PubMed1988

Comparative study of a novel plasmid-mediated beta-lactamase, CAZ-2, and the CTX-1 and CAZ-1 enzymes conferring resistance to broad-spectrum cephalosporins.

Infections caused by strains of Klebsiella pneumoniae resistant to broad-spectrum cephalosporins have been observed recently in hospitals in Clermont-Ferrand, France. beta-Lactam resistance resulted primarily from the plasmid-mediated, expanded-spectrum CTX-1 beta-lactamase. Furthermore, since 1987 some K. pneumoniae isolates more resistant to ceftazidime than to other cephalosporins have been observed. This new resistance phenotype was the result of the production of ceftazidimase CAZ-1 and, more recently, CAZ-2. As in CTX-1-producing strains, resistance to beta-lactams resulting from CAZ-2 was associated with resistance to aminoglycosides except gentamicin, sulfonamide, and tetracycline and was transferable to Escherichia coli by conjugation. Agarose gel electrophoresis of plasmid DNA from wild-type strains and transconjugants indicated that CAZ-2 production was mediated by a plasmid of 85 kilobases highly related to plasmid pCFF04 coding for CTX-1 beta-lactamase. The isoelectric point, close to 6.0, of this novel enzyme differed from those of CTX-1 and CAZ-1. Like CAZ-1, the CAZ-2 enzyme efficiently hydrolyzed ceftazidime and aztreonam, but as with CTX-1, cefotaxime gave the maximal reaction rate. For each expanded-spectrum beta-lactamase, the activity of broad-spectrum cephalosporins was restored by clavulanic acid or sulbactam.

Cefotaxime↗
PubMed1988

Novel plasmid-mediated beta-lactamase in clinical isolates of Klebsiella pneumoniae more resistant to ceftazidime than to other broad-spectrum cephalosporins.

Multiresistant Klebsiella pneumoniae strains isolated from three patients in the same intensive care unit were more resistant to ceftazidime than to cefotaxime and aztreonam but remained susceptible to moxalactam and imipenem. Resistance to beta-lactams, kanamycin, streptomycin, sulfonamides, and tetracyclines was transferable to Escherichia coli by conjugation and was lost en bloc after treatment with ethidium bromide. Agarose gel electrophoresis of wild types and transconjugants indicated that these resistances were mediated by a 150-kilobase plasmid, pCFF14. The strains constitutively produced a beta-lactamase with isoelectric point close to 5.6 and which had a higher Vmax for ceftazidime and cephalothin than for cefotaxime. The substrate profile and isoelectric point of this enzyme thus differ from those of other known plasmid-mediated beta-lactamases, including the broad-spectrum enzyme CTX-1. Hybridization studies support the derivation of the novel enzyme from a TEM-type beta-lactamase.

Ceftazidime↗
PubMed1988

Opine utilization by Agrobacterium spp.: octopine-type Ti plasmids encode two pathways for mannopinic acid degradation.

Octopine-type strains of Agrobacterium tumefaciens degrade the opine mannopinic acid through a specific pathway which involves cleavage of the molecule at the C--N bond between the amino acid and the sugar moieties. Mannose was identified as a product of the reaction. This pathway was inducible by mannopinic and agropinic acids, but not by mannopine or agropine, the two other mannityl opines. The transport system for this pathway appeared to be specific for mannopinic acid. A second, nonspecific pathway for mannopinic acid degradation was also identified. This involved some of the catabolic functions associated with the metabolism of mannopine and agropine. This second pathway was inducible by mannopine and agropine but not by mannopinic or agropinic acids. The transport system for this pathway appeared to have a broad specificity. Transposon Tn5 insertion mutants affected in the specific catabolic pathway were isolated and analyzed. These mutants continued to catabolize mannopine and agropine. Both mapped to a region of the Ti plasmid previously shown to be associated with the catabolism of mannopinic acid. Restriction enzyme analysis of the Ti plasmid from strain 89.10, an octopine strain that is naturally unable to utilize mannopinic acid, showed a deletion in this same region encoding the specific mannopinic acid degradation pathway. Analysis of recombinant clones showed that the second, nonspecific pathway was encoded in a region of the Ti plasmid associated with mannopine and agropine catabolism. This region shared no structural overlap with the segment of the plasmid encoding the specific mannopinic acid degradative pathway.

Arginine↗
PubMed1988

Congenital diverticulum of the right atrium situated on the floor of the coronary sinus.

A diverticulum of the right atrium was found on the floor of the coronary sinus in a neonate. The diverticulum was distinguished from a pericardial cyst by contrast echocardiography, and its relations with coronary sinus and coronary venous return were identified by coronary angiography. Because the diverticulum compressed the left ventricular inferior wall and prevented its growth, it was excised. Thebesian veins were discovered at operation and prevented complete correction of the defect.

Coronary Angiography↗
PubMed1988

Functional opioid receptor sites in human placentas.

We characterized the presence of opioid peptide receptor sites in plasma membranes and cells from human midterm and term placentas. Incubations with [3H]ethylketo-cyclazocine (EKC) at increasing doses revealed the presence of high affinity, low capacity, opioid peptide receptor-specific binding of the kappa-type. Scatchard analysis of the binding data showed, in the plasma membranes, linear plots at both stages of pregnancy with similar mean equilibrium association constants of 1.31 +/- 0.29 (+/- SE) X 10(9) mol/L-1 (n = 4) at midterm and 0.52 +/- 0.63 X 10(9) mol/L-1 at term (n = 4). In placental cells (n = 4) from term gestations, the binding plots were curvilinear; the first component had a Ka of 5.51 +/- 0.50 X 10(9) mol/L-1, and the second component had a Ka of 1.33 +/- 0.81 X 10(8) mol/L-1 (P less than 0.01). When standardized per mg tissue protein, the number of binding sites in plasma membranes increased from 13.8 +/- 9.8 fmol at midterm to 50.0 +/- 18.6 fmol at term (P less than 0.05). For term placental cells, the concentration of binding sites was 81.2 +/- 36.0 fmol for the high affinity sites and 713 +/- 390 fmol for the lower affinity sites. Specificity for the kappa-type of OPR was found based on the inability of mu- or delta-opioid peptides, as well as LHRH and TRH, to compete for [3H]EKC binding. Term placental cells incubated with various doses of opioid peptides had a 50% increase in placental lactogen production. The increase was significantly higher than controls only with kappa-agonists (P less than 0.05), maximal with 10(-9) mol/L EKC, and completely inhibited by 5 X 10(-6) mol/L naloxone. These results expand on previous data demonstrating the presence of opioid peptide receptor in placental plasma membranes and suggest a role for opioid peptides in regulating secretion of placental lactogen by placental cells.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1988

[Attempt at in vitro decalcification of aortic valves using various types of lasers].

The effects of three types of laser were studied in vitro on calcified aortic valves removed in the course of valve replacement. These were: 1) argon laser; 2) Nd-YAG laser with a long (1 ms) impulse, and 3) Nd-YAG laser with a short (10 ns) impulse. With the first two types of laser, lesions of carbonization and fragments detached from the areas treated were observed. With the 10 ns ND-YAG laser, a mean energy of 100 mj per shot excavated the calcified valves by drilling holes that were 0.5 to 1.5 mm in diameter and had clear-cut non carbonized borders. No residue was found during the procedure: the substance was simply vaporized. The splitting of several calcareous nodules on a valve made it more pliable. If it were possible to transfer this high peak energy onto a flexible optic fibre, the aortic valves could be decalcified by interventional catheterization.

Calcinosis↗