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Biomedical subjects

A Petit

Publications and source records attributed to A Petit.

At least 109 records · Page 6Linked to original sources
PubMed1992

[Identification of a new penicillinase in a Klebsiella pneumoniae strain of which a mutant also produces an esterase hydrolyzing cephalothin and cefotaxime].

Klebsiella pneumoniae strain L 164 produces a penicillinase whose isoelectric point is 8.1, an unusual figure for this bacterial species. This strain exhibits resistance to conventional penicillins and a synergistic effect is seen with clavulanic acid. In contrast, susceptibility to cephalosporins is marked, as shown by the low minimum inhibitory concentrations (MICs). This phenotype is characteristic of strains with no acquired resistance. A first mutant with MICs for cephalothin and cefotaxime 8-fold to 16-fold those of the initial strain was obtained spontaneously. This mutant's MICs for the other beta-lactams were not substantially changed. In addition to the same penicillinase as the one produced by the parent strain, this mutant produced an acetyl-esterase capable of hydrolyzing the cephalosporins with an acetoxyl side-chain, i.e., cefalothin and cefotaxime, to deacetylated derivates which retain substantial antibacterial activity. Another mutant selected on an amoxicillin gradient produced ten times more penicillinase than the parent strain but no esterase. This second mutant exhibited very high MICs for penicillins and first and second generation cephalosporins. The MIC for cefotaxime was comparable to that seen with the esterase-producing mutant. Among the antimicrobials tested, only third generation cephalosporins and cefoxitin showed adequate activity.

Acetylesterase↗
PubMed1991

Adenosine 3':5'-cyclic monophosphate (cAMP) is not the mediator of kappa opiate effect on human placental lactogen release.

We previously reported that kappa opiates stimulated the release of human placental lactogen (hPL) from human placental cells. In this study, we investigated the role of adenylate cyclase as a potential cellular mediator of such an effect. Incubations with ethylketocyclazocine (EKC) led to a time- and dose-dependent inhibition of adenylate cyclase activity. The maximal inhibition was 45 +/- 5% of control value after 15 min exposure to 10(-7)M EKC. This inhibition was reversed by opiate antagonist naloxone and was specific to kappa opiate type. Preincubation of human trophoblastic cells with 0.1 microgram/ml Islet-Activating-Protein (IAP; also called pertussis toxin) did not modify basal adenylate cyclase activity but abolished the inhibition of adenylate cyclase activity by EKC, indicating that the effect of opiates on cAMP production was mediated by an IAP-sensitive GTP binding protein. Also, IAP stimulated basal hPL release; the control levels were 22.4 ng/ml and 46.5 ng/ml without and with IAP respectively. However, the EKC-stimulated hPL levels were unchanged by preincubation with IAP. This difference in cAMP and hPL response in IAP-treated cells suggested that the opiate receptors are not directly coupled to adenylate cyclase. This hypothesis was confirmed by 1) experiments on placental membranes showing that in absence of the cytoplasmic elements (membranes only), EKC had no effect on membrane adenylate cyclase and 2) experiments on placental cells showing that dibutyryl-cAMP (dbcAMP) stimulated hPL release.

Adenylate Cyclase Toxin↗
PubMed1990

Molecular epidemiology of TEM-3 (CTX-1) beta-lactamase.

A total of 33 clinical isolates encoding TEM-3 (CTX-1) from four French hospitals were studied. The strains belonged to seven species, Klebsiella pneumoniae (n = 24), Escherichia coli (n = 3), Serratia marcescens (n = 2), Citrobacter freundii (n = 1), Enterobacter aerogenes (n = 1), Enterobacter cloacae (n = 1), and Klebsiella oxytoca (n = 1). All the strains harbored an Inc7 or M self-transferable plasmid with a size of approximately 85 kilobases. The plasmids had closely related EcoRI, HincII, HindIII, and PvuII restriction endonuclease-generated patterns and conferred resistance to all beta-lactams, except cephamycins and imipenem; to tetracycline, because of the presence of the genes blatem-3 and tetC, respectively, as determined by hybridization with specific probes; and to sulfonamide. Depending on the presence or absence and level of expression of the genes aacA4, aadA, and dfrI and of insertion element IS15, four types of plasmids could be distinguished. Plasmid pCFF04, the prototype plasmid encoding TEM-3, was widespread and appeared, by Southern hybridization, as the progenitor of the other types of replicons. The plasmid epidemic responsible for dissemination of TEM-3 in clinical isolates of members of the family Enterobacteriaceae may have originated in S. marcescens since pCFF04 was first detected in this species.

Aminoglycosides↗
PubMed1990

An islet-activating protein-sensitive G-protein is involved in dopamine inhibition of both angiotensin-stimulated inositol phosphate production and human placental lactogen release in human trophoblastic cells.

In isolated human trophoblastic cells, dopamine (DA) significantly inhibited the angiotensin-II (AII)-stimulated inositol phosphate (IP) accumulation by 44 +/- 8% (EC50, 0.5 +/- 0.2 microM) and human placental lactogen (hPL) release by 85 +/- 5% (EC50, 1.0 +/- 0.8 microM). These effects were blocked by sulpiride, a specific D2 antagonist. On the contrary, scherring 23390 (a specific D1 antagonist) and propranolol (a specific beta-adrenergic antagonist) were ineffective, suggesting that these DA effects are mediated through a DA receptor of the D2 subtype. The mechanism by which DA inhibited AII-stimulated inositol phosphate production implicates a GTP-binding protein sensitive to the islet-activating-protein (IAP), since DA's effects on IP accumulation and hPL release were blocked by this toxin. To further characterize this GTP-binding protein, particulate fractions of placental cells were incubated with [alpha-32P]NAD and IAP. Solubilized extracts were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Two proteins of 40 and 41 kDa mol wt were specifically ADP ribosylated. They were probably involved in the DA inhibitory processes, since IAP treatment, known to suppress the effects of DA, also reduced the labeling of these two molecules by around 40%. The effects of AII and DA on hPL release appear to be insensitive to the external calcium concentration, since the results were not significantly different in normal (1.8 mM Ca2+) and low Ca2+ (10(-5) M Ca2+) concentrations. On the other hand, increasing the intracellular concentration of cAMP by adding forskolin did not modify the effect of DA on either IP accumulation or hPL release, suggesting that cAMP is not implicated in hPL release from freshly isolated human trophoblastic cells.

Adenosine Diphosphate↗
PubMed1990

Presence of D2-dopamine receptors in human term placenta.

We studied the binding of [3H]-spiperone on human term placental membranes. This binding reached plateau level after 30 min incubation at 37 degrees C and was reversed (t1/2 approximately 5 min) by addition of an excess of unlabeled spiperone. Scatchard analysis of saturation experiments with increasing doses of [3H]-spiperone (0-25 nM) showed one class of high affinity binding sites with a dissociation constant (Kd) of 14 +/- 2 nM and a maximal binding capacity (Bmax) of 222 +/- 9 fmoles/mg protein. The affinity of 5 competitors was determined in competitive binding assays. The D2-dopamine antagonists were the most potent inhibitors: Ki for spiperone and haloperidol were 8 +/- 2 and 56 +/- 22 nM respectively. Dopamine inhibited [3H]-spiperone binding with a Ki of 570 +/- 50 microM whereas Schering 23390 (D1 antagonist) and propranolol (beta-adrenergic antagonist) were without effect. The binding was also inhibited by 100 microM GTP gamma S (38 +/- 8% inhibition), indicating that the dopamine receptor is coupled with a GTP binding protein. These results demonstrate for the first time the presence of D2-dopamine receptors in human placenta.

Dopamine↗
PubMed1990

A case of cicatricial pemphigoid with circulating IgA and IgG antibodies directed against 280 kD, 165 kD and 120-130 kD epidermal antigens.

A case of subepidermal autoimmune blistering disease in an 86-year-old woman is reported. Clinical features were those of a cicatricial pemphigoid, with prominent mucosal involvement leading to conjunctival and nasal scarring. Direct immunofluorescence findings were consistent with either cicatricial pemphigoid or linear IgA dermatosis, since both IgG and IgA linear deposits were found at the basal membrane zone. Immunoelectron microscopy of perilesional skin revealed IgA deposits within the lamina lucida and immunoblotting of the patient's serum disclosed IgA and IgG antibodies directed against epidermal antigens of 280, 165 and 120-130 kD.

Aged↗
PubMed1990

[What are the indications for digitalis glycosides in the current treatment of cardiac insufficiency?].

Digitalis was discovered over two centuries ago and has been in everyday use for 100 years: however nowadays it is not considered to be the almost exclusive treatment of heart failure as it used to be with diuretic therapy. In the last decade, our understanding of the physiopathology of heart failure and the body's mechanisms of adaptation have improved and this has lead to the use of new molecules and a different approach to the problem of left ventricular failure. The classical contra-indications and precautions of use of digitalis have been studied in detail. The use of digitalis is contested especially in patients in sinus rhythm or with ischemic heart disease and it is used less often in adult cardiac emergencies. The competition between digitalis and vasodilator therapy is now very apparent in some situations; however, the choice between these two groups of drugs (as treatment of first intention or in association) has to be carefully considered in each individual case. The future of digitalis therapy lies without doubt in pediatric cardiology where it remains irreplaceable.

Clinical Trials as Topic↗
PubMed1990

["Ambulatory" ischemic colitis. Clinical course and etiologic features in 88 cases].

From January 1983 to December 1988, 88 consecutive patients with ambulatory ischemic colitis without severe disease or surgical operation were observed. The diagnosis was established in all cases by endoscopy, and in 64 cases by histologic examination. The study included 55 women and 33 men with a mean age of 65.4 years (22-90). Symptoms included: abdominal pain (73 percent), diarrhea (60 percent) and bloody stools (85 percent). The sequence abdominal pain-diarrhea-bloody stools was noted in 41 percent of cases. Most cases of colitis were located in the sigmoid and left colon. The immediate course was uneventful in 81 patients. Six patients underwent surgery and of these, three died. The mortality rate was 4.5 percent (4 cases). Long-term outcome was known in 41 cases. None of the patients were symptomatic, but a moderate secondary stenosis was noted in 4 of 31 patients who underwent endoscopic or radiological follow-up examination. In 80 cases, one or more potentially etiological factors were observed including vascular obstruction (32 cases), low-flow states (27 cases), and drugs (78 cases). Twenty patients were taking non steroidal anti-inflammatory drugs (23 percent). Drug treatment was recent in 10 cases, and in four, it was the only possible etiological factor. This suggests the responsibility of anti-inflammatory drugs in the onset of certain cases of ischemic colitis.

Adult↗
PubMed1990

[Myocardial infarction in patients aged 70 years and over].

109 subjects aged 70 years (58 women, 51 men; average age 77 years) were hospitalized in the CICU (Cardiology Intensive Care Unit) over the period stretching from 1984 to 1986. The average length of stay in the CICU was 1 week, completed by an average stay of 5 days in the cardiology department. 100 per cent of the patients were followed up. Of the clinical parameters made evident by this study, the authors note that hypertension was the predominant risk factor (52.2 per cent); a history of coronary disease was noted in 60.5 per cent; 26.6 per cent of the patients were hospitalized before the 6th hour, chest pain being typical in 78 per cent versus painless in 11 per cent of patients; topographically, the infarction was anterior in 55 per cent, posterior in 40.4 per cent, and around the circumference in 4.6 per cent of cases; 80.8 per cent of the infarctions were transmural versus 19.2 per cent of infarctions without the Q wave--the latter accounted for a higher hospital mortality rate (38 per cent versus 27.3 per cent). The main complications were disturbances in rhythm (60.6 per cent) and LVI (56.9 per cent). Complications on the form of infections were noted in 15.6 per cent. Apart from the usual indicators of severity (cardiogenic shock, VF, LVI), infarction of the RV and AF had a serious effect on the prognosis. latrogenic disease accounted for 18.9 per cent. From the point of view of prognosis, hospital mortality was 30 per cent; mortality after one year was 44 per cent and 47.7 per cent after 2 years (in a group of 76 subjects).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Characterization of the plasmid genes blaT-4 and blaT-5 which encode the broad-spectrum beta-lactamases TEM-4 and TEM-5 in enterobacteriaceae.

We have determined the nucleotide sequence of the plasmid genes blaT-4 and blaT-5 which encode the broad-substrate-range beta-lactamases TEM-4 and TEM-5, respectively. The TEM-4 enzyme, which confers high-level resistance to cefotaxime (Ctx) and ceftazidime (Caz), differed from the TEM-1 penicillinase by four amino acid substitutions. Two of the mutations are identical to those responsible for the wide substrate range of the TEM-3 beta-lactamase which hydrolyses Ctx and Caz. The amino acid sequence of TEM-5, which confers higher levels of resistance to Caz than to other recently developed cephalosporins, differed from that of TEM-1 by three mutations distinct from those of TEM-4. Analysis of the location of the mutations in the primary and tertiary structures of class A beta-lactamases suggests that interactions between the substituted residues and beta-lactam antibiotics non-hydrolysable by TEM-1 and TEM-2 allow TEM-4 and TEM-5 to hydrolyse efficiently novel broad-spectrum cephalosporins such as Ctx and Caz.

Amino Acid Sequence↗
PubMed1989

Induction and growth properties of carrot roots with different complements of Agrobacterium rhizogenes T-DNA.

Single and multiple infections of carrot discs were carried out with Agrobacterium strains harbouring different segments of pRi1855 TL-DNA cloned in the binary vector Bin 19 and with a strain carrying the TR-DNA from the same Ri plasmid. Roots induced by the various co-inoculations were cultured and their growth patterns were followed. Abundant roots could be induced by TL-DNA rol genes A, B and C as a single insert (rolA + B + C) and by rolB alone provided an extended segment beyond its 5' non-coding region was included in the construction. A depression of rooting capability was caused by the inclusion of rolC together with rolB (rolB + C). In all cases co-inoculation with the Agrobacterium carrying TR-DNA-borne auxin genes was necessary for root induction since none of the rol constructions was in itself capable of eliciting any response; an exceeding majority of these roots were however shown to contain rol genes but no TR-DNA. Rooting was also elicited if rol constructions were co-inoculated with a strain carrying TL-DNA genes 13 and 14 (ORF13 + 14) instead of the TR-DNA strain. These roots were shown to contain both rol genes and ORF13 + 14. Striking differences in growth properties were shown by roots containing different complements of TL-DNA genes. Typical hairy root traits, high growth rate, branching and, most noticeably, absence of geotropism, were shown by roots containing rolB alone, while roots with rolA + B + C were geotropic as normal carrot roots. Hairy root traits were conferred to rolA + B + C roots by the concomitant presence of ORF13 + 14 and by the addition of auxin to the culture medium. A model is presented which attempts to rationalize the growth patterns by assigning interplaying roles to the various TL-DNA genes involved.

Blotting, Southern↗
PubMed1989

Characterization of angiotensin II binding sites in the human term placenta.

Specific angiotensin II (AII) binding sites were identified and characterized in membranes from human term placenta. The binding of iodinated [125I](Sar1)AII was time-dependent and saturable; it could be totally reversed on addition of unlabelled (Sar1)AII and GTP + NaCl. Scatchard plot analysis of dose-dependent [125I](Sar1)AII binding indicated the presence of a single class of binding sites with an equilibrium dissociation constant of 0.27 +/- 0.06 nM and a maximum binding capacity of 38.4 +/- 4.3 fmol/mg protein. The affinity of five AII analogues for the placental receptor was determined in competitive binding assays; the order of inhibitory potency was: (Sar1)AII greater than (Sar1, Ile8)AII approximately (Sar1, Ala8)AII approximately AII greater than angiotensin I greater than (Des-Phe8)AII. (Sar1)AII did not cause any significant change in the basal or stimulated adenylate cyclase activity. In order to investigate the subunit molecular structure of the placenta AII receptor, membranes were covalently labelled with the photoaffinity ligand [125I](Sar1, (4N3Phe)8)AII. Sodium dodecylsulfate-polyacrylamide gel electrophoresis followed by autoradiography showed that the labelling was specifically incorporated into a protein of Mr 92,000 in the presence or absence of dithiothreitol. It therefore appears that the AII receptor from human placenta has the same binding and pharmacological properties as other well-known AII receptors; by contrast, it is characterized by a significantly higher molecular weight, pointing out that structural differences in AII receptors may exist between species.

Adenylyl Cyclases↗