Search PubMed⌕ Search

Biomedical subjects

D Perrin

Publications and source records attributed to D Perrin.

At least 37 records · Page 2Linked to original sources
PubMed2000

Isosorbide mononitrate and propranolol compared with propranolol alone for the prevention of variceal rebleeding.

The aim of this study was to test the effectiveness of isosorbide-5-mononitrate (IM) as an adjunct to propranolol (PR) in the prevention of variceal rebleeding. Ninety-five cirrhotic patients with variceal bleeding were randomly assigned to treatment with PR + IM (46 patients) or PR alone (49 patients). Eighteen patients in the PR + IM group and 28 in the PR group had rebleeding during the 2 years after randomization. The actuarial probability of rebleeding 2 years after randomization was lower in the PR + IM group (40.4% vs. 57.4%) but the difference was not significant (P =. 09). However, the decrease in the risk of rebleeding reached statistical significance after stratification according to age, i.e. less than 50 versus >/=50 years old, (P =.03) or by adding an additional year of follow-up (P =.05). No significant difference was found in rebleeding index and survival. The multivariate Cox analysis indicated first, that both treatment (P =.03) and age (P =. 001) were factors predictive of rebleeding and second, that PR + MI reduced the risk of rebleeding by half (relative risk: 0.51, 95% confidence interval: 0.28-0.95). Seven patients in the PR + MI group and 1 patient in the PR group had to discontinue one of the drugs because of adverse events (P =.03). These results suggest that the addition of IM improves the efficacy of PR alone in the prevention of variceal rebleeding in cirrhotic patients. However no beneficial effects were observed on other parameters reflecting the efficacy of treatment.

Adrenergic beta-Antagonists↗
PubMed2000

Preclinical antitumour activity of F 11782, a novel dual catalytic inhibitor of topoisomerases.

F 11782 is a novel inhibitor of topoisomerases I and II, with an original mechanism of action (Perrin et al, 2000). This study, aimed to define its anticancer efficacy against a series of murine and human tumour models, has provided evidence of major antitumour activity for F 11782. This was demonstrated as a high level of activity against the P388 leukaemia, as reflected by increased survival of 143-457%, when administered i.p., p.o. or i.v. as single or multiple doses, and proved consistently superior to etoposide or camptothecin tested concurrently. Single or multiple i.p. doses of F 11782 also proved highly active against the s.c. grafted B16 melanoma, significantly increasing survival (P < 0.001) and inhibiting tumour growth (T/C of 0.3%), again superior to etoposide tested concurrently. Furthermore, F 11782 inhibited the number of pulmonary metastatic foci of the B16F10 melanoma by 99%. In human tumour xenograft studies, multiple i.p. doses of F 11782 resulted in major inhibitory activity against MX-1 (breast) tumours (T/C of 0.1%), as well as causing definite tumour regressions, whereas none resulted from similar experimental treatments with etoposide. Significant activity was also recorded with F 11782 against the relatively refractory LX-1 (lung) xenografts, with an optimal T/C value of 19%. It was notable that the antitumour activity of F 11782 was consistently demonstrated over a wide range of 2-6 dose levels, providing evidence of its good overall tolerance. In conclusion, these results emphasize the preclinical interest of this novel molecule and support its further preclinical development.

Animals↗
PubMed2000

Low-dose twice-daily fractionated X-irradiation of ovarian tumor cells in vitro generates drug-resistant cells overexpressing two multidrug resistance-associated proteins, P-glycoprotein and MRP1.

Failure of chemotherapy is frequently observed in patients previously treated with radiotherapy. To establish a cellular model for examining this resistance phenotype a series of mammalian tumor cell lines were exposed in vitro to fractionated X-irradiation and were then shown to express resistance to multiple antitumor drugs, including vincristine, etoposide and cisplatin. In these experiments the radiation was delivered as 10 fractions of 5 Gy (dose resulting in 1 log cell kill) given intermittently over several months. We now report that a comparable multidrug-resistance profile is expressed by human SK-OV-3 human ovarian tumor cells exposed in vitro to low dose (2 Gy) twice-daily fractions of X-rays given for 5 days on two consecutive weeks, essentially mimicking clinical practice, involving an overexpression of two MDR-associated proteins, P-glycoprotein and the multidrug resistance protein 1 (MRP1), with the latter being readily detectable by immunocytochemistry.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2000

Expression in yeast and purification of functional recombinant human poly(ADP-ribose)polymerase (PARP). Comparative pharmacological profile with that of the rat enzyme.

Human poly(ADP-ribose)polymerase (PARP) was expressed in the yeast line JEL1 under the control of a GAL promoter. Proteins were extracted and human recombinant PARP purified to apparent homogeneity. The pharmacological profile of this human enzyme was characterised in terms of the effects of known inhibitors of PARP belonging to various chemical families and this was compared with that of the rat enzyme purified from rat testes, using the same purification protocol. The rat and the human enzymes appeared very similar in terms of their sensitivities to those selected inhibitors.

1-Naphthylamine↗
PubMed1999

Differential in vitro interactions of a series of clinically useful topoisomerase-interacting compounds with the cleavage/religation activity of the human topoisomerase IIalpha and IIbeta isoforms.

The topoisomerase II (TOP2)-associated DNA cleavage activity and the DNA sequence preference of 20 antitumor drugs, including 15 TOP2-interacting compounds, have been defined. Four major classes of drugs have been identified: (i) those which enhanced the stabilization of cleavable complexes at a single major site (e.g. amsacrine, doxorubicin), or (ii) at many sites (e.g. etoposide, azatoxin), with chemically related compounds having very similar, although not identical, cleavage patterns (e.g. etoposide, GL331 and Top-53); (iii) those which inhibited DNA breakage (e.g. aclarubicin, actinomycin D); and (iv) those which did not visibly interfere with TOP2-mediated cleavable complexes (e.g. ICRF-187, camptothecin). All drugs tested induced similar overall patterns of sites of preferred DNA cleavage, in the presence either of the two known isoforms, TOP2alpha or TOP2beta, although relative intensities of signals at each position varied. It has been further shown that etoposide and its derivatives blocked the religation step downstream of the DNA cleavage step, whereas amsacrine, ellipticine, azatoxin and genistein acted upstream through enhancement of DNA cleavage. The information provided by this mechanistically based comparison can now be exploited in designing or synthesizing novel TOP2-interacting agents.

Antineoplastic Agents↗
PubMed1998

Differential sensitivities of recombinant human topoisomerase IIalpha and beta to various classes of topoisomerase II-interacting agents.

A series of topoisomerase-interacting antitumour agents were tested for their ability to differentially inhibit the catalytic activity of either topoisomerase (TOPO) IIalpha or beta, as judged by a DNA decatenation assay. The alpha form, relative to the beta isoform, proved 1 to 3 times more sensitive to nonintercalating complex-stabilizing TOPO II-interacting agents (etoposide and derivatives) and up to 18 times more sensitive to non-complex-stabilizing inhibitors of TOPO II ((+/-)-1,2-bis(3,5-dioxopiperazinyl-1-yl)propane [ICRF 159] and meso-2,3-bis(3,5-dioxopiperazine-1-yl)butane [ICRF 193]). However, the beta form of the enzyme appeared 1 to 3 times more sensitive to intercalating TOPO II-interacting agents (daunorubicin, aclarubicin and mitoxantrone). A possible implication of these data are that tumours preferentially expressing either the alpha or the beta isoform may be differentially responsive to various classes of TOPO II-interacting agents.

Antineoplastic Agents↗
PubMed1998

Vinflunine (20',20'-difluoro-3',4'-dihydrovinorelbine), a novel Vinca alkaloid, which participates in P-glycoprotein (Pgp)-mediated multidrug resistance in vivo and in vitro.

Vinflunine (VFL) is a novel derivative of vinorelbine (NVB, Navelbine), which has shown markedly superior antitumor activity to NVB, in various experimental animal models. To establish whether this new Vinca alkaloid participates in P-glycoprotein (Pgp)-mediated multidrug resistance (MDR), VFL-resistant murine P388 cells (P388/VFL) were established in vivo and used in conjunction with the well established MDR P388/ADR subline, to define the in vivo resistance profile for VFL. P388/VFL cells proved cross-resistant to drugs implicated in MDR (other Vinca alkaloids, doxorubicin, etoposide), but not to campothecin or cisplatin and showed an increased expression of Pgp, without any detectable alterations in topoisomerase II or in glutathione metabolism. The P388/ADR cells proved cross-resistant to VFL both in vivo and in vitro, and this VFL resistance was efficiently modulated by verapamil in vitro. Cellular transport experiments with tritiated-VFL revealed differential uptake by P388 sensitive and P388/ADR resistant cells, comparable with data obtained using tritiated-NVB. In various in vitro models of human MDR tumor cells, whilst full sensitivity was retained in cells expressing alternative non-Pgp-mediated MDR mechanisms, cross resistance was identified in Pgp-overexpressing cells. Differences were, however, noted in terms of the drug resistance profiles relative to the other Vinca, with tumor cell lines proving generally least cross-resistant to VFL. Overall, these results suggest that VFL, like other Vinca alkaloids, participates in Pgp-mediated MDR, with tumor cells selected for resistance to VFL overexpressing Pgp, yet MDR tumor cell lines proved generally less cross resistant to VFL relative to the other Vinca alkaloids.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Further genetic analysis of the C-terminal external loop region in Escherichia coli maltoporin.

LamB specifically facilitates the diffusion of maltose and maltodextrins through the bacterial outer membrane, and acts as a general (i.e. non-specific) porin for small hydrophilic molecules (< 600 daltons). We reported previously that deletion of the last predicted external domain near the C-terminus of the Eschirichia coli LamB protein (residues 376 to 405), affected in vivo the binding and transport of maltodextrins (specific pore functions), and also increased bacterial sensitivity to large antibiotics. The residues covered by this deletion correspond almost exactly to the major cell surface loop of LamB on the structural model based on X-ray crystallography (loop L9, residues 375 to 405). The L9 loop comprises a large central portion, which varies in size and sequence between the LamB proteins from different species. This variable region is flanked by two highly charged and conserved portions, which overlap with the adjacent beta strands. To identify subregions in L9 that influence the pore properties of LamB, we constructed and analysed nine mutants in loop L9 and its flanking sequences. Deletion of the 23-amino-acids central variable portion of the loop (residues 379 to 401), and deletion of the downstream conserved region (residues 402 to 409), only moderately affected specific maltoporin function. In contrast, deletion of the conserved region (residues 372 to 378) upstream of the variable portion strongly decreased specific maltoporin function and also increased sensitivity to large antibiotics, accounting for most, if not all, of the effects of the complete deletion of L9.

Amino Acid Sequence↗
PubMed1997

Effect of laser irradiation on latency of herpes simplex virus in a mouse model.

Low power Laser irradiation is used in medical practice for different indications. Several firms which commercialise Laser claim that Laser irradiation may be beneficial towards Herpes virus pathogenicity. We observe that, in the ear experimental model of HSV latency [3], repeated exposure to infrared Laser radiation of cervical ganglia following HSV inoculation appears to specifically hinder the establishment of virus latency in mouse.

Animals↗
PubMed1997

[Inhibitors of Ras farnesylation: tomorrow's anticancer agents?].

Increasing evidence implicates a critical role for aberrant Ras function in promoting the development of human tumours and has provided the impetus for identifying anti-Ras drugs for therapy. In order to be active the protooncogene ras must be associated with the plasma membrane. This feature depends crucially upon its farnesylation (addition of a 15 carbon moiety) by the enzyme farnesyl protein transferase. In the search for new anticancer strategies and agents, potent and selective inhibitors of this enzyme have been designed. The more recent of these compounds have produced impressive results in vivo against human tumours xenografted onto nude mice, without notable toxicity, making them promising candidates for clinical evaluation.

Alkyl and Aryl Transferases↗
PubMed1996

The role of protein kinase C in carbachol-induced and of cAMP-dependent protein kinase in isoproterenol-induced secretion in primary cultured guinea pig parotid acinar cells.

Stimulation of secretion by muscarinic agonists in guinea pig parotid or pancreatic acini is accompanied by a translocation of protein kinase C (PKC) from the cytosol to the particulate fraction [Machado-De Domenech and Söling (1987) Biochem. J. 242, 749-754] and by a PKC-mediated phosphorylation of the ribosomal protein S6 [Padel and Söling (1985) Eur. J. Biochem. 151, 1-10]. In order to decide whether PKC is directly involved in the secretory process, the effect of down regulation of PKC by phorbol 12-myristate 13-acetate (PMA) was studied in primary cultured guinea pig parotid acinar cells. These cells secrete in response to carbachol and isoproterenol. Only the carbachol response is associated with an increase in cytosolic calcium. Carbachol plus isoproterenol lead to an over-additive stimulation of secretion, an effect which depends completely on the presence of external calcium. Down regulation of PKC by about 90% did not significantly affect carbachol-induced exocytosis, whereas isoproterenol-stimulated secretion was almost doubled. The secretory response to permeable cAMP analogues was also enhanced in PKC-down-regulated acini, indicating a post-receptor effect. The increased response to isoproterenol was also observed in the absence of external calcium. The isoproterenol effect was significantly inhibited by the relatively specific cAMP-dependent protein kinase inhibitor H-89, which had only a minor effect on carbachol-induced exocytosis. Although down regulation of total PKC by up to 90% did not significantly affect the secretory response to carbachol, RO 31-8220, a relatively specific inhibitor of PKC, abolished carbachol-induced secretion in normal as well as in PMA-down-regulated cells. This indicates that a PKC isoform resistant to down regulation by PMA is involved in carbachol- but not in cAMP-mediated secretion.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1996

Peptide bond cleavage site determination of novel proteolytic enzymes found in ROS 17/2.8 cell lysates.

We have identified proteolytic activities in the rat osteoblastic osteosarcoma cell line ROS 17/2.8 which are capable of cleaving a peptide substrate for protein kinase C-mediated phosphorylation (PSPKC, Pro-Leu-Ser-Arg-Thr-Leu-Ser-Val-Ala-Ala-Lys). Using polyacrylamide gel electrophoresis conditions similar to those used to resolve small molecular weight proteins, the peptide bonds of PSPKC which are cleaved by the proteolytic activities present in ROS 17/2.8 cell lysates have been determined. These activities cleave the Ser-Arg, Thr-Leu, and Ser-Val peptide bonds. To date, no proteolytic activities present in osteoblast cell lysates have been described with the aforementioned peptide bond specificities, suggesting that these activities are novel. The PSPKC-cleaved peptide fragment pattern generated was similar for several different osteoblast cell lysates. Lysates generated from different rat tissues were also able to cleave PSPKC, but the peptide fragment pattern generated by ROS 17/2.8 cell lysates appeared to be unique amongst these tissues.

Amino Acid Sequence↗
PubMed1995

Enhanced cAMP production mediates the stimulatory action of pituitary adenylate cyclase activating polypeptide (PACAP) on in vitro catecholamine secretion from bovine adrenal chromaffin cells.

The 38 amino acid peptide pituitary adenylate cyclase activating polypeptide (PACAP) induced a dose dependent increase of catecholamine secretion in cultures of bovine chromaffin cells. This secretagogue activity of PACAP was strictly dependent on the presence of calcium in the culture medium. If calcium was omitted from the medium no effect of PACAP on catecholamine secretion could be detected during an incubation of 20 min. Preincubation of cells with 1 nM PACAP for 5 min facilitated the subsequent nicotine stimulated catecholamine secretion during a 20 min incubation without addition of the peptide. PACAP induced catecholamine secretion was clearly accompanied by a dose dependent increase of intracellular cAMP concentrations. The percentage of cells responding to PACAP with increased catecholamine secretion was assessed by immunocytochemistry of the transient appearance of dopamine-beta-hydroxylase, associated with the membranes of the chromaffin granules on the cell surface during the secretory process. About 70% of adrenal medullary cells responded to 100 nM PACAP with enhanced secretory activity. Though PACAP stimulated catecholamine secretion, we did not observed major effects on intracellular free calcium concentrations ([Ca2+]i) as determined with fura-2 by single cell fluorescence microscopy. In maximally 20% of the cells a rise in [Ca2+]i in response to a challenge with 500 nM PACAP was observed. Lower concentrations of PACAP were without an effect on [Ca2+]i. These data indicate that the stimulatory action of PACAP on in vitro catecholamine secretion from bovine chromaffin cells is linked to a rise of intracellular cAMP.

Adrenal Medulla↗
PubMed1994

Structural and functional diversity among bacterial interspersed mosaic elements (BIMEs).

Palindromic units (PU or REP) were defined as 40-nucleotide DNA sequences which are highly repeated in the genome of several members of the Enterobacteriaceae. They were shown to be a constituent of the bacterial interspersed mosaic element (BIME), in which they are associated with other repetitive sequences. We report here that Escherichia coli PU sequences contain three motifs (Y, Z1 and Z2), leading to the definition of two BIME families. The BIME-1 family, highly conserved over 145 nucleotides, contains two PUs (motifs Y and Z1). The BIME-2 family contains a variable number of PUs (motifs Y and Z2). We present evidence, using band shift experiments, that each PU motif binds DNA gyrase with a different affinity. This suggests that the two families are functionally distinct.

Bacterial Proteins↗
PubMed1993

The stimulatory effect of pituitary adenylate cyclase activating polypeptide (PACAP) on LH release from rat pituitary cells in vitro does not involve calcium mobilization.

The hypothalamic peptide "pituitary adenylate cyclase activating polypeptide (PACAP)" stimulates cAMP production in cultured rat pituitary cells and enhances LH release. It has been suggested that the stimulation of LH release by PACAP comprises two distinct mechanisms: a direct stimulatory action on LH secretion and a potentiation of the response of the gonadotrophes to LHRH. Thus the possibility exists that PACAP may enhance LH secretion not only by increased cAMP production but also by increasing cytosolic Ca2+ concentrations ([Ca2+]). In the present study we examined whether PACAP affects cytosolic [Ca2+] in identified rat gonadotrophes (as determined by the fura-method) and whether the suggested potentiating effect of PACAP on LHRH induced LH release is dependent on Ca2+. PACAP (1 nM) and 0.1 nM LHRH significantly increased LH concentrations in the culture medium after 5 hrs of incubation. Coincubation of cells with both peptides resulted in an additive increase of LH release. While the stimulatory effect LHRH was blunted in Ca(2+)-free medium, PACAP remained stimulatory to LH release. PACAP stimulated cAMP formation regardless whether the culture medium contained Ca2+ or not. Gonadotrophes were selected by their response to LHRH (1 microM) and were subsequently challenged with PACAP (1 microM). About 75% of gonadotrophes responded also to PACAP with an increase of cytosolic [Ca2+] which was blunted by removal of extracellular Ca2+. We suggest that in the rat pituitary the majority of the gonadotrophes are PACAP responsive as determined by an increase of cytosolic [Ca2+].(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Bacterial interspersed mosaic elements (BIMEs) are present in the genome of Klebsiella.

Bacterial interspersed mosaic elements (BIMEs) constitute a family of highly repetitive sequences containing palindromic units (PUs), also called repetitive extragenic palindromes (REPs). BIMEs were originally described in Escherichia coli and Salmonella typhimurium. We show here, by determining the nucleotide sequence of two intergenic regions of Klebsiella pneumoniae, by computer searches, and by hybridization, that sequences with similar characteristics are found in the genome of several Klebsiella species. This reinforces the idea that BIMEs play general and important roles in enterobacteria such as in the organization of the bacterial chromosome.

Base Sequence↗
PubMed1992

No evidence for calpain I involvement in fodrin rearrangements linked to regulated secretion.

Stimulation of secretion in chromaffin and parotid acinar cells is associated with dramatic rearrangements of the subplasmalemmal cytoskeleton, notably of fodrin and F-actin. It has been proposed that a proteolytic cleavage of fodrin resulting from an activation of the neutral calcium activated protease (calpain) could be responsible for these changes. Using an affinity-purified anti-alpha-fodrin antibody, several cleavage products of fodrin could clearly be detected following incubation of total cell homogenates from chromaffin and parotid acinar cells with purified calpain I. On the other hand, maximum stimulation of secretion of chromaffin cells by nicotine, and of parotid acinar cells by carbachol plus isoproterenol, was not associated with an increased appearance of cleavage products of fodrin. This result is not compatible with the 'proteolytic cleavage' hypothesis.

Adrenal Medulla↗