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Biomedical subjects

M Lippa

Publications and source records attributed to M Lippa.

12 recordsLinked to original sources
PubMed1999

Selection of RNA replicons capable of persistent noncytopathic replication in mammalian cells.

The natural life cycle of alphaviruses, a group of plus-strand RNA viruses, involves transmission to vertebrate hosts via mosquitoes. Chronic infections are established in mosquitoes (and usually in mosquito cell cultures), but infection of susceptible vertebrate cells typically results in rapid shutoff of host mRNA translation and cell death. Using engineered Sindbis virus RNA replicons expressing puromycin acetyltransferase as a dominant selectable marker, we identified mutations allowing persistent, noncytopathic replication in BHK-21 cells. Two of these adaptive mutations involved single-amino-acid substitutions in the C-terminal portion of nsP2, the viral helicase-protease. At one of these loci, nsP2 position 726, numerous substitution mutations were created and characterized in the context of RNA replicons and infectious virus. Our results suggest a direct correlation between the level of viral RNA replication and cytopathogenicity. This work also provides a series of alphavirus replicons for noncytopathic gene expression studies (E. V. Agapov, I. Frolov, B. D. Lindenbach, B. M. Prágai, S. Schlesinger, and C. M. Rice, Proc. Natl. Acad. Sci. USA 95:12989-12994, 1998) and a general strategy for selecting RNA viral mutants adapted to different cellular environments.

Adaptation, Biological↗
PubMed1997

Safety-modified episomal vectors for human gene therapy.

The effectiveness of ongoing gene therapy trials may be limited by the expression characteristics of viral and plasmid-based vectors. To enhance levels of heterologous gene expression, we have developed a safety-modified episomal expression vector that replicates extrachromosomally in human cells. This vector system employs a simian virus 40 (SV40) large T antigen mutant (107/402-T) that is deficient in binding to human tumor suppressor gene products, including p53, retinoblastoma, and p107, yet retains replication competence. These SV40-based episomes replicate to thousands of copies by 2-4 days after gene transfer in multiple types of human cell lines, with lower activity in hamster cells, and no detectable activity in dog, rat, and murine cell lines. Importantly, 107/402-T has enhanced replication activity compared with wild-type T antigen; this finding may be due, in part, to the inability of p53 and retinoblastoma to inactivate 107/402-T function. We demonstrate that the level and duration of 107/402-T expression regulates the observed episomal copy number per cell. Compared with standard plasmid constructs, episomes encoding 107/402-T yield approximately 10- to 100-fold enhanced levels of gene expression in unselected populations of transient transfectants. To determine if 107/402-T-based episomes replicate extrachromosomally in vivo, tumor explants in nude mice were directly injected with liposome/DNA complexes. Using a PCR-based assay, we demonstrate that SV40-based episomes replicate in human cells after direct in vivo gene transfer. These data suggest that safety-modified SV40-based episomes will be effective for cancer gene therapy because high level expression of therapeutic genes in transient transfectants should yield enhanced tumor elimination.

Animals↗
PubMed1997

[Conservative treatment using mesalazine in ischemic colitis].

The authors propose the conservative treatment of ischemic colitis using slow-release mesalazine and enema. The excellent tolerability of the treatment and the good level of therapeutic efficacy was confirmed in 13 cases treated without signs of recurrence of disease.

English Abstract↗
PubMed1997

[Prosthetic repair of inguinal and crural hernias].

335 inguino-femoral hernias were repaired with polypropylene mesh from December 1991 through December 1995. Eleven patients underwent mesh reinforced Bassini, 167 modified Lichtenstein's technique and 108 Trabucco's repair. Forty-three patients were treated under regional anesthesia. Bilateral hernia was diagnosed in 33 patients and in 20 out of 33 the surgical procedure was entirely performed under regional anesthesia. Early complications referred were 32 scrotal hematomas which spontaneously healed. Two patients showed a recidive hernia and were retreated with and additional mesh; plug rejection (early experience) was referred in one patient who was reoperated on employing a mesh. The indications for the more suitable technique were directly deducted from Nyhus' hernia classification. The authors finally point out the: 1) importance of regional inguinal anesthesia; 2) correct cutting and application of the mesh in the inguinal canal; 3) internal inguinal ring repair; 4) bilateral hernia repair under regional anesthesia.

Adolescent↗
PubMed1995

[Hemorrhage of the upper digestive tract in the elderly patient: is the limit of 60 years of age still biologically valid? Statistical study].

The authors examine 192 consecutive cases of upper gastrointestinal hemorrhage; the series included 133 males and 59 females with a mean age of 55.78 years (SD +/- 17.88) and range of 18-97. All patients underwent emergency esophagogastroduodenoscopy within 6-12 hours of hospitalisation. Adequate infusion and; when necessary, transfusion therapy associated with protection using anti H2 (ranitidine 200 mg/24 h) and octreotide (0.2 mg x 3/day sc), proportionately scaled over the following 72 hours, were used in all patients. Nasogastric aspiration (nasogastric probe or Sengstaken-Blakemore probe) were used for at most 48 h after endoscopy. Patients were then subdivided into 2 age groups: under (104 cases) and over (88 cases) 60 years. Statistical relations were studied (Chi-square test), assuming the reference value to be p = 5%, between age and diagnosis, sex, symptoms on presentation, hemotransfusion, Forrest's classification, the onset of renewed bleeding and lastly the evolution of each case. Hemorrhage was more frequent in males aged < 60 years and in females aged > 60 (p < 0.004), hemorrhagic shock, the presence of Forrest 1a and 1b and death were significant in elderly subjects (p < 0.004; p < 0.01; p < 0.01). The latter finding included patients with esophageal varices, group which was significantly correlated with mortality independent of age. The overlap of statistical results in hemorrhage not related to varices suggests, on the one hand, that appropriate early treatment has a greater influence on the prognosis rather than the type of pathology, and on the other that being aged over 60 does not correspond to an increased biological risk.

Adolescent↗
PubMed1994

[Ogilvie's syndrome: does it have to be redefined? An analysis of 8 cases and contribution to the discussion].

The authors examine eight cases of acute pseudo-obstruction of the colon and point out that these may be inserted in the wider context of intestinal pseudo-obstructions. These comments raise questions concerning Ogilvie's syndrome since the dilatations observed do not only affect the colon, according to the classic definition, but also the ileo-jejunal tract, in spite of the fact that the main target continues to be the colon. The term Ogilvie's syndrome is still significant in the clinical identification of colic dilatation, in particular the right colon in which possible complications are more severe. The authors identify colonoscopy as the best instrumental test owing to the possibilities its offers, including therapeutic, and also underline that there does not appear to be a real risk of iatrogenic lesions if an appropriate technique is used.

Aged↗
PubMed1994

p53 mutations in bladder carcinoma cell lines.

Point mutations and deletions in the p53 tumor suppressor gene occur frequently in advanced stage bladder tumors. To extend these observations to an in vitro model of bladder tumorigenicity, we have evaluated the presence of p53 mutations in a panel of bladder carcinoma cell lines. p53 alleles were cloned using the reverse transcriptase-polymerase chain reaction method, and exons 2-11 were sequenced. Of 11 cell lines examined, 5 cell lines had missense point mutations, and each overexpressed p53 protein on western blot analysis. Except for the HT-1197 cell line, these point mutations occurred in evolutionarily conserved domains, which are characteristic hot spots for mutations. HT-1197 encodes an unusual C-terminal point mutation in codon 365, within the basic motif tetramerization domain, suggesting a linkage between induction of a mutant p53 conformation and alterations in protein oligomerization. Six of 11 cell lines had wild-type levels of p53 expression, with 4 producing p53 proteins having either internal deletions or truncations, and 2 producing wild-type p53. Presence of wild-type p53 was found only in cell lines derived from either a low-grade, papillary tumor (RT4) or fetal bladder (FHs 738Bl). The T24 cell line was found to contain a novel p53 mutant having an in-frame deletion of tyrosine 126. This p53 mutant does not bind SV40 large T antigen, yet is expressed at low levels, comparable to cell lines containing wild-type p53 alleles. Our findings characterize p53 mutations in a panel of bladder carcinoma cell lines, and provide a model for testing the role of wild-type or mutant p53 cDNA to suppress or induce tumorigenic properties.

Animals↗
PubMed1992

[Acute intestinal ischemia. Our experience].

Acute intestinal ischemia is a pathology which is relatively often encountered in elderly patients where the concomitance of other diseases make its prognosis more severe, especially since diagnosis is usually late. Laboratory tests and imaging techniques are not of great value to diagnosis since they do not provide pathognomonic data, but together with a careful anamnesis they contribute a series of findings which, taken as a whole, lead to the diagnosis of intestinal ischemia. The sole therapy is surgery--when still possible and the best results are obtained when surgery is performed at an early stage. The authors report a series of 12 cases of acute intestinal ischemia and underline the difficulty of diagnosing this subtle pathology and the advantages of aggressive surgical techniques.

Abdomen↗