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At least 37 records · Page 2Linked to original sources
PubMed1983

Studies on the methylation of avian sarcoma proviruses in permissive and non-permissive cells.

The extent of methylation of several avian oncogenic proviruses was determined by using the restriction endonucleases HpaII and MspI. The results indicated that the transformation-defective proviruses (RAV-O or B77-td), which are exogenously introduced into avian host cells, were not methylated. However, endogenous proviruses (RAV-O) or ASV proviruses present in non-permissive host cells were found to be partly or completely methylated. The methyl-sensitive restriction endonuclease PvuI, which recognizes a unique site within the long terminal repeat in the ASV genome, failed to cleave proviruses present in several non-permissive host cells. From these results we suggest that modification of the sequence around the PvuI site results in reduced levels of transcription.

Animals↗
PubMed1985

Susceptibility to herpes simplex virus type 1 infection of non-permissive rat XC(HPRT-) x permissive mouse L(TK-) hybrid cells.

Somatic cell hybrids between rat XC(HPRT-) cells, non-permissive for herpes simplex virus type 1 (HSV-1) infection, and permissive mouse L(TK-) cells were constructed and karyotyped. Infection of these hybrid cells by HSV-1 strains F and MP revealed that they were susceptible to the virus. The amounts of virus produced by the hybrid cells, as well as the cytopathic effect observed, was very similar to that of the parental L(TK-) cells. Our results suggest that failure of HSV-1 to replicate in XC cells is more likely to be due to the absence of cellular elements required for efficient virus multiplication rather than to the presence of blocking or inhibiting factors.

Animals↗
PubMed1978

Scanning electron microscope observations on tegument maturation in Schistosoma mansoni grown in permissive and non-permissive hosts.

Observations were made on details of tegument development of schistosomes grown in mouse, hamster, and rat hosts. In permissive hosts (mouse and hamster) the surface of the worm alters rapidly during early maturity and is characterized by fusing of a highly undulate surface network into smooth folds and spine-covered tubercles. In non-permissive hosts maturation of the tegument is both delayed and incomplete, and the tubercles are aspinous. Scanning views of the oral cavity and the gynegophoral canal, both sites of transitional tegumental organization, are also shown. The gynecophoral canal tegument seems to be a site of active lipid secretion.

Animals↗
PubMedDate not supplied

Intracorporeal CO2 removal and permissive hypercapnia to reduce airway pressure in acute respiratory failure. The theoretical basis for permissive hypercapnia with IVOX.

Initial studies have shown that the intravascular oxygenator and carbon dioxide removal device (IVOX, Cardiopulmonics, Inc., Salt Lake City, UT) removes approximately 30% of VCO2. After noting increased CO2 removal with increased venous CO2, we developed a conceptual analytical model based on data obtained from patients and laboratory experiments. Increasing the CO2 gradient across the hollow fiber membranes of IVOX increases the operating efficiency of the device. Using the patient management technique of permissive hypercapnia (limiting tidal volumes, respiratory rates, and airway pressures) serves to increase the CO2 gradient across the membrane. The conceptual analytical model predicts that a PaCO2 of 75-80 mm Hg is required to obtain a CO2 gradient that results in IVOX CO2 removal of approximately 90-100 ml CO2/min. This technique may allow a broader application of both permissive hypercapnia and IVOX in acute respiratory failure.

Acute Disease↗
PubMedDate not supplied

Sprouting of adult Purkinje cell axons in lesioned mouse cerebellum: "non-permissive" versus "permissive" environment.

Adult rat Purkinje cells are extremely resistant to axotomy and, although they lack spontaneous regeneration, are able to sprout. Axon sprouting is a late process that occurs mainly 6 to 18 months after the lesion and results from an interplay between Purkinje cell intrinsic properties and chemical remodeling of the glial scar. To better appraise the role of the local environment in the late sprouting, we performed new axotomy experiments in mice. In this species, unlike the rat, there is no cavitation because the post-lesional necrotic tissue is invaded by astrocytes and incorporated into the glial scar. In this scarring tissue, chondroitin sulfate proteoglycans (CS-PGs) and PSA-NCAM are present one week after the lesion, but the time courses of their expression differ: the former are transiently expressed and rapidly disappears (by one month), thus preventing early sprouting and providing a negative spatiotemporal correlation with the late sprouting. PSA-NCAM expression, which is maintained up till 12 months, is by itself not sufficient to attract the sprouts, since the core of the glial scar--which exhibits high level of PSA-NCAM--is always devoid of them. Finally, by using a double experimental approach (lesion and graft) aimed at providing a permissive environment to the terminal bulbs of axotomized Purkinje cells, we show that the presence of grafted cerebellum at the lesion site neither changes the time course of the sprouting nor enhances the Purkinje cell axonal regeneration. Nevertheless, these experiments have revealed a new type of altered Purkinje cells, the "irritated" Purkinje cells with a high potentiality for axon sprouting.

Animals↗
PubMed1979

High molecular weight virus DNA in KB cells infected with ts mutants of adenovirus type 2 under permissive and non-permissive conditions.

Temperature-sensitive (ts) mutants of adenovirus type 2 (Ad2), which are deficient in virus DNA synthesis at the non-permissive temperature, have been used to investigate whether virus DNA replication is required for the occurrence of high mol. wt. Ad2 DNA (greater than 100S, 50 to 90S) in human cells productively infected with Ad2. The high mol. wt. virus DNA has been previously shown to consist of virus and cellular DNA molecules covalently linked. The present data indicate that after infection with DNA-ts mutants, the production of high mol.wt. virus DNA is much less sensitive to restrictive conditions than the synthesis of unit length (34S) Ad2 DNA. This finding lends further support to the idea that the occurrence of high mol. wt. virus DNA is independent of the synthesis of unit length virus DNA.

Adenoviruses, Human↗
PubMed1994

Short and long term dissemination of deletion mutants of adenovirus in permissive (cotton rat) and non-permissive (mouse) species.

As a first step in the evaluation of the safety of replication-defective adenoviruses used as gene transfer vectors, the dissemination of wild-type (wt) adenovirus (Ad) type 5, Ad-d1327 (deleted for the E3 gene) and Ad-gp50 (deleted for E3 and E1A and therefore replication defective) was studied in mice and cotton rats. Of each virus, 10(8) p.f.u. was inoculated, either by the intranasal or the intramuscular route, and virus isolation was undertaken after sacrifice of the animals 3 or 31 days after inoculation. E3 deletion had no significant effect on viral spread, whereas E1A deletion reduced it significantly. After intramuscular inoculation of the E3-/E1A- virus, it could be isolated only from the local lymph node. Intranasal inoculation led to a wider distribution including lungs, liver, kidneys and lymph nodes. The pattern of dissemination of the E3-/E1A- virus was the same in mice and cotton rats, providing indirect evidence of the lack of replication of this virus in this species permissive for the wt virus. However, in the case of infection with a wt strain in E3-/E1A- adenovirus-inoculated recipients, both viruses were found in lymph nodes. In this situation the risk of phenotypic complementation of the E1A gene remains to be studied further.

Adenoviridae↗
PubMed1995

Isogenic adenoviruses type 5 expressing or not expressing the E1A gene: efficiency as virus vectors in the vaccination of permissive and non-permissive species.

We have previously constructed a recombinant adenovirus type 5 (Ad5) vector expressing the gD gene of pseudorabies virus (Ad-gD). In this virus the E1A gene was deleted, so that Ad-gD was replication defective. When high doses of this virus were inoculated into target species, it was nevertheless able to elicit a strong and protective immune response. We have restored a functional E1A gene in Ad-gD, by rescuing the E1A transcription unit in an ectopic position, far from the enhancer sequences of E1A. Unlike Ad-gD, this new virus (Ad-gD-E1A) was able to replicate in non-transcomplementing Vero cells. The kinetics of replication of Ad-gD-E1A were similar to that of the wild-type Ad5 when cells were infected at medium or high m.o.i. Nevertheless, the level of virus replication was low when Ad-gD-E1A was plated at low m.o.i. Cotton rats and mice were vaccinated once with 10(9) to 10(5) TCID50 of each of the two viruses. In both species, Ad-gD and Ad-gD-E1A induced similar antibody responses for each dose tested. Both were able to give a high level of protection against the challenge. However, the protective dose of Ad-gD-E1A was at least 250-fold lower in cotton rats, an Ad5-permissive species, than that of Ad-gD. In mice, a species restricted for Ad5 replication, the protective dose of Ad-gD-E1A was still not significantly different from that of Ad-gD. These data indicate that the protective dose of such an adenovirus vector vaccine for an animal species is strictly linked to the capacity of the virus to replicate in this species, at least in the model used. So, in designing an adequate vector one needs to balance the use of low dose vaccines against risks in terms of biosafety. Nevertheless, for diseases in which the protective immune response is mainly based on the antibody response, defective and non-defective adenovirus vectors should demonstrate similar protective doses.

Adenoviridae Infections↗
PubMed1998

Replication of Spodoptera exigua nucleopolyhedrovirus in permissive and non-permissive lepidopteran cell lines.

The Spodoptera exigua multinucleocapsid nucleopolyhedrovirus (SeMNPV) was inoculated to eight lepidopteran cell lines derived from Spodoptera exigua (Se301), Spodoptera frugiperda (SF21AEII), Spodoptera littoralis (CLS-79), Spodoptera litura (SpLi-221), Pseudaletia separata (LeSe-11), Trichoplusia ni (hi-5), Plutella xylostella (PXL/C) and Bombyx mori (BmN4). The productive infection of SeMNPV was observed only in Se301 cells. However, a dot-blot hybridization analysis revealed that SeMNPV DNA replicated in five non-permissive cell lines: SF21AEII, CLS-79, SpLi-221, hi-5 and BmN4. In addition, the virus-infected hi-5 and BmN4 cells displayed morphological changes. In contrast, CLS-79 cells inoculated with SeMNPV showed membrane blebbing at 20 hrs post inoculation (p.i.) and fragmentation of genomic DNA. All that indicated that the infected CLS-79 cells underwent apoptosis. These findings indicate that the SeMNPV replication was restricted at various points in dependence upon each cell line.

Animals↗
PubMed1986

Surface antigens of Angiostrongylus cantonensis developing in permissive and non-permissive hosts.

The immunofluorescent antibody test and immunocytochemical method were employed to study the surface antigens of Angiostrongylus cantonensis obtained from infected rats, mice and guinea pigs. Positive results with intense fluorescence and brownish peroxidase staining were observed on the cuticular surface of A. cantonensis recovered from rats 22 days (late cerebral phase) and 34 days (lung phase) post-infection when tested with antisera against host (normal rat serum) antigens as well as crude extracts of A. cantonensis. However, host antigens were not observed on the surface of the nematode recovered from the brain of mice and guinea pigs 15 days post-infection.

Angiostrongylus↗
PubMed1999

Parapoxviruses: potential alternative vectors for directing the immune response in permissive and non-permissive hosts.

Parapoxvirus (PPV) represents a genus of the poxviridae, and particularly PPV ovis (Orf virus, OV) seems to offer several potential advantages for the use of vector vaccine. Therefore, we started to investigate the genome of the highly attenuated OV strain D1701, which was only poorly characterised until now. Due to recombination of non-homologous sequences, part of the right hand end of the D1701 genome was duplicated and translocated to the opposite end of the genome. As a consequence gene deletion had occurred and the inverted terminal repeat region is increased. Results are described to identify viral genes, which are non-essential for virus replication and potentially influence viral pathogenesis, virulence, and host immunity. In more detail, we analysed the expression and functional activity of the OV-specific vascular endothelial growth factor (VEGF) gene homologue. Finally the construction and production of a D1701 mutant lacking the VEGF gene homologue is reported.

Animals↗