Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “persistence”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1977

Studies of L cells persistently infected with VSV: factors involved in the regulation of persistent infection.

Infection of interferon-treated L cells with VSV led frequently to the establishment of L cells persistently infected with VSV (LVSV cells). These cells were characterized by the following properties; (I) no supplement of antiviral factors such as anti-VSV antiserum, interferon, was required for their maintenance; (2) virus antigens were detected in about 5 to 30% of the cells by immunofluorescence staining; (3) the cells were not only resistant to superinfection by homologous virus, but also resistant to challenge by heterologous viruses such as Mengo virus; (4) the cells were destroyed by co-cultivation with heterologous cells susceptible to VSV infection; (5) the cells could be cured by serial cultivation in medium containing antiviral antibody, and the cured cells were as susceptible to VSV as normal L cells. It was shown that at least three factors (interferon, defective interfering [DI] particles and a selection of small-plaque temperature-sensitive [ts] mutants) took part in the maintenance of LVSV cells although it was difficult to evaluate exactly the relative importance of these factors. The effect of antiviral antibody, interferon and incubation temperature upon the maintenance of LVSV cells are discussed further.

Animals↗
PubMed1973

Persistent infection of cells in culture by measles virus. 3. Comparison of virus-specific RNA synthesized in primary persistent infection in HeLa cells.

The pattern of actinomycin D-resistant RNA synthesis was examined during primary infection of HeLa cells by virulent Edmonston measles virus and in two HeLa clones persistently infected by the same strain of virus. One of these clones, K11, produces infectious virus of low virulence for HeLa cells, and the other, K11A-HG-1, has thus far failed to yield infectious virus. The patterns of virus-specific RNA synthesized in these three types of infection are qualitatively similar to each other and to the patterns of virus-specific RNA synthesis in other paramyxovirus infections. There were, however, quantitative differences. In addition, virions of the virulent Edmonston strain of measles virus were found to contain high-molecular-weight RNA with a sedimentation constant identical to that of Newcastle disease virus.

Carbon Isotopes↗
PubMed1970

Cells persistently infected with Newcastle disease virus. II. Ribonucleic acid and protein synthesis in cells infected with mutants isolated from persistently infected L cells.

A comparison of the replication patterns in L cells and in chick embryo (CE) cell cultures was carried out with the Herts strain of Newcastle disease virus (NDV(o)) and with a mutant (NDV(pi)) isolated from persistently infected L cells. A significant amount of virus progeny, 11 plaque-forming units (PFU)/cell, was synthesized in L cells infected with NDV(o), but the infectivity remained cell-associated and disappeared without being detectable in the medium. In contrast, in L cells infected with NDV(pi), progeny virus (30 PFU/cell) was released efficiently upon maturation. It is suggested that the term "covert" rather than "abortive" be used to describe the infection of L cells with NDV(o). In both L and CE cells, the latent period of NDV(pi) was 2 to 4 hr longer than for NDV(o). The delay in synthesis of viral ribonucleic acid (RNA) in the case of NDV(pi) coincided with the delay in the inhibition of host RNA and protein synthesis. Although both NDV(o) and NDV(pi) produced more progeny and more severe cell damage in CE cells than in L cells, the shut-off of host functions was significantly less efficient in CE cells than in L cells. Paradoxically, no detectable interferon was produced in CE cells by either of the viruses, whereas in L cells most of the interferon appeared in the medium after more than 90% of host protein synthesis was inhibited. These results suggest that the absence of induction of interferon synthesis in CE cells infected with NDV is not related to the general shut-off of host cell synthetic mechanisms but rather to the failure of some more specific event to occur. In spite of the fact that NDV(pi) RNA synthesis commenced 2 to 4 hr later than that of NDV(o), interferon was first detected in the medium 8 hr after infection with both viruses. This finding suggests that there is no relation between viral RNA synthesis and the induction of interferon synthesis.

Animals↗
PubMed1971

Cells persistently infected with Newcastle disease virus. 3. Thermal stability of hemagglutinin and neuraminidase of a mutant isolated from persistently infected L cells.

Data were obtained which indicated the possible cause of the defective elution from erythrocytes of the mutant virus (NDV(pi)) isolated from L cells persistently infected with the Herts strain of Newcastle disease virus (NDV(o)). The chicken erythrocyte receptors for the mutant and wild-type viruses were equally sensitive to the action of Vibrio cholera filtrate neuraminidase; this suggests that the failure of NDV(pi) to elute from chicken erythrocytes is not due to a specific neuraminidase-resistant receptor for this virus on the erythrocyte membrane. There was no difference in the enzyme content of the intact virions of NDV(o) and NDV(pi) when tested with a soluble substrate, indicating that the inefficient elution of NDV(pi) was not due to a reduced enzyme content. The neuraminidase activity of intact NDV(pi) virions was significantly more stable at 55 C than the enzyme of NDV(o) virions, whereas the dissociated enzymes of the two viruses were inactivated at the same rate. On the basis of these findings, it seems likely there is a structural difference between the two viruses. The neuraminidase protein of the mutant NDV(pi) may be incorporated into the viral envelope in such a manner that it is prevented from reacting with the substrate in the erythrocyte membrane, although it can react with a soluble substrate. The hemagglutinin activity of both intact and disrupted NDV(pi) was significantly more resistant to thermal inactivation than that of the wild-type NDV(o). This finding suggests a genetic difference in the hemagglutinin protein of the two viruses.

Animals↗
PubMed1998

Persistent iron and folate deficiency in a patient with deletional hereditary persistence of fetal hemoglobin; the effect on the relative levels of Hb F and G gamma chains and the corresponding mRNAs.

We describe a Black female who has suffered for many years from an (often) severe anemia (Hb 5-9 g/dl) with iron deficiency (serum Fe 8 microg/dl; TIBC 462 microg/dl; ferritin 7 ng/ml or less) and folate deficiency. The patient had hypermenorrhea which was appropriately treated resulting in an increase in hemoglobin level but not affecting the Fe deficiency. Splenomegaly was present, perhaps resulting from a clay-eating habit, although this was consistently denied. The patient had an alpha-thalassemia-2 (-3.7 kb) trait and a deletional hereditary persistence of fetal hemoglobin (HPFH) (type II) which were inherited from her father. Over the last six years the level of Hb F varied between 8.5 and 16% (25-29% in the father), while the G gamma value was also low (15-22% versus 32-34% in the father). Comparable reductions were seen in the relative levels of gamma-mRNA and G gamma-mRNA. These data support results published by Adams et al who showed a severe reduction in Hb F level in another HPFH heterozygote with Fe deficiency; these investigations suggested that a reduction in alpha-globin synthesis resulted in preferential formation of alpha beta dimers rather than alpha gamma dimers. Our data suggest that the decrease of Hb F and G gamma levels is due to a reduction in gamma-mRNA formation, mainly of the G gamma type, rather than through a posttranslational mechanism alone.

Adult↗
PubMed1989

Ultrastructural analysis of germinal centers in lymph nodes of patients with HIV-1-induced persistent generalized lymphadenopathy: evidence for persistence of infection.

Germinal centers play an important role in the pathogenesis of HIV-1-induced lymphadenopathy. Cell-free retrovirus particles, gag proteins of HIV-1, and cells expressing viral RNA can be detected in these areas of the lymph node. In the present study, the ultrastructural changes and the interactions of virus with different cell types of the germinal centers were investigated. We compared the alterations of lymph nodes obtained shortly after seroconversion with those seen in longstanding lymphadenopathy. The results demonstrated that germinal centers were already infected in the early phase of the disease. However, the number of cell free virions was low. During the course of the disease, large amounts of cell free virions accumulated in the germinal centers. The persistence of germinal center infection for up to 2 years was demonstrated by detecting retrovirus particles in repeated biopsy specimens. In addition, the presence of numerous small, moderately electron dense structures that might represent defective particles of HIV-1 and influence the course of the disease were described. HIV-1 was found to replicate in lymphocytes, macrophages, and follicular dendritic cells. Quite possibly, a genomic shift may occur at the time of transmission of the virus to a novel target cell, thus, germinal centers may be one of the anatomic sites where HIV-1 acquires the ability to develop into a variant with preferential tropism for a given cell type.

AIDS-Related Complex↗
PubMed1981

Persistence of tic-borne encephalitis virus in monkeys. III. Phenotypes of the persisting virus.

The properties of tick-borne encephalitis (TBE) virus persisting for 90-383 days after intracerebral and subcutaneous inoculation of Macaca rhesus monkeys were studied, namely (1) the type of infection produced directly in the tissues of the experimental monkeys; (2) the activating effect of co-cultivation and explantation procedures; and (3) the phenotype of the isolates by a set of markers. The virus was detected and analysed in 52 instances. Directly in monkey tissues the virus induced a productive infection rarely (5.8%) but more frequently (71.2%) an abortive infection detectable by immunofluorescence (presence of virus-specific antigen). In 23% of instances a nonproductive infection was observed in monkey tissues. Like abortive infection it could be activated by the co-cultivation of cells and explantation procedures. The latter exerted a more marked activating effect than co-cultivation. The strains isolated from monkey tissues in productive infection or activated by explanation or co-cultivation were heterogeneous in their properties. The following virus phenotypes were found: virus highly virulent for mice, cytocidal and antigenically complete; a cytocidal virus of low virulence, possessing haemagglutinin; and a cytocidal virus apathogenic for mice, devoid of haemagglutinin but synthesizing complement-fixing antigen and an antigen detectable by immunofluorescence.

Animals↗
PubMed1995

[Persistent carotid-superior cerebellar artery anastomosis presenting with cerebellar ischemic attack: a case of persistent trigeminal artery variant].

A rare case of persistent primitive trigeminal artery variant (PTAV) with cerebellar ischemia is reported. A 23-year-old male complained of sudden dizziness and nausea after playing valley ball. CT scan and MRI on admission revealed no abnormal findings. Left carotid angiography demonstrated a PTAV anastomoting precavernous portion of left internal carotid artery to the left superior cerebellar artery. The 37 cases reported in literature were reviewed to characterise PTAV. Ninety-seven% of the cases arising from precavernous portion of internal carotid artery, and terminated in anterior inferior cerebellar artery in 73%, posterior inferior cerebellar artery in 13.5% and superior cerebellar artery in 13.5%. Approximately 22.2% of patients with PTAV have cerebral aneurysms. The hypotension or mechanical compression of PTAV on playing valley ball with poor vascular supply to the part of cerebellum possibly caused cerebellar ischemia in this case.

Adult↗
PubMed1983

Persistent increase in striatal dopamine stimulated adenylate cyclase activity persists for more than 6 months but disappears after 1 year following withdrawal from 18 months cis-flupenthixol intake.

Administration of cis-flupenthixol to rats for 18 months enhanced apomorphine-induced stereotyped behaviour, increased the number of specific [3H]spiperone binding sites in striatum and potentiated striatal dopamine stimulated cyclic AMP formation, but did not alter specific [3H]piflutixol binding. Following withdrawal of cis-flupenthixol intake, apomorphine-induced stereotypy returned to control values after 1 month and Bmax for [3H]spiperone binding returned to normal after 3 months. In contrast, the increased dopamine stimulated adenylate cyclase activity remained elevated 6 months after drug removal, but was normal 1 year after drug withdrawal.

Adenylyl Cyclases↗