PubMed Health⌕ Search

Biomedical subjects

S St Jeor

Publications and source records attributed to S St Jeor.

At least 19 recordsLinked to original sources
PubMed2005

Characterization of an antisense transcript spanning the UL81-82 locus of human cytomegalovirus.

In this study we present the characterization of a novel transcript, UL81-82ast, UL81-82 antisense transcript, and its protein product. The transcript was initially found in a cDNA library of monocytes from a seropositive donor. mRNA was obtained from monocytes isolated from a healthy donor with a high antibody titer against human cytomegalovirus (HCMV). The mRNAs were cloned into a lambda phage-derived vector to create the cDNA library. Using PCR, UL81-82ast was amplified from the library. The library was tested for the presence of numerous HCMV genes. Neither structural genes nor immediate-early genes were found. UL81-82ast was detected in five bone marrow samples from healthy antibody-positive donors. This same transcript was also found in in vitro-infected human fibroblasts early after infection but disappears at the same time that UL82 transcription begins. Not only was the transcript amplified using reverse transcription-PCR and sequenced but its protein product (UL82as protein) was detected by both Western blot and immunofluorescence. Phylogenetic studies using UL82as protein were conducted, showing a high degree of conservation in clinical isolates, laboratory strains of HCMV, and even in chimpanzee CMV. The transcript could be involved in the posttranscriptional regulation of the UL82 gene, affecting its mRNA stability or translation. Since the UL82 product, pp71, functions as an immediate-early transactivator, its posttranscriptional control could have some effect over latency reactivation and lytic replication.

Amino Acid Sequence↗
PubMed2003

Complete coding sequences of dengue-1 viruses from Paraguay and Argentina.

We have determined the complete coding sequences of six dengue-1 (DEN-1) viruses isolated from Paraguay and Argentina in 2000 from patients with dengue fever. Sequences of strains 259par00, 280par00, 295arg00, 297arg00 and 301arg00 can encode a polyprotein of 3392 amino acids. Strain 293arg00 circulated as a "wild type+deletion mutant" quasispecies, with a subpopulation characterized by a 3-nucleotide deletion in the NS4A region. This variant, which would encode a three amino acid change in the NS4A protein, was found as a minority population in one additional partially-sequenced isolate from the same outbreak. These six South American strains group into two different clades of the "American-African" DEN-1 genotype-one clade is most closely related to strains isolated from Brazil in 1997, the other to a Peruvian strain isolated in 1991 for which only partial sequence information is available. DEN-1 viruses isolated worldwide comprise at least four different genotypes according to previously defined classification criteria.

Amino Acid Sequence↗
PubMed2002

Phylogenetic relationships of dengue-1 viruses from Argentina and Paraguay.

We sequenced the Capsid-pre Membrane (C/prM) and the Envelope-Nonstructural protein 1 (E/NS1) regions of 24 recent isolates of dengue-1 (DEN-1) from South America. This included 12 Argentinean and 11 Paraguayan DEN-1 strains isolated in 2000 plus a Paraguayan strain isolated in 1988. These sequences were compared with published sequences of DEN-1 isolated worldwide to determine the origin of these isolates. Pairwise comparisons of strains from Paraguay and Argentina revealed a nucleotide divergence of 0-5% in the E/NS1 region and 0-3% in the C/prM region. Our results showed that these viruses belong to the same genotype, but can be separated into two clades. Interestingly, both clades circulated simultaneously in the same geographic area during the 2000 outbreaks. Amino acid differences were found between both clades in the C/prM region at position 100 (Lys vs. Arg) and in the E/NS1 region at positions 722 (Ala vs. Thr). Although the geographic movement of DEN-1 virus can not be unequivocally traced from the genetic relationship determined here, our results suggest that the recent epidemics in Argentina and Paraguay were due to the re-emergence of a previously circulating strain, or to the virus circulating unnoticed, rather than to the introduction of a new genotype.

Amino Acid Sequence↗
PubMed2000

In vitro infection of megakaryocytes and their precursors by human cytomegalovirus.

Apart from congenital human cytomegalovirus (HCMV) infection, manifest HCMV disease occurs primarily in immunocompromised patients. In allogeneic bone marrow transplantation, HCMV is frequently associated with graft failure and cytopenias involving all hematopoietic lineages, but thrombocytopenia is the most commonly reported hematologic complication. The authors hypothesized that megakaryocytes (MK) may be a specific target for HCMV. Although the susceptibility of immature hematopoietic progenitors cells to HCMV has been established, a productive viral life cycle has only been linked to myelomonocytic maturation. The authors investigated whether HCMV can also infect MK and impair their function. They demonstrated that HCMV did not affect the thrombopoietin (TPO)-driven proliferation of CD34(+) cells until MK maturation occurred. MK challenged with HCMV showed a 50% more rapid loss of viability than mock-infected cells. MK and their early precursors were clearly shown to be susceptible to HCMV in vitro, as evidenced by the presence of HCMV in magnetic column-purified CD42(+) MK and 2-color fluorescent staining with antibodies directed against CD42a and HCMV pp65 antigen. These findings were confirmed by the infection of MK with a laboratory strain of HCMV containing the beta-galactosidase (beta-gal) gene. Using chromogenic beta-gal substrates, HCMV was detected during MK differentiation of infected CD34(+) cells and after infection of fully differentiated MK. Production of infectious virus was observed in cultures infected MK, suggesting that HCMV can complete its life cycle. These results demonstrate that MK are susceptible to HCMV infection and that direct infection of these cells in vivo may contribute to the thrombocytopenia observed in patients infected with HCMV. (Blood. 2000;95:487-493)

Antigens, CD↗
PubMed2000

Diet controversies in lipid therapy.

Increasing awareness of the relationship between diet and disease has prompted a notable increase in nutrition research. The focus of many of these studies continues to be on amount and type of fat in the diet. At the same time, a great deal of attention is being directed at other dietary components and their mode of action. The results are promising. More definitive answers must await future clinical trial data. However, the total dietary approach, including compliance measures, remains the foundation on which other nutrition recommendations should be based.

Antioxidants↗
PubMed1999

Apoptosis induced by human cytomegalovirus infection can be enhanced by cytokines to limit the spread of virus.

Fas-mediated apoptosis is one of the immune effector pathways leading to the elimination of virus infected cells. In vivo, apoptotic signals are delivered to virus infected cells by Fas-L and other cytokines secreted by specific T lymphocytes. Cellular immune response appears to be essential in prevention of human cytomegalovirus (HCMV) disease. We have hypothesized that HCMV infection might directly or indirectly result in upregulation of Fas receptor and in the presence of Fas ligand, lead to apoptosis of infected cells. We show that infection of human fibroblasts with HCMV is associated with upmodulation of Fas-R process that could be further potentiated by interferon (IFN-gamma). Using DNA agarose gel electrophoresis, terminal dideoxy transferase reaction, and annexin assay, we demonstrated that in a productive HCMV infection of human fibroblasts, loss of cell viability was not only due to virus-mediated cell lysis but also to due to apoptosis. IFN-gamma induced relative HCMV resistance and prevented loss in cell viability. In contrast, anti-Fas monoclonal antibody CH11, serving as Fas agonist, resulted in an accelerated loss in viability of infected cells. IFN-gamma in combination with CH11 further increased the rate of apoptosis and compared to cultures with CH11 only, this effect was not restricted to only infected cells. While IFN-gamma did not affect the number of cells expressing immediate early antigen, it markedly reduced structural protein expression. IFN-gamma in combination with CH11, decreased the expression of HCMV matrix protein pp65, reduced the amount of HCMV DNA and infectious virus produced. Our results are consistent with the theory that cells infected with HCMV can be eliminated by immune effector cells via Fas-mediated apoptosis. IFN-gamma, in addition to its intrinsic antiviral activity, primes HCMV infected cells to the action of Fas ligand and Fas-mediated apoptosis.

Antibodies, Monoclonal↗
PubMed1998

Generation of a nude mouse tumor model for in vivo replication of human cytomegalovirus.

Human cytomegalovirus (HCMV) is a common opportunistic infection resulting in retinitis in 15%-40% of AIDS patients. Several anti-HCMV therapies are currently available, and new treatments are in various stages of development. An HCMV animal model involving in vivo infection of human cells without the dependence on human fetuses or multiple surgical procedures has been developed. A human glioblastoma cell line that is permissive for HCMV replication (U373MG) was adapted to grow as a subcutaneous tumor in nude mice. These tumors arise in approximately 7 days and grow progressively. An evaluation of HCMV DNA replication demonstrated an increase in the accumulation of HCMV DNA within infected tumors from 48 to 168 h after infection. Immunohistochemical analysis showed focal areas of HCMV infection in which expression of immediate-early and late antigens was detected. In addition, it was demonstrated that ganciclovir inhibited HCMV DNA replication in vivo in a dose-dependent manner.

Animals↗
PubMed1998

Physical activity, genetic, and nutritional considerations in childhood weight management.

Almost one-quarter of U.S. children are now obese, a dramatic increase of over 20% in the past decade. It is intriguing that the increase in prevalence has been occurring while overall fat consumption has been declining. Body mass and composition are influenced by genetic factors, but the actual heritability of juvenile obesity is not known. A low physical activity (PA) is characteristic of obese children and adolescents, and it may be one cause of juvenile obesity. There is little evidence, however, that overall energy expenditure is low among the obese. There is a strong association between the prevalence of obesity and the extent of TV viewing. Enhanced PA can reduce body fat and blood pressure and improve lipoprotein profile in obese individuals. Its effect on body composition, however, is slower than with low-calorie diets. The three main dietary approaches are: protein sparing modified fast, balanced hypocaloric diets, and comprehensive behavioral lifestyle programs. To achieve long-standing control of overweight, one should combine changes in eating and activity patterns, using behavior modification techniques. However, the onus is also on society to reduce incentives for a sedentary lifestyle and over-consumption of food. To address the key issues related to childhood weight management, the American College of Sports Medicine convened a Scientific Roundtable in Indianapolis.

Adolescent↗
PubMed1998

Identification of persistent RNA-DNA hybrid structures within the origin of replication of human cytomegalovirus.

Human cytomegalovirus (HCMV) lytic-phase DNA replication initiates at the cis-acting origin of replication, oriLyt. oriLyt is a structurally complex region containing repeat elements and transcription factor binding sites. We identified two site-specific alkali-labile regions within oriLyt which flank an alkali-resistant DNA segment. These alkali-sensitive regions were the result of the degradation of two RNA species embedded within oriLyt and covalently linked to viral DNA. The virus-associated RNA, vRNA, was identified by DNase I treatment of HCMV DNA obtained from sucrose gradient purified virus. This heterogeneous population of vRNA was end labeled and used as a hybridization probe to map the exact location of vRNAs within oriLyt. vRNA-1 is localized between restriction endonuclease sites XhoI at nucleotide (nt) 93799 and SacI at nt 94631 and is approximately 500 bases long. The second vRNA, vRNA-2, lies within a region which exhibits a heterogeneous restriction pattern located between the SphI (nt 92636) and BamHI (nt 93513) and is approximately 300 bases long. This region was previously shown to be required for oriLyt replication (D. G. Anders, M. A. Kacica, G. S. Pari, and S. M. Punturieri, J. Virol. 66:3373-3384, 1992). RNase H analysis determined that vRNA-2 forms a persistent RNA-DNA hybrid structure in the context of the viral genome and in an oriLyt-containing plasmid used in the transient-replication assay.

Binding Sites↗
PubMed1997

Spread of human cytomegalovirus (HCMV) after infection of human hematopoietic progenitor cells: model of HCMV latency.

Clinical experience and laboratory data suggest that human cytomegalovirus (HCMV) is present in peripheral blood of seropositive individuals in a latent or persistent state and can be transmitted via blood products and be reactivated in seropositive immunocompromised patients. The pathophysiology of HCMV latency and the nature of HCMV interaction with hematopoietic cells remains unknown. In this study, we investigated the infection of bone marrow (BM) progenitor cells and their progeny as a model of HCMV latency. A clinical isolate and the recombinant laboratory strain Towne/lox containing the Escherichia coli beta galactosidase (beta-gal) gene regulated by immediately early (IE) HCMV promoter were used to infect highly purified CD34+ cells. Although the infection of these cells with a clinical isolate was associated with an inhibition of proliferation by 59%, an expansion of progeny derived from these cells was possible. Polymerase chain reaction analysis and staining for beta-gal have shown that HCMV persisted in infected BM CD34+ cells and their progeny for up to 4 weeks. However, IE and late gene products (mRNA and protein) were detected only late in the course of infection and their expression correlated with terminal macrophage differentiation of the CD34+-derived progeny. Although early infection of CD34+ progenitor cells was not productive (as shown by the plaque assay), infectious virus could be recovered from the terminally differentiated cultures. BM progenitor cells may serve as a reservoir of the latent virus with limited transcription. Proliferation and monocytic maturation of infected progenitors may lead to the numerical expansion of HCMV-infected cells, which serve as a source of HCMV dissemination and reactivation.

Antigens, CD34↗