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At least 595 records · Page 33Linked to original sources
PubMed1992

Molecular approaches to the characterization of cell and blood/biomaterial interactions.

In order to address questions related to cell/biomaterial interactions with respect to cell function and production of extracellular matrix proteins that support or maintain cell/tissue specific properties, we have developed molecular approaches for analysis of in vivo implanted materials and in vitro studies. In an explant of a human left ventricular assist device (LVAD), intact total cellular RNA could be isolated in sufficient quantities for hybridization analyses with gene-specific probes to evaluate cell growth, cytoskeletal organization, and production of extracellular matrix proteins. Cells harvested from a 132-day implanted LVAD exhibited proliferative activity and expressed genes for fibronectin and collagen types I, III, and IV. In vitro studies revealed that endothelial cells cultured on two different segmented polyurethane biomaterials (Biomer and Tecoflex 60D) exhibited different patterns of gene expression that reflected differences in cell growth rates, morphology, and composition of the extracellular matrix. These methodologies provide a valuable approach for a detailed evaluation of: (1) the biocompatibility of cells colonizing implanted cardiac assist devices; and (2) the functionality of cells seeded onto biomaterials.

Adult↗
PubMed1995

Message of nexin 1, a serine protease inhibitor, is accumulated in the follicular papilla during anagen of the hair cycle.

A group of specialized mesenchymal cells located at the root of the mammalian hair follicle, known as the follicular or dermal papillary cells, are involved in regulating the hair cycle, during which keratinocytes of the lower follicle undergo proliferation, degeneration and regrowth. Using the arbitrarily primed-PCR approach, we have identified a 1.3 kb messenger RNA that is present in large quantities in cultured rat follicular papillary cells, but not in skin fibroblasts. This mRNA encodes nexin 1, a potent protease inhibitor that can inactivate several growth-modulating serine proteases including thrombin, urokinase and tissue plasminogen activator. In situ hybridization showed that nexin 1 message is accumulated in the follicular papilla cells of anagen follicles, but is undetectable in keratinocytes or other skin mesenchymal cells. In addition, nexin 1 message level varies widely among several immortalized rat vibrissa papillary cell lines, and these levels correlate well with the reported abilities of these cell lines to support in vivo follicular reconstitution. These results suggest a possible role of nexin 1 in regulating hair follicular growth.

Amyloid beta-Protein Precursor↗
PubMed1988

Expression of tyrosinase gene in amelanotic mutant mice.

In order to study the molecular aspects of albinism, we analyzed the expression of tyrosinase gene in some amelanotic mutant mice by Northern blotting using mouse tyrosinase cDNA as a probe. It hybridized with a species of 2.1 kilobase RNA prepared from the skin of wild-type mice and two albino strains in the same quantity. In black-eyed white mouse, however, no RNA transcript encoding tyrosinase was detected. Our results suggest that these albinism is due to a point mutation in the structural region of the tyrosinase gene, not to a deficiency of tyrosinase gene expression and that the black-eyed white mouse has a deficiency in the gene expression possibly related to melanocyte differentiation.

Albinism↗
PubMed2004

Gene expression analysis in platelets from a single donor: evaluation of a PCR-based amplification technique.

BACKGROUND: Genetic analysis of platelet mRNA may facilitate the diagnosis of disorders affecting the megakaryocytic-platelet lineage. Its use, however, is limited by the exceptionally small yield of platelet mRNA and the risk of leukocyte contamination during platelet preparation. METHODS: We depleted platelet suspensions of leukocytes by filtration and used a PCR-based RNA amplification step [switching mechanism at the 5' end of RNA templates (SMART)]. We tested the reliability and precision of the RNA amplification procedure by use of real-time PCR to measure quantities of specific transcripts: von Willebrand factor (vWF), A-subunit of coagulation factor XIII (F13A), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Microarray analysis was performed on platelet RNA with and without amplification. RESULTS: Microgram quantities of platelet-specific cDNAs were produced from as little as 50 ng of total platelet RNA or 40 mL of whole blood. At cycle numbers <16, amplification of all transcripts tested was exponential with slightly more efficient amplification of low-abundance transcripts. Expression profiling of 9850 genes gave identical results for 9815 genes (1576 positive/8239 negative). Eight transcripts failed to be amplified by the SMART procedure. Expression of vWF, F13A, and GAPDH transcripts showed only minor day-to-day variations in three healthy individuals. CONCLUSION: The proposed protocol makes extremely small amounts of platelet RNA available for gene expression analysis in single patients.

Blood Platelets↗
PubMed1976

Preferential synthesis of viral late RNA by nuclei isolated from SV40 lytically infected cells.

Nuclei from SV40-infected monkey cells were isolated late in lytic infection and their cell-free transcriptional activity was characterized. 3H-RNA synthesized in vitro was hybridized to excess quantities of separated SV40 DNA strands which were each covalently bound to Sepharose. It was found that 3-5% of the newly synthesized RNA is virus-specific and that the plus-strand DNA, coding for late RNA sequences, is transcribed at a rate about 15 times higher than that of the minus-strand DNA, which codes for early RNA sequences. This indicates that transcriptional control has a major role in determining the relative abundancy of early and late RNA classes in lytically infected cells.

Amanitins↗
PubMed1998

The quantity of dietary protein affects brain protein synthesis rate in aged rats.

The purpose of this study was to determine whether the quantity of dietary protein affects the rate of brain protein synthesis in aged rats. Experiments were conducted on three groups of 30-wk-old rats fed diets containing 0, 5 or 20 g casein/100 g for 10 d. The fractional rates of protein synthesis in brain, liver and kidney declined with a decrease in quantity of dietary protein. In brain, liver and kidney, RNA activity [g protein synthesized/(g RNA.d)] was significantly correlated with the fractional rate of protein synthesis. The RNA concentration (mg RNA/g protein) was not related to the fractional rate of protein synthesis in any organ. The results suggest that the rate of protein synthesis in the brain declines with a decrease in quantity of dietary protein in aged rats, and that RNA activity is at least partly related to the fractional rate of brain protein synthesis.

Aging↗
PubMed1993

Epstein-Barr virus (EBV) nuclear-antigen-2-induced up-regulation of CD21 and CD23 molecules is dependent on a permissive cellular context.

The Epstein-Barr virus (EBV) induces unlimited growth of B lymphocytes in vitro, a phenomenon known as immortalization. The elucidation of the mechanisms by which EBV de-regulates B-cell proliferation in vitro will permit an understanding of how the virus contributes in vivo to the genesis of Burkitt's lymphoma (BL) and of lymphoproliferations in immunosuppressed patients. At present, no single EBV immortalizing gene has been identified, and the hypothesis has been made that many viral genes cooperate in establishing an autocrine loop of secretion leading to immortalization. Constitutive expression of B-cell surface molecules such as CD21 and CD23, specifically implicated in the control of B-cell proliferation, is indeed induced at the surface of immortalized B lymphocytes. The expression of the viral nuclear antigen 2 (EBNA2) has been shown to be in part responsible for CD21 and CD23 up-regulation, and EBNA2 is suspected to be a transactivator of cellular genes, although this point remains to be demonstrated. The role of EBNA2 gene, independently of other viral genes, has been investigated by transfection into B-lymphoma lines, but conflicting results have been reported. To further investigate its role in the regulation of CD21 and CD23 molecules, we have compared the effects of EBNA2 expression in 2 sets of B-lymphoma lines infected with P3HR1 EBV strain, and/or transfected with EBNA2 gene. We report here that: (i) EBNA2 expression is not a sufficient condition to induce CD21 and CD23 upregulation, EBNA2's effects are highly dependent on the cellular context, and moreover can be modified by infection with P3HR1 virus; (ii) EBNA2 induces activation of CD23 expression in a very particular way, namely, an increased quantity of CD23 steady-state RNA coding for the form A of the protein, which is not detectable at the cell surface but directly secreted.

Antigens, Viral↗
PubMed1984

Induction of cytochrome P-450 isozymes in rat hepatoma-derived cell cultures.

We have investigated the responsiveness of established rat hepatocyte cell cultures to inducers of cytochrome P-450. One Reuber hepatoma-derived line (Fu5-C8), which under normal culture conditions produces no detectable cytochrome P-450(MC) or cytochrome P-450(PB)--the major cytochrome P-450 isozymes induced by 3-methylcholanthrene and phenobarbital, respectively--was tested for the ability to accumulate either cytochrome P-450 isozyme in response to treatment with various xenobiotics. By immune-precipitation from [35S]-methionine-labeled cell extracts, using monospecific anticytochrome P-450(MC) antibody or monoclonal anticytochrome P-450(PB) antibody, it was demonstrated that these cells possess the capability to synthesize cytochrome P-450(MC) in response to 3-methylcholanthrene treatment, while none of the drug treatments caused the synthesis of detectable quantities of cytochrome P-450(PB). RNA extracted from Fu5-C8 cells directed the in vitro synthesis of immune-precipitable cytochrome P-450(MC) only after treatment of the cells with 3-methylcholanthrene. Kinetic analysis of the response of these cells to 3-methylcholanthrene induction revealed detectable levels of immune-precipitable cytochrome P-450(MC) 2 h after drug treatment with maximal induction occurring between 12 and 16 h of exposure. Another cell line (HF 1.5), obtained originally by hybridization of Fao X H5 variants of a Reuber H35 hepatoma, produces cytochrome P-450(MC) and also cytochrome P-450(PB) constitutively, as determined by specific immune-precipitation from labeled cell extracts. Exposure of confluent monolayers to either phenobarbital or 3-methylcholanthrene resulted in an induction of cytochrome P-450(PB) or cytochrome P-450(MC), respectively. Double-labeling immunofluorescence studies indicate that all cells in the culture produce albumin and most of the cells produce cytochrome P-450(MC), but only a subset of cells synthesize cytochrome P-450(PB). Our results demonstrate that some continuously dividing hepatocyte cell cultures retain the capacity to respond to xenobiotics, including phenobarbital, a response which is typically exhibited by fully differentiated liver cells. Such established hepatocyte cell cultures should prove useful for investigating the mechanism of induction of cytochrome P-450(PB).

Animals↗
PubMed1987

Changes of SCE frequency and chromatin molecular composition in rat progeny whose mothers were treated with oral contraceptives in early pregnancy.

Wistar female rats were fed with oral contraceptives (OC, containing ethinylestradiolum and methylnorethrindronum) in early pregnancy. The dosage used for rats was 6.6 times more than the clinical dosage for humans in weight per kilogram. The SCE frequencies of liver and ovary cells and the changes of chromatin molecular composition in progeny of the rats fed with OC were observed. The results showed that the liver and ovary cells of newborns 12 h after birth exhibited increased SCEs value (liver: p less than 0.03; ovary: p less than 0.0004). These elevated SCE frequencies declined to the normal level about the 15th day after birth. The results for the quantity of nonhistone (NHP) and chromatin RNA in mother rats and their progenies also exhibited a significant increase, and declined to the normal level at the same period mentioned above. The results suggested that the high level of NHP and chromatin RNA may be induced by OC fed in early pregnancy and be maintained for some time after withdrawal of the OC pills. The changes of the chromatin molecular composition are perhaps somehow related to the increased SCE frequencies in the rat-liver cells. We suggest that the external steroids and their metabolites may activate more genes which were originally inactive and result in increased junctions between euchromatin and heterochromatin, resulting in more SCEs in quickly dividing embryo cells. The report here suggests that during early pregnancy the pills taken by women following OC failures may have a potential mutagenic effect on their progeny for some time after the pills have been stopped.

Animals↗
PubMed1999

Molecular cloning of a major Alternaria alternata allergen, rAlt a 2.

BACKGROUND: Sensitivity to the fungus Alternaria alternata is a common cause of asthma. Epidemiologic studies from a variety of locations worldwide indicate that A alternata sensitivity is closely linked with the development of asthma. Furthermore, A alternata sensitivity has been associated with severe and potentially fatal attacks of asthma. OBJECTIVE: The diagnosis of A alternata sensitivity is hampered by the lack of standardized and well-characterized allergenic extracts. Molecular cloning of allergens offers the possibility of providing large quantities of purified, well-characterized allergens not only for diagnostic purposes but also for studying the pathogenesis of A alternata sensitivity. We used molecular cloning to identify, purify, and produce a major A alternata allergen in quantity. METHODS: We prepared messenger (m)RNA from A alternata to produce a complementary (c)DNA library. The library was screened for A alternata allergens by using sera from A alternata-sensitive individuals. A recombinant allergen was isolated, the cDNA sequence was determined, and the protein was expressed in Pichia pastoris. RESULTS: A unique A alternata allergen, rAlt a 2, was identified. A 2.2-kb cDNA sequence was obtained that has homology with a common transposable region and mouse RNA-dependent eukaryote initiation factor-2 alpha-kinase but no homology to any known allergen. No N-glycosylation sites were found in the cDNA sequence. The recombinant allergen was recognized by IgE antibodies in the sera of 16 of 26 (61%) individuals allergic to A alternata, which defines Alt a 2 as a major allergen. CONCLUSIONS: We have molecularly cloned a unique major A alternata allergen, rAlt a 2. Identification and expression of the recombinant allergen should enhance the development of standardized A alternata allergenic extracts and provide stable reagents for investigating the pathogenesis of A alternata sensitivity.

Allergens↗
PubMed1996

Reconstitution of the 2Fe-2S center and g = 1.89 electron paramagnetic resonance signal into overproduced Nostoc sp. PCC 7906 Rieske protein.

The Rieske 2Fe-2S protein is a distinguishing subunit of the photosynthetic electron transport cytochrome b6f complex in chloroplast and cyanobacterial thylakoid membranes. We have constructed plasmids for overproduction in Escherichia coli of fusion, full-length, and truncated forms of the Rieske (PetC) protein from the cyanobacterium Nostoc sp. PCC 7906. A glutathione S-transferase/Rieske fusion protein was used to prepare specific chicken egg-yolk antibodies against the Rieske protein. Expression of the nonfusion petC gene in a T7 RNA polymerase promoter vector produced copious quantities of the full-length Rieske protein predominantly as inclusion bodies. The highly enriched, Rieske protein from inclusion bodies has been denatured in guanidine hydrochloride and refolded and the characteristic 2Fe-2S cluster reconstituted in vitro by incubation with iron and sulfide under reducing conditions. Purification by chromatography on Whatman DE52 cellulose and ultrafiltration through a 30000 molecular weight cutoff membrane yielded pure and predominantly monomeric Rieske protein. Reconstituted Rieske preparations showed intense and highly characteristic gx = 1.74, gy = 1.89, and gz = 2.03 "Rieske-type" electron paramagnetic resonance signals at 15 K. Two methods of reconstitution yielded Rieske preparations in which 20-60% of the protein contained 2Fe-2S clusters as determined by EPR spin quantitation. The reconstituted Rieske protein was soluble and stable at 4 degrees C in buffers containing nonionic detergents and showed a redox midpoint potential of +321 mV at pH 7.0 as determined by optical circular dichroism (CD) spectroscopy. These data demonstrate the in vitro restoration of a Cys and His liganded 2Fe-2S cluster and provide the basis for mutational and structural analysis of a PetC Rieske protein of oxygenic photosynthesis.

Animals↗
PubMed1994

In vivo generation of highly abundant sequence-specific oligonucleotides for antisense and triplex gene regulation.

Antisense and triplex oligonucleotides continue to demonstrate potential as mediators of gene-specific repression of protein synthesis. However, inefficient and heterogeneous cellular uptake, intracellular sequestration, and rapid intracellular and extracellular degradation represent obstacles to their eventual clinical utility. Efficient cellular delivery of targeted ribozymes can present similar problems. In this report we describe a system for circumventing these obstacles and producing large quantities of short, sequence-specific RNA oligonucleotides for use in these gene regulation strategies. The oligonucleotides are generated from a vector containing promoter, capping, and termination sequences from the human small nuclear U6 gene, surrounding a synthetic sequence incorporating the oligonucleotide of interest. In vivo, these oligonucleotides are produced constitutively and without cell type specificity in levels up to 5 x 10(6) copies per cell, reach steady-state levels of expression within 9 hours post-transfection, and are still readily detectable 7 days post-transfection. In addition, these oligonucleotides are retained in the nucleus, obtain a 5' gamma-monomethyl phosphate cap, and have an intracellular half-life of approximately one hour. This expression vector provides a novel and efficient method of intracellular delivery of antisense or triplex RNA oligonucleotides (and/or ribozymes) for gene regulation, as well as a cost-effective means of comparing the biological activity arising from a variety of different potential oligonucleotide sequences.

Base Sequence↗
PubMed1986

Rat embryo fibroblast cells expressing human papillomavirus 1a genes exhibit altered growth properties and tumorigenicity.

Human papillomavirus 1a (HPV1a) induces benign tumors (papillomas or warts) in humans under natural conditions of infection but has not been found to replicate significantly in cell culture or in experimental animals. To establish model systems to study the oncogenic properties and expression of HPV genes, we established cell lines by cotransfecting the 3Y1 rat fibroblast cell line with HPV1a DNA constructs containing an intact early gene region and the Tn5 neomycin resistance gene. Most cell lines selected for expression of the neomycin resistance gene by treatment with the antibiotic G-418 contained viral DNA in a high-molecular-weight form. The growth characteristics of several cell lines containing high copy numbers of HPV1a DNA were studied further. They were shown to differ from the parental cell line and from G-418-resistant cell lines that did not incorporate viral DNA in the following properties: morphological alteration, increased cell density at confluence, growth in 0.5% serum, efficient anchorage-independent growth in soft agar, and rapid formation of tumors in nude mice. Those cell lines that possessed altered growth properties and tumorigenicity were found to express abundant quantities of polyadenylated virus-specific RNA species in the cytoplasm.

Animals↗
PubMed2005

A mouse model of aortic angioplasty for genomic studies of neointimal hyperplasia.

We describe here a mouse model of diffuse aortic remodelling triggered by combined endothelial denudation/vascular distension injury using a novel balloon microcatheter. We validated this model in both outbred (NMRI) and inbred (BALB/c, C57BL/6) mouse strains and found evidence for differential strain susceptibility to neointimal hyperplasia, possibly attributable to genetic factors. Neointimal lesions were approximately 50% smaller in the inbred strains, a finding associated with profound cell loss in the aortic media at the early stages of the response to injury. A further insight from this model suggests an essential role for platelets in the initiation of neointimal hyperplasia, which apparently progresses through monocyte influx from the peripheral circulation. Our findings are consistent with monocyte recruitment driving neointimal growth, a minority expressing the endothelial cell marker FVIII. Overall, the time course and gross histological features of vascular remodelling seen here resemble those seen in other rodent models. However, this new mouse model offers distinct advantages over existing ones in that it involves the actual use of a catheter in a clinical manner, and because it allows the recovery of intact RNA from injured vessels in sufficient quantities for downstream molecular analyses.

Angioplasty↗
PubMed1987

Interleukin 1 gene expression in adult T cell leukemia.

The adult T cell leukemia (ATL) is a T cell neoplasm etiologically associated with human T lymphotropic virus type I (HTLV-I) infection. ATL cells often abnormally express interleukin 2 (IL-2) receptors, and ATL patients may show clinical evidence of hypercalcemia, osteolytic bone lesions, or increased bone turnover. Whereas interleukin 1 (IL-1) is not generally recognized as a product of T cells, this cytokine is capable of both altering IL-2 receptor expression and activating osteoclasts. Thus, we investigated the possibility that primary ATL leukemic T cells and HTLV-I-infected long-term ATL cell lines produce IL-1. S1 nuclease protection assays demonstrated that primary leukemic ATL cells from five out of six patients, as well as one patient with T4+ chronic lymphocytic leukemia, contained considerable quantities of IL-1 beta messenger RNA (mRNA) and small amounts of IL-1 alpha mRNA. These primary leukemic T cells also released biologically active IL-1 protein as evaluated in the murine thymocyte comitogenesis bioassay. In contrast to primary tumor cells, four out of six long-term ATL cell lines produced variable amounts of IL-1 alpha mRNA in the absence of detectable IL-1 beta mRNA as measured by S1 nuclease protection. These data demonstrate that IL-1 gene (especially IL-1 beta) expression occurs in many primary HTLV-I-infected leukemic T cells raising the possibility that this mediator may play a role in the pathological changes associated with this leukemia. Also, these studies show that the pattern of IL-1 alpha and IL-1 beta gene expression differs between primary ATL tumor cells and long-term cultured ATL cell lines, indicating an interesting biological difference in these two HTLV-I-infected cell populations.

Adult↗
PubMed1993

Immunocytochemical delineation of thyroid hormone receptor beta 2-like immunoreactivity in the rat central nervous system.

The thyroid hormone receptors (TR) are nuclear proteins that include TR alpha and TR beta subtypes, each encoded by a separate gene. Both TR alpha and TR beta give rise to several isoforms of which three, TR alpha 1, TR beta 1, and TR beta 2 bind T3 and mediate the action of thyroid hormone. Although TR beta 2 was initially thought to be confined to the anterior pituitary, we recently observed small quantities of TR beta 2 messenger RNA (mRNA) by polymerase chain reaction analysis of discrete hypothalamic regions. To further examine the distribution of TR beta 2 in the brain, we performed immunocytochemical studies using a highly specific antiserum to TR beta 2, raised against a unique amino acid sequence (TR beta 2[131-145]) that is not present in the other known TRs. This antiserum immunoprecipitated TR beta 2 but not TR alpha 1 or TR beta 1. Immunoreactive TR beta 2 was widely distributed throughout the brain and primarily localized to the cell nucleus. Particularly intense immunostaining was present in the cerebral cortex, cerebellum, and hypothalamus, including regions where TR beta 2 mRNA had not previously been identified. In addition, immunoprecipitation of nuclear extracts with anti-TR beta 2 reduced total T3 binding capacity by approximately 20%, suggesting that immunoreactive TR beta 2 comprises a substantial portion of the total content of nuclear thyroid hormone binding proteins. These studies demonstrate that immunoreactive TR beta 2 is more widely represented in the central nervous system than previously suspected and may play an important role in mediating the action of T3 in many different regions of the brain. The finding of TR beta 2-like material could be due to a disproportionately high ratio of the TR beta 2 translation product and its mRNA in certain regions of the brain, or could indicate the existence of a novel TR beta 2-related protein that is important for T3 binding.

Amino Acid Sequence↗
PubMed2006

Cervine (Cervus elaphus) cytokine mRNA quantification by real-time polymerase chain reaction.

It has been difficult to perform cytokine studies for many wildlife and nontraditional species because of a lack of immunologic reagents at the protein level. Recently, simple and rapid assays for quantifying mRNA expression by real-time reverse transcription-polymerase chain reaction (RT-PCR) have been used for analysis of cytokine profiles in humans and other mammalian species. This report describes the development and application of real time RT-PCR to measure the expression of several important elk (Cervus elaphus) cytokine mRNAs, including interleukin (IL)-2, IL-4, IL-10, IL-12p40, interferon-gamma, tumor necrosis factor (TNF)-alpha, and the enzyme-inducible nitric oxide synthase, all of which are involved in immune responses and regulation. For the broadest potential application of the assay, primers and probes were designed using consensus sequences from several species of interest. To obtain standardized quantitative results, external controls consisting of a DNA template for each target gene were used to generate linear standard curves over a 6 to 8 log range with detection of as few as 10 copies of amplicon per reaction. Sample-to-sample variation in the efficiency of the RT, as well as in the quantity and quality of the starting RNA, was compensated for by normalizing the results to the endogenous housekeeping gene beta(2)-microglobulin. The assay was evaluated by monitoring the kinetics of cytokine mRNA synthesis induced by mitogenic and antigenic stimulation of peripheral blood mononuclear cells (PBMCs) from Mycobacterium bovis-infected elk. Concanavalin A-stimulated PBMCs demonstrated a rapid but transient increase in cytokine mRNA expression following in vitro mitogenic activation with optimal mRNA induction observed after 4 to 16 hr. The PBMCs stimulated with the mycobacterial recall antigen, bovine-purified protein derivative (PPD-bovis), demonstrated variable mRNA induction kinetics for each cytokine. Whereas PPD-bovis optimally induced IL-2 mRNA after 8 hr of in vitro stimulation, longer in vitro stimulation times were necessary for the optimal induction of IL-4 and TNF-alpha mRNA (up to 48 hr). We demonstrate real-time RT-PCR to be a rapid, sensitive, and reproducible technique, which will make it a valuable tool in the study of immunologic responses and cytokine profiles of cervids and other nontraditional livestock and wildlife species.

Animals↗
PubMed1990

Mode of replication of lymphocytic choriomeningitis virus in persistently infected cultivated mouse L cells.

During persistent infection of mouse L cells with strain Armstrong lymphocytic choriomeningitis virus, the latter undergoes characteristic changes, including loss of mouse pathogenicity and failure to form plaques on cultivated cells. We call this virus L(Arm) and have analyzed transcription and translation of its S-RNA, which codes for the viral nucleoprotein (NP) and the glycoprotein precursor (GP-C). In L(Arm) virus-infected L cells, S-RNA and genomic-sized viral complementary S-RNA (VC-S-RNA) were detected and, in addition, considerable quantities of shortened molecules of either species. The cells' content of NP was high, but they contained little GP-C; instead, a viral glycoprotein with MW 65,000 was present. We propose a hypothesis in which it is assumed that along the VC-S-RNA there is more than one recognition site for the viral RNA-dependent RNA polymerase, which leads to the generation of truncated forms of S-RNA, VC-S-RNA, and mRNA for GP-C; this, in turn, results in relative overproduction of NP and relative underproduction of GP-C as well as the emergence of a new form of viral glycoprotein.

Animals↗