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Biomedical subjects

R Wall

Publications and source records attributed to R Wall.

194 records · Page 11Linked to original sources
PubMed1973

Production of viral mRNA in adenovirus- transformed cells by the post- transcriptional processing of heterogeneous nuclear RNA containing viral and cell sequences.

Adenovirus 2-transformed cells contain virus-specific sequences which are covalently linked to cell-specific RNA sequences in heterogeneous nuclear RNA (HnRNA) molecules larger than 45S. Virus sequences are identified by hybridization to viral DNA, and the cell sequences are detected by hybridization to cellular DNA under conditions where hybridization only occurs to reiterated sites in cell DNA. Such large composite viral-cell HnRNA molecules presumably arise through the uninterrupted transcription of host sequences and integrated viral DNA. Adenovirus-specific polysomal RNA from these cells sediments as three discrete species at 16, 20, and 26S. These specific classes of viral mRNA do not contain rapidly hybridizing host-specific RNA sequences. Both virus-specific HnRNA and mRNA contain polyadenylic acid sequences since they bind to polyU columns at levels characteristics of other polyA-terminated HnRNA and mRNA. Thus, the discrete species of virus-specific mRNA in adenovirus 2 transformed cells appear to be derived from high-molecular-weight virus-specific HnRNA through a series of post-transcriptional modifications involving polyA addition. Subsequently the HnRNA is cleaved so that the cell-specific RNA sequences that originate from the reiterated sites in cell DNA do not accompany the adenovirus mRNA to the cytoplasm. These events for the adenovirus-specific mRNA appear, therefore, to be similar to the stages in the biogenesis of the majority of mRNA in eukaryotic cells.

Adenoviridae↗
PubMed1971

Polyadenylic acid sequences: role in conversion of nuclear RNA into messenger RNA.

Polyadenylic acid [poly(A)] segments containing 150 to 250 nucleotides appear to be covalently linked to heterogeneous nuclear RNA (HnRNA) and messenger RNA (mRNA) in eucaryotic cells. The poly(A) is synthesized in the nucleus, and is probably linked initially to HnRNA that is ultimately transported as mRNA to the cytoplasm. Studies with inhibitors of RNA or poly(A) synthesis indicate that synthesis of poly(A) segments is independent of transcription. The poly(A) marker may prove useful to elucidate mRNA modification and transport in eucaryotic cells.s

Adenine↗
PubMed1971

Addition of polyadenylate sequences to virus-specific RNA during adenovirus replication.

Adenovirus-specific nuclear and polysomal RNA, both early and late in the infectious cycle, contain a covalently linked region of polyadenylic acid 150-250 nucleotides long. A large proportion of the adenovirus-specific messenger RNA contains poly(A). As revealed by hybridization experiments, the poly(A) is not transcribed from adenovirus DNA. Furthermore, an adenosine analogue, cordycepin, blocks the synthesis of poly(A) and also inhibits the accumulation of adenovirus messenger RNA on polysomes. Addition of poly(A) to viral RNA may involve a host-controlled mechanism that regulates the processing and transport of messenger RNA.

Acrylamides↗
PubMed1971

An adenylic acid-rich sequence in messenger RNA of HeLa cells and its possible relationship to reiterated sites in DNA.

Messenger RNA from HeLa cells contains, as part of the polynucleotide chain, RNase-resistant sequences that are labeled by adenosine but not by uridine. Heterogeneous nuclear RNA also contains adenylate-rich RNase-resistant regions, but in lower proportion than messenger RNA. Hybridization to DNA of (32)P-labeled messenger RNA reveals that some of the adenylate-rich region is included in the rapidly-hybridizing fraction.

Adenine Nucleotides↗
PubMed1969

Host-dependent restriction of mengovirus replication.

Mengovirus infection of a restrictive cell line, Maden's bovine kidney (MDBK), results in a virus yield 1,000-fold less than that obtained from productively infected cell lines such as L cells or Ehrlich ascites tumor cells (EAT). Cells of both types of host systems are infected with comparable efficiencies and are completely killed as a consequence of infection. Infective center assays, coupled with the observation of total cell killing, suggest that comparable numbers of cells synthesize viral antigen and release virus in both types of host system. Viral-specific ribonucleic acid (RNA) synthesis is initiated and proceeds in an identical fashion for approximately 4 hr after the infection of MDBK, EAT, or L-cells. At this time, viral RNA synthesis in MDBK ceases, whereas viral RNA synthesis in EAT and L-cells continues at a linear rate. These results indicate that none of the early viral events leading to the initiation of viral-specific RNA synthesis constitutes the primary site of mengovirus restriction in MDBK. Rather it appears that the cessation of viral RNA synthesis in restrictive cells constitutes the primary limiting event. Based on its delayed interaction with mengovirus RNA synthesis, it appears that the host-related restrictive agent is initially compartmentalized and then released as a consequence of infection subsequent to those early events in mengovirus infection leading to the initiation and continued synthesis of viral RNA.

Animals↗
PubMedDate not supplied

Rapid diagnosis and determination of duration of viraemia in dengue fever using a reverse transcriptase polymerase chain reaction.

A rapid, simple diagnostic polymerase chain reaction (PCR) method for the diagnosis of dengue fever was developed using a pair of consensus oligonucleotide primers and validated with laboratory-derived strains of dengue serotypes 1-4 and other common flaviviruses. A cluster of 13 patients with clinical dengue fever admitted to a single infectious diseases unit over a period of 3 months allowed evaluation of this technology. The PCR was positive in all 11 acute dengue cases and negative in 2 convalescent cases and 10 febrile patients recently returned from the tropics in whom an alternative diagnosis was established. In some of the acute cases, viraemia was detected before the development of a diagnostic antibody response (indirect immunoglobulin (Ig) G enzyme-linked immunosorbent assay (ELISA) and capture IgM ELISA). In patients from whom sequential sera were taken, defervescence and recovery from thrombocytopenia coincided with the disappearance of dengue ribonucleic acid from the blood. Nucleotide sequencing of the PCR products was undertaken in 2 cases (from India and Guyana) and the results showed a close match with previously reported serotype 2 sequencies, suggesting a potential for use of this region of the genome in epidemiological studies.

Adult↗
PubMedDate not supplied

Environmental consequences of treating cattle with the antiparasitic drug ivermectin.

Ivermectin (22,23-dihydroavermectin B1) is a recently discovered, persistent, broad-spectrum, antiparasitic drug of unpredecented potency which is now routinely administered to cattle, horses, sheep and pigs in many countries. In cattle, it is an efficient control for parasitic gastrointestinal and respiratory tract nematodes, warble fly, mites, lice and ticks. However, most of the ivermectin dose is ultimately eliminated in the faeces of the treated animals where it has been shown to have an insecticidal effect on the larvae of economically important, dung-breeding, haematophagous Diptera. Nevertheless, the effects of excreted ivermectin on the cowpat fauna as a whole and the wider consequences of such effects have not previously been considered. In field trials reported here, the faeces of calves fitted with rumenal boluses delivering ivermectin at 40 micrograms per kg per day, failed to degrade in the normal way and this failure was associated with the absence of dung-degrading insects. Faeces from placebo-treated controls contained a characteristic dung-degrading invertebrate community and were largely degraded within 100 days. These results indicate that the increasing widespread use of ivermectin may have important environmental consequences for pastureland.

Animals↗
PubMedDate not supplied

Gastrointestinal tolerability of ibuprofen compared with paracetamol and aspirin at over-the-counter doses.

This multicentre, randomized, investigator-blinded, parallel-group study compared the gastrointestinal (GI) tolerability of ibuprofen, paracetamol and aspirin at over-the-counter doses for common pain indications. Patients (of whom 8633 were evaluable) took either ibuprofen up to 1200 mg daily, or paracetamol or aspirin, each up to 3000 mg daily, for 1-7 days. The main outcome was the proportion of patients with GI adverse events. There were significantly more patients who suffered GI adverse events, principally abdominal pain, dyspepsia, nausea and diarrhoea, with aspirin (18.5%) than with ibuprofen (11.5%), but the difference between ibuprofen and paracetamol (13.1%) was not significant. Significantly more of those patients with a history of non-ulcer GI disease (n = 371) developed GI adverse events than did those with no such history; the incidence of GI adverse events in both groups was lowest with ibuprofen. More women than men experienced GI adverse events (15.5% versus 12.8%). The higher incidence of GI adverse events with aspirin was evident from the first day of treatment. In conclusion, the GI tolerability of ibuprofen, at over-the-counter doses of up to 1200 mg daily for up to 7 days, was at least as good as that of paracetamol and significantly better than that of aspirin.

Acetaminophen↗
PubMedDate not supplied

A simple method of producing a monolayer of cervical cells for digital image processing.

A manual method of producing a monolayer of isolated and evenly distributed cervical epithelial cells has been developed for use in an automated digital image analysis system. The cervical scrape specimen is vortexed from the spatula into a solution of Mucosol. The suspension is filtered through a 10 micro nylon mesh to remove polys and debris and then syringed to disaggregate epithelial clumps. The cells are plated out on a Nuclepore filter. The filter is touched directly onto a glass microscopic slide to transfer cells, which are then fixed and stained in a routine manner. Cell counts reveal elimination of 92% polys, with only 2% loss of squamous cells.

Autoanalysis↗