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R J Jackson

Publications and source records attributed to R J Jackson.

At least 127 records · Page 7Linked to original sources
PubMed1994

The immediate downstream codon strongly influences the efficiency of utilization of eukaryotic translation initiation codons.

Nucleotide substitutions were introduced into the initiation site of an influenza virus NS cDNA derivative at the +4, +5 and +6 positions (where the A of the AUG codon is defined as +1), in the background of either AUG or CUG as the initiation codon. Capped transcripts of these constructs were translated in rabbit reticulocyte lysate under conditions where the selection of initiation sites conformed to the scanning ribosome model. With CUG as the initiation codon, the efficiency of initiation was as strongly influenced by the nature of the residue in the +5 position as at +4, whilst the influence of the +6 position was smaller. The residues favourable to initiation were as follows: at +4, only G was stimulatory; at +5, A was strongly stimulatory and C fairly beneficial; and at +6, only U exerted any positive influence. The positive influence of the favourable residues (or the negative influence of unfavourable residues) at each position appeared to be additive. With AUG as the initiation codon, the pattern of response to mutations in the +4 and +5 positions was qualitatively similar, but the quantitative effects were smaller. Thus the optimum downstream context for initiation is A/CUGGAU.

Base Sequence↗
PubMed1994

Translation of encephalomyocarditis virus RNA: parameters influencing the selection of the internal initiation site.

The initiation of encephalomyocarditis virus RNA translation is by internal ribosome entry almost exclusively at the 11th AUG codon from the 5'-end, which is the central of the three AUG codons in the sequence..[sequence: see text].., and is located some 25 nt downstream from an oligopyrimidine tract conserved amongst related viruses. As the sequences between the oligopyrimidine tract and AUG-10/11 are poorly conserved and thus possibly serve only as a spacer, the influence of this spacer length on initiation frequency at the three AUG codons was examined in vitro and in vivo. Deletion of 11 residues resulted in initiation almost exclusively at AUG-12 but at significantly reduced overall efficiency. Insertion of eight residues caused a 15-fold increase in initiation frequency at AUG-10 and a decrease at AUG-11. Longer insertions reduced overall efficiency without changing the initiation site preferences. With the wild-type spacing, complete substitution of the oligopyrimidine tract by purines caused a 30-35% decrease in initiation efficiency, and partial substitution only a 10-15% decrease. Thus the internal initiation mechanism selects the initiation site partly on the basis of its distance from upstream elements, of which the oligopyrimidine tract is not the most critical, but for reasons not yet understood a preference for AUG-11 is superimposed on this selection.

Base Composition↗
PubMed1994

The role of the mucus gel layer in intestinal bacterial translocation.

The mucus gel layer is thought to be a vital component of the intestinal mucosal barrier. The purpose of this study is to determine if decreasing mucus production following ischemia and reoxygenation of the intestinal mucosa would alter bacterial translocation in an in vitro rat mucosal model. Clonidine was used to decrease mucus production associated with an ischemia/reoxygenation insult. Bacterial translocation was studied in a modified Ussing chamber using Escherichia coli K100. The quantity of mucus produced, as well as the incidence and quantity of bacteria translocating was measured. In the clonidine-treated animals, there was a significant decrease in the amount of mucus produced compared to the control animals. The clonidine animals also had a higher quantity of bacteria translocating during the reoxygenation period compared to the control animals. The mucus gel layer is protective against in vitro translocation of bacteria following an ischemia/reoxygenation insult.

Animals↗
PubMed1994

Delayed gastric emptying in neurologically impaired children with gastroesophageal reflux: the role of pyloroplasty.

The presence of delayed gastric emptying in neurologically impaired children with gastroesophageal reflux has led to controversy regarding appropriate surgical management. The authors reviewed the charts of neurologically impaired children requiring fundoplication to answer two questions: (1) is pyloroplasty needed in addition to fundoplication for delayed gastric emptying? and (2) Does delayed gastric emptying influence the morbidity associated with fundoplication? To answer the first question, 40 neurologically impaired children with delayed gastric emptying undergoing fundoplication were divided into two groups: Nissen and pyloroplasty (n = 21) and Nissen only (n = 19). The Nissen and pyloroplasty group had significantly more postoperative complications (23.8% v 5.0%) and took longer to reach full feeding (14.6 v 3.9) days. There were no differences in the incidence of recurrent symptoms, readmissions, or reoperations. To answer the second question, 58 neurologically impaired children undergoing fundoplication were grouped based on gastric emptying scan results: normal gastric emptying (> 32% in 1 hour) (n = 29) and delayed gastric emptying (n = 29). There were no differences in postoperative feeding tolerance, postoperative complications, recurrent symptoms, readmissions, or reoperations between the two groups. Delayed gastric emptying in neurologically impaired children with gastroesophageal reflux did not increase postoperative morbidity after fundoplication, and the addition of a pyloroplasty to fundoplication provided no additional benefit. The authors conclude that the procedure of choice for neurologically impaired children with gastroesophageal reflux is a fundoplication without pyloroplasty, regardless of the degree of delay in gastric emptying.

Child↗
PubMed1994

Helper Th1 and Th2 cell responses following mucosal or systemic immunization with cholera toxin.

We have used the potent mucosal immunogen cholera toxin (CT) to assess antigen-specific CD4+ T-cell responses, including Th1- and Th2-type cells in mucosa-associated tissues, e.g. Peyer's patches (PP), and systemic tissue, e.g. spleen (SP), for their regulatory role in the induction of CT-specific B-cell antibody responses in the gastrointestinal (GI) tract as well as in systemic sites. The CT was given by either oral or intravenous (i.v.) routes and the mice orally immunized with CT exhibited brisk IgA anti-CT antibody responses in faecal extracts and elevated IgG anti-CT antibody responses in serum. Further, significant IgA anti-CT spot-forming cells (SFCs) were seen in lamina propria lymphocytes (LPLs) from mice orally immunized with CT. In contrast, i.v. immunization with CT induced IgM and IgG anti-CT SFC responses in SP, and serum anti-CT antibodies of these two isotypes; no anti-CT responses were induced in the GI tract after immunization by this route. The CD4+ T cells isolated from PP and SP of mice orally immunized with CT were stimulated in vitro with CT-B-coated latex microspheres for 1-6 days, and the induction of IL-2 and interferon gamma (IFN-gamma) (Th1-type) or IL-4 and IL-5 (Th2-type) producing SFCs were analysed by a cytokine-specific ELISPOT and cytokine-specific mRNA was detected by reverse transcriptase (RT)-PCR assays.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1994

Regulation of translation by specific protein/mRNA interactions.

This review will focus on cases of specific translational control by protein/RNA interactions in the 5'- or 3'-UTR of eukaryote mRNA where either the cis-acting RNA determinant or the trans-acting protein (or preferably both) have been identified with fair certainty. Examples of messages that are regulated by 5' motifs, which are proposed to occlude ribosome binding when bound by their specific factors, include ferritin and ribosomal protein mRNAs and the autoregulated thymidylate synthase and poly(A)-binding mRNAs. However, it has become increasingly evident recently that 3' UTR determinants and their specific binding proteins also regulate translation efficiency either directly, or indirectly via an influence on the polyadenylation status of the mRNA. It is still unclear how events at the 3' end of mRNA influence ribosome binding. Most, if not all, of the mRNAs known to be regulated by 3' UTR motifs are subject to regulation during early development or during differentiation such as several spermatocyte and oocyte mRNAs and erythroid lipoxygenase mRNA. To date, in all cases where translation is controlled directly by specific protein/mRNA interactions, the protein seems to act as a negative regulator, a translational repressor, whose binding to the specific site on the mRNA results in inhibition of initiation. The only cases of translational activation known so far concern internal initiation of translation of picornaviral RNAs, but this topic is beyond the scope of this review.

Animals↗
PubMed1994

Mucosal immunity to infection with implications for vaccine development.

The induction of effective mucosal immunity that also provides systemic immunity is a considerable challenge. Over the past two years, efforts to develop novel mucosal vaccine delivery systems to induce mucosal immunity against bacterial and viral diseases, including HIV, have dramatically increased. Here we cite novel vaccines and delivery systems being used to establish effective mucosal immunity.

Animals↗
PubMed1994

The common mucosal immune system: from basic principles to enteric vaccines with relevance for the female reproductive tract.

The realization that induction of immune responses at mucosal surfaces may prevent colonization, invasion or dissemination of pathogenic microorganisms has spurred intensive efforts to develop vaccines which elicit effective mucosal immunity. In this paper, recent results are discussed for mice given cholera toxin as both an immunogen and as an adjuvant for inducing both humoral and gastrointestinal mucosal immune responses. Oral administration of cholera toxin alone or with a co-administered protein vaccine tetanus toxoid induces a strong T helper type 2 (TH2) cell response in both Peyer's patches and spleen. Both serum IgG and secretory IgA antibodies specific for cholera toxin or for the co-administered protein tetanus toxoid were induced. When administered parentally, however, no mucosal antibody responses were evident and a mixed TH1- and TH2-type CD4+ T cell response was noted in the spleen. Various vectors are being employed in an effort not only to induce mucosal immune responses but also to direct the response to a TH1-type response, thought to promote strong cell-mediated immune responses, or to a TH2-type response for maximum B cell antibody responses. The ability to manipulate the TH cell responses may provide a more rational approach for the design of vaccines. Although lymphoid tissues of the female reproductive tract differ from that of the gut, many of the strategies and evolving principles may be directly applicable to the development of vaccines designed to prevent sexually transmitted diseases.

Administration, Oral↗
PubMed1994

Virus-vectored immunocontraception for control of wild rabbits: identification of target antigens and construction of recombinant viruses.

The need to control animal populations arises in many situations in the world from a variety of motives. Present control strategies are almost universally based on lethal procedures. Increasingly, there is dissatisfaction with such approaches from many different perspectives. In response to these concerns, the concept of controlling populations of pest species through control of their fertility has been mooted. Successful examples of this approach exist in cases of small, discrete pest populations but application of this to a widely distributed species over a broad geographical area has not yet been achieved. In this article, we report on a new approach to fertility control, virus-vectored immunocontraception, and discuss its applicability to control of wild rabbit populations. Particular emphasis is placed on the strategy for selection of a target molecule capable of inducing an immunocontraceptive response and on how the gene encoding such a molecule might be engineered into the myxoma virus for distribution into the population. The fact that the procedures for antigen identification and the viral engineering methods used are, to varying extents, generic means that the broad principles of this approach are applicable in other species.

Animals↗
PubMed1994

Hantavirus pulmonary syndrome in California: report of two cases and investigation.

We report two cases of hantavirus pulmonary syndrome that were probably acquired in California. Genetic analysis of tissue specimens from one of the patients revealed that the virus isolated is a variant of the strain (Sin Nombre virus) identified in the outbreak of hantavirus pulmonary syndrome that occurred in the Four Corners region of the southwestern United States in 1993. In addition to presenting the clinical features of the two cases, we discuss the possible risk factors for infection.

Adult↗
PubMed1994

Dose-response assessment of airborne methyl isothiocyanate (MITC) following a metam sodium spill.

A tank car derailment in northern California in 1991 spilled metam sodium into the Sacramento River, and released its breakdown product, methyl isothiocyanate (MITC), into the air. This paper describes the risk evaluation process used. Over 240 individuals reported symptoms such as eye and throat irritation, dizziness, and shortness of breath. Reference exposure levels (RELs) for 1 hr were developed for MITC and compared to exposure concentrations. Ocular irritation in cats was the most sensitive endpoint reported. The no observed adverse effect level (NOAEL), divided by an uncertainty factor (UF) of 100, produced an REL of 0.5 ppb of MITC in air to prevent discomfort. An REL to prevent disability was estimated to be 40 ppb. An REL to prevent life-threatening injury was estimated to be 150 ppb. Measured MITC levels ranged from 0.2-37 ppb and estimated peak levels ranged from 140-1600 ppb. The usefulness of RELs for emergency planning is discussed.

Accidents↗
PubMed1994

Cell-associated collagenolytic activity by group B streptococci.

Group B streptococci (GBS) are important pathogens in neonatal sepsis, pneumonia, and meningitis. The ability of GBS to invade the collagen-rich amniotic membrane of the placenta has been shown in vitro. In the presence of GBS, the collagen fibrils of the amnion appear disordered, suggesting a role for GBS in premature rupture of membranes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Sephadex G-200 column chromatography, and gelatin zymograms were used in this study to characterize cell-associated collagenolytic activities of GBS. The synthetic peptide 2-furanacryloyl-Leu-Gly-Pro-Ala (FALGPA), which mimics the primary structure of collagen, was degraded by GBS USF704, a clinical isolate from the placenta of a septic newborn. Cells of GBS USF704 (9 x 10(7) CFU/ml) hydrolyzed 902 nmol of FALGPA over a 24-h period. As reported for zinc metalloenzymes such as collagenase, the hydrolysis of FALGPA by GBS was inhibited by addition of EDTA or 1,10-phenanthroline. Boiling of the cells resulted in loss of activity, while higher activity was observed with crude GBS cell lysates (hydrolysis of 970 nmol of FALGPA in 1.5 h). Antiserum raised against collagenase from Clostridium histolyticum was found to cross-react with cell-associated proteins produced by GBS and to inhibit GBS FALGPA hydrolysis. Twenty-five additional GBS clinical isolates were screened and found to have various levels of FALGPA hydrolytic activity. These observations suggest a cell-associated collagenolytic activity by GBS which may be involved in premature rupture of membranes and neonatal disease.

Amino Acid Sequence↗
PubMed1993

Helper T cell subsets for immunoglobulin A responses: oral immunization with tetanus toxoid and cholera toxin as adjuvant selectively induces Th2 cells in mucosa associated tissues.

Antigen-specific B cell responses to mucosally delivered proteins are dependent upon CD4-positive T helper (Th) cells, and the frequency of Th1 and Th2 cell responses after oral immunization may determine the level and isotype of mucosal antibody responses. We have used a protein-based vaccine, tetanus toxoid (TT), together with the mucosal adjuvant cholera toxin (CT), for oral immunization of mice to study the nature of antigen-specific Th cell subsets induced in Peyer's patches (PP) of the gastrointestinal (GI) tract and in the spleen (SP) during peak antibody responses. Mice orally immunized with TT and CT responded with antigen-specific secretory immunoglobulin A (S-IgA) antibodies in the GI tract, and with both IgG and IgA antibody responses in serum. PP and SP CD4+ T cells from mice orally immunized with TT plus CT were cultured with antigen-coated latex microspheres for induction of proliferative responses and for enumeration of cytokine producing CD4+ T cells. Interestingly, both PP and SP CD4+ T cell cultures showed increased numbers of IL-4- and IL-5 (Th2-type)-producing, spot-forming cells (SFCs) after 21 d of immunization, while essentially no interferon-gamma (IFN-gamma) or IL-2 (Th1-type) SFCs were noted. Cytokine-specific Northern blots and RT-PCR also revealed that significant IL-4 and IL-5 mRNA levels, but not IFN-gamma or IL-2 mRNA, were present in CD4+ T cells isolated from antigen-stimulated cultures. However, systemic immunization with TT and CT induced antigen-specific IgG and IgM but not IgA antibodies in serum. Further, both IL-2 and IFN-gamma-producing Th1-type cells as well as IL-4- and IL-5-secreting Th2-type cells were generated in SP. Our results show that oral immunization with TT and the mucosal adjuvant CT selectively induced antigen-specific Th2-type responses which may represent the major helper cell phenotype involved in mucosal IgA responses in the GI tract.

Administration, Oral↗
PubMed1993

Substitution mutations at the putative catalytic triad of the poliovirus 3C protease have differential effects on cleavage at different sites.

Picornavirus 3C proteases are substrate-specific cysteine proteases, proposed to be homologous to the trypsin/chymotrypsin-like serine proteases on the basis of structural predictions. Substitutions at the putative active-site residues (Glu71 and Cys147) of the poliovirus 3C protease did not completely abolish proteolytic processing in vitro. The activity of mutated 3C proteases was in the following hierarchy: Glu71-Cys147 (wild type) > Asp71-Cys147 > Glu71-Ser147 > Gln71-Cys147 > Asp71-Ser147 > Gln71-Ser147 (inactive at all sites). Such mutations had differential effects on cleavage at different sites of the poliovirus polyprotein. Cleavage within the P1 region of the polyprotein was the most defective, at the 1ABC/VP1 junction and particularly at the VP0/VP3 junction. Cleavage at the 3AB/3CD and 2B/2C junctions was less affected by the mutations, and the P2/P3 and 2A/2BC junctions were cleaved efficiently by all mutants except Gln71-Ser147. All the 3C mutants gave negative results in infectivity and replication assays after transfection, indicating that mutation of Glu71 or Cys147 virtually abolishes viral replication, irrespective of the efficiency of processing of the nonstructural part of the polyprotein.

3C Viral Proteases↗