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Biomedical subjects

R C Thompson

Publications and source records attributed to R C Thompson.

At least 271 records · Page 15Linked to original sources
PubMed1990

Recombinant human secretory leukocyte-protease inhibitor: in vitro properties, and amelioration of human neutrophil elastase-induced emphysema and secretory cell metaplasia in the hamster.

Studies were undertaken to evaluate the in vitro properties of recombinant human secretory leukocyte-protease inhibitor (rSLPI) that had been made in Escherichia coli in an inactive form and refolded, and to determine whether emphysema and bronchial secretory cell metaplasia, induced in hamsters by intratracheal treatment with human neutrophil elastase (HNE), could be amelio-rated by prior intratracheal instillation of rSLPI. Chromatographic studies indicated that 3H-rSLPI formed a 1:1 complex with HNE. Blockage of the active site of HNE by a covalently bound tetrapeptide chloromethyl ketone reduced complex formation with 3H-rSLPI by more than 98%. Incubation of 3H-rSLPI-HNE complex with alpha 1-protease inhibitor for 3 hours at 37 degrees C decreased the amount of complex compared with incubation in the presence of bovine serum albumin (70% vs 27% dissociated). The calculated dissociation rate constant was 1.1 x 10(-4) sec-1, indicating a 1.8 hour dissociation half-life. Dissociated 3H-rSLPI retained its ability to recombine with HNE. rSLPI was as effective at inhibiting HNE released from stimulated neutrophils as 3H-rSLPI was at inhibiting purified HNE. Intratracheal pretreatment of hamsters with 3000 micrograms of rSLPI as long as 8 hours before the intratracheal instillation of 250 micrograms of HNE, resulted in significant protection against induction of emphysema and secretory cell metaplasia. One and 4 hours after instillation of rSLPI, 59% and 44%, respectively, of the initial functional activity was recovered in lung lavage supernatant, indicating a half-life of approximately 2 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Uniform strobilar development of Echinococcus multilocularis in vitro from protoscolex to immature stages.

The aim of this study was to obtain uniformity in strobilar development of Echinococcus multilocularis from protoscoleces in vitro. The isolate of E. multilocularis used was derived initially from a human case in France and subsequently maintained in the laboratory by intraperitoneal passage in Meriones unguiculatus. Protoscoleces used for culture were obtained using preparative procedures in which parasite tissue was disrupted gently with minimal exposure to pepsin and acidic conditions followed by immediate exposure to pancreatin in alkaline solution. Resultant cultures contained large numbers of evaginated, active, vermiform stages, which exhibited uniform strobilar development with formation of the first proglottid and segment and limited maturation of the first proglottid. All worms that exhibited proglottization subsequently segmented. Further proglottization did not occur and all worms degenerated within a few days following segmentation. The results are discussed in light of current knowledge of the relationships of somatic and germinal processes in Echinococcus. In view of these results, further studies should be encouraged to improve strobilar development of E. multilocularis in vitro.

Animals↗
PubMed1990

A contribution to the etiology of racemose cysticercosis.

An aberrant case of proliferating coenurosis caused by Taenia serialis in immunosuppressed mice is described. The coenuri closely resembled examples of racemose cysticerci described in the literature and the present results are discussed with reference to human cases of asexually proliferating larval cestode infections.

Animals↗
PubMed1989

An IL-1 inhibitor from human monocytes. Production and characterization of biologic properties.

Previous studies have described a 22 kD IL-1 inhibitor in the supernatant of human monocytes cultured on adherent immune complexes (J. Immunol. 134:3868, 1985). The studies reported herein further detail the conditions of production and biological properties of this IL-1 inhibitor. The inhibitor was produced by human monocytes cultured on adherent human IgG with maximal production between 8 and 24 hr. The IL-1 inhibitor was not performed in the cells but required transcription and new protein synthesis. The inhibitor blocked IL-1 augmentation of PHA-induced murine thymocyte proliferation but not IL-2-induced stimulation of CTLL or HT-2 cell lines. In addition, the inhibitor blocked IL-1-stimulated collagenase production from rabbit articular chondrocytes and IL-1-induced PGE2 production from human fibroblasts and synovial cells. The IL-1 inhibitor was not transforming growth factor beta (TGF beta) as determined by: the failure of anti-TGF beta antibodies to reduce IL-1 inhibitory activity, the separation of TGF beta from the IL-1 inhibitor by ion exchange chromatography, and the failure of TGF beta to inhibit IL-1-induced PGE2 production from synovial cells. IL-1 and the inhibitor showed no immunological cross-reactivity by Western blot analysis. The inhibitor specifically blocked binding of IL-1 to its receptor on the murine thymoma cell line EL4-6.1. These results indicate that a specific inhibitor of IL-1-induced immune and inflammatory cell responses is produced by monocytes cultured on adherent immune complexes or adherent IgG. This IL-1 inhibitor may be of importance in modulating the effects of IL-1 in the monocyte microenvironment.

Binding, Competitive↗
PubMed1989

Echinococcus granulosus of camel origin: development in dogs and parasite morphology.

The developmental characteristics of Echinococcus granulosus of camel origin were studied in four dogs artificially infected with protoscolices originating from hydatid cysts isolated from the lung of a camel (Camelus dromedarius). Two dogs each were necropsied 34/35 and 41 days post-infection (p.i.); one dog had a low worm burden and the others were heavily infected (27,625-41,150 worms). At day 35 p.i., 20% of the parasites had developed three segments and the uterus of the vast majority of the total population was full of developing eggs in the terminal segment. At day 41, up to 58% of the parasites contained mature eggs (embryonated eggs with fully developed, "thick-shelled" embryophores). Morphological studies revealed the following major characteristics for 35 day-old worms: the mean length of the terminal segment accounted for 54% of the total worm length; the position of the sexually mature segment was always terminal; the female reproductive system possessed an elongated ovary with compact lobules; the female ducts were also compact; the Mehlis' gland was covered by the vitelline gland and the testes were distributed throughout the segment, with 1 row posterior to the vitelline gland. The camel isolate can readily be distinguished from the horse and sheep strains, but it is similar to the cattle strain in some respects, particularly in its precocious development. However, the camel isolate differs from the cattle strain in the position of the sexually mature segment, arrangement of the testes and structure of the female reproductive system. As in the cattle strain, the metacestodes in the principal intermediate host are mostly localised in the lung and have a high fertility rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Genetic differences between cysts of Echinococcus granulosus from the same host.

Isozyme differences were found between protoscoleces derived from different cysts in three sheep and three macropod marsupials. Isozymes were interpreted as the products of different alleles at corresponding enzyme loci, indicating that the same host may contain cysts derived from genetically different embryos. Genetic variation on this scale may cause confusion in epidemiological studies, if protoscoleces from several cysts are pooled prior to strain-typing.

Alleles↗
PubMed1989

Comment on the status of Echinococcus granulosus in the UK.

Echinococcus granulosus is composed of a complex of strains, the status of which has caused controversy and doubt. All have different characteristics which have arisen from animal husbandry practices, resulting in isolation and restriction of gene flow, and/or from the reproductive characteristics of the organisms. Whatever the mechanism for strain variation, Don McManus, Alan Lymbery and Andrew Thompson have no doubts that distinct variants occur in spite of a recent publication that suggests there is only one form of E. granulosus in the UK.

Journal Article↗
PubMed1989

Codon choice and gene expression: synonymous codons differ in translational accuracy.

Ribosomes programmed by different synonymous codons also differ in discriminating among near-cognate aminoacylated tRNAs. In the initial step of the recognition reaction ribosomes programmed by UUC discriminate less well than ribosomes programmed by UUU against ternary complexes containing three types of Leu-tRNA, and ribosomes programmed by CUC discriminate less well than ribosomes programmed by CUU against ternary complexes containing Phe-tRNA. Furthermore, in the proofreading step ribosomes programmed by UUC discriminate less well than ribosomes programmed by UUU against two of three near-cognate Leu-tRNAs, and ribosomes programmed by CUC discriminate less well than ribosomes programmed by CUU against near-cognate Phe-tRNA. The codon-induced change in reaction rate with near-cognate ternary complexes is greater than that with cognate ternary complexes: the most efficient codon is, therefore, the least accurate. Because the efficient, but inaccurate, codon UUC is used preferentially in highly expressed mRNAs of Escherichia coli, maximization of translational accuracy apparently has not been significant in the evolution of this particular biased codon choice in E. coli.

Anticodon↗
PubMed1989

Secretory leukocyte protease inhibitor binding to mRNA and DNA as a possible cause of toxicity to Escherichia coli.

The expression of the positively charged human protein secretory leukocyte protease inhibitor (SLPI) in Escherichia coli causes severe cellular toxicity. After induction of SLPI synthesis in a high-level-expression strain, SGE61, the growth of the strain is arrested and total protein and RNA synthesis rates decline by 60 to 70%. The mechanism of SLPI-mediated inhibition of macromolecular synthesis was examined in cell-free transcription-translation systems. SLPI proved to be a potent inhibitor of translation in vitro. When SLPI was added to translation reactions at SLPI/mRNA ratios attained during maximal SLPI accumulation in SGE61, translation of a test mRNA was inhibited by 75%. The mechanism of translation inhibition was deduced from in vitro experiments showing that SLPI bound to mRNA and interfered with the interaction of RNA-metabolizing enzymes, such as RNase. In addition, SLPI bound to DNA in vitro, but transcription was not inhibited as strongly in cell-free reactions as it was in SGE61. Similar nucleic acid-binding and translation inhibition properties were displayed in vitro by another basic protein, chicken egg white lysozyme, but were not displayed by the relatively acidic protein bovine serum albumin. On the basis of these results, we concluded that SLPI binds to nucleic acids via charge interactions and inhibits translation by competing with ribosomes for binding to mRNA. Since SLPI-mRNA and SLPI-DNA binding occurred at SLPI/mRNA and SLPI/DNA ratios existing in SGE61, nucleic acid binding may contribute to the toxicity of SLPI to E. coli. These results indicate that, in general, high-level expression of basic recombinant proteins in E. coli may be problematic.

Bacterial Proteins↗
PubMed1989

Isolation and sequence analysis of cDNA for rat carboxypeptidase E [EC 3.4.17.10], a neuropeptide processing enzyme.

Carboxypeptidase E (CPE) is the carboxypeptidase B-like enzyme associated with the biosynthesis of numerous peptide hormones and neurotransmitters. This enzyme has been previously purified to homogeneity from bovine tissues, and cDNA clones (non-full length) isolated from a bovine pituitary cDNA library. In the present study, cDNA encoding full-length rat CPE has been isolated and sequenced. Both the nucleotide and amino acid sequences of rat CPE show substantial homology with the bovine sequences. The bovine and rat nucleotide sequences are homologous within the entire coding region, as well as within several portions of the 3'-untranslated region. The predicted amino acid sequence of rat CPE is greater than 90% homologous with the bovine enzyme. Northern blot analyses indicate a single species of CPE mRNA approximately 2100 nucleotides in length to be present in many neural and endocrine tissues. High levels of CPE mRNA are present in rat hypothalamus, hippocampus, midbrain, striatum, and cerebral cortex; and moderate levels are present in the brain stem, cerebellum, heart, adrenal, and eye. Low levels are detected in testis and duodenum, but not in liver or thymus. This tissue-specific expression of CPE mRNA is consistent with the proposed role for this enzyme in the production of numerous peptide hormones and neurotransmitters.

Adrenal Glands↗
PubMed1989

Local administration of human pancreatic secretory trypsin inhibitor prevents the development of experimental acute pancreatitis in rats and dogs.

The objective of this investigation was to test the capacity of recombinant human pancreatic secretory trypsin inhibitor (rhPSTI) to provide prophylaxis against experimental pancreatitis. Acute hemorrhagic pancreatitis was induced by intraductal injection of sodium taurocholate in rats and by intraductal injection of bile in dogs. In one treatment group of rats the injection of taurocholate was preceded by injection of rhPSTI. In a second group of rats the rhPSTI was given intraperitoneally starting 15 min after the induction of acute pancreatitis. The survival rate in a control group of rats was 13%. In contrast, the survival rate in groups receiving rhPSTI intraductally or intraperitoneally was 80% and 63%, respectively. The survival rate in a control group of dogs was 40% at 24 h and 0% at 48 h. In contrast, all the dogs receiving a single intraductal dose of rhPSTI, either immediately before the bile injection or mixed with the bile, survived for up to 6 weeks. Detailed biochemical and immunohistologic studies in the dog indicate that, whereas rhPSTI cannot prevent the initial bile-induced injury, it does prevent the subsequent development of that injury to the point where there is massive damage to the pancreas and the surrounding tissues, and changes in blood chemistry. The development of the initial injury is, therefore, presumed to involve activation of trypsinogen. Since rhPSTI prevents the serious consequences of experimental pancreatic injury by blocking the action of trypsin, and since the pathobiochemistry of human acute pancreatitis also implies an important role for trypsin, it is possible that rhPSTI could protect humans from the pancreatitis that complicates endoscopic retrograde cholangiopancreatography and endoscopic papillotomy.

Acute Disease↗
PubMed1989

Characterization of Giardia isolates using a non-radiolabeled DNA probe, and correlation with the results of isoenzyme analysis.

Forty-seven isolates, identified morphologically as Giardia duodenalis, were compared by restriction endonuclease analysis of DNA with hybridization to a non-radiolabeled probe. Seven schizodemes were distinguished, compared to 15 zymodemes identified by isoenzyme electrophoresis. Despite the greater sensitivity of isoenzyme electrophoresis, DNA analysis did detect previously unsuspected variations between isolates in 1 zymodeme. Eighteen different genetic groups were detected among the 49 isolates by isoenzyme and DNA analyses. Genetic differences between groups, calculated from DNA restriction fragment variation, were significantly correlated with differences calculated from allozyme variation. This correlation between the 2 techniques suggests that G. duodenalis consists of a complex of genetically diverse clones. Such a genetic structure has important implications for the taxonomy of Giardia and the epidemiology of giardiasis.

Animals↗