Search PubMed⌕ Search

Biomedical subjects

J Riley

Publications and source records attributed to J Riley.

At least 19 recordsLinked to original sources
PubMed1992

Effects of fluconazole on the sterol and carbohydrate composition of four species of Candida.

The effects of fluconazole, a bis-triazole antifungal agent, on the sterol and carbohydrate composition of Candida albicans, Candida tropicalis, Candida krusei and Candida parapsilosis were investigated. Exposure of Candida species to fluconazole resulted in a profound depletion of ergosterol with a corresponding increase in lanosterol content versus control cells. Carbohydrate analysis revealed a significant increase in chitin and either a decrease (Candida albicans, Candida tropicalis and Candida parapsilosis) or an increase (Candida krusei) in glucan content in fluconazole-treated cells. The decreased ergosterol and increased lanosterol content is consistent with 14-alpha-demethylase inhibition by fluconazole. The increase in cell wall chitin is most likely due to deregulation of chitin synthesis secondary to ergosterol depletion in the cell membrane. Because chitin, glucan and ergosterol are critical components of the fungal cell, perturbation of the production and localization of these components by fluconazole is likely to contribute to the selective toxicity of this compound to Candida species and other fungi.

Candida↗
PubMed1992

Preliminary characterization of the lipid and protein components of the protective surface membranes of a pentastomid Porocephalus crotali.

All instars of the pentastomid Porocephalus crotali, in the tissues of rat intermediate hosts and the lung of rattlesnake definitive hosts, are covered by a vesicular or stacked membranous secretory product which is synthesized in sub-parietal cells (SPC) and channelled to the cuticle via multitudinous chitin-lined ducts. In rats this enveloping foam of vesicles survives for the duration of a cuticle. We have purified and partially characterized the lipid and protein composition of lamellate droplets from SPC of infective nymphs. Lipids in the droplets comprised a mixture of neutral and polar lipid classes with cholesterol being the major neutral lipid and phosphatidylcholine the dominant polar lipid. In addition, Triton X-114 phase separation of the protein component of droplets partitioned these into an aqueous phase (with a major band at 60 kDa), a detergent phase with two hydrophobic polypeptides (24 and 16 kDa) and an insoluble pellet containing several minor proteins and major bands at 31 and 107 kDa. Western blotting, with rabbit anti-lamellate droplet antiserum, strongly label only the 60 kDa and the two hydrophobic proteins. Significantly no proteins at all label with serum from infected rats from 50-150 days post-infection, a finding endorsed by indirect fluorescent antibody tests on sectioned V-VII stage nymphs. Possible immunomodulatory functions of SPC-derived surface membranes are discussed and, in this regard, they are compared with pulmonary surfactant, a product of alveolar Type II cells which lines all vertebrate lungs.

Animals↗
PubMed1992

Sulfasalazine-induced fulminant hepatic failure.

We report two cases of massive hepatic necrosis associated with sulfasalazine. Both patients had underlying inflammatory bowel disease. One of the patients had a history of an ill-defined autoimmune disorder (Sjögren's syndrome). Symptoms and signs of a generalized hypersensitivity reaction were present in both patients. One patient died of a subarachnoid hemorrhage while awaiting transplant, the second died 2 weeks after transplant from disseminated aspergillosis. These two cases remind us of one of the potential hazards of sulfasalazine at a time when alternative therapies are now available.

Adult↗
PubMed1991

Sequence and transcriptional activity of the Escherichia coli K-12 chromosome region between rrnC and ilvGMEDA.

We previously identified a protein related to the expression of the ilvGMEDA cluster of Escherichia coli K-12. It was observed that this ilv-related protein was produced at higher levels in UV irradiated cells infected with lambda dilvGMEDA phage with specific ilvG mutations (ValR), compared to phage carrying the wild-type(ValS) ilvG allele. The gene encoding this protein was further localized to a region between rrnC and ilvGMEDA by analyzing restriction fragment subsets in maxicells. We have now determined the nucleotide (nt) sequence of the 3.5-kb segment between rrnC and ilvGMEDA, and two open reading frames (ORFs) are present in the region expected to contain the ilv-related gene. These ORFs predicts Mrs of 18,751 (ORFI) and 20,085 (ORFII) Da, and both ORFs have a strong probability to encode proteins based on codon frequency analysis. Maxicell analysis revealed that a 1319-bp HindIII-SmaI fragment containing ORFI encodes the ilv-related peptide. We deleted a ClaI fragment that removed a portion of ORFI encoding the C-terminal region of the peptide, and maxicell analysis revealed a decrease in the size of the protein produced in accord with the prediction. RNA slot blots and Northern blots were used to characterize transcripts encoding ORFI. A transcript initiated 112 nt from the ilvGp2 promoter, but proceeding in the opposite direction, may encode the ORFI peptide.

Amino Acid Sequence↗
PubMed1991

Isolation and preliminary characterization of a 48-kilodalton metalloproteinase from the excretory/secretory components of the frontal glands of Porocephalus pentastomids.

Porocephalid pentastomids possess prominent paired frontal glands which discharge secretion through large ducts onto the cuticle in the region of the cephalothorax. We have purified and partially characterized a 48-kDa protein with proteolytic activity from the major secretory cell type in the glands of Porocephalus crotali, removed from the tissues of rodent intermediate hosts. It comprises 30% of total protein isolated from secretory droplets. Antibody to the enzyme was detectable at 50 days post-infection in sera from infected hosts indicating in vivo release. Biochemical characterization has shown the enzyme is an elastase-like metallo proteinase with an alkaline pH dependency. In addition to the proteinase, 3 or 4 peptides (16-22.0 kDa) were visible in SDS-PAGE gels of gland cell proteins; on boiling, these peptides aggregated to 31 kDa. No antibody response to these peptides could be detected in infected hosts although they can be harvested from culture media following in vitro maintenance of the parasite. Possible immunomodulatory functions of these proteins are discussed. Preliminary data concerning frontal gland proteins of the related species Porocephalus clavatus are included for comparative purposes.

Animals↗
PubMed1991

Identification of CpG islands in a physical map encompassing the Friedreich's ataxia locus.

The Friedreich's ataxia locus has been previously assigned to chromosome 9q 13-21.1 by the demonstration of tight linkage to two anonymous DNA markers. MCT112 (Z greater than 80, theta = 0) and DR47 (Z greater than 50, theta = 0). The absence of recombination between these three loci has prevented the resolution of gene/probe order in this region, impeding strategies for gene isolation. We report physical mapping over a 4-Mb genomic interval, linking the markers MCT112 and DR47 on a common 460-kb NotI fragment and identifying 11 CpG islands in the 1.7-Mb interval most likely to contain the Friedreich's ataxia locus. Four of these islands were detected only by analysis of three YAC clones spanning a 700-kb interval including the MCT112/DR47 cluster. Without clear evidence of the precise location of the disease locus from recombination events, each of these regions must be considered as specifying a potential "candidate" sequence for the mutated gene.

Chromosome Mapping↗
PubMed1991

An ELISA for the detection of pentastomid infections in the rat.

A specific enzyme-linked immunosorbent assay, based on a 48 kDa metallo-proteinase isolated from the frontal glands of a porocephalid pentastomid (Porocephalus crotali) in rat intermediate hosts, is described. SDS-PAGE analysis of whole nymphal homogenate, followed by Western blotting and probing with immune rat serum, revealed that only 2 protein bands label consistently; these are the 48 kDa metallo-proteinase and a 150 kDa metallo-proteinase from the body fluid, but only the former labels strongly. Furthermore this response is detected earlier and persists much longer. These characteristics uniquely qualify the 48 kDa metallo-proteinase as a diagnostic antigen. We review the literature concerning the related porocephalid Linguatula serrata from the nasal cavities of domestic dogs, which can zoonotically infect man principally through the ingestion of eggs. We conclude that the high prevalences in dogs in certain areas, most notably the Middle East, must inevitably signal significant human infections. Our ELISA can be readily adapted for the serodiagnosis of linguatulosis and this should establish whether our prediction is true.

Animals↗
PubMed1991

The isolation and culture of DHBV-infected embryo and duckling hepatocytes and the effect of aflatoxin B1 or irradiation on these cells.

The preparation of primary cultures of control and DHBV-infected duck hepatocytes from embryos and young ducklings is described. Cultures of both embryo and duckling hepatocytes secreted duck serum proteins. Cultures of hepatocytes established from ducklings maintained initial morphology for up to 3 weeks in culture and also exhibited high levels of metabolism of aflatoxin B1. Embryonic cell cultures rapidly lost ability to metabolise AFB1 and became overgrown by spindle-shaped cells. Both embryo and duckling cell cultures secreted infective DHBV, and had intracellular replicative forms of the virus. No integration of the virus into the duck genome was observed, and attempts to induce viral integration in the duckling hepatocytes using irradiation and aflatoxin B1 toxicity were unsuccessful. The results of the study lend further support to the suggestion that the rarity of liver cancer in DHBV-infected experimental ducks is related to an innate resistance of the hepatocytes to develop DHBV-DNA integration. Another possibility may be related to the lower oncogenic potential of the DHBV strain used for the study. However DHBV infected duckling hepatocytes would appear to offer a suitable material for studying viral replication and mechanisms of aflatoxin B1 toxicity during prolonged cell culture.

Aflatoxin B1↗
PubMed1991

Safe harbor regulations are official, but provide little room to anchor.

In summary, the safe harbor regulations, while welcome in certain instances, do not provide a great deal of comfort or assurance with regard to investments by referrers such as physicians, or in ventures between providers and potential referrers. Individuals in relationships not covered by the safe harbors should at least reexamine those relationships and evaluate the risk involved in continuing in the relationship.

Fraud↗
PubMed1990

Isolation of cDNA clones using yeast artificial chromosome probes.

The cloning of large DNA fragments of hundreds of kilobases in Yeast artificial chromosomes, has simplified the analysis of regions of the genome previously cloned by cosmid walking. The mapping of expressed sequences within cosmid contigs has relied on the association of genes with sequence motifs defined by rare-cutting endonucleases, and the identification of sequence conservation between species. We reasoned that if the contribution of repetitive sequences to filter hybridizations could be minimised, then the use of large cloned DNAs as hybridisation probes to screen cDNA libraries would greatly simplify the characterisation of hitherto unidentified genes. In this paper we demonstrate the use of this approach by using a YAC, containing 180 kb of human genomic DNA including the aldose reductase gene, as a probe to isolate an aldose reductase cDNA from a lambda gt11 human foetal liver cDNA library.

Aldehyde Reductase↗
PubMed1990

A novel, rapid method for the isolation of terminal sequences from yeast artificial chromosome (YAC) clones.

The recent development of yeast artificial chromosome (YAC) vectors has provided a system for cloning fragments that are over ten times larger than those that can be cloned in more established systems. We have developed a method for the rapid isolation of terminal sequences from YAC clones. The YAC clone is digested with a range of restriction enzymes, a common linker is ligated to the DNA fragments and terminal sequences are amplified using a vector specific primer and a linker specific primer. Sequence data derived from these terminal specific products can be used to design primers for a further round of screening to isolate overlapping clones. The method also provides a convenient method of generating Sequence Tagged Sites for the mapping of complex genomes.

Base Sequence↗
PubMed1990

Polyamine depletion and growth inhibition of Cryptococcus neoformans by alpha-difluoromethylornithine and cyclohexylamine.

The ability of two known inhibitors of polyamine synthesis alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase (ODC), and cyclohexylamine, an inhibitor of spermidine synthase, to inhibit the in vitro growth and polyamine synthesis of clinical isolates of Cryptococcus neoformans was examined. Treatment of C. neoformans with either DFMO or cyclohexylamine resulted in depletion of cellular polyamines and inhibition of growth. Cryptococcus neoformans was shown to lack detectable spermine and to require high concentrations of spermidine, but not putrescine, for growth. The growth inhibition by DFMO and cyclohexylamine was reversed by exogenous polyamines. These findings document the ability of cyclohexylamine and DFMO to inhibit polyamine synthesis and growth in clinically important isolates of C. neoformans.

Cryptococcus neoformans↗