Biomedical subjects

Frank C Odds

Publications and source records attributed to Frank C Odds.

42 records · Page 3Linked to original sources

PubMed2002

Efficacy of parenteral itraconazole against disseminated Candida albicans infection in two mouse strains.

The efficacy of a new cyclodextrin intravenous formulation of itraconazole was evaluated by intraperitoneal treatment of experimental disseminated Candida albicans infections in BALB/c and DBA/2 mice. Mice were treated with doses of 5 or 20 mg/kg for 14 days and observation was continued for 28 days. Mice were randomly assigned to groups given either water or grapefruit juice as drinking fluid, since components of grapefruit juice that inhibit cytochrome P450 enzymes might influence the pharmacokinetic behaviour of itraconazole. The experiments showed that the itraconazole/cyclodextrin solution unequivocally prolonged survival and reduced weight loss over the first 4 days post-challenge, relative to placebo-treated control animals, in both mouse strains. However, the antifungal treatments did not reduce burdens of C. albicans in kidneys or brain. Placebo-treated DBA/2 mice given grapefruit juice to drink had a significantly shorter mean survival time than the equivalent group given water. In BALB/c mice the placebo-treated animals given grapefruit juice survived longer, though not significantly longer, than placebo-treated animals given water. These results give a preliminary hint that grapefruit juice alters the susceptibility of some mouse strains to C. albicans infection, regardless of any effects or non-effects it may have on itraconazole pharmacokinetics in the animals.

Animals↗

PubMed2002

Influence of grapefruit juice on itraconazole plasma levels in mice and guinea pigs.

Levels of itraconazole and its metabolite hydroxy-itraconazole were measured by HPLC in plasma samples from guinea pigs and DBA/2 and BALB/c mice after oral or intraperitoneal treatment with itraconazole/cyclodextrin solution at 5 and 20 mg/kg daily for 7 days. The animals were randomly assigned to receive grapefruit juice or drinking water in their fluid bottles, since components of grapefruit juice have been found to alter the pharmacokinetic behaviour of pharmaceuticals that interact with cytochrome P450 enzymes. The results demonstrated clear differences in itraconazole pharmacokinetics between the three animal types studied. The total levels of antifungally active azole were highest in DBA/2 mice and lowest in guinea pigs, regardless of the route of administration. Guinea pigs that drank grapefruit juice had higher plasma levels of azoles after oral administration of the drug, but the juice did not influence levels of itraconazole or its metabolite in guinea pigs treated intraperitoneally, or in either mouse strain treated orally or intraperitoneally. This result indicates that grapefruit juice effects on the pharmacokinetics of itraconazole are species dependent and confined to the gastrointestinal tract, influencing drug absorption. Differences in itraconazole pharmacokinetics between mouse strains need to be considered in the design of experiments involving itraconazole treatment of mice experimentally infected with fungi.

Administration, Oral↗

PubMed2000

Single allele knock-out of Candida albicans CGT1 leads to unexpected resistance to hygromycin B and elevated temperature.

Almost all eukaryotic mRNAs are capped at their 5'-terminus. Capping is crucial for stability, processing, nuclear export and efficient translation of mRNA. We studied the phenotypic effects elicited by depleting a Candida albicans strain of mRNA 5'-guanylyltransferase (mRNA capping enzyme; CGT1). Construction of a Cgt1-deficient mutant was achieved by URA-blaster-mediated genetic disruption of one allele of the CGT1 gene, which was localized on chromosome III. The resulting heterozygous mutant exhibited an aberrant colony morphology resembling the 'irregular wrinkle' phenotype typically obtained from a normal C. albicans strain upon mild UV treatment. Its level of CGT1 mRNA was reduced two- to fivefold compared to the parental strain. Proteome analysis revealed a large number of differentially expressed proteins confirming the expected pleiotropic effect of CGT1 disruption. The disrupted strain was significantly more resistant to hygromycin B, an antibiotic which decreases translational fidelity, and showed increased resistance to heat stress. Proteome analysis revealed a 50-fold overexpression of Ef-1alphap and a more than sevenfold overexpression of the cell-wall heat-shock protein Ssa2p. Compared to a reference strain, the cgt1/CGT1 heterozygote was equally virulent for mice and guinea pigs when tested in an intravenous infection model of disseminated candidiasis.

Alleles↗

PubMed2000

Survival in experimental Candida albicans infections depends on inoculum growth conditions as well as animal host.

Evidence is presented that the growth medium used to prepare a Candida albicans challenge inoculum is a significant factor determining the ability of a fungus strain to gain an initial invasive hold immediately after injection into an animal host, and thus determining gross strain lethality. Three C. albicans strains, one known to be attenuated in virulence, were grown in two broth media and injected intravenously at different doses into female NMRI mice and male albino guinea pigs. For each fungus strain and challenge dose, survival was longer from inocula grown in a diluted, buffered peptone-based broth than from inocula grown in Sabouraud glucose broth. When animals were challenged intravenously with yeast doses adjusted to give the same mean survival time regardless of strain or growth medium, the progression of fungus tissue burdens (c. f.u. g(-1)) in kidneys, lungs, liver, spleen and brain samples was broadly similar for all three C. albicans strains but differed between the two animal hosts. The morphological form of C. albicans recovered from infected tissues differed at the level of both the fungus strain and the host tissue. Use of survival-standardized inocula provides a means of distinguishing differences in progression of experimental disseminated Candida infections that are related to the infecting strain from those related to the animal host.

Animals↗

PubMed1999

Contribution of mutations in the cytochrome P450 14alpha-demethylase (Erg11p, Cyp51p) to azole resistance in Candida albicans.

The cytochrome P450 14alpha-demethylase, encoded by the ERG11 (CYP51) gene, is the primary target for the azole class of antifungals. Changes in the azole affinity of this enzyme caused by amino acid substitutions have been reported as a resistance mechanism. Nine Candida albicans strains were used in this study. The ERG11 base sequence of seven isolates, of which only two were azole-sensitive, were determined. The ERG11 base sequences of the other two strains have been published previously. In these seven isolates, 12 different amino acid substitutions were identified, of which six have not been described previously (A149V, D153E, E165Y, S279F, V452A and G4655). In addition, 16 silent mutations were found. Two different biochemical assays, subcellular sterol biosynthesis and CO binding to reduced microsomal fractions, were used to evaluate the sensitivity of the cytochromes for fluconazole and itraconazole. Enzyme preparations from four isolates showed reduced itraconazole susceptibility, whereas more pronounced resistance to fluconazole was observed in five isolates. A three-dimensional model of C. albicans Cyp51p was used to position all 29 reported substitutions, 98 in total identified in 53 sequences. These 29 substitutions were not randomly distributed over the sequence but clustered in three regions from amino acids 105 to 165, from 266 to 287 and from 405 to 488, suggesting the existence of hotspot regions. Of the mutations found in the two N-terminal regions only Y132H was demonstrated to be of importance for azole resistance. In the C-terminal region three mutations are associated with resistance, suggesting that the non-characterized substitutions found in this region should be prioritized for further analysis.

Amino Acid Sequence↗

PubMed1999

Distribution of chitinase in guinea pig tissues and increases in levels of this enzyme after systemic infection with Aspergillus fumigatus.

Intravenous infection of guinea pigs with the fungus Aspergillus fumigatus resulted in increased levels of chitinase in serum and tissues of the animals. The molecular properties of the enzyme were demonstrated to be different from those of the fungal chitinase, but also from guinea pig lysozyme and beta-N-acetylhexosaminidase. Bio-Gel P-100 gel filtration showed that in liver, spleen, heart and lung tissue of control animals there were two molecular mass forms present with apparent molecular masses of 35 kDa and 15 kDa. In brain and serum, only the 35 kDa form was detectable. Kidney showed only the 15 kDa form. Upon infection the 35 kDa form appeared in kidney and increased in the other tissues. When a less pathogenic form of the fungus was used the 35 kDa form remained absent in kidney. In contrast to human serum chitinase, the enzyme from guinea pig serum and tissues did bind to concanavalin A-Sepharose. This was the case for both molecular mass forms. The mode of cleavage of the substrate 4-methylumbelliferyl-tri-N-acetylchitotrioside (MU-[GlcNAc]3, where GlcNAc is N-acetylglucosamine) by the two forms of the enzyme was the same: both [GlcNAc]2 and [GlcNAc]3 were released. The chitinase activity levels in the control tissues showed a large variation in this order: spleen > lung, kidney > liver > heart > brain. The fact that spleen showed the highest chitinase level is in agreement with its major role as a lymphoid organ in cases of systemic infections. The relative increases upon infection were the highest for the tissues that showed low control values.

Acetylglucosamine↗