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Biomedical subjects

K G Davey

Publications and source records attributed to K G Davey.

At least 19 recordsLinked to original sources
PubMed1999

Comparison of the API Candida system with the AUXACOLOR system for identification of common yeast pathogens.

Two commercial systems for the identification of yeasts were evaluated by using 159 clinical isolates that had also been identified by conventional biochemical and morphological methods. The API Candida system correctly identified 146 isolates (91.8%), and the AUXACOLOR system correctly identified 145 isolates (91.2%). However, of the 146 isolates identified by the API Candida system, 23 required supplemental biochemical tests or morphological assessment to obtain the correct identification. The AUXACOLOR system gave no identification in 13 cases (8.2%), while the API Candida system gave an unreadable profile in only one case. Incorrect identifications were more common with the API Candida system (12 isolates; 7.5%) than with the AUXACOLOR system (1 isolate; 0.6%).

Automation↗
PubMed1998

Identification and developmental expression of the mitochondrial phosphate transport protein gene from the spruce budworm, Choristoneura fumiferana.

Phosphate transport protein (PTP) is a mitochondrial inner membrane protein responsible for the translocation of inorganic phosphate into the mitochondrial matrix. A full length cDNA clone encoding the PTP was isolated from the spruce budworm, Choristoneura fumiferana. The deduced amino acid sequence of the longest ORF of CfPTP cDNA showed high similarity with the amino acid sequences of PTPs cloned from several species. Phylogenetic tree analysis indicated that CfPTP occupied an intermediate position between vertebrates on the one side and yeast and nematodes on the other side. Studies on the developmental expression of CfPTP mRNA showed that higher levels of mRNA were present during the feeding and growing stages than during molting periods.

Amino Acid Sequence↗
PubMed1998

The correlation of the visual field with scanning laser ophthalmoscope measurements in glaucoma.

PURPOSE: To assess the relationship between Humphrey visual field data and optic disc topographical data collected by the Heidelberg Retina Tomograph (HRT) scanning laser ophthalmoscope in chronic glaucoma patients. METHODS: The mean deviation (MD) and corrected pattern standard deviation (CPSD) from Humphrey visual fields of 106 eyes of 106 patients with glaucoma were analysed for correlation with the multiple topographical measures calculated by the HRT. RESULTS: Significant correlations were found between MD of the visual field and several optic disc measurements. These included neuroretinal rim volume, mean nerve fibre layer thickness and cross-sectional area, and the cup shape measure. CPSD correlated significantly only with mean nerve fibre layer cross-sectional area. This pattern was common to the whole circumference of the disc with the exception of the directly temporal segment. CONCLUSION: Optic disc topography performed by HRT reflects the optic disc pathology in correlation with perimetry.

Aged↗
PubMed1998

In-vitro susceptibility of Cryptococcus neoformans isolates to fluconazole and itraconazole.

The in-vitro susceptibilities of 143 isolates of Cryptococcus neoformans, collected from British patients between 1994 and 1996, to fluconazole and itraconazole were compared with those of 36 isolates collected between 1971 and 1985, 41 isolates collected between 1986 and 1989, and 43 Ugandan isolates collected in 1996. Testing was done with a broth microdilution method in YNB medium supplemented with glucose, incubation at 30 degrees C for 72 h, and an endpoint of 50% inhibition. The results showed that the MIC ranges, MIC50s and MIC90s of fluconazole and itraconazole for C. neoformans isolates from the UK have remained unchanged despite the recent widespread use of triazoles for long-term maintenance of patients with AIDS-associated cryptococcal meningitis. The MIC ranges, MIC50s and MIC90s of the 43 isolates from untreated Ugandan patients with AIDS were similar to those of the British isolates. Examination of our records for 1994-96 revealed six cases in which a four-fold or greater rise in the MIC of fluconazole was associated with relapsed cryptococcal meningitis.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Comparison of a new commercial colorimetric microdilution method with a standard method for in-vitro susceptibility testing of Candida spp. and Cryptococcus neoformans.

The Sensititre Yeast One method (AccuMed International Ltd, East Grinstead, UK) is a microplate-based procedure that incorporates an oxidation-reduction indicator, Alamar Blue, for the in-vitro testing of five antifungal agents (amphotericin B, fluconazole, itraconazole, ketoconazole and flucytosine). We compared this colorimetric method with a standard broth microdilution test, performed according to US National Committee for Clinical Laboratory Standards document M27-A guidelines, for determining the in-vitro susceptibilities of 180 isolates of Candida spp. (50 Candida albicans, 50 Candida glabrata, ten Candida kefyr, 20 Candida krusei, ten Candida lusitaniae, 20 Candida parapsilosis and 20 Candida tropicalis) and 20 isolates of Cryptococcus neoformans. The overall agreement between the results of the two methods (colorimetric MICs within +/- two log2 dilutions of standard MICs) were 99% for amphotericin B, 96.5% for flucytosine, 93% for itraconazole, 91.5% for fluconazole and 85.5% for ketoconazole. The overall levels of agreement between the two methods were > or = 94% for six of the eight species tested, the exceptions being C. neoformans and C. tropicalis where the overall agreement was 89% and 80% respectively. The poorest agreement between the results for individual agents was seen with C. tropicalis and the three azole agents (60-75% of colorimetric MICs within +/- two log2 dilutions of standard MICs), and C. neoformans for ketoconazole (50%). The Yeast One method appears to be a suitable alternative procedure for routine antifungal susceptibility testing of Candida spp. and C. neoformans.

Antifungal Agents↗
PubMed1998

Comparative evaluation of FUNGITEST and broth microdilution methods for antifungal drug susceptibility testing of Candida species and Cryptococcus neoformans.

The FUNGITEST method (Sanofi Diagnostics Pasteur, Paris, France) is a microplate-based procedure for the breakpoint testing of six antifungal agents (amphotericin B, flucytosine, fluconazole, itraconazole, ketoconazole, and miconazole). We compared the FUNGITEST method with a broth microdilution test, performed according to National Committee for Clinical Laboratory Standards document M27-A guidelines, for determining the in vitro susceptibilities of 180 isolates of Candida spp. (50 C. albicans, 50 C. glabrata, 10 C. kefyr, 20 C. krusei, 10 C. lusitaniae, 20 C. parapsilosis, and 20 C. tropicalis isolates) and 20 isolates of Cryptococcus neoformans. Overall, there was 100% agreement between the methods for amphotericin B, 95% agreement for flucytosine, 84% agreement for miconazole, 83% agreement for itraconazole, 77% agreement for ketoconazole, and 76% agreement for fluconazole. The overall agreement between the methods exceeded 80% for all species tested with the exception of C. glabrata (71% agreement). The poorest agreement between the results for individual agents was seen with C. glabrata (38% for fluconazole, 44% for ketoconazole, and 56% for itraconazole) and C. tropicalis (50% for miconazole). The FUNGITEST method misclassified as susceptible 2 of 12 (16.6%) fluconazole-resistant isolates, 2 of 10 (20%) itraconazole-resistant isolates, and 4 of 8 (50%) ketoconazole-resistant isolates of several Candida spp. Further development of the FUNGITEST procedure will be required before it can be recommended as an alternative method for the susceptibility testing of Candida spp. or C. neoformans.

Antifungal Agents↗
PubMed1996

Fenoxycarb and thyroid hormones have JH-like effects on the follicle cells of Locusta migratoria in vitro.

Earlier work had shown that JH acts on the membrane of the follicle cell of Locusta migratoria, bringing about a rapid reduction in volume which can be detected in vitro by measuring the increase in optical path difference using quantitative interference microscopy. The juvenoid fenoxycarb, a phenoxyphenyl derivative, is unrelated in structure to the juvenile hormones (which are derivatives of farnesoic acid), but it also caused a reduction in volume of the cells in vitro as measured by an increase in the optical path difference. The vertebrate hormone thyroxine, and thyronine, the non-iodinated derivative of thyroxine, also phenoxy phenyl compounds, evoked a response like fenoxycarb. The effect of thyroxine was abolished by ouabain, which inhibits Na+/K+ ATPase, the effector molecule for JH, and inhibited by ethoxyzolamide which inhibits the binding of JH to a putative membrane receptor. Triiodothyronine, the effective vertebrate hormone, acted at a lower threshold and optimum concentration, and had a greater magnitude of effect than the other compounds tested. These facts suggest that these phenoxyphenyl compounds are JH agonists and that the membrane receptor for JH may resemble a possible membrane receptor for thyroxine.

Animals↗
PubMed1995

Toxic gas generation from plastic mattresses and sudden infant death syndrome.

Microbial generation of toxic gases from antimony, arsenic, or phosphorus in compounds used as fire retardants in cot mattresses has been proposed as a cause of sudden infant death. To test this hypothesis, 23 polyvinyl chloride mattress samples from cot death cases were incubated on malt agar plates until good microbial growth was obtained. Silver nitrate and mercuric chloride test papers were then inserted and the colour reactions recorded. The predominant organism, recovered from all mattresses tested, was not, as claimed in earlier work, the fungus Scopulariopsis brevicaulis, but a mix of common environmental Bacillus spp. Test paper colour changes occurred whenever bacterial growth was present, but these reactions also occurred in control tests in which no mattress material was present on the plates. Chemical and instrumental analyses of exposed test papers showed that the colour reactions were not due to deposits of antimony, arsenic, or phosphorus. Our findings do not support the hypothesis that toxic gases derived from antimony, arsenic, or phosphorus are a cause of sudden infant death. More sulphur was found in test papers exposed in plates containing bacterial growth than in those without such growth. This result suggests that the test paper reactions were due to the generation of sulphur-containing compounds during bacterial growth on the agar medium.

Bacillus↗
PubMed1995

Itraconazole susceptibilities of fluconazole susceptible and resistant isolates of five Candida species.

The in-vitro susceptibilities of 1380 isolates of five Candida species were determined in order to establish whether isolates resistant to fluconazole were cross-resistant to itraconazole. IC50 values were determined by a broth microdilution method. 690 Candida albicans isolates, seven Candida glabrata isolates, seven Candida krusei isolates, 120 Candida parapsilosis isolates and 37 Candida tropicalis isolates were susceptible to both fluconazole (IC50 < or = 32 mg/L) and itraconazole (IC50 < or = 4 mg/L). Twenty eight of 160 C. albicans isolates (17.5%), 180 of 293 C. glabrata isolates (61.4%), six of 48 C. krusei isolates (12.5%), and 10 of 18 C. tropicalis isolates (55.5%) resistant to fluconazole (IC50 > or = 64 mg/L) were also resistant to itraconazole (IC50 > or = 8 mg/L). In contrast, drug-specific resistance to itraconazole was not observed in any of the isolates tested. However, the itraconazole IC50s for fluconazole susceptible isolates were lower than those for fluconazole resistant isolates, which suggests that patients who fail fluconazole treatment might require itraconazole at higher dosages than usual.

Antifungal Agents↗
PubMed1995

Evaluation of the AUXACOLOR system, a new method of clinical yeast identification.

AIMS: To compare the AUXACOLOR yeast identification system with the API 20C system. METHODS: Yeast isolates (n = 215), comprising 16 species, were identified using the AUXACOLOR system and the API 20C system. Isolates that could not be identified with the API 20C system or which produced discrepant results in the two systems were identified by assimilation and fermentation procedures. RESULTS: AUXACOLOR correctly identified 150 (85.7%) of 175 germ tube negative isolates while API 20C identified 155 (88.6%). Incorrect identifications were more common with API 20C (7.4%) than with AUXACOLOR (3.7%). Of 110 isolates of four common pathogens (Candida glabrata, C parapsilosis, C tropicalis, and Cryptococcus neoformans), 82.7% (91/110) were identified by AUXACOLOR while API 20C identified 74.5% (82/110). Of 65 less common germ tube negative isolates, 55.4% (36/65) were identified by AUXACOLOR while API 20C identified 63.1% (41/65). CONCLUSION: Although it has a limited database of 26 species, the AUXACOLOR system is a useful method for identification of germ tube negative clinical yeast isolates. Compared with the API 20C, the AUXACOLOR system is simpler and quicker to set up, easier to interpret, and comparable in cost.

Candida↗
PubMed1993

Osmoregulation in the parasitic nematode Pseudoterranova decipiens.

When subjected to hyper- or hypo-osmotic stress at 5 degrees C for 24 h, third-stage larvae of the parasitic nematode Pseudoterranova decipiens do not exhibit changes in mass or in the osmotic pressure of the pseudocoelomic fluid. Immersion in solutions containing 3H2O demonstrates that exchange with the water in the pseudocoelomic fluid is substantially complete within 24 h. Sacs composed of cylinders of body wall without the intestine and pseudocoelomic fluid do not gain weight when immersed for 24 h in hypotonic medium. Metabolic poisons abolish the ability of whole worms and sacs to maintain their weight when immersed in hypotonic media. These observations support the conclusion that the nematode is capable of at least short-term osmoregulation and that the site of osmoregulation is the body wall. The observations that more fluid is passed from the anus in some hypo-osmotically stressed worms and that worms ligatured at the tail exhibit a small increase in mass when exposed to hypo-osmotic conditions may indicate that the intestine plays a minor and subsidiary role in osmoregulation.

Anal Canal↗
PubMed1993

Water compartments and osmoregulation in the parasitic nematode Pseudoterranova decipiens.

A study of the time course of penetration of 3H2O into whole worms suggests that worms immersed in a hypo-osmotic environment (15% artificial sea water) reach full exchange equilibrium more slowly than worms in an iso-osmotic environment (40% artificial sea water). The apparent water content, determined by dry mass, matches that determined by 3H2O exchange when worms are immersed for 24 h in 40% artificial sea water (ASW), but the water content measured by 3H2O exchange is lower when worms are kept in a hypo-osmotic environment for 24 h. These differences disappear after 48 h. No such differences are apparent when sacs, consisting of cylinders of body wall lacking their intestines and pseudocoelomic fluid and closed at both ends by ligatures, are immersed in either 40% or 15% ASW for 24 h. The placing of ligatures at the head, but not at the tail, results in a failure of worms immersed in 40% ASW or 15% ASW containing 3H2O to achieve full exchange equilibrium within 24 h. These results suggest that although worms immersed in an iso-osmotic environment drink, those immersed in a hypo-osmotic environment do not, a conclusion supported by studies involving the addition of [14C]inulin to the medium. The application of ligatures to the head and tail of worms immersed in 40% ASW results in a slower penetration of 3H2O into the pseudocoelomic fluid, whereas similar ligatures do not further retard the penetration in worms exposed to 15% ASW. The results are consistent with a model which sees the pseudocoelomic fluid as consisting of two compartments containing water, one of which exchanges more slowly than the other.

Animals↗
PubMed1993

Stress-induced failure of osmoregulation in the parasitic nematode Pseudoterranova decipiens: indirect evidence for hormonal regulation.

When third-stage larvae of Pseudoterranova decipiens maintained at 5 degrees C are placed in either 40% artificial sea water (ASW, iso-osmotic) or 15% ASW (hypo-osmotic) and weighed once at 0 h and again at 24 h, they neither lose nor gain weight, and the osmotic pressure (OP) of their pseudocoelomic fluid (PCF) remains unchanged. In contrast, when worms are weighed six additional times during the 24 h interval, those maintained in isoosmotic conditions lose weight, while those maintained in hypo-osmotic conditions gain weight. Worms which had been exposed to hypo-osmotic conditions and weighed at various times between 0 and 24 h exhibited an increase in weight which was correlated with the number of weighings. Worms exposed to hypo-osmotic conditions and weighed three additional times between 0 and 24 h also gained weight, and the OP of the PCF decreased such that worms experiencing the greatest increase in weight suffered the greatest dilution of the PCF. In worms ligatured at the head or tail or at the head and tail, and then exposed to either 15% or 40% ASW, the effect of multiple weighings is exaggerated in a complex way. The presence of a ligature on the tail in worms immersed in an iso-osmotic medium leads to an increase in weight and to a very marked additional increase in weight in worms immersed in a hypo-osmotic medium. The presence of a head ligature in worms in an iso-osmotic medium leads to a decrease in weight and to a smaller weight gain in a hypo-osmotic medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A FMRFamide-like peptide is associated with the myotropic ovulation hormone in Rhodnius prolixus.

The protocerebral neurosecretory cells previously shown to be the source of the myotropin controlling ovulation in Rhodnius prolixus react in an immunocytochemical assay using an antiserum against FMRFamide. When the same antiserum was injected into fed mated females at the appropriate time the timing of oviposition was delayed, but the total number of eggs developed was unaffected compared to controls injected with pre-immune rabbit serum. The titer of FMRFamide-like peptide (assayed by RIA) in the hemolymph of mated and virgin females was found to fluctuate with the egg laying cycle, and to reflect earlier determinations of the titer of myotropic activity. Western blots of SDS-PAGE revealed a FMRFamide-immunoreactive peptide of approximately 8.5 kDa in both hemolymph and extracts of the ovulation hormone cells.

Animals↗
PubMed1992

Insulin-like immunoreactivity and molting in Rhodnius prolixus.

Two prominent cells were observed when fifth stage Rhodnius female larval brains were stained with anti-insulin serum. The staining intensity of these cells varied during the instar, being lowest on Day 1 and Days 5 and 6 after feeding. Injection of anti-insulin serum into 5th stage larvae immediately after feeding and on Days 4 and 5 in females and on Days 5 and 6 in males prevented molting. Control antiserum had no effect on the molting process. Injections at other times during the instar had no effect unless serum was injected just prior to ecdysis. Control or anti-insulin serum injected at this time disrupted normal ecdysis. These results are discussed in terms of the control of the developmental program of the insect.

Animals↗
PubMed1990

Morphology of the dorsal vessel in the abdomen of the blood-feeding insect Rhodnius prolixus.

The dorsal vessel (DV) in the abdomen of the blood-feeding insect Rhodnius prolixus was divided functionally into two regions, the heart, into which haemolymph entered the DV through four pairs of ostia located in abdominal segment VII, and the aorta, along which the haemolymph was propelled from abdominal segment VI to the thorax. Osmium-fixed whole mounts revealed the DV to consist of spirally arranged striated muscle fibers and to possess two rows of ventrally attached longitudinal fibers extending the length of the abdomen. Seven pairs of alary muscles were found attached to the DV in the posterior abdominal segments. Contractions of the alary muscles attached to the ventral surface of abdominal segments VII and VIII served to expand the heart. Electron microscopy revealed the DV to consist of a thin layer of contractile elements surrounded by an inner (intima) and outer (adventitia) connective tissue layer. Embedded in the intima along each lateral side of the DV were two large groups of endocardial cells extending the length of the DV. A small group of pericardial cells was embedded in the adventitia along the mid-ventral side of the DV, and clusters of pericardial cells were found attached to the alary muscles. Nerve terminals were found only on the heart: they contained agranular synaptic vesicles approximately 30 nm in diameter and densely stained granules approximately 100-120 nm in diameter. These structural components are discussed in relation to the role of the DV in circulation.

Abdomen↗