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Biomedical subjects

P T Holland

Publications and source records attributed to P T Holland.

15 recordsLinked to original sources
PubMed2006

Changes in concentrations of microcystins in rainbow trout, freshwater mussels, and cyanobacteria in Lakes Rotoiti and Rotoehu.

Microcystin concentrations in cyanobacteria and their accumulation in rainbow trout (Oncorhynchus mykiss) and freshwater mussels (Hyridella menziesi) in Lakes Rotoiti and Rotoehu (New Zealand) were investigated. Hatchery rainbow trout were added to an enclosure in Lake Rotoiti where concentrations of microcystins in the phytoplankton and cyanobacterial cell concentrations could be closely monitored. Rainbow trout that were free to roam in the entire area of each lake were also included in the study. Freshwater mussels were suspended subsurface in cages in the enclosure. Phytoplankton samples, rainbow trout liver and muscle tissue, and the tissues of mussels were analyzed for microcystins using the ADDA-ELISA method, and selected samples were analyzed using LC-MS. A maximum concentration of microcystins in the phytoplankton samples of 760 microg L(-1) was recorded in Te Weta Bay, Lake Rotoiti, in March 2004. ELISA results confirmed microcystin immunoreactivity in rainbow trout liver and muscle tissues and in freshwater mussels. The microcystin congeners LR, YR, RR, AR, FR, LA, and WR were detected by LC-MS in caged freshwater mussels in Lake Rotoiti but were not detected in either muscle or liver tissue of rainbow trout. The daily tolerable intake limit of microcystins for human consumption recommended by the World Health Organisation is 0.04 microg kg(-1) day(-1). Modeling was carried out for the human intake of microcystin compounds from rainbow trout muscle tissue, and the potential health risks were estimated, assuming the ADDA-ELISA was determining compounds of toxicity equivalent to microcystin-LR.

Animals↗
PubMed1996

Ruakuric acid: a natural product from Aspergillus fumigatus.

A new chroman derivative, named ruakuric acid, was isolated from a strain of Aspergillus fumigatus growing in conjunction with a coral lichen. The structure was determined as 6-acetyl-5-hydroxy-4-methoxy-chroman-2-carboxylic acid (mixture of 2,4-cis,trans isomers).

Aspergillus fumigatus↗
PubMed1994

Contribution of dialysis to endogenous oxalate production in patients with chronic renal failure.

We tested the possibility that the buffering agents in dialysis bath fluid might contribute to increased endogenous oxalate production in dialyzed patients. Using stable isotope dilution mass spectrometry, we obtained oxalate production rates and pool sizes directly for 10 patients in chronic renal failure, 5 of whom were undergoing continuous ambulatory peritoneal dialysis (lactate-buffered fluid). All peritoneal dialysis patients had either increased oxalate production rates or expanded oxalate pools when compared with undialyzed patients in renal failure. From a further four patients receiving maintenance hemodialysis we took blood samples immediately before and after three consecutive dialysis sessions in which the bath-fluid buffering agent (bicarbonate or acetate) was alternated; we analyzed these samples for oxalate and key precursors by capillary gas chromatography. Plasma glycine and serine concentrations remained within the physiological range. Glycolate and oxalate concentrations decreased, but the oxalate remained above normal after dialysis. All changes were independent of the bath-fluid buffering agent. We suggest that dialysis might stimulate the formation of oxalate by removing product inhibition of a late catabolic step.

Acetates↗
PubMed1988

Measurement of plasma oxalate by capillary gas chromatography and its validation by isotope dilution mass spectrometry.

A capillary gas chromatographic method for plasma oxalate and an isotope dilution mass spectrometric reference method, both using the same tert.-butyldimethylsilyl derivatives, are described. Similar reference ranges for both were found (4.93 +/- 1.48 and 4.70 +/- 1.44 mumol/l, respectively), together with a close correlation for results covering a wide range of oxalate concentrations.

Carbon Radioisotopes↗
PubMed1988

Mass spectrometry.

Explore the source record for details and available documents.

Mass Spectrometry↗
PubMed1988

Carcinogenicity of bracken fern (Pteridium esculentum) in New Zealand.

Bracken fern (Pteridium esculentum) was harvested from two sites LB and TB one of which (TB) was on a central North Island New Zealand farm where bovine enzootic haematuria (BEH) was known to occur. The fern was dried, ground and incorporated (25% w/w) into a pelleted diet and fed to female rats for a total of 162 days. Fifteen weeks later when the rats were autopsied it was found that numerous tumours, mainly of the ileum and urinary bladder were present in the animals fed the bracken fern from the TB site. Neoplasms were found in 85% of rats from the TB group compared with 11% in the LB group while only a single tumour (a haemangioma of the uterus) was observed in the controls. In all, there were neoplasms in 42, 5 and 1 organ/s from the TB, LB and control rat groups respectively (p<0.001). Analysis of the fern and pellets for ptaquiloside, the carcinogen in bracken fern, showed much higher levels present in the material from the TB site. There was 26 and 2270 microg ptaquiloside/g of dried fern and, for pellets from the same fern, 6.5 and 355 microg ptaquiloside/g of pellets, for one collection from the LB and TB sources respectively.

Journal Article↗
PubMed1983

Multiresidue method for determination of pesticides in kiwi fruit, apples, and berry fruits.

A rapid multiresidue procedure for fruits, based on methanol extraction, is presented. Water and highly water-soluble co-extractives are removed by partitioning the pesticides into toluene. Carbon-cellulose-Florisil cleanup is performed before gas chromatography on OV-225 with electron capture detection. A wide range of pesticides can be determined to 0.1 mg/kg without concentrating the extract. Gas chromatography of the crude toluene partition using SE-30 and an alkali flame ionization detector provides confirmatory data and allows detection of some carbamates. Dichlorvos, dimethoate, and acephate are determined directly in the methanol extract by flame photometric detection. High recoveries were obtained for 4 organochlorine insecticides, 13 organophosphorus insecticides, 2 synthetic pyrethroids, two N-methyl carbamates, and 10 fungicides. The method is economical of solvents, glassware, and time, and is recommended for routine surveillance of residue levels on fruit.

Chromatography, Gas↗