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Biomedical subjects

D Weber

Publications and source records attributed to D Weber.

At least 217 records · Page 12Linked to original sources
PubMed1966

Alkanes in fungal spores.

The chlamydospores of Ustilago maydis, U. nuda, and Sphacelotheca reiliana were analyzed by gas chromatography and mass spectrometry for their hydrocarbon contents. For the first time we observed that they contain paraffinic hydrocarbons; the average contents were 42, 58, and 146 parts per million, respectively. n-Alkanes having odd numbers of carbon atoms predom-inate, with carbon-chain lengths ranging from C(14) to C(37). The major alkanes are n-C(27) in U. maydis, n-C(27) and n-C(35) in U. nuda, and n-C(29) in S. reiliana. Each type of spore carried a distinctly characteristic population of hydrocarbons.

Alkanes↗
PubMedDate not supplied

Correlation of cine MR velocity measurements in the internal carotid artery with collateral flow in the circle of Willis: preliminary study.

The velocity-phase relationship intrinsic to phase-contrast magnetic resonance (MR) angiography permits the quantitative and qualitative assessment of blood flow. The ability to measure velocity and vessel cross-sectional area allows noninvasive assessment of volume flow rate (VFR) in the internal carotid artery (ICA). Phase-contrast techniques also demonstrate flow direction. Using two-dimensional cine phase-contrast angiography, the authors evaluated VFR in the ICA and collateral flow about the circle of Willis in 15 patients with ischemic neurologic symptoms. The VFR in each carotid artery was correlated with the degree of stenosis and presence or absence of abnormal circle of Willis collateral flow. There was a correlation between a decrease in VFR and abnormal circle of Willis collateral flow. In addition, a correlation between severe stenosis and a decrease in VFR was found. In patients with ischemic neurologic symptoms without severe stenosis (< 70% diameter stenosis), no decrease in VFR was seen. It is hoped that flow quantification and directional flow imaging with phase-contrast angiography will help further characterize carotid artery occlusive disease by enabling assessment of VFR changes associated with ischemic neurologic symptoms. This study also supports the hypothesis that two mechanisms--hemodynamic and embolic--play a role in ischemic neurologic symptoms.

Aged↗
PubMedDate not supplied

Application of capillary gas chromatography to a survey of wheat for five trichothecenes.

A previously published method for the determination of deoxynivalenol (DON) and nivalenol (NIV) in grains by capillary gas chromatography (GC) with electron-capture detection (ECD) has been modified to include HT-2 toxin (HT-2), T-2 toxin (T-2) and diacetoxyscirpenol (DAS). Recoveries of the five trichothecenes from wheat averaged 71-92% in the range 0.8-4 micrograms/g. Detection or quantitation limits found in two laboratories were from 0.02 to 0.4 micrograms/g, with those for T-2 and DAS at the high end of this range. The method proved of practical use in survey work for the screening and determination of these trichothecenes in wheat from the 1987 western Canadian crop. There were no false positives for HT-2, T-2 and DON in durum and HY-320 wheat. However, interferences precluded the determination of 4- and 15-monoacetoxyscirpenol (MAS) by GC-ECD. The natural occurrence of HT-2 toxin (0.06-0.59 micrograms/g) was demonstrated by GC-ECD and confirmed by GC-mass spectrometry (MS) in 23 samples of durum and HY-320 wheats (1986 and 1987 crops); it was almost always accompanied by DON and in one sample a low concentration of NIV (0-05 micrograms/g). False positives for HT-2 and DAS in red spring wheat detected in 1987 by GC-ECD were 6% (nearly all identified as variety Katepwa) and 8%, respectively. Hence confirmation of suspected HT-2 and DAS by GC-MS is necessary, particularly with red spring wheat.

Chromatography, Gas↗
PubMedDate not supplied

Analytical methods for the determination and mass spectrometric confirmation of 1-methyl-2-nitroso-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid and 2-nitroso-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in foods.

A method is described for the determination of the two title compounds that is based on: (a) extraction of the acidified sample with methanol, (b) removal of fats and lipids by partitioning of the extract with n-hexane, (c) clean-up on acidic alumina extraction cartridge, and (d) determination by a post-HPLC column chemical denitrosation-thermal energy analyser (TEA) technique or by conventional HPLC-TEA analysis after derivatization of the compounds with diazomethane. Confirmation was carried out by HPLC-mass spectrometry of the free acids and also by gas chromatography-mass spectrometry of the methyl esters. The formation of both 1-methyl-2-nitroso-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid and 2-nitroso-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in nitrosated samples of several Japanese and Chinese pickled vegetables, one soy sauce, and two cheeses was demonstrated.

Carbolines↗
PubMedDate not supplied

A method for the determination of methyl carbamate and ethyl carbamate in wines.

A method is described for the simultaneous determination of methyl carbamate (MC) and ethyl carbamate (EC) in wines that is based on: (a) extraction of the sample with dichloromethane using an extraction tube or an alumina-Celite column, (b) concentration of the extract to a small volume, and (c) determination by gas-liquid chromatography-thermal energy analyser (N-mode). The method is highly sensitive (1-2 ng/ml), accurate (recoveries greater than 80%), and precise (CV, 5-10%). Nineteen of 27 samples of wines analysed contained traces (up to 2.7 ng/ml) of MC, and most contained EC (up to 70 ng/ml). Wines treated in the laboratory with 200 ppm dimethyl pyrocarbonate (DMPC)-a cold sterilant recently approved for use in wines-indicated that such a treatment may increase the MC contents of the wines to 10 ng/ml. Additional studies suggested that formation of MC in DMPC-treated wines is dependent on both pH and ammonia content of the wines. The identity of MC in a few selected samples was confirmed by gas-liquid chromatography-high resolution (10 K) mass spectrometry. The natural low levels of MC found in these wines are not considered to pose a risk to human health.

Ammonia↗
PubMedDate not supplied

Determination of butyltin, cyclohexyltin and phenyltin compounds in beers and wines.

Butyl- cyclohexyl- and phenyltin compounds were extracted from enzymically-hydrolysed wine and beer samples with 0.05% tropolone in pentane. Methyl derivatives were made by Grignard reaction for determination by gas chromatography-atomic absorption spectrometry. Wine and beer samples contained less than 0.1 to 160 nl/ml of butyltins from an undetermined source of contamination. GC-MS confirmation of butyltins also detected phenyltin, and di- and tricyclohexyltin compounds at levels less than the GC-AAS based method detection limits of 0.05-0.13 ng Sn/mL.

Beer↗
PubMedDate not supplied

Analysis of Canadian and imported beers for Fusarium mycotoxins by gas chromatography-mass spectrometry.

A sensitive method was developed for the determination of deoxynivalenol (DON), nivalenol (NIV), alpha-zearalenol (alpha-ZEL), beta-zearalenol (beta-ZEL) and zearalenone (ZEN) in beer by capillary gas chromatography-mass spectrometry (GC-MS) of their heptafluorobutyrate (HFB) derivatives. Recoveries averaging 90-103% were obtained from beers spiked with each mycotoxin in the 5-20 ng/ml concentration range. Limits of detection were 0.1-1.5 ng DON/ml, 0.01-0.3 ng NIV/ml, 2.5-3 ng alpha- and beta-ZEL/ml, and 1.5-2 ng ZEN/ml. Twenty-nine of 50 samples of Canadian and imported beer surveyed were found to contain DON; of these nine contained greater than 5 ng/ml (up to 50 ng/ml). The identity of DON was confirmed by response ratios at m/z 670 and m/z 884 for the HFB derivative and m/z 497 and m/z 512 for the trimethylsilyl (TMS) derivative. NIV was also detected in three beer samples (0.1-0.84 ng/ml) but no alpha-ZEL, beta-ZEL or ZEN was found.

Beer↗
PubMedDate not supplied

Levels of chlorinated hydrocarbon residues in Canadian human breast milk and their relationship to some characteristics of the donors.

A total of 412 breast milk samples from women in all provinces of Canada were analysed for polychlorinated biphenyls, eight chlorinated benzenes, 2,3-dichloronaphthalene, Mirex, alpha, beta, gamma and delta hexachlorocyclohexane, alpha and gamma chlordane, oxychlordane, transnonachlor, p,p'-DDT and some analogues, heptachlor epoxide, dieldrin and octachlorostyrene. No delta-hexachlorocyclohexane, heptachlor or aldrin were found in any of the samples, while median levels of the 1,2,4- and 1,3,5-trichlorobenzene, 1,2,3,4- and 1,2,3,5-tetrachlorobenzenes, gamma chlordane, o,p'-DDT and octachlorostyrene were all less than the minimum detectable level (MDL). All other compounds were present at median levels ranging from < 0.1 to 7.2 ng/g whole milk, but did not occur in all samples. Di to tetrachlorobenzenes, except 1,2,4-trichlorobenzene, 2,3-dichloronaphthalene and alpha-chlordane were observed in < 50% of the samples. From 1967 to 1986 a steady decline of hexachlorobenzene, gamma-hexachlorocyclohexane, DDTs, heptachlor epoxide and dieldrin was observed in Canadian breast milk. In addition, a decrease in some chlorinated benzenes, gamma-hexachlorocyclohexane and PCBs was also observed between 1982 and 1986. Levels of oxychlordane and trans-nonachlor remained constant. Canadian breast milk contamination appears to be one of the lowest among the industrialized nations. Regional and provincial differences in residue levels appeared minimal, although more often samples from Quebec and British Columbia had higher levels of some contaminants, such as oxychlordane, than samples from other provinces. No relationship was found between maternal age and residue levels, but some contaminants, such as PCBs, were significantly higher in the milk of mothers who breastfed their first child as compared to multiparous mothers. Breast milk residue levels were not related to fish consumption.

Adult↗
PubMedDate not supplied

Single-dose therapy with trimethoprim-sulfamethoxazole for urinary tract infection in women.

One-hundred-four women with symptoms of lower urinary tract inflammation (dysuria, frequency, and suprapubic tenderness) were randomly assigned to one of two treatment regimens: either a single dose of two double-strength trimethoprim-sulfamethoxazole, (TMP-SMZ) tablets (320 mg of TMP and 1,600 mg of SMZ) or conventional therapy of one double-strength tablet (160 mg of TMP and 800 mg of SMZ) twice a day for 10 days. Eighty-one patients had true bacteriuria; 93% of the infections were eradicated by single-dose therapy and 95% by conventional therapy. Results of an antibody-coated bacteria assay showed no correlation with therapeutic outcome. Clinically important side effects were observed in 4% of patients treated with single-dose therapy and 24% (P less than 0.05) of those treated with conventional therapy. Twenty-three patients had acute urethral syndrome, 14 with and nine without pyuria on initial urinalysis. The 14 with pyuria responded to antimicrobial therapy, whereas those without pyuria did not. This response pattern is consistent with recent data concerning the etiology of acute urethral syndrome. It is concluded that single-dose TMP-SMZ therapy is effective, easily administered, inexpensive, and free from significant side effects, and that it should have broad applicability in the treatment of women with acute, uncomplicated urinary tract infection.

Adolescent↗
PubMedDate not supplied

Monoclonal antibodies to E92, an endothelial cell surface antigen.

Two hybridoma-derived monoclonal antibodies have been developed that react with an antigen of molecular weight 92,000 daltons on the surface of human endothelial cells. Cultured human umbilical vein endothelial cells were used for immunization, but the antigen is present on arterial, venous and capillary endothelium, as determined by biotin-avidin immunoperoxidase staining of tissue sections. With this technique, other cell types in the tissues which were examined were not reactive, except for scattered fibroblasts and histiomonocytic cells, trophoblastic cells of the placenta, and benign immature mesenchymal cells in a renal cystadenocarcinoma. By cytofluorography, the antibodies were found to be unreactive with granulocytes, T lymphocytes, B lymphocytes, and the majority of monocytes. Fibroblasts were reactive with the antibodies, but the fluorescence tracings indicated a lower density of antigen on these cells than on endothelial cells. Immunoreactivity of fibroblasts could be decreased by treatment of the cells with thrombin, trypsin, or neuraminidase, whereas these enzymes did not affect the immunoreactivity of endothelial cells. The reactive antigen (E92) does not appear to be any of several previously described endothelial cell proteins, because of its molecular weight and its absence on other cell types. The presence of E92 on trophoblastic cells of the placenta and immature mesenchymal cells, as well as fibroblasts and endothelial cells, may indicate that it is a primitive antigen of mesodermal tissue that is lost by most cell types during differentiation.

Adenocarcinoma↗
PubMedDate not supplied

Load-bearing capacity of functioning alumina dental endosseous implants.

The average load that did not produce measurable plastic deformation (5 mum) of the bone that supported six Al2O3 implants in this study was 57.5 kg. Histological slides from specimens that were loaded to the point that measurable plastic deformation (5 mum) was produced showed lines along which stain was concentrated. These lines emanated from the point of maximum stress and extended in the direction of the applied load. They were concluded to indicate regions of microplastic deformation. No untoward histological response to the solid Al2O3 implants was observed and no evidence of apical migration of epithelial tissue was noted.

Aluminum↗
PubMedDate not supplied

An early rise in urine N-telopeptide predicts the growth response of normal prepubertal short children to growth hormone therapy.

The effects of growth hormone (GH) therapy on biochemical markers of bone turnover were investigated in 11 short prepubertal children without GH deficiency by measuring serum osteocalcin, a marker for bone formation, and urinary concentrations of pyridinium cross-linked amino acids of collagen (PCL), and the peptide-bound pyridinoline residue N-telopeptide (NT), which are specific markers for bone resorption. GH treatment for three months increased bone turnover in this group of children: urinary PCL concentrations increased from 69 +/- 6.2 to 114 +/- 9.3 nmol/mmol Cr (p < 0.01), and urinary NT levels increased from 512 +/- 65 to 766 +/- 74 pmol BCE/mumol Cr (p = 0.058). Serum osteocalcin concentrations increased from 13.64 +/- 2.57 ng/ml to 26.45 +/- 1.39 ng/ml (p < 0.01). The increment in 12-hour urinary concentrations of PCL was highly correlated with the increment in 12-hour urinary NT levels (r = 0.92, p < 0.01). Stepwise multiple regression analysis revealed that the urinary concentrations of NT after 3 months of GH therapy were the best predictor of growth after 12 months of treatment (r = 0.78, F = 7.9, p = 0.037).

Body Height↗