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Biomedical subjects

D A Klein

Publications and source records attributed to D A Klein.

35 records · Page 2Linked to original sources
PubMed1984

Bladder freeze ulceration and sodium saccharin feeding in the rat: examination for urinary nitrosamines, mutagens and bacteria, and effects on hepatic microsomal enzymes.

We previously demonstrated that long-term feeding of sodium saccharin, a non-mutagen, induced bladder carcinomas when administered to F344 male rats with regenerative hyperplasia of the urothelium induced by the freeze-ulceration technique, even without prior chemical initiation (Cohen et al. Cancer Res. 1982, 42, 65). In the present study, we examined the urine of rats subjected to freeze ulceration of the bladder and then fed sodium saccharin at 5% in the diet to evaluate the possibility of a mutagen being generated as a result of ulceration and/or saccharin feeding. Urine was collected into a syringe by aspiration from the urinary bladder after ligating the urethra for 2 hr at intervals from day 0 to day 14 after ulceration. After ulceration and/or sodium saccharin feeding, the urine showed no bacterial contamination, no mutagenic activity in the standard Ames assay, no production of nitrosamines, and no nitrosating environment. In addition, no significant changes in activities of liver microsomal enzymes (i.e. cytochrome P-450, NADPH-cytochrome c reductase, aniline hydroxylase, or ethylmorphine N-demethylase) were observed in rats fed sodium saccharin for 1, 5 or 14 days. Thus, freeze ulceration, and the consequent regenerative hyperplasia of the epithelium, compared with sodium saccharin feeding do not involve the administration of an exogenous mutagenic substance or the generation of a detectable mutagen in the urine.

Administration, Oral↗
PubMed1984

Determination of N-nitrosobis(2-hydroxypropyl)amine in environmental samples.

N-Nitrosobis(2-hydroxypropyl)amine (ND2HPA) is a potent pancreatic carcinogen in hamsters and induces gastrointestinal and respiratory tract cancer in rats. The precursor amines, diisopropanolamine (Di-PA) and triisopropanolamine (Ti-PA), are used in some manufacturing processes and in cosmetic preparations. We have found low levels of ND2HPA in commercial Ti-PA (21-270 ng/g) and in Di-PA (20-1 300 ng/g) and have demonstrated that ND2HPA is formed from Ti-PA and nitrite in a yield comparable to that observed for formation of N-nitrosodiethanolamine (NDELA) from triethanolamine under relatively mild conditions. After reaction for 4 h at 37 degrees C (10 mmol/L amine, 40 mmol/L nitrite, pH 3.0), the ND2HPA yield was 0.51%. The NDELA yield under the same conditions was 0.96%. ND2HPA was determined by gas chromatography-thermal energy analysis (GC-TEA) and GC-high-resolution mass spectrometry (GC-MS) selected ion monitoring of the tert-butyldimethylsilyl (t-BDMS) ether after extraction on a Celite 560 column. The t-BDMS ethers of ND2HPA and NDELA yielded intense, structurally significant peaks at m/z 333.2030 and 305.1716, respectively. The GC-MS procedure provides sensitivity and selectivity comparable to that of GC-TEA.

Carcinogens, Environmental↗
PubMed1982

Relationship between fluorescein diacetate-stained hyphae and oxygen utilization, glucose utilization, and biomass of submerged fungal batch cultures.

The relationship between fungal activity and staining with fluorescein diacetate (FDA) was investigated by growing Penicillium citrinum and Rhizoctonia solani in submerged batch cultures at different initial glucose concentrations and aeration rates. A modified FDA staining method, similar to the Jones and Mollison technique (P. Jones and J. Mollison, J. Gen. Microbiol. 2:54-69, 1948), was developed to assess both total and FDA-stained hyphae. In previous studies, soil hyphae stained with FDA were considered viable. However, determination of a quantitative relationship between FDA staining and fungal activity is necessary before such an assumption can be made. Growth rates and the rate of change in the percentage of FDA-stained hyphae were significantly correlated. The regression equation calculated for the relationship was: growth rate (mg . ml-1 . h-1) = 0.34 + 1.1 (rate of change in the percentage of FDA-stained hyphae [. ml-1 . h-1]). Changes in activity as measured by O2 utilization, glucose utilization, and biomass correlated significantly with changes in the percentage of FDA-stained hyphae, although the relationships among these parameters were different for each fungal species. Fungal growth stage was also correlated with the percentage of FDA-stained hyphae. Staining was 10% or greater during fungal growth and less than 10% during the late growth, stationary, and death phases. Thus, the rate of change in the percentage of FDA-stained hyphae can be used to predict fungal activity rate changes for single fungal cultures and growth rates for mixed fungal cultures, and the growth stage can be assessed by the percentage of FDA-stained hyphae.

Aerobiosis↗
PubMed1980

Mineralization capacity of bacteria and fungi from the rhizosphere-rhizoplane of a semiarid grassland.

A radiotracer glucose mineralization assay was used with streptomycin and actidione to monitor the relative seasonal contributions of bacteria and fungi to mineralization processes in soils derived from the rhizosphere-rhizoplane zone of plants from a shortgrass prairie ecosystem. Bacteria played a major role in glucose mineralization in both the rhizosphere and rhizoplane. These results indicate that the bacteria may play a greater role in glucose mineralization processes in the rhizosphere and rhizoplane zones of a semiarid grassland than would be assumed, based on available biomass estimates. This technique appears to be valuable for determining bacterial versus fungal contributions to glucose mineralization in the rhizosphere and rhizoplane and may be useful for measuring the decomposition of other more complex substances in this zone of intense microbial activity.

Journal Article↗
PubMed1979

Decomposition of microbial cell components in a semi-arid grassland soil.

Cell component fractions (C-labeled) were prepared from bacterial and fungal cultures isolated from the Pawnee National Grassland in northeastern Colorado and tested for seasonal changes in degradability. The decomposition of cell component fractions was monitored from May to December of 1977 and during March of 1978, using soil samples taken at 2- to 3-week intervals. The release of CO(2) from bacterial and fungal cell walls was inversely related (P < 0.01) to the soil moisture content. Except for cytoplasm isolated from an Aspergillus sp., all other cytoplasmic and polysaccharide fractions did not demonstrate a significant relationship between soil moisture and decomposability. In general, bacterial cell walls and polysaccharides were more susceptible to decomposition than fungal cell walls, although the seasonal changes in decomposability for both fractions were similar. These patterns of cell component utilization indicate that the decomposition of cell wall material may be more closely linked, on an inverse basis, to the availability of soil moisture and release of soluble, low-molecular-weight organics resulting from primary production events.

Journal Article↗
PubMed1976

Starvation effects on Escherichia coli and aquatic bacterial responses to nutrient addition and secondary warming stresses.

A gram-negative polar flagellated rod, isolated from a Colorado mountain stream and considered to be an Aeromonas sp., a mixed aquatic microbial population, and a culture of Escherichia coli were starved to determine their responses to the short-term presence of nutrients and mild warming stress (49.5 C for 2 min) in relation to starvation time. At the beginning of the starvation period, the Aeromonas isolate was extremely sensitive to the secondary warming stress. This response was markedly diminished after a 3-week starvation period. The mixed aquatic microbial population showed a similar trend in becoming less sensitive to stress with increased starvation. E coli under similar conditions, became more sensitive to the secondary stress after exposure to glucose. Respiration measurements after glucose additions also indicated that E. coli responded in a different manner to starvation stress and glucose presence than the Aeromonas isolate. The increased sensitivity of E. coli to secondary stress and short-term nutrient availability after starvation may contribute to the exclusion of this organism from aquatic environments.

Aeromonas↗
PubMed1974

Stress: a factor to be considered in heterotrophic microorganism enumeration from aquatic environments.

Heterotrophic microorganisms in water samples are susceptible to the transient stress of warmed agar used in the standard methods pour plate procedure, causing significantly decreased recoveries in comparison with a spread plate technique. Microbial starvation can increase susceptibility to a transient warming stress. The standard plate count procedure, as presently described, should not be considered for quantitation of microorganisms from aquatic environments.

Agar↗
PubMed1971

Structural effects on Arthrobacter methylene hydroxylase activity.

Arthrobacter 4-44-2 (ATCC 25581), capable of subterminal oxidation of n-hexadecane to 2-, 3-, and 4-alcoholic and ketonic products, was examined for the ability of this methylene hydroxylase capability to be induced and repressed and for structural relationships influencing methylene function oxidation. Induction was best carried out by use of n-alkanes from 10 to 16 carbons in length and was especially strong with methylcyclohexane among cyclic compounds tested. Induction was not observed with several related alcohols, 1-unsaturated compounds, or methoxy and ethoxy compounds tested. After induction, n-alkanes 14 and 16 carbons in length were transformed to the corresponding internal oxidation products; however, no activity was observed with even-carbon alkanes of shorter chain length. Hexadecene-1 and all alcohols tested, including cyclododecanol, were transformed to corresponding ketonic or aldehydic products. Cyclic compounds tested, including cyclododecane, were not oxidized by induced cells, suggesting that a methyl group plays a role in orientation of the substrate for the methylene hydroxylation but that the methyl function was not as critical after completion of the hydroxylation step regardless of structural configuration. Acetate strongly repressed induction of n-hexadecane methylene hydroxylase activity. Inducibility of methylene hydroxylase activity was confirmed by use of cell-free systems with methylcyclohexane as an inducer. A stimulation of methylene hydroxylase activity by addition of reduced pyridine nucleotides and ferrous ion was indicated.

Alcohols↗
PubMed1969

Role of alcoholic intermediates in formation of isomeric ketones from n-hexadecane by a soil Arthrobacter.

A soil Arthrobacter species isolated from an Oregon soil was capable of transforming n-hexadecane to a series of ketonic products, the 2-,3-, and 4-hexadecanones, with evidence for accumulation of 2- and 3-hexadecanols as oxidative intermediates when yeast extract or peptone was used as a growth substrate. The accumulation and participation of internal alcohols in this type of hydrocarbon transformation has not been previously reported. In the absence of yeast extract or peptone, growth from low-level inocula was not observed when n-hexadecane or two oxidation products, 2-hexadecanol and 3-hexadecanone, were used as substrates. However, washed resting cell suspensions of the organism transformed 2-hexadecanol, or a mixture of 2-,3-, and 4-hexadecanols, to the corresponding ketones without lag, indicating the possible constitutive nature of the alcohol dehydrogenase enzyme(s) carrying out this reaction. The addition of glucose to these resting cells stimulated transformation of n-hexadecane to alcoholic and ketonic oxidation products. Formation of isomeric internal alcohols appears to be a limiting step in ketone formation by this Arthrobacter isolate.

Alcohols↗
PubMedDate not supplied

Delivering mental health care to HIV-positive individuals. A comparison of two models.

Data on initial psychiatric evaluations performed in 1995 were compared to assess whether psychiatric consultation for human immunodeficiency virus (HIV)-positive/acquired immunodeficiency syndrome (AIDS) patients provided on-site in an infectious disease (ID) clinic improved compliance and were preferred by staff to evaluations performed in a specialized AIDS psychiatric program. Compliance with initial appointments remained below 50% in both settings, but more patients seen in the ID clinic had received prior psychiatric treatment and medication and they were more likely to receive a psychotropic prescription at this initial visit. The ID clinic staff preferred on-site consultations. Stationing psychiatric consultants in the ID clinic may reach a more impaired population but did not improve compliance with the initial visit.

Acquired Immunodeficiency Syndrome↗