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Biomedical subjects

M Alexander

Publications and source records attributed to M Alexander.

At least 217 records · Page 12Linked to original sources
PubMed1985

Reasons for possible failure of inoculation to enhance biodegradation.

Pseudomonas strains capable of mineralizing 2,4-dichlorophenol (DCP) and p-nitrophenol (PNP) in culture media were isolated from soil. One DCP-metabolizing strain mineralized 1.0 and 10 micrograms of DCP but not 2.0 to 300 ng/ml in culture. When added to lake water containing 10 micrograms of DCP per ml, the bacterium did not mineralize the compound, and only after 6 days did it cause the degradation of 1.0 microgram of DCP per ml. The organism did not grow or metabolize DCP when inoculated into sterile lake water, but it multiplied in sterile lake water amended with glucose or with DCP and supplemental nutrients. Its population density declined and DCP was not mineralized when the pseudomonad was added to nonsterile sewage, but the bacterium grew in sterile DCP-amended sewage, although not causing appreciable mineralization of the test compound. Addition of the bacterium to nonsterile soil did not result in the mineralization of 10 micrograms of DCP per g, although mineralization was evident if the inoculum was added to sterile soil. A second DCP-utilizing pseudomonad failed to mineralize DCP when added to the surface of sterile soil, although activity was evident if the inoculum was mixed with the soil. A pseudomonad able to mineralize 5.0 micrograms of PNP per ml in culture did not mineralize the compound in sterile or nonsterile lake water. The bacterium destroyed PNP in sterile sewage and enhanced PNP mineralization in nonsterile sewage. When added to the surface of sterile soil, the bacterium mineralized little of the PNP present at 5.0 micrograms/g, but it was active if mixed well with the sterile soil.(ABSTRACT TRUNCATED AT 250 WORDS)

Chlorophenols↗
PubMed1985

Effect of bacterial density and substrate concentration on yield coefficients.

Measurements were made of the yield coefficient during the aerobic metabolism of glucose by a heterogeneous bacterial mixture. Expressed in terms of carbon, the coefficient was approximately 0.48. The value did not vary with initial bacterial densities ranging from 0.4 pg to 40 micrograms of cell carbon per ml and with glucose concentrations ranging from 43 pg to 100 micrograms of carbon per ml. Under all these circumstances, about 44% of the glucose carbon was converted to CO2, and 7.4% was excreted as organic products. The significance of uncharacterized organic substrates contaminating the medium to the coefficients calculated for low glucose concentrations is discussed.

Bacteria↗
PubMed1985

[Binding activity of circulating HBsAg particles for polymerized human albumin in acute hepatitis B].

The binding activity of circulating HBsAg particles to polymerized human serum albumin (pHSA) was determined by radioimmunoassay in 18 patients with acute hepatitis B at follow-up and compared with other hepatitis B virus (HBV) markers. All patients had serum HBsAg particles with binding sites for pHSA during the acute phase of disease. Elimination of HBsAg particles with pHSA receptors occurred within 1 to 8 weeks in uncomplicated courses and in one case with a protracted course of 16 weeks before total elimination of HBsAg. The pHSA-test became negative after elimination of HBsAg in most instances. Three patients developed chronic hepatitis with persistence of pHSA-binding HBsAg particles. Circulating HBcAg dissociated by chaotropic ions was detectable in the first week of observation in 4 of 15 patients who recovered and persisted in 3 cases with transition to chronic disease. The results show that acute hepatitis B is associated with circulating pHSA-binding HBsAg particles which can serve as a prognostic marker of the early phase of the disease.

Adult↗
PubMed1984

Relation of riboflavin nutriture in healthy elderly to intake of calcium and vitamin supplements: evidence against riboflavin supplementation.

The status of riboflavin nutriture was evaluated in 24 healthy elderly female residents of a private, nonprofit facility for the care of ambulatory elderly. Riboflavin intake by history was greater than or equal to the recommended dietary allowances (RDA) for this nutrient in all but three subjects, and the average intake in the group as a whole was 50% greater than the RDA. Confirmatory of the findings by history, the status of riboflavin nutriture was excellent in nearly all subjects as evaluated by urinary riboflavin excretion and erythrocyte glutathione reductase activity coefficient. By contrast, calcium intake was greater than or equal to the RDA in ony four of the 24 subjects. The adequacy of calcium intake was found to depend upon a sufficiently high percentage of the total dietary intake of riboflavin being derived from milk and dairy products. It was observed that individual calcium intakes were less than 80% of the RDA unless 40% or more of the total intake of riboflavin was derived from milk and dairy products rather than from other food sources. In those subjects taking daily supplementation with a single multivitamin tablet containing low levels of riboflavin, the total intake of riboflavin and its urinary excretion were increased similarly, suggesting that even small amounts of riboflavin are not retained by elderly subjects consuming a diet adequate in riboflavin.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1984

Fingerprinting Acinetobacter strains from clinical sources by numerical analysis of electrophoretic protein patterns.

A total of 57 strains of Acinetobacter calcoaceticus was fingerprinted by SDS-PAGE of cellular protein. All strains were also examined by conventional, API and N/F-Tek methods, and antibiotic sensitivity patterns were determined. In general, using the API 20E and N/F-Tek methods, it was possible to assign isolates of A. calcoaceticus to the two accepted "biotypes" or "varieties", A.c. anitratus and A.c. lwoffi, but these methods did not offer useful subdivision of the biotypes. Gel electrophoresis permitted subdivision of the strains into clusters in a manner which suggests that the technique may be valuable in typing strains isolated during outbreaks of infection in hospital.

Acinetobacter↗
PubMed1984

Mineral soils as carriers for Rhizobium inoculants.

Mineral soil-based inoculants of Rhizobium meliloti and Rhizobium phaseoli survived better at 4 degrees C than at higher temperatures, but ca. 15% of the cells were viable at 37 degrees C after 27 days. Soil-based inoculants of R. meliloti, R. phaseoli, Rhizobium japonicum, and a cowpea Rhizobium sp. applied to seeds of their host legumes also survived better at low temperatures, but the percent survival of such inoculants was higher than peat-based inoculants at 35 degrees C. Survival of R. phaseoli, R. japonicum, and cowpea rhizobia was not markedly improved when the cells were suspended in sugar solutions before drying them in soil. Nodulation was abundant on Phaseolus vulgaris derived from seeds that had been coated with a soil-based inoculant and stored for 165 days at 25 degrees C. The increase in yield and nitrogen content of Phaseolus angularis grown in the greenhouse was the same with soil-and peat-based inoculants. We suggest that certain mineral soils can be useful and readily available carriers for legume inoculants containing desiccation-resistant Rhizobium strains.

Journal Article↗
PubMed1984

Effect of substrate concentration and organic and inorganic compounds on the occurrence and rate of mineralization and cometabolism.

Isopropyl N-phenylcarbamate (IPC) at 400 pg and 1 mug/ml was mineralized in samples of sewage, but only the lower concentration was mineralized in lake water samples in a 50-day period. IPC at 1 mug/ml disappeared from lake water, but it was converted to organic products. Mineralization of IPC at 400 pg/ml in lake water was enhanced by additions of inorganic nutrients or a mixture of nonchlorinated water pollutants but not by yeast extract or mixtures containing aromatic compounds or excretions of primary producers. The mineralization of 200 pg of 2,4-dichlorophenoxyacetate per ml of lake water was not affected by additions of low levels of yeast extract or compounds excreted by primary producers but was enhanced by low concentrations of mixtures of water pollutants. It is suggested that some chemicals that are found to be converted only to organic products, presumably by cometabolism, in tests using the concentrations commonly employed in laboratory evaluations may be mineralized at the lower concentrations prevailing in natural waters.

Journal Article↗
PubMed1984

Models for mineralization kinetics with the variables of substrate concentration and population density.

The rates of mineralization of [14C]benzoate by an induced population of Pseudomonas sp. were measured at initial substrate concentrations ranging from 10 ng/ml to 100 micrograms/ml. Plots of the radioactivity remaining in the culture were fit by nonlinear regression to six kinetic models derived from the Monod equation. These models incorporate only the variables of substrate concentration and cell density. Plots of the mineralization kinetics in cultures containing low, intermediate, and high initial substrate concentrations were well fit by first-order, integrated Monod, and logarithmic kinetics, respectively. Parameters such as maximum specific growth rate, half-saturation constant, and initial population density divided by yield agreed between cultures to within a factor of 3.4. Benzoate mineralization by microorganisms in acclimated sewage was shown to fit logistic (sigmoidal), Monod, and logarithmic kinetics when the compound was added at initial concentrations of 0.1, 1.0, and 10 micrograms/ml, respectively. The mineralization of 10 micrograms of benzoate per ml in sewage also followed logarithmic kinetics in the absence of protozoa. It is concluded that much of the diversity in shapes of mineralization curves is a result of the interactions of substrate concentration and population density. Nonlinear regression with models incorporating these variables is a valuable means for analysis of microbial mineralization kinetics.

Benzoates↗
PubMed1984

Role of resistance to starvation in bacterial survival in sewage and lake water.

A study was conducted to determine the significance of starvation resistance to the ability of a species to survive in sewage and lake water. Tests were conducted for periods of up to 14 days. Rhizobium meliloti and one fluorescent and one nonfluorescent strain of Pseudomonas were resistant to starvation because their population sizes did not fall appreciably in buffer and sterile lake water, and the first two maintained high numbers after being added to sterile sewage. Cell densities of these bacterial species dropped slowly in nonsterile sewage, and more cells of these three organisms than of the other test organisms remained in nonsterile lake water. Rhizobium leguminosarum was moderately resistant to starvation because its numbers fell slowly in buffer and sterile lake water and did not change appreciably in sterile sewage. The abundance of Micrococcus flavus added to buffer and sterile lake water did not change, but the density of M. flavus declined in nonsterile lake water. The abundance of R. leguminosarum fell in nonsterile lake water and nonsterile sewage. Streptococcus faecalis, Staphylococcus aureus, an asporogenous strain of Bacillus subtilis, and Streptococcus sp. were susceptible to starvation because their populations were markedly reduced in buffer. Populations of the last three species declined rapidly in nonsterile and sterile samples of lake water and sewage. S. faecalis declined rapidly when added to nonsterile lake water and sewage and sterile lake water but not when added to sterile sewage, the persistence in the last instance probably being associated with the availability of organic nutrients.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacillus subtilis↗
PubMed1984

Enhancing Soybean Rhizosphere Colonization by Rhizobium japonicum.

A study was conducted to seek means to increase the colonization of the rhizosphere of soybeans (Glycine max L. Merrill) by Rhizobium japonicum. For this purpose, a strain of R. japonicum that was resistant to benomyl, streptomycin, and erythromycin was used. The numbers of R. japonicum rose quickly in the first 2 days after soybean seeds were planted in soil and then rapidly fell. The decline was slower if the seeds were coated with benomyl. This fungicide reduced the numbers of bacteria and protozoa in the rhizosphere, but the effect became less or disappeared as the plants grew. In sterile soil inoculated with R. japonicum and a mixture of microorganisms, the numbers of R. japonicum were usually lower if protozoa were present than if they were absent. Nodulation and plant yield were increased by the addition of benomyl to soybean seeds sown in sterile soil inoculated with R. japonicum and a mixture of microorganisms. The addition of streptomycin and erythromycin to soil stimulated the growth of R. japonicum but inhibited other bacteria in the presence or absence of soybeans. The data indicate that colonization can be increased by the use of antimicrobial agents and R. japonicum strains resistant to those inhibitors.

Journal Article↗
PubMed1983

Overlapping connective tissue diseases in children.

Of 18 children with different connective tissue diseases four were found to have overlaps. Two presented features of SLE and PSS or SLE and PM and 2 had features of SLE, PSS and JRA. In two of them antiribonucleoprotein antibodies were detected by radical immunodiffusion. But these antibodies were also detected in a few children suffering from a single connective tissue disease. On the other hand, the six children with anti-RNP were not characterized by a particular clinical picture or a better prognosis; when compared to adults, no significant difference could be observed except that the Raynaud phenomenon, sausage fingers and myositis seemed less frequent in childhood. It may be concluded that combinations of connective tissue disease can occur in children but anti-RNP does not appear as a good biological marker.

Adolescent↗
PubMed1983

Netilmicin in human CSF after parenteral administration in patients with slightly and severely impaired blood CSF barrier.

After administration of 150 mg netilmicin samples of CSF and blood were obtained. In one group of nine patients with no or only slight impairment of the blood-CSF-barrier 29 samples of CSF were assayed for netilmicin concentrations. All samples, obtained after the first dose, failed to reveal detectable drug levels. Drug levels up to 0.18 mg/l were detected in samples of CSF of three patients after 3 to 22 doses. Only the lumbar CSF of one patient contained netilmicin concentrations higher than 1.0 mg/l. In comparison 19 samples of CSF, obtained from patients with meningitis after more than one dose of netilmicin, had levels of 0.27-5.0 mg/l. Three CSF samples from patients out of this group, collected after the first dose of netilmicin failed to show any drug activity.

Adult↗