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Biomedical subjects

M Alexander

Publications and source records attributed to M Alexander.

At least 163 records · Page 9Linked to original sources
PubMed1990

Inoculum size as a factor limiting success of inoculation for biodegradation.

A study was conducted to determine the role of inoculum size of a bacterium introduced into nonsterile lake water in the biodegradation of a synthetic chemical. The test species was a strain of Pseudomonas cepacia able to grow on and mineralize 10 ng to 30 micrograms of p-nitrophenol (PNP) per ml in salts solution. When introduced into water from Beebe Lake at densities of 330 cells per ml, P. cepacia did not mineralize 1.0 microgram of PNP per ml. However, PNP was mineralized in lake water inoculated with 3.3 X 10(4) to 3.6 X 10(5) P. cepacia cells per ml. In lake water containing 1.0 microgram of PNP per ml, a P. cepacia population of 230 or 120 cells per ml declined until no cells were detectable at 13 h, but when the initial density was 4.3 X 10(4) cells per ml, sufficient survivors remained after the initial decline to multiply at the expense of PNP. The decline in bacterial abundance coincided with multiplication of protozoa. Cycloheximide and nystatin killed the protozoa and allowed the bacterium to multiply and mineralize 1.0 microgram of PNP, even when the initial P. cepacia density was 230 or 360 cells per ml. The lake water contained few lytic bacteria. The addition of KH2PO4 or NH4NO3 permitted biodegradation of PNP at low cell densities of P. cepacia. We suggest that a species able to degrade a synthetic chemical in culture may fail to bring about the same transformation in natural waters, because small populations added as inocula may be eliminated by protozoan grazing or may fail to survive because of nutrient deficiencies.

Animals↗
PubMed1990

Effect of growth rate and hydrophobicity on bacteria surviving protozoan grazing.

Measurements were made of the predation by Tetrahymena thermophila on several bacterial species in media containing heat-killed Escherichia coli cells to serve as an alternative prey. If grazing pressure was initially not intense on a mixture of bacterial species, the species that survived protozoan feeding at greater densities were those that grew quickly before the onset of active predation. If members of several species were incubated individually at similar initial densities with actively grazing T. thermophila, some species survived at ca. 10(4)/ml, some survived at ca. 10(2)/ml, and others were eliminated. Members of the first two groups but not the third group were able to multiply in the medium in the absence of the protozoan, but the growth rates in the protozoan-free medium did not correlate with the number of survivors. However, the species that persisted at the higher densities possessed highly hydrophobic cell surfaces. The size of the surviving population of four bacterial species whose growth was prevented by chloramphenicol correlated with the initial cell density that was incubated with T. thermophila. It is concluded that the individual species surviving predation on a mixture of species is related to the capacity of the bacterium to grow, the hydrophobicity of its cell surface, and the population density of the species before the onset of intense grazing.

Animals↗
PubMed1990

Digital augmentation for ectrodactyly: management and planning.

Selection of the most appropriate operations for a patient is as important as technical expertise in performing the procedures. Web deepening may be performed alone or in addition to tissue augmentation and should be planned in conjunction with bone lengthening. Skeletal augmentation is useful if fingers are missing or inadequate, and it is necessary to add bony tissue. In general, in order to grow, skeletal transfers must be performed on very young children or must include vascularized physes; complex cases may require microvascular composite toe-to-hand transfer. Distraction-lengthening for intercalary skeletal enhancement is indicated for patients with multiple hypoplastic, aplastic, and missing digits, but the cosmetic result is limited. The major procedures should be started by age 2 years and finished by age 4; unfortunately, it is most often not advisable to perform microvascular surgery at such an early age. Modification of functional patterns, even though they are abnormal or the result of incomplete anatomy, should be avoided in the older child or adult because tinkering does not lead to significant benefits. For a cooperative, and often difficult, staged venture to be maximally successful, physicians and parents must share realistic expectations of aesthetic and functional results.

Age Factors↗
PubMed1989

[Atypical pneumonias with special reference to prognosis].

The term "atypical pneumonia" was proposed for pneumoniae which ran another course than lobar or bronchopneumoniae. In opposite to the usual bacteriologic pneumoniae in "atypical pneumoniae" there are only seen slight palpatory and auscultatory findings. In spite of high fever there are no tachycardia and no leucocytosis. The diagnosis succeed by X-ray mostly. "Atypical pneumoniae" were caused by mycoplasmae, rickettsiae (Q-fever), chlamydiae, (ornithosis), viruses (influenca, adenoviruses, cytomegalia, measles, varicellae) or protozoa (pneumocystitis carinii). In the following we enter into the particular clinical pictures and their prognoses.

Diagnosis, Differential↗
PubMed1989

Generation of chemotactic activity for neutrophils by liver cells metabolizing ethanol.

The mechanism of polymorphonuclear leukocyte (PMN) infiltration of the liver in acute alcohol-related liver injury is unknown. We have reported that ethanol metabolism by hepatocytes incubated with moderate concentrations of ethanol (2-50 mM) results in the release into the medium of a chemoattractant for human PMN. This response to ethanol is time- and concentration-dependent with peak activity at 10 mM ethanol. Generation of the factor is specific for hepatocytes and is blocked by inhibiting ethanol metabolism with 4-methylpyrazole. It does not appear to be due to cell death. The activity has been partially characterized: it behaves as a polar lipid, possibly an arachidonic acid metabolite distinct from leukotriene B4. Preliminary studies indicate that a cell-free system derived from liver generates a similar activity. In that system scavengers of oxygen-derived free radicals block production of the factor.

Animals↗
PubMed1989

Sequential photochemical and microbial degradation of organic molecules bound to humic Acid.

We studied the effects of photochemical processes on the mineralization by soil microorganisms of [2-C]glycine bound to soil humic acid. Microbial mineralization of these complexes in the dark increased inversely with the molecular weight of the complex molecules. Sunlight irradiation of glycine-humic acid complexes resulted in loss of absorbance in the UV range and an increase in the amount of C-labeled low-molecular-weight photoproducts and the rate and extent of mineralization. More than half of the radioactivity in the low-molecular-weight photoproducts appears to be associated with carboxylic acids. Microbial mineralization of the organic carbon increased with solar flux and was proportional to the loss of A(330). Mineralization was proportional to the percentage of the original complex that was converted to low-molecular-weight photoproducts. Only light at wavelengths below 380 nm had an effect on the molecular weight distribution of the products formed from the glycine-humic acid complexes and on the subsequent microbial mineralization. Our results indicate that photochemical processes generate low-molecular-weight, readily biodegradable molecules from high-molecular-weight complexes of glycine with humic acid.

Journal Article↗
PubMed1988

Isolation and complete sequence of a functional human glyceraldehyde-3-phosphate dehydrogenase gene.

Glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.2.12) (GAPDH) mRNA levels, protein, and enzymatic activity increase in 3T3-F442A adipocytes after exposure to physiological concentrations of insulin (Alexander, M., Curtis, G., Avruch, J., and Goodman, H. (1985) J. Biol. Chem. 260, 11978-11985). In order to understand the mechanism of this regulation, we have isolated and sequenced 5.4 kilobase pairs of a 12-kilobase pair human genomic clone encoding a functional GAPDH gene. The gene consists of 9 exons and 8 introns with eukaryotic signals necessary for the transcription and translation of GAPDH mRNA. The exon sequence confirms previously published cDNA sequences for human GAPDH in muscle, liver, and erythrocytes. The organization of the human and the unique chicken GAPDH genes is strikingly similar. Although chicken exons VIII-XI have been fused into human exon 8, introns which separate exons encoding the NAD binding, catalytic, and helical domains of the GAPDH protein have been retained. Stable transfection of rodent cells with the intact human GAPDH gene resulted in the expression of a correctly initiated human GAPDH mRNA and an enzymatically active human GAPDH polypeptide. Thus, the gene contains a functional promoter and intact coding sequences. Although many processed GAPDH pseudogenes and GAPDH-like sequences are present in the human genome, Southern blot analysis of human genomic DNA using a probe derived from the 3'-untranslated region of the GAPDH gene detected only two genes, a 10-copy processed pseudogene and a single copy of the isolated gene. In contrast, a probe derived from an intron segment of the isolated gene detected only a single copy of the GAPDH gene. Collectively, these findings strongly suggest that the human genome encodes a single functional GAPDH gene.

Amino Acid Sequence↗
PubMed1988

Factors affecting the survival and growth of bacteria introduced into lake water.

The populations of Pseudomonas sp. B4, Escherichia coli, Klebsiella pneumoniae, Micrococcus flavus, and Rhizobium leguminosarum biovar phaseoli declined rapidly in lake water. The initially rapid decline of the two pseudomonads and R. phaseoli was followed by a period of slow loss of viability, but viable cells of the other species were not found after 10 days. The rapid initial phase of decline was not a result of Bdellovibrio spp., bacteriophages, or toxins in the water since Bdellovibrio spp. were not present and passage of the lake water through filters that should not have removed bacteriophages or soluble toxins led to the elimination of the rapid phase of decline. The addition of 250 micrograms of cycloheximide and 30 micrograms of nystatin per ml eliminated viable protozoa form the lake water, and the population of Pseudomonas sp. B4 did not fall and the decline of E. coli and K. pneumoniae was delayed or slowed under these conditions. Pseudomonas sp. L2 proliferated rapidly in lake water amended with glucose, phosphate, and NH4NO3, but its numbers subsequently fell abruptly; however, in water amended with cycloheximide and nystatin, which killed indigenous protozoa, the population density was higher and the fall in numbers was delayed. Of the nutrients, the chief response was to carbon, but when glucose was added, phosphorus and nitrogen stimulated growth further. Removing other bacteria by filtering the lake water before inoculation with Pseudomonas sp. L2 suggested that competition reduced the extent of response of the pseudomonad to added nutrients.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
PubMed1988

A study of the value of electrophoretic and other techniques for typing Acinetobacter calcoaceticus.

Forty-four isolates of Acinetobacter calcoaceticus var anitratus collected during hospital outbreaks were studied using polyacrylamide gel electrophoresis (PAGE), plasmid analysis, antibiograms and biochemical tests to determine their degree of similarity. Reproducibility tests were also carried out on the PAGE and biochemical techniques to determine their validity when used to compare bacteria of the same type isolated intermittently. PAGE data was analysed densitometrically and isolates compared using a similarity matrix. All methods were able to subdivide the isolates, but results did not always correlate well between methods. Reproducibility data indicated that careful attention to technique is required when organisms are examined by PAGE sequentially. Results suggest that no single biotyping technique is likely to be adequate and that electrophoretic, biochemical and antibiogram data may complement one another and other epidemiological data in the typing of these organisms.

Acinetobacter↗
PubMed1988

Cardiac morbidity due to Chagas' disease in a rural community in Bolivia.

The prevalence of cardiac morbidity due to Chagas' disease was assessed in a rural community in Central Bolivia. Sixty-nine of 104 persons (66%) were seropositive to Trypanosoma cruzi by two serological methods. Two of 35 (6%) seronegative individuals presented with modest ECG alterations (left anterior hemiblock), but 21 of 69 (30%) seropositives showed modest and severe abnormalities (6 complete right bundle branch block, 2 polyfocal or frequent extrasystoles, 9 ischaemic ST alterations). A high percentage (56%) of domiciliary Triatoma infestans was infected with T. cruzi. There was a significant association between seropositivity and substandard housing. Priority preventive measures should thus include house improvement (to reduce bug infestation) and health education.

Adult↗
PubMed1988

Role of chemical concentration and second carbon sources in acclimation of microbial communities for biodegradation.

A study was conducted to determine the role of concentration of the test chemical, of a second organic compound, and of mutation in the acclimation period before the mineralization of organic compounds in sewage. The acclimation period for the mineralization in sewage of 2 micrograms of 4-nitrophenol (PNP) per liter increased from 6 to 12 days in the presence of 10 mg of 2,4-dinitrophenol per liter. The extension of the acclimation period was equivalent to the time required for mineralization of 2,4-dinitrophenol. In contrast, the time for acclimation for the degradation of 2 micrograms of PNP per liter was reduced when 10 or 100 mg of phenol per liter was added. Lower phenol levels increased the acclimation period to 8 days. The length of the acclimation period for PNP mineralization decreased as the initial concentration of PNP increased from 2 micrograms to 100 mg/liter. The acclimation period for phenol mineralization was lengthened as the phenol concentration increased from 100 to 1,400 mg/liter. The length of the acclimation period for PNP and phenol biodegradation was reproducible, but it varied among replicates for the biodegradation of other nitro-substituted compounds added to sewage or lake water, suggesting that a mutation was responsible for acclimation to these other compounds. The acclimation period may thus reflect the time required for the destruction of toxins, and it also may be affected by the concentration of the test compound or the presence of other substrates.

2,4-Dinitrophenol↗
PubMed1988

Role of sublethal injury in decline of bacterial populations in lake water.

Following their addition to lake water, the populations of Escherichia coli and of antibiotic-resistant strains of Pseudomonas fluorescens, Agrobacterium tumefaciens, Micrococcus flavus, Rhizobium meliloti, and Klebsiella pneumoniae declined rapidly, as determined by counting on media containing antibacterial compounds. The estimates of population sizes were occasionally higher if procedures were used that permitted possible resuscitation of injured cells. No resuscitation procedure yielded consistently higher estimates of populations of surviving cells than the use of selective media alone. The patterns of survival of the test bacteria in lake water amended with eucaryotic inhibitors were essentially the same whether a resuscitation procedure was used or not, and the patterns of survival in sterile lake water or buffer were the same whether counts were made on selective media or on media without antibacterial agents. On the basis of the methods used to show sublethal injury caused by stress, we suggest that such injury to the test bacteria is not a significant factor involved in their decline in lake water.

Bacteria↗
PubMed1988

Effect of inorganic nutrients on the acclimation period preceding mineralization of organic chemicals in lake water.

The addition of phosphate, nitrate, or sulfate (each at 10 mM) decreased the acclimation period for the mineralization of low concentrations of p-nitrophenol (PNP) in lake water. Added phosphate shortened the acclimation period for biodegradation of 2 ng to 2 micrograms of PNP per ml in various lake water samples and of 2,4-dichlorophenoxyacetate at 100 ng/ml. Added P enhanced the rate of growth of PNP-mineralizing microorganisms in waters containing 200 ng or 2 micrograms of PNP per ml. We suggest that the effect of P on the acclimation period results from an increase in the growth rate of the initially small population of microorganisms able to mineralize the synthetic chemicals.

Acclimatization↗