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Biomedical subjects

A J Anderson

Publications and source records attributed to A J Anderson.

At least 19 recordsLinked to original sources
PubMed2001

Activated caspase-3 expression in Alzheimer's and aged control brain: correlation with Alzheimer pathology.

Several studies have suggested that activated caspase-3 has properties of a cell death executioner protease. In this study, we examined the expression of activated caspase-3 in AD and aged control brains. Activated caspase-3 immunoreactivity was seen in neurons, astrocytes, and blood vessels, was elevated in AD, and exhibited a high degree of colocalization with neurofibrillary tangles and senile plaques. These data suggest that activated caspase-3 may be a factor in functional decline and may have an important role in neuronal cell death and plaque formation in AD brain.

Aged↗
PubMed2001

Variability in response to UV-B among species and strains of Metarhizium isolated from sites at latitudes from 61 degrees N to 54 degrees S.

The effects of irradiances of 920 and 1200 mW m(-2) (biologically effective weighted irradiance) were examined in 2 Metarhizium album strains, 26 M. anisopliae strains, 1 M. flavoviride strain, and 1 M. taii strain isolated from sites located at latitudes from 61 degrees N to 54 degrees S. Conidia were exposed to UV-B from 1 to 6 h and subsequently examined for relative percentage culturability. Total dosage received at the end of the exposure periods ranged from 3.3 to 19.9 kJ m(-2) for the lower irradiance and from 4.3 to 25.9 kJ m(-2) for the higher irradiance. Both the irradiance values and the doses are environmentally realistic and can be observed even in temperate regions. The relationships between latitude of origin and UV-B tolerance were compared for the two levels of irradiance for the data from 1 and 2 h exposure. Exposure to both irradiances drastically reduced the relative percentage culturability of all strains. Tolerance to UV-B varied widely among strains and high variation was observed for both irradiances after all periods of exposure. After 1 h of exposure, a difference between the two irradiance levels was detectable, and this difference was magnified at longer irradiations. A significant quadratic relationship of decreasing UV-B tolerance with increasing latitude was observed after exposure of 1 and 2 h. The shape of the relationship did not differ for the two levels of irradiance. Also, we studied the effect of 1200 mW m(-2) irradiance on conidial germination time in 1 M. album strain, 7 M. anisopliae strains, and 1 M. taii strain. Exposure to UV-B delayed the germination of surviving conidia of all strains. In general, the delay in germination was directly proportional to the dose.

Genetic Variation↗
PubMed2001

Catalase activities of Phanerochaete chrysosporium are not coordinately produced with ligninolytic metabolism: catalases from a white-rot fungus.

Phanerochaete chrysosporium uses hydrogen peroxide as a substrate in its ligninolytic phase. To determine how the fungus protects itself against detrimental effects of reactive oxygen species, catalase activity was examined. The fungus produced up to four different catalase isozymes, Cat A to D. Isozyme CatC was the dominant activity in all growth conditions. A minor catalase, CatD, was apparent in low-carbon culture and upon exposure of mycelium grown on high-nitrogen medium with 5-50 mm of hydrogen peroxide. In low-nitrogen culture, an increase in catalase-specific activity preceded the onset of ligninolysis by 3 days. In low-carbon culture, catalase was produced at an even higher level without development of ligninolysis. Thus, catalase activity was not coordinately produced with ligninolytic metabolism.

Catalase↗
PubMed2001

The rpoS gene in Pseudomonas syringae is important in surviving exposure to the near-UV in sunlight.

The near-UV component of sunlight decreased culturability of the leaf epiphyte and plant pathogen Pseudomonas syringae. Exposure of the wild-type cells for 4 h to UV-A and UV-B in sunlight was ten fold more detrimental than exposure to sunlight with just UV-A. Sensitivity to UV-A especially increased in a mutant of P. syringae lacking the global regulatory sigma factor, RpoS. No RpoS-mutant cells were culturable after 4 h of exposure to near-UV sunlight. These findings suggest that both UV-A and UV-B wavelengths cause damage to the bacterial cell and that the RpoS protein regulates protective measures for the leaf-associated pseudomonad.

Bacterial Proteins↗
PubMed2001

Production of docosahexaenoic acid by Crypthecodinium cohnii grown in a pH-auxostat culture with acetic acid as principal carbon source.

Crypthecodinium cohnii, a marine alga used for the commercial production of docosahexaenoic acid (DHA), was cultivated in medium containing sodium acetate as principal carbon source; the pH was maintained at a constant value by addition of acetic acid, which also provided an additional carbon source in a controlled manner. The accumulation of lipid by C. cohnii in this pH-auxostat culture was significantly greater than previously reported for batch cultures using glucose as principal carbon source. Of six strains tested in pH-auxostat cultures, C. cohnii ATCC 30772 was the best, with the cells reaching 20 to 30 g dry weight per liter after 98 to 144 h and containing in excess of 40% (w/w) total lipid, with DHA representing approximately half of the total fatty acids in the triacylglycerol fraction. A productivity of 36 mg DHA L(-1) h(-1) was achieved during cultivation for 98 h using a 5% (vol/vol) inoculum, and DHA production was in excess of 3 g per liter of culture. Most of the DHA was present in neutral lipids.

Acetic Acid↗
PubMed2001

Correlation between caspase activation and neurofibrillary tangle formation in Alzheimer's disease.

Although evidence suggests that neurofibrillary tangles (NFTs) and neuronal cell loss are prominent features of Alzheimer's disease (AD), the relationship between the two remains unknown. In the present study, the relationship between the activation of apoptotic mechanisms and NFT formation in AD was investigated using a caspase-cleavage site-directed antibody to fodrin, an abundant neuronal cytoskeleton protein. This antibody recognized cleavage products of fodrin after digestion by caspase-3, but did not recognize full-length fodrin. In vitro analysis of this fodrin caspase-cleavage product (CCP) antibody demonstrates that it is a specific probe for the detection of apoptotic but not necrotic pathways in cultured neurons. To determine whether caspases cleave fodrin in vivo, tissue sections from controls and AD were immunostained for fodrin (CCPs). Although no staining was observed in control cases, labeling of neurons was observed in the hippocampus of all AD cases, which increased as a function of disease progression. To determine a possible relationship between caspase activation and NFT formation, double-labeling experiments with fodrin CCP and PHF-1 were performed. Co-localization of these markers was observed in many neurons, and quantitative analysis showed that as the extent of NFT formation increased, there was a significant corresponding increase in fodrin CCP immunolabeling (r = 0.84). Taken together, these results provide evidence for the activation of apoptotic mechanisms in neurons in the AD brain and suggest that there is an association between NFT formation and the activation of apoptotic pathways in AD.

Adult↗
PubMed2001

Multiple processes mediate flicker sensitivity.

By systematically manipulating the luminance of a flickering spot and the area immediately surrounding it, we investigated why thresholds from flickering stimuli that cause a change in average luminance are elevated relative to those from stimuli with no luminance change. Threshold elevation resulted from local light adaptation and from temporal-frequency-specific interactions between the spot and its surround: at low frequencies, the contrast between the spot and the surround elevated thresholds, whereas at high frequencies, dark adaptation within the surround elevated thresholds. Our findings suggest that two common ways of determining temporal sensitivity may give markedly different outcomes.

Adaptation, Ocular↗
PubMed2001

Corticosterone selectively attenuates 8-OH-DPAT-mediated hypothermia in mice.

The 5-HT1A agonist 8-OH-DPAT produces a hypothermia in mice mediated by somatodendritic 5-HT1A receptors, that is attenuated by antidepressants and corticosterone. The present study investigated if the effect of corticosterone is specific to the serotonergic system or a non-specific effect on thermoregulation. Administration of corticosterone for 3 d had no effect on dopaminergic (apomorphine) or adrenergic (clonidine) hypothermic challenges. However in addition to 8-OH-DPAT, nicotine-induced hypothermia was attenuated by corticosterone. Administration of the selective nicotinic antagonist mecamylamine had no effect on 8-OH-DPAT-induced hypothermia, although nicotine-induced hypothermia was attenuated by the selective 5-HT1A antagonist WAY-100635. This demonstrates a serotonergic-nicotinic interaction in the generation of hypothermia in mice and is consistent with corticosterone selectively attenuating somatodendritic 5-HT1A receptor function.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2001

Repetitive administration of tetrabenazine induces irreversible changes in locomotion and morphology of the substantia nigra in rats.

We investigated the effects of a 7 day repetitive administration of tetrabenazine (TBZ), which depletes monoamines, on both locomotor behavior and histomorphometrial findings of substantia nigra in rats. These results were compared with the effects of a single dose of TBZ, which is a common paradigm in animal models of depression. A single dose of TBZ causes reversible decrease of voluntary movement and no histological changes. In contrast, as for repetitive administration, this experiment demonstrated irreversible and significant decrease in spontaneous locomotion, as well as histological changes in the neurons of the substantia nigra pars compacta. These results have led us to propose that prolonged TBZ administration could provide a novel and useful model for the behavioral characteristics and anatomical pathology of Parkinson's disease as one of the oxidative stress models induced by abnormal dopamine metabolism.

Adrenergic Uptake Inhibitors↗
PubMed2001

Catalase activity and the survival of Pseudomonas putida, a root colonizer, upon treatment with peracetic acid.

Peracetic acid is used as a sterilant in several industrial settings. Cells of a plant-colonizing bacterium, Pseudomonas putida in liquid suspension, were more sensitive to killing by peracetic acid when they lacked a major catalase activity, catalase A. Low doses of peracetic acid induced promoter activity of the gene encoding catalase A and increased total catalase specific activity in cell extracts. Microbes present in native agricultural soils rapidly degraded the active oxygen species present in peracetic acid. The simultaneous release of oxygen was consistent with a role for catalase in degrading the hydrogen peroxide that is part of the peracetic acid-equilibrium mixture. Amendment of sterilized soils with wild-type P. putida restored the rate of degradation of peracetic acid to a higher level than was observed in the soils amended with the catalase A-deficient mutant. The association of the bacteria with the plant roots resulted in protection of the wild-type as well as the catalase-deficient mutant from killing by peracetic acid. No differential recovery of the wild-type and catalase A mutant of P. putida was observed from roots after the growth matrix containing the plants was flushed with peracetic acid.

Acetic Acid↗
PubMed2001

Effects of UVB irradiance on conidia and germinants of the entomopathogenic Hyphomycete Metarhizium anisopliae: a study of reciprocity and recovery.

We tested the effects of irradiances of 920 and 1200 mW m-2 (weighted irradiance) on the conidia and germinants of the entomopathogenic Hyphomycete Metarhizium anisopliae. The conidia were exposed to the two irradiances for 1, 2, 4, 6, 7 or 8 h. Increased exposure decreased relative percent culturability. The inactivation provoked by the irradiance of 1200 mW m-2 was higher than for the 920 mW m-2, with a reduction in the 50% lethal time (LT50) from 6 h 40 min to 4 h 26 min. Reciprocity was not observed when conidia in water suspension and germinants in different stages of the germinative process were exposed to a 17.3 kJ m-2 total dose at both irradiance levels. Although nonreciprocity was observed in all situations, its magnitude varied as a function of metabolic state and/or cell-cycle phase in which the conidia were at the exposure time. The least difference between the effects of the two irradiance levels was observed when nongerminating conidia in suspension were exposed, and the greatest was observed when conidia were exposed during an advanced germination phase. Doses of 6.6 and 17.3 kJ m-2 supplied through the two irradiance levels delayed the germination of the surviving conidia. At both doses, delay was greater during exposure to the higher irradiance. Nonreciprocity was higher for the 17.3 kJ m-2 dose. Nonreciprocity magnitude, in addition to depending on the conidial physiological state, also depended on dose. The results demonstrate the importance of evaluating the impact of the increase in irradiance during the different stages of the fungal life cycle, especially during the stages which are more sensitive to UV, and not simply in dormant conidia.

Animals↗
PubMed2001

Both solar UVA and UVB radiation impair conidial culturability and delay germination in the entomopathogenic fungus Metarhizium anisopliae.

The entomopathogenic hyphomycete Metarhizium anisopliae has been used in programs of agricultural pest and disease vector control in several countries. Exposure to simulated solar radiation for a few hours can completely inactivate the conidia of the fungus. In the present study we determined the effect of exposures to full-spectrum sunlight and to solar ultraviolet A radiation at 320-400 nm (UVA) on the conidial culturability and germination of three M. anisopliae strains. The exposures were performed in July and August 2000 in Logan, UT. The strains showed wide variation in tolerance when exposed to full-spectrum sunlight as well as to UVA sunlight. Four-hour exposures to full-spectrum sunlight reduced the relative culturability by approximately 30% for strain ARSEF 324 and by 100% for strains ARSEF 23 and 2575. The relative UV sensitivity of the two more sensitive strains was different under solar UV from that under ultraviolet B radiation at 280-320 nm (UVB) in the laboratory. Four-hour exposures to solar UVA reduced the relative culturability by 10% for strain ARSEF 324, 40% for strain ARSEF 23 and 60% for strain ARSEF 2575. Exposures to both full-spectrum sunlight and UVA sunlight delayed the germination of the surviving conidia of all three strains. These results, in addition to confirming the deleterious effects of UVB, clearly demonstrate the negative effects of UVA sunlight on the survival and germination of M. anisopliae conidia under natural conditions. The negative effects of UVA in sunlight also emphasize that the biological spectral weighting functions for this fungus must not neglect the UVA wavelengths.

Dose-Response Relationship, Radiation↗
PubMed2000

Characterization and expression of the pseudomonas putida bacterioferritin alpha subunit gene.

The root-colonizing pseudomonad Pseudomonas putida (Pp) appears to produce two subunits, alpha and beta, of the iron-binding protein, bacterioferritin. A gene encoding the alpha-bacterioferritin subunit was located adjacent to the major catalase in Pp. The deduced protein sequence of the Pp bfralpha gene had a very high identity with other alpha-subunits, possessing conserved amino acids responsible for ferroxidase activity. The gene also lacked a deduced methionine at residue 52, associated with heme binding in beta-subunits. An antibody generated toward the Escherichia coli (E. coli) multifunctional single subunit bacterioferritin recognized two proteins in the Pp extract, a 22 kDa protein likely to be a beta-subunit and, to a lesser extent, a 23 kDa band. The 23 kDa band was absent in a Pp mutant in which the bfralpha gene was disrupted. Loss of alpha-bacterioferritin stimulated production of fluorescent siderophore. Growth on media and on root surfaces was not impaired by deletion of the alpha-bacterioferritin. Transcription of bfralpha was independent of the catalase gene and was dependent on iron. The transcript levels from bfralpha decreased in iron deficiency experienced during stationary-phase or upon treatment during growth with an iron chelator.

Bacterial Proteins↗
PubMed2000

Neurotrophic effects of FPF-1070 (Cerebrolysin) on cultured neurons from chicken embryo dorsal root ganglia, ciliary ganglia, and sympathetic trunks.

We examined the effect of FPF-1070 (Cerebrolysin) on neurite outgrowth in explant cultures of dorsal root ganglia (DRG), sympathetic trunks (ST), and ciliary ganglia (CG) from 10- to 11-day chicken embryos. FPF-1070 significantly promoted neurite outgrowth in DRG and ST neurons at all concentrations examined, in comparison with phosphate buffered saline-treated negative controls; however, this effect on neurite outgrowth was not as significant as that observed for nerve growth factor-treated positive controls on DRG and ST neurons. Additionally, FPF-1070 exhibited an inverted U relationship between concentration and effectiveness in DRG and ST neurons. In contrast, FPF-1070 did not affect neurite outgrowth in CG neurons although ciliary neurotrophic factor-treated positive controls showed striking neurite outgrowth. Our results demonstrate that FPF-1070 has different neurotrophic effects depending on the subpopulation of neurons. This study clarifies a role for neurotrophic activity in the mechanism of action of FPF-1070.

Amino Acids↗
PubMed2000

Interactions between flicker thresholds and luminance pedestals.

We investigated the interactions between flicker thresholds and luminance pedestals using threshold versus contrast (TvC) and method of constant stimuli paradigms. High amplitude luminance pedestals were found to elevate flicker thresholds, but low amplitude luminance pedestals were unable to reduce flicker thresholds. Luminance pedestals elevated flicker thresholds more at low temporal frequencies. A simple model based on local light adaptation was able to capture the general form of the TvC functions. Our results suggest that flicker thresholds derived in the presence of a luminance pedestal (luminance-pedestal flicker) may vary from those obtained by modulating about a mean luminance (mean-modulated flicker).

Adaptation, Ocular↗
PubMed2000

DNA damage and apoptosis in the aged canine brain: relationship to Abeta deposition in the absence of neuritic pathology.

1. In addition to beta-amyloid (Abeta) deposition and cytoskeletal neuropathology, both the Alzheimer's disease (AD) and Down's syndrome (DS) human brain exhibit marked evidence of DNA damage, however, it is difficult to separate events that occur in conjunction with neurofibrillary pathology versus Abeta pathology in these systems. 2. In contrast, the aged canine brain exhibits the accumulation of Abeta into diffuse deposits similar to those found in early AD and DS in the absence of neurofibrillary pathology. Furthermore, Abeta deposition in canine brain is correlated with cognitive deficits. 3. In order to test the hypothesis that TUNEL labeling for DNA damage in AD is not simply a consequence of agonal artifacts, postmortem artifacts, or neurofibrillary pathology, and may be directly related to Abeta deposition, we examined Abeta immunoreactivity, PHF-1 immunoreactivity, and TUNEL labeling in this animal model. 4. These experiments reveal a relationship between the amount of DNA damage detected by TUNEL labeling and levels of Abeta deposition. Further, in animals with no TUNEL labeling, we detected no Abeta immunoreactivity. 5. These data support the hypothesis that TUNEL labeling in AD ans DS is not a consequence of agonal artifact, postmortem artifact, or tau pathology, and may be directly related to Abeta deposition and perhaps AD pathogenesis.

Aging↗
PubMed2000

Effect of stimulus duration in flicker perimetry.

We investigated the relationship between stimulus duration and flicker thresholds when flickering stimuli were presented on luminance pedestals. Mean-modulated flicker thresholds remained constant with changes in stimulus duration. However, flicker presented on a luminance pedestal gave masking at short durations, decaying exponentially to stable thresholds with time. These stable thresholds were elevated when compared with the mean-modulated condition. The lowest threshold in a stimulus onset asynchrony function predicted the threshold obtained from a luminance-pedestal flicker stimulus of the same duration. This suggests that luminance-pedestal flicker thresholds are determined by the most detectable cycle in a multiple cycle stimulus. We find that the 800 ms stimulus duration used in the Medmont M600 perimeter (Medmont, Camberwell, Australia) is suitable to determine stable flicker thresholds.

Adult↗