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Biomedical subjects

K Storey

Publications and source records attributed to K Storey.

16 recordsLinked to original sources
PubMed2005

Possible reasons for difference in sensitivity to oxygen of two Escherichia coli strains.

In preliminary experiments it was found that Escherichia coli strains AB1157 and KS400 are different in their abilities to grow under various oxygen levels in cultivation medium: the first strain does not grow under high oxygen conditions, unlike the second one. To investigate whether the damage to cellular components due to production of reactive oxygen species (ROS) was responsible for this difference, the intensity of free radical oxidation of proteins and lipids as well as the activities of selected antioxidant and associated enzymes (superoxide dismutase, catalase, peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase) were compared in the two strains. The level of thiobarbituric acid-reactive substances was 1.8-2.5-fold higher in AB1157 than in KS400, but the concentration of carbonyl proteins was lower in the AB1157 strain. In both strains growth under higher oxygen levels resulted in higher superoxide dismutase and peroxidase activities in both exponential and stationary phases. Overall, the activities of antioxidant enzymes were always higher in the KS400 strain than in AB1157. The results for both lipid and protein oxidative damage and antioxidant enzyme activities suggest that the differences in oxygen tolerance between these two strains may be due to their different abilities to cope with ROS.

Antioxidants↗
PubMed2000

Structural analysis of yeast HSF by site-specific crosslinking.

We have introduced cysteine substitutions into the yeast HSF1 gene at a variety of locations. Most have no phenotypic effect, and therefore provide site-specific probes for thiol-specific reagents. Crosslinking of single mutants identifies locations where equivalent regions of individual monomers can approach each other in the HSF trimer. Crosslinking of double mutants indicates regions that can approach closely within a single subunit. Results for the DNA binding domain and trimerization domain are consistent with known structural information, and provide essential controls on the validity of the technique. In contrast to these two domains, the N-terminal and C-terminal domains, wherein lie the transcriptional activators, are highly flexible, and do not appear to be in stable contact with any other portions of the protein. None of these patterns are affected by the conformational change that is induced by superoxide or heat shock. We suggest a new model for the mechanism of HSF regulation that accomodates the structural information provided by these studies.

Amino Acid Substitution↗
PubMed2000

Complex regulation of the yeast heat shock transcription factor.

The yeast heat shock transcription factor (HSF) is regulated by posttranslational modification. Heat and superoxide can induce the conformational change associated with the heat shock response. Interaction between HSF and the chaperone hsp70 is also thought to play a role in HSF regulation. Here, we show that the Ssb1/2p member of the hsp70 family can form a stable, ATP-sensitive complex with HSF-a surprising finding because Ssb1/2p is not induced by heat shock. Phosphorylation and the assembly of HSF into larger, ATP-sensitive complexes both occur when HSF activity decreases, whether during adaptation to a raised temperature or during growth at low glucose concentrations. These larger HSF complexes also form during recovery from heat shock. However, if HSF is assembled into ATP-sensitive complexes (during growth at a low glucose concentration), heat shock does not stimulate the dissociation of the complexes. Nor does induction of the conformational change induce their dissociation. Modulation of the in vivo concentrations of the SSA and SSB proteins by deletion or overexpression affects HSF activity in a manner that is consistent with these findings and suggests the model that the SSA and SSB proteins perform distinct roles in the regulation of HSF activity.

DNA-Binding Proteins↗
PubMed2000

Why employment in integrated settings for people with disabilities?

This paper reviews the reasons why work in integrated settings for people with disabilities is important. Current controversial issues in employment of people with disabilities are discussed. These issues are sheltered work versus supported employment and natural supports versus the job coach model.

Persons with Disabilities↗
PubMed1999

Impact of microclimate on immature tick-rodent host interactions (Acari: Ixodidae): implications for parasite transmission.

Rodents play a significant role in enzootic cycles of tick-borne pathogens, notably, in the northern hemisphere, tick-borne encephalitis virus and Lyme borreliosis spirochaetes. The relative numbers of nymphal and larval ticks feeding on rodents are crucial variables in determining the probability of rodent infection and the degree of amplification of infection prevalence in the tick population. Manipulation of the microclimate within quasinatural experimental arenas revealed that under increasingly dry conditions the numbers of unfed nymphal Ixodes ricinus L. questing in upper layers of the herbage decreased, whereas the rate of fat use and the numbers of nymphs feeding on small rodents, both increased. This is consistent with nymphs descending to the moist lower vegetation layers for water replenishment, where they would come into contact with small hosts. Very few larvae quested or fed on rodents under the dry conditions, but many more did so once the humidity increased, suggesting that larvae escape desiccation by becoming quiescent. The ratio of larvae to nymphs feeding on rodents thus increases with increasing humidity, contributing to the seasonal and geographical variation in disease transmission dynamics.

Animals↗
PubMed1996

Oxidative stress and antioxidants in overwintering larvae of cold-hardy goldenrod gall insects

Antioxidant and pro-oxidant systems were studied in overwintering larvae of two cold-hardy gall insect species, the freeze-tolerant fly Eurosta solidaginis and the freeze-avoiding moth Epiblema scudderiana. An increase in the levels of the oxidized form of glutathione suggested slight oxidative stress in both species during the winter. Freeze-tolerant Eurosta solidaginis larvae generally had decreased activities of antioxidant enzymes in the winter, indicating that these larvae do not face increased challenge from oxidative stress during the numerous freeze-thaw events they experience. Instead, existing defences must be sufficient to prevent any damage. By contrast, increased winter activities of antioxidant enzymes in freeze-avoiding Epiblema scudderiana suggest that these larvae must defend against the formation of reactive oxygen species. This may result from the oxidative nature of winter metabolism in these larvae, as well as a dependence on lipid oxidation as their fuel over this season. Xanthine dehydrogenase activity decreased dramatically in both species during the autumn, reducing the potential for the formation of the pro-oxidant xanthine oxidase. Indeed, xanthine oxidase activity fell to undetectable levels by winter in Epiblema scudderiana and was not detectable at any time in Eurosta solidaginis.

Journal Article↗
PubMed1995

Changes in motoneuron membrane potential and reflex activity induced by sudden cooling of isolated spinal cords: differences among cold-sensitive, cold-resistant and freeze-tolerant amphibian species.

The effects of sudden cooling of the spinal cord were studied in three species of amphibians--a cold-sensitive tropical toad (Bufo marinus), a cold-resistant, aquatic, hibernating frog (Rana pipiens, northern leopard frog) and a freeze-tolerant frog (Rana sylvatica, wood frog). Ventral root (motoneuron) potentials were recorded from isolated, hemisected spinal cords of each species mounted in a sucrose-gap recording apparatus and superfused with HCO3(-)-buffered Ringer's solution at room temperature (21 degrees C). In the toad, sudden cooling to 6-8 degrees C produced large, sustained motoneuron depolarizations that returned slowly to baseline levels and were accompanied by extensive paroxysmal activity. Larger, but shorter-lasting, motoneuron depolarizations associated with only a limited amount of paroxysmal activity were generated by rapid cooling of the leopard frog spinal cord. Small, brief motoneuron depolarizations followed by a hyperpolarization, or hyperpolarizations not preceded by depolarizations, were seen in cooled wood frog spinal cords. The wood frog displayed a large amount of spontaneous motoneuron activity, but little paroxysmal activity in response to sudden cooling. Following prolonged cooling, rewarming the spinal cords of all three species resulted in motoneuron hyperpolarizations that slowly decayed towards the baseline value. The amplitude of the rewarming-induced response was larger and longer in toad motoneurons than in leopard frog and wood frog motoneurons. At room temperature, a single supramaximal dorsal root stimulus evoked a depolarizing ventral root potential in toad and leopard frog motoneurons that was decreased in amplitude and prolonged when the spinal cords were cooled to 8 degrees C or below. In contrast, at room temperature, the ventral root reflex in the wood frog was followed by a distinct hyperpolarization. Cooling the wood frog spinal cord only slightly reduced the amplitude of the ventral root potential. In contrast, the evoked hyperpolarization was blocked by sudden cooling and also by the addition of dihydro-ouabain to the Ringer's solution. The motoneuron hyperpolarizations induced by sudden cooling in the wood frog were converted to depolarizations when Cl- in the superfusate was replaced with isethionate. The depolarizations elicited by sudden cooling were reduced by the addition of kynurenate in all three species. A dose-response curve generated by short applications of L-glutamate demonstrated that wood frog motoneurons were less sensitive than leopard frog motoneurons to L-glutamate. In summary, three species of amphibians, differing in their adaptations to the temperature of their environments, vary in their responses to sudden reductions in temperature. The relationship of these responses to their environmental adaptations remains to be determined.

Animals↗
PubMed1992

Influence of long-term hypoxia on the energy metabolism of the haemoglobin-containing bivalve Scapharca inaequivalvis: critical O2 levels for metabolic depression.

The oxygen consumption rate of Scapharca inaequivalvis measured under normoxic conditions over 48 h showed a significant daily cycle with lowest values occurring shortly after the dark period; all hypoxia exposure experiments were carried out during the declining part of the cycle. Animals were exposed to a constant level of hypoxia for a 12-h period in a series of 14 experiments, each at a different oxygen tension. The oxygen consumption was measured continuously, and the extent of accumulation of end-products (succinate and propionate), and the inhibitory effect of adenosine triphosphate on phosphofructokinase were determined at the end of exposures. All three parameters (oxygen consumption, end-product accumulation, phosphofructokinase inhibition) showed a remarkable correlation with major changes occurring between 2.5 and 1.5 ppm (7 and 4 kPa) O2. The oxygen consumption rates showed a drop to 6% of the normoxic rate, but a consistent low consumption remained below 2 ppm (5.5 kPa) which partly recovered over the 12-h exposure period by about three-fold. Succinate and propionate accumulated progressively between 2.5 and 1.5 ppm (7 and 4 kPa); at [O2] less than 1.5 ppm (4 kPa) the concentration did not increase further, indicating that anaerobic metabolism had reached a maximum. Over the same range, phosphofructokinase showed an increased sensitivity for adenosine triphosphate, the lower inhibitor concentration at 50% Vmax value pointing to depression of glycolytic rate. Despite the activation of anaerobic metabolism and the evident depression of aerobic metabolism, simple calculation demonstrates that Scapharca inaequivalvis relies mainly on aerobic metabolism even during severe hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1991

Social interactions in three supported employment options: a comparative analysis.

Controversy exists over the benefits that workers with severe disabilities accrue under different supported employment options. This study focused upon one benefit of supported employment: social integration. Direct observation procedures were used to assess the social interactions of 37 adults with severe disabilities in 18 employment programs representing three different supported employment contexts (individual, enclave, and work crew). Results indicated that workers employed in individual and enclave programs had significantly more contact with nondisabled persons than did members of work crews. No differences were detected in the social contact rate between disabled and nondisabled workers in individual versus enclave sites. Furthermore, few differences in type of interactions across the three different work options were revealed. Results suggest that both individual and enclave models are capable of facilitating social integration. However, characteristics of specific job sites, more so than the employment model per se, may determine whether a particular employment setting is conducive to social integration.

Adult↗
PubMed1990

Changes in enzyme binding and activity during aestivation in the frog Neobatrachus pelobatoides.

1. The proportion of aldolase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) associated with the particulate fraction of a cell was measured in aestivating and non-aestivating Neobatrachus pelobatoides. 2. Reduced binding of these enzymes was found in the brain, indicating lower glycolytic flux. This was not correlated to metabolic rate suggesting that glycolytic rate was reduced in this tissue in the early stages of aestivation, possibly due to a change in fuel use. 3. Measurement of total enzyme levels showed that the liver of aestivating frogs had less GAPDH and less aldolase than non-aestivating frogs.

Adaptation, Physiological↗
PubMed1990

Effects of case manager feedback on the quality of individual habilitation plan objectives.

The functional relation between feedback by a case manager and improved writing of Individual Habilitation Plan (IHP) objectives in adult service agencies was assessed. Feedback on seven features of IHP objectives was delivered by the local case manager to program staff of four agencies providing residential or vocational support to adults with moderate to severe disabilities. The results demonstrate that each of the four agencies improved the quality of their written objectives after receiving feedback from the case manager and maintained those gains 18 months after feedback was terminated. Implications for case managers as feedback agents were discussed.

Community Mental Health Services↗
PubMed1987

Increasing positive social interactions by handicapped individuals during a recreational activity using a multicomponent treatment package.

A multicomponent treatment package increased the rate of positive statements among handicapped youth during a social/leisure activity at a work training setting. The package of role playing, graphic feedback, contingent reinforcement, and self-monitoring was directly replicated across three experiments in producing normative rates of positive verbal statements. There was no evidence of generalization to other stimulus activities. There was limited response generalization to a class of negative verbal statements. The study further examined the critical components of the maintenance package through a withdrawal design. It was found that contingent reinforcement and self-monitoring could maintain substantial rates of positive behaviors. In the third experiment it was further demonstrated that self-monitoring alone could maintain positive statements in three of the four students in the group.

Adolescent↗
PubMed1986

Carriage of penicillin resistant pneumococci.

A survey of 303 urban and 156 rural children showed nasopharyngeal carriage of relatively resistant Streptococcus pneumoniae organisms in 14.2% and 19.2% of children, respectively. These organisms have minimum inhibitory concentrations for penicillin in the range of 0.12-1 microgram/ml. An analysis of 40 relatively resistant S. pneumoniae strains showed resistance to co-trimoxazole in 47.5%, trimethoprim in 42.5%, fusidic acid in 20%, tetracycline in 2.5%, and rifampicin in 5%. All the strains were susceptible to chloramphenicol and vancomycin, while the minimum inhibitory concentrations of third generation cephalosporins and imipenem were comparable with or lower than those of penicillin. Eighty three per cent of the strains tested belonged to serogroups 6 and 19. These findings are discussed in relation to the poor clinical response to treatment with penicillin for relatively resistant S. pneumoniae meningitis, and the minimum inhibitory concentrations of alternate agents under review for treatment of systemic pneumococcal disease are presented.

Anti-Bacterial Agents↗
PubMed1984

Reducing the self-stimulatory behavior of a profoundly retarded female through sensory awareness training.

Sensory awareness training procedures were used to reduce the self-stimulatory behavior of a profoundly retarded female. Self-stimulatory behaviors were directly observed and recorded using a 15-second momentary time sample procedure for 10-minute recording periods. An alternating treatment design was used to compare the effects of treatment and nontreatment. Tactile, olfactory, and gustatory materials were used to stimulate the person's senses. Generalization was assessed across noncompliant behaviors. The results indicate that sensory awareness training reduced self-stimulatory behaviors, but that these behaviors were still being emitted at a high rate. Suggestions for further research are made, and the use of "traditional" sensory awareness training procedures is questioned.

Awareness↗
PubMed1984

Teaching social/sexual skills to mentally retarded adults.

A social/sexual skills training program for institutionalized mentally retarded adults was evaluated. The target behaviors involved a verbal action or reaction within six skill areas and were taught using a commercially available table game, Sorry, and a specially designed card deck. The program featured response-specific feedback, self-monitoring, individualized reinforcers, and individualized performance criterion levels. A multiple baseline across two groups (N = 3 per group) revealed that there were increases in all skill areas. Generalization occurred in individual and group tests conducted by a retarded peer. The program appears to be an effective method of training social/sexual skills because it produces effects that generalize.

Education of Persons with Intellectual Disabilitie↗