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Biomedical subjects

R E Lee

Publications and source records attributed to R E Lee.

At least 19 recordsLinked to original sources
PubMed2006

Habitat requirements of the seabird tick, Ixodes uriae (Acari: Ixodidae), from the Antarctic Peninsula in relation to water balance characteristics of eggs, nonfed and engorged stages.

The seabird tick Ixodes uriae is exposed to extreme environmental conditions during the off-host phase of its life cycle on the Antarctic Peninsula. To investigate how this tick resists desiccation, water requirements of each developmental stage were determined. Features of I. uriae water balance include a high percentage body water content, low dehydration tolerance limit, and a high water loss rate, which are characteristics that classify this tick as hydrophilic. Like other ticks, I. uriae relies on water vapor uptake as an unfed larva and enhanced water retention in the adult, while nymphs are intermediate and exploit both strategies. Stages that do not absorb water vapor, eggs, fed larvae and fed nymphs, rely on water conservation. Other noteworthy features include heat sensitivity that promotes water loss in eggs and unfed larvae, an inability to drink free water from droplets, and behavioral regulation of water loss by formation of clusters. We conclude that I. uriae is adapted for life in a moisture-rich environment, and this requirement is met by clustering in moist, hydrating, microhabitats under rocks and debris that contain moisture levels that are higher than the tick's critical equilibrium activity.

Animals↗
PubMed2005

Anoxia tolerance and freeze tolerance in hatchling turtles.

Freezing survival in hatchling turtles may be limited by ischemic anoxia in frozen tissues and the associated accumulation of lactate and reactive oxygen species (ROS). To determine whether mechanisms for coping with anoxia are also important in freeze tolerance, we examined the association between capacities for freezing survival and anoxia tolerance in hatchlings of seven species of turtles. Tolerance to freezing (-2.5 degrees C) was high in Emydoidea blandingii, Chrysemys picta, Terrapene ornata, and Malaclemys terrapin and low in Graptemys geographica, Chelydra serpentina, and Trachemys scripta. Hatchlings survived in a N(2) atmosphere at 4 degrees C for periods ranging from 17 d (M. terrapin) to 50 d (G. geographica), but survival time was not associated with freeze tolerance. Lactate accumulated during both stresses, but plasma levels in frozen/thawed turtles were well below those found in anoxia-exposed animals. Activity of the antioxidant enzyme catalase in liver increased markedly with anoxia exposure in most species, but increased with freezing/thawing only in species with low freeze tolerance. Our results suggest that whereas oxygen deprivation occurs during somatic freezing, freeze tolerance is not limited by anoxia tolerance in hatchling turtles.

Acclimatization↗
PubMed2003

Adaptations to terrestrial overwintering of hatchling northern map turtles, Graptemys geographica.

We conducted a 3-year field and laboratory study of winter biology in hatchlings of the northern map turtle ( Graptemys geographica). At our study area in northern Indiana, hatchlings routinely overwintered in their natal nests, emerging after the weather warmed in spring. Winter survival was excellent despite the fact that hatchlings were exposed frequently to subfreezing temperatures (to -5.4 degrees C). In the laboratory, cold-acclimated hatchlings exhibited low rates of evaporative water loss (mean=2.0 mg g(-1) day(-1)), which would enable them to conserve body water during winter. Laboratory-reared hatchlings were intolerant of freezing at -2.5 degrees C for 24 h, conditions that are readily survived by freeze-tolerant species of turtles. Winter survival of hatchling G. geographica probably depended on their extensive capacity for supercooling (to -14.8 degrees C) and their well-developed resistance to inoculative freezing, which may occur when hatchlings contact ice and ice-nucleating agents present in nesting soil. Supercooled hatchlings survived a brief exposure to -8 degrees C. Others, held at -6 degrees C for 5 days, maintained ATP concentrations at control levels, although they did accumulate lactate and glucose, probably in response to tissue hypoxia. Therefore, anoxia tolerance, as evidenced by the viability of hatchlings exposed to N(2) gas for 8 days, may promote survival during exposure to subfreezing temperatures.

Acclimatization↗
PubMed2003

Acquisition of freezing tolerance in early autumn and seasonal changes in gall water content influence inoculative freezing of gall fly larvae, Eurosta solidaginis (Diptera, Tephritidae).

We examined seasonal changes in freeze tolerance and the susceptibility of larvae of the gall fly, Eurosta solidaginis to inoculative freezing within the goldenrod gall (Solidago sp.). In late September, when the water content of the galls was high (approximately 55%), more than half of the larvae froze within their galls when held at -2.5 degrees C for 24 h, and nearly all larvae froze at -4 or -6 degrees C. At this time, most larvae survived freezing at > or = -4 degrees C. By October plants had senesced, and their water content had decreased to 33%. Correspondingly, the number of larvae that froze by inoculation at -4 and -6 degrees C also decreased, however the proportion of larvae that survived freezing increased markedly. Gall water content reached its lowest value (10%) in November, when few larvae froze during exposure to subzero temperatures > or = -6 degrees C. In winter, rain and melting snow transiently increased gall water content to values as high as 64% causing many larvae to freeze when exposed to temperatures as high as -4 degrees C. However, in the absence of precipitation, gall tissues dried and, as before, larvae were not likely to freeze by inoculation. Consequently, in nature larvae freeze earlier in the autumn and/or at higher temperatures than would be predicted based on the temperature of crystallization (T(c)) of isolated larvae. However, even in early September when environmental temperatures are relatively high, larvae exhibited limited levels of freezing tolerance sufficient to protect them if they did freeze.

Adaptation, Physiological↗
PubMed2001

Intracellular freezing, viability, and composition of fat body cells from freeze-intolerant larvae of Sarcophaga crassipalpis.

Although it is often assumed that survival of freezing requires that ice formation must be restricted to extracellular compartments, fat body cells from freeze-tolerant larvae of the gall fly, Eurosta solidaginis (Diptera, Tephritidae) survive intracellular freezing. Furthermore, these cells are highly susceptible to inoculative freezing by external ice, undergo extensive lipid coalescence upon thawing, and survive freezing better when glycerol is added to the suspension medium. To determine whether these traits are required for intracellular freeze tolerance or whether they are incidental and possessed by fat body cells in general, we investigated the capacity of fat body cells from nondiapause-destined and diapause-destined (i.e., cold-hardy) larvae of the freeze-intolerant flesh fly Sarcophaga crassipalpis (Diptera, Sarcophagidae) to survive intracellular freezing. Fat body cells from both types of larvae were highly susceptible to inoculative freezing; all cells froze between -3.7 to -6.2 degrees C. The highest rates for survival of intracellular freezing occurred at -5 degrees C. The addition of glycerol to the media markedly increased survival rates. Upon thawing, the fat body cells showed little or no lipid coalescence. Fat body cells from E. solidaginis had a water content of only 35% compared to cells from S. crassipalpis larvae that had 52-55%; cells with less water may be less likely to be damaged by mechanical forces during intracellular freezing.

Animals↗
PubMed2001

Diapause development in frozen larvae of the goldenrod gall fly, Eurosta solidaginis fitch (diptera: tephritidae).

Seasonal changes in metabolic rate and the potential for morphological development demonstrated that third-instar larvae of the goldenrod gall fly, Eurosta solidaginis Fitch, exhibit a distinct winter diapause. Metabolic rate (CO2 production) was significantly lower from 15 October to 9 February than in early autumn (9 September) and spring (1 March) samples. The induction of diapause coincided with the development of cold-hardening, maximum larval mass, and gall senescence, but our experiments did not identify specific cues triggering diapause induction. We examined the influence of exposure to 0 degrees C and -20 degrees C on diapause development. Diapause development in larvae stored at 0 degrees C occurred at approximately the same rate as in nature. Until 15 December the larvae were in the refractory phase of diapause (incapable of morphological development, even at permissive temperatures), but afterward moved to the activated phase within which diapause intensity decreased until termination in February. Diapause development occurred in larvae collected during the winter and stored at -20 degrees C for periods of 1 week to 3 months. Diapause intensity decreased in frozen larvae through the winter but at a slower rate than in larvae stored at 0 degrees C.

Animals↗
PubMed2001

Physiological responses to supercooling and hypoxia in the hatchling painted turtle, Chrysemys picta.

We investigated physiological responses to supercooling in hatchling painted turtles (Chrysemys picta) which remain in their natal nests over winter and therefore may become exposed to subzero temperatures. These turtles are freeze tolerant but also must rely on supercooling to survive exposure to the lower temperatures occurring in nests during winter. We compared whole-body concentrations of lactate, glucose, glycerol, and ATP in turtles chilled at 0 degrees C, -4 degrees C, or -6 degrees C for 5 days, or at 6 degrees C for 19 days. In a companion experiment, we measured metabolite concentrations in turtles exposed to a hypoxic environment for 1 day, 4 days, or 8 days. Supercooling and hypoxia exposure were both associated with an increase in concentrations of lactate and glucose and a decrease in glycerol concentrations (albeit no change in the ATP pool), suggesting that supercooling induces functional hypoxia. We conclude that hypoxia tolerance may be an important pre-adaptation for surviving exposure to subzero temperatures in hatchling C. picta.

Animals↗
PubMed2001

Validating motivational readiness for exercise behavior with adolescents.

The stages of motivational readiness as conceptualized by the Transtheoretical Model have been widely used among adult samples to assess readiness for adopting exercise behavior. To date, little research has been conducted using a staging framework with adolescent samples. There is a need for validation of the staging framework prior to a substantial amount of research with this age group. The current article presents two studies assessing stage and reported exercise behavior (Study 1: n = 819; M age = 15.0 years, SD = 1.2; 51% men; Study 2: n = 184; M age = 18.6 years, SD = .5; 45% men). As hypothesized in both studies, reported exercise consistently varied as a function of stage classification; those in earlier stages of readiness reported less exercise than those in later stages. Staging algorithms showed good sensitivity to detect reported exercise; however, specificity was distinctly better with the algorithm that used a specific activity criterion and immediate intention, as opposed to irregular behavior, in defining the preparation stage. Results support the validity of the staging framework for measuring motivational readiness for exercise behavior among North American adolescents.

Adolescent↗
PubMed2001

Functional phosphorylation sites in the C-terminal region of the multivalent multifunctional transcriptional factor CTCF.

CTCF is a widely expressed and highly conserved multi-Zn-finger (ZF) nuclear factor. Binding to various CTCF target sites (CTSs) is mediated by combinatorial contributions of different ZFs. Different CTSs mediate distinct CTCF functions in transcriptional regulation, including promoter repression or activation and hormone-responsive gene silencing. In addition, the necessary and sufficient core sequences of diverse enhancer-blocking (insulator) elements, including CpG methylation-sensitive ones, have recently been pinpointed to CTSs. To determine whether a posttranslational modification may modulate CTCF functions, we studied CTCF phosphorylation. We demonstrated that most of the modifications that occur at the carboxy terminus in vivo can be reproduced in vitro with casein kinase II (CKII). Major modification sites map to four serines within the S(604)KKEDS(609)S(610)DS(612)E motif that is highly conserved in vertebrates. Specific mutations of these serines abrogate phosphorylation of CTCF in vivo and CKII-induced phosphorylation in vitro. In addition, we showed that completely preventing phosphorylation by substituting all serines within this site resulted in markedly enhanced repression of the CTS-bearing vertebrate c-myc promoters, but did not alter CTCF nuclear localization or in vitro DNA-binding characteristics assayed with c-myc CTSs. Moreover, these substitutions manifested a profound effect on negative cell growth regulation by wild-type CTCF. CKII may thus be responsible for attenuation of CTCF activity, either acting on its own or by providing the signal for phosphorylation by other kinases and for CTCF-interacting protein partners.

Amino Acid Sequence↗
PubMed2001

Cigarette advertising and promotional strategies in retail outlets: results of a statewide survey in California.

OBJECTIVE: To examine the extent and types of cigarette advertising materials in stores and to assess tobacco company compliance with the 1998 Master Settlement Agreement (MSA). DESIGN: A cross-sectional analysis of a random sample of 586 stores that sold cigarettes. SETTING: US state of California. MAIN OUTCOME MEASURES: Trained data collectors classified cigarette advertising materials by type (signs, displays, functional items), location (interior or exterior), and placement (below 3 feet (1 m) or near candy). RESULTS: California retail outlets featured 17.2 (SD 16.1) tobacco advertising materials on average, and 94% of stores featured at least some advertising. About 85% of these were within 4 feet (1.3 m) of the counter. About 50% of the stores had ads at or below 3 feet, and 23% had cigarette product displays next to candy. In violation of the MSA, 3% of stores featured signs with cartoons and 11% had large exterior signs. CONCLUSIONS: Tobacco companies are aggressively using stores to market cigarettes. Moreover, the spirit of the MSA-to protect children from cigarette advertising-has not been realised. Future studies should monitor industry use of this venue and assess the impact of exposure to cigarette advertising materials in stores on adult smokers and youth.

Advertising↗
PubMed2001

Rapid cold-hardening of Drosophila melanogaster (Diptera: Drosophiladae) during ecologically based thermoperiodic cycles.

In contrast to most studies of rapid cold-hardening, in which abrupt transfers to low temperatures are used to induce an acclimatory response, the primary objectives of this study were to determine (i) whether rapid cold-hardening was induced during the cooling phase of an ecologically based thermoperiod, (ii) whether the protection afforded was lost during warming or contributed to increased cold-tolerance during subsequent cycles and (iii) whether the major thermally inducible stress protein (Hsp70) or carbohydrate cryoprotectants contributed to the protection afforded by rapid cold-hardening. During the cooling phase of a single ecologically based thermoperiod, the tolerance of Drosophila melanogaster to 1 h at -7 degrees C increased from 5 +/- 5% survival to 62.5 +/- 7.3% (means +/- S.E.M., N=40-60), while their critical thermal minima (CTmin) decreased by 1.9 degrees C. Cold hardiness increased with the number of thermoperiods to which flies were exposed; i.e. flies exposed to six thermoperiods were more cold-tolerant than those exposed to two. Endogenous levels of Hsp70 and carbohydrate cryoprotectants were unchanged in rapidly cold-hardened adults compared with controls held at a constant 23 degrees C. In nature, rapid cold-hardening probably affords subtle benefits during short-term cooling, such as allowing D. melanogaster to remain active at lower temperatures than they otherwise could.

Acclimatization↗
PubMed2001

A prospective analysis of the relationship between walking and mood in sedentary ethnic minority women.

Walking for exercise is becoming widely recognized for bestowing health benefits. This study examined the association of walking for exercise and mood in sedentary, ethnic minority women over a five-month period. Ethnic minority women (N = 102) participated in a randomized, controlled trial of a 7-week behaviorally based telephone and mail intervention that promoted the adoption of walking for exercise compared to a non-behavioral minimal intervention. At 2-month post-test and 5-month follow-up, participants reported significant decreases in depressive mood and increases in vigor. Increase in walking over the course of the study was associated with change in vigor. Limited evidence was found to support a relationship between walking for exercise and mood improvement in ethnic-minority women.

Adult↗
PubMed2001

The relation between community bans of self-service tobacco displays and store environment and between tobacco accessibility and merchant incentives.

OBJECTIVES: These studies investigated (1) the effect of community bans of self-service tobacco displays on store environment and (2) the effect of consumer tobacco accessibility on merchants. METHODS: We counted cigarette displays (self-service, clerk-assisted, clear acrylic case) in 586 California stores. Merchant interviews (N = 198) identified consumer tobacco accessibility, tobacco company incentives, and shoplifting. RESULTS: Stores in communities with self-service tobacco display bans had fewer self-service displays and more acrylic displays but an equal total number of displays. The merchants who limited consumer tobacco accessibility received fewer incentives and reported lower shoplifting losses. In contrast, consumer access to tobacco was unrelated to the amount of monetary incentives. CONCLUSIONS: Community bans decreased self-service tobacco displays; however, exposure to tobacco advertising in acrylic displays remained high. Reducing consumer tobacco accessibility may reduce shoplifting.

Advertising↗
PubMed2000

Use of genomics and combinatorial chemistry in the development of new antimycobacterial drugs.

With the completion of the genome of Mycobacterium tuberculosis comes the promise of a new generation of potent drugs to combat the emerging epidemic of multiply drug-resistant isolates. Translating this genomic information into realistic assays, valid targets, and preclinical drug candidates represents the next great hope in tuberculosis control. We propose a paradigm for exploiting the genome to inform the development of novel antituberculars, utilizing the techniques of differential gene expression as monitored by DNA microarrays coupled with the emerging discipline of combinatorial chemistry. A comparison of currently used antituberculars with the properties of other pharmaceuticals suggests that such compounds will have a defined range of physiochemical properties. In general, we can expect the next generation of antituberculars to be small, relatively hydrophilic molecules that bind tightly to specific cellular targets. Many current antimycobacterials require some form of cellular activation (e.g. the activation of isoniazid by a catalase-peroxidase). Activation corresponds to the oxidative, reductive, or hydrolytic unmasking of reactive groups, which occurs with many current antimycobacterial prodrugs. Understanding the mechanisms involved in activation of current antimycobacterial therapeutics also may facilitate the development of alternative activation strategies or of analogs that require no such processes.

Animals↗
PubMed2000

Isoniazid affects multiple components of the type II fatty acid synthase system of Mycobacterium tuberculosis.

Genetic and biochemical evidence has implicated two different target enzymes for isoniazid (INH) within the unique type II fatty acid synthase (FAS) system involved in the production of mycolic acids. These two components are an enoyl acyl carrier protein (ACP) reductase, InhA, and a beta-ketoacyl-ACP synthase, KasA. We compared the consequences of INH treatment of Mycobacterium tuberculosis (MTB) with two inhibitors having well-defined targets: triclosan (TRC), which inhibits InhA; and thiolactomycin (TLM), which inhibits KasA. INH and TLM, but not TRC, upregulate the expression of an operon containing five FAS II components, including kasA and acpM. Although all three compounds inhibit mycolic acid synthesis, treatment with INH and TLM, but not with TRC, results in the accumulation of ACP-bound lipid precursors to mycolic acids that were 26 carbons long and fully saturated. TLM-resistant mutants of MTB were more cross-resistant to INH than TRC-resistant mutants. Overexpression of KasA conferred more resistance to TLM and INH than to TRC. Overexpression of InhA conferred more resistance to TRC than to INH and TLM. Co-overexpression of both InhA and KasA resulted in strongly enhanced levels of INH resistance, in addition to cross-resistance to both TLM and TRC. These results suggest that these components of the FAS II complex are not independently regulated and that alterations in the expression level of InhA affect expression levels of KasA. Nonetheless, INH appeared to resemble TLM more closely in overall mode of action, and KasA levels appeared to be tightly correlated with INH sensitivity.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗
PubMed2000

Clinical assessment using the Clinical Rating Scale: Thomas and Olson revisited.

Does the Clinical Rating Scale retain its validity when it is used, not by researchers, but by psychotherapists in their clinical practice? Students in a marital and family therapy training center routinely used the Clinical Rating Scale as part of the intake process. Although they had modest training in its use, confirmatory factor analysis indicated that they produced data that provided a reasonable approximation of the underlying factor structure. Therefore, although primarily considered a research instrument, the Clinical Rating Scale may have a role in clinical assessment and treatment planning.

Family↗
PubMed2000

Seasonal changes in physiology and development of cold hardiness in the hatchling painted turtle Chrysemys picta.

Hatchling painted turtles (Chrysemys picta) commonly hibernate in shallow, natal nests where winter temperatures may fall below -10 degrees C. Although hatchlings are moderately freeze-tolerant, they apparently rely on supercooling to survive exposure to severe cold. We investigated seasonal changes in physiology and in the development of supercooling capacity and resistance to inoculative freezing in hatchling Chrysemys picta exposed in the laboratory to temperatures that decreased from 22 to 4 degrees C over a 5.5 month period. For comparison, we also studied hatchling snapping turtles (Chelydra serpentina), a less cold-hardy species that usually overwinters under water. Although Chrysemys picta and Chelydra serpentina differed in some physiological responses, both species lost dry mass, catabolized lipid and tended to gain body water during the acclimation regimen. Recently hatched, 22 degrees C-acclimated Chrysemys picta supercooled only modestly (mean temperature of crystallization -6.3+/-0.2 degrees C; N=6) and were susceptible to inoculation by ice nuclei in a frozen substratum (mean temperature of crystallization -1.1+/-0.1 degrees C; N=6) (means +/- s.e.m.). In contrast, cold-acclimated turtles exhibited pronounced capacities for supercooling and resistance to inoculative freezing. The development of cold hardiness reflected the elimination or deactivation of potent endogenous ice nuclei and an elevation of blood osmolality that was due primarily to the retention of urea, but was not associated with accumulation of the polyols, sugars or amino acids commonly found in the cryoprotection systems of other animals. Also, Chrysemys picta (and Chelydra serpentina) lacked both antifreeze proteins and ice-nucleating proteins, which are used by some animals to promote supercooling and to initiate freezing at the high temperatures conducive to freezing survival, respectively.

Acclimatization↗