Inter-familiar differences in sprint speed of hatchling Sceloporus occidentalis (Reptilia: Iguanidae)

Hatchling Sceloporus occidentalis from the same dam had more similar sprint speeds than did hatchlings from different dams. Families (e.g. siblings from the same dam) of hatchlings differ significantly in body size. However, family differences in sprint speed remain significant when the size differences are removed statistically. Genetic differences among the families of lizards may account for most of the family differences in speed, although environmental or maternal effects may also contribute to family differences in sprint speed.     

The role of stress proteins in responses of a montane willow leaf beetle to environmental temperature variation

The heat shock response is a critical mechanism by which organisms buffer effects of variable and unpredictable environmental temperatures. Upregulation of heat shock proteins (Hsps) increases survival after exposure to stressful conditions in nature, although benefits of Hsp expression are often balanced by costs to growth and reproductive success. Hsp-assisted folding of variant polypeptides may prevent development of unfit phenotypes; thus, some differences in Hsp expression among natural populations of ectotherms may be due to interactions between enzyme variants (allozymes) and Hsps. In the Sierra willow leaf beetle Chrysomela aeneicollis, which lives in highly variable thermal habitats at the southern edge of their range in the Eastern Sierra Nevada, California, allele frequencies at the enzyme locus phosphoglucose isomerase (PGI) vary across a climatic latitudinal gradient. PGI allozymes differ in kinetic properties, and expression of a 70 kDa Hsp differs between populations, along elevation gradients, and among PGI genotypes. Differences in Hsp 70 expression among PGI genotypes correspond to differences in thermal tolerance and traits important for reproductive success, such as running speed, survival and fecundity. Thus, differential Hsp expression among genotypes may allow functionally important genetic variation to persist, allowing populations to respond effectively to environmental change.     

Expression and localization of Hsps in the heart and blood vessel of heat-stressed broilers

The objective of this study was to investigate the kinetics of Hsp60, Hsp70, Hsp90 protein, and messenger RNA (mRNA) expression levels and to correlate these heat shock protein (Hsp) levels with tissue damage resulting from exposure to high temperatures for varying amounts of time. One hundred broilers were heat-stressed for 0, 2, 3, 5, and 10 h, respectively, by rapidly increasing the ambient temperature from 22 +/- 1 degrees C to 37 +/- 1 degrees C. Obvious elevations of plasma creatine kinase indicate damage to myocardial cells after heat stress. Hsp70 and Hsp90, and their corresponding mRNAs in the heart tissue of heat-stressed broilers, elevated significantly after 2 h of heat exposure and decreased quickly with continued heat stress. However, the levels of hsp60 mRNA in the heart of heat-stressed broilers increased sharply (P < 0.01) at 2 h of heat stress but then decreased quickly after 3 h, while the level of Hsp60 protein in the heart increased (P < 0.01) at 2 h of heat stress and maintained a high level throughout heat exposure. The results indicate that the elevation of the three Hsps, especially Hsp60 in heart, may be important markers at the beginning of heat stress and act as protective proteins in adverse environments. The reduction of Hsp signals in the cytoplasm of myocardial cells implies that myocardial cell lesions may have an adverse impact on the function of Hsps during heat stress. Meanwhile, the localization of Hsp70 in blood vessels of broiler hearts suggests another possible mechanism for protection of the heart after heat exposure.     

Differential expression of heat shock protein 70 in relation to stress type in the flatworm <Emphasis Type="Italic">Schmidtea polychroa</Emphasis>

Most heat shock proteins help to cope with stress in organisms ranging from bacteria to vertebrates. Many stress types acting on the intensity of intracellular protein can induce expression of heat shock proteins. Here, we studied changes in expression level of heat shock protein 70 (Hsp70), one of the best investigated stress proteins, in response to five potential stress factors in the planarian flatworm Schmidtea polychroa: (1) homogenized planarian tissue, which releases an alarm substance that signals predation injury, (2) physical damage by puncturing, (3) a simulation of ecological competition by adding a mixture of naturally co-occurring species: one Dendrocoelum and two Polycelis flatworms, one Asellus water louse and one leech, and (4) magnesium chloride, which inhibits regeneration ability. We found that alarm substance (1), physical harm (2), and magnesium chloride (4) led to increased expression of Hsp70, while interspecific competition (3) did not result in elevated Hsp70 expression. There was no difference between the experimental negative control and two temporal controls immediately after collection and just before the experiment. Results show that Schmidtea polychroa is not sensitive to sampling and lab maintenance. However, planarian homogenate, magnesium chloride and physical harm all caused Hsp70-inducing stress. We conclude that Hsp70 quantification is appropriate to study the current stress level in planaria in response to specific conditions.     

Abundance of Ticks (Acari: Ixodidae) Infesting the Western Fence Lizard, Sceloporus Occidentalis, in Relation to Environmental Factors

We examined the impact of environmental characteristics, such as habitat type, topographic exposure and presence of leaf litter, on the abundance of Ixodes pacificus ticks infesting the western fence lizard (Sceloporus occidentalis) at the University of California Hopland Research and Extension Center (HREC), Mendocino County, California. A total of 383 adult lizards were slip-noosed and examined for tick infestation in April and May 1998. At least 94% of the lizards were infested by ticks and at least 20% of the females and 33% of the males carried > 15 ticks. This intensive utilization of western fence lizards (which do not serve as natural reservoirs for Lyme disease spirochetes) by subadult ticks, is probably the primary reason for the low prevalence of infection with Borrelia burgdorferi in I. pacificus nymphs and adults previously recorded at the HREC. Tick loads were higher on male than female lizards. Also, male lizards were generally more heavily infested in late April than in late May. The prevalence of tick infestation exceeded 88% in all habitat types but males collected in woodland and grass/woodland edges had higher tick loads than those collected in open grassland. Male lizards captured in open, exposed grassland tended to carry heavier tick loads in northern/eastern, as compared to southern/western, exposures, and when leaf litter was present.     

Field and laboratory investigations of the thermal influence on tissue-specific Hsp70 levels in common carp (Cyprinus carpio).

Thermal discharge from power stations can affect normal environmental conditions and change in heat shock proteins expression of native fish with increasing temperature. In this study, we investigated levels of Hsp70 in the heart, kidney, brain and gill of the common carp Cyprinus carpio both in long-term heat discharge environment and after 24 h acute heat shock exposure. In laboratory exposure experiments, fish acclimated at 10 degrees C were exposed to various elevated temperatures (20, 24 and 28 degrees C). Hsp70 concentrations were determined in tissues by Western blotting analysis after one dimensional SDS-PAGE separation. In the field study, the level of Hsp70 in the gill of the carp remained at control values, and Hsp70 expression in the heart, kidney and brain underwent a 2.8 to 3.7-fold increase. A lower thermal sensitivity of the Hsp70 response of the brain, compared with the heart, kidney and gill, was observed in the laboratory experiments. Our data show that these tissues had different levels of Hsp70 responses to thermal influence both in acute exposure and long-term acclimation. The pattern of tissue Hsp70 expression may have a close relationship with the thermal tolerance of the carp and allows the fish to survive long-term thermal pollution.     

Effects of Limb Length,Body Mass,Gender, Gravidity,and Elevation on Escape Speed in the Lizard Psammodromus algirus

Most animals rely on their escape speed to flee from predators. Here, we test several hypotheses on the evolution of escape speed in the lizard Psammodromus algirus. We test that: (1) Longer limbs should improve speed sprint. (2) Heavier lizards should be impaired regarding their sprint speed ability, suggesting a trade-off between fat storage and escape capability. (3) Males should achieve faster speeds due to their higher exposure to predators. (4) Gravid females, with increased body mass, should perform lower speed than non-gravid females. And (5) there are inter-population differences in sprint speed across an elevational gradient. We measured lizards sprint speed in a lineal raceway in the laboratory, filming races in standardized conditions and then calculating their maximal speed. We found that hind limb length greatly determined maximal sprint speed, lizards with longer limbs being faster. In parallel, higher body masses reduced maximal speed, which points to a trade-off between fat storage and escaping capability. Sexual differences also arose, as males were faster than females, as a consequence of males having longer limbs. Regarding females, gravidity did not impair maximal sprint speed, suggesting adaptations which compensate for the increased body mass. Finally, we found no elevational trend in both limbs length and sprint speed. In any case, this study suggests that selection on escape capacity may cast morphological evolution, and affect other life-history traits, such as fat storage and reproduction.     

Habitat-related variation in infestation of lizards and rodents with Ixodes ticks in dense woodlands in Mendocino County, California

During the spring and early summer of 2002, we examined the relative importance of Borrelia-refractory lizards (Sceloporus occidentalis, Elgaria spp.) versus potential Borrelia burgdorferi sensu lato (s.l.)-reservoirs (rodents) as hosts for Ixodes pacificus immatures in 14 woodland areas (six oak, five mixed oak/Douglas fir, and three redwood/tanoak areas) distributed throughout Mendocino County, California. Lizards were estimated to serve as hosts for 93-98% of all larvae and > or =99.6% of all nymphs infesting lizards or rodents in oak woodlands and oak/Douglas fir sites in the southern part of the county. In redwood/tanoak woodlands and oak/Douglas fir sites in northern Mendocino County, the contribution of rodents to larval feedings reached 36-69% but lizards still accounted for 94-100% of nymphal bloodmeals. From late April to mid-June, I. pacificus larvae were recovered from 95 to 96% of lizards and dusky-footed woodrats (Neotoma fuscipes) and from 59% of Peromyscus spp. mice. In contrast, 99% of lizards but few woodrats (15%) and none of the mice were infested by nymphs. Comparisons of tick loads for 19 lizard-Peromyscus spp. mouse pairings, where the lizard and mouse were captured within 10m of each other, revealed that the lizards harbored 36 times more larvae and >190 times more nymphs than the mice. In oak woodlands, loads of I. pacificus larvae decreased from late April/early May to late June for S. occidentalis lizards but increased for Peromyscus spp. mice. We conclude that the relative utilization of Borrelia-refractory lizards, as compared to rodents, by I. pacificus larvae was far higher in dry oak woodlands than in moister habitats such as redwood/tanoak and oak/Douglas fir woodlands in northern Mendocino County. Non-lizard-infesting potential enzootic vectors of B. burgdorferi s.l. (I. angustus and I. spinipalpis) were recorded from rodents in three of six oak woodland areas, two of five oak/Douglas fir woodland areas, and two of three redwood/tanoak woodland areas.     

Field and laboratory investigations of the thermal influence on tissue-specific Hsp70 levels in common carp (Cyprinus carpio)

Thermal discharge from power stations can affect normal environmental conditions and change in heat shock proteins expression of native fish with increasing temperature. In this study, we investigated levels of Hsp70 in the heart, kidney, brain and gill of the common carp Cyprinus carpio both in long-term heat discharge environment and after 24 h acute heat shock exposure. In laboratory exposure experiments, fish acclimated at 10 °C were exposed to various elevated temperatures (20, 24 and 28 °C). Hsp70 concentrations were determined in tissues by Western blotting analysis after one dimensional SDS-PAGE separation. In the field study, the level of Hsp70 in the gill of the carp remained at control values, and Hsp70 expression in the heart, kidney and brain underwent a 2.8 to 3.7-fold increase. A lower thermal sensitivity of the Hsp70 response of the brain, compared with the heart, kidney and gill, was observed in the laboratory experiments. Our data show that these tissues had different levels of Hsp70 responses to thermal influence both in acute exposure and long-term acclimation. The pattern of tissue Hsp70 expression may have a close relationship with the thermal tolerance of the carp and allows the fish to survive long-term thermal pollution.     

Complex patterns of expression of heat-shock protein 70 across the southern biogeographical ranges of the intertidal mussel Mytilus californianus and snail Nucella ostrina

Aim It is often assumed that species reach their highest densities in the centre of their ranges and decline in abundance toward the edges of the range. Implicit in this notion, which we call the abundant centre hypothesis, is the assumption that the edges of the range are more stressful to organisms and are more likely to show responses to climate change. However, an earlier review and empirical study of patterns of abundance across the range of intertidal invertebrates show little support for the abundant centre hypothesis and further demonstrated that few studies have examined patterns in either abundance or stress across species ranges. In part this gap is due to the logistical difficulties of sampling species across large geographical ranges. Here we use intertidal invertebrates, which have relatively simple linear latitudinal ranges, and heat‐shock proteins, which have been shown to be an integrative measure of organismal stress, to test the hypothesis that species are more stressed at the edges of their range. We use complementary data on population density to test the relationship between stress proteins and overall species density across the species’ range. Location Our sampling programme covered the southern half of the large geographical ranges of two intertidal invertebrates on the Pacific Coast of North America. Sites were spread between northern Baja California, Mexico and Vancouver Island, Canada, a range of c. 22 degrees of latitude. Method We sampled levels of heat‐shock protein 70 (Hsp70) in eight to 12 individuals from each of 20 sites for the intertidal mussel Mytilus californianus and 11 sites for the intertidal snail Nucella ostrina, spread throughout the southern half of their geographical ranges. The relationships between levels of Hsp70 in individuals from a site and (1) latitude of the site, (2) the site's position in the species’ range and (3) average population density were determined. Results No significant relationship was found in either species between levels of Hsp70 and latitude, position in the range or population density. Complex patterns that did emerge may be explained by nonlinear gradients in environmental conditions along the Pacific coast. Specifically, we observed peak values of Hsp70 for both species in northern Oregon, where intertidal zones are disproportionately exposed to daytime emersion (exposure to air) in the summer months of collections. A second peak for M. californianus was found south of Point Conception, California, which is marked by dramatic shifts toward warmer sea temperatures and decreased wave exposure. Main conclusions Patterns that emerged were not predicted by simple models based on the abundant centre hypothesis. However, they are consistent with more complex pictures of heat stress, organismal condition and abundance along a latitudinal gradient that have been demonstrated in recent studies. We suggest that latitudinal complexity, species‐specific differences and local effects must be considered before generalizing the relationship between environmental stress, abundance, range limits and responses of ranges to climate change.     

Deoxyribonucleic acid damage induced by doxorubicin in peripheral blood mononuclear cells: possible roles for the stress response and the deoxyribonucleic acid repair process

Doxorubicin is an antineoplastic drug widely used in cancer treatment. However, many tumors are intrinsically resistant to the drug or show drug resistance after an initial period of response. Among the different molecules implicated with doxorubicin resistance are the heat shock proteins (Hsps). At present we do not know with certainty the mechanism(s) involved in such resistance. In the present study, to advance our knowledge on the relationship between Hsps and drug resistance, we have used peripheral blood mononuclear cells obtained from healthy nonsmoker donors to evaluate the capacity of a preliminary heat shock to elicit the Hsp response and to establish the protection against the deoxyribonucleic acid (DNA) damage induced by doxorubicin. DNA damage and repair were determined using the alkaline comet assay. We also measured the expression of Hsp27, Hsp60, Hsp70, Hsp90, hMLH1, hMSH2, and proliferating cell nuclear antigen by immunocytochemistry. The damage induced by doxorubicin was more efficiently repaired when the cells were previously heat shocked followed by a resting period of 24 hours before drug exposure, as shown by (1) the increased number of undamaged cells (P < 0.05), (2) the increased DNA repair capacity (P < 0.05), and (3) the high expression of the mismatch repair (MMR) proteins hMLH1 and hMSH2 (P < 0.05). In addition, in the mentioned group of cells, we confirmed by Western blot high expression levels of Hsp27 and Hsp70. We also noted a nuclear translocation of Hsp27 and mainly of Hsp70. Furthermore, inducible Hsp70 was more expressed in the nucleus than Hsc70, showing a possible participation of Hsp70 in the DNA repair process mediated by the MMR system.     

Association of plasma antibodies against the inducible Hsp70 with hypertension and harsh working conditions

Autoantibodies against certain stress or heat shock proteins (Hsps) may play a role in the pathogenesis and/ or prognosis of some diseases. Using immunoblotting with human recombinant Hsps and univariate and multivariate logistic regression models, we have investigated the presence of antibodies against Hsp70, the inducible member of the 70-kDa family of heat shock proteins, and analyzed its possible association with hypertension and working conditions. Plasma and serum were collected from 764 steel mill workers from 6 work sites exposed to (1) severe noise; (2) severe noise and dust; (3) noise, dust, and heat; (4) noise and heat; (5) severe noise and heat; and (6) office conditions (control). Workers with prolonged exposure to stresses such as noise, dust, and high temperature and a combination of these in the workplace had a high incidence (26.6% to 40.2%) of antibodies to Hsp70 compared to the lowest incidence (18.6%) of antibodies to Hsp70 in the control group of office workers. Moreover, there was a statistical association of antibodies against Hsp70 with hypertension. The statistical correlation between the presence of antibodies to Hsp70 and hypertension is higher in the group of workers with blood pressure of 160/95 mmHg than in the 140/90-mmHg group after excluding possible effects of the workplace stresses. These results suggest that harsh workplace conditions can increase the production of antibodies against Hsp70 and that the presence of antibodies to this stress protein may be associated with hypertension. The precise mechanism for the elevation of antibodies against Hsps by environmental and workplace stresses and their relation to hypertension remains to be established.     

Effects of inbreeding and rate of inbreeding in Drosophila melanogaster- Hsp70 expression and fitness

Induction of heat shock proteins (Hsp) is a well-known mechanism through which cells cope with stressful conditions. Hsp are induced by a variety of extrinsic stressors. However, recently intrinsic stressors (aging and inbreeding) have been shown to affect expression of Hsp. Increased homozygosity due to inbreeding may disrupt cellular homeostasis by causing increased expression of recessive deleterious mutations and breakdown of epistatic interactions. We investigated the effect of inbreeding and the rate of inbreeding on the expression of Hsp70, larval heat resistance and fecundity. In Drosophila melanogaster we found that inbred lines (F approximately 0.67) had significantly up-regulated expression of Hsp70, and reduced heat resistance and fecundity as compared with outbred control lines. A significant negative correlation was observed between Hsp70 expression and resistance to an extreme heat stress in inbred lines. We interpreted this as an increased requirement for Hsp70 in the lines suffering most from inbreeding depression. Inbreeding depression for fecundity was reduced with a slower rate of inbreeding compared with a fast rate of inbreeding. Thus, the effectiveness of purging seems to be improved with a slower rate of inbreeding.     

华北丽斑麻蜥食物同化和疾跑速的热依赖性

作者研究山西阳泉丽斑麻蜥(Eremias argus)成体的选择体温、热耐受性及食物同化和疾跑速的热依赖性。选择体温、临界低温和临界高温无显著的两性差异,分别为36·0℃、1·0℃和44·9℃。在实验温度范围内,体温显著影响食物通过时间、日摄食量、日粪尿排量、表观消化系数和同化效率。食物通过时间在26 -34℃范围内随体温升高而缩短,在更高的体温下则延长。蜥蜴在30、32、34和36℃体温下明显摄入较多的食物、排出明显较多的粪尿。34℃和36℃下的表观消化系数和同化效率大于其它更低或更高温度下的对应数值,但这两个变量未因体温变化而呈现清晰的规律性变化。疾跑速在18 -36℃范围内随体温升高而加快,在38℃体温下则减缓。36℃或附近体温最适合疾跑速。疾跑速最适体温接近蜥蜴的选择体温,表明蜥蜴疾跑速的最适温度可能与其选择体温密切相关[动物学报52 (2) : 256 -262 , 2006]。