Response of Development and Body Mass to Daily Temperature Fluctuations: a Study on Tribolium castaneum.

Differences in thermal regimes are of paramount importance in insect development. However, experiments that examine trait development under constant temperature conditions may yield less evolutionarily relevant results than those that take naturally occurring temperature fluctuations into account. We investigated the effect of different temperature regimes (constant 30 °C, constant 35 °C, fluctuating with a daily mean of 30 °C, or fluctuating with a daily mean of 35 °C) on sex-specific development time and body mass in Tribolium castaneum. Using a half-sib breeding design, we also examined whether there is any evidence for genotype-by-environment interactions (GEI) for the studied traits. In response to fluctuating temperature regimes, beetles demonstrated reaction norm patterns in which thermal fluctuations influenced traits negatively above the species' thermal optimum but had little to no effect close to the thermal optimum. Estimated heritabilities of development time were in general low and non-significant. In case of body mass of pupae and adults, despite significant genetic variance, we did not find any GEI due to crossing of reaction norms, both between temperatures and between variability treatments. We have observed a weak tendency towards higher heritabilities of adult and pupa body mass in optimal fluctuating thermal conditions. Thus, we have not found any biasing effect of stable thermal conditions as compared to fluctuating temperatures on the breeding values of heritable body-size traits. Contrary to this we have observed a strong population-wide effect of thermal fluctuations, indicated by the significant temperature-fluctuations interaction in both adult and pupa mass.

Response of body size and developmental time of Tribolium castaneum to constant versus fluctuating thermal conditions.

Temperature has profound effects on biological functions at all levels of organization. In ectotherms, body size is usually negatively correlated with ambient temperature during development, a phenomenon known as The Temperature-Size Rule (TSR). However, a growing number of studies have indicated that temperature fluctuations have a large influence on life history traits and the implications of such fluctuations for the TSR are unknown. Our study investigated the effect of different constant and fluctuating temperatures on the body mass and development time of red flour beetles (Tribolium castaneum Herbst, 1797); we also examined whether the sexes differed in their responses to thermal conditions. We exposed the progeny of half-sib families of a T. castaneum laboratory strain to one of four temperature regimes: constant 30°C, constant 25°C, fluctuating with a daily mean of 30°C, or fluctuating with a daily mean of 25°C. Sex-specific development time and body mass at emergence were determined. Beetles developed the fastest and had the greatest body mass upon emergence when they were exposed to a constant temperature of 30°C. This pattern was reversed when beetles experienced a constant temperature of 25°C: slowest development and lowest body mass upon emergence were observed. Fluctuations changed those effects significantly - impact of temperature on development time was smaller, while differences in body mass disappeared completely. Our results do not fit TSR predictions. Furthermore, regardless of the temperature regime, females acquired more mass, while there were no differences between sexes in development time to eclosion. This finding fails to support one of the explanations for smaller male size: that selection favors the early emergence of males. We found no evidence of genotype × environment interactions for selected set of traits.

Evaluation of alternative waveforms for animated mimic displays.

Animated mimic displays can be used to present system information regarding physical form, function, and causality. However, a potential limitation in current designs has been identified: the presence of ambiguous apparent motion. Two theoretical explanations of ambiguous apparent motion are discussed (Fourier and correspondence hypotheses). Two alternative designs (stair-step and approximate sinusoid luminance waveforms) were evaluated. The velocity matches obtained in Experiment 1 indicate that the sinusoidal waveform produced significantly better performance for both accuracy and latency than the stair-step wave-form. The velocity estimates obtained in Experiment 2 indicate that ambiguous apparent motion was not visible with the sinusoidal waveform, but was with the stair-step waveform. One of the two hypotheses (correspondence) provides a reasonable fit with the obtained velocity estimates. A fundamental goal in the design of animated mimic displays is to provide unambiguous mappings between perceived velocity and actual flow rates. Critical factors in design (e.g., waveform, chromatic/luminance contrast, spatial/temporal frequency) are discussed. Actual or potential applications of this research include the design of more effective animated mimic displays.

Repeated dose toxicity study (28 days) in rats and mice with N-methylpyrrolidone (NMP).

Twenty-eight day feeding studies were conducted to evaluate the repeated dose toxicity of NMP, a widely used industrial solvent, in Crl:CD BR rats and B6C3F1 mice. Groups of 5 male and 5 female rats each were fed either 0, 2,000, 6,000, 18,000, or 30,000 ppm NMP; similar groups of mice were fed either 0, 500, 2,500, 7,500, or 10,000 ppm. In vivo parameters, hematology and clinical chemistry parameters, and complete pathology evaluations were conducted after approximately 28 days. Decrements in mean body weight gains, reflecting decreases in food consumption and efficiency, were seen in male rats fed 18,000 ppm and in both sexes fed 30,000 ppm. In rats, clinical chemical changes, indicating possible compound-related alterations in lipid, protein, and carbohydrate metabolism, occurred at 18,000 ppm in males and 30,000 ppm in both sexes. No histopathological changes in rats were judged to be directly related to NMP exposure. Hematological (mild to moderate leukopenia) and histopathological alterations (hypocellular bone marrow, testicular degeneration and atrophy, and thymic atrophy) were judged to be secondary to nutritional and body weight effects in male and/or female rats at 30,000 ppm. In mice, cloudy swelling of the epithelia of the distal parts of the renal tubuli was observed in 4 males and 3 females at 10,000 ppm and in 2 male mice at 7,500 ppm. For both rats and mice, abnormal urine coloration was observed (in mice at 2,500 ppm and above, and in rats at 18,000 ppm and above). The discoloration was interpreted as a sign of systemic availability of the test substance, but not as an adverse effect. The NOAEL was 6,000 ppm for male rats and 18,000 ppm for female rats. In mice, the NOAEL was 2,500 ppm based on the kidney histopathology.

Cloning and characterization of a G protein-activated human phosphoinositide-3 kinase.

Phosphoinositide-3 kinase activity is implicated in diverse cellular responses triggered by mammalian cell surface receptors and in the regulation of protein sorting in yeast. Receptors with intrinsic and associated tyrosine kinase activity recruit heterodimeric phosphoinositide-3 kinases that consist of p110 catalytic subunits and p85 adaptor molecules containing Src homology 2 (SH2) domains. A phosphoinositide-3 kinase isotype, p110 gamma, was cloned and characterized. The p110 gamma enzyme was activated in vitro by both the alpha and beta gamma subunits of heterotrimeric guanosine triphosphate (GTP)-binding proteins (G proteins) and did not interact with p85. A potential pleckstrin homology domain is located near its amino terminus. The p110 gamma isotype may link signaling through G protein-coupled receptors to the generation of phosphoinositide second messengers phosphorylated in the D-3 position.

Two sites in the third inner loop of the dopamine D2 receptor are involved in functional G protein-mediated coupling to adenylate cyclase.

Synthetic peptides, corresponding to the amino acid sequences of the N- and C-terminal parts of the 3rd intracellular loop of the dopamine D2 receptor, attenuate dopaminergic adenylate cyclase inhibition in membranes. Both peptides also activate directly GTPase activity in membranes. We suggest a functional model for G(i)-coupled receptors where two sites in the 3rd inner loop compose the links for the receptor-G protein interaction thus providing the tools for a selective and adjustable response. Functional coupling was not affected by a peptide representing the insert in the long form of the dopamine D2 receptor (D2(long)). The selectivity pattern of conventional G protein-linked receptors also sheds some light on the recently observed interaction of beta-amyloid protein precursor (APP) complexes with G proteins.

Identification of a Gs-protein coupling domain to the beta-adrenoceptor using site-specific synthetic peptides. Carboxyl terminus of Gs alpha is involved in coupling to beta-adrenoceptors.

Competition between Gs-protein and the synthetic peptide, GSA 379-394, derived from the carboxyl-terminal region of the alpha s-subunit, led to complete inhibition of receptor-mediated adenylate cyclase activation in turkey erythrocyte membranes. Related peptides corresponding to the homologous carboxyl-terminal region of alpha t-, alpha il- or alpha o-subunits did not interfere with beta-receptor-Gs coupling. The direct coupling between Gs and adenylate cyclase was not influenced by any of these peptides. These results emphasize the important role of the carboxyl-terminus of G-protein alpha-subunits for the specific recognition of their corresponding receptors and for signal transduction.

Ergometer within a whole-body plethysmograph to evaluate performance of guinea pigs under toxic atmospheres.

A guinea pig ergometer was constructed within an enclosure, with inlet and outlet ports for continuous ventilation, designed so that the enclosure would work as a whole-body plethysmograph as well as an inhalation exposure chamber. This system provided continuous measurement of tidal volume, respiratory frequency, oxygen uptake, and carbon dioxide output which enabled an evaluation of performance in terms of distance traveled over time with the animals running at a known speed and constant oxygen uptake. The effects of CO or HCl in running versus sedentary animals were investigated using this apparatus. For CO, exercise increased the rapidity of the onset of incapacitation as would be predicted by the increase in metabolic rate. HCl produced a more severe incapacitating effect in exercising animals that was out of proportion with the increase in minute volume induced by exercise.

Performance evaluation under intoxicating atmospheres.

A new behavioral model has been developed and used to assess the performance of mice during exposure to carbon monoxide, hydrogen chloride, or subambient levels of oxygen. The apparatus is a ventilated 150-ft series of glass tubes forming an S-shaped exposure system. Performance evaluation was obtained for two sublethal responses: distance traveled/time and incapacitation. Performance of normal mice (Type I) or mice previously fitted with a tracheal cannula (Type II) was very reproducible and similar. Concentration-response relationships were obtained showing the deterioration of performance with exposures to CO from 2500 ppm, HCl from 1095 ppm, and below 8.8% ambient O2 level. This model is likely to be sensitive to other asphyxiants and irritants. It includes both distance traveled and time of performance prior to incapacitation. Both are critical parameters to be included in escape hazard analysis in fire situations and possibly in other accidents involving chemical spills.

Evaluation of the pulmonary effects of wood smoke in guinea pigs by repeated CO2 challenges.

Male, English smooth haired guinea pigs were exposed to thermal decomposition products, i.e., smoke, generated by heating Douglas fir in an open system. Various amounts of Douglas fir were placed in a furnace, at room temperature, and heated at a rate of 11 degrees C/min until completely decomposed. Major decomposition occurred between 160 and 490 degrees C, and the animals were exposed during this time for a period of 30 min. Immediately before exposure and at various times after exposure, each animal was evaluated by whole-body plethysmography to measure tidal volume and respiratory frequency during air breathing as well as during challenge with 10% CO2. Exposure to smoke from Douglas fir resulted in a diminished ventilatory response to 10% CO2. Comparing the effect of wood smoke to the effect of smoke from polyvinylchloride from previous experiments wood smoke was found to be 10 times less potent than smoke from polyvinylchloride and animals recovered much more rapidly than with smoke from polyvinylchloride.

Study of biological samples obtained from victims of MGM Grand Hotel fire.

Eighty blood samples and 17 respiratory-tract tissue samples containing fluid taken from victims of the MGM Grand Hotel fire were studied to assist in the determination of the cause of death. The blood and tissue-fluid samples were analyzed for carboxyhemoglobin, oxyhemoglobin, methemoglobin, and total hemoglobin. Outgassing studies were done on the tissue samples using gas chromatography/mass spectroscopy, and heavy metal analysis on inhaled soot was done by x-ray fluorescence. The carboxyhemoglobin values obtained on the samples were significantly higher than those reported by Clark County. However, the percentage of the victims with a carboxyhemoglobin saturation level of 50% or less is higher than that found in the Maryland fire fatality study, suggesting that other toxic factors may have contributed to the lethal nature of the fire.

Pathologic findings in rats following inhalation of combustion products of polytetrafluoroethylene (PTFE).

Adult male Fischer 344 rats received single 30-min exposures to the aerosolized products of polytetrafluoroethylene (PTFE) heated to 595 degrees C. The concentrations of thermal degradation products of PTFE were at the LC50 dose of 0.045 mg/l for most rats, but some rats received doses ranging from 0.005 to 5.025 mg/l. Serial measurements of cardiopulmonary function were obtained and will be published subsequently. Necropsies were performed at 0, 2, 12, 24 and 36 h post-exposure, and a few rats were killed between 2 and 17 days. Signs of respiratory impairment were followed by death in some rats. Pathologic findings included focal hemorrhages, edema and fibrin deposition in the lungs. With time focal interstitial thickenings developed due to hypertrophy and hyperplasia of alveolar cells, and macrophages accumulated in alveoli. Thrombosis of pulmonary capillaries was common. Disseminated intravascular coagulation (DIC) occurred in 53% of test rats; its incidence and severity were positively related to the degree of pulmonary damage. Renal infarcts were common due to DIC. No lesions were seen in kidneys or other tissue (except lung and thymus) unless they were affected with DIC. Thymic lymphocytes underwent necrosis in many test and some vehical (warm air) control rats, possibly due to stress. The finding of DIC in PTFE combustion product exposure has not been reported to our knowledge. The toxicity of the thermal degradation products of PTFE requires further study, especially relative to induction of DIC.