Fear and distress in Japanese quail chicks of two lines genetically selected for low or high adrenocortical response to immobilization stress.

Behavioral and adrenocortical reactivity to stressful stimulation was examined in 12- and 13-day-old chicks of two lines of Japanese quail selected over several generations for exaggerated (HS: high stress) or reduced (LS: low stress) plasma corticosterone (B) response to brief immobilization stress. Plasma B concentrations and tonic immobility (TI) fear reactions were measured in unstressed (control) and stressed (overnight cooping) chicks of both lines. The stress treatment was applied over a period of 12-20 hr and it involved capture by the experimenter, inescapable exposure to an unfamiliar environment and to strange conspecifics, reductions in ambient temperature and floor space, and the deprivation of food and water. Chicks of the HS line were more susceptible to the induction of TI and they remained immobile longer than did LS chicks. Therefore HS chicks were considered to be more fearful than their LS counterparts. Stress treatment elicited a marked adrenocortical response that was more pronounced in HS than in LS chicks. Stress treatment also increased susceptibility to TI but did not significantly affect the duration of immobility. These findings suggest that selecting the quail for differential corticosterone response to a particular stressor had exerted an unconscious and concomitant effect on underlying fearfulness as well as on their adrenocortical reactivity to several other stressful situations. The results are further discussed in terms of a putative relationship between adrenocortical activation and fearfulness.     

Biological differences between strains of Tribolium castaneum selected for resistance to hypoxia and hypercarbia, and the unselected strain

Abstract. A strain of the red flour beetle Tribolium castaneum (Herbst) was selected separately for resistance to hypoxia and hypercarbia. At the 21st generation, adults and pupae of the line selected for resistance to hypoxia were significantly heavier than those selected for resistance to hypercarbia and the unselected line. It also exhibited a more prolonged developmental range than the unselected line. The line selected for resistance to hypercarbia was also significantly heavier than the unselected line. When the selected and unselected lines were subjected to starvation at the 26th generation, metabolism in both selected lines proceeded at a lower rate than in the unselected line and consequently the selected lines survived for much longer periods.     

Physiological differences between strains of Tribolium castaneum selected for resistance to hypoxia and hypercarbia, and the unselected strain

Abstract. The metabolic rates, as expressed by oxygen (O₂) consumption, carbon dioxide (CO₂) production, and losses in wet and dry weights, were examined for adults of three strains of the red flour beetle Tribolium castaneum (Herbst), during exposure to two modified atmospheres (MAs). Exposure of a strain selected for resistance over twenty-one generations to an atmosphere of 65% CO₂, 20% O₂ and the balance nitrogen (N₂), termed a high carbon dioxide concentration atmosphere (HCC) and exposure of an unselected strain to HCC, showed considerable levels of aerobic metabolism during exposure. For the unselected strain water loss and mobilization of energy reserves were rapid and mortality was followed by rapid desiccation. For the HCC-resistant strain water balance was maintained and energy reserves were utilized more slowly over a prolonged period. Exposure of a strain selected for resistance over twenty-one generations to a low oxygen concentration atmosphere (LOC) of 0.5% O₂ in N₂, and an unselected strain to LOC, revealed that even at 0.5% O₂, metabolism was largely aerobic in both strains. Maintenance of water balance was not a major factor causing mortality of either strain during exposure to LOC. In air, metabolic rates of both the resistant strains were lower than that of the unselected strain.     

Delayed hypersensitivity and migration inhibition in two lines of mice genetically selected for high or low responsiveness to phytohemagglutinin

Delayed-type hypersensitivity (DTH) and cell migration inhibition (MI) were studied in two lines of mice genetically selected for the high (Hi/PHA) or low (Lo/PHA) in vitro response of their lymphoid cells to phytochemagglutinin (PHA). A rapid photoelectric procedure for reading cell migrations enabled the study of MI over a wide range (10 log) of antigen concentrations in vitro. Hi/PHA mice required immunization with a 10 times higher dose of ovalbumin (OVA) in Freund's complete adjuvant (FCA) than Lo/PHA mice for a comparable response in DTH (footpad swelling) and MI of their induced peritoneal exudate cells (PEC). Lo/PHA spleen showed marked bizonal MI on Day 5 after immunization with low doses (0.1 and 0.5 micrograms) of OVA in FCA, one peak being obtained in presence of in vitro concentrations of 10(-3) or 10(-2) micrograms/ml OVA and another peak at 1 or 10 micrograms/ml, whereas Hi/PHA spleen showed stimulation of migration. In contrast, MI in Lo/PHA spleen failed to persist beyond Day 19, whereas it appeared progressively in Hi/PHA spleen, being maximal by Day 27. Low-zone inhibition in Hi/PHA spleen and PEC was lacking or poor even after immunization with higher doses of OVA in FCA. The implications of these findings are discussed.     

A comparison of genetic variability in strains of Japanese quail selected for heavy body weight.

Electrophoretic analyses of body tissues from three strains of Japanese quail from the Quail Genetic Stock Centre at the University of British Columbia, two selected for heavy body weight and one randombred, were carried out to determine whether genetic variations in selected strains were different from randombred strains. In addition, the data were also compared with those obtained from domestic and wild populations in Japan. The proportion of polymorphic loci was higher in the heavy strains than in the randombred strain. The selected strains also differed from the randombred strain in the allelic frequencies of liver esterase and phosphogluconate dehydrogenase. While the randombred strain was genetically similar to the domestic strains in Japan, the two selected strains were different from each other and from the domestic strains in Japan. This indicates that (1) polymorphic loci have adaptive importance, and (2) heavy body weight can be achieved by separate genetic mechanisms. A previously unreported allele that affects the migration pattern of muscle adenylate kinase was also discovered in one of the selected strains.     

Ventilatory and hematopoietic responses to chronic hypoxia in two rat strains.

Hilltop (H) and Madison (M) strains of Sprague-Dawley rats exhibit strikingly different susceptibilities to the effects of chronic altitude exposure. The H rats develop greater polycythemia, hypoxemia, and pulmonary hypertension. We studied ventilation, pulmonary gas exchange, tissue oxygenation, and hematologic adaptations in the two rat strains during a 50-day exposure to a simulated altitude (HA) of 5,500 m (18,000 ft). There were no strain differences among the variables we studied under sea level (SL) conditions. Within the first 14 days of hypoxic exposure, the only significant strain differences were that erythropoietin (EPO) rose much higher and erythroid activity was greater in the H rats, even though arterial Po2 and PCo2 (Pao2 and PaCo2, respectively), renal venous PO2 (Prvo2), and ventilation (VE) were equivalent in the two strains during this time. By day 14 at HA, the H rats had significantly higher erythroid activity, hematocrit (Hct), and EPO levels, significantly lower PaO2 and PrvO2, but equivalent VE and PaCO2. These changes persisted for the remainder of the exposure, except that the Hct continued to rise and the increase was greater in H rats. Despite the greater O2-carrying capacity of H rats in the later stages of hypoxic exposure, PaO2 and PrvO2 were significantly lower in H rats. There were no strain differences at either SL or HA in ventilatory responses to hypercapnia or hypoxia, in blood O2 affinity or 2,3-diphosphoglycerate, in extrarenal production of EPO, or in EPO clearance. We conclude that early in the hypoxic exposure the H rats produce more EPO at apparently equivalent levels of hypoxia, and this is the first step in the pathogenesis of the maladaptation to HA manifest by H rats. We find no consistent evidence that differences in VE contribute to the variable susceptibility to hypoxia in the two rat strains.     

Differences between strains of rhizobium in sensitivity to canavanine

Summary Four strains of rhizobia that nodulate canavanine-synthesizing legumes and four strains that nodulate noncanavanine-synthesizing legumes were tested for sensitivity to L-canavanine. The effect of canavanine on growth depends upon the strain of Rhizobium tested rather than the canavanine synthesizing capability of the host legume. In both groups of rhizobia, some strains were inhibited in growth by canavanine. Canavanine enhancement of growth was observed in rhizobia that nodulate noncanavanine-synthesizing legumes.Canavanine was found to enhance incorporation of uridine-H³ and L-leucine-H³ into trichloroacetic acid insoluble fractions of starved cells of two strains of rhizobia tested. This demonstrated that under certain conditions some rhizobia can detoxify canavanine and utilize it in synthetic processes. re]19760729     

Oxidative phosphorylation and ion transport in the mitochondria of two strains of rats varying in their resistance to stress and hypoxia

The role of mitochondria in the inherited or ontogenetically acquired reactions of organism to stress is not studied enough. In the present work, we examined the functional state of the coupled respiratory chain, potassium and calcium transport and rate of hydrogen peroxide production on two rat lines: August and Wistar—which possess different resistance to emotional stress and hypoxia. It was established that the respiration rate and efficiency of oxidative phosphorylation were higher in August rats than in Wistar ones. In August rats, the rate of potassium transport and ATP-dependent mitochondrial swelling as well as the concentration of the ion in the mitochondrial matrix were almost twice as higher comparatively to those parameters in Wistar rats. The rate of H₂O₂ production was found to be decreased in the mitochondria of August rats. It was also demonstrated that the two rat lines differed by their resistance to the opening of the palmitate/Ca²⁺-induced pore and by their ability to retain calcium within mitochondria. The paper discusses the involvement of the mitochondrial ATP-dependent potassium channel in the adaptation of animals to adverse effects.     

Characterization of herpes simplex viruses selected in culture for resistance to penciclovir or acyclovir

Penciclovir (PCV), an antiherpesvirus agent in the same class as acyclovir (ACV), is phosphorylated in herpes simplex virus (HSV)-infected cells by the viral thymidine kinase (TK). Resistance to ACV has been mapped to mutations within either the TK or the DNA polymerase gene. An identical activation pathway, the similarity in mode of action, and the invariant cross-resistance of TK-negative mutants argue that the mechanisms of resistance to PCV and ACV are likely to be analogous. A total of 48 HSV type 1 (HSV-1) and HSV-2 isolates were selected after passage in the presence of increasing concentrations of PCV or ACV in MRC-5 cells. Phenotypic analysis suggested these isolates were deficient in TK activity. Moreover, sequencing of the TK genes from ACV-selected mutants identified two homopolymeric G-C nucleotide stretches as putative hot spots, thereby confirming previous reports examining Acv(r) clinical isolates. Surprisingly, mutations identified in PCV-selected mutants were generally not in these regions but distributed throughout the TK gene and at similar frequencies of occurrence within A-T or G-C nucleotides, regardless of virus type. Furthermore, HSV-1 isolates selected in the presence of ACV commonly included frameshift mutations, while PCV-selected HSV-1 mutants contained mostly nonconservative amino acid changes. Data from this panel of laboratory isolates show that Pcv(r) mutants share cross-resistance and only limited sequence similarity with HSV mutants identified following ACV selection. Subtle differences between PCV and ACV in the interaction with viral TK or polymerase may account for the different spectra of genotypes observed for the two sets of mutants.     

多巴胺对急性间歇性低氧诱导的大鼠颈动脉体低氧敏感性的影响

目的:观察急性间歇性低氧刺激后大鼠颈动脉体对低氧的敏感性以及多巴胺对颈动脉体低氧敏感性的影响。方法:将分离SD大鼠的颈动脉体-窦神经移入到孵育槽,然后把分离的窦神经吸入到记录的玻璃电极中行电信号记录。记录基线部分缓冲液充入气体为95%O2+5%CO2混合气,低氧应激给予5%O2+5%CO2+90%N2混合气,低氧刺激给予30 s,95%O2+5%CO2给予90 s,共10个循环,每组实验大鼠数量n大于等于5。结果:大鼠离体的颈动脉体,给予急性间歇性低氧应激,再给予低氧刺激,窦神经较之前低氧刺激放电活动增强。但加入多巴胺后,可以抑制窦神经对低氧的反应,急性间歇性低氧后,多巴胺对窦神经的低氧放电活动抑制作用加强。结论:大鼠颈动脉体给予急性间歇性低氧可增强窦神经对低氧的反应,多巴胺可抑制急性低氧诱导的颈动脉体对低氧敏感性的增强。     

Dissociation between resistance to apoptosis and the transformed phenotype in IGF-I receptor signaling

Programmed Cell Death (PCD) is known to play an important role in both the development and the growth rate of human tumors. It has in fact been suggested that suppression of the apoptotic pathway is a requirement for the establishment of the transformed phenotype. In order to elucidate the relationship between resistance to apoptosis and transformation, we have asked in this investigation whether or not the two processes can be directly correlated. For this purpose, we have used mouse embryo fibroblasts (MEF) expressing either the wild-type or several mutants of the type 1 insulin-like growth factor receptor (IGF-IR). The wild-type IGF-IR has both transforming and anti-apoptotic activities, and we have asked whether these two activities can be or not separated in mutant receptors. Using this well-defined system, our results show that certain mutants of the IGF-IR that have strong anti-apoptotic and mitogenic activities, are incapable of transforming MEF (colony formation in soft agar). We have, instead, a good correlation between mitogenic and anti-apoptotic activities, suggesting the possibility that the two processes may share similar signaling pathways from the IGF-IR. On the other hand, our results indicate that transformation requires an additional signal, above and beyond the mitogenic and survival signals. Our conclusion is that, at least in this system, the establishment of the malignant phenotype and resistance to apoptosis can be dissociated, implying the possibility of separate targeting.     

Variation in sensitivity to aflatoxin B1 among several strains of Drosophila melanogaster (Diptera).

Eggs of five different wild-type strains of fruit flies, Drosophila melanogaster, were allowed to develop into adults on media containing 0.27 and 0.40 ppm of the toxic and carcinogenic mycotoxin, aflatoxin B₁ (AFB₁). Egg-to-adult viability and development time, adult sex ratio and size, and pupa case size were measured for each treatment and compared to control values for each strain. Adult size and pupa size were not affected significantly by the AFB₁ treatments, while egg-to-adult development time increased for strains grown on AFB₁-containing media. Strain-specific changes in egg-to-adult viability and adult sex ratio were observed. The most probable explanation for these differences is genetic variation among the strains. Crimea, Hikone-R, Lausanne-S, Oregon-R, and Swedish-C were the strains tested.     

Biochemical genetic variants in mice selectively bred for sensitivity or resistance to ethanol-induced sedation

The distribution of biochemical genetic variants was examined among eight inbred strains of mice, which served as contributors to a heterogeneous stock of mice (HS), and in short-sleep (SS) and long-sleep (LS) mice, selectively bred from the HS stock for differential ethanol sensitivity. Fifteen loci for enzymes of alcohol and aldehyde metabolism, as well as 12 other biochemical loci, were investigated. Thirteen of these loci exhibited allelic variation between strains, of which six were separately fixed in the SS and LS mice. Comparisons of genetic similarity coefficients, based upon the distributions of allelic variants for the loci examined, with behavioural sensitivities (sleep-time) to an acute dose of ethanol for the inbred and selected strains of mice, indicated no correlations between these data. This suggests that this collective group of loci are not useful indicators of the genes selectively bred in the SS and LS strains, which are responsible for the differential sensitivities to acute doses of ethanol.     

Mammalian mitochondrial mutants selected for resistance to the cytochrome b inhibitors HQNO or myxothiazol

Mouse LA9 cell lines were selected for increased resistance to either HQNO or myxothiazol, inhibitors of electron transport which bind to the mitochondrial cytochrome b protein. Two phenotypically distinguishable HQNO-resistant mutants were recovered while the myxothiazol-resistant isolates had a common phenotype. All three mutant phenotypes were transmitted cytoplasmically in cybrid crosses. Biochemical studies further established that for all three mutant types, resistance at the cellular level was paralleled by an increase in inhibitor resistance of mitochondrial succinate-cytochrome c oxidoreductase, the respiratory complex containing cytochrome b. As with the previously described mitochondrial antimycin-resistant mutant, the initial biochemical and genetic studies indicated that these mutations occur within the mitochondrial cytochrome b gene. This conclusion was strongly supported by the results of mtDNA restriction fragment analyses in which it was found that one HQNO-resistant mutant had undergone a small insertion or duplication in the apocytochrome b gene. Finally, all four mitochondrial cytochrome b mutants have been analyzed in both cell plating studies and succinate-cytochrome c oxidoreductase assays to determine the pattern of cross-resistance to inhibitors of cytochrome b other than the one used for selection.     

Identification of a major QTL together with several minor additive or epistatic QTLs for resistance to fire blight in apple in two related progenies

Although fire blight, caused by the bacterium Erwinia amylovora, is one of the most destructive diseases of apple (Malus × domestica) worldwide, no major, qualitative gene for resistance to this disease has been identified to date in apple. We conducted a quantitative trait locus (QTL) analysis in two F₁ progenies derived from crosses between the cultivars Fiesta and either Discovery or Prima. Both progenies were inoculated in the greenhouse with the same strain of E. amylovora, and the length of necrosis was scored 7 days and 14 days after inoculation. Additive QTLs were identified using the mapqtl software, and digenic epistatic interactions, which are an indication of putative epistatic QTLs, were detected by two-way analyses of variance. A major QTL explaining 34.3–46.6% of the phenotypic variation was identified on linkage group (LG) 7 of Fiesta in both progenies at the same genetic position. Four minor QTLs were also identified on LGs 3, 12 and 13. In addition, several significant digenic interactions were identified in both progenies. These results confirm the complex polygenic nature of resistance to fire blight in the progenies studied and also reveal the existence of a major QTL on LG7 that is stable in two distinct genetic backgrounds. This QTL could be a valuable target in marker-assisted selection to obtain new, fire blight-resistant apple cultivars and forms a starting point for discovering the function of the genes underlying such QTLs involved in fire blight control.     

Relationship between ethylene production and sensitivity to ethylene in roots of several species

Ethylene concentrations in the soil atmosphere can greatly exceed levels known to markedly influence plant growth. The ethylene is microbial in origin and the rate of production under anaerobic conditions is correlated with organic matter content. Under field conditions the highest concentrations occur when soil temperatures and moisture levels are high, resulting in development of anaerobic zones. Crop species differ widely in the sensitivity of their roots to ethylene, this sensitivity being broadly correlated with known intolerance of waterlogged (anaerobic) environments.