Modeling incubation temperature: the effects of incubator design, embryonic development, and egg size

A simple model to describe the relationship between the temperature of the developing embryo, incubator temperature, embryo heat production, and thermal conductivity of the egg and surrounding air is presented. During early incubation, embryo temperature is slightly lower than incubator temperature because of evaporative cooling. However, from midincubation onwards, metabolic heat production from the embryo raises embryo temperature above incubator temperature. The extent of the rise in embryo temperature depends on thermal conductivity, which, in turn, is mainly influenced by the air speed over the egg. The importance of air speed and restrictions to air flow within artificial incubators is discussed. Exact determinations of optimum incubation temperatures from studies reported in the literature are difficult because only incubator temperatures are reported. Embryo temperatures can differ from incubator temperature because of differences in thermal conductivity between different incubation systems and differences between incubators in their ability to control temperatures uniformly. It is suggested that shell surface temperatures are monitored in experiments to investigate temperature effects to allow consistent comparisons between trials. Monitoring shell temperatures would also make it easier to translate optimum temperatures derived in small experimental incubators to the large commercial incubators used by the poultry industry. The relationship between egg temperature, the metabolism of the developing embryo and egg size is discussed.     

Metabolic assessment of wallaby blastocysts during embryonic diapause and subsequent reactivation

The metabolism of tammar wallaby (Macropus eugenii) blastocysts was analysed by means of quantitative fluorescence microscopy during embryonic diapause and 2, 3, 4, 5, 8 and 10 days after reactivation to determine nutrient preferences during metabolic reactivation of the blastocyst. The surface area of quiescent blastocysts was 0.16 +/- 0.02 mm2 (mean +/- s.e.m.), and increased to 0.44 +/- 0.04 mm2 (P < 0.05) by Day 8 after removal of the sucking stimulus of the pouch young (RPY). Day-10 blastocysts, analysed over two successive breeding seasons, were significantly different in size from each other (Group A, 1992: 4.44 +/- 1.47 mm2; Group B, 1993: 18.87 +/- 4.62 mm2; P < 0.01), and both groups were significantly different in size from diapausing blastocysts (P < 0.01). There was no significant difference in carbohydrate uptake or production by blastocysts during the first five days after RPY. Glucose uptake by blastocysts recovered 8 days after RPY (61.9 +/- 30.0 pmol embryo-1 h-1) was significantly greater than that by Day-0 blastocysts (17.9 +/- 5.5 pmol embryo-1 h-1) and glucose uptake by both groups of Day-10 blastocysts (Group A, 174.0 +/- 28.4 pmol embryo-1 h-1; Group B, 616.0 +/- 239.0 pmol embryo-1 h-1) was significantly different from that by Day-0 blastocysts (P < 0.01). Pyruvate uptake by Day-10 blastocysts (Group A, 46.0 +/- 32.2 pmol embryo-1 h-1; Group B, 250.0 +/- 136.0 pmol embryo-1 h-1; P < 0.01) increased significantly compared with that by Day-0 blastocysts (6.4 +/- 1.6 pmol embryo-1 h-1; P < 0.01). Lactate production by Day-10 blastocysts (Group A, 186.7 +/- 30.3 pmol embryo-1 h-1; Group B, 285 +/- 129 pmol embryo-1 h-1; P > 0.01) was also significantly different from that by quiescent blastocysts (41.20 +/- 9.6 pmol embryo-1 h-1). There was a linear relationship between surface area and glucose uptake and surface area and pyruvate uptake (r2 = 0.965 and r2 = 0.971 respectively). Despite increases in carbohydrate uptake, there was a proportional decrease in lactate production indicating an increase in oxidative metabolism during reactivation. This suggests that there may be a metabolic switch at, or around, Day 5 after RPY.     

Rate and environmental effects on fracture of a two-phase TiAl-alloy

The influence of strain rate and environment on the fracture behavior of a two-phase TiAl-alloy, Ti-47Al-2.6Nb-2(Cr + V), heat-treated to a nearly fully lamellar microstructure has been studied by performing conventional tensile, compression, and fracture toughness tests in air, argon, and vacuum at 25 °C and 800 °C. Both tensile and compression tests were conducted at strain rates of 1 × 10⁻³ and 1 × 10⁻⁵ s⁻¹, and fracture toughness tests were performed under displacement rates of 0.25 to 2.5 mm/min. In addition,in situ fracture toughness tests were conducted at slow rates both in vacuum and in air. The results indicated that both strain rate and environment affected the tensile stress-strain behavior and ductility and the fracture resistance of the TiAl-alloy at 800 °C. In contrast, neither the tensile ductility nor the fracture toughness was significantly affected by the environment at ambient temperature. For compression in air, the stress-strain behavior was insensitive to both strain rate and test temperature within the conditions tested. Studies of fracture surfaces revealed that low tensile ductility in this alloy at ambient temperature is associated with the tendency to delaminate alongγ/γ andγ/α ₂ interfaces. formerly with Metcut-Materials Research Group, Wright-Patterson AFB, Dayton, OH 45433-0511     

Studying electric field effects on embryonic myocytes

OBJECTIVE: Little attention has been paid to the occurrence of aortic regurgitation after complete repair in patients with pulmonary atresia and ventricular septal defect or tetralogy of Fallot. To highlight the development of aortic regurgitation or aortic root dilation severe enough to necessitate aortic valve replacement with or without aortic aneurysmorrhaphy or aortic root replacement, we retrospectively reviewed the records of patients who underwent aortic valve operation at our institution subsequent to repair of pulmonary atresia and ventricular septal defect or tetralogy of Fallot. METHODS: We searched the Mayo Clinic database for patients with pulmonary atresia and ventricular septal defect or tetralogy of Fallot who subsequently had aortic valve or aortic root operations. The degree of aortic regurgitation before operation was noted. Aortic sinus and root dimensions were measured. RESULTS: Sixteen patients underwent complete repair at a median age of 17 years, followed by an aortic operation a median of 13.5 years later. All 16 patients had dilated aortic sinuses at the time of the aortic valve operation. These 16 patients had aortic valve replacement: 11 with mechanical prostheses and 5 with bioprostheses. Five of the 16 also had reduction of aortic dilation by lateral aneurysmorrhaphy, and 1 had graft replacement of the ascending aorta. Five patients had associated conditions (evidence of valvular damage, recurrent ventricular septal defect, or history of endocarditis) discovered at the aortic valve operation that have been reported to be related to the development of aortic regurgitation. The remaining 11 patients had progressive aortic regurgitation despite complete, uncomplicated repair. CONCLUSIONS: Progressive aortic regurgitation and aortic root dilation can occur despite complete repair of pulmonary atresia and ventricular septal defect or tetralogy of Fallot.     

Normal aging and environmental effects on communication

This article focuses on the role of communication in the successful adjustments and adaptations to normal aging by elders. It views communication as an essential tool for living safely and independently, for maintaining interests and a sense of purpose, for continuing important social and family relationships, and for exercising active control over quality of life and care. The discussion emphasizes the importance of physical and social environments to elders' communication efforts and suggests that an environmental approach to the communication problems of many elders may be more beneficial than the remediation of specific speech-language skills.     

Effects of incubation temperature on the energetics of embryonic development and hatchling morphology in the Brisbane river turtle Emydura signata

AIMS: To investigate the malignant potential of lichen sclerosus, a study using the cell proliferation marker Ki67 comparing lichen sclerosus with and without associated squamous cell carcinoma was performed. METHODS AND RESULTS: Formalin-fixed, paraffin-embedded slides of 13 cases of lichen sclerosus with associated carcinoma, and 31 cases without associated carcinoma, including 16 random cases, seven with epidermal thickening and eight with epidermal thinning, were examined by the immunoperoxidase technique for Ki67, a cell proliferation marker. Ki67 reactivity was mostly seen in the basal and parabasal cells in both groups of lichen sclerosus and this pattern was similar to normal skin, squamous cell hyperplasia and analogous to that of one form of squamous cell carcinoma. There was a mean of 50 Ki67 positive cells per 100 basal cells in lichen sclerosus with associated squamous cell carcinoma; however, in squamous cell hyperplasia adjacent to carcinoma this rose to 90 Ki67 positive cells per 100 basal cells. In lichen sclerosus without associated carcinoma, the random cases had a count of 53 per 100 basal cells, those with epidermal thickening 53 and those with thinning 42. Non-genital normal skin had a count of 71 per 100 basal cells. CONCLUSION: The lack of qualitative differences of Ki67 expression in normal skin, in lichen sclerosus with and without carcinoma, in squamous cell hyperplasia and in one form of squamous cell carcinoma indicates that these conditions share a common localized pattern of cell proliferation and does not support or deny the malignant potential of lichen sclerosus. The higher Ki67 count in squamous cell hyperplasia adjacent to carcinoma could indicate premalignancy or a reaction to the carcinoma. In patients without carcinoma, the higher Ki67 count in thickened lichen sclerosus compared to thinned suggests that some or all of the cases of thickened lichen sclerosus were lichen sclerosus with squamous cell hyperplasia or that lichen simplex chronicus superimposed on lichen sclerosus has a higher Ki67 expression or that the distinction between squamous cell hyperplasia and lichen simplex chronicus is only one of terminology.     

Temporal and environmental effects on quinpirole-induced biphasic locomotion in rats

The dopamine D2/D3 agonist quinpirole induces suppression of locomotor activity at low doses, and suppression followed by activation at high doses when given to rats of 30 days of age and older that are immediately placed in activity monitors. The duration of suppression is longer and the level of activation is lower at 60 than at 30 days of age, suggesting that the mechanism responsible for the suppression may play a role in the lesser activation in the older rats. However, habituation limits the ability to measure the duration of locomotor suppression. Therefore, 0, 0.2, or 0.2 mg/kg quinpirole was injected S.C. either 30, 60, or 120 min before placing male or female rats of 30 or 60 days of age in activity monitors for 30 min. At both ages, both doses of quinpirole suppressed activity when the animal was placed in the monitor 30 or 60 min after injection; at 60 days the drug also suppressed activity at 120 min after injection. Previously, 0.2 mg/kg quinpirole elicited locomotor activity 60 min after injection in rats placed immediately in activity monitors at both ages. Thus, not only time after injection but novelty of the environment are critical factors in the expression of locomotor suppression or activation in response to quinpirole.     

Dose-dependent effects of oral acyclovir in the incubation period of varicella

Dose of acyclovir (ACV) and clinical features of varicella were evaluated in 65 household contacts (0.8-9 y) who received oral ACV (5-80 mg/kg daily in four divided doses) during the latter half of the incubation period of varicella. The severity of the disease was compared with that of 23 children who did not receive ACV. Infection was confirmed by a fluorescent antibody to membrane antigen assay. The antibody titers and the rate of apparent infection increased as the dose of ACV administered decreased. The number of skin lesions in patients who received ACV was significantly reduced when compared to the control group. These data suggest dose-dependence of ACV for modification of varicella during secondary viremia in the incubation of the disease.     

The effects of environmental hormones on reproduction

Considerable attention has been given in the past few years to the possibility that man-made chemicals (xenobiotics) in the environment may pose a hazard to human reproductive health. The endocrine-disrupting effects of many xenobiotics can be interpreted as interference with the normal regulation of reproductive processes by steroid hormones. Evidence reviewed here indicates that xenobiotics bind to androgen and oestrogen receptors in target tissues, and to androgen-binding protein and to sex hormone-binding globulin. Although environmental chemicals have weak hormonal activity, their ability to interact with more than one steroid-sensitive pathway provides a mechanism by which their hazardous nature can be augmented. A given toxicant may be present in low concentration in the environment and, therefore, harmless. However, we are not exposed to one toxicant at a time, but, rather, to all of the xenobiotics present in the environment. Therefore, numerous potential agonists/antagonists working together through several steroid-dependent signalling pathways could prove to be hazardous to human reproductive health.     

The effects of arginine vasotocin on the calling behavior of male cricket frogs in changing social contexts

We investigated the effects of the neurohypophysial peptide, arginine vasotocin (AVT), on the calling behavior of male Acris crepitans during and immediately following a simulated acoustic agonistic encounter. AVT did not block the aggressive response to agonistic calls, as the changes in temporal call characteristics in response to the encounter were similar to those of saline-treated males. However, AVT caused males to begin calling sooner during the agonistic encounter and to call significantly more than saline males during and after the agonistic encounter. In addition, AVT-treated males maintained a higher dominant frequency compared to saline animals during and following the agonistic encounter. Changes in temporal characteristics in the period following the agonistic encounter indicated that control males were more likely to exhibit a rebound effect which resulted in larger changes in calling parameters compared to AVT-treated animals. The results indicate that AVT causes changes in calling behavior in male A. crepitans during and following an agonistic encounter that are consistent with animals highly motivated to maintain vigorous active calling throughout changing social conditions.     

尾矿区地下水环境质量现状评价

矿床开采过程中，矿区的地下水环境质量受到相应的影响。通过对矿区地下水污染源、污染特点和污染途径的分析，确定合适的地下水污染评价因子，对矿区地下水环境质量现状，分别进行了单要素污染指数评价和多要素污染指数综合评价。其结果能全面地反映出矿区地下水整体的环境质量现状。     

The biomechanics of fast bowling in men's cricket: a review

This review concentrates on synthesizing and analysing the biomechanical research which has been carried out on fast bowling in men's cricket. Specifically, it relates to those elements of the bowling technique which contribute towards a fast ball release, the aerodynamics and technique of swing bowling, and the association between fast bowling and lower back injury. With regard to bowling technique, no firm conclusions are drawn on the relationships between elements of the fast bowling technique and ball release speed. Recommendations for future research in this area include intra-player studies to establish the bowler-specific factors which contribute to fast ball release and features of body segment dynamics. There is general agreement that the phenomenon of differential boundary layer separation is the reason for normal and reverse cricket ball swing. Systematic research to establish the essential aspects of the bowling technique which contribute to successful swing bowling is recommended, along with studies of the behaviour of the ball in games to ascertain the effects of ball asymmetries on ball swing. There is sufficient evidence in the literature to establish a strong link between injury to the lower back and the use of the mixed technique. Recommendations are made for screening and intervention to reduce the use of the mixed technique, and for research into other aspects of injury. Fundamental research to develop biomechanical models of the lower back in fast bowling is strongly recommended.     

Testing hypotheses on specific environmental causal effects on behavior.

There have been strong critiques of the notion that environmental influences can have an important effect on psychological functioning. The substance of these criticisms is considered in order to infer the methodological challenges that have to be met. Concepts of cause and of the testing of causal effects are discussed with a particular focus on the need to consider sample selection and the value (and limitations) of longitudinal data. The designs that may be used to test hypotheses on specific environmental risk mechanisms for psychopathology are discussed in relation to a range of adoption strategies, twin designs, various types of "natural experiments," migration designs, the study of secular change, and intervention designs. In each case, consideration is given to the need for samples that "pull-apart" variables that ordinarily go together, specific hypotheses on possible causal processes, and the specification and testing of key assumptions. It is concluded that environmental risk hypotheses can be (and have been) put to the test but that it is usually necessary to use a combination of research strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Examining genetic and environmental effects on reactive versus proactive aggression.

This study compared the contribution of genes and environment to teacher-rated reactive and proactive aggression in 6-year-old twin pairs (172 pairs: 55 monozygotic girls, 48 monozygotic boys, 33 dizygotic girls, 36 dizygotic boys). Genetic effects accounted for 39% of the variance of reactive aggression and for 41% of the variance of proactive aggression. The remainder of the variance was explained by unique environmental effects. Genetic as well as unique environmental effects were significantly correlated across reactive and proactive aggression (genetic correlation = .87, environmental correlation = .34), but this overlap was largely due to a common underlying form of aggression (i.e., teacher-rated physical aggression). Once common etiological factors due to physical aggression were accounted for, reactive and proactive aggression shared no other genes and only a few environmental influences, although additional specific genetic and environmental effects were observed for both reactive and proactive aggression. These specific effects indicate that both reactive and proactive aggression may be influenced mostly by socialization experiences that are specific to each type of aggression and only to a very small degree by specific genes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)