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891.
Gordon G. Gallup Rebecca L. Burch Tracy J. Berene Mitchell 《Human nature (Hawthorne, N.Y.)》2006,17(3):253-264
Using a sample of 652 college students, we examined several implications of the hypothesis that the shape of the human penis
evolved to enable males to substitute their semen for those of their rivals. The incidence of double mating by females appears
sufficient to make semen displacement adaptive (e.g., one in four females acknowledge infidelity, one in eight admit having
sex with two or more males in a 24-hour period, and one in 12 report involvement in one or more sexual threesomes with two
males). We also document several changes in post-ejaculatory behavior (e.g., reduced thrusting, penis withdrawal, loss of
an erection) which may have evolved to minimize displacement of the male’s own semen. Consistent with predictions derived
from a theoretical model (Gallup and Burch 2006), we discovered that most females report waiting at least 48 hours following
an instance of infidelity before resuming sex with their in-pair partners. 相似文献
892.
Evans ES Kocak Z Zhou SM Kahn DA Huang H Hollis DR Light KL Anscher MS Marks LB 《Cytokine》2006,35(3-4):186-192
The purpose of the study was to reassess the utility of transforming growth factor-beta-1 (TGF-beta1) together with dosimetric and tumor parameters as a predictor for radiation pneumonitis (RP). Of the 121 patients studied, 32 (26.4%) developed grade > or =1 RP, and 27 (22.3%) developed grade > or =2 RP. For the endpoint of grade > or =1 RP, those with V30>30% and an end-RT/baseline TGF-beta1 ratio> or =1 had a significantly higher incidence of RP than did those with V30>30% and an end-RT/baseline TGF-beta1 ratio<1. For most other patient groups, there were no clear associations between TGF-beta1 values and rates of RP. These findings suggest that TGF-beta1 is generally not predictive for RP except for the group of patients with a high V30. 相似文献
893.
894.
Nameeta Baichoo William MacNaughtan John R. Mitchell Imad A. Farhat 《Food biophysics》2006,1(4):169-177
STEPSCAN differential scanning calorimetry, a form of temperature-modulated differential scanning calorimetry (DSC), was used to study the thermal transitions occurring during the heating of chocolate of varying thermal histories. Conventional DSC thermograms acquired during heating of chocolate can be complex, with the observation of a series of overlapping endothermic and exothermic events. STEPSCAN DSC was used to deconvolute the total heat flow into reversing (rapid) and nonreversing (slow) components, which were assigned to melting and recrystallization events, respectively. Such a separation is usually difficult using conventional DSC. The recrystallization events were more pronounced in rapidly cooled samples where the polymorphic form V had been nucleated through tempering. Because of the presence of artifacts, STEPSCAN can only provide a crude separation of reversing and nonreversing signals in this system. The general applicability and limitations of STEPSCAN DSC as well as the effects of prenucleation and rate of cooling of chocolate are discussed. 相似文献
895.
Selective brain cooling (SBC) is defined as the lowering of brain temperature below arterial blood temperature. Artiodactyls employ a carotid rete, an anatomical heat exchanger, to cool arterial blood shortly before it enters the brain. The survival advantage of this anatomy traditionally is believed to be a protection of brain tissue from heat injury, especially during exercise. Perissodactyls such as horses do not possess a carotid rete, and it has been proposed that their guttural pouches serve the heat-exchange function of the carotid rete by cooling the blood that traverses them, thus protecting the brain from heat injury. We have tested this proposal by measuring brain and carotid artery temperature simultaneously in free-living horses. We found that despite evidence of cranial cooling, brain temperature increased by about 2.5 degrees C during exercise, and consistently exceeded carotid temperature by 0.2-0.5 degrees C. We conclude that cerebral blood flow removes heat from the brain by convection, but since SBC does not occur in horses, the guttural pouches are not surrogate carotid retes. 相似文献
896.
897.
898.
Meijer WM Werler MM Louik C Hernandez-Diaz S de Jong-van den Berg LT Mitchell AA 《Birth defects research. Part A, Clinical and molecular teratology》2006,76(10):714-717
BACKGROUND: Several studies have suggested a protective effect of folic acid (FA) on congenital heart anomalies. Down syndrome (DS) infants are known to have a high frequency of heart anomalies. Not all children with DS suffer from heart anomalies, which raises the question whether maternal factors might affect the risk of these anomalies. Our objectives were to investigate whether first-trimester FA use protects against heart anomalies among DS children. METHODS: Women with liveborn DS children participating in the Slone Epidemiology Center Birth Defects Study between 1976 and 1997 were included. We performed case-control analyses using DS, with heart anomalies as cases and DS, without heart anomalies as controls. Subanalyses were performed for defects that have been associated with FA in non-DS populations (conotruncal, ventricular septal [VSD]) and for those that are associated with DS (ostium secundum type atrial septal defects [ASD] and endocardial cushion defects [ECD]). Exposure was defined as the use of any FA-containing product for an average of at least 4 days per week during the first 12 weeks of pregnancy, whereas no exposure was defined as no use of FA in these 12 weeks. RESULTS: Of the 223 cases, 110 (49%) were exposed versus 84 (46%) of the 184 controls. After adjustment for possible confounders, no protective effect of FA was found on heart anomalies overall (OR 0.95, 95% CI: 0.61-1.47) nor separately for conotruncal defects, VSDs, ASDs, or ECDs. CONCLUSIONS: Our study does not show a protective effect of FA on heart anomalies among infants with DS. 相似文献
899.
Leena S. Patel Cheryl K. Mitchell William P. Dubinsky John O'Brien 《Cell communication & adhesion》2006,13(1):41-54
Gap-junctional coupling among neurons is subject to regulation by a number of neurotransmitters including nitric oxide. We studied the mechanisms by which NO regulates coupling in cells expressing Cx35, a connexin expressed in neurons throughout the central nervous system. NO donors caused potent uncoupling of HeLa cells stably transfected with Cx35. This effect was mimicked by Bay 21-4272, an activator of guanylyl cyclase. A pharmacological analysis indicated that NO-induced uncoupling involved both PKG-dependent and PKG-independent pathways. PKA was involved in both pathways, suggesting that PKG-dependent uncoupling may be indirect. In vitro, PKG phosphorylated Cx35 at three sites: Ser110, Ser276, and Ser289. A mutational analysis indicated that phosphorylation on Ser110 and Ser276, sites previously shown also to be phosphorylated by PKA, had a significant influence on regulation. Ser289 phosphorylation had very limited effects. We conclude that NO can regulate coupling through Cx35 and that regulation is indirect in HeLa cells. 相似文献
900.
The subjective value of a reward (gain) is related to factors such as its size, the delay to its receipt and the probability of its receipt. We examined whether the subjective value of losses was similarly affected by these factors in 128 adults. Participants chose between immediate/certain gains or losses and larger delayed/probabilistic gains or losses. Rewards of $100 were devalued as a function of their delay (“discounted”) relatively less than $10 gains while probabilistic $100 rewards were discounted relatively more than $10 rewards. However, there was no effect of outcome size on discounting of delayed or probabilistic losses. For delayed outcomes of each size, the degree to which gains were discounted was positively correlated with the degree to which losses were discounted, whereas for probabilistic outcomes, no such correlation was observed. These results suggest that the processes underlying the subjective valuation of losses are different from those underlying the subjective valuation of gains. 相似文献