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1.
Ultrasound emission in infant rats as an indicant of arousal during appetitive learning and extinction 总被引：1，自引：0，他引：1
Infant rats rewarded for crawling by being allowed to suckle on the dry nipple of an anesthetized dam showed a decreasing rate of ultrasound production during acquisition and an increasing rate during extinction. These results suggest that infant rats can be stressed and are aroused as a result of successive nonrewards just as adult rats are. In addition, these results do not support the hypothesis that infant rats lack inhibitory mechanisms related to poorly developed neural centers. 相似文献
2.
利用耕地功能指数、功能优势指数等分析2010—2020年湖南省武陵山片区耕地多功能的时空演变趋势,探讨功能视角的片区耕地分区优化措施。结果表明：耕地功能时间演变存在差异,总体持续增长,文化、生产、生态安全、社会保障功能的变化率依次降低;耕地功能呈现明显的空间异质性,总功能由2010年的东高西低、北高南低演变为2020年的4个高值中心;生产功能由北低南高演变为高值集中于东部;社会保障功能由东高西低演变为高值局部凸出、中等值普遍分布;生态安全功能由四周高、中间低演变为极高值三足鼎立,文化功能由北高南低演变为极高值和高值贯穿全域。将研究区划分为生产–生活、生态–文化、生产、文化和生活–生态功能优势区等5类。 相似文献
3.
The transition from aquatic to terrestrial locomotion was a key development in vertebrate evolution. We present a spinal cord model and its implementation in an amphibious salamander robot that demonstrates how a primitive neural circuit for swimming can be extended by phylogenetically more recent limb oscillatory centers to explain the ability of salamanders to switch between swimming and walking. The model suggests neural mechanisms for modulation of velocity, direction, and type of gait that are relevant for all tetrapods. It predicts that limb oscillatory centers have lower intrinsic frequencies than body oscillatory centers, and we present biological data supporting this. 相似文献
4.
Darlington RB Royce JM Snipper AS Murray HW Lazar I 《Science (New York, N.Y.)》1980,208(4440):202-204
At follow-up in 1976, low-income children who had attended infant and preschool programs in the 1960's had significantly higher rates of meeting school requirements than did controls, as measured by lower frequency of placement in special education classes and of being retained in grade (held back). 相似文献
5.
Infantile experience with suckling odors determines adult sexual behavior in male rats 总被引：3，自引：0，他引：3
Because infant rats learn about odors that elicit suckling, and because certain chemosensory cues that help elicit mating behavior in adults are similar to those that elicit suckling, an experiment was undertaken to assess the influence of suckling-associated odors experienced during infancy on adult sexual behavior. Rat pups lived with and suckled dams whose nipple and vaginal odors were altered with citral, a lemon scent. The rats were weaned and never exposed again, until testing, to citral or females. At about 100 days of age, the males were paired in mating tests with a normal sexually receptive female or with a sexually receptive female that had been treated perivaginally with citral immediately before testing. The males ejaculated readily when paired with citral-treated females but were slow to achieve ejaculation when paired with normal females. These findings implicate an infantile experience as a determinant of adult sexual behavior in a mammal. 相似文献
6.
中华鳖不同发育阶段氨基酸组成的研究 总被引：4，自引：0，他引：4
中华鳖不同生长发育时期的氨基酸组成分析表明：与稚鳖期和成鳖期相比,幼鳖期的甘氨酸含量较高;而氨基酸总量、必需氨基酸总量和其中８种氨基酸的含量较低;两种半必需氨基酸及其总量、ＮＥＡＡ、ＥＡＡ／ＴＡＡ和另４种氨基酸３个阶段无明显差异。 相似文献
7.
A M Altschul 《Science (New York, N.Y.)》1967,158(798):221-226
Adequate protein nutrition is possible at lower cost without the undermining of man's satisfaction with his food. This potential requires the upgrading of the proteins of cereals by supplementation with amino acids and the development of new protein foods from low-cost sources such as the oilseeds; infant malnutrition can be eliminated by such means. The more sophisticated new foods such as protein beverages and textured products are proving acceptable to man and will supplement meager supplies of animal protein. 相似文献
8.
Hasegawa K Martin F Huang G Tumas D Diehl L Chan AC 《Science (New York, N.Y.)》2004,303(5658):685-689
Protein tyrosine kinases and phosphatases cooperate to regulate normal immune cell function. We examined the role of PEST domain-enriched tyrosine phosphatase (PEP) in regulating T cell antigen-receptor function during thymocyte development and peripheral T cell differentiation. Although normal na?ve T cell functions were retained in pep-deficient mice, effector/memory T cells demonstrated enhanced activation of Lck. In turn, this resulted in increased expansion and function of the effector/memory T cell pool, which was also associated with spontaneous development of germinal centers and elevated serum antibody levels. These results revealed a central role for PEP in negatively regulating specific aspects of T cell development and function. 相似文献
9.
婴儿配方乳中n-3系多不饱和脂肪酸的研究 总被引：1，自引：0，他引：1
近年来的研究表明,n-3系多不饱和脂肪酸(n-3Polyunsaturotted Fatty Acids)具有防治心血管疾病、促进脑组织及视网膜的正常生长发育等生理功能和保健作用,因此越来越引起人们的关注。目前,在婴儿配方乳中n-3系多不饱和脂肪酸的应用越来越受到世界各国的重视。如何考虑n-3系多不饱和脂肪酸的平衡和摄取量,以充分发挥其对人体健康有益的作用,确保婴儿安全有效地利用n-3系多不饱和脂肪酸是值得注意的问题。 相似文献
10.
The lower continental crust is one of the least known variables in the crust-mantle evolutionary equation. In order to study the nature and compositional heterogeneity of the lower crust, more than 20 inclusions of lower crustal granulites in volcanic rocks from the McMurdo Sound region of Antarctica were analyzed for strontium and oxygen isotopes. These inclusions were erupted from volcanic centers covering an area of 12,000 square kilometers. Along with results from analyses of major and trace elements, the isotopic data reveal a profound discontinuity in the composition and probably the age of the lower crust that coincides with the boundary between the Transantarctic Mountains and the Ross Embayment. Although this topographic boundary between East and West Antarctica is largely a Cenozoic development, which apparently reflects a simple subvertical faulting relationship due to crustal rifting, the isotopic differences in the lower crust across the boundary suggest that the current faulting and rifting may coincide with an older crustal suture, the age of which is uncertain. 相似文献
11.
呼和浩特市作为中国"乳都",因人口基数较大,对婴幼儿配方奶粉的需求较高,但存在进口婴幼儿配方奶粉消费需求远高于国产婴幼儿配方奶粉的现象。通过对呼和浩特地区婴幼儿配方奶粉市场的调查,分析其国产婴幼儿配方奶粉和进口婴幼儿配方奶粉的消费者特征和消费现状,提出提高国产婴幼儿配方奶粉市场占有率的相关建议。 相似文献
12.
[目的]鉴于婴幼儿食品的特殊性和重要性,对婴幼儿配方奶粉中的铁、锌元素含量进行测定。[方法]采用干法灰化法处理6种婴幼儿配方奶粉,探究适合奶粉灰化的温度,并且用火焰原子吸收光谱法测定奶粉中铁、锌元素的含量。[结果]试验表明,测定铁、锌元素含量时奶粉的灰化温度为450～500℃;同一厂家生产的同一品牌不同成长阶段的婴幼儿配方奶粉,铁含量存在一定的差异,锌含量存在显著性差异,同一厂家生产的不同品牌的婴儿(较大婴儿)配方奶粉,铁、锌含量均不存在显著性差异,不同品牌幼儿配方奶粉的铁、锌含量存在显著性差异;6种奶粉的铁、锌元素含量均符合国家标准GB/T5413.21-1997。[结论]科学全面地评价婴幼儿配方奶粉中铁和锌元素的含量,对评价奶粉的品质以及正确引导消费者消费具有积极的现实意义。 相似文献
13.
14.
Mace R 《Science (New York, N.Y.)》2008,319(5864):764-766
Reproducing in cities has always been costly, leading to lower fertility (that is, lower birth rates) in urban than in rural areas. Historically, although cities provided job opportunities, initially residents incurred the penalty of higher infant mortality, but as mortality rates fell at the end of the 19th century, European birth rates began to plummet. Fertility decline in Africa only started recently and has been dramatic in some cities. Here it is argued that both historical and evolutionary demographers are interpreting fertility declines across the globe in terms of the relative costs of child rearing, which increase to allow children to outcompete their peers. Now largely free from the fear of early death, postindustrial societies may create an environment that generates runaway parental investment, which will continue to drive fertility ever lower. 相似文献
15.
The rate of biosynthesis of ribonucleic acid (as judged by the rate of incorporation of uridine into ribonucleic acid) in infant and adullt rat brain cortex slices, incubated (aerobically in tile presenice of various substrates, is directly proportionial to the adenosine triphosphate concentration. This suggests that the adenosine triphosphate concentration is one of the factors involved in the control of ribonucleic acid biosynthesis in infant and adult rat brain. Acetoacetate or beta-hydroxybutyrate is about 70 percent as effective as glucose, with both infant and adult brain, for the promotion of ribonucleic acid biosynthesis. but they are considerably mnore effective than succinate in infant brain than in adult brain. 相似文献
16.
An infant who died with neurological abnormalities, mental retardation, and dislocated ocular lenses excreted in his urine abnormally large amounts of S-sulfo-L-cysteine, sulfite, and thiosulfate and virtulally no inorganic sutlfate. The present report establishes the occurrence of an ezymatic defect in this infant. His liver, brain, and kidney specifically lacked sulfite oxidase activity. Deficiency of sulfite oxidase, which has not apparently been described in man, provides a reasonable explanation for the abnormalities in this infant. 相似文献
17.
The mammalian auditory cortex normally undergoes rapid and progressive functional maturation. Here we show that rearing infant rat pups in continuous, moderate-level noise delayed the emergence of adultlike topographic representational order and the refinement of response selectivity in the primary auditory cortex (A1) long beyond normal developmental benchmarks. When those noise-reared adult rats were subsequently exposed to a pulsed pure-tone stimulus, A1 rapidly reorganized, demonstrating that exposure-driven plasticity characteristic of the critical period was still ongoing. These results demonstrate that A1 organization is shaped by a young animal's exposure to salient, structured acoustic inputs-and implicate noise as a risk factor for abnormal child development. 相似文献
18.
An infant chimpanzee (Pan troglodytes) with clinical, behavioral, and cytogenetic features similar to those in Down's syndrome is described. The infant shows retarded growth rate, congenital abnormalities, retarded neurologic and postural development, epicanthus, hyperflexibility of the joints, muscle hypotonia, and trisomy of a small acrocentric chromosome. 相似文献
19.
牛乳很容易被掺加其它廉价物质,以谋取暴利,严重损害消费者和生产厂家的利益.而传统的乳成份检测方法过于烦琐,不适于快速生产.本文分析了新近研发的超声波乳成份分析仪对牛乳掺食盐和食糖的检测效果,并将结果与与目前大量使用的Foss红外分析仪和国标法作了比较.结果表明,对加水原料牛乳,3种测定方法均可有效测定其结果.对于加食盐,超声乳成份分析仪的蛋白质含量和固形物含量会显著上升,而脂肪下降不明显.对于加食糖,超声乳成份分析仪的蛋白含量和固形物含量会明显上升.从乳品成分的均衡性分析,超声乳成份分析仪可有效地用于检测牛乳中的食盐和食糖掺假. 相似文献
20.
用Ｗｉｓｔａｒ大鼠脑新皮质组织移植于同种幼鼠相应区域，术后分别于７天，１５天，３０天，６０天、１５０天应用光镜，电镜、免疫组织化学及酶组织化学的方法，观察移植物生长与发育成熟的形态特征，并应用辣极过氧化物酶追踪技术观察移植物和受体脑之间的神经纤维联系。结果表明：大部分移植物内的神经元不仅能存活，且能生长发育成熟为和受体脑相似的正常神经元，部分存活的移植物和受体脑之间可形成程度不同的神经纤维联系。 相似文献