Coordination of circadian timing in mammals

Time in the biological sense is measured by cycles that range from milliseconds to years. Circadian rhythms, which measure time on a scale of 24 h, are generated by one of the most ubiquitous and well-studied timing systems. At the core of this timing mechanism is an intricate molecular mechanism that ticks away in many different tissues throughout the body. However, these independent rhythms are tamed by a master clock in the brain, which coordinates tissue-specific rhythms according to light input it receives from the outside world.     

Basal metabolic rate and energetics of reproduction in therian mammals

Traditionally, the fact that reproduction in eutherian (= placental) mammals tends towards prolonged intrauterine development and short lactation has been interpreted as an evolutionary advance over the metatherian (= marsupial) short gestation and prolonged lactation. However, it has recently been postulated that marsupial reproduction involves low initial energy investment and may be advantageous by minimizing energy loss if conditions necessitate early termination. Moreover, because marsupials have basal metabolic rates (BMRs) 30% lower than those of most eutherians, it has been suggested that daily and total energy expenditures during reproduction may also be lower. We have now tested the predictions that low BMR is maintained during reproduction and that initial investment is lower in marsupials. Using indirect calorimetry, we have made the first longitudinal measurements of energy expenditure during reproduction for a marsupial and for two eutherian species with low BMRs. We find that initial investment is lowest in a eutherian and total energetic expenditures were greatest for the marsupial. We also find that, relative to BMR, all three species have increased mean maternal resting metabolic rates (RMRs) during both gestation and lactation; this is the first evidence that mammals with low BMRs can substantially elevate metabolism for prolonged periods during gestation and lactation.     

Regulation between nitric oxide and MAPK signal transduction in mammals

Nitric oxide (NO) is an important biological messenger in the regulation of tissue homeostasis. It exhibits a wide range of effects during physiological and pathophysiological processes. Typical beneficial properties of NO include the regulation of vascular tone,the protection of cells against apoptosis, the modulation of immune responses, and the killing of microbial pathogens. On the other hand,NO may cause severe vasodilation and myocardial depression during bacterial sepsis or act as a cytotoxic and tissue-damaging molecule in autoimmune diseases. Mitogen-activated protein kinase (MAPK) is a family of serine/threonine protein kinases that are widely distributed in mammalian cells. MAPK cascade plays pivotal roles in gene expression, cell proliferation, differentiation, neuronal survival and programmed cell death under a variety of experimental conditions. MAPKs transduce the signal for the cellular response to extracellular stresses or stimuli. The relation between them, however, has never been reviewed. Based on our researches and other reports in the field, we review their reciprocal regulatory functions.     

Lrp4 is a retrograde signal for presynaptic differentiation at neuromuscular synapses

Motor axons receive retrograde signals from skeletal muscle that are essential for the differentiation and stabilization of motor nerve terminals. Identification of these retrograde signals has proved elusive, but their production by muscle depends on the receptor tyrosine kinase, MuSK (muscle, skeletal receptor tyrosine-protein kinase), and Lrp4 (low-density lipoprotein receptor (LDLR)-related protein 4), an LDLR family member that forms a complex with MuSK, binds neural agrin and stimulates MuSK kinase activity. Here we show that Lrp4 also functions as a direct muscle-derived retrograde signal for early steps in presynaptic differentiation. We demonstrate that Lrp4 is necessary, independent of MuSK activation, for presynaptic differentiation in vivo, and we show that Lrp4 binds to motor axons and induces clustering of synaptic-vesicle and active-zone proteins. Thus, Lrp4 acts bidirectionally and coordinates synapse formation by binding agrin, activating MuSK and stimulating postsynaptic differentiation, and functioning in turn as a muscle-derived retrograde signal that is necessary and sufficient for presynaptic differentiation.     

关于近拟常曲率空间具有常平均曲率超曲面

研究了近拟常曲率空间中具有常平均曲率的紧致超曲面,得到了这类超曲面关于其第二基本形式模长平方S的J.Simons型积分不等式.     

Spliceosomal RNA U6 is remarkably conserved from yeast to mammals

The small nuclear RNA U6 and its gene have been isolated from yeast. In striking contrast to other yeast spliceosomal RNAs, U6 is very similar in size, sequence and structure to its mammalian homologue. The single-copy gene is essential. These properties suggest a central role in pre-mRNA processing. An extensive base-pairing interaction with U4 snRNA is described; the destabilization of the U4/U6 complex seen during splicing thus requires a large conformational change.     

球面中常平均曲率子流形

本文将陈省身和Yau的定理推广到完备子流形的情形和M~n是全脐子流形的情形,得到如下定理。定理1 设M~n(n≥2,是S~(n+p) (1) (P>((n-1)(n-2))/2)中完备的极小子流形,如果supS≤n/(2-(2/((n-1)(n-2))))则M~n是全测地的或supS=n/(2-(2/((n-1)(n-2)))) 定理2 设M~n(n≥2)是S~(n+p) (1) (P>(((n-1)(n-2))/2)中具有平行平均曲率向量的紧致子流形,如果M~n的截面曲率为正且S<((((1+H~2)n)/2-(1/(q-1)))+nH~2),则M~n是全脐子流形。(q=((n-1)(n+2))/2) 其中M~n是浸入在单位球面S~(n+p) (1)中的n维子流形,S是M~n的第二基本形式长度平方,H是M~n的平均曲率。     

球面上常中曲率的子流形

从Ｒｉｃｃｉ曲率角度讨论了单位素中具有常平均中曲率的紧致子流形，以及具有常数量曲率的紧致子流形，得到了两个Ｐｉｎｃｈｉｎｇ定理。     

球面上具有常数量曲率的超曲面

令Ｍ是单位球面Ｓｎ＋１的具有常数量曲率ρ的紧超曲面,ｎ≥３,ρ≥ｎ（ｎ－１）．｜Ｂ｜２为第二基本形式的模平方．如果｜Ｂ｜２－２ｎ－１拟负,那么Ｍ是一个小超球面．     

光本性否定光速不变原理及现行米定义

1961年、1967年、2005年、2006年国外公布了几个实验报告,直接和间接地示意:光子带有微量负电荷。加之牛顿在1704年和爱因斯坦在1905年都曾经明示过:光束可能是经典性质点流。于是,光子就应该是带着微量负电荷的经典性质点。随之,光的折射、反射、衍射、干渉及偏振等各种光学实验现象,都是光子与其近旁的介质原子核及其核外电子之间的库仑力作用,所产生的光子速度方向发生了改变后才形成的可视影像。光本性中的这种经典性质点特征,逻辑地否定了光速不变原理及现行米定义。     

Creatine accelerates the circadian clock in a unicellular alga

The circadian clock is considered to be a universal feature of eucaryotic organisms, controlling the occurrence and rates of many different aspects of life, ranging from single enzymatic reactions and metabolism to complex behaviours such as activity and rest. Although the nature of the underlying cellular/biochemical oscillator is still unknown, many substances are known to influence either phase or period of circadian rhythms in different organisms. These include D2O, electrolytes and ion channel inhibitors, small organic molecules such as alcohols and aldehydes, inhibitors of protein synthesis and amino-acid analogues. Certain transmitter and neurochemical drugs also influence the circadian clock in higher animals. We report here that the period of free-running circadian rhythms in the unicellular marine alga Gonyaulax polyedra is shortened by extracts from mammalian cells. The effect is dose-dependent, accelerating the circadian clock by as much as 4 hours per day. The substance responsible for this effect has been isolated from bovine muscle and identified as creatine. Authentic creatine has identical biological effects at micromolar concentrations and is known in animal systems for its involvement in cellular energy metabolism. A period shortening substance with similar chemical properties is also present in extracts of Gonyaulax itself.     

贵州省赤水桫椤自然保护区兽类的初步研究

2003年11月9日～18日对贵州赤水桫椤自然保护区兽类进行了初步调查和采集,共采获兽类标本10余号,经鉴定和分类,加上原有资料的记载,该保护区共有60种兽类,隶属8目21科45属,其中国家重点保护野生动物Ⅰ级3种,Ⅱ级11种。从区系组成看,以东洋界种为主体,共45种,占保护区兽类种数的75％。分布型以东南亚热带-亚热带型为主,有35种,占保护区兽类种数的58.3％,中国特有种有6种,占保护区兽类种数的10％。此外,易危兽类有13种,濒危兽类有3种,稀有兽类有1种。分别占中国濒危动物的9.8％,2.3％和0.75％。     

Inhibition of climbing fibres is a signal for the extinction of conditioned eyelid responses

A fundamental tenet of cerebellar learning theories asserts that climbing fibre afferents from the inferior olive provide a teaching signal that promotes the gradual adaptation of movements. Data from several forms of motor learning provide support for this tenet. In pavlovian eyelid conditioning, for example, where a tone is repeatedly paired with a reinforcing unconditioned stimulus like periorbital stimulation, the unconditioned stimulus promotes acquisition of conditioned eyelid responses by activating climbing fibres. Climbing fibre activity elicited by an unconditioned stimulus is inhibited during the expression of conditioned responses-consistent with the inhibitory projection from the cerebellum to inferior olive. Here, we show that inhibition of climbing fibres serves as a teaching signal for extinction, where learning not to respond is signalled by presenting a tone without the unconditioned stimulus. We used reversible infusion of synaptic receptor antagonists to show that blocking inhibitory input to the climbing fibres prevents extinction of the conditioned response, whereas blocking excitatory input induces extinction. These results, combined with analysis of climbing fibre activity in a computer simulation of the cerebellar-olivary system, suggest that transient inhibition of climbing fibres below their background level is the signal that drives extinction.