Androgens alter the tuning of electroreceptors

Weakly electric fish possess electroreceptors that are tuned to their individual electric organ discharge frequencies. One genus, Sternopygus, displays both ontogenetic and seasonal shifts in these frequencies, possibly because of endocrine influences. Systemic treatment with androgens lowers the discharge frequencies in these animals. Concomitant with these changes in electric organ discharge frequencies are decreases in electroreceptor best frequencies; hence the close match between discharge frequency and receptor tuning is maintained. These findings indicate that the tuning of electroreceptors is dynamic and that it parallels natural shifts in electric organ discharge frequency.     

Covariation of synaptonemal complex length and mammalian meiotic exchange rates

Analysis of recombination between loci (linkage analysis) has been a cornerstone of human genetic research, enabling investigators to localize and, ultimately, identify genetic loci. However, despite these efforts little is known about patterns of meiotic exchange in human germ cells or the mechanisms that control these patterns. Using recently developed immunofluorescence methodology to examine exchanges in human spermatocytes, we have identified remarkable variation in the rate of recombination within and among individuals. Subsequent analyses indicate that, in humans and mice, this variation is linked to differences in the length of the synaptonemal complex. Thus, at least in mammals, a physical structure, the synaptonemal complex, reflects genetic rather than physical distance.     

Inhibition of neighboring motoneurons in conscious control of single spinal motoneurons

Multiple fine-wire electrodes were implanted in the biceps brachii of five subjects, and artificial electronic feedback was provided to subjects from only one electrode. By this technique, it was shown that neighboring units progressively stop firing as subjects concentrate on activating an isolated unit. The inhibition of neighboring spinal motoneurons in the same pool further indicates that selective inhibition is an automatic part of single motor-unit training.     

Excitatory and inhibitory motoneurons in the central nervous system of the leech

The locomotion and reflex responses of the leech are brought about by inmuscles that are arranged in a regular, simple pattern in the body wall and that flatten, shorten, lengthen, or bend the animal. In the segmental ganglia, it is possible to recognize by morphological and physiological criteria the individual motoneurons that cause contractions and relaxations of these muscles.     

黄瓜把长和瓜长的遗传分析

以温室黄瓜品种拉迪特(Z9)与东农黄瓜品系129及其构建的150个F6代重组自交系群体为研究材料,利用主基因+多基因混合遗传模型对把长和瓜长进行遗传分析。结果表明,把长的遗传为2对连锁主基因+加性多基因混合遗传模型(E-2-6),主基因遗传率为56.27%,多基因遗传率为17.08%;瓜长的遗传为2对主基因+加性多基因混合遗传模型(E-1-8),主基因遗传率为43.75%,多基因遗传率为10.18%,主基因遗传率均比多基因遗传率高。黄瓜把长和瓜长的遗传以主基因遗传为主,且环境对把长和瓜长的遗传影响较大。     

丝瓜果长及果柄长的遗传规律分析

以有棱丝瓜自交系28-0-0 为母本,普通丝瓜自交系37-0-1-1 为父本,对6 个世代(P1、P2、F1、B1、B2、F2) 群体采用主基因+多基因混合遗传模型对丝瓜果长和果柄长进行遗传分析。结果表明,丝瓜果长遗传受到多基因（C- 0 模型）遗传控制,且受环境影响较大;果柄长遗传受到1 对加性-显性主基因+加性-显性-上位性多基因（D-0 模型） 遗传控制,主基因遗传率在F2和B1世代较高,分别为57.60%、61.90%,环境方差占总方差的比率为38.10%耀80.00%。     

Postsynaptic inhibition: intracellular effects of various ions in spinal motoneurons

Long-lasting depolarizing shifts of the electromotive force of post-synaptic inhibition occurred after tracellular injection of ammonium ions, basic amino acids, hydrogen ions, and some bivalent heavy-metal ions. These substances act on specific postsynaptic membrane sites.     

Different genotypes regulate the microbial community structure in the soybean rhizosphere

The soybean rhizosphere has a specific microbial community, but the differences in microbial community structure between different soybean genotypes have not been explained. The present study analyzed the structure of the rhizosphere microbial community in three soybean genotypes. Differences in rhizosphere microbial communities between different soybean genotypes were verified using diversity testing and community composition, and each genotype had a specific rhizosphere microbial community composition. Co-occurrence network analysis found that different genotype plant hosts had different rhizosphere microbial networks. The relationship between rhizobia and rhizosphere microorganisms in the network also exhibited significant differences between different genotype plant hosts. The ecological function prediction found that different genotypes of soybean recruited the specific rhizosphere microbial community. These results demonstrated that soybean genotype regulated rhizosphere microbial community structure differences. The study provides a reference and theoretical support for developing soybean microbial inoculum in the future.     

Long-term modulation of electrical synapses in the mammalian thalamus

Electrical synapses are common between inhibitory neurons in the mammalian thalamus and neocortex. Synaptic modulation, which allows flexibility of communication between neurons, has been studied extensively at chemical synapses, but modulation of electrical synapses in the mammalian brain has barely been examined. We found that the activation of metabotropic glutamate receptors, via endogenous neurotransmitter or by agonist, causes long-term reduction of electrical synapse strength between the inhibitory neurons of the rat thalamic reticular nucleus.     

Fate-restricted neural progenitors in the mammalian cerebral cortex

During development of the mammalian cerebral cortex, radial glial cells (RGCs) generate layer-specific subtypes of excitatory neurons in a defined temporal sequence, in which lower-layer neurons are formed before upper-layer neurons. It has been proposed that neuronal subtype fate is determined by birthdate through progressive restriction of the neurogenic potential of a common RGC progenitor. Here, we demonstrate that the murine cerebral cortex contains RGC sublineages with distinct fate potentials. Using in vivo genetic fate mapping and in vitro clonal analysis, we identified an RGC lineage that is intrinsically specified to generate only upper-layer neurons, independently of niche and birthdate. Because upper cortical layers were expanded during primate evolution, amplification of this RGC pool may have facilitated human brain evolution.     

Retinal stem cells in the adult mammalian eye

The mature mammalian retina is thought to lack regenerative capacity. Here, we report the identification of a stem cell in the adult mouse eye, which represents a possible substrate for retinal regeneration. Single pigmented ciliary margin cells clonally proliferate in vitro to form sphere colonies of cells that can differentiate into retinal-specific cell types, including rod photoreceptors, bipolar neurons, and Müller glia. Adult retinal stem cells are localized to the pigmented ciliary margin and not to the central and peripheral retinal pigmented epithelium, indicating that these cells may be homologous to those found in the eye germinal zone of other nonmammalian vertebrates.     

哺乳动物克隆技术研究进展

哺乳动物克隆是目前生物技术领域研究的热点之一 ,具有重大的科学意义和应用价值。文章着重介绍了哺乳动物克隆细胞核移植方法和进展 ,以及体细胞核移植的应用前景     

A gustotopic map of taste qualities in the mammalian brain

The taste system is one of our fundamental senses, responsible for detecting and responding to sweet, bitter, umami, salty, and sour stimuli. In the tongue, the five basic tastes are mediated by separate classes of taste receptor cells each finely tuned to a single taste quality. We explored the logic of taste coding in the brain by examining how sweet, bitter, umami, and salty qualities are represented in the primary taste cortex of mice. We used in vivo two-photon calcium imaging to demonstrate topographic segregation in the functional architecture of the gustatory cortex. Each taste quality is represented in its own separate cortical field, revealing the existence of a gustotopic map in the brain. These results expose the basic logic for the central representation of taste.     

成年大鼠面神经低位切断后面运动神经元的死亡进程及GDNF的保护作用

目的 观察大鼠面神经低位切断伤后,大鼠面运动神经元死亡的时间进程和胶质细胞源性神经营养因子(GDNF)局部应用对伤后面运动神经元的作用.方法 手术制作大鼠右侧面神经的低位切断伤 GDNF模型,左侧为切断伤 PBS液对照.用HE、甲苯胺蓝染色技术观测面运动神经元死亡情况及其形态学变化.结果 面神经低位切断伤可引起面运动神经元死亡且于伤后4周时达到高峰.损伤后1、2、4、6周时,GDNF侧神经元数量明显多于对照侧(P＜0.01).伤后2、4、6周时,GDNF侧的神经元数量较第1周时均减少(P＜0.01),而第4周与第6周的神经元数量差异无统计学意K(P＞0.05).结论 局部应用GDNF对低位切断伤后的面运动神经元有显著的保护作用,这种作用在损伤4周内完全发挥.