The molecular basis of neuronal excitability

Neurons process and transmit information in the form of electrical signals. Their electrical excitability is due to the presence of voltage-sensitive ion channels in the neuronal plasma membrane. In recent years, the voltage-sensitive sodium channel of mammalian brain has become the first of these important neuronal components to be studied at the molecular level. This article describes the distribution of sodium channels among the functional compartments of the neuron and reviews work leading to the identification, purification, and characterization of this membrane glycoprotein.     

The molecular basis of erythrocyte shape

Recent discoveries about the molecular organization and physical properties of the mammalian erythrocyte membrane and its associated structural proteins can now be used to explain, and may eventually be used to predict, the shape of the erythrocyte. Such explanations are possible because the relatively few structural proteins of the erythrocyte are regularly distributed over the entire cytoplasmic surface of the cell membrane and because the well-understood topological associations of these proteins seem to be stable in comparison with the time required for the cell to change shape. These simplifications make the erythrocyte the first nonmuscle cell for which it will be possible to extend our knowledge of molecular interactions to the next hierarchical level of organization that deals with shape and shape transformations.     

The molecular basis of the sparse fur mouse mutation

The ornithine transcarbamylase-deficient sparse fur mouse is an excellent model to study the most common human urea cycle disorder. The mutation has been well characterized by both biochemical and enzymological methods, but its exact nature has not been revealed. A single base substitution in the complementary DNA for ornithine transcarbamylase from the sparse fur mouse has been identified by means of a combination of two recently described techniques for rapid mutational analysis. This strategy is simpler than conventional complementary DNA library construction, screening, and sequencing, which has often been used to find a new mutation. The ornithine transcarbamylase gene in the sparse fur mouse contains a C to A transversion that alters a histidine residue to an asparagine residue at amino acid 117.     

The molecular basis for wine grape quality--a volatile subject

Volatile organic compounds are important flavor components of finished wines. In addition to winemaking practices, which shape wine quality, cultivation of the grape berries in the vineyard each season affects the production of volatile organic compounds as well as other chemical components that ultimately contribute to our perception of flavor in finished wines. By studying how berry flavor components are determined by the interplay of vine genotypes, the environment, and cultivation practices at the molecular level, scientists will develop advanced tools and knowledge that will aid viticulturalists in consistently producing balanced, flavorful berries for wine production.     

The cell and molecular basis of mechanical, cold, and inflammatory pain

Peripheral pain pathways are activated by a range of stimuli. We used diphtheria toxin to kill all mouse postmitotic sensory neurons expressing the sodium channel Nav1.8. Mice showed normal motor activity and low-threshold mechanical and acute noxious heat responses but did not respond to noxious mechanical pressure or cold. They also showed a loss of enhanced pain responses and spontaneous pain behavior upon treatment with inflammatory insults. In contrast, nerve injury led to heightened pain sensitivity to thermal and mechanical stimuli indistinguishable from that seen with normal littermates. Pain behavior correlates well with central input from sensory neurons measured electrophysiologically in vivo. These data demonstrate that Na(v)1.8-expressing neurons are essential for mechanical, cold, and inflammatory pain but not for neuropathic pain or heat sensing.     

A molecular basis for natural selection at the timeless locus in Drosophila melanogaster

Diapause is a protective response to unfavorable environments that results in a suspension of insect development and is most often associated with the onset of winter. The ls-tim mutation in the Drosophila melanogaster clock gene timeless has spread in Europe over the past 10,000 years, possibly because it enhances diapause. We show that the mutant allele attenuates the photosensitivity of the circadian clock and causes decreased dimerization of the mutant TIMELESS protein isoform to CRYPTOCHROME, the circadian photoreceptor. This interaction results in a more stable TIMELESS product. These findings reveal a molecular link between diapause and circadian photoreception.     

小麦赤霉酸不敏感基因Gai3的遗传研究

以小麦Ｒｈｔ３的两个株高等基因系及其ＢＣ２３Ｆ２分离群体为材料,分析了与Ｒｈｔ３矮秆基因连锁的赤霉酸不敏感基因Ｇａｉ３的遗传规律及其与Ｒｈｔ３的遗传关系。结果表明：赤霉酸不敏感性由单个显性基因控制,Ｆ２分离比率为３∶１（不敏感∶敏感）,非常符合χ２测验。Ｇａｉ３基因与Ｒｈｔ３基因连锁紧密,交换值为０．０６０±０．０１２和０．０５５±０．０１３。     

梁山慈竹体细胞突变体特性及分子水平变化

以同期生长的梁山慈竹体细胞突变体No.29植株和实生植株(对照)为材料,对其茎秆化学成分和光合生理相关指标进行测定,并基于RNA高通量转录组测序结果,对No.29植株的纤维素、木质素等合成有关的基因差异表达进行分析。结果表明,与实生植株相比,No.29植株具有较高的株高、胸径、茎秆的鲜重和干重以及纤维素含量、纤维长度和宽度;纤维素含量比实生植株高12.89%;外方和内方纤维股明显增大;灰分含量、卷曲指数和扭结指数明显降低;但发笋量、木质素含量和细小纤维含量没有明显差异。No.29植株中的Ces A、Su Sy、UDPase基因分别比实生植株上调了117%、205%、115%,转录因子MYB基因表达上调了214%,驱动蛋白基因表达上调了10倍,动力蛋白基因表达上调了760%。No.29植株纤维素含量与纤维形态上明显的改变有其遗传基础,为No.29的进一步研究与利用奠定了基础。     

裸粒水稻花序和小穗的发育进程研究

裸粒水稻是水稻和小麦远缘杂交的产物袁此前的研究已表明OsMADS1基因功能的改变是其特有花部性状的主要原因袁但目前仍对其花序和小穗的发育进程缺乏详细的认识遥通过扫描电镜观察袁发现从枝穗分化期至顶端小花内外稃分化期袁裸粒 水稻的发育仍与水稻没有明显区别袁但在其后花器官的发育上较为紊乱袁花器官确定性丧失袁从而产生额外的花器官和次级小穗遥这些观察有助于更好地理解裸粒水稻形态变异的分子机理遥     

云南青稞种质抗大麦黄矮病抗性鉴定研究初报

本研究收集云南丰富的青稞种质资源,进行抗大麦黄矮病(BYDV)抗病性鉴定。通过对61份青稞种质或品种进行连续2年田间抗BYDV鉴定及抗性评价,结果表明:44份种质表现易感BYDV,17份种质表现出不同程度的抗BYDV抗性,其中3份种质(52、54,I10)表现出对BYDV明显抗性,且抗性较为稳定。为培育抗性品种、持续有效地控制黄矮病的危害提供了新的抗源。     

不同浓度"麦草光"对青稞田除草效果比较

以不同浓度“麦草光”除草剂对青稞产量、主要性状的影响及除草效果进行试验 ,结果表明 :每公顷用 30 0 0～ 315 0ml的“麦草光”除草剂效果最佳 ,青稞产量可达 2 10 6 3～ 2 2 5 3kg/hm2 。     

Suppressor selectrion for amino acid replacements expected on the basis of the genetic code

In studies with A protein mutants of the tryptophan synthetase of Escherichia coli, missense supressors have been used to select for codon changes and corresponding amino acid replacements that are normally unobservable. The technique has permitted the detection of additional amino acid replacements expected on the basis of the genetic code.     

The neural basis of economic decision-making in the Ultimatum Game

The nascent field of neuroeconomics seeks to ground economic decision making in the biological substrate of the brain. We used functional magnetic resonance imaging of Ultimatum Game players to investigate neural substrates of cognitive and emotional processes involved in economic decision-making. In this game, two players split a sum of money;one player proposes a division and the other can accept or reject this. We scanned players as they responded to fair and unfair proposals. Unfair offers elicited activity in brain areas related to both emotion (anterior insula) and cognition (dorsolateral prefrontal cortex). Further, significantly heightened activity in anterior insula for rejected unfair offers suggests an important role for emotions in decision-making.     

The African American experience in agriculture

Shrinking enrollments in the agricultural programs of the 1890 schools can be partly explained by negative attitudes of Blacks toward agriculture. This attitude has roots in the historical experiences of African Americans and has negative implications for the agricultural programs of the 1890 schools. A collection of data from a sample of Black Louisiana Farmers lends credence to the claim that Black Farmers are not encouraging their children to go into farming. To counter the impact on the 1890 schools, an active recruiting program should be undertaken, partly to show Black students that career openings in various agricultural fields offer excellent opportunities for Black students. These fields extend beyond the traditional farmgate.     

新城疫病毒的一般生物学特性及其致病的分子基础

新城疫病毒(NDV)所致疫病鸡新城疫(ND)又称亚洲鸡瘟,是禽类的一种以呼吸道、消化道黏膜出血为典型症状的高度接触性急性败血性传染病,严重危害养禽业的发展。我国于1935年首次发现有ND的流行,但到1948年才得以最后证实。由于ND给世界养禽业造成的巨大损失,故对其病原NDV的研究一直是禽病研究的重点。现就新城疫病毒的一般生物学特性及其致病的分子学基础综述如下。     

Structural basis for substrate delivery by acyl carrier protein in the yeast fatty acid synthase

In the multifunctional fungal fatty acid synthase (FAS), the acyl carrier protein (ACP) domain shuttles reaction intermediates covalently attached to its prosthetic phosphopantetheine group between the different enzymatic centers of the reaction cycle. Here, we report the structure of the Saccharomyces cerevisiae FAS determined at 3.1 angstrom resolution with its ACP stalled at the active site of ketoacyl synthase. The ACP contacts the base of the reaction chamber through conserved, charge-complementary surfaces, which optimally position the ACP toward the catalytic cleft of ketoacyl synthase. The conformation of the prosthetic group suggests a switchblade mechanism for acyl chain delivery to the active site of the enzyme.     

旱地裸燕麦丰产栽培技术

裸燕麦(Avenanuda L.)也称莜麦,是禾本科燕麦属(Avena)一年生草本植物.莜麦在甘肃省通渭县有悠久的种植历史,种植面积仅次于小麦.随着生产的发展和人们对食品多样化的需要,莜麦以其较高的营养价值及药用价值深受人们的喜爱.据报道,莜麦有高于其它谷类作物的蛋白质含量及均衡的氨基酸组成,含油率也高于各类谷类作物,且非饱和脂类比例大,还含有较多的维生素E和β-葡聚糖.据临床实验证明,长期食用燕麦可降低人体胆固醇含量,对动脉粥样硬化与冠心病、高血压等均有很好的疗效.因此,莜麦加工工业发展很快,许多加工制品如燕麦片、燕麦冲剂等已成为人们早餐、快餐以及产妇和婴幼儿的上好补品.为了克服过去管理粗放以及干旱等自然因素带来的影响,提高莜麦生产水平,增加农民收入,现将近几年来大田示范总结的莜麦栽培技术介绍如下:     

Specialized fatty acid synthesis in African trypanosomes: myristate for GPI anchors

African trypanosomes, the cause of sleeping sickness, need massive amounts of myristate to remodel glycosyl phosphatidylinositol (GPI) anchors on their surface glycoproteins. However, it has been believed that the parasite is unable to synthesize any fatty acids, and myristate is not abundant in the hosts' bloodstreams. Thus, it has been unclear how trypanosomes meet their myristate requirement. Here we found that they could indeed synthesize fatty acids. The synthetic pathway was unique in that the major product, myristate, was preferentially incorporated into GPIs and not into other lipids. The antibiotic thiolactomycin inhibited myristate synthesis and killed the parasite, making this pathway a potential chemotherapeutic target.