Differential lysosomal proteolysis in antigen-presenting cells determines antigen fate

Antigen-presenting cells (APCs) internalize antigens and present antigen-derived peptides to T cells. Although APCs have been thought to exhibit a well-developed capacity for lysosomal proteolysis, here we found that they can exhibit two distinct strategies upon antigen encounter. Whereas macrophages contained high levels of lysosomal proteases and rapidly degraded internalized proteins, dendritic cells (DCs) and B lymphocytes were protease-poor, resulting in a limited capacity for lysosomal degradation. Consistent with these findings, DCs in vivo degraded internalized antigens slowly and thus retained antigen in lymphoid organs for extended periods. Limited lysosomal proteolysis also favored antigen presentation. These results help explain why DCs are able to efficiently accumulate, process, and disseminate antigens and microbes systemically for purposes of tolerance and immunity.     

Outward currents in developing Drosophila flight muscle

The development of two different voltage-sensitive potassium channels was studied in Drosophila flight muscle by voltage clamp techniques. Early in development active channels are not present in the membrane. The first channels to appear are the A current channels, which carry a fast, rapidly inactivating potassium current. The channels for delayed rectification appear later. Channels carrying inward current also appear only after the A current channels. During development, the A current may be easily studied in isolation from other currents and thus provides a desirable system for studying the genetic determinants of this current.     

Visceral reflex activity: development in postnatal rabbit

In postnatal rabbits there is progressive development of central regulation of the micturition reflex. During the first 1 to 2 days of postnatal life a coordinated sustained reflex may be obtained from the bladder which has been isolated from the central nervous system. Changes in reflex integration occur over the following 7 to 12 days, which result in a coordinated reflex dependent upon supraspinal influiences.     

Differential classical conditioning of a defensive withdrawal reflex in Aplysia californica

The defensive siphon and gill withdrawal reflex of Aplysia is a simple reflex mediated by a well-defined neural circuit. This reflex exhibits classical conditioning when a weak tactile stimulus to the siphon is used as a conditioned stimulus and a strong shock to the tail is used as an unconditioned stimulus. The siphon withdrawal component of this reflex can be differentially conditioned when stimuli applied to two different sites on the mantle skin (the mantle shelf and the siphon) are used as discriminative stimuli. The differential conditioning can be acquired in a single trial, is retained for more than 24 hours, and increases in strength with increased trials. Differential conditioning can also be produced within the field of innervation of a single cluster of sensory neurons (the LE cluster) since two separate sites on the siphon skin can serve as discriminative stimuli. The finding that two independent afferent inputs that activate a common set of interneurons and motor neurons can be differentially conditioned restricts the possible cellular loci involved in the associative learning.     

Serotonin and octopamine produce opposite postures in lobsters

Serotonin and octopamine, injected into the circulation of freely moving lobsters and crayfish, produce opposite behavioral effects. Octopamine injection produces sustained extension of the limbs and abdomen; serotonin injection produces sustained flexion. Neurophysiological analyses show that these postures can be accounted for by opposing, coordinated effects of these amines on patterns of motoneuron activity recorded from the ventral nerve cord.     

Ribonuclease activity in the developing seeds of normal and opaque-2 maize

During development, the ribonuclease activity of maize endo sperm homozygous for the opaque-2 gene increased earlier and, after a longer period of exponential increase, was much higher finally than in normal endosperm. The maximum difference was about sixfold and occurred 22 to 25 days after pollination. Heterozygotes on day 23 did not show a comparable in crease in endosperm activity. No differ ence in the activity ratio (pH 6.0: pH 5.2) was found between normal and opaque-2 endosperm, indicating that the increase in activity in opaque-2 was due solely to an increase in ribo nuclease A. The ribonuclease activity of opaque-2 embryos increased more rapidly than that of normal embryos, but the final activity was the same in each case.     

Localization of calcium pump activity in smooth muscle

A microsomal fraction isolated from longitudinal smooth muscle of guinea pig ileum actively sequesters calcium ion in the presence of magnesium and adenosine triphosphate in a fashion previously described for microsomes of the rabbit aorta. This activity in guinea pig ileum appears to be associated primarily with the plasma membrane as is found in the red cell. By contrast the uptake of calcium in aortic smooth muscle appears to be associated to an appreciable extent with intracellular membranes, possibly analogous to the sarcoplasmic reticulum of skeletal muscle.     

Hormonal control of behavior: amines and the biasing of behavioral output in lobsters

Hormones and neurohormones act on the nervous system to produce important changes in behavior. Amine actions in the lobster nervous system and their possible relations to aggressive behavior in lobsters were studied in order to explore how such changes might come about.     

Functional differences between two classes of sodium channels in developing rat skeletal muscle

Excitability is generated in developing skeletal muscle by the incorporation of sodium-selective ion channels into the surface membrane. Whole-cell and patch voltage-clamp recording from myotubes and their embryologic precursors, myoblasts, indicated that voltage-activated sodium current in myoblasts was more resistant to block by tetrodotoxin (TTX) than that in myotubes. Single-channel recording from both cell types showed two classes of sodium channels. One class had a lower single-channel conductance, activated at more hyperpolarized voltages, and was more resistant to TTX than the other. The proportion of TTX-resistant to TTX-sensitive sodium channels was higher in myoblasts than in myotubes. Thus, the difference in TTX sensitivity between myoblasts and myotubes can be explained by a difference in the proportion of the two classes of sodium channels. In addition, the lower conductance of TTX-resistant channels provides insight into the relationship between the TTX binding site and the external mouth of the sodium channel.     

Differential development of two classes of acetylcholine receptors in Xenopus muscle in culture

Physiological properties of acetylcholine receptors on muscle cells at very early stages of ontogeny were compared with those of cells at later stages. Two changes were observed that contributed to an overall shortening of the mean open time of single-channels. First, there was a shift in the relative proportions of two receptor types with different conductances and mean open times, such that the contribution of receptors with large conductance and short open time increased as development proceeded. Second, there was a sharp reduction in the mean open time of channels having small conductance, with no similar change in channels having large conductance.     

异黄酮对雄性大鼠芳香化酶活性及骨骼肌生长的影响

研究3种异黄酮(Da、IPF和7HF)对雄性大鼠芳香化酶活性及骨骼肌生长的影响。试验选用20只28日龄雄性SD大鼠,随机分成4组,每组5只,其中1组为对照组,另外3组在每千克日粮中分别添加5mg的Da、IPF和7HF。实验结果表明,Da、IPF和7HF均能升高腿肌中RNA／DNA的比值,分别较对照组升高了19．09％、9．09％和15．45%;同时显增加血清中睾酮的含量,降低血清中雌二醇的含量,抑制睾丸组织中芳香化酶的活性。提示异黄酮(Da、IPF、7HF)通过抑制芳香化酶活性而降低睾酮向雌二醇的转化,使体内睾酮含量升高,有助于促进动物的生长发育。     

Exercise: effects on hexokinase activity in red and white skeletal muscle

Single bouts of exercise increase hexokinase activity in red and white skeletal muscle of guinea pigs. Multiple bouts of exercise cause two-fold increases. In contrast to other enzymes associated with glycolysis, hexokinase activity is higher in red than in white skeletal muscle.     

Histochemical phosphorylase activity in regenerating muscle fibers from myophosphorylase-deficient patients

Fresh frozen sections of mature skeletal muscle fibers from patients with genetically determined "absence" of skeletal muscle phosphorylase (McArdle's disease) have no histochemical phosphorylase activity. That regenerating muscle fibers, in vitro and in vivo, from such patients do have histochemical phosphorylase activity present suggests a loss of enzyme activity with fiber maturity.     

水稻种子成熟和萌发过程中脂氧合酶同工酶活性及其表达水平

水稻种子中有3种脂氧合酶（LOX）同工酶,分别为LOX-1、LOX-2、LOX-3。以本实验室筛选到的LOX-3缺失突变体北陆PL2和正常的水稻品种Koshihikari为材料,研究种子成熟及萌发过程中LOX活性的变化规律。结果显示,2个水稻品种在种子成熟中LOX活性变化规律不一致,Koshihikari开花后10～25d活性升高,以后趋于下降,而北陆PL2花后种子LOX活性基本没有变化;在种子萌发过程中两品种LOX活性变化规律基本一致,萌发初期活性迅速升高,浸水萌发后2d达到峰值,以后开始下降。同工酶分析、半定量RT-PCR结果都显示,在水稻成熟过程中,种子中LOX-3活性和表达水平都显著高于其他两种酶（LOX-1和LOX-2）;在种子萌发过程中,LOX-2活性和表达水平占优势,而LOX-1在种子成熟和萌发过程中都显示较低的活性和表达水平。这表明,水稻种子LOX-3可能与水稻的贮藏特性有关,LOX-2在水稻萌发过程中起主要作用,可能与水稻萌发期间储藏脂质的利用有关或者具有萌发信号的作用,而LOX-1的功能还有待进一步研究。     

Phosphorylase a activity in uterine muscle: stimulation by ethylenediaminetetraacetic acid

Injection of ethylenediaminetetraacetic acid into spayed rats or its use in phosphorylase extraction increases the activity of glycogen-phosphorylase a in uterine smooth muscle tissue. Since the total phosphorylase activity is not increased, the increase in phosphorylase a appears to result from a conversion of inactive phosphorylase b to the active form of the enzyme.     

苏尼特羊不同生长时期肌肉组织lncRNA的差异表达分析

为鉴定和分析苏尼特羊肌肉不同发育时期lncRNA的差异表达,利用RNA-seq技术对120d苏尼特羊胎儿和5月龄羔羊肌肉组织进行了lncRNA比较分析,筛选出差异表达的lncRNA及其靶基因,并对预测的mRNA进行了GO和KEGG分析,同时对随机筛选的差异表达lncRNA进行qRT-PCR验证。结果显示,120d和5月龄羔羊肌肉之间差异表达的lncRNA数共为626个,共靶向1 273个mRNA编码基因。GO和KEGG分析表明,这些差异基因主要涉及代谢过程的调控,生物合成,基因表达,蛋白结合以及mTOR信号通路、FoxO信号通路、胰岛素信号、肌动蛋白细胞骨架的调节、Wnt信号通路和间隙连接等信号通路。qRT-PCR验证证明,随机选取的8个lncRNA在肌肉组织中的表达量与RNA-seq结果一致。综上,本研究利用RNA-Seq技术分析了苏尼特羊120d胎儿和5月龄羔羊的差异表达lncRNA及其靶基因,发现其参与了不同生长时期苏尼特羊的肌肉发育和生长过程,为从lncRNA的角度更好地理解苏尼特羊肌肉生长发育的遗传调控机制提供了理论基础,也为绵羊分子辅助育种提供参考。     

Differential phosphorylation of c-Abl in cell cycle determined by cdc2 kinase and phosphatase activity

The product of the c-abl proto-oncogene (c-Abl) is phosphorylated on three sites during interphase and seven additional sites during mitosis. Two interphase and all mitotic c-Abl sites are phosphorylated by cdc2 kinase isolated from either interphase or mitotic cells, with the mitotic cdc2 having an 11-fold higher activity. Inhibition of phosphatases with okadaic acid in interphase cells leads to the phosphorylation of c-Abl mitotic sites, indicating that those sites are preferentially dephosphorylated during interphase. The differential phosphorylation of c-Abl in the cell cycle is therefore determined by an equilibrium between cdc2 kinase and protein phosphatase activities. Treatment of interphase cells with okadaic acid leads to a rounded morphology similar to that observed during mitosis.