Glutamate induces de novo growth of functional spines in developing cortex

Mature cortical pyramidal neurons receive excitatory inputs onto small protrusions emanating from their dendrites called spines. Spines undergo activity-dependent remodelling, stabilization and pruning during development, and similar structural changes can be triggered by learning and changes in sensory experiences. However, the biochemical triggers and mechanisms of de novo spine formation in the developing brain and the functional significance of new spines to neuronal connectivity are largely unknown. Here we develop an approach to induce and monitor de novo spine formation in real time using combined two-photon laser-scanning microscopy and two-photon laser uncaging of glutamate. Our data demonstrate that, in mouse cortical layer 2/3 pyramidal neurons, glutamate is sufficient to trigger de novo spine growth from the dendrite shaft in a location-specific manner. We find that glutamate-induced spinogenesis requires opening of NMDARs (N-methyl-D-aspartate-type glutamate receptors) and activation of protein kinase A (PKA) but is independent of calcium-calmodulin-dependent kinase II (CaMKII) and tyrosine kinase receptor B (TrkB) receptors. Furthermore, newly formed spines express glutamate receptors and are rapidly functional such that they transduce presynaptic activity into postsynaptic signals. Together, our data demonstrate that early neural connectivity is shaped by activity in a spatially precise manner and that nascent dendrite spines are rapidly functionally incorporated into cortical circuits.     

Nerve growth factor induces adrenergic neuronal differentiation in F9 teratocarcinoma cells

Teratocarcinoma cells have been used as a model to study differentiation and development in vertebrates. Treatment with retinoic acid (RA) and dibutyryl cyclic AMP can in some embryonal carcinoma (EC) cell lines lead to neural differentiation, as judged by neurofilament expression and by the induction of enzymes involved in cholinergic transmission. Short-term culture of F9 line cells with RA and dibutyryl cyclic AMP results in a biochemically demonstrable rise in acetylcholinesterase (AChE) activity. We now report that long-term culture of F9 cells with RA and dibutyryl cyclic AMP induces neurofilament expression, demonstrated by immunofluorescence with specific antibodies. Furthermore, if nerve growth factor (NGF) is also added, the developing neurone-like cells exhibit immunoreactivity to tyrosine hydroxylase, a rate-limiting enzyme of catecholamine synthesis specific for adrenergic neurones. Immunoreactivity for Leu-enkephalin-like peptides is also induced. These results suggest that F9 cells can differentiate into cells with adrenergic characteristics.     

Depletion of phosphatidyl-glycerol head-group induces changes in oxygen evolution and protein secondary struc-tures of photosystem Ⅱ

The techniques of oxygen electrode polarogra-phy and Fourier transform infrared (FT-IR) spectroscopy were employed to explore the roles of polar head-group of phosphatidylglycerol (PG) molecules in the functional and structural aspects of photosystem Ⅱ (PS Ⅱ) through enzymatic approach. It was shown that the depletion of PG by treatment of phospholipase C (PLC) on PS Ⅱ particles caused the inhibition of oxygen evolving activity in PS Ⅱ. This effect also gave rise to changes in the protein secondary structures of PS Ⅱ, that is, an increase in a-helical conformation which is compensated by the loss of p-strand structures. It revealed that the head-group of PG molecules plays an important structural role in the maintenance of normal structure of PS Ⅱ proteins, which is required to maintain the appropriate physiological activity of the PS Ⅱ complex such as the oxygen evolving activity. It is suggested that there most probably exist hydrogen-bonding interactions between PG molecules and PS Ⅱ proteins.     

Depletion of phosphatidylglycerol head-group induces changes in oxygen evolution and protein secondary structures of photosystemⅡ

The techniques of oxygen electrode polarography and Fourier transform infrared (FT-IR) spectroscopy were employed to explore the roles of polar head-group of phosphatidylglycerol (PG) molecules in the functional and structural aspects of photosystemⅡ(PSⅡ) through enzymatic approach. It was shown that the depletion of PG by treatment of phospholipase C (PLC) on PSⅡ particles caused the inhibition of oxygen evolving activity in PSⅡ. This effect also gave rise to changes in the protein secondary structures of PSⅡ, that is, an increase in α-helical conformation which is compensated by the loss of β-strand structures. It revealed that the head-group of PG molecules plays an important structural role in the maintenance of normal structure of PSⅡ proteins, which is required to maintain the appropriate physiological activity of the PSⅡ complex such as the oxygen evolving activity. It is suggested that there most probably exist hydrogen-bonding interactions between PG molecules and PSⅡ proteins.     

铜绿微囊藻对浮游动物生长繁殖的影响

分离并纯化培养草履虫、绿眼虫及枝角类的大型氵蚤等浮游动物 ,同时培养产毒铜绿微囊藻 .逐日观察、计数稳定期的铜绿微囊藻培养液在不同密度时对不同种类浮游动物生长繁殖的影响 .结果表明 :铜绿微囊藻对不同类别浮游动物的影响因藻类浓度变化而异 ,铜绿微囊藻对草履虫的抑制影响不明显 ;对绿眼虫的生长繁殖能较强抑制 ,当铜绿微囊藻的密度大于 9× 1 0 6 个 /L时 ,绿眼虫几乎无法生存 ;当铜绿微囊藻密度大于 9× 1 0 9个 /L时 ,对大型氵蚤表现出一定程度的抑制     

Protein kinase C activation induces conductance changes in Hermissenda photoreceptors like those seen in associative learning

Phosphorylation of ion channels has been suggested as one molecular mechanism responsible for learning-produced long-term changes in neuronal excitability. Persistent training-produced changes in two distinct K+ currents (IA (ref. 2), IK-Ca (refs 3,4)) and a voltage-dependent calcium current (ICa; refs 3,4) have previously been shown to occur in type B photoreceptors of Hermissenda, as a result of associative learning. But the identity of the phosphorylation pathway(s) responsible for these changes has not as yet been determined. Injections of cyclic AMP-dependent protein kinase reduce a K+ current (IK) in B cells which is different from those changed by training, but fails to reduce IA and IK-Ca. Phosphorylase b kinase (an exogenous calcium/calmodulin-dependent kinase) reduces IA, but whether IK-Ca and ICa are changed in the manner of associative training is not yet known. Another protein kinase present in high concentrations in both mammalian brain and molluscan nervous systems is protein kinase C, which is both calcium- and phospholipid-sensitive. We now present evidence that activation of protein kinase C by the tumour promoter phorbol ester (PDB) and intracellular injection of the enzyme induce conductance changes similar to those caused by associative training in Hermissenda B cells (that is a reduction of IA and IK-Ca, and enhancement of ICa). These results represent the first direct demonstration that protein kinase C affects membrane K+ ion conductance mechanisms.     

A novel thioredoxin reductase inhibitor inhibits cell growth and induces apoptosis in HL-60 and K562 cells

Human thioredoxin reductase （TrxR） system is associated with cancer cell growth and anti-apoptosis process. Effects of 1,2-[bis（1,2-benzisoselenazolone-3（2H）-ketone）]ethane （BBSKE）, a novel TrxR inhibitor, were investigated on human leukemia cell lines HL-60 and K562. BBSKE treatment induced cell growth inhibition and apoptosis in both cell lines. Apoptosis induced by BBSKE is through Bcl-2/Bax and caspase-3 pathways. Ehrlich＇s ascites carcinoma-bearing mice were used to investigate the anti-tumor effect of BBSKE in vivo. Tumor-bearing mice treated with BBSKE showed an increase of life span with a comparable effect to cyclophosphamide （CTX）. These results suggest a potential usage of BBSKE as a therapeutic agent against non-solid tumors.     

大豆多糖的降解及其对草酸钙生长的抑制作用

采用过氧化氢法对水提法从大豆中提取了大豆多糖(SPS)进行了降解.降解后,SPS的平均相对分子质量由115 200下降至10 200,羧基(-COOH)质量分数由13.8%下降至11.8%,特性黏度[η]由0.498 L/g下降至0.1056 L/g,溶解度由8 g/L增加至40 g/L降解后的SPS比降解前更能抑制草...     

拮抗菌HT-6对致病疫霉的竞争及诱导性抑制

为深入了解细菌HT-6对致病疫霉(Phytophthora infestans)菌丝生长的抑制机理,采用琼脂柱对接法观察细菌HT-6对致病疫霉空间位点的竞争,铬天青(CAS)培养基观察嗜铁素的产生,硫酸-蒽铜比色法和水杨酸浓硫酸比色法分别比较葡萄糖和硝态氮的利用率,同时以致病疫霉及其细胞壁制剂(CWP)为诱导物,采用平板透明圈法观察HT-6产生的纤维素酶和β-1,3-葡聚糖酶,DNS法测定酶活并评价含有2种酶的无菌体发酵液对致病疫霉的抑制活性.结果显示,单独接种在PDA琼脂柱上的致病疫霉能沿琼脂柱生长并迅速扩展至黑麦固体培养基(Rye)表面生长,与致病疫霉菌饼对接的HT-6也能沿着琼脂柱生长并扩展至Rye培养基表面迅速蔓延,而与HT-6对接的致病疫霉菌丝体仅在PDA琼脂柱上生长,没有扩展至Rye表面,被HT-6的生长所阻止;HT-6能产生嗜铁素,致病疫霉不产生嗜铁素;HT-6对葡萄糖和硝态氮的利用率(75.66%和69.05%)均显著高于致病疫霉(55.97%和56.87%);HT-6菌株单独培养时不产生纤维素酶和β-1,3-葡聚糖酶,但致病疫霉菌体和CWP均能诱导HT-6产生这2种酶,其中菌体诱导后的2种酶活,分别为6.638、2.913 U,均显著高于CWP的诱导处理(1.326、1.289 U,P<0.05);CWP诱导后含有2种酶的HT-6无菌体发酵液对致病疫霉菌丝生长具有明显抑制作用(抑菌率为33.25%),但显著低于单独培养的HT-6菌液原液的抑菌活性(抑菌率为81.33%).这表明HT-6能够通过空间和营养竞争以及致病疫霉诱导产生的细胞壁降解酶抑制致病疫霉,其中以空间和营养竞争为主.