Retrograde signaling by Syt 4 induces presynaptic release and synapse-specific growth

The molecular pathways involved in retrograde signal transduction at synapses and the function of retrograde communication are poorly understood. Here, we demonstrate that postsynaptic calcium 2+ ion (Ca2+) influx through glutamate receptors and subsequent postsynaptic vesicle fusion trigger a robust induction of presynaptic miniature release after high-frequency stimulation at Drosophila neuromuscular junctions. An isoform of the synaptotagmin family, synaptotagmin 4 (Syt 4), serves as a postsynaptic Ca2+ sensor to release retrograde signals that stimulate enhanced presynaptic function through activation of the cyclic adenosine monophosphate (cAMP)-cAMP-dependent protein kinase pathway. Postsynaptic Ca2+ influx also stimulates local synaptic differentiation and growth through Syt 4-mediated retrograde signals in a synapse-specific manner.     

Transformation of olfactory representations in the Drosophila antennal lobe

Molecular genetics has revealed a precise stereotypy in the projection of primary olfactory sensory neurons onto secondary neurons. A major challenge is to understand how this mapping translates into odor responses in these second-order neurons. We investigated this question in Drosophila using whole-cell recordings in vivo. We observe that monomolecular odors generally elicit responses in large ensembles of antennal lobe neurons. Comparison of odor-evoked activity from afferents and postsynaptic neurons in the same glomerulus revealed that second-order neurons display broader tuning and more complex responses than their primary afferents. This indicates a major transformation of odor representations, implicating lateral interactions within the antennal lobe.     

Signal-processing machines at the postsynaptic density

Dendrites of individual neurons in the vertebrate central nervous system are contacted by thousands of synaptic terminals relaying information about the environment. The postsynaptic membrane at each synaptic terminal is the first place where information is processed as it converges on the dendrite. At the postsynaptic membrane of excitatory synapses, neurotransmitter receptors are attached to large protein "signaling machines" that delicately regulate the strength of synaptic transmission. These machines are visible in the electron microscope and are called the postsynaptic density. By changing synaptic strength in response to neural activity, the postsynaptic density contributes to information processing and the formation of memories.     

Pentobarbital: selective depression of excitatory postsynaptic potentials

The effects of pentobarbital (Nembutal) on synaptic transmission and postsynaptic potentials were studied by the use of several invertebrate preparations. Pentobarbital selectively and reversibly depressed both excitatory postsynaptic potentials and sodium-dependent postsynaptic responses to putative excitatory transmitters without affecting either inhibitory postsynaptic potentials or chloride- and potassium-dependent postsynaptic responses to putative transmitters. A selective depression of postsynaptic excitatory events was also observed with other central nervous system depressants (ethanol, chloroform, chloralose, diphenylhydantoin, and urethane). The results suggest that central and peripheral depression observed during general anesthesia is due to a selective depression of excitatory synaptic events.     

Adenosine 3',5'-monophosphate: electrophysiological evidence for a role in synaptic transmission

Synaptic potentials and changes in resting membrane potentials of superior cervical ganglia of the rabbit were measured in the presence of adenosine 3',5'-monophosphate and agents that affect its metabolism. Adenosine 3',5'-monophosphate and its mono- and dibutyryl derivatives caused a hyperpolarization of the postganglionic neurons. Theophylline potentiated the slow inhibitory postsynaptic potential that follows synaptic transmission, as well as the hyperpolarization of postganglionic neurons caused by exogenous dopamine. Conversely, prostaglandin E(1) inhibited both the slow inhibitory postsynaptic potential and the dopamine-induced hyperpolarization. We hypothesize that the slow inhibitory postsynaptic potential as well as the dopamine-induced hyperpolarization result from increased amounts of adenosine 3'5'-monophosphate in the postganglionic neurons. The dibutyryl derivative of guanosine 3'5'-monophosphate caused a depolarization of the postganglionic neurons, which is consistent with the possibility that guanosine 3'5'-monophosphate mediates synaptic transmission at muscarinic cholinergic synapses.     

不同配方培养基对果蝇生长和繁殖的影响

为了筛选出最适果蝇生长的培养基,以遗传实验室饲养的4种果蝇为试验对象,比较了5种不同培养基对果蝇生长发育周期和繁殖后代的影响,结果筛选出了水果培养基和改进的玉米粉培养基,对比得出前者所培养的果蝇三龄幼虫个体明显较大,生长周期也较后者缩短1d左右,而后者所培养的果蝇子代数量要多于前者。     

Axons guided by insulin receptor in Drosophila visual system

Insulin receptors are abundant in the central nervous system, but their roles remain elusive. Here we show that the insulin receptor functions in axon guidance. The Drosophila insulin receptor (DInR) is required for photoreceptor-cell (R-cell) axons to find their way from the retina to the brain during development of the visual system. DInR functions as a guidance receptor for the adapter protein Dock/Nck. This function is independent of Chico, the Drosophila insulin receptor substrate (IRS) homolog.     

果蝇热应激生理机制研究进展

受全球温室效应和城市热岛效应的影响,高温环境对人类健康的危害越来越严重,生物热应激生理机制的研究逐渐成为热点.由于果蝇对温度敏感、神经元结构简单且基因遗传稳定,因此成为热应激研究的最佳模式生物.文章综述了以果蝇为模型的热感知处理、热偏好及耐热性的研究进展,说明利用果蝇研究热感知过程的优势,以及果蝇应对无害高温的热感受器和应对有害高温的高温伤害感受器,解释果蝇的热偏好及其可能影响因素,阐述果蝇热休克蛋白的诱导表达、表达量与温度阈值、基因结构变异及功能植物和营养素对其耐热性的影响等.今后可将果蝇热感知机制在人体体温调节、食物对生物体热偏好的影响及功能植物和营养素在分子水平上对果蝇耐热性的影响方面进一步探究和深化,以期探索出通过食物调节人体最适温度的方法及更合理的热损伤预防措施.     

Drosophila egg-laying site selection as a system to study simple decision-making processes

The ability to select a better option from multiple acceptable ones is important for animals to optimize their resources. The mechanisms that underlie such decision-making processes are not well understood. We found that selection of egg-laying site in Drosophila melanogaster is a suitable system to probe the neural circuit that governs simple decision-making processes. First, Drosophila females pursue active probing of the environment before depositing each egg, apparently to evaluate site quality for every egg. Second, Drosophila females can either accept or reject a sucrose-containing medium, depending on the context. Last, communication of the "acceptability" of the sucrose-containing medium as an egg-laying option to the reproductive system depends on the function of a group of insulin-like peptide 7 (ILP7)-producing neurons. These findings suggest that selection of egg-laying site involves a simple decision-making process and provide an entry point toward a systematic dissection of this process.     

Postsynaptic membrane response predicted from presynaptic input pattern in lobster cardiac ganglion

Given the pattern of impulses impinging on a neuron, it should be possible to predict its output firing pattern if enough is known about pre- and postsynaptic properties. A quantitative reproduction of the first part of this input-output conversion is reported, namely the translation of input pattern into a sequence of postsynaptic membrane potential variations.     

Hawaiian courtship songs: evolutionary innovation in communication signals of Drosophila

In Hawaii, flies of the genus Drosophila have undergone spectacular adaptive radiation, resulting in the evolution of more than 500 species of Drosophila that are found nowhere else on earth. This taxonomic uniqueness is reflected in behavior and morphology. Hawaiian Drosophila sing songs, as do continental Drosophila; however, the Hawaiian songs have diverged strongly in form and mechanism of production. The click-song of D. fasciculisetae's (Maui) has a carrier frequency an order of magnitude higher than those reported in familiar continental species, such as D. melanogaster (170 hertz). Drosophila fasciculisetae's song resembles a cicada's more than a fly's song. The song of D. cyrtoloma (Maui) has a complex pulse rhythm more typical of crickets than flies. The pulse song of D. silvestris (Hawaii) closely resembles that of D. melanogaster in both pulse rhythm and carrier frequency, but D. melanogaster sings by vibrating its wings, whereas D. silvestris sings through abdominal vibrations. These mechanisms are radical departures from the continental wing song mechanism and are further examples of the remarkable behavioral innovation that has occurred in the Drosophila of Hawaii during their evolutionary transit through these islands.     

Modulating sphingolipid biosynthetic pathway rescues photoreceptor degeneration

Mutations in proteins of the Drosophila phototransduction cascade, a prototypic guanine nucleotide-binding protein-coupled receptor signaling system, lead to retinal degeneration and have been used as models to understand human degenerative disorders. Here, modulating the sphingolipid biosynthetic pathway rescued retinal degeneration in Drosophila mutants. Targeted expression of Drosophila neutral ceramidase rescued retinal degeneration in arrestin and phospholipase C mutants. Decreasing flux through the de novo sphingolipid biosynthetic pathway also suppressed degeneration in these mutants. Both genetic backgrounds modulated the endocytic machinery because they suppressed defects in a dynamin mutant. Suppression of degeneration in arrestin mutant flies expressing ceramidase correlated with a decrease in ceramide levels. Thus, enzymes of sphingolipid metabolism may be suitable targets in the therapeutic management of retinal degeneration.     

乌骨鸡黑色素对延缓果蝇衰老的作用

用盐酸降解蛋白质法提取乌骨鸡黑色素,研究其对超氧阴离子（Ｏ－·２）的清除作用,并进行了延缓果蝇衰老的生物学实验。结果表明：（１）在核黄素和甲硫氨酸光照生成的Ｏ－·２体系中,乌骨鸡黑色素能减少氮蓝四唑（ＮＢＴ）还原产物甲的生成,光化还原抑制率和黑色素浓度有一定的关系,证明乌骨鸡黑色素能清除Ｏ－·２,具有类似ＳＯＤ的功能。（２）乌骨鸡黑色素能延长果蝇的平均寿命,提高果蝇的性活力,降低果蝇的脂褐素含量（Ｐ＜０．０５）,表明乌骨鸡黑色素具有延缓衰老的作用。     

Rescue of the Drosophila phototransduction mutation trp by germline transformation

Phototransduction is the process by which light-stimulated photoreceptor cells of the visual system send electrical signals to the nervous system. Many of the steps that follow the initial event in phototransduction, absorption of light by rhodopsin, are ill-defined. The fruitfly, Drosophila melanogaster, provides a means to dissect phototransduction genetically. Mutations such as transient receptor potential (trp) affect intermediate steps in phototransduction. In order to facilitate molecular studies of phototransduction, the trp gene was isolated and its identity was confirmed by complementing the mutant trpCM allele of the trp gene by P-element mediated germline transformation of a 7.1-kilobase DNA fragment. Expression of the trp gene begins late in pupal development and appears to be limited to the eyes and ocelli.     

北冬虫夏草提取液对果蝇繁殖力及寿命的影响

采用不同浓度的北冬虫夏草(简称北虫草)提取液(0.625%,1.250%,5.000%)分别处理野生黑腹果蝇,研究北虫草提取液对果蝇繁殖力及寿命的影响。结果表明:5.000%浓度组F1果蝇数与对照组比较有极显著差异(p<0.01),当北虫草提取液浓度低于1.250%时,果蝇的繁殖力有增加趋势;北虫草提取液对果蝇平均寿命无显著延长作用,但可显著提高第一子代果蝇营养物质的积累,促进其生长发育。     

Correlates of sleep and waking in Drosophila melanogaster

Drosophila exhibits a circadian rest-activity cycle, but it is not known whether fly rest constitutes sleep or is mere inactivity. It is shown here that, like mammalian sleep, rest in Drosophila is characterized by an increased arousal threshold and is homeostatically regulated independently of the circadian clock. As in mammals, rest is abundant in young flies, is reduced in older flies, and is modulated by stimulants and hypnotics. Several molecular markers modulated by sleep and waking in mammals are modulated by rest and activity in Drosophila, including cytochrome oxidase C, the endoplasmic reticulum chaperone protein BiP, and enzymes implicated in the catabolism of monoamines. Flies lacking one such enzyme, arylalkylamine N-acetyltransferase, show increased rest after rest deprivation. These results implicate the catabolism of monoamines in the regulation of sleep and waking in the fly and suggest that Drosophila may serve as a model system for the genetic dissection of sleep.     

The muscle protein Dok-7 is essential for neuromuscular synaptogenesis

The formation of the neuromuscular synapse requires muscle-specific receptor kinase (MuSK) to orchestrate postsynaptic differentiation, including the clustering of receptors for the neurotransmitter acetylcholine. Upon innervation, neural agrin activates MuSK to establish the postsynaptic apparatus, although agrin-independent formation of neuromuscular synapses can also occur experimentally in the absence of neurotransmission. Dok-7, a MuSK-interacting cytoplasmic protein, is essential for MuSK activation in cultured myotubes; in particular, the Dok-7 phosphotyrosine-binding domain and its target in MuSK are indispensable. Mice lacking Dok-7 formed neither acetylcholine receptor clusters nor neuromuscular synapses. Thus, Dok-7 is essential for neuromuscular synaptogenesis through its interaction with MuSK.     

Drosophila males contribute to oogenesis in a multiple mating species

Two species of Drosophila that differ in their ecology and mating systems have been compared with respect to male contribution to the somatic tissues and developing oocytes of females. In the species Drosophila mojavensis females remate daily, exhibit a copulatory plug, and have been shown to obtain a contribution from the male ejaculate. In contrast, Drosophila melanogaster males do not contribute to females. Female Drosophila melanogaster do not remate as frequently as Drosophila mojavensis females nor is a copulatory plug formed.