Generation of torsional and vertical eye position signals by the interstitial nucleus of Cajal

The neural integrator, which converts eye velocity signals into position signals, is central to oculomotor theory. Similar integrators are probably necessary in any neural system that changes and maintains muscular tension. The integrator for horizontal eye position is in the pons, but the locations of the vertical and torsional integrators have not been clearly defined. Recording three-dimensional eye movements in alert monkeys during microstimulation and pharmacological inactivation of midbrain sites showed that the interstitial nucleus of Cajal generates both the torsional and vertical eye position signals. Up and down signals are linked with clockwise signals in the right brain and counterclockwise signals in the left brain. This three-dimensional coordinate system achieves orthogonality and bilateral symmetry without redundancy and optimizes energy efficiency for horizontal visual scanning.     

Visual adaptation to an altered correlation between eye movement and head movement

A visual target was mloved left and right in exact synchrony with vertical movements of the head. A few minutes' exposure to this novel head-movement feedback led to a change in the visual discrimlination of head movement from object movement. The critical factor in the adaptation is the novel correlation of eye and head movement elicited during the period of exposure.     

Local retinal regions control local eye growth and myopia

In chicks, visual deprivation leads to myopia and enlargement of the vitreous chamber of the eye. When chicks were raised with white translucent occluders over their eyes so that either the nasal half, the temporal half, or all of the retina was visually deprived, the resulting myopia (median = -15 diopters) was limited to the deprived part of the retina, regardless of which half of the retina was visually deprived; the nondeprived part remained nearly emmetropic. Correspondingly, the vitreous chamber was elongated only in the region of the visual deprivation, resulting in eyes with different asymmetric shapes depending on which retinal region was deprived. These results argue for a local regulation of ocular growth that is dependent on vision and suggest a hypothesis to explain the epidemiological association of myopia in humans with large amounts of reading. Because most nonfoveal retinal neurons have large receptive fields, they cannot resolve the individual letters on the printed page; this may lead to their activity being less during reading than during most other forms of visual stimulation. Thus, the impoverished stimulus situation of reading may lead to myopia, as do other types of visual form deprivation.     

An eagle's eye: quality of the retinal image

The optical quality of a living eagle's eye was determined by an ophthalmoscopic method. The performance of the eye was substantially better than that reported for humans, but did not confirm some of the wilder claims made for such birds.     

眼动技术在现代家具创新设计中的应用研究

眼动技术在平面设计和心理学研究领域已有广泛的应用,可以进行平面优化设计评估和视觉心理学探究,在家具设计领域应用还比较少见。近几年中国家具企业越来越重视家具的创新性设计,为此以座椅靠背搭脑的造型的评价为例,介绍了眼动技术在家具视觉因素评价方面的应用,并在此基础上探讨了家具创新的新方法和心思路。试验研究表明,注视时间、平均注视时间、注视次数、首视点次数、综合热点图以及注视模式等视觉行为评价指标不仅能够较好地反映家具视觉元素对人体生理、心理的影响,还可以将家具各视觉因素的程度及分布在家具上比较直观地反映出来。     

Retrograde amnesia: electroconvulsive shock effects after termination of rapid eye movement sleep deprivation

Mice that were deprived of rapid eye movement sleep for 2 days immediately after one-trial training in an inhibitory avoidance task and were given an electroconvulsive shock after deprivation displayed retrograde amnesia on a retention test given 24 hours later. Electroconvulsive shock produced no amnesia in comparable groups of animals that were not deprived of rapid eye movement sleep.     

Sleep: suppression of rapid eye movement phase in the cat after electroconvulsive shock

Electroconvulsive shock, administered for 5 to 7 days, reduced the daily rapid eye movement sleep time of seven cats to as little as 28 percent of base line levels. After day 4, eye movements during periods of cortical activation without tonic electromyographic activity were greatlyreduced. Although partially deprived of rapid eye movements for as long as 7 days, the cats showed no compensatory rise in rapid eye movement time during the recovery period, but controls equally deprived gave significant rebounds. Rapid eye movement time of anesthetized cats was not affected by current that usually produces con vulsions; it was lowered in animals convulsed with metrazol, but the same dosage of this drug, administered so as to avoid convulsions, had little eflect.It appears that some aspect of the convulsion is responsible for lowering the rapid eye movement time.     

Transduction of receptor signals by beta-arrestins

The transmission of extracellular signals to the interior of the cell is a function of plasma membrane receptors, of which the seven transmembrane receptor family is by far the largest and most versatile. Classically, these receptors stimulate heterotrimeric G proteins, which control rates of generation of diffusible second messengers and entry of ions at the plasma membrane. Recent evidence, however, indicates another previously unappreciated strategy used by the receptors to regulate intracellular signaling pathways. They direct the recruitment, activation, and scaffolding of cytoplasmic signaling complexes via two multifunctional adaptor and transducer molecules, beta-arrestins 1 and 2. This mechanism regulates aspects of cell motility, chemotaxis, apoptosis, and likely other cellular functions through a rapidly expanding list of signaling pathways.     

The endocrine regulation of aging by insulin-like signals

Reduced signaling of insulin-like peptides increases the life-span of nematodes, flies, and rodents. In the nematode and the fly, secondary hormones downstream of insulin-like signaling appear to regulate aging. In mammals, the order in which the hormones act is unresolved because insulin, insulin-like growth factor-1, growth hormone, and thyroid hormones are interdependent. In all species examined to date, endocrine manipulations can slow aging without concurrent costs in reproduction, but with inevitable increases in stress resistance. Despite the similarities among mammals and invertebrates in insulin-like peptides and their signal cascade, more research is needed to determine whether these signals control aging in the same way in all the species by the same mechanism.     

Perception of environmental signals by a marine diatom

Diatoms are a key component of marine ecosystems and are extremely important for the biogeochemical cycling of silica and as contributors to global fixed carbon. However, the answers to fundamental questions such as what diatoms can sense in their environment, how they respond to external signals, and what factors control their life strategies are largely unknown. We generated transgenic diatom cells containing the calcium-sensitive photoprotein aequorin to determine whether changes in calcium homeostasis are used to respond to relevant environmental stimuli. Our results reveal sensing systems for detecting and responding to fluid motion (shear stress), osmotic stress, and iron, a key nutrient that controls diatom abundance in the ocean.     

Regulation of phagosome maturation by signals from toll-like receptors

In higher metazoans, phagocytosis is essential in host defense against microbial pathogens and in clearance of apoptotic cells. Both microbial and apoptotic cells are delivered on a common route from phagosomes to lysosomes for degradation. Here, we found that activation of the Toll-like receptor (TLR) signaling pathway by bacteria, but not apoptotic cells, regulated phagocytosis at multiple steps including internalization and phagosome maturation. Phagocytosis of bacteria was impaired in the absence of TLR signaling. Two modes of phagosome maturation were observed, constitutive and inducible; their differential engagement depended on the ability of the cargo to trigger TLR signaling.     

Induction of pancreatic differentiation by signals from blood vessels

Blood vessels supply developing organs with metabolic sustenance. Here, we demonstrate a role for blood vessels as a source of developmental signals during pancreatic organogenesis. In vitro experiments with embryonic mouse tissues demonstrate that blood vessel endothelium induces insulin expression in isolated endoderm. Removal of the dorsal aorta in Xenopus laevis embryos results in the failure of insulin expression in vivo. Furthermore, using transgenic mice, we show that ectopic vascularization in the posterior foregut leads to ectopic insulin expression and islet hyperplasia. These results indicate that vessels not only provide metabolic sustenance, but also provide inductive signals for organ development.     

Initiation of proximal-distal patterning in the vertebrate limb by signals and growth

Two broad classes of models have been proposed to explain the patterning of the proximal-distal axis of the vertebrate limb (from the shoulder to the digit tips). Differentiating between them, we demonstrate that early limb mesenchyme in the chick is initially maintained in a state capable of generating all limb segments through exposure to a combination of proximal and distal signals. As the limb bud grows, the proximal limb is established through continued exposure to flank-derived signal(s), whereas the developmental program determining the medial and distal segments is initiated in domains that grow beyond proximal influence. In addition, the system we have developed, combining in vitro and in vivo culture, opens the door to a new level of analysis of patterning mechanisms in the limb.     

Dendritic computation of direction selectivity by retinal ganglion cells

Direction-selective ganglion cells (DSGCs) in the retina respond strongly when stimulated by image motion in a preferred direction but are only weakly excited by image motion in the opposite null direction. Such coding represents an early manifestation of complex information processing in the visual system, but the cellular locus and the synaptic mechanisms have yet to be elucidated. We recorded the synaptic activity of DSGCs using strategies to observe the asymmetric inhibitory inputs that underlie the generation of direction selectivity. The critical nonlinear interactions between the excitatory and inhibitory inputs took place postsynaptically within the dendrites of the DSGCs.     

Distinguishing inchworm and hand-over-hand processive kinesin movement by neck rotation measurements

The motor enzyme kinesin makes hundreds of unidirectional 8-nanometer steps without detaching from or freely sliding along the microtubule on which it moves. We investigated the kinesin stepping mechanism by immobilizing a Drosophila kinesin derivative through the carboxyl-terminal end of the neck coiled-coil domain and measuring orientations of microtubules moved by single enzyme molecules at submicromolar adenosine triphosphate concentrations. The kinesin-mediated microtubule-surface linkage was sufficiently torsionally stiff (>/=2.0 +/- 0.9 x 10(-20) Newton meters per radian2) that stepping by the hypothesized symmetric hand-over-hand mechanism would produce 180 degree rotations of the microtubule relative to the immobilized kinesin neck. In fact, there were no rotations, a finding that is inconsistent with symmetric hand-over-hand movement. An alternative "inchworm" mechanism is consistent with our experimental results.     

Insect sex-pheromone signals mediated by specific combinations of olfactory receptors

We describe two male-specific olfactory receptors (ORs) in the silk moth, Bombyx mori, that are mutually exclusively expressed in a pair of adjacent pheromone-sensitive neurons of male antennae: One is specifically tuned to bombykol, the sex pheromone, and the other to bombykal, its oxidized form. Both pheromone ORs are coexpressed with an OR from the highly conserved insect OR subfamily. This coexpression promotes the functional expression of pheromone receptors and confers ligand-stimulated nonselective cation channel activity. The same effects were also observed for general ORs. Both odorant and pheromone signaling pathways are mediated by means of a common mechanism in insects.     

利用AFLP分子标记鉴定库尔勒香梨的分类地位

利用AFLP分子标记技术,通过聚类分析和遗传相似系数分析,对库尔勒香梨进行分类研究.从聚类树状图可以看出,库尔勒香梨首先与新疆梨品种早熟句句聚在一起,并和杂交品种柠檬黄聚在了一起.库尔勒香梨与白梨系统、沙梨系统、秋子梨系统、西洋梨系统的平均欧氏距离分别为8.243、7.894、8.717、8.405,表明库尔勒香梨与沙梨系统的亲缘关系最近.     

Multimodal signals: enhancement and constraint of song motor patterns by visual display

Many birds perform visual signals during their learned songs, but little is known about the interrelationship between visual and vocal displays. We show here that male brown-headed cowbirds (Molothrus ater) synchronize the most elaborate wing movements of their display with atypically long silent periods in their song, potentially avoiding adverse biomechanical effects on sound production. Furthermore, expiratory effort for song is significantly reduced when cowbirds perform their wing display. These results show a close integration between vocal and visual displays and suggest that constraints and synergistic interactions between the motor patterns of multimodal signals influence the evolution of birdsong.