A neuronal circuitry for relative movement discrimination by the visual system of the fly

We propose the basic structure of a neuronal circuitry possibly underlying the detection of discontinuities in the optical flow by the visual system of the housefly. The main features of the circuitry are: binocular cells summate elementary movement detectors over a large visual field and inhibit each one of them; inhibition is of the shunting type, with an inhibitory equilibrium potential very near the resting potential. A specific model implementing our proposal accounts for all the behavioral data on relative movement discrimination, including the characteristic dynamics of the response.     

两种有机磷农药对缢蛏(Sinonovacula constricta)鳃超微结构的影响

在实验室模拟缢蛏生长环境,研究结构、性质不同的两种典型有机磷农药(OPs)乐果和三唑磷对滩涂养殖生物缢蛏的毒性效应,通过电镜观察乐果和三唑磷对缢蛏鳃超微结构的影响.结果发现:乐果和三唑磷对缢蛏鳃超微结构的影响主要表现在对细胞核和各种细胞器(如线粒体、内质网、高尔基体)的伤害.主要病变为:细胞核变形,核膜凸起或凹陷,染色质发生凝聚或边缘化;线粒体肿大,双层膜溶解,内嵴部分消失;个别线粒体内嵴完全瓦解,形成电子透明区;粗面内质网水肿,核糖体部分脱落,片层结构间距增大;高尔基膜囊水肿,膜溶解,高尔基小泡破裂消失.本研究为了解不同OPs对缢蛏的毒性效应提供了病理形态学证据,为预测OPs对近海海洋生物及人类健康的影响提供有力的证据,为规范OPs的应用、制定海洋环境质量标准提供了部分基础理论依据.     

A case of prenatal paternity discrimination

A case is described in which prenatal paternity determination was required, on account of suspected incest. Chromosome heteromorphisms were uninformative, but discrimination was achieved by HLA typing.     

The visual system of male scale insects

Animal eyes generally fall into two categories: (1) their photoreceptive array is convex, as is typical for camera eyes, including the human eye, or (2) their photoreceptive array is concave, as is typical for the compound eye of insects. There are a few rare examples of the latter eye type having secondarily evolved into the former one. When viewed in a phylogenetic framework, the head morphology of a variety of male scale insects suggests that this group could be one such example. In the Margarodidae (Hemiptera, Coccoidea), males have been described as having compound eyes, while males of some more derived groups only have two single-chamber eyes on each side of the head. Those eyes are situated in the place occupied by the compound eye of other insects. Since male scale insects tend to be rare, little is known about how their visual systems are organized, and what anatomical traits are associated with this evolutionary transition. In adult male Margarodidae, one single-chamber eye (stemmateran ocellus) is present in addition to a compound eye-like region. Our histological investigation reveals that the stemmateran ocellus has an extended retina which is formed by concrete clusters of receptor cells that connect to its own first-order neuropil. In addition, we find that the ommatidia of the compound eyes also share several anatomical characteristics with simple camera eyes. These include shallow units with extended retinas, each of which is connected by its own small nerve to the lamina. These anatomical changes suggest that the margarodid compound eye represents a transitional form to the giant unicornal eyes that have been described in more derived species.     

Social partner discrimination based on sounds and scents in Asian small-clawed otters (Aonyx cinereus)

Ability to discriminate familiar conspecifics is an essential competence in any group-living species, ensuring socio-spatial cohesion, but in many animals, such as mustelids, the relative importance of the different communicative modalities for discrimination is poorly understood. In otters, there is evidence of intra-specific variation in physical appearance and in feces chemical profile, but the potential for acoustic identity coding as well as for identity decoding in visual, acoustic and olfactive domains remains unexplored. We investigated the acoustic structure of contact calls in five captive groups of small-clawed otters and found that it is possible to reliably assign one particular call to a given adult male caller. Females discriminated between familiar and unfamiliar adult males based on their sound (playback) and smell (feces) but not based on their picture, suggesting abilities to memorize and use acoustic and olfactive signatures in their daily social life.     

Representation of complex visual stimuli in the brain

A method was developed to investigate transfer properties of neurons in the visual system using pictures of complex visual stimuli. The picture is moved over the receptive field of a neuron so that it can scan it along programmed lines. The activity of the neuron during the scanning procedure is presented in a two-dimensional dot display on scale with the original picture. By superposition of the stimulus and the transfer pattern, one can find out to which detail of a stimulus the neuron responds. Neurons in the first intracerebral relay of the visual system, the lateral geniculate body, reduce a complex stimulus, such as a photograph of a natural environment, to its contours. Cortical cells only respond to contours either of a limited or of a wider range of orientations (simple and complex cells, respectively). But the course of contours is only described by a continuous representation of these contours in the cortical map of the visual field. This is done by the simple cells, which have small receptive fields and thus a higher resolving power, whereas complex cells with their large receptive fields monitor the approximate location of a moving stimulus. The function of these two classes of neurons is discussed in terms of visual behavior, i.e., for fixation, hold, and binocular vergence movements (simple cells), and for detection of moving objects and motor command signals towards these objects (complex cells). These functions are an important condition for foveal vision which is the basis of perception in primates. An important function of orientation sensitivity of simple cells may be the binocular alignment of contours in binocular fusion and stereoscopic vision.     

The effect of flower-like and non-flower-like visual properties on choice of unrewarding patterns by bumblebees

How do distinct visual stimuli help bumblebees discover flowers before they have experienced any reward outside of their nest? Two visual floral properties, type of a pattern (concentric vs radial) and its position on unrewarding artificial flowers (central vs peripheral on corolla), were manipulated in two experiments. Both visual properties showed significant effects on floral choice. When pitted against each other, pattern was more important than position. Experiment 1 shows a significant effect of concentric pattern position, and experiment 2 shows a significant preference towards radial patterns regardless of their position. These results show that the presence of markings at the center of a flower are not so important as the presence of markings that will direct bees there.     

雌二醇对生物体内分泌系统毒性作用机制的研究

雌二醇可扰乱生物体内激素的正常分泌,对生物体生殖发育、神经系统及免疫系统造成损伤.本文通过查阅大量文献,结合临床试验及动物试验,研究了雌二醇干扰生物体内分泌系统的作用机制,结果发现:持续大剂量的雌二醇可显著扰乱动物体的内分泌系统;脂溶性的雌二醇不易被降解,在人体内也没有特定的代谢途径,因此微量的雌二醇即可在体内蓄积进而对机体造成损伤.     

铅对泥鳅的致毒效应

铅作为环境重金属激素之一 ,对水生生物泥鳅具有明显的致毒效应。毒性实验揭示 ,铅可导致泥鳅发生各种生理、生殖反应 (甚至死亡 ) ,并诱发泥鳅血红细胞和卵细胞畸形 ,破坏血红细胞和卵细胞的正常生长 ,降低细胞的存活率 ,影响泥鳅的正常生理、生殖功能 ,显示较强的雌激素活性     

聚合硫酸铁对污泥脱水性能研究

采用聚合硫酸铁作为化学调理剂,对浓缩池污泥进行调理.以污泥比阻为主要指标考察了投药量、调理剂浓度、pH值和搅拌强度对污泥过滤脱水性能的影响;同时,考察了污泥经过沉降后上清液的浊度变化.调理实验结果表明,PFS的适宜调理参数为:投加量1mL,浓度6％,pH为7(未调节),快速搅拌速度120 rpm,慢速搅拌速度50 rpm.污泥经PFS调理后,比阻降低到1.56×10-14 m/kg,显然,调理剂影响污泥调理脱水效果和它们的种类、浓度和投加量等条件相关.