Large-scale recording of neurons by movable silicon probes in behaving rodents

A major challenge in neuroscience is linking behavior to the collective activity of neural assemblies. Understanding of input-output relationships of neurons and circuits requires methods with the spatial selectivity and temporal resolution appropriate for mechanistic analysis of neural ensembles in the behaving animal, i.e. recording of representatively large samples of isolated single neurons. Ensemble monitoring of neuronal activity has progressed remarkably in the past decade in both small and large-brained animals, including human subjects. Multiple-site recording with silicon-based devices are particularly effective because of their scalability, small volume and geometric design. Here, we describe methods for recording multiple single neurons and local field potential in behaving rodents, using commercially available micro-machined silicon probes with custom-made accessory components. There are two basic options for interfacing silicon probes to preamplifiers: printed circuit boards and flexible cables. Probe supplying companies (http://www.neuronexustech.com/; http://www.sbmicrosystems.com/; http://www.acreo.se/) usually provide the bonding service and deliver probes bonded to printed circuit boards or flexible cables. Here, we describe the implantation of a 4-shank, 32-site probe attached to flexible polyimide cable, and mounted on a movable microdrive. Each step of the probe preparation, microdrive construction and surgery is illustrated so that the end user can easily replicate the process.     

一氧化氮通过巯基亚硝化途径抑制海马神经元的延迟整流型钾电流

应用膜片钳全细胞记录模式研究了内源性一氧化氮(NO)对培养海马神经元延迟整流型钾电流的调控作用及其机制.给予NO合成酶的底物L-精氨酸(L-Arg,2mmol/L)可显著抑制海马神经元上的延迟整流型钾电流,但其同分异构体D-精氨酸(2mmol/L)对钾电流则无明显影响.并且,经一氧化氮合成酶抑制剂L-NAME(nomega-nitro-L-argininemethylester,0.5mmol/L)预处理后,L-Arg对钾电流的抑制作用消失,表明L-Arg抑制钾电流是通过产生NO而不是精氨酸本身.特异性鸟苷酸环化酶抑制剂ODQ(1H-[1,2,4]oxadiazolo[4,3-a]-quinoxalin-1-one,10!mol/L)预处理不影响L-Arg对钾电流的抑制作用,但巯基烷化剂NEM(N-ethylmaleimide,1mmol/L)预处理可完全阻断L-Arg的抑制效应.以上结果表明,内源性NO主要通过巯基亚硝化途径抑制海马神经元的延迟整流型钾电流.     

过氧亚硝酸阴离子通过鸟苷酸环化酶途径抑制钠电流影响海马神经元兴奋性

过氧亚硝酸阴离子（ONOO-）是一种性质活泼的自由基,可引起强的氧化性损伤,介导了一氧化氮（NO）的大部分毒性作用．应用全细胞膜片钳技术,探讨ONOO-对脑片海马神经元电压门控钠通道电流（INa）和神经元兴奋性的影响．结果表明,ONOO-供体SIN-1（10,500,2000μmol／L）可浓度依赖性抑制INa电流峰值．SIN-1与ONOO-清除剂尿酸共处理,并不影响INa．500μmol／L的SIN-1可使INa的I-V曲线上移,并可抑制其失活后恢复过程,但对INa的激活和失活过程无影响．SIN-1还可抑制动作电位发放频率和幅值．脑片预处理腺苷酸环化酶（adenylate cyclase,AC）抑制剂MDL-12,330A（25μmol／L）和NEM（50μmol／L）对SIN-1的作用无影响．然而,预处理鸟苷酸环化酶（CG）抑制剂ODQ可抑制SIN-1对INa的作用．以上结果提示,ONOO-通过cGMP-INa-AP信号级联系统作用于海马神经元,与PKA和蛋白巯基亚硝化途径无关,这可能是ONOO-神经毒性的机制之一．     

Genetic structure of natural Nasonia vitripennis populations: validating assumptions of sex-ratio theory

The parasitic wasp Nasonia vitripennis has been used extensively in sex allocation research. Although laboratory experiments have largely confirmed predictions of local mate competition (LMC) theory, the underlying assumptions of LMC models have hardly been explored in nature. We genotyped over 3500 individuals from two distant locations (in the Netherlands and Germany) at four polymorphic microsatellite loci to validate key assumptions of LMC theory, in terms of both the original models and more recent extensions to them. We estimated the number of females contributing eggs to patches of hosts and the clutch sizes as well as sex ratios produced by individual foundresses. In addition, we evaluated the level of inbreeding and population differentiation. Foundress numbers ranged from 1 to 7 (average 3.0 ± 0.46 SE). Foundresses were randomly distributed across the patches and across hosts within patches, with few parasitizing more than one patch. Of the hosts, 40% were parasitized by more than one foundress. Clutch sizes of individual foundresses (average 9.99 ± 0.51 SE) varied considerably between hosts. The time period during which offspring continued to emerge from a patch or host correlated strongly with foundress number, indicating that sequential rather than simultaneous parasitism is the more common. Genetic differentiation at the regional level between Germany and the Netherlands, as estimated by Slatkin's private allele method (0.11) and Hedrick's corrected G' _LT (0.23), indicates significant substructuring between regions. The level of population inbreeding for the two localities ( F _IL = 0.168) fitted the expectation based on the average foundress number per patch.     

Wildlife habitat analysis – a multidimensional habitat management model

In intensively cultivated landscapes, the effects of land use – changing habitat quality and habitat availability - on wildlife populations are of major importance for wildlife management. Populations of some species reach high densities, grow rapidly, and can therefore cause damage to tree regeneration in forests; chamois (Rupicapra rupicapra) is an example. Other species, like capercaillie (Tetrao urogallus), suffer from substantial habitat loss resulting in a population decline. Consequently, the number of individuals and the quality of habitat are of crucial relevance for the development of wildlife management concepts. It is critical to know, which areas provide suitable habitat conditions for a species, and what quantity and quality of habitat is required to achieve a certain population size.

In order to evaluate habitat quality and to link wildlife research to practical habitat management, an integrated habitat management model has been designed. The model is based on a multi-dimensional habitat analysis which employs different methodological levels, which were defined according to different spatial scales. On a country scale (level 1), the wildlife ecological landscape type (WELT) is introduced. For this study the federal state of Baden-Wuerttemberg is divided into units which represent distinct regions with similar landscape ecological habitat conditions for wildlife species. On an eco-regional scale (level 2), the landscape ecological habitat potential (LEHP) was developed. It is based on the evaluation of species-related landscape parameters within an exemplary eco-region and provides information about the potential habitat available to a population. On two local scales (level 3: forest district, level 4: forest stand), a habitat structure analysis was conducted, which serves as a foundation for habitat improvement and the monitoring of habitat conditions. The three methodological elements WELT, LEHP and habitat structure analysis were integrated into a habitat management model. The model uses chamois and capercaillie as examples, but can be equally applied to other species and wildlife management regimes.     

Nectar secretion dynamics of Hungarian local pear cultivars

 The dynamics of daily nectar secretion was studied in 28 local pear cultivars in a Hungarian cultivar collection and three main types were distinguished. 1. Cultivars secreting nectar continuously are the most favourable for pollinators, rewarding them both with nectar and pollen. 2. Cultivars with discontinuous nectar secretion have sufficient insect attraction only if anther dehiscence is continuous during the day. In the first two types nectar secretion peaks usually appeared at 9:00 or 10:00, 14:00 or 15:00 and 18:00 or 19:00, with 4–5-hour intervals. 3. In some cultivars no nectar secretion was observed in any or some of the studied years, these being the least attractive for pollinators. The cultivars studied did not necessarily show the same type of nectar secretion dynamics in each season. From the viewpoint of pollination it is also of high importance, in which developmental phase nectar secretion begins. Received August 27, 2002; accepted January 7, 2003 Published online: June 2, 2003     

Neuronal ribonucleoprotein granules: Dynamic sensors of localized signals

Membrane‐less organelles, because of their capacity to dynamically, selectively and reversibly concentrate molecules, are very well adapted for local information processing and rapid response to environmental fluctuations. These features are particularly important in the context of neuronal cells, where synapse‐specific activation, or localized extracellular cues, induce signaling events restricted to specialized axonal or dendritic subcompartments. Neuronal ribonucleoprotein (RNP) particles, or granules, are nonmembrane bound macromolecular condensates that concentrate specific sets of mRNAs and regulatory proteins, promoting their long‐distance transport to axons or dendrites. Neuronal RNP granules also have a dual function in regulating the translation of associated mRNAs: while preventing mRNA translation at rest, they fuel local protein synthesis upon activation. As revealed by recent work, rapid and reversible switches between these two functional modes are triggered by modifications of the networks of interactions underlying RNP granule assembly. Such flexible properties also come with a cost, as neuronal RNP granules are prone to transition into pathological aggregates in response to mutations, aging, or cellular stresses, further emphasizing the need to better understand the mechanistic principles governing their dynamic assembly and regulation in living systems.     

Wing morphology of the active flyer Calliphora vicina (Diptera: Calliphoridae) during its invasion of a sub‐Antarctic archipelago where insect flightlessness is the rule

The cosmopolitan blowfly Calliphora vicina became established in the sub‐Antarctic Kerguelen Islands in the late 1970s, following a warming period that allowed its full development. Although temperature and wind may limit flight activity, the fly invaded the archipelago, reaching sites remote from the introduction point. Most native competitors have converged to flightlessness as a response to stringent environmental conditions and therefore the flight strategy of C. vicina might be either a handicap or a competitive advantage under ongoing climate change. Using geometric morphometrics, we investigated whether the wing had changed over time in C. vicina within the archipelago (1998 vs. 2009) and compared its morphology with that of a continental population from a temperate area (1983 vs. 2009). Wing shape plasticity to temperature was also experimentally investigated. We found no clues of relaxed selection on flight morphology in the range invaded. However, rapid changes of wing shape occurred over time in females from the Kerguelen Islands compared with both males and females of the continental population, despite a shorter time‐lag between samples in the former. The thermal reaction norms for wing shape found for C. vicina from Kerguelen were also different from those of the continental population, but it remains unknown whether this resulted from or preceded the introduction. These combined findings are consistent with a fingerprint of local adaptation in the invasive population. However, the adaptive significance of the changes, in terms of their aerodynamic consequences and the future evolution of C. vicina in the Kerguelen Islands, requires further investigation. From an evolutionary standpoint, sustaining flight capability under the novel sub‐Antarctic conditions might be critical to the invasive success of C. vicina as most competitors are flightless.     

Host dispersal as the driver of parasite genetic structure: a paradigm lost?

Understanding traits influencing the distribution of genetic diversity has major ecological and evolutionary implications for host–parasite interactions. The genetic structure of parasites is expected to conform to that of their hosts, because host dispersal is generally assumed to drive parasite dispersal. Here, we used a meta‐analysis to test this paradigm and determine whether traits related to host dispersal correctly predict the spatial co‐distribution of host and parasite genetic variation. We compiled data from empirical work on local adaptation and host–parasite population genetic structure from a wide range of taxonomic groups. We found that genetic differentiation was significantly lower in parasites than in hosts, suggesting that dispersal may often be higher for parasites. A significant correlation in the pairwise genetic differentiation of hosts and parasites was evident, but surprisingly weak. These results were largely explained by parasite reproductive mode, the proportion of free‐living stages in the parasite life cycle and the geographical extent of the study; variables related to host dispersal were poor predictors of genetic patterns. Our results do not dispel the paradigm that parasite population genetic structure depends on host dispersal. Rather, we highlight that alternative factors are also important in driving the co‐distribution of host and parasite genetic variation.