What image characteristics are selected by neurons in the cat primary visual cortex?]

About 40% of neurons (114/289) studied in the cat area 17 gave a larger (by 3.06 +/- 0.32 times on average) response to a flashed cross, corner or y-like figures centered in the RF than to an optimal single bar. Most such neurons (72%) were found to be highly selective both to shape (angle between the lines) and to orientation of these figures. In the studied neuronal selection we have also found all possible types of invariance of sensitivity to orientation and/or shape of these figures. Separated and combined stimulation of RF center and surrounding area revealed in 44 units summation, antagonism or absence of interaction of these zones by the selectivity index (cross/bar response ratio). Cross-sensitivity was investigated in 85 V1 neurons before, during and after local blockade of GABAA ergic inhibition by microiontophoretical application of bicuculline. Inhibition either emerged or increased cross-sensitivity (32% of cells), or depressed it (36% of cases), while in some neurons it does not influenced the function. Possible mechanisms of the described effects are discussed as well as their functional implication for second-order feature extraction in the visual cortex: selective or invariant sensitivity of neurons to the shape and orientation of the line-crossings.     

Simulation model of the tuning mechanism in the visual cortex neuron for the perception of Y-shape images

We performed an imitation simulation of receptive fields (RF) of cat cortical neurons in the primary visual cortex, which were able to detect symmetrical and asymmetrical Y-like figures. We investigated the models of the receptive fields of neurons sensitive to Y-like figures through either the convergence from half-bar detectors or disinhibition mechanism. The model of an of the receptive fields of neurons sensitive to Y-like figures through either the convergence from half-bar detectors or disinhibition mechanism. The model of an-like figure detector on the basis of convergence from the angle and orientation detectors was advanced. Tuning of the simulated receptive fields to Y-like figures was compared with their tuning to cross-like figures. It was shown that the detectors of asymmetric Y-like figures are also detectors of a cross, whereas the detectors of symmetric Y-like figures are more sensitive to Y-like figures than to crosses. The features of the model critical for sensitivity to Y-like figures (the shape, localization, and weight of the RF zones) were specified.     

Sensitivity of striate neurons to Y-like figures: experiment and simulation

Under stimulation of the receptive fields (RF) of neurons in the cat area 17 by flashing Y-like figures of different shape and orientation, the sensitivity to these figures was revealed in 72% of the studied cells, while 62% of units were sensitive to cross-like figures as well. Tuning to Y-like figures was typically selective to their shape and orientation, but in some cases it was invariant to these features. Response magnitudes to single bar, Y-like figure and cross were positively correlated. Simulation showed that the disinhibition might be a sufficient mechanism for effective detection of Y-like figures in a classical receptive field.     

Temporal course of disinhibition of the visual cortex neurons and their sensitivity to cross-like figures

In acute experiments with narcotized and paralyzed cats, we studied responses of 74 striate neurons to cross-like figure under synchronous and asynchronous presentation of its lines. The aim of the study was to characterize the temporal course of interaction between three RF zones: main excitatory, end-inhibitory, and side disinhibitory ones. Previously we have found that this interaction is responsible for sensitivity to a cross in near 3/4 of cat striate cells with such sensitivity. In neurons with sensitivity to a cross, we found two types of temporal interaction between zones of RF. In the 1st type cells (14/23), the response significantly increased if the disinhibitory and the main excitatory zones of RF were stimulated simultaneously. Neurons of the 2nd type (9/23) revealed opposite temporal function: synchronous activation of RF zones evoked a minimal response. Simulation shows that the 1st type of behavior is connected with disinhibitory mechanism, while that of the 2nd type--with combination of this mechanism with convergence of orientation detectors of the previous functional level.     

Simulation of the role of intracortical inhibition as a source of sensitivity to cross-like figures

Simulation of receptive fields of striate neurons sensitive to cross-like figures under the blockade of intracortical inhibition was performed. It was shown that without the inhibition, a neuron with convergence of signals from two orientation detectors widens its tuning to a cross in such a way that the tuning becomes invariant to the shape and orientation of the cross. Detector of a cross whose orientation is based on the disinhibition mechanisms becomes a bar orientation detector under conditions of inhibition blockade. Another scheme of receptive field is advanced, in which the inhibitory zones mask tuning to cross-like figures, but the blockade of inhibition unveils such sensitivity. We specified the features of the receptive fields (shape, localization, and weight of their zones), which, being applied in simulation, imitate properties of the real striate neurons sensitive to shape and orientation of a cross-like figures.     

Reciprocal Interaction of On- and Off-Systems as a Mechanism of Sensitivity of Visual Neurons to The Orientation of the Vector of the Brightness Gradient in Cats

An experimental study has been performed on neuronal mechanisms of sensitivity of cat visual neurons (lateral geniculate body) to the value and orientation of the vector of brightness gradient in a test stimulus. With changes of the value and orientation of the brightness gradient vector, there exists an optimal (preferred) orientation of the gradient vector, at which the neuronal response is maximal. The sensitivity of neurons to the brightness gradient at shifts of the gradient vector towards the preferred orientation increases not due to an increased excitation in neuronal reactions, but due to a reduction of reciprocal (on- and off-) inhibition, affecting this neuron, of adjacent neurons in neuronal pools. The reciprocal inhibitory interaction of on- and off-systems is enhanced by inhibiting the response of the antagonistic neuron at shifts of the brightness gradient vector in the stimulus from the preferred to the non-preferred orientation. This reciprocal inhibitory interaction is clearly seen in pairs of on- and off-neurons with superposed receptive fields (RF) at their simultaneous analysis of on- and off-responses at a change of the orientation of the brightness gradient vector by 180 degrees. Dependencies of the parameters (duration and intensity of inhibitory phases in responses) of reciprocal inhibitory interaction on orientation of the brightness gradient vector in RF of neurons are determined. Dependencies of responses of the total sample of neurons, which are plotted for on- and off-neurons, to their adequate and inadequate (on- and off-) stimuli on the orientation of the brightness gradient vector are inversely proportional.     

Maternally transmitted resistance to lymphoma development in mice of reciprocal crosses of the RF/J and AKR/J strains

Females but not males of the low-lymphoma RF/J strain transmit a non-Mendelian factor which suppresses the development of lymphoma in F1 crosses with mice of the high-lymphoma AKR/J strain. Suppression of lymphoma was also evident in the first backcross generation to the parental AKR strain, but only when (RF female x AKR male)F1 mice had been the female parent. This "maternal resistance factor" was transmitted independently of the dominant, lymphoma-suppressing Fv-1n allele transmitted by both males and females of the RF strain, but the suppressive capacities of the two factors appeared to be additive. In this cross, F1 progeny of RF females also showed marked suppression of ecotropic murine leukemia virus expression by comparison with mice of the reciprocal F1 cross, but this suppression of virus expression was not detected in the lymphoma-suppressed AKR backcross population. The observation of lymphoma suppression in the absence of ectropic virus suppression in mice of the (RF X AKR)F1 female x AKR male backross generation indicates a qualitative or quantitative difference in the determination of these two effects.     

Genetic and nongenetic factors in expression of infectious murine leukemia viruses in mice of the DBA/2 x RF cross

Mice of the RF and DBA/2 strains possess endogenous ecotropic murine leukemia virus (E-MuLV) genomes but express only low to undetectable levels of infectious virus in their lymphoid tissues. F1 mice of this cross showed high levels of infectious E-MuLV if DBA/2 was the maternal parent but very low levels if RF was the maternal parent. E-MuLV expression, if present, was always higher in the spleen than in the thymus. Studies of reciprocal backcross generations with both parental strains indicated that the presence of the virus was governed by a single dominant autosomal locus present in the RF strain, and that RF females, but neither RF males nor DBA/2 females or males, transmitted a non-Mendelian factor which powerfully suppressed virus expression in their progeny. Some but not all (DBA/2♀ × RF♂)F1 females also possessed the capacity to transmit this maternal suppression to their progeny. Xenotropic murine leukemia virus (X-MuLV) showed a different pattern of expression in this cross. In the thymus it was detected in a minority of DBA/2 and in no RF mice; in crosses the presence of X-MuLV in this organ was independent of the presence of E-MuLV. In the spleen, X-MuLV was detected only in a percentage of E-MuLV-positive mice. The maternal factor from RF mothers which suppressed E-MuLV did not suppress thymic expression of X-MuLV. Skin painting with 3-methylcholanthrene induced a high incidence of thymic lymphoma in mice of both parental strains and in F1 hybrids, all of which normally show only low incidences of the diseases; the treatment did not induce markedly increased expression of E-MuLV or X-MuLV in mice of either parental strain, although it did abrogate the diminution of E-MuLV titers seen with age in (DBA/2♀ × RF♂)F1 mice beyond the age of three months.     

A dynamic model of facilitation on environmental stress gradients

Theories based on competition for resources in animals and other non‐sessile organisms rarely consider the role of facilitative interactions. Yet these interactions are important for community assembly, especially under stressful environments (e.g. the stress‐gradient hypothesis, SGH). To make an explicit link between species interaction theory and SGH patterns, I used a classic resource competition model promoting coexistence between a beneficiary and its facilitator sharing a common resource along a stress gradient. I compared model outcomes for two fundamentally different mechanisms of facilitation (alleviation of resource versus non‐resource stress), and also tested the effect of a reciprocal cost of facilitation from the beneficiary. I then tested model's biological relevance using experimental data from two tuber moth species (Lepidoptera, Gelechiidae) for which facilitation in resource access was previously established. Simulation outcomes revealed that both the mode of facilitation and the incorporation of facilitation costs affected the shape of the facilitation–stress relationship. These predictions are in line with current SGH observations and experiments on both plants and animals and reconcile the frequently reported variability of this relationship in nature. Moreover, a sensitivity analysis of model's parameters confirmed the robustness of the modelling framework to uncover the mechanisms responsible for observed species interaction–stress patterns. Finally, when parameterized with tuber moth demographic data, model's results corresponded to observed interaction outcomes along resource stress gradients. Overall, having a common model for plants and animals may simplify assumptions in SGH studies, allow contrasting the shapes of different consumer–resource relationships and specifying the conditions that favour one type of interaction outcome over another.     

RF nonlinear interactions in living cells--II: detection methods for spectral signatures

The presence of harmonic products due to possible nonlinear interaction of amplitude modulated RF signals in living cells is best detected by using a cavity with high quality factor. Harmonic products generated by elementary oscillators can be trapped and accumulated in a cavity, permitting detection sensitivity much greater than in an open environment, where they would be radiated in all directions. The experimental method described herein is a systematic approach to detection of the non-Planck RF energy (if any) emitted by an exposed sample of living cells. Balzano and Sheppard [Balzano and Sheppard (2003): Bioelectromagnetics 24:473-482] classified the non-Planck RF emissions from living cells as coming from (1). nonlinear interactions and (2). inelastic interactions. Nonlinear harmonic products would appear in the band at twice the frequency of an amplitude modulated RF carrier. Inelastic interaction products resulting from the interaction between the incident RF energy and normally occurring mechanical vibrations are found in the band immediately adjacent to the carrier. Detection of the latter signals is difficult because of this close spectral proximity, for example, 1 part in 10(7) for 100 Hz modulation of a GHz carrier. Modern audio spectrum analyzers have excellent selectivity, providing 60 dB rejections only 2 kHz away from the carrier. By judicious selection of the amplitude modulation (AM) frequency, frequency of the RF carrier, and size of the biological sample, it is possible to achieve very high sensitivity (about -90 dBm) with commercially available instrumentation. The presence (or absence) of harmonics in the band adjacent to the amplitude modulated RF carrier would establish (or negate) the existence of coherent interactions between mechanical vibrations in the cell ensemble and the incident RF signal.     

Coevolutionary clines across selection mosaics

Abstract. Much of the dynamics of coevolution may be driven by the interplay between geographic variation in reciprocal selection (selection mosaics) and the homogenizing action of gene flow. We develop a genetic model of geographically structured coevolution in which gene flow links coevolving communities that may differ in both the direction and magnitude of reciprocal selection. The results show that geographically structured coevolution may lead to allele-frequency clines within both interacting species when fitnesses are spatially uniform or spatially heterogeneous. Furthermore, the results show that the behavior and shape of clines differ dramatically among different types of coevolutionary interaction. Antagonistic interactions produce dynamic clines that change shape rapidly through time, producing shifting patterns of local adaptation and maladaptation. Unlike antagonistic interactions, mutualisms generate stable equilibrium patterns that lead to fixed spatial patterns of adaptation. Interactions that vary between mutualism and antagonism produce both equilibrium and dynamic clines. Furthermore, the results demonstrate that these interactions may allow mutualisms to persist throughout the geographic range of an interaction, despite pockets of locally antagonistic selection. In all cases, the coevolved spatial patterns of allele frequencies are sensitive to the relative contributions of gene flow, selection, and overall habitat size, indicating that the appropriate scale for studies of geographically structured coevolution depends on the relative contributions of each of these factors.     

Determination of the pairwise interaction potential between dust grains in plasma

Results are presented from measurements of the pairwise interaction potential between dust grains in plasma. The experiments were carried out with RF capacitive discharges over a wide range of dusty plasma parameters. All the experiments under analysis revealed a repulsive interaction potential that was close in shape to the screened Coulomb potential. The grain charges and the radii at which they were screened are determined.     

The effects of vinblastine in assessment of the influence of age on proliferative activity of murine palate and footpad epithelium

Abstract
Data concerning changes in the rate of cell proliferation of stratified epithelia with increasing age are conflicting. In the present study young (3-month-old) and old (22-month-old) C57B1/6NNia male mice were injected intraperitoneally with 2, 3, 4 or 8 mg vinblastine sulfate/kg body weight and killed after 1.5, 3, 4.5 or 6 h. The number of arrested metaphase figures per 1000 basal cells was counted in histological sections. Data were analysed using a multivariate analysis of variance. There was a significant difference between the accumulation of mitotic figures in footpad epidermis and palate epithelium and both tissues contained an increased number of mitotic figures with increasing periods of accumulation at all dose levels. In the footpad epidermis neither the age of the animal nor the dose of vinblastine had a significant effect on the number of mitotic figures. In contrast, for palate epithelium the accumulation of mitotic figures was significantly less in the old mice compared with the young mice and at a dose of vinblastine of 2mg/kg compared with the higher doses. There was a statistically signifycant interaction between the dose of vinblastine and its period of action. It was concluded that the different tissues manifest a differential sensitivity to vinblastine and that only palate epithelium showed a significant reduction in proliferative activity with age.     

Self-consistent modeling of radio-frequency plasma generation in stellarators

A self-consistent model of radio-frequency (RF) plasma generation in stellarators in the ion cyclotron frequency range is described. The model includes equations for the particle and energy balance and boundary conditions for Maxwell’s equations. The equation of charged particle balance takes into account the influx of particles due to ionization and their loss via diffusion and convection. The equation of electron energy balance takes into account the RF heating power source, as well as energy losses due to the excitation and electron-impact ionization of gas atoms, energy exchange via Coulomb collisions, and plasma heat conduction. The deposited RF power is calculated by solving the boundary problem for Maxwell’s equations. When describing the dissipation of the energy of the RF field, collisional absorption and Landau damping are taken into account. At each time step, Maxwell’s equations are solved for the current profiles of the plasma density and plasma temperature. The calculations are performed for a cylindrical plasma. The plasma is assumed to be axisymmetric and homogeneous along the plasma column. The system of balance equations is solved using the Crank-Nicholson scheme. Maxwell’s equations are solved in a one-dimensional approximation by using the Fourier transformation along the azimuthal and longitudinal coordinates. Results of simulations of RF plasma generation in the Uragan-2M stellarator by using a frame antenna operating at frequencies lower than the ion cyclotron frequency are presented. The calculations show that the slow wave generated by the antenna is efficiently absorbed at the periphery of the plasma column, due to which only a small fraction of the input power reaches the confinement region. As a result, the temperature on the axis of the plasma column remains low, whereas at the periphery it is substantially higher. This leads to strong absorption of the RF field at the periphery via the Landau mechanism.     

Reissner's fiber,massa caudalis and ampulla caudalis in the spinal cord of lamprey larvae (Geotria australis)

Summary The subcommissural organ (SCO), Reissner's fiber (RF) and its massa caudalis of lamprey larvae (Geotria australis) were investigated immunocytochemically by use of an antiserum raised against bovine RF as primary antibody. The affinities of RF and massa caudalis for Ricinus communis agglutinin I (RCA) with and without previous acid hydrolysis, concanavalin A (Con A), wheat-germ agglutinin (WGA), aldehyde fuchsin, and PAS reaction were also studied.SCO and massa caudalis were strongly immunoreactive, whereas RF proper was distinctly negative. RF did not react with Con A and RCA. Only the periphery of RF was WGA-positive. RCA showed affinity for RF only after acid hydrolysis. RF was homogeneously stained by the aldehyde-fuchsin and PAS-methods. At variance with RF proper, the periphery of the massa caudalis reacted with RCA without previous acid hydrolysis, but its core was WGA-positive and reacted with RCA only after hydrolysis. It is suggested that (i) RF has a coat of glycoproteins containing sialic acid as terminal residue, whereas the massa caudalis possesses a coat with galactose as terminal residue; (ii) in RF proper and the massa caudalis the spatial arrangement of glycoproteins might be different.Routine transmission electron-microscopic observations indicate that in larvae of Geotria australis an open communication exists between the ampulla caudalis and blood capillaries via large cavities or lacunae.Supported by Grant I 38259 from the Stiftung Volkswagenwerk, Federal Republic of Germany, Grant S-85-39 from the Dirección de Investigaciones, Universidad Austral de Chile, and Grant 6027 from Fondo Nacional de Desarrollo Científico y Tecnológico, Chile     

Torocyte membrane endovesicles induced by octaethyleneglycol dodecylether in human erythrocytes

Endovesicles induced in human erythrocytes by octaethyleneglycol dodecylether (C12E8) were studied by confocal laser scanning microscopy, using fluorescein isothiocyanate dextran as a nonspecific fluid marker. The endovesicles appeared to consist mainly of a ring-formed toroidal part joined with a central flat membrane segment. The torocyte contour length was several microm. There was usually one torocyte endovesicle per cell. The endovesicles seemed to be located near the cell surface. In sections of C12E8-treated erythrocytes transmission electron microscopy revealed the frequent occurrence of flat membrane structures with a bulby periphery, which apparently are cross sections of torocyte endovesicles. The possible physical mechanisms leading to the observed torocyte endovesicle shape are discussed. The torocyte endovesicles seem to be formed in a process in which an initially stomatocytic invagination loses volume while maintaining a large surface area. Because intercalation of C12E8 in the erythrocyte membrane induces inward membrane bending (stomatocytosis) we assume that C12E8 is preferentially located in the inner lipid layer of the erythrocyte membrane, i.e., in the outer lipid layer of the endovesicle membrane. It is suggested that local disturbances of the lipid molecules in the vicinity of the C12E8 molecules in the outer lipid layer of the endovesicle membrane form membrane inclusions with the effective shape of an inverted truncated cone. If the interaction between the inclusion and the membrane is weak, the membrane of such an endovesicle can be characterized by its negative spontaneous curvature, which may lead to a torocyte endovesicle shape with a small relative volume. Effects of a possible strong interaction between the C12E8-induced membrane inclusions and the membrane on the stability of the torocyte endovesicles are also indicated.     

浙江茶尺蠖地理种群已分化成为不同种

【目的】明确茶尺蠖Ectropis obliqua Prout不同地理种群的种群分化和生殖隔离程度。【方法】对分别在浙江杭州和衢州两地田间采集的茶尺蠖杭州种群（H）和衢州种群（Q）两个种群,进行形态学鉴定、生物学特征观察以及正反交试验。【结果】形态学与生物学观察结果表明,除Q种群的体形较大和体翅颜色略深外,两个种群的外部形态、生殖器解剖结构和雌蛾产卵量等基本相同。遗传杂交试验结果表明,无论是正交还是反交,杂交后均能获得子一代（F1）;与种群内自交相比,杂交后雌成虫的产卵量下降,卵的孵化率显著降低;幼虫的历期明显缩短且化蛹时间分布不规则,蛹重变轻;蛹的羽化率降低,羽化的成虫雌雄性比严重失调。【结论】茶尺蠖杭州种群（H）和衢州种群（Q）两个种群存在生殖隔离,有明显的种群分化,应属于不同种。     

玉米籽粒性状的遗传模型研究

用１０个遗传上和籽粒形态性状上具有差异的玉米自交系,依多种可能的交配方法获得亲本Ｐ１、Ｐ２、Ｆ１（Ｐ１× Ｐ２）、Ｆ２、Ｂ１（Ｆ１×Ｐ１）、Ｂ２（Ｆ１× Ｐ２）及其相应反交ＲＦ１、ＲＦ２、ＲＢ１、ＲＢ２共１０个种子世代。种植２年。依广义遗传模型建立包括种子胚乳加性、胚乳显性、母体加性、母体显性和细胞质效应的遗传模型,运用种子数量性状的精细鉴别法［１］和混合模型分析法［２,３］,对粒长、粒宽、粒长宽比、粒厚及百粒重作了性状表达遗传机制的鉴别与探讨。单个组合的遗传模型精细测验表明,５个籽粒性状的遗传主要受母体显性和胚乳基因型（包括加性和灵性）的控制,一个组合的粒宽、粒厚和百粒重上还检测到细胞质效应。对２５对 Ｆ１正反交组合世代均值依ＭＩＮＱＵＥ法分析的结果表明,５个籽粒性状的遗传方差中,母体遗传方差占６０％以上,胚乳基因型方差低于４０％,粒长和百粒重还有细胞质效应,约占１０％～３０％。可见,籽粒性状的遗传特点是受多套遗传系统控制,其中以母体基因型的作用最大。     

Shape and size variation on the wing of <Emphasis Type="Italic">Drosophila mediopunctata</Emphasis>: influence of chromosome inversions and genotype-environment interaction

The second chromosome of Drosophila mediopunctata is highly polymorphic for inversions. Previous work reported a significant interaction between these inversions and collecting date on wing size, suggesting the presence of genotype-environment interaction. We performed experiments in the laboratory to test for the joint effects of temperature and chromosome inversions on size and shape of the wing in D. mediopunctata. Size was measured as the centroid size, and shape was analyzed using the generalized least squares Procrustes superimposition followed by discriminant analysis and canonical variates analysis of partial warps and uniform components scores. Our findings show that wing size and shape are influenced by temperature, sex, and karyotype. We also found evidence suggestive of an interaction between the effects of karyotype and temperature on wing shape, indicating the existence of genotype-environment interaction for this trait in D. mediopunctata. In addition, the association between wing size and chromosome inversions is in agreement with previous results indicating that these inversions might be accumulating alleles adapted to different temperatures. However, no significant interaction between temperature and karyotype for size was found--in spite of the significant presence of temperature-genotype (cross) interaction. We suggest that other ecological factors--such as larval crowding--or seasonal variation of genetic content within inversions may explain the previous results.