光化学法脑缺血后细胞凋亡及其相关基因bcl-2表达的变化

采用ＴＵＮＥＬ染色及免疫组织化学技术对光化学法脑缺血后细胞凋亡及其相关基因ｂｃｌ－２表达的变化进行了研究。结果发现，缺血后１２ｈ，损伤侧皮层缺血区内凋亡细胞数及ｂｃｌ－２免疫反应阳性细胞数明显增加，一直持续至缺血后７２ｈ；并呈现下列时程变化：在缺血后３ｈ每张切片上几乎无凋亡细胞出现，以后逐渐增加，缺血后１２ｈ达到峰值，缺血后２４ｈ和缺血后７２ｈ逐渐减少，但仍高于假手术组水平。凋亡相关基因ｂｃｌ－２的表达在缺血后３ｈ以前不明显，缺血后１２ｈ逐渐增加，缺血后２４ｈ最多，以后逐渐下降。上述结果提示，缺血后凋亡细胞的时程变化可能与缺血后梗塞灶的发生和发展有关，而ｂｃｌ－２表达的变化可能与抑制细胞凋亡、发挥内源性细胞保护作用有关。     

Temporal fluctuations and experimental effects in desert plant communities

In the Chihuahuan Desert of the southwestern United States we monitored responses of both winter and summer annual plant communities to natural environmental variation and to experimental removal of seed-eating rodents and ants for 13 years. Analyses of data on population densities of the species by principal component analysis (PCA) followed by repeated measures analysis of variance (rmANOVA) on PCA scores showed that: (1) composition of both winter and summer annual communities varied substantially from year to year, presumably in response to interannual climatic variation, and (2) community composition of winter annuals was also significantly affected by the experimental manipulations of seed-eating animals, but the composition of the summer annual community showed no significant response to these experimental treatments. Canonical discriminant analysis (CDA) was then applied to the data for winter annuals to more clearly identify the responses to the different classes of experimental manipulations. This analysis showed that removing rodents or ants or both taxa caused distinctive changes in species composition. There was a tendency for large-seeded species to increase on rodent removal plots and to decrease on ant removal plots, and for small-seeded species to change in the opposite direction. In the winter annual community there was a significant time x treatment interaction: certain combinations of species that responded differently to removal of granivores also showed opposite fluctuations in response to long-term climatic variation. The large year-to-year variation in the summer annual community was closely and positively correlated across all experimental treatments. The use of multivariate analysis in conjunction with long-term monitoring and experimental manipulation shows how biotic interactions interact with variation in abiotic conditions to affect community dynamics.     

Neural correlates of behavioral gap detection in the inferior colliculus of the young CBA mouse

The gap detection paradigm is frequently used in psychoacoustics to characterize the temporal acuity of the auditory system. Neural responses to silent gaps embedded in white-noise carriers, were obtained from mouse inferior colliculus (IC) neurons and the results compared to behavioral estimates of gap detection. Neural correlates of gap detection were obtained from 78 single neurons located in the central nucleus of the IC. Minimal gap thresholds (MGTs) were computed from single-unit gap functions and were found to be comparable, 1–2 ms, to the behavioral gap threshold (2 ms). There was no difference in MGTs for units in which both carrier intensities were collected. Single unit responses were classified based on temporal discharge patterns to steady-state noise bursts. Onset and primary-like units had the shortest mean MGTs (2.0 ms), followed by sustained units (4.0 ms) and phasic-off units (4.2 ms). The longest MGTs were obtained for inhibitory neurons (xˉ = 14 ms). Finally, the time-course of behavioral and neurophysiological gap functions were found to be in good agreement. The results of the present study indicate the neural code necessary for behavioral gap detection is present in the temporal discharge patterns of the majority of IC neurons. Accepted: 6 February 1997     

Regional and Cortical Laminar Distributions of Serotonin S2, Benzodiazepine, Muscarinic, and Dopamine D2 Receptors in Human Brain

Serotonin S2, benzodiazepine, and muscarinic receptors showed different regional distributions in the human brain but were present in all cortical areas. The laminar distributions of [3H]ketanserin, [3H]diazepam, and [3H]quinuclidinylbenzilate were investigated in the temporal cortex and revealed a high density in the IIIrd and IVth layers. Dopamine D2 receptors were not detected in the cortex.     

Temporal selectivity for complex signals by single neurons in the torus semicircularis of Pleurodema thaul (Amphibia: Leptodactylidae)

Responses of auditory neurons in the torus semicircularis (TS) of Pleurodema thaul, a leptodactylid from Chile, to synthetic stimuli having diverse temporal patterns and to digitized advertisement calls of P. thaul and three sympatric species, were recorded to investigate their temporal response selectivities. The advertisement call of this species consists of a long sequence of sound pulses (a pulse-amplitude-modulated, or PAM, signal) having a dominant frequency of about 2000 Hz. Each of the sound pulses contains intra-pulse sinusoidal-amplitude-modulations (SAMs). Synthetic stimuli consisted of six series in which the following acoustic parameters were systematically modified, one at a time: PAM rate, pulse duration, number of pulses, and intra-pulse SAM rate. The carrier frequency of these stimuli was set at the characteristic frequency (CF) of the isolated units (n = 47). Response patterns of TS units to synthetic call variants reveal different degrees of selectivities for each of the temporal variables, with populations of neurons responding maximally to specific values found in the advertisement call of this species. These selectivities are mainly shaped by neuronal responsiveness to the overall sound energy of the stimulus and by the inability of neurons to discharge to short inter-pulse gaps. Accepted: 30 October 1996     

Song recognition by temporal cues in a group of closely related bushcricket species (genus Tettigonia)

Female phonotaxis of Tettigonia viridissima and T. caudata was investigated on a walking compensator to determine the temporal parameters of the male song used for song recognition, and to compare them with the previously described pulse rate filtering of T. cantans. The T. cantans song is continuous with a ≈30-Hz pulse rate. The T. caudata song has a higher pulse rate (≈40 Hz) and duty cycle than T. cantans and a distinct verse structure. The T. viridissima song is continuous with a double-pulse pattern. While the pulse rate is essential for song recognition in T. cantans, neither pulse rate not verse structure were essential for song recognition in T. caudata: females responded to signals above a minimum duty cycle. T. viridissima females did not require the double-pulse structure, but a single long pulse, equivalent to the duration of the double pulses and interval between them, was effective. Song attractiveness was limited by a minimum duration of the merged double pulse, and by minimum and maximum duration of the interval between them. Pulse rate recognition had little if any importance in either of the species investigated. Thus, the three congeners use different mechanisms for temporal song recognition. Accepted: 18 June 1998     

Multivariate statistical approach to the temporal and spatial patterns of selected bioindicators observed in the North Sea during the years 1995–1997

A comprehensive database, containing biological and chemical information, collected in the framework of the bilateral interdisciplinary MARS project (”biological indicators of natural and man-made changes in marine and coastal waters”) during the years 1995–1997 in the coastal environment of the North Sea, was subjected to a multivariate statistical evaluation. The MARS project was designated to combine a variety of approaches and to develop a set of methods for the employment of biological indicators in pollution monitoring and environmental quality assessment. In total, nine ship cruises to four coastal sampling sites were conducted; 765 fish and 384 mussel samples were analysed for biological and chemical parameters. Additional information on the chemical background at the sampling sites was derived from sediment samples, collected at each of the four sampling sites. Based on the available chemical data in sediments and black mussel (Mytilus edulis) a pollution gradient between the selected sites, was established. The chemical body burden of flounder (Platichthys flesus) from these sites, though, did not reflect this gradient equally clear. In contrast, the biological information derived from measurements in fish samples displayed significant a regional as well as a temporal pattern. A multivariate bioindicator data matrix was evaluated employing a factor analysis model to identify relations between selected biological indicators, and to improve the understanding of a regional and temporal component in the parameter response. In a second approach, applying the k-means algorithm on the data matrix, two significantly different clusters of samples, characterised by the current health status of the fish, were extracted. Using this classification a temporal, and in the second order, a less pronounced spatial effect was evident. In particular, during July 1996, a clear sign of deteriorating environmental conditions was extracted from the biological data matrix. Received: 20 June 1999 / Received in revised form: 8 November 1999 / Accepted: 8 November 1999     

许家窑人颞骨研究

本文记述1979年在许家窑遗址获得的人类左侧颞骨化石一块。通过与北京猿人、欧洲早期智人和现代人等的比较,表明许家窑人颞骨的某些性状较原始,有些性状则较为进步,但更主要的是许多特征介于直立人与现代人之间。     

Response characteristics of neurons in the medial geniculate body of the little brown bat to simple and temporally-patterned sounds

We examined the auditory response properties of neurons in the medial geniculate body of unanesthetized little brown bats (Myotis lucifugus). The units' selectivities to stimulus frequency, amplitude and duration were not significantly different from those of neurons in the inferior colliculus (Condon et al. 1994), which provides the primary excitatory input to the medial geniculate body, or in the auditory cortex (Condon et al. 1997) which receives primary input from the medial geniculate body. However, in response to trains of unmodulated tone pulses, the upper cutoff frequency for time-locked discharges (64 ± 46.9 pulses per second or pps) and the mean number of spikes per pulse (19.2 ± 12.2 pps), were intermediate to those for the inferior colliculus and auditory cortex. Further, in response to amplitude-modulated pulse trains, medial geniculate body units displayed a degree of response facilitation that was intermediate to that of the inferior colliculus and auditory cortex inferior colliculus: 1.32 ± 0.33; medial geniculate body: 1.75 ± 0.26; auditory cortex: 2.52 ± 0.96, P < 0.01). These data suggest that the representation of isolated tone pulses is not significantly altered along the colliculo-thalamo-cortical axis, but that the fidelity of representation of temporally patterned signals progressively degrades along this axis. The degradation in response fidelity allows the system to better extract the salient feature in complex amplitude-modulated signals. Accepted: 9 January 1999