Activation of various areas of the ventral horn of lumbar segments during stimulation of the motor cortex

Focal potentials (FP) in segments L₆–L₇ of the ventral horn, evoked by stimulation of the motor cortex with series of stimuli of threshold magnitude for the flexor nerve response, were studied in acute experiments on cats. Appreciable differences were found to exist between the FP arising in the medial zone (layer VIII of Rexed) and those in the inner and outer parts of the lateral zone (layer IX). The FP of the medial zone appear earlier than in other zones (with a latency of 5–12 msec); they are multiphasic, negative components predominating over the positive ones. The FP from the inner part of layer IX possess the largest amplitude (up to 500 µV), a latency of 7–13 msec, a large first negative phase, and marked late positivity. Positive — negative FP (latency 9–15 msec) of small amplitude are recorded from the outermost portion of the ventral horn. The FP of the three zones mentioned above differ also with respect to other functional criteria. The FP of the medial zone are assumed to reflect the realization at the segmental level of the extrapyramidal component of descending cortical activity, the FP of both lateral zones reflecting reciprocal interrelations between postsynaptic processes in the motoneurons of flexor and extensor nuclei during implementation of a cortical motor reaction.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 3, No. 2, pp. 175–184, March–April, 1971.     

Effect of electrical stimulation of the hippocampus and neocortex on cingulate cortical neurons in rabbits

Extracellular unit activity of the anterior and posterior zones of the cingulate cortex and also of the anterior and posterior cortical association areas was analyzed in unanesthetized rabbits. In the posterior zone considerably more cells (60%) responded to hippocampal stimulation than in the anterior zone (18%). In 43% of these cells in the posterior zone but only in 5% in the anterior zone, the responses followed the frequency of stimulation. Unit responses in the posterior zone could be divided into two discrete groups: those with short (12.3 ± 6.5 msec) and those with long (50.2 ± 10.0 msec) latent periods. Inhibitory phenomena also were well marked during hippocampal stimulation. More than one-third of cells of the cingulate cortex responded to stimulation of the posterior association zones by spikes which followed the stimulus, and by subsequent inhibition. Responses of this kind to stimulation of the anterior association zones were found in only a few cells in the anterior zone of the cingulate cortex. The results are discussed in the light of data from morphological investigations relating to connections between these structures.Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oka. Translated from Neirofiziologiya, Vol. 14, No. 3, pp. 270–277, May–June, 1982.     

Effects of stimulating the caudal zones of the mesencephalic reticular formation on the postcruciate cortex of the cat]

The influence of the electrical stimulation of the dorsolateral (DL) and the ventromedial (VM) portions of the caudal area of the mesencephalic reticular formation on the neuronal activity of the lateral zone of the gyrus sygmoideus posterior was investigated in cats. The mesencephalo-cortical influences were mainly excitatory in character; the predominance of the neuronal reactions with a short latency (3--12 msec) during the VM stimulation and reactions with a longer latency (20--25 msec) during the DL stimulation was revealed. The VM and the DL were found to influence both cortical neurones, the ones sensitive to somesthetic stimuli (mono-, di- and polyvalent) and the ones which failed to respond to the electrocutaneous stimulation of the limbs.     

Direct interaction between the ARF-specific guanine nucleotide exchange factor msec7-1 and presynaptic Munc13-1.

Msec7-1, a mammalian homologue of yeast sec7p, is a specific GDP/GTP exchange factor for small G-proteins of the ARF family. Overexpression of msec7-1 in Xenopus neuromuscular junctions leads to an increase in synaptic transmitter release that is most likely caused by an increase in the pool of readily releasable vesicles. However, the molecular mechanisms by which msec7-1 is targeted to presynaptic compartments and enhances neurotransmitter release are not known. In the present study, we demonstrate that msec7-1 interacts directly with Munc13-1, a phorbol ester-dependent enhancer of neurotransmitter release that is specifically localized to presynaptic transmitter release zones. Given that Munc13-1 and msec7-1 participate in very similar presynaptic processes and because Munc13-1 is specifically targeted to presynaptic active zones, we suggest that the msec7-1/Munc13-1 interaction serves to colocalize the two proteins at the active zone, a subcellular compartment with extremely high membrane turnover.     

LiDAR derived ecological integrity indicators for riparian zones: Application to the Houille river in Southern Belgium/Northern France

Riparian zones are central landscape features providing several ecosystem services and are exceptionally rich in biodiversity. Despite their relatively low area coverage, riparian zones consequently represent a major concern for land and water resource managers confirmed within several European directives. These directives involve effective multi-scale monitoring to assess their conditions and their ability to carry out their functions. The objective of this research was to develop automated tools to provide from a single aerial LiDAR dataset new mapping tools and keystone riparian zone attributes assessing the ecological integrity of the riparian zone at a network scale (24 km).Different metrics were extracted from the original LiDAR point cloud, notably the Digital Terrain Model and Canopy Height Model rasters, allowing the extraction of riparian zones attributes such as the wetted channel (0.89 m; mean residual) and floodplain extents (6.02 m; mean residual). Different riparian forest characteristics were directly extracted from these layers (patch extent, overhanging character, longitudinal continuity, relative water level, mean and relative standard deviation of tree height). Within the riparian forest, the coniferous stands were distinguished from deciduous and isolated trees, with high accuracy (87.3%, Kappa index).Going further the mapping of the indicators, our study proposed an original approach to study the riparian zone attributes within different buffer width, from local scale (50 m long channel axis reach) to a network scale (ca. 2 km long reaches), using a disaggregation/re-agraggation process. This novel approach, combined to graphical presentations of the results allow natural resource managers to visualise the variation of upstream–downstream attributes and to identify priority action areas.In the case study, results showed a general decrease of the riparian forests when the river crosses built-up areas. They also highlighted the lower flooding frequency of riparian forest patches in habitats areas.Those results showed that LiDAR data can be used to extract indicators of ecological integrity of riparian zones in temperate climate zone. They will enable the assessment of the ecological integrity of riparian zones to be undertaken at the regional scale (13,000 km, completely covered by an aerial LIDAR survey in 2014).     

Seasonal changes in soil phosphorus dynamics and root mass along a flooded tropical forest gradient in the lower Orinoco river,Venezuela

The effects of natural hydrological fluctuations on the nature and bioavailability of soil phosphorus (P) in relation to iron (Fe) and aluminum (Al) chemistry and root mass were studied along a flooded tropical forest gradient in Mapire river, Venezuela. Soil samples were collected following a complete natural hydroperiod: end of the dry season (May 2004), end of the rainy season (November 2004) and end of the subsequent dry season (May 2005), and from three zones subjected to different flooding intensities: MAX, MED and MIN zones inundated for 8, 5 and 2 months per year respectively. The results showed that flood induced the increase of resin-Pi in the MAX zone, but not in the MED and MIN zones. Flood in the soil of the MAX zone also induced the increase of the NaOH-Pi fraction, which removes inorganic P sorbed onto secondary Fe and Al minerals. Changes in this redox-sensitive P form can be considered indirect evidence that P in the MAX zone can be released from the dissolution of iron oxyhydroxide. This field study also showed that along the flooded forest gradient, fine root mass declined during the flood event. However, such decline was more pronounced in the MIN zone than in the MAX zone. In this zone fine root mass was higher than in the other zones.     

Enteroendocrine cells in the digestive tract of Barbus conchonius (teleostei,cyprinidae)

Just as in other cyprinids, three zones can be distinguished in the digestive tract of Barbus conchonius. A fat absorptive zone (65--75%), including the intestinal bulb, is followed by a protein absorptive zone (25--35%) and a small ion and water absorptive zone (less than 5%). The main characteristics of these zones are described. Four types of enteroendocrine cells can be distinguished between the intestinal epithelial cells. The number decreases in the caudal direction, and there are very few in the protein absorptive zone. All the enteroendocrine cells are argyrophilic and differ mainly in the size and shape of their secretory granules. Serotonin producing and hence argentaffin cells have not been found. Amine precursor uptake and decarboxylation (APUD) by the enteroendocrine cells of adult fishes has not been observed. The possible functions of the enteroendocrine cells are discussed. (Auto-)phagosomes, common in epithelial cells of the gut of B. conchonius, show similar staining characteristics as the enteroendocrine cells; their function is discussed.     

Unit responses of the reticular and ventral anterior thalamic nuclei of cats to orbitofrontal cortical stimulation

Responses of 98 neurons of the reticular (R) and 72 neurons of the ventral anterior (VA) thalamic nuclei to stimulation of various zones of the orbitofrontal cortex were investigated in acute experiments on cats immobilized with D-tubocurarine. Not all zones of this cortex were found to be connected equally closely with R and VA. Most of the R (82.7%) and VA (66.7%) neurons responded to stimulation of the proreal gyrus, and fewest (37.3 and 48.9%, respectively) to stimulation of the posterior orbital gyrus. Among the responding neurons, 85.2–86.3% of R cells and 78.2–81.2% of VA cells were excited by cortical stimulation and the rest were inhibited. Excitation was expressed as the appearance of a single spike or of discharges of varied duration in response to each stimulus. The latent period of the spike responses varied from 0.5 to 55.0 msec and the minimal latent period of the discharges was 0.8 msec and its maximal value over 500 msec. The spike frequency in the discharge was 120–250/sec. Unit responses consisting of spikes with a latent period of under 1.3 msec and, it is assumed, some of the responses with a latent period of under 4.0 msec were antidromic. The axons of some R and VA neurons were shown to form branches terminating in different zones of the orbitofrontal cortex.     

Effect of high temperature on active oxygen species,senescence and photosynthetic properties in cucumber leaves

To gain a physiological understanding of the effects of high temperatures on cucumber (Cucumis sativus L.), we subjected seedlings to heat treatment at daytime temperatures of 28 °C, 32 °C, and 36 °C for 7 h a day for 30 days. The amount of active oxygen species, indicators of senescence, and photosynthetic properties in the second and third leaves were determined at the start of temperature treatment and on the 15th and 30th days of treatment. The amount of active oxygen species superoxide in leaves was greatest in the high temperature zones on the 15th day of treatment, and the amount of hydrogen peroxide was greatest in the high temperature zones on both the 15th and 30th days of treatment. The reduction in the amount of protein and the increase in the amount of malondialdehyde, both indicators of senescence, were greatest in the high temperature zones on both the 15th and 30th days of treatment, and the amount of chlorophyll was lowest in the 36 °C zone on the 15th day, and lower in the high temperature zones on the 30th day. It is clear from these results that a large amount of active oxygen species is generated and accumulated in the leaves at high temperatures, and senescence is significantly accelerated. The photosynthetic properties of stomatal conductance, sub-stomatal CO₂ concentration, and transpiration rate were at the same level on both the 15th and 30th days of treatment in all three temperature treatment zones. No significant difference was seen in the net photosynthesis rate between the 28 °C and 32 °C zones, was lower in the 36 °C zone than the 32 °C zone on the 15th day, and lowest in the 36 °C zone on the 30th day. CO₂ intake and water absorption are only mildly affected by high temperatures, and the reduction in net photosynthesis rate due to the 36 °C high temperature stress suggests that the large amount of active oxygen species induces inhibition of photosynthesis and damage to the mechanism of photosynthesis.     

The effect of stimulation of the deep layers of somatosensory zones CI and CII on the activity of motor zone MI of the cat cortex]

The influence of electrical stimulation of deep layers of the somatosensory zones CI and CII on unit responses and intercortical evoked potentials (IEP) in the motor cortical zone MI in projection areas of the anterior contralateral limb was studied in cats anaesthetized with Nembutal and immobilized with diplacine. Latencies of the main IEP components and their different behaviour during repeated stimulation, experimental hypoxia and Nembutal administration suggested the presence of intercortical connections of an oligo- and polysynaptic nature. Only 22% of the MI zone units proved to be responsive to CI and CII stimulation; the latencies of the unit discharges varied from 4.3 to 35 msec. A relatively smaller effectiveness of short-latency inputs from CI and CII to MI was recorded as compared with long latency ones.     

Variation in the abundance of Pseudo-nitzschia and domoic acid with surf zone type

Most harmful algal blooms (HAB) originate away from the shore and, for them to endanger human health, they must be first transported to shore after which they must enter the surf zone where they can be feed upon by filter feeders. The last step in this sequence, entrance into the surf zone, depends on surf zone hydrodynamics. During two 30-day periods, we sampled Pseudo-nitzschia and particulate domoic acid (pDA) in and offshore of a more dissipative surf zone at Sand City, California (2010) and sampled Pseudo-nitzschia in and out of reflective surf zones at a beach and rocky shores at Carmel River State Beach, California (2011). At Sand City, we measured domoic acid in sand crabs, Emerita analoga. In the more dissipative surf zone, concentrations of Pseudo-nitzschia and pDA were an order of magnitude higher in samples from a rip current than in samples collected just seaward of the surf zone and were 1000 times more abundant than in samples from the shoals separating rip currents. Domoic acid was present in all the Emerita samples and varied directly with the concentration of pDA and Pseudo-nitzschia in the rip current. In the more reflective surf zones, Pseudo-nitzschia concentrations were 1–2 orders of magnitude lower than in samples from 125 and 20 m from shore. Surf zone hydrodynamics affects the ingress of Pseudo-nitzschia into surf zones and the exposure of intertidal organisms to HABs on the inner shelf.     

Hybrid zones and cultural traits of the Australian ringneck Platycercus zonarius

Two hybrid zones between subspecies of the Australian ringneck parrot (Psittacidae: Platycercus zonarius ) were examined for morphological (plumage patterns) and cultural (learned contact flight calls) traits. Mensural traits and plumage patterns also were quantified in a study in the 1960s. My samples were taken from populations in the allopatric distributions of the parental taxa P. z. zonarius (Port Lincoln parrot), P. z. semitorquatus (twenty-eight parrot), and P. z. barnardi (Mallee ringneck) and within the hybrid zones. The two hybrid zones differed in the distribution of plumage patterns: (a) in the zonarius – semitorquatus zone of intergradation all sample locations comprised birds of both subspecies' plumage patterns as well as numerous birds in hybrid plumage and (b) in the zonarius – barnardi zone of intergradation all birds were in hybrid plumage. The cultural trait also differed in the two hybrid zones: the acoustic features of P. z. zonarius flight call predominated in the birds in the hybrid zone with P. z. semitorquatus , regardless of plumage displayed by the individuals; whereas in the P. z. zonarius – P. z. barnardi zone of hybridization the acoustic features of the P. z. barnardi flight call notes evidently have swamped out those of P. z. zonarius . The results on the cultural trait reject 'coexistence' and 'blending' models of cultural interchange but support a 'cultural dominance' model. Hypotheses are discussed concerning historical and behavioral means by which the patterns arise.     

Temporal–spatial variation and source analysis of carbon and nitrogen in a tidal wetland of Luoyuan Bay

Carbon and nitrogen are important elements in biogeochemical studies of tidal wetlands. Three wetland zones in Luoyuan Bay in the Fujian province were chosen for this study; the Spartina alterniflora flat zone with Spartina alterniflora growing, the silt zone with no Spartina alterniflora growing and the Spartina alterniflora-silt flat zone – a transition zone between the two. The spatial and seasonal variations of total organic carbon (TOC), total nitrogen (TN), stable isotopes of organic material (δ¹³C, δ¹⁵N), C/N ratio, average particle size and sediment composition in surface and vertical sediments of different ecological zones were analyzed. Carbon and nitrogen accumulation and particle size effects in the different ecological zones were discussed and the indicators of δ¹³C and C/N ratios were also compared. TOC, TN, δ¹³C contents, C/N ratios, and average particle size varied within the ranges of 0.611–1.133%, 0.053–0.090%, ?22.60 to ?18.92‰, 12.3–15.7, and 6.4–8.7 μm, respectively. Sediments were mainly silt-sized. Besides δ¹⁵N values, the other parameters, such as TOC, TN, δ¹³C contents, C/N ratios, and average particle size showed an obvious zonal distribution in surface sediments. The distribution of TOC and TN contents reflected the distribution of Spartina alterniflora within the bay. The profile and seasonal variations of these parameters in different ecological zones indicated that variations in the Spartina alterniflora flat and transition zones were complex because of the effect of Spartina alterniflora. Vertical and seasonal variations were sampled in the silt flat area. The profile and seasonal variations of TOC, TN and δ¹³C were similar in the transition zone and the Spartina alterniflora flat zone. Seasonal concentrations of TOC, TN and δ¹³C decreased from autumn > spring > winter > summer. The seasonal variation of carbon and nitrogen in the sediments may be influenced by temperature, particle size, plankton and benthos. The particle size effect was significant in the surface sediments and profile sediments of the transition zone. However, other factors had a greater effect on the distributions of TOC and TN in the Spartina alterniflora flat and silt flat zones. C/N ratios in sediments of the Spartina alterniflora flat, transition zone and silt flat were close to or > 12, indicating that the organic material source was dominated by terrestrial inputs. However, δ¹³C values decreased from the Spartina alterniflora flat zone > transition zone > silt flat zone indicating that the organic material source was predominantly from marine inputs. Thus the indications from C/N ratios and δ¹³C were different. There was no clear relationship between C/N ratios and δ¹³C values and a better relationship between δ¹³C values and TOC concentrations suggested that δ¹³C values provided a better indication of the organic source. Limited amounts of organic material came from Spartina alterniflora. This study has provided basic data for researching biogeochemical processes of biogenic elements in tidal wetlands and vegetation restoration, and has also provided a reference for assessing and protecting the environment and ecological systems in wetlands.     

Regional respiratory clearance of aerosolized 99mTc-DTPA: posture and smoking effects

We studied 10 healthy nonsmokers and 8 healthy smokers, in both the upright and supine position, to investigate whether regional differences in respiratory clearance of technetium-99m-labeled diethylenetriamine pentaacetic acid 99mTc-DTPA (RC-DTPA) existed and to assess the influence of posture and smoking on the regional RC-DTPA. RC-DTPA was assessed by the lung clearance rates (%/min) of aerosolized 99mTc-DTPA (0.8 micron MMD; 2.4 GSD), using data corrected for recirculating radioactivity, in the upper (zone 1), middle (zone 2), and lower (zone 3) posterior lung fields. In nonsmokers, RC-DTPA in zone 1 was faster than in zone 2 or 3 in both the upright (P less than 0.001) and supine positions (P less than 0.0). No effect was produced by changes in posture on the regional RC-DTPA. In smokers, RC-DTPA was increased in all zones compared with the nonsmokers (P = 0.004), with a further increase in RC-DTP in zone 1 in the upright posture compared with the other regions (P less than 0.001). We conclude that in nonsmokers regional RC-DTPA is faster in zone 1 than in other zones, and this is not related to recirculation of radioactivity; posture does not modify the regional RC-DTPA of nonsmokers; smoking increases RC-DTPA in all zones and more in zone 1 in the upright posture.     

Impact of landscape pattern at multiple spatial scales on water quality: A case study in a typical urbanised watershed in China

Buffer zones along rivers and streams can provide water quality services by filtering nutrients, sediment and other contaminants from the surface. Redundancy analysis was used to determine the influence of the landscape pattern at the entire catchment scale and at multiple buffer zone scales (100 m, 300 m, 500 m, 1000 m and 1500 m) on the water quality in a highly urbanised watershed. Change-point analysis was further applied to estimate the specific locations along a gradient of landscape metric that result in a sudden change in the water quality variable. The landscape characteristics for 100 m buffer zones appeared to have a slightly greater influence on the water quality than the entire catchment. The patch density of urban land and the large patch index of water were recognised as the dominant variables influencing the water quality for a 100 m buffer zone. The result of change-point analysis indicated key interval values of the two landscape metrics within the 100 m buffer zone. When the patch density of urban land was >30–40 n/100 ha and the largest patch index of water was >2.5–3.5%, the watershed water quality appeared to be better protected.     

Nonlinear features and complexity patterns of vegetation dynamics in the transition zone of North China

Normalized Difference Vegetation Index (NDVI) has been commonly used to estimate terrestrial vegetation distribution and productivity. In this study, we adopted recurrence quantification analysis (RQA) to investigate the spatial patterns of determinism of the vegetation dynamics ecological-geographical transition zones in North China, especially the differences between transition zone and the surrounding areas. The results indicated that there were obvious regional variances in spatial patterns of RQA indices—determinism, laminarity, entropy, and averaged diagonal line length. Remarkable differences of the determinism of NDVI time series also existed between transition zones and the surrounding areas. Moreover, the correlation analysis between the RQA indices and climatic factors suggested that the determinism of the NDVI time series was nonlinearly affected by hydrothermal conditions. Influenced by vegetation patterns, determinism reached the maximum when the annual precipitation is about 400 mm, which is the lower bound of cultivation and forest distribution, and along the 400 mm isohyet is the area where transition zones locate.     

Does predation risk influence habitat use by northern redbelly dace Phoxinus eos at different spatial scales?

This study investigated the relationship between spatial variations in predation risk and abundance of northern redbelly dace Phoxinus eos at both macroscale (littoral v. pelagic zones) and microscale (structured v. open water habitats in the littoral zone) of Canadian Shield lakes. Minnow traps were placed in both structured and open water habitats in the littoral zone of 13 Canadian Shield lakes, and estimates of the relative predation risk of P. eos in both the pelagic and the littoral zones were obtained from tethering experiments. Results showed that (1) the mean abundance of P. eos in the littoral zone was positively correlated with the relative predation risk in the pelagic zone, (2) P. eos preferentially used structured over open water habitats in the littoral zone and (3) this preference was not related to the relative predation risk in the littoral zone but decreased as the relative predation risk increased in the pelagic zone. At the lake level, these results support the hypothesis that P. eos enter the littoral zone to avoid pelagic piscivores. At the littoral zone level, the results do not necessarily contradict the widely accepted view that P. eos preferentially use structured over open habitats to reduce their predation risk, but suggest that flexibility in antipredator tactics ( e.g. shelter use v. shoaling) could explain the spatial distribution of P. eos between structured and open water habitats.     

Barrier to gene flow between two ecologically divergent Populus species, P. alba (white poplar) and P. tremula (European aspen): the role of ecology and life history in gene introgression

The renewed interest in the use of hybrid zones for studying speciation calls for the identification and study of hybrid zones across a wide range of organisms, especially in long-lived taxa for which it is often difficult to generate interpopulation variation through controlled crosses. Here, we report on the extent and direction of introgression between two members of the "model tree" genus Populus: Populus alba (white poplar) and Populus tremula (European aspen), across a large zone of sympatry located in the Danube valley. We genotyped 93 hybrid morphotypes and samples from four parental reference populations from within and outside the zone of sympatry for a genome-wide set of 20 nuclear microsatellites and eight plastid DNA restriction site polymorphisms. Our results indicate that introgression occurs preferentially from P. tremula to P. alba via P. tremula pollen. This unidirectional pattern is facilitated by high levels of pollen vs. seed dispersal in P. tremula (pollen/seed flow = 23.9) and by great ecological opportunity in the lowland floodplain forest in proximity to P. alba seed parents, which maintains gene flow in the direction of P. alba despite smaller effective population sizes (N(e)) in this species (P. alba N(e)c. 500-550; P. tremula N(e)c. 550-700). Our results indicate that hybrid zones will be valuable tools for studying the genetic architecture of the barrier to gene flow between these two ecologically divergent Populus species.     

Border zone geometry increases wall stress after myocardial infarction: contrast echocardiographic assessment

After myocardial infarction (MI), the border zone expands chronically, causing ventricular dilatation and congestive heart failure (CHF). In an ovine model (n = 4) of anteroapical MI that results in CHF, contrast echocardiography was used to image short-axis left ventricular (LV) cross sections and identify border zone myocardium before and after coronary artery ligation. In the border zone at end systole, the LV endocardial curvature (K) decreased from 0.86 +/- 0.33 cm(-1) at baseline to 0.35 +/- 0.19 cm(-1) at 1 h (P < 0.05), corresponding to a mean decrease of 55%. Also in the border zone, the wall thickness (h) decreased from 1.14 +/- 0.26 cm at baseline to 1.01 +/- 0.25 cm at 1 h (P < 0.05), corresponding to a mean decrease of 11%. By Laplace's law, wall stress is inversely proportional to the product K. h. Therefore, a 55% decrease in K results in a 122% increase in circumferential stress; a 11% decrease in h results in a 12% increase in circumferential stress. These findings indicate that after MI, geometric changes cause increased dynamic wall stress, which likely contributes to border zone expansion and remodeling.