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61.
The specific binding of [N-methyl-3H]flunitrazepam ([3H]FNZP) to a membrane fraction from the supraoesophageal ganglion of the locust (Schistocerca gregaria) has been measured. The ligand binds reversibly with a KD of 47 nM. The binding is Ca2+-dependent, a property not found for the equivalent binding site in vertebrate brain. The pharmacological characteristics of the locust binding site show similarities to both central and peripheral benzodiazepine receptors in mammals. Thus binding is enhanced by gamma-aminobutyric acid (GABA), a feature of mammalian central receptors, whereas the ligand Ro 5-4864 was more effective in displacing [3H]FNZP than was clonazepam, which is the pattern seen in mammalian peripheral receptors. The locust benzodiazepine binding site was photoaffinity-labelled by [3H]FNZP, and two major proteins of Mr 45K and 59K were specifically labelled. In parallel experiments with rat brain membranes a single major protein of Mr 49K was labelled, a finding in keeping with many reports in the literature. We suggest that the FNZP binding site described here is part of the GABA receptor complex of locust ganglia. The insect receptor appears to have the same general organization as its mammalian counterpart but differs significantly in its detailed properties.  相似文献   
62.
Summary Rainfall simulation at an average intensity of 124 mm·h-1 was used to compare infiltration and run off on arid areas where subterranean termites had been eliminated four years prior to the initiation of the study (termite free) with adjacent areas populated by subterranean termites (termites present). Infiltration rates on termite free plots with less than 5% perennial plant cover were significantly lower 51.3±6.8 mm·h-1 than rates on comparable termites present plots 88.4±5.6 mm·h-1. On plots centered on Larrea tridentata shrubs, there were no differences in infiltration rates with or without termites. Plots with shrub cover had the highest infiltration rates 101±6 mm·h-1. Highest run-off volumes were recorded from termite free <5% grass cover plots and the lowest from plots with shrubs. There were no differences in suspended sediment concentrations from termites present and termite free plots. Average bed load concentration was more than three times greater from termite free, <5% cover plots than from termites present, <5% cover plots.The reduction in infiltration, high run-off volumes and high bedloads from termite free areas without shrub cover is related to increased soil bulk density resulting from the collapse of subterranean galleries of the termites that provide avenues of bulk flow into the soil. Subterranean termites affect the hydrology of Chihuahuan desert systems by enhancing water infiltration and retention of top soil. The presence of a shrub canopy and litter layer cancels any effect of subterranean termites on hydrological parameters. Since approximately 2/3 of the area is not under shrub canopies, subterranean termites are considered to be essential for the maintenance of the soil water characteristics that support the present vegetation.  相似文献   
63.
Rhodocybe pulchrisperma is described as a new species of Agaricales from North America. It belongs in section Rhodocybe due to the brightly colored pseudocystidia and lack of clamp connections. The very large, handsomely ornamented basidiospores distinguish this species from others in the section. A key to taxa from Florida, Papua New Guinea, and India that exhibit similar features is presented.  相似文献   
64.
65.
Local names of vascular plants, accompanied by botanical specimens, were collected in the John Crow Mountains, Portland Parish, Jamaica. Each of the names was volunteered by one local informant; many were independently corroborated by others. We recorded 91 names of forest trees and shrubs, 20 names of climbers, and 33 names of other plants. The uneven distribution of local names among different categories of plants is discussed. The names are mostly of English origin, with a scattering from Spanish, Amerindian and West African languages. Many names are not listed in the standard floras; 20 names are apparently hitherto unrecorded in print. The same name was often found to be applied to a different species from the usage given in the floras, showing the variation in vernacular names from one part of the island to another.  相似文献   
66.
The nitrogen cycle in lodgepole pine forests,southeastern Wyoming   总被引:7,自引:4,他引:3  
Storage and flux of nitrogen were studied in several contrasting lodgepole pine (Pinus contorta spp.latifolia) forests in southeastern Wyoming. The mineral soil contained most of the N in these ecosystems (range of 315–860 g · m–2), with aboveground detritus (37.5–48.8g · m–2) and living biomass (19.5–24.0 g · m–2) storing much smaller amounts. About 60–70% of the total N in vegetation was aboveground, and N concentrations in plant tissues were unusually low (foliage = 0.7% N), as were N input via wet precipitation (0.25 g · m–2 · yr–1), and biological fixation of atmospheric N (<0.03 g · m–2 · yr–1, except locally in some stands at low elevations where symbiotic fixation by the leguminous herbLupinus argenteus probably exceeded 0.1 g · m–2 · yr–1).Because of low concentrations in litterfall and limited opportunity for leaching, N accumulated in decaying leaves for 6–7 yr following leaf fall. This process represented an annual flux of about 0.5g · m–2 to the 01 horizon. Only 20% of this flux was provided by throughfall, with the remaining 0.4g · m–2 · yr–1 apparently added from layers below. Low mineralization and small amounts of N uptake from the 02 are likely because of minimal rooting in the forest floor (as defined herein) and negligible mineral N (< 0.05 mg · L–1) in 02 leachate. A critical transport process was solubilization of organic N, mostly fulvic acids. Most of the organic N from the forest floor was retained within the major tree rooting zone (0–40 cm), and mineralization of soil organic N provided NH4 for tree uptake. Nitrate was at trace levels in soil solutions, and a long lag in nitrification was always observed under disturbed conditions. Total root nitrogen uptake was calculated to be 1.25 gN · m–2 · yr–1 with estimated root turnover of 0.37-gN · m–2 · yr–1, and the soil horizons appeared to be nearly in balance with respect to N. The high demand for mineralized N and the precipitation of fulvic acid in the mineral soil resulted in minimal deep leaching in most stands (< 0.02 g · m–2 · yr–1). These forests provide an extreme example of nitrogen behavior in dry, infertile forests.  相似文献   
67.
Synopsis Critical thermal maxima (CTM) and genetic variation were compared for red shiners, Notropis lutrensis, from regulated and unregulated sites on the Brazos River in northcentral Texas. Tailwater fish acclimated to 25°C had significantly lower CTM's than those from a site upstream from the dam and unregulated downstream sites. Significantly different intrasite variances were observed, with two- and four-fold larger CTM variances in fish from within 1 km and 30 km of the dam. Genetic variation was determined from electrophoretic comparisons at 21 structural gene loci. Mean heterozygosity was greatest at regulated sites. Tests for locus heterogeneity at five variable loci indicated that regulated and unregulated populations are not homogeneous. Fish under regulation were genetically more similar to each other than they were to those not affected by regulation. The proportions of the gene variance attributable to habitat alteration were partitioned, and fully one-third of the gene variation was attributed to stream regulation. Patterns of variation in thermal tolerance and metabolic enzymes in the red shiner correlated closely with temperature regimes associated with hypolimnion release from the dam. These adaptive responses have occurred in less than 40 years.  相似文献   
68.
A new algorithm is described that will rapidly produce restrictionmaps of cloned DNA fragments. Information concerning the vectoris stored as a data file and used in constructing probable maps.As the program is based upon a permutation analysis it has twoprimary uses. First, preliminary restriction maps can be createdfrom fragment length data as a starting point for further analysis.Second, existing maps can be confirmed as being highly probable,and other probable maps examined to ensure certain combinationshave not been overlooked. Although primarily designed for linearvectors, the program can be used to calculate circular maps. Received on June 5, 1985; accepted on September 27, 1985  相似文献   
69.
We have developed an inexpensive yet versatile microcomputer-basedsystem for quantitating light intensity levels in autoradiographs.This system employs a standard video camera interfaced to ananalog-to-digital convertor. A program has been written forthis system which can measure intensities within a defined regionof an autoradiograph, permitting an easy and accurate quantitationof spots or bands of irregular shape. Received on June 18, 1985; accepted on September 3, 1985  相似文献   
70.
Summary A hamster trachea organ culture system was utilized to evaluate quantitatively the effects of a strain of nontypeableHaemophilus influenzae (NTHI) and culture supernatants of the same strain on ciliary activity. Tracheal explants were maintained in organ culture for 96 to 144 h and ciliary activity was observed daily with an inverted microscope. Explants continuously exposed to a strain of NTHI had a progressive decline in ciliary activity which was significantly lower than uninfected controls evaluated concomitantly by 48 h of exposure and thereafter. Histologic studies revealed a progressive degeneration of mucosal cells and exfoliation of ciliated cells. Scanning electron microscopy showed little adherence of NTHI to the mucosal surface. Sterile broth cultures of NTHI and supernatants of organ cultures infected with the same NTHI strain had no adverse effect on ciliary activity. Infected tracheal explants treated with ampicillin 24, 48, or 72 h after continuous bacterial challenge had no significant decline in ciliary activity compared to controls. The lack of adherence and the histologic changes observed when hamster trachea cultures were infected with NTHI suggested a toxin might mediate the damage observed. Broth and organ culture supernatants, however, produced no damage. Therefore, further studies are needed to determine the role, if any, of a toxin in the production of damage to hamster tracheal explants by NTHI. This work was supported by a Merit Review grant from the Veterans Administration and by Grant AI-19641 from the National Institute of Allergy and Infectious Diseases.  相似文献   
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