Biochemical and autoradiographic studies of TRH receptors in sections of rabbit spinal cord

Receptors for thyrotropin-releasing hormone (pGlu-His-Pro-NH2, TRH) on thaw-mounted sections of rabbit spinal cord have been identified biochemically and visualized by light microscopic autoradiography. Binding of [3H] [3-Me-His2]TRH to 20 microns sections exhibited high apparent affinity and a pharmacological specificity almost identical to that previously demonstrated for spinal TRH receptors in membranes. In autoradiograms, the highest density of TRH receptors appeared in the substantia gelatinosa of the dorsal gray and around the central canal, with intermediate levels in the ventral gray.     

Observations on the separation of Theileria sporozoites from ticks

Hyalomma anatolicum anatolicum ticks infected with Theileria annulata were partially fed on rabbits and then ground up with tissue culture medium. The ground up ticks were treated by centrifugation at 100 g, filtration through membranes of 8 μm pore diameter and centrifugation on a discontinuous density gradient of Percoll. Counts of sporozoites and tick debris were made from Giemsa stained slides of samples at each stage of the separation. Debris was removed during light centrifugation and filtration at a greater rate than sporozoites. After filtration approximately 41% of the original sporozoites remained in the suspension. After density gradient centrifugation most sporozoites were found in a distinct zone, at approx. 1·08 g/cm³ density, separate from most dense debris and light debris and soluble contaminants. After this final centrifugation approximately 24% of the original sporozoites remained in the recovered suspension.     

Scavenger lipoprotein receptors are more effective in ligand internalization than low density lipoprotein receptors in human monocyte-macrophages

Human monocyte-macrophages in culture express specific receptors for low density lipoproteins (LDL receptor) and human acetylated LDL (AcLDL receptors or scavenger receptors). After 24 h in lipoprotein-deficient serum, the cells expressed 2-3 fold more AcLDL receptors than LDL receptors as measured by trypsin releasable radioactivity after exposure to 125I-LDL or 125I-AcLDL at 37 degrees C. The efficiency of intracellular ligand delivery by the two receptors was evaluated as an internalization index (defined as intracellular + degraded/bound ligand). This index was several fold greater for 125I-AcLDL than for 125I-LDL, in the same cells exposed to either ligand under identical conditions. These results suggest that the scavenger receptors recycle more rapidly than do LDL receptors.     

Plant spacing effect on yield of cotton irrigated with saline waters

Summary The response of the cotton plant (Gossypium hirsutum L.) to 9.0 and 12.5 cm intra- and 75.0 and 96.5 cm inter-row spacing was studied under irrigation with saline water (5.5 dS/m, SAR 18). In general, the dry weight per plant matter, the leaf area, number of bolls and flowers, and yield per plant were all affected significantly by intra-row spacing but, not by inter-row spacing. However, on a unit area basis, they were affected only by the inter-row spacing. This indicates that competition between plants exists when intra-row spacing is reduced, whereas no significant competition occurs due to a decrease in the inter-row spacing. Although the effect of intra-row spacing on yield for a unit area was found to be not significant, the effect of inter-row spacing was significant. Yield in plots with the conventional spacing (96.5 cm between rows and 12.5 cm between plants in the row) was 4863 kg/ha, whereas the yield in plots with 75 cm between rows was about 23% higher (5974 kg/ha). The lint percentage and the plant height were not affected significantly by either intra- or inter-row spacings.Contribution from the Institute of Soils and Water, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel. No.676-E, 1983 series.     

Glucuronidation and sulfation of p-nitrophenol in isolated rat hepatocyte subpopulations. Effects of phenobarbital and 3-methylcholanthrene pretreatment

Parenchymal cells, isolated from untreated (control), phenobarbital(PB)-or 3-methylcholanthrene(3-MC)-treated rats, were separated into four subpopulations according to cell density, and glucuronidation and sulfation of p-nitrophenol (PNP) in the hepatocyte subpopulations were investigated. PB enhanced the glucuronidation almost 2-fold but not the sulfation, while 3-MC enhanced both glucuronidation (3-fold) and sulfation (2-fold) in the original cell suspensions. Some gradation trends were found in the conjugation activities among the hepatocyte subpopulations: In the control experiment, the extent of glucuronidation in four subpopulations was virtually the same but sulfation in high-density hepatocytes was slightly higher than in low-density ones. Both glucuronidation and sulfation were higher in low-density hepatocytes from PB-treated rats, though the gradation was very modest. Glucuronidation and sulfation tended to be slightly higher in middle-density hepatocytes in the 3-MC experiment. However, no definite correlation in conjugation activities vs. cell density, like those seen in cytochrome P-450s vs. cell density in the hepatocytes isolated from PB-treated rats, were found in the subpopulations from control or inducer-treated rats. Simultaneous studies on acetylation of p-aminobenzoic acid (PABA) revealed that the activities in the subpopulations were virtually the same and the inducers had little influence on the activity.     

几个生态因子对黄盖鲽的影响

黄盖鲽(Psuedopleuronectes yokohameGünther)是鲽科中的冷温性鱼类,广泛分布在日本、朝鲜及我国的东海、黄海和渤海。地方种群多,洄游范尉小,适应能力强,既是底栖生物食性,又可耐较低的温度,虽非名贵鱼种,却具有一定的经济价值,在开展近海增殖时,不存在越冬和效益外流问题。因此,早在60年代,日本山口县和大分县的学者们,便开始着手该品种的人工孵化和增殖放流试验。80年代初已达年放流2—3cm的稚鱼苗7.0×10~6尾的水平。为了在渤海开展增殖工作,建立综     

Development of Bursaphelenchus xylophilus Populations in Wood Chips with Different Moisture Contents

Bags of Pinus strobus wood chips with moisture contents of 38, 92, 164, and 217% (oven dry weight) were inoculated with Bursaphelenchus xylophilus and incubated at 30 C in order to determine the effect of wood moisture on nematode population development. Nematodes were extracted after 2, 4, 8, and 12 weeks. Population levels were greatest in wood chips with a moisture content of 38% and decreased successively with each higher moisture content. In chips with the three lower moisture contents, populations peaked at 2 weeks, but at 217% moisture, they peaked at 8 weeks. By 12 weeks, nematode populations had declined in wood chips with 92 and 164% moisture contents. The fungi most frequently isolated from the wood chips were Alternaria, Fusarium, Gliocladium, Graphium, Penicillium, Trichoderma, and Mucorales.     

The role of litter in an old-field community: impact of litter quantity in different seasons on plant species richness and abundance

Summary We studied the effect of removing and adding plant litter in different seasons on biomass, density, and species richness in a Solidago dominated old-field community in New Jersey, USA. We removed all the naturally accumulated plant litter in November (658 g/m²) and in May (856 g/m²) and doubled the amount of litter in November and May in replicated plots (1 m²). An equal number of plots were left as controls. Litter removal and addition had little impact on total plant biomass or individual species biomass in the growing season following the manipulations. Litter removal, however, significantly increased plant densities but this varied depending upon the season of litter removal, species, and life history type. Specifically, the fall litter removal had a much greater impact than the spring litter removal suggesting that litter has its greatest impact after plant senescence in the fall and prior to major periods of early plant growth in spring. Annual species showed the greatest response, especially early in the growing season. Both spring and fall litter removal significantly increased species richness throughout the study. Litter additions in both spring and fall reduced both plant densities and species richness in June, but these differences disappeared near the end of the growing season in September. We concluded than in productive communities where litter accumulation may be substantial, litter may promote low species richness and plant density. This explanation does not invoke resource competition for the decline in species richness. Finally, we hypothesize that there may be broad thresholds of litter accumulation in different community types that may act to either increase or decrease plant yield and diversity.     

Natal dispersal in relation to population density and sex ratio in the field vole,Microtus agrestis

Summary In a sample of 240 juvenile field voles 8% of the males and 22% of the females reached sexual maturity within their natal home range. Among individuals retrapped as adults, 58% of males and 23% of females had dispersed, i.e. had moved more than one home range diameter. The mean distance moved for males (58.5 m) exceeded that for females (28.6 m). Male movement distances were negatively associated with total density, and with density of adult females, but not with male density. Female movements were not related to population density. There were no relation between sex ratio and distance moved. The distribution of distances moved for both males and females fit a geometrical distribution, suggesting the importance of competitive processes.     

Frankia strains of soil underBetula pendula: Behaviour in soil and in pure culture

A K/Rb isotope dilution method was used to determine the uptake of K from undisturbed subsoils. Rb was applied to the topsoil (0–30 cm) to trace the K taken up from the topsoil by crops. The K/Rb ratio in the crops increases when roots contact the Rb-free subsoil. This change in the K/Rb ratio enables the calculation of the uptake of K from the subsoil. Results of 34 field experiments on loess-parabrown soils in N. Germany showed that the subsoil (>30 cm) supplied, on average, 34% of the total K uptake by spring wheat (range 9–70%). The range between the experimental sites is considered in relation to the contents of K in the top and subsoils (as extracted by 0.025 N CaCl₂ solution), the proportion of the total root length in the subsoils, and competition for K between roots in the top and subsoil. In subsoils with similar K contents, uptake from the subsoil decreased significantly from 65 to 21% of total K uptake, as K contents in the topsoils increased from 4 to 8 mg K/100 g. On sites with the same K contents in topsoils (9 mg K/100 g), the subsoil supplied 12 to 61% of total K uptake as the K contents of the subsoil increased from 2 to 27 mg K/100 g. The contribution of uptake of K from the subsoil increased with the development of the crop, from 8% at first node stage to 35% at ear emergence, as the proportion of total root length in the subsoil increased. High root length densities in the topsoil (9 cm/cm³) resulted in competition for K between roots and increased uptake of K from the subsoil.