内蒙东部地区绵羊中华双腔吸虫生物学和流行病学的研究

中华双腔吸虫(Dicrocoelium chinensis Tang et Tang,1978)的生活史虽经研究,但本吸虫在第二中间宿主及终末宿主体内发育的情况尚未经阐明(唐崇惕等,1980).内蒙科右前旗附近数个旗县是本吸虫的流行区,1980—1981年我们在那里进行本项工作,从     

Root growth and litter decomposition in a coffee plantation under shade trees

In a non-fertilized coffee plantation under shade trees the root biomass was excavated to estimate its distribution in the soil profile. One third of total fine (less than 1 mm) roots was found in the first 10 cm of soil; the cumulative total to 30 cm reached 73%. A highly variable and transient amount of fine roots colonized the litter layer. Root production both in the litter and in the first 7.5 cm of mineral soil was estimated from sequential samplings and was 10 g m^–2 yr^–1 and 660 g m^–2 yr^–1 respectively. The decomposition rate of weighed averages of litter fractions in the coffee plantation, calculated as the ratio of litter fall rate to the amount found in the soil was k=4.8. Shade tree leaves, the major component of litter descomposed slower than coffee leaves and these slower than flowers and fruits. Litter bag experiments showed considerable slower rates when mesh was 0.03 mm than 0.5 mm. Nitrogen and phosphorous showed increases in concentrations as decomposition progressed while potassium, calcium and magnesium followed a decrease in concentration that paralleled that of dry weight loss. In comparing the decomposition rate for litter with or without coffee roots growing in the bags, a tendency to show faster decomposition rates was found for the treatment with roots. These differences were however, only significant for one month for shade tree leaves litter. Nitrogen amounts remaining in shade tree leaves litter was lower in the treatment with roots that without roots. Potassium concentration in roots was positively correlated with potassium concentration in decomposing leaf litter where roots were growing. These results suggest that while roots growing attached to decomposing litter had little or no effect in speeding the decomposition process, the superficial roots seem to play an important role in absorbing very efficiently the mineralized nutrients from litter. The anatomical study of roots showed that the plantation is intensely infected with V-A mycorrhiza. External mycorrhizal hyphae did not to play a role in attachment of roots to decomposing litter while root hairs were found to grow in profusion on root surfaces oriented toward litter.     

Soybean leaf urease: Comparison with seed urease

Soybeans, Glycine max (L.) Merr., from ureides for transport of nitrogen from the root nodule to the shoot. The most direct routes for ureide utilization include the degradation of ureide-derived urea to NH₃ and CO₂. Ureolytic activity was found in leaf disks of soybean and exhbited optimal activity at pH 7 in the presence of a high concentration of urea (250 m M ). In vitro studies showed neither urea amidolyase nor urea dehydrogenase activity in soybean leaves and the ureolytic activity was characterized as urease. Several biochemical properties of soybean leaf urease were determined and compared to seed urease properties. Soybean leaf urease differed from that of seed in five ways: pH optima (5.25 and 8.75), apparent K_m (0.8 m M ), no inhibition by hydroxyurea, faster electrophoretic mobility and no cross-reactivity with soybean seed urease antibodies. The data suggest that urease is the primary urea metabolizing enzyme present in soybean leaves. The properties of soybean leaf urease support the conclusion that a unique isozyme of urease is present in leaf tissue.     

Effects of decapitation and ovariectomy on the regulation of juvenile hormone synthesis in the cockroach, Diploptera punctata

Corpora allata from Diploptera punctata females at adult ecdysis or at the end of the last-larval stadium, when implanted into decapitated females, underwent a cycle of juvenile hormone synthesis similar in timing and magnitude to that of glands implanted into control animals which had been starved and allatectomized. Starvation did not alter the cycle in rates of juvenile hormone synthesis of sham-operated animals.Decapitation of ovariectomized animals resulted in no cycle in rates of juvenile hormone synthesis by implanted adult corpora allata; however, implantation of an ovary along with the corpora allata into decapitated, ovariectomized hosts resulted in a cycle of juvenile hormone synthesis. In control animals, which retained their heads but were starved and allatectomized as well as ovariectomized, the implanted corpora allata showed a cycle of juvenile hormone synthesis only when implanted with an ovary. The maximal rates of juvenile hormone synthesis by the corpora allata in both experimental and control conditions were lower than normal, likely due to the repeated trauma of surgery. However, at no time from eclosion to the end of the first gonotrophic period was the brain necessary for the cyclic response of the corpora allata to the presence of the ovary.     

Effects of temperature changes on thymidine kinase in heat- and cold-sensitive cell-cycle mutants and ‘wild-type’ murine P-815 cells

Two heat-sensitive (arrested in G1 at 39.5°C) and two cold-sensitive (arrested in G1 at 33°C) clonal cell-cycle mutants that had been isolated from the same clone (K 21), of the murine mastocytoma P-815 cell line, were tested for thymidine kinase (EC 2.7.1.21) activity. After shift of mutant cells to the nonpermissive temperature, thymidine kinase activity decreased, and minimal levels (i.e., less than 3% of those observed for ‘wild-type’ K 21 cells at the respective temperature) were attained within 16 h in heat-sensitive and after 3–4 days in cold-sensitive mutants, which is in good agreement with kinetics of accumulation of heat-sensitive and cold-sensitive cells in G1 phase. After return of arrested mutant cells to the permissive temperature, thymidine kinase of heat-sensitive cells increased rapidly and in parallel with entry of cells into the S phase. In cultures of cold-sensitive cells, however, initiation of DNA synthesis preceded the increase of thymidine kinase activity by approx. one cell-cycle time. Thymidine kinase activities in revertants of the heat-sensitive and cold-sensitive mutants were similar to those of ‘wild-type’ cells. In ‘wild-type’ K 21 cells incubated at 39.5°C, thymidine kinase activity was approx. 30% of that at 33°C. This difference is attributable, at least in part, to a higher rate of inactivation of the enzyme at 39.5°C, as determined in cultures incubated with cycloheximide. The rapid increase of thymidine kinase activity that occurred after shift of K 21 cells and of arrested heat-sensitive mutant cells from 39.5°C to 33°C was inhibited by actinomycin D and cycloheximide.     

In vivo interactions of acrylonitrile with macromolecules in rats

The irreversible binding of [2,3-14C]acrylonitrile (VCN) to proteins, RNA and DNA of various tissues of male Sprague-Dawley rats after a single oral dose of 46.5 mg/kg (0.5 LD50) has been studied. Proteins were isolated by chloroform-isoamyl alcohol-phenol extraction. RNA and DNA were separated by hydroxyapatite chromatography. Binding of VCN to proteins was extensive and was time dependent. Radioactivity in nucleic acids was registered in the liver and the target organs, stomach and brain. DNA alkylation, which increased by time, was significantly higher in the target organs, brain and stomach (119 and 81 pmol/mg, respectively, at 24 h) than that in the liver. The covalent binding indices for the liver, stomach and brain at 24 h after dosing were, 5.9, 51.9 and 65.3, respectively. These results suggest that VCN is able to act as a multipotent carcinogen by alkylation of DNA in the extrahepatic target tissues, stomach and brain.     

Localization of Glyoxylate Cycle Enzymes in Glyoxysomes in Euglena*

SYNOPSIS. We demonstrated previously microbodies in Euglena gracilis grown in the dark on 2-carbon substrates. We have now established in Euglena the particulate nature of enzymes known in other organisms to be localized in microbodies (glyoxysomes and leaf peroxisomes). On a linear sucrose gradient the glyoxylate cycle enzymes band together at a nigner equilibrium density (1.20 g/cm3) than mitochondrial marker enzymes (1.17 g/cm3), establishing the existence in Euglena of glyoxysomes similar to those of higher plants. Glyoxylate (hydroxypyruvate) reductase and, under certain conditions, also glycolate dehydrogenase co-band with the glyoxylate cycle enzymes, suggesting that Euglena glyoxysomes, like those of higher plants, may contain peroxisomal-type enzymes. Catalase, an enzyme characteristic of microbodies from a variety of sources, was not detected in Euglena.     

Observations on the Endogenous Stages of Eimeria confusa Joseph, 1969 from the Grey Squirrel Sciurus carolinensis*

SYNOPSIS. Stages in the endogenous cycle of Eimeria confusa from the grey squirrel, Sciurus carolinensis, are described from mixed infections with another species, Eimeria lancasterensis. All corresponding stages were markedly different in the 2 species. In E. confusa infections, the parasites were located below the host cell nuclei of the epithelial cells of the villi of the jejunum and ileum. Mature schizonts were ellipsoidal, averaged 20.9 × 18.6 μm and had 18–30 merozoites. The mature microgamonts measured 34.3 × 24.7 μm and had hundreds of microgametes. Mature macrogametes were ovoid, averaged 31.3 × 25.6 μm, and contained 2 kinds of plastic granules.     

Organic Acids of Ditylenchus triformis and Turbatrix aceti

Pyruvic acid, lactic acid and several tricarboxylic acid cycle acids were extracted from Ditylenchus triformis and Turbatrix aceti and identified. Fumaric acid was predominant in both nematodes. Small amounts o f malic and α-ketoglutaric acids and intermediate quantities o f lactic, citric, succinic, and pyruvic acids occurred in D. triformis. In T. aceti citric, lactic, and α-ketoglutaric acids were less abundant than succinic, malic and pyruvic acids. Only traces of aconitic and oxalacetic acids occurred in both nematodes. All the organic acids detected accounted for only about one per cent of the dry weight of nematodes o f the two species.     

Biochemical and physiological studies of certain ticks (Ixodoidea): specific gravity of hemolymph and coxal and gut fluids of Argas (Persicargas) persicus and Argas (Persicargas) arboreus (Argasidae)

Specific gravity (sp. gr.) of cell-free hemolymph and gut and coxal fluids was determined at different states of the gonotrophic cycle (unfed + 15 days, engorgement day before and after coxal fluid emission, engorgement + 1 day, oviposition day, and oviposition completion + 1 day) of female Argas (Persicargas) persicus and A. (P.) aboreus (Argasidae). The patterns of hemolymph and gut fluid sp. gr. change differed from each other during the gonotrophic cycle, but both patterns were similar in the 2 Argas species. Hemolymph sp. gr. decreased to a minimum one day after feeding (1.0085 and 1.0081 for persicus and arboreus, respectively), and increased through oviposition to a maximum on oviposition + 1 day (1.0187 and 1.0221). Minimum gut fluid sp. gr. occurred on engorgement day before coxal fluid emission (1.0565 and 1.0697). Afterward, gut fluid sp. gr. increased to a maximum on engorgement day + 1 for persicus (1.1089) and on oviposition day for arboreus (1.0973), and then decreased during oviposition in both species. In each tested state of each species, the sp. gr. was consistently higher in gut fluid than in hemolymph. In each species, coxal fluid and hemolymph sp. gr. were the same on engorgement day.