Identification of a developmentally regulated sialidase inEimeria tenella that is immunologically related to theTrypanosoma cruzi enzyme

Sporozoites and merozoites of three species ofEimeria, E. tenella, E. maxima, andE. necatrix, that cause diarrhea in chickens worldwide, were examined for their expression of sialidase (SA) activity. The enzyme was found in three species, and the activity of merozoites was 10–20 times higher than that of sporozoites. The enzyme was resistant to degradation by proteases that are normally present in the intestine, a site inhabited by theEimeria parasites, and it was relatively resistant to heat, with optimum activity being at 40°C, which is within the range of temperature in the chicken intestine (40–43°C).E. tenella SA was immuniprecipitated by monoclonal and polyclonal antibodies raised against theTrypanosoma cruzi SA (TCSA), and enzyme activity was neutralized by these antibodies.E. tenella SA was identified by immunoblots as a doublet of molecular weight 190 000 and 180 000 using, as a probe, anti-TCSA antibodies and antibodies against a synthetic peptide (TR) derived from the long tandem repeat domain of TCSA. Binding of the monoclonal and polyclonal antibodies toE. tenella was completely blocked by TR, but not by an irrelevant peptide (BR). Therefore,E. tenella expresses a developmentally regulated SA that is structurally related to theT. cruzi counterpart. Because of the high SA activity in merozoites, and by analogy with other SA-producing microbes that inhabit mucin-rich epithelia, we suggest that theEimeria SA plays a role in desialylating intestinal mucins to reduce viscosity of the local environment and thereby facilitate parasite migration. The enzyme could also play a role in host cell-parasite interaction.Abbreviations SA sialidase (neuraminidase) - Neu5Ac N-acetylneuraminic acid - 4-MU-Neu5Ac 2-(4-methylumbelliferyl)--N-acetyl-d-neuraminic acid - BSA bovine serum albumin - PBS phosphate buffered saline - PMSF phenylmethylsulfonyl fluoride - PNA peanut agglutinin - Ab antibody - TCN-2 monoclonal antibody toT. cruzi sialidase, anti-Ars, monoclonal antibody top-azophenylarsonate - TCSA Trypanosoma cruzi sialidase     

大鼠肝癌中α_2-巨球蛋白等几种分泌性蛋白基因表达的变化

用Northern blot方法对二乙基亚硝胺所诱发的大鼠肝癌中内源性蛋白酶抑制因子α_2-巨球蛋白(α_2-M)、非特异性免疫抑制剂α_1-酸性糖蛋白(α_1-AGP)及雄性激素正调控的α-2u球蛋白(α-2u)三种分泌性蛋白基因表达情况进行了分析。结果表明在大部分(14/16)肝癌样品中α_2-M RNA水平显著降低;而α_1-AGP RNA水平显著高于正常对照水平;α-2u RNA水平明显下降,但在某些雄性大鼠肝癌样品中该基因却有一定程度的表达。这些结果说明,一些肿瘤宿主血浆中α_2-M水平的显著下降及α_1-AGP水平的明显升高分别是由于基因表达活性的下降及升高所致。α-2u基因表达的异常提示,在癌变过程中机体的内分泌功能发生了某些变化。     

Effects of media composition on substrate removal by pure and mixed bacterial cultures

Continuous culture experiments with identical experimental designs were run with a mixed microbial community of activated sludge origin and an axenic bacterial culture derived from it. Each culture received 2-chlorophenol (2-CP) at a concentration of 160 mg/L as COD and L-lysine at a concentration of 65 mg/L as COD. A factorial experimental design was employed with dilution rate and media composition as the two controlled variables. Three dilution rates were studied: 0.015, 0.0325, and 0.05 h^–1. Media composition was changed by adding four biogenic compounds (butyric acid, thymine, glutamic acid and lactose) in equal COD proportions at total concentrations of 0, 34, 225, and 1462 mg/L as COD. The measured variables were the effluent concentrations of 2-CP as measured by the 4-aminoantipyrene test and lysine as measured by the o-diacetylbenzene procedure. The results suggest that community structure and substrate composition play important roles in the response of a microbial community to mixed substrates. The addition of more biogenic substrates to the axenic culture had a deleterious effect on the removal of both lysine and 2-CP, although the effect was much larger on lysine removal. In contrast, additional substrates had a positive effect on the removal of 2-CP by the mixed community and much less of a negative effect on the removal of lysine. The dilution rate at which the cultures were growing had relatively little impact on the responses to the additional substrates.Abbreviations COD chemical oxygen demand - 2-CP 2-chlorophenol - DOC dissolved organic carbon - MDL method detection limit - SS suspended solids     

Infection of SARS-CoV-2 causes severe pathological changes in mouse testis

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected more than 600 million people worldwide. Several organs including lung, intestine, and brain are infected by SARS-CoV-2. It has been reported that SARS-CoV-2 receptor angiotensin-converting enzyme-2 (ACE2) is expressed in human testis. However, whether testis is also affected by SARS-CoV-2 is still unclear. In this study, we generate a human ACE2 (hACE2) transgenic mouse model in which the expression of hACE2 gene is regulated by hACE2 promoter. Sertoli and Leydig cells from hACE2 transgenic mice can be infected by SARS-CoV-2 pseudovirus in vitro, and severe pathological changes are observed after injecting the SARS-CoV-2 pseudovirus into the seminiferous tubules. Further studies reveal that Sertoli and Leydig cells from hACE2 transgenic mice are also infected by authentic SARS-CoV-2 virus in vitro. After testis interstitium injection, authentic SARS-CoV-2 viruses are first disseminated to the interstitial cells, and then detected inside the seminiferous tubules which in turn cause germ cell loss and disruption of seminiferous tubules. Our study demonstrates that testis is most likely a target of SARS-CoV-2 virus. Attention should be paid to the reproductive function in SARS-CoV-2 patients.     

EFFECTS OF HELPER PROTEINS ENCODED BY p19 AND orf1-orf2 GENES ON Cyt1Aa PROTEIN EXPRESSION IN ACRYSTALLIFEROUS STRAIN OF BACILLUS THURINGIENSIS

A series of plasmids were constructed to examine the effects of p19 and orf1‐orf2 genes from Bacillus thuringiensis on Cyt1Aa synthesis and inclusion formation. The plasmids expressed the cyt1Aa gene along with either p19 or orf1‐orf2, or each of them coordinatively with p20 in the acrystalliferous strain of B. thuringiensis subsp. israelensis 4Q7. No effect on the expression of Cyt1Aa protein was found when P19 or Orf1‐Orf2 co‐expressed with Cyt1Aa. However, when including p20 gene, the constructs with p19 or orf1‐orf2 gene produced lower yield of Cyt1Aa proteins than without p19 or orf1‐orf2 gene. Electron microscopy observation and bioassay showed that P19 and Orf1‐Orf2 have no influence on the crystal size and toxicity of Cyt1Aa protein. It is presumed that P19 and Orf1‐Orf2 might have negative effects on Cyt1Aa synthesis in B. thuringiensis.     

Inhibition by trifluoperazine of ATP synthesis and hydrolysis by particulate and soluble mitochondrial F1: Competition with H2PO 4 −

The effect of trifluoperazine (TFP) on the ATPase activity of soluble and paniculate F₁ATPase and on ATP synthesis driven by succinate oxidation in submitochondrial particles from bovine heart was studied at pH 7.4 and 8.8. At the two pH. TFP inhibited ATP hydrolysis. Inorganic phosphate protected against the inhibiting action of TFP. The results on the effect of various concentrations of phosphate in the reversal of the action of TFP on hydrolysis at pH 7.4 and 8.8 showed that H₂PO ₄ ^– is the species that competes with TFP. The effect of TFP on oxidative phosphorylation was studied at concentrations that do not produce uncoupling or affect the aerobic oxidation of succinate (<15M). TFP inhibited oxidative phosphorylation to a higher extent at pH 8.8 than at pH 7.4; this was through a diminution in theV _max, and an increase in theK _m for phosphate. Data on phosphate uptake during oxidative phosphorylation at several pH showed that H₂PO ₄ ^– is the true substrate for oxidative phosphorylation. Thus, in both synthesis and hydrolysis of ATP, TFP and H₂PO ₄ ^– interact with a common site. However, there is a difference in the sensitivity to TFP of ATP synthesis and hydrolysis; this is more noticeable at pH 8.8, i.e. ATPase activity of soluble F₁ remains at about 40% of the activity of the control in a concentration range of TFP of 40–100M, whereas in oxidative phosphorylation 14M TFP produces a 60% inhibition of phosphate uptake.     

Carbon isotope composition of N2-fixing and N-fertilized legumes along an elevational gradient

Dinitrogen-fixing legumes are frequently assumed to be less water-use efficient than plants utilizing soil mineral N, because of the high respiratory requirements for driving N₂ fixation. However, since respiration is assumed not to discriminate against ¹³C, any differences in water-use efficiency exclusively due to respiration should not be apparent in carbon isotope discrimination () values. Our objective was to determine if the source of N (N₂ fixation versus soil N) had any effect on of field-grown grain legumes grown at different elevations. Four legume species, Glycine max, Phaseolus lunatus, P. vulgaris, and Vigna unguiculata, were grown on five field sites spanning a 633 m elevational gradient on the island of Maui, Hawaii. The legumes were either inoculated with a mixture of three effective strains of rhizobia or fertilized weekly with urea at 100 kg N ha^-1 in an attempt to completely suppress symbiotic N₂-fixing activity. In 14 of 20 analyses of stover and 12 of 15 analyses of seed values were significantly higher (p=0.10) in the inoculated plants than the N-fertilized plants. Nitrogen concentrations were generally higher in the fertilized treatments than the inoculated treatments. The different values obtained depending on N-source may have implications in using as an indicator of water-use efficiency or yield potential of legumes.     

Rhizodeposition under ambient and elevated CO2 levels

As global CO₂ levels rise, can soils store more carbon and so buffer atmospheric CO₂ levels? Answering this question requires a knowledge of the rates of C inputs to soil and of CO₂ outputs via decomposition. Below-ground inputs from roots are a major component of the C flow into soils but are still poorly understood. In this article, new techniques for measuring rhizodeposition are reviewed and discussed and the need for cross-comparisons between methods is identified. One component of rhizodeposition, root exudation, is examined in more detail and evidence is presented which suggests that current estimates of exudate flow into soils are incorrect. A mechanistic mathematical model is used to explore how exudate flows might change under elevated CO₂.