Antimicrobial defense mechanisms in the horseshoe crab, Limulus polyphemus: preliminary observations with heat-derived extracts of Limulus amoebocyte lysate.

Heat-derived (60°C) extracts of Limulus amoebocyte lysate (LAL) were found to contain potent “broad-spectrum” antimicrobial activity. Additional heating of the LAL extracts to 100°C for 30 min completely inactivated the antimicrobial activity and served as a control. Antimicrobial activity was observed over a temperature range of 0° to 37°C (higher temperatures not tested) with greatest activity at 37°C. Antimicrobial activity of LAL extracts was variable when tested against Gram-negative bacteria of the family Enterobacteriaceae. A twofold concentration of the extracts resulted in a significant decrease in antimicrobial effectiveness. Dialysis of single- and double-strength LAL extracts against deionized water produced a marked and significant enhancement of antimicrobial activity against both resistant and sensitive species, confirming the presence of a dialyzable inhibitor(s). Dialyzed LAL extracts were active against 13 of 14 species of Enterobacteriaceae tested. Two strains of Pseudomonas aeruginosa were susceptible as were two of three Gram-positive cocci tested. Highly sensitive bacterial species were rapidly killed with a greater than 90% reduction in viable counts occurring within the first 30 min of reaction time. Dialyzed LAL extracts also possessed considerable antifungal activity. The role of the Limulus polyphemus amoebocyte in defense against microbial invasion and dissemination is discussed.     

Rat and human embryo and post-natal sera contain a potent endogenous competitor of estrogen-rat alpha-fetoprotein interactions

A highly active inhibitor of the binding of estrone and estradiol-17β to rat alpha-fetoprotein is demonstrated for the first time in embryo, immature and adult rat sera as well as in fetal and adult human sera. The competitive character and the narrow specificity of this inhibition effect is shown. The major compound responsible for this activity is isolated by successive column Sephadex LH₂₀ and thin layer chromatography : it is characterized as a nonpolar, nonphenolic, dialysable and thermostable substance, unreactive towards anti-estrone and anti-estradiol-17β anti-bodies. The possible biological role of an endogenous non-estrogen ligand of rodent fetoproteins is discussed.     

Isolation and characterization of fluorescent Pseudomonas associated with the roots of rice and banana grown in Sri Lanka

Bacterial populations in different parts of the rhizosphere of rice and banana in Sri lanka were examined. On rice, the number of aerobic bacteria and the population of fluorescent bacteria were higher in the rhizoplane as compared to the exorhizosphere. However, the opposite was observed with banana. Percentage of fluorescent bacteria was significantly higher on banana (10.8%) than on rice from the wet and dry zones of Sri Lanka (4.3% and 2.7%, respectively). In the endorhizosphere fraction of rice, bacterial populations were very low. Fluorescent bacteria were absent.Based on 33 phenotypical tests, 89 fluorescent isolates were grouped into 5 clusters. The three major clusters covered the isolates belonging to the Pseudomonas fluorescens-putida group, whereas the remaining small clusters contained other UV-fluorescent bacteria. SDS-PAGE of total cell proteins enabled classification of the isolates into one of 12 different protein-polymorphic types. Only a partial correlation was found between the latter classification and the phenotypical one. Cyanogenesis was observed with strains of P. fluorescens only. Isolates P. fluorescens RW9S1 and P. cepacia RW5P1 displayed a potent antagonism against several fungi.     

Light and ethylenediamine tetraacetic acid mediated differential effects of ammonium on nitrate reductase activity in maize seedlings

Abstract Effect of ammonium on in vivo activity of nitrate reductase in roots, shoots and leaves of maize (Zea mays L.) seedlings was studied in relation to light/dark conditions and EDTA supply. Supply of 5 mM (NH₄)₂SO₄ increased the steady state level of enzyme only in leaves and in light, while it had no effect in roots and shoots and in the dark. The substrate induction of enzyme was also little affected by 1 to 10 mM (NH₄)₂SO₄ in roots and shoots. In the leaves the activity in the dark was either inhibited (minus EDTA) or stimulated (plus EDTA) by 5 to 10 mM (NH₄)₂SO₄. The activity was stimulated in the light also in the presence of EDTA at higher concentrations of ammonium. When different concentrations of ammonium were supplied without any exogenous nitrate in the light, the enzyme activity increased at low concentration and was either inhibited or unaffected at higher concentrations depending upon the tissue used. Supply of EDTA with ammonium modified its effect to some extent. It is suggested that the effect of ammonium on nitrate reductase activity depends upon the tissue used and the effective concentration of the ammonium.     

Nitrofuran-Reducing Enzymes of Euglena*

SYNOPSIS. Euglena gracilis strain Z, green, dark-grown, and “bleached”with N-methyl-N-nitro-N-nitrosoguanidine, was found to contain 2 soluble enzymes which reduce nitrofurans. A small amount of activity was demonstrated also in a particulate fraction of sonic extracts, but none in isolated chloroplasts. The reduction of 5 nitrofurans, having widely differing bleaching activities, by each of the 2 enzymes was examined.     

Emergence activity at hibernacula differs among four bat species affected by white‐nose syndrome

Prior to the introduction of white‐nose syndrome (WNS) to North America, temperate bats were thought to remain within hibernacula throughout most of the winter. However, recent research has shown that bats in the southeastern United States emerge regularly from hibernation and are active on the landscape, regardless of their WNS status. The relationship between winter activity and susceptibility to WNS has yet to be explored but warrants attention, as it may enable managers to implement targeted management for WNS‐affected species. We investigated this relationship by implanting 1346 passive integrated transponder (PIT) tags in four species that vary in their susceptibility to WNS. Based on PIT‐tag detections, three species entered hibernation from late October to early November. Bats were active at hibernacula entrances on days when midpoint temperatures ranged from −1.94 to 22.78°C (mean midpoint temperature = 8.70 ± 0.33°C). Eastern small‐footed bats (Myotis leibii), a species with low susceptibility to WNS, were active throughout winter, with a significant decrease in activity in mid‐hibernation (December 16 to February 15). Tricolored bats (Perimyotis subflavus), a species that is highly susceptible to WNS, exhibited an increase in activity beginning in mid‐hibernation and extending through late hibernation (February 16 to March 31). Indiana bats (M. sodalis), a species determined to have a medium–high susceptibility to WNS, remained on the landscape into early hibernation (November 1 to December 15), after which we did not record any again until the latter portion of mid‐hibernation. Finally, gray bats (M. grisescens), another species with low susceptibility to WNS, maintained low but regular levels of activity throughout winter. Given these results, we determined that emergence activity from hibernacula during winter is highly variable among bat species and our data will assist wildlife managers to make informed decisions regarding the timing of implementation of species‐specific conservation actions.     

Antioxidant Activity of New Sulphur- and Selenium-Containing Analogues of Potassium Phenosan against H2O2-Induced Cytotoxicity in Tumour Cells

Among known phenolic antioxidants, the overwhelming majority of compounds have lipophilic properties and the number of known water-soluble compounds is very small. The list of hydrophilic phenolic antioxidants can be expanded via the synthesis of a structurally related series of polyfunctional compounds for further research on their biological activity in vitro. New sulphur- and selenium-containing analogues of antioxidant potassium phenosan were synthesised. In vitro cytotoxicity and cytostaticity as well as antioxidant activity against H₂O₂-induced cytotoxicity to human cell lines (HepG2, Hep-2 and MCF-7) were investigated by high-content analysis. A selenium-containing analogue showed higher biological activity than did a sulphur-containing one. As compared to the activity of potassium phenosan, the selenium-containing analogue had a cell line-dependent antioxidant effect against H₂O₂-induced cytotoxicity: comparable in HepG2 cells and greater in Hep-2 cells. The selenium-containing analogue significantly increased the death of MCF-7 cells at concentrations above 50 µM. The sulphur-containing analogue has lower biological activity as compared to potassium phenosan and the selenium-containing analogue.     

Design,synthesis, and biological evaluation of novel carbazole derivatives as potent DNMT1 inhibitors with reasonable PK properties

The DNA methyltransferases (DNMTs) were found in mammals to maintain DNA methylation. Among them, DNMT1 was the first identified, and it is an attractive target for tumour chemotherapy. DC_05 and DC_517 have been reported in our previous work, which is non-nucleoside DNMT1 inhibitor with low micromolar IC₅₀ values and significant selectivity towards other S-adenosyl-_L-methionine (SAM)-dependent protein methyltransferases. In this study, through a process of similarity-based analog searching, a series of DNMT1 inhibitors were designed, synthesized, and evaluated as anticancer agents. SAR studies were conducted based on enzymatic assays. And most of the compounds showed strong inhibitory activity on human DNMT1, especially WK-23 displayed a good inhibitory effect on human DNMT1 with an IC₅₀ value of 5.0 µM. Importantly, the pharmacokinetic (PK) profile of WK-23 was obtained with quite satisfying oral bioavailability and elimination half-life. Taken together, WK-23 is worth developing as DNMT1-selective therapy for the treatment of malignant tumour.     

火针层孔菌（桑黄）粗多糖对荷瘤小鼠的免疫调节研究

研究了火针层孔菌不同粗多糖对荷瘤小鼠的免疫调节作用。荷瘤小鼠随机分为四组:胞外粗多糖组、菌丝体粗多糖组、子实体粗多糖组和生理盐水阴性对照组。给药10d后测定荷瘤小鼠脾NK细胞活性和脾淋巴细胞的增殖率。结果显示火针层孔菌粗多糖组与阴性对照组相比能够提高小鼠脾NK细胞活性和脾淋巴细胞的增殖率(P<0.01),表明火针层孔菌液体发酵粗多糖和子实体粗多糖对荷瘤小鼠免疫功能均有调节作用。