Effect of cobalt-60 irradiation on the infectivity of Paragonimus westermani metacercariae.

A study was made to observe the effect of cobalt-60 irradiation on the viability of Paragonimus westermani metacercariae in Sinopotamon chekiangense crabs. The crabs were collected in mountain regions of the Zhejiang Province of China in which paragonimiasis is endemic. Adult cats and albino mice were infected with metacercariae irradiated at different doses. Dissection of the host animals was conducted 90 or 30 days, respectively, after infection for recovery of lung flukes. Anti-metacercariae antibody in infected mice was measured by enzyme-linked immunosorbent assay (ELISA). Results showed that metacercariae were unable to grow into adult worms in cats after exposure to gamma irradiation at a dose of 0.10 kGray. However, a small number of metacercariae exposed to a dose of 2.0 kGray excysted and survived in 1 mouse for 30 days. No worm was recovered from mice when the metacercariae were irradiated at a dose of 2.5 kGray. Seropositive results by ELISA were obtained when the mice were infected with metacercariae irradiated at doses ranging from 2.0 to 3.5 kGray.     

Synthesis and structure-activity study of myxoma virus growth factor

Myxoma virus growth factor (MGF) is an 85-residue peptide derived from the gene product of a DNA tumor virus that infects rabbits. The carboxyl domain of MGF possesses about 40% sequence homology with the epidermal growth factor (EGF). This EGF-like domain covering residues 30-83 was synthesized and found to possess putative activities of EGF. It was, however, about 200-fold less active than EGF in the competitive binding of EGF receptor in A431 cells and the stimulation of [3H]-thymidine uptake in NRK 49F cells. MGF(30-83) is a basic and a hydrophobic peptide rich in beta-sheet structure. These features in MGF tend to promote aggregation, leading to precipitation even in strongly denaturing solutions. Thus, the refolding of MGF was achieved with difficulty and resulted in low yield. To increase the synthetic yield of MGF(30-83), a cluster of acidic amino acids was added to the NH2-terminus of MGF(30-83). This approach was found to be effective in minimizing the refolding difficulties and allowed accessibility to the synthesis of analogues in this class of compounds. The relationships of structure and function of MGF were studied by using analogues with point substitution by the corresponding D-amino acid or by Ala at position 44 or 52 and analogues with deletion of basic residues from the amino terminus. Modifications of both the receptor contact and the structural residues greatly reduced the potency of MGF(30-83), and the overall result correlated well with the known structure-activity of the EGF family.     

Effect of intermolecular orientation upon proton transfer within a polarizable medium.

Ab initio calculations are used to investigate the proton transfer process in bacteriorhodopsin. HN = CH2 serves as a small prototype of the Schiff base while HCOO- models its carboxylate-containing counterion and HO- the hydroxyl group of water of tyrosine, leading to the HCOO-..H+..NHCH2 and HO-..H+..NHCH2 complexes. In isolation, both complexes prefer a neutral pair configuration wherein the central proton is associated with the anion. However, the Schiff base may be protonated in the former complex, producing the HCOO-..+HNHCH2 ion pair, when there is a high degree of dielectric coupling with an external polarizable medium. Within a range of intermediate level coupling, the equilibrium position of the proton (on either the carboxylate or Schiff base) can be switched by suitable changes in the intermolecular angle. pK shift resulting from a 60 degrees reorientation are calculated to be some 5-12 pK U within the coupling range where proton transfers are possible. The energy barrier to proton transfer reinforces the ability of changes in angle and dielectric coupling to induce a proton transfer.     

中国大麦叶绿体DNA和核糖体RNA基因限制性片段长度多型性

本文报道了我们对我国不同大麦区80份大麦品种叶绿体DNA和核糖体RNA基因限制性片段长度多型性的研究。结果表明:rDNA间隔序列长度存在丰富的多样性,80份材料中出现了8种长度变异炎型共组成8种表现型。长度变异类型及其表现型在地理分布上存在着明显的区域性。推测这种分布上的地区性与植物对环境的适应性有关。所用的两个叶绿体DNA克隆片段未检测到限制性片段长度多型性,说明栽培大麦叶绿体DNA变异程度低。     

Regulation of excitation energy distribution in Photosystem-II fragments by magnesium ions

Fluorescence characteristics of Photosystem-II subchloroplasts (TSF-II and TSF-IIa) fractionated by Triton X-100 treatment were studied in relation to cation-induced regulation of excitation-energy distribution within subchloroplast fragments. Absorption spectra and fluorescence-emission spectra at 77 K showed that TSF-II contains the light-harvesting chlorophyll-protein complex in addition to the reaction-center complex, which is present alone in TSF-IIa.Mg²⁺ increased the ratio of F_695nm to F_685nm in the fluorescence-emission spectrum of TSF-II particles at 77 K, but had no effect on TSF-IIa particles. Mg²⁺ also induced a quenching of chlorophyll fluorescence at room temperature in TSF-II, an effect that was insensitive to the presence of DCMU. The DCMU-insensitive fluorescence quenching was not observed in the TSF-IIa preparation. These results suggest an existence of cation-induced regulation of excitation-energy transfer in TSF-II preparations. Presence of antenna chlorophyll molecules alone does not seem to be sufficient for observing energytransfer regulation by cations in Photosystem-II preparations.     

Frequent Unanticipated Alleles of lethal giant larvae in Drosophila Second Chromosome Stocks

Forty years ago, a high frequency of lethal giant larvae (lgl) alleles in wild populations of Drosophila melanogaster was reported. This locus has been intensively studied for its roles in epithelial polarity, asymmetric neural divisions, and restriction of tissue proliferation. Here, we identify a high frequency of lgl alleles in the Bloomington second chromosome deficiency kit and the University of California at Los Angeles Bruinfly FRT40A-lethal P collection. These unrecognized aberrations confound the use of these workhorse collections for phenotypic screening or genetic mapping. In addition, we determined that independent alleles of insensitive, reported to affect asymmetric cell divisions during sensory organ development, carry lgl deletions that are responsible for the observed phenotypes. Taken together, these results encourage the routine testing of second chromosome stocks for second-site alleles of lgl.     

Circular RNA AFF4 modulates osteogenic differentiation in BM-MSCs by activating SMAD1/5 pathway through miR-135a-5p/FNDC5/Irisin axis

Bone marrow-derived mesenchymal stem cells (BM-MSCs), the common progenitor cells of adipocytes and osteoblasts, have been recognized as the key mediator during bone formation. Herein, our study aim to investigate molecular mechanisms underlying circular RNA (circRNA) AFF4 (circ_AFF4)-regulated BM-MSCs osteogenesis. BM-MSCs were characterized by FACS, ARS, and ALP staining. Expression patterns of circ_AFF4, miR-135a-5p, FNDC5/Irisin, SMAD1/5, and osteogenesis markers, including ALP, BMP4, RUNX2, Spp1, and Colla1 were detected by qRT-PCR, western blot, or immunofluorescence staining, respectively. Interactions between circ_AFF4 and miR-135a-5p, FNDC5, and miR-135a-5p were analyzed using web tools including TargetScan, miRanda, and miRDB, and further confirmed by luciferase reporter assay and RNA pull-down. Complex formation between Irisin and Integrin αV was verified by Co-immunoprecipitation. To further verify the functional role of circ_AFF4 in vivo during bone formation, we conducted animal experiments harboring circ_AFF4 knockdown, and born samples were evaluated by immunohistochemistry, hematoxylin and eosin, and Masson staining. Circ_AFF4 was upregulated upon osteogenic differentiation induction in BM-MSCs, and miR-135a-5p expression declined as differentiation proceeds. Circ_AFF4 knockdown significantly inhibited osteogenesis potential in BM-MSCs. Circ_AFF4 stimulated FNDC5/Irisin expression through complementary binding to its downstream target molecule miR-135a-5p. Irisin formed an intermolecular complex with Integrin αV and activated the SMAD1/5 pathway during osteogenic differentiation. Our work revealed that circ_AFF4, acting as a sponge of miR-135a-5p, triggers the promotion of FNDC5/Irisin via activating the SMAD1/5 pathway to induce osteogenic differentiation in BM-MSCs. These findings gained a deeper insight into the circRNA-miRNA regulatory system in the bone marrow microenvironment and may improve our understanding of bone formation-related diseases at physiological and pathological levels.Subject terms: Stem cells, Diseases     

Study of general toxic properties and side effects of polymethylsiloxane and gentamicin immobilized on it

A long-acting dosage form for local use of gentamicin immobilized on polymethylsiloxane, a silicon organic adsorbent was developed. It combined the antimicrobial spectrum of gentamicin and the local sorption-detoxication action of the matrix. In acute and chronic experiments on 5 species of laboratory animals it was shown that polymethylsiloxane had no general toxic action on the animals, no damaging action on their internal organs, did not affect their functions and the state of the biological fluids, had no pyrogenic or allergenic effect. During gentamicin immobilization on polymethylsiloxane there was observed no increase in the antibiotic toxicity as compared to the nonimmobilized dosage form of the antibiotic. Further study of the immobilized dosage form of gentamicin is advisable.