IgG3 production in MRL/lpr mice is responsible for development of lupus nephritis

MRL/Mp-lpr/lpr (MRL/lpr) mice spontaneously develop lethal glomerulonephritis (GN) similar to human lupus nephritis, associated with the expression of lymphoproliferation gene lpr. To examine whether a particular IgG subclass is responsible for development of GN in these mice, first quantitative analysis of IgG subclasses in serum and in kidney eluates was performed. Although IgG2a was the dominant subclass in serum throughout the lifespan of mice, the IgG3 level in kidney eluates was three times higher than that of IgG2a at the 16 wk of age, which is the time of onset of development of severe GN. In sera of the 12-wk-old mice, half of the IgG3 was in immune complex form, whereas IgG2a in this form was only 17% of the total amount. Second, cyclosporin A, which ameliorates GN in MRL/lpr mice despite autoantibody production, was found to reduce serum IgG3 and mRNA levels, associated with the revision of cationic shift of the serum IgG3 spectrotype seen in isoelectric focusing. Third, among the hybrid mice with non-autoimmune-prone C3H/HeJ-lpr/lpr (C3H/lpr) mice, MRL/lpr x (MRL/lpr x C3H/lpr) F1, in which the genetic background for GN is likely segregated, the mRNA level for IgG3 correlated well with the degree of glomerular lesion. These findings indicate that production of IgG3 in MRL/lpr mice is one of the major factors responsible for development of GN in these mice, and that this is due to the genetic background of the MRL strain.     

Comparing the effects of rapid evolution and phenotypic plasticity on predator-prey dynamics

Ecologists have increasingly focused on how rapid adaptive trait changes can affect population dynamics. Rapid adaptation can result from either rapid evolution or phenotypic plasticity, but their effects on population dynamics are seldom compared directly. Here we examine theoretically the effects of rapid evolution and phenotypic plasticity of antipredatory defense on predator-prey dynamics. Our analyses reveal that phenotypic plasticity tends to stabilize population dynamics more strongly than rapid evolution. It is therefore important to know the mechanism by which phenotypic variation is generated for predicting the dynamics of rapidly adapting populations. We next examine an advantage of a phenotypically plastic prey genotype over the polymorphism of specialist prey genotypes. Numerical analyses reveal that the plastic genotype, if there is a small cost for maintaining it, cannot coexist with the pairs of specialist counterparts unless the system has a limit cycle. Furthermore, for the plastic genotype to replace specialist genotypes, a forced environmental fluctuation is critical in a broad parameter range. When these results are combined, the plastic genotype enjoys an advantage with population oscillations, but plasticity tends to lose its advantage by stabilizing the oscillations. This dilemma leads to an interesting intermittent limit cycle with the changing frequency of phenotypic plasticity.     

Two novel steroidal alkaloid glycosides from the seeds of Lycium barbarum

Two novel steroidal alkaloid glycosides, lycioside A (1) and lycioside B (2) were isolated from the seeds of Lycium barbarum. Their structures were determined by various spectroscopic analyses. Compounds 1 and 2 showed inhibitory activities with the IC(50) values of 75.3 and 72.8 μM against rat intestinal sucrase, and 63.4 and 59.1 μM against rat intestinal maltase.     

Crucial role of the small GTPase ARF6 in hepatic cord formation during liver development

The mammalian small GTPase ADP-ribosylation factor 6 (ARF6) plays important roles in a wide variety of cellular events, including endocytosis, actin cytoskeletal reorganization, and phosphoinositide metabolism. However, physiological functions for ARF6 have not previously been examined. Here, we described the consequence of ARF6 ablation in mice, which manifests most obviously in the context of liver development. Livers from ARF6-/- embryos are smaller and exhibit hypocellularity, due to the onset of midgestational liver cell apoptosis. Preceding the apoptosis, however, defective hepatic cord formation is observed; the liver cells migrate abnormally upon exiting the primordial hepatic epithelial sheet and clump rather than becoming dispersed. Consistent with this observation, the ability of hepatocyte growth factor/scatter factor (HGF) to induce hepatic cord-like structures from ARF6-/- fetal hepatocytes cultured in vitro in collagen gel matrix is impaired. Finally, we show that endogenous ARF6 in wild-type fetal hepatocytes is activated in response to HGF stimulation. These results provide evidence that ARF6 is an essential component in the signaling pathway coupling HGF signaling to hepatic cord formation.     

Possible involvement of ethylene-activated {beta}-cyanoalanine synthase in the regulation of cocklebur seed germination

A possible involvement of ß-cyanoalanine synthase(CAS: EC 4.4.1.9 [EC] ) in germination processes of seeds was demonstratedusing pre-soaked upper seeds of cocklebur (Xanthium pennsylvanicumWallr.). Pretreatment in anoxia not only with KCN but also cysteine,as the substrates for CAS, stimulated the subsequent germinationof cocklebur seeds in air. However, the effect of cysteine wasmanifested even in air when applied together with C₂H₄, andits effect was further enhanced in combination with KCN. Thegermination-stimulating effect of KCN was intensified by C₂H₄only when 0₂ was present. In contrast, serine, another substrateof CAS, was effective in air only when combined with C₂H₄ and/orKCN. The addition of cysteine greatly reduced the cyanogenicglycoside content of seeds, but increased HCN evolution. Onthe other hand, glutathione did not have any effect on cockleburseed germination, HCN evolution or bound cyanogen content, suggestingthat cysteine is not acting as a reducing reagent. It is suggestedthat CAS regulates the process of cocklebur seed germinationby the dual action of enlarging the pool of amino acids andsupplying sulphydryl bases, the latter being more determinatelyimportant. Serine is effective only via the former action, whilecysteine would act via both. Key words: Cyanide, cyanogenic glycoside, ß-cyanoalanine synthase, seed germination, Xanthium pennsylvanicum     

In vivo conformation of mitochondrial DNA revealed by pulsed-field gel electrophoresis in the true slime mold, Physarum polycephalum.

Pulsed-field gel electrophoresis (PFGE) was used to examine the in vivo and in vitro conformations of Physarum polycephalum mitochondrial DNA (mtDNA). We used plugs containing isolated mitochondria, isolated mitochondrial nucleoids (mt-nuclei), and isolated mtDNA, in addition to whole cells. The mtDNA contained in the myxamoebae, plasmodia, isolated mitochondria, and isolated mt-nuclei was circular, but most of the isolated mtDNA had been site-specifically fragmented and linearized during DNA preparation and storage under low ionic strength conditions. Restriction mapping of Physarum mtDNA by the direct digestion of the isolated mt-nuclei from two different strains, DP89 x AI16 and KM88 x AI16, resulted in the circular form. A linear mitochondrial plasmid, mF, is known to promote mitochondrial fusion and integration of itself into the mtDNA in Physarum. Linearization of mtDNA by the integration of the mF plasmid was demonstrated when we used PFGE to analyze isolated mitochondria from the plasmodial strain DP89 x NG7 carrying the mF plasmid (mF+). The PFGE system can be used not only to determine whether the form of mtDNA is linear or circular but also to analyze the dynamic conformational changes of mtDNA.     

Efficient and rapid purification of drug- and gene-carrying bio-nanocapsules, hepatitis B virus surface antigen L particles, from Saccharomyces cerevisiae

Bio-nanocapsules (BNCs) are hollow particles (approx. 50 nm diameter) consisting of hepatitis B virus surface antigen (HBsAg) large (L, pre-S1+pre-S2+S) proteins embedded in a unilamellar liposome, sharing the same transmembrane S region with an immunogen of hepatitis B vaccine (i.e., HBsAg small (S) protein particle). BNCs can incorporate drugs and genes into the hollow space and systemic administration of the BNCs can deliver the products to human liver via the human hepatocyte-specific receptor within the pre-S (pre-S1+pre-S2) region displayed on BNC's surface. Thus, BNCs are expected to offer efficient and safe non-viral nanocarriers to deliver human liver-specific genes and drugs. To date, BNCs have been purified from the crude extract of BNC-overexpressing yeast cells by fractionation with polyethylene glycol followed by one CsCl equilibrium and two sucrose density gradient ultracentrifugation steps. However, the process was inefficient in terms of yield and time, and was not suitable for mass production because of the ultracentrifugation step. Furthermore, trace contamination with yeast-derived proteinases degraded the pre-S region, which is indispensable for liver-targeting, during long-term storage. In this study, we developed a new purification method involving heat treatment and sulfated cellulofine column chromatography to facilitate rapid purification, completely remove proteinases, and enable mass production. In addition, the BNCs were functional for at least 14 months after lyophilization with 5% (w/v) sucrose as an excipient. This new process will significantly contribute to the development of forthcoming BNC-based nanomedicines as well as hepatitis B vaccines.