Monitoring insecticide resistance and diagnostics of resistance mechanisms in the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) in China.

Myzus persicae (Sulzer) is one of the most serious agricultural pests in China, and management strategies mainly rely on insecticidal treatment. To evaluate the resistance of field populations of M. persicae to seven insecticides, we assessed the susceptibility of 11 field populations collected from eight provinces in China using leaf-dip bioassays. Toxicity assays showed that M. persicae field populations have developed several levels of resistance to each tested insecticide. For pyrethroids, the field populations have developed a high level of resistance to ß-cypermethrin and cypermethrin, while the resistance to bifenthrin is still low. The resistance ratios of field populations to imidacloprid ranged from 1.48 to 52.36, and eight populations have developed moderate to high resistance. Resistance to acetamiprid is low, and only two populations have a moderate level of resistance. Most of the field populations of M. persicae developed moderate to high resistance to methomyl and omethoate. To investigate potential resistance mechanisms, we analyzed the enzyme activity of carboxylesterases, the type of amplified esterase genes, as well as the kdr (L1014F) mutation. All of the field populations exhibited a higher esterase activity compared to the laboratory susceptible strain. An amplified FE4, as well as the L1014F mutation, were also found in all of our experimental field populations. These results provide valuable insight into the current status of insecticide resistance and will prove to be a valuable resource in designing appropriate resistance management strategies for M. persicae in China.

Differentiation of human umbilical cord mesenchymal stem cells into germ-like cells in mouse seminiferous tubules.

Our previous study demonstrated that human umbilical cord mesenchymal stem cells (HUMSCs) were capable of differentiation into germ cells in vitro. To assess this potential in vivo, HUMSCs were microinjected into the lumen of seminiferous tubules of immunocompetent mice, which were treated with busulfan to destroy endogenous spermatogenesis. Bromodeoxyuridine labeling studies demonstrated that HUMSCs survived in the tubule for at least 120 days, exhibited a round cell shape typical of proliferating or differentiating germ cells, migrated to the basement of the tubule, where proliferating spermatogonia reside and returned to the luminal compartment, where differentiating spermatids and spermatozoa reside. The migration pattern resembled that of germ cell development in vivo. Immunohistochemical and colocalization studies revealed that transplanted HUMSCs expressed the germ cell markers octamer-binding transcription factor 4, α6 integrin, C-kit and VASA, confirming the germ cell differentiation. In addition, it was observed that tubules transplanted with HUMSCs exhibited marked improvement in the histological features damaged by the chemotherapeutic busulfan, as judged by morphology and quantitative histology. Taken together, these data demonstrated the capacity of HUMSCs to form germ cells in the testes and to repair testicular tissue. These findings suggest a potential utility of HUMSCs to treat the infertility and testicular insufficiency caused by cancer therapeutics.

Differentiation of human umbilical cord Wharton's jelly-derived mesenchymal stem cells into germ-like cells in vitro.

Recent studies have demonstrated that mesenchymal stem cells could differentiate into germ cells under appropriate conditions. We sought to determine whether human umbilical cord Wharton's jelly-derived mesenchymal stem cells (HUMSCs) could form germ cells in vitro. HUMSCs were induced to differentiate into germ cells in all-trans retinoic acid, testosterone and testicular-cell-conditioned medium prepared from newborn male mouse testes. HUMSCs formed "tadpole-like" cells after induction with different reagents and showed both mRNA and protein expression of germ-cell-specific markers Oct4 (POUF5), Ckit, CD49(f) (alpha6), Stella (DDPA3), and Vasa (DDX4). Our results may provide a new route for reproductive therapy involving HUMSCs and a novel in vitro model to investigate the molecular mechanisms that regulate the development of the mammalian germ lineage.

Triterpenoid saponins from the roots of Clematis chinensis Osbeck.

A new triterpenoid saponin named clematichinenoside AR(2), along with the six known compounds, was isolated and characterized from Clematis chinensis Osbeck (Ranunculaceae), a commonly used traditional Chinese medicine with anti-inflammatory and anti-rheumatoid activities. The structure of the new saponin was elucidated as 3-O-beta-[(O-alpha-L-rhamnopyranosyl-(1 --> 6)-O-beta-D-glucopyranosyl-(1 --> 4)-O-beta-D-glucopyranosyl-(1 --> 4)-O-beta-D-ribopyranosyl-(1 --> 3)-O-alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-L-arabinopyranosyl)oxy]olean-12-en-21alpha-hydroxy-28-oic acid-O-alpha-L-rhamnopyranosyl-(1 --> 4)-O-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (1) by spectral analysis and chemical methods. The effects of two major saponins (clematichinenosides AR and AR(2)) on the secretion of TNF-alpha in murine peritoneal macrophages induced by lipopolysaccharides were further investigated. The result indicated that a majority of triterpenoid saponins of this herb may be useful in the exploration of lead compounds for the treatment of some autoimmune diseases.