Cdc25B phosphatase participates in maintaining metaphase II arrest in mouse oocytes

Cdc25B is an essential regulator for meiotic resumption in mouse oocytes. However, the role of this phosphatase during the later stage of the meiotic cell cycle is not known. In this study, we investigated the role of Cdc25B during metaphase II (MII) arrest in mouse oocytes. Cdc25B was extensively phosphorylated during MII arrest with an increase in the phosphatase activity toward Cdk1. Downregulation of Cdc25B by antibody injection induced the formation of a pronucleus-like structure. Conversely, overexpression of Cdc25B inhibited Ca²⁺-mediated release from MII arrest. Moreover, Cdc25B was immediately dephosphorylated and hence inactivated during MII exit, suggesting that Cdk1 phosphorylation is required to exit from MII arrest. Interestingly, this inactivation occurred prior to cyclin B degradation. Taken together, our data demonstrate that MII arrest in mouse oocytes is tightly regulated not only by the proteolytic degradation of cyclin B but also by dynamic phosphorylation of Cdk1.     

Distinct roles for β‐arrestin2 and arrestin‐domain‐containing proteins in β2 adrenergic receptor trafficking

β‐arrestin 1 and 2 (also known as arrestin 2 and 3) are homologous adaptor proteins that regulate seven‐transmembrane receptor trafficking and signalling. Other proteins with predicted ‘arrestin‐like’ structural domains but lacking sequence homology have been indicated to function like β‐arrestin in receptor regulation. We demonstrate that β‐arrestin2 is the primary adaptor that rapidly binds agonist‐activated β₂ adrenergic receptors (β₂ARs) and promotes clathrin‐dependent internalization, E3 ligase Nedd4 recruitment and ubiquitin‐dependent lysosomal degradation of the receptor. The arrestin‐domain‐containing (ARRDC) proteins 2, 3 and 4 are secondary adaptors recruited to internalized β₂AR–Nedd4 complexes on endosomes and do not affect the adaptor roles of β‐arrestin2. Rather, the role of ARRDC proteins is to traffic Nedd4–β₂AR complexes to a subpopulation of early endosomes.     

Design and Synthesis of Dually Branched 5′-Norcarbocyclic Adenosine Phosphonodiester Analogue as a New Anti-HIV Prodrug

A novel 3′,4′-dimethyl-5′-norcarbocyclic adenosine phosphonic acid was prepared using acyclic stereoselective route from 4-hydroxybutan-2-one (4). To improve the cellular permeability and enhance the anti-HIV activity of this phosphonic acid, a (bis)SATE phosphonodiester nucleoside prodrug (20) was prepared and its chemical stability was evaluated. The newly synthesized bis(SATE) analogue (20) and its parent nucleoside phosphonic acid (18) were assayed for anti-HIV activity using an in vitro assay system in a CEM cell line.     

Simple Synthesis and Anti-Hiv Activity of Novel 3′-Vinyl Branched Apiosyl Pyrimidine Nucleosides

Novel vinyl branched apiosyl nucleosides were synthesized in this study. Apiosyl sugar moiety was constructed by sequential ozonolysis and reductions. The bases (uracil and thymine) were efficiently coupled by glycosyl condensation procedure (persilyated base and TMSOTf). The antiviral activities of the synthesized compounds were evaluated against the HIV-1, HSV-1, HSV-2, and HCMV. Compound 10β displayed moderate anti-HIV activity (EC₅₀ = 17.3 μg/mL) without exhibiting any cytotoxicity up to 100 μM.     

Rice cell wall polysaccharides: Structure and biosynthesis

Rice is the most widely consumed staple food, and is cultivated worldwide to satisfy our daily caloric needs. Thus, extensive efforts on rice breeding and biotechnology have substantially focused on the development of elite cultivars with high yields and better grain quality, as well as enhanced resistance against biotic and abiotic stresses. Recently, it has been observed that rice is more than a just grain-producing crop. Carbon-rich materials of the rice cell wall polysaccharides from post-harvest wastes, including the straw and husk, have been converted into bioethanol and other invaluable, renewable materials. In order to maximize the utilization of cell wall-derived resources, it is imperative to understand cell wall chemistry and molecular mechanism underlying cell wall biosynthesis in rice. In the last decade, several approaches, including mutational genetics and the functional characterization of candidate genes, have been successful in isolating some of cell wall biosynthetic genes in rice, marking the first step forward in obtaining a complete understanding of rice cell wall biosynthesis, although the exact biochemical functions have not been conclusive. In this paper, we focus on integrating old and new information to provide an updated perspective in the cell wall formation of rice, highlighting the chemical structures and biosynthesis of rice cell wall polysaccharides.     

Evaluation of a novel pneumatic bioreactor system for culture of recombinant Chinese hamster ovary cells

Single use culture systems are a tool in research and biotechnology manufacturing processes and are employed in mammalian cell-based manufacturing processes. Recently, we characterized a novel bioreactor system developed by PBS Biotech. The Pneumatic Bioreactor System? (PBS) employs the Air-wheel?, which is a mixing device similar in structure to a water wheel but is driven by the buoyant force of gas bubbles. In this study, we investigated the physical properties of the PBS system, with which we performed biological tests. In 2 L PBS, the mixing times ranged from 6 (30 rpm, 0.175 vvm) to 15 sec (10 rpm, 0.025 vvm). The k_La value reached upto 7.66/h at 0.5 vvm, even without a microsparger, though this condition is not applicable for cell cultures. Also, when a 10 L PBS equipped with a microsparger was evaluated, a k_La value of upto approximately 20/h was obtained particularly in mild cell culture conditions. We performed cultivation of Chinese hamster ovary (CHO) cells in 2 and 10 L PBS prototypes. Results from the PBS were compared with those from an Erlenmeyer flask and conventional stirred tank type bioreactor (STR). The maximum cell density of 10.6 × 106 cells/mL obtained fromthe 2 L PBSwas about 2 times higher than that from the Erlenmeyer flask (5.6 × 10⁶ cells/mL) andwas similar to the STR (9.7 × 10⁶ cells/mL) when the CHO-S cells were cultured. These results support the general suitability of the PBS system using pneumatic mixing for suspension cell cultivation as a novel single-use bioreactor system.