Improved cryopreservation of bovine preimplantation embryos cultured in chemically defined medium

The aim of this study was to examine the effects of modifications to a standard slow freezing protocol on the viability of in vitro produced bovine embryos. Bovine oocytes were matured, fertilized with frozen-thawed semen, and presumptive zygotes cultured in defined two-step culture media. The standard freezing medium was 1.5M ethylene glycol (EG), 0.1M sucrose, 10% fetal bovine serum (FBS) in Dulbecco's phosphate buffered saline (D-PBS). A preliminary trial showed that in vitro produced embryos cryopreserved in this medium had a survival rate of 74.6% at 24h and 53.5% at 48 h post-thaw. Experiment 1 studied the effects of omitting the sucrose supplement or replacing it with 0.1M xylose. In Experiment 2, the effects of partial (0%, 25% or 50%) or total (100%) replacement of sodium chloride with choline chloride in the cryopreservation medium were examined (the medium with 100% replacement was designated CJ1). The effects of replacing the 10% FBS with 0.4% BSA or 0.4% lipid-rich BSA (Albumax I) in CJ1 was studied in Experiment 3. In Experiment 4, pregnancy/calving rates following the post-thaw transfer of in vitro produced embryos cryopreserved in the standard freezing medium were compared with those of in vitro and in vivo produced embryos cryopreserved in the improved medium (Albumax I in CJ1). Supplementation of the cryopreservation medium with 0.1M sucrose resulted in higher post-thaw survival rates at 24 h (71.3% versus 53.5 and 51.7%; P<0.05), 48 h (51.1% versus 45.3 and 40.2%), and 72 h (34.0% versus 24.4 and 23.0%) than 0.1M xylose or no supplement, respectively, in Experiment 1. Experiment 2 showed that embryos cryopreserved in the standard medium had poorer survival rates at 24 h (72.8% versus 86.5%; P<0.05), 48 h (53.1% versus 66.3%) or 72 h (28.4% versus 44.9%) than those frozen in CJ1. The post-thaw survival rate of embryos frozen in medium supplemented with Albumax I was better than that for the FBS or BSA supplements at 24h (92.0% versus 90.7 and 87.3%), 48 h (87.3% versus 76.9 and 70.9%; P<0.05), and 72 h (70.4% versus 49.1 and 46 4%; P<0.05; Experiment 3). In Experiment 4, in vitro produced embryos cryopreserved in CJ1 medium supplemented with Albumax I resulted in higher pregnancy rates at Day 35 (31.9% versus 22.9%) and Day 60 (24.1% versus 14.3%) of gestation, and calving rates (22.6% versus 10.0%; P<0.05) than similar embryos frozen in the standard medium. However, in vivo produced embryos cryopreserved in Albumax I in CJ1 resulted in higher pregnancy rates at Day 35 (50.7%; P<0.05) and Day 60 (45.1%; P<0.05) of gestation, and calving rate (43.7%; P<0.05). It was concluded that modification of the freezing medium by addition of lipid-rich BSA and replacing sodium chloride with choline chloride improves the post-thaw survival of in vitro produced embryos, and their viability post-transfer.     

Antioxidant activity of polar lichens from King George Island (Antarctica)

Antioxidant agents prevent reactive oxygen species, which can cause degenerative diseases. Natural antioxidants are preferred over many synthetic antioxidants, which can be toxic, for therapeutic applications. Five lichen species were collected from King George Island, Antarctica. Antioxidant activities as assessed by DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical and ABTS^•+ [2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonate)] radical scavenging capacities were determined and compared with those of commercial standards BHA (butylated hydroxyanisole) and trolox [(±)-6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid]. The results indicated that two lichens exhibited comparatively high antioxidant activities with the remaining three exhibiting less activity. The antioxidant activity was concentration-dependent. When compared, the antioxidant activity of crude extracts from polar lichens to previously published data for tropical and temperate lichen species, we concluded that lichens of Antarctic origin may be the potent sources of strong antioxidant agents. Such species should be explored as novel sources of effective antioxidant metabolites.     

Molecular dynamics simulations and coupled nucleotide substitution experiments indicate the nature of A·A base pairing and a putative structure of the coralyne-induced homo-adenine duplex

Coralyne is an alkaloid drug that binds homo-adenine DNA (and RNA) oligonucleotides more tightly than it does Watson–Crick DNA. Hud’s laboratory has shown that poly(dA) in the presence of coralyne forms an anti-parallel duplex, however attempts to determine the structure by NMR spectroscopy and X-ray crystallography have been unsuccessful. Assuming adenine–adenine hydrogen bonding between the two poly(dA) strands, we constructed 40 hypothetical homo-(dA) anti-parallel duplexes and docked coralyne into the six most favorable duplex structures. The two most stable structures had trans glycosidic bonds, but distinct pairing geometries, i.e. either Watson–Crick Hoogsteen (transWH) or Watson–Crick Watson–Crick (transWW) with stability of transWH > transWW. To narrow down the possibilities, 7-deaza adenine base substitutions (dA→7) were engineered into homo-(dA) sequences. These substitutions significantly reduced the thermal stability of the coralyne-induced homo-(dA) structure. These experiments strongly suggest the involvement of N7 in the coralyne-induced A·A base pairs. Moreover, due to the differential effect on melting as a function of the location of the dA→7 mutations, these results are consistent with the N1–N7 base pairing of the transWH pairs. Together, the simulation and base substitution experiments predict that the coralyne-induced homo-(dA) duplex structure adopts the transWH geometry.     

Production and characterization of long-acting recombinant human albumin–EPO fusion protein expressed in CHO cell

A long-lasting recombinant human albumin-linker-erythropoietin (EPO) is a human albumin gene fused to the N-terminal of EPO with a (GGSGG)_n-repeated linker inserted between albumin and EPO. Albumin–EPO fusion genes were co-transfected with the dhfr gene. Albumin–EPO fusion protein has three kinds of sub-types (IALE, AD2LE, AD1LE). Albumin–EPO fusion protein was quantified with human EPO ELISA. The in vitro efficacy of albumin–EPO fusion protein was estimated using F-36E cell, and in vivo efficacy of albumin–EPO fusion protein was estimated using normocythemic mice (B6D2F1). We also determined the in vivo half-life in a Sprague–Dawley rat. A PLA program analysis result demonstrated that the albumin–EPO fusion protein IALE is about 7.8-fold more potent than rHuEPO in increasing the hematocrit of normal mice.     

Momilactone B Inhibits Ketosis In Vitro by Regulating the ANGPTL3-LPL Pathway and Inhibiting HMGCS2

Ketogenesis is the production of ketone bodies, which provide energy when the body lacks glucose. Under ketogenic conditions, the body switches from primarily carbohydrate to fat metabolism to maintain energy balance. However, accumulation of high levels of ketone bodies in the blood results in ketosis. Treating ketosis with natural substances is preferable, because they are unlikely to cause side-effects. Momilactone B is an active compound isolated from Korean rice. Based on previous studies, we hypothesized that momilactone B could inhibit ketosis. We constructed an in vitro ketosis model by glucose starvation. We used this model to test the anti-ketosis effects of momilactone B. A primary target for treating ketosis is angiopoietin-like-3 (ANGPTL3), which modulates lipoprotein metabolism by inhibiting lipoprotein lipase (LPL), a multifunctional enzyme that breaks down stored fat to produce triglycerides. We showed that momilactone B could regulate the ANGPTL3-LPL pathway. However, a strong anti-ketosis candidate drug should also inhibit ketogenesis. Ketogenesis can be suppressed by inhibiting the expression of 3-hydroxy-3-methylglutaryl-CoA synthase-2 (HMGCS2), a mitochondrial enzyme that converts acetyl-CoA to ketone bodies. We found that momilactone B suppressed the expression of HMGCS2 through the increased expression of STAT5b. We also elucidated the relationship of STAT5b to ANGPTL3 and LPL expression.     

Cloning, characterization and evaluation of potent inhibitors of Shigella sonnei acetohydroxyacid synthase catalytic subunit

Acetohydroxyacid synthase (AHAS) is a thiamin diphosphate (ThDP)- and flavin adenine dinucleotide (FAD)-dependent plant and microbial enzyme that catalyzes the first common step in the biosynthesis of essential amino acids such as leucine, isoleucine and valine. To identify strong potent inhibitors against Shigella sonnei (S. sonnei) AHAS, we cloned and characterized the catalytic subunit of S. sonnei AHAS and found two potent chemicals (KHG20612, KHG25240) that inhibit 87-93% S. sonnei AHAS activity at an inhibitor concentration of 100uM. The purified S. sonnei AHAS had a size of 65kDa on SDS-PAGE. The enzyme kinetics revealed that the enzyme has a K(m) of 8.01mM and a specific activity of 0.117U/mg. The cofactor activation constant (K(s)) for ThDP and (K(c)) for Mg(++) were 0.01mM and 0.18mM, respectively. The dissociation constant (K(d)) for ThDP was found to be 0.14mM by tryptophan fluorescence quenching. The inhibition kinetics of inhibitor KHG20612 revealed an un-competitive inhibition mode with a K(ii) of 2.65mM and an IC(50) of 9.3μM, whereas KHG25240 was a non-competitive inhibitor with a K(ii of) 5.2mM, K(is) of 1.62mM and an IC(50) of 12.1μM. Based on the S. sonnei AHAS homology model structure, the docking of inhibitor KHG20612 is predicted to occur through hydrogen bonding with Met 257 at a 1.7? distance with a low negative binding energy of -9.8kcal/mol. This current study provides an impetus for the development of a novel strong antibacterial agent targeting AHAS based on these potent inhibitor scaffolds.