SN2 DNA-alkylating agent-induced phosphorylation of p53 and activation of p21 gene expression

p53 is an important player in the cellular response to genotoxic stress whose functions are regulated by phosphorylation of a number of serine and threonine residues. Phosphorylation of p53 influences its DNA-binding and gene regulation activities. This study examines p53 phosphorylation in HCT-116 (MMR-deficient) and HCT-116+ch3 (MMR-proficient) human colon cancer cells treated with a S(N)2 DNA-alkylating agent, methylmethane sulfonate (MMS). MMS induces phosphorylation of p53 on Ser15 and Ser392 in a dose- and time-dependent manner. MMS-induced p53 phosphorylation is independent of DNA mismatch repair (MMR) activity. Nuclear extracts from MMS-treated HCT-116 cells had higher p21WAF1/Cip1 (p21) promoter DNA-binding activity in vitro opposed to untreated cells. After MMS treatment, the activation of the cloned p21 promoter in a transient transfection assay and endogenous p21 mRNA levels in HCT-116(p53+/+) versus HCT-116(p53-/-) cells increased, which correlates with an increased levels of phospho-p53(Ser15) and phospho-p53(Ser392). These results suggest that SN2 DNA-alkylating agent-induced phosphorylation of p53 on Ser15 and Ser392 increases its DNA-binding properties to cause an increased expression of p21 that may play a role in cell cycle arrest and/or apoptosis of HCT-116 cells.     

Selectivity in heavy metal- binding to peptides and proteins

The metal-binding affinities and three-dimensional structures of three synthetic 18-residue peptides with sequences derived from that of the highly conserved metal-binding motif MXCXXC found in many heavy metal-binding proteins were determined. A change in register of the cysteines and alanines of the sequence from the periplasmic mercury-binding protein, MerP, i.e., CAAC, CACA, and CCAA, affects the specificity of metal binding, in particular, the peptide with vicinal cysteines binds only mercury. The three-dimensional structures of the mercury-bound forms of the three peptides determined in solution by NMR spectroscopy peptides differ considerably, even though they are all linear bicoordinate complexes. The three-dimensional structure of the peptide with CAAC bound to Cd(II) demonstrates that the metal-binding loop is malleable enough to accommodate modes of coordination other than linear bicoordinate.     

Synthesis of bifunctional antibodies for immunoassays

The synthesis of bifunctional antibodies using the principle of solid-phase synthesis is described. Two Fab' fragments were chemically linked together via a bismaleimide crosslinking reagent. The F(ab')(2) fragments from intact immunoglobulin G (IgG) were prepared using an immobilized pepsin column. Goat, mouse, and human antibodies were digested completely within 4 h. The F(ab')(2) fragments thus produced did not contain any IgG impurities. Fab' fragments were produced by reducing the heavy interchain disulfide bonds using 2-mercaptoethylamine. Use of the solid-phase reactor in the preparation of the bifunctional antibodies eliminated many of the time-consuming separation steps between the fragmentation and conjugation steps. This procedure facilitates the automation of bifunctional antibody preparation and the rapid optimization of reaction conditions.     

Effect of acyclovir on the radiation-induced micronuclei and cell death

Treatment of HeLa cells with 0.1 microM Acyclovir [9-(2-hydroxyethoxymethyl)guanine] (ACV) before exposure to 0, 0.25, 0.5, 1, 2 and 3 Gy of gamma-radiation resulted in a dose-dependent decline in the growth kinetics and cell proliferation indices at 20, 30 and 40 h post-irradiation when compared with the PBS+irradiation group. These results were reflected in the cell survival, which declined in a dose-dependent manner and the surviving fraction of cells was significantly lower in ACV+irradiation group than that of PBS+irradiation group. The effect of ACV+1 Gy irradiation was almost similar to PBS+3 Gy irradiation suggesting an enhancement of the radiation effect by ACV pretreatment. The frequency of micronuclei increased in a dose-dependent manner at all the post-irradiation time periods in both PBS+irradiation and ACV+irradiation group and it was significantly elevated in the latter when compared with the former group. The dose-response for both groups was linear. The surviving fraction of HeLa cells declined with the increasing MN frequency and a close linear quadratic correlation between cell survival and micronuclei-induction was observed.     

Comparative Pharmacokinetic Study of Mangiferin After Oral Administration of Pure Mangiferin and US Patented Polyherbal Formulation to Rats

The US patented polyherbal formulation for the prevention and management of type II diabetes and its vascular complications was used for the present study. The xanthone glycoside mangiferin is one of the major effector constituents in the Salacia species with potential anti-diabetic activity. The pharmacokinetic differences of mangiferin following oral administration of pure mangiferin and polyherbal formulation containing Salacia species were studied with approximately the same dose 30 mg/kg mangiferin and its distribution among the major tissue in Wistar rats. Plasma samples were collected at different time points (15, 30, 60, 120, 180, 240, 360, 480, 600, 1,440, 2,160, and 2880 min) and subsequently analyzed using a validated simple and rapid LC-MS method. Plasma concentration versus time profiles were explored by non-compartmental analysis. Mangiferin plasma exposure was significantly increased when administered from formulation compared to the standard mangiferin. Mangiferin resided significantly longer in the body (last mean residence time (MRT_last)) when given in the form of the formulation (3.65 h). C_max values of formulation (44.16 μg/mL) administration were elevated when compared to equivalent dose of the pure mangiferin (15.23 μg/mL). Tissue distribution study of mangiferin from polyherbal formulation was also studied. In conclusion, the exposure of mangiferin is enhanced after formulation and administration and could result in superior efficacy of polyherbal formulation when compared to an equivalent dose of mangiferin. The results indicate that the reason which delays the elimination of mangiferin and enhances its bioavailability might the interactions of the some other constituents present in the polyherbal formulation. Distribution study results indicate that mangiferin was extensively bound to the various tissues like the small intestine, heart, kidney, spleen, and liver except brain tissue.

Electronic supplementary material

The online version of this article (doi:10.1208/s12249-014-0206-8) contains supplementary material, which is available to authorized users.KEY WORDS: bioavailability, mangiferin, pharmacokinetics, polyherbal formulation, tissue distribution     

Implementing a mathematical model to compare oxygen uptake kinetics between cyclists and noncyclists during steady state

The purpose was to compare a mathematical model of oxygen uptake and bioenergetic systems to an experimental protocol. Twelve (N = 12) noncyclists (NC), age (21.8 ± 1.4 years), and 8 (N = 8) cyclists (C), age (30.5 ± 5.7 years), were subjects. All subjects signed an informed consent. Oxygen consumption (VO2, ml·kg?1·min?1) was measured with steady-state VO2 requirements and responses determined using the mathematical model from the following equation: VO2 (WR) = VO2 (rest) + VO2 (unloading pedaling) + α.WR; ΔVO2(t, WR) = ΔVO2 (WR) = [1-e[-(t-td)/tO2]. Exercise means (SD) included the following: VO2NC(WR) = 48.4 (16.6) ml?1·min?1 for NCs and VO2C(WR) = 56.4 (24.95) ml?1·min?1 for Cs ; ΔVO2C(t, WR) = 6:38 ml?1·min?1 for NCs and ΔVO2C(t, WR) = 7.44 ml?1·min?1 for Cs. The correlation between the mathematical model and actual measure was statistically significant (p < 0.01) with a coefficient of r = 0.947. The experimental protocol was significantly associated with the mathematical model. This allows for a quantitative analysis and safe prediction of steady-state oxygen uptake conditions on populations before exposure to exercising conditions. Through more precise analysis of conditions, greater specificity of training may lead to more predictable adaptation outcomes.     

Fruit fly parasitoids in coffee in Mpumalanga Province,South Africa

Bracon celer, Psyttalia perproxima, Psyttalia humilis (all Hymenoptera: Braconidae) and Tetrastichus giffardianus (Hymenoptera: Eulophidae) were reared from fruit flies (Diptera: Tephritidae) infesting Coffea canephora in Mpumalanga, South Africa. Psyttalia perproxima and T. giffardianus were recorded for the first time from southern Africa. Ceratitis capitata was likely the main tephritid host.