Quantitative detection of bisphenol A and bisphenol A diglycidyl ether metabolites in human plasma by liquid chromatography–electrospray mass spectrometry

Due to the ubiquity of epoxy resin compounds and their potential role in increasing the risk for reproductive dysfunction and cancer, the need for an assessment of human exposure is urgent. Therefore, we developed a method for measuring bisphenol A (BPA) and bisphenol A diglycidyl ether (BADGE) metabolites in human blood samples using high-performance liquid chromatography–electrospray ionization mass spectrometry (LC–MS). Human blood samples were processed using enzymatic deconjugation of the glucuronides followed by a novel sample preparation procedure using a solid-phase-cartridge column. This selective analytical method permits rapid detection of the metabolites, free BPA and a hydrolysis product of BADGE (BADGE-4OH) with detection limits in the low nanogram per milliliter range (0.1 ng ml⁻¹ of BPA and 0.5 ng ml⁻¹ of BADGE-4OH). The sample extraction was achieved by Oasis HLB column on gradient elution. The recoveries of BPA and BADGE-4OH added to human plasma samples were above 70.0% with a standard deviation of less than 5.0%. This selective, sensitive and accurate method will assist in elucidating potential associations between human exposure to epoxy-based compounds and adverse health effects.     

Membrane viscosity of lymphocytes and influence of phytohemagglutinin

The membrane viscosity of peripheral blood lymphocytes (PBLs) of equine, bovine and canine was measured by the use of time-resolved fluorescence depolarization technique with 1, 6-diphenyl-1,3,5-hexatriene (DPH). The viscosity values were 0.55, 0.59 and 0.50 poise for equine, bovine and canine PBLs, respectively. These values were compared with steady-state anisotropies and order parameters measured from electron spin resonance (ESR) of 5-doxyl stearic acid. Both values were increased with increase of viscosity. The fluid property of the membranes stimulated with phytohemagglutinin-P (PHA) was measured with steady-state fluorescence anisotropy and ESR. Little change of membrane fluidity was recognized with both methods during the stimulation with PHA. It appears that PHA activation process for these lymphocytes does not included large increase of the membrane fluidity which significantly accelerate the diffusion velocity of receptors in the plasma membrane.     

Membrane Viscosity Correlates with α1-Adrenergic Signal Transduction of the Aged Rat Cerebral Cortex

We investigated, using adult (2-month-old) and senescent (12- and 24-month-old) rats, the effects of aging on the relationship between the alpha 1-adrenergic coupling system and the membrane viscosity of the cerebral cortex. There was no age-related difference in the KD values of [3H]prazosin binding on the membranes. The Bmax values of [3H]prazosin binding were reduced with advanced age. Norepinephrine-induced formation of 3H-labeled inositol phosphates (3H-IPs) in the slices increased with advanced age. The EC50 values for norepinephrine to stimulate the formation of 3H-IPs at advanced age were lower than that at adult age. The cholesterol content in membranes increased with advanced age. No changes in the phospholipid content in membranes were observed with advanced age. Concomitantly, an increase of the molar ratio of cholesterol to phospholipids was observed with advanced age. The membrane viscosity as measured by 1,6-diphenyl-1,3,5-hexatriene increased with advanced age. These results indicate that the altered cholesterol content and/or viscosity in cortical membranes of the aged rat may account for the loss of alpha 1-adrenergic receptor density and/or compensatory changes in the receptor-phospholipase C coupling system.     

Prevention of Vascular Graft Infection by Sisomicin Incorporated into Fibrin Glue

To examine the efficacy of sisomicin (SISO) incorporated into fibrin glue (FG) for the prevention of graft infection in animal models, the susceptibility to infection of Dacron grafts (control) and SISO-FG Dacron grafts following the inoculation of Staphylococcus aureus or S. epidermidis was compared. The results showed that SISO-FG Dacron grafts displayed resistance to graft infection.     

Spectrum of chloroperoxidase compound I

When compound I of chloroperoxidase is formed from the native enzyme the absorption peak in the Soret region diminishes in intensity, and shifts to a maximum absorbance at 367 nm. This unusual Soret spectrum decreases in intensity in a linear fashion as the wavelength increases. The first visible spectrum of chloroperoxidase compound I is reported which has a peak at 689 nm as its most prominent feature.     

Horseradish peroxidase. XXXVI. On the difference between peroxidase and metmyoglobin.

A mechanism for the reaction of hydrogen peroxide with horseradish peroxidase is proposed which involves the catalytic activity of the carboxylate side chain of aspartate residue 43. The corresponding residue in the active site of metmyoglobin is glycine E8, which explains the inability of metmyoglobin to form compound I. Certain aspects of the proposed peroxidase mechanism may be relevant to the catalytic triad for the serine proteases.     

Kinetic analysis of the acid-alkaline conversion of horseradish peroxidases.

The nature of the acid-alkaline conversion of horseradish peroxidases was studied by measuring four rate constants in reactions, E + H+ (k1) in equilibrium (k2) EH+ and E + H2O (k3) in equilibrium (k4) EH+ + OH-, where EH+ and E denote the acid and alkaline forms of the enzymes. The values of k1, (k2 + k3), and k4 were obtained by measuring the relaxation rates of the acid leads to alkaline and alkaline leads to acid conversions by means of th pH jump method with a stopped-flow apparatus. The value of k3 could also be obtained by measuring the rate of reactions between hydrogen peroxide and peroxidases at alkaline pH. The measurements were conducted with four peroxidases having different pKa values: peroxidase A )pKa = 9.3), peroxidase C (pKa = 11.1), diacetyldeuteroperoxidase A (pKa = 7.7), and diacetyldeuteroperoxidase C (pKa = 9.1). The value of k1 was about 10(10) M-1 s-1 in the reaction of the four enzymes while k4 was quite different between the enzymes. The pKa was determined by k3 and k4 for the natural peroxidases and by k1 and k2 for the diacetyldeuteroperoxidases. The mechanism of the acid-alkaline conversion was discussed in comparison with that of metmyoglobin.     

A novel enzymatic process for glycogen production

Two well-established methods to prepare glycogen are available: (1) extraction from natural resources such as shellfish and animal tissues; (2) synthesis from glucose-1-phosphate using two enzymes, α-glucan phosphorylase (EC 2.4.1.1) and branching enzyme (EC 2.4.1.18). We have developed a novel enzymatic process for glycogen production, in which short-chain amylose is first prepared from starch or dextrin by using isoamylase (EC 3.2.1.68), and then branching enzyme and amylomaltase (EC 2.4.1.25) are added to synthesize glycogen. Our enzymatic process, using isoamylase, branching enzyme and amylomaltase, is currently the most efficient for glycogen production. Furthermore, the molecular weight of glycogen is controllable in a range of 3.0×10⁶ to 3.0×10⁷ by adjusting some parameters of the reaction.