Simultaneous determination of maltose and glucose using a screen-printed electrode system

A screen-printed sensor system consisting of a glucose oxidase (GOD) electrode and an amyloglucosidase/glucose oxidase (A/G) electrode was constructed to determine maltose and glucose simultaneously in a mixture. Sensor construction was optimised so that it contained 20 units of GOD/40 units of amyloglucosidase and 0.2 mM 1,1'-ferrocenedimethanol. These components were deposited onto a screen-printed carbon electrode and an outer membrane was printed from 3.5% hydroxyethyl cellulose (HEC) solution. The optimum pH was 4.8. The linear range of the system was up to 40 mM glucose or 20 mmol/L maltose with coefficients of variation (CVs) ranging from 3.5% to 5.29%. The results obtained by using the enzyme electrode system agreed well with those obtained by the Fehling titration method. When stored dry, especially at 4 degrees C, the enzyme electrodes showed good stability over four months.     

Differential effects of short photoperiod on 2-[125I]iodomelatonin binding in the testis and brain of quail

The affinities and densities of 2-[125I]iodomelatonin binding sites in the brains and gonads of male Japanese quail following short photoperiod treatment were studied. At 6 weeks old, control quail were placed under a 14 hour light/10 hour dark photo-stimulatory cycle and experimental quail were housed under a 7 hour light/17 hour dark photo-inhibitory lighting regime. Eighteen weeks after photic manipulation, the birds were killed at mid-light. The photo-inhibited quail had very small testes. Brains and testes of control and experimental quail were collected for receptor binding studies. The maximum number of binding sites (Bmax) of 2-[125I]iodomelatonin determined by saturation studies and the number of 2-[125I]iodomelatonin binding sites determined by a one-point binding assay in the testes of short-day quail were significantly lower (p < 0.05) than those of the testes in reproductively active birds kept under long photoperiod. There was no significant difference (p > 0.05) between the testicular Kd (equilibrium dissociation constant) values of these two groups. As for the Kd and Bmax of 2-[125I]iodomelatonin binding sites in the whole brain, there were no significant differences (p > 0.05) between the two groups. The higher level of testicular 2-[125I]iodomelatonin binding sites in photostimulated birds may be related to an up-regulation of melatonin receptors by the suppressed pineal melatonin secretion under long photoperiod. The lower testicular 2-[125I]iodomelatonin binding sites under short photoperiod may be the result of down-regulation of melatonin receptors by the stimulated melatonin pattern in the photo-inhibited birds.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of alpha 2-adrenoceptors mediating contraction of dog saphenous vein: identity with the human alpha 2A subtype

1. In the dog saphenous vein alpha 1- and alpha 2-adrenoceptors mediate noradrenaline-induced contractions in vitro. In order to study the alpha 2-adrenoceptor in isolation, alpha 1-adrenoceptors were inactivated by treatment of tissues with the alkylating agent phenoxybenzamine (3.0 microM for 30 min) in the presence of rauwolscine (1 microM) to protect alpha 2-adrenoceptors. 2. Noradrenaline-induced contractions of tissues treated with phenoxybenzamine were antagonized competitively by the selective alpha 2-adrenoceptor antagonist rauwolscine, pKB = 8.63 +/- 0.07 (means +/- s.e. mean; n = 3), consistent with an interaction at alpha 2-adrenoceptors. 3. Noradrenaline was a full agonist at alpha 2-adrenoceptors in dog saphenous vein. By use of the method of partial receptor alkylation and analysis of concentration-effect curve data by direct, operational model fitting methods, the affinity (pKA) and efficacy (tau) were 5.74 +/- 0.07 and 7.50 +/- 1.05, respectively (n = 6). Nine other agonists which were examined each had affinities higher than noradrenaline, but with the exception of the imidazoline, A-54741 (5,6-dihydroxy-1,2,3,4-tetrahydro-1-naphthyl-imidazoline) had relatively lower efficacies. 4. To compare the alpha 2-adrenoceptor in dog saphenous vein to the human recombinant subtypes, the affinities of twenty-one compounds were estimated in functional studies in the dog saphenous vein and in radioligand binding studies for the human alpha 2A, alpha 2B and alpha 2C receptor subtypes expressed in Chinese hamster lung (CHL) cells. 5. Of twenty-one compounds examined in ligand binding studies, only nine had greater than ten fold selectivity for one human receptor subtype over either of the other two. These compounds were A-54741, oxymetazoline, guanfacine, guanabenz, prazosin, spiroxatrine, tolazoline, WB 4101 and idazoxan. In dog saphenous vein, their affinities (pKA and pKB for agonists and antagonists respectively) were: A-54741 (pKA = 8.03 +/- 0.05), oxymetazoline (pKA = 7.67 +/- 0.09), guanfacine (pKA = 6.79 +/- 0.03); guanabenz (pKA = 7.02 +/- 0.13); prazosin (pKB = 5.19 +/- 0.08), spiroxatrine (pKB = 6.59 +/- 0.04), tolazoline (pKB = 6.21 +/- 0.07), WB 4101 (pKB = 7.42 +/- 0.09) and idazoxan (pKB = 7.11 +/- 0.08). 6. Comparisons of affinity estimates for these nine compounds at the receptor in dog saphenous vein and at the human recombinant subtypes suggest that the vascular receptor is most similar to the h alpha 2A subtype; correlation coefficients (r) were 0.82 (h alpha 2A), 0.24 (h alpha 2B) and 0.04 (h alpha 2C).     

Ultra low dose interleukin-2 therapy promotes a type 1 cytokine profile in vivo in patients with AIDS and AIDS-associated malignancies

To investigate the coordinated occurrence of loss of heterozygosity (LOH) at the BRCA1 locus and microsatellite instability (MI) in sporadic breast carcinomas, 56 tumors were analysed for both genetic alterations. The comparison of clinicopathological features with the obtained data revealed that LOH at the BRCA1 locus was significantly correlated with features specific for familial BRCA1 tumors and with absence of hormone receptors. No correlation was found between LOH and MI. These results suggest that sporadic and familial breast tumors, where BRCA1 is altered, could display similar clinicopathological features and that LOH and MI are distinct genetic events in sporadic breast carcinogenesis.     

Arg278, but not Lys229 or Lys236, plays an important role in the binding of retinoic acid by retinoic acid receptor gamma

The diverse biological actions of retinoic acid (RA) are mediated by retinoic acid receptors (RARalpha, beta and gamma) and retinoid X receptors (RXR alpha, beta, and gamma). Although the ligand-binding domains of RARs share the same novel folding pattern, many RAR subtype-specific retinoids have been synthesized indicating that the ligand-binding pocket of each RAR subtype has unique features. Previously we have demonstrated the importance for RA binding and RA-dependent transactivation of Arg276 of RARalpha alone and in RARbeta Arg269 in conjunction with Lys220. In this study, we have examined the role of the homologous amino acid residues (Lys229 and Arg278) in RARgamma for these activities. Like RARalpha but dissimilar to RARbeta, Arg278 in RARgamma alone was found to play an important role in RA binding and RA-dependent transactivation. Since Lys236 in RARgamma was suggested from the crystal structure of holo-RARgamma to interact with RA, we also examined its role and that of its homologs in RARalpha and RARbeta. Despite the suggestion from the crystal structure, neither Lys236 nor its homologs in RARalpha and RARbeta play a role in the binding of RA or RA-dependent transactivation. It is likely that Lys236 in RARgamma and its homologs in RARalpha and RARbeta are solvent exposed rather than pointing into the RA-binding pocket.     

Relationship of tuberculosis course in adolescents with acute phase blood proteins and genetic types of haptoglobin

The phenotype of haptoglobin (Hp) was determined and Hp and alpha 1-antitrypsin (alpha 1-AT) were many times measured in the sera of 131 adolescents with first identified tuberculosis. The phenotype of Hp was found to produce no effects on tuberculosis morbidity among adolescents, but Hp2-2 carriers fall ill more frequently if they have a baseline gastrointestinal abnormality. In tuberculosis patients with Hp2-2, resolution of infiltrative changes in the lung tissue occurs less rapidly than in those with other Hp variants. Great increases in the serum levels of alpha 1-AT, which reflects the severity of tissue damages, suggest a less favourable prognosis. By the end of sixth-month continuous combined drug therapy, an inflammatory reaction diminishes and the synthesis of acute phase reactants (APR) becomes normal in patients without baseline lung tissue decay. In the presence of the latter, the intensity of inflammation considerably decreases in the first 3 months of combined drug therapy, then becomes steady-state at a definite level, which is potentiated by continuous invasion of proteolytic enzymes. APR monitoring more accurately assesses the time course of therapy-induced changes in the process.