Immunochemistry of apamin—bee venom neurotoxin—I. Radioimmunoassay with apamin and its derivatives

Antibodies against apamin, a neurotoxic polypeptide from bee venom were raised in rabbits by immunization with apamin or apamin-BSA conjugates. ³H-apamin or ¹²⁵I-apamin were used in radioimmunoassay with anti-apamin for the detection of the apamin antigenic site. The inhibitory activity toward the labelled apamin-anti-apamin binding was maximal with unlabelled apamin and decreased in the range: apamin > Cys¹, Lys⁴-disuccinilated apamin > Cys¹, Lys⁴-diacetylated apamin > Cys¹, Lys₄-diacetylated apamin with carboxymethylated His¹⁸. Dipyrimidyl-Orn¹³,Orn¹⁴-apamin derivative almost had no inhibitory activity on labelled apamin binding emphasizing that Arg¹³, Arg¹⁴ are the most essential for the apamin topographic antigenic site.     

CYP17 and CYP19 genetic polymorphisms in endometrial cancer: association with intratumoral aromatase activity

Excessive estrogenic influence is known to be associated with initiation/promotion of endometrial cancer (EC). Allelic polymorphisms of the genes involved in steroidogenesis/steroid metabolism may contribute to EC susceptibility. It is important to know endocrine mechanisms by which such susceptibility is acquired. Here, we compared CYP19 (aromatase) and CYP17 (17alpha-hydroxylase/17,20-lyase) gene polymorphisms correspondingly in 136 and 165 EC patients and in 116 and 188 non-affected women primarily of postmenopausal age. In these expanded studies we confirmed our previous observations that genotypes with longest alleles of CYP19 (A6 or A7) are over-represented (64.7+/-4.0 vs. 49.1+/-4.6%, P = 0.04, and 11.0+/-2.7 vs. 1.7+/-1.2%, P = 0.01)) and A2/A2 CYP17 genotype is under-represented (12.1+/-2.5 vs. 25.0+/-3.2%, P = 0.001) in patients as compared to controls. Additionally, aromatase activity was studied by tritiated water release assay in tumor tissues of 32 EC patients. In carriers of A2/A2 CYP17 genotype this activity was significantly lower than in carriers of A1/A1 genotype or in combined group of A1/A1 and A1/A2 CYP17 carriers (P = 0.04 in both cases). On the other side, intratumoral aromatase activity demonstrated tendency to higher values in carriers of longest CYP19 alleles (A6A6 and A6A7) than in carriers of all other CYP19 allele variants (P = 0.066). Thus, specific set of genetic polymorphisms (carrying of CYP17 A1 allele and combination of longest A6 or A7 CYP19 alleles) may predispose to the induction of higher rate of local estrogen biosynthesis in malignant endometrium, that in its turn may support growth of the latter. Further studies are warranted to connect revealed regularities with the type I or II of EC.     

Convex Arrhenius plots and their interpretation

This paper draws attention to selected experiments on enzyme-catalyzed reactions that show convex Arrhenius plots, which are very rare, and points out that Tolman's interpretation of the activation energy places a fundamental model-independent constraint on any detailed explanation of these reactions. The analysis presented here shows that in such systems, the rate coefficient as a function of energy is not just increasing more slowly than expected, it is actually decreasing. This interpretation of the data provides a constraint on proposed microscopic models, i.e., it requires that any successful model of a reaction with a convex Arrhenius plot should be consistent with the microcanonical rate coefficient being a decreasing function of energy. The implications and limitations of this analysis to interpreting enzyme mechanisms are discussed. This model-independent conclusion has broad applicability to all fields of kinetics, and we also draw attention to an analogy with diffusion in metastable fluids and glasses.     

Isolation and characterization of a novel indigenous intestinal N4-related coliphage vB_EcoP_G7C

Lytic coliphage vB_EcoP_G7C and several other highly related isolates were obtained repeatedly from the samples of horse feces held in the same stable thus representing a component of the normal indigenous intestinal communities in this population of animals. The genome of G7C consists of 71,759 bp with terminal repeats of about 1160 bp, yielding approximately 73 kbp packed DNA size. Seventy-eight potential open reading frames, most of them unique to N4-like viruses, were identified and annotated. The overall layout of functional gene groups was close to that of the original N4 phage, with some important changes in late gene area including new tail fiber proteins containing hydrolytic domains. Structural proteome analysis confirmed all the predicted subunits of the viral particle. Unlike N4 itself, phage G7C did not exhibit a lysis-inhibited phenotype.     

Hormonal imbalance in two types of endometrial cancer and genetic polymorphism of steroidogenic enzymes

OBJECTIVES: Modern data on endometrial cancer (EC) incidence demonstrate that it is one of the most prevalent gynecologic malignancies. It is possible that some allelic polymorphisms of the genes involved in steroidogenesis or steroid metabolism differently contribute into susceptibility to described types of this disease, namely to type I (which is considered to be hormone dependent) and type II. METHODS: Distribution of allelic polymorphisms of CYP17 (17alpha-hydroxylase/17,20-lyase), CYP19 (aromatase), catechol-O-methyltransferase (COMT) and CYP1B1 (primarily, estrogen 4-hydroxylase) genes was compared totally in 156 endometrial cancer patients, approximately two-third of who belonged (on the basis of case history and some characteristics of host and tumor) to type I of the disease, and one-third to type II. Blood leukocytes were used as source of normal DNA for PCR-genotyping. RESULTS: No differences were found in distribution of CYP17 and CYP1B1 genotypes between patients belonging to type I or II of the disease. On the other side, in case of CYP19, the ratio of incidence of A6A6 genotype to the frequency of A1A6 and A3A6 genotypes was higher in type II patients (1.0) than in type I patients (0.3). Besides, incidence of high activity (HH) COMT genotype was higher among patients with type I of disease than in patients with type II of it (33.3% versus 14.7%, OR=2.9, z=1.96, p=0.05) revealing tendency to the lower inactivation of catecholestrogens in the latter group. CONCLUSION: It may be suggested that more aggressive clinically and frequently receptor-negative type II of endometrial cancer is associated with indirect signs of mainly intratumoral hyperproduction of estrogens (excess of CYP19 A6A6 genotype) without their sufficient inactivation into methoxyderivatives that warrants further study.