Imidazole antimycotics: selective inhibitors of steroid aromatization and progesterone hydroxylation

Econazole, imazalil, and prochloraz, which have broad spectrum antimycotic activity, are shown to be potent inhibitors of steroid aromatase activity of human placental microsomes. The IC50 values for the inhibition of aromatase activity by econazole, imazalil, miconazole, prochloraz, clotrimazole, ketoconazole, and aminoglutethimide are 0.03, 0.15, 0.6, 0.7, 1.8, 60, and 45 microM, respectively. Econazole and 4-hydroxyandrostenedione also inhibit the steroid aromatase activity of human fetal liver, a finding which suggests that extraplacental aromatase may have many similarities to the placental enzyme. Econazole is a more effective inhibitor of placental aromatization of 19-hydroxyandrostenedione than of androstenedione. This observation is consistent with the competitive nature of the inhibition of aromatase by imidazole antimycotic agents and the reduced affinity of the placental aromatase enzyme for 19-hydroxyandrostenedione compared to androstenedione. The effectiveness of these imidazole antimycotic agents to inhibit the multiple hydroxylations of progesterone which are catalyzed by human fetal adrenal microsomes is also defined. While all of the imidazole antimycotic agents are potent inhibitors of the 16 alpha-, 17 alpha-, and 21-hydroxylations of progesterone, selective inhibitory profiles are apparent. Ketoconazole is a most potent inhibitor of human fetal adrenal progesterone 16 alpha- and 17 alpha-hydroxylases while clotrimazole and imazalil are the most potent inhibitors of progesterone 21-hydroxylase. These results are strongly supportive that imidazole drugs are selective inhibitors not only of steroid aromatase but also of other microsomal steroid hydroxylases.     

Motor asymmetry of the forelimbs of the rat

Preference was studied of one of the forelimbs during performance of different manipulating movements in white rats. High degree of "handedness" was observed in all studied movements. However it was not absolute--no animals performed all movements by one and the same limb. Degree and character of "handedness" were different for different movements, though the number of "righthanded" rats in most tests as a whole exceeded the number of "lefthanded" ones. The "handedness" depends on the individuality of the animal, the character of the motor task, learning and interference of different motor tasks during training.     

Role of motor activity in the development of hypothyroid rat pups

Studies have been made on the role of the thyroid in the development of rats. In the first group of experiments, newborn rat received within a month mercazolyl which inhibits the activity of the thyroid; in animals of the second group, mercazolyl injections were combined with cold exposures which stimulated motor activity in animals. It was found that hypothyroid rats in both groups exhibit retardation of growth as compared to normal animals. However, retardation is less significant in animals of the second group, as it is indicated by smaller changes in the protein content and total mass of skeletal muscles.     

Effects of isotretinoin on the behavior of neural crest cells in vitro

Isotretinoin (13-cis-retinoic acid), an anti-acne medication, has been found to cause severe birth defects which affect the craniofacial elements, ear, heart, thymus, and central nervous system. Many of these structures receive contributions from the cranial neural crest. Here, we examine the possibility that these teratogenic effects are due to disturbances in neural crest development. Cranial and trunk neural crest explant cultures were exposed to different concentrations of isotretinoin and the cell morphology was monitored at daily intervals. Treated neural crest cells often became rounded or spindle shaped, separated from their neighbors, and frequently detached from the substrate or clumped together. In contrast, neural tube cells and cardiac fibroblasts were relatively unaffected by the drug. These results suggest that isotretinoin selectively affects neural crest cells by decreasing their cell-substratum adhesion.     

Interactions of actin and tubulin with human deoxyhemoglobin. Their possible occurrence within erythrocytes

Short actin filaments are an essential component of the red-cell membrane skeleton, and microtubules are also present in nucleated erythrocytes as a marginal band. Actin and tubulin share the property of possessing a very anionic terminal peptide. Since deoxyhemoglobin (Hb) is known to be a strong polyanion-binding protein, we have considered how it may interact with actin and tubulin within the intact cell. Here we demonstrate that actin and tubulin form in vitro a high-affinity complex with Hb. This is shown by measuring, by stopped-flow experiments, the decrease of the binding rate constant of CO to Hb in the presence of increasing amounts of actin and tubulin. One tetramer of Hb is bound by an actin monomer, and about two tetramers by an alpha, beta-tubulin heterodimer. Binding assays in batch experiments with immobilized tubulin give the same stoichiometry. Formation of the complexes involves the 2,3-bisphosphoglycerate-binding site of Hb and a negatively charged domain, most likely the highly acidic N and C-terminal peptides of actin and tubulin. In addition to providing new opportunities to study the structural and functional properties of actin and tubulin, these results support the idea that in the case of partial metabolic depletion of bisphosphoglycerate and ATP in erythrocytes, Hb may interact with oligomeric actin and tubulin present in the cytoskeleton.     

The effect of myosin light chain phosphorylation on the actin-stimulated ATPase activity of myosin minifilaments

It has been shown that in the absence of KCl, the actin-stimulated Mg2+-ATPase activity of rabbit skeletal myosin minifilaments with phosphorylated regulatory lights chains (LC2) exceeds 3-4-fold that of myosin minifilaments with dephosphorylated LC2. Addition of KCl leads to a decrease in the difference between the two ATPase activities. LC2 phosphorylation considerably increases the rate of ATPase reaction and only slightly decreases the affinity of myosin minifilaments for F-actin. It is suggested that the unusual effect of LC2 phosphorylation on the kinetic parameters of the actin-stimulated ATPase reaction of myosin minifilaments can be accounted for by its influence on the interaction between myosin heads which results in the ordered self-assembly of minifilaments.     

Genetic analysis of the microevolutionary processes in cattle populations (the example of the B locus of blood groups)

Dynamics of allele frequencies for the B-locus of blood groups in cattle populations and of a number of phenotype indexes in these animals was studied. It is determined that natural stabilizing selection and prezygotic selection, leading to a change in genetic structure, act in every population. The role of sires' influence on this process is insignificant.     

Genetics and evolution of the Lpm-system in American mink. VI. Identification, genetic control and phylogenesis of the new allotype Lpm13

Data on immuno- and biochemical identification, genetic control and phylogenesis of new allotype Lpm13 of the Lpm system in domestic mink are presented. This allotype is encountered in mink populations with the frequency 0.9 and higher. The availability of Lpm13 genetic marker permitted another haplotype to be revealed, in addition to the eight known Lpm haplotypes by means of genetic analysis. It was established that, alongside with the earlier described haplotype Lpm3,4,6,8,9,10,11 (abbreviation H3), there exists a similar haplotype, Lpm3,4,6,8,9,10,11,13 (abbreviation H3.13), containing the Lpm13 gene. Of the rest seven haplotypes, five have the Lpm13 gene and two do not. Taking into account this gene and corresponding antigenic marker, the differentiation of 28, instead of 25, phenotypes and 45, instead of 36, genotypes for the Lpm system became possible. Lpm13 antigenic specificity was found with no exception in all individual serum samples taken from ten species and interspecific hybrids of Mustelidae which are closely related to domestic mink. The data obtained give grounds to refer the newly identified Lpm13 gene to the first evolutionary conservative category of genes of the multigenic Lpm system which is also represented by the Lpm6, Lpm9, Lpm10 and Lpm11 genes. The hypotheses of instantaneous formation of polymorphism of the Lpm system in domestic mink are briefly regarded.