A Genetic Polymorphism in Coumarin 7-Hydroxylation: Sequence of the Human CYP2A Gnes and Identification of Variant CYP2A6 Alleles

A group of human cytochrome P450 genes encompassing the CYP2A, CYP2B, and CYP2F subfamilies were cloned and assembled into a 350-kb contig localized on the long arm of chromosome 19. Three complete CYP2A genes—CYP2A6, CYP2A7, and CYP2A13—plus two pseudogenes truncated after exon 5, were identified and sequenced. A variant CYP2A6 allele that differed from the corresponding CYP2A6 and CYP2A7 cDNAs previously sequenced was found and was designated CYP2A6ν2. Sequence differences in the CYP2A6ν2 gene are restricted to regions encompassing exons 3, 6, and 8, which bear sequence relatedness with the corresponding exons of the CYP2A7 gene, located downstream and centromeric of CYP2A6ν2, suggesting recent gene-conversion events. The sequencing of all the CYP2A genes allowed the design of a PCR diagnostic test for the normal CYP2A6 allele, the CYP2A6ν2 allele, and a variant—designated CYP2A6ν1—that encodes an enzyme with a single inactivating amino acid change. These variant alleles were found in individuals who were deficient in their ability to metabolize the CYP2A6 probe drug coumarin. The allelic frequencies of CYP2A6ν1 and CYP2A6ν2 differed significantly between Caucasian, Asian, and African-American populations. These studies establish the existence of a new cytochrome P450 genetic polymorphism.     

Cpn60 is exclusively localized into mitochondria of rat liver and embryonic Drosophila cells

Several reports have claimed that the mitochondrial chaperonin cpn60, or a close homolog, is also present in some other subcellular compartments of the eukaryotic cell. Immunoelectron microscopy studies, using a polyclonal serum against cpn60, revealed that the protein is exclusively localized within the mitochondria of rat liver and embryonic Drosophila cells (SL2). Furthermore, no cpn60 immunoreactive material could be found within the nucleus of SL2 cells subjected to a 1 h 37°C heat-shock treatment. In contrast to these findings, immunoelectron microscopy studies, using a cpn60 monoclonal antibody, revealed mitochondrial and extramitochondrial (plasma membrane, nucleus) immunoreactive material in rat liver cells. Surprisingly, the monoclonal antibody also reacted with fixed proteins of the mature red blood cell. The monoclonal antibody, as well as cpn60 polyclonal sera, only recognize mitochondrial cpn60 in Western blots of liver proteins. Furthermore, none of the cpn60 antibodies used in this study recognized blotted proteins from rat red blood cells. Therefore, we suggest that the reported extramitochondrial localization of cpn60 in metazoan cells may be due to cross-reactivity of some of cpn60 antibodies with conformational epitopes also present in distantly related cpn60 protein homologs that are preserved during fixation procedures of the cells. © 1995 Wiley-Liss, Inc.     

Dinucleotide repeat polymorphism at the D4S2458 locus close to the PKD2 locus on human chromosome 4q

A new polymorphic CA repeat sequence was identified within the candidate region fot the autosomal dominant polycystic kidney disease type 2 (PKD2) locus. It should be a useful marker in the localization of this gene.     

A newZornia species in the Flora of Cuba

A newZornia species from Cuba, the endemicZornia arenicola sp. nova, is described. It was found on moving sand dunes between the town of Guane and the village of Cortes (Pinar del Rio province).     

Host related factors affecting oviposition behavior in Brachymeria intermedia

Some behavioral and physical defenses of Lymantria dispar (L.) pupae are described. It was found that the layer of webbing surrounding pupae significantly reduced oviposition rates in the pupal parasitoid Brachymeria intermedia (Nees) (Hymenoptera, Chalcididae). The reasons for this reduction and consequent parasitoid responses were investigated. The role of these behaviors in this host parasitoid relationship are discussed.

---

Résumé Le comportement défensif des chrysalides de Lymantria dispar L. consiste en cambrage et en tournoiement. Les chrysalides encoconées étaient plus sensibles aux stimuli tactiles que celles qui ont été extraites des cocons. Brachymeria intermedia Nees avait moint de succès dans l'insertion complète de la tarière dans des chrysalides encoconées qu'extraites, car elles devenaient empêtrées dans le cocon quand la chrysalide se défendait. Il y avait différentes réponses du parasitoïde à l'empêtrement. Elles comprenaient l'abandon de l'attaque par un départ, la remise en selle sur l'hôte, la morsure à travers les fils du cocon, l'attaque d'un hôte voisin, le repos ou la toilette. Les taux d'insertion de la tarière pouvaient être augmentés par l'élimination artificielle de quelques fils. La durée des opérations était plus courte sur les chrysalides plus petites. La discussion a porté sur l'importance de ces comportements sur les relations de ces parasitoïdes avec leurs hôtes.

     

Effects of light quality,CO2 tensions and NO 3 +− concentrations on the inorganic nitrogen metabolism of Chlamydomonas reinhardii

The blue light dependent utilization of nitrate by green algae under common air and high irradiances, besides its assimilatory nature, is associated with the release of NO₂ ^– and NH₄ ⁺ to the culture medium. If the CO₂ content of the sparging air was increased up to 2%, previously excreted NO₂ ^– and NH₄ ⁺ were rapidly assimilated. When under air and high irradiances the cell density in the culture reached values corresponding to 25 g Ch 1.ml^-1, no further growth was observed and the highest values of NO₃ ^– consumption and NO₂ ^– and NH₄ ⁺ release were attained. Besides low CO₂ tensions, increasing NO₃ ^– concentrations in the medium stimulated the release of NO₃ ^– and NH₄ ⁺. Under CO₂-free air the consumption of NO₃ ^– and the release of NO₂ ^– and NH₄ ⁺ on a total N bases were almost stoichiometric and their rates saturated at much lower irradiances than under air. Under CO₂-free air high rates of NO₂ ^– release were only observed under the blue radiations that were effectively absorbed by photosynthetically active pigments, i.e. 460 nm, but not under 404 and 630 nm radiations. However, the simultaneous illumination of the cells with 404 and 630 nm monochromatic light showed a remarkable synergistic effect on NO₂ ^– release.The results are discussed in terms of the close relationship between C and N metabolism, the photosynthetic reducing power required to convert NO _inf3 ^sup± -N into R – NH₂-N and the blue light activation of nitrate reductase.     

Rat hepatocyte primary cultures

Summary Primary cultures of rat hepatocytes survived well for up to 4 days in defined medium in the presence of dexamethasone but not in its absence. The loss of viability was accompanied by a loss of ultrastructural features characteristic of hepatocytes. The cultures began producing plasminogen activator and a neutral protease after 24 hr in culture. Dexamethasone inhibited the production of both of these substances. The deterioration of the cultures appeared not to be related to plasminogen activator, but prolongation of survival by a variety of protease inhibitors suggested that the neutral protease might contribute to deterioration. Dr. Goldblatt was supported by Grant No. SG-87 from the American Cancer Society as an American Cancer Society Scholar while on sabbatical leave from the Department of Pathology, University of Connecticut Health Center, Farmington, Connecticut. This study was supported by Contracts NO1-CP-55705 from the National Cancer Institute and 68-02-2483 from the Environmental Protection Agency.     

Metabolic cost of sodium transport in toad urinary bladder

Summary The metabolic cost of active sodium transport was determined in toad bladder at different gradients of transepithelial potential, , by continuous and simultaneous measurements of CO₂ production and of transepithelial electric current. Amiloride was used to block active sodium transport in order to assess the nontransport-linked, basal, production of CO₂ and the passive permeability of the tissue. From these determinations active sodium transport,J _Na, and suprabasal CO₂ production, , were calculated. Since large transients inJ _Na and frequently accompanied any abrupt change in , steady state conditions were carefully defined.Some 20 to 40 min were required after a change in before steady state of transport activity and of CO₂ production were achieved. The metabolic cost of sodium transport proved to be the same whether the bladder expended energy moving sodium against a transepithelial electrical potential grandient of +50 mV or whether sodium was being pulled through the active transport pathway by an electrical gradient of –50 mV. In both cases the value of the ratio averaged some 20 sodium ions transported per molecule of CO₂ produced.When the Na pump was blocked by 10^–2 m ouabain, the perturbations of the transepithelial electrical potential did not elicit changes ofJ _Na nor, consequently, of .The independence of the ratio from over the range ±50 mV indicates a high degree of coupling between active sodium transport and metabolism.