Isolation of four HSP70 genes in the pig and localization on Chromosomes 7 and 14

For insight into the general organization of the swine leukocyte antigen (SLA) complex, the swine major histocompatibility complex (MHC), four sequences related to the heat-shock proteins HSP70 were characterized by screening of a pig genomic cosmid library with a swine cDNA HSP70 2.6-kb probe. This yielded three positive clones: HC2.2, HC3.2, and HC4.2. Restriction site maps revealed a large overlap of HC2.2 with HC3.2, whereas HC4.2 was independent. Southern blot hybridization with the 5 section, the central section, and the 3 section of the 2.6-kb probe and also with a swine 4.5-kb HSP70 genomic probe suggested the existence, within the overlapping clones, of three distinct HSP70 sequences encompassing a segment no longer than 22 kb. The HC4.2 clone, which hybridized with the same probes, displayed a single band of 7.3 kb, probably corresponding to one gene only. Fluorescent in situ hybridization on swine chromosome metaphases with the whole HC2.2 or HC4.2 cosmids allowed the assignment of HC2.2 to MHC region on Chromosome (Chr) 7 (Cen-p1.1), and of HC4.2 to Chr 14 (q2.4–2.5). Thus, as in humans, the swine MHC comprises three closely linked HSP70 loci. The presence of additional genes belonging to the same inducible HSP70 gene family can be expected from what is known in humans. The HSP70 gene found here on the pig Chr 14 may be one of these putative unidentified genes.     

A NEW HYBRID BETWEEN A BLUE WHALE, BALAENOPTERA MUSCULUS, AND A FIN WHALE, B. PHYSALUS: FREQUENCY AND IMPLICATIONS OF HYBRIDIZATION

A female hybrid between a fin ( Balaenoptera physalus ) and a blue whale ( B. mnusculus ) was caught in whaling operations in 1984 off northwestern Spain. Its coloration and body proportions were intermediate between those of a fin and a blue whale, although it was anomalously large (19.4 m) when compared to fin whales of similar age (4 yr). It was sexually immature, concomitant with its age but not its length if it were a fin whale. Molecular analyses revealed that the mother of the hybrid was a blue whale and the father a fin whale. Examination of data for the five fin-blue whale hybrids in the literature, plus other anecdotal reports, indicates that hybridization between these two species occurs in various geographic regions and is relatively frequent, notably in light of the absence of reported hybrids between other mysticetes. Either species may act as father or mother, and there does not appear to be a selection for a given sex among the hybrids. The reproductive capacity of these hybrids remains unknown, although incidence of reproductive impairment appears to be higher in hybrid males than in hybrid females.     

Thiomorpholine and morpholine oxidation by a cytochrome P450 in Mycobacterium aurum MO1. Evidence of the intermediates by in situ 1H NMR

Spectrophotometric assays of Mycobacterium aurum MO1 cells extracts gave evidence of a soluble cytochrome P450, involved in the degradative pathway of morpholine, a waste product from the chemical industry. In order to get further information, the kinetics of the biodegradation of the sulfur analogue thiomorpholine was monitored by using in situ nuclear magnetic resonance (NMR). This technique allowed the identification of two intermediates: the sulfoxide of thiomorpholine resulting from S-oxidation and thiodiglycolic acid owing to ring cleavage. The S-oxidation (S SO) represents one of the well-known reactions catalyzed by cytochromes P450. The inhibitory effect of metyrapone, a cytochrome P450 inhibitor, on the thiomorpholine and morpholine degradative abilities of M. aurum MO1 confirmed the involvement of a cytochrome P450. These results and the decrease of the rate of formation of the first intermediate during the morpholine degradation, 2-(2-aminoethoxy) acetate, proved the key role of the cytochrome P450 in the early events of the biodegradation, i.e, in the C–-N bond cleavage.     

Up to 100-Fold Increase of Apparent Gene Expression in the Presence of Epstein-Barr Virus oriP Sequences and EBNA1: Implications of the Nuclear Import of Plasmids

A 100-fold increase in luciferase activity was observed in 293 cells, stably expressing Epstein-Barr nuclear antigen 1 (EBNA1; 293-EBNA1 cells), that had been transiently transfected with plasmids carrying Epstein-Barr virus (EBV) oriP sequences. This increase was observed in comparison to reporter gene activity obtained after transfection with a plasmid carrying no oriP sequences. The luciferase gene on these plasmids was under the control of either the cytomegalovirus immediate-early 1 gene enhancer-promoter (CMV IE1) or the Rous sarcoma virus promoter. The increase of reporter gene activity was not due to plasmid replication, since a similar enhancement was observed in the presence of aphidicolin, an inhibitor of replicative DNA synthesis, or after deletion of the dyad symmetry (DS) element within oriP. Luciferase production was not increased in the presence of only the DS element. Microinjection of plasmids carrying the CMV IE1 promoter-driven luciferase gene with or without oriP sequences into the nuclei of 293-EBNA1 cells resulted in a 17-fold increase in luciferase activity. Cytoplasmic injection of these plasmids led to an enhancement of luciferase activity of up to 100-fold. This difference in the factor of activation after nuclear or cytoplasmic injection could be ascribed to increased transport of plasmids carrying oriP from the cytoplasm to the nucleus in the presence of EBNA1. These data suggest the possibility of substantially increasing the apparent expression of a gene under the control of a strong constitutive promoter in the presence of oriP sequences and EBNA1. This improvement in expression is due to intranuclear enhancement of gene expression. oriP-specific transport of plasmid DNA from the cytoplasm of 293-EBNA1 cells to the nucleus seems to contribute to the observed effect.     

Constitutive Activity and Structural Instability of the Wild-Type Human H2 Receptor

Abstract: Stable expression of the human H₂ receptor in Chinese hamster ovary cells resulted in an increase in basal cyclic AMP (cAMP) production, which was inhibited by the inverse agonists cimetidine, famotidine, and ranitidine with potencies similar to those found for the rat H₂ receptor. Burimamide, a neutral antagonist at the rat H₂ receptor, behaved as a weak partial agonist at the human H₂ receptor. Burimamide competitively antagonized both the histamine-induced increase in cAMP and the cimetidine-induced reduction of the basal cAMP level with apparent K _B values that were similar to its H₂ receptor affinity. Investigation of the modulation of receptor expression after long-term drug treatment revealed that at low concentrations histamine induced a significant reduction in H₂ receptor expression, whereas at high concentrations receptor expression was slightly increased. The partial agonist burimamide induced, like inverse agonists, an upregulation of the human H₂ receptor after prolonged treatment. These findings suggest a structural instability of the constitutively active human H₂ receptor in transfected Chinese hamster ovary cells. Occupation of the H₂ receptor by any ligand reduces the instability, thus resulting in higher cellular expression levels.     

Duplication of theAce.1 locus inCulex pipiens mosquitoes from the Caribbean

InCulex pipiens mosquitoes, AChE1 encoded by the locusAce.1 is the target of organophosphorus and carbamate insecticides. In several resistant strains homozygous forAce.1 ^RR , insensitive AChE1 is exclusively found. An unusual situation occurs in two Caribbean resistant strains where each mosquito, at each generation, displays a mixture of sensitive and insensitive AChE1. These mosquitoes are not heterozygotes,Ace.1 ^RS , as preimaginal mortalities cannot account for the lethality of both homozygous classes. This situation is best explained by the existence of twoAce.1 loci, coding, respectively, a sensitive and an insensitive AChE1. Thus, we suggest that in the Caribbean a duplication of theAce.1 locus occurred before the appearance of insecticide resistance at one of the two copies.     

Chemical defences in leaf beetles and their larvae: The ecological, evolutionary and taxonomic significance

The chemical defences of the Chrysomelinae are reviewed. Defensive glandular secretions have evolved independently in larvae and adults, and faster than the morphology of the glands. Both characters are used in a phylogenetic study of the Chrysomelini, disclosing suprageneric affinities. First, a close relationship between the Chrysomelina and Phratora is proposed. Secondly, Leptinotarsa and Gonioctena are probably more closely related to the Chrysolinina than to the Chrysomelina and Phratora. The qualitative and quantitative composition of larval and adult secretions sometimes differs between geographically isolated populations of the same species, which are therefore probably genetically distinct. The host plant shows an influence which explains discrepancies between the current classification and the chemical nature of the secretions. Some beetles sequester secondary plant metabolites or use them as precursors for their own defences. The original biosynthetic pathway has been lost in these species. Other factors which could affect the chemical diversity of the secretions are discussed: random events such as neutral mutations and genetic drift, conditioning or adaptation of predators to specific defensive mixtures, and the diversity of potential predators. The latter could help to explain the divergence in the chemical nature of the larval and adult secretions. The volatile irritants produced by the larvae are well suited to repel small arthropods, such as ants, whereas poisons associated with aposematic coloration in the adults could be directed against small vertebrates, such as birds.