Linkage analysis of the Bcg gene on mouse chromosome 1. Identification of a tightly linked marker

We have mapped and determined the gene order of five cloned genes in the vicinity of the murine host resistance gene Bcg on mouse chromosome 1. For this, we have used a RFLP-type analysis in panels of 43 recombinant inbred strains, 3 congenic mouse strains, and 186 segregating backcross progeny derived from inbred strains of Bcgr and Bcgs genotypes. The Bcg alleles of segregating animals were established by in vivo infection with Mycobacterium bovis (Bacillus Calmette-Guérin) strain Montreal. Genomic DNA prepared from progenitor mouse strains was isolated, digested with restriction endonucleases, and analyzed by Southern blotting to identify strain-specific RFLP for each DNA marker tested. Among a number of DNA markers tested, Len2, Fn, Vil, Alpi, and Achrg were found to co-segregate with Bcg in mouse strains congenic for this locus. Detailed segregation analysis of the five markers and Bcg showed that Vil was extremely close to Bcg with no recombinant identified, whereas Fn and Len2 were located 4.5 and 9 cM proximal of Bcg, respectively. Alpi and Achrg mapped 5 and 5.5 cM distal from Bcg, respectively. Pedigree analysis in the recombinant inbred strains and backcross animals indicated the gene order: centromere-Len2-Fn-Vil,Bcg-Alpi-Achrg. The tightly linked Vil marker can now be used as an entry point in recombinant genomic DNA libraries to clone sequences overlapping Bcg. This group of five genes flanking Bcg on mouse chromosome 1 is precisely conserved on the telomeric end of the long arm of human chromosome 2q. Our results suggest that a likely location for a putative human homologue to the murine host resistance gene Bcg is the long arm of human chromosome 2 (2q32-qter).     

Membrane-associated carbonic anhydrase IV in skeletal muscle: subcellular localization

 Carbonic anhydrase IV (CA IV) was examined by light microscopy and electron microscopy in rat soleus muscle. Semithin sections of aldehyde-fixed Epon-embedded muscle were stained with rabbit anti-rat lung CA IV and the avidin-biotin-peroxidase complex. With this technique, capillaries and sarcolemma showed positive CA IV staining. For electron microscopy, rat soleus specimens were aldehyde-fixed, with or without subsequent osmication, and embedded in Epon. Ultrathin sections were immunostained with anti-rat lung CA IV/immunogold. Omitting osmium allowed ample antigen-antibody reactions but could not prevent the release of glycosylphosphatidylinositol-anchored CA IV from the membranes, which led to apparent background staining. Postosmication significantly reduced tissue antigenicity but kept the antigen bound to the membranes and thus allowed a very precise localization of CA IV. By electron microscopy, membrane-bound CA IV is found to be associated with capillary endothelium, sarcolemma, and sarcoplasmic reticulum (SR). Conceivably, the presence of SR staining in ultrathin sections and its absence in semithin sections reflect a problem of accessibility of the antigenic sites. Accepted: 17 May 1996     

Embryonic, Larval and Postlarval Development of the Tropical Clam, Anomalocardia Brasiliana (Bivalvia, Veneridae)

Anomalocardia brasiliana (Gmelin, 1791) is a venerid clam, distributed fromthe West Indies to Brazil, which lives shallowly burrowed inmuddy sands of mangrove lagoons in Guadeloupe. Development frominduced spawning to metamorphosed juveniles is described byusing light and scanning electron microscopy. The shell-fieldappears at the gastrula stage, 6 h after fertilization, andrapid embryonic development results in straight-hinge veligers, 18h after fertilization. These swimming veligers develop to swimming-crawlingpediveligers, then to benthic plantigrades with functional elongatedgill filaments without interruption in 15 days. The transitionalarched structures observed at the end of the pediveliger stagewere called `ctenidial crypts' to distinguish them from functionalgill filaments which exist only in metamorphosed juveniles.Metamorphosis, which occurs without a special environmental cue,is completed with the differentiation of the siphons in 300µmjuveniles. Thus, there is no delay of metamorphosis in thisspecies whereas a developmental hiatus has been described in mostplanktotrophic bivalves. Juveniles, 1 mm in shell-length withthe triangular shape, pointed posterior end and brown zig-zagstripes on the shell, typical of A. brasiliana have been obtained7 weeks after fertilization. However, a large variability ofindividual sizes and developmental stages within the same batchesmay indicate a high genetic variability. (Received 11 December 1997; accepted 30 April 1998)     

An improved procedure for chemospecific acylation of 2-mercaptoethanol by lipase-catalyzed transesterification

Summary Various O-acyl derivatives of 2-mercaptoethanol have been obtained enzymatically by lipase-catalyzed chemospecific esterification reactions of the substrate and several aliphatic carboxylic acid ethyl esters.     

Degradation of [β-14C]hordenine in Hordeum vulgare plants

[β-¹⁴C]Hordenine is ultimately degraded by intact plants of Hordeum vulgare to C₆-C₁ intermediates that are incorporated into polymeric material.