Receptor-like stereospecific binding of a pyrethroid insecticide to mouse brain membranes

A heterogeneous particulate fraction of mouse brain homogenates binds NRDC 157 (3-phenoxybenzyl [1$\text{R}$,$\text{cis}$]-3-(2,2-dibromovinyl)-2,2- dimethylcyclopropanecarboxylate), a potent pyrethroid insecticide, stereospecifically and with high affinity. Stereospecific binding is a minor component of total binding (2.8%); the remainder of observed binding is predominantly nonspecific and unsaturable. Stereospecific binding is half-saturated at 4×10^?8$\text{M}$ and fully saturated at concentrations in excess of 1×10^?7$\text{M}$. The stereospecific binding capacity of this preparation was 200–250 pmoles of NRDC 157 per gram equivalent of brain tissue (2.3–2.8 pmol/mg protein). This binding site may represent the neural receptor involved in the stereospecific toxic action of pyrethroids.     

Gene mapping and determination of the structure of chloroplast transfer RNA from various photosynthetic organisms

The review sums up data on gene mapping studies of tRNAs of chloroplasts from maize, beans, Euglena, Cyanophora. The mechanisms of splicing of tRNA2Ile from maize chloroplasts and coded for by a gene of unusual length was investigated.     

Transfer RNA genes ofZea mays chloroplast DNA

A minimum of 37 genes corresponding to tRNAs for 17 different amino acids have been localized on the restriction endonuclease cleavage site map of theZea mays chloroplast DNA molecule. Of these, 14 genes corresponding to tRNAs for 11 amino acids are located in the larger of the two single-copy regions which separate the two inverted copies of the repeat region. One tRNA gene is in the smaller single-copy region. Each copy of the large repeated sequence contains, in addition to the ribosomal RNA genes, 11 tRNA genes corresponding to tRNAs for 8 amino acids. The genes for tRNA₂ ^Ile and tRNA^Ala map in the ribosomal spacer sequence separating the 16S and 23S ribosomal RNA genes. The three isoaccepting species for the tRNAs^Leu and the three for tRNAs^Ser, as well as the two isoaccepting species for tRNA^Asn, tRNA^Gly, tRNAs^Ile, tRNAs^Met, tRNAs^Thr, are shown to be encoded at different loci. Two independent methods have been used for the localization of tRNA genes on the physical map of the maize chloroplast DNA molecule: (a) cloned chloroplast DNA fragments were hybridized with radioactively-labelled total 4S RNAs, the hybridized RNAs were then eluted, and identified by two-dimensional polyacrylamide gel electrophoresis, and (b) individual tRNAs were³²P-labelledin vitro and hybridized to DNA fragments generated by digestion of maize chloroplast DNA with various restriction endonucleases.     

Maize chloroplast DNA encodes a protein sequence homologous to the bacterial ribosome assembly protein S4.

A cloned restriction fragment of maize chloroplast DNA (Bam H1 fragment 5) is shown to contain an open reading frame which encodes a basic protein of 201 amino acid residues with 40-50% sequence homology to E. coli ribosomal protein S4. Based on the experimentally determined sequence homology between the highly conserved bacterial ribosomal protein L12 and its chloroplast homologue (Bartsch M., Kimura, M. and Subramanian, A.R. (1982) Proc. Natl. Acad. Sci. USA 79, 6871), we conclude that this reading frame represents the maize chloroplast S4 gene. The nucleotide sequence of a 1100 base pair DNA segment containing the putative gene is presented.     

Energy Sources for the Absorption of Rubidium by Chlorella

Die aktive (stoffwechselabängige) Aufnahme von Radiorubidium aus 8.10^?5 molarer Lösung durch Chlorella pyrenoidosa wurde in Langzeitversuchen (1–2 Tage) untersucht. Die Annahinc ist, daβ die dafür notwendige Energie in Form von ATP bereitgestellt werden muβ. Es wurde gefunden, daβ Gegenwart von Na- Oder Cl-Ionen für die aktive Rb-Aufnahme nicht notwendig ist; die Rb-Pumpe ist also nicht an eine Na- Oder Cl-Pumpe gekoppelt. Vorbeladene Chlorella gibt Rb über längere Zeiten langsam an das Medium ab. Durch Experimente im Licht bzw. Dunkel und in Gegenwart bzw. Abwesenheit von Luft wurde gezeigt, daβ bei 9000 lux die Beleuchtung mehr Energie für die aktive Aufnahme erbringt als die Atmung. Der Ersatz von Luft durch Sauerstoff hat keine Auswirkung. Die Versorgung mit ATP durch Atmung—nicht aber durch (zyklische) Photophosphorylierung—wird durch 5.10^?4 M DNP weitgehend unterdrückt. Die aktive Aufnahme ist klein, wenn sie sich nur auf Glykolyse stützt. Gleichzeitige Einwirkung von Licht, Luft (Sauerstoff) und DNP auf Chlorella führt zu irreversibler Schädigung und Ausbleichung der Algen. Sie hören auf, Rb aufzunehmen und verlieren vorher absorbiertes Rb wieder. Gründe für diesen Effekt werden diskutiert. Die aktive Aufnahme von Rb wird durch 5.10^?2 M Glukose gefördert, u.z.w. im Licht und im Dunkel, in Luft- und in Stickstoffatmosphäre. In dieser Beziehung unterscheidet sich die aktive Rb- von der aktiven Bromid-Aufnahme. Die Förderung durth Glukose wird durch DNP gehemmt, ausgenommen im Dunkel in Stickstoffatmosphäre. In Gegenwart von DNP wird die Rb-Aufnahme durch 1% CO₂ sowohl im Licht als auch im Dunkel stark herabgedrückt.     

Structure of the murine mb-1 gene encoding a putative sIgM-associated molecule

Genomic DNA clones containing the B cell-specific murine mb-1 gene were isolated and a 5.6-kb BamH I fragment was characterized. It is 5629 bp long and contains five exons: an exon containing the 5' untranslated and the coding sequence of the signal peptide, an exon of 294 bp, which contains most of the extracellular sequence of the MB-1 protein, a 119-bp long exon coding mainly for the transmembrane portion, and two exons of 69 bp and 427 bp encoding the cytoplasmic domain and the 3'-untranslated region, respectively. The mb-1 gene does not contain a "TATA box" found in many eukaryotic promoters. The 5'-flanking region has sequence stretches homologous to IgVH 5'-promoter regions and a bcl 2 intron sequence. It contains the decanucleotide sequence (ATGGCAAATA) almost identical to the octamer motif of IgVH promoters. A B cell-specific DNase I-hypersensitive site was found in the 3'-flanking region indicating that this region might be involved in B cell-specific expression of mb-1. Southern blot analysis of genomic liver DNA with the cloned mb-1 cDNA suggests the existence of another mb-1-related gene segment.     

Recombinational hotspot specific to female meiosis in the mouse major histocompatibility complex

Thewm7 haplotype of the major histocompatibility complex (MHC), derived from the Japanese wild mouseMus musculus molossinus, enhances recombination specific to female meiosis in theK/A interval of the MHC. We have mapped crossover points of fifteen independent recombinants from genetic crosses of thewm7 and laboratory haplotypes. Most of them were confined to a short segment of approximately 1 kilobase (kb) of DNA between theA 3 andA 2 genes, indicating the presence of a female-specific recombinational hotspot. Its location overlaps with a sex-independent hotspot previously identified in theMus musculus castaneus CAS3 haplotype. We have cloned and sequenced DNA fragments surrounding the hotspot from thewm7 haplotype and the corresponding regions from the hotspot-negative B10.A and C57BL/10 strains. There is no significant difference between the sequences of these three strains, or between these and the published sequences of the CAS3 and C57BL/6 strains. However, a comparison of this A3/A2 hotspot with a previously characterized hotspot in theE gene revealed that they have a very similar molecular organization. Each hotspot consists of two elements, the consensus sequence of the mouse middle repetitive MT family and the tetrameric repeated sequences, which are separated by 1 kb of DNA.The nucleotide sequence data reported in this paper have been submitted to the DNA Data Bank of Japan nucleotide sequence database and have been assigned the accession numbers d90007-9. Offprint requests to: T. Shiroishi.     

T-cell specific rearrangement of T-cell receptor beta transgenes in mice.

To study rearrangement of T cell receptor (TCR) genes, transgenic mice were generated with a TCR beta minilocus in germline configuration, containing three V beta, two D beta, fourteen J beta and two C beta gene segments and the TCR beta enhancer. Using the polymerase chain reaction as an analytical tool both partial DJ as well as complete VDJ rearrangements were seen, indicating that the minilocus contained all sequence elements required for rearrangment. Rearrangements of minilocus gene segments were restricted to T cells in the thymus and the periphery and did not occur in B cells. V beta 8.3 and V beta 5 sequences encoded by the minilocus were expressed on the surface of peripheral T cells at high frequencies. Transgenic mice with TCR minilocus genes will be a useful system to identify DNA sequence elements required for regulation of rearrangement in vivo.