TheRT1.G locus in the rat encodes a Qa/TL-like antigen

A new antigenic system in the rat homologous to theQa/TL antigen system in the mouse has been characterized. It was detected by antibodies raised in donor-recipient combinations that were matched for theRT1. A, B, D, E loci in the major histocompatibility complex (MHC): (R11×BN)F₁ anti-BN.1L(LEW), (R18×BN)F₁ anti-BN.1L, and BN.1LV1(F344) anti-BN.1L. Absorption analyses using these antisera and a variety of inbred, congenic and recombinant strains identified three alleles,RT1.G ^a ,G ^b ,G ^c , of whichG ^c is a null allele. The strain distribution of these alleles was determined, using 37 strains of rats representative of all of the prototypic haplotypes and a number of congenic and recombinant strains. The use of the congenic and recombinant strains showed that theRT1.G locus was linked to the MHC and that the most probable gene order wasA-E-G. Testcross analysis showed that the map distance betweenA andG was 1.4 cM(4/285 recombinants). The RT1.G antigen has a heavy chain ofM _r 46 000 and is present on both T and B cells.     

A selective differential medium for the isolation of Listeria monocytogenes

A new medium has been developed for the isolation of Listeria monocytogenes from clinical specimens with a mixed flora. Almost complete inhibition of unwanted organisms was achieved and recognition of colonies of Listeria spp. was usually possible after 24 h using the aesculin-ferric ammonium citrate indicator system. Compared to McBride agar the new medium was more inhibitory to representative contaminating species in pure culture and more successful in isolating small numbers of L. monocytogenes from artificially seeded clinical specimens.     

Photosynthetic properties of leaves of a yellow green mutant of wheat compared to its wild type

We investigated several photosynthetic parameters of a virescent mutant of durum wheat and of its wild-type. Electron transport rate to ferricyanide was the same in the two genotypes when expressed on leaf area basis while O₂ evolution of the leaf tissue in saturating light and CO₂ was slightly higher in the yellow genotype. RuBPCase was also slightly higher. Quantum yield per absorbed light was similar in the two genotypes. P700 and Cyt f were less concentrated in the mutant while PS II was only marginally lower. The light response curve of CO₂ assimilation indicated higher level of photosynthesis of the mutant in high light, which corresponded to a lower non-photochemical quenching compared to the wild-type. It is concluded that the reaction centres, cyt f and chlorophyll are not limiting factors of electron transport in wheat seedlings and that electron transport capacity is in excess with respect to that needed for driving photosynthesis. Since the differences in photosynthesis reflect differences in RuBPCase activity, it is suggested that this enzyme limits photosynthesis in wheat seedlings also at high light intensities.Abbreviations cyt f cytochrome f - chl chlorophyll - PS II photosystem II - Pn_max maximum photosynthesis - RuBCase Ribulose, 1-5,bisphosphate carboxylase     

Altered growth factor sensitivity in EL2 rat fibroblasts: influence of this biological characteristic on cell growth

Extensive evidence indicate that platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) play a key role in the stimulation of the 3T3 fibroblast replication: in this connection, PDGF and EGF act as a competence and a progression factor, respectively. We have previously demonstrated that EGF alone leads density-arrested EL2 rat fibroblasts to synthesize DNA and proliferate in serum-free cultures. Here, we have analyzed the role of EGF in the control of EL2 cell proliferation. Our data show a dose-related effect of EGF on DNA synthesis and cell growth, with maximal stimulation for both parameters at 20 ng/ml. On the other hand, autocrine production of PDGF or PDGF-like substances by EL2 cells is seemingly excluded by experiments with anti-PDGF serum or medium conditioned by EL2 fibroblasts. EGF binding studies show that EL2 cells possess high affinity EGF receptors, at a density level 3 to 4-fold higher than other fibroblastic lines. In addition, EL2 cells show a normal down-regulation of EGF receptors, following exposure to EGF, but PDGF, fibroblast growth factor (FGF), transforming growth factor beta (TGF beta) and bombesin have not decreased the affinity of EGF receptor for its ligand. Moreover, in EL2 cells, the EGF is able to induce the synthesis of putative intracellular regulatory proteins that govern the PDGF-induced competence in 3T3 cells. Our data indicate that EGF in EL2 cells may act as both a competence and a progression factor, via induction of the mechanisms, regulated in other cell lines by cooperation between different growth factors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of ethanol on the activities of 3-hydroxy-3-methylglutaryl-coenzyme A-reductase and squalene-hopene-cyclase in Zymomonas mobilis

Summary The influence of different primary aliphatic alcohols on the activities of two key enzymes in hopanoid biosynthesis of Zymomonas mobilis was investigated. By use of ¹⁴C- and ³H-labelled substrates the enzymes 3-hydroxy-3-methylglutaryl-CoA-reductase and squalene-hopenecyclase were detected with activities of 1.6 pmol x (min x mg protein)^-1 and 2.3 pmol x- (min x mg protein)^-1, respectively. Cells grown in the presence of 6% (v/v) ethanol did not show higher activities of these enzymes than cells grown in the presence of 1% (v/v) ethanol. Furthermore, 3-hydroxy-3-methylglutaryl-CoA-reductase was not activated by ethanol. However, ethanol activated the squalene-hopene-cyclase when added to the enzyme test system. Besides ethanol, propanol also had a positive effect on the squalene-hopene-cyclase: the enzyme's activity increased 1.7-fold in the presence of either alcohol at a concentration of 6% (v/v). This corresponded with a similar increase of hopanoid content of whole cells when grown in the presence of 6% (v/v) added ethanol or propanol. These results indicated that the squalene-hopene-cyclase has a regulatory function in the alcohol dependent hopanoid biosynthesis of Z. mobilis.Abbreviation HMG-CoA-reductase 3-hydroxy-3-methylglutaryl-coenzyme A-reductase     

Neural activity pattern is not necessary for the development of adult ultrastructure in katydid (Neoconocephalus robustus) singing muscles

Summary The singing muscles of the katydid Neoconocephalus robustus develop adult ultrastructure late in the last nymphal instar and during the first few days of adult life. The ultrastructural changes during early adulthood were not affected by unilateral axotomy shortly after the adult molt. Both denervated and innervated muscles developed adult proportions of mitochondria, myofibril, and sarcoplasmic reticulum and transverse tubules.     

Analysis of the reversible binding of virginiamycin M to ribosome and particle functions after removal of the antibiotic

Type A synergimycins (VM) were shown to act catalytically and to induce two ribosomal alterations: (a) inability to promote polypeptide synthesis; (b) high-affinity binding of type B synergimycins (VS). A claim for irreversible binding of type A synergimycins to ribosomes has promoted the present reinvestigation. Submission of ribosomes from VM-treated bacteria to a purification procedure (supposed to remove the drug, according to a low association constant previously reported) yielded particles still holding residual VM. The formation of VM.ribosome complexes, more stable than previously inferred but without covalent linkage, was deduced from the extractability of complexed VM by organic solvents. Moreover, incubation of these complexes with increasing amounts of anti-VM immunoglobulins progressively restored ribosome activity in protein synthesis. Binding of VS to ribosomes, by fluorimetric titrations in the presence of substoichiometric concentrations of VM, was incompatible with catalytic action of type A synergimycins. Ribosomes from VM-treated bacteria displayed also a higher affinity for VS than did control ribosomes. This property did not disappear when ribosome.VM complexes were incubated with anti-VM IgG, nor when VM-IgG complexes were withdrawn from the reaction mixture by protein A-agarose binding. We can conclude that VM binding produces: (1) an inhibition of ribosome-promoted peptide bond formation, which occurs only in the presence of the drug; and (2) an increase of ribosome affinity for VS, which lasts after VM removal. The linkage of this drug with ribosomes is tight but reversible and its action is stoichiometric.     

Mono and two-dimensional 500-MHz characterization of synthetic bombesin and related peptides in DMSO and DMSO-water

The proton nmr characterization of bombesin (BBS) and of two peptide fragments corresponding to the (1-6) and (6-14) sequences has been carried out at 500 MHz in dimethyl sulfoxide (DMSO-d6) using two-dimensional (2D) homo and 1H-13C heterocorrelated techniques. All resonances in the nmr spectra have been assigned and several coupling constants have been measured. The backbone J alpha CH-NH coupling constants are quite similar and around 7.8-8.2 Hz, pointing to an unfolded structure in DMSO-d6. The possibility of secondary structures in highly viscous mixtures of DMSO-d6-water was investigated. The existence of sequential nuclear Overhauser enhancement (NOE) effects in the C-terminal nonapeptide section may indicate a preferential site for secondary structuring.     

Genomic distribution of copia-like transposable elements in somatic tissues and during development of Drosophila melanogaster

The genomic distribution of elements of the copia, 412, B 104, mdg 1, mdg 4 and 1731 transposon families was compared by the Southern technique in DNA preparations extracted from brains, salivary glands and adult flies of two related Drosophila lines. The copia, 412 and mdg 1 sequences were also probed in DNA from sperm, embryos, and 1st and 2nd instar larvae. The homogeneity of the patterns observed shows that somatic transposition is unlikely to occur frequently. A correlation between mobility and the euchromatic or heterochromatic location of transposable elements is discussed. In addition, an explanation of the variable band intensities of transposable elements in Southern autoradiographs is proposed.