Locus-specific cDNA cloning in the class I multigene family: structure of H-2D r and H-2D s

The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers M34961-2.     

Electron spin resonance studies of changes in membrane fluidity of Chinese hamster ovary cells during the cell cycle

Electron spin resonance (ESR) spin-label methods were used with 5-doxyl-stearic acid as a probe to investigate membrane fluidity of Chinese hamster ovary (CHO) cells during the cell cycle. A 35 GHz ESR technique was developed to study membrane fluidity of intact cells. This technique requires only about $\text{1}\text{6}$ the amount of cells compared to the conventional spin-label techniques. With this technique we observed a cyclic change of membrane fluidity during the cell cycle of CHO cells: cells in mitosis had the highest membrane fluidity, whereas cells in G₁ and early S phases had the lowest membrane fluidity.     

Functional properties of plasmids in lactic streptococci

Plasmid biology has become an important area of investigation in dairy starter cultures since it now appears that some properties, vital for successful milk fermentations, are coded by genes located on plasmid DNA. Some of these metabolic properties observed in lactic streptococci have been clearly established as being plasmid-mediated. Examples would be lactose utilization and in Streptococcus lactis subsp. diacetylactis the ability to produce a bacteriocin-like substance. Phenotypic and physical evidence for plasmid linkage has been obtained for other traits such as citrate, sucrose, galactose, glucose, mannose, and xylose utilization, proteinase activity, modification/restriction systems, as well as for nisin production. Further genetic evidence is now needed to confirm plasmid association to these properties. For some characteristics the association with plasmids is highly speculative and is solely based on the phenotypic loss of a metabolic property. In this category would be sensitivity to agglutinins, sensitivity to the lactoperoxidase-thiocyanate-hydrogen peroxide inhibitory system, arginine hydrolysis, and slime production. Other properties which appear plasmid-mediated in lactic streptococci and which will be discussed include inorganic ion resistance, drug resistance, and diplococcin production.     

Sleep,activity, temperature and arousal responses of mice deficient for muscarinic receptor M2 or M4

AimsThe type 2 muscarinic receptor (M2R) differs from the other G-protein-coupled muscarinic receptor (type 4, or M4R) in tissue distribution and physiologic effects. We studied the impact of these receptors on sleep and arousal by using M2R and M4R knock-out (KO) mice.Main methodsM2R and M4R KO and genetically intact mice were compared in terms of normal patterns of sleep, responses to sleep loss, infectious challenge and acoustic startle, and acoustic prepulse inhibition of startle (PPI).Key findingsUnder basal conditions, M2R and M4R KO mice do not differ from the background strain or each other in the amount or diurnal pattern of sleep, locomotor activity, and body temperature. After enforced sleep loss, M2R KO mice, in contrast to the other two strains, show no rebound in slow-wave sleep (SWS) time, although their SWS is consolidated, and they show a greater rebound in time spent in REMS (rapid-eye-movement sleep) and REMS consolidation. During influenza infection, M2R KO mice, as compared with the other strains, show marked hypothermia and a less robust increase in SWS. During Candida albicans infection, M2R KO mice show a greater increase in SWS and a greater inflammatory response than do the other strains. M2R KO mice also show greater acoustic startle amplitude than does the background strain, although PPI was not different across the 3 strains over a range of stimulus intensities.SignificanceTaken together, these findings support different roles for M2R and M4R in the modulation of sleep and arousal during homeostatic challenge.     

A novel concatenated dimer of recombinant bovine somatotropin

A novel protein concatenated dimer structure was generated during the folding/oxidation of inclusion bodies of recombinant bovine somatotropin synthesized inEscherichia coli. The structure of this dimeric molecule was determined by peptide mapping with trypsin, and limited proteolysis by thrombin. Peptide mapping demonstrated that the two disulfide pairs in bovine somatotropin dimer were identical to those in monomer. Limited proteolysis with thrombin resulted in the cleavage of only a single peptide bond between arginine-132 and alanine-133 in bovine somatotropin dimer. This single peptide bond cleavage was sufficient to convert this dimer to a monomeric molecular weight species as analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and HPLC. Since the single cleaved peptide bond is present in the large disulfide loop of bovine somatotropin, these data demonstrate that the dimeric molecule exists as a novel concatenated structure through the interlocking of the disulfide loops of this protein.