bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevention of phagosome-lysosome fusion in cultured macrophages by sulfatides of Mycobacterium tuberculosis.
Authors: Goren M B , D'Arcy Hart P , Young M R , Armstrong J A
Published: May 2006

Intracellular parasites (e.g., Mycobacterium tuberculosis, Toxoplasma gondii, and some Chlamydiae) may promote their survival within the host by acting from within phagosomes to prevent phagolysosome formation, thus avoiding exposure to the lysosomal hydrolases. The present studies demonstrate that when sulfatides of M. tuberculosis (anionic trehalose glycolipids largely responsible for the neutral red reactivity of virulent strains) are administered to cultured mouse peritoneal macrophages, they accumulate in the secondary lysosomes, which are rendered incompetent for fusion with phagosomes containing suitable target particles such as viable yeasts. This antifusion effect is also exhibited when small amounts of sulfatide are introduced directly into phagosomes by attachment to the target yeasts prior to their ingestion. The sulfatides evidently exert a selective inhibitory influence on membrane fusion, analogous to what occurs typically when macrophage cultures are infected with tubercle bacilli. This effect may be due to ionic interaction between the polyanionic micelles of bacterial sulfatide and organelle membranes, modifying the latter and inducing dysfunction.
Biosynthesis of lipid-linked oligosaccharides and glycoprotein in aorta: stimulation by acceptor lipids isolated from liver.
Authors: Forsee W T , Elbein A D
Published: May 2006

An acidic glycolipid fraction was isolated from porcine liver and partially purified on DEAE-cellulose. This material markedly stimulated the incorporation of mannose from GDP-[14C]mannose into lipid-linked oligosaccharides and into glycoprotein, but did not stimulate incorporation into the mannosyl-phosphoryl-polyprenol. The products formed from GDP-[14C]mannose in the presence of acceptor lipid were a series of lipid-linked oligosaccharides of mannose and N-acetylglucosamine (GlcNAc) which differ from each other in the size of the oligosaccharide moieties. The acceptor lipid fraction was partially characterized in terms of its carbohydrate composition by mild acid hydrolysis and reduction with NaB3H4. The [3H]sugars were then separated into a number of monosaccharides and oligosaccharides by paper chromatography. Strong acid hydrolysis of two of the larger oligosaccharides released from the acceptor lipid followed by reduction with NaB3H4 gave [3H]mannitol and [3H]GlcN-ol in ratios of 2.8:2 and 3.8:2, indicating that these compounds probably were penta- and hexasaccharides. In addition, GlcNAc was shown to be at the reducing terminus and alpha-linked mannose at the nonreducing ends of the molecules. The results suggest that the acceptor lipid fraction is composed of oligosaccharides of (Man)n leads to GlcNAc leads to GlcNAc, probably attached to a polyprenol through a pyrophosphoryl linkage.
Mechanism of action of beta-bungarotoxin on synaptosomal preparations.
Authors: Sen I , Grantham P A , Cooper J R
Published: May 2006

The neurochemical activity of beta-bungarotoxin was investigated using a synaptosomal preparation of rat cerebral cortices. In preparations preincubated with [3H]choline in order to label acetylcholine the toxin caused a rapid release of the transmitter, which was calcium dependent but only a little affected by a depolarizing concentration of potassium. beta-Bungarotoxin was also shown to be a potent inhibitor of the high affinity transport system for choline, producing 50% inhibition at a concentration of 50 nM. These findings explain the observed electrophysiological effects of the toxin. Electron microscopy revealed no discernible effect of 0.1 muM beta-bungarotoxin on either synaptic vesicles or mitochondria. Neither the release of transmitter nor the inhibition of choline uptake by the toxin was affected by the presence of an inhibitor of phospholipase activity.
Isolation and characterization of the protein coded by gene A of bacteriophage phiX174 DNA.
Authors: Ikeda J E , Yudelevich A , Hurwitz J
Published: May 2006

Replication of phiX174 circular replicative form (RFI) DNA by extracts of Escherichia coli infected with bacteriophage phiX174 (amber in gene A) requires the phiX174 gene A product. This requirement has been used as an assay for the isolation of this protein. The gene A product (purified 4000-fold) caused relaxation of superhelical phiX174 RFI and formation of discontinuities in the viral strand of phiX174 RFI uniquely situated in the A region of the genome, and yielded a complex after interacting with phiX174 RFI that is active in replication of phiX RFI.
Appearance in vivo of single-stranded complementary ends on parental herpesvirus DNA.
Authors: Jean J H , Ben-Porat T
Published: May 2006

Intracellular forms of pseudorabies virus parental DNA were examined before and after the onset of viral DNA synthesis. Before initiation of synthesis, parental viral DNA acquires single-stranded ends. Circular and concatemeric molecules are also observed, indicating that the single-stranded ends are complementary. Viral DNA replication is initiated at an internal site within the DNA molecule, giving rise to characteristic replicative loops with single-stranded regions in the trans position. Such replicative loops were seen in unit-size (and smaller than unit-size) linear molecules as well as in circular and concatemeric molecules. These results show that the parental viral DNA molecules that acquire single-stranded ends, and consequently are able to form circles and concatemers, proceed to replicate.
Regulation of protein synthesis in rabbit reticulocyte lysates: characteristics of inhibition of protein synthesis by a translational inhibitor from heme-deficient lysates and its relationship to the initiation factor which binds Met-tRNAf.
Authors: Ranu R S , Levin D H , Delaunay J , Ernst V , London I M
Published: May 2006

In heme-deficient reticulocyte lysates a translational inhibitor which regulates protein synthesis is formed or activated. To define the mechanism of action of the translational inhibitor (RI), RI was partially purified. We have utilized the isolated RI to examine its relationship to the translational inhibitor formed in situ in heme-deficiency, some quantitative aspects of inhibition of protein synthesis, and the relationship of RI concentration to the initiation factor (IF-MP) which forms a ternary complex with Met-tRNAf and GTP (IF-MP-Met-tRNAf-GTP). The results demonstrate that the activity of isolated RI is related to the in situ heme-deficiency inhibitor by several criteria: (a) the biphasic kinetics of inhibition manifested by RI in lysates containing optimal levels of hemin are very similar to those observed in heme-deficiency, i.e., an initial period in which several rounds of protein synthesis proceed at the control rate followed by an abrupt decline in the rate of protein synthesis. (b) Both inhibitions are accompanied by the disaggreagation of polyribosomes with a concomitant increase in 80S ribosomes. (c) Both inhibitions are reversed by IF-MP. The isolated RI blocked protein synthesis in lysates at temperatures ranging from 15 degrees to 30 degrees. Although the rate of protein synthesis was a function of the temperature of incubation, the number of rounds of protein synthesis prior to shut-off was essentially the same at various temperatures. When RI was added to lysates, at increasing intervals after the start of incubation, the period of synthesis before shut-off (lag) progressively decreased. The inhibition of protein synthesis by RI was immediately reversed by the addition of IF-MP. The extent of reversal increased with increasing concentrations of IF-MP; at low levels of RI almost complete reversal of inhibition by IF-MP was obtained. However, at high levels of RI which did not appreciably increase the degree of inhibition of protein synthesis, equivalent amounts of IF-MP were less effective in reversing inhibition. These results suggest that the inhibition of protein synthesis by the isolated inhibitor involves the initiation factor IF-MP.
Binding of [3H]dihydroazapetine to alpha-adrenoreceptor-related proteins from rat vas deferens.
Authors: Ruffolo R R , Fowble J W , Miller D D , Patil P N
Published: May 2006

The potent alpha-adrenoreceptor blocking agent, azapetine, has been catalytically reduced with tritium gas to form [3H]dihydroazapetine. [3H]Dihydroazapetine retains significant ability to block alpha-adrenoreceptors and has been used as a ligand to study the receptor in a subcellular fraction containing membrane fragments from rat vas deferens. Specific binding of [3H]dihydroazapetine rapidly reaches equilibrium and is also reversible and saturable with a dissociation constant similar to that determined pharmacologically. The binding capacity is approximately 40 pmol/mg of protein. All alpha-adrenergic blockers tested were able to inhibit specific binding. High concentrations of alprenolol, atropine, or chlorpheniramine had no effect. In addition, all alpha-adrenergic agonists of the imidazoline class inhibit binding in low concentrations, whereas soterenol or carbamylcholine did not. There is good correlation (r=0.84) between blockade or stimulation of the receptor in intact tissues and inhibition of binding of [3H]dihydroazapetine to the subcellular fraction. These findings suggest that the fraction contains alpha-adrenoreceptor-related proteins. Alpha-adrenergic agonists structurally related to norepinephrine caused a stereoselective increase in binding in favor of the (-)-isomer, possibly reflecting an allosteric interaction at a different binding site on the receptor protein. The possibility of two different modes of binding for structurally dissimilar agonists is suggested.
Determination of molecular weights by fluctuation spectroscopy: application to DNA.
Authors: Weissman M , Schindler H , Feher G
Published: May 2006

A method for determining molecular weights of macromolecules by measuring spontaneous concentration fluctuations is described. The method is absolute, rapid, and requires no shearing forces on the molecules. We have applied this technique to the determination of molecular weight of DNA molecules. The molecular weight values obtained for T2 phage DNA (1.14 X 10(8)) and replicating Escherichia coli DNA (3.9 X 10(9)) agree with previous results. By monitoring individual molecules, an estimate of the molecular weight of nuclei and individual chromosomal DNA molecules of Drosophila melanogaster was obtained.
Recombination in Saccharomyces cerevisiae: a DNA repair mutation associated with elevated mitotic gene conversion.
Authors: Boram W R , Roman H
Published: May 2006

A mutant haploid strain of Saccharomyces cerevisiae has been isolated that is sensitive to the alkylating agent methyl methanesulfonate at a concentration of 0.01% (vol/vol). The strain also shows sensitivities to x-rays and ultra-violet light, which cosegregate with sensitivity to methyl methanesulfonate as a single gene defect. An analysis of the sensitivity to ultraviolet light indicates that the mutation interferes with the excision of pyrimidine dimers. Diploids homozygous for the mutant gene exhibit elevated frequencies of spontaneous mitotic recombination at the ade6 locus. The results indicate that all the events are due to gene conversion. Mitotic recombination was also found to be elevated for three loci other than ade6. Thus, the recombinational effect seems not to be locus specific. Linkage and allelism tests indicate that the mutation is an allele of the known radiation-sensitive gene rad18. The various effects of this new rad18 allele (rad18-3) are discussed in terms of a defect in DNA repair mechanisms.
Evidence for a gonadotropin from nonpregnant subjects that has physical, immunological, and biological similarities to human chorionic gonadotropin.
Authors: Chen H C , Hodgen G D , Matsuura S , Lin L J , Gross E , Reichert L E , Birken S , Canfield R E , Ross G T
Published: May 2006

Substances from urinary extracts of normal, nonpregnant subjects and human pituitary gonadotropin preparations were found to react similarly to human chorionic gonadotropin (hCG) in a radioimmunoassay system that is highly specific for hCG and without crossreactivity to human luteinizing hormone (hLH). The antiserum was produced in a rabbit immunized with a bovine albumin conjugate of the unique carboxyl-terminal peptide (residues 123-145) isolated from a tryptic digest of the reduced, S-carboxymethylated hCGbeta subunit. The antibody recognition site on the peptide was found to reside on the last 15 amino acid residues of the carboxyl-terminal peptide, as evidenced by the competitive binding activities against 125I-labeled hCG of a series of peptides chemically synthesized according to the carboxyl-terminal sequence of HCGbeta. In order to elucidate the nature of the crossreacting substance in urinary extracts, a human postmenopausal urinary preparation (Pergonal) and a kaolin-acetone extract of urine from a patient with Klinefelter's syndrome were subjected to gel chromatography on Sephadex G-100. The results indicate that fractions showing immunocrossreactivity with the antiserum to hCGbeta-carboxyl-terminal peptide coeluted with 125I-labeled hCG which was separated distinctly from hLH. The same fractions from this postmenopausal urinary gonadotropin preparation exhibited in vitro biological activity proportional to the immunocrossreactivity of the hCG-specific antiserum. Concentration of postmenopausal women's urine by acetone precipitation retained approximately five times more immunoreactivity per unit volume than kaolin-acetone extraction, when assayed with the antiserum to hCGbeta-carboxyl-terminal peptide.
Localization and specificity of binding of subprimate placental lactogen in rabbit tissues.
Authors: Bolander F F , Hurley T W , Handwerger S , Fellows R E
Published: May 2006

A search for specific placental lactogen binding was undertaken in tissues obtained from late pregnant rabbits using the placental lactogens from sheep, cows, and human beings. 125I-labeled ovine lactogen exhibited highest specific binding to the adrenal gland (57.8%), followed by liver (21.5%), ovary (19.9%), mammary gland (15.9%), uterus (12.2%), kidney (8.8%), brain (8.5%), and adipose tissue (7.9%). In liver and mammary gland, the displacement curves for ovine and human lactogen were identical to that for bovine prolactin, indicating that they share the same receptor site. Although the displacement curve for bovine lactogen was parallel to that of the other lactogens the bovine hormone is less active in the radioreceptor assay.
Influenza virus genome consists of eight distinct RNA species.
Authors: McGeoch D , Fellner P , Newton C
Published: May 2006

The genomic RNA of the avian influenza A virus, fowl plague, was fractionated into eight species by electrophoresis in polyacrylamide-agarose gels containing 6 M urea. The separated 32P-labeled RNA species were characterized by digestion with RNase T1 and fractionation of the resulting oligonucleotides by two-dimensional gel electrophoresis; this demonstrated that each species has a distinct nucleotide sequence. A tentative correlation of each genome RNA species with the virus protein that it encodes was made.
Importance of the third amino acid residue of oxytocin for its action on isolated rat uterus: study of relationship between hormone conformation and activity.
Authors: Walter R , Smith C W , Roy J
Published: May 2006

In a continued effort to relate the three-dimensional structure of a peptide hormone to its biological activity, the dose-response relationships of [3-phenylalanine] oxytocin (oxypressin), with an aromatic amino acid residue in position 3, and [3-beta-cyclohexylalanine]oxytocin, with an aliphatic amino acid residue to position 3, were determined in the rat uterine assay in vitro and compared to that of oxytocin. Oxypressin has not only a lower affinity for the smooth muscle receptor than the natural hormone, but also a decreased maximal response (efficacy). [3-beta-Cyclohexylalanine]oxytocin exhibits an even lower affinity than oxypressin, but retains the same maximal response as oxytocin. A reorientation of the tyrosine sidechain, caused by the presence of a neighboring aromatic sidechain in position 3, away from the surface of the 20-membered ring is though to remove the phenolic hydroxyl group from its optimal position in the "active center" of oxytocin and give rise to the reduced efficacy of oxypressin.
Specific binding of formylated initiator-tRNA to Escherichia coli RNA polymerase.
Authors: Pongs O , Ulbrich N
Published: May 2006

E. coli fMet-tRNAfMEet and E. coli RNA plymerase (RNA nucleotidyltransferase; EC 2.7.7.6; nucleoside-triphosphate:RNA nucleotidyltransferase) form a 1:1 complex with an apparent association constant of 9.0 X 10(6)M-1 at 37 degrees. The affinity of polymerase to tRNA depends on the tRNA as well as the formyl methionine moiety. Core polymerase has a greatly reduced affinity for initiator tRNA. Optimal binding conditions are similar to those that are also optimal for binding initiator tRNA to ribosomes. Binding of initiator tRNA to polymerase stimulates the transcription of lambda plac DNA, as determined in a crude cell-free system for beta-galactosidase (EC 3.2.1.23; beta-D-galactoside galactohydrolase) synthesis as well as in a highly purified transcription system.
Enzymatic replication of viral and complementary strands of duplex DNA of phage phiX174 proceeds by seprate mechanisms.
Authors: Eisenberg S , Scott J F , Kornberg A
Published: May 2006

Multiplication of the duplex, circular, phage phiX174DNA (replicative form, RF) in stage II of the replicative life cycle has been observed with a crude enzyme preparation [Eisenberg et al. (1976) Proc, Natl. Acad, Sci. USA 73, 1594-1597]. This stage has now been partially reconstituted with purified proteins and subdivided into two stages: II(+) and II(-). In stage II(+), viral (+) strand synthesis is carried out by four proteins: the phage-induced, cistron A-dependent protein, rep-dependent protein, DNA unwinding protein, and DNA polymerase III holenzyme. In stage II(-), complementary (-) strand synthesis utilizes the product of stage II(+) as template and the multiprotein system previously identified in the stage I synthesis of a complementary strand on the viral DNA template to produce RF. The multiprotein system includes DNA unwinding protein, proteins i and n, dnaB protein, dnaC protein, dnaG protein, and DNA polymerase III holoenzyme. A discussion of these two separate mechanism for synthesis of (+) and (-) strands suggests that they may account for essentially all the replicative stages in the life cycle of phiX174.
Regulation of reserve protein metabolism in the cotyledons of mung bean seedlings
Authors: Chrispeels Maarten J. , Baumgartner Bruno , Harris Nick
Published: May 2006

Seedling growth in mung beans (
Phaseolus aureus
, Roxb.) is accompanied by the metabolism of the reserve proteins, and the appearance in the cotyledons of a proteolytic enzyme with endopeptidase activity. Enzyme activity increases 25-fold during the first 5 days of growth. Cotyledon extracts prepared from seeds imbibed for 24 hr with water do not react with rabbit endopeptidase antiserum, which suggests that the enzyme is not present in the seeds as a zymogen. Labeling experiments show that the enzyme is synthesized in the course of seedling growth. The endopeptidase is localized in the protein bodies, and the specific activity of the enzyme in these organelles increases 30-fold. Ultrastructural studies show that the rough endoplasmic reticulum proliferates and may give rise to vesicles which fuse with the protein bodies prior to reserve protein digestion. These vesicles could be the primary lysosomes which transport the enzyme from its site of synthesis to its site of action.
Insulin effect on the cell cycle: analysis of the kinetics of growth parameters in confluent chick cells.
Authors: Teng M H , Bartholomew J C , Bissell M J
Published: May 2006

Several techniques, including flow microfluorometry, were utilized to study the effect of insulin on the growth of cultured cells. It was demonstrated that chick fibroblasts can be stimulated to synthesize DNA and undergo mitosis after insulin addition. The kinetics of the cell movement through the cell cycle as well as the length of the cycle itself, however, were distinctly different in insulin- and serum-treated cultures. The insulin-treated cells had a shorter G1, an extended S, and a much extended G2 residence time compared to cells treated with serum. A model of growth regulation which includes both primary cultures and cell lines is proposed.
Localization of the neurofilament protein in neuroblastoma cells by immunofluorescent staining.
Authors: Jorgensen A O , Subrahmanyan L , Turnbull C , Kalnins V I
Published: May 2006

Neurofilament protein (54,000-56,000 daltons) has been localized in murine neuroblastoma cells by indirect immunofluorescent staining with antisera to purified calf brain neurofilament protein. In some cells with only short processes, specific staining of fibrous material was present in the perinuclear region while in other cells similar fibers, coiled to varying degrees, were present in other regions of the cytoplasm. In cells with longer processes a stained fiber extended throughout each process. The staining pattern observed followed the distribution of bundles of 100 A filaments as determined by electron microscopy. The fibers did not stain with antisera to tubulin or tropomyosin. The observations reported strongly indicate (i) that neurofilament protein isolated from calf brain is antigenically related to a component of the bundles of 100 A filaments in neuroblastoma cells, and (ii) that the neurofilament protein is an integral part of bundles of 100 A filaments in neuroblastoma cells, while neither tubulin nor tropomyosin is present in these bundles.
Specialized transduction of colicin E1 DNA in Escherichia coli K-12.
Authors: Fukumaki Y , Shimada K , Takagi Y
Published: May 2006

Genetic studies were made on E. coli K-12 TM96, which carries recombinant molecules constructed by in vitro combination of colicin E1 DNA and a DNA fragment of E. coli for guanine synthesis derived from transducing phage. The recombinant molecules existed as stable plasmids within the cell and contained genes for colicin E1 immunity and the guaA enzyme (xanthosine 5'-monophosphate aminase) together with a part of the lambda genome, R through J: (R-A-F-J)+. A block of the lambda genome, int through Q, was not detected in the recombinant molecule. Thus, this recombinant molecule was named ColEl-coslambda-guaA, and the specialized tranduction of the ColEl-coslambda-guA DNA into various E. coli K-12 cells by lambda phage was described. Lysates prepared by lytic infection of lambda phage onto TM96 or by induction of TM96(lambda) lysogens contained transducing particles which could transduce gua-deleted E. coli to stable guaA+ cells. These transductants were proved to have similar genetic properties as those of TM96. The frequency of transduction was not affected by the presence of an attachement site for lambda, prophage lambda, colicin E1 plasmids, or the recA property within gua-deleted recipient cells. Transducing particles were resistant to EDTA treatment and most of them had an average density of about 1.472. This value corresponds to that of lambda phage particles, which contain about 72% of the lenght of lambda DNA.
Growth of transplanted tails of infant rats in adolescent allogeneic recipients.
Authors: Huggins C B , Anderson K P
Published: May 2006

The tails of newborn rats, consisting of slender continuous cones of avascular cartilage, were transplanted in subcutaneous spaces of allogeneic adolescents; colloidal carbon was injected in a vein before the transplants were harvested on days 7-28. Between 97 and 100% of the transplants were accepted, underwent differentiation into bone with bone marrow, and grew at a brisk rate. Acceptance was recognized by (i) a zebra-stripe effect, visible in the gross, resulting from accumulation of carbon in reticuloendothelial cells; (ii) increase of alkaline phosphatase [or-thophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1] and of incorporated 45Ca in the transplant; and (iii) the presence of dense cortical bone with lacunae populated with osteocytes demonstrable by histology. Differentiation of the cartilaginous transplant into bone with subsequent growth of the transplant occurred in recipients fed sucrose as their sole ration.
Interaction of tetraiodofluorescein with a modified form of aspartate transcarbamylase.
Authors: Kantrowitz E R , Jacobsberg L B , Landfear S M , Lipscomb W N
Published: May 2006

Low concentrations of the dye tetraiodofluorescein activate native aspartate transcarbamylase (aspartate carbomoyltransferase, carbomoylphosphate:L-aspartate carbomoyltransferase, EC 2.1.3.2), while high concentrations inhibit the enzyme's activity [Jacobsberg, L. B., Kantrowitz, E. R. & Lipscomb, W. N. (1975) J. Biol. Chem. 250, 9238-9249]. This dye is now shown to produce similar effects upon a modified form of aspartate transcarbamylase produced by Escherichia coli grown in a culture medium supplemented with thiouracil. Significantly, the ATP-induced activation is reduced in the modified form of the enzyme to the same extent as is the tetraiodofluorescein-induced activation. Thus, a relationship is demonstrated between the internal mechanisms by which ATP and tetraiodofluorescein activate aspartate transcarbamylase.
Distinctions between the two-state and sequential models for cooperative ligand binding.
Authors: Gibson R E , Levin S A
Published: May 2006

The two-state and sequential models for positive cooperativity in ligand binding can produce significantly different theoretical binding curves when presented in a Scatchard plot. The conditions that produce the greatest differences have been examined. The theoretical differences have been used to select the two-state model as the best model for describing the binding of acetylcholine to acetylcholine receptors that have been solubilized by Triton X-100 and sodium cholate.
Inhibitors of genetic recombination in pneumococci.
Authors: Seto H , Tomasz A
Published: May 2006

Treatment of transformable pneumococci with DNA-intercalating agents shortly after the uptake of DNA molecules inhibited the appearance of genetic transformants. The same drug treatments applied 20 min after DNA uptake were ineffective. Ethidium bromide, proflavin, daunomycin, actinomycin D, and platinum red were found to be effective inhibitors. Donor DNA molecules reisolated from the drug-treated bacteria appeared to be associated with the resident DNA in an abnormal manner, and they had only poor transforming activity.
Extension of longevity in Drosophila mojavensis by environmental ethanol: differences between subraces.
Authors: Starmer W T , Heed W B , Rockwood-Sluss E S
Published: May 2006

Drosophila mojavensis adults, which breed and feed on necrotic cacti, show an increase in longevity when exposed to atmospheric ethanol. The increase in longevity is accompanied by retention of mature ovarioles and is independent of diet. Differences in longevity among strains from different localities were detected for females. Strains from Arizona and Sonora, Mexico, showed the greatest increase in longevity, while strains from Baja California, Mexico, showed the least increase. These differences may be controlled by the alcohol dehydrogenase locus, the octanol dehydrogenase locus, and modifier genes, because the aduld response is correlated with the frequency of alcohol dehydrogenase alleles, as well as second chromosomal inversions containing the octanol dehydrogenase locus. The longevity response is also consistent with the more uneven distribution and availability of the host plant in Arizona and Sonora, Mexico. Strains from Arizona and Sonora, Mexico, have a high frequency of Adh-S, the allele whose product is heat and pH tolerant. The host plant, organpipe cactus, exhibits extremes in temperature and pH in the same geographic region. Strains from Baja California, Mexico, possess a high frequency of Adh-F, whose product is heat and pH sensitive. The substrate in this region, agria cactus, has moderate temperature and pH extremes and contains relatively high concentrations of isopropanol. Isopropanol is presumable a selective agen favorable to Adh-F. The environmental heterogeneity that is proposed for maintaining the alleles at the alcohol dehydrogenase locus is the interaction of substrate alcohol content with temperature and pH. Substrates that do not contain appreciable amounts of isopropanol and are exposed to high temperatures and exhibit variable pH favor Adh-S, while substrates containing isopropanol and having moderate temperatures and pH favor Adh-F.
Effect of gangliosides and substrate analogues on the hydrolysis of nicotinamide adenine dinucleotide by choleragen.
Authors: Moss J , Osborne J C , Fishman P H , Brewer H B , Vaughan M , Brady R O
Published: May 2006

Choleragen and its A protomer catalyzed the hydrolysis of NAD to ADP-ribose and nicotinamide. NADase activity was inhibited by gangliosides GM1 (galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosylceramide), GM2 (N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosylceramide), GM3 (N-acetylneuraminyl-galactosylglucosylceramide), and GD1a (N-acetylneuraminylgalactosyl-N-acetylgalactosaminyl-E1N-acetylneuraminyl]-galactosylglucosylceramide). These gangliosides also increased the intensity of the tryptophanyl fluorescence of the isolated A protomer (lambda max = 328 nm). GM1 but not GM2, GM3, and GD1a caused a "blue shift" in the fluorescence spectrum of the B protomer. These results are consistent with other evidence that the specificity of GM1 as the choleragen receptor resides in its carbohydrate moiety. The NADase activity of choleragen was similar to that of diphtheria toxin previously described [J. Kandel, R. J. Collier & D. W. Chung (1974) J. Biol. Chem. 249, 2088-2097]. As with diphtheria toxin, analogues of NAD were inhibitory, adenine being the most effective. Significant inhibition was also noted with adenosine, AMP, ADP-ribose, nicotinamide, nicotinamide mononucleotide, and NADP. NADP was hydrolyzed only slowly by choleragen. In the NADase reaction catalyzed by diphtheria toxin, water serves as an acceptor for the ADP-ribose moiety of NAD in lieu of the natural acceptor molecule, which is elongation factor II (Kandel et al., 1974). It seems probable that the natural protein acceptor for ADP-ribose in the reaction catalyzed by choleragen is adenylate cyclase or a protein component of a cyclase complex that regulates enzymatic activity.
Cellular transformation and differentiation. Effect of Rous sarcoma virus transformation on sulfated proteoglycan synthesis by chicken chondrocytes.
Authors: Muto M , Yoshimura M , Okayama M , Kaji A
Published: May 2006

Incorporation of sulfate into sulfated proteoglycans by isolated chicken chondrocytes was inhibited up to 74% by transformation with the Rous sarcoma virus, and a similar inhibitory effect was observed on acetate incorporation into chondroitin sulfate. Slower sedimenting sulfated proteoglycans appear after the viral transformation. The ratio of chondroitin 4-sulfate to chondroitin 6-sulfate in these slower sedimenting sulfated proteoglycans was different from that of normal chondrocytes, but the chain lengths of sulfated glycosaminoglycans produced by normal chondrocytes and transformed chondrocytes were not significantly different. Chondrocytes were also infected with a temperature-sensitive mutant of RSV, ts LA24, which has a temperature-sensitive lesion in the transforming gene. Hyaluronic acid production by these cells was increased, and the slower sedimenting sulfated proteoglycan was produced only at the permissive temperature.
On the existence of a steady state in a biological system.
Authors: Fichera G , Sneider M A , Wyman J
Published: May 2006

This paper deals with the existence, uniqueness, and stability of a critical point (steady state) in the case of a macromolecular system, such as an allosteric or polysteric protein, for which the first-order kinetic equations are nonlinear. It presents a brief outline of a rigorous proof (to be given in full elsewhere) that, in a restricted but not unrepresentative system of this kind, there always exists one and only one positive critical point and that this point is asymptotically stable in the large: no matter what its starting point, the system will always approach this point by some kind of relaxation process, however complex.
Migration of
Escherichia coli dnaB
protein on the template DNA strand as a mechanism in initiating DNA replication
Authors: McMacken Roger , Ueda Kunihiro , Kornberg Arthur
Published: May 2006

The first step in conversion of ϕX174 singlestranded DNA to the duplex replicative form
in vitro
is the synthesis of a nucleoprotein intermediate [Weiner, J. H., McMacken, R. & Kornberg, A. (1976)
Proc. Natl. Acad. Sci. USA
73, 752-756]. We now demonstrate that
dnaB
protein (approximately one molecule per DNA circle) is an essential component of the intermediate and retains its ATPase activity. Synthesis of RNA primers, dependent on
dnaG
protein (primase), occurred only on DNA that had been converted to the intermediate form. In a coupled RNA priming-DNA replication reaction the first primer synthesized was extended by DNA polymerase III holoenzyme into full-length complementary strand DNA. In RNA priming uncoupled from replication, multiple RNA primers were initiated on a ϕX174 circle. The single
dnaB
protein molecule present on each DNA circle participated in initiation of each of the RNA primers, which appear to be aligned at regular intervals along the template strand. We propose that
dnaB
protein, once bound to the template, migrates in a processive fashion along the DNA strand, perhaps utilizing energy released by hydrolysis of ATP for propulsion; in this scheme the actively moving
dnaB
protein acts as a “mobile promoter” signal for
dnaG
protein (primase) to produce many RNA primers. Schemes are proposed for participation of
dnaB
protein both in the initiation of replication at the origin of the
Escherichia coli
chromosome and in the initiation of primers for nascent (Okazaki) fragments at a replication fork.
Proof of
de novo
synthesis of the
qa
enzymes of
Neurospora crassa
during induction
Authors: Reinert William R. , Giles Norman H.
Published: May 2006

In
Neurospora crassa
three inducible enzymes are necessary to catabolize quinic acid to protocatechuic acid. The three genes encoding these enzymes are tightly linked on chromosome VII near methionine-7 (
me-7
). This
qa
cluster includes a fourth gene,
qa-1
, which encodes a regulatory protein apparently exerting positive control over transcription of the other three
qa
genes. However, an alternative hypothesis is that the
qa-1
protein simply activates preformed polypeptides derived from the three structural genes. The use of density labeling with D
2
O demonstrated conclusively that the
qa
enzymes are synthesized
de novo
only during induction on quinic acid. Native catabolic dehydroquinase (5-dehydroquinate dehydratase; 5-dehydroquinate hydro-lyase, EC 4.2.1.10) (a homopolymer of
ca
22 identical subunits) has a density of 1.2790 g/cm
3
as determined by centrifugation in a modified cesium chloride density gradient. Growth in H
2
O followed by induction in 95% D
2
O shifts the density of the enzyme to 1.3130 g/cm
3
, indicating
de novo
synthesis during induction. In the reciprocal experiment, i.e., growth in 80% D
2
O followed by induction in either 95% D
2
O or H
2
O, the densities of catabolic dehydroquinase were 1.3135 and 1.2800 g/cm
3
, respectively. Because growth on D
2
O does not affect the density of the H
2
O-induced enzyme, there can be no significant synthesis of catabolic dehydroquinase prior to induction. Similar results were obtained for a second
qa
enzyme, quinate dehydrogenase (quinate:NAD
+
oxidoreductase, EC 1.1.1.24). Thus, induction of two
qa
enzymes involves
de novo
protein synthesis, not enzyme activation or assembly.
In vitro biosynthesis of beta-endorphin, gamma-lipoprotein, and beta-lipotropin by the pars intermedia of beef pituitary glands.
Authors: Crine P , Benjannet S , Seidah N G , Lis M , Chrétien M
Published: May 2006

Labeled amino acids were incorporated with proteins during incubations of isolated cells from the pars intermedia of beef pituitary glands. After 3 hr of incubation with methionine and [3H]lysine, approximately equivalent amounts of labeled gamma-lipotropin and beta-endorphins were isolated. They were found to be major synthesis products of the pars intermedia. In contrast, very little labeled beta-lipotropin was recovered. Another major synthesis product of the pars intermedia was also purified. Its partial amino acid sequence and molecular weight were determined and it was concluded that this peptide cannot be identified as any known pituitary hormone or protein fragment.
Replication of adenovirus type 2 DNA in vitro.
Authors: Kaplan L M , Kelinman R E , Horwitz M S
Published: May 2006

A soluble replication system that synthesizes full-sized adenovirus DNA molecules has been developed. The extraction of infected HeLa nuclei solubilizes approximately 25% of the viral replicating DNA and leaves the HeLa chromatin associated with the insoluble nuclear material. Both the extracted viral DNA and the DNA product synthesized in vitro are intact and identical to the adenovirus DNA or its replicating intermediates produced in whole infected cells. The direction of elongation and the termini of replication of progeny DNA in vitro are essentially identical to those observed in vivo. Nuclear extract replication is dependent on Mg2+ and the four deoxyribonucleoside triphosphates and partially stimulated by ATP.
Use of
125
I-labeled phytochrome to quantitate phytochrome binding to membranes of
Avena sativa
Authors: Georgevich Gradimir , Cedel Thomas E. , Roux Stanley J.
Published: May 2006

Purified oat phytochrome was labeled with
125
I without altering the photoreversibility or absorbance properties of the pigment. The radiolabeled phytochrome was used in experiments
in vitro
to quantitate the binding of the pigment to both crude and purified membrane preparations from oat tissue. After the membranes were allowed to react with
125
I-labeled phytochrome, washed free of unbound material, and pelleted, they were found to have significant levels of radioactivity bound to them. Qualitative identification of phytochrome as the bound radioactive species was confirmed by autoradiography of sodium dodecyl sulfate gels after electrophoresis of the proteins contained in the washed membranes. Data supporting the specificity of the binding are that the binding shows saturation kinetics and that unlabeled phytochrome, but not bovine serum albumin, will competitively inhibit the binding of labeled phytochrome. This technique permits the detection of less than a nanogram of phytochrome and provides a new method for quantifying bound phytochrome that is independent of the spectral detectability of the pigment. It should be useful in elucidating the nature of phytochrome attachment to cellular membranes.
Surface antigen in early differentiation.
Authors: Kemler R , Babinet C , Eisen H , Jacob F
Published: May 2006

Addition of Fab fragments from rabbit antiserum to surface antigen F9 to 2-cell stage mouse embryos in culture does not alter cleavage; however, the addition prevents culture does not alter cleavage; however, the addition prevents the formation of compact morulae and blastocysts. A similar effect is observed when Fab fragments are added to already compact 8-cell stage or even older morulae, but disappears at the beginning of blastocoel formation. This effect is reversible: uncompact 30-cell embryos washed free of Fab become compact in a few hours, produce blastocysts, and upon reimplantation into pseudopregnant mothers can produce mice. Development is not altered by divalent anti-F9 antibodies, by Fab fragments from sera directed against other embryo surface antigens, or by succinyl concanavalin A.
Comparison of contact-mediated communication in normal and transformed human cells in culture.
Authors: Corsaro C M , Migeon B R
Published: May 2006

With an assay that quantitates the transfer of 6-thioguanylic acid from hypoxanthine phosphoribosyltransferase (IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8)-positive donor cells to negative recipient cells through gap junctions, differences in contact-mediated communication between normal and transformed human cells in culture have been detected. We have compared cells cultured from human tumors and simian virus 40-transformed cells with the normal human fibroblasts from which they were derived as well as with gap junction-deficient L cells. The communication, which is extensive in normal cells, is significantly reduced when transformed cells are used as either donors or recipients in the contact-feeding assay. Furthermore, the reduction in the transfer of nucleotides is enhanced when transformed cells are used as both donors and recipients, indicating a dosage effect or synergism, independent of enzyme activity. Fetal cells have a contact-feeding phenotype intermediate between that of normal and that of transformed cells. We suggest that the decrease in communication of nucleotides in transformed cells reflects quantitative or qualitative changes in membrane components responsible for gap junction formation.
Friend strain of spleen focus-forming virus is a recombinant between ecotropic murine type C virus and the env gene region of xenotropic type C virus.
Authors: Troxler D H , Lowy D , Howk R , Young H , Scolnick E M
Published: May 2006

The spleen focus-forming virus (SFFV), a replication-defective murine leukemia virus that causes the rapid transformation of certain hematopoietic target cells, has acquired specific xenotropic viral genetic information not contained in Friend helper virus. In the current studies, it is shown that a cDNA that represents a xenotropic virus portion of SFFV detects genetic sequences derived from the env gene region of murine xenotropic virus. The significance of the acquisition of these xenotropic viral sequences by SFFV is discussed with regard to their possible role in the rapid leukemogenicity of SFFV, and an analogy is drawn between the formation of SFFV and the formation of the Kirsten and Harvey sarcoma viruses.
Transient magnetic effects in a scale model of the earth's core
Authors: Crane H. R.
Published: May 2006

Scale model experiments are described in which the contribution to the dipole magnetic field of a conducting sphere (simulating the earth's core) by initially closed, internal flux loops is measured. A magnetic loop is maintained by constant current in a toroidal coil, in a mercury sphere. The circuit is then opened, which allows the magnetic loop to diffuse and dissipate. The time development of the magnetic effects outside the sphere is recorded, especially the contribution in the dipole mode of the sphere. In a sample application of the result, a doughnut-shaped flux loop, of major and minor radii 0.17 and 0.053

R
c

(

R
c

= earth's core radius) and centered at 0.68

R
c

, of field strength 100 gauss, in optimal orientation and in a core of conductivity 3 × 10
-6
emu is assumed. If one such flux loop is set free on the average of every 40 years, the earth's dipole field is maintained. The relative intensity of the short-lived nondipole component that would accompany the process in the simplified example is estimated from the data and found not to be inconsistent with that observed in the real earth. Only the basic process of the feeding of a poloidal field by initially closed free flux loops in a static conducting sphere is investigated. The requirement that, in a real situation, the loops would have to be set free in a preferred orientation is discussed, and an existing model of a system that in some degree answers the requirement is cited.
Occurrence of partial deletion and substitution of the
src
gene in the RNA genome of avian sarcoma virus
Authors: Lai Michael M. C. , Hu Sylvia S. F. , Vogt Peter K.
Published: May 2006

The genome size of 20 transformation-defective (
td
) viruses derived from different strains of Rous sarcoma viruses [Prague (subgroups A and C), Schmidt-Ruppin (subgroups A and D) (SR-D), Bratislava 77, and Carr-Zilber subgroup D)] was examined by polyacrylamide gel electrophoresis. All of the
td
viruses except
td
SR-D have 35S RNA of the same size—i.e., class
b
RNA. Two of five
td
SR-D viruses examined have a slightly larger RNA, corresponding to a
td
deletion that is about 25% smaller than that of class
b
RNA. However, the RNase T
1
-oligonucleotide fingerprints of all the
td
SR-D viruses are identical, lacking two sarcoma-specific oligonucleotides. The fingerprints of these viruses also showed a minor oligonucleotide present at very low concentration. A study of heteroduplex molecules formed between genome-length cDNA made from wild-type SR-D and 35S RNA of
td
SR-D showed a deletion loop of 2.0 and 1.5 kilobases, respectively, at the map position of the
src
gene for these two classes of
td
SR-D viruses, confirming the results of polyacrylamide gel electrophoresis. In addition, some heteroduplex molecules with a substitution loop of 0.6-0.7 kilobase at the same site as the deletion loop were observed in all five of the
td
SR-D viruses. We conclude that some of the
td
SR-D viruses have a partially deleted
src
gene and that all of the
td
SR-D viruses have incorporated heterologous sequences of distinct length in some RNA molecules at the position of the
src
gene. The nature and origin of these heterologous sequences are discussed.
Differential effects of cholesterol and lanosterol on artificial membranes.
Authors: Yeagle P L , Martin R B , Lala A K , Lin H K , Bloch K
Published: May 2006

The effects of cholesterol, 4,4-dimethylcholesterol, and lanosterol (4,4',14alpha-trimethyl-delta8,24-cholestadiene-3beta-ol) on some properties of lecithin vesicles have been compared. Unlike cholesterol, lanosterol retards the exit of trapped glucose from phospholipid vesicles only slightly. The 13C nuclear magnetic resonance spectrum of cholesterol/lecithin vesicles shows no resonances attributable to the sterol. By contrast, several resonances attributable to quaternary carbon atoms or methyl groups are seen in the 13C nuclear magnetic resonance spectrum of lanosterol/lecithin vesicles, indicating that lanosterol is much less immobilized than cholesterol. Because the membrane behavior of 4,4-dimethylcholesterol is closely similar to that of cholesterol, it is concluded that the axial 14-alpha-methyl group is responsible for the lessened membrane immobilization of lanosterol. The results emphasize the importance of a planar sterol alpha-face for interaction with phospholipid acyl chains.
Fate of lipid vesicles in vivo: a gamma-ray perturbed angular correlation study.
Authors: Hwang K J , Mauk M R
Published: May 2006

The structural integrity of unilamellar vesicles has been studied in vitro and in vivo by use of gamma-ray perturbed angular correlation techniques. These studies utilize 111In3+ weakly bound to the chelator nitrilotriacetic acid as a probe to monitor the percentage of intact vesicles. When complexes of 111In3+ and nitrilotriacetic acid is encapsulated in vesicles, 111In3+ exhibits a fast tumbling rate. Upon alteration of the membrane, 111In3+ is released from the liposomes and becomes bound to macromolecules, consequently exhibiting a decrease in 111In3+ tumbling rate. The in vitro experiments show that the present technique is capable of determining quantitatively the percentage of material released from the vesicles upon the addition of serum or Triton X-100 to vesicles. The percentage of vesicles remaining intact in vivo can also be monitored continuously by the present technique. In mice, the half-life of dipalmitoyl phosphatidylcholine-cholesterol vesicles after intraperitoneal injection was estimated to be 10-13 hr. The present study suggest that the vesicles remain intact in various tissues for extended periods, thereby allowing a slow release of the encapsulated material at those sites.