bluuebunny/crossref_metadata_2025 huggingface dataset:
Translation of messenger ribonucleic acid from isolated pancreatic islets and human insulinomas.
Authors: Yip C C , Hew C L , Hsu H
Published: May 2006

RNA preparations from isolated rat pancreatic islets and from human insulinomas were injected into oocytes of Xenopus laevis which were then incubated with [3H]leucine. Acid-ethanol extracts of the oocytes were immunoprecipitated with anti-insulin serum using the double antibody technique. Sodium dodecyl sulfate disc gel electrophoresis of the immunoprecipitates showed the presence of an insulin-displaceable immunoreactive material with a molecular weight of about 18,000 in extracts from oocytes injected with RNA of 9-11 S. This immunoreactive product was not detected in extracts from oocytes injected with buffer or 4-8S RNA or RNA heavier than 11 S. These observations suggest the involvement of a precursor larger than proinsulin in the biosynthesis of insulin.
Reconstruction of bacteriophage T4 DNA replication apparatus from purified components: rolling circle replication following de novo chain initiation on a single-stranded circular DNA template.
Authors: Morris C F , Sinha N K , Alberts B M
Published: May 2006

The protein products of T4 bacteriophage genes 41, 43, 45, 44, and 62 have been purified to near homogeneity using an assay which measures their stimulation of DNA synthesis in a crude lysate of Escherichia coli cells in fected by an appropriate mutant phage. When all of these proteins and T4 gene 32 protein are incubated in the presence of deoxyribonucleoside and ribonucleoside triphosphates, extensive DNA synthesis occurs on both single and double-stranded DNA templates. Analysis of this in vitro system reveals most of the features attributed to in vivo DNA replication: (1) De novo DNA chain initiation is found on a single-stranded DNA template only if ribonucleoside triphosphates are present (as expected for RNA priming of Okazaki pieces on the "lagging" strand of a replication fork). (2) With single-stranded circular DNA as template, synthesis continues for many doublings. The products after extensive synthesis resemble a rolling circle as visualized in the electron microscope, with discontinuous "lagging" strand synthesis generating a long, unbranched double-stranded tail. The fact that all six mutationally identified T4 replication gene products are required for these syntheses suggests the existence of a large multienzyme complex, constituting the T4 replication apparatus.
Influence of a novel hypophyseal factor on steroid metabolism in cultured hepatoma cells.
Authors: Gustafsson J A , Larsson A , Skett P , Stenberg A
Published: May 2006

A rat hepatoma cell line in tissue culture (HTC cells) was treated with hypophyseal extracts from adult male and female rats. Cell homogenates were then assayed for steroid metabolizing enzymes using 4-androsten-3,17-dione as substrate. The major products were the 5 alpha-reduced derivatives (5 alpha-androstane-3,17-dione, androsterone, and epiandrosterone). When the cells were grown in the presence of female hypophyseal extract the apparent activity of the 5 alpha-reductase increased markedly, whereas treatment with male hypophyseal extract was without effect. Treatment with female hypophyseal extract resulted in a marked decrease in the apparent Km for 5 alpha-reductase from 667 +/- 102 to 99 +/- 4 muM in addition to a decrease in the apparent Vmax from 67 +/- 12 to 46 +/- 2 pmol of product/min per mg of protein. A logarithmic dose-response was obtained with female hypophyseal extract. Treatment of the HTC cells with purified rat hypophyseal follicle-stimulating hormone, luteinizing hormone, growth hormone, thyrotropic hormone, and prolactin had only marginal effects on 5 alpha-reductase activity. Crude female hypophyseal extracts were at least 6-fold more potent than any of the standard hormone preparations and at least 250-fold more potent than male hypophyseal extracts when based on activity per mg of pituitary tissue. Chromatography of crude female hypophyseal extracts on Sephadex G-25 indicated that the factor was of high molecular weight. The identity of this activity with a hypophyseal "feminizing" factor is postulated.
Regulation of histidine operon does not require hisG enzyme.
Authors: Scott J F , Roth J R , Artz S W
Published: May 2006

Mutations are described which delete all or part of the first structural gene (hisG) of the histidine operon of Salmonella typhimurium. Physiological regulation of histidine enzymes occurs normally in strains carrying any deletion that has both endpoints within the hisG gene. Constitutive high operon expression is observed in strains carrying any hisG deletion and an unlinked regulatory mutation, hisT1504. These results strongly indicate that the hisG protein is not an essential component of the mechanism for regulating expression of the histidine operon.
Detection of carcinogens as mutagens in the Salmonella/microsome test: assay of 300 chemicals.
Authors: McCann J , Choi E , Yamasaki E , Ames B N
Published: May 2006

About 300 carcinogens and non-carcinogens of a wide variety of chemical types have been tested for mutagenicity in the simple Salmonella/microsome test. The test uses bacteria as sensitive indicators for DNA damage, and mammalian liver extracts for metabolic conversion of carcinogens to their active mutagenic forms. Quantitative mutagenicity data from linear dose-response curves are presented: potency varies over a 10(6)-fold range. There is a high correlation between carcinogenicity and mutagenicity: 90% (156/174) of carcinogens are mutagenic in the test and despite the severe limitations inherent in defining non-carcinogenicity, few "non-carcinogens" show any degree of mutagenicity. The results also demonstrate the great utility, and define the limitations, of the test in detecting environmental carcinogens.
The in vitro addition of a polyadenylate sequence to the 3' end of phage Qbeta RNA and the biological activity of the product.
Authors: Gilvarg C , Bollum F J , Weissmann C
Published: May 2006

Terminal riboadenylate transferase, purified from calf thymus, has been used to add a poly(A) extension to the 3' end of Qbeta RNA. The modified Qbeta RNA retains full infectivity in a spheroplast assay system. However, the progeny viruses do not contain poly(A) termini, indicating an in vivo rectification of the in vitro alteration.
Magnetic Circular Dichroism of Molecules in Dense Media: Relation Between Magnetic Circular Dichroism and Hammett's Constants
Authors: Shieh D. J. , Lee Soo-Tae , Yim Yung-Chang , Lin S. H. , Eyring H.
Published: May 2006

The linear relation between the magnetic circular dichroism (benzene
1
A
1g
→
1
B
2u
transition) of monosubstituted and 1,4-disubstituted benzenes and the substituent constants σ and σ
R
are compared. In all cases, better linear correlations were found between the magnetic circular dichroism and σ
R
. Three series of 1,4-disubstituted benzenes, XC
6
H
4
I, XC
6
H
4
NO
2
, and XC
6
H
4
CO
2
H, have been chosen for the magnetic circular dichroism measurements.
Control of ovarian cell growth in culture by serum and pituitary factors.
Authors: Nishikawa K , Armelin H A , Sato G
Published: May 2006

An ovarian cell line was developed that requires hormonal conditioning of the host for growth in vivo and that requires special factors for growth in vitro. It is necessary to prepare special culture media to demonstrate the effects of growth factors in vitro. To this end, methods were developed for removing from serum those essential factors required for the growth of ovarian cells in culture. Minimal growth occurred in medium containing fetal calf serum that had been passed through a porcelain filter. This method of depleting serum was replaced by a procedure involving passage through a carboxymethylcellulose column. Either pituitary extract or the eluate from the column restored growth in these depleted media. The eluate was more active than pituitary extract with regard to maximal growth enhancement. When the cells were incubated in the depleted media, viability, as measured by plating efficiency, decreased with incubation time. Either pituitary extract or the eluate from the column prevented such death of cells. Based on these findings, we postulate that the eluate contains both a survival factor and a growth-promoting factor for these ovarian cells, while pituitary extract contains only the survival factor.
Induction of endogenous murine C-type virus in spleen cell cultures treated with mitogens and 5-bromo-2'-deoxyuridine.
Authors: Moroni C , Schumann G , Robert-Guroff M , Suter E R , Martin D
Published: May 2006

In short-term cultures of BALB/c spleen cells, treatment with a combination of 5-bromo-2'-deoxyuridine (BrdU) and either lipopolysaccharide W. Escherichia coli or concanavalin A resulted in release of C-type virus into the medium. Only lipopolysaccharide induced virus release when given alone. This could be potentiated by a combined treatment with BrdU. In contrast, phytohemagglutinin at mitogenic concentration had no effect with or without BrdU, suggesting that inducibility may vary between various mitogen-responsive spleen cell populations. In AKR mice, spontaneous virus release was detectable in nonstimulated spleen cell cultures. This could be potentiated by lipopolysaccharide, whereas no further increase occurred upon additional BrdU treatment. The induced viruses had C-type characteristics in that they contained reverse transcriptase that could be distinguished from cellular enzymes by template-primer preference experiments. Furthermore, the enzyme activities were particle-associated, banding in isopycnic sucrose gradients at 1.15-1.17 g/cm-3. The presence of C-type viruses was confirmed by electron microscopy.
Methionine and formylmethionine specific tRNAs coded by bacteriophage T5.
Authors: Chen M J , Shiau R P , Hwang L T , Vaughan J , Weiss S B
Published: May 2006

By RNA-DNA hybridization, as well as chemical and chromatographic analysis, evidence is provided that the bacteriophage T5 codes for the synthesis of two isoacceptor methionine transfer RNA species, tRNA-Met and tRNA-f-Met. Because of the differences in chromatographic properties of T5 phage and host methionine tRNAs, the phage tRNA species are readily distinguishable.
Further evidence of a quantitative deficiency of chain-specific globin mRNA in the thalassemia syndromes.
Authors: Kazazian H H , Ginder G D , Snyder P G , Van Beneden R J , Woodhead A P
Published: May 2006

Formamide gel electrophoresis separates the mRNA fraction from reticulocyte polyribosomes of adult humans into two major RNA species with migratory rates identical to those of the alpha- and beta-globin mRNAs of the rabbit. That these two RNAs of human origin are the globin mRNAs is further supported by the deficiency of the presumed beta mRNA in reticulocyte polyribosomes of fetuses and premature infants, whose cells make gamma chains in preference to beta chains. The globin mRNAs of reticulocyte polyribosomes from patients with hematological disorders were estimated by scanning the stained formamide gels. In contrast to individuals with either hemolytic anemia without hemoglobinopathy or sickle cell anemia who had beta mRNA to alpha mRNA ratios of approximately one, a patient with Hb S-beta-thalassemia had a ratio of beta mRNA to alpha mRNA of 0.75 while two subjects with homozygous beta-thalassemia had severe deficiencies of beta mRNA. Conversely, a patient with alpha-thalassemia (Hb H disease) had a ratio of beta mRNA to alpha mRNA on reticulocyte polyribosomes of 6. These data provide further evidence of a quantitative deficiency of chain-specific globin mRNA in patients with the thalassemia syndromes.
Viral-related information in oncornavirus-lik particles isolated from cultures of marrow cells from leukemic patients in relapse and remission.
Authors: Mak T W , Kurtz S , Manaster J , Housman D
Published: May 2006

Characterization of ribonucleic acid content of particles released from cultures of marrow cells of leukemic patients indicates the presence of RNA molecules of size and base sequence characteristic of oncornarviruses. Seventeen marrow samples obtained from leukemic patients in relapse or in a chronic phase of the disease yielded particles containing high-molecular-weight RNA with a sedimentation velocity (about 70 S) similar to that obtained for murine oncornavirus RNA. Eight of nine marrow samples from non-leukemic patients did not yield detectable high-molecular weight RNA. Among patients in firm hematological remission, three of three samples from patients with acute lymphoblastic leukemia and three of nine samples from patients with acute myeloblastic leukemia were positive for high-molecular-weight RNA. The base sequence of the RNA in particles was characterized by synthesizing complementary (3-H)DNA in an endogenous reaction and hybridizing to excess RNA from known oncornaviruses. Hybridization of 40-60% of input complementary DNA to simian sarcoma virus RNA was detected. No monology was detected with an avian oncornavirus (Rous sarcoma virus) while an intermediate level of homology (10-30%) was detected in hybridization to murine sarcoma virus (Kirsten) and murine leukemia viruses (Rauscher, Moloney, and Gross).
Inverted repetitious sequences in the macronuclear DNA of hypotrichous ciliates.
Authors: Wesley R D
Published: May 2006

The low-molecular-weight macronuclear DNA of the hypotrichous ciliates Oxytricha, Euplotes, and Paraurostyla contains inverted repetitious sequences. Up to 89% of the denatured macronuclear DNA molecules form single-stranded circles due to intramolecular renaturation of complementary sequences at or near the ends of the same polynucleotide chain. Other ciliated protozoans, such as Tetrahymena, with high-molecular-weight macronuclear DNA and an alternative mode of macronuclear development, appear to lack these selfcomplementary sequences. The denatured macronuclear molecules of hypotrichs are held in the circular conformation by a hydrogen-bonded duplex region, which is probably less than 50 base pairs in length, since the duplex regions are not visible by electron microscopy and since the circles in 0.12 M phosphate buffer are not retained during hydroxylapatite chromatography at 60 degrees. The existence of extremely small circles, with contour lengths shorter than the smallest pieces of native DNA, suggests that inverted repetitions containing nicks (broken phosphodiester bonds in duplex DNA) or gaps (interruptions with missing nucleotides) are present at internal positions as well as at the ends of native molecules. Estimates from length measurements of native and denatured Oxytricha macronuclear DNA indicate an average of 1.7 nicks per duplex molecule. Thus, in order to account for the high frequency of circle formation, a restriction-type enzyme(s) must exist which inserts single-strand, site-specific nicks or gaps at internal positions in the macronuclear DNA of Oxytricha.
Mutations simultaneously affecting endonuclease II and exonuclease III in Escherichia coli.
Authors: Yajko D M , Weiss B
Published: May 2006

We studied mutants of E. coli originally identified as being deficient in either endonuclease II (deoxyribonucleate oligonucleotidohydrolase, EC 3.1.4.30) or exonuclease III [deoxyribonucleate (double-stranded) 5'-nucleotidohydrolase, EC 3.1.4.27] activity. Twelve independently derived mutants were tested, including three new endonuclease II mutants. Deficiency of one enzyme was always accompanied by deficiency of the other. Furthermore, temperature-sensitivity of one activity was always accompanied by temperature-sensitivity of the other, and the enzymes were co-purified. The results suggested a physical association between exonuclease III and endonuclease II, which may be of advantage in the excision-repair of DNA. A thermolabile endonuclease II was purified from one of the new mutants, indicating that it had an altered structural gene. This mutation, and all similar ones mapped by genetic transduction, was located between the pncA and aroD genes on the E. coli chromosome. One mutant had a prolonged generation time, an increased sensitivity to the alkylating agents methyl-methanesulfonate and mitomycin C, and a decreased plating efficiency for bacteriophage lambda, but no marked sensitivity to ultraviolet or gamma-irradiation. Its enzymatic and biological abnormalities were simultaneously revertible, suggesting they were caused by a single mutation. These results suggested a role for these enzymes in normal cell growth processes and in the repair of alkylation damage.
Repetitive hinge region sequences in human IgG3: isolation of an 11,000-dalton fragment.
Authors: Adlersberg J B , Franklin E C , Frangione B
Published: May 2006

The heavy chain (gamma-3) of the IgG3 subclass of human immunoglobulins has a molecular weight of 60,000, instead of the 50,000 value reported for gamma-1, gamma-2, and gamma-4 heavy chains. By use of protein Omm, a gamma-3 heavy chain disease protein, it was possible to isolate and analyze the extra fragment. Protein Omm had a molecular weight of 40,000, glycine as its sole NH-2-terminal, and contained only the hingee region and the C-H-2 and C-H-3 domains. CNBr cleavage at Met 252 (gamma-1 numbering) yielded the hinge fraction (Fh fragment). On the basis of the molecular weight of Fh (11,000), its amino-acid composition, its partial sequence, and its unexpectedly low number of tryptic peptides, it is postulated that the extra fragment in gamma-3 heavy chains represents a series of similar or identical duplications of sections of the previously reported gamma-3 hinge region. In addition, there are striking homologies with the hinge region of alpha-1 and alpha-2 heavy chains, one of which also has duplications. The relationship of these hinge structures in different immunoglobulins supports the concept that this region is coded by a unique, small piece of DNA, which has evolved in parallel manner with the immunogolbulin genes by partial duplications and/or crossingover.
Nucleotide sequence of an RNA polymerase binding site from the DNA of bacteriophage fd.
Authors: Schaller H , Gray C , Herrmann K
Published: May 2006

The primary structure of a strong RNA polymerase binding site in the replicative form DNA of phage fd has been determined by direct DNA sequencing. It is: (see article). The molecule contains regions with 2-fold symmetry and sequence homologies to promoter regions from other DNAs. The startpoint of transcription is located in the center of the binding site.
Genetic complexity of aggregation in the cellular slime mold Polysphondylium violaceum.
Authors: Warren A J , Warren W D , Cox E C
Published: May 2006

Complementation tests were performed between pairs of independently isolated aggregation defective mutants of P. violaceum. Analysis of the results suggests that the approximate number of genes controlling aggregation in this organism is 50.
Antibodies reactive with cell surface carbohydrates.
Authors: Sela B A , Wang J L , Edelman G M
Published: May 2006

Normal and immune sera from various animal species were fractionated on columns of Sepharose covalently coupled with the glycoprotein fetuin. Elution of the material bound to fetuin yielded low but reproducible amounts of protein, ranging from 0.02 to 0.2% of the protein mass of the input sera. This material has been identified by immunoelectrophoresis in agar and by zone electrophoresis on cellulose acetate as immunoglobulin. The Ig fractions bound and agglutinated erythrocytes of various species, and also bound to cells from various mouse tissues including heart, kidney, thymus, and spleen. In all cases, the binding was inhibited by glycoproteins such as fetuin and thyroglobulin, by a glycopeptide isolated from fetuin, and by some bacterial lipopolysaccharides. When the binding of these Ig fractions to mouse splenocytes was tested in the presence of 17 saccharides, no inhibition of binding was observed except by sialic acid, D-galactose, N-acetyl-D-glucosamine, and D-mannose, all of which showed partial inhibition. Inasmuch as these four saccharides are present on the carbohydrate moiety of fetuin, the results suggest that the isolated material is a carbohydrate-specific Ig (CS-Ig) fraction of serum capable of binding to the carbohydrate portion of cell surface receptors and glycoproteins. When bound to lymphocytes, these CS-Ig molecules induced redistribution (patching and capping) of cell surface receptors. Moreover, the CS-Ig fractions from chicken and rabbit sera were weakly mitogenic for mouse splenic lymphocytes. CS-Ig fractions are useful new reagents for studying glycoproteins and the interactions and activities of cell surface carbohydrates.
Experimental alcohol-induced hepatic necrosis: suppression by propylthiouracil.
Authors: Israel Y , Kalant H , Orrego H , Khanna J M , Videla L , Phillips J M
Published: May 2006

We have previously reported that a hypermetabolic state, resembling that produced by thryoid hormones, exists in the livers of animals treated chronically with ethanol. We propose that this alteration produces a relative hypoxia in the centrilobular zone of the liver which, if severe enough, leads to cellular death and to the production of hepatitis. Rats consuming ethanol for 30 days, given with a nutritionally adequate diet, and exposed to reduced oxygen tensions for only 6 hr, developed histological and biochemical evidence of hepatocellular necrosis and inflammatory lesions confined to the centrilobular zone. The severity was proportional to the degree of hypoxia. Pair-fed (nonalcohol) controls showed no such lesions. Treatment of the animals with propylthiouracil for 3-10 days abolished the hypermetabolic state of the liver in ethanol-consuming animals, and drastically reduced the histological and biochemical effects of hypoxia in them. These findings may have implications for pathogenesis and treatment of alcoholic hepatitis in man.
Repression and autogenous stimulation in vitro by bacteriophage lambda repressor.
Authors: Dottin R P , Cutler L S , Pearson M L
Published: May 2006

Purified lambda repressor protein is shown to reduce the lambda DNA-directed synthesis of proteins in vitro as determined both by net amino-acid incorporation and by analysis of specific lambda-coded proteins resolved by sodium dodecyl sulfate/polyacrylamide slab gel electrophoresis. By means of different lambda DNA templates carrying deletion and point mutations in the operators o-L or o-R, it has been possible to demonstrate repression of the synthesis of two classes of lambda proteins. The synthesis of one, class c, appears to be controlled from the operator o-L and is more efficiently repressed at low concentrations of the repressor than that of the other class of repressible lambda proteins, class d, which is controlled from the operator o-R. Several other proteins synthesized in vitro are not repressible. Some of these are coded by the J-att region. In addition, the repressor appears to have another activity, that of stimulating the synthesis of a protein identified as the repressor itself. Lambda repressor appears to stimulate its own synthesis by acting at prm, a site defined by the cis-acting mutation prm 116.
Evolutionary Changes in the Mating System of an Experimental Population of Barley (
Hordeum vulgare
L.)
Authors: Kahler A. L. , Clegg M. T. , Allard R. W.
Published: May 2006

An analysis is presented of the reproductive cycle in an experimental population of barley. The experimental design included growing three different generations of the population in the same year and environment, thus permitting an assessment of the mating system at three stages in the evolutionary history of the population, unconfounded by environmental differences. Gene frequencies sometimes differed significantly in adults and in the effective pollen pool. It was also found that out-crossing rate more than doubled during the twenty generations spanned by the study. These results provide evidence for selection during reproductive phases of the life cycle. They also demonstrate that evolution in this predominantly self-pollinating population was in the direction of increased recombinational potential.
Melanoma cells resistant to inhibition of growth by melanocyte stimulating hormone.
Authors: Pawelek J , Sansone M , Koch N , Christie G , Halaban R , Hendee J , Lerner A B , Varga J M
Published: May 2006

Melanocyte stimulating hormone (MSH) enhances melanization but inhibits proliferation of Cloudman S91 melanoma cells in culture. We have isolated variants of these cells that can grow in the presence of MSH. The conclusions we have reached from analyses of these cells are the following: (1) Basal tyrosinase activity (monophenol monooxygenase; monophenol, dihydroxyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1), i.e., the activity that is present in the absence of added MSH, is related through a common biochemical pathway to MSH-mediated control of growth. (2) MSH-inducible tyrosinase activity does not appear to be related to MSH control of growth. (3) The morphological changes that occur following the addition of MSH or cAMP are related to controls of growth and not to those of melanization.
Life games and statistical models.
Authors: Dresden M , Wong D
Published: May 2006

A set of equations is obtained, which describes the rules of a class of games (life games). These games simulate the processes of growth, death, survival, and competition. The equations are nonlinear difference equations, where the degree of nonlinearity is directly related to the number of interacting neighbors. The time evolution and the development of geometric patterns can be studied starting from these equations. Extensions and generalizations, such as the introduction of stochastic elements, can easily be accommodated in the formalism. Some significant unsolved problems are noted.
Control of the synthesis of a single enzyme by multiple regulatory circuits in Neurospora crassa.
Authors: Hanson M A , Marzluf G A
Published: May 2006

Neurospora crassa synthesizes and secretes an extracellular protease into its growth medium when an exogenous protein serves as its principal source of sulfur, nitrogen, or carbon. The enzymes produced under these three growth conditions have been compared by a number of criteria. The results indicate that the same extracellular protease with a molecular weight of 31,000 is synthesized during the three different metabolic conditions. A regulatory mutant, which lacks a positive signal required for the synthesis of a family of related enzymes for sulfur metabolism, cannot synthesize the protease in response to a limitation for sulfur; yet, this same mutant is capable of producing the enzyme when it is limited for either nitrogen or carbon. A second regulatory mutant, defective in the control of nitrogen metabolism, fails to synthesize the protease only when it is limited for nitrogen. The evidence suggests that a single structural gene for this extracellular protease exists and that it is regulated in a complex fashion such that control signals arising from any one of the three distinct regulatory circuits can activate it for expression. A model is proposed for complex regulation of the synthesis of this enzyme.
Almost All Roots of ζ(
s
) =
a
Are Arbitrarily Close to σ = 1/2
Authors: Levinson Norman
Published: May 2006

Let
s
= σ +
it
. For any complex
a
, all but
O
(1/log log
T
) of the roots of ζ(
s
) =
a
in
T
<
t
< 2
T
lie in|σ - 1/2| < (log log
T
)
2
/log
T
. The results extend easily to other functions satisfying a functional equation such as the Dirichlet
L
-functions, the Lerch functions, etc.
Mapping of late adenovirus genes by cell-free translation of RNA selected by hybridization to specific DNA fragments.
Authors: Lewis J B , Atkins J F , Anderson C W , Baum P R , Gesteland R F
Published: May 2006

Cytoplasmic RNA, isolated from cells late after infection by adenovirus type 2 and fractionated by hybridization to specific fragments of adenovirus DNA produced by cleavage with the endonuclease R-EcoRI, was used as template for protein synthesis in cell-free mammalian extracts. Each of the R-EcoRI fragments of DNA selects RNA that encodes specific subsets of the viral polypeptides. From the known order of the R-EcoRI fragments, the following partial map is deduced: (III, IIIa, IVa2, V, P-VII, IX), (II, P-VI), 100K, IV-where the relative order of the components enclosed in parentheses has not yet been determined.
Nature of the tumor-associated determinant(s) of carcinoembryonic antigen.
Authors: Hammarström S , Engvall E , Johansson B G , Svensson S , Sundblad G , Goldstein I J
Published: May 2006

The carbohydrate moiety of carcinoembryonic antigen could be sequentially degraded by repeated cycles of periodate oxidation, reduction, and mild acid hydrolysis (Smith degradation). After three complete degradations, all fucose and sialic acid, 80% of the galactose, 65% of the mannose, and about 40% of the N-acetylglucosamine were eliminated without impairing the ability of degraded carcinoembryonic antigen to react with specific antisera against the antigen. Inhibition studies in a carcinoembryonic antigen/rabbit anti-carcinoembryonic antigen precipitating system with oligosaccharides covering previously known internal structures of glycoproteins and presumably corresponding to the internal carbohydrate region of the antigen, demonstrated that none of the compounds tested was inhibitory. Nor could any inhibitory effect on the binding of carcinoembryonic antigen to antibody against the antigen in a radioimmunoassay system be domonstrated for the carbohydrate moiety prepared by hydrazinolysis or the glyco peptide fraction isolated after papain degradation of the antigen. However, if carcinoembryonic antigen is completely reduced and alkylated, with three intrachain disulfide bonds cleaved per 10-5 g, the immunological activity is reduced to 3-5% of untreated antigen. Furthermore, treatment of the antigen with 0.5 NaOH at 20 degrees for 2 hr completely abolished its ability to react with antiserum, whereas its ability to precipitate with a series of lectins was unchanged. No release of low-molecular-weight carbohydrate orchange in sugar composition of alkali-treated antigen was observed. Our tentative conclusion is that the carbohydrate moiety of carcinoembryonic antigen does not contain the tumor-associated determinant(s).
Beta-cyanoalanine synthase: purification and characterization.
Authors: Akopyan T N , Braunstein A E , Goryachenkova E V
Published: May 2006

Beta-cyano-L-alanine synthase [L-cysteine hydrogen-sulfide-lyase (adding HCN), EC 4.4.1.9] was purified about 4000-fold from blue lupine seedlings. The enzyme was homoegeneous on gel electrophoresis and free of contamination by other pyridoxal-P-dependent lyases. The enzyme has a molecular weight of 52,000 and contains 1 mole of pyridoxal-P per mole of protein; its isoelectric point is situated at pH 4.7. Its absorption spectrum has two maxima, at 280 and 410 nm. L-Cysteine is the natural primary (amino acid) substrate; beta-chloro- and beta-thiocyano can serve (with considerably lower affinity) instead of cyanide as cosubstrates for cyanoalanine synthase. The synthase is refractory to DL-cycloserine and D-penicillamine, potent inhibitors of many pyridoxal-P-dependent enzymes. Cyanoalanine synthase catalyzes slow isotopic alpha-H exchange in cysteine and in end-product amino acids; the rates of alpha-H exchange in nonreacted (excess) cysteine are markedly increased in the presence of an adequate cosubstrate; no exchange is observed of H atoms in beta-position.
Cytotoxic effector cells specific for B Cell lines transformed by Epstein-Barr virus are present in patients with infectious mononucleosis.
Authors: Svedmyr E , Jondal M
Published: May 2006

Peripheral lymphoid cells, from 12 cases of acute infectious mononucleosis (IM), were tested in a micro chromium-51 release assay for cytotoxic activity against a variety of cell lines that did or did not carry the Epstein-Barr virus (EBV) genome. Unfractionated lymphocytes from these patients were cytotoxic to both types of cell lines, as were lymphocytes from healthy individuals. If, however, lymphocytes bearing complement receptors were removed, the residual IM lymphocyte fraction was specifically cytotoxic for EBV-genome-carrying cell lines. The residual lymphocyte fraction in normal donors had no such effect. Heterophile-positive IM is caused by EBV, and these results indicate that, during the acute phase of this disease, patients harbor killer cells, probably T cells, which specifically kill EBV-genome-carrying B cells in vitro. No such specificity for EBV-genome-psitive target cells was found in normal lymphocytes stimulated in vitro with autologous EBV-genome-positive lymphoblastoid cells. Such stimulated cells were highly cytotoxic to both genome-positive and negative lines after removal of complement receptor-positive lymphocytes.
Augmentation of lymphocyte cytotoxicity by antibody to herpesvirus saimiri associated antigens.
Authors: Prevost J , Orr T W , Pearson G R
Published: May 2006

Sera from owl monkeys infected with Herpesvirus saimiri (HVS) mediated antibody-dependent lymphocyte cytotoxicity (ADLC) against virus-infected owl monkey kidney cells. Peripheral blood lymphocytes from rhesus monkeys served as effector cells in this cytotoxic assay. ADLC titers increased along with membrane immunofluorescence (MF) titers but among some sera, the ADLC titers were much higher than expected from the MF titers, suggesting that multiple serum factors were involved in mediating ADLC in this system. Absorption of both low and high titered sera with HVS-infected owl monkey kidney cells removed all ADLC activity. Preliminary results from serial serum samples from two infected monkeys that developed leukemia and/or lymphoma demonstrated that ADLC but not MF titers increased to high titers with progression of disease and followed essentially a different kinetic pattern than that noted by MF. The possible significance of these findings in relation to malignant disease induced by this virus is discussed.
Visualization of actin fibers associated with the cell membrane in amoebae of Dictyostelium discoideum.
Authors: Clarke M , Schatten G , Mazia D , Spudich J A
Published: May 2006

Amoebae of Dictyostelium discoideum were attached to a surface coated with polylysine, and the upper portion of the cells was sheared off with a stream of buffer. Scanning and transmission electron microscopy showed that the cytoplasmic surface of the exposed membrane was covered with fibers consisting of actin-containing filaments. The actin was identified by its solubility properties and its ability to interact with muscle myosin.
Nuclear receptors for thyroid hormone: evidence for nonrandom distribution within chromatin.
Authors: Charles M A , Ryffel G U , Obinata M , McCarthy B J , Baxter J D
Published: May 2006

Chromatin receptor proteins appear to mediate some actions of thyroid hormone. In this study, sheared mammalian chromatin containing [125I]triiodothyronine (T3) bound by these receptors was separated using sucrose gradient velocity sedimentation. T3-receptor complexes were distributed throughout the chromatin fractions, but were enriched in the slowly sedimenting fractions. The latter contain most of the template capacity for RNA synthesis and most of the endogenous RNA polymerase activity but a minor portion of the total DNA. Formaldehyde treatment of chromatin containing receptor-bound [125 I ]T3 resulted in fixation of radioactivity, as evidenced by its migration with chromatin after equilibrium density gradient sedimentation in both cesium chloride and Conray. This fixation implies that the T3 receptor protein is closely associated with chromatin. These results suggest that proteins involved in the regulation of gene function may be nonrandomly distributed within chromatin subfractions, and are consistent with a direct role for thyroid hormone in regulating genetic expression.
Structural changes inducted by follicle-stimulating hormone or dibutyryl cyclic AMP on presumptive Sertoli cells in culture.
Authors: Tung P S , Dorrington J H , Fritz I B
Published: May 2006

Cells isolated from testes of 20-day-old rats, maintained in primary culture in a defined medium, are shown to respond to follicle-stimulating hormone or 3:5-cyclic AMP with characteristic morphological changes. No response is observed in cells treated with luteinizing hormone or 5-?AMP. The cells form a mono-layer, and have been identified as presumptive Sertoli cells structurally by identification of unique tight junctions in electron micrographs of the preparations, along with other ultrastructural properties characteristic of Sertoli cells in situ. These cells do not undergo mitosis. The presumptive Sertoli cells are shown to be morphologically and functionally different from peritubular fibroblasts grown in parallel cultures. Fibroblasts have high rates of mitosis, do not respond to follicle-stimulating hormone, and frequently form multilayers. Other information on the biochemical responses of the cells is cited, which supports the conclusion that the cultured cell preparations consist primarily of Sertoli cells.
In vitro transformation of lymphoid cells by Abelson murine leukemia virus.
Authors: Rosenberg N , Baltimore D , Scher C D
Published: May 2006

Cell cultures prepared from fetal murine liver were infected by Abelson murine leukemia virus. After about 2 weeks, proliferating cells of lymphoid morphology appeared in some of the cultures. Addition of 2-mercaptoethanol to the initial culture medium greatly enhanced the appearance of the lymphoid cells. Immunoglobulin determinants were evident on the cells in some cultures. Continuous passage of the cells in certain cultures was possible and the passaged cells could form tumors after animal inoculation. Because Abelson murine leukemia virus is able to induce in vitro malignant transformation of lymphoid cells, it probably causes leukemia by directly affecting cellular growth control.
Relationship between sterol synthesis and DNA synthesis in phytohemagglutinin-stimulated mouse lymphocytes.
Authors: Chen H W , Heiniger H J , Kandutsch A A
Published: May 2006

Incubation of peripheral blood or isolated lymphocytes of C57L/J mice with phytohemagglutinin stimulated the incorporation of thymidine into DNA of lymphocytes as they transformed into large lymphoblasts. DNA synthesis began after about 24 hr of incubation and reached a peak at 48 hours. The de-novo synthesis of sterols from acetate was stimulated much earlier, at 4 hr of incubation, and the rate reached a maximum at 24 hr, approximately at the time DNA synthesis began. Rates of incorporation of radioactivity from [14-C]acetate into fatty acids and into CO2 by phytohemagglutinin-treated blood were not significantly different from control values. Phytohemagglutinin stimulation of sterol synthesis could be abolished by the addition of certain oxygenated derivatives of cholesterol (e.g., 25-hydroxycholesterol and 20alpha-hydroxycholesterol) which specifically depress the activity of the regulatory enzyme in the sterol synthesis pathway, 3-hydroxy-3-methylglutaryl CoA reductase [mevalonate:NADP-nOXIDOREDUCTASE (CoA acylating); EC 1.1.1.34]. This treatment also abolished DNA synthesis and blastogenesis which otherwise followed the peak of sterol synthesis. Furthermore, DNA synthesis was repressed only if the inhibitor was added early enough to prevent sterol synthesis from reaching its usual maximum. When the compound was added after the rate of sterol synthesis had reached its maximum, DNA synthesis was not affected. These findings suggest that the synthesis of cholesterol is an essential prerequisite for successful initiation and completion of the cell cycle in lymphocytes after phytohemagglutinin activation.
Interaction of partially purified simian virus 40 T antigen with circular viral DNA molecules.
Authors: Jessel D , Hudson J , Landau T , Tenen D , Livingston D M
Published: May 2006

Mixing chromatographic fractions containing simian virus 40 (SV40) T antigen with SV40 [3H]-DNA I (double-stranded, circular, supercoiled) results in the conversion of the nucleic acid to a form that will bind to a nitrocellulose filter. Unlabeled SV40 DNA I successfully competes with this reaction. Under the conditions employed, the antigen-containing fractions bind a variety of circular, viral DNA molecules. Chromatography of the antigen in three systems reveals that the T immunoreactivity migrates with DNA binding activity. In a kinetic heat inactivation experiment, the antigenic reactivity disappears simultaneously with the DNA binding activity. The data indicate the presence of a discernible DNA binding activity in fractions containing T antigen and suggest that the T antigen is the DNA binding protein being measured.
Reactions of migrating birds to lights and aircraft.
Authors: Larkin R P , Torre-Bueno J R , Griffin D R , Walcott C
Published: May 2006

Midair collsions between birds and aircraft pose a hazard for both. While observing migrating birds with a tracking radar, we find that birds often react, by taking evasive maneuvers, at distances of 200-300 m to both searchlight beams and the approach of a small airplane with its landing lights on. Appropriately arranged lights on aircraft should decrease the hazard of collisions with birds.
Mechanism and modification of bradykinin-induced coronary vasodilation.
Authors: Needleman P , Key S L , Denny S E , Isakson P C , Marshall GROUSI, Missouri 63110
Published: May 2006

In isolated perfused rabbit hearts, bradykinin produced a concentration-dependent decrease in coronary resistance directly associated with biosynthesis and release of prostaglandin-E-like substance. An inhibitor of bradykinin destruction (the nonapeptide SQ-20881) markedly enhanced both the coronary vasodilation and release of prostaglandin-E-like substance produced by cardiac injection of bradykinin. Indomethacin inhibited both the myocardial prostaglandin biosynthesis and the decrease in coronary resistance induced by bradykinin. The demonstration that bradykinin is a potent stimulator of prostaglandin biosynthesis in the heart has implications as to the cause of the afferent cardiovascular reflexes and pain in myocardial infarction and angina pectoris.
Isolation of rabbit reticulocyte initiation factors by means of heparin bound to sepharose.
Authors: Waldman A A , Marx G , Goldstein J
Published: May 2006

Passage of cell-free extracts of rabbit reticulocytes through heparin-Sepharose affinity columns results in the loss of the ability of the effluent to initiate protein synthesis. This is shown by the loss of response to added rabbit globin mRNA or to inhibitors of initiation of protein synthesis, such as heparin and aurin tricarboxylic acid, and by recovery of initiation activity by addition of protein retained and subsequently eluted from the columns. The effluent retains, however, the ability to elongate protein chains. Only 0.8% of the applied cell extract protein binds to heparin-Sepharose columns. This bound protein, which can be recovered by increasing the salt concentration of the eluting buffer, has initiation factor activity equal to that of a crude initiation factor preparation obtained from rabbit reticulocyte ribosomes by extraction with 0.5 M KCl. The protein patterns on polyacrylamide gels of the initiation factors prepared by either method are very similar and indicate a protein mixture, which may represent a complex. These data confirm that heparin interacts specifically with initiation factos, and indicate that heparin-Sepharose chromatography will simplify procedures for the preparation of initiation factors.
Recognition of immunoglobulin idiotypes by thymus-derived lymphocytes.
Authors: Janeway C A , Sakato N , Eisen H N
Published: May 2006

The ability of thymus-derived lymphocytes (T cells) from BALB/c mice to recognize the individually specific antigenic determinants (idiotypes) of BALB/c myeloma proteins was tested. Spleen cells from donor mice immunized with a given myeloma protein greatly augmented the response of hapten-specific bone marrow-derived, thymus-independent lymphocytes (cells) to a hapten conjugate of the immunizing myeloma protein. This helper effect was specific for the myeloma protein idiotype; responses to hapten conjugates of similar myeloma proteins, bearing different idiotypic determinants, were not augmented by these spleen cells. That the helper cell is a T cell was shown by its marked sensitivity to cytolysis with an isoantiserum specific for T cells (anti-Thy-1-2) and complement. The discrimination between idiotypes by such T cells is roughly comparable to that of the antibody produced by the donors of the helper cells.
Presence of actin during chromosomal movement.
Authors: Sanger J W
Published: May 2006

Actin has been shown to be present in the nucleoli, kinetochore and centriolar regions, and in the mitotic spindle of rat kangaroo cells which have been stained with fluorescently labeled heavy meromyosin. The actin in the spindle is confined to the fibers that connect the chromosomes with the centriolar region. Actin was not present in astral fibers, in the continuous spindle fibers that connect the poles, or in non-kinetochore regions of the chromosomes. The specific localization of actin in chromosomal spindle fibers suggests an actin-mvosin interaction as the force-producing mechanism for chromosomal movement.
Coenzyme A requirement of malaria parasites: enzymes of coenzyme A biosynthesis in normal duck erythrocytes and erythrocytes infected with Plasmodium lophurae.
Authors: Brohn F H , Trager W
Published: May 2006

Normal duck erythrocytes and erythrocytes infected with Plasmodium lopharae have all of the enzymes for coenzyme A biosynthesis, whereas parasites freed from their host cells have non. Since erythrocytefree cultivation of P. lophurae requires an exogenous source of coenzyme A, this parasite must obtain its coenzyme A entirely from the host cell during infection.
In vivo and in vitro phosphorylation of DNA-dependent RNA polymerase of Escherichia coli by bacteriophage-T7-induced protein kinase.
Authors: Zillig W , Fujiki H , Blum W , Janeković D , Schweiger M , Rahmsdorf H , Ponta H , Hirsch-Kauffmann M
Published: May 2006

After infection with bacteriophage T7 the beta' and to a lesser extent the beta subunits of E. coli DNA-dependent RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) are phosphorylated by a phage-gene-encoded protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37). The phosphorylation occurs on threonine residues and appears site-specific. It is probably the molecular basis of the early transcriptional control.
RNAs of simian virus 40 in productively infected monkey cells: kinetics of formation and decay in enucleate cells.
Authors: Aloni Y , Shani M , Reuveni Y
Published: May 2006

We demonstrate here the usefulness of cytochalasin B enucleate cells for the study of the metabolism of cytoplasmic mRNA and for determining its half-life in animal cells. Simian virus 40 infected monkey cells in which the RNA had been labeled with [3H]uridine were enucleated, and the decay of the two prominent RNAs of simian virus 40, the 19S and 16S species, was measured by analysis on sucrose gradients. The results of these experiments, together with kinetic analysis of nuclear and cytoplasmic viral RNA, indicate a precursor-product relationship between the 19S and 16S cytoplasmic viral RNA species, which decay by first-order kinetics with a mean half-life of about 3 hr and 6 hr, respectively.
Minimal requirements for template recognition by bacteriophage Qβ replicase: Approach to general RNA-dependent RNA synthesis
Authors: Küppers Bernd , Sumper Manfred
Published: May 2006

Any oligo- or polynucleotide able to offer a C-C-C-sequence at the 3′-terminus and a second C-C-C-sequence in a defined steric position to Qβ replicase is an efficient template. Corresponding chemical modifications convert non-template RNAs to template RNAs.