bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of the alkaline tetramer leads to dimer dissociation in liganded human hemoglobin: a laser light-scattering stopped-flow study.
Authors: Flamig D P , Parkhurst L J
Published: May 2006

The first-order dissociation of tetrameric HbCO to the dimer has been studied overthe pH range 10.30-11.57 in a light-scattering stopped-flow apparatus using argon-ion laser excitation. The first-order dissociation rate constant varies from 0.25 sec-1 to 24.0 sec-1over this pH interval. A semilogarithmic plot of k versus pH has a slope of 2.56 at pH 11.07, the midpoint. The pH dependence of the dissociation of the tetramer is consistent with progressive titration of alpha1-alpha2 and beta1-beta2 salt bridges. At pH 10.66, the dissociation rates of HbO2, HbCO, methemoglobin, and HbCN vary less than 20% from their mean value. A study of the dissociation kinetics as a function of protein concentration allows one to obtain both association and dissociation rate constants, and hence equilibrium constants, for the tetramer in equilibrium dimer reaction. In this manner, equilibrium constants were obtained on protein solutions with less than 15 sec of exposure to dissociating conditions.
X-ray absorption edge studies on oxidized and reduced cytochrome c oxidase.
Authors: Hu V W , Chan S I , Brown G S
Published: May 2006

The x-ray absorption edge spectra of the Cu and Fe-centers in oxidized and reduced cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase: EC 1.9.3.1) have been obtained using synchrotron radiation from the SPEAR storage ring at the Stanford Linear Accelerator Center. In addition, oxidized and reduced plastocyanin as well as a number of model copper compounds in various oxidation states were also examined. A comparison of the absorption edge fine structure of cytochrome oxidase with those of the models indicates that one of the two coopers in the oxidized protein is in the +1 oxidation state. Upon reduction of the protein with dithionite, the second copper becomes Cu(I). The shift in the Fe K-edge of cytochrome oxidase upon reduction is small (about 2 e V or 3 times 10(-19 J) and is comparable to that previously observed for the reduction of the heme iron of cytochrome c.
Involvement of DNA-dependent RNA polymerase in a recA-independent pathway of genetic recombination in Escheria coli.
Authors: Ikeda H , Kobayashi I
Published: May 2006

Recombinant DNA molecule of phage lambda formed in Escherichia coli in the presence of chloramphenicol and/or rifampin can be assayed by their biological activity. recA- cells were found to be capable of forming recombinant lambda phage DNA in the presence of chloramphenicol. The relatively high recA-independent recombination observed in this system contrasts with the relatively low recA-independent recombination when recombinant phage particles rather than recombinant DNA are titrated. Formation of the recombinant DNA was suppressed by the the addition of rifampin. The introduction of the rif-r mutation into host bacteria made their recombination activity rifampin-resistant. These results show that DNA-dependent RNA polymerase (EC 2.7.7.6) is involved in this recA-independent pathway of recombination, which is named the "Rpo pathway." This is distinct from Red, Int, RecBC, RecE, or Der pathways of recombination. Crossover was much more frequent in the N-PL-cI and cI-PR-O regions than in the A-D and O-S regions. The crossover seems to occur in the regions that are transcribed actively. Some local change of DNA structure caused by transcription might be required for the Rpo pathway of recombination.
Antibodies to tubulin in normal nonimmunized animals.
Authors: Karsenti E , Guilbert B , Bornens M , Avrameas S
Published: May 2006

Sera of normal nonimmunized rabbits, pigs, calves, and humans contain tubulin-reactive antibodies. Usually, low amounts of antibodies against tubulin of the IgG class (2.5-4 mg/100 ml of serum from nonimmunized animals) were isolated. Anti-tubulin antibodies were also produced by injecting pig tubulin in complete Freund's adjuvant into rabbits. Slightly higher amounts of anti-tubulin antibody were isolated from sera of immunized rabbits (7 mg/100 ml of serum). The cytoplasmic network of microtubules of Tcc 36 mouse cells in culture was not clearly stained by natural anti-tubulin antibodies, but dense staining of the centrosphere was observed. In contrast, induced anti-tubulin antibodies densely stained cytoplasmic microtubular networks. Vinblastine-induced tubulin paracrystals were equally stained by natural and induced anti-tubulin antibodies.
Effectof MgATP on stiffness measured at two frequencies in Ca2+-activated muscle fibers.
Authors: Kawai M , Brandt P W
Published: May 2006

The stiffness of skinned crayfish single muscle fibers was continuously monitored at two frequencies. The length of the fibers was oscillated by the sum of two sine waves (5 Hz and 100 Hz) of small amplitudes. In saline containing saturating amounts of Ca2+, the stiffness ratio (5 Hz:100Hz) was constant as the MgATP (substrate) concentration was raised from 0 to 2 mu M, then it decreased with a further increment in MgATP. The systematic decrease in the stiffness ratio in MgATP above 2 mu M indicates the presence of faster transitions in the cross-bridge cycle. This dependence of the stiffness ratio on MgATP is predictable if we use the two-state model of A. F. Huxley (1957) with a modification, in which MgATP promotes the dissociation of the attached cross-bridges.
Coupling of
lac
mRNA transcription to translation in
Escherichia coli
cell extracts
Authors: Jacobs K. A. , Shen V. , Schlessinger D.
Published: May 2006

In an extract containing all the components for
lac
gene expression except washed ribosomes,
lac
mRNA formation was increased 4- to 6-fold by the addition of washed ribosomes. The formation of β-galactosidase mRNA and enzyme showed very different dependency on added ribosomes. Enzyme was formed in proportion to the number of ribosomes added, whereas 10% of the standard level of ribosomes promoted full levels of transcription. Consistent with their action
in vivo
, chloramphenicol and erythromycin blocked the ribosome-dependent
lac
transcription. The same inhibition was seen with RNA pulse-labeled for 1 or 5 min, so that the effect was truly a blockage of formation rather than an increased hyperlability of nascent mRNA. The effect was specified for some RNA species, as it is
in vivo
: phage λ N gene transcription was increased rather than inhibited in the presence of chloramphenicol. Chloramphenicol did not stop
lac
transcription as a result of its blockage of formation of the regulatory nucleotide tetraphosphate (ppGpp), because addition of the nucleotide did not restore mRNA formation in chloramphenicol-treated extracts. Rather, the data are consistent with the ideas that one or a few ribosomes moving closely behind RNA polymerase can prevent its arrest and that, when ribosome movement is blocked by chloramphenicol, the RNA polymerase is exposed to factors that provoke premature RNA chain termination.
Absence of evidence for an intermediate in the deacetylation of acetylchymotrypsin
Authors: Riddles P. W. , de Jersey J. , Zerner B.
Published: May 2006

A recent paper [Chibber, B. A. K., Tomich, J. M., Mertz, E. T. & Viswanatha, T. (1977)
Proc. Natl. Acad. Sci. USA
74, 510-514] presented evidence that was taken to support the existence of an intermediate in the deacetylation of acetylchymotrypsin. It was observed that deacylation, as measured by following the decrease in [
14
C]acetylchymotrypsin (decrease in acid-precipitable radioactivity), occurred at 1/10 the rate of reactivation, as measured by return of activity toward
N
-acetyl-L-tyrosine ethyl ester. Our experiments have shown that, at pH 6, the deacylation rate constant (measured by the loss of [
14
C]acetylchymotrypsin and by the formation of [
14
C]acetate) is identical (within experimental error) with the rate constant for reactivation (measured by determining the activity of aliquots of reactivating enzyme against
N
-acetyl-L-tryptophan ethyl ester) and with
K
cat
for the turnover of
p
-nitrophenyl acetate by α-chymotrypsin. Part of the 10-fold greater reactivation rate observed by Chibber
et al.
has been shown to be due to the presence of 10% (vol/vol) isopropanol in their reactivation mixture, and it is argued that the balance of the effect is a manifestation of the “indole effect” produced by the simultaneous presence of 10 mM
N
-acetyl-L-tyrosine ethyl ester throughout the reactivation experiments. The results presented are entirely consistent with the three-step mechanism of catalysis by α-chymotrypsin and negate the existence of the proposed additional acetyl-enzyme intermediate.
Inhibition of Rous sarcoma virus replication and cell transformation by a specific oligodeoxynucleotide.
Authors: Zamecnik P C , Stephenson M L
Published: May 2006

The tridecamer d(A-A-T-G-G-T-A-A-A-A-T-G-G), which is complementary to 13 nucleotides of the 3'- and 5'-reiterated terminal sequences of Rous sarcoma virus 35S RNA, was added to chick embryo fibroblast tissue cultures infected with Rous sarcoma virus. Inhibition of virus production resulted. The inference emerges that the tridecamer and its counterpart with blocked 3'- and 5'-hydroxyl termini enter the chick fibroblast cells, hybridize with the terminal reiterated sequences at the 3' and 5' ends of the 35S RNA, and interfere with one or more steps involved in viral production and cell transformation. Likely sites of action are (i) the circularization step of the proviral DNA intermediate, and (ii) the initiation of translation, the latter being described in the following communication [Stephenson, M. L. & Zamecnik, P. C. (1978) Proc. Natl. Acad. Sci. USA 75, 285--288].
Channel open time and metabolic stability of synaptic and extrasynaptic acetylcholine receptors on cultured chick myotubes.
Authors: Schuetze S M , Frank E F , Fischbach G D
Published: May 2006

The mean channel open time and metabolic stability of acetylcholine receptors were studied in developing chick muscle fibers in vitro. Analysis of acetylcholine noise recorded from small patches of surface membrane on uninnervated myotubes indicates that the mean ionic channel open time is independent of receptor density. On myotubes innervated in vitro by spinal cord neurons, the mean open time of synaptic receptors was identical to that of extrasynaptic receptors on the same fibers. Receptor stability was estimated by autoradiography of cultures labeled with 125I-labeled alpha-bungarotoxin. Synaptic and extrasynaptic toxin--receptor complexes disappear at the same, relatively rapid rate. Both the mean channel open time and the apparent rate of receptor degradation are comparable to values obtained at extrasynaptic sites on denervated adult muscles in other species.
General properties of the Yang-Mills equations in physical space
Authors: Segal I. E.
Published: May 2006

With the formulation of the gauge group as a Banach-Lie group of suitable Sobolev type, the Cauchy problem for the Yang-Mills equation in physical space-time reduces rigorously to the case of the temporal gauge. In this gauge there exist spatially global strong solutions for given data for field and potential that are L
2
together with one or two derivatives (respectively). Regarding global existence in time, there is strong unicity, strong existence unless the potential becomes unbounded, and existence of a quasi-solution for arbitrary finite-energy Cauchy data. The variety of solutions of the equations is endowed with a canonical symplectic structure. This structure is degenerate to an extent precisely reflecting gauge-invariance and is conformally invariant.
Kinematics of faint white dwarfs
Authors: Luyten Willem J.
Published: May 2006

An analysis has been made for solar motion for 128 very faint white dwarfs of color class b or a. While about 40% of these stars may be high-velocity objects, it seems definitely indicated that the luminosity of all of them is considerably lower than that for the “normal” white dwarf of the same color.
Second Leray spectral sequence of relative hypercohomology
Authors: Lubkin Saul , Kato Goro C.
Published: May 2006

A second Leray spectral sequence of relative hypercohomology is constructed. (This is skew in generality to an earlier one constructed by S. Lubkin [(1968)
Ann. Math.
87, 105-255].) The Mayer-Vietoris sequence of relative hypercohomology [Lubkin, S. (1968)
Ann. Math.
87, 105-255] is also generalized.
Inversion problem for singular integral operators: C
*
-approach
Authors: Dynin Alexander
Published: May 2006

The inversion problem is solved for a wide class of singular integral operators, in particular for Wiener-Hopf operators in several variables, Mihlin-Calderon-Zygmund operators on bounded domains, and Folland-Stein operators on compact nondegenerate Cauchy-Riemann manifolds.
Actinomycin D-deoxynucleotide interactions: binding isotherms at the benzenoid and quinoid portions of the drug.
Authors: Auer H E , Thompson T N
Published: May 2006

Titrations of actinomycin D (AMD) with dG and with dG-dC were monitored by circular dichroism at 380 nm and 470 nm. These wavelengths are sensitive predominantly to nucleotide binding processes at the benzenoid and quinoid portions, respectively, of the phenoxazone ring of the drug chromophore [Auer, H.E., Pawlowski-Konopnicki, B.E., Chiao, Y.C.C. & Krugh, T.R. (1978), Biopolymers, 17, 1891-1911.]. The temperature dependence of these isotherms was analyzed by the van't Hoff equation to obtain values for the enthalpy and entropy changes. For dG these are about -11 kcal mol-1 and -20 cal mol-1 deg-1, respectively, for complex formation at both the benzenoid and quinoid sites (1 cal = 4.184 J). The enthalpy and entropy changes for complex formation with dG-dC remain unchanged at the benzenoid site, but both values are more negative at the quinoid site. These results indicate that the additional process of binding C in the intercalated AMD-(dG-dC)2 complex, with respect to the simply stacked AMD-dG2 complex, has distinctive properties at the two sites, reflecting their structural differences. The ability to resolve binding processes at the two sites by circular dichroism has permitted us to suggest assignments for the two 31P magnetic resonance lines from the phosphodiester groups observed in the AMD-(pdG-dC)2 complex.
Asymmetric displacement currents in giant axons and macromolecular gating processes.
Authors: Dorogi P L , Neumann E
Published: May 2006

An electrical-chemical gating model is proposed that describes basic observations on asymmetric displacement currents and transient Na+ conductivity changes in squid giant axons. A previously developed single-parameter analysis of primary voltage clamp data yields normal mode relaxation times that agree well with the time constants of asymmetric capacitative currents, suggesting these currents as gating currents associated with charge displacement in a subunit of a complex gating system. The physical-chemical approach correlates the opening of Na+ channels with charge-charge interactions amongst displaceable membrane charges or dipoles and conformational changes in gating macromolecules. The model covers the close correspondence between the voltage dependence of the peak value of the Na+ conductance change and that of the square of the total displaced charge for small depolarizing voltage steps. The quadratic charge relationship also describes the two-mode relaxation of asymmetric displacement currents; the transiently inhibited return transition of two-thirds of the displaced charge after a prolonged depolarization is interpreted to reflect a dissipative chemical gating process.
Mechanism of phage Mu-1 integration: nalidixic acid treatment causes clustering of Mu-1-induced mutations near replication origin.
Authors: Paolozzi L , Jucker R , Calef E
Published: May 2006

Frequencies of Mu-1-induced mutants of Escherichia coli have been compared under two different experimental conditions: cells in exponential growth and the same cells treated with nalidixic acid. The average of values obtained from the nalidixic acid-treated culture is 3 times higher than that obtained from the control. Individual ratios of the frequency of mutants in the two cultures yield decreasing values from 6 to 1, starting from the point of origin of DNA replication to the termini of DNA replication. These results are compatible with the idea that Mu-1 integrates at the replication fork.
Stimulation of
in vitro
activation and the acrosome reaction of hamster spermatozoa by catecholamines
Authors: Cornett Lawrence E. , Meizel Stanley
Published: May 2006

Capacitation and the acrosome reaction of mammalian spermatozoa are essential for fertilization.
In vitro
results are presented that demonstrate that catecholamines stimulate activation (a whiplash flagellar movement characteristic of capacitated hamster spermatozoa) and the acrosome reaction. Protein-free ultrafiltrates of bovine adrenal cortex and medulla preparations stimulated motility, activation, and acrosome reactions of hamster spermatozoa in the presence of bovine serum albumin. The medulla preparation was more effective than the cortex preparation in the stimulation of activation and acrosome reactions. Epinephrine (0.5-50 μM) and norepinephrine (50.0 μM) in the presence of bovine serum albumin and a partially purified protein-free cortex preparation also stimulated activation and the acrosome reactions. Both activation and acrosome reactions in the presence of epinephrine were inhibited by the adrenergic antagonists phentolamine and propranolol, suggesting the involvement of α- and β-adrenergic receptors in the stimulation of capacitation and the acrosome reaction. In addition, phenylephrine, an α-adrenergic agonist, was as potent as epinephrine in the stimulation of acrosome reactions, but activation was reduced. Isoproterenol, a β-adrenergic agonist, was as potent as epinephrine in the stimulation of activation, but acrosome reactions were reduced. High percentages of both activation and acrosome reactions were observed only in the presence of epinephrine, norepinephrine, or phenylephrine and isoproterenol together.
Interaction of phosphatidylserine with mast cells.
Authors: Martin T W , Lagunoff D
Published: May 2006

Phosphatidylserine (PtdSer) potentiates histamine secretion from mast cells exposed to concanavalin A and Ca2+. In order to identify the form of PtdSer that is responsible for its effect on mast cell secretion, PtdSer containing a tritium-labeled serine moiety (3H-PtdSer) was synthesized from egg yolk phosphatidylcholine. The critical micelle concentration (CMC) of 3H-PtdSer and the binding isotherm for 3H-PtdSer interaction with mast cells were determined. The midpoints of the binding isotherm and the dose-response curve for potentiation of secretion coincide and are 2 orders of magnitude greater than the CMC. The shape of the binding curve is explicable either in terms of simple binding of preformed PtdSer micelles or of cooperative binding of monomeric PtdSer in which the number of molecules cooperatively associating with a mast cell binding site is equal to the number of monomers in a PtdSer micelle. In either case, at equilibrium, PtdSer micelles are bound to the mast cells. The number of PtdSer molecules bound to a single mast cell at equilibrium was estimated to be 3.7 X 10(9).
Purinogenic immunodeficiency diseases: selective toxicity of deoxyribonucleosides for T cells.
Authors: Mitchell B S , Mejias E , Daddona P E , Kelley W N
Published: May 2006

Deoxyadenosine at low concentrations and in the presence of an inhibitor of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) is markedly toxic to lymphoblast cell lines of T cell origin but does not impair growth of B cell lines. Deoxyguanosine is also more toxic for T lymphoblasts. In the presence of deoxyadenosine or deoxyguanosine, elevation of the corresponding deoxyribonucleoside triphosphate (dATP or dGTP) occurs in T cell, but not in B cell, lines. The addition of deoxycytidine or dipyridamole results in lower dATP and dGTP levels and prevents deoxyribonucleoside toxicity. These findings provide a molecular basis for the immunodeficiency observed in individuals with several inborn errors of purine metabolism.
Neurotransmitter modulation, phosphodiesterase inhibitor effects, and cyclic AMP correlates of afterdischarge in peptidergic neurites
Authors: Kaczmarek L. K. , Jennings K. , Strumwasser F.
Published: May 2006

The neuroendocrine bag cells in the abdominal ganglion of
Aplysia
generate a long-lasting synchronous afterdischarge upon brief stimulation of an afferent pathway. After this afterdischarge the cells become refractory to further synaptic stimulation. We find that synchrony, afterdischarge, and prolonged refractoriness are properties that can be expressed in the isolated asomatic neurites of the bag cells. We have distinguished two independent types of refractoriness. The first (type I) is seen as a failure of action potentials generated in the tips of bag cell neurites to invade cell somata. The second form of refractoriness (type II) controls the duration of afterdischarge such that stimuli after the first afterdischarge produce only very short afterdischarges or fail to elicit an afterdischarge. Type II refractoriness is sensitive to serotonin and certain of its analogues, and to dopamine and the methylxanthine phosphodiesterase inhibitors. Extracellularly applied serotonin suppresses an ongoing afterdischarge while dopamine and the phosphodiesterase inhibitors, when applied at the end of the first afterdischarge, generate a subsequent afterdischarge of long duration without further electrical stimulation. None of these compounds influenced the degree of type I refractoriness. We have shown that both serotonin and dopamine stimulate the formation of cyclic AMP in the bag cell clusters and in the pleurovisceral connectives and that the occurrence of an afterdischarge is associated with a specific increase in total cyclic AMP in bag cell bodies. Moreover, afterdischarges can be generated in unstimulated preparations by extracellular application of the cyclic AMP analogues, 8-benzylthio-cyclic AMP or 8-methylthio-cyclic AMP. Our data suggest that serotonin and/or dopamine may control bag cell activity and that activation of adenylate cyclase is linked to bag cell afterdischarge.
Serum stimulates the Na+,K+ pump in quiescent fibroblasts by increasing Na+ entry.
Authors: Smith J B , Rozengurt E
Published: May 2006

Two ionophores (monensin and gramicidin) that carry Na+ into 3T3 cells markedly enhance the rate of 86Rb+ uptake. Ouabain prevents both ionophores from increasing 86Rb+ uptake, indicating that the ionophores activate the Na+,K+ pump. Measurements of 86Rb+ uptake and cell Na+ and K+ over a range of monensin concentrations show that the activity of the Na+,K+ pump in 3T3 cells is limited by the supply of internal Na+ and is extremely sensitive to small changes in internal Na+. Serum rapidly enhances the rate of 22Na+ uptake and net Na+ entry when Na+ exit is inhibited by ouabain. At 0.3 microgram/ml, monensin increases the rate of net Na+ entry and activates the Na+,K+ pump by the same degree as serum. The stimulation of 86Rb+ uptake by serum or the ionophores has an absolute requirement for external Na+. Thus, serum appears to stimulate the Na+,K+ pump in quiescent 3T3 cells by increasing its supply of Na+.
Monoclonal antibody defining a stage-specific mouse embryonic antigen (SSEA-1).
Authors: Solter D , Knowles B B
Published: May 2006

A monoclonal antibody derived by fusion of mouse myeloma cells with spleen cells from a mouse immunized with F9 teratocarcinoma cells is described. This antibody, which reacts with embryonal carcinoma cells of mouse and human origin and with some preimplantation stage mouse embryos, defines an embryonic stage-specific antigen. This stage-specific antigen (SSEA-1) is first detected on blastomeres of 8-cell stage embryos. Trophectodermal cells are transitorily positive; however, each cell in the inner cell mass eventually expresses this antigen.
Molecular association between transplantation antigens and cell surface antigen in adenovirus-transformed cell line.
Authors: Kvist S , Ostberg L , Persson H , Philipson L , Peterson P A
Published: May 2006

A rat cell line (A2T2C4) transformed with adenovirus type 2 elicited cytotoxic T lymphocytes in syngeneic rats. Cytotoxicity was abolished by a rabbit antiserum directed against the major histocompatibility (AgB) antigens and by a syngeneic rat antiserum raised against the virus-transformed cell line. The syngeneic antiserum immunoprecipitated surface proteins with apparent molecular weights of 45,000, 19,000, 17,000, and 12,000 from the A2T2C4 cells but it displayed no reactivity against primary rat fibroblasts and spleen cells. The rabbit antiserum against AgB antigens precipitated a 19,000-dalton component from the A2T2C4 cells which was not observed in primary rat fibroblasts. Sequential immunoprecipitation revealed identity between the major polypeptides recognized by the two antisera. Because the rabbit anti-AgB antigen serum was specific for the transplantation antigen subunits and because the syngeneic rat antiserum against the A2T2C4 cells failed to react with the AgB antigens in normal cells, it is concluded that the 19,000-dalton component is coprecipitated with the AgB antigens. Antisera directed specifically against beta2-microglobulin and the alloantigenic AgB antigen subunit also coprecipitated the 19,000-dalton component. These results indicate that the AgB antigen subunits form a ternary complex with a virus-coded protein on the surface of the virus-transformed A2T2C4 cells. This molecular complex may be recognized by the cytoloytic T lymphocytes
Induction of secondary cytotoxic T lymphocytes by purified HLA-A and HLA-B antigens reconstituted into phospholipid vesicles.
Authors: Engelhard V H , Strominger J L , Mescher M , Burakoff S
Published: May 2006

Mouse cytotoxic T lymphocytes were induced by culturing primed spleen cells with cells, membranes, or detergent-solubilized and dialyzed membranes from the human lymphoblastoid cell line JY. Cytotoxic T cells could also be induced by coculturing primed spleen cells with phospholipid vesicles containing purified HLA-A and -B antigens derived from JY cells. The induction of killer cells by all subcellular fractions demonstrated an optimal response as a function of the amount of material added and, in the case of HLA-containing liposomes, this optimum was dependent upon the density of the HLA molecules in the liposomes. In addition, the maximal level of cytotoxicity elicited was also dependent upon this density. Finally, the cytotoxic cells demonstrated specificity as judged by a lower level of lysis on an HLA-unrelated lymphoblastoid cell line than on the appropriate target, JY. These results suggest that major histocompatibility antigens alone are sufficient for the induction of a secondary cytotoxic T lymphocyte response. It is proposed that this system may be useful in defining possible sites on the HLA molecule recognized by cytolytic T lymphocytes.
Distribution of yeast fatty acid synthetase subunits: three-dimensional model of the enzyme.
Authors: Wieland F , Siess E A , Renner L , Verfürth C , Lynen F
Published: May 2006

Rabbit and goat antibodies against the isolated alpha and beta subunits of yeast fatty acid aynthetase were raised and characterized. The purified IgG fractions were studied as to their capability to precipitate their antigens and the holoenzyme and to inhibit the partial reactions involved in overall fatty acyl-CoA synthesis. The specificity of the antibodies was investigated by immunodiffusion and by immunotitration. Native enzyme was crosslinked with each of the antibodies, and dimeric and oligomeric groups of IgG-crosslinked fatty acid synthetase molecules were isolated by sucrose density gradient centrifugation. Electron microscopic investigation of the crosslinked material as well as other data led us to suggest a three-dimensional model of yeast fatty acid synthetase.
Translation of mRNA from calf thymus in the wheat germ system: evidence for a precursor of thymosin alpha1.
Authors: Freire M , Crivellaro O , Isaacs C , Moschera J , Horecker B L
Published: May 2006

When translated in the wheat germ system, mRNA from fresh calf thymus stimulates incorporation of radioactive amino acids into an acid-insoluble product, and 10--20% of the total radioactivity incorporated is precipitated with antisera to active thymosin fractions. In sodium dodecyl sulfate disc gel electrophoresis, radioactivity was recovered mainly in two peptides, corresponding to 16,000 and 11,000 daltons; the latter probably represents incomplete chains. Tryptic digests of each of these peptides yielded fragments corresponding to the sequence of residues 15--19 of thymosin alpha1; these peptides were characterized by cochromatography with digests of synthetic thymosin alpha1 and by Edman degradation. Thus, the 16,000-dalton peptide synthesized in the cell-free system appears to be q precursor of thymosin alpha1 and possibly of other peptides in the fractions isolated from calf thymus. The results support the conclusion that this peptide is synthesized in the thymus gland.
Control of expression of a cloned yeast (Saccharomyces cerevisiae) gene (trp5) by a bacterial insertion element (IS2).
Authors: Walz A , Ratzkin B , Carbon J
Published: May 2006

A hybrid ColE1 plasmid [pYe(trp5)1], containing a yeast DNA segment that complements auxotrophic point mutations and deletions in the Escherichia coli tryptophan synthetase gene (trpAB), has been isolated. Expression of the yeast tryptophan synthetase activity from the cloned yeast gene (trp5) is relatively inefficient in E. coli, as measured by growth rates of trpAB/pYe(trp5)1 strains on minimal media lacking tryptophan and by enzyme assays. Faster growing variants occur spontaneously at a frequency of one in 10(4)--10(5) cells plated and produce higher levels of the yeast enzyme. Plasmid DNA [pYe(trp5)2] from one of these variants was shown to contain a DNA insertion (1.3 kilobase pairs) in the cloned yeast DNA segment in relatively close proximity to the trp5 gene. This DNA insert was identified as a bacterial IS2 element, which carries a promoter for RNA transcription when inserted in the proper orientation. The spontaneous integration of a bacterial DNA insertion element into cloned eukaryotic DNA can result in more efficient expression of the foreign gene.
Observational validation of the chronometric cosmology: The redshift—magnitude relation for quasi-stellar objects
Authors: Nicoll J. F. , Segal I. E.
Published: May 2006

A statistical study is made of the redshift—magnitude relation for a recent comprehensive catalogue of quasi-stellar objects. The chronometric theory, although devoid of free parameters such as the
q
0
and Λ of the expansion theory, provides an excellent fit to the observed relation. The expansion theory does not provide an empirically meaningful fit.
Cytochemical studies on GERL, provacuoles, and vacuoles in root meristematic cells of
Euphorbia
Authors: Marty Francis
Published: May 2006

The genesis of plant vacuoles has been studied by high-voltage and conventional electron microscopy. Vacuole genesis is a lysosomal multistep process: (
i
) GERL (Golgi-associated Endoplasmic Reticulum from which Lysosomes apparently form) produces provacuoles into which lysosomal enzymes and probably other materials appear to be concentrated and packaged; (
ii
) GERL-derived provacuoles cooperate to drive a programmed cellular autophagy leading to young vacuoles; and (
iii
) the young vacuoles swell and fuse together into a few large mature vacuoles which continue to collect the GERL-derived provacuoles throughout the life of the cell.
Chemotactic attraction of human fibroblasts to type I, II, and III collagens and collagen-derived peptides.
Authors: Postlethwaite A E , Seyer J M , Kang A H
Published: May 2006

The chemotactice response of human dermal fibroblasts of type I, II, and III human collagens and collagen-derived peptides was quantitated by an in vitro assay. All three native human collagens and constituent alpha chains can serve as chemoattractants for fibroblasts in vitro. When type I, II, and III collagens were digested by bacterial collagenase, the resulting peptides were also chemotactic. In addition, synthetic di- and tripeptides containing hydroxyproline were also chemotactic for fibroblasts. Since collagen is degraded and remodeled at sites of tissue injury and inflammation, these findings suggest that collagen and collagen-degradation peptides might function as chemotactic stimuli for fibroblasts in vivo and attract these cells to effect repair of damaged tissue.
RNA sequences complementary to citrus exocortis viroid in nucleic acid preparations from infected
Gynura aurantiaca
Authors: Grill L. K. , Semancik J. S.
Published: May 2006

Molecular hybridization with
125
I-labeled citrus exocortis viroid RNA has been used to survey nucleic acid preparations from
Gynura aurantiaca
for viroid complementary molecules. A differential hybridization effect was detected between nucleic acid extracts from healthy and infected tissue in which significant RNase-resistant
125
I-labeled citrus exocortis viroid resulted in hybridization studies with the infected tissue extracts. Subsequent characterization indicated that RNA from infected tissue was involved in the formation of a duplex molecule with citrus exocortis viroid RNA and had properties of an RNA·RNA hybrid. Subcellular fractionation of infected tissue indicates that the complementary RNA is present in nuclear and soluble RNA fractions. This RNA may represent an intermediate molecule in the replication of the viroid or a pathogenic expression and may have a regulatory role in the host cell.
Inhibition of growth and guanylate cyclase activity of an undifferentiated prostate adenocarcinoma by an extract of the balsam pear (Momordica charantia abbreviata).
Authors: Claflin A J , Vesely D L , Hudson J L , Bagwell C B , Lehotay D C , Lo T M , Fletcher M A , Block N L , Levey G S
Published: May 2006

We have recently described the presence of a guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] inhibitor (GCI) in an aqueous extract of the balsam pear (Momordica charantia abbreviata). Because the guanylate cyclase-cyclic GMP system is though to be involved in cell growth, DNA and RNA synthesis, and possible malignant transformation, we examined the effect of the aqueous extract containing GCI on an undifferentiated adenocarcinoma of the rat prostate and concanavalin-A-stimulated [3H]thymidine incorporation into cultured splenic lymphocytes, a process thought to be mediated by cyclic GMP. The results demonstrate that the extract of the balsam pear blocks both the growth of the rat prostatic adencarcinoma in vitro and [3H]thymidine incorporation into DNA. DNA histograms from flow cytometry indicated that the extract containing GCI inhibited in the G2 + M phase of the cell cycle, a presumed locus of cyclic GMP effects. In addition, guanylate cyclase activity was significantly greater in the tumor than normal prostate tissue and was decreased by the extract containing GCI. Cyclic GMP levels in the tumor in culture wer also decreased by addition of the extract. It remains to be determined whether or not the anti-tumor agent and GCI are the same substance.
Increased incorporation of adenosine into adenine nucleotide pools in serum-deprived mammalian cells.
Authors: Rapaport E , Zamecnik P C
Published: May 2006

The effects of serum deprivation on the incorporation of adenosine into the intracellular adenine nucleotide pools by several mamalian cell lines were studied. Cells arrested in the G1 phase of the cell cycle showed increased incorporation of exogenous adenosine into their adenine nucleotide pools as compared with growing cells. This phenomenon is unexpected because salvage pathways from all other preformed nucleosides and bases as well as the de novo synthesis of adenine nucleotides is decreased after arrest of growth by serum deprivation. The incorporation of adenosine into adenine nucleotides may serve as an intracellular signal in the regulation of growth in mammalian cells.
Transglutaminase activity in human lymphocytes: early activation by phytomitogens.
Authors: Novogrodsky A , Quittner S , Rubin A L , Stenzel K H
Published: May 2006

Transglutaminase activity is present in human peripheral lymphocytes and is enhanced up to 15-fold within 10-30 min after treatment of the cells with concanavalin A. Phytohemagglutinin has a similar effect. The enzyme is not detected when intact cells are assayed; it is detected only in cell lysates. Concanavalin A enhances transglutaminase activity only when it is incubated with intact cells; concanavalin A treatment of cell lysates has no effect, alpha-Methyl-D-mannoside specifically inhibits the enhancement of transglutaminase activity in cells treated with concanavalin A results from the specific interaction of the lectin with its saccharide binding site on the cell surface, rather than by direct interaction with the enzyme itself. The increased activity of transglutaminase in cells treated with concanavalin A, as compared to unstimulated cells, is maintained under assay conditions in which saturating levels of Ca2+ are present. Transglutaminase may be involved in early cellular events leading to lymphocyte blastogenesis.
Phenotypically cryptic EcoRI endonuclease activity specified by the ColE1 plasmid.
Authors: Miller C A , Cohen S N
Published: May 2006

An endonuclease having EcoRI specificity is produced by bacteria containing the ColE1 plasmid. Such bacterial cells fail to express restriction or modification functions in vivo, and phage or plasmid DNA obtained from ColE1-containing cells has unmodified EcoRI sites that are cleaved in vitro by purified EcoRI endonuclease or by enzyme extracted from bacteria that carry ColE1. No EcoRI DNA methylase activity associated with ColE1 has been detected. The finding of phenotypically cryptic ColE1-dependent EcoRI endonuclease activity and the absence of any detectable EcoRI modification system in ColE1-containing cells suggest a control mechanism that appears to prevent functional expression of the ColE1-determined enzyme in vivo.
Molecular cloning of genetically active fragments of Bacillus DNA in Bacillus subtilis and properties of the vector plasmid pUB110.
Authors: Keggins K M , Lovett P S , Duvall E J
Published: May 2006

Plasmid pUB110 (approximately 2.8 x 10(6) daltons), originally detected in Staphylococcus aureus, specifies resistance to neomycin and has been transformed into Bacillus subtilis 168, In B. subtilis, pUB110 is stably maintained at about 50 copies per chromosome and renders the host resistant to neomycin sulfate at 5 microgram/ml. pUB110 isolated from B. subtilis transforms Rec+ and recE4-containing strains of B. subtilis at frequencies greater than or equal to 10(3) transformants per microgram of plasmid. pUB110 was transferred by PBS1 or SP10 transduction from B. subtilis to strains of B. pumilus and B. licheniformis. pUB110 is compatible with each of four previously described Bacillus plasmids, including pPL576, pPL10, pPL7065, and pPL2. pUB110 contains a single EcoR1-sensitive site and was used as vector to clone DNA fragments that complement the trpC2 mutation in B. subtilis 168 from EcoR1 digests of the chromosome DNA isolated from B. pumilus strains NRRL B-3275 and NRS576, B. licheniformis strains 9945A and 749C, and B. subtilis 168. Genetic and physical properties of each of the constructed Trp derivatives of pUB110 are described.
Altered pattern of replication of human chromosomes in a human fibroblast-mouse cell hybrid.
Authors: Farber R A , Davidson R L
Published: May 2006

The pattern of terminal replication of the human chromosomes in a clone of hybrids between diploid human fibroblasts and mouse cells was analyzed by autoradiography. An average of 10 human chromosomes was present in the hybrid cells. Several of these chromosomes were found to terminate replication in a different order from the same chromosomes in the parental human fibroblasts. Chromosomes 4 and 5 completed replication later in the hybrid than in the fibroblasts (relative to the other human chromosomes). In contrast, chromosomes 7, 12, and 15 completed replication earlier in the hybrid than in the fibroblasts. These results suggest that the sequence of terminal chromosome replication in human fibroblasts is not irreversibly programmed into each chromosome.
Morphine sulfate stimulates the adenylate cyclase in mouse caudate nuclei.
Authors: Tang L C , Cotzias G C
Published: May 2006

The effect of several concentrations of morphine on the activity of adenylate cyclase [ATP pyrophosphate-lyase (cyclizing): EC 4.6.1.1.] was measured in homogenates of caudate nuclei of mice. Morphine stimulated the enzyme at 500 micron and inhibited slightly at 5 micron. Morphine stimulation was blocked by naloxone. Depending on its dose, morphine also increased or decreased the stimulating effect of dopamine on the dopamine-sensitive adenylate cyclase activity of caudate homogenate. Like dopamine, morphine'e effect on the adenylate cyclase activity was increased or decreased, respectively, by pretreating the animals with poly(I).poly(C) or with chloramphenicol. Thus, both dopamine and morphine appear to act on the same receptor. This "new" receptor differs from the one described by Snyder et al. and others, who demonstrated only binding affinity and no enzymatic activity. These data indicate that certain functions of the opiates might be mediated through the dopamine-sensitive adenylate cyclase of the caudate nuclei, which are the dopamine receptors in the brain.
Degradation of basic protein in myelin by neutral proteases secreted by stimulated macrophages: A possible mechanism of inflammatory demyelination
Authors: Cammer Wendy , Bloom Barry R. , Norton William T. , Gordon Siamon
Published: May 2006

In inflammatory demyelinating diseases such as multiple sclerosis and experimental allergic encephalomyelitis, myelin destruction occurs in the vicinity of infiltrating mononuclear cells. The observations that myelin can be altered prior to phagocytosis and in areas not contiguous with inflammatory cells suggests a common mechanism for the initial stages of demyelination. Because stimulated macrophages secrete several neutral proteases, including plasminogen activator, we have investigated the possibility that myelinolysis could be mediated directly or indirectly by these enzymes. Isolated myelin was incubated with conditioned media from cultures of thioglycollate-stimulated mouse peritoneal macrophages in the presence and absence of plasminogen. Myelin appeared to be vulnerable to attack by at least two proteolytic activities secreted by the macrophages, a plasminogen-dependent and a plasminogen-independent activity; of the major proteins in myelin, the basic protein was most susceptible. The direct myelinolytic activity of macrophage-conditioned media was abolished by EDTA, and the plasminogen-dependent hydrolysis was abolished by
p
-nitrophenylguanidinobenzoate, an inhibitor of plasminogen activator and plasmin. These results suggest that the plasminogen activator released by the stimulated macrophages generated plasmin which hydrolyzed basic protein in intact myelin. This interpretation was confirmed by the observation that urokinase, a plasminogen activator, in the presence of plasminogen brought about marked degradation of basic protein in myelin. We propose that the release of neutral proteases by stimulated macrophages involved in cell-mediated reactions, and its amplification by the plasminogen-plasmin system, may play a significant role in the demyelination observed in several inflammatory demyelinating diseases.
On the derivation of linear irreversible thermodynamics for classical fluids
Authors: Theodosopulu M. , Grecos A. , Prigogine I.
Published: May 2006

We consider the microscopic derivation of the linearized hydrodynamic equations for an arbitrary simple fluid. Our discussion is based on the concept of hydrodynamical modes, and use is made of the ideas and methods of the theory of subdynamics. We also show that this analysis leads to the Gibbs relation for the entropy of the system.
Inhibition of cholesteryl ester formation in human fibroblasts by an analogue of 7-ketocholesterol and by progesterone
Authors: Goldstein Joseph L. , Faust Jerry R. , Dygos John H. , Chorvat Robert J. , Brown Michaels S.
Published: May 2006

The synthesis of cholesteryl esters in cultured human fibroblasts is catalyzed by a microsomal acyl-coenzyme A:cholesterol acyltransferase (EC 2.3.1.26). The acyltransferase activity is enhanced when fibroblasts take up cholesterol contained in plasma low density lipoprotein. In the current studies two steroids, SC-31769 (an analogue of 7-ketocholesterol) and progesterone, were shown to inhibit acyltransferase activity in cell-free extracts of human fibroblasts. When added to intact cells, these steroids inhibited the incorporation of [
14
C]oleate into cellular cholesteryl [
14
C]oleate and reduced the accumulation of cholesteryl esters in fibroblasts exposed to low density lipoprotein. The inhibition of cholesteryl ester formation in intact cells by SC-31769 and progesterone was readily reversible. Neither compound inhibited the incorporation of [
14
C]oleate into [
14
C]triglycerides or [
14
C]phospholipids. When incubated with fibroblast monolayers at a concentration of 1 μg/ml, SC-31769 suppressed the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase [mevalonate:NADP
+
oxidoreductase (CoA-acylating); EC 1.1.1.34], the rate-controlling enzyme in cholesterol synthesis. In contrast, progesterone had no effect on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity at concentrations as high as 25 μg/ml. The availability of two types of steroid compounds that inhibit the acyltransferase activity and cholesteryl ester synthesis in human fibroblasts should prove useful in further studies of the regulatory mechanisms responsible for cholesteryl ester accumulation in human cells under normal and pathologic conditions.
Mathematical theory of group selection: Structure of group selection in founder populations determined from convexity of the extinction operator
Authors: Boorman Scott A.
Published: May 2006

Genetic analysis for group selection is developed for the case of a biallelic locus (
A, a
) undergoing group selection of founder populations only. By contrast to R. Levins“
E
=
E
(
x
) models, extinction now depends on genetics at the propagule stage but acts uniformly on larger populations. Biological evidence supports this hypothesis, which also allows mathematical treatment at once simpler and biologically more general than the Fokker-Planck partial differential equation formalism adopted by Levins. It is presently possible to handle cytogenetics of both diploid and haplodiploid type. The model is set up as a quasideterministic recursion in the 5-simplex Σ
5
, collapsing both drift and mendelian selection effects into a single parameter
u
, which is a Fisher-Kimura-Ohta fixation probability. In the analysis, it is shown that the stability of the fixed points is determined by the convexity of the extinction operator acting on propagules, assumed to be of size 2.

Thus, [Formula: see text] in which
E
1
and
E
3
are extinction probabilities for phenotypically uniform founder populations and
E
2
is the corresponding probability for founder populations of mixed phenotype. Further parameter regions are defined where fixation of the group-selected gene is globally stable, and this is still possible even when extinction pressure acting on carrying capacity populations becomes weak relative to a fixed mendelian selection strength.
Purification of nuclear antigens in Novikoff hepatoma.
Authors: Fujitani H , Chiu J F , Hnilica L S
Published: May 2006

Nuclear antigen in Novikoff hepatoma chromatin was partially purified and characterized. As indicated by complement fixation assay, this antigen was present in chromatin of embryonic livers and several transplantable tumors. It was not detected in normal tissue chromatins of the same animals. For its immunological specificity this protein antigen (molecular weight 45,000-60,000) had to be complexed with DNA. Preliminary experiments indicate that specific nuclear protein antigens are also present in human tissues and spontaneous malignancies.