bluuebunny/crossref_metadata_2025 huggingface dataset:
Extensive homology between the subunits of the phytohemagglutinin mitogenic proteins derived from Phaseolus vulgaris.
Authors: Miller J B , Hsu R , Heinrikson R , Yachnin S
Published: May 2006

The phytohemagglutinin mitogenic proteins derived from Phaseolus vulgaris comprise a class of five glycoproteins that are isomeric tetramers composed of varying proportions of two different subunits (L and R). Within the native tetramer, the L subunit is a potent leukoagglutinin and mitogen that lacks hemagglutinating properties, whereas the R subunit is a potent hemagglutinin with little or no mitogenic activity. The subunits have been isolated in homogeneous form by isoelectric focusing in 8 M urea. Previous work has shown that they have equal molecular weights and differ in amino-acid sequence from residues 1-7, but are identical in positions 8-24 [(1973) J. Exp. Med. 138, 939-951]. We now report amino-acid composition studies which reveal striking similarities between the subunits. Both lack methionine and cysteine. The twelfth residue in each subunit is a glycosylated asparagine, with the identical carbohydrate composition in each. The last three residues of the subunits, as determined by carboxypeptidase A digestion, are identical. Tryptic peptide mapping of the succinylated phytohemagglutinin subunits reveals a high degree of similarity. We conclude that the substantial difference in biological properties among the tetrameric phytohemagglutinin mitogens is a result of relatively restricted differences in the primary structure of their constituent subunits.
Interwining Operators and Automorphic Forms for the Metaplectic Group
Authors: Gelbart Stephen , Sally Paul
Published: May 2006

The local results announced in this paper concern the analytic continuation of interwining operators for the metaplectic covering group of
SL
(2) over an arbitrary local field and the decomposition of Weil's representation attached to the quadratic form
q
(
x
) =
x
2
. The global results concern Eisenstein series on the metaplectic group and a Siegel-Weil type formula relating the residues of these series to certain generalized theta functions.
Physiological role of an endoperoxide in human platelets: hemostatic defect due to platelet cyclo-oxygenase deficiency.
Authors: Malmsten C , Hamberg M , Svensson J , Samuelsson B
Published: May 2006

The endoperoxide prostaglandin G2 (PGG2) induced platelet aggregation as well as the platelet release reaction (release of ADP and serotonin) when added to human platelet-rich plasma. Formation of a metabolite of PGG2 [8-(l-hydroxy-3-oxopropyl)-9,12L-dihydroxy-5,10-heptadecadienoic acid] and a lipoxygenase product [12L-hydroxy-5,8,10,14-eicosatetraenoic acid] accompanied the release reaction caused by aggregating agents such as collagen, ADP, epinephrine, and thrombin. Indomethacin inhibited the release reaction and PGG2 formation induced by these agents but had no effect on PGG2-induced release reaction. The aggregating effect of PGG2 was abolished by furosemide, which is a competitive inhibitor of ADP-induced primary aggregation. These data indicate that the aggregating effect of PGG2 is due to release of ADP and that PGG2 synthesis is required for induction of the release reaction by various aggregating agents. A subject with a hemostatic defect due to abnormal release mechanism [decreased aggregation with epinephrine (second wave) and collagen and normal platelet ADP] had a deficiency of the cyclo-oxygenase that catalyzes formation of PGG2. Normal aggregation and release reaction were obtained with added PGG2. Ii is concluded that the endoperoxide (PGG2) is essential in normal hemostasis because of its role in initiating the release reaction required for aggregation by collagen and the second wave of aggregation caused by, e.g., ADP.
Presynaptic action of barbiturates in the frog spinal cord.
Authors: Nicoll R A
Published: May 2006

The action of pentobarbital on primary afferents of the isolated frog spinal cord was analyzed with sucrose gap and intracellular recordings techniques. Pentobarbital in concentrations generally considered to be in the anesthetic range greatly prolonged presynaptic inhibition and also depolarized primary afferents. The depolarization was accompanied by an increase in excitability and resulted from activation of gamma-aminobutyric acid receptors, possibly by a direct action on these receptors, since the depolarization was reversibly blocked by gamma-aminobutyric acid, but not by glycine, antagonists, and magnesium ions. Furthermore, dorsal root ganglion cells exhibited a reduced sensitivity to both gamma-aminobutyric acid and pentobarbital after a "desensitizing" dose of gamma aminobutyric acid. The prolongation of presynaptic inhibition and the activation of gamma-aminobutyric acid receptors on primary afferents by pentobarbital should act to reduce the amount of transmitter released from the first synapse in sensory pathways.
The amphisbaenian ear: Blanus cinereus and Diplometopon zarudnyi.
Authors: Gans C , Wever E G
Published: May 2006

Observations on the structure and function of the ear in amphisbaenians have been extended to two new species: to Blanus cinereus of the family Amphisbaenidae and Diplometopon zarudnyi of the family Trogonophidae. Blanus, considered one of the most primitive of this group of reptiles, shows a distinctive form of sound-receptive mechanism. The usual extracolumella is lacking, and the columella attaches to a cartilaginous plate beneath the skin posterior to the facial area. Diplometopon zarudnyi, a highly modified trogonophid, shows a columella and extracolumella of massive dimensions, with considerable calcification of the latter process. Cochlear potential measurements revealed the levels of auditory sensitivity in these species. A peculiar feature is the degree of stability of the ear's responses in the presence of large variations in body temperature.
Source Theory Discussion of Deep Inelastic Scattering with Polarized Particles
Authors: Schwinger Julian
Published: May 2006

A general phenomenological framework is provided for the discussion of the inelastic scattering of polarized electrons (muons) on polarized nucleons, when regarded as the absorption of polarized virtual photons. The relevant cross sections compare parallel and antiparallel orientations of the photon helicity and nucleon spin, and also deal with linear combinations of longitudinal and transverse polarization. The polarization asymmetry for transverse polarization,
P
, assumes a scaling form in the deep inelastic scattering region, and should go to zero as ω
-1
for large ω. The latter behavior is connected, through the use of the improved scaling variable ω

s

, with the high energy real photon situation. A sum rule is exhibited which implies that
P
must change sign in the deep inelastic region. This sum rule also yields the known Drell-Hearn sum rule for real photon Compton scattering, when combined with another, new, sum rule for the anomalous magnetic moment. The latter is verified in the context of pure electrodynamics to the lowest order in α. Finally, it is conjectured that
P
specifically changes from negative to positive values as ω varies from 1 to ∞.
Regulation of sensitivity to beta-adrenergic stimulation in induction of pineal N-acetyltransferase.
Authors: Romero J A , Axelrod J
Published: May 2006

Stimulation by isoproterenol causes large increases in the activity of rat pineal N-acetyltransferase (arylamine acetyltransferase or acetyl-CoA:arylamine N-acetyltransferase, EC 2.3.1.5) after a variable lag period. Lengthening periods of exposure to light cause rapid increases in the sensitivity of pineal N-acetyltransferase to induction by isoproterenol. This supersensitivity, which develops gradually over a 12 hr period, is correlated with increasingly longer lag periods in the induction of the enzyme, and with progressively greater maximal response. Repeated administration of isoproterenol to supersensitive animals rapidly reverses the above changes and causes relative subsensitivity. The sensitivity of N-acetyltransferase to induction by dibutyryl-cyclic tamp added to pineals in organ culture was found to change in parallel with the sensitivity to isoproterenol. Stimulation of cyclic AMP levels in the pineal by isoproterenol was also greater in supersensitive rats than in the subsensitive animals, whether the supersensitivity had been caused by denervation or by exposure to light for 12 hr. The above experiments suggest that there are two sites for the regulation of the sensitivity of N-acetyltransferase to induction by catecholamines. The first site regulates the capacity of intracellular processes (i.e., induction of tn-acetyltransferase) to respond to cyclic AMP as a second messenger.
Biological properties of plasmin digests of S-carbamidomethylated human growth hormone.
Authors: Reagan C R , Mills J B , Kostyo J L , Wilhelmi A E
Published: May 2006

Reduction and carbamidomethylation of the intrachain disulfide bridges of human growth hormone did not destroy its ability to stimulate weight gain or cartilage metabolism in hypophysectomized rats. The reduced and alkylated hormone also stimulated glucose oxidation in isolated adipose tissue of hypophysectomized rats when added in vitro. When the S-carbamidomethylated hormone was incubated overnight with human plasmin, approximately 95% of the starting material was completely digested, as judged by polyacrylamide gel electrophoresis. The plasmin digest retained the ability to stimulate weight gain, cartilage metabolism, and glucose oxidation. A fraction consisting of two major electrophoretic components was isolated from the digest by chromatography on tsephadex G-50. This fraction possessed the biological properties of the whole digest.
Neoantigens of the membrane attack complex of human complement.
Authors: Kolb W P , Müller-Eberhard H J
Published: May 2006

The membrane attack complex of complement is a fusion product of five complement proteins: C5b, C6, C7, C8, and C9. The complex causes complement-dependent cell membrane damage. It is assembled following complement activation both on the target cell surface and in the fluid phase. The isolated soluble complex, which has a molecular weight of one million, exhibited reduced expression of the antigenic determinants of the native precursor proteins. Antisera produced to the intact complex contained antibodies to neoantigens which were not detectable on the five precursor proteins. Antisera were rendered neoantigen-specific by adsorption with fresh human serum. Since the adsorbed antisera precipitated the complex, the complex must contain multiple neoantigenic sites. The complex-specific antibodies not only reacted with the soluble complex, but also with the target cell-bound membrane attack complex.
Remark on the Phase Problem in Crystallography
Authors: Grünbaum F. Alberto
Published: May 2006

The ambiguities found in determining a crystal structure from x-ray diffraction can be resolved if one takes into account the random thermal motion of the atoms.
Action of feedback regulator on adenylate cyclase.
Authors: Ho R J , Sutherland E W
Published: May 2006

A factor [the feedback regulator (FR)] formed by adipocytes after the stimulation of a cAMP raising hormone has been found to be a potent inhibitor of membrane-bound adenylate cyclase [EC 4.6.1.1.; ATP pyrophosphate-lyase (cyclizing)]. In a standard assay system using rat adipocyte plasma membrane as the source of adenylate cyclase, the FR inhibited adenylate cyclase by lowering the Vmax without affecting the apparent Km for ATP (0.3-0.6 mM). The apparent Ka for epinephrine (5-6 muM) was also not affected by FR. The inhibitory action of FR was partially countered by Mg2+ ions. An increase in phosphorylation of plasma membrane was observed when FR was present in the incubation system. The concentration required for a 50% inhibition was four times higher when adenosine 5-(beta,gamma-imino) triphosphate [AMP-P(NH)P] replaced ATP as the substrate for adenylate cyclase, implying that adenylate cyclase was inactivated by phosphorylation caused by FR. Increase in FR inhibition obtained by adding low concentrations of adenosine 5-(alpha,beta-methylene) triphosphate or ATP to AMP-(NH)P as the substrate supports this view. The inhibitory action was reversible. These results are consistent with the previously reported phenomena that (1) the undue to the formation of FR, and (2) the recovery of responsiveness of the stimulated cells by washing the cells with regular buffer medium is a result of the removal of FR. The hormone-initiated biphasic curve of cAMP levels in adipocytes is believed to be due to the negative feedback action of FR on adenylate cyclase. The mechanism of action of FR on inhibition of adenylate cyclase appears to be related to the phosphorylation of certain membrane components.
Cell-division factors from Vinca rosca L. crown gall tumor tissue.
Authors: Miller C O
Published: May 2006

A cell-division factor has been precipitated from extracts of cultured Vinca rosea L. crown gall tumor tissue by using the mercuric acetate procedure previously employed by Wood and colleagues to obtain their "cytokinesin I." On the basis of its mass spectrum, ultraviolet light absorbancy spectra, solubilities, chromatographic migration values, and growth activity, the factor is ribosyl-trans-zeatin, that is, 6-(4-hydroxy-3-methyl-trans-2-butenylamino)-9-beta-D-ribofuranosylpurine. Ribosylzeatin has now been isolated from tumor tissue by four experimental techniques; any possibility that it is an artifact seems to have been eliminated. Contrary to the report by Wood and colleagues, synthetic ribosylzeatin is precipitated from an aqueous solution by mercuric acetate, provided the complete precipitation procedure is utilized. These facts and others discussed strongly support our suggestion that ribosylzeatin was present in the preparation ("cytokinesin I") examined by Wood and colleagues in several biological assays. The reasons advanced by Wood and others for rejecting this suggestion have been found either not to be pertinent to the question or to have insufficient experimental bases.
Formation of cholinergic synapses between dissociated sympathetic neurons and skeletal myotubes of the rat in cell culture.
Authors: Nurse C A , O'Lague P H
Published: May 2006

Sympathetic principal neurons, dissociated from superior cervical ganglia of newborn rats, were plated into cultures containing rat skeletal myotubes formed from previously plated primary myoblasts. Electrophysiological evidence is presented that the neurons developed cholinergic synapses with the myotubes. In addition, the neurons developed cholinergic synapses with each other as previously reported [O'Lague et al. (1974) Proc. Nat. Acad. Sci. USA 71, 3602-3606]. The acetylcholine receptors of myotubes differed from those of the neurons in their sensitivities to curare and hexamethonium, in a manner expected of adult muscle and ganglionic receptors. alpha-Bungarotoxin blocked synaptic transmission from neuron to myotube, but not from neuron to neuron in the same culture.
Kinetic Theory of Viscosity of Compressed Fluids
Authors: Hildebrand J. H.
Published: May 2006

The viscosity of a compressed gas is a function of three variables: (
1
) the degree of crowding of the molecules; (
2
) their capacity, by reason of softness, flexibility, or rotational inertia, to absorb the vector momentum applied to cause flow; (
3
) the resistance to this vector momentum offered by the randomly oriented thermal momenta, which becomes significant when the liquid expands sufficiently to permit molecular mean free paths between binary collisions to be long enough for thermal momenta to acquire fractions of their thermal momentum in free space.

The fluidity ϕ of simple liquids obeys the linear equation ϕ =
B
(
V
-
V
0
)/
V
0
and its viscosity is, therefore, η

a

=
V
0
/
B
(
V
-
V
0
); this accounts for components
1
and
2
. The contribution of random thermal momenta,
3
, obeys the equation, η

b

= η
0
(1 -

V
t

/
V
). η
0
is the viscosity of the dilute gas;

V
t

is the molal volume at which the thermal contribution begins. The total momentum, η = η

a

+ η

b

.

Values of η
0
vary linearly with
T
1/2
. Values of

V
t

are related to heat capacities.
Immunohistochemical localization of 3': 5'-cyclic AMP and 3': 5'-cyclic GMP in rat liver, intestine, and testis.
Authors: Ong S H , Whitley T H , Stowe N W , Steiner A L
Published: May 2006

Cyclic GMP and cyclic AMP have been localized in rat liver, small intestine, and testis by a fluorescent immunocytochemical procedure. In liver, cyclic AMP is distributed along sinusoids predominantly, and increased fluorescence is seen sinusoidal areas after glucagon administration. Cyclic GMP is located in nuclear elements and on the plasma membranes of hepatocytes. In jejunum, cyclic AMP is found predominantly at the basal and lateral sides of brush border cells and in the lamina propria, while cyclic GMP is located to the brush border membrane, smooth muscle, and nuclear elements. In testis, cyclic AMP is found in cytoplasm of cells at the perimeter of the seminiferrous tubules and in interstitial cells, while cyclic AMP is visualized on the plasma membrane of the cells lining the tubules. Cyclic GMP is also seen on chromosomes of premeiotic spermatocytes and in sperm. These data provide histological evidence implicating diverse roles for the nucleotides in these tissues. The nuclear localization of cyclic GMP in all of these tissues suggests a role for the nucleotide in nucleus-directed events.
Involvement of nicotinamide adenine dinucleotide in the action of cholera toxin in vitro.
Authors: Gill D M
Published: May 2006

NAD is a necessary cofactor for the activation of adenylate cyclase (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) by cholera toxin. Lysates of certain types of cell that hydrolyze their endogenous store of NAD after cell disruption respond poorly or not at all to cholera toxin. Lysates of pigeon erythrocytes, which lack enzymes that degrade NAD, provide a convenient and reproducible system for assaying the activity of cholera toxin in vitro and allow investigation of the mechanism of action of the toxin upon broken cells.
Neutron scattering study of human serum low density lipoprotein.
Authors: Stuhrmann H B , Tardieu A , Mateu L , Sardet C , Luzzati V , Aggerbeck L , Scanu A M
Published: May 2006

Regions of different proton density in the low density lipoprotein (LDL) particle from human serum have been determined by neutron scattering. From measurements in various H2O/D2O mixtures, the LDL particle appears to be quasi-spherical, with the centers of gravity of the hydrocarbon and polar regions coinciding. The average volume occupied by a particle was found to be 3.2 X 10-6 A-3, with the volume fraction occupied by the hydrocarbons being 60%. The ratius of gyration of the hydrocarbon region was 64 A, while that of the polar region was 100 A. consequently, the core of LDL is predominantly occupied by the hydrocarbon chains, while the outer shell is sparsely occupied by protein emerging from the lipid core.
Ribosomal protein S1 and polypeptide chain initiation in bacteria.
Authors: Szer W , Hermoso J M , Leffler S
Published: May 2006

Among several subspecies of 30S subunits of Escherichia coli observed by polyacrylamide-agarose gel electrophoresis, only the slow-moving, protein S1-containing subspecies participates in the formation of the 30S initiation complex with coliphage MS2 RNA as mRNA; the other subspecies retain activity with AUG as mRNA; they are also active in the poly(U)-directed binding of Phe-tRNA. Protein S1 from Caulobacter crescentus substitutes for E. coli S1 despite the fact that C. crescentus ribosomes do not bind MS2 RNA. Under appropriate conditions, the entire population of E. coli 30S subunits can be isolated as the S1-containing subspecies. Protein S1 is lost by salt treatment of ribosomes.
Phylogenetic origin of the chloroplast and prokaryotic nature of its ribosomal RNA.
Authors: Zablen L B , Kissil M S , Woese C R , Buetow D E
Published: May 2006

The 16S ribosomal RNA of the Euglena gracilis chloroplast has been characterized in terms of its two-dimensional electrophoretic "fingerprint" (T1 ribonuclease). Results show it to be a typically prokaryotic 16 S rRNA. By the present criterion, different chloroplasts are shown to be related to one another and at least distantly to blue-green algae and perhaps to Bacillaceae. These results argue in favor of an endosymbiont origin of the chloroplast.
Singular Integrals and the Principal Series, IV
Authors: Knapp A. W. , Stein E. M.
Published: May 2006

The intertwining operators that have been constructed for all the series of unitary representations appearing in the Plancherel formula of a connected real semisimple Lie group of matrices are given a new normalization and then applied in two ways. The first is to obtain dimension formulas for the commuting algebras of the unitary representations in question. The second is to establish the existence of complementary series. These bear the same relationship to the unitary representations under study that the complementary series found earlier bear to the principal series.
Attraction of the oriental fruit fly, Dacus dorsalis, to methyl eugenol and related olfactory stimulants.
Authors: Metcalf R L , Mitchell W C , Fukuto T R , Metcalf E R
Published: May 2006

The attraction of male oriental fruit flies to methyl eugenol and 34 analogues was investigated quantitatively using the characteristic feeding response. Methyl eugenol was the most active compound studied, with a feeding response to 0.01 mug, but saturation of the allyl side chain or replacement of allyl by allyloxy produced compounds almost as effective. Replacement of the methoxy groups by methylenedioxy, methyl, or chloro groups abolished all response. The ring geometry of the methoxy groups was critical, with orthodimethoxy most active and meta-dimethoxy inactive. Replacement of methoxy with hydroxy, methylthio, or amino groups did not abolish the response. The failure of the oriental fruit fly to respond to the methyl and chloro isosteres of methyl eugenol was contrasted with the response of a human odor panel which perceived these compounds as having weak floral odors.
Preparation and microbial decomposition of synthetic [14C]ligins.
Authors: Kirk T K , Connors W J , Bleam R D , Hackett W F , Zeikus J G
Published: May 2006

A definitive assay for microbiological and biochemical research on the biodegradation of lignin was developed using radioactive synthetic lignins specifically labeled in the side chains, aromatic rings or in the methoxyl groups. The [14C]lignins were prepared by oxidative polymerization with peroxidase and H2O2 Of specifically labeled coniferyl alcohol (4-hydroxy-3-methyoxycinnamyl alcohol). The synthetic polymers were shown by spectroscopic and chemical methods to contain the same intermonomer linkages found in natural lignins. Incubation of the [14C]lignins with known lignin-degrading fungi and with a forest soil resulted in 14CO2 evolution.
Modification of the 5'-terminus of mRNA by soluble guanylyl and methyl transferases from vaccinia virus.
Authors: Ensinger M J , Martin S A , Paoletti E , Moss B
Published: May 2006

RNA guanylyl and methyl transferases have been solubilized from vaccinia virus cores. The guanylyl transferase specifically adds a GMP residue to the 5'-terminus of unmethylated vaccinia virus mRNA to form the structures G(5')ppp(5')Gp- and G(5')ppp(5')Ap-. Studies with [alpha-32P]GTP and [beta, gamma-32P]GTP indicated that only the alpha-phosphate is transferred. In the presence of S-adenosylmethionine, the methyl transferases convert the blocked 5'-termini to m7G(5')ppp(5')Gmp- and m7G(5')ppp(5')Amp-. Similarly, the enzymes can modify synthetic poly(A) to form the structure m7G(5')ppp(5')Amp-.
Transformation by polyoma virus alters expression of a cell mutation affecting cycle traverse.
Authors: Burstin S J , Basilico C
Published: May 2006

A temperature-sensitive mutant of hamster BHK 21/13 cells, tsAF8, which at 39 degrees becomes arrested in the G1 (G0) phase of the cell cycle, is phenotypically altered with respect to temperature sensitivity after transformation with polyoma virus. Polyoma transformation does not produce reversion to a non-temperature-sensitive phenotype but causes increased entry into S and increased rate of cell death at the nonpermissive temperature, compared to untransformed tsAF8 cells. The increased frequency of cells synthesizing DNA is not accompanied by an increased frequency of mitosis, since most of the polyoma-transformed tsAF8 cells that synthesize DNA at the nonpermissive temperature do not divide. At the permissive temperature, polyoma-transformed tsAF8 cells, unlike tsAF8, also lose viability when exposed to other methods of arresting cells in G1. The most likely explanation for this phenomenon is that polyoma virus transformation interferes with the cellular response to this mutation as well as to other conditions that cause cell cycle arrest in G1.
Metabolic pathways of 7,12-dimethylbenz[a]anthracene in hepatic microsomes.
Authors: Yang S K , Dower W V
Published: May 2006

High pressure liquid chromatography has enabled quantitative analysis of the in vitro metabolism of 7,12-dimethylbenz[a]anthracene, 7-methyl-12-hydroxymethylbenz[a]anthracene, 7-hydroxymethyl-12-methylbenz[a]anthracene, and 7,12-dihydroxymethylbenz[a]anthracene by 3-methylcholanthrene-induced and control rat liver microsomes. The following previously unrecognized metabolites have been tentatively identified: 5,6-dihydro-5,6-dihydroxy-7-methyl-12-hydroxymethylbenz[a]anthracene, 3-hydroxy-7,12-dihydrodihydroxymethylbenz[a]anthracene, 4-hydroxy-7,12-dihydrodihydroxymethylbenz[a]anthracene, and 8,9-dihydro-8,9-dihydroxy-7,12-dihydroxymethylbenz[a]anthracene. The epoxide hydratase inhibitor 1,2-epoxy-3,3,3-trichloropropane was found to eliminate all dihydrodiol formation and markedly inhibit the formation of several dimethylbenzanthracene metabolites. It is proposed that the tentatively identified 3-hydroxy and 4-hydroxy derivatives are formed by an enzymatic mechanism that does not involve epoxides as intermediates. The metabolic pathways of 7,12-dimethylbenz[a]anthracene in hepatic microsomal enzymes are proposed.
Sulfonamide resistance mechanism in Escherichia coli: R plasmids can determine sulfonamide-resistant dihydropteroate synthases.
Authors: Wise E M , Abou-Donia M M
Published: May 2006

Several natural isolate E. coli strains highly resistant to sulfonamides and antibiotics are shown to contain a sulfonamide-resistant dihydropteroate synthase (2-amino-4-hydroxy-6-hydroxymethyl-7,8-dihydropteridine-diphosphate:4-aminobenzoate 2-amino-4-hydroxydihydropteridine-6-methenyltransferase, EC 2.5.1.15) in addition to the normal sensitive enzyme. The resistant dihydropteroate synthases examined are determined by an R plasmid and are smaller and less heat stable than the normal sulfonamide-sensitive enzyme. One synthase resistant to any sulfonamide tested, and to sulfanilic and arsanilic acids, was still inhibited by several non-sulfonamide analogs of p-aminobenzoate. Citrobacter and Klebsiella pneumoniae strains also show similar mechanisms of sulfonamide resistance.
Chromatin architecture: investigation of a subunit of chromatin by dark field electron microscopy.
Authors: Langmore J P , Wooley J C
Published: May 2006

Dark field scanning electron microscopy of unstained, unfixed samples of chromatin, histone-1-depleted chromatin, and nucleohistone has been used to identify an apparent subunit of chromatin, namely a disk-shaped structure we term the unit particle, which is probably about 135 A wide and 50 A thick in the hydrated state. The unit particles are found at rather uniform intervals along thin DNA-like fibers. Histone 1 depletion leads to a bimodal distribution of these spacings. Our observations suggest that the unit particle consists of a loop of nucleoprotein, perhaps around a histone core.
Biosynthesis of delta-aminolevulinic acid from the intact carbon skeleton of glutamic acid in greening barley.
Authors: Beale S I , Gough S P , Granick S
Published: May 2006

The customary route in animals and bacteria for delta-aminolevulinic acid biosynthesis is from glycine and succinyl CoA, catalyzed by the enzyme delta-aminolevulinic acid synthetase [succinyl-CoA:glycine C-succinyltransferase (decarboxylating), EC 2.3.1.37]. Attempts to demonstrate this route in plants have been unsuccessful. Evidence is given for a new enzymic route of synthesis of delta-aminolevulinic acid in plants. This route involves the incorporation of the intact five-carbon skeleton of glutamic acid into delta-aminolevulinic acid. Demonstration of the new pathway in plants has been made by feeding specifically labeled [14C]glutamic acid to etiolated barley shoots greening in the light. In the presence of levulinate, a competitive inhibitor of delta-aminolevulinic acid dehydrastase [porphobilinogen synthase; delta-aminolevulinate hydro-lyase (adding delta-aminolevulinate and cyclizing); EC 4.2.1.24], delta-aminolevulinate accumulates. The delta-aminolevulinate formed was chemically degraded by periodate to formaldehyde and succinic acid. The C5 (formaldehyde) fragment was separated, as the 5,5-dimethyl-1,3-cyclohexanedione (dimedone) derivative, from the C1-C4 (succinic acid) fragment. The C5 atom contained radioactivity predominantly derived from C1 of glutamic acid. Conversely, the labeled C3 and C4 atoms of glutamic acid were found primarily in the succinic acid (C1-C4) fragment of delta-aminolevulinate. This labeling pattern for delta-aminolevulinic acid is consistent with a biosynthetic route utilizing the intact five-carbon skeleton of alpha-ketoglutarate, glutamate, or glutamine, and is inconsistent with the delta-aminolevulinic acid synthetase pathway utilizing glycine and succinyl CoA as precursors.
Initiation of cell proliferation in cultured mouse fibroblasts by prostaglandin F2alpha.
Authors: De Asua L J , Clingan D , Rudland P S
Published: May 2006

Prostaglandin (PG) F2alpha added to quiescent Swiss mouse 3T3 cell cultures initiates DNA synthesis and cell proliferation in a small proportion of the cells. Insulin, which markedly potentiates the effect of PGF2alpha on the initiation of cell division when added with PGF2alpha, causes a simultaneous reduction in intracellular cyclic AMP and an increase in cyclic GMP concentrations similar to those observed after serum addition. Prostaglandins E1 and E2 are less effective than PGF2alpha in initiating DNA synthesis and this effect is only observed at higher concentrations. Therefore, some prostaglandins can act as extracellular factors to regulate cell proliferation.
Very stable prokaryotic messenger RNA in chromosomeless Escherichia coli minicells.
Authors: Levy S B
Published: May 2006

E. coli minicells lack DNA, yet they make protein, the synthesis of which is sensitive to chloramphenicol but insensitive to rifamycin. This protein is coded for by very stable cellular mRNA with an estimated half-life of 40-80 min. In an R factor-containing minicell, two very different species of mRNA are observed: (i) R factor-specific mRNA with a short half-life whose synthesis is rifamycin-sensitive and (ii) cellular mRNA with a long half-life whose synthesis is rifamycin-insensitive. These findings indicate that minicells contain normal degradative mechanisms for mRNA and point out the existence of a unique class of very stable cellular mRNA. Greater than 80% of the rifamycin-insensitive protein synthesized goes into the outer minicell membrane. Relatively stable mRNA, half-life 5.5-11.5 min, for outer membrane protein in whole cells has been reported [Hirashima et al. (1973) J. Mol. Biol. 79, 373-389]. The stability of minicell mRNA is significantly greater. This and other observations suggest that there are two functional species of mRNA for outer membrane protein perhaps in different sites in the cell. Furthermore, these studies suggest that a class of cellular proteins is synthesized in bacteria without concomitant transcription and in the absence of association with chromosomal DNA.
Electrophoretic patterns of deadenylylated chorion and globin mRNAs.
Authors: Vournakis J N , Efstratiadis A , Kafatos F C
Published: May 2006

Treatment of silkmoth chorion mRNAs with calf thymus RNase H (EC 3.1.4.34; RNA-DNA-hybrid ribonucleotidohydrolase) in the presence of oligo(dT) specifically and effectively removes the 3'-terminal poly(A) sequences. Excision of non-poly(A) fragments cannot be detected. Under these conditions, RNase H leads to increased electrophoretic homogeneity of rabbit globin mRNA, presumably as a result of removal of poly(A) sequences that are inherently variable in length. Treatment with RNase H converts the three diffuse zones of messages for the several chorion proteins into multiple sharp bands.
Photoincorporation of puromycin and N-(ethyl-2-diazomalonyl)puromycin into Escherichia coli ribosomes.
Authors: Cooperman B S , Jaynes E N , Brunswick D J , Luddy M A
Published: May 2006

[3H]Puromycin and N-(ethyl-2-diazomalonyl)[3H]puromycin are incorporated into E. coli ribosomes on irradiation at 253.7 nm. Both compounds incorporate into both protein and nucleic acid. Two-dimensional gel electrophoresis of ribosomal protein shows that L23 is the major protein labeled by puromycin. Although incorporation is clearly a complex process, evidence is presented that L23 is labeled via an affinity labeling process, thus placing L23 at the aminoacyl-tRNA receptor (A) site. N-(ethyl-2-diazomalonyl)puromycin is a ribosomal ligand, as shown by its inhibition of two ribosomal assays, but it is not a good puromycin analog, and it is unclear whether its incorporation, which proceeds via both carbene-dependent and carbene-independent processes, results from affinity labeling.
Dual regulation of adenylate cyclase accounts for narcotic dependence and tolerance.
Authors: Sharma S K , Klee W A , Nirenberg M
Published: May 2006

Narcotics affect adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] in two opposing ways, both mediated by the opiate receptor. The first process is the readily reversible inhibition of the enzyme by narcotics; the second is a compensatory increase in enzyme activity which is delayed in onset and relatively stable. Late positive regulation of the enzyme counteracts the inhibitory influence of morphine and is responsible for narcotic dependence and tolerance. The coupled inhibitory and positive regulatory mechanisms for adenylate cyclase provide a means of activating and deactivating neural circuits hours after the initial event and thus may play a role in a memory process.
Mutagenic and cytotoxic activity of benzol[a]pyrene 4,5-, 7,8-, and 9,10-oxides and the six corresponding phenols.
Authors: Wood A W , Goode R L , Chang R L , Levin W , Conney A H , Yagi H , Dansette P M , Jerina D M
Published: May 2006

The benzo[a]pyrene 4,5-, 7,8-, and 9,10-oxides and the six corresponding phenols (4-, 5-, 7-, 8-, 9-, and 10-hydroxybenzo[a]pyrene) have been tested for mutagenic and cytotoxic activity in bacteria and in a mammalian cell culture system. Benzo[a]pyrene 4,5-oxide (K-region) was highly mutagenic in two histidine-dependent strains (TA1537 and TA1538) of Salmonella typhimurium which detect frameshift mutagens. In contrast, benzo[a]pyrene 7,8- and 9,10-oxides were less than 1% as mutagenic as the 4,5-oxide. Benzo[a]pyrene 7,8- and 9,10-oxides were unstable in aqueous media, whereas the 4,5-oxide was stable for several hours. This difference in stability could not account for the different mutagenic activities of the three arene oxides. The benzo[a]pyrene oxides were inactive in a strain (TA1535) that is reverted by base pair mutagens such as N-methyl-N'-nitro-N-nitrosoguanidine or in a strain (TA1536) that detects framshift mutagens similar to the acridine half-mustard ICR-191. Benzo-[a]-pyrene and the six phenols were all stable in aqueous media, but they had little or no mutagenic activity in any of the four Salmonella strains. Conversion of 8-azaguanine-sensitive Chinese hamster V79 cells to 8-azaguanine-resistant variants was increased by benzo[a]pyrene 4,5-oxide, whereas the 9,10-oxide was considerably less active. Benzo[a]pyrene and the other derivatives had little or no effect. Benzo[a]yrene 4,5-oxide was more cytotoxic to the Chinese hamster V79 cells than the 7,8- and 9,10-oxides, while 8-hydroxybenzo[a]pyrene was the most cytotoxic of the six phenols.
Leukocyte migration inhibitory factor (LMIF) induced by concanavalin A: standardized microassay for production in vitro.
Authors: Górski A J , Dupont B , Hansen J A , Good R A
Published: May 2006

A standardized microculture system has been developed to assess the ability of lymphocytes to secrete leukocyte migration inhibitory factor (LMIF) in response to the nonspecific mitogen concanavalin(Con A). LMIF-rich supernates collected from stimulated lymphocytes cultured in plastic microtiter plates are assayed by pulse exposure of purified human granulocytes and inhibition of their migration in agarose medium. LMIF activity in this system is suppressed by the protein synthesis inhibitor puromycin, but not by inhibition of lymphocyte proliferation by irradiation. It is demonstrated that normal lymphocytes stimulated with mitogen elaborate LMIF activity, while lymphocytes from malignant lymphoma patients are frequently unable to produce it. Thus, mitogen-induced mediator production may be a useful parameter in further characterization of primary and secondary immunodeficiencies.
Structural similarities between a product of the T/t-locus isolated from sperm and teratoma cells, and H-2 antigens isolated from splenocytes.
Authors: Vitetta E S , Artzt K , Bennett D , Boyse E A , Jacob F
Published: May 2006

Molecules specified by the H-2-linked T/t locus in the mouse are expressed on H-2-negative cells such as early embryos, sperm, and teratoma cells. By means of enzymatic radioiodination of cells and immunoprecipitation of lysates with congenic antiserum, one of these molecules, known as F9, has been obtained from sperm and teratoma cells and compared to H-2 isolated from murine splenocytes. Our studies indicate that both H-2 and F9 have identical molecular weights and subunit structure, including the presence of a B2-microglobulin-like subunit. These findings, taken together with previous studies of TL alloantigens, suggest that a number of gene products of the 9th linkage group show structural homology with each other and, in addition, with immunoglobulin. The genes in question may therefore have arisen from a primitive gene concerned with cellular recognition.
Effect of estrogen on gene expression: purification of vitellogenin messenger RNA.
Authors: Wetekam W , Mullinix K P , Deeley R G , Kronenberg H M , Eldridge J D , Meyers M , Goldberger R F
Published: May 2006

We report initial studies on estrogen-mediated regulation of egg yolk protein synthesis in the rooster. Egg yolk proteins are normally synthesized as a large precursor, vitellogenin, in the liver of the laying hen; roosters synthesize vitellogenin only when treated with estrogen. Polysomal RNA from the liver of estrogen-treated roosters was translated in a reticulocyte cell-free system, and the newly synthesized proteins were identified by a highly specific and sensitive indirect immunoprecipitation reaction. The messenger RNA that specifies vitellogenin has been purified more than 800-fold from rooster liver polysomal RNA by a combination of methods, including immunoprecipitation of polysomes and chromatography of RNA on poly(U)-Sepharose.
Nonribosomal proteins associated with eukaryotic native small ribosomal subunits.
Authors: Freienstein C , Blobel G
Published: May 2006

The native small ribosomal subunit (Sn) from rabbit reticulocytes which is able to initiate translation of globin mRNA in a cell-free system carries additional protein components. The latter can be separated from the subunit in a high salt sucrose gradient yielding a top fraction (T) and a complex fraction (C), sedimenting at about 4 and 15 S, respectively. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate revealed that fraction T contained four dominant polypeptides, while fraction C represents a large protein complex consisting of at least 10 polypeptides. Sn isolated from other sources showed similar patterns of their nonribosomal proteins. Reconstitution experiments revealed that fraction C is absolutely required for protein synthesis, while fraction T enhances protein synthesis only in the presence of C. The adherence of these protein factors to the subunit is not mediated by magnesium ions. Treatment of Sn with EDTA and centrifugation in a magnesium-free sucrose gradient caused unfolding of the subunits and dissociation of several ribosomal proteins, but not of the factors. The unfolded ribosomal subunits sedimented as two distinct peaks. The more slowly sedimenting peak contained proteins of fraction T and the faster sedimenting one contained the 15S complex, indicating heterogeneity of the Sn population with respect to the factors attached to them.
Characterization of a novel, low-molecular-weight DNA-binding protein from Escherichia coli.
Authors: Rouvière-Yaniv J , Gros F
Published: May 2006

A low-molecular-weight (7000), heat-stable protein--HU--that stimulates transcription of bacteriophage lambda DNA by E. coli RNA polymerase was purified from E. coli extracts using affinity chromatography on DNA-cellulose. HU binds to native DNA, resulting in an apparent thickening of the DNA chains as revealed by electron microscopy. Contrary to DNA unwinding proteins, it causes no destabilization of the double helix. HU differs from previously described transcription factors (H1, D, etc.) and from the low-molecular-weight omega subunit of the RNA polymerase. By its amino-acid composition and characteristics, HU displays an interesting resemblance to some eukaryotic histones, such as H2B and H1.
Relaxation measurements on the acetylcholine receptor.
Authors: Sheridan R E , Lester H A
Published: May 2006

In Electrophorus electroplaques, the agonist-induced postsynaptic conductance depends on membrane potential. During steady exposure to agonists, after a voltage step the conductance relaxes on a millisecond time scale, exponentially approaching a new equilibrium value. The relaxation rate constant k is an instantaneous function of voltage, insensitive to the past or present conductance. Two components sum to form k. A concentration-sensitive component increases linearly with agonist concentration and decreases during desensitization or exposure to curare. Thus this component reflects the average frequency at which acetylcholine receptors are opening. The voltage-sensitive component, obtained by extrapolating k to zero agonist concentration, increases at more positive potentials. For acetylcholine, the voltage-sensitive component equals the rate constant for the exponential decay of postsynaptic currents; it thus seems to be the closing rate for active receptors. The voltage-sensitive component has the relative amplitudes acetylcholine less than carbamoylcholine less than decamethonium, and for each agonist equals the closing rate determined from "noise" measurements at neuromuscular junctions. The kinetic data explain several aspects of the steady-state conductance induced by agonists, but shed no light on apparent cooperative effects.
Relationship between nuclear and cytoplasmic poly(adenylic acid).
Authors: Brandhorst B P , McConkey E H
Published: May 2006

The kinetics of accumulation of radioactive poly(A) in the nucleus and cytoplasm of mouse L cells have been determined using labeling conditions in which the cellular ATP pool is shown to have a nearly constant specific radioactivity. Most or all nuclear poly(A) accumulates with kinetics very similar to those of heterogeneous nuclear RNA, having a half-time of about 25 min. There is little or no lag before attainment of a maximal rate of accumulation of cytoplasmic poly(A). These data are consistent with a variety of models in which nuclear poly(A) does or does not all serve as a precursor of cytoplasmic poly(A). In either type of model there must be a class of poly(A) either synthesized in the cytoplasm or passing through a small nuclear pool separate from the main pool of nuclear poly(A).
Oncornavirus-like particles in human skin cancers.
Authors: Balda B R , Hehlmann R , Cho J R , Spiegelman S
Published: May 2006

A high-molecular-weight RNA encapsulated with an RNA-instructed DNA polymerase in particles possessing the density characteristic of the RNA tumor viruses has been detected in 13 out of 14 human malignant melanomas. The [3H]DNA synthesized by these particles in an endogenous reaction hybridizes to RNA extracted from the human melanoma particulate structures, but not to RNA from normal skin. Similar particles containing RNA and enzyme have been found in basal cell and squamous cell carcinomas of the skin. The RNA of the melanoma particles is easily distinguishable by hybridization from the RNAs found in the particles of the basal and squamous cell carcinomas.
beta-Bungarotoxin, a pre-synaptic toxin with enzymatic activity.
Authors: Strong P N , Goerke J , Oberg S G , Kelly R B
Published: May 2006

beta-Bungarotoxin, a pre-synaptic neurotoxin isolated from the venom of the snake Bungarus multicinctus, has been shown to modify release of neurotransmitter at the neuromuscular junction. In this communication, we demonstrate that beta-bungarotoxin is a potent phospholipase A2 (phosphatide 2-acyl hydrolase, EC 3.1.1.4), comparable in activity with purified phospholipase enzymes from Naja naja and Vipera russellii. The phospholipase activity of beta-bungarotoxin requires calcium and is stimulated by deoxycholate. When strontium replaces calcium, no phospholipase activity is detected. Since neuromuscular transmission is not blocked when calcium is replaced by strontium, it was possible to examine the effects of the toxin on neuromuscular transmission in the presence of strontium. Under these conditions, when the phospholipase activity should be inhibited, the toxin has little or no effect on neuromuscular transmission. If beta-bungarotoxin owes its toxicity in part to its enzymatic activity, then it must be placed in a different class from those toxins which produce their effect by binding passively to an appropriate receptor.
Does somatostatin inhibition of insulin secretion involve two mechanisms of action?
Authors: Curry D L , Bennett L L
Published: May 2006

Somatostatin, the hypothalamic growth hormone release inhibitory factor (GHRIF), directly inhibits both the first and second phases of insulin secretion. The sensitivities of these two phases of insulin secretion to somatostatin differ remarkably. The first phase of secretion is approximately 25 to 50 times more sensitive to somatostatin inhibition than is the second phase. In addition, somatostatin inhibition of insulin secretion during the second phase is "reversed" by supplemental calcium, whereas the somatostatin effect on the first phase is unaffected by additional calcium. These findings suggest that the cellular events which produce the two phases of insulin secretion are separate processes, and that somatostatin has a dual mechanism of action in inhibiting insulin secretion.