bluuebunny/crossref_metadata_2025 huggingface dataset:
Observational model of the ionized gas in Seyfert and radio-galaxy nuclei
Authors: Osterbrock Donald E.
Published: May 2006

Equivalent widths of the total emission-line Hβ in Seyfert 1, Seyfert 2, and intermediate-type Seyfert galaxies, expressed in terms of the featureless continuum, all have approximately the same frequency distribution. This suggests that the energy-input mechanism to both the narrow-line, low-density gas and the broad-line, high-density gas is photoionization by the featureless continuum. The reason for the weakness of the narrow emission lines in extreme Seyfert 1 galaxies is then the absorption of most of the ionizing photons in the dense gas near the central source. The statistics of line widths can be fitted by a model in which the dense gas has typical rotational velocity 5000 km/sec and typical turbulent velocity 2000 km/sec. A model is proposed in which the dense gas forms a rotating, turbulent disk with dimension ≈0.1 pc and height/diameter ≈2/5. Seyfert 2 galaxies are objects with little dense gas, and intermediate-type Seyfert galaxies are objects in which the dense gas is optically thin to ionizing radiation at least along the poles. Most radio galaxies have strong narrow emission lines, suggesting that escape of radio plasma can only occur where some ionizing photons can also escape from the dense gas. Other predictions, implications, and tests of this model are discussed.
Lie algebras and classical partition identities
Authors: Lepowsky J. , Milne S.
Published: May 2006

In this paper we interpret Macdonald's unspecialized identities as multivariable vector partition theorems and we relate the well-known Rogers—Ramanujan partition identities to the Weyl—Kac character formula for an infinite-dimensional Euclidean generalized Cartan matrix Lie algebra.
Homology-dependent cutting in trans of DNA in extracts of Escherichia coli: an approach to the enzymology of genetic recombination.
Authors: Cassuto E , Mursalim J , Howard-Flanders P
Published: May 2006

An in vitro system is described in which the cutting of crosslinked phiX replicative form (RF) I DNA molecules by the uvr system of Escherichia coli induces the cutting of homologous undamaged DNA during incubation with crude extracts of thermally induced E. coli (lambda precA+) lysogens. This reaction, which has also been observed in intact E. coli lysogens infected with lambda phages, is dependent on the presence of functional recA+ and uvrB+ gene products. Extracts from thermally induced lambda precA+ lysogens of E. coli proved to be substantially more active than extracts from nonlysogenic cells of the same strain. The results provide preliminary evidence for an endonuclease activity that cuts intact superhelical DNA in response to interaction with homologus damaged DNA. In the present paper, we describe an in vitro system in which both the endonucleolytic cutting of DNA containing crosslinks and the induced cutting of undamaged DNA can be studied without purification of the participating enzymes. Although the information obtained is fragmentary and often puzzling, we feel that this system can contribute to an understanding of the complex mechanisms involved in repair and recombination.
An RNA transcribed from DNA at the origin of phage fd single strand to replicative form conversion.
Authors: Geider K , Beck E , Schaller H
Published: May 2006

Phage fd DNA complexed with DNA binding protein I was used by Escherichia coli RNA polymerase (nucleoside triphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) to synthesize an RNA at the origin of single strand to double strand replication. The isolated ori-RNA gave a simple fingerprint after nucleolytic digestion and has a length of about 30 nucleotides. The characterization of the oligonucleotides from the nuclease digest and the extension of the ori-RNA with DNA polymerase I and subsequent restriction of the DNA gave its exact localization in the fd genome, and its total sequence was deduced from the known DNA sequence in this region.
Accumulation of a slowly dissociable peptide hormone binding component by isolated target cells.
Authors: Donner D B , Martin D W , Sonenberg M
Published: May 2006

The overall rate of dissociation and the fraction of bound radioiodinated human growth hormone that dissociated from hepatocytes varied with time of association. A smaller fraction of bound hormone was dissociable from isolated target cells with increased receptor occupancy and increased incubation time prior to the onset of dissociation. The inability of bound label to reequilibrate completely with the medium was demonstrated further by preincubating cells with labeled hormone prior to the initiation of saturation experiments. In such experiments, time-dependent changes in the binding properties of bound label were observed in Scatchard plots, as a result of the inability of prebound label to reequilibrate rapidly with the medium over the time course of such experiments. These data suggest that bound hormone may be distributed between at least two kinetic components. This phenomenon could be interpreted in terms of heterogeneity of sites, a slow conformational change in the receptor, or a model incorporating spatial compartmentalization of sites.
Amino acid sequence of honeybee prepromelittin synthesized in vitro.
Authors: Suchanek G , Kreil G , Hermodson M A
Published: May 2006

Translation of melittin messenger RNA from queen bee venom glands in a cell-free system from wheat germ yielded prepromelittin. Sequence analysis of the labeled in vitro product was performed by automatic Edman degradation of the intact polypeptide as well as by analysis of some of its proteolytic fragments. Prepromelittin was shown to be composed of 70 amino acids, two of which have not been identified. The sequence of melittin is located in the COOH-terminal third of the polypeptide chain (residues 44--69). Prepromelittin starts with a very hydrophobic pre-region, probably 21 residues long, followed by a pro-part of unusual sequence, containing only alanine, proline, and acidic residues. At least three post-translational reactions are required to convert prepromelittin to mellitin.
Regulation of protein synthesis in rabbit reticulocyte lysates by the heme-regulated protein kinase: Inhibition of interaction of Met-tRNA
f
Met
binding factor with another initiation factor in formation of Met-tRNA
f
Met
·40S ribosomal subunit complexes
Authors: Ranu R. S. , London I. M. , Das A. , Dasgupta A. , Majumdar A. , Ralston R. , Roy R. , Gupta N. K.
Published: May 2006

Protein synthesis in reticulocytes and their lysates is regulated by heme. In heme deficiency a heme-regulated translational inhibitor (HRI) that blocks initiation of polypeptide chains is activated. HRI is a protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) that specifically phosphorylates the 38,000-dalton subunit of the Met-tRNA
f
Met
binding factor (IF), which forms a ternary complex with Met-tRNA
f
Met
and GTP, a finding that suggests that the inhibition by HRI involves the phosphorylation of IF.

We have investigated the effect of HRI in the partial reactions of protein chain initiation in which the IF-promoted binding of Met-tRNA
f
Met
to 40S ribosomal subunits is enhanced by another initiation factor [ternary complex dissociation factor (TDF)] and AUG. The results show that HRI at very low concentrations markedly inhibits the binding of Met-tRNA
f
Met
to 40S subunits. The inhibitory effect of HRI requires ATP. Under these conditions HRI phosphorylates only the 38,000-dalton subunit of IF.

The TDF preparations not only promote the binding of the ternary complex to 40S subunits but also promote the dissociation of the ternary complex in the presence of 5 mM Mg
2+
at 0°. The preincubation of purified IF alone with low concentrations of HRI and ATP does not significantly affect its capacity to form the ternary complex; however, the TDF-promoted dissociation of the ternary complex is inhibited. The nonhydrolyzable analog adenosine 5′-[β,γ-imido]triphosphate does not substitute for ATP. These findings suggest that phosphorylation causes a conformational modification in IF, which results in inhibition of the interaction between the ternary complex and TDF that is required for the binding of the ternary complex to 40S subunits.
In vitro transcription of heat-shock-specific RNA from chromatin of Drosophila melanogaster cells.
Authors: Biessmann H , Levy B , McCarthy B J
Published: May 2006

Polyadenylylated RNA synthesized after heat shock was isolated from polysomes of cultured cells of Drosophila melanogaster and used as template to prepare cDNA. An excess of poly(A)-RNA from heat-shocked cells hybridized to 80% of the cDNA, whereas cytoplasmic poly(A)-RNA from cells grown at 25 degrees could drive only half of the cDNA probe into hybrid. These sequences were removed from the cDNA population by annealing to poly(A)-RNA from cells grown at 25 degrees. The unreacted material represented only heat-shock-induced mRNA sequences, as shown by a second cycle of hybridization. Isolated chromatin was transcribed in vitro at 25 degrees with Escherichia coli RNA polymerase, with mercurated UTP as precursor. RNA transcribed from chromatin that was prepared from cells 1 hr after the temperature was shifted to 37 degrees hybridized with 100-fold faster kinetics to the heat-shock-specific cDNA probe than did RNA transcribed from chromatin of cells grown at 25 degrees. Therefore, heat shock results in a change in chromatin structure recognizable by E. coli RNA polymerase.
Erythrocyte membrane abnormalities in Duchenne muscular dystrophy monitored by saturation transfer electron paramagnetic resonance spectroscopy.
Authors: Wilkerson L S , Perkins R C , Roelofs R , Swift L , Dalton L R , Park J H
Published: May 2006

Saturation transfer electron paramagnetic resonance and the spin label 2-(3-carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyloxyl were used to study erythrocytes from patients with Duchenne muscular dystrophy or Becker syndrome and from age-matched normal boys. There were significant differences in the spectral intensities of erythrocytes from Duchenne patients when compared to controls. Spectral intensities increased with time in the former; no such change was observed in the latter. Saturation transfer electron paramagnetic resonance spectra of erythrocytes from patients with Becker syndrome were significantly different from those from Duchenne patients but were not significantly different from normals. These observations suggest the possible usefulness of these techniques in the differential diagnosis of Duchenne muscular dystrophy. Spin label concentration spectral studies suggest that the observed spectral differences between Duchenne patients and controls were due to differential spin exchange phenomena.
Unsymmetrical and concerted examples of the effect of enzyme--enzyme interactions on steady-state enzyme kinetics.
Authors: Hill T L
Published: May 2006

In previous papers of this series, emphasis has been placed on the steady-state phase transition and critical properties of large lattices of interacting, symmetrical, and identical enzyme molecules. The present paper is concerned with a number of examples of enzyme--enzyme interactions that do not belong to the class of models of the earlier papers. These are more biochemically oriented and include heterologous dimers, a linear chain with unsymmetrical interactions, and concerted isologous dimers (half-the-sites reactivity).
Mammalian cytoplasmic actins are the products of at least two genes and differ in primary structure in at least 25 identified positions from skeletal muscle actins
Authors: Vandekerckhove Joél , Weber Klaus
Published: May 2006

Muscle and cytoplasmic actins from several species have been compared by extensive fingerprint analysis and by partial amino acid sequence determination with the known amino acid sequence of rabbit muscle actin. Although complete sequences have not been established, the following characteristics are apparent. (
a
) Cytoplasmic actins are the products of two different genes. The difference seen in isoelectric focusing studies is probably determined only by the nature of the three amino-terminal acidic residues. (
b
) Mammalian cytoplasmic actins are exceedingly similar and perhaps identical. (
c
) Cytoplasmic actins may differ by at least 25 amino acid replacement from rabbit muscle actin. These replacements have been identified for calf thymus actin; however, other cytoplasmic actins show the same replacements. (
d
) The replacements always involve—except for the first five residues—neutral amino acid residues. (
e
) The replacements are not randomly distributed. Residues 18-75 are constant whereas residues 2-18 and 259-298 show many substitutions. (
f
) The main component of smooth muscle actin from chicken gizzard shows the charge characteristics found at the amino terminus of the less acidic cytoplasmic actin species. In the rest of the polypeptide chain, gizzard actin resembles skeletal muscle actin, although two substitutions of the cytoplasmic type have been identified. (
g
) Heart muscle actin is very similar to skeletal muscle actin. Only two amino acid replacements have been found; they are of the cytoplasmic type. (
h
) Skeletal muscle actins from chicken and beef have not shown a replacement.
Multiple receptors for brain dopamine.
Authors: Titeler M , Weinreich P , Sinclair D , Seeman P
Published: May 2006

This study was done to obtain direct in vitro evidence for the possible existence of more than one type of dopaminergic binding site in homogenates of the caudate nucleus from calf brain. Five radioligands for dopaminergic sites were tested. The inhibitions of two agonist radioligands ([3H]dopamine, [3H]apomorphine) by haloperidol, chlorpromazine, or piflutixol were biphasic. The inhibitions of [3H]haloperidol, [3H]spiroperidol, and [3H]dihydroergocryptine binding by dopamine and (-)-norepinephrine were also biphasic. Thus, both 3H-labeled agonists and 3H-labeled antagonists were possibly binding to two high-affinity sites.
Oligosaccharides containing glucose and mannose in glycoproteins of the thyroid gland.
Authors: Staneloni R J , Leloir L F
Published: May 2006

The glucose-containing oligosaccharides formed by calf thyroid slices incubated with radioactive glucose were studied. A compound soluble in chloroform/methanol/water, 1:1:0.3 (vol/vol), was found that was indistinguishable from the previously described glucose-containing dolichyl diphosphate oligosaccharide formed by liver microsomes. Glycopeptides were prepared by treating the glycoproteins with pronase, the amino acids were removed with alkaline borohydride, and the products were examined by paper electrophoresis and chromatography. A saccharide equal to that which occurs in the glucose-containing dolichyl diphosphate oligosaccharide could not be detected but glucose was found in oligosaccharides that seemed to be smaller by about three to five monosaccharide residues. The same results were obtained by direct treatment of the glycoproteins with alkaline borohydride.
Oligonucleotide inhibitor of protein synthesis made in extracts of interferon-treated chick embryo cells: Comparison with the mouse low molecular weight inhibitor
Authors: Ball L. Andrew , White Carol N.
Published: May 2006

Cytoplasmic extracts of interferon-treated primary chick embryo cells contain an enzyme activity that synthesized an inhibitor of chick cell-free protein synthesis. The same activity was detected in extracts of cells treated with mock preparations of interferon, but at <0.3% of the level found in interferon-treated cell extracts. The enzyme was activated by double-stranded RNA and could be isolated by binding to columns of poly(I)-poly(C)-agarose. In the column-bound state, the enzyme reacted with ATP to synthesize the inhibitor, which could then be continuously eluted from the column. The inhibitor was purified and its structure and function were compared with those of the low molecular weight inhibitor of protein synthesis made by an enzyme from interferon-treated mouse L cells. The avian and mammalian inhibitors comigrated on thin layers of polyethyleneimine-cellulose during chromatography in three different solvent systems, and they coeluted as a series of peaks from columns of DEAE-cellulose during sodium chloride gradient elution. Digestion with bacterial alkaline phosphatase or snake venom phosphodiesterase yielded products that similarly comigrated. Functionally, the two inhibitors were interchangeable: both inhibited protein synthesis in extracts of mammalian and avian cells, producing 50% inhibition at a concentration of about 0.3 nM (AMP equivalents). We conclude that the chick cell-derived oligonucleotide inhibitor has a structure that is closely related or identical to that of the inhibitor made in the mouse system, and that both preparations inhibit cell-free protein synthesis in a non-species-specific manner.
Hemoglobin Lincoln Park: a betadelta fusion (anti-Lepore) variant with an amino acid deletion in the delta chain-derived segment.
Authors: Honig G R , Shamsuddin M , Mason R G , Vida L N
Published: May 2006

An electrophoretically slow-moving hemoglobin variant was identified in three members of a family originating from Southern Mexico. The variant, Hb Lincoln Park, made up approximately 14% of the total hemoglobin and appeared to have normal stability and functional properties. None of the individuals in whom the abnormal hemoglobin was present was anemic, but each had a mildly elevated reticulocyte count. Structural data suggest that the non-alpha chain of Hb Lincoln Park represents a betadelta gene-fusion product, with normal beta chain structure of the amino-terminal portion of the chain and delta sequences subsequently, the crossover point occurring between animo acid residues 22 and 50. An additional abnormality is the deletion of valine-137, a component of the delta gene-derived segment of the betadelta chain. To account for the development of this abnormal globin chain, a series of intergenic crossovers is proposed; the first, a nonhomologous crossover between the beta and delta genes, presumably gave rise to the betadelta fusion gene; two additional crossovers, one of them unequal, may then have occurred between the same beta and delta genes to produce the amino acid deletion.
Repertoire of antiviral antibodies expressed by somatic cell hybrids.
Authors: Gerhard W , Croce C M , Lopes D , Koprowski H
Published: May 2006

Fusion between P3 x 63 Ag8 mouse myeloma cells and spleen cells from BALB/c mice immunized with influenza type A or B or parainfluenza type 1 virus generated reproducibly antiviral antibody-producing somatic cell hybrids (hybridomas). Eleven hybridomas derived from spleen cells of mice immunized with influenza type A virus were directed against the viral hemagglutinin, one reacted with a host component derived from chickens, and one expressed a specificity not further characterized. The hybridoma antibodies tended to be highly specific for the hemagglutinin of the immunizing virus and seemed to express the same repertoire of strain-specific antibody reactivities as splenic precursor B cells, they did not express any of the frequently occurring crossreactive anti-hemagglutinin specificities. Hybridomas producing crossreactive antibodies against hemagglutinin could be obtained if priming and boosting virus were heterologous.
Detection of viral proteins in mouse mammary tumors by immunoperoxidase staining of paraffin sections.
Authors: Keydar I , Mesa-Tejada R , Ramanarayanan M , Ohno T , Fenoglio C , Hu R , Spiegelman S
Published: May 2006

An indirect immunoperoxidase method is described, which can readily detect viral antigens in paraffin sections of primary, transplanted, and metastatic mammary tumors of mice. In addition to having the obvious advantage of not being limited to fresh specimens, immunoperoxidase staining of paraffin sections proved to be superior in many respects when compared with immunofluorescence and frozen sections. Immunoperoxidase staining of paraffin sections is permanent and provides the kind of histological detail required for precise cytological identification and localization with light microscopy. All of 25 tumors and 4 metastatic lesions showed evidence of glycoprotein gp52 as well as other mouse mammary tumor viral antigens. The pattern and intensity of the stain were related to the degree of histologic differentiation of the tumor. Wide variations in expression of viral antigens by individual malignant cells were observed within the same tumor.
Diet, genetics, and mental retardation interaction between phenylketonuric heterozygous mother and fetus to produce nonspecific diminution of IQ: Evidence in support of the justification hypothesis
Authors: Bessman Samuel P. , Williamson Malcolm L. , Koch Richard
Published: May 2006

The justification hypothesis postulates that an individual genetically deficient in the synthesis of any of the 12 nonessential amino acids requires that amino acid in the diet just as a normal individual requires any essential amino acid. The deficiency of that single amino acid causes diminished protein synthesis. The hypothesis proposes that mental retardation develops during the late stage of fetal development, when the brain is growing most rapidly, as a result of the inability of the mother to deliver an appropriate amount of that nonessential amino acid to her fetus who, in turn, is unable to correct for this deficiency due to his genetic constitution. A paradigm is provided by the disease phenylketonuria in which the homozygote lacks the enzyme for synthesis of the nonessential amino acid tyrosine. By measuring the appearance of tyrosine in the plasma after an oral dose of phenylalanine, it is possible to show differential capability among siblings of known phenylketonuric children, in the expected Mendelian ratio. The mean IQ of the two-thirds of the siblings who were least able to convert phenylalanine to tyrosine (presumably heterozygotes) was 10 points lower than the mean IQ of the “normals,” who were most able to synthesize tyrosine. The difference is statistically significant (
P
<0.01). The mean maternal IQ was halfway between that of the heterozygote group and that of the normal group, confirming the prediction of maternal—fetal interaction.
Neurons containing beta-endorphin in rat brain exist separately from those containing enkephalin: immunocytochemical studies.
Authors: Bloom F , Battenberg E , Rossier J , Ling N , Guillemin R
Published: May 2006

Well-characterized antisera to porcine beta-endorphin were used to localize immunoreactive sites in cryostat sections of formaldehyde-fixed rat brain by indirect immunohistochemistry. Specificity was established by absorption of immune sera with synthetic peptide fragments. Specific immunoreactivity was localized to neuronal perikarya in the basal tuberal hypothalamus, and to varicose nerve fibers which were distributed to midline nuclear areas throughout the diencephalon and anterior pons. These patterns of reactivity were unaffected by preabsorption of the immune sera with millimolar concentrations of Met5- or Leu5-enkephalin or alpha-endorphin. The beta-endorphin immunoreactive structures were morphologically separate from those cells and fibers reported to react with antisera to the enkephalins. One anti-beta-endorphin serum gave additional immunoreactivity with myelinated axons in limbic cortical zones; when absorbed with purified rat myelin basic protein, only the specific patterns of immunoreactivity remained. Thus, discrete beta-endorphin-containing neuronal circuits exist in rat brain and are anatomically distinguishable from enkephalin-containing nerve cell and fiber pathways.
Differential effects of perhydrohistrionicotoxin on neurally and iontophoretically evoked endplate currents.
Authors: Albuquerque E X , Gage P W
Published: May 2006

Perhydrohistrionicotoxin, at concentrations of 10(-12)-10(-7) M, depressed the current generated by iontophoretic application of acetylcholine to endplate regions of soleus and extensor digitorum longus muscles of rats. However, no changes in the amplitude or time course of spontaneous miniature endplate potentials or currents were seen with these concentrations of toxin. Evoked endplate currents were also unaffected by the toxin. Similarly, the responses to iontophoretic acetylcholine were depressed by these concentrations of perhydrohistrionicotoxin in chronically denervated muscles. Depression of responses in both normal and chronically denervated muscles developed gradually, was greater at higher concentrations, and was reversible. The different effects of the toxin on neurally evoked currents and currents produced by iontophoretic application of acetylcholine raise the possibility of the existence of two different population of receptor complexes.
Preparation and template activities of polynucleotides containing O2- and O4-alkyluridine.
Authors: Singer B , Fraenkel-Conrat H , Kuśmierek J T
Published: May 2006

O2-Ethyl-UDP and O4-methyl-UDP have been prepared and copolymerized in various proportions with UDP or CDP, using polynucleotide phosphorylase. The copolymers were used as templates for DNA-dependent RNA polymerases in the presence of Mn2+. Both of the O-alkylated uridines caused a similar misincorporations. When copolymerized with U they led to incorporation of CMP and GMP into the poly(A). No AMP or UMP incorporation seemed to be caused by the introduction of O-alkyluridines into either poly(U) or poly(C). The mispairing of O2- and O4-alkyluridine to behave like C or G represents mutagenic events. O2 alkylation of U or T is, in contrast to O4 alkylation, a relatively frequent result of treatment of double-stranded nucleic acids with N-nitroso alkylating agents. In single-stranded nucleic acids both O2 and O4 alkylations of U and T occur to similar extents. Thus, the observed mutagenic effects of O2 and O4 alkylation of U may be involved in the high carcinogenicity of these alkylating agents.
Participation of spectrin in Sendai virus-induced fusion of human erythrocyte ghosts.
Authors: Sekiguchi K , Asano A
Published: May 2006

Fusion of washed human erythrocyte ghosts could be induced by the addition of Sendai virus after they were loaded with bovine serum albumin and resealed. Antispectrin antibody purified on a spectrin-Sepharose column and sequestered in the ghosts at 4-5 mg/ml together with the albumin was highly inhibitory for the virus-induced cell fusion, whereas Fab fragments prepared from the same antibody were without effect. The virus-induced aggregation of intramembrane particles of human erythrocytes was also inhibited by the same concentrations of the antispectrin antibody. The virus-induced agglutinations of the ghosts and release of bovine serum albumin from the ghosts (which might be caused by fusion of the viral envelope to the erythrocyte membrane) were not inhibited by the sequestered antibody. Therefore, the antibody seems to inhibit fusion at the last step--i.e., fusion between adjacent erythrocyte membranes. Similarities and differences of the mode of participation of spectrin in the virus-induced fusion and in other membrane-linked phenomena of human erythrocytes are discussed.
Differential desensitization of functional adrenergic receptors in normal and malignant myeloid cells: Relationship to receptor-mediated hormone cytotoxicity
Authors: Simantov Rabi , Sachs Leo
Published: May 2006

Malignant myeloid leukemic cells and normal macrophages and granulocytes have functional β-adrenergic receptors, which have been quantitated by radioreceptor binding with the β-adrenergic antagonist [
3
H]dihydroalprenolol and by induction of cyclic AMP by adrenergic hormones. Both the normal and leukemic cells have β
2
-adrenergic receptors, and the [
3
H]dihydroalprenolol binding was saturable, reversible, and stereospecific. The leukemic cells consisted of clones that could be induced to differentiate (MGI
+
D
+
) and clones that could not be induced to differentiate to mature macrophages and granulocytes by the protein inducer MGI. The different types of leukemic clones all had 1100-2300 receptor sites per cell, whereas normal macrophages had 7000 receptors per cell. The differentiation of MGI
+
D
+
leukemic cells was associated with an increase in receptors to a number similar to that found with normal macrophages. MGI
+
D
+
leukemic cells and normal macrophages were able to densensitize to the β-adrenergic agonist (-)isoproterenol, shown by termination of cyclic AMP induction within 10-15 min and the lack of a second induction. The leukemic cells that could not be induced to differentiate lacked this capacity for desensitization, possibly due to an alteration in the uncoupling system between the receptor and adenylate cyclase. The lack of desensitization in these leukemic cells was associated with a higher sensitivity to the receptor-mediated cytotoxic effects of adrenergic hormones. It is suggested that cells, like some leukemic cells, that are unable to desensitize to adrenergic and possibly other hormones may be appropriate targets for differential destruction by hormones under conditions that do not affect normally desensitizing cells.
Genetic regulation of galactokinase in
Tetrahymena
by cyclic AMP, glucose, and epinephrine
Authors: Roberts Charles T. , Morse Daniel E.
Published: May 2006

We have found evidence that transcription of the galactokinase (ATP:D-galactose 1-phosphotransferase; EC 2.7.1.6) gene is inhibited, in the animal-like protozoan
Tetrahymena
, by dibutyryl adenosine 3′:5′-cyclic monophosphate, glucose, and epinephrine. The specific activities of galactokinase in
Tetrahymena
cells grown in defined media with galactose or glycerol as the principal carbon source are equivalent; the specific activity in glucose minimal medium is [unk] the value. Thus, while there seems to be no specific induction of the enzyme by the substrate, galactose, there is a strong “repression” by glucose. This repression by glucose is
mimicked
, in glycerol-grown cells, by the addition of millimolar amounts of dibutyryl adenosine 3′:5′-cyclic monophosphate or phosphodiesterase inhibitors such as caffeine and theophylline. When glucose-grown cells are washed and resuspended in carbohydrate-free medium, the galactokinase specific activity increases by as much as 10-fold within 12 hr. This increase is blocked by dibutyryl adenosine 3′:5′-cyclic monophosphate and by epinephrine (synthesized by
Tetrahymena
, and previously shown to activate a membrane-bound adenylate cyclase in extracts of this organism), as well as by inhibitors of mRNA synthesis, maturation, and translation. Our results suggest that glucose and epinephrine can regulate transcription of the galactokinase gene by modulation of cyclic nucleotide levels. The observation that the nonmetabolized sugars 2-deoxyglucose, 2-deoxygalactose, and α-methylglucoside are as effective as glucose suggests that the sugar itself, or an immediate metabolite such as the 1-phosphate derivative, may be the effector.
Fluorescent light-induced chromosome damage and its prevention in mouse cells in culture.
Authors: Parshad R , Sanford K K , Jones G M , Tarone R E
Published: May 2006

Twenty-hour-exposure to fluorescent light produces chromatid breaks in a line of adult mouse lung cells grown in Dulbecco-Vogt medium supplemented with fetal bovine serum. The light-induced damage appears to be enhanced by increasing the concentration of oxygen in the gas phase of the culture. The effective wavelength(s) of light is in the visible range between 400 and 450 nm andis probably the mercury emission peak at 405 or 436 nm. Addition of catalase or glutathione with ascorbic acid to the culture medium reduced the number of chromatid breaks to a level not significantly different from that in the shielded cultures. It thus appears that the production of H2O2 in the culture medium or in the cell is responsible for the chromatid breaks. Most of the chromosomal abnormalities observed in long-term culture of mouse cells may result from exposure of cells or medium to fluorescent room lights in the presence of atmospheric oxygen. These genetic abnormalities can be minimized by shielding cells and medium from light, lowering the PO2 of the medium, and including reducing agents such as glutathione and ascorbic acid in the medium formulation.
Establishment of clonal human placental cells synthesizing human choriogonadotropin.
Authors: Chou J Y
Published: May 2006

Seven clonal human placental cell lines were established by transformation of human first-trimester placental cells with simian virus 40. These transformed cells synthesized native human choriogonadotropin (chorionic gonadotropin) (hCG) as well as the free alpha and beta subunits of hCG. The amount of native hCG synthesized by these cells was, however, lower than the amount of free beta subunit. (Both hCG and the beta subunit are detected by the radioimmunoassay for beta subunit, but only hCG is detected by the radioreceptor assay.) The alpha and beta subunits produced by these transformed placental cells were heterogeneous in size; the sizes of the predominant alpha and beta species, however, corresponded to those of urinary alpha and beta subunits, respectively. The seven cell lines transformed by simian virus 40 had chromosome numbers from the near diploid to the near tetraploid range. Fluorescent staining demonstrated the Y chromosome in all the transformants. Furthermore, B-type glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP+ 1-oxidoreductase; EC 1.1.1.49) was present in all seven lines. These characteristics ruled out possible HeLa contamination of the transformed lines. Regulation of the synthesis of alpha and beta subunits plus hCG in these transformed human placental cells differed from the regulation in choriocarcinoma cells.
Conjugation of poly-L-lysine to albumin and horseradish peroxidase: a novel method of enhancing the cellular uptake of proteins.
Authors: Shen W C , Ryser H J
Published: May 2006

The carbodiimide-catalyzed conjugation of a 6700 molecular weight fragment of poly-L-lysine to radiolabeled human serum albumin or to horseradish peroxidase enhances the membrane transport of each protein into cultured mouse fibroblasts approximately 11- and 200-fold, respectively. At least 50% of the peroxidase activity remained after conjugation. Trypsinization and carbamylation of the two conjugates demonstrates that the enhancement of their cellular uptake is related to their poly-L-lysine content. Simple addition to the medium of comparable amounts of free poly-L-lysine has no effect on the transport of either native protein. Addition of poly-L-ornithine (molecular weight 200,000) at 3-30 microgram/ml, a condition known to cause enhancement of 125I-labeled human serum albumin uptake by mouse sarcoma cells, has no visible effect on the cellular uptake of native horseradish peroxidase. The intracellular localization of the enzyme-poly-L-lysine conjugate can be demonstrated cytochemically by either light or transmission electron microscopy. A concentration of conjugate that increases the uptake more than 200-fold does not cause any detectable morphological change suggestive of cell toxicity. Furthermore, because poly-L-lysine is an excellent substrate for intracellular proteolytic enzymes, it can be expected to be broken down and reutilized in the cell.
RNA content in human lymphocyte subpopulations.
Authors: Andreeff M , Beck J D , Darzynkiewicz Z , Traganos F , Gupta S , Melamed M R , Good R A
Published: May 2006

Human peripheral blood lymphocytes are stained with the metachromatic dye acridine orange and the fluorescence of individual cells is measured by flow cytometry. The relative content of stainable RNA per cell is estimated by comparison with RNase-treated cells. Non-T and T lymphocytes have different mean quantities of RNA per cell, and these classes exhibit different distributions of RNA content. Non-T cells have a unimodal distribution with a sharp peak and exponential distribution towards higher RNA values. T cells have a bimodal distribution with two separate peaks. When T cells having receptors for IgG (Tgamma cells) and IgM (Tmu cells) are separated, each of these cell populations displays a unimodal distribution. Of these three lymphocyte subpopulations, Tgamma cells have the lowest content of RNA per cell. Non-T cells have slightly higher RNA content than Tgamma, and Tmu cells have twice as much RNA as Tgamma cells. The RNA content, which surely relates to the different functions of these lymphocyte subpopulations, may also be a useful marker for rapidly distinguishing the lymphocyte subpopulations.
Components in multiple sclerosis cerebrospinal fluid that are detected by radioimmunoassay for myelin basic protein
Authors: Carson J. H. , Barbarese E. , Braun P. E. , McPherson T. A.
Published: May 2006

Components in cerebrospinal fluid that are antigenically related to myelin basic protein have been identified by a technique described recently [Barbarese, E., Braun, P. E. & Carson, J. H. (1977)
Proc. Natl. Acad. Sci. USA
74, 3360-3364] involving separating the cerebrospinal fluid proteins by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and measuring the individual components by radioimmunoassay for myelin basic protein. Samples of cerebrospinal fluid from 48 different patients (23 with definite multiple sclerosis, 4 with suspected multiple sclerosis, and 21 with other neurological diseases) were examined by this technique. The results indicate that cerebrospinal fluid can contain at least three separate components that are detected by radioimmunoassay for myelin basic protein. On the basis of their apparent molecular weights, the three components were identified as follows: component I, intact myelin basic protein; component II, proteolytic fragments of myelin basic protein; and component III, a protein of unknown origin with an apparent molecular weight of 50,000. Most samples of cerebrospinal fluid (45 of 48) from patients with multiple sclerosis and from patients with other neurological diseases contained components I and II. Component III was detected in all of the samples from patients with definite multiple sclerosis, in three of four samples from patients with suspected multiple sclerosis, and in none of the samples from patients with other neurological diseases. Some implications of these findings are discussed.
Statistics of self-avoiding walks confined to strips and capillaries
Authors: Wall Frederick T. , Seitz William A. , Chin John C. , Gennes P. G. De
Published: May 2006

A long self-avoiding chain confined to a narrow strip or thin tube tends to be elongated in the direction of the strip or tube. The mean end-to-end separation of a long chain so confined becomes asymptotically proportional to the number of links in the chain as the contour chain length becomes infinite. By use of scaling arguments, it is shown that the mean end-to-end separation also becomes proportional to
D
-1/3
for chains confined to two-dimensional strips and proportional to
D
-2/3
for three-dimensional capillaries, where
D
is the width or diameter of the strip or capillary. These predictions have been verified by Monte Carlo studies of self-avoiding walks. The agreement is excellent for two-dimensional systems, but less certain for those of three dimensions since less data are available for verification.
Aminoacyl-tRNA synthetases: affinity labeling of the ATP binding site by 2', 3' -ribose oxidized ATP.
Authors: Fayat G , Fromant M , Blanquet S
Published: May 2006

Homogeneous Escherichia coli methionyl-, isoleucyl-, tryptophanyl-, and phenylalanyl-tRNA synthetases and Bacillus stearothermophilus methionyl- and tyrosyl-tRNA synthetases are irreversibly inactivated by reaction of their active ATP sites with the 2',3'-dialdehyde derivative of ATP obtained by periodate oxidation. In each case, the amount of 14C-labeled dialdehyde derivative incorporated per molecule of inactivated enzyme appears consistent with the expected active stoichiometry of the synthetase. These results strongly support the presence, at the active site of the studied aminoacyl-tRNA synthetases, of a common residue, probably a lysine whose epsilon-NH2 group is known, from the work of others, to form a Schiff's base specifically with the 2',3'-dialdehyde derivatives of ribonucleotides.
Isolation of a low molecular weight Ca2+ carrier from calf heart inner mitochondrial membrane.
Authors: Jeng A Y , Ryan T E , Shamoo A E
Published: May 2006

A protein was isolated from calf heart inner mitochondrial membrane with the aid of an electron paramagnetic resonance assay based on the relative binding properties of Ca2+, Mn2+, and Mg2+ to the protein. The molecular weight of this protein has been estimated to be about 3000 by urea/sodium dodecyl sulfate gel electrophoresis and amino acid analysis. The protein is shown to have two classes of binding sites for Ca2+ by flow dialysis studies and can extract Ca2+ into an organic phase. The selectivity sequence of this protein determined from the organic solvent extraction experiments shows that it favors divalent cations over monovalent cations. Also, the relative selectivity sequence for divalent cations is Ca2+, Sr2+ greater than Mn2+ greater than Mg2+. Ruthenium red and La3+ are shown to inhibit the protein-mediated extraction of Ca2+ into the organic solvent. The calcium translocation in a Pressman cell by this protein is selectively driven by a hydrogen ion gradient. Control experiments indicate that the Ca2+ trnsport properties of the protein are not due to the contaminating phospholipids. It appears that we have isolated from the inner mitochondrial membrane a calcium carrier, which we have named "calciphorin."
BK virus DNA: cleavage map and sequence analysis.
Authors: Yang R C , Wu R
Published: May 2006

A detailed physical map of the BK virus (MM strain) genome has been constructed with respect to the cleavage sites of 11 different restriction enzymes. The enzymes cut BKV(MM) DNA at 61 specific sites whose locations have been determined. Preliminary nucleotide sequence was carried out in the region from 0.70-0.75 map positions on BKV(MM) DNA. An 80% homology was found at 0.714-0.744 map positions on BKV(MM) DNA with 0.722-0.752 map positions on simian virus 40 DNA. This region of simian virus 40 DNA codes for the synthesis of the leader sequence of late mRNA.
Adenosine 5'-O-([gamma-18O]gamma-thio)triphosphate chiral at the gamma-phosphorus: stereochemical consequences of reactions catalyzed by pyruvate kinase, glycerol kinase, and hexokinase.
Authors: Orr G A , Simon J , Jones S R , Chin G J , Knowles J R
Published: May 2006

The 2-[18O]phosphorothioate of D-glycerate, chiral at phosphorus, was prepared. The chiral phosphoryl group was transferred enzymically to ADP [by using enolase and pyruvate kinase (ATP:pyruvate 2-O-phosphotransferase; EC 2.7.1.40)] resulting in the synthesis of adenosine 5'-O-([gamma-18O],gamma-thio)triphosphate. This labeled ATP was used as a thiophosphoryl group donor in the reactions catalyzed by glycerol kinase (ATP:glycerol 3-phosphotransferase; EC 2.7.1.30) and by hexokinase (ATP:D-hexose 6-phosphotransferase; EC 2.7.1.1). The product from the latter (glucose 6-phosphorothioate) was converted enzymically into glycerol phosphorothioate. Determination of the relative configurations and diastereoisomeric purities of the samples of glycerol phosphorothioate demonstrates that all three phosphokinases (pyruvate kinase, glycerol kinase, and hexokinase) transfer the thiophosphoryl group with complete stereospecificity, and further shows that these reactions follow an identical stereochemical course.
Expression of a high molecular weight cell surface glycoprotein (LETS protein) by preimplantation mouse embryos and teratocarcinoma stem cells
Authors: Zetter Bruce R. , Martin Gail R.
Published: May 2006

The expression of a high molecular weight cell surface glycoprotein (LETS, fibronectin) by preimplantation mouse embryos as well as cultured teratocarcinoma stem cells was detected by using indirect immunofluorescent staining. When each stage of preimplantation embryonic development was tested for the presence of LETS protein, none was observed on two-cell, four-cell, or eight-cell embryos, or on the morula or the outer cell layer (trophectoderm) of the early or late blastocyst. However, when the inner cell mass was isolated by immunosurgery, positive staining was observed. The intensity of the staining was significantly greater on the inner cell mass isolated from the expanded (day 4) blastocyst than on that from the early (day 3) blastocyst.

Certain established cell lines of teratocarcinoma stem cells (embryonal carcinoma cells) also express cell surface LETS protein. “Nullipotent” (Nulli-SCC-1) as well as pluripotent (PSA 1) embryonal carcinoma cell lines have deposits of LETS protein concentrated in areas of cell-cell contact. In addition, a teratocarcinoma-derived endodermal cell line (PYS) was found to be capable of depositing LETS onto the substratum in a fibrillar network.

Taken together, our results indicate that LETS protein is synthesized at a specific stage of preimplantation mouse embryonic development. In particular, they suggest that LETS protein is a product of the embryonic ectoderm, and that some types of embryonic endoderm are also capable of synthesizing this protein.
Enzymatic synthesis and rapid translocation of phosphatidylcholine by two methyltransferases in erythrocyte membranes.
Authors: Hirata F , Axelrod J
Published: May 2006

The synthesis of phosphatidylcholine from phosphatidylethanolamine is carried out by two methyltransferases in erythrocyte membranes. The first enzyme uses phosphatidylethanolamine as a substrate, requires Mg2+, and has a high affinity for methyl donor, S-adenosyl-L-methionine. The second enzyme methylates phosphatidyl-N-monomethylethanolamine to phosphatidylcholine and has a low affinity for S-adenosyl-L-methionine. The first enzyme is localized on the cytoplasmic side of the membrane and the second enzyme faces the external surface. This asymmetric arrangement of the two enzymes across the membrane makes possible the stepwide methylation of phosphatidylethanolamine localized on the cytoplasmic side and facilitates the rapid transmembrane transfer of the final product, phosphatidylcholine, to the external surface of the membrane. A mechanism for an enzyme-mediated flip-flop of phospholipids from the cytoplasmic to the outer surface of erythrocyte membranes is described.
Restricted classes of immunoglobulin produced by a lymphoid cell line from a patient with agammaglobulinemia.
Authors: Schwaber J , Lazarus H , Rosen F S
Published: May 2006

Restricted expression of immunoglobulin by a long-term B lymphoid cell line derived from a patient with X-linked agammaglobulinemia is reproted. The patient had peripheral blood B lymphocytes with surface IgD and IgM. Culture of the B cells in vitro with mitogens did not stimulate immunoglobulin secretion, although pokeweed mitogen stimulation resulted in the development of cytoplasmic IgD and IgM. The lymphoid cell line established from these B lymphocytes primarily bore surface IgD, with a small population of cells also bearing surface IgM. These cells also had cytoplasmic immunoglobulin, primarily IgD. The cell line did not have a cytoplasmic pool of immunoglobulin for export and did not secrete immunoglobulin. This B lymphoid cell line is an in vitro analogue of the arrest in differentiation of the patient's B lymphocytes. The IgD-bearing phenotype may represent a normal transitional stage in the differentiation of B lymphocytes.