bluuebunny/crossref_metadata_2025 huggingface dataset:
Oligosaccharide moieties of glycoprotein hormones: bovine lutropin resists enzymatic deglycosylation because of terminal O-sulfated N-acetylhexosamines.
Authors: Parsons T F , Pierce J G
Published: May 2006

The oligosaccharides of the bovine pituitary gonadotropin lutropin are N-linked to asparagine residues. These carbohydrates are unusual in that, although they contain the mannose, N-acetylglucosamine, and fucose typical of N-linked oligosaccharides, they also contain one residue of N-acetylgalactosamine but insignificant amounts of sialic acid or galactose. These oligosaccharides exhibit complete resistance to several exoglycosidases. This is in contrast to the ready release of peripheral sugars from human chorionic gonadotropin, a placenta hormone which has oligosaccharides of the complex type with terminal sialic acid and galactose residues. Stability of the lutropin hexosamines to periodate oxidation and reduction (Smith degradation) together with other data show that one residue of N-acetylgalactosamine and one of N-acetylglucosamine are peripheral to two periodate-sensitive mannose residues. The insensitivity to periodate of these two terminal amino sugars is found to result from a sulfate group covalently linked to each; sulfation of these hexosamines is also the most probable reason for the resistance to enzymatic deglycosylation. The alpha subunits of bovine thyrotropin and human pituitary lutropin also contain sulfate, in contrast to human chorionic gonadotropin. The results indicate that sulfating enzymes are present in the pituitary and that sulfation of peripheral sialic acids in the placental gonadotropin. The data lead to a partial structure for the oligosaccharides of bovine LH as follows: (formula see text).
Two interferon mRNAs in human fibroblasts: in vitro translation and Escherichia coli cloning studies.
Authors: Weissenbach J , Chernajovsky Y , Zeevi M , Shulman L , Soreq H , Nir U , Wallach D , Perricaudet M , Tiollais P , Revel M
Published: May 2006

Two mRNA species that produce biologically active interferon were isolated from human fibroblasts and studied by size fractionation and cloning in Escherichia coli plasmid pBR322. The major fibroblast interferon (Hu IFN-beta 1) is coded for by the smaller of the two mRNAs, an 11S species, 900 nucleotides long, which in cell-free systems yields a 20,000 Mr protein. The second interferon mRNA species (Hu IFN-beta 2) is 14S, about 1300 nucleotides long, and codes for another protein of 23,000-26,000 Mr. The two interferon mRNAs do not cross-hybridize. Both are induced by poly(rI.rC), but IFN-beta 2 mRNA is induced to about 10% in cells by cycloheximide treatment alone whereas under these conditions IFN-beta 1 is not induced.
Cell cycle-specific mutagenesis at the hypoxanthine phosphoribosyltransferase locus in adult rat liver epithelial cells.
Authors: Tong C , Fazio M , Williams G M
Published: May 2006

The cell cycle specificity of chemical mutagenesis was studied by use of two cell synchronization techniques, one a nontoxic technique involving serum deprivation and the other a double thymidine block, to obtain rat liver epithelial cells in different phases of the cell cycle to be exposed to chemical mutagens. For both methyl methanesulfonate and N-methyl-N'-nitro-N-nitrosoguanidine, there was a cell cycle specificity of chemical mutagenesis, with the most sensitive phase being the period of DNA synthesis.
Anti-alprenolol anti-idiotypic antibodies bind to beta-adrenergic receptors and modulate catecholamine-sensitive adenylate cyclase.
Authors: Schreiber A B , Couraud P O , Andre C , Vray B , Strosberg A D
Published: May 2006

Rabbit antibodies induced against alprenolol, a potent beta-adrenergic antagonist, bind to other antagonists, and, with less avidity, to catecholamine agonists. Anti-idiotypic antibodies were raised against the anti-alprenolol immunoglobulins. The anti-idiotypic antibodies specifically bind and agglutinate turkey erythrocytes; this is not observed for human agglutinate turkey erythrocytes; this is not observed for human or sheep erythrocytes, which are devoid of beta-adrenergic receptors. The anti-idiotypic antibodies compete with (--)-[3H]-dihydroalprenolol for binding on the beta-adrenergic receptors on purified turkey erythrocyte membranes. The binding to the membrane-bound receptors is prevented by preincubation of the anti-idiotypic antibodies with their immunogen, the antialprenolol immunoglobulins. The binding to the receptor is not merely passive: the anti-idiotypic antibodies stimulate basal adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] and enhance adenylate cyclase activation by catecholamine. These observations support the notion that antiidiotypic antibodies may constitute an "internal image" of the original antigen and may mimic its biological effects.
Detection and isolation of type C retrovirus particles from fresh and cultured lymphocytes of a patient with cutaneous T-cell lymphoma
Authors: Poiesz Bernard J. , Ruscetti Francis W. , Gazdar Adi F. , Bunn Paul A. , Minna John D. , Gallo Robert C.
Published: May 2006

Retrovirus particles with type C morphology were found in two T-cell lymphoblastoid cell lines, HUT 102 and CTCL-3, and in fresh peripheral blood lymphocytes obtained from a patient with a cutaneous T-cell lymphoma (mycosis fungoides). The cell lines continuously produce these viruses, which are collectively referred to as HTLV, strain CR (HTLV
CR
). Originally, the production of virus from HUT 102 cells required induction with 5-iodo-2′-deoxyuridine, but the cell line became a constitutive producer of virus at its 56th passage. Cell line CTCL-3 has been a constitutive producer of virus from its second passage in culture. Both mature and immature extracellular virus particles were seen in thin-section electron micrographs of fixed, pelleted cellular material; on occasion, typical type C budding virus particles were seen. No form of intracellular virus particle has been seen. Mature particles were 100–110 nm in diameter, consisted of an electron-dense core surrounded by an outer membrane separated by an electron-lucent region, banded at a density of 1.16 g/ml on a continuous 25–65% sucrose gradient, and contained 70S RNA and a DNA polymerase activity typical of viral reverse transcriptase (RT; RNA-dependent DNA nucleotidyltransferase). Under certain conditions of assay, HTLV
CR
RT showed cation preference for Mg
2+
over Mn
2+
, distinct from the characteristics of cellular DNA polymerases purified from human lymphocytes and the RT from most type C viruses. Antibodies to cellular DNA polymerase γ and antibodies against RT purified from several animal retroviruses failed to detectably interact with HTLV
CR
RT under conditions that were positive for the respective homologous DNA polymerase, demonstrating a lack of close relationship of HTLV
CR
RT to cellular DNA polymerases γ or RT of these viruses. Six major proteins, with sizes of approximately 10,000, 13,000, 19,000, 24,000, 42,000, and 52,000 daltons, were apparent when doubly banded, disrupted HTLV
CR
particles were chromatographed on a NaDodSO
4
/polyacrylamide gel. The number of these particle-associated proteins is consistent with the expected proteins of a retrovirus, but the sizes of some are distinct from those of most known retroviruses of the primate subgroups.
Preparation of antibodies specific to choline acetyltransferase from bovine caudate nucleus and immunohistochemical localization of the enzyme.
Authors: Cozzari C , Hartman B K
Published: May 2006

Choline acetyltransferase (CATase; acetyl-CoA:choline O-acetyltransferase, EC 2.3.1.6) has been purified from bovine caudate nucleus. The specific activity of the pure enzyme was 120-160 mumol of acetylcholine formed per mg per min. The purified enzyme separated into two bands (band A and band B) when electrophoresed in a pH 4.3 gradient gel. Both bands exhibited CATase activity. Antisera were prepared in rabbits to each form. Immunotitrations using either antisera resulted in quantitative precipitation of CATase activity from enzyme preparations at all stages of purification. Both antisera produced single immunoprecipitin lines in double-diffusion experiments when run against the enzyme at each stage of purity. Immunoprecipitin lines cut from double-diffusion gels contained CATase activity, demonstrating that the observed reaction was due to antibody interaction with the enzyme. Immunoelectrophoresis also showed a single immunoprecipitin line against the purified enzyme as well as against a crude caudate extract. These results indicated that immunochemically pure and specific antisera have been prepared to bovine CATase and that both the A and B forms of the enzyme have common antigenic sites. The antisera were utilized to localize the enzyme in bovine brain. The localization was exclusively neuronal with both antisera, and both forms of CATase were present in the same population of neurons. Subtle differences in the precise intracellular distribution of enzyme were observed with the two antisera, indicating that although the two molecular forms of CATase have antigenic sites in common they are not antigenically identical.
Synthesis of zona pellucida proteins by denuded and follicle-enclosed mouse oocytes during culture
in vitro
Authors: Bleil Jeffrey D. , Wassarman Paul M.
Published: May 2006

During growth of the ovarian follicle, the mammalian oocyte becomes surrounded by an acellular coat called the zona pellucida. Whether the zona pellucida originates from the oocyte, surrounding follicle cells, or both has remained an unresolved issue. In experiments described here, denuded and follicle-enclosed mouse oocytes at various stages of growth were isolated and cultured
in vitro
in the presence of either [
35
S]methionine or [
3
H]fucose in order to determine the site of synthesis of the three, recently identified, zona pellucida proteins, ZP1, ZP2, and ZP3 [Bleil, J. D. & Wassarman, P. M. (1980)
Dev. Biol.
, in press]. Approximately 1.5% of the [
35
S]methionine, and as much as 45% of the [
3
H]fucose, that was incorporated into trichloroacetic acid-insoluble material by denuded or follicle-enclosed oocytes during a 12-hr culture period was found associated with zonae pellucidae removed from the cultured oocytes. Incorporation of [
35
S]methionine into zona pellucida proteins was depressed to less than 1/50th when denuded oocytes were cultured in the presence of puromycin, and secretion of zona pellucida proteins by denuded oocytes was demonstrated by pulse-chase experiments. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis of [
35
S]methionine- and [
3
H]fucose-labeled proteins present in oocytes, zonae pellucidae, and follicle cells revealed that denuded oocytes synthesize and secrete zona pellucida proteins, whereas no evidence was obtained to suggest that follicle cells synthesize these proteins. Denuded oocytes, ranging in diameter from 48 to 68 μm, incorporated both [
35
S]methionine and [
3
H]fucose into zona pellucida proteins during culture
in vitro
, whereas zonae pellucidae removed from fully-grown oocytes (85 μm) were not radiolabeled to a significant extent. After culture of denuded or follicle-enclosed oocytes for 12 hr, more than 95% of the [
3
H]fucose incorporated into oocyte proteins was found in ZP1, ZP2, and ZP3, indicating that the zona pellucida proteins are the major class of proteins glycosylated during oocyte growth. These results provide biochemical evidence supporting the idea that the zona pellucida originates from the mammalian oocyte itself, rather than from the surrounding follicle cells.
Isolation of diploid human lymphoblast mutants presumably homozygous for ouabain resistance
Authors: Choy Wai Nang , Littlefield John W.
Published: May 2006

From a mass culture of diploid human lymphoblasts we have isolated a subline resistant to 1 μM ouabain, and from this, a subline resistant to 10 μM ouabain. These sublines occurred spontaneously, but similar mutants were induced with 10-fold increased frequency by treatment with mutagens, in which case they could be selected as clones in soft agarose. Scatchard plot analyses of ouabain binding indicated that the subline resistant to 1 μM ouabain retained an average of 39% of the high-affinity ouabain receptors of the parental lymphoblast line, and the subline resistant to 10 μM ouabain retained an average of 8.4%. The ouabain binding site is known to be located in the Na
+
,K
+
-ATPase (ATP phosphohydrolase, EC 3.6.1.3) molecule, an essential cell membrane enzyme that mediates ion transport. Studies on Na
+
,K
+
-ATPase activity, using
86
Rb in the absence and presence of ouabain, indicated that our parental lymphoblasts contained one population of Na
+
,K
+
-ATPase molecules highly sensitive to ouabain inhibition, the subline resistant to 10 μM ouabain contained one population relatively insensitive to ouabain, and the subline resistant to 1 μM ouabain contained both populations. Thus, the moderately resistant subline appears to be heterozygous for ouabain resistance, probably containing a structural mutation in the ouabain receptor region of the Na
+
,K
+
-ATPase molecule in one of the two homologous loci for this enzyme, whereas the highly resistant subline derived from it appears to be homozygous, containing an additional mutation in the other Na
+
,K
+
-ATPase locus.
IgM antibodies induce the production of antibodies of the same specificity.
Authors: Forni L , Coutinho A , Köhler G , Jerne N K
Published: May 2006

Injection in normal mice of IgM antibodies against sheep erythrocytes or dextran, in the form of an immune serum depleted og IgG, induces direct plaque-forming cells of the same specificity as the injected antibodies. The response is 10--70 times higher than the background plaque-forming cell titer of untreated control mice. Nanogram amounts of IgM induce a detectable response, and a ceiling is reached with a few hundred nanograms of monoclonal IgM. The inducing agent is not residual antigen: (i) treatment of the injected material and the recipients with dextranase abolishes the immunogenicity of dextran, but not the response to anti-dextran IgM; (ii) monoclonal IgM specific for sheep erythrocytes or trinitrophenyl likewise induces plaque-forming cells of the respective specificity, but variant hybridoma products (in which the light chain is that of the myeloma parent) are inactive. In normal mice, IgM-induced antibody responses were observed with antibodies to both thymus-dependent and thymus-independent antigens, but such could not be induced in athymic (nude) mice. Because the mechanism underlying this phenomenon would operate also in a normal immune response and, presumably, in the normal dynamic state of the immune system of unstimulated animals, a network regulation among the elements of the immune system itself is implied.
Altered nerve growth factor in fibroblasts from patients with familial dysautonomia.
Authors: Schwartz J P , Breakefield X O
Published: May 2006

Nerve growth factor was measured in cultured human skin fibroblasts from controls and from patients with familial dysautonomia and dystonia musculoram deformans. Cells from these sources grown over a range of cell densities contained similar levels of beta-nerve growth factor as measured by radioimmunoassay. Results of bioassay demonstrated that the nerve growth factor from dysautonomic cells was only approximately 10% as active per ng of immunoreactive protein as that from control and dystonic cells. Treatment of fibroblasts with the beta-adrenergic agonist isoproterenol resulted in a 17- to 170-fold rise in the cyclic AMP content of both control and dysautonomic cells in 10 min. The content of immunoreactive beta-nerve growth factor in control fibroblasts increased 50--300% after 3--4 hr of exposure to isoproterenol. At no time, throughout a 7.5 hr period, was there a change in the amount of immunoreactive beta-nerve growth factor in the dysautonomic cells. These studies suggest that the molecular basis of the genetic defect in familial dysautonomia may lie in processing of the precursor or in the structure of the biologically active beta subunit of nerve growth factor.
Nonlinear wave equations and constrained harmonic motion
Authors: Deift Percy , Lund Fernando , Trubowitz Eugene
Published: May 2006

The study of the Korteweg-deVries, nonlinear Schrödinger, Sine-Gordon, and Toda lattice equations is simply the study of constrained oscillators. This is likely to be true for any nonlinear wave equation associated with a second-order linear problem.
DNA sequence of the
Serratia marcescens
lipoprotein gene
Authors: Nakamura Kenzo , Inouye Masayori
Published: May 2006

The
Serratia marcescens
gene for the outer membrane lipoprotein (
lpp
) was cloned in λ phage vector Charon 14. The recombinant phage was very unstable, and the
lpp
gene with a 300-base-pair deletion at the transcription termination site was further cloned in pBR322. The DNA sequence of 834 base pairs encompassing the
lpp
gene was determined and compared with that of the
Escherichia coli lpp
gene. The sequence comparisons exhibit several unique features. (
i
) The promoter region is highly conserved (84% homology) and has an extremely high A+T content (78%) as in
E. coli
(80%). (
ii
) The 5′ nontranslated region of the lipoprotein mRNA is also highly conserved (95% homology). (
iii
) In the DNA sequence corresponding to the signal peptide of this secretory protein, there are three drastic changes, including addition of one base pair and deletion of four base pairs in
S. marcescens
as compared to
E. coli
. The resultant alterations in the amino acid sequence, however, do not change the basic properties of the signal peptide, which are assumed to be essential for its function in the secretory mechanism. (
iv
) The DNA sequence from the amino terminus to the 51st residue of the mature lipoprotein is highly conserved (95% homology) and there is no amino acid substitution. (
v
) The DNA sequence corresponding to the seven amino acid residues at the carboxyl terminus has only 42% homology, resulting in four amino acid substitutions. (
vi
) Within the section of 40 base pairs beginning with the termination codon (UAA) and ending immediately before the oligo(T) transcription termination site in the
E. coli lpp
gene, there is about 60% homology. However, after this section, there is no obvious homology between the two sequences, probably because of a deletion of 300 base pairs at this region. (
vii
) Seven stable stem-and-loop structures could be formed in the mRNA region. (
viii
) Alterations in the third position of codons used in the
lpp
gene suggest that the gene has evolved somewhat differently from other genes in
S. marcescens
.
In vitro
metabolism of 25-hydroxyvitamin D
3
by isolated rat kidney cells
Authors: Turner Russell T. , Bottemiller Brian L. , Howard Guy A. , Baylink David J.
Published: May 2006

Cells were dispersed from rat kidney after enzymatic digestion of the extracellular matrix. When the cells were suspended in a serum-free medium and incubated with
3
H-labeled 25-hydroxyvitamin D
3
(25-OH-D
3
) several polar metabolites, including 1,25-(OH)
2
[
3
H]D
3
and 24,25-(OH)
2
[
3
H]D
3
were produced. The specific activities of the 25-OH-D
3
:1- and 24-hydroxylases in isolated rat kidney cells were 10-100 times greater than in avian kidney homogenates. The rates of production of 1,25-(OH)
2
D
3
and 24,25-(OH)
2
D
3
were linear over a wide range in cell densities (0.65-5.0 × 10
6
cells per ml) and substrate concentrations (3.5-70 nM). The rate of production of 24,25-(OH)
2
[
3
H]D
3
from 25-OH-[
3
H]D
3
by cells isolated from rats fed control diet was linear with time for up to 30 min, while the synthesis of 1,25-(OH)
2
[
3
H]D
3
was linear for over 90 min. The specific activity of the 25-OH-D
3
:1-hydroxylase was increased in kidney cells from vitamin D-deficient rats (11.5 fmol/min per 10
6
cells) as well as calcium-deficient rats (8.1 fmol/min per 10
6
cells) when compared to cells from rats fed the control diet (2.0 fmol/min per 10
6
cells). Also, the specific activity of the 25-OH-D
3
:24-hydroxylase was reduced in cells from the vitamin D-deficient rats (<0.2 fmol/min per 10
6
cells) and calcium-deficient rats (5.1 fmol/min per 10
6
cells) compared to the controls (15.2 fmol/min per 10
6
cells). On the basis of these results, as well as previous
in vivo
studies, we conclude that the metabolism of 25-OH-D
3
by freshly isolated rat kidney cells reflects the
in vivo
activities of the renal vitamin D-metabolizing enzymes and may prove useful as an assay.
Humans have antibodies capable of recognizing oncoviral glycoproteins: demonstration that these antibodies are formed in response to cellular modification of glycoproteins rather than as consequence of exposure to virus.
Authors: Barbacid M , Bolognesi D , Aaronson S A
Published: May 2006

There is controversy in the literature concerning the presence in humans of antibodies directed against the envelope glycoproteins of known oncoviruses. In the present report, we show that antibodies capable of precipitating a wide variety of oncoviral glycoproteins can be demonstrated under certain assay conditions. Substances as diverse as normal components of serum, extracts of bacteria, and even nonprotein molecules such as glycogen also shared the oncoviral glycoprotein determinants recognized by normal human sera. It was found that immunoprecipitation of a given viral glycoprotein by human sera was entirely dependent upon the cell in which the virus was grown. Human sera specifically did not recognize glycoproteins purified from oncoviruses grown in human or higher primate cells. These findings not only demonstrate that the antibodies were directed against cellular rather than the virus-coded antigenic determinants but also exclude the possibility that this immune response was elicited as a consequence of oncovirus exposure.
Nucleotide sequence of ilvGEDA operon attenuator region of Escherichia coli.
Authors: Nargang F E , Subrahmanyam C S , Umbarger H E
Published: May 2006

The nucleotide sequence of the DNA thought to contain the control region for the ilvGEDA operon in Escherichia coli has been determined by the Maxam-Gilbert procedure. The sequence includes a region that, upon transcription, would yield a leader transcript specifying a peptide 32 residues long. This putative peptide would contain four leucine, five isoleucine, and six valine residues. A model is proposed that correlates the multivalent control of the ilvGEDA operon with the extent to which this leader transcript is translated. In vitro transcription experiments yielded a transcript of about 183 nucelotides, compatible with the predictions of the model.
DNA gyrase action involves the introduction of transient double-strand breaks into DNA.
Authors: Mizuuchi K , Fisher L M , O'Dea M H , Gellert M
Published: May 2006

DNA gyrase from Escherichia coli, in the presence of ATP, can both separate catenated DNA circles and unknot knotted DNA. Both these reactions require passage of a DNA segment through a transient double-strand break in DNA. Evidence that transient double-strand breaks are also involved in the supercoiling and relaxing activities of DNA gyrase is derived from experiments showing that the linking number of circular DNA is changed in steps of two. A mechanism is proposed for the action of the enzyme.
Deoxyribopyrimidine triphosphatase activity specific for cells infected with herpes simplex virus type 1.
Authors: Wohlrab F , Francke B
Published: May 2006

Nuclei from baby hamster kidney cells infected with herpes simplex virus type 1 contain a virus-specific deoxyribonucleoside triphosphate degrading activity. The reaction proceeds at 4 degrees C and can thus be distinguished from host enzymes. Under these conditions the enzyme is specific for deoxyribopyrimide triphosphates and catalyzes pyrophosphate cleavage to produce the monophosphates, dUTP being the best substrate followed by dCTP and dTTP. The appearance of the activity after infection parallels that of viral DNA-synthesis-related functions. Of a series of eight temperature-sensitive mutants tested, two (tsD and tsK) exhibit significantly decreased triphosphatase levels after infection at nonpermissive temperature, whereas a viral deoxypyrimidine kinase-deficient mutant induced wild-type levels.
Protein synthetic errors do not increase during aging of cultured human fibroblasts.
Authors: Harley C B , Pollard J W , Chamberlain J W , Stanners C P , Goldstein S
Published: May 2006

To test the error catastrophe theory of aging we determined the error frequency of protein synthesis in several strains of cultured human fibroblasts at early and late passage. Error rates were calculated from analysis of native and substituted actins on two-dimensional gels of cellular proteins after induction of mistranslation by histidine starvation in the presence of histidinol. Early-passage cells from fetal, young, and old donors and cells from subjects with the Hutchinson-Gilford and Werner syndromes of accelerated aging had similar error frequencies. Late-passage cells from fetal, young, and old normal donors had similar or lower error frequencies than corresponding early-passage cells. No correlation was observed between error frequency, donor age, or maximal life span in vitro. We also examined an immortal cell line, simian virus 40-transformed W138 fibroblasts. These cells had a significantly elevated rate of mistranslation (2.8 +/- 0.2 x 10(-4))(+/- SEM) compared to their untransformed counterpart WI38 (0.6 +/- 0.1 X 10(-4)) or all diploid cells combined (1.1 +/- 0.1 x 10(-4)). Taken together, the data fail to support the error catastrophe theory of aging.
Changes in the abscisic acid content of oat leaves during senescence
Authors: Gepstein Shimon , Thimann Kenneth V.
Published: May 2006

To investigate the possibility that experimental promotion of retardation of the senescence of oat leaves may be mediated by abscisic acid (AbA), determinations of AbA were made in leaves senescing under different conditions. The extracts were subjected to thin-layer chromatography, the spots were eluted and esterified, and the AbA was determined by gas chromatography (overall recovery, about 75%). In darkness, where the stomata are closed and senescence is rapid, the concentration of AbA increases to at least 5 times its initial value by the second day, the time when chlorophyll loss is most rapid. In light, where the stomata are open and senescence is very slow, no such increase occurs. But when, in light, the stomata are closed by floating the leaves on 1 M mannitol, the AbA level again increases to about 5 times the initial value; if the stoma response is prevented by kinetin, the increase in AbA is largely suppressed. Similarly, phenylmercuric nitrate, at a concentration that closes the stomata, causes a 4-fold increase in AbA. It is concluded that stomatal closure itself causes AbA accumulation and, thus, that AbA may indeed be the proximal cause of leaf senescence.
Relationship of polypeptide products of the transforming gene of Rous sarcoma virus and the homologous gene of vertebrates
Authors: Sefton Bartholomew M. , Hunter Tony , Beemon Karen
Published: May 2006

All vertebrate cells have been shown to contain a gene,
sarc
, that has some homology with the transforming gene of Rous sarcoma virus,
src
. We have compared the polypeptide products of the
sarc
gene, p60

sarc

, of human, mouse, and chicken cells with the polymorphic polypeptide product of the
src
gene, p60

src

, of several strains of Rous sarcoma virus by two-dimensional peptide mapping. p60

sarc

from chicken cells was clearly related to every viral p60

src

. Eleven of its 13 methionine-containing tryptic peptides were present in some viral p60

src

. Conversely, the other two peptides were not present in any p60

src

we have examined so far. The 11 peptides from p60

sarc

of chickens that were shared with viral p60

src

, however, were not all present in any single viral p60

src

. These 11 peptides most closely resemble those in the p60

src

s of B77 virus and the Prague strain of Rous sarcoma virus. These data are consistent with the hypothesis that cellular
sarc
is the progenitor of viral
src
. The p60

sarc

s of human, mouse, and chicken cells were so similar in tryptic peptide composition that they were more closely related to each other than were some viral p60

src

s. The two mammalian p60

sarc

s differed from avian p60

sarc

most notably in that they lacked a peptide that chicken p60

sarc

shares with all the viral p60

src

s. The similarity of these maps suggests that the sequence of the p60

sarc

polypeptide has diverged very little during evolution. This may imply that p60

sarc

is an essential cellular component.
Synthesis and localization of fibronectin during collagenous matrix-mesenchymal cell interaction and differentiation of cartilage and bone in vivo.
Authors: Weiss R E , Reddi A H
Published: May 2006

The biosynthesis of fibronectin during the in vivo development of matrix-induced endochondral bone was investigated by using [35S]methionine in rats. The dmineralized bone matrix that was implanted subcutaneously to induce local bone formation bound circulating fibronectin. This may be an important initial requirement for cell attachment to the matrix. Fibronectin was present throughout the development of bone but accounted for the largest percentage of total protein synthesized during mesenchymal cell proliferation and hematopoiesis. Fibronectin was identified in tissue extracts by its (i) comigration on electrophoretic NaDodSO4/polyacrylamide gels with human and rat plasma fibronectin, (ii) affinity for denatured collagen, (iii) crossreactivity with purified antibody of rat plasma fibronectin, and (iv) insensitivity to collagenase digestion. Fibronectin was localized by immunofluorescence in the extracellular matrix during the period of mesenchymal cell proliferation. During chondrogenesis, fibronectin was demonstrated in the differentiating chondrocytes. Fibronectin was detectable in the cartilage matrix only after hyaluronidase treatment. During vascular invasion, prior to osteogenesis, fibronectin was localized in association with endothelial cells. These observations demonstrate a possible role of fibronectin in collagenous matrix-mesenchymal cell interaction in vivo.
Isolation of the centromere-linked CDC10 gene by complementation in yeast.
Authors: Clarke L , Carbon J
Published: May 2006

A hybrid plasmid colony bank was constructed in Escherichia coli using the E. coli-Saccharomyces cerevisiae shuttle vector pLC544 and randomly sheared segments of yeast DNA. By transformation with a hybrid plasmid DNA pool from this collection and complementation of a temperature-sensitive cdc10 mutation in yeast, a plasmid was isolated that carries 8 kilobase pairs of DNA around the chromosome III centromere-linked CDC10 locus. This DNA segment overlaps a larger region of DNA (40 kilobase pairs) previously identified to be around the LEU2 locus on chromosome III [Chinault, A.C. & Carbon, J. (1979) Gene 5, 111-126] and physically establishes the directionality of the cloned DNA sequences with respect to the genetic map and the centromere. In the leu2-cdc10 interval, the relationship between physical distance on the DNA and genetic distance as measured by recombinational frequencies is about 3 kilobase pairs per centimorgan.
Membrane potential changes during mitogenic stimulation of mouse spleen lymphocytes
Authors: Kiefer Hansruedi , Blume Arthur J. , Kaback H. Ronald
Published: May 2006

By monitoring differences in accumulation of the lipophilic cation [
3
H]tetraphenylphosphonium in media containing low or high potassium concentrations [Lichtshtein, D., Kaback, H. R. & Blume, A. J. (1979)
Proc. Natl. Acad. Sci. USA
76, 650-654], the membrane potential of lymphocytes from various sources has been estimated. On the basis of this method, the potential of normal mouse spleen lymphocytes (T and B cells) is -65 ± 2 mV (mean ± SEM, interior negative). During the course of mitogenic stimulation by concanavalin A, lipopolysaccharide, or fetal calf serum, the membrane potential of murine spleen lymphocytes changes systematically according to the following pattern: (
i
) early depolarization lasting 2-3 hr, (
ii
) repolarization over the next 7 hr, and (
iii
) a final hyperpolarization phase during the last 24-48 hr. During repolarization and hyperpolarization, moreover, there is a direct correlation between the membrane potential and DNA synthesis, as judged by [
3
H]thymidine incorporation. By using isolated T and B cells, it is observed that concanavalin A depolarizes T cells only, whereas lipopolysaccharide depolarizes B cells only. Thus, both mitogens exhibit the same specificity for depolarization as for mitogenic stimulation. On the basis of these observations, it is suggested that the transition of lymphocytes from a resting state to mitotic activity is initiated by depolarization of the plasma membrane.
Malondialdehyde alteration of low density lipoproteins leads to cholesteryl ester accumulation in human monocyte-macrophages
Authors: Fogelman Alan M. , Shechter Ishaiahu , Seager Janet , Hokom Martha , Child John S. , Edwards Peter A.
Published: May 2006

Glutaraldehyde treatment of
125
I-labeled low density lipoprotein (
125
I-native-LDL) produced a modified LDL (
125
I-glut-LDL) with a molecular weight of 10 × 10
6
or more. Malondialdehyde treatment of
125
I-native-LDL produced a product (
125
I-MDA-LDL) with a molecular weight not appreciably different from that of the original lipoprotein. However, the electrophoretic mobility of MDA-LDL indicated a more negative charge than native-LDL.
125
I-MDA-LDL was degraded by two processes: a high-affinity saturable process with maximal velocity at 10-15 μg of protein per ml and a slower, nonsaturable process. The degradation of
125
I-MDA-LDL was readily inhibited by increasing concentrations of nonradioactive MDA-LDL but was not inhibited by acetylated LDL or native-LDL even at concentrations as high as 1600 μg of protein per ml. After exposure of native-LDL to blood platelet aggregation and release
in vitro
, 1.73 ± 0.19 nmol of malondialdehyde per mg of LDL protein was bound to the platelet-modified-LDL. No detectable malondialdehyde was recovered from native-LDL that had been treated identically except that the platelets were omitted from the reaction mixture.

After incubation with glut-LDL, MDA-LDL, or platelet-modified-LDL for 3 days, human monocyte-macrophages showed a dramatic increase in cholesteryl ester content whereas the cholesteryl ester content of cells incubated with the same concentration of native-LDL did not. Based on these experiments we propose that modification of native-LDL may be a prerequisite to the accumulation of cholesteryl esters within the cells of the atherosclerotic reaction. We further hypothesize that one modification of LDL
in vivo
may result from malondialdehyde which is released from blood platelets or is produced by lipid peroxidation at the site of arterial injury.
Interferon-treated cells release vesicular stomatitis virus particles lacking glycoprotein spikes: correlation with biochemical data.
Authors: Maheshwari R K , Demsey A E , Mohanty S B , Friedman R M
Published: May 2006

Earlier we reported a reduction to 1/30th-1/100th of the original number of infectious particles in the infectious vesicular stomatitis virus (VSV) released from L cells treated with 10 or 30 reference units of interferon per ml. However, in these cultures virus particle production, as measured by VSV particle-associated viral RNA, virus nucleocapsid protein, and viral transcriptase, was inhibited by less than 10%. Data reported in this paper show that there was a significant reduction in glycoprotein and membrane protein of VSV particles released from interferon-treated cells. Evidence supporting the deficiency of glycoprotein in VSV released from interferon-treated cells was derived from electron microscopic studies. Under conditions where glycoprotein spikes or projections were clearly detectable on the surface of VSV released from cells not treated with interferon, very few spikes were observed on VSV released from interferon-treated cells. These results suggested that interferon-treated cells produced VSV particles with low infectivity and that this low infectivity may be related to the reduced amount of glycoprotein and membrane protein incorporated into such particles.
Regulation of hippocampal glutamate receptors: evidence for the involvement of a calcium-activated protease.
Authors: Baudry M , Lynch G
Published: May 2006

Specific [3H]glutamate binding to rat hippocampal membranes and the calcium-induced increase in this binding are markedly temperature-sensitive and are inhibited by alkylating or reducing agents as well as by various protease inhibitors. N-Ethylmaleimide, chloromethyl ketone derivatives of lysine and phenylalanine, and tosylarginine methyl ester decrease the maximum number of [3H]glutamate binding sites without changing their affinity for glutamate. Preincubation of the membranes with glutamate does not protect the glutamate "receptors" from the suppressive effects of these agents. The proteases trypsin and alpha-chymotrypsin increase the maximum number of [3H]glutamate binding sites. The effects of calcium on glutamate binding are different across brain regions. Cerebellar membranes are almost insensitive whereas hippocampal and striatal membranes exhibit a strong increase in the number of binding sites after exposure to even low concentrations of calcium. These results suggest that an endogenous membrane-associated thiol protease regulates the number of [3H]glutamate-associated thiol protease regulates the number of [3H]glutamate binding sites in hippocampal membranes and that this is the mechanism by which calcium stimulates glutamate binding. The possibility is discussed that the postulated mechanisms participate in synaptic physiology and in particular may be related to the long-term potentiation of transmission found in hippocampus under certain conditions.
Biological competition: Decision rules, pattern formation, and oscillations
Authors: Grossberg Stephen
Published: May 2006

Competition solves a universal problem about pattern processing by cellular systems. Competition allows cells to automatically retune their sensitivity to avoid noise and saturation effects. All competitive systems induce decision schemes that permit them to be classified. Systems are identified that achieve global pattern formation, or decision-making, no matter how their parameters are chosen. Oscillations can occur due to contradictions in a system's decision scheme. The pattern formation and oscillation results are extreme examples of a complementarity principle that seems to hold for competitive systems. Nonlinear competitive systems can sometimes appear, to a macroscopic observer, to have linear and cooperative properties, although the two types of systems are not equivalent. This observation is relevant to theories about the evolutionary transition from competitive to cooperative behavior.
Localization of the amino acid substitution site in a new variant of human serum albumin, albumin Mexico-2
Authors: Franklin Samuel G. , Wolf Susan I. , Zweidler Alfred , Blumberg Baruch S.
Published: May 2006

Using an electrophoretic screening procedure, we have discovered that two species of human serum albumin Mexico occur that are indistinguishable by conventional electrophoretic methods. We suggest that these species be referred to as albumins Mexico-1 and Mexico-2. Isolation and determination of the partial sequence of the cyanogen bromide fragment of albumin Mexico-2 that differs from the corresponding fragment of the common albumin A revealed this variant to arise from at least a glycine/aspartic acid substitution at position 550. This region of the albumin molecule is involved in the binding of the fatty acid, palmitate.
Recognition of duplex DNA containing single-stranded regions by recA protein.
Authors: West S C , Cassuto E , Mursalim J , Howard-Flanders P
Published: May 2006

Genetic recombination in Escherichia coli requires recA protein, the product of the recA+ gene. In this paper we show that purified recA protein, which binds strongly to denatured DNA, cooperatively recognizes DNA containing short single-stranded regions. The interaction of varying amounts of recA protein with DNA molecules was investigated by measuring its DNA-dependent ATPase activity. In 3mM Mg2+, the ATPase activity was stimulated by excess single-stranded DNA and was minimal with either intact circular or blunt-ended linear duplexes. Single-strand gaps of about 30 nucleotides were sufficient to increase the ATPase activity to a level almost as great as that observed with single-stranded DNA. Sedimentation studies at neutral pH showed cooperative binding of recA protein to single-stranded DNA or to duplex DNA containing single-stranded regions. In the presence of ATP, an intermediate rate of sedimentation was observed; in contrast, adenosine 5'-gamma-thiotriphosphate (ATP[S]) caused the formation of fast-sedimenting DNA-protein complexes. Gapped plasmid DNA plus recA protein and ATP[S] formed large aggregates containing thousands of molecules. Complex formation and stimulation of the ATPase activity of recA protein with duplex DNA containing single-stranded regions indicates that recA protein may change the conformation of the normally duplex molecules to a conformation prepared for homologous pairing.
Genomic integration of bovine leukemia provirus: comparison of persistent lymphocytosis with lymph node tumor form of enzootic.
Authors: Kettmann R , Cleuter Y , Mammerickx M , Meunier-Rotival M , Bernardi G , Burny A , Chantrenne H
Published: May 2006

Integration of bovine leukemia proviral DNA in the genome of infected cells was investigated in cattle affected by either the persistent lymphocytosis or the lymph node tumor form of enzootic bovine leukosis. In persistent lymphocytosis, proviral DNA was found to be integrated at a large number of genomic sites in one-fourth to one-third of circulating leukocytes. In the lymph node tumor form, in contrast, proviral DNA was found to be integrated at one or very few sites in the genomes of a larger fraction of both circulating leukocytes and lymph node tumor cells.
Regulation of ornithine decarboxylase activity by corticotropin in adrenocortical tumor cell clones: roles of cyclic AMP and cyclic AMP-dependent protein kinase.
Authors: Kudlow J E , Rae P A , Gutmann N S , Schimmer B P , Burrow G N
Published: May 2006

In Y1 adrenocortical tumor cells, corticotropin (ACTH), cyclic AMP, and 8-bromoadenosine 3',5'-monophosphate (8BrcAMP) stimulated ornithine decarboxylase activity (L-ornithine carboxy-lyase, EC 4.1.1.17) and steroidogenesis. The concentrations required for half-maximal activation of ornithine decarboxylase were 60 pM for ACTH and 1 mM for 8BrcAMP; the concentrations required for half-maximal activation of steroidogenesis were 50 pM for ACTH and 0.2 mM for 8BrcAMP. Ornithine decarboxylase activity increased 1.5 hr after the addition of these agents, reached a maximum between 4 and 6 hr, and then declined. Mutant clones with impaired ACTH-responsive adenylate cyclase systems [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1]did not respond to ACTH with increased ornithine decarboxylase activity, but they responded normally to added cyclic AMP. These results indicate that adenylate cyclase and cyclic AMP are necessary for the stimulation of ornithine decarboxylase activity by ACTH. In a series of Y1(Kin) mutants with altered cyclic AMP-dependent protein kinase activities (ATP:protein phosphotransferase, EC 2.7.1.37), the effects of ACTH on ornithine decarboxylase also were attenuated. These findings suggest that cyclic AMP-dependent protein kinase also plays a necessary role in the stimulation of ornithine decarboxylase activity by ACTH. The effects of ACTH on ornithine decarboxylase in the Kin mutants, however, were quantitatively different from the effects on steroidogenesis and did not closely reflect the degree of defect in cyclic AMP-dependent protein kinase activity. These differences suggest that the pathways of ACTH action leading to stimulation of steroidogenesis and ornithine decarboxylase activity diverge subsequent to activation of the protein kinase.
Evidence for a naturally occurring anti-spermine antibody in normal rabbit serum.
Authors: Furuichi K , Ezoe H , Obara T , Oka T
Published: May 2006

Normal rabbit serum contains an IgG-like component(s) that binds spermine as well as other polyamines. This molecule(s) has the same physicochemical properties as anti-spermine antibody obtained from rabbits immunized with spermine-thyroglobulin conjugates. However, the polyamines-binding IgG-like molecule(s), unlike anti-spermine antibody, is incapable either of precipitating a spermine-bovine serum albumin complex or of binding to a spermine-Sepharose column. These results suggest the existence of a naturally occurring anti-polyamine antibody that may have defective antibody functions.
A virus in Beechey ground squirrels that is related to hepatitis B virus of humans.
Authors: Marion P L , Oshiro L S , Regnery D C , Scullard G H , Robinson W S
Published: May 2006

A virus given the name ground squirrel hepatitis virus (or GSHV), with many of the unique characteristics of human hepatitis B virus (HBV), has been found in Beechey ground squirrels in northern California. Common features include virus morphology, viral DNA size and structure, a virion DNA polymerase that repairs a single-stranded region in the viral DNA, crossreacting viral antigens, and persistent infection with viral antigen continuously in the blood. Although similar, GSHV and HBV Are not identical. The ground squirrel virion has a slightly greater diameter, the viral surface antigens crossreact only partially and, thus, are not identical, and GSHV DNA has two restriction endonuclease EcoRI cleavage sites in contrast to the single site in HBV DNA. Thus, GSHV is a member of the virus group that includes HBV and the virus recently found in woodchucks in the eastern United States and named woodchuck hepatitis virus. It is not yet known how closely the ground squirrel and woodchuck viruses are related.
A test for the radomness of the occurrence of a disease trait in familial or other similar ordered sequences of epidemiological data.
Authors: Chakraborty R , Weiss K M , Schull W J
Published: May 2006

Through the construction of a probability distribution, a test is proposed for the randomness of the occurrence of an epidemiological event in a series of structured ordered sequences. Such sequences may be of persons admitted to hospital in some specified order, individuals seen in a large set of extended screening program, or individuals in a large set of extended genealogies. Modifications to account for the limited length of ascertained sequences are also given. The method will be particularly important in the first-stage evaluation of genealogical data to indicate the existence and degree of familial aggregation of diseases such as cancer and to justify more complex methods of analysis designed to evaluate the specific elements of causation that may be operating. The statistical power of this approach is also derived, considering the anticipated sample sizes in its application, to detect some forms of familial aggregation in a large genealogical data base from Laredo, Texas.