bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of proliferation and differentiation in B lymphocytes by anti-Ig antibodies and a serum-derived cofactor.
Authors: Sidman C L , Unanue E R
Published: May 2006

The effects of various anti-Ig antibodies on different B lymphocyte functions were investigated. With the proper accessory cofactor(s) derived from serum, anti-IgM antibodies induced a vigorous proliferative response in normal adult murine B cells, while polyspecific anti-Ig and anti-IgD had no effect. Without the required cofactor, all three anti-Ig antibodies were inhibitory for mitogenic responses. All three anti-Ig antibodies were also inhibitory for mitogen-induced antibody responses with or without the cofactor. Even with the required cofactor, neonatal B cells as well as adult C3H/HeJ B cells were not triggered into proliferation by anti-IgM. Finally, the cofactor required for anti-IgM-triggered mitogenesis was shown to be generated from serum by 2-mercaptoethanol and to be approximately 65,000 in molecular weight. These results indicate that, for at least some responses, B lymphocyte surface IgM molecules are involved in both triggering and suppression, depending both on the developmental state of the B cell and the presence or absence of accessory influences. In these experiments, IgD gave evidence only of being suppressive.
Generation of oncogenic type C viruses: Rapidly leukemogenic viruses derived from C3H mouse cells
in vivo
and
in vitro
Authors: Rapp Ulf R. , Todaro George J.
Published: May 2006

A type C virus was isolated from C3H/10T1/2 mouse cells in culture after activation with iododeoxyuridine. This virus was poorly infectious for mouse cells and did not cause tumors upon inoculation into newborn NIH Swiss mice. Variants with increased infectivity for mouse cells were then derived both
in vivo
and
in vitro
by selecting for variants able to grow to high titers. The highly infectious variants were found to induce mouse fibroblasts to grow in soft agar. When the viruses were inoculated into newborn NIH Swiss mice, 100% of the animals died of leukemia within 4 months. Solid tumors developed at the injection site. Both mouse-tropic and dualtropic viruses were isolated from the leukemic mice and plaque purified. The first group of viruses produced large syncytial plaques on rat XC cells and did not grow in mink cells. The viruses of the other group replicated well in both mouse and mink cells, producing morphologic changes similar to transformation but not XC syncytia; they, therefore, are members of the newly described MCF class of mouse type C viruses. Isolates from either group were highly leukemogenic on retesting, the mean latent period being 67 days for a mouse-tropic virus and 105 days for one of the dual-tropic viruses. The results led to the conclusion that the better a mouse type C virus grows in cell culture the more effective it is as a leukemogen. Further, it is possible to start with a weakly infectious, nonleukemogenic virus and to convert it to a rapidly replicating, highly leukemogenic virus by passage either in cell culture or in the animal. The availability of a defined series of viruses from a low-leukemia mouse strain that differ greatly in their biologic properties should facilitate studies of the molecular basis for the acquisition of type C virus oncogenicity.
Conformation of dopamine at the dopamine receptor.
Authors: Komiskey H L , Bossart J F , Miller D D , Patil P N
Published: May 2006

Tritiated dopamine was used to label the dopamine receptor in membranes isolated from the rat corpus striatum. Scatchard analysis of displacement of [3H]dopamine by nonradioactive dopamine indicated the presence of two binding sites. The similarities in affinity, capacity, and drug specificity of the high-affinity site in the striatal membranes from rat and the binding site in the membranes from the calf caudate nucleus suggest that [3H]dopamine labels the same site in both species. In order to determine what conformation of dopamine is preferred at the dopamine receptor site, conformationally restricted analogs of dopamine--namely, the cis and trans 2-amino-1(3,4-dihydroxyphenyl)cyclobutane hydrochlorides--were tested for their affinity to the receptor. Compared to the cis conformation, the trans-restricted analogs had more affinity for the receptor site, indicating that dopamine probably interacts with the receptor in the trans conformation.
Inverted repeated DNA from Chinese hamster ovary cells studied with cloned DNA fragments.
Authors: Jelinek W R
Published: May 2006

Fragments from the DNA of Chinese hamster ovary cells produced by restriction endonuclease EcoRI were cloned in Charon 16A lambda bacteriophage and examined for the ability to hybridize in situ with 32P-labeled double-stranded regions from heterogeneous nuclear RNA (hnRNA). Of 235 clones tested, 87 (37%) contained sequences that hybridized with the double-stranded hnRNA. Nine of these were examined for the presence of inverted repeat DNA structures (ir-DNA) by electron microscopy. All nine contained at least two elements of ir-DNA. Analysis of heteroduplexes formed from the DNAs of the different clones as well as T1 fingerprint analysis of the double-stranded hnRNA hybridized to each of the nine clones suggest that there is detectable nucleotide sequence homology in the various ir-DNAs. There are ca 3 X 10(5) ir-DNA pairs in the haploid Chinese hamster ovary cell genome.
Cloned single repeating units of 5S DNA direct accurate transcription of 5S RNA when injected into Xenopus oocytes.
Authors: Brown D D , Gurdon J B
Published: May 2006

Single and multiple repeating units of three types of Xenopus 5S DNA recombined with the plasmid pMB9 serve as templates for the accurate synthesis of 5S RNA after their injection into Xenopus laevis oocyte nuclei. All 15 cloned single repeating units of X. laevis oocyte 5S DNA that were tested supported 5S RNA synthesis. Three cloned fragments of X. borealis oocyte 5S DNA and one cloned single repeating unit of X. borealis somatic 5S DNA were templates for 5S RNA synthesis. We conclude that the majority of repeating units of 5S DNA in these multigene families contain the information for accurate initiation and termination of 5S RNA synthesis. The ability of this system to detect sequence changes that affect transcription is demonstrated.
Nutritional inhibition of genetically determined renal disease and autoimmunity with prolongation of life in kdkd mice.
Authors: Fernandes G , Yunis E J , Miranda M , Smith J , Good R A
Published: May 2006

Striking inhibition of development of renal disease and prolongation of lifespan have been achieved in kdkd mice by restricting their daily food intake. Restricting protein intake alone did not prolong life nor did it inhibit development of kidney disease. The kdkd nephronophthisis, although very different histologically from the renal disease of B/W mice, may also have immunological components. Like the immunologically based renal disease of B/W mice, renal disease in kdkd mice is decreased or eliminated histologically by dietary restriction, which inhibits development of autoimmunity directed toward the erythrocytes of these mice. Further analysis will be needed to elucidate the cause of progressive renal disease in both the kdkd and B/W models and to permit understanding of the profound influence of restriction of food intake on development and progression of these very different renal diseases.
Existence of a nonarithmetic lattice in
SU
(2,1)
Authors: Mostow G. D.
Published: May 2006

The proof of the well-known conjecture that lattices in groups of R-rank greater than 1 are arithmetic has raised speculation about the existence of nonarithmetic lattices in the R-rank 1 group
SU
(
n
,1),
n
> 1. This paper presents an example of such a lattice Γ
1
. Γ
1
consists of the intersection with
SU
(2,1) of a group Γ generated by three complex reflections of order 5. The quotient
SU
(2,1)/Γ
1
is compact.
Rat liver microsomal and lysosomal beta-glucuronidases differ in both carbohydrate and amino acid compositions.
Authors: Tulsiani D R , Six H , Touster O
Published: May 2006

To investigate the chemical relationships between rat liver lysosomal and microsomal beta-D-glucuronidases (EC 3.2.1.31), which are essentially identical catalytically and in reactivity with antibody and similar in molecular weight, the two enzymes were isolated by procedures in which modifications of the proteins were avoided. The purified enzymes were found to differ in both sugar and amino acid compositions. The microsomal enzyme contained much more mannose and, in contrast to the lysosomal enzyme, contained sialic acid but no glucose. Moreover, although the amino acid compositions generally agreed closely, the microsomal enzyme contained much more serine and somewhat less arginine than the lysosomal form. These findings of specific differences in composition should have a bearing on the consideration of intracellular glycoprotein synthesis, translocation, and compartmentalization.
Regio- and stereoselectivity of various forms of purified cytochrome
P
-450 in the metabolism of benzo[
a
]pyrene and (-)
trans
-7,8-dihydroxy-7,8-dihydrobenzo[
a
]pyrene as shown by product formation and binding to DNA
Authors: Deutsch J. , Leutz J. C. , Yang S. K. , Gelboin H. V. , Chiang Y. L. , Vatsis K. P. , Coon M. J.
Published: May 2006

Highly purified cytochromes
P
-450
LM2
and
P
-450
LM4
and partially purified
P
-450
LM1
,
P
-450
LM3b
, and
P
-450
LM7
from rabbit liver microsomes exhibit different catalytic activities in the metabolism of benzo[
a
]pyrene (BzP) and (-)-
trans
-7,8-dihydroxy-7,8-dihydrobenzo[
a
]pyrene [(-)
trans
-7,8-diol] in a reconstituted enzyme system. The two highly purified cytochromes also exhibit differences in the activation of BzP and (-)
trans
-7,8-diol to intermediates that bind to DNA, as well as in the stereoselective conversion of (-)
trans
-7,8-diol to the highly mutagenic and carcinogenic diol-epoxides
r
-7,
t
-8-dihydroxy-
t
-9,10-oxy-7,8,9,10- tetrahydrobenzo[
a
]pyrene (diol-epoxide I) and
r
- 7,
t
- 8 - dihydroxy -
c
- 9,10 - oxy - 7,8,9,10 - tetrahydrobenzo[
a
]pyrene (diol-epoxide II).
P
-450
LM2
is more active than
P
-450
LM4
in the metabolism of BzP and in its conversion to products that bind to DNA. In contrast,
P
-450
LM4
is more active than
P
-450
LM2
in the metabolism of (-)
trans
-7,8-diol and in its conversion to products that bind to DNA. The ratio of activity (percent substrate metabolized) with BzP relative to that with (-)
trans
-7,8-diol is 21 for
P
-450
LM2
and 0.3 for
P
-450
LM4
;
P
-450
LM1
,
P
-450
LM3b
, and
P
-450
LM7
gave intermediate ratios. Marked stereoselectivity in the oxygenation of the (-)
trans
-7,8-diol to the highly mutagenic and putatively carcinogenic diol-epoxides I and II was observed with
P
-450
LM4
, whereas the other preparations showed less selectivity. The ratio of diolepoxide I to diol-epoxide II ranges from 0.3 for
P
-450
LM7
to 11 for
P
-450
LM4
. The substrate specificity and regio- and stereo-selectivity of the different forms of cytochrome
P
-450 may regulate the balance between activation and detoxification pathways of BzP and therefore determine the susceptibility of individual tissues, strains, and species to the carcinogenic action of BzP.
Changes in genome composition of the Friend virus complex in erythroleukemia cells during the course of differentiation induced by dimethyl sulfoxide
Authors: Ostertag W. , Pragnell I. B.
Published: May 2006

The Friend spleen focus-forming virus (SFFV) complex released by Friend virus-transformed erythroid cells has been analyzed with respect to changes in the genome composition that may occur during induction of erythropoiesis with dimethyl sulfoxide. It is shown that: (
a
) There are three types of virus particles, one with buoyant density 1.20 g/ml, one with density 1.17 g/ml (the density of the cloned lymphatic leukemia virus helper component of the complex), and a major fraction that has a density of 1.14 g/ml. (
b
) Three RNA subunits-35S, 32S, and 30S-have previously been shown to be detectable in the Friend virus complex. The 1.20-g/ml particles contain only 30S RNA, whilst the 1.14- to 1.17-g/ml particles contain a mixture consisting of predominantly 30S and 32S RNA and about 5-10% 35S RNA. (
c
) Induction of differentiation results in an increase in the 1.14-g/ml particles and 32S RNA. The amount of 30S RNA does not change. (
d
) Hybridization of the different genomic viral RNAs with full-length virus cDNA shows that the 30S RNA (of induced and uninduced Friend virus) is more closely related to the 32S RNA of the induced Friend virus than to the 32S RNA of the constitutively released Friend virus. (
e
) The 30S RNA contains SFFV-specific sequences. (
f
) A hypothesis is presented in which the induction of the new 32S RNA species is related to the increase of SFFV activity and to a specific function of the SFFV during induction of erythropoiesis.
The
N
-soliton solution of the Benjamin-Ono equation
Authors: Case K. M.
Published: May 2006

A theorem is deduced that reduces the problem of finding the
N
-soliton solution of the Benjamin-One equation to that of solving an algebraic equation of degree
N
.
Specific phosphorylation at serine-283 of alpha tropomyosin from frog skeletal and rabbit skeletal and cardiac muscle.
Authors: Mak A , Smillie L B , Bárány M
Published: May 2006

Tropomyosin, extracted from the leg muscle of frogs that had been injected with [32P]orthophosphate, was fractionated into two components, alpha and beta, on a CM-cellulose column. Radioactivity was associated only with the alpha component. A single phosphorylation site was located at serine-283 (pentultimate at the COOH-terminal end) of the frog alpha tropomyosin. The same phosphorylated peptide was recovered in low yields from both rabbit skeletal alpha and cardiac tropomyosin. The presence of covalently bound phosphate in alpha tropomyosin and its absence in the beta component of rabbit skeletal muscle was suggested by 31P NMR spectroscopy. The amino acid sequences around the phosphorylation sites of frog and rabbit tropomyosin are identical. Because this sequence is not similar to any other known phosphorylation site in proteins, this indicates the existence of either specific kinase or phosphatase that can distinguish between alpha and beta tropomyosins. In a model proposed for the head-to-tail overlap of alpha tropomyosin molecules, one O-phosphoserine-283 residue could form a salt linkage with lysine-6 on one side of the overlap region and another with lysine-12 on the other side. This would predict a difference in the stability of polymers of phosphorylated and nonphosphorylated alphaalpha and alphabeta dimers of tropomyosin.
A rationale for stabilization of oxygen-labile enzymes: application to a clostridial hydrogenase.
Authors: Klibanov A M , Kaplan N O , Kamen M D
Published: May 2006

A general procedure for stabilization of O2-labile enzymes exploiting "salting out" of oxygen from the microenvironment in the molecular layers immediately adjacent to charged surfaces of polyionic solid adsorbents has been developed. Empirical verification of this rationale is provided. The half-life of air inactivation of the O2-labile hydrogenase (EC 1.12.7.1) from Clostridium pasteurianum is increased 20- to 25-fold simply by adsorption (noncovalent binding) in dilute Tris.HCl buffer on common anion exchange supports such as DEAE-cellulose or Dowex 1-X2. Predicted increases in degree of stabilization by using more densely charged adsorbents (such as polyethyleneimine-cellulose), as well as bulkier solvent counter-anions, are found; half-lives for air inactivation for the bound hydrogenase can be increased to 3000-fold longer than that of the free enzyme. Most of the total catalytic activity, assayed as H2 evolution from dithionite mediated by methyl viologen or ferredoxin, is retained, whereas the expected suppression of H2 uptake in the reverse reaction is observed.
Histone packing in the nucleosome core particle of chromatin
Authors: Carter C. W.
Published: May 2006

The chromatin core particle DNA conformation deduced in broad outline by Finch
et al.
[Finch, J. T., Lutter, L. C., Rhodes, D., Brown, R. S., Rushton, B., Levitt, M. & Klug, A. (1977)
Nature
269, 29-36] can be described in detail using other available experimental results. Histone binding sites compatible with the pattern of pancreatic DNase I digestion (Simpson, R. T. & Whitlock, J. P., Jr. (1976)
Cell
9, 347-353; Noll, M. (1977)
J. Mol. Biol.
116, 49-71; Lutter, L. C. (1977)
J. Mol. Biol.
117, 53-69] lend to core particle DNA pseudosymmetry characteristic of molecular point group
D
3
. DNA symmetry and pseudosymmetry, in turn, imply equivalence and quasi-equivalence properties of the histone packing arrangement that support the following deductions: (
i
) One and only one α
2
β
2
histone tetramer, presumably (H3)
2
(H4)
2
, can serve as a stable subassembly within the histone octamer. (
ii
) There is a unique, strand-specific way to assign DNA binding domains to the arginine-rich histones (H3 and H4). (
iii
) Histones H3 and H4 alone should suffice to impose a supercoiled structure on DNA, as is observed experimentally, because only the tetramer can mimic a screw dislocation and thereby complement the screw symmetry of the DNA supercoil. (
iv
) The two slightly lysine-rich histones H2A and H2B are probably responsible, each in a different way, for dividing the eukaryotic chromatin fiber into discrete subunits. (
v
) The proposed arrangement of four distinct proteins appears to be a minimum formal requirement for making nucleosomes; that is, for introducing regularly spaced supercoiled DNA folds without also allowing formation of an indefinitely long (and genetically inert) DNA superhelix.
Modulation of the conformation of a membrane glycosyltransferase by specific lipids.
Authors: Beadling L , Rothfield L I
Published: May 2006

Fluorescence techniques were used to study conformational changes in UDPgalactose:lipopolysaccharide alpha,3-galactosyltransferase (EC 2.4.1.44). Intramolecular energy transfer was measured from the single tryptophan residue in the peptide to a pyridoxal phosphate group linked to the same peptide via a reduced Schiff's base. Significant differences in energy transfer were seen when the enzyme was studied in aqueous solution and after entry into a phospholipid-lipopolysaccharide matrix, paralleling the restoration of its catalytic activity. Further differences were seen when the structures of the phospholipids and lipopolysaccharides were changed. Application of the Förster theory indicated that the changes in energy transfer resulted from changes in distances between the chromophores and/or changes in their relative orientations. The results suggest that entry of this membrane protein into a lipid matrix induces a change in conformation of the protein and that other alternative conformations can be induced by further changes in its lipid environment.
Fluorescent localization of membrane sites in glycerinated chicken skeletal muscle fibers and the relationship of these sites to the protein composition of the Z disc
Authors: Lazarides Elias , Granger Bruce L.
Published: May 2006

Didansyl derivatives of amino acids and
N
-phenyl-1-naphthylamine were used to localize membrane hydrophobic sites in glycerol-extracted chicken skeletal muscle fibers. Epifluorescence microscopy revealed that such sites coincide with the distribution of mitochondria, the transverse tubular (T) system and the sarcoplasmic reticulum (SR). They are specifically associated with myofibril Z lines and occasionally extend from one Z plane to the next longitudinally along the muscle fiber. The hydrophobic probes interact noncovalently with the Z lines, and their induced fluorescence can be eliminated by exposure of the myofibrils to ionic detergents, nonionic detergents, or phospholipase C, before or after addition of the hydrophobic label.

Extraction of glycerinated fibers with 0.6 M KI removes the majority of sarcomeric actin and myosin and leaves a scaffold of longitudinally interconnected Z planes. Membrane fluorescence remains tightly associated with these Z planes and with the remnant mitochondria. Shearing of such scaffolds results in the cleavage of the longitudinal connections and the production of large sheets of interconnected, close-packed Z discs in a honeycomb-like array. Comparison of the localization of two Z disc proteins, desmin and α-actinin, with that of the membrane material reveals that α-actinin is localized in the interior of each myofibril Z disc whereas both desmin and the membrane material surround each disc. Thus, glycerination and KI extraction of muscle fibers leaves remnants of T system and SR membranes tightly associated with the Z disc honeycomb lattice. Because the Z discs are connected at their peripheries through the T system appear to the plasma membrane, desmin and this membrane structure appear to be connected throughout the whole Z plane up to and including the plasma membrane. The congruent localization of desmin and the T system strongly suggests that this molecule mediates the adhesion of this membrane system around each Z disc.
In vitro
system from
Escherichia coli
that catalyzes generalized genetic recombination
Authors: Potter Huntington , Dressler David
Published: May 2006

This paper reports an
in vitro
system for studying generalized genetic recombination. The system uses extracts from
Escherichia coli
as a source of enzymes and plasmid DNA molecules as substrates. Unit-size plasmid DNA rings are converted into genomes fused at a region of DNA homology at a frequency of about 5-10% over a period of hours. That the fused structures are the result of recombination is supported by two lines of evidence. When two partially homologous plasmids of different sizes are used as substrates for the
in vitro
system, intermediates containing one plasmid of each size are obtained. Furthermore, fused structures are not formed with high efficiency in extracts from recombination-deficient (Rec A
-
) cells.

DNA synthesis does not appear to be required for the formation of the recombination intermediates; it is possible to omit DNA precursors from the reaction mixture and, furthermore, to develop the fused structures even in the presence of chaintermininating dideoxynucleoside triphosphates.

The structures formed
in vitro
have the basic properties of recombination intermediates previously recovered from intact cells. That is, two genomes are demonstrably fused at a region of homology. However, in one way the molecules formed
in vitro
have a property less frequently observed
in vivo
—the fused genomes often appear to be connected over an extended region of homology ranging up to several hundred base pairs in length. This extended region of pairing may indicate the presence of two crossover connections very close together and, as will be discussed, may provide an insight into the mechanism by which the recombination intermediate is formed.
Matrix protein from Escherichia coli outer membranes forms voltage-controlled channels in lipid bilayers.
Authors: Schindler H , Rosenbusch J P
Published: May 2006

Matrix protein from Escherichia coli was integrated into planar lipid bilayers. The incorporated protein generates aqueous channels across these membranes. Channels are induced irreversibly by voltage, and their number is proportional to the protein content of the membrane and stays constant over hours. They are uniform in size, with a diameter of about 1 nm and a single-channel conductance of 0.14 nS in 0.1 M NaCl. In addition to ionic conductance, the channels allow free diffusion of small, uncharged molecules. Channels assume either an open or a closed state. Membrane potentials shift this two-state equilibrium distribution in favor of closed channels, an observation that explains both negative resistance and inactivation at high potentials. Channels are not randomly distributed in the membrane but interact cooperatively within aggregates. The smallest entity inducible consists of three channels.
Retention of susceptibility to mitogens after direct dansylation of viable human lymphocytes.
Authors: Coleman P S , Ewell A J , Good R A
Published: May 2006

The covalently binding fluorescent probe 5-dimethylamino-1-naphthalenesulfonyl (dansyl) chloride was affixed directly to the plasma membrane of viable human peripheral blood lymphocytes via a solid phase transfer method utilizing Sephadex G-10 as the transfer vehicle. After dansylation, lymphocytes retain maximal short-term viability. Dansyl, as the protein conjugate or as the free acid, does not appear to penetrate the cells to any significant extent. Dansylated mixed lymphocyte cultures respond to lectin mitogen stimulation for at least 72 hr. Furthermore, differential response of dansylated lymphocytes in culture to three plant lectin mitogens provides a clue to the binding loci of concanavalin A with respect to phytohemagglutinin and pokeweed mitogen on the lymphocyte surface receptors for these lectins. The ability to sustain functionally responsive dansylated lymphocytes for several days in culture suggest that such probe-tagged cells may be useful in elucidating aspects of the plasma membrane in the regulation of cell behavior.
A gene on human chromosome 6 functions in assembly of tissue-specific adenosine deaminase isozymes
Authors: Koch George , Shows Thomas B.
Published: May 2006

In human tissues, adenosine deaminase (ADA) (adenosine aminohydrolase; EC 3.5.4.4) activity can be separated by gel electrophoresis into several isozymes. A structural gene (
ADA
) on chromosome 20 codes for the “erythrocyte” isozyme, ADA-1, which is also expressed in some nonerythroid tissues. Nonerythroid cells also differentially express five ADA “tissue isozymes” of a greater molecular weight than ADA-1. Each ADA tissue isozyme has a characteristic electrophoretic mobility and tissue distribution. It has been suggested that these ADA tissue isozymes are composed of ADA-1 and other components. We report that the expression of one of these tissue isozymes, ADA-d, is dependent upon
ADA
on chromosome 20 and another gene on chromosome 6 which functions in the assembly of the ADA tissue isozymes. In human-mouse hybrids segregating human chromosomes, chromosome 6
+
,20
+
hybrids express both ADA-1 and ADA-d; chromosome 6
-
,20
+
hybrids express only ADA-1; while 6
+
,20
-
hybrids have no human ADA activity. ADA-d formation also occurs
in vitro
by self-assembly when an extract of human erythrocytes or chromosome 6
-
,20
+
hybrids is mixed with a homogenate of chromosome 6
+
,20
-
hybrids. The gene on chromosome 6, designated
ADCP
, codes for an adenosine
d
eaminase
c
omplexing
p
rotein. The product of
ADCP
presumably combines with ADA-1 to form the ADA tissue isozymes. The data are consistent with the hypothesis that the distribution of enzymatic activity between ADA-1 and the tissue isozymes depends on the expression of the gene for ADA complexing protein, while the differences in the electrophoretic mobilities of the ADA isozymes, except ADA-1, are generated, as suggested by others, by the degree of glycosylation of the complexing protein.
Requirement of S-adenosyl-L-methionine-mediated methylation for human monocyte chemotaxis.
Authors: Pike M C , Kredich N M , Snyderman R
Published: May 2006

The chemotactic response of motile bacteria requires the methylation of specific proteins by S-adenosyl-L-methionine. To determine whether methylation is required for the chemotaxis of human leukocytes, we studied the effects of inhibition of S-adenosyl-L-methionine-mediated methylation on monocyte chemotactic responsiveness. Methylation was inhibited in monocytes by treating the cells with substances that produced elevations in intracellular S-adenosyl-L-homocysteine, a competitive inhibitor of S-adenosyl-L-methionine methylation. Treatment of isolated monocytes with the adenosine deaminase inhibitor, erythro-9-(2-hydroxy-3-nonyl)adenine, plus exogenous adenosine and L-homocysteine thiolactone increased intracellular S-adenosyl-L-homocysteine levels by as much as 1500-fold. Concomitant with increases in S-adenosyl-L-homocysteine were a decrease in monocyte protein carboxy-O-methylation as well as a marked inhibition of monocyte chemotactic responsiveness. Conditions that almost completely inhibited methylation and chemotaxis did not depress monocyte phagocytosis, indicating that this latter function either is independent of S-adenosyl-L-methionine-mediated methylation or is extremely resistant to inhibition of such reactions by S-adenosyl-L-homocysteine. These studies indicate that S-adenosyl-L-methionine-mediated methylation is required for the chemotaxis of eukaryotic cells and that the chemotactic and phagocytic functions of human monocytes have different requirements for methylation.
Murine Ia and human DR antigens: homology of amino-terminal sequences.
Authors: Allison J P , Walker L E , Russell W A , Pellegrino M A , Ferrone S , Reisfeld R A , Frelinger J A , Silver J
Published: May 2006

Murine Ia and human DR antigens were isolated and purified by immunoprecipitation and sodium dodecyl sulfate/polyacrylamide gel electrophoresis with allo- and xenoantisera, respectively. The I-A subregion antigen consists of two chains, designated Aalpha and Abeta, with molecular weights of 35,000 and 26,000, respectively. The I-C subregion antigen likewise consists of two chains, designated Calpha and Cbeta, with molecular weights of 32,000 and 29,000, respectively. Under nonreducing conditions, the Cbeta chain migrates appreciably more rapidly on sodium dodecyl sulfate/polyacrylamide gels than the reduced Cbeta chain, reflecting the presence of an intrachain disulfide bond. The human DR antigen is also a two-chain unit and contains DRalpha and DRbeta components with molecular weights of 34,000 and 28,000, respectively. The DRbeta chain migrates more rapidly before reduction than afterward, like the murine Cbeta chain. The DRbeta and Cbeta chains are also strikingly homologous if a single amino acid shift is imposed on one of those chains. Thus, human DR antigens strongly resemble the murine I-C subregion antigens.
Neurocytotoxic antibodies in serum of patients with systemic lupus erythematosus
Authors: Bluestein Harry G.
Published: May 2006

Sera from patients with systemic lupus erythematosus (SLE) have been tested for antibody to a human neuronal cell line, SK-N-SH, derived from a metastatic neuroblastoma. With a complement-dependent
51
Cr-release cytotoxicity assay, 75% of SLE sera had antineuronal activity mediated by IgM antibody. Most of the sera containing this IgM neurocytotoxic antibody were also cytotoxic to the human glial cell lines A-172 and U-118MG. The sera did not mediate complement-dependent
51
Cr release when tested against normal human fibroblasts or peripheral blood lymphocytes. IgG antineuronal antibody was detected in 17% of SLE sera by an antibody-dependent, cell-mediated cytotoxicity assay with SK-N-SH cells as targets.

The relationship of IgM and IgG antineuronal antibodies to the antilymphocyte antibodies present in SLE sera was evaluated by a series of crossabsorption experiments using SK-N-SH cells to remove neuronal antibodies and WI-L2 (human lymphoblasts) to remove antilymphocyte antibodies. Most of the complement-dependent neurocytotoxicity was not removed by multiple lymphoblast absorptions, although the WI-L2 cells readily removed lymphocytotoxic activity as assayed on normal lymphocytes. Absorption with SK-N-SH cells removed most, but not all, of the lymphocytotoxic antibody. Thus, although lymphocytotoxic antibodies reactive with membrane antigens shared by lymphocytes and brain may constitute a subset of the antibodies to neural cells, most of the antineuronal activity in SLE serum is directed at other cell surface antigens expressed on neuronal and glial cells. Should they gain access to the brain, these antibodies have the potential to produce neuropathology, but their presence in the nervous system of patients with the neuropsychiatric manifestations of SLE is yet to be documented.
Gaucher disease: isolation and comparison of normal and mutant glucocerebrosidase from human spleen tissue.
Authors: Pentchev P G , Brady R O , Blair H E , Britton D E , Sorrell S H
Published: May 2006

Glucocerebrosidase was purified 26,000-fold from spleens from normal humans and from patients with Gaucher disease (Gaucher spleens). The specific activities of the purified normal and mutant enzymes with glucocerebroside as substrate were 8.5 X 10(5) and 5.4 X 10(4) nmol/mg of protein per hr, respectively. The ratio of enzymatic activities was constant throughout the isolation procedure. The two enzymes appeared to be similar by other parameters such as substrate affinity, heat lability, and pH optimum. Immunotitration with glucocerebrosidase antiserum showed equivalent quantities of crossreacting material in extracts of normal and Gaucher spleens. These data strongly suggest that the genetic basis of Gaucher disease is a strucutral mutation of glucocerebrosidase. The results of sodium dodecyl sulfate gel electrophporesis also indicate that there are differences between the normal and the Gaucher disease enzyme.
Release of neurotransmitters and depletion of synaptic vesicles in cerebral cortex slices by alpha-latrotoxin from black widow spider venom.
Authors: Tzeng M C , Cohen R S , Siekevitz P
Published: May 2006

The effect of alpha-latrotoxin on cerebral cortex slices was studied by both biochemical and morphological methods. This toxin greatly stimulates the release of preloaded gamma-amino[3H]butyric acid from cortex slices. The response increases linearly with dose. The release is not dependent on the presence of extracellular Ca2+, and therefore it is not mediated by the release of other transmitters from other types of neurons. In contrast, no significant increase in the release of a nontransmitter substance alpha-amino[14C]isobutyric acid is observed. Since previously we have shown that alpha-latrotoxin stimulated the release of acetylcholine and norepinephrine from cortex slices, it appears that the toxin probably selectively releases all neurotransmitters. The toxin also profoundly depletes the synaptic vesicle population in boutons in the cortex slices. The results suggest that the release of neurotransmitter and the depletion of synaptic vesicle in boutons are manifestations of a single action of the toxin. Therefore, alpha-latrotoxin can be used as a good tool for the identification of neurotransmitters and in studies on the mechanism of neurotransmitter release.
Temperature-sensitive mutants of mouse hepatitis virus produce a high incidence of demyelination.
Authors: Haspel M V , Lampert P W , Oldstone M B
Published: May 2006

Mutagenesis of mouse hepatitis virus with 5-azacytidine or 5-fluorouracil yielded several temperature-sensitive mutants. Mutants have been isolated that dramatically enhance the production of demyelinating disease over that previously noted with the wild-type virus. This reproducible model should now make possible the precise elucidation of the pathogenic mechanism and molecular basis of this virus-induced demyelination.
Nucleotide sequences related to the transforming gene of avian sarcoma virus are present in DNA of uninfected vertebrates.
Authors: Spector D H , Varmus H E , Bishop J M
Published: May 2006

We have detected nucleotide sequences related to the transforming gene of avian sarcoma vius (ASV) in the DNA of uninfected vertebrates. Purified radioactive DNA (cDNAsarc) complementary to most of all of the gene (src) required for transformation of fibroblasts by ASV was annealed with DNA from a variety of normal species. Under conditions that facilitate pairing of partially matched nucleotide sequences (1.5 M NaCl, 59 degrees), cDNAsarc formed duplexes with chicken, human, calf, mouse, and salmon DNA but not with DNA from sea urchin, Drosophila, or Escherichia coli. The kinetics of duplex formation indicated that cDNAsarc was reacting with nucleotide sequences present in a single copy or at most a few copies per cell. In contrast to the preceding findings, nucleotide sequences complementary to the remainder of the ASV genome were observed only in chicken DNA. Thermal denaturation studies of the duplexes formed with cDNAsarc indicated a high degree of conservation of the nucleotide sequences related to src in vertebrate DNAs; the reductions in melting temperature suggested about 3--4% mismatching of cDNAsarc with chicken DNA and 8--10% mismatching of cDNAsarc with the other vertebrate DNAs.
Inhibition of protein synthesis initiation by oxidized glutathione: Activation of a protein kinase that phosphorylates the α subunit of eukaryotic initiation factor 2
Authors: Ernst Vivian , Levin Daniel H. , London Irving M.
Published: May 2006

Oxidized glutathione (GSSG) (0.02-0.5 mM) inhibits reticulocyte lysates by a mechanism similar to that observed in heme deficiency. Incubation of hemin-supplemented postribosomal supernates with GSSG results in the activation of a translational inhibitor [I(GSSG)]. The activation of I(GSSG) is enhanced by the presence of an energy-regenerating system. The simultaneous addition of 1 mM dithiothreitol blocks the activation of the GSSG-induced inhibitor; however, once inhibitor is formed, its activity is not affected by 1 mM dithiothreitol. GSSG-treated postribosomal supernates and partially purified preparations of I(GSSG) inhibit protein synthesis in hemin-supplemented lysates with biphasic kinetics. Inhibition by I(GSSG) is blocked by cyclic AMP (2-10 mM) and is potentiated by ATP (2 mM). The inhibition is also blocked or reversed by eukaryotic initiation factor eIF-2. The activation of I(GSSG) is accompanied by an increased cyclic AMP-independent protein kinase activity which phosphorylates the 38,000-dalton component (α subunit) of eIF-2; however, GSSG treatment of supernates does not alter the activity of the cyclic AMP-independent protein kinase activity that phosphorylates the 49,000-dalton polypeptide component (β subunit) of eIF-2. These data indicate that GSSG treatment of reticulocyte lysates results in the activation of a protein kinase with inhibitory and phosphorylation properties similar to those of the heme-regulated cyclic AMP-independent protein kinase which is activated in heme deficiency.
Mechanism of the in vitro breakdown of guanosine 5'-diphosphate 3'-diphosphate in Escherichia coli.
Authors: Heinemeyer E A , Richter D
Published: May 2006

Degradation of guanosine tetraphosphate (ppGpp) involves an enzyme associated with the ribosomal fraction from spoT+ strains of Escherichia coli. Double-label experiments with pp[3h]gpp, pp[3H]Gpp, or pp[3H]Gpp as substrate strongly suggest that ppG is the degradation product and that the enzyme releases two phosphates coordinately from the 3' position of ppGpp. In the absence of pppA this reaction proceeds in an uncoupled fashion, yielding ppG and PPi, but in the presence of pppA the decay is considerably enhanced and a pppA-ppi exchange reaction occurs in which the 3'-pyrophosphoryl group of ppGpp displaces the gamma and beta phosphates of pppA. Sodium PPi at 4 m7 inhibits decay of ppGpp regardless of whether or not pppA is present.
Primary organization of nucleosome core particle of chromatin: sequence of histone arrangement along DNA.
Authors: Mirzabekov A D , Shick V V , Belyavsky A V , Bavykin S G
Published: May 2006

A high-resolution map for the arrangement of histones along DNA in the nucleosome core particle has been determined by a sequencing procedure based on crosslinking histones to the 5'-terminal DNA fragments produced by scission of one DNA strand at the point of crosslinking. The position of histones on DNA has been identified by measuring the length of crosslinked DNA fragments. The results demonstrate that each of the histones is arranged within several adjacent or dispersed DNA segments of a little less than 10 nucleotides in length. Histone-free intervals are located between these segments at the regular distances of about (10)n nucleotides from the 5' end of the DNA and are likely to face one side of the DNA helix. Histones appear to be arranged in a similar manner on both DNA strands and do not form "locks" around DNA. A linearized model of the core particle is proposed.
Does irehdiamine kink DNA?
Authors: Dattagupta N. , Hogan M. , Crothers D. M.
Published: May 2006

We report equilibrium, relaxation kinetic, and transient electric dichroism studies on the complex of the diamino steroid irehdiamine A with DNA. The results are consistent with a β-kinked structure for the complex at saturation, with a kink in the DNA structure induced by a bound steroid every second base pair. The results that favor this hypothesis include an apparent length decrease of rod-like bacterial DNA molecules when only a small amount of drug is bound, followed by an apparent length increase at saturation. The limiting dichroism amplitude implies a substantial increase in the tilt of the bases relative to the orientation axis; at saturation the base UV transition moments are tilted about 31° from the plane perpendicular to the orientation axis. Because of the direction of polarization of the 260-nm transition moments, the results indicate that the tilt of the bases must be predominantly in the short rather than the long axis of the base pair. The large hyperchroism of the complex is consistent with loss of base stacking, as required by a kinked structure. The kinetic results imply a bimolecular reaction mechanism, with a temperature-dependent association rate constant of roughly 10
8
M
-1
sec
-1
, and a dissociation rate constant of about 5 × 10
3
sec
-1
, nearly independent of temperature. The association activation energy and apparent reaction enthalpy vary from 12 to 22 kcal mol
-1
; heat is absorbed on complex formation as expected for loss of base-stacking interactions. An anomalous result of the experiments is the larger apparent length increase (13%) exhibited by two eukaryotic DNAs, compared to 6% for three prokaryotic DNAs. Differences were also observed in the kinetic properties of the complexes.
Monovalent antibodies against MM-creatine kinase remove the M line from myofibrils.
Authors: Wallimann T , Pelloni G , Turner D C , Eppenberger H M
Published: May 2006

Column-purified antibodies against creatine kinase (EC 2.7.3.2) from chicken skeletal muscle (the homodimeric isoenzyme designated MM-CK) bind specifically to the M lines of chicken pectoral muscle myofibrils. Incubation of myofibrils with monovalent Fab' fragments of these antibodies solubilizes most of the myofibril-bound creatine kinase, concomitantly removing most of the electron-dense material from the M lines. This strongly indicates that MM-CK is an integral part of the M-line structure and is consistent with the suggestion that MM-CK molecules form the M bridges that are responsible for the principle M-line substriations.
Molecular orientation of bacteriorhodopsin within the purple membrane of Halobacterium halobium.
Authors: Hayward S B , Grano D A , Glaeser R M , Fisher K A
Published: May 2006

The direction of orientation of the protein bacteriorhodopsin within the purple membrane of Halobacterium halobium has been determined by selected-area electron diffraction of membranes preferentially oriented by adsorption to polylysine. Purple membrane is known to adsorb preferentially to polylysine by its cytoplasmic surface at neutral pH and by its extracellular surface at low pH. To maintain the adsorbed membranes in a well-ordered state in the electron microscope, an improved technique of preparing frozen specimens was developed. Large areas of frozen-hydrated specimens, devoid of bulk water, were obtainable after the specimen was passed through a Ca stearate film at an air-water interface. High-resolution microscopy was used to relate the orientation observed in the electron diffraction patterns to the orientation of the projected structure that is obtained from images. We have found that the three-dimensional structure determined by Henderson and and Unwin [Henderson, R. & Unwin, P.N.T. (1975) Nature 257, 28--32] is oriented with the cytoplasmic side uppermost--i.e., the helices fan outward on the cytoplasmic side of the membrane.
Rat oocyte maturation
in vitro
: Relief of cyclic AMP inhibition by gonadotropins
Authors: Dekel Nava , Beers William H.
Published: May 2006

The hormone-independent, spontaneous maturation that rat oocytes undergo
in vitro
can be inhibited by derivatives of cyclic AMP and inhibitors of cyclic nucleotide phosphodiesterase. In this study, we have shown that this inhibition of maturation can be partially relieved by preparations of ovine and rat luteinizing hormone or follicle-stimulating hormone. The ability of gonadotropins to foster the resumption of maturation in cultures of cyclic AMP-inhibited oocytes suggests that this system is suitable for studies of the hormonal control of oocyte development. The dose and time dependency of the response to gonadotropins has been examined in order to study the role of these hormones in oocyte maturation and to compare this effect to other known responses of the cumulus-oocyte complex. These studies show that highly purified preparations of rat gonadotropins are less effective inducers of maturation than the more commonly used, but considerably less purified, preparations of ovine gonadotropins. Almost complete relief of inhibition is observed, however, when the oocytes are exposed to a combination of rat luteinizing hormone and follicle-stimulating hormone. Oocyte maturation was not influenced by the sex steroids progesterone or 17β-estradiol. Our results suggest that: (
i
) cyclic AMP is involved in the intrafollicular inhibition of oocyte maturation; (
ii
) both gonadotropins are required for maximal stimulation of the resumption of oocyte meiosis; and (
iii
) steroids are not involved in this response to gonadotropins.
Age-dependent relaxation of gene repression: Increase of endogenous murine leukemia virus-related and globin-related RNA in brain and liver of mice
Authors: Ono Tetsuya , Cutler Richard G.
Published: May 2006

A progressive loss in the ability of cells to maintain their normal specialized states of differentiation could be the common denominator underlying much of the physiology and pathology associated with the mammalian aging process. We investigated this possibility by searching for an age-dependent derepression of endogenous genes in tissues in which they are not normally expected to be expressed. Complementary DNA (cDNA) probes to globin genes and to the murine leukemia type C RNA virus (MuLV) genome were used to detect the presence of RNA complementary to these genes in RNA extracted from brain and liver in young and old mice. Significant amounts of globin RNA were found in brain nuclei and cytoplasm. No age difference was found in the globin RNA sequences present, but the number of globin RNA molecules increased from about 15 in 6-month to 34 in 27-month-old animals for nuclei and 280 in 6-month to 500 in 27-month-old animals for cytoplasm. Similar results were found for liver. RNA complementary to the MuLV cDNA probe was also found but, in contrast to globin, the different RNA sequences increased in both brain and liver nuclei from about 45% of the MuLV genome in 6-month to 72% in 27-month-old animals. The number of MuLV-related RNA molecules remained constant at about 22 and 38 per nuclei for brain and liver, respectively. Derepression of genes of this magnitude could result in a time-dependent increase in virus-related diseases and a general deterioration of the organism.