bluuebunny/crossref_metadata_2025 huggingface dataset:
Biochemical mechanisms of glucose-6-phosphate dehydrogenase deficiency.
Authors: Morelli A , Benatti U , Gaetani G F , De Flora A
Published: May 2006

A solid-phase radioimmunoassay for human glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP+ 1-oxidoreductase; EC 1.1.1.49) was developed that allowed the specific activity of this enzyme protein to be measured in lysates from whole erythrocyte populations, in lysates from erythrocytes of different ages, and in purified samples. The enzyme was highly purified from erythrocytes of single donors by a simple procedure of affinity chromatography with insolubilized adenosine 2',5'-bisphosphate. These techniques were used in an attempt to elucidate the molecular mechanisms leading to deficiency of glucose-6-phosphate dehydrogenase activity in two genetic variants of the enzyme, i.e., the Mediterranean and the Seattle-like variants. The results indicate that the lowered activity of erythrocytes containing the Mediterranean variant of glucose-6-phosphate dehydrogenase is related to an enhanced rate of degradation of a catalytically defective protein synthesized at a nearly normal rate. Synthesis of a normally functioning protein and an increased breakdown of it are involved in the Seattle-like variant of the enzyme.
Energies of polypeptides: theoretical conformational study of polyglycine using quantum mechanical partitioning.
Authors: Scheiner S , Kern C W
Published: May 2006

A method is developed for evaluating the total energy of polypeptides based on a combination of quantum mechanical and empirical potentials. Adjacent and nonadjacent peptide units are allowed to interact through these respective means. Our hybrid procedure is applied to a study of polyglycine and compared to the results obtained by the method of Scheraga and coworkers. We find the alpha helical conformation of a single strand of polyglycine to be most stable in vacuo. Other less-stable configurations include the 3(10) helix, the 2(7) ribbon structure, and the fully extended conformation.
Transduction of a bacterial gene into mammalian cells.
Authors: Upcroft P , Skolnik H , Upcroft J A , Solomon D , Khoury G , Hamer D H , Fareed G C
Published: May 2006

The transduction of an Escherichia coli gene into mammalian cells is described. A supressor tRNA gene was linked to a simian virus 40 (SV40) vector in vitro and the recombinant was used to transfect rat embryo cells and monkey kidney cells. The hybrid SV40 genome, SV40-su+ III, retained genetic information required for autonomous replication and cellular transformation and had a 1300-base-pair DNA segment in the late gene region (between the restriction endonuclease sits Hpa II at 0.735 and EcoRI at 0/1.0 on the SV40 genetic map) replaced by an 870-base-pair bacterial DNA segment containing the suppressor tRNA gene, su+ III (tRNATyrsu+III). The structure and fate of the SV40-su+III chimera were determined by DNA reassociation kinetic analysis and restriction enzyme cleavage of the total cellular DNA from transformed rat embryo cells and persistently infected monkey cells. Hybridization with radiolabeled probes specific for vector (SV40) or su+III DNA sequences revealed primarily nonintegrated or free hybrid genomes. In cloned lines of both cell types, the bacterial DNA segment was recovered intact, as judged by the length of the segment excised by restriction endonucleases and its ability to hybridize to the radiolabeled bacterial DNA probe and not to the SV40 probe.
Large and small tumor antigens from simian virus 40 have identical amino termini mapping at 0.65 map units.
Authors: Paucha E , Mellor A , Harvey R , Smith A E , Hewick R M , Waterfield M D
Published: May 2006

Large and small tumor (T)antigens of simian virus 40 were synthesized in vitro with L-cell extracts that had been treated by the method of Palmiter to prevent amino-terminal acetylation of nascent proteins. Partial amino-terminal amino acid sequences of both forms of T-antigen were determined and found to be identical. Methionine residues were located at positions 1 and 14, a lysine residue at position 3, and leucine residues at positions 5, 11, 13,16, 17, and 19. These amino acid sequence data match perfectly the amino acid sequence predicted from a sequence of nucleotides in the E strand of simian virus 40 DNA which begins near the junction between HindII/III fragments A and C at about 0.65 map units. This strongly suggests that the sequence coding for the amino terminus of both proteins is located at this position. Furthermore, the data are consistent with a model for the synthesis of both forms of T-antigen that predicts that (i) small T-antigen is coded for by a sequence of nucleotides from the 5' end of the early region and (ii) large T-antigen is coded for by nucleotide sequences from two noncontiguous regions of simian virus 40 DNA.
31P nuclear magnetic resonance studies of bioenergetics and glycolysis in anaerobic Escherichia coli cells.
Authors: Ugurbil K , Rottenberg H , Glynn P , Shulman R G
Published: May 2006

31P nuclear magnetic resonance spectra of glycolyzing, anaerobic Escherichia coli cells and their perchloric acid extracts were obtained at 145.7 MHz. Time-dependent intracellular concentrations of nucleoside di- and triphosphates, Pi, and sugar phosphates were measured during glycolysis with 2-min resolution, while intracellular and extra-cellular pH values were monitored simultaneously. Upon glucose addition, anaerobic E. coli cells rapidly produce acids and develop a transmembrane pH gradient (delta pH). Glycolysis rates were calculated from the changes in the external pH. It was found that glycolysis rates are strongly dependent on internal pH, sharply decreasing when the pH drops below approximately 7.2. The ATPase inhibitor, dicyclohexylcarbodiimide (DCCD), prevented NTP hydrolysis and inhibited delta pH formation. The uncoupler, carbonyl cyanide p-triflouromethoxyphenyl hydrazone (FCCP), drastically reduced both the delta pH and the NTP level. When the cells were previously treated with DCCD, FCCP collapsed the delta pH while the NTP levels remained high. It is concluded that ATP produced by glycolysis is hydrolyzed by the membrane ATPase to generate a delta pH and that FCCP stimulates ATP hydrolysis by ATPase and collapses the proton gradient.
Decreased microviscosity of membrane lipids in leukemic cells: Two possible mechanisms
Authors: Petitou M. , Tuy F. , Rosenfeld C. , Mishal Z. , Paintrand M. , Jasnin C. , Mathe G. , Inbar M.
Published: May 2006

Steady-state fluorescence polarization studies with the fluorescent lipid probe 1,6-diphenyl 1,3,5-hexatriene were done to determine the degree of microviscosity of cellular membrane lipids and serum lipoproteins in human normal donors and leukemic patients. The results show a marked decrease in microviscosity of cellular membrane lipids in both intact lymphocytes and isolated cellular plasma membranes obtained from leukemic patients in clinical relapse as compared to intact lymphocytes and isolated cellular plasma membranes obtained from normal donors and leukemic patients in complete clinical remission. Concomitant to these dynamic changes in cellular membrane lipids, the degree of microviscosity of lipids in the blood serum of leukemic patients in clinical relapse is markedly reduced as compared to serum obtained from normal donors and leukemic patients in complete clinical remission. Moreover, an
in vitro
incubation of leukemic lymphocytes with normal low density lipoproteins results in an increased microviscosity of cellular membrane lipids. In addition to the interrelation between cellular membrane lipids and serum lipoproteins, plasma membrane vesicles with a high degree of lipid microviscosity were isolated from the blood serum and pleural effusion of leukemic patients in clinical relapse. Such membrane vesicles could not be detected in normal serum. Therefore, we suggest that the two major mechanisms associated with the decreased microviscosity of membrane lipids in human leukemic cells are an abnormal exchange in lipids between the leukemic cell surface membrane and leukemic serum lipoproteins and an exfoliation of plasma membrane vesicles with a high degree of microviscosity from the cell surface of leukemic cells.
General relativity, the Dirac equation, and higher symmetries
Authors: Ward J. C.
Published: May 2006

An invariant derived from the curvature of a
Sp
(2) fiber bundle over a Riemannian manifold reduces to the Dirac Lagrangian for flat space-time.
Somatic cell origin of teratocarcinomas
Authors: Mintz Beatrice , Cronmiller Claire , Custer R. Philip
Published: May 2006

Malignant teratocarcinomas arise from developmentally totipotent normal stem cells. Whether the targets are embryonal somatic cells or germinal cells has long been a matter of controversy. Past experiments on teratocarcinoma induction by ectopic grafting of early rodent embryos or fetal germinal ridges have remained ambiguous because embryos ordinarily soon form germ cells, and parthenogenetic germ cells form “embryos.” In order to interrupt the developmental cycle at its most telling point, day 6 (egg-cylinder stage) mouse embryos of genetically sterile types were grafted; in such grafts, only a terminal residue of totipotent embryonal somatic (“ectoderm”) cells is available, and subsequent germ cell development is severely impaired. One graft series, from

S1
J

/+ matings, comprised 25%

S1
J
/S1
J

presumptive sterile embryos; these grafts formed tumors containing embryonal carcinoma cells as often (47%) as did control +/+ grafts (41%) on the same genetic background. In another series, from
W
/+ matings, tumors of the sterile
W/W
genotype were
individually
identified by means of a closely linked marker, phosphoglucomutase (PGM, EC 2.7.5.1;
Pgm-1
locus), coding for electrophoretic enzyme variants and incorporated into the stock. Four tumors were obtained (out of 16) that had the PGM-1D phenotype diagnostic for
W/W
, and that also contained embryonal carcinoma cells. Therefore, the malignancy arises here in susceptible
somatic
embryonal stem cells at the terminal stage of their capacity for totipotency. Other teratocarcinomas—whether induced or spontaneous—of ostensible germ-cell origin by parthenogenesis may also depend upon development of the same somatic target cells before neoplastic conversion can occur. A general model based on these experiments is proposed for all malignancies: Malignant transformation of a particular kind of normal stem cell may be possible only when that stem cell has progressed to the threshold of further differentiation.
Dispersal in relation to carrying capacity
Authors: Grant P. R.
Published: May 2006

Dispersal of the herbivorous vole
Microtus pennsylvanicus
from grassland to woodland was studied in an experimental field system during spring to autumn 1969. Dispersal first occurred when there was at least 100 times more energy available than was required by the population. Sodium and phosphorus were in short supply in the food. By feeding selectively or copiously, voles could make up nutrient deficits and still consume only 10% of what was available. However, calculations show that depletion of the food was potentially severe in the forthcoming winter; consumption of energy- and nutrient-sufficient food had the potential of approaching 100%. These results suggest the following explanation of presaturation dispersal. Nutrients may be more limiting to herbivores than is total energy. Selective or copious harvesting becomes increasingly necessary as density increases. Natural selection, acting upon known genetic variation in dispersal propensity, has favored a dispersal response to environmental conditions that presage food shortage. Aggressive behavior and other forms of interactive behavior are the means by which land-tenured breeding individuals control their access to food resources and by which nontenured individuals are excluded and induced to disperse. Herbivore populations in general are limited well below carrying capacity. Carrying capacity may have been overestimated by ignoring chemical quality of the food, but the relationship is still probably true. The above explanation helps us to understand it. Because animals need to feed selectively, exploitation is based on cost-benefit balances and is less than total.
Magnetic susceptibility studies of laccase and oxyhemocyanin.
Authors: Dooley D M , Scott R A , Ellinghaus J , Solomon E I , Gray H B
Published: May 2006

The magnetic susceptibility of Rhus vernicifera laccase has been remeasured over the temperature range 5-260 K. In contrast to our previous results [Solomon, E.I., Dooley, D. M., Wang R.-H., Gray, H.B., Cerdonio, M., Mogno, F. & Romani, G. L. (1975) J. Am. Chem. Soc. 98, 1029-1031] linear chi versus T-1 behavior was observed. The susceptibility of Limulus polyphemus oxyhemocyanin has also been measured in the range 5-260 K. Only weak paramagnetism, attributable to dissolved oxygen and a small amount of paramagnetic impurities, was observed. Analysis of the data establishes a lower limit of 550 cm-1 for J, consistent with our earlier work. The temperature dependence of the susceptibility of laccase is quantitatively accounted for by the presence of two paramagnetic copper ions (types 1 and 2) per enzyme molecule. Curie law behavior at low temperatures rules out significant interaction between the two coppper types, indicating that these redox centers are well separated (several angstroms) and are not connected by bridging ligands. Formulation of the type 3 site as binuclear Cu(II) requires J greater than or equal to 500 cm-1.
Use of computerized multidimensional scaling to compare immunoelectron microscopy data with protein near-neighbor information: application to the 30S ribosome from Escherichia coli.
Authors: Gaffney P T , Craven G
Published: May 2006

A three-dimensional model of the protein arrangement in the Escherichia coli 30S ribosome was constructed by using computerized multidimensional scaling of immunoelectron microscope data. This enabled data comparison between the new electron microscope technique and other methods such as crosslinking, chemical protection, affinity labeling, energy transfer, and assembly interactions. The immunoelectron microscopy data are reasonably consistent with those from other sources. Reasons for some inconsistent data are discussed and our calculation of the dimensions of the proteins, both globular and elongated, are summarized.
Nucleotide sequence homology at the 3' termini of RNA from vesicular stomatitis virus and its defective interfering particles.
Authors: Keene J D , Schubert M , Lazzarini R A , Rosenberg M
Published: May 2006

Vesicular stomatitis virus (VSV) and defective interfering (DI) particle RNAs were labeled at their 3' ends by using RNA ligase and cytidine 3',5'-bis[32P]phosphate. The RNAs were subjected to partial digestion with alkali and analyzed by oligonucleotide fingerprinting in two dimensions. VSV and DI particle RNAs have complete sequence homology for the first eight bases from the 3' end. The following four positions contain three mismatched nucleotides in which guanosine residues in one strand are replaced by uridine residues in the other. There is again complete homology for the next five bases (positions 13-17). The locations of purine residues within the sequence were confirmed by partial digestion with RNase T1 and RNase U2 and separation by size on 20% acrylamide gels. The latter method also indicated that sequences of VSV and DI particle RNAs diverge beyond the 18th nucleotide from the 3' termini.
Reconstitution of purified detergent-soluble HLA-A and HLA-B antigens into phospholipid vesicles.
Authors: Engelhard V H , Guild B C , Helenius A , Terhorst C , Strominger J L
Published: May 2006

Purified detergent-soluble human histocmpatibility antigens (HLA-A and HLA-B) were reconstituted into phospholipid vesicles by mixing the protein and lipid together in the presence of either octylglucoside (octyl-beta-D-glucopyranoside) or deoxycholate and removing the detergent by dialysis. The resulting preparation consisted of lipid vesicles containing all or most of the added protein. The protein in the vesicles was antigenically active, as demonstrated by specific binding to anti-beta2-microglobulin IgG-Sepharose beads and by specific inhibition of alloantibody and complement-mediated cytotoxicity. Protein incorporated into vesicles at a protein/phospholipid ratio of 1:10 showed an asymmetric distribution of the HLA-A and HLA-B molecules, with virtually all of the antigens oriented facing the external medium. Cleavage experiments with proteases showed that the molecule was attached to the vesicle membrane via the COOH terminus, consistent with its proposed structure in intact cellular plasma membranes. Electron micrographs of the vesicles showed 50-60 A knobs on the outer surface similar to structures observed for other membrane proteins. HLA-A and HLA-B could also be incoporated into vesicles together with Semliki Forest virus membrane proteins. The resulting preparations should be useful in defining the molecular interactions involving HLA-A and HLA-B antigens in the immune response.
Visualization by fluorescence of the binding and internalization of epidermal growth factor in human carcinoma cells A-431.
Authors: Haigler H , Ash J F , Singer S J , Cohen S
Published: May 2006

The binding and internalization of epidermal growth factor (EGF) in human epithelioid carcinoma cells (A-431), which have approximately 2.6 X 10(6) receptors per cell, has been followed with 125I-labeled EGF and by fluorescence microscopy. We have prepared a fluorescent derivative of EGF that is biologically active and retains substantial binding affinity for cell receptors. After binding of this derivative to cells at 6 degrees, the cellular borders were prominently stained and the fluorescence on the remainder of the membrane was uniform. Upon warming of these cells to 37 degrees for 10 min, the surface fluorescence diminished and randomly distributed endocytotic vesicles appeared in the cytoplasm. After 20 min at 37 degrees these fluorescent vesicles formed a perinuclear ring. The binding of EGF to the surface of these cells was also visualized by immunofluorescence using rabbit antibodies to EGF and rhodamine-labeled goat anti-rabbit antibodies. We did not detect large fluorescent clusters or cap formation in these experiments. These data provide direct confirmation of the previous biochemical data that suggested that cell membrane-bound EGF is rapidly internalized.
Biochemical evidence that "new" influenza virus strains in nature may arise by recombination (reassortment).
Authors: Desselberger U , Nakajima K , Alfino P , Pedersen F S , Haseltine W A , Hannoun C , Palese P
Published: May 2006

Oligonucleotide analysis of two avian influenza A viruses (Hav6N2 and Hav6Nav4) isolated in nature showed identical or almost identical patterns for the corresponding M and HA genes; 24 of 25 and 13 of 13 large oligonucleotides were indistinguishable by two-dimensional gel analysis. On the other hand, remarkable differences in the oligonucleotide patterns of the remaining genes were observed. Only 2 of 11 oligonucleotide spots of the NS gene, 10 of 27 spots of the NA/NP genes, and 22 of 49 spots of the P genes were indistinguishable between the two strains. On the basis of this observation that at least two genes of these viruses are virtually identical whereas others show easily detectable differences, we conclude that the two avian strains are related to each other by a recombinational event. In addition, it was found that animals in nature can be doubly infected with influenza viruses. Both lines of evidence strongly suggest that recombination is at least one mechanism by which "new" influenza virus strains emerge in nature.
Induction of ouabain-resistant mutations in C3H 10T1/2 mouse cells by ultraviolet light.
Authors: Chan G L , Little J B
Published: May 2006

Ouabain-resistant mutants were induced in C3H mouse embryo 10T1/2 fibroblasts by exposure to ultraviolet light, thus making available an in vitro system for studying mutagenesis and oncogenic transformation in parallel. 86Rb uptake studies showed that biochemical mutants at the plasma membrane Na+,K+ transport ATPase (EC 3.6.1.3) locus were being selected for in this system. The optimal expression time for the mutants was found to depend on the dose of ultraviolet light, as was the induced mutation frequency. The ratio of transformation to mutation frequencies was found to be on the order of 10 for four different doses, suggesting that the target size in the cellular genome for transformation may be approximately 10 times the size of the Na+,K+ ATPase gene. We propose that both transformation and mutation induction can now be quantitatively studied in this single system.
Sites of integration of reticuloendotheliosis virus DNA in chicken DNA.
Authors: Keshet E , Temin H M
Published: May 2006

The pattern of integration of spleen necrosis virus (SNV) DNA in DNA from a large population of SNV-infected chicken cells was studied by nucleic acid hybridization with iodinated viral RNA by the blotting technique of Southern. SNV DNA was found to be integrated at multiple sites in acutely infected chicken cells. Concomitant with the transition from acute to chronic infection, a shift in the pattern of integration was observed. The majority of integrated SNV DNA found in acutely infected cells was absent from chronically infected cells. This result is consistent with the hypothesis that the cell death that occurs after infection of avian cells with reticuloendotheliosis viruses is a consequence of the multiple integrations of the provirus. Viral DNA was also integrated at multiple sites in chronically infected cells. However, infectious viral DNA molecules in chronically infected cells migrated in a uniform manner in agarose gel electrophoresis after EcoRI digestion (which does not cut viral DNA), indicating that not all integrated SNV copies are equally infectious.
Structure determination of crystalline substances by diffraction methods: Philosophic concepts and their implementation (A Review)
Authors: Karle Jerome
Published: May 2006

Structure determination of single crystals by diffraction methods is reviewed in terms of the philosophical and mathematical aspects of the analytical techniques that are used. A key problem concerns the need to determine the relative phases of the scattered rays. A major advance in treating this problem resulted from recognition that useful consequences ensue from the fact that electron densities in crystals are non-negative functions. Advantage is also taken of the fact that the problem is usually greatly overdetermined by the number of experimental data. For biological macromolecules, the data available are more limited in range and accuracy and great use is made of the introduction of suitable heavy atom moieties. The developments in crystal structure analysis have had a considerable impact on progress in many scientific disciplines.
Pompeiu's problem on discrete space
Authors: Zeilberger Doron
Published: May 2006

Let [unk] be a finite family of finite subsets of the
n
-dimensional lattice

Z
n

, and let τ denote the group of all translations of

Z
n

. We shall here consider the
Pompeiu problem
for the family [unk]—namely, to determine when the only function

f:Z
n

→ C such that [Formula: see text] is the zero function.
Purine metabolism in cultured human fibroblasts derived from patients deficient in hypoxanthine phosphoribosyltransferase, purine nucleoside phosphorylase, or adenosine deaminase.
Authors: Thompson L F , Willis R C , Stoop J W , Seegmiller J E
Published: May 2006

Rates of purine synthesis de novo, as measured by the incorporation of [14C]formate into newly synthesized purines, have been determined in cultured human fibroblasts derived from normal individuals and from patients deficient in adenosine deaminase, purine nucleoside phosphorylase, or hypoxanthine phosphoribosyltransferase, three consecutive enzymes of the purine salvage pathway. All four types of cell lines are capable of incorporating [14C]formate into purines at approximately the same rate when the assays are conducted in purine-free medium. The purine overproduction that is characteristic of a deficiency in either the transferase or the phosphorylase and that results from a block in purine reutilization can be demonstrated by the resistance of [14C]formate incorporation into purines to inhibition by hypoxanthine in the case of hypoxanthine phosphoribosyltransferase-deficient fibroblasts and by resistance to inhibition by inosine in the case of purine nucleoside phosphorylase-deficient fibroblasts.
Relative loss of oncogenic potency of mouse leukemia virus (Gross) after prolonged propagation in tissue culture.
Authors: Gross L , Dreyfuss Y
Published: May 2006

Since the initial development of the "passage A" mouse leukemia virus in 1957, this virus has been propagated in our laboratory by serial passage in newborn C3H(f) mice. At the present time, 10(-2)-10(-3) dilutions in physiological saline solution of this mouse-passaged virus induce lymphatic leukemia in practically all inoculated mice after a latency of 3-5 months. On the other hand, when the same virus was propagated on NIH 3T3 mouse embryo cells in tissue culture for more than 10 years, its leukemogenic potency became considerably reduced. Recent bioassay experiments carried out in our laboratory demonstrated that after such prolonged propagation in tissue culture this virus now induced leukemia in less than 15% of the inoculated suckling C3H(f) mice; only undiluted or 10% dilutions of the tissue culture fluid (very occasionally 10(-2) or 10(-3) dilutions) induced leukemia after a prolonged latency varying from 5.5 to 18 months. The passaged and the tissue-culture-grown virus strains are identical immunologically and indistinguishable in their morphology when examined by electron microscopy. The tissue-culture-grown virus, attenuated in its leukemogenic potency, does not, however, confer immunity against a challenge with the mouse-passaged virus.
Determination of lipid A and endotoxin in serum by mass spectroscopy
Authors: Maitra Shyamal K. , Schotz Michael C. , Yoshikawa Thomas T. , Guze Lucien B.
Published: May 2006

A quantitative technique for determining lipid A content of endotoxin added to serum by combined gas chromatography-mass spectrometry is described. This technique uses detection of the β-hydroxymyristic acid content of
Salmonella minnesota
R595 lipopolysaccharide by selected ion monitoring at atomic mass unit of 315.4 The fatty acids produced on hydrolysis of serum containing lipopolysaccharide were extracted and the methyl esters were made. Silica gel chromatography was used to separate methyl esters of hydroxy fatty acids from other fatty acid methyl esters. Trimethylsilyl ether derivatives of the hydroxy fatty acid methyl ester fraction were quantitated by this technique. As little as 200 fmol of β-hydroxymyristic acid could be detected.
Purification of an endogenous protein inhibitor of the high affinity binding of gamma-aminobutyric acid to synaptic membranes of rat brain.
Authors: Toffano G , Guidotti A , Costa E
Published: May 2006

In a medium without Na+, gamma-aminobutyric acid (GABA) binds at 0 degrees to freshly prepared crude synaptic membranes from rat cerebral cortex with an apparent dissociation constant of 218 nM. An endogenous inhibitor of the Na+-independent GABA binding was removed from these membranes by freezing and thawing and by repeated washing with Tris citrate buffer (50 mM, pH 7.1) containing 0.01% Triton X-100. As a result, the crude synaptic membranes bind GABA at 0 degrees with two dissociation constants, 20 nM and 111 nM. The endogenous inhibitor is a thermostable (95 degrees for 15 min) acidic protein of approximately 1.5 X 10(4) daltons. It was purified (about 500-fold) with a series of procedures including gel chromatography on Sephadex G-100 and ion exchange chromatography on Dowex 50W-X8 (H+). Recombination of the purified endogenous inhibitor with crude synaptic membrane preparations deprived of the endogenous inhibitor showed that the purified inhibitor blocked noncompetitively the sites for high-affinity GABA binding. A role of this endogenous regulator in the functional of GABA-ergic synapses is discussed.
One class of meromorphic solutions of general two-dimensional nonlinear equations, connected with the algebraic inverse scattering method
Authors: Chudnovsky D. V.
Published: May 2006

For systems of nonlinear equations having the form [

L
n

- (∂/∂
t
),

L
m

- (∂/∂
y
)] = 0 the class of meromorphic solutions obtained from the linear equations [Formula: see text] is presented.
Stability of local rings of dimension 2
Authors: Shah Jayant
Published: May 2006

The notion of stability of a local ring arises naturally in investigating completed moduli spaces via geometric invariant theory. A scheme corresponding to a boundary point of a moduli space of nonsingular varieties cannot have unstable singular points. This paper reports some results concerning the stability of surface singularities. If a two-dimensional Cohen-Macaulay local ring R is semistable, its multiplicity must be less than seven and either equal to or 1 less than its embedding dimension. If the multiplicity of R is equal to its embedding dimension, the singularity of R must be a simple or cyclic elliptic singularity or the nonnormal limit of such a singularity. The results for the case when the multiplicity of R is less than its embedding dimension are still incomplete; the possible singularities that may arise when the multiplicity of R is equal to 2 or 3 are described.
Kinetic factors and form determination of the head of bacteriophage T4.
Authors: Showe M K , Onorato L
Published: May 2006

The form of the bacteriophage T4 prehead is described by its icosahedral symmetry, its diameter, and its length. We show how each of these parameters is regulated during prehead formation and ascribe specific form-determining functions to the prehead proteins. The major protein of the head shell can assemble in several different forms. The structure produced in vivo depends on the rate of synthesis of the major protein relative to the rates of synthesis of minor shell proteins and the major core protein. From our observations, we propose a model for form determination of the prehead and suggest a pathway for the evolution of its prolate shape.
Amplification of the proliferative response to alloantigen by a factor present in an extract of syngeneic thymic lymphoid cells.
Authors: Wright P W , Loop S M
Published: May 2006

A synergistic interaction in the proliferative response to alloantigen has been previously noted when intact thymus cells are cultured with post-thymic (peripheral) lymphoid cells. In the present study, a factor extracted from the thymus has been shown to similarly enhance the reactivity of syngeneic lymph node cells and thus to retain the amplifier activity of intact thymus cells. The factor has no effect on lymphoid cell proliferation in the absence of alloantigen. Cells with amplifier activity are found in highest concentration in the thymus but also may be detected in spleen cells that are nonadherent to nylon wool. The factor is shown in these experiments to be derived from thymic lymphoid cells and to act primarily upon post-thymic (peripheral) lymphoid cells. As such, this factor appears to be distinct from various other thymus factors that have been localized to thymic reticuloepithelial elements and that are thought to effect predominantly the differentiation of T-cell precursors.
Isolation of a herpesvirus-specific DNA polymerase from tissues of an American patient with Burkitt lymphoma.
Authors: Allaudeen H S , Bertino J R
Published: May 2006

A DNA polymerase (DNA nucleotidyltransferase) has been partially purified from a neck mass of an American patient with Burkitt lymphoma and separated from the cellular DNA polymerases. The molecular weight of the enzyme was approximately 90,000. The enzyme differs from the cellular DNA polymerases, but resembles herpes-virus-induced DNA polymerase in its primer template preference, high monovalent cation requirement for activity, and sensitivity to phosphonoacetate. Enzyme activity was inhibited specifically by an antibody directed against herpes-simplex-virus-induced DNA polymerase but not by antibodies directed against DNA polymerase alpha of HeLa cells and DNA polymerase gamma of a normal human lymphoblast cell line, NC37. Although serum of the patient with Burkitt lymphoma contained high Epstein-Barr virus titer, addition of the serum to the assay mixture did not have any effect on the activity of Burkitt lymphoma DNA polymerase. Tissues from spleen and liver of the patient with Burkitt lymphoma did not contain the herpes-virus-induced DNA polymerase. Detection of the herpes virus polymerase in the Burkitt lymphoma tissue provides additional evidence for the association of Epstein-Barr virus with this malignancy.
Isolation and characterization of colonic tissue-bound antibodies from patients with idiopathic ulcerative colitis
Authors: Das Kiron M. , Dubin Richard , Nagai Tadanori
Published: May 2006

To determine if specific anticolon antibodies bound to colonic mucosa occur in ulcerative colitis, we obtained surgical specimens of colon from five patients with ulcerative colitis, one patient with diverticulitis, and three control subjects with carcinoma. Two specimens of ileum and cecum were also obtained from patients with Crohn ileocolitis. Tissue was homogenized and washed and bound Ig was eluted by citrate buffer, pH 3.2. Concentrated eluates of all specimens from patients with ulcerative colitis reacted with antisera to κ and γ and not with antisera to α and μ chains. Corresponding eluates from all other specimens did not react with these antisera, but did react with antialbumin. The presence of IgG in ulcerative colitis eluates was also determined by immunoelectrophoresis, immunocoprecipitation, and affinity chromatography with antisera against human IgG.

Indirect immunofluorescence and uptake of radiolabeled antibody demonstrated antigenic sites in diseased colonic epithelium of biopsy specimens obtained from six additional patients with ulcerative colitis and three patients with idiopathic proctitis, but not in patients with Crohn disease, nonspecific diarrhea, and bacillary dysentery and control subjects. Although the role of colitis colon-bound antibody in the pathogenesis of ulcerative colitis is unclear, local antibody-antigen complexes may initiate colonic epithelial cytolysis by various immunologically mediated mechanisms.
Coupled enzyme systems in a vesicular membrane: oxidative phosphorylation as an example.
Authors: Hill T L
Published: May 2006

We consider a small vesicle whose membrane transports a ligand L into the vesicle through enzymatic units of type A and transports L out of the vesicle through units of type B. Oxidative phosphorylation in mitochondria provides an example, in which L is H+. The kinetics of the two membrane systems (A and B) are coupled through the concentration of L in the vesicle. This interdependence causes the combined membrane system (A plus B) to simulate a single system whenever the net ligand transport into the vesicle is zero. For example, in oxidative phosphorylation, it was thought for some time that ATP was synthesized by the respiratory chain system (via an "active intermediate"). We give the simplest possible analyses of this kind of coupled system, which is very common, by using two-state enzymes for both A and B above. A numerical example is included that illustrates respiratory control in a qualitative way: although the respiratory chain flux by itself does not depend on ADP concentration, the steady-state flux of the coupled systems (respiratory chain and reverse ATPase) does depend on ADP concentration through the interior ligand (H+) concentration.
Yeast ribosomal DNA genes are located on chromosome XII.
Authors: Petes T D
Published: May 2006

Two lines of experimental evidence indicate that the repeating ribosomal DNA (rDNA) genes of the yeast Saccharomyces cerevisiae are located on chromosome XII. First, the rDNA genes are linked mitotically to genes that have been previously mapped to chromosome XII. Second, yeast strains that have two copies of the chromosome containing the rDNA genes in every strain examined also have two copies of chromosome XII; this is not true for the other yeast chromosomes. These data also establish that in mitosis most of the rDNA genes in yeast are not extrachromosomal.
Evolutionary effects of contagious and familial transmission
Authors: Uyenoyama M. , Feldman M. W. , Cavalli-Sforza L. L.
Published: May 2006

Two models involving non-Mendelian transmission of a discrete valued trait through within- and across-generation contagion are proposed in an investigation of the joint evolution of phenotype and genotype. A single locus with two alleles determines susceptibility to contagion. The incorporation of within-generation contagious transmission extends the parameter ranges allowing phenotypic polymorphism and introduces a new phenotypic equilibrium configuration. The latter is characterized by a threshold in the initial value of the trait which determines whether the trait can increase. Phenotypic evolution is accelerated by within-generation contagion, but the rate of genetic evolution is retarded relative to that under uniparental transmission across generations. The second model studied allows the trait to be acquired, at genotype-dependent rates, even if the transmitting parent does not have the trait. Both the pattern of phenotypic transmission and the selection on the trait influence the course of evolution. Some important aspects of the structure of the one locus-two allele model are shown to be preserved with more alleles. At equilibrium, the leading eigenvalue of the transmission-selection matrix assumes the role of genotypic fitness.
Humoral factor that specifically regulates prothrombin (factor II) levels (coagulopoietin-II).
Authors: Karpatkin M , Karpatkin S
Published: May 2006

Prothrombin (Factor II) was decreased in rabbits by injection of a goat antiserum to prothrombin. When plasma from these rabbits was injected into normal animals, circulating prothrombin increased in the recipients, suggesting transfer of a humoral regulating factor ("coagulopoietin-II"). This coagulopoietin-II resisted boiling for 20 min. On Sephadex G-50 gel filtration, it remained in the retained volume, suggesting a molecular weight of less than 30,000. In an in vitro liver system, prothrombin increased in the incubation medium in the presence of coagulopoietin-II.
Tetraethylammonium: Voltage-dependent action on endplate conductance and inhibition of ligand binding to postsynaptic proteins
Authors: Adler Michael , Oliveira Antonio C. , Eldefrawi Mohyee E. , Eldefrawi Amira T. , Albuquerque Edson X.
Published: May 2006

Tetraethylammonium (Et
4
N
+
) ions depressed the amplitude and accelerated the decay rate of spontaneously occurring and nerve-evoked endplate currents (EPCs) in frog sartorius muscle. The relationship between peak EPC amplitude and membrane potential became nonlinear in the presence of 100 μM Et
4
N
+
, and with drug concentrations of 250 μM or greater the current-voltage relationship exhibited negative conductance in the hyperpolarized region. Et
4
N
+
modified the exponential dependence of the EPC decay on membrane potential such that the decays between -150 and -50 mV were abbreviated and voltage independent but remained near control levels at more positive membrane potentials. The minimal effective concentration of Et
4
N
+
for altering the EPC time course was 10, and maximal effects were attained with 100 μM. Little additional shortening in the EPC decay phase was detected on raising the drug concentration to 1000 μM. Acetylcholine noise analysis revealed a voltage-dependent reduction in the mean channel open time, which was comparable in magnitude to the shortening in the EPC decay, and a depression of single-channel conductance. In concomitant biochemical studies, Et
4
N
+
was found to inhibit the binding of both [
3
H]acetylcholine and [
3
H]perhydrohistrionicotoxin to receptor-rich membranes from the electric organ of
Torpedo ocellata
with
K
i
values of 200 μM and 280 μM, respectively. These results suggest that Et
4
N
+
interacts with both the acetylcholine receptor and its associated ionic channel. The voltage-dependent actions of Et
4
N
+
are attributed to blockade of the ionic channel in closed as well as open conformation.
Gene 2 protein of bacteriophage T7: purification and requirement for packaging of T7 DNA in vitro.
Authors: LeClerc J E , Richardson C C
Published: May 2006

The gene 2 protein of bacteriophage T7 is required for a late stage of T7 DNA replication because T7 gene 2 mutants fail to form normal concatemeric structures during the processing of newly synthesized T7 DNA. Extracts of gene 2 mutant phage-infected cells are unable to package T7 DNA into phage heads to form viable phage, as determined by an in vitro packaging assay for T7 DNA. Packaging activity can be stimulated greater than 100-fold in mutant extracts by the addition of extract prepared from cells infected with phage carrying a wild-type T7 gene 2, thus providing a complementation assay for the gene 2 protein. With this assay, the gene 2 protein has been purified to approximately 50% homogeneity. Purified preparations of the protein inhibit the activity of Escherichia coli RNA polymerase but have little effect on the activity of T7 RNA polymerase but have little effect on the activity of T7 RNA polymerase. The requirement for the gene 2 protein during T7 DNA replication may involve inactivation of E. coli RNA polymerase because the antibiotic rifampicin, a specific inhibitor of E. coli RNA polymerase, can substitute for the gene 2 protein in the in vitro packaging assay.
Transposition of the Escherichia coli insertion element gamma generates a five-base-pair repeat.
Authors: Reed R R , Young R A , Steitz J A , Grindley N D , Guyer M S
Published: May 2006

We have determined DNA sequences surrounding the termini of the Escherichia coli insertion element gamma delta, both at its normal locus on the F (fertility) factor and at three different sites of insertion into the plasmid pBR322. After transposition, a five-base-pair pBR322 sequence is duplicated and appears in direct orientation adjacent to each end of the element. No such duplication flanks the ends of gamma delta in F, and there is no apparent homology between the sequences surrounding gamma delta in F and the five-base-pair duplications generated by insertion. These findings suggest that the duplications are not essential for transposition and that they do not act to direct gamma delta to a homologous site in the target chromosome. In addition, we find that the 35-base-pair inverted repeat that comprises the termini of gamma delta is strikingly similar in sequence to the ends of both the ampicillin-resistance transposon Tn3 and a 200-nucleotide-long sequence on the plasmid pSC101 which has been shown to mediate recombination with phage f1 replicative form. Within the terminal region, there is a specific heptanucleotide sequence common to each of the above elements and to bacteriophage Mu, all of which generate five-base-pair repeats upon insertion.
Peptide maps comparing subunits of maize chloroplast and type II nuclear DNA-dependent RNA polymerases.
Authors: Kidd G H , Bogorad L
Published: May 2006

Both one- and two-dimensional peptide mapping techniques have been used to compare the 180-kilodalton subunits from maize chloroplast and type II nuclear DNA-dependent RNA polymerases (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6). Despite their similar molecular mass, these 180-kilodalton subunits are not the same. Also, two-dimensional tryptic maps of the 160-, 43-, and 28-kilodalton polypeptides from maize type II nuclear RNA polymerase and of the 140-, 42-, and 27-kilodalton polypeptides from maize chloroplast RNA polymerase show that each of these six polypeptides is unique.
Characterization of the protein kinase activity of avian sarcoma virus src gene product.
Authors: Maness P F , Engeser H , Greenberg M E , O'Farrell M , Gall W E , Edelman G M
Published: May 2006

The avian sarcoma virus src gene product, p60src, has been purified 650-fold from cytoplasmic extracts of the rat tumor cell line RR1022 by using ammonium sulfate fractionation, hydrophobic chromatography on omega-aminohexyl agarose, and ion exchange chromatography on phosphocellulose. Partially purified p60src is a monomer, with a native molecular weight of about 60,000 and an apparent pI of 6.0. In immunoprecipitates, p60src catalyzed phosphorylation of anti-p60src IgG heavy chains within the variable (VH) domain, which contains the heavy chain portion of the antigen combining site. Crude preparations of p60src contained phosphatase activity able to cleave phosphate from IgG heavy chains; this activity was removed by the purification procedure, and partially purified p60src could phosphorylate the heavy chain of specific antibody in solution. Furthermore, purified p60src catalyzed phosphorylation in solution of the general protein kinase substrate, alpha-casein, strengthening the hypothesis that it may in fact function as a protein kinase in vivo.
A 3.0-A resolution study of nucleotide complexes with aspartate carbamoyltransferase.
Authors: Honzatko R B , Monaco H L , Lipscomb W N
Published: May 2006

The binding sites of CTP, CDP, 5-BrCTP, and ATP to the allosteric site of aspartate carbamoyltransferase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2) have been found in electron-density maps obtained at about 3 A resolution from x-ray diffraction studies of single crystals. The activator ATP binds in the anti conformation, whereas the inhibitor 5-BrCTP binds in the syn conformation. Both activator and inhibitor bind to the same local region of the enzyme. All of the cytidine nucleotides show important interactions of the base with the protein. The triphosphate conformations are similar, whereas the terminal phosphate of CDP occupies the site of the gamma-phosphate of CTP, thus implying a protein-nucleotide interaction at this site. These results are then related to biochemical studies.
Significant structure theory applied to electrolyte solution
Authors: Lee Jong Myung , Jhon Mu Shik , Eyring Henry
Published: May 2006

The significant structure theory has been successfully applied to an aqueous NaCl solution. Liquid water is assumed to have a domain structure and the ions are hydrated by water molecules. The partition function is composed of the partition function for the water and that for the salt, and the excess free energy term from the Debye—Hückel theory is also added. The thermodynamic properties, such as molar volume, vapor pressure, entropy of vaporization, and heat capacity, as well as the dielectric constant are calculated over the whole concentration ranges and wide temperature ranges. The agreement between theory and experiment is satisfactory.
Lower bounds for eigenvalues of self-adjoint problems
Authors: Gundersen Gary G.
Published: May 2006

The equation
y
″ + [λ -
q
(
x
)]
y
= 0 on (0, ∞) or (-∞, ∞), in which
q
(
x
) → ∞ as
x
→ ∞ or
x
→ ± ∞, has a complete set of eigenfunctions with discrete eigenvalues {λ

n

}

n
=0

∞
. We derive an inequality that contains λ

n

, by using a quick and elementary method that does not employ a comparison theorem or assume anything special. Explicit lower bounds for λ

n

can often be easily obtained, and three examples are given. The method also gives respectable lower bounds for λ

n

in the classical Sturm—Liouville case.