bluuebunny/crossref_metadata_2025 huggingface dataset:
Unified picture of mechanisms of catalysis by carboxypeptidase A.
Authors: Breslow R , Wernick D L
Published: May 2006

We have reported evidence that an anhydride intermediate is not involved in the hydrolysis of typical peptide substrates by carboxypeptidase A (peptidyl-L-amino-acid hydrolase, EC 3.4.12.2), and we describe further evidence here. Recently an anhydride intermediate has been detected in the hydrolysis of an ester substrate by this enzyme. Other evidence also suggests that esters and peptides may not be cleaved by the same type of mechanism. A possible explanation is that the substrate carbonyl and a water molecule are always aligned between glutamate-270 and the zinc atom of the enzyme, but not always in the same sequence. With peptides the carbonyl is coordinated to zinc, and the water is delivered by glutamate acting as a general base. Esters are weaker ligands, and in some cases the ester carbonyl may not displace water from zinc. This would lead to a nucleophilic mechanism, with glutamate-270 forming an anhydride while zinc-aquo serves as a Brönsted acid. This picture is consistent with other evidence on ester cleavage, and resolves the otherwise baffling discrepant data on peptide as compared to ester substrates.
Radiationless relaxation in “large” molecules: Experimental evidence for preparation of true molecular eigenstates and Born-Oppenheimer states by a coherent light source
Authors: Zewail A. H. , Orlowski T. E. , Jones K. E.
Published: May 2006

Photon absorption and emission by molecules that undergo radiationless transitions are examined using the single modes of lasers having well-defined coherence properties. Contrary to the usual beliefs, where it is assumed that the molecule is prepared in a Born-Oppenheimer singlet state and then “crosses-over” to other states (vibrationally “hot” singlets and/or triplets), it is shown
experimentally
that the true eigenstates of the molecule can be prepared, even in “large” molecules, if the laser correlation time is relatively long and the molecular relaxation is made slow. On the other hand, lasers with short (psec) correlation time have yielded
effectively
the singlet Born-Oppenheimer state, which has a much shorter lifetime than the true eigenstates. Effects of magnetic fields and temperature are also reported. The former changes the amount of mixing amongst the Born-Oppenheimer states. The latter, on the other hand, swings the molecule from being “small” (i.e., sparse vibronic structure with long lifetimes) to being “large” (i.e., dense statistical distribution of levels) since the relaxation between levels is very effective at high temperatures. Finally, the results of this work show that the words
fluorescence
and
phosphorescence
in their strict meaning are misleading if the true eigenstates, which may contain both singlet and triplet character, are prepared.
High superconducting transition temperatures of new rare earth ternary borides
Authors: Matthias Bernd T. , Corenzwit E. , Vandenberg J. M. , Barz H. E.
Published: May 2006

A new group of ternary borides has been found that show either ferromagnetism or superconductivity. Their general formula is MRh
4
B
4
where M is a transition or rare-earth element. Their superconducting transition temperatures range from approximately 2.5 K for the Sm compound to approximately 12 K for the Lu compound.
Synthesis and activation of mitotic Ca2+-adenosinetriphosphatase during the cell cycle of mouse mastocytoma cells.
Authors: Petzelt C , Auel D
Published: May 2006

The activity of a Ca2+-adenosinetriphosphatase (ATP phosphohydrolase, EC 3.6.1.3) increases during the mitotic phase of synchronized mouse mastocytoma P-815X2 cells. The enzyme is synchronized mouse mastocytoma P-815X2 cells. The enzyme is synthesized mainly during a distinct period of the interphase and is activated at mitosis. It is thought to regulate the formation of the mitotic apparatus by controlling the concentration of Ca2+ ions at the site of formation of the mitotic spindle.
Extinction of hemoglobin inducibility in Friend erythroleukemia cells by fusion with cytoplasm of enucleated mouse neuroblastoma or fibroblast cells.
Authors: Gopalakrishnan T V , Thompson E B , Anderson W F
Published: May 2006

Friend mouse erythroleukemia cells (T3c1-2 and its subline 5000) can be induced to synthesize hemoglobin after treatment with 1.5% (vol/vol) dimethylsulfoxide. When these cells are fused with nonerythroid cells (namely, mouse neuroblastoma or L cells) hemoglobin induction is extinguished. In order to determine if the nucleus of the nonerythroid cell is necessary for this extinction, fusions were performed between mouse erythroleukemia cells and enucleated neuroblastoma or L cells. Hemoglobin induction was reduced or eliminated in clones of these hybrids even after 6 months of continuous culture. These results suggest that the cytoplasm of nonerythroid cells contains factor(s) that extinguish hemoglobin inducibility in erythroleukemic cells and that this new phenotype can be inherited.
H+/ATP ratio during ATP hydrolysis by mitochondria: modification of the chemiosmotic theory.
Authors: Brand M D , Lehninger A L
Published: May 2006

The stoichiometry of H+ ejection by mitochondria during hydrolysis of a small pulse of ATP (the H+/ATP ratio) has been reexamined in the light of our recent observation that the stoichiometry of H+ ejection during mitochondrial electron transport (the H+/site ratio) was previously underestimated. We show that earlier estimates of the H+/ATP ratio in intact mitochondria were based upon an invalid correction for scaler H+ production and describe a modified method for determination of this ratio which utilizes mersalyl or N-ethylmaleimide to prevent complicating transmembrane movements of phosphate and H+. This method gives a value for the H+/ATP ratio of 2.0 without the need for questionable corrections, compared with a value of 3.0 for the H+/site ratio also obtained by pulse methods. A modified version of the chemiosmotic theory is presented, in which 3 H+ are ejected per pair of electrons traversing each energy-conserving site of the respiratory chain. Of these, 2 H+ return to the matrix through the ATPase to form ATP from ADP and phosphate, and 1 H+ returns through the combined action of the phosphate and adenine nucleotide exchange carriers of the inner membrane to allow the energy-requiring influx of Pi and ADP3- and efflux of ATP4-. Thus, up to one-third of the energy input into synthesis of extramitochondrial ATP may be required for transport work. Since other methods suggest that the H+/site significantly exceeds 3.0, an alternative possibility is that 4 h+ are ejected per site, followed by return of 3 H+ through the ATPase and 1 H+ through the operation of the proton-coupled membrane transport systems.
Amino acid sequence of human prothrombin fragments 1 and 2.
Authors: Walz D A , Hewett-Emmett D , Seegers W H
Published: May 2006

The amino acid sequence of the nonthrombin half of human prothrombin is presented. Prothrombin fragment 1 has 155 amino acid residues as compared with 156 for the bovine equivalent. Ten gamma-carboxyglutamic acid residues are at the same location in each species. Human prothrombin fragment 2 contains 118 amino acid residues, as does the similar bovine fragment. Comparing bovine and human prothrombin fragment 1 we found 131 residues to be identical (84%). In prothrombin fragment 2, 84 residues were identical (71%). Assuming a time span of 90 million years since the radiation of several orders of placental mammals, prothrombin fragments 1 and 2 incorporated one substitution site per 100 amino acid sites every 11.2 and 6.3 million years, respectively. Internal homology is acribed to partial gene duplication, with the most likely crossover point located between residues 60-61 and residues 165-166.
Current-induced flow through living sponges in nature.
Authors: Vogel S
Published: May 2006

Flow velocities through and immediately adjacent to the excurrent openings (oscula) were measured in eight species of marine sponges in their natural environments with a two-channel thermistor flowmeter. Flow through the oscula was positively correlated with both normal and artificially augmented ambient flow in both normally pumping and inactive animals. These results indicate that the passage of water through these sponges is, in part, induced by ambient currents.
Sufficient conditions for subellipticity on weakly pseudo-convex domains
Authors: Kohn J. J.
Published: May 2006

Herein is outlined a method for studying
a priori
estimates by using the theory of ideals of functions. With this method a criterion is obtained for subelliptic estimates for the δ-Neumann problem. In case the boundary is real analytic, the theory of ideals of real-analytic functions gives a geometric interpretation of the criterion. For forms of type (
p,n
- 1), in which
n
is the complex dimension of the domain, we obtain necessary and sufficient conditions for subellipticity on pseudo-convex domains. The study of propagation of singularities for δ leads one to conjecture that, for pseudo-convex domains, with real-analytic boundaries, subellipticity for (
p,q
)-forms holds if and only if there are no complex-analytic varieties of dimension greater than or equal to
q
in the boundary. The methods described here give results concerning the sufficiency of the condition in this conjecture.
Amino acid sequence of human platelet factor 4.
Authors: Deuel T F , Keim P S , Farmer M , Heinrikson R L
Published: May 2006

Human platelet factor 4, a protein that binds heparin, has been purified to apparent homogeneity and the complete amino acid sequence of the protein has been determined. The 70-residue polypeptide chain contains no methionine, tryptophan, or phenylalanine, and contains only a single tyrosyl residue. The sequence analysis demonstrates a highly negatively charged amino-terminal region. The carboxyl-terminal region of the polypeptide is unusual in that it contains a repetitive clustering of positively charged and hydrophobic pairs of amino acids; preliminary evidence suggests that this domain may play a role in the binding of heparin.
Immunoflourescent staining of cytoplasmic and spindle microtubules in mouse fibroblasts with antibody to tau protein.
Authors: Connolly J A , Kalnins V I , Cleveland D W , Kirschner M W
Published: May 2006

tau protein isolated from porcine brain microtubules was further purified by electrophoretic elution from polyacrylamide gels and used to prepare antisera in rabbits. The antiserum to tau specifically stains mitotic spindles and a filamentous network within mouse fibroblasts when the indirect immunofluorescence technique is used. The staining of the filamentous network and mitotic spindles is identical to that observed when cells are treated with antiserum prepared against electrophoretically purified tubulin. The filamentous network observed with either serum is sensitive to Colcemid. Absorption of anti-tau serum with electrophoretically purified tubulin does not remove the immunofluorescent staining of the mitotic spindle, whereas absorption with electrophoretically purified tau protein does. Conversely, absorption of antitubulin serum with tubulin eliminates its ability to stain the mitotic spindle, whereas absorption with tau has no effect. We conclude that tau protein and tubulin are antigenically distinct proteins and that tau is an integral part of microtubules in vivo. These results also provide evidence that tau protein, or an antigenically related protein, is associated with microtubules not only in brain but also in other cell types.
Amino acid sequence of the first 217 residues of a mouse heavy chain (MOPC 47A) with a domain deletion.
Authors: Robinson E A , Appella E
Published: May 2006

Cyanogen bromide cleavage of the deleted heavy (alpha) chain of mouse IgA 47A yielded five peptides, CNBr 1-5, consisting of 34, 50, 28, 70, and 160 residues. A 217-residue NH2-terminal sequence, which comprises the variable region and the first domain of the constant region (CH1), and a 19-residue COOH-terminal sequence of the chain were obtained from the sequences of CNBr 1-4 and the NH2-terminal and COOH-terminal sequences of CNBr 5. The tryptic peptides of the remainder of the chain have been partially characterized. Comparison of these data with the sequences of other, nondeleted, chains reveals that the 47A chain terminates exactly at the end of the CH2 domain and that there are no deletions up to that point. It is concluded that the deletion in the chain is a single, large deletion consisting of the entire CH3 domain. The 47A chain also differs from other, nondeleted, mouse alpha chains derived from BALB/c strains in that it contains a labile cysteine at position 135, which is believed to participate in the light-heavy chain bond, and contains galactosamine in the hinge region. This may mean that the 47A alpha chain, in addition to being deleted, represents a mouse IgA subclass analogous to human IgA1.
Isolation of a type C RNA virus from an established human histiocytic lymphoma cell line.
Authors: Kaplan H S , Goodenow R S , Epstein A L , Gartner S , Declève A , Rosenthal P N
Published: May 2006

A type C RNA virus has been detected in the culture fluids of the SU-DHL-1 human histiocytic lymphoma cell line previously established in this laboratory. In electron micrographs, the virus closely resembled other typical mammalian type C RNA tumor viruses in size and morphology. Viral RNA-dependent DNA polymerase activity has been demonstrated in particles (densities of 1.15 and 1.22 g/ml) in the microsomal cytoplasmic fraction and in pellets of culture fluids. The enzyme is partially inhibited by antibodies to the RNA-dependent DNA polymerases of simian sarcoma virus and RD-114 virus but not by antibody to the polymerase of murine leukemia virus, suggesting some degree of relatedness to type C viruses of subhuman primate origin. Typical syncytial microplaques were induced when SU-DHL-1 cells were cocultivated with rat XC cells. Although no focus formation was noted in similarly cocultivated mouse UC1-B cell cultures, the numbers of foci induced in rat embryo fibroblasts by murine sarcoma virus were significantly increased by coinfection with the virus from SU-DHL-1 cell culture fluids. No other evidence of infectivity, inducibility, or capacity for helper rescue of defective murine sarcoma virus genomes has been detected to date in cocultivation studies with a spectrum of fibroblastic and other nonlymphoid indicator cell lines of human and other species of origin.
Pseudo-monotone operators and nonlinear elliptic boundary value problems on unbounded domains
Authors: Browder Felix E.
Published: May 2006

A general boundary value problem of variational type is considered for a general quasi-linear elliptic partial differential operator of order 2
m
in generalized divergence form. Such problems are considered on an arbitrary domain in a Euclidean space without hypotheses of boundedness on the domain or smoothness on its boundary. Contrary to the prevailing doctrine in the literature, it is shown that the corresponding operator between Banach spaces is pseudo-monotone, and that a wide variety of existence results can be derived from this fact.
Cell-to-cell stimulation of movement in nonmotile mutants of
Myxococcus
Authors: Hodgkin Jonathan , Kaiser Dale
Published: May 2006

A large number of nonmotile mutants of the gliding bacterium
Myxococcus xanthus
have been isolated and partly characterized. About [unk] of these mutants are conditional mutants of a novel kind: mutant cells become transiently motile after contact with nonmutant cells or with cells of a different mutant type. These “stimulatable” mutants fall into five phenotypic classes (types B, C, D, E, and F). Most mutants are nonstimulatable (type A) and never become motile, but type A cells (and wild-type cells) can stimulate cells of any of the other five types. Stimulatable mutants of different types are capable of stimulating each other. For example, in a mixture of B and C cells, both become motile. Linkage analysis using a generalized transducing phage has shown that each of types B, C, D, E, and F corresponds to a single distinct genetic locus. Type A mutants, by contrast, belong to at least 17 different loci. Stimulation depends on close apposition of interacting cells, because stimulation does not occur when contact between cells is prevented. It is possible that the stimulatable mutants are defective in components of the gliding mechanism that can be exchanged between cells. Alternatively, they may be defective in a system of cell communication controlling the coordinated cell movements observed in
Myxococcus
.
Nonlinear analysis of cat retinal ganglion cells in the frequency domain.
Authors: Victor J D , Shapley R M , Knight B W
Published: May 2006

We have analyzed the responses of cat retinal ganglion cells to luminosity gratings that are modulated in time by a sum of sinusoids. A judicious choice of the component temporal frequencies permits a separation of the linear and second-order nonlinear components. Y cell responses show harmonic generation and intermodulation distortion over a wide frequency range. These nonlinear components predominate over the linear components for certain types of spatial stimuli. Nonlinear components in X cells are greatly diminished in comparison. The character of the nonlinear responses provides strong constraints on prospective models for the nonlinear pathway of the Y cell.
Serotonergic neurons in the peripheral nervous system: identification in gut by immunohistochemical localization of tryptophan hydroxylase.
Authors: Gershon M D , Dreyfus C F , Pickel V M , Joh T H , Reis D J
Published: May 2006

A specific antibody to tryptophan hydroxylase [L-tryptophan, tetrahydropteridine:oxygen oxidoreductase (5-hydroxylating), EC 1.14.16.4] has been used to localize the enzyme immunohistochemically in neurons of the mammalian gut. The enzyme was found in perikarya of intestinal neurons of mice, rats, and guinea pigs. Neurons containing the enzyme survived for up to 3 weeks in organotypic tissue culture and were intrinsic to the gut. These neurons are probably serotonergic and are the first such neurons to be found in the peripheral nervous system.
Uterine peroxidase as a marker for estrogen action.
Authors: Lyttle C R , DeSombre E R
Published: May 2006

Administration of a single dose of estradiol to immature rats gives rise to the appearance of substantial amounts of peroxidase (donor:hydrogen-peroxide oxidoreductase, EC 1.11.1.7) enzyme activity in the uterus. This enzyme induction, which is inhibited by administration of actinomycin D and cycloheximide, can be detected at 4 hr after administration of estradiol, reaches a maximum level by 20 hr, and thereafter declines. The amount of uterine peroxidase seen at 20 hr after a single dose increases with dose from 0.1 to 100 microgram of estradiol. Estrone and estriol also show dose-dependent induction of peroxidase, and the quantitative peroxidase responses to these steroids follow their uterotropic capacities. The antiestrogen CI628, capable of low levels of enzyme induction by itself, can inhibit the induction due to estrogen. Solubilization of the uterine enzyme with divalent cations, especially calcium, results in a substantially increased yield of peroxidase. This extraction method provides an enzyme of about 50,000 molecular weight in distinction to the large aggregated form obtained by the usual extraction with sodium chloride.
ϕX174
cistron A
protein is a multifunctional enzyme in DNA replication
Authors: Eisenberg Shlomo , Griffith Jack , Kornberg Arthur
Published: May 2006

The
cistron A
protein induced by phage ϕX174 nicks (produces a single-strand break in) the viral strand of the superhelical ϕX duplex DNA, thereby forming a complex with the DNA. The protein, seen bound to the DNA in the electron microscope, was located in the restriction endonuclease fragment between nucleotides 4290 and 4330 on the ϕX map [Sanger, F., Air, G. M., Barrel, B. G., Brown, N. L., Coulson, A. R., Fiddes, J. C., Hutchison, C. A., III, Slocomb, P. M. Y. & Smith, M. (1977)
Nature
265, 687-695]. Replication also was initiated at this point, thus identifying the site of
cistron A
protein nicking and binding as the origin of replication.

The
cisA
-DNA complex (separated from free
cistron A
protein), upon the addition of
Escherichia coli rep
protein, ATP, and DNA binding protein, is unwound to generate a single-stranded linear [presumably the nicked (+) strand] and a circular [presumably the (-) strand] molecule. The
cisA
-DNA complex, upon the further addition of DNA polymerase III holoenzyme and deoxynucleoside triphosphates, supports replication to generate viral, single-stranded circles, as many as 15 circles per
cisA
-DNA complex.

The replicating intermediates seen in the electron microscope are a novel form of “rolling circle” [Gilbert, W. & Dressler, D. H. (1969)
Cold Spring Harbor Symp. Quant. Biol.
33, 473-485]. The 5′ end (presumably with the
cistron A
protein bound to it) is locked in the replication fork and loops back to accompany the strand-separation and replication fork around the template [(-) strand] circle. Thus, the multiple functions of
cistron A
protein include: (
i
) nicking the viral strand at the origin of replication to initiate a round of replication, (
ii
) participating in a complex which supports fork movement in strand separation and replication, (
iii
) nicking again at the regenerated origin to produce a unit-length DNA, and (
iv
) ligating the newly generated 3′-OH end to the 5′-phosphate-complexed end to form a circular viral molecule.
Binding of synthetic lactose operator DNAs to lactose repressors
Authors: Goeddel D. V. , Yansura D. G. , Caruthers M. H.
Published: May 2006

The nitrocellulose filter assay was used to study the interactions of wild-type (SQ) and tight-binding (QX86)
lac
repressors with synthetic
lac
operators 21 and 26 base pairs long. The repressor binding properties of both operators were very similar, indicating that both contain the same specific repressor recognition sites. The repressor-operator association rate constants (
k
a
) were more sensitive than dissociation rate constants (
k
d
) to changes in ionic strength. The responses of both
k
a
and
k
d
to ionic strength were relatively small compared to the effects previously observed with λh80
dlac
as operator DNA. These results suggest that under natural conditions there are electrostatic interactions between
lac
repressor and DNA regions outside of the 26 base pair operator sequence. Association rate constants for SQ repressor with either operator are higher than have been predicted for diffusion-limited reactions. We postulate that long-range electrostatic attractions between repressor and operator accelerate the association reaction. The presence of nonoperator DNA decreased association rate constants, the effect being more noticeable at an ionic strength of 0.05 M than at 0.20 M. Nonoperator DNA reduced
k
a
values for associations involving QX86 repressor to a greater extent than for those with SQ repressor. The two types of repressors also had different rate constants for interactions with synthetic operators. The values for
k
a
and
k
d
were both higher with SQ repressor than with QX86 repressor. However, the rate constants were more sensitive to ionic strength when the repressor used was QX86.
Quantum efficiency of photosynthetic energy conversion.
Authors: Chain R K , Arnon D I
Published: May 2006

The quantum efficiency of photosynthetic energy conversion was investigated in isolated spinach chloroplasts by measurements of the quantum requirements of ATP formation by cyclic and noncyclic photophosphorylation catalyzed by ferredoxin. ATP formation had a requirement of about 2 quanta per 1 ATP at 715 nm (corresponding to a requirement of 1 quantum per electron) and a requirement of 4 quanta per ATP (corresponding to a requirement of 2 quanta per electron) at 554 nm. When cyclic and noncyclic photophosphorylation were operating concurrently at 554 nm, a total of about 12 quanta was required to generate the two NADPH and three ATP needed for the assimilation of one CO2 to the level of glucose.
Parental investment, mate choice, and mate quality.
Authors: Burley N
Published: May 2006

Current theory in sexual selection is extended to predict within-sex variability with regard to selectivity towards mates in different mating systems. Generally, the sex that invests more in the care of each offspring should be more selective of mates than the sex investing less. Within each sex, individuals of low male quality should be less selective than individuals of high quality, but there should be less variation in selectivity among individuals of the sex investing more. When only one sex contributes parental care, however, individuals of that sex should be uniformly selective, while the other sex is expected to mate indiscriminately. Using feral pigeons (Columba livia), these hypotheses are tested for the case in which both sexes contribute substantial parental care, but in which females contribute more than males. As predicted, females were found to be more selective of mates than males were. On certain criteria, males of lower quality were less selective of mates than males of higher quality.
Cloning of an immunoglobulin variable region gene from mouse embryo.
Authors: Tonegawa S , Brack C , Hozumi N , Schuller R
Published: May 2006

A 4.8-kilobase DNA fragment carrying an immunoglobulin gene coding for a mouse lambda chain variable region (Vlambda gene) was enriched about 350-fold from a total endonuclease EcoRI digest of embryonic DNA by a combination of preparative agarose gel electrophoresis of double-stranded DNA and CsCl density gradient centrifugation of R-loops formed with a purified lambda chain mRNA. DNA fragments thus enriched for the immunoglobulin gene were inserted in vitro in the middle of the genome of the vector phage lambdagt Wam 403, Eam 100, Sam 100 by use of the EcoRI cohesive ends. Transfection of CaCl2-treated Escherichia coli 803 [rk-, mk- (lacking restriction and modification systems for K-12)] with such hybrid DNA and subsequent screening of about 4000 plaques by in situ hybridization with purified 125I-labeled lambda chain mRNA led to isolation of a clone that carries a Vlambda gene (lambdagtWES-Ig 13). Electron microscopy of R-loops confirmed the presence of sequences homologous to part of the lambda chain mRNA in its 5'-end.
Immunohistochemical localization of 3′:5′-cyclic AMP and 3′:5′-cyclic GMP in rat renal cortex: Effect of parathyroid hormone
Authors: Dousa Thomas P. , Barnes Larry D. , Ong Shu-Hui , Steiner Alton L.
Published: May 2006

Adenosine 3′:5′-cyclic monophosphate (cAMP) and guanosine 3′:5′-cyclic monophosphate (cGMP) were localized in cells of rat kidney cortex by an immunocytochemical technique before and after perfusion with parathyroid hormone (PTH). In control tissues the cAMP antiserum detected approximately the same intensity of fluorescence in cytoplasmic epithelial cell elements of cortical tubules and glomeruli (cells of Bowman's capsule and podocytes). PTH increased fluorescence in these glomerular cells and increased cAMP fluorescence in cytoplasmic granules in proximal tubular cells. These granules, whose structure has not been identified, were located predominantly on the luminal side of the tubular cells. In control rats, the renal cortical fluorescence detected with the cGMP antiserum was more pronounced in glomeruli (predominantly in the mesangial areas) and lesser amounts of fluorescence were observed in tubules. After PTH treatment, cGMP fluorescence increased in glomeruli and in renal tubular cells. A bright linear pattern of fluorescence was found in the area of the tubular luminal membrane. Perfusion with PTH caused relatively small increases in total tissue cAMP and no consistent increases in total tissue cGMP. Our observations suggest that both cAMP and cGMP are involved in the glomerular and tubular responses to PTH and point out the added dimension that this immunocytochemical technique brings to studies of cyclic nucleotide dynamics in heterogeneous tissues.
Thyrotropin-releasing hormone-like material in the rat retina: changes due to environmental lighting.
Authors: Schaeffer J M , Brownstein M J , Axelrod J
Published: May 2006

Material reacting with an antibody to thyrotropin-releasing hormone (TRH) has been found to be present in the rat retina. The compound present in the retina cochromatographed with authentic TRH and most of its activity was lost when incubated with pyroglutamate aminopeptidase (L-pyroglutamyl-peptide hydrolase, EC 3.4.11.8), an enzyme that degrades TRH. The TRH-like activity in the rat retina was low during the night and high during the day. There was a 4-hr lag period after the lights were turned on before peak TRH levels were attained. A decrease in TRH was seen after 2 hr of darkness and the level of TRH was lowest after 4 hr of darkness. Retinal TRH is elevated by environmental lighting regardless of the time of the day. These findings suggest that TRH may be involved in retinal photorecptive mechanisms.
Resolution of prostaglandin endoperoxide synthase and thromboxane synthase of human platelets.
Authors: Hammarström S , Falardeau P
Published: May 2006

Thromboxane synthase was localized to the microsomes of human platelets. The enzyme was insensitive to sulfhydryl reagents and thiols but was inhibited by 12L-hydroperoxy-5, 8, 10, 14-eicosatetraenoic acid (concentration for 50% inhibition = 0.1 mM). Treatment of microsomes with Triton X-100 solubilized the enzymes that catalyze the conversion of arachidonic acid to thromboxane B2. The solubilized material was resolved by DEAE-cellulose chromatography into two components, one converting arachidonic acid to prostaglandins G2 and H2 and the other converting prostaglandin H2 to thromboxane B2.
Specific benzodiazepine receptors in rat brain characterized by high-affinity (3H)diazepam binding.
Authors: Braestrup C , Squires R F
Published: May 2006

[3H]Diazepam appears to bind specifically to a single, saturable, binding site located on rat brain membranes, with an affinity constant near 3 nM at pH 7.4. Specific binding constitutes more than 90% of total binding at 0 degrees and less than 10% of total binding at 37 degrees. Arrhenius plots suggest a sharp conformational change in the diazepam receptor near 18 degrees. Mitochondrial fractions from rat kidney, liver, and lung exhibit some [3H]diazepam binding that can be displaced by nonradioactive diazepam and several other benzodiazepines. However, Ro-4864, which is almost inactive in displacing [3H]diazepam from brain membranes, is extremely potent in displacing it from kidney mitochondria. Conversely, clonazepam, the most potent inhibitor of brain binding, is an extremely weak inhibitor of kidney binding. Furthermore, diazepam binding to kidney mitochondria has an affinity constantof 40 nM, about 15 times higher than that in brain. No specific diazepam binding was detected in intestine or skeletal muscle. Thus, specific [3H]diazepam binding to membranes appears to be restricted to brain, where it is unevenly distributed: the density of diazepam receptors is about five times higher in cortex (the highest density) than in pons-meddula (lowest density). Trypsin and chymotrypsin completely abolished specific [3H]diazepambinding in brain and kidney.
Presence of tadpole and adult globin RNA sequences in oocytes of
Xenopus laevis
Authors: Perlman S. M. , Ford P. J. , Rosbash M. M.
Published: May 2006

Complementary DNA transcribed from adult
Xenopus laevis
globin mRNA was used to assay ovary RNA from
Xenopus
for the presence of globin sequences by RNA·cDNA hybridization. These sequences are present at approximately the same concentration as the majority of poly(A)-containing ovary sequences. The sequences are also found at approximately 200,000 copies per cell in poly(A)-containing RNA extracted from mature oocytes.

To rule out contamination of the oocytes with somatic cells, two additional experiments were performed. First, RNA isolated from ovulated unfertilized eggs, which are devoid of somatic cells, was also shown to contain the globin sequences. Second, globin mRNA was isolated from
Xenopus
tadpoles. Adult globin mRNA is free of the tadpole sequence and no homology was detected between adult and tadpoles globin RNA. The ovary was shown to contain tadpole globin RNA at nearly the same concentration as the adult sequences. Thus, the results cannot be explained by contamination with erythroid cells which should contain only the adult sequence.

The swimming tadpole, which possesses an active circulatory system, was also assayed for the tadpole and adult globin sequences. Whereas the adult sequences are present at approximately the same concentration as in the mature oocyte, the concentration of the tadpole sequences increases at least 300-fold in the first 3 days following fertilization.
Glucose depletion accounts for the induction of two transformation-sensitive membrane proteinsin Rous sarcoma virus-transformed chick embryo fibroblasts.
Authors: Shiu R P , Pouyssegur J , Pastan I
Published: May 2006

Chick embryo fibroblasts transformed by Rous sarcoma virus have an increased content of two membrane proteins of molecular weights 78,000 and 95,000. The increased content of the 95,000-dalton protein and the principal increase in the content of the 78,000-dalton protein are not an early consequence of cell transformation but instead are secondary to the rapid depletion of glucose from the growth medium of transformed cells. When glucose is maintained at high levels in the growth medium of transformed cells, the synthesis of the 95,000-dalton protein is arrested and that of the 78,000-dalton protein is markedly suppressed. Upon removal of glucose from the growth medium of normal cells, these proteins increase to levels comparable to those of transformed cells. Because the amount of these two proteins is influenced by the presence or absence of glucose, we suggest they be referred to as "glucose-regulated proteins." GRP-78 and GRP-95. These proteins may have an important role in regulating the utilization of glucose in cultured cells.
Induction of spectrin in erythroleukemic cells transformed by Friend virus.
Authors: Eisen H , Bach R , Emery R
Published: May 2006

The presence and accumulation in murine erythroleukemic cells transformed by Friend virus of the erythrocyte membrane-associated protein spectrin has been investigated. Spectrin was present in the uninduced cells and was induced 10- to 20-fold in dimethyl sulfoxide-treated differentiating cells. The intracellular concentration of spectrin reached a peak on the third day of dimethyl sulfoxide treatment, after which it fell to levels found in mouse erythrocytes. We also found that the small subunit of spectrin was phosphorylated in the cells.
Potentiation of a primary in vivo antibody response by alloantisera against gene products of the I region of the H-2 complex.
Authors: Pierres M , Germain R N , Dorf M E , Benacerraf B
Published: May 2006

Mice were immunized intravenously with suboptimal numbers (3.5-5 X 10(5)) of sheep erythrocytes together with various anti-Ia antisera or with sheep erythrocytes alone, and the primary IgM and IgG plaque-forming cell responses were assayed 6 days later9 A/J (H-2a) mice given 5 X 10(5) sheep erythrocytes together with as little as 0.4 mul of a (129 X A.TH)F1 anti-A.TL (anti-Iak) antiserum developed 2-3 times as many IgM and IGG plaque-forming cells as mice injected with antigen alone or together with various antisera not containing anti-Ia antibodies. Similar results were obtained with BALB/c (H-2d) mice and a (C3H X LG/Ckc)F1 anti-C3H. OH (anti-Iad) antiserum plus sheep erythrocytes. In the case of the anti-Iad antiserum, the potentiating activity could be absorbed with C3H. OH (Id) but not C3H(Ik) spleen cells, demonstrating that the active antibodies were specific for the Id region. Antiserum to I-Jk subregion-coded determinants was tested in A/J (I-Jk) mice and found to also potentiate 2- to 3-fold the plaque-forming cell response to suboptimal erythrocyte immunization. This antiserum [(BIO.A(3R) X DBA/2)F1 anti-B10.(5R)] failed to potentiate responses in BALB/c (I-Jd) mice, as expected on a genetic basis. The potentiating antibodies could be removed by absorption with B10.BR (I-Jk) but not B10 (I-Jb) spleen cells, also confirming the I-J specificity of the activity. The interference of anti-I-J antibodies with T lymphocyte suppressor mechanisms is prposed as a possible explanation for this phenomenon.
Heterogeneity of nephritic factor and its identification as an immunoglobulin.
Authors: Davis A E , Ziegler J B , Gelfand E W , Rosen F S , Alper C A
Published: May 2006

Complement C3 nephritic factor (NeF) produces alternative pathway-meciated C3 cleavage by binding to and stabilizing the alternative pathway C3 convertase, C3bBb. Some studies have suggested that NeF is an immunoglobulin, while others conclude that it is a distinct serum protein. The heterogeneity of NeF was evaluated by electrophoresis and isoelectric focusing of NeF-containing serum followed by hemolytic demonstration of NeF activity in agar gel. With each method, diffuse cathodal zones or multiple bands of hemolysis developed, which revealed remarkable variations in patterns from patient to patient. NeF activity was absorbed by and eluted from insolubilized antibody to Fc and Fab fragments of IgG. Immunoabsorption of six NeF-containing sera with insolubilized anti-kappa and anti-lambda light chain antisera revealed that NeF had kappa antigenic determinants in three, lambda antigenic determinants in one, and both kappa and lambda antigenic determinants in two. These data indicate that NeF is an oligoclonal immunoglobulin. Because NeF binds to the alternative pathway C3 convertase, C3bBb, we suggest that it is an antibody to a conformational antigen of the C3-factor B complex, and thereby stabilizes this complex.
Chemical composition of gaseous nebula NGC 6302
Authors: Aller L. H. , Czyzak S. J.
Published: May 2006

The irregular emission nebula NGC 6302 exhibits a rich spectrum of lines ranging in excitation from [NI] to [FeVII]. An assessment of available spectroscopic data, covering a large intensity range, indicates excess of helium and nitrogen as compared with average planetary nebulae, but deficiencies in iron and calcium. These metals are presumably tied up in solid grains, as suggested by Shields for iron in NGC 7027.
Stochastic theory of ligand migration in biomolecules.
Authors: Alberding N , Frauenfelder H , Hänggi P
Published: May 2006

When ligand binding to proteins involves the presence of more than one ligand inside a given biomolecule, linear deterministic rate equations become useless. A stochastic approach, however, permits a treatment of the migration and binding of small molecules to proteins even at high ligand concentrations. An appropriate linear master equation and its analytic solution are given. As an example, the binding of carbon monoxide to myoglobin at partial pressures from 1 to 10(3) bars (0.1 to 100 MPa) is treated.
On unstable cohomology classes of

SL
n

(
Z
)
Authors: Lee Ronnie
Published: May 2006

From algebraic
K
-theory, we show that there exists a spectral sequence that has real cohomology of

SL
n

(
Z
) as its
E
1
-terms and converges to the tensor product of a polynomial algebra and an exterior algebra. On the basis of this spectral sequence, we discovered several families of real unstable cohomology classes of

SL
n

(
Z
).
Characterization of the residual adenosine deaminating activity in the spleen of a patient with combined immunodeficiency disease and adenosine deaminase deficiency
Authors: Schrader William P. , Pollara Bernard , Meuwissen Hilaire J.
Published: May 2006

A number of infants with an autosomal recessive form of combined immunodeficiency disease also lack adenosine deaminase (adenosine aminohydrolase; EC 3.5.4.4) activity in their erythrocytes. Other tissues from these infants contain only a few percent of the adenosine-deaminating activity present in corresponding normal tissue. The residual adenosine-deaminating activity in extracts from the spleen of a combined immunodeficient, adenosine deaminase-deficient patient was compared with adenosine deaminase from normal spleen. Affinity and immunoadsorbant column chromatography revealed distinct differences between the adenosine-deaminating activity in the patient's spleen and adenosine deaminase from normal spleen. The point of maximum activity and general configuration of the pH optimum curves were also different.
erythro
-9-(2-Hydroxyl-3-nonyl)adenine, a potent inhibitor of adenosine deaminase from normal spleen, had relatively little effect on the activity from the patient's spleen. In contrast, adenine was a better inhibitor of the activity in the patient's spleen than it was of the enzyme from normal tissue. An adenosine-deaminating activity with the same characteristics and specific activity as that in the patient's spleen was also isolated from normal spleen. These results suggest that the adenosine-deaminating activity in the spleen of this patient is not due to a mutant form of adenosine deaminase.
Analysis of human tumors and human malignant cell lines for BK virus-specific DNA sequences
Authors: Wold William S. M. , Mackey Jesse K. , Brackmann Karl H. , Takemori Nobuyuki , Rigden Patricia , Green Maurice
Published: May 2006

Most humans in the United States have been infected with BK virus (BKV), a human papovavirus. Because BKV has oncogenic properties, we have investigated whether it may be a cause of human cancer. Basic principles of tumor virology imply that BKV-induced tumors should contain BKV DNA sequences. Therefore, we assayed (by molecular hybridization) DNA from human tumors and malignant cell lines for BKV DNA, using BKV [
32
P]DNA as probe. The BKV [
32
P]DNA was labeled
in vitro
(nick translation) to specific activities of 1 to 2 × 10
8
cpm/μg. The BKV DNA used to prepare our probes had the properties expected of authentic BKV genomes, including density of superhelical DNA, sedimentation velocity in alkaline and neutral sucrose gradients, production of one fragment by endonuclease
Eco
RI cleavage and four fragments by endonuclease
Hin
II + III cleavage and reassociation properties. From these studies we conclude that our BKV probes hybridized well, and represented bona fide BKV DNA. Using three different BKV [
32
P]DNA probes, i.e., from three distinct plaque isolates, we have analyzed DNA from BKV-transformed cells, normal human tissues, and a large number of human tumors. All human DNAs (cell lines, normal tissues, tumors) hybridized 5% with BKV DNA. Hybridization analysis of BKV-transformed hamster cell DNA indicated 5-6 copies of at least 88% of the BKV genome per cell. No BKV DNA sequences were detected (above the normal 5% hybridization to all human DNAs) in the following normal human tissues: 10 kidney (BKV is usually isolated from urine), 3 spleen, 13 lung, 23 colon, 2 rectum, 1 ileum, and 1 skin. No BKV-specific DNA was found in 166 tumors, including 5 carcinomas (Ca) of stomach, 3 Ca small intestine, 26 Ca colon, 9 Ca rectum, 31 Ca lung, 9 adenocarcinomas and 5 oat cell carcinomas of lung, 17 melanomas, 5 Ca prostate, 4 Ca bladder, 6 Wilms tumors, 4 hypernephromas, 15 Ca kidney, 7 brain tumors, 5 Hodgkin lymphomas, 10 lymphomas (immunosuppressed patients have a high incidence of lymphomas), 2 reticulum cell sarcomas (spleen), and 3 skin tumors. We have also analyzed 7 human malignant cell lines (melanoma, lung, rhabdomyosarcoma, and glioblastomas), including several clones of a lung melanoma line; no BKV DNA sequences were detected. Because our probes could detect one copy of BKV DNA if only 10% of the cells were tumor cells, our results are very strong evidence that the tumors we analyzed did not have a BKV etiology. The tumors we tested represent about 50% of all cancers in the United States; there is no evidence that BKV is involved in the etiology of these types of tumors.
Evidence for X-linkage of human phosphoribosylpyrophosphate synthetase
Authors: Yen Richard C. K. , Adams William B. , Lazar Cheri , Becker Michael A.
Published: May 2006

The mode of genetic transmission of human phosphoribosylpyrophosphate synthetase (ribosephosphate pyrophosphokinase; ATP:D-ribose-5-phosphate pyrophosphotransferase; EC 2.7.6.1) was studied in fibroblasts cultured from members of a family with a structurally and electrophoretically altered phosphoribosylpyrophosphate synthetase that has increased activity per enzyme molecule. Enzyme activity in fibroblast lysates from the daughter of an affected male patient was intermediate to the activities in lysates from her father (and her affected paternal uncle) and from her mother and other normal individuals. Two bands of enzyme activity corresponding to normal and mutant phosphoribosylpyrophosphate synthetases were found in fibroblast lysates from the daughter after cellulose acetate strip electrophoresis. In contrast, only mutant enzyme was detectable in lysates derived from the male patients. Fibroblasts cloned from the daughter contained two phenotypically distinct (normal and mutant) populations of cells with respect to phosphoribosylpyrophosphate synthetase activity and electrophoretic mobility. These studies support assignment of the structural gene for human phosphoribosylpyrophosphate synthetase to the X-chromosome. No evidence for the presence of the normal enzyme was found in erythrocyte or lymphocyte lysates or in partially purified erythrocyte enzyme preparations from the heterozygous daughter, suggesting either nonrandom X-chromosome inactivation in precursors of these cells or selection against hematopoietic cells bearing the normal enzyme after random X-chromosome inactivation.
Iron, an essential element for biosynthesis of aromatic compounds.
Authors: McCandliss R J , Herrmann K M
Published: May 2006

Homogeneous preparations of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase [7-phospho-2-keto-3-deoxy-D-arabino-heptonate D-erythrose-4-phosphate lyase (pyruvate phosphorylating), EC 4.1.2.15] isolated as the enzyme-phosphoenolpyruvate complex from Escherichia coli are shown by atomic absorption analysis to contain approximately one mole of iron per mole of native enzyme. No cobalt was found, in contrast to suggestions of earlier workers. Pure enzyme preparations show a unique absorption maximum around 350 nm with an epsilon value of about 3500 M-1cm-1. The 350-nm band as well as the enzyme activity is lost when the enzyme is denatured with guanidine-hydrochloride, or when phosphoenolpyruvate, the first substrate to bind to the enzyme, is totally removed from the enzyme by incubation with an excess of erythrose 4-phosphate, the second substrate to bind to the enzyme. The iron remains bound to the enzyme when phosphoenolpyruvate is removed from the enzyme-phosphoenolpyruvate complex.
Visualization of an inverted terminal repetition in vaccinia virus DNA.
Authors: Garon C F , Barbosa E , Moss B
Published: May 2006

An inverted terminal repetition was observed in DNA molecules extracted from vaccinia virus. The repeated sequence was visualized by (i) nicking the hairpin loops present of the ends of vaccinia virus DNA, (ii) separating the strands of DNA by alkali denaturation, (iii) allowing the single strands to self-anneal, and (iv) examining the DNA with an electron microscope. Single-stranded circular molecules, each of which contained a duplex projection (3.54 +/- 0.12 micron) representing the terminal repetition, readily formed. Similar size projections were also seen in heteroduplex structures formed by crosshybridization of the separated strands of the two terminal HindIII restriction fragments. Based on contour length measurements and the electrophoretic mobility of the isolated inverted terminal repetition, a molecular weight of approximately 6.9 X 10(6), equivalent to about 10,500 nucleotide base pairs, was estimated. Evidence was obtained from DNA-RNA hybridization studies that the terminal repetition is transcribed.