bluuebunny/crossref_metadata_2025 huggingface dataset:
Photochemical dimerization of parinaric acid in lipid bilayers
Authors: Morgan Christopher G. , Hudson Bruce , Wolber Paul K.
Published: May 2006

Parinaric acid (9,11,13,15-octadecatetraenoic acid), a conjugated tetraene fatty acid, undergoes a second-order photochemical reaction in phospholipid bilayers. The reaction results in the loss of the characteristic absorption of this chromophore and the development of new absorption demonstrating the presence of a triene chromophore. The progress of this reaction is easily monitored by measurement of the decrease in the fluorescence intensity from a uniformly illuminated sample. The reaction rate measured in this way is sensitive to the thermal phase transition of the bilayer and to the presence of cholesterol. The relationship of the second-order rate constant to the lipid diffusion coefficient is discussed. This relationship differs from that previously used for the analysis of similar photochemical processes.
Diphtheria toxin: nucleotide binding and toxin heterogeneity.
Authors: Lory S , Collier R J
Published: May 2006

We have used flow dialysis to demonstrate binding of ATP and related compounds to diphtheria toxin. The results define a new site on the toxin molecule (the P site), which has distinctly different properties from the NAD+-binding site of the fragment A moiety. The relative affinities of various compounds for the P site are similar to their capacities to inhibit toxin attachment to cell surfaces and its action on cells. This suggests that the P site may correspond to the binding site for cell surface receptors. Affinity of nucleotides for the toxin depends strongly on the number of phosphates, although both nucleoside and phosphate moieties contribute to the interaction. A substantial fraction of the toxin in any given preparation did not bind ATP in a rapidly reversible manner and was not retained on ATP-Sepharose. This fraction, which varied in magnitude from preparation to preparation, was isolated and shown to contain an endogenous, firmly bound nucleotide or nucleotide-like compound. The presence of this compound may explain some of the physical heterogeneity within individual preparations of purified toxin as well as variations in physical and biological properties among various preparations.
Acetone metabolism in mice: increased activity in mice heterozygous for obesity genes.
Authors: Coleman D L
Published: May 2006

Mice were found to convert acetone to lactate at appreciable rates. The conversion of acetone to gluconeogenic precursors could provide additional glycolytic intermediates that would allow the more complete utilization of lipid stores and increase survival time during starvation. In mice that were starved for 3 days or were provided with acetone in the drinking water the acetone-metabolizing pathway was induced to levels severalfold normal. Mice heterozygous for obesity-producing mutations, either obese (ob/+) or diabetes (db/+), showed induction of the activity of this pathway to a significantly higher degree than did homozygous normal (+/+) mice of the same strain. This more effective conversion of acetone to lactate exhibited by heterozygous mice could account for their prolonged survival on a starvation regimen compared to that of normal homozygotes. The rate-limiting step in the pathway appears to be the conversion of acetone to a hydroxylated derivative. The enzyme system effecting this conversion is an NADPH-requiring microsomal oxygenase found in the liver.
Interaction of 16 alpha-[125I]iodo-estradiol with estrogen receptor and other steroid-binding proteins.
Authors: Hochberg R B , Rosner W
Published: May 2006

This communication describes the synthesis of 16 alpha-[125I]iodo-estradiol (125I-E2) with specific activities greater than 1000 Ci/mmol (1 Ci = 3.7 x 10(10) becquerels). We show that it binds to the same specific estrogen receptor sites as does [3H]estradiol and that it does so with an affinity that is indistinguishable from that for the latter steroid. This is true for receptor obtained from calf uterus and from a pool of human mammary carcinomas. There is no significant binding of 125 I-E2 to the testosterone-estradiol-binding globulin of human plasma. 125I-E2 also binds tightly to anti-estradiol antibodies raised against estradiol derivatized at carbons 3, 6, and 17. Finally, we show that unlabeled I-E2 is an active estrogen in vivo as demonstrated by its ability to increase uterine weight in ovariectomized rats.
A selective inhibitor of cell proliferation from normal serum.
Authors: Harrington W N , Godman G C
Published: May 2006

A factor in normal serum that selectively and reversibly inhibits proliferation of cells in culture has been enriched 160-fold from calf serum by sequential ammonium sulfate precipitation, gel filtration, and lectin-affinity chromatography. DNA synthesis of normal (but not transformed) rat hepatocytes, human lymphoblast lines, and mitogen-stimulated murine spleen cells is inhibited by greater than 90%, and Vero, murine myeloma, MELC, and a human colon carcinoma cell line to a lesser extent. Growth of other cell lines tested was not affected. Responsive cells are arrested apparently in G1 by this inhibitor, the effect of which is maximal by 24 hr and is spontaneously reversible thereafter unless it is renewed. The active fraction is a protein that migrates with the alpha 2-globulins; it is not a lipoprotein, and it is of high apparent molecular weight.
Hypotensive action of parathyroid hormone preparations on rats and dogs.
Authors: Pang P K , Tenner T E , Yee J A , Yang M , Janssen H F
Published: May 2006

Bovine parathyroid extract and two commercial preparations containing the first 34 amino acids of synthetic bovine parathyroid hormone [bPTH-(1-34)]produced dose-related hypotension in anesthetized rats. Dogs were 10 times more sensitive to the two bPTH-(1-34) preparations than were rats. Propranolol, phentolamine, atropine, and promethazine did not affect the hypotensive action of bPTH-(1-34) in rats and dogs. bPTH-(1-34) decreased perfusion pressure in rat hindlimbs perfused in situ with Ringer's solution and was a vasodilator in dog kidneys perfused in vitro with Ringer's solution. Helical strips of rabbit aorta were also relaxed by bPTH-(1-34). We conclude that the direct vasodilatory action of bPTH preparations represents an intrinsic property of parathyroid hormone and that the hypotensive effect of this hormone is produced by part or all of the first NH2-terminal 34 amino acids.
Host nuclear proteins expressed in simian virus 40-transformed and -infected cells.
Authors: Melero J A , Tur S , Carroll R B
Published: May 2006

Two new families of host proteins (Mr, 48,000 and 55,000), in additional to the viral large (T) and small tumor antigens, are precipitable, with anti-T antiserum, from cells transformed or infected by the DNA tumor virus simian virus 40 (SV40). Rabbit anti-mouse 48,000 protein antiserum reacts specifically with SV40-infected or -transformed mouse cells to give nuclear staining indistinguishable from T-antigen staining but does not react with SV40-transformed human cells which nevertheless have structurally analogous 48,000 proteins, nor does it give nuclear fluorescence with untransformed mouse cells. Comparison of the partial proteolytic digests of the 48,000 proteins from cultured cells of various mammalian species shows that they are structurally related but not related to the 55,000 or large T-antigen proteins. The 55,000 proteins from the various mammalian species were also structurally related.
Nuclear Overhauser effect in specifically deuterated macromolecules: NMR assay for unusual base pairing in transfer RNA.
Authors: Sánchez V , Redfield A G , Johnston P D , Tropp J
Published: May 2006

We demonstrate a fairly general method for identification of NMR absorption lines of macromolecues extracted from microorganisms, based on nuclear Overhauser effects (NOE). Several NOE in tRNA are observable between resolved imino proton resonances and ring carbon resonances that are either C(2) protons of adenine or C(8) protons of adenine or guanine. Yeast tRNAPhe was deuterated at the purine C(8) positins by heating in 2H2O and also biosynthetically. NOE between imino protons and adenine C(2) protons of standard A . U base pairs would not be affected by such a label, but some other NOE that might be otherwise similar, such as those of reverse Hoogsteen base pairs, should disappear. Six NOE were shown to be from standard A . U pairs by their nondisappearance. Four NOE from methyl resonances to aromatic proton resonances did disappear. The results disagree with previous assignments based on ring-current theories of imino proton NMR shifts.
Adrenal glucocorticoid permissive regulation of muscle glycogenolysis: action on protein phosphatase(s) and its inhibitor(s).
Authors: Green G A , Chenoweth M , Dunn A
Published: May 2006

Adrenal glucocorticoids exert a permissive action on the glycogen phosphorylase cascade. Epinephrine activation of muscle phosphorylase and phosphorylase b kinase is depressed in adrenalectomized rats. Phosphorylase phosphatase activity is increased by steroid lack, and normal epinephrine inhibition of the enzyme does not occur. Phosphorylase b kinase phosphatase activity is also increased; epinephrine, however, does not inhibit activity in muscle from normal or adrenalectomized rats. Protein phosphatase inhibitor activity is depressed in boiled dialyzed preparations made from adrenalectomized rat muscle. Cortisol resplacement therapy restores protein phosphatase inhibitor activity, decreases increased protein phosphatase activity, and restores normal epinephrine-induced activation of phosphorylase b kinase and phosphorylase and epinephrine inhibition of phosphorylase phosphatase.
Nucleotide sequence of the thrA gene of Escherichia coli.
Authors: Katinka M , Cossart P , Sibilli L , Saint-Girons I , Chalvignac M A , Le Bras G , Cohen G N , Yaniv M
Published: May 2006

The thrA gene of Escherichia coli codes for a single polypeptide chain having two enzymatic activities required for the biosynthesis of threonine, aspartokinase I and homoserine dehydrogenase I. This gene was cloned in a bacterial plasmid and its complete nucleotide sequence was established. It contains 2460 base pairs that encode for a polypeptide chain of 820 amino acids. The previously determined partial amino acid sequence of this protein is in good agreement with that predicted from the nucleotide sequence. The gene contains an internal sequence that resembles the structure of bacterial ribosome-binding sites, with an AUG preceded by four triplets, each of which can be converted to a nonsense codon by a single mutation. This suggests that the single polypeptide chain was formed by the fusion of two genes and that initiation of translation may occur inside the gene to give a protein fragment having only the homoserine dehydrogenase activity.
(R)-mevalonate excretion in human and rat urines.
Authors: Kopito R R , Brunengraber H
Published: May 2006

(R)-Mevalonate was identified by radioenzymatic assay in human and rat urines. This was confirmed by spectrophotometric enzymatic assay of an ether extract of human urine. The average excretion rate of (R)-mevalonate in humans was 1.7 mumol/24 hr which corresponds to 29% of the glomerular filtration rate. In anesthetized rats the average rate of (R)-mevalonate excretion was 350 pmol/min, corresponding to 44% of the glomerular filtration rate. These rates were not affected by the sex of the subjects or animals. After bilateral nephrectomy, the concentration of (R)-mevalonate in rat serum increased within 2 hr to a new level that was 5 times that of sham-operated controls. Nephrectomized rats showed a decrease in their tolerance to an intravenous load of mevalonate. These data show that (R)-mevalonate is normally excreted in the urine of humans and rats. Urinary excretion of (R)-mevalonate should therefore be taken into account in in vivo studies on the metabolism of this compound.
New molecular forms of human liver alcohol dehydrogenase: isolation and characterization of ADHIndianapolis.
Authors: Bosron W F , Li T K , Vallee B L
Published: May 2006

The biochemical determinants of alcoholism and genetic correlates for the variability in man's response to alcohol have remained obscure until recently. The identification of genetically determined isoenzymes of alcohol dehydrogenase with different catalytic properties may bear importantly upon this problem. New molecular forms of human liver alcohol dehydrogenase (ADH; alcohol:NAD+ oxidoreductase, EC 1.1.1.1) have recently been identified in 16% of the liver specimens from an urban population from Indianapolis, Indiana [Bosron, W. F., Li, T.-K. & Vallee, B. L. (1979) Biochem. Biophys. Res. Commun. 91, 1549-1555]. The distinguishing features of these specimens were (i) they showed activity optima for ethanol oxidation at both pH 7.0 and 10.0 and (ii) they formed electrophoretic bands cathodic to the beta beta isoenzyme. From such livers, three new ADH forms have now been isolated, one of which has a single pH optimum at 7.0 and two of which have dual optima at pH 7.0 and 10.0. These new forms were designated ADHIndianapolis forms 1,2, and 3, respectively. They can be differentiated from previously described ADH isoenzymes, including the so-called "atypical" isoenzyme, by their electrophoretic mobility, pH optima, and Km for ethanol (approximately 60 mM at pH 7.5). Based upon the electrophoretic pattern of livers containing ADHIndianapolis and the mobility of the three isolated molecular forms, ADHIndianapolis may be the result of polymorphism at the ADH2 gene locus, which codes for the beta subunit.
Catabolite repression in Escherichia coli mutants lacking cyclic AMP receptor protein.
Authors: Guidi-Rontani C , Danchin A , Ullmann A
Published: May 2006

Pleiotropic carbohydrate-positive pseudorevertants have been isolated from a specific class of rho-crp double mutants of Escherichia coli carrying both defective transcription termination protein, rho, and cyclic AMP receptor protein. The modulation of catabolite repression of beta-galactosidase, amylomaltase, and tryptophanase has been studied in the pseudorevertants. It has been found that these mutants exhibit catabolite repression. Because catabolite-sensitive operons can be expressed in the absence of functional cyclic AMP receptor protein, this would suggest on the one hand that the cyclic AMP-receptor protein complex is not the exclusive mediator of catabolite repression and on the other hand that rho might be involved in the regulation of catabolite-sensitive operons.
Calcium-regulated phosphorylation in synaptosomal cytosol: dependence on calmodulin.
Authors: O'Callaghan J P , Dunn L A , Lovenberg W
Published: May 2006

Calcium stimulated the phosphorylation of several specific synaptosomal cytosolic proteins. The effects of calcium were both concentration and time dependent and were most apparent for proteins with molecular weights of 50,000, 55,000, and 60,000. Exogenous calcium (1.0-100 microM) enhanced the net incorporation of phosphate into protein by as much as 23-fold. In the absence of added calcium, the calcium chelator [ethylenebis(oxyethylenenitriolo)]tetraacetic acid did not lower the phosphorylation of any protein below control levels. The antipsychotic, fluphenazine (1.0-100 microM), caused a concentration-dependent decrease in calcium-stimulated protein phosphorylation. When the heat-stable calcium-binding protein, calmodulin, was removed from synaptosomal cytosol by affinity chromatography on fluphenazine-Sepharose, calcium-stimulated protein phosphorylation was abolished. Responsiveness to calcium could be restored by the addition of calmodulin to the phosphorylation assay. These results indicate that calcium-dependent protein kinases are of major importance in regulating the phosphorylation of specific cytosolic proteins in neuronal tissue. Furthermore, it would appear that one of the three substrates under investigation is specific to synaptosomal cytosol whereas the other two are present in both the cytosol and membrane fractions.
Affinity chromatography in nonionic detergent solutions.
Authors: Robinson J B , Strottmann J M , Wick D G , Stellwagen E
Published: May 2006

Anionic dye affinity chromatography is commonly unproductive in the presence of nonionic detergents used to extract particulate proteins. Using lactate dehydrogenase as a model protein, Cibacron blue F3GA as a model dye, and Triton X-100 as a model detergent, we find that the dye is encapsulated in nonionic detergent micelles, rendering the dye incapable of ligation with the enzyme. However, the dye can be liberatd from the micelles without altering the nonionic detergent concentration by addition of an anionic detergent, such as deoxycholate or sodium dodecyl sulfate, forming mixed anionic/nonionic micelles that displace the anionic dye. Encapsulation of the anionic detergents prevents their activity as protein denaturants. These observations have been successfuly translated to the dye affinity chromatography of a detergent extract of brain particulate cyclic nucleotide phosphodiesterase.
Nigericin-stimulated ATPase activity in microsomal vesicles of tobacco callus
Authors: Sze Heven
Published: May 2006

The effect of ionophores on K
+
-stimulated adenosinetriphosphatase (ATPase; ATP phosphohydrolase, EC 3.6.1.3) activity of microsomal vesicles from tobacco callus was investigated. A nigericin-stimulated K
+
-ATPase activity was enriched in a purified microsomal fraction, which was obtained from the interphase of a dextran density gradient between 1.03 and 1.06 g/ml. The purified microsomal fraction was free of mitochondrial membranes and was composed partly of tightly sealed vesicles as indicated by the low K
+
permeability coefficient. The K
+
-dependent ATPase of this fraction was stimulated slightly by either carbonyl cyanide
m
-chlorophenylhydrazone (CCCP) (29%) or valinomycin (31%) alone; this ATPase was significantly stimulated by a combination of CCCP and valinomycin (73%) or by nigericin alone (80%). The K
+
-ATPase activity was stimulated by nigericin at pH 6.5 but not at pH 8.5. At pH 6.5, the K
+
-ATPase was inhibited by
N,N′
-dicyclohexylcarbodiimide but not by oligomycin. Nigericin stimulated the ATPase activity in the absence of initial KCl or pH gradients across the vesicle membrane. These results suggest that nigericin stimulates the ATPase activity by dissipating the H
+
or K
+
gradient or both, and support the hypothesis that the K
+
-ATPase mediates a H
+
/K
+
transport.
Deletion mutants of Neurospora crassa mitochondrial DNA and their relationship to the "stop-start" growth phenotype.
Authors: Bertrand H , Collins R A , Stohl L L , Goewert R R , Lambowitz A M
Published: May 2006

"Stoppers" are a class of Neurospora crassa extranuclear mutants characterized by gross deficiencies of cytochromes b and aa3 and an unusual growth phenotype which involves irregular periods of growth andnongrowth. In the present work, mtDNAs from all four stopper mutants were found to contain deletions or insertions detectable by restriction enzyme analysis. [stp] mtDNA consists predominantly of defective molecules which retain a 16-megadalton segment (EcoRI-1, -4, and -6) of wild-type mtDNA (40 megadaltons). The other stopper mutants show smaller alterations: [stp A18t]-618, a 0.35-kilobase deletion in EcoRI-7b; [stp B2]-651, a 4-kilobase insertion in EcoRI-2; and [stp A]-574, a 5-kilobase deletion in EcoRI-2 and -10. Based on these results, we propose that "stop-start" growth results from competition between certain defective mtDNAs which have a tendency to predominate and low concentrations of less defective mtDNA species which must be retained to sustain growth. Three additional extranuclear mutants ("nonstoppers") have also been found to contain deletions in mtDNA. Remarkably, the defective mtDNA species in two of these mutants ([poky]H1-10 and [SG-3]-551) retain different sizes (18 and 13 megadlatons, respectively) of the same region retained in [stp] mtDNA (i.e., EcoRI-1, -4, and -6). The findings suggest that production of defective mtDNAs in Neurospora is nonrandom with a preferred mechanism leading to retention of this segment. It may be significant that the retained segment contains both mitochondrial rRNA genes and most mitochondrial tRNA genes. These deletion mutants may provide a tool for genetic mapping of Neurospora mtDNA.
Site specificity of mutations arising in dysgenic hybrids of Drosophila melanogaster.
Authors: Simmons M J , Lim J K
Published: May 2006

Mutations arising in dysgenic hybrids of Drosophila melanogaster were collected in the zeste-white region of the X chromosome. A preponderance of the mutations affected the zw1 locus; many of these were asociated with structural abnormalities including inversions, deficiencies, and insertions in the 3A3-4 region of the polytene chromosome map. The extreme sensitivity of the zw1 locus to the mutator activity of dysgenic hybrids contrasted with the apparent insensitivity of the zw2 locus. Other loci in the zeste-white region were weakly sensitive to the mutator activity. Insertions of two and six bands were seen between bands 3A4 and 3A6 in the chromosomes of one of the zw1 mutant stocks examined. Another insertion was detected at position 2F4-5 in a different stock. Many of the mutant chromosome were evidently unstable, as judged by secondary breakage in other parts of the X chromosome. The cytogenetic data are consistent with the idea that mutations arising in dysgenic hybrids are caused by transposable elements which insert preferentially at certain sites on the chromosomes.
Cellular interactions in the generation of cytolytic T lymphocyte responses: role of Ia-positive splenic adherent cells in presentation in H-2 antigen.
Authors: Weinberger O , Herrmann S H , Mescher M F , Benacerraf B , Burakoff S J
Published: May 2006

Splenic adherent cells are required for generation of both primary and, at limiting antigen dose, secondary allogeneic responses of cytolytic T lymphocytes to intact stimulator cells. Secondary responses to purified allogeneic plasma membranes or purified H-2Kk antigens in liposomes are also dependent upon splenic adherent cells. Generation of these responses requires the presence of an Ia-positive. Thy 1,2-negative, radiation-resistant cell in the splenic adherent cell population that is adherent to glass, plastic, and nylon wool. Stimulation of cytolytic T lymphocyte precursors with purified H-2Kk alloantigen bound to Ia+ splenic adherent cells is 10-20 times more efficient than stimulation with antigen added directly to culture. Furthermore, a marked decrease in the response of cytolytic T lymphocytes to liposomes was observed when antiserum against Iad specific for the Ia of the responder cells was added to culture. These results demonstrate that, for purified proteins of the major histocompatibility complex, antigen presentation by Ia+ splenic adherent cells plays a role in the generation of a cytolytic T lymphocyte response.
Cell surface antigens of human malignant melanoma: definition of six antigenic systems with mouse monoclonal antibodies.
Authors: Dippold W G , Lloyd K O , Li L T , Ikeda H , Oettgen H F , Old L J
Published: May 2006

Eighteen mouse monoclonal antibodies were selected for reactivity with cell surface antigens of the immunizing human melanoma cell line SK-MEL-28. Six distinct antigenic systems were defined by direct serological assays and absorption tests with a panel of 41 cell lines derived from normal and malignant human tissues. Biochemical analysis indicated that two of the antigens are glycoproteins with molecular sizes of 95,000 and 150,000 daltons (gp95 and gp150). Two other antigenic systems (O5 and the R24 group) are associated with heat-stable molecules having the characteristics of glycolipids. The remaining two antigens (M19 and R8) are heat labile, but molecular characterization has not been possible. Each of the antigenic systems has a distinctive pattern of distribution on various cell types, varying from a broad representation to a more restricted occurrence. O5 appears to be a species antigen, being present on virtually every human cell type tested. gp95, gp150, M19, and R8 are found on a characteristic proportion of melanomas, astrocytomas, and epithelial cancers and on normal kidney cells. The antigen defined by the R24 antibody has the most restricted distribution of all. Reactivity is found with melanomas and astrocytomas, whereas epithelial cell types, fibroblasts, and cells of hematopoietic origin lack R24. Although occurrence of gp95, gp150, M19, and R8 distinguishes a small subset of melanomas not expressing these antigens, R24 is found on all melanoma cells.
Purification and some characteristics of human T-cell growth factor from phytohemagglutinin-stimulated lymphocyte-conditioned media.
Authors: Mier J W , Gallo R C
Published: May 2006

Human T-cell growth factor (TCGF), a mitogenic protein that appears in the media of cultured lymphocytes after phytohemagglutinin-stimulation, has been purified more than 400-fold from serum-free conditioned media by using a sequence of ion exchange chromatography and gel filtration. The purified growth factor elutes as a broad peak from DEAE-Sepharose, focuses diffusely at a pH of about 6.8 on isoelectric focusing (suggesting heterogeneity in electrical charge), has an estimated molecular weight of approximately 23,000 as judged by gel filtration (12,000-13,000 on Na-DodSO4/polyacrylamide gel electrophoresis), is resistant to DNase and RNase, is degraded by trypsin, and does not adhere to any of several lectin-Sepharoses. These characteristics indicate that it is nonglycosylated and protein in nature. The activity of the factor determined by cell counts or [3H]thymidine incorporation in human T lymphoblasts, is stable at room temperature in crude conditioned media, but the partially purified factor requires the addition of albumin or polyethylene glycol to maintain stability. Unlike the crude conditioned media, the purified factor lacks colony-stimulating activity and, unlike lectins, antigens, and crude conditioned media, it does not initiate blastogenesis in peripheral blood lymphocytes but is a selective mitogen for T cells that have undergone blast transformation secondary to exposure to a lectin or antigen. This indicates that the factor is a second signal in the T-cell immune response. The partially purified factor has been used to selectively grow several human T-cell lines, including cells that are cytotoxic to a variety of target cells.
An endonuclease isolated from Epstein-Barr virus-producing human lymphoblastoid cells.
Authors: Clough W
Published: May 2006

An endonuclease has been isolated from human B lymphoblastoid cells that copurifies with an exonucleolytic activity and has been shown to produce double-strand breaks and a high proportion of single-strandedness in phage lambda DNA in vitro. The data are consistent with a model in which single-strand cuts are made by the endonucleolytic activity, possibly in A+T-rich regions of the DNA, followed by creation of single-stranded regions (gaps) precessing from the site of a cut. Generation of overlapping gaps on opposite strands or of a gap opposite a nick would lead to the creation of the banding patterns that we have seen on electrophoretic gels. This endonucleolytic activity copurifies with other enzymes induced by Epstein-Barr virus that relate to the process of viral DNA replication in productively infected cells. However, a more general role is proposed for this class of eukaryotic endonuclease activities. A marked degree of single-strandedness has been found in the replicating DNAs of many eukaryotes, ad these gaps could be generated by endonucleases with associated exonucleolytic activity such as that reported here. This Epstein-Barr virus-induced nuclease activity has been shown to resemble the recBC nuclease isolated from the prokaryote Escherichia coli and also the endonuclease isolated from the eukaryote Chlamydomonas.
Rapid taste-aversion learning by an isolated molluscan central nervous system.
Authors: Chang J J , Gelperin A
Published: May 2006

The isolated lips and nervous system of the terrestrial slug Limax maximus will produce some of the feeding behavior of the intact animal; i.e., they generate the rhythmic neural activity characteristic of ingestion in response to food extracts applied to the lips. This preparation will respond to a variety of food extracts that elicit feeding in the whole animal. This provides the opportunity for aversive conditioning experiments involving taste discrimination. Pairing lip chemostimulation by attractive food extracts with lip chemostimulation by using bitte plant secondary substances can cause the isolatd brain to selectively suppress its neural response to one food extract while remaining responsive to another. Such isolated brains can learn after one or two trials and retain the learning for more than 8 hr.
Electrical inhibition of Purkinje cells in the cerebellum of the rat.
Authors: Korn H , Axelrad H
Published: May 2006

Monosynaptic activation of cerebellar Purkinje cells by a volley of parallel-fiber impulses is followed by a powerful disynaptic chemical inhibition mediated by molecular layer interneurons, including basket cells. Active zone established by basket preterminal axons on the body surface of the Purkinje cell account for this inhibition. However, morphological studies indicate that branches of the presynaptic fibers further descend along the initial segment of the Purkinje axon. Terminals from several basket cells converge and encapsulate each initial segment with a peculiar architectural structure that is reminiscent of that characterizing the axon cap of the teleost Mauthner cell. Because no function has yet been attributed to this pinceau, we have reanalyzed the successive Purkinje cell responses to activation of their presynaptic elements. Electrophysiological data provided by field-potential and single-unit measurements indicate that the classical phases of excitation and inhibition after a parallel-fiber volley are preceded by a brief inhibition of the Purkinje cells. Transmembrane hyperpolarizing potentials that exhibit the characteristics expected of electrically mediatd potentials underlie this early phase of inhibition; their properties are consistent with the hypothesis that they are generated by currents through terminals of nearby basket cells. Therefore, these hyperpolarizations, which are similar in their mechanism of generation to those described in the Mauthner cell system, represent a known case of electrical inhibition in the mammalian central nervous system.
Gene-culture translation in the avoidance of sibling incest
Authors: Lumsden Charles J. , Wilson Edward O.
Published: May 2006

A preliminary analysis is made of the relation between the epigenetic rules of brother-sister incest avoidance, which operate during individual development, and the frequency of occurrence of this form of incest among cultures.
Spinor representations of affine Lie algebras
Authors: Frenkel I. B.
Published: May 2006

Let [unk] be an infinite-dimensional Kac-Moody Lie algebra of one of the types
D

l
+1

(2)
,
B

l

(1)
, or
D

l

(1)
. These algebras are characterized by the property that an elimination of any endpoint of their Dynkin diagrams gives diagrams of types

B
l

or

D
l

of classical orthogonal Lie algebras. We construct two representations of a Lie algebra [unk], which we call spinor representations, following the analogy with the classical case. We obtain that every spinor representation is either irreducible or has two irreducible components. This provides us with an explicit construction of fundamental representations of [unk], two for the type
D

l
+1

(2)
, three for
B

l

(1)
, and four for
D

l

(1)
. We note the profound connection of our construction with quantum field theory—in particular, with fermion fields. Comparing the character formulas of our representations with another construction of the fundamental representations of Kac-Moody Lie algebras of types
A

l

(1)
,
D

l

(1)
,
E

l

(1)
, we obtain classical Jacobi identities and addition formulas for elliptic θ-functions.
Glutathione transport by inside-out vesicles from human erythrocytes.
Authors: Kondo T , Dale G L , Beutler E
Published: May 2006

Purified inside-out vesicles from human erythrocytes were used to investigate the active transport of oxidized glutathione (GSSG). Incubation of vesicles and GSSG in the presence of ATP resulted in the transport of GSSG into the vesicles. When vesicles were incubated with reduced glutathione (GSH), no transport was observed. At GSSG concentrations of less than 5 mM, transport was linear up to 4 hr at 37 degrees C. A Lineweaver-Burk plot of the transport rate as a function of GSSG concentration was biphasic and gave apparent Km values of 0.1 and 7.1 mM. The Km for ATP . Mg in this transport process was 0.63 mM at a GSSG concentration of 20 microM and 1.25 mM at a GSSG concentration of 5 mM. The transport rate at low GSSG concentrations was inhibited by CTP or UTP, which acted as competitive inhibitors of ATP; Ki=0.51 mM. This inhibition may account for the high erythrocyte GSH levels observed in pyrimidine-5'-nucleotidase deficiency, a disorder in which erythrocytic levels of CTP and UTP are elevated.
Sodium-dependent silicate transport in the apochlorotic marine diatom
Nitzschia alba
Authors: Bhattacharyya Pinakilal , Volcani Benjamin E.
Published: May 2006

Silicate uptake by
Nitzschia alba
cells is higher in medium containing Na
+
than in media lacking Na
+
but containing K
+
, Rb
+
, NH
4
+
, Li
+
, or choline
+
. The initial rate is inhibited by monensin and gramicidin but not by valinomycin or nigericin and is less sensitive to inhibition by carbonyl cyanide
m
-chlorophenylhydrazone (CCCP). In isolated membrane vesicles, silicate is taken up when a Na
+
gradient is imposed across the membrane or is generated by cytoplasmic Na
+
,K
+
-ATPase. H
+
or K
+
gradients in either direction do not stimulate uptake. Na
+
-gradient-dependent uptake is inhibited by monensin but not by CCCP, valinomycin, or vanadate, which inhibits the cytoplasmic Na
+
,K
+
-ATPase. Uptake increases if an internally negative potential is imposed across the membrane. The vesicular uptake shows saturation kinetics with a
K
m
of 62 μM and a
V
max
of 4.1 nmol/mg of protein per min. In intact cells, the initial rate of silicate uptake increases with pH up to 9.5. Thus, in
N. alba
, silicate is symported with Na
+
, and the transport system is driven by the Na
+
gradient that is generated and maintained across the membrane by the activity of Na
+
,K
+
-ATPase.
Aggregation of small oligonucleosomal chains into 300-A globular particles.
Authors: Jorcano J L , Meyer G , Day L A , Renz M
Published: May 2006

Chicken erythrocyte oligonucleosomes (trimers to about 20-mers) are able to interact with each other through the very lysine-rich histones (H1 and H5) and form heterogeneous globular particles with a mean diameter of about 300 A. These particles assemble spontaneously during micrococcal nuclease digestion of chromatin in the presence of 30 mM NaCl and contain approximately 25 nucleosomes. They are sensitive to ionic strength and unfold at lower salt concentrations but can be reconstituted by restoring the initial salt concentration. Even at 30 mM NaCl, the particles remain dynamic structures, being in equilibrium with their oligonucleosomal components as revealed by the fact that particle stability depends on the concentration of oligonucleosomes.
Characterization of slow reacting substances (SRSs) of rat basophilic leukemia (RBL-1) cells: effect of cysteine on SRS profile.
Authors: Sok D E , Pai J K , Atrache V , Sih C J
Published: May 2006

When RBL-1 cells were incubated with L-cysteine (7.5 mM) and the ionophore A23187, the slow reacting substances SRS-GSH and SRS-Cys-Gly were formed. When L-cysteine was omitted in the incubation, SRS-GSH and SRS-Cys were isolated but only a trace amount of SRS-Cys-Gly was detectable. Each of the characterized SRSs was accompanied by an as yet uncharacterized structural isomer showing UV absorption at 278 nm. L-Cysteine and other thiols inhibited an aminopeptidase that transforms the highly bioactive SRS of anaphylaxis (SRS-Cys-Gly) into the less bioactive SRS-Cys. SRS-GSH, SRS-Cys-Gly, and SRS-Cys may be readily distinguished from each other by means of their bioactivities, antagonism by FPL 55712, and relative susceptibilities to the actions of soybean lipoxygenase, microsome-bound leucine aminopeptidase, and gamma-glutamyl transpeptidase.
Three-dimensional structure of a protein from scorpion venom: a new structural class of neurotoxins.
Authors: Fontecilla-Camps J C , Almassy R J , Suddath F L , Watt D D , Bugg C E
Published: May 2006

The three-dimensional crystal structure of variant-3 toxin from the scorpion Centruroides sculpturatus Ewing has been determined at 3 A resolution. Phases were obtained by use of K2PtCl4 and K2IrCl6 derivatives. The most prominent secondary structural features are two and a half turns of alpha-helix and a three-strand stretch of antiparallel beta-sheet, which runs parallel to the alpha-helix. The helix is connected to the middle strand of the beta-sheet by two disulfide bridges; a third disulfide bridge is located nearby. Several loops extend out of this dense core of secondary structure. The largest loop is joined to the COOH terminus of the molecule by the fourth disulfide bridge. The overall shape of the molecule resembles a right-hand fist: the alpha-helix runs along the knuckles of the fist; the beta-sheet lies along the second and third joints of the fingers; the thumb is defined by two short loops that are composed of residues 16-21 and residues 41-46; the wrist corresponds to the COOH-terminal stretch of residues 52-65 and a loop composed of residues 5-14; and the second joint of the little finger is near the NH2 terminus of the molecule. The alpha-carbon backbone displays a large flat surface that lies along the second joints of the fingers and the heel of the hand in the fist model. Several of the conserved residues in the scorpion neurotoxins are clustered on this surface, which may play a role in interactions of scorpion toxins with sodium channels of excitable membranes.
Mechanism of action of glucagon on hepatocyte phosphofructokinase activity.
Authors: Claus T H , Schlumpf J R , el-Maghrabi M R , Pilkis J , Pilkis S J
Published: May 2006

Addition of glucagon to isolated hepatocytes reduced the activity of 6-phosphofructokinase (ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) and pyruvate kinase (ATP:pyruvate 2-O-phosphotransferase, EC 2.7.1.40). Phosphorylation contributed to the inhibition of pyruvate kinase, but several lines of evidence indicated that this reaction was not responsible for the inhibition of phosphofructokinase. First, the increase in phosphorylation in intact cells induced by increasing the concentration of glucagon did not correlate well with the decrease in enzyme activity. Second, phosphorylation of phosphofructokinase induced by addition of cyclic AMP and Mg2+-ATP or by addition of Mg2+-ATP and the catalytic subunit of the cyclic AMP-dependent protein kinase to hepatocyte extracts had no effect on enzyme activity. Third, ammonium sulfate precipitation of the enzyme from extracts of cells incubated with glucagon abolished the hormone effect. The effect could be restored, however, by the addition of a phosphofructokinase-free extract from glucagon-treated cells to the ammonium sulfate-treated enzyme from either untreated or glucagon-treated cells. These results suggest that the inhibition of phosphofructokinase by glucagon is due to changes in the level of an allosteric effector(s).
Homology exists among the transforming sequences of avian and feline sarcoma viruses.
Authors: Shibuya M , Hanafusa T , Hanafusa H , Stephenson J R
Published: May 2006

Fujinami sarcoma virus (FSV) of chickens does not contain nucleotide sequences related to the src gene of Rous sarcoma virus, but it carries unique sequences of at least 3000 bases, which are likely to code for the transforming protein of this virus. Using radioactive DNA complementary to FSV-unique sequences, we investigated the relatedness of FSV to other sarcoma-leukemia retroviruses in vertebrates. Under conditions of moderate stringency, no cross-hybridization was detected between FSV cDNA and RNAs of Rous sarcoma virus, Y73 avian sarcoma virus, several representative avian acute leukemia viruses, or Abelson murine leukemia virus. This cDNA, however, did hybridize with RNA of PRCII sarcoma virus of chickens to the extent of 56%. In addition, FSV cDNA was found to hybridize with RNAs of Gardner-Arnstein and Snyder-Theilen strains of feline sarcoma virus to the extent of 27% and 19%, respectively, but not with RNA of McDonough feline sarcoma virus. Studies on thermal denaturation of hybrids showed that the melting temperatures of the heteroduplexes of the FSV cDNA with RNAs of PRCII and Gardner-Arnstein feline sarcoma virus were 7 degrees C and 12 degrees C lower, respectively, compared with the melting temperature of the homologous hybrid of FSV, and suggested less than 10% mismatching in both heteroduplexes. These results indicate that nucleotide sequences closely related to at least a part of FSV-unique sequences are present in the genomes of other sarcoma viruses obtained in chickens and in cats.
Evidence for a 3-O-sulfated D-glucosamine residue in the antithrombin-binding sequence of heparin.
Authors: Lindahl U , Bäckström G , Thunberg L , Leder I G
Published: May 2006

An octasaccharide with high affinity for antithrombin was isolated after partial deaminative cleavage of heparin with nitrous acid. After conversion of the 2,5-anhydro-D-mannose end group to anhydro[1-3H]mannitol, labeled pentasaccharide was released from the octasaccharide by periodate-alkali treatment. Incubation of the pentasaccharide with a recently discovered 3,O-sulfatase from human urine resulted in desulfation, suggesting the occurrence of a 3-sulfate group on the terminal glucosamine residue. The same glucosamine residue was recovered as a 2,5-anhydro[1-3H]mannitol derivative by a procedure involving deamination of the octasaccharide with nitrous acid, reduction of the products with sodium boro[3H]hydride, isolation of 3H-labeled tetrasaccharide by gel chromatography, and release of the labeled end-group by periodate-alkali treatment. Paper electrophoresis indicated disulfated anhydro[3H]mannitol, presumably sulfated at C3 and C6, as a major component, along with smaller amounts of monosulfated (presumably 3-sulfated) anhydro[3H]mannitol. Similar treatment of an analogous tetrasaccharide derived from heparin with low affinity for antithrombin failed to produce any disulfated anhydromannitol. These results suggest that 3-sulfated glucosamine is a unique component of high-affinity heparin, located at a specific position in the antithrombin-binding sequence of the molecule.
Lateral distribution and diffusion of the C3b receptor of complement, HLA antigens, and lipid probes in peripheral blood leukocytes.
Authors: Petty H R , Smith L M , Fearon D T , McConnell H M
Published: May 2006

Fluorescence microscopy and fluorescence redistribution after pattern photobleaching have been used to measure the distribution and motion of a number of fluorescent molecules bound to the plasma membranes of human leukocytes. The fluorescent molecules include fluorescein-labeled F(ab')2 and Fab' fragments of an anti-C3b receptor antibody, fluorescein-labeled IgG and Fab fragments of a monoclonal anti-HLA antibody, and the two lipid probes 3,3'-dioctadecylindocyanine and N-4-nitrobenzo-2-oxa-1,3-diazole L-alpha-dimyristoyl phosphatidylethanolamine. From these studies we have concluded that the C3b receptors on human polymorphonuclear leukocytes and monocytes are predominantly present in discrete clusters. No diffusive motion of these clusters could be detected. In contrast, HLA antigens hve a dispersed distribution and have diffusion coefficients between 10(-9) and 10(-10) cm2/sec in these peripheral blood leukocytes. Cell-membrane-bound monoclonal IgG anti-HLA undergoes a rapid patching in all these leukocytes except lymphocytes. In about 50% of the lymphocytes, fluoresceinated IgG diffuses slowly, if at all, whereas in the other 50%, fluoresceinated IgG diffuses with a diffusion coefficient of 6.9 X 10(-10) cm2/sec. The two above-mentioned fluorescent lipid probes have the usual rapid lipid diffusion coefficient (approximately 10(-8) cm2/sec) in leukocytes.
Genetic variability and effective population size when local extinction and recolonization of subpopulations are frequent
Authors: Maruyama Takeo , Kimura Motoo
Published: May 2006

If a population (species) consists of
n
haploid lines (subpopulations) which reproduce asexually and each of which is subject to random extinction and subsequent replacement, it is shown that, at equilibrium in which mutational production of new alleles and their random extinction balance each other, the genetic diversity (1 minus the sum of squares of allelic frequencies) is given by 2

N
e
v

/(1 + 2

N
e
v

), where [Formula: see text] in which
Ñ
is the harmonic mean of the population size per line,
n
is the number of lines (assumed to be large), λ is the rate of line extinction, and
v
is the mutation rate (assuming the infinite neutral allele model). In a diploid population (species) consisting of
n
colonies, if migration takes place between colonies at the rate
m
(the island model) in addition to extinction and recolonization of colonies, it is shown that effective population size is [Formula: see text] If the rate of colony extinction (λ) is much larger than the migration rate of individuals, the effective population size is greatly reduced compared with the case in which no colony extinctions occur (in which case

N
e

=
nÑ
). The stepping-stone type of recolonization scheme is also considered. Bearing of these results on the interpretation of the level of genetic variability at the enzyme level observed in natural populations is discussed from the standpoint of the neutral mutation-random drift hypothesis.
Immunoreactive helix-destabilizing protein localized in transcriptionally active regions of Drosophila polytene chromosomes.
Authors: Patel G L , Thompson P E
Published: May 2006

A highly purified helix-destabilizing protein (HDP) obtained from rat liver has been used to elicit specific, high-titer anti-HDP sera in rabbits. These antisera show immunological crossreaction with single-stranded DNA binding proteins from several very diverse eukaryotic sources, including Drosophila embryos. The use of such antisera in the labeling of Drosophila salivary gland chromosomes by indirect immunofluorescence shows concentrations of immunoreactive HDP in many regions, but especially in chromosome puffs. There is a striking localization of HDP in heat shock puffs known to be sites of new transcription. The pattern of HDP distribution seems to implicate a transcriptional role, with some specificities independent of puffing itself.
Initial characterization of monoclonal antibodies against human monocytes.
Authors: Ugolini V , Nunez G , Smith R G , Stastny P , Capra J D
Published: May 2006

Three monoclonal antibodies against human monocytes have been produced by somatic cell fusion. Extensive specificity analysis suggests that these antibodies react with most if not all human peripheral blood monocytes and not with highly purified T or B cells. Initial chemical characterization of the monocyte antigen recognized by two of these antibodies is presented. The molecule is a single polypeptide chain with an apparent molecular weight of 200,000. These reagents should prove useful in the clinical definition of disorders of monocyte differentiation, in studies of monocyte function, and in the elucidation of the genetics and structure of monocyte cell surface antigens.