bluuebunny/crossref_metadata_2025 huggingface dataset:
Isomeric aminoacyl-tRNAs are both bound by elongation factor Tu.
Authors: Hecht S M , Tan K H , Chinault A C , Arcari P
Published: May 2006

Recent suggestions that elongation factor Tu (EF-Tu) is specific for 2'-O-aminoacyl-tRNA, as compared with the 3'-isomer, prompted us to assay [3H]aminoacyl-tRNAs from Escherichia coli terminating in 2'- or 3'-deoxyadenosine for binding to EF-Tu to determine the possible positional specificity of the factor. Binding of modified aminaocyl-tRNAs to EF-Tu-GTP was measured both as a function of the ability of EF-Tu-GTP to diminish the rate of chemical deacylation of [3H]aminoacyl-tRNAs and by gel filtration of the individual ternary complexes. Fifteen different tRNA isoacceptors were tested by the deacylation procedure, including three (tRNAAsp, tRNACys, and tRNATyr) for which isomeric modified aminoacyl-tRNAs were available. All of the modified aminoacyl-tRNAs were protected fromdeacylation, although generally to a lesser extent than the corresponding unmodified species. Six modified tRNA isoacceptors (including tRNATrp and tRNATyr, for which both modified aminoacyl-tRNAs were accessible by enzymatic aminoacylation) were used in gel filtration experiments to permit direct measurement of the individual aminoacyl-tRNA-EF-Tu-GTP complexes. These experiments were also done in the presence of equimolar amounts of the corresponding unmodified [14C]aminoacyl-tRNAs, and the relative affinities for a limiting amount of EF-Tu-GTP were measured. The results were completely consistent with those obtained by the deacylation procedure and indicated that EF-Tu can bind to both positional isomers of aminoacyl-tRNA with no obvious preference for either.
Heteroduplex analysis of avian RNA tumor viruses.
Authors: Junghans R P , Hu S , Knight C A , Davidson N
Published: May 2006

Electron microscopic heteroduplex analysis of avian RNA tumor viruses has been undertaken by using 35S viral RNA and long, complementary DNA synthesized in vitro. In this initial study, heteroduplex molecules were formed between complementary DNA from Rous sarcoma virus [Prague B strain (Pr-B)] and RNAs from Pr-B and Rous sarcoma virus [Prague C strain (Pr-C)] and from their transformation defective (td) derivatives, td-Pr-B and td-Pr-C. In the case of heteroduplexes with the td viruses, a deletion loop was observed of the order of two kilobases in size and less than one kilobase from the 3' terminus of the RNA. This deletion probably spans part or all of the sequences of one or more genes in the nondefective sarcoma virus which are essential for cell transformation. The sizes and the positions of the deletions in the td-Pr-B and td-Pr-C viruses were slightly, but significantly, different. No nonhomology features were observed in the Pr-B-Pr-C hybrids, thus confirming the close genetic relatedness of the two viruses. All heteroduplexes contained a proportion of circular and dimer molecules. This observation is a direct demonstration that (-) strand DNA transcription begins at an internal position of the RNA genome, proceeds to the 5' end, reinitiates at the 3' end of the RNA, and copies the remainder of the viral genome. Other implications for models of RNA tumor virus replication are also developed from these data.
A thermostable sequence-specific endonuclease from Thermus aquaticus.
Authors: Sato S , Hutchinson C A , Harris J I
Published: May 2006

A sequence-specific endonuclease, Taq I, of novel specificity has been partially purified from an extreme thermophile, Thermus aquaticus. The enzyme cleaves bacteriophage lambda DNA at many (greater than 30) sites and bacteriophage psiX174 RF DNA at 10 sites. The enzyme is active at temperatures up to 70 degrees. The cleavage sites on psiX174 RF DNA have been mapped. The sequence recognized and cleaved by Taq I has been shown to be the symmetrical tetranucleotide: (formula: see text).
Polymorphism and the subunit structure of enzymes: a contribution to the neutralist-selectionist controversy.
Authors: Harris H , Hopkinson D A , Edwards Y H
Published: May 2006

The occurrence of polymorphism in a series of 87 different loci coding for enzyme structure in human populations has been related to the size and the number of subunits in the corresponding enzymes. Polymorphic and nonpolymorphic enzymes did not differ on average in subunit size. However, multimeric enzymes showed a significantly lower incidence of polymorphism than didmonomeric enzymes. A particularly low incidence of polymorphism was noted among multimeric enzymes in which interlocus molecular hybrids occur. The findings are discussed in terms of the "neutralist" and "selectionist" hypotheses of polymorphism.
A sex-limited serum protein of Syrian hamsters: definition of female protein and regulation by testosterone.
Authors: Coe J E
Published: May 2006

Normal Syrian hamster females contain a serum protein not found by simple gel diffusion assay in normal adult males. This sex-limited protein was called female protein (FP). Low levels of FP were found in sera from normal weanling male hamsters. Adult male hamsters castrated or treated with diethylstilbestrol also developed serum FP, which could be suppressed by administration of testosterone. Exogenous testosterone also suppressed serum FP in adult females, and ovarian function did not appear to be critical for maintenance of serum FP. Although FP is present in significant amounts (1-2 mg/ml) in adult females, its function is presently unknown.
Studies on nucleic acid reassociation kinetics: rate of hybridization of excess RNA with DNA, compared to the rate of DNA renaturation.
Authors: Galau G A , Britten R J , Davidson E H
Published: May 2006

The rate of reaction of double-stranded replicative form (RF) [3H]DNA of bacteriophage phiX174 with excess (+)strand DNA and (+)strand RNA was measured by standard methods of hydroxyapatite chromatography. The reactions follow pseudo-first-order kinetics and the observed rate constant for the RNA-DNA reaction differs less than 25% from that of the DNA-DNA reaction. The pseudo-first-order rate constants are close to the value predicted on the basis of the second-order rate constant measured in the renaturation of the double-stranded phiX RF [3H]DNA.
Differential effects of chemical inducers on expression of beta globin genes in murine erythroleukemia cells.
Authors: Nudel U , Salmon J E , Terada M , Bank A , Rifkind R A , Marks P A
Published: May 2006

Murine erythroleukemia cells are induced to erythrodifferentiate by polar compounds such as dimethyl sulfoxide and hexamethylene bisacetamide as well as by fatty acids such as butyric acid and propionic acid. The effect of these inducers on the expression of two beta globin genes, betamaj and betamin, during the course of differentiation of the cells has been examined. After 4 days of culture with hexamethylene bisacetamide or dimethyl sulfoxide, the betamaj-containing hemoglobin (Hbmaj) predominates. By contrast, in the presence of butyric acid or propionic acid, after 4 days of culture, relatively equal amounts of Hbmaj and Hbmin are found. When cultured with dimethyl sulfoxide or hexamethylene bisacetamide, murine erythroleukemia cells synthesize more betamaj than betamin, while about equal amounts of the two globins are synthesized in the presence of butyric acid. When poly(A)-containing RNA from the cells exposed to different inducers is translated in a wheat germ cell-free system, the ratio of betamaj to betamin synthesized reflects that in whole cells. In a strain of murine erythroleukemia cells resistant to dimethyl sulfoxide (DR-10), the preferential stimulation of betamaj synthesis by hexamethylene bisacetamide of the betamin synthesis by butyric acid is more pronounced than with the dimethyl sulfoxide-sensitive cells (DS-19). These data suggest that polar compounds and fatty acids cause different expression of the betamaj and betamin genes in murine erythroleukemia cells.
180 degrees rotation of ciliary rows and its morphogenetic implications in Tetrahymena pyriformis.
Authors: Ng S F , Frankel J
Published: May 2006

With quasi-surgical techniques, longitudinal somatic ciliary rows in Tetrahymena pyriformis have been rotated 180 degrees. New structures formed in the rotated ciliary rows during growth and reproduction are disposed 180 degrees opposite to their normal positions or orientations, confirming the earlier findings of Beisson and Sonneborn on Paramecium. However, during cell fission the rotated ciliary rows exhibit abnormality in orientation along the fission zone; the configuration of these rows near the anterior end of the posterior product of fission is consequently affected. Rotated ciliary rows have been employed as a tool in the analysis of morphogenetic problems: (a) The contractile vacuole pore is normally located on the left side of a ciliary row; but it is on the right of inverted rows. Hence, the morphogenetic properties of the two sides of the ciliary row associated with the contractile vacuole pore are different and this difference is the sole determinative factor as to the side of the ciliary row on which the contractile vacuole pore is located. (b) The process that generates the rotated ciliary rows frequently also brings about the implantation of an extra band of longitudinal microtubules at a specific site on the cell surface. This extra structure is inheritable, which opens up opportunities for the study of microtubular assembly in vivo.
Chromatium hydrogenase.
Authors: Kakuno T , Kaplan N O , Kamen M D
Published: May 2006

Previous reports of a relatively air-stable soluble hydrogenase from the photosynthetic anaerobe, Chromatium vinosum, have been substantiated. The properties of this enzyme, as seen in highly purified samples prepared by procedures that permit improved yields, are described. A possible role for flavin mediation is noted.
Nitrogen-15 nuclear magnetic resonance of aliphatic tripeptides.
Authors: Markowski V , Posner T B , Loftus P , Roberts J D
Published: May 2006

The 15N chemical shifts of eight aliphatic tripeptides have been measured at the natural-abundance level. For a given tripeptide, the resonances of the COOH-terminal and NH2-terminal amino acids can be identified by measurements at low or high pH. The shifts of the NH2-terminal amino acid nitrogens are essentially independent of the amino acids in the rest of the peptide. The shifts of the other nitrogens are characteristic of the amino acids themselves and of the immediately preceding amino acid toward the NH2 terminus. Non-terminal amide nitrogens have shifts of about 6 ppm upfield of COOH-terminal amide nitrogens at the isoelectric point of measurement. 15N chemical shifts appear to have considerable potential value for peptide sequencing.
Fourier analysis on the Heisenberg group
Authors: Geller Daryl
Published: May 2006

We obtain a usable characterization of the (group) Fourier transform of 𝒮(H

n

) (Schwartz space on the Heisenberg group). The characterization involves writing elements of [Formula: see text] as asymptotic series in Planck's constant. In the process, we derive a new “discrete” version of spherical harmonics, and elucidate the theory of group contractions. We give an application to Hardy space theory.
A bacteriophage system for screening and study of biologically active polycyclic aromatic hydrocarbons and related compounds.
Authors: Hsu W T , Harvey R G , Lin E J , Weiss S B
Published: May 2006

The usefulness of bacterial viruses for detecting substances that are potentially carcinogenic is reexamined as a model system for screening biologically active polycyclic aromatic hydrocarbons. A modification of the original assay procedure allows one to distinguish between aromatics that can modify the biological activity of infectious nucleic acids directly and those polycyclic aromatic hydrocarbons that require metabolic activation by Escherichia coli enzymes. The effect of chemical modification of several different polycyclic aromatic hydrocarbons, with respect to their biological activity in the phage assay system, is described. Among the 31 different compounds examined, (+/-)-anti-benzo[a]pyrene-7,8-diol-9,10-epoxide was the most potent inhibitor of infectious phage nucleic acid. The (+) and (-) isomers of the above racemic mixture did not differ significantly in their capacity to inhibit phage replication.
Heterogeneous nuclear RNA secondary structure: oligo (U) sequences base-paired with poly (A) and their possible role as binding sites for heterogeneous nuclear RNA-specific proteins.
Authors: Kish V M , Pederson T
Published: May 2006

HeLa cell heterogeneous nuclear RNA derived from high-molecular-weight nuclear ribonucleoprotein (RNP) particles contains oligo(U) sequences of 15-50 nucleotides base-paired with poly(A). These duplexes are resistant to pancreatic RNase at 0.5 M NaCl in native RNP, remain so after chemical deproteinization of the RNP digests, and then copurify with poly(A) on oligo(dT)-cellulose chromatography. Oligo(dT)-cellulose binding capacity of the oligo(U)-poly(A) duplexes is abolished by prior titration of the nonduplex poly(A) regions with excess poly(U). The oligo(dT)-purified fraction is 97.5 mole % A + U and the [3H]uridine-labeled component is resistant to redigestion by pancreatic RNase at 0.5 M NaCl but not at 0.01 M NaCl. After thermal denaturation, the [3H]uridine-labeled chains become RNase-sensitive at 0.5 M NaCl. Electrophoresis of [3H]adenosine- or [3H]uridine-labeled material in polyacrylamide gels containing 99% formamide confirms that the oligo(U) sequences are not covalently linked to poly(A). Controls establish that the A-U duplexes are not formed artifactually during isolation of heterogeneous nuclear RNP or subsequent fractionation. The oligo(U)-poly(A) duplexes appear to be associated with protein in native heterogeneous nuclear RNP, as reflected by the differential pancreatic RNase sensitivity of the duplexed oligo(U) in RNP (resistant) and RNA (sensitive), measured at physiological ionic strength.
Biological function of gramicidin: selective inhibition of RNA polymerase.
Authors: Sarkar N , Langley D , Paulus H
Published: May 2006

This paper describes a novel biochemical effect of gramicidin, a class of peptide antibiotics produced by Bacillus brevis during the transition from vegetative growth to sporulation. Gramicidin inhibits RNA synthesis by purified RNA polymerase (nucleosidetriphosphate:RNA nucleotidyl-transferase, EC 2.7.7.6) by interfering with the binding of RNA polymerase to DNA. This effect seems to involve the destabilization of the "open" RNA polymerase-DNA complex, a mode of action consistent with the control of promoter selection. Selectivity in the inhibition of RNA synthesis by gramicidin is observed when transcription is partially blocked by low levels of actinomycin D. Since the inhibition of RNA synthesis by gramicidin is obtained in a highly purified system devoid of membranes, it must be distinct from the ionophoretic activity of the antibiotic. It is possible that this new mode of action reflects the function of gramicidin during bacterial sporulation.
Relationship between interferon production and interferon messenger RNA synthesis in human fibroblasts.
Authors: Raj N B , Pitha P M
Published: May 2006

Poly(A) containing mRNA prepared from poly(rI)-poly(rC)-induced human fibroblasts stimulated [14C]leucine incorporation into protein in wheat germ cell-free extracts. For the translation of interferon mRNA into a biologically active product, the presence of spermine was essential. The protein synthesized in vitro fulfilled the criteria for human interferon--namely, its antiviral activity was species specific, and its activity was completely neutralized by antiserum to human fibroblast interferon. The amount of interferon synthesized in human fibroblasts induced by poly(rI)-poly(rC) (normal induction) and poly(rI)-poly(rC) in the presence of cycloheximide (superinduction) was compared to the amount of translatable interferon mRNA both in the wheat germ cell-free system and the Xenopus oöcyte system. Although the production of interferon after the termination of transcription by actinomycin D was markedly increased in superinduced cells, the measurable amount of interferon mRNA as assayed in the oöcyte system was only slightly higher in superinduced cells than in cells induced with poly(rI)-poly(rC) alone. When compared in the wheat germ cell-free system, however, the translational product of mRNA preparation from cells induced with poly(rI)-poly(rC) alone was inactive while that from superinduced cells was active.
Purified DNAs are transcribed after microinjection into Xenopus oocytes.
Authors: Mertz J E , Gurdon J B
Published: May 2006

The possibility of using DNA-injected Xenopus laevis oocytes and eggs for studying the control of transcription in eukaryotes has been investigated. When purified DNA of simian virus 40 (SV40) is injected into Xenopus laevis oocytes, tritiated RNA precursors are incorporated into DNase-I-resistant, RNase-A- and alkali-sensitive material that hybridizes specifically to SV40 DNA. This viral transcription continues for at least 5 days and occurs only when the injected DNA is directed to the nucleus of the oocyte. The quantity of SV40-specific RNA produced is roughly proportional to the amount of DNA injected; above 1 ng per oocyte, most of the nonribosomal RNA made in successfully injected oocytes is virus-specific. Transcription also occurs, although at a lower efficiency, after injection of the DNA into unfertilized eggs. The DNAs of adenovirus 5, cloned Drosophila melanogaster histone genes, and even bacteriophage phiX174 replicative form, bacteriophage phi80plac, and the ColE1 plasmid are also transcribed after injection into oocytes or eggs.
Characterization of the integration protein of bacteriophage lambda as a site-specific DNA-binding protein.
Authors: Kotewicz M , Chung S , Takeda Y , Echols H
Published: May 2006

The Int protein specified by bacteriophage lambda is required for the recombination event that integrates the viral DNA into the host genome at its specific attachment site. Using a DNA-binding assay, we have partially purified the Int protein and studied some of the features of its binding specificity and regulation. The DNA-binding activity is attributed to Int protein because the activity is eliminated by a nonsense mutation or a deletion in the int gene, and is rendered thermolabile by temperature-sensitive mutations in the int gene. The DNA-binding activity is specific for DNA carrying an appropriate attachment site, suggesting that Int protein directs the sequence-specific recognition essential for integrative recombination. The specific DNA-binding activity is also missing after infection by phage carrying mutations in the cII and cIII regulatory genes of lambda. This finding corroborates the conclusion from other types of experiments that regulation of the int and cI genes by cII/cIII provides for coordinate regulation of both major events of the lysogenic response, establishment of repression and insertion of viral DNA.
Local starvation for epidermal growth factor cannot explain density-dependent inhibition of normal human glial cells.
Authors: Westermark B
Published: May 2006

Mouse epidermal growth factor (mEGF) is a potent growth promoter of human glial cells in sparse cultures, whereas very little stimulation of growth in dense cultures is induced by the factor. In the present communication, the possibility that the density-dependent inhibition is caused by a reduced binding/uptake of the factor was scrutinized. It was found that the number of mEGF binding sites was 20,000 and 35,000 per cell in sparse and dense cultures, respectively. The dissociation constant of the binding reaction was not influenced by the cell density. It was concluded that crowded cells are not starved for the factor and that a decrease in number or affinity of the EGF receptors can be excluded as a cause of the inhibition.
Radioimmunoassay of creatine kinase-B isoenzyme in human sera: results in patients with acute myocardial infarction.
Authors: Willerson J T , Stone M J , Ting R , Mukherjee A , Gomez-Sanchez C E , Lewis P , Hersh L B
Published: May 2006

A radioimmunoassay was developed to measure serum levels of the B isoenzyme of creatine kinase(ATP: creatine N-phosphotransferase, EC 2.7.3.2) (CPK) in order to evaluate the time course and frequency of MB isoenzyme elevation in patients with acute myocardial infarction. The method can identify as little as 0.2 ng of the B portion of the CPK-MB isoenzyme, does not significantly crossreact with CPK-MM isoenzyme, and is not affected by storage of serum at --20 degrees CPK isoenzyme containing B subunits was detected in 48 out of 51 sera from normal adults; serum levels in these individuals ranged between 1.2 and 12.5 ng/ml [mean +/- SEM was 2.7 +/- 0.30 ng/ml]. The mean serum level of CPK-B isoenzyme in a pool of sera obtained from 100 normal subjects was 2.9 +/- 0.35 ng/ml; two patients with rhabdomyolysis that were studied had serum CPK-B isoenzyme levels of 2.5 and 3.5 ng/ml, respectively. In contrast, serum levels of the CPK-B isoenzyme were markedly elevated in sera from 18 patients with acute myocardial infarcts when obtained within 12 hr after hospital admission; the mean +/- SEM concentration was 56 +/- 7.8 ng/ml. We performed serial determinations on 14 patients with acute myocardial infarcts and demonstrated that maximal serum CPK-B levels occurred within the first 12 hr after admission and were lower thereafter. The serum concentration of B-containing CPK isoenzyme in 19 additional patients admitted with chest pain but without acute myocardial infarction was 3.4 +/- 0.50 ng/ml. Thus, radioimmunoassay measurement of CPK-B isoenzyme appears to be a useful and sensitive test for the detection of acute myocardial infarcts in patients.
Effect of regenerated endothelium on lipid accumulation in the arterial wall.
Authors: Minick C R , Stemerman M G , Insull W
Published: May 2006

We tested the hypothesis that loss of endothelium results in increased transport of lipoprotein into the arterial wall, favors accumulation of lipid, and thus predisposes to atherosclerosis. In rabbits initially fed a diet low in lipid, the aortas were de-endothlialized with an intraarterial balloon catheter; 28 days later, the animals were divided into two groups. Group I animals were continued on a diet low in lipid and sacrificed at 8, 11, 13, and 15 weeks after de-endothelialization. Group II animals were fed the same diet supplemented with 0.5% cholesterol and sacrificed at comparable intervals. Aortas of group I animals revealed proliferative fibromuscular intimal thickening in both de-endothelialized and re-endothelialized areas, with little or no fatty change in the intima. In contrast, aortas of group II animals revealed slight to marked fatty change in the intima, characterized by accumulation of oil red O-positive material with anisotropic lipid inclusions. The greatest quantity of lipid was present in intimal thickening beneath regenerated endothelium, and not in adjacent intimal thickening lacking an endothelial lining. These results do not support the hypothesis that the absence of endothelium favors accumulation of lipid and predisposes to atherosclerosis. The experiments indicate that lipid accumulates preferentially in areas of intimal thickening covered by regenerated endothelium.
Relationship between serum sex hormones and glucose, insulin and lipid abnormalities in men with myocardial infarction.
Authors: Phillips G B
Published: May 2006

Fifteen patients who had had a myocardial infarction before the age of 43 were compared with thirteen age-matched normal subjects. Twelve of the patients and three of the controls had a delayed glucose and insulin peak in the glucose and insulin areas than normal curves. When the measurements of the four patients with the largest areas under the glucose tolerance curve were separated, significant correlations were observed in the remaining patients and controls. The ratio in serum of the concentrations of estradiol-17beta to testosterone (E/T) correlated with serum glucose area (r equals + 0.69, P is less than 0.001), insulin area (r equals + 0.80, P is less than 0.001), and the ratio of insulin area to glucose area (I/G) (r equals + 0.64, P is less than 0.005) in the glucose tolerance test. Serum cholesterol concentration correlated with E/T, insulin area, and I/G, and serum triglyceride concentration correlated with glucose area, I/G, and serum cholesterol concentration. The hypothesis is presented (i) that in men who have had a myocardial infarction, an abnormality in glucose tolerance and insulin response and elevation in serum cholesterol and triglyceride concentrations are all part of the same defect (glucose-insulin-lipid defect), (ii) that this glucose-insulin-lipid defect when glucose intolerance is present is the "mild diabetes" commonly associated with myocardial infarction but is based on a mechanism different from that of classical diabetes, (iii) that this glucose-insulin-lipid defect is secondary to an elevation in E/T, and (iv) that an alteration in the sex hormone milieu is the major predisposing factor for myocardial infarction.
Specific projection of displaced retinal ganglion cells upon the accessory optic system in the pigeon (Columbia livia).
Authors: Karten J H , Fite K V , Brecha N
Published: May 2006

In the pigeon, the nucleus of the basal optic root, a component of the accessory optic system, projects directly upon the vestibulo-cerebellum. This nucleus receives a prominent projection composed of large-diameter retinal axons, known as the basal optic root. The cells of origin of this tract were identified using horseradish peroxidase (donor:hydrogen-peroxide oxidoreductase, EC 1.11.1.7) as a retrograde marker. Injections of horseradish peroxidase confined primarily to the basal optic root nucleus labeled displaced ganglion cells of the contralateral retina. Cell sizes were 18-30 micronm and the dendrites of these cells were confined to the first stratum of the inner plexiform layer. Approximately 3700 displaced ganglion cells were labeled after injections of horseradish peroxidase into basal optic root. In contrast, no displaced ganglion cells were labeled after injections of horseradish peroxidase into the optic tectum, which labeled only cells in the ganglion cell layer proper. These findings indicate that displaced ganglion cells constitute a unique population of retinal neurons that give rise to a bisynaptic pathway directed to the cerebellum via the nucleus of the basal optic root. These displaced ganglion cells may play a major role inoculomotor reflexes.
On the bonding of FeO2 in hemoglobin and related dioxygen complexes.
Authors: Reed C A , Cheung S K
Published: May 2006

The celebrated Fe(II)0(2) versus Fe(III) (02-) debate over the formal representation of the Fe02 moiety in hemoglobin can be resolved by consideration of the utility of each formalism. In the context of rationalizing the gross structural and electronic features of end-bound dioxygen, particularly in light of a new closely related chromium complex, the M(III)-(02-) formulation is both chemically reasonable and most useful. In conjunction with a qualitative molecular orbital overlap picture, the differing magnetic states of enc-bound M02 complexes and other geometrical features can be rationalized or predicted.
Radioimmunoassay of a human serum growth factor for Balb/c-3T3 cells: derivation from platelets.
Authors: Antoniades H N , Scher C D
Published: May 2006

A radioimmunoassay has been developed for the detection and quantification of a human serum polypeptide that has growth-promoting activity for confluent Balb/c-3T3 cells. Antiserum to this growth factor does not recognize antigens in mouse, guinea pig, or bovine serum but does detect some crossreacting antigen in the serum of the New World monkey Cebus albifrons and more in the serum of the Old World rhesus monkeys Macaca mulatta and M. fascicularis, demonstrating that the antigenic determinants of the growth factor have a degree of species specificity. Serum derived from whole human blood contains approximately 770 pg of the growth factor per mg of protein; serum derived from platelet-poor blood contains about 112 pg of the growth factor per mg of protein. As much as 1 microng of the growth factor per mg of protein has been recovered from human platelets by heating them at 100 degrees for 2 min. Approximately 1-2 ng of the growth factor, in either whole serum or platelets, stimulates 5 to 10 X 10(3) confluent Balb/c-3T3 cells to replicate. The heat treatment of platelets allows the purification and quantitative recovery of the growth factor from blood.
L-3,4-dihydroxyphenylalanine-induced hypersensitivity simulating features of denervation.
Authors: Tang L C , Cotzias G C
Published: May 2006

The manner in which dyskinesia and intermittency of neurological control had emerged late in the therapy of Parkinsonism with L-3,4-dihydroxyphenylalanine (levodopa) had suggested to us that this drug can imprint on the brain a chemical memory of its passage. The majority of authors ascribed these events to denervation hypersensitivity caused by the nigral and other lesions of the disease. By feeding levodopa to mice, however, we induced a state that simulated denervations hypersensitivity, including hyperreaction to single injections of levodopa and increased dopamine-stimulated adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] activity in homogenates of caudate nuclei. These phenomena were not caused by actual denervation, because the hypersensitivity declined and disappeared some weeks after the dietary levodopa was stopped.
Association of e antigen with Dane particle DNA in sera from asymptomatic carriers of hepatitis B surface antigen.
Authors: Werner B G , O'Connell A P , Summers J
Published: May 2006

Sera containing hepatitis B surface antigen from 30 asymptomatic blood donors were assayed for e antigen (HBeAg) and antibody to e antigen (anti-HBe) by rheophoresis,. Fourteen samples (47%) had detectable HBeAg, ten (33%) had anti-HBe, and six (20%) had neither. DNA was extracted from 26 of these sera and assayed for its ability to anneal to a [32P]-DNA probe that is a copy of Dane particle DNA. All 10 HBeAg-positive samples tested contained DNA that formed specific hybrids with the DNA probe, as did one of 10 anti HBe-positive samples. Hybridization was not detected in nine sera containing anti-HBe and six sera without HBeAg or anti-HBe. Because the Dane particle is thought to be the hepatitis B virus, this association between HBeAg positivity and Dane particle DNA strongly supports the hypothesis that e antigen is a marker of the presence of the virus and, consequently, potential infectivity.
A defined minimal medium for axenic strains of
Dictyostelium discoideum
Authors: Franke Jakob , Kessin Richard
Published: May 2006

A defined, minimal medium for the cellular slime mold
Dictyostelium discoideum is reported
.
3':5'-cyclic AMP and hormonal control of puparium formation in the fleshfly Sarcophaga bullata.
Authors: Fraenkel G , Blechl A , Blechl J , Herman P , Seligman M I
Published: May 2006

Injection of 3':5'-cyclic AMP (cAMP) into larvae of the fly Sarcophaga bullata 3-4 hr before the beginning of puparium formation (red-spiracle stage) greatly accelerates the onset of tanning without affecting initiation of puparium formation (anterior retraction). Accelerated tanning resembles real tanning in two important respects: the solubility of cuticular proteins becomes reduced and [U-14C]tyrosine is incorporated into the cuticle. Of a number of cAMP analogues tested, 3':5'- cyclic GMP, 2':3'-cyclic AMP, and 5'-AMP were inactive, dibutyryl-3':5'-cAMP had only slight activity, and cyclic IMP and deoxy-3':5'-cAMP showed some activity. Theophylline enhanced the effect of small doses of cAMP or of blood, diluted 1:8, active in the puparium tanning factor. Injection of dopa, dopamine, acetyldopamine, or epinephrine, but not of tyrosine, had an accelerating effect similar to that of cAMP. The tanning-inhibiting effect of DL-alpha-methyl-alpha-hydrazino-beta-(3,4-dihydroxyphenyl)propionic acid monohydrate is reversed by dopamine or epinephrine, but not by tyrosine, dopa, or cAMP. Evidence is presented to indicate that the responses to cAMP are not artifacts but reflect actual biochemical events during tanning.
On the cyclonic mean circulation of large lakes
Authors: Csanady G. T.
Published: May 2006

In large lakes, during the heating season, the combination of surface wind drift and solar heating results in the horizontal transport of some of the absorbed heat into the coastal zone. Large-scale vertical movements associated with alternating upwellings and downwellings distribute the heat over a deeper water mass than at mid-lake. As a result, the mean shape of isotherm surfaces is “domed” and, correspondingly, the lake surface is slightly raised near shore and depressed over the center thermocline dome. The mean circulation in geostrophic equilibrium with this surface elevation field is a cyclonic gyre. In Lake Ontario, the amplitude of the mean surface velocity associated with this gyre is of the order of 3 cm sec
-1
.
Experimental evidence for kinetic proofreading in the aminoacylation of tRNA by synthetase.
Authors: Yamane T , Hopfield J J
Published: May 2006

The enzymatic aminoacylation of tRNA can be viewed as a means of proofreading either the amino acid or the tRNA or both. We have conducted further experimental tests of kinetic proofreading in discriminating between cognate and noncognate amino acids and tRNAs as follows: (formula: see text). In cases (i) and (ii) the amino acids are proofread, in cases (iii) and (iv) the tRNA is proofread, and in case (v), both the amino acid and the tRNA are proofread. ATP consumed per acylation was 400, 1.5, 40, 25, and 1000, respectively. High ATP/aminoacylation ratios are diagnostic for kinetic proofreading.
Unwinding protein specific for mRNA translation fractionated together with rabbit reticulocyte initiation factor 3 complex
Authors: Ilan Joseph , Ilan Judith
Published: May 2006

Experiments with a rabbit reticulocyte cell-free system dependent on the addition of initiation factor 3 (eIF-3) and mRNA were carried out. In this system, using ribosomal subunits, AUG(U)

n

can direct polyphenylalanine synthesis in the absence of eIF-3 at 3 mM MgCl
2
. Globin mRNA was not translated under similar conditions; its translation requires the addition of eIF-3. Moreover, the maximal rate of globin synthesis was achieved when the molar ratio of eIF-3 to ribosomes was approximately 1. This was taken to indicate that some ribosomal proteins were fractionated with eIF-3 and functioned in reconstitution of salt-washed ribosomes. In our system, almost all ribosomes were active, as evident from the fact that all were found in polysomes when analyzed at the time of linear incorporation, and the molar ratio of ribosomes to mRNA was maintained at 4:1. When AUG(U)

n

was hybridized with poly(A), it could not direct polyphenylalanine synthesis with or without eIF-3 and was a potent inhibitor of the translation of globin mRNA in the presence of eIF-3. When poly(A) containing 10% U was hybridized with AUG(U)

n

and added to the cell-free system, addition of eIF-3 promoted polyphenylalanine synthesis to about 80% of control. Moreover, eIF-3 was seen to shift significantly the melting temperature of globin and synthetic double-stranded RNA. These observations suggest that extraction of ribosomes with 0.5 M KCl may release a ribosomal protein that fractionates with eIF-3. This protein may function in unwinding or melting the secondary structure of mRNA and thus facilitate translation.
4,4'-Bis (1-anilinonaphthalene 8-sulfonate) (bis-ANS): a new probe of the active site of myosin.
Authors: Takashi R , Tonomura Y , Morales M F
Published: May 2006

The interaction of myosin subfragment-1 (S-1) with 4,4'-bis(1-anilinonaphthalene 8-sulfonate) (bis-ANS) has been studied by monitoring the fluorescence of the latter when the two components form a complex. Because ATP and ATP analogs partially displace complexed bis-ANS it has also been possible to study interactions of S-1 and nucleotides by using the displacement effect. Approximate values of the parameters of these various interactions have been measured. Some possible applications of bis-ANS have been explored. For example, it provides a very convenient method for obtaining the Michaelis constant, Km, in steady-state S-1 nucleoside triphosphatase; this particular application has also provided some evidence for inferring that in Ca2+ (but not in Mg2+) adenosinetriphosphatase (ATP phosphohydrolase, EC 3.6.1.3) S-1 behaves like a mixture of two components, each with its own Km. Clear energy transfer occurs between tryptophan residues and bound bis-ANS. The fluorescence also suggests that S-1 undergoes some slow relaxations following substrate binding.
Nascent prehormones are intermediates in the biosynthesis of authentic bovine pituitary growth hormone and prolactin.
Authors: Lingappa V R , Devillers-Thiery A , Blobel G
Published: May 2006

Major translation products of bovine pituitary RNA in a wheat germ cell-free system were identified as larger forms (prehormones) of growth hormone and prolactin containing amino-terminal extensions of 26 or 27 and 30 amino acid residues, respectively. However, translation of bovine pituitary RNA in the wheat germ cell-free system in the presence of microsomal membranes prepared from canine pancreas or bovine pituitary yielded products that were of the same size as authentic growth hormone and prolactin; by partial amino-terminal sequence analysis they were shown to contain the correct unique amino-terminal sequence of prolactin and the two correct amino termini of authentic growth hormone; moreover, they were found to be segregated within the microsomal vesicles in that they were largely inaccessible to degradation by proteolytic enzymes. When microsomal membranes were present after rather than during translation, prehormones were neither cleaved nor segregated. These results strongly suggest that the synthesis and segregation of the authentic hormone observed in the presence of membranes proceeds via a nascent prehormone rather than a completed prehormone.
Sex differences in response to hepatitis B infection among patients receiving chronic dialysis treatment.
Authors: London W T , Drew J S
Published: May 2006

Patients undergoing treatment at a community-based renal dialysis clinic were monitored monthly for hepatitis B surface antigen (HBsAg) and antibody to HBsAg (anti-HBs). Of 160 patients who began treatment HBsAg(-)/anti-HBs(-), 77 subsequently became HBsAg(+). Once HBsAg(+), males were more likely to remain HBsAg(+) indefinitely, whereas females were more likely to convert to HBsAg(-) and develop anti-HBs. This was not due to a sex difference in exposure to hepatitis B virus because only patients who became infected while undergoing treatment were included in the analysis. These data are clear evidence of a sex difference in response to hepatitis B virus, which may partially explain the greater incidence of several chronic liver diseases, including primary hepatocellular carcinoma, in males.
A new class of counterexamples to the integrability problem
Authors: Conn Jack F.
Published: May 2006

For many years, it was believed that the solvability of the integrability problem for a transitive Lie pseudogroup depends only on the local solvability of linear differential operators arising from the abelian quotients in Guillemin's Jordan-Hölder decomposition for the transitive Lie algebra associated to the pseudogroup. We provide an example of a transitive pseudogroup for which the integrability problem is not solvable and whose corresponding Jordan-Hölder sequence has only non-abelian quotients.
Nerve growth factor receptors: identification of distinct classes in plasma membranes and nuclei of embryonic dorsal root neurons.
Authors: Andres R Y , Jeng I , Bradshaw R A
Published: May 2006

Two classes of receptors for 125I-labeled nerve growth factor in chick embryonic dorsal root neurons have been observed. One type is associated with the plasma membrane (or microsomal fraction) and can be completely solubilized by Triton X-100. These receptors display the nonsaturable binding isotherms and curvilinear Scatchard plots previously reported for nerve growth factor receptors in whole cells. The second class of binding sites is located in the nucleus, firmly bound to chromatin. These receptors are not solubilized by detergent, show saturable binding, and yield linear Scatchard plots of the type associated with a single class of binding sites of high affinity. The presence of the two receptor types suggests a bimodal mechanism of action for nerve growth factor.
Inhibition of cytokinesis in Friend leukemia cells by membrane mobility agents.
Authors: Lustig S , Kosower N S , Pluznik D H , Kosower E M
Published: May 2006

Treatment of a line of Friend leukemia cells with a dispersion of the membrane mobility agent, A2C, yields cells that undergo successive nuclear divisions without cytokinesis, resulting eventually in cells with as many as 30 nuclei. Neither the DNA replication rate of the cells nor the generation time is different after treatment; in addition, the multiple nuclei divide synchronously, and the chromosome number corresponds to the number of nuclei in the cell. Inhibition of cytokinesis is not observed if the cells are washed with reagent-free medium within 1 hr of treatment, but is observed if washing is delayed for 24 hr. Membrane mobility agent loaded with the fluorescent probe, Flomol F20C, leads to fluorescent membrane; fluorescence disappears from the membrane after a change of medium within 1 hr, but not after a change of medium within 24 hr. Some stages in the overall development resemble those seen for cytochalasin B inhibition of cytokinesis, although the mechanisms may well be different for the inhibition promoted by membrane mobility agent. The inhibition of cytokinesis by A2C provides a potentially interesting means of studying cytokinesis and the regulation of differentiation.
Mannosidosis: assignment of the lysosomal alpha-mannosidase B gene to chromosome 19 in man.
Authors: Champion M J , Shows T B
Published: May 2006

Human alpha-mannosidase activity (alpha-D-mannoside mannohydrolase, EC 3.2.1.24) from tissues and cultured skin fibroblasts was separated by gel electrophoresis into a neutral, cytoplasmic form (alpha-mannosidase A) and two closely related acidic, lysosomal components (alpha-mannosidase B). Human mannosidosis, an inherited glycoprotein storage disorder, has been associated with severe deficiency of both lysosomal alpha-mannosidase B molecular forms. Chromosome assignment of the gene coding for human alpha-mannosidase B (MANB) has been determined in human-mouse and human-Chinese hamster somatic cell hybrids. The human alpha-mannosidase B phenotype showed concordant segregation with the human enzyme glucosephosphate isomerase (GPI) (D-glucose-6-phosphate ketolisomerase, EC 5.3.1.9) but discordant segregation with 30 other enzyme markers representing 20 linkage groups. The glucose-phosphate isomerase gene has been assigned to chromosome 19 in man. This MANB-GPI linkage and confirming chromosome studies demonstrate assignment of the alpha-mannosidase B structural gene to chromosome 19 in man. Since mannosidosis is believed to result from a structural defect in alpha-mannosidase B, these findings suggest that the mannosidosis mutation is located on chromosome 19 in man.
Sodium-stimulated glutamate uptake in membrane vesicles of Escherichia coli: the role of ion gradients.
Authors: MacDonald R E , Lanyi J K , Greene R V
Published: May 2006

Membrane vesicles prepared from Escherichia coli B/r grown on glutamate as a sole source of carbon and energy require sodium for glutamate accumulation when energized by D-lactate oxidation. Glutamate uptake can also be driven by a prearranged sodium gradient (out to in) in the absence of an energy source or a protonmotive force. Sodium ions are exchanged rapidly in respiring vesicles and the sodium gradient may be large enough under certain conditions to drive glutamate uptake after the protonmotive force is abolished with m-chlorocarbonylcyanide phenylhydrazone. Glutamate uptake due to a prearranged sodium gradient or lactate oxidation is inhibited by monensin but not by nigericin. Transport does not occur in response to valinomycin-induced membrane potential. We interpret these results to indicate that glutamate transport is obligately coupled to sodium transport and can only occur when there is a net flux of sodium ions. This flux is driven by a chemical gradient of sodium that is created by the protonmotive force generated by respiration.
DNA-directed synthesis in vitro of beta-galactosidase: requirement for a ribosome release factor.
Authors: Kung H F , Treadwell B V , Spears C , Tai P C , Weissbach H
Published: May 2006

The DNA-directed synthesis of beta-galactosidase in Escherichia coli extracts has been investigated in a partially fractionated system. A dependency was obtained for 3',5'-cyclic AMP receptor protein and also for a factor, from the salt wash of ribosomes, that has been purified to near homogeneity. This factor has been identified with a ribosome release factor previously purified from the supernatant fraction by A. Hirashima and A. Kaji [(1972) Biochemistry 11,4037-4044]. In the coupled transcription-translation system this factor stimulates beta-galactosidase synthesis and total protein synthesis 2- to 4-fold. It is thus clear that the ribosome release factor has a physiological function in translation. It may also affect transcription, because it stimulated total RNA synthesis up to 50% in this in vitro system.
Subunit structure of chromatin and the organization of eukaryotic highly repetitive DNA: Nucleosomal proteins associated with a highly repetitive mammalian DNA
Authors: Musich Phillip R. , Brown Fred L. , Maio Joseph J.
Published: May 2006

Component α DNA is a homogeneous, highly repetitive fraction that comprises nearly a quarter of the African green monkey (
Cercopithecus aethiops
) genome. By restriction enzyme analysis, it has a repeat periodicity of 176 ± 4 nucleotide base pairs, corresponding closely with the length of DNA contained within a nucleosome. The sequence is organized into large blocks of constitutive heterochromatin. A method is described here for the isolation of intact polynucleosomal arrays containing only component α sequences. Isolated monkey nuclei are treated with
Eco
RI, which releases only component α nucleosomal arrays; the arrays are then fractionated and purified by sedimentation in sucrose gradients. The method permits a compositional analysis of the proteins associated with a constitutively repressed, heterochromatic sequence.

The major differences in the proteins associated with component α nucleosomes that distinguish them from the bulk DNA nucleosomes are a decrease in the content of the H1 histones in the component α nucleosomes and a concomitant increase in the amount of certain nonhistone proteins. The specific observations are: (
i
) In the component α nucleosomes, 65-70% of the proteins were nonhistone proteins; this contrasts with the value, 40%, for nonhistone proteins associated with nucleosomes containing bulk DNA. (
ii
) The amount of H1 histone in chromatin containing predominantly bulk DNA was about 13.7%. However, the H1 histone was depleted and possibly absent in component α oligonucleosomes. (
iii
) Coincident with the decrease in the H1 histones and in the same molecular weight range (24,000-43,000), there appeared five minor nonhistone proteins. The minor, low-molecular-weight, nonhistone proteins were not detected in chromatin containing bulk DNA but they represented nearly 12% of the protein in component α nucleosomes. The resistance to salt extraction (0.6-2.0 M NaCl) indicates that the low-molecular-weight nonhistone proteins are tenaciously bound to the component α nucleosomes. In addition, a class of high-molecular-weight (>100,000) nonhistone proteins was enriched 5- or 6-fold in component α oligonucleosomes. The relative amounts of the nucleosome core histones were not changed.