bluuebunny/crossref_metadata_2025 huggingface dataset:
Subunit interaction in cyclic AMP-dependent protein kinase of mutant lymphoma cells.
Authors: Hochman J , Bourne H R , Coffino P , Insel P A , Krasny L , Melmon K L
Published: May 2006

We have previously selected and characterized mutant S49 mouse lymphoma cells that possess an adenosine 3':5'-cyclic monophosphate (cAMP)-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) with an increased apparent affinity constant (Ka) for activation by cAMP. The Ka lesion in one such mutant clone has been shown to result from a structural mutation involving the kinase holoenzyme's regulatory (R) subunit. The present report examines the interaction of R and catalytic (C) subunits of the kinases in extracts of the mutant cells and the normal "wild type" (WT) parental line. Subunit recombination experiments were performed, by using purified WT and mutant R subunits, and C subunits purified from WT cells. As compared to WT R subunits, only 1/6 as much mutant R subunit was required to reassociate with and suppress 50% of C subunit activity, at equilibrium. NaSCN activates cAMP-dependent kinase of both cell types by causing the holoenzyme to dissociate. In comparison with WT, a 2-fold higher concentration of NaSCN is required to maximally activate the kinase in mutant extracts. Both the reassociation result and the increased resistance of the mutant enzyme to a nonspecific dissociating agent strongly suggest that the mutant R subunit binds C subunit more tightly than does the WT R subunit. This interpretation raises the possibility that increased R-C subunit binding affinity in the mutant cell is responsible for the increased Ka for activation by cAMP of the mutant holoenzyme, and thus for the decreased potency of cAMP in regulating intact mutant cells.
Surface, catalytic, and magnetic properties of small iron particles: The effect of chemisorption of hydrogen on magnetic anisotropy
Authors: Boudart M. , Dumesic J. A. , Topsøe H.
Published: May 2006

The superparamagnetic behavior of very small particles of metallic iron (
ca
1.5 nm), with about half of their atoms at the surface, is changed reversibly by adsorption and desorption of hydrogen below the superparamagnetic transition temperature. The change after adsorption implies a lowering of the anisotropy energy barrier for the magnetic relaxation of iron and is ascribed to a change in crystalline shape. No such changes are observed for larger particles of iron (
ca
8 nm) with about 10% of their atoms at the surface.
Isopeptide linkage between nonhistone and histone 2A polypeptides of chromosomal conjugate-protein A24.
Authors: Goldknopf I L , Busch H
Published: May 2006

Chromosomal protein A24 has a unique structure inasmuch as it contains histone 2A and a nonhistone polypeptide the sequence of which has been partially determined. Comparative analysis of the ninhydrin-insensitive amino-terminal tryptic peptides of protein A24 and histone 2A and a quantitative analysis of their carboxyl-terminal amino acid indicated that protein A24 has two amino termini and one carboxyl terminus. The amino acid sequence analysis of tryptic peptide 17' of protein A24: (see text) showed it contains tryptic peptide 17 of histone 2A, Lys-Thr-Glu-Ser-His-His-Lys. Lysine 119, the amino terminus of this peptide, which is derived from the histone 2A portion of protein A24, is linked by an isopeptide bond to the carboxyl group of a glycine residue. Accordingly, the branched structure of protein A24 proposed is: (see text).
Histaminase (diamine oxidase) activity in human tumors: an expression of a mature genome.
Authors: Baylin S B
Published: May 2006

High histaminase [amine:oxygen oxidoreductase (deaminating) (pyridoxal-containing), EC 1.4.3.6] activity is found in certain human tumors and in the placenta of most mammals. The present study explores the relationship of tumor histaminase to histaminases found in placenta and other human, pig, and rat tissues. The electrophoretic mobility and Michaelis constants for the deamination of histimine and putrescine were identical for histaminases from human placenta and from medullary thyroid carcinoma. An antibody was raised in rabbits against human placental histaminase that was highly purified by a new affinity procedure. In separate studies, using inhibitory concentrations of antibody and a second antibody precipitation technique, identical patterns of immunoreactivity were found for histaminases from human placenta, kidney, medullary thyroid carcinoma, and small cell lung carcinoma; human intestinal histaminase crossreacted well but less strongly than did enzymes from these other tissues. Histaminases from pig kidney, pig intestine, and rat intestine showed no crossreaction; histaminases from rat thymus and adrenal gland showed minimal crossreactivity. The findings suggest that placental histaminase activity is not a unique product of a fetal or trophoblastic genome. The presence of histaminase in malignancies does not appear to be an example of ectopic tumor production of a placental trophoblastic protein.
Electron spin resonance absorption of tissue constituents.
Authors: Pohl H A , Gascoyne P R , Szent-Györgyi A
Published: May 2006

The electron spin resonance spectra at g = 2 of the structural and soluble proteins of mouse liver have been investigated separately. The structural materials have signals an order of magnitude stronger. Radicals with important similarities to those occurring in natural tissue can be induced by treating casein with methylglyoxal or crotonaldehyde. The structural proteins of cancer give little or no signal. The color of the proteins and their electron spin resonance signal seem closely related.
Hydrogen-bonded protons in the tertiary structure of yeast tRNAPhe in solution.
Authors: Römer R , Varadi V
Published: May 2006

Temperature-dependent lowfield proton magnetic resonance spectra of yeast tRNAPhe were recorded between 10 and 15 parts per million. Seven resonances of hydrogen-bonded protons disappeared reversibly under two sets of conditions where the selective broadening of tertiary structure resonances were predicted by temperature jump experiments. The seven resonances were assigned to the seven tertiary hydrogen bonds expected between 10 and 15 parts per million from the crystal structure of yeast tRNAPhe. Some of the non-Watson-Crick base pairs have unusual unshifted standard chemical shifts after the ring current contributions calculated from the crystal coordinates were subtracted. The differences of the chemical shifts of homologous tertiary structure base pairs in Escherichia coli tRNAfMet and yeast tRNAPhe give experimental evidence for details of the conformational differences postulated by model building on the basis of the x-ray coordinates of yeast tRNAPhe and sequence homologies.
Membrane fusion: studies with a calcium-sensitive dye, arsenazo III, in liposomes.
Authors: Dunham P , Babiarz P , Israel A , Zerial A , Weissmann G
Published: May 2006

Fusion between vesicles, cells, or organelles may be defined as confluence of two membrane-bound compartments without access of their solutes to external milieu. To study fusion by this criterion, we have trapped the metallochromic calcium-sensitive dye, arsenazo III (AIII), partially calcium-saturated (AIII-Ca) in one population of liposomes (phoshatidylcholine 90:dicetylphosphate 10), and ethylene glycol-bis(beta-aminoethyl ether)-N,N'-tetraacetate (EGTA) in a second. In such mixtures, interaction of EGTA with AIII-Ca was measured by a large color shift from blue leads to red (decreased absorbance at 660 nm). Fusion of liposomes (but also lysis and diffusion across the membranes) was proportional to these decrements. The exogenous "fusogens," lysolecithin and retinol, were added to liposomes for 5-24 hr at 37 degrees; after rechromatography, measurements were made of total dye, fraction of dye converted from AIII-Ca to AIII, and total lipid. After correction for lysis and diffusion, lysolecithin (200 microng/ml) induced 23% fusion (volume of AIII liposomes confluent with EGTA liposomes) and retinol (300 microng/ml) induced 15%. With one molar percent cortisol (a membrane stabilizer) in the liposome membranes, fusion induced by fusogens was reduced 2-fold. Neither multi-nor unilamellar liposomes fused with each other in the absence of exogenous fusogens, despite wide variations in molar lipid ratios. Results suggest that liposome-liposome fusion is a slow process requiring exogenous fusogens, which may depend upon contributions of other membrane constituents to mimic closely the fusion of natural membranes.
Extension of the lifespan of cultured normal human diploid cells by vitamin E: a reevaluation.
Authors: Packer L , Smith J R
Published: May 2006

Previously we reported [Packer, L. & Smith, J.R. (1974) Proc. Natl. Acad. Sci. USA 71, 4763-4767] that the lifespan of WI-38 human diploid fibroblasts in vitro was significantly increased by continuously growing the cell cultures in the presence of vitamin E(dl-alpha-tocopherol), but in 19 subsequent subcultivation series we were unable to reproduce these findings. While vitamin E is incorporated into the cells and is able to act effectively as an antioxidant, apparantly is intracellular antioxidant properties alone do not routinely result in an increase of cell lifespan. A synergism between vitamin E and some component(s) in the first of two lots of serum used in the original experiments seems the most likely explanation for our earlier findings.
Activation of the alternative complement pathway due to resistance of zymosan-bound.
Authors: Fearon D T , Austen K F
Published: May 2006

The surface of zymosan (Zy), by affording a protected microenvironment for C3b and the amplification convertase stabilized by properdin, P,C3b,Bb, shifts the alternative complement pathway from slow fluid phase turnover to the amplification phase of its expression. This mode of activation is in contradistinction to that of the classical pathway, which follows conversion of a proenzyme, Cl, to its active form, C1. Under conditions in which the control proteins, C3b inactivator (C3bINA) and beta1H, completely, inactivated C3b on the sheep erythrocyte intermediate, EAC4b,3b, the activity of C3b bound to Zy,ZyC3b, was diminished by only one-third. Further, when ZyC3b was converted to ZyC3b,Bb,P there was an additional point of deregulation in that the convertase was resistant to beta1H-mediated decay-dissociation while P,C3b,Bb on the sheep erythrocyte exhibited the usual susceptibility to beta1H. That Zy alone could indeed promote rapid C3 cleavage by the alternative pathway through assembly and protection of the amplification convertase on its surface was demonstrated with a mixture of alternative pathway proteins, C3,B,D,P, C3bINA, and beta1H, that had each been purified to homogeneity. Interaction of these proteins at one-tenth their relative serum concentrations with Zy permitted low-grade inactivation of C3 and B to advance to the level of amplification after a 15 min lag period. Because the reaction of the purified proteins proceeded spontaneously when either regulatory protein was deleted, the effect of Zy was attributed to deregulation rather than to conversion of one of the proteins to a specific initiating state. The alternative pathway, through the normal presence of D, interacts with a microbial surface, such as Zy, to amplify deposition of C3b by circumvention of endogenous regulatory mechanisms, thereby augmenting host defense.
X-ray absorption studies of halide binding to carbonic anhydrase.
Authors: Brown G S , Navon G , Shulman R G
Published: May 2006

X-ray absorption measurements of bovine carbonic anhydrase B have been made at the the Stanford Synchrotron Radiation Project with a spectrometer operating in the fluorescence mode. Differences in absorption at and beyond the zinc K-edge near 9664 ev have been observed upon the addition of bromide or iodide. The additional absorption in k space, out to k approximately 7 A-1, obtained upon the addition of iodide has been compared with the absorption in this region of a ZnI2 sample. The similarities between these absorptions lead to the conclusion that the zinc-iodide distance in the protein is 2.65 +/-0.06 A; it is known to be 2.62 A in ZnI2. This shows that the iodide binds directly to the zinc in the protein.
Identification of Rauscher murine leukemia virus-specific mRNAs for the synthesis of gag- and env-gene products.
Authors: Zaane D V , Gielkens A L , Hesselink W G , Bloemers H P
Published: May 2006

Polyadenylylated mRNA isolated from cells infected with Rauscher murine leukemia virus was fractionated by centrifugation in in a denaturing sucrose gradient into different sizes. Each RNA fraction was injected into oocytes of Xenopus laevis and the virus-specific products were analyzed by immunoprecipitation with polyvalent and monospecific antisera against polypeptides of Rauscher murine leukemia virus, and then by gel electrophoresis and scintillation autoradiography. It was shown that a 35S mRNA species directs the synthesis of a precursor of the internal or group-specific antigens of the virion (the gag-gene products). A 22S mRNA species directs the synthesis of two viral envelope polypeptides and their precursor polypeptide (env-gene products). The results indicate that the gag- and env-related polypeptides of Rauscher murine leukemia virus are synthesized uncoordinately and provide evidence for open and closed cistrons on the virus-specific mRNAs.
Albumin synthesis in mouse uterus in response to liver mRNA.
Authors: Yang S F , Niu M C
Published: May 2006

Messenger RNA was isolated, by means of its attachment to poly(A), from calf liver and the livers of mice, rats, and chickens. When injected into the uterine lumen of immature or spayed mice, both mouse albumin and the albumins characteristic of the species donating the mRNA were synthesized. Studies with inhibitors disclosed that puromycin blocked the synthesis of both albumin species, while dactinomycin affected only mouse albumin synthesis. It appears, therefore, that in the experimental situation used, the function of exogenous liver mRNA is 2-fold: (i) it programs the synthesis of alien albumin in uterine epithelial cells, and (ii) it stimulates the synthesis of mRNA in epithelial cells. The mRNA thus produced primes the synthesis of mouse albumin.
Sendai virus-induced hemolysis: reduction in heterogeneity of erythrocyte lipid bilayer fluidity.
Authors: Lyles D S , Landsberger F R
Published: May 2006

Hemolysis of human or chicken erythrocytes by Sendai virus causes a change in the structure of the erythrocyte membrane lipid bilayer that can be detected by spin label electron spin resonance. In the intact erythrocyte, the phosphatidylcholine derivative spin label exists in a more rigid environment than the corresponding phosphatidylethanolamine label. Virus-induced hemolysis tends to abolish this difference in fluidity, i.e., the region of the phosphatidylcholine spin label becomes more fluid and that of the phosphatidylethanolamine spin label becomes more rigid. Fatty acid derivative spin labels, which may detect some "average" environment, show no change in fluidity. The fluidity change is detected at several different positions in the fatty acyl chain of the phosphatidylcholine spin label. Sendai virions grown in Madin-Darby bovine kidney (MDBK) cells or grown in eggs and harvested early, which lack hemolytic activity, cause no significant change in bilayer structure. Hemolytic activity and the ability to alter erythrocyte bilayer fluidity can be activated in MDBK-grown Sendai virions by trypsin treatment in vitro and in early-harvest egg-grown Sendai virions by freezing and thawing. Erythrocyte ghosts prepared by osmotic hemolysis and resealed by treatment with Mg2+ or elevated ionic strength exhibit a difference in fluidity between phosphatidylcholine and phosphatidylethanolamine spin labels, although less than that observed in whole cells. Incubation of resealed ghosts with Sendai virus abolishes the difference in fluidity. Unsealed ghosts that have been extensively washed show no heterogeneity in membrane bilayer fluidity, and incubation with Sendai virus causes no further fluidity change. Virus-induced hemolysis as measured by hemoglobin release is more sensitive to inhibition by Ca2+ than is the associated fluidity change in the bilayer.
9S binding protein for androgens and progesterone.
Authors: Wilson E M , Lea O A , French F S
Published: May 2006

A steroid binding protein fraction with a sedimentation coefficient of approximately 9 S (molecular weight approximately equal to 200,000) has been identified in 105,000 X g supernatants of several androgen-responsive organs. Highest concentrations were found in epididymis and testis, but small amounts were detected in prostate, seminal vesicle, kidney, submandibular gland, and lung. The 9S protein binds [3H]dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one) and [3H]progesterone (4-pregnene-3,20-dione) with equilibrium binding constants of approximately 10(5) M-1 and 10(6) M-1, respectively. The concentration of 9S binding sites in epididymis is approximately 10(-11) mol/mg of supernatant protein, which is at least 10(5) times greater than the concentration of androgen receptor. 9S binding protein appears to be a nonsecretory, intracellular protein and has properties different from the andorgen receptor. It is unretarded on DEAE-Sephadex chromatography at pH 8.0, and its sedimentation rate on sucrose gradients is not altered at high ionic strength (0.4 M KCl). Like the androgen receptor, its binding activity, which is maximal between pH 7 and 9.5, is heat labile, decreased by sulfhydryl reagents, and enhanced by 2-mercaptoethanol. It is suggested that because of its high concentration and low affinity, 9S binding protein may function in the intracellular accumulation of compartmentalization of androgens or progesterone.
Colony-specific territorial pheromone in the African weaver ant Oecophylla longinoda (Latreille).
Authors: Hölldobler B , Wilson E O
Published: May 2006

Major workers of Oecophylla longinoda mark their territories with persistent pheromones that are distinguishable to the ants at the colony level. Workers detecting the deposits of an alien colony respond with increased amounts of aversive and aggressive behavior, and they later recruit nestmates to the area at a higher rate. Colonies entering a field impregnated with their own scent also gain an initial advantage in warfare with other colonies. The pheromones are located at least in part in drops of rectal sac fluid deposited by workers over the territorial surface.
Killer cells reactive to altered-self antigens can also be alloreactive.
Authors: Bevan M J
Published: May 2006

Murine cytotoxic thymus-derived lymphocytes immunized against cells bearing foreign minor histocompatibility antigens are specific for the immunizing minor antigens and for their own major H-2 antigens; they do not lyse target cells that bear the correct minor antigens plus a different H-2 haplotype. These are referred to as "altered-self" or "self-plus-X" killer cells. Alloreactive killer cells are those which respond to allogeneic cells expressing a foreign (non-self) H-2 haplotype. In this study, cytotoxic lymphocytes were immunized against minor histocompatibility differences in vivo and in vitro. These effector cells killed the immunizing altered-self target very well and showed about 1% cross-reactive lysis of an allogeneic target differing from themselves only at H-2. These cross-reactive clones were then selected for by repeated in vitro stimulation with the cells bearing foreign H-2 such that an effector population was obtained which lysed both the altered-self and the alloreactive target with the same efficiency. Cold target competition experiments established that the same killer cell could lyse either target; however, it was not determined if a killer cell uses the same receptor to respond to altered-self antigens as it does respond to foreign H-2 antigens.
Degradation of cellular mRNA during infection by herpes simplex virus.
Authors: Nishioka Y , Silverstein S
Published: May 2006

The fate of preexisting mRNA sequences was examined after infection by herpes simplex virus. Murine erythroid cells transformed by Friend leukemia virus were used as the host. Such cells, when exposed to 2% dimethyl sulfoxide, produce large amounts of globin and globin mRNA. The protein and its mRNA are easily recognized at 4 days by electrophoresis in high percentage acrylamide gels and by hybridization to cDNA, respectively. Herpes simplex virus replicates in these cells. By 2 hr after infection the rate of protein synthesis decreases to 30% of the level in mock-infected cells and only 49+/-8% (SEM) of the globin mRNA sequences present prior to infection could be detected by hybridization to cDNA. At 4 hr after infection, when the rate of protein synthesis in infected cells is at a maximum, only about 15% of the globin mRNA sequences remained. Control experiments support the hypothesis that globin mRNA sequences are degraded after infection by herpes simplex virus.
13
C nuclear magnetic resonance studies of radiation damage: Radiation-induced degradation of glycine
Authors: Box Harold C. , Lilga Kenneth T. , Potienko George
Published: May 2006

The stable products generated in polycrystalline glycine exposed to ionizing radiation and subsequently dissolved in water were identified by using
13
C nuclear magnetic resonance spectroscopy. The study was done on isotopically enriched samples. The results can be correlated with the results of many other studies on irradiated glycine using other methods.
Selection of reconstituted cells from karyoplasts fused to chloramphenicol-resistant cytoplasts
Authors: Shay Jerry W.
Published: May 2006

Murine Balb/3T3 and murine A-MT-BU-A1 mammary tumor cells were separated in the presence of cytochalasin B into enucleated cytoplasmic components (cytoplasts) and nucleated subcellular components (karyoplasts). Karyoplasts were derived from 3T3 cells, while cytoplasts were derived from A-MT-BU-A1 cells that were both chloramphenicol-resistant (CAP
r
) and sensitive to hypoxanthine/aminopterin/thymidine (HAT
s
). CAP
r
has been shown to be cytoplasmically transmitted (possibly a mitochondrial gene mutation), while sensitivity to medium containing HAT has been shown to be transmitted by the nucleus (i.e., nuclear gene mutation). Such CAP
r
cytoplasts derived from A-MT-BU-A1 cells were then fused, using polyethylene glycol, to HAT-resistant 3T3 karyoplasts. The mononucleated reconstituted cells produced by such procedures were cloned in medium containing both HAT and CAP. Some of the reconstituted cells survived, because they were resistant to both drugs, while the nuclear and cytoplasmic whole cell contaminants were killed by one or the other of the two drugs. The results of these experiments indicate that reconstituted cells that are derived from two different cell lines are viable, as indicated by their ability for long-term proliferation in culture. Most of the clones derived resembled morphologically the 3T3 nuclear donor parent cells, but some of the clones did not resemble either parental cell line. It is anticipated that such selection techniques will permit more complete analysis of interrelationships between nucleus and cytoplasm.
Structures of enzyme-substrate complexes of lysozyme
Authors: Pincus Matthew R. , Zimmerman S. Scott , Scheraga Harold A.
Published: May 2006

Conformational energy calculations were used to determine the binding structures of two oligosaccharides (GlcNAc)

n

, in which
n
= 5 and 6, in the
rigid
active site of lysozyme (mucopeptide
N
-acetylmuramoylhydrolase, EC 3.2.1.17). Starting with the lowest energy binding structures of (GlcNAc)
4
as determined in a previous publication, we added a fifth GlcNAc residue to this tetramer in three different conformations, corresponding to the left-handed and right-handed helical structures and an intermediate structure, and the energy of each complex was minimized. The most stable binding conformation of the fifth residue of the pentamer was closest to the left-handed helical one. During energy minimization, the fourth residue of the pentamer moved from its initial position near the surface of the active site farther into the active site cleft at binding site D. Binding structures of (GlcNAc)
6
were then examined by addition of a residue to the lowest energy structure of (GlcNAc)
5
, and it was found that the sixth residue of the hexamer binds in a conformation again close to the left-handed helical one. Stable binding regions of the rigid active site for the fifth and sixth residues were found to be near arginyl 45 and asparaginyl 46, on the opposite side of the active site cleft from arginyl 114. When the calculated structure of the lysozyme-(GlcNAc)
4
complex (used here as the starting structure for addition of the fifth and sixth residues) is compared with recent experimental data, it is found that the calculated structure is a reasonable one. Of all binding regions available to the saccharide residues, the C site binds GlcNAc with the lowest energy, in agreement with experiments.
Ultraviolet resonant Raman spectroscopy of nucleic acid components.
Authors: Blazej D C , Peticolas W L
Published: May 2006

The first resonant Raman excitation profile using UV as well as visible radiation is presented. Measurements of the intensity of the Raman spectrum of adenosine 5'-monophosphate as a function of the frequency of the incident laser light are presented in the range from 20 to 38 kK (1000 cm-1). The scattering intensity per molecule increases by about 10(5) as the laser is tuned from low to high frequencies. The Raman excitation profile has been calculated by using a simple form of the vibronic theory of Raman scattering. The theoretical curves are found to adequately fit the data using only the frequencies of the excited electronic states of AMP and their corresponding vibronic linewidths as adjustable parameters. The Raman bands at 1484 cm-1 and 1583 cm-1 appear to obtain virtually all of their intensity from a weak electronic transition at 276 nm. The set of Raman bands in the range 1300 cm-1-1400 cm-1 appear to derive at least part of their intensity from an electronic band whose 0-0 transition is in the 269-259 nm region although the possibility of some intensity arising from the vibronic mixing between these two electronic states cannot as yet be ruled out.
Electromagnetism and gravitation
Authors: Teller Edward
Published: May 2006

Generation of electric fields in rapidly rotating insulators is discussed and calculated. An interesting effect is expected in TlCl. A possible appearance of magnetic fields near rapidly rotating gravitating bodies is proposed. The simple suggestion made here would lead to magnetic fields of negligible magnitude.
Strong consistency of least-squares estimates in regression models
Authors: Lai T. L. , Robbins Herbert
Published: May 2006

A general theorem on the limiting behavior of certain weighted sums of i.i.d. random variables is obtained. This theorem is then applied to prove the strong consistency of least-squares estimates in linear and nonlinear regression models with i.i.d. errors under minimal assumptions on the design and weak moment conditions on the errors.
Prediction and estimation for the compound Poisson distribution
Authors: Robbins Herbert
Published: May 2006

An empirical Bayes method is proposed for predicting the future performance of certain subgroups of a compound Poisson population.
Interaction of rabbit reticulocyte ribosomes with bacteriophage f1 mRNA and of
Escherichia coli
ribosomes with rabbit globin mRNA
Authors: Legon Steve , Model Peter , Robertson Hugh D.
Published: May 2006

We have compared the behavior of a prokaryotic mRNA in a eukaryotic ribosome binding system and of a eukaryotic mRNA in a prokaryotic ribosome binding system. Using
32
P- and
125
I-labeled bacteriophage f1 mRNA, we have shown that rabbit reticulocyte 80S ribosomes can protect specific sequences from pancreatic RNase digestion, including those sequences protected by
Escherichia coli
ribosomes. We have also found that
E. coli
ribosomes fail to protect any region of
125
I-labeled globin mRNA. Iodination of the mRNA appeared to have little or no effect on the specificity of binding or protection by the ribosomes of either system.

The eukaryotic and prokaryotic systems differ markedly in the ability of the small ribosomal subunits to protect mRNA from nuclease digestion. The regions of phage f1 mRNA protected by
E. coli
30S subunits are virtually identical to those protected by the 70S ribosomes. By contrast, rabbit reticulocyte 40S subunits protect substantially larger fragments of mRNA from nuclease digestion than do the 80S ribosomes. These 40S-protected fragments are specific in the case of globin mRNA and overlap the shorter region protected by the 80S ribosomes. However, the 40S-protected fragments of phage f1 mRNA were found to be extremely heterogeneous, reflecting perhaps an important difference between the initial interactions made by these two mRNAs with the ribosomes.
Distribution of 5-methylcytosine in chromatin.
Authors: Razin A , Cedar H
Published: May 2006

The content of 5-methylcytosine in eukaryotic DNA was measured by mass spectrometry. Almost equal amounts of methylated cytosine were found in the DNA of various tissues of the chicken. When chromatin or nuclei were digested with micrococcal nuclease, 50% of the DNA was found to be nuclease resistant. In contrast to this, over 75% of the 5-methylcytosine was protected from nuclease digestion by chromatin proteins. These results suggest that 5-methylcytosine is nonrandomly distributed with respect to the nucleoproteins.
Enzymes as reagents in peptide synthesis: enzyme-labile protection for carboxyl groups.
Authors: Glass J , Pelzig M
Published: May 2006

N-Benzyloxycarbonyl derivatives of isoglutamine and isoasparagine were coupled with arginine methyl ester through the action of dicyclohexylcarbodiimide. The resulting benzyloxycarbonyl derivatives of isoglutaminylarginine methyl ester and isoasparaginylarginine methyl ester were treated with trypsin for removal of the ester groups and then with porcine pancreatic carboxypeptidase B for liberation of arginine and the original benzyloxycarbonyl derivatives of isoglutamine and isoasparagine. This scheme represents a reversible masking of the side-chain carboxyl functions of aspartic and glutamic acid residues. Possible applications of esters and amides of arginine as reversible blocking groups in protein semi-synthesis are discussed along with prospects and strategies for developing related techniques of higher efficiency.
The living state and cancer.
Authors: Szent-Györgyi A
Published: May 2006

Complex living structures developed on our globe after the appearance of light and oxygen. In functions of these structures, solid state phenomena play a major role. The structural proteins were made into radicals by doping, the covalent incorporation of electron acceptors. This lent mobility to their electrons and a subtle reactivity to their molecules. Cancer is unable to go into the radical state.
Replication of pea enation mosaic virus RNA in isolated pea nuclei
Authors: Powell C. A. , Zoeten G. A. de
Published: May 2006

Isolated nuclei from healthy pea plants were primed with pea enation mosaic virus (PEMV), southern bean mosaic virus (SBMV), radish mosaic virus (RdMV), tobacco mosaic virus (TMV), PEMV RNA, SBMV RNA, RdMV RNA, or TMV RNA. RNA replication occurred only with PEMV RNA and not with intact PEMV or any of the other viruses or RNAs, as judged by ensuing actinomycin D-insensitive polymerase activity. Molecular hybridization experiments showed that some of the product of the polymerase was PEMV-specific (-)RNA. The substrate and ionic requirements of this polymerase were the same as those for the RNA-dependent RNA polymerase present in nuclei isolated from PEMV-infected pea plants. No virus particles could be recovered from nuclei primed with PEMV RNA. These results are discussed in relation to the possible mechanism for
in vivo
infection of pea cells.
Isolation and characterization of the opioid peptides from rat pituitary: beta-lipotropin.
Authors: Rubinstein M , Stein S , Gerber L D , Udenfriend S
Published: May 2006

Rat beta-lipotropin was isolated from 40 anterior pituitaries using high efficiency chromatography columns and sensitive fluorometric methods. The beta-lipotropin was characterized as to molecular weight, amino acid composition, and generation of opioid activity by trypsinization. Other opioid peptides, as well as a precursor to opioid peptides with a molecular weight larger than that of beta-lipotropin, were observed in this tissue.
Reduction of pore area of the avian eggshell as an adaptation to altitude
Authors: Rahn H. , Carey C. , Balmas K. , Bhatia B. , Paganelli C.
Published: May 2006

Standard measurements of water vapor conductance in units of mg of H
2
O · day
-1
· torr
-1
(SI equivalent is mg of H
2
O · day
-1
· pascal
-1
) of fresh eggs of the red-winged blackbird (
Agelaius phoeniceus
) and the native chicken of India (
Gallus gallus
) collected at altitude are significantly less than those of eggs of the same species collected near sea level. This decrease is caused by a reduction of the total effective pore area of the eggshell at altitude. It appears to be proportional to the reduction in barometric pressure and the simultaneous increase in the diffusion coefficient of water vapor. Thus, reduction in pore area offsets increased diffusivity at altitude, and water vapor loss through the eggshell at any altitude remains the same as at sea level. The data suggest a structural adaptation of the shell to altered diffusivity of gases at altitude in order to prevent excessive water loss of eggs during natural incubation.
Hyperbolic almost periodic solutions and toroidal limit sets
Authors: Sell George R.
Published: May 2006

We consider an almost periodic solution φ(
t
) of an autonomous differential equation
x
′ =
f
(
x
). Let
k
denote the topological dimension of the hull
H
(φ). By considering the linearized equation
x
′ =
A
(
t
)
x
alone [where
A
(
t
) is the Jacobian matrix of
f
evaluated along φ(
t
)], one can derive a sufficient condition in order that φ(
t
) be quasi-periodic and that the hull
H
(φ) be diffeomorphic to a
k
-dimensional torus

T
k

. The proof is based upon an extension of the center manifold theorem to nonautonomous nonperiodic differential systems.
Complex submanifolds in real-analytic pseudoconvex hypersurfaces
Authors: Diederich Klas , Fornaess John Erik
Published: May 2006

A theorem is given that guarantees the existence of nontrivial complex analytic submanifolds in real-analytic pseudoconvex boundaries near real-analytic submanifolds with holomorphic vectorfields on which the Levi form vanishes. Applications to the δ̄-Neumann problem and to the existence of Stein neighborhoods are discussed.
Enucleation and reconstruction of interferon-producing cells.
Authors: Burke D C , Veomett G
Published: May 2006

Enucleation of L cells leads to loss of the capacity to produce interferon, showing that the cell nucleus is essential for interferon formation. However, when the cells were enucleated while interferon formation. However, when the cells were enucleated while interferon formation was proceeding, the cytoplasts were capable of continuing to synthesize interferon by a process shown to be protein synthesis, showing that the interferon messenger RNA leaves the nucleus after synthesis. Reconstructed cells were obtained by Sendai virus fusion of karyoplasts and cytoplasts. Such reconstructed cells were capable of producing at least as much interferon (43 interferon units/10(4) nucleated cells) as control cells (31 interferon units/10(4) nucleated cells).
Effects of colchicine on cyclic AMP levels in human leukocytes
Authors: Rudolph Stephen A. , Greengard Paul , Malawista Stephen E.
Published: May 2006

The increase in human leukocyte adenosine 3′:5′-cyclic monophosphate (cyclic AMP) levels seen in response to various substances was markedly potentiated by colchicine and other agents that affect microtubule assembly. Addition of
dl
-isoproterenol (2 μM) or prostaglandin E
1
(10 μM), together with the phosphodiesterase inhibitor isobutylmethylxanthine (1 mM), caused a much greater increase in cyclic AMP in colchicine-pretreated cells than in control cells. With isoproterenol (2 μM) plus isobutylmethylaxanthine (1 mM), cyclic AMP levels rose about 3-fold but, in combination with colchicine, these drugs caused a more than 15-fold increase in cyclic AMP. The effects of colchicine were both time- and dose-dependent; they could be seen within 1 min after addition of colchicine or at concentrations as low as 10 nM. In addition to its potentiation of hormonally induced increases in cyclic AMP levels, colchicine also potentiated the effect of isobutylmethylxanthine alone on leukocyte cyclic AMP levels. Vinblastine, vincristine, podophyllotoxin, and oncodazole all had effects similar to those of colchicine but lumicolchicine did not. The data suggest that cytoplasmic microtubules interact with the leukocyte plasma membrane to impose constraints on the expression of hormone-sensitive adenylate cyclase; the therapeutic effects of colchicine may depend in part upon the relaxation of such constraints. Moreover, the synergism described here between colchicine-like agents and hormones is of potential therapeutic importance in clinical conditions in which either alkaloid or hormone has been useful separately.
Addition of colchicine-tubulin complex to microtubule ends: The mechanism of substoichiometric colchicine poisoning
Authors: Margolis Robert L. , Wilson Leslie
Published: May 2006

Colchicine blocks microtubule polymerization by an unusual substoichiometric poisoning mechanism. We have investigated the mechanism by which this poisoning occurs with several experimental approaches, and have found that colchicine acts by addition to microtubule ends as a colchicine-tubulin complex.
Theories of quasi-linkage and "affinity": some implications for population structure.
Authors: Miké V
Published: May 2006

"Quasi-linkage" refers to nonrandom assortment of genes located on different chromosomes. Although this phenomenon has been widely observed in many organisms since the early part of this century, it is barely known. Interest in it was recently rekindled by the report of an association between quasi-linkage and the expression of genes belonging to a group of cancer viruses whose genomes are integrated in mouse chromosomes. This prompted an examination of the question whether "sustained meiotic affinity," which is one of the explanations proposed for quasi-linkage, can influence population structure in a manner unattainable by other known modes of heredity. It is shown for a two-locus two-allele system that equilibrium is attained with the gametic phase disequilibrium D greater than 0, leading to a permanent excess of the preferred genotypes. The possible relationship of these concepts to the inheritance of susceptibility to cancer and other diseases is discussed.
Mutation frequencies in female mice and the estimation of genetic hazards of radiation in women.
Authors: Russell W L
Published: May 2006

The female germ cell stage of primary importance in radiation genetic hazards is the immature, arrested oocyte. In the mouse, this stage has a near zero or zero sensitivity to mutation induction by radiation. However, the application of these mouse results to women has been questioned on the ground that the mouse arrested oocytes are highly sensitive to killing by radiation, while the human cells are not; and, furthermore, that the mature and maturing oocytes in the mouse, which are resistant to killing, are sensitive to mutation induction. The present results have a 2-fold bearing on this problem. First, a more detailed analysis of oocyte-stage sensitivity to killing and mutation induction shows that there is no consistent correlation, either negative or positive, between the two. This indicates that the sensitivity to cell killing of the mouse immature oocyte may not be sufficient reason to prevent its use in predicting the mutational response of the human immature oocyte. Second, if the much more cautious assumption is made that the human arrested oocyte might be as mutationally sensitive as the most sensitive of all oocyte stages in the mouse, namely the maturing and mature ones, then the present data on the duration of these stages permit more accurate estimates than were heretofore possible on the mutational response of these stages to chronic irradiation.
Supercoiled circular DNA of an insect granulosis virus
Authors: Tweeten Kathleen A. , Bulla Lee A. , Consigli Richard A.
Published: May 2006

The DNA of the granulosis virus of the Indian meal moth,
Plodia interpunctella
, was characterized by physical chemical and electron microscopic techniques. Twenty-five percent of the DNA extracted from purified virus was isolated as supercoiled circular molecules. The remaining 75% consisted of relaxed circular molecules. These molecular forms were indicated by the production of two radioactive bands during sedimentation of
3
H-labeled granulosis virus DNA in alkaline sucrose gradients or in equilibrium density gradients of neutral cesium chloride/propidium iodide. Electron microscopic visualization of the DNA that banded at the higher density in the latter gradients revealed supercoiled structures whereas that of DNA that banded at the lower density demonstrated relaxed circular molecules. The superhelical molecules were converted to relaxed circles by treatment with pancreatic DNase.

The molecular weight of the viral DNA was calculated to be 81 × 10
6
by sedimentation in neutral sucrose and 78 × 10
6
by sedimentation in alkaline sucrose. The molecular weight estimated from length measurements in electron micrographs was 76 × 10
6
. The buoyant density of the granulosis virus DNA was 1.703 g/cm
3
and that of its insect host DNA was 1.697 g/cm
3
. Equilibrium sedimentation in cesium chloride and thermal denaturation indicated G + C contents of 44% and 39% for the viral and host DNA, respectively.
Calcium translocation by Golgi and lateral-basal membrane vesicles from rat intestine: decrease in vitamin D-deficient rats.
Authors: Freedman R A , Weiser M M , Isselbacher K J
Published: May 2006

Intestinal Ca2+ transport was studied in membrane vesicles isolated from microvillus, Golgi, and lateral-basal membrane preparations. Ca2+ uptake by these vesicles was measured by determination of 45Ca2+ associated with these membranes after collection by micropore filtration. Golgi membranes showed the highest initial rate and equilibration level of Ca2+ uptake. Approximately 90% of this Ca2+ uptake was into an osmotically responsive space, suggesting that what was measured was predominantly Ca2+ translocation. Vitamin D-deficient rats showed a markedly diminished rate of uptake and level of equilibration. These data indicate that a Ca2+-translocating process was associated with Golgi membranes to a greater extent than with surface membranes and that this process was markedly decreased in vitamin D-deficient rats. The results suggest that the Golgi apparatus participates in intestinal Ca2+ absorption.
Antipain and leupeptin restrict uterine DNA synthesis and function in mice.
Authors: Katz J , Troll W , Adler S W , Levitz M
Published: May 2006

As in rats, administration of estradiol to ovariectomized mice results in a trypsin-like proteolytic activity in the uterus. After fractionation of uteri from estradiol-treated ovariectomized mice the protease activity was found in the 12,000 times g pellet and the nucleus, appearing first in the former. Further fractionation of the pellet by discontinuous sucrose gradient centrigugation resulted in sedimentation of the protease with 5'-nucleotidase, a marker enzyme for plasma membrane and separate from mitochondrial and lysosomal enzyme markers. Solubilization was best accomplished by lysis at 37 degrees. The soluble enzyme from mouse uterus had optimal activity at about 43 degrees and pH 8.3 and was inhibited by diisopropylfluorophosphate, tosylarginine methyl ester, antipain, and leupeptin, but not by soybean trypsin inhibitor. Inhibition in vitro by antipain and leupeptin, two low molecular weight peptides, prompted the study of their effect in vivo on the mouse uterus. After intact, cycling female mice received subcutaneous injections of antipain and leupeptin for 16 days, their uteri showed significant diminution in weight and total DNA when compared to untreated controls. Fertility rates were also diminished. Trypsin-like protease activity may be essential to normal uterine metabolism and function.
Transfer of mannose from mannosyl retinyl phosphate to protein.
Authors: Rosso G C , Masushige S , Quill H , Wolf G
Published: May 2006

Upon incubation of [14C]mannose-labeled mannosyl retinyl phosphate with a membrane fraction from rat liver, mannose was transferred to an endogenous acceptor precipitable withchloroform/methanol to the extent of about 7%. The reaction proceeded linearly with time for 120 min at a pH optimum of about 7.0. The acceptor thus labeled with mannose could be solubilized by sodium dodecyl sulfate/mercaptoethanol. More than half of this acceptor appeared in the void volume of a Sephadex G-100 column. When it was digested with Pronase, a substantial proportion of it appeared between the void and bed volumes of a Sephadex G-100 column, thus indicating that it was a glycopeptide. In high-voltage paper electrophoresis, this glycopeptide moved to the cathode at low pH and to the anode at highpH. When digested with highly purified jack bean alpha-mannosidase, the glycopeptide released almost 50% of its radioactivity as mannose. That this transfer of mannose to glycoprotein from mannosyl retinyl phosphate does not take place via dolichyl mannosyl phosphate was shown by the fact that it is Mn2+ and Mg2+ independent, it is not inhibited by the presence of a 10-fold molar excess of nonradioactive GDP-mannose, and neither 14C-labeled dolichyl mannosyl phosphate nor 14-C labeled lipid pyrophosphoryl oligosaccharide could be detected during the incubation.
Arrangement of subunits in assembled histone H4 fibers.
Authors: Sperling R , Amos L A
Published: May 2006

The structure of assembled histone H4 fibers has been studied by analysis of electronmicrographs, including optical diffraction. An individual fiber has the appearance of an 80-A wide ribbon, twisted at intervals of about 330 A. Thicker fibers which have been observed seem to be bundles of ribbons. In diffraction patterns from both kinds of fiber, layer lines at axial spacings of about 1/55 A-1, 1/37 A-1, and 1/27 A-1 were most consistently observed. The possible arrangements of molecules within the twisted ribbons have been deduced and are found to be fairly closely related. The ribbons appear to consist of two parallel, unstaggered rows of repeating units, which are probably H4 dimers. The similarity between the observed layer line spacings of the H4 fibers and the spacings of the maxima in x-ray diffraction patterns from whole chromatin suggests that the H4 fibers have a structure related to that of chromatin. Since homogeneous preparations of histones H2A, H2B, and H3, or any mixture of these four histones, can form similar structures, it seems likely that the basic organization of chromatin is determined by a fibrous histone core around which the DNA is wrapped.