bluuebunny/crossref_metadata_2025 huggingface dataset:
Tumorigenicity of virus-transformed cells in nude mice is correlated specifically with anchorage independent growth in vitro.
Authors: Shin S I , Freedman V H , Risser R , Pollack R
Published: May 2006

Clonal isolates of mouse 3T3 cells and primary rat embryo cells, recovered nonselectively after infection by simian virus 40 (SV40), have been tested for tumorigenicity in the immune-deficient nude mice in order to determine the cellular growth properties in vitro specifically correlated with neoplastic growth in vivo. In addition, mouse 3T3 cells transformed by murine sarcoma virus (MuSV, Kirsten strain), and revertants isolated from cells fully transformed by either SV40 or MuSV were also studied. Results suggest that the single cellular property consistently associated with tumorigenicity in nude mice is the acquisition by virus-transformed cells of the ability to proliferate in vitro in the absence of anchorage. Other cellular parameters of virus-induced transformation, such as lack of sensitivity to high cell density and the capacity to grow in low serum concentration, are dissociable from cellular tumorigeneicity. This conclusion is supported further by the demonstration that specific selection in vivo for tumorigenic cells from anchorage-dependent cells results in the isolation of anchorage-independent cells. Conversely, a single-step selection in vitro for anchorage-independent cells from nontumorigenic cells results in a simultaneous selection of highly tumorigenic subclones.
Deposition of histones onto replicating chromosomes.
Authors: Jackson V , Granner D K , Chalkley R
Published: May 2006

The mode of distribution of newly synthesized and pre-existing histones has been studied during the process of chromosome replication. Newly synthesized histone was labeled with [3H]lysine and newly synthesized DNA was density labeled with iododeoxyuridine. The histone was covalently linked to DNA, and radiolabeled histone was analyzed on CsCl density gradients. We have defined conditions that do not give rise to histone randomization during isolation, and also developed a method of defining the distribution of histones in chromatin on a density gradient in the unavoidable presence of nonhistone protein. Three possible modes of distribution of histone onto the replicating chromosome can be conceived; we describe experiments designed to distinguish unequivocally among these possibilities and conclude that histones are deposited randomly onto the chromosome.
Serum rapidly stimulates ouabain-sensitive 86-RB+ influx in quiescent 3T3 cells.
Authors: Rozengurt E , Heppel L A
Published: May 2006

Serum causes a 4-fold increase in 86Rb+ (a K+ tracer) influx in quiescent 3T3 mouse fibroblast cells. It is one of the earliest changes caused by serum, being seen in 2 min and reaching a maximum in 10 min. Removal of serum causes rapid reversal of this effect. Serum acts mainly by increasing the maximum velocity, Vmax, of entry. Ouabain inhibits entry of 86Rb+ (82-90%) both in the presence and absence of serum, but does not alter exit. The rapid increase in cation influx is unaffected by cycloheximide and by changes in cyclic AMP and GMP. Low concentrations of insulin, epidermal growth factor, and prostaglandins (E1 and F2alpha) produced a smaller (80%) activation of 86Rb+ entry. Ouabain, at a level that inhibits cation influx, also prevents the onset of DNA synthesis following serum addition; this is reversible effect dependent on the concentration of K+ in the medium. This suggests that cation pumping activity may be required for initiation of DNA synthesis.
General kin selection models for genetic evolution of sib altruism in diploid and haplodiploid species.
Authors: Levitt P R
Published: May 2006

A population genetic approach is presented for general analysis and comparison of kin selection models of sib and half-sib altruism. Nine models are described, each assuming a particular mode of inheritance, number of female inseminations, and Mendelian dominance of the altruist gene. In each model, the selective effects of altruism are described in terms of two general fitness functions, A(beta) and S(beta), giving respectively the expected fitness of an altruist and a nonaltruist as a function of the fraction of altruists beta in a given sibship. For each model, exact conditions are reported for stability at altruist and nonaltruist fixation. Under the Table 3 axions, the stability conditions may then be partially ordered on the basis of implications holding between pairs of conditions. The partial orderings are compared with predictions of the kin selection theory of Hamilton.
Absence of an intracellular cobalamin-binding protein in cultured fibroblasts from patients with defective synthesis of 5′-deoxyadenosylcobalamin and methylcobalamin
Authors: Rosenberg Leon E. , Patel Lekha , Lilljeqvist Anne-Charlotte
Published: May 2006

Three distinct classes of human mutations (cbl A, cbl B, and cbl C) cause defective synthesis of cobalamin (Cbl; vitamin B
12
) coenzymes. Cultured fibroblasts from that unique class (cbl C) deficient in the synthesis of both Cbl coenzymes, 5′-deoxyadenosylcobalamin (AdoCbl) and methylcobalamin (MeCbl), were used to explore the underlying defect. We compared the uptake of transcobalamin II(TC II)-bound cyano[
57
Co]cobalamin (CN-Cbl) by cbl cells with that of other control and mutant cell lines. Although the cbl C cells initially took up CN-[
57
Co]Cbl normally, they were unable to retain it. To characterize this “leak” further, cell extracts were prepared following incubation and chromatographed on Sephadex G-150. After incubations of 1-2 hr, most of the CN-[
57
Co]Cbl accumulated by control cells was still bound to TC II; the remainder was free. Thereafter, an ever-increasing fraction of the labeled Cbl eluted with an intracellular cobalamin-binding protein (ICB); more than 80% of the total was so bound after 76 hr incubations. ICB had an apparent molecular weight similar to that of several Cbl “R” binders (about 120,000), but was distinguished from them by its failure to react with specific anti-“R”binder antiserum. Significantly, no ICB was detected in extracts of three different cbl C lines even aftr prolonged incubations, whereas its appearance in cbl A, cbl B, and mutase apoenzyme mutants was normal. We propose: that ICB is required for retention of cobalamins by cells; and that cbl C cells “leak” cobalamins and show defective synthesis of Cbl coenzymes because they lack this intracellular binder.
A Bruhat decomposition for the loop space of a compact group: A new approach to results of Bott
Authors: Garland Howard , Raghunathan M. S.
Published: May 2006

We give a new proof of Bott's result, that the loop space of a compact, simply connected, simple Lie group has a cellular decomposition of a certain type. In particular, one obtains the Poincaré polynomial for the loop space and Bott periodicity for the unitary group.
Source theory analysis of electron-positron annihilation experiments
Authors: Schwinger Julian
Published: May 2006

The phenomenological viewpoint already applied to deep inelastic scattering is extended to the discussion of electron-positron annihilation experiments. Some heuristic arguments lead to simple forms for the pion differential cross section that are in reasonable accord with the published experimental data in the energy interval 3-4.8 Gev.
Energy transfer between terbium (III) and cobalt (II) in thermolysin: a new class of metal--metal distance probes.
Authors: Horrocks W D , Holmquist B , Vallee B L
Published: May 2006

The visible fluorescence of terbium(III) when bound to a calcium binding site of thermolysin is greatly enhanced with an excitation maximum at 280 nm but substitution of cobalt(II) for zinc at the active site decreases the intensity by 89.5%. Treatment with N-bromosuccinimide quenches enzyme tryptophan and Tb(III) fluorescence to a similar extent and suggests the operation of tryptophan vector Tb(III) vector Co(II) energy relay system in the enzyme. Dipoledipole radiationless energy transfer between the Tb(III) donor and the Co(II) acceptor can account for this quenching. The inherent characteristics of the metal pair limits the value of the orientation factor, K2, of the Förster equation, thereby reducing uncertainties in distance measurements by energy transfer compared with other systems. A quantum yield of 0.51 yields a value of R0, the distance for 50% energy transfer, of 19.6 A, and a distance, R, between Tb(III) and Co(II) of 13.7 A, a value identical to that measured for the distance between the active site zinc atom and calcium atom number 1 by x-ray analysis in native thermolysin crystals. The limits of confidence of this measurement are discussed. Energy transfer between two different metal atom sites of a protein provides a new class of probes to measure intramolecular distances of biological macromolecules in solution.
On the iron-sulfur cluster in hydrogenase from Clostridium pasteurianum W5.
Authors: Erbes D L , Burris R H , Orme-Johnson W H
Published: May 2006

Hydrogenase, purified to an average specific activity of 328 mumol of H2 evolved/(min X mg of protein) from Clostridium pasteurianum W5, was found to have 4-5 Fe and 4-5 labile sulfur atoms per molecule of 60,000 molecular weight, in contrast with earlier reports of 12 Fe per molecule. Displacement of the iron-sulfur cluster from hydrogenase by thiophenol in 80% hexamethyl phosphoramide:20% H2O yielded the Fe4S4 (thiophenyl)4 dianion according to absorption spectroscopy. Electron paramagnetic resonance spectroscopy at 12 K showed that the iron-sulfur cluster in the enzyme could be reduced by the H2 to a state (g-values of 2.098, 1.970, and 1.898) similar to that in reduced ferredoxin and could be oxidized by dichlorophenolindophenol or H+ to a state (g-values at 2.099, 2.041, and 2.001) similar to that in high potential iron-sulfur proteins. These oxidations and reductions appeared to occur within the turnover time of the enzyme. Deuterium failed to narrow the electron paramagnetic resonance signal in either state, but the competitive inhibitor carbon monoxide reversibly formed a compound with either state and substantially altered the electron paramagnetic resonance. 13CO produced a broadening of these signals, suggesting the formation of a direct CO complex with the iron-sulfur cluster. These data are consistent with a model of the active site of the enzyme in which a four-iron four-sulfur cluster is a component that can accept one or two electrons from and donate either one or two electrons to substrates, and in which the iron-sulfur cluster serves as the site of binding of gaseous ligands.
Synthesis of specific functional messenger RNA in vitro by phage-SP01-modified RNA polymerase of Bacillus subtilis.
Authors: Swanton M , Smith D H , Shub D A
Published: May 2006

RNA polymerase (nucleosidetriphosphate: RNA nucleotidyltransferase, EC 2.7.7.6) was purified from rifampicin-resistant Bacillus subtilis, from both uninfected cells and cells infected with bacteriophage SP01. The enzyme from infected cells lacked all traces of the sigma subunit, contained several polypeptides absent from the enzyme made in uninfected cells, and had an altered template specificity in a transcription assay. A cell-free protein synthesizing system from Escherichia coli, when poisoned with rifampicin, was completely dependent on addition of either of these RNA polymerase preparations for DNA-dependent protein synthesis. Under these conditions, the SP01-modified RNA polymerase preferentially stimulated the synthesis of functional mRNA for the phage enzyme dCMP deaminase (deoxycytidylate aminohydrolase, EC 3.5.4.12), whereas unmodified B. subtilis RNA polymerase could stimulate synthesis of this mRNA in small quantity and only after prolonged incubation. This mRNA belongs to a class of phage transcripts (m) which cannot be transcribed in vivo in the absence of phage-specific protein synthesis.
Infectious viral DNA of murine leukemia virus.
Authors: Smotkin D , Gianni A M , Rozenblatt S , Weinberg R A
Published: May 2006

A fraction of the unintegrated viral DNA that appears early after infection of mouse cells by Moloney leukemia virus is infectious. The infectivity could be deomonstrated by an XC plaque assay of the cells exposed to DNA co-precipitated with calcium phosphate. The number of plaques deriving from closed-circular, supercoiled DNA was proportional to the concentration of added DNA, indicating that a single DNA molecule of about 5.5 X 10(6) daltons carries all the viral information. Nonsupercoiled viral DNA is also infectious; these molecules appear to be largely double-stranded and 5 to 6 X 10(6) dalthons in mass.
Effects of bacteriophage T4-induced modification of Escherichia coli RNA polymerase on gene expression in vitro.
Authors: Mailhammer R , Yang H L , Reiness G , Zubay G
Published: May 2006

After T4 bacteriophage infection of E. coli a complex series of events take place in the bacterium, including gross inhibition of host transcription and discrete changes in the classes of the genes of T4 that are transcribed. Accompanying these changes in the pattern of transcription one finds T4-induced changes in the RNA polymerase (EC 2.7.7.6; nucleosidetriphosphate:RNA nucleotidyltransferase). The effects of modified polymerase on transcription can be advantageously analyzed in a DNA-directed cell-free system for protein synthesis. In this system gene activity is measured indirectly by the amounts and types of proteins sythesized. In the DNA-directed cell-free system this modified polymerase, like normal polymerase, transcribes T4 DNA with a high efficiency but transcribes bacteriophage lambda and host DNA very poorly. Polymerase reconstruction experiments show that modification of the alpha subunit of the RNA polymerase is sufficient for inhibition of host transcription. Host transcription is also inhibited in vitro by T4 DNA. This latter type of inhibition is presumed to involve competition between host DNA and T4 DNA for some factor essential for transcription. The T4-modified polymerase transcribes from T4 DNA many of the same genes as normal unmodified polymerase; it also shows a capability for transcribing certain "non-early" T4 genes which is enhanced in the presence of protein-containing extracts from T4-infected cells.
Analogue solution for electrical capacity of membrane covered square cylinders in square array at high concentration.
Authors: Cole K S
Published: May 2006

Analytical solutions of Laplace equations have given the electrical characteristics of membranes and interiors of spherical, ellipsoidal, and cylindrical cells in suspensions and tissues from impedance measurements, but the underlying assumptions may be invalid above 50% volume concentrations. However, resistance measurements on several nonconducting, close-packing forms in two and three dimensions closely predicted volume concentrations up to 100% by equations derived from Maxwell and Rayleigh. Calculations of membrane capacities of cells in suspensions and tissues from extensions of theory, as developed by Fricke and by Cole, have been useful but of unknown validity at high concentrations. A resistor analogue has been used to solve the finite difference approximation to the Laplace equation for the resistance and capacity of a square array of square cylindrical cells with surface capacity. An 11 x 11 array of resistors, simulating a quarter of the unit structure, was separated into intra- and extra-cellular regions by rows of capacitors corresponding to surface membrane areas from 3 x 3 to 11 x 11 or 7.5% to 100%. The extended Rayleigh equation predicted the cell concentrations and membrane capacities to within a few percent from boundary resistance and capacity measurements at low frequencies. This single example suggests that analytical solutions for other, similar two- and three-dimensional problems may be approximated up to near 100% concentrations and that there may be analytical justifications for such analogue solutions of Laplace equations.
Failure of human cells transformed by simian virus 40 to form tumors in athymic nude mice.
Authors: Stiles C D , Desmond W , Sato G , Saier M H
Published: May 2006

Four individual lines and one subline of human cells, permanently established in tissue culture after infection with simian virus 40, failed to form tumors when inoculated into athymic nude mice. Under identical conditions, three established human cell lines of neoplastic origin and a spontaneously established human lymphocyte line formed tumors. Nude mice that failed to grow tumors from inocula of simian virus 40-transformed human cells, grew tumors from subsequent injections of authentic human cancer cells. Further efforts to demonstrate an immunologic basis for the growth suppression of human simian virus 40 transformants were also negative. The data suggest that the changes in morphology and in vitro growth behavior induced by the viral information are not sufficient for, or are only coincidentally related to, the neoplastic state.
Chicken neutrophils: oxidative metabolism in phagocytic cells devoid of myeloperoxidase.
Authors: Penniall R , Spitznagel J K
Published: May 2006

Polymorphonuclear leukocytes isolated from chicken peritoneal exudates have been found to catalyze cyanide-insensitive stimulation of respiration and the hexose monophosphate shunt upon exposure to heat-inactivated Staphylococcus aureus. However, there was no demonstrable formate oxidation concomitant with phagocytosis in either the presence or absence of exogenous catalase. Moreover, chicken polymorphonuclear leukocytes failed to oxidize scopoletin concomitant with phagocytosis in the presence of horseradish peroxidase. While oxygen uptake was increased 2- to 3-fold by the stimulus of phagocytosis, the oxidation of [1-(14)C]glucose was increased approximately 20-fold. The cells contain two mechanisms, a glutathione reductase-glutathione peroxidase system and an NADPH-NAD+ transhydrogenase, each of which is present in sufficient capacity to accommodate the enhanced shunt activity. Although chicken polymorphonuclear leukocytes were found to possess a substantial capacity to catalyze the cyanide-insensitive oxidation of either NADH or NADPH, the total or specific activities of such processes were not demonstrably affected by phagocytosis.
Immunosurgery of mouse blastocyst.
Authors: Solter D , Knowles B B
Published: May 2006

Mouse blastocysts with and without zonae pellucidae are susceptible to complement-dependent antibody cytotoxicity. Exposure of blastocysts to rabbit anti-mouse serum together with complement results in the death of all cells; however, when blastocysts are exposed to antiserum alone and then transferred to guinea pig complement, only the trophoblastic cells are killed. These results suggest that the mouse blastocyst is not permeable for certain antibodies. The inner cell masses can easily be separated from the remnants of trophoblastic cells and are then able to grow and differentiate in vitro. This method of immunosurgery can be used to obtain large quantities of pure inner cell masses in a relatively short period of time.
Sequential production of fatty liver, hepatitis, and cirrhosis in sub-human primates fed ethanol with adequate diets.
Authors: Lieber C S , DeCarli L , Rubin E
Published: May 2006

This study reproduces in experimental animals the sequential development of all the liver lesions seen in the human alcoholic: in 15 baboons fed ethanol, all developed fatty liver, five progressed to hepatitis, and five had cirrhosis. Maintenance of a nutritionally adequate regimen despite the intake of inebriating amounts of ethanol (50% of total calories) was achieved by incorporation of the ethanol in a totally liquid diet. Upon ethanol withdrawal, signs of physical dependence, such as seizures and tremors, developed. Ultrastructural changes of the mitochondria and the endoplasmic reticulum were already present at the fatty liver stage and persisted throughout the hepatitis and cirrhosis. The lesions were similar to those observed in alcoholics (including the inflammation and the central sclerosis) and differed from the alterations produced by choline and protein defiencies. At the fatty liver stage, some "adaptive" increases in activity of microsomal enzymes [aniline hydroxylase (EC 1.14.14.1) and the microsomal ethanol oxidizing system] were observed, but these tended to disappear with the development of hepatitis and cirrhosis. Fat accumulation was also much more pronounced in the animals with the hepatitis as compared with those with simple fatty liver (an 18-fold compared with 3- to 4-fold increase in liver triglycerides). The demonstration that these lesions can develop despite an adequate diet indicates that in addition to correction of the nutritional status, control of alcohol intake is mandatory for the management of patients with alcoholic liver injury.
Insertion Compounds of 2H-TaS
2
·NH
3
Authors: Meyer S. F. , Acrivos J. V. , Geballe T. H.
Published: May 2006

A new method of intercalating metals into layer compounds has been developed using electrolytic generation from the salt solution in ammonia. The results suggest that metals that are soluble in ammonia will form a homogeneous metal-ammonia intercalate layer, NH
3
·M

x

, when
x
is less than the limiting solubility of M in NH
3
. The superconducting transition temperature (

T
c

) was found to increase as the
c
-axis expansion [2δ =
c
(TaS
2
·NH
3
·M

x

) -
c
(2H-TaS
2
)] decreased when M = lithium, sodium, and potassium. Of all the alkali metals, potassium gave the most stable compounds and the highest

T
c

, 4.7°K.
A zinc protein isolated from human parotid saliva.
Authors: Henkin R I , Lippoldt R E , Bilstad J , Edelhoch H
Published: May 2006

A zinc protein has been isolated and purified to apparent homogeneity from subjects with normal taste acuity by gel filtration and ion-exchange chromatography. The protein has a molecular weight of 37,000 and does not appear to have subunits. It is composed of 8% histidine residues and has 2 moles of zinc per mole of protein.
The Power of the Optimal Asymptotic Tests of Composite Statistical Hypotheses
Authors: Singh Avinash C. , Zhurbenko Igor G.
Published: May 2006

The easily computable asymptotic power of the locally asymptotically optimal test of a composite hypothesis, known as the optimal
C
(α) test, is obtained through a “double” passage to the limit: the number
n
of observations is indefinitely increased while the conventional measure ξ of the error in the hypothesis tested tends to zero so that ξ

n

n
½
→ τ ≠ 0. Contrary to this, practical problems require information on power, say β(ξ,
n
), for a fixed ξ and for a fixed
n
. The present paper gives the upper and the lower bounds for β(ξ,
n
). These bounds can be used to estimate the rate of convergence of β(ξ,
n
) to unity as
n
→ ∞. The results obtained can be extended to test criteria other than those labeled
C
(α). The study revealed a difference between situations in which the
C
(α) test criterion is used to test a simple or a composite hypothesis. This difference affects the rate of convergence of the actual probability of type I error to the preassigned level α. In the case of a simple hypothesis, the rate is of the order of
n
-½
. In the case of a composite hypothesis, the best that it was possible to show is that the rate of convergence cannot be slower than that of the order of
n
-½
ln
n
.
On the Homology of Congruence Subgroups and
K
3
(Z)
Authors: Lee Ronnie , Szczarba R. H.
Published: May 2006

Let Γ(
n;
p) be the congruence subgroup of
SL
(
n;
Z) of level
p
. We study the homology and cohomology of Γ(
n;p
) as modules over
SL
(
n;
F

p

) and apply our results to obtain an upper bound for the order of
K
3
(Z).
Fatty acid chain flexibility in the membranes of normal and transformed fibroblasts.
Authors: Gaffney B J
Published: May 2006

Fatty acid spin labels were used to measure the inherent flexibility of the lipid acyl chains in intact cell membranes of 3T3 mouse fibroblasts and several varieties of transformed 3T3 cells. No significant differences in inherent lipid flexibility were detected in the normal and transformed mouse fibroblasts. These results are compared with similar results obtained earlier for chick embryo fibroblasts. For the cells studied, a difference in the mobility of membrane glycoproteins of normal and transformed fibroblasts has either been demonstrated directly or inferred from differential agglutinability by other investigations. Therefore, a basis for correlating glycoprotein mobility and lipid motion in these cells was not found.
Role of amino groups in formation of human lymphocyte-xenogeneic erythrocyte rosettes; a proposed mechanism for antigen recognition.
Authors: Lalezari P , Nehlsen S L , Novodoff J , Lalezari I
Published: May 2006

Formation of coulombic and possible hydrogen bonds between amino groups on human lymphocytes and negatively charged sites on sheep erythrocytes is involved in rosette formation. Supportive evidence includes rosette inhibition by chemical binding of lymphocyte membrane amino groups, and the results of changing the pH, ionic concentration, and temperature of the reaction. Although the possibility has not been excluded that the amino group dependence of this reaction is related to the property of certain proteins attached to the T-cell (thymus processed) surface, it is suggested that this dependence may be related to a charge pattern recognition in the form of "codes" present on the T-cell membrane. It is speculated that this type of recognition may be a contributory mechanism in the initiation of the T-cell-dependent immune response.
Contact inhibition of phagocytosis in epithelial sheets: alterations of cell surface properties induced by cell-cell contacts.
Authors: Vasiliev J M , Gelfand I M , Domnina L V , Zacharova O S , Ljubimov A V
Published: May 2006

Contact inhibition of phagocytosis was found to be characteristic for epithelial sheets formed in cultures by several cell types: normal and transformed mouse kidney cells, and differentiated mouse hepatoma cells. In these sheets most central cells surrounded by other cells had very low phagocytic activity. In contrast, marginal cells having a free edge were able to perform an active phagocytosis. Contact inhibition of phagocytosis was absent in dense cultures of mouse embryo fibroblasts and in cultures of anaplastic mouse hepatoma 22a. The upper surface of epithelial sheets was nonadhesive for prelabeled epithelial cells and fibroblasts. In contrast, the upper surface of dense cultures of mouse fibroblasts was adhesive for these cells. These and other data strengthen the suggestion that contact inhibition of phagocytosis is a result of different adhesiveness of the upper cell surface and of the surfaces near the free edge. Agents inhibiting cell surface movements at the free edges of marginal epithelial cells (cytochalasin, azide, sorbitol, low temperature) prevented adhesion of particles to these edges. Possibly, the surface of actively moving cytoplasmic processes is the only cell part that has adhesive properties necessary for the formation of attachments with other cellular and noncellular surfaces. In epithelial sheets, in contrast to fibroblast cultures, Colcemid did not activate movements of immobile contacting cell edges. These results indicate that mechanisms of contact immobilization of cell surface may be different in epithelium and fibroblasts. Firm contacts formed between epithelial cells are sufficient for stable immobilization of the surface; additional stabilization of the surface by microtubules is not essential. Fibroblasts do not form firm contacts and the Colcemid-sensitive stabilization process is essential for maintenance of the immobile state of their surfaces. Differences in the stability of cell surface immobilization produced by cell-cell contacts may also explain different adhesiveness of the upper surfaces of dense fibroblastic and epithelial cultures.
Quaternary structure of chromatin.
Authors: Bram S , Butler-Browne G , Baudy P , Ibel K
Published: May 2006

Neutron scattering experiments on chromatin solutions have been carried out at Bragg spacings several times larger than in any previous x-ray work. A new series of very low angle reflections at about 400, 200, and 140 A were observed. These reflections demonstrate the existence of a higher order structure of the 100 A unit fibril. A coiled-coil model with a major pitch of 500 A and a radius of center to fibril center of 130 A is proposed to explain the results.
Development of a Mn-2+-sensitive, "soluble" adenylate cyclase in rat testis.
Authors: Braun T , Dods R F
Published: May 2006

A distinctive Mn-2+-sensitive adenylate cyclase [ATP pyrophosphate-lyase(cyclizing), EC 4.6.1.1] system insensitive to fluoride has been found in rat seminiferous tubules and epididymal sperm. The development of this distinctive adenylate cyclase in testis was studied during spermatogenesis. It was first detectable in seminiferous tubules in immature rats at about the time of the first reductive divisions and the appearance of spermatid cells. The specific activity of the enzyme increased substantially during the period of spermatogenesis when spermatids develop into mature spermatozoa, and reached maximal values in the testis of adult rats. After centrifugation of testis tissue homogenates at 105,000 X g for 60 min, the Mn-2+-sensitive adenylate cyclase activity was found in the cytosol. The enzyme remains in solution after centrifugation at 300,000 X g for 5 hr or at 180,000 X g for 24 hr and passes through a 0.22 mum Millipore filter. Electron microscopic examination showed no visible membrane fragments or vesicles in the filtered supernatant. The Mn-2+-sensitive adenylate cyclase system is also present in epidiymal sperm. However, in the sperm obtained from either the caput or the cauda of epididymis, the adenylate cyclase is membrane-associated and found in particulate fractions of sperm homogenates. It therefore appears that the Mn-2+-sensitive adenylate cyclase is initially present in the cytoplasm either unattached or loosely bound to intracellular membranes and becomes firmly attached to sperm membranes later in development. This occurs either during the process of maturation of spermatids into sperm or during the transport of the testicular sperm into the epididymis.
Nucleotide sequence of the rightward operator of phage lambda.
Authors: Maniatis T , Jeffrey A , Kleid D G
Published: May 2006

The sequence of 72 base pairs of the rightward operator (O-R) of bacteriophage lambda is presented as determined with simple and rapid methods for direct DNA sequencing. The sequence of an operator mutant is also described. The methods are of general use in sequencing DNA fragments with unique 5' ends up to 50 base pairs in length. Previous experiments have shown that this operator contains multiple sites recognized by the lambda phage repressor. We believe we have identified three of these sites.
Evolution of Social Behavior Through Interpopulation Selection
Authors: Gadgil Madhav
Published: May 2006

Under certain special conditions natural selection can be effective at the level of local populations, or demes. Such interpopulation selection will favor genotypes that reduce the probability of extinction of their parent population even at the cost of a lowered inclusive fitness. Such genotypes may be characterized by altruistic traits only in a viscous population, i.e., in a population in which neighbors tend to be closely related. In a non-viscous population the interpopulation selection will instead favor spiteful traits when the populations are susceptible to extinction through the overutilization of the habitat, and cooperative traits when it is the newly established populations that are in the greatest danger of extinction.
Physical properties of New Jersey serotype of vesicular stomatitis virus and its defective particles.
Authors: Hartford S L , Lesnaw J A , Flygare W H , MacLeod R , Reichmann M E
Published: May 2006

The wild-type New Jersey serotype of vesicular stomatitis virus generated two types of defective interfering T-particles. The physical properties of these particles and the wild-type virion were determined by laser light scattering spectroscopy, sedimentation measurements, and electron microscopy.
On a Variational Formula for the Principal Eigenvalue for Operators with Maximum Principle
Authors: Donsker Monroe D. , Varadhan S. R. S.
Published: May 2006

In this paper a variational formula is obtained for the principal eigenvalue for operators with maximum principle. This variational formula does not require the operators to be self-adjoint. But if they are self-adjoint this formula reduces to the classical Rayleigh-Ritz formula.
Purification and characterization of the retina-specific cell-aggregating factor.
Authors: Hausman R E , Moscona A A
Published: May 2006

The tissue-specific, cell-aggregating component of embryonic neural retina cells was purified from the retina cell-aggregating factor and characterized as a glycoprotein. Its molecular weight in solution is in the range of 50,000, and it contains 10-15% carbohydrate. The amino-acid and carbohydrate compositions have been determined. The glycoprotein is produced by embryonic neural retina cells in primary monolayered cultures and is released into the medium. Its tissue-specific, cell-aggregating effect requires integrity of the polypeptide portion, but not of the carbohydrate portion. We suggest that the isolated molecule is a specific determinant of the embryonic retina cell-surface and that it is involved in mediating self-recognition and selective adhesiveness of these cells.
Sexuality in the cellular slime mold Dictyostelium giganteum.
Authors: Erdos G W , Raper K B , Vogen L K
Published: May 2006

By pairing of strains of Dictyostelium giganteum in various combinations this species was shown to be heterothallic. Four mating types were identified. Some strains could not be assigned a mating type and others showed no mating reaction. No self-compatible strains were found. Mutations were introduced in several strains and genetic crosses were performed. The results of these crosses show that mating and macrocyst formation are controlled by a single locus-multiple allele incompatibility system. The results also support the view that the myxamoebae that emerge upon germination of the macrocysts are the products of meiosis.
Physical characteristics of the gonadotropin receptor-hormone complexes formed in vivo and in vitro.
Authors: Dufau M L , Podesta E J , Catt K J
Published: May 2006

The physical properties of detergent-solubilized gonadotropin receptor-hormone complexes, determined by density gradient centrifugation and gel filtration, were compared after in vivo and in vitro labeling of specific ovarian binding sites with radioiodinated human chorionic gonadotropin (hCG). Following intravenous administration of biologically active 125I-labeled hCG, up to 50% of the gonadotropin tracer was bound to the luteinized ovaries of immature female rats treated with pregnant mare serum/human chorionic gonadotropin. Comparable binding of 125I-labeled hCG was observed after equilibration of ovarian particles with the labeled hormone in vitro. The sedimentation properties of the solubilized receptor-hormone complexes formed in vivo were identical with those derived for the corresponding complexes formed in vitro and extracted with Triton X-100 and Lubrol PX, with sedimentation constants of 8.8 S for the Triton-solubilized complex and 7.0 S for the complex extracted with Lubrol PX. During analytical gel filtration of the Triton-solubilized receptor-hormone complex on Sepharose 6B in 0.1% Triton X-100, the partition coefficient (Kav) of the "in vivo" complex (0.32) was not significantly different from that of the complex formed in vitro (0.29). Gel filtration of the Lubrol-solubilized ovarian particles on Sepharose 6B in 0.5% Lubrol PX gave Kav values for the "in vivo" and "in vitro" labeled complexes of 0.36 and 0.32, respectively. These findings demonstrate that the physical properties of size and shape which determine the partition coefficient and sedimentation characteristics of detergent-solubilized gonadotropin receptor-hormone complexes formed in vitro are not distinguishable from those of the complexes extracted after specific interaction of the ovarian gonadotropin receptors with radioiodinated hCG in vivo.
Metabolites influence control of lysine transfer ribonucleic acid synthetase formation in Escherichia coli K-12.
Authors: Hirshfield I N , Yeh F M , Sawyer L E
Published: May 2006

A mutant of E. coli K-12 has been isolated which has only 1-3% of the wild-type lysyl-tRNA synthetase activity [L-lysine:tRNA ligase (AMP forming), EC 6.1.1.6]. Additions of 20 mM L-alanine or 6 mM leucine dipeptides to the culture medium can restore the activity of lysyl-tRNA synthetase in the mutant strain to the wild-type level. Experiments on the in vivo charging of lysine tRNA in the mutant show that in the absence of the metabolites lysine tRNA is charged 15-23%. Upon the addition of 3 mM L-leucyl-L-alanine to the medium the lysyl tRNA synthetase activity increases 25-fold and the in vivo charging of lysine tRNA returns to the wild-type level. Experiments with antibody against lysyl-tRNA synthetase show that the stimulation of lysyl-tRNA synthetase activity by the metabolites is the result of new protein synthesis.
A beta-D-galactoside binding protein from electric organ tissue of Electrophorus electricus.
Authors: Teichberg V I , Silman I , Beitsch D D , Resheff G
Published: May 2006

Extracts of electric organ tissue of Electrophorus electricus contain a saccharide-binding protein, named electrolectin, which agglutinates trypsin-treated rabbit erythrocytes and is specifically inhibited by disaccharides containing nonreducing terminal beta-D-galactosyl residues. Electrolectin seems at least partially membrane-bound but is also found in soluble fractions of homoge-nates from which it can be purfied by affinity chromatography on cross-linked and desulfated agarose (ECD-Sepharose) as a protein of molecular weight 33,000. About 400 mg of electrolectin are present per kg of tissue. It has an affinity for lactose of 1.0 mM-1 and 5.5mM-1 as estimated, respectively, by hapten inhibition and fluorescence spectroscopy. Studies on the distribution of beta-D-galactoside-binding activity in animal tissues reveal particularly high levels in sheletal muscle tissue and in cultures of embryonic skeletal muscle and neuroblastoma cells.
Estrogen-directed synthesis of specific prostaglandins in uterus.
Authors: Ham E A , Cirillo V J , Zanetti M E , Kuehl F A
Published: May 2006

Endogenous uterine prostaglandin levels were monitored in the cycling rat and prostaglandins of the F-type were found to rise at proestrus when estrogen levels have been shown to be maximal. Evidence that this is an estrogen-induced event is furnished by the finding that estradiol-17beta caused a similar rise in prostaglandin F levels in uteri of ovariectomized rats, an action blocked by coadministration of progesterone. Examination of in vitro prostaglandin synthetase by uterine microsomal fractions from cycling rats and estrogen-treated ovariectomized rats revealed that the action of estrogen to control prostaglandin synthesis in a directional manner is accomplished, at least in part, by regulation of the prostaglandin synthetase complex, resulting in a patterned alteration in the ratio of prostaglandin F to prostaglandin E. These results demonstrate that prostaglandins are involved in the expression of estrogen action in the rat uterus.
Photoassisted Electrolysis of Water by Irradiation of a Titanium Dioxide Electrode
Authors: Wrighton Mark S. , Ginley David S. , Wolczanski Peter T. , Ellis Arthur B. , Morse David L. , Linz Arthur
Published: May 2006

Ultraviolet irradiation (351, 364 nm) of the n-type semiconductor TiO
2
as the single crystal electrode of an aqueous electrochemical cell evolves O
2
at the TiO
2
electrode and H
2
at the Pt electrode. The gases are typically evolved in a two: one (H
2
:O
2
) volume ratio. The photoassisted reaction seems to require applied voltages, but values as low as 0.25 V do allow the photoassisted electrolysis to proceed. Prolonged irradiation in either acid or base evolves the gaseous products in amounts which clearly demonstrate that the reaction is catalytic with respect to the TiO
2
. The wavelength response of the TiO
2
and the correlation of product yield and current are reported. The results support the claim that TiO
2
is a true photoassistance agent for the electrolysis of water. Minimum optical storage efficiencies of the order of 1% can be achieved by the production of H
2
.
Identification of cardiac beta-adrenergic receptors by (minus) [3H]alprenolol binding.
Authors: Alexander R W , Williams L T , Lefkowitz R J
Published: May 2006

(Minus) [3-H] alprenolol, a potent beta-adrenergic antagonist, was used to identify binding sites in a fraction of canine cyocardium. Beta adrenergic agonists and antagonists compete for these binding sites in a manner which directly parallels their known affinity for the cardiac beta-adrenergic receptor. Thus, binding was highly stereo-specific, with the (minus) isomers of beta-adrenergic agonists or antagonists being at least two orders of magnitude more potent than were the (plus) isomers in competing for these sites. The order of potency for inhibition of binding by beta-adrenergic agonists was (minus) isoproterenol greater than (minus) epinephrine greater than (minus) norepinephrine. The dissociation constant (KD) of (minus) alprenolol for the beta-adrenergic receptors was 7-11 nM as determined independently by direct binding studies or by inhibition of isoproterenol-stimulated adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1]. The beta-adrenergic antagonist (minus) propranolol also had high affinity for the binding sites (KD equals 12 nM). The physiologically inactive catechol-containing compounds pyrocatechol and (plus or minus) dihydroxymandelic acid, as well as the metabolite (plus or minus) normetanephrine, and the alpha-adrenergic antagonist phentolamine did not compete for the binding sites at a concentration of 160 muM. Binding was rapid (t1/2 less than 30 sec) and was rapidly reversible (t1/2 less than 15 sec). The binding sites were saturable and bound 0.35 pmol of (minus) [3-H] alprenolol per mg of membrane protein. These characteristics suggest that these binding sites represent the cardiac beta-adrenergic receptors.
Modulation of lymphocyte receptor mobility by locally bound concanavalin A.
Authors: Yahara I , Edelman G M
Published: May 2006

Binding of concanavalin A (con A) to the lymphocyte surface at room temperature leads to restriction of the mobility of a variety of cell surface receptors including those from immunoglobulin (Ig), O, H-2, beta2-microglobulin, Fc receptors results in "co-capping" of Ig, H-2, theta, Fc receptors, as well as receptors for other lectins. Addition of colchicine to the cell suspensions reverses this effect and allows Con A receptors as well as other receptors to form patches and caps. Capping of Con A receptors, and beta2-microglobulin in the absence of ligands specific for these receptors. Receptors binding Limulus hemagglutinin and wax bean agglutinin, as well as those interacting with carbohydrate-specific antibodies, were partially co-capped with Con A but receptors for wheat germ agglutinin were not co-capped, excluding the possibility that restriction of receptor mobility by Con A resulted simply from cross-linkage of mobile receptors to immobilized glycoproteins (Con A receptors). Latex beads and platelets coupled to Con A were bound to lymphocytes under the same conditions as free Con A. Binding of these particles to local regions of the cell surface resulted in restriction of the mobility of those receptors that could be co-capped with free Con A. In contrast to the findings with free Con A, however, addition of colchicine resulted in capping of the bound particles but did not cause co-capping of either the unbound Con A receptors or other receptors. These findings support the hypothesis that modulation occurs via a submembranous assembly containing microtubules, and they further suggest that the transitions of this assembly induced locally by Con A may be propagated via cooperative processes.
Biologic and antigenic similarity of virus-induced migration inhibition factor to conventional, lymphocyte-derived migration inhibition factor.
Authors: Yoshida T , Bigazzi P , Cohen S
Published: May 2006

Macrophage migration inhibition factor (MIF) is one of a class of lymphocyte-derived mediator substances (lymphokines) which plays a role in the mechanism of cellular immunity. A variety of other soluble factors produced by non-lymphoid cells have been shown to have effects on macrophage mobility similar to that of MIF. In the present study we demonstrate that one such factor, (MIFV) derived from simian virus 40-infected kidney cells in culture, has several other properties in common with lymphocyte-derived MIF (MIFL), MIFV can be adsorbed on Sepharose bead columns conjugated with an antiserum prepared against MIFL, demonstrating at least some antigenic similarity. Moreover, MIFV can substitute for MIFL in an in vivo system involving the suppression of cutaneous manifestations of cellular immunity by intravenous injection of the lymphokine. These observations, taken in conjunction with the similarity of the in vitro effect of MIFV and MIFL, and their similar chromatographic behavior, suggest that MIFV and MIFL may be identical molecular species.
Scanning transmission ion microscope with a field ion source.
Authors: Escovitz W H , Fox T R , Levi-Setti R
Published: May 2006

Experiments with a low-resolution scanning transmission ion microscope, using hydrogen ions from a field ionization source, indicate that it will be feasible by this approach to aim at high-resolution ion microscopy. Micrographs of unstained biological specimens have been obtained by critical range absorption of a 55 keV hydrogen ion beam at a resolution of 2000 A.
Identification of human RNA transcripts among heterogeneous nuclear RNA from man-mouse somatic cell hybrids.
Authors: Di Cioccio R A , Voss R , Krim M , Grzeschik K H , Siniscalco M
Published: May 2006

In man-mouse hybrid line from our cell library, the only cytological detectable portion of the human genome is the X chromosome, and the only genetic markers regularly expressed are coded by genes known to be ?X-linked. A component of the heterogeneous nuclear RNA of these cells was found to be complementary to repetitive human DNA sequences by means of RNA-DNA hybridization on nitrocellulose filters. The same procedure also permitted the identification of hybrid cell DNA sequences that are complementary to human heterogeneous nuclear RNA. This experimental approach, coupled with hybridization studies in situ, is expected to yield critical data on the distribution and the specificity of the repetitive DNA sequences present in the human genome and to provide a new tool for cytological mapping of human chromosomes.
Method for predicting RNA secondary structure.
Authors: Pipas J M , McMahon J E
Published: May 2006

We report a method for predicting the most stable secondary structure of RNA from its primary sequence of nucleotides. The technique consists of a series of three computer programs interfaced to take the nucleotide sequence of any RNA and (a) list all possible helical regions, using modified Watson-Crick base-pairing rules; (b) create all possible secondary structures by forming permutations of compatible helical regions; and (c)evaluate each structure for total free energy of formation from a completely extended chain. A free energy distribution and the base-by-base bonding interactions of each possible structure are catalogued by the system and are readily available for examination. The method has been applied to 62 tRNA sequences. The total free-energy of the predicted most stable structures ranged from -19 to -41 kcal/mole (-22 to -49 kJ/mole). The number of structures created was also highly sequence-dependent and ranged from 200 to 13,000. In nearly all cases the cloverleaf is predicted to be the structure with the lowest free energy of formation.