bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum chemical calculations of model systems for ascorbic acid adducts with Schiff bases of lysine side chains: possibility of internal charge transfer in proteins.
Authors: Otto P , Ladik J , Szent-Györgyi A
Published: May 2006

Ab initio self-consistent field calculations for neutral and cationic ascorbic acid and model compounds have been performed. Furthermore, the bicyclic addition products of alpha-hydroxytetronic acid with methylglyoxal and with the Schiff base formed between methylglyoxal and methylamine have been calculated, again in their neutral and cationic forms, respectively. The results indicate that the investigated cations can act as strong electron acceptors. With the help of space-filling molecular models it has been demonstrated that such conformations of the Schiff base formed between the primary amino group of lysine side chains in proteins and the ascorbic acid methylglyoxal acetal are possible in which the lactone carbonyl group comes near to the N atoms of the peptide groups, so that charge can be transferred between these subunits.
Pore formation in lipid membranes by alamethicin.
Authors: Fringeli U P , Fringeli M
Published: May 2006

The conformation of the linear peptide antibiotic alamethicin in dipalmitoyl phosphatidylcholine multilayers was investigated in the absence of an electric field by means of infrared attenuated total reflection spectroscopy. Alamethicin was found to be incorporated into the lipid membrane not only in the dry state but also in an aqueous environment. Its molecular conformation, however, changed from a helix when dry to an extended chain when aqueous. The extended chain aggregated to di- and multimers spanning the lipid bilayer. The equilibrium concentration of alamethicin in the surrounding water was 90 nM, which is in the range of concentrations used in black film experiments. The corresponding molar ratio of lipid to peptide was 80:1. Concerning the molecular mechanism of electric field-induced pore formation, one has to conclude that the dipole model proposed by several authors is very unlikely because it is based on the assumption that the major part of alamethicin is adsorbed on the membrane surface, from which small amounts flip into the membrane under the influence of an electric field. An alternative mechanism is proposed, based on a field-induced conformational change of the peptide from the extended state to a helix. This transition is favored by the resulting dipole moment of the alamethicin helix.
Epigenetic activation of phenylalanine hydroxylase in mouse erythroleukemia cells by the cytoplast of rat hepatoma cells.
Authors: Gopalakrishnan T V , Anderson W F
Published: May 2006

Friend mouse erythroleukemia cells do not synthesize detectable levels of phenylalanine hydroxylase [phenylalanine 4-monooxygenase; L-phenylalanine, tetrahydropteridine:oxygen oxidoreductase (4-hydroxylating), EC 1.14.16.1] and hence are unable to grow in medium totally lacking tyrosine. These cells were fused with the cytoplasts of rat hepatoma cells that synthesize phenylalanine hydroxylase constitutively. Cytoplasmic hybrids [cybrids, Bunn, C. L., Douglas, C. W. & Eisenstadt, J. M. (1974) Proc. Natl. Acad. Sci. USA 71, 1681--1685] were selecte in medium without tyrosine. Cybrid clones expressed phenylalanine hydroxylase enzyme, which was of mouse type as determined by immunotitration and isoelectric focusing. This phenotype has been mainta ined even in the absence of any selective pressure. In contrast, in whole cell hybrids derived between the same parents, the expression of the phenylalanine hydroxylase gene was totally extinguished. One interpretation of these results is that the cytoplasm of rat hepatoma cells contain a positively acting factor(s) for the phenylalanine hydroxylase gene that brings about the activation of this gene in erythroleukemia cells.
Further examination of presumptive
Rhizobium trifolii
mutants that nodulate
Glycine max
Authors: Ludwig R. A. , Raleigh E. A. , Duncan M. J. , Signer E. R. , Gibson A. H. , Dudman W. F. , Schwinghamer E. A. , Jordan D. C. , Schmidt E. L. , Tran D. T.
Published: May 2006

Two recent reports described the isolation of derivatives of a
Rhizobium trifolii
strain that had gained the ability to nodulate
Glycine max
and
Vigna radiata
and that had demonstrated altered patterns of carbon source utilization, free-living nitrogen fixation, and hydrogen uptake. More extensive characterization of these strains now supports the conclusion that these strains are
R. japonicum
and are not derived from the putative parent
R. trifolii
.
Stereospecific hexose transport by membrane vesicles from mouse fibroblasts: Membrane vesicles retain increased hexose transport associated with viral transformation
Authors: Inui Ken-ichi , Moller David E. , Tillotson Loyal G. , Isselbacher Kurt J.
Published: May 2006

Membrane vesicles isolated from nontransformed BALB/c 3T3 mouse fibroblasts (3T3) and from those cells transformed by simian virus 40 (SV3T3) displayed carrier-mediated and stereospecific uptake of hexose as measured by the difference between D-[
14
C]glucose or its analogues and L-[
3
H]glucose uptake. Stereospecific uptake appeared to be linear for 5 sec and reached a maximum at 5-10 min. Stereospecific D-[
14
C]glucose uptake, osmotically sensitive and temperature dependent, was inhibited by unlabeled D-glucose or its analogues and was stimulated by the countertransport of accumulated unlabeled D-glucose. As with whole cells, the initial rate of stereospecific uptake by SV3T3 membrane vesicles was approximately 2.5-fold greater than that by 3T3 vesicles. Efflux of preloaded D-[
14
C]glucose was also faster from SV3T3 than from 3T3 membrane vesicles. The
K
m
value was 5 mM for both the 3T3 and the SV3T3 membrane vesicles, but the
V
max
values were 36 and 86 nmol/mg of protein per min, respectively, suggesting an increase in the number or availability of hexose carriers in transformed cell membranes. Cytochalasin B competitively inhibited stereospecific hexose uptake in both types of membrane vesicles. The binding of cytochalasin B to the SV3T3 membrane vesicles was significantly greater than that to 3T3 vesicles. Thus, the membrane vesicles retained many of the features of the altered hexose transport observed in whole cells in association with viral transformation.
Bed load transport by submerged jets
Authors: Francis J. R. D. , McCreath P. S.
Published: May 2006

Some similarities are presented between the bed load transport of noncohesive grains in long rivers and at a local, jet-induced scour. Experiments are described in which a submerged two-dimensional slot nozzle, inclined downward, eroded a deep sand bed. The rate of erosion at the very beginning of a scour was evaluated and compared with river data by use of the idea of “stream-power.” Empirical relationships for the two cases are similar, although the geometry of the boundaries is quite different.
The homogeneity conjecture
Authors: Shore Richard A.
Published: May 2006

We show that, for any function
f
in which Kleene's
O
is computable, the ordering of Turning degrees (i.e., degrees of difficulty of computation of functions) is not isomorphic to the ordering of degrees of functions from which
f
is computable. This refutes a well-known conjecture of H. Rogers, Jr., and others.
Oncogenicity of simian virus 40 deletion mutants that induce altered 17-kilodalton t-proteins.
Authors: Lewis A M , Martin R G
Published: May 2006

Plaque-purified viable simian virus 40 deletion mutants containing deletions between map positions 0.54 and 0.59 induced tumors in 21--92% of LSH hamsters inoculated during the first 24 hr of life. HinfI restriction endonuclease digestion patterns of the genomes of virions rescued from the tumor cells and the distribution of simian virus 40 early proteins in these cells associated tumor induction with the inoculated mutants. These results imply that the DNA sequences comprising that portion of the early simian virus 40 genome between map positions 0.54 and 0.59 are not essential for simian virus 40 oncogenicity.
Conserved primary sequences of the DNA terminal proteins of five different human adenovirus groups
Authors: Green Maurice , Brackmann Karl , Wold William S. M. , Cartas Maria , Thornton Helen , Elder John H.
Published: May 2006

The 31 human adenoviruses (Ad) from five groups (A-E) whose DNAs are <20% homologous by molecular hybridization. Ad5 (group C) DNA contains a 55,000-dalton protein probably covalently bound to each 5′ terminus. This covalently bound protein may be analogous to polypeptides found in other viral and nonviral systems that are covalently bound to genomic DNAs or RNAs and that are thought to function in DNA or RNA replication. Because of the importance of proteins linked to nucleic acids, we have investigated whether DNAs from all five groups of human adenoviruses have terminal proteins, as well as the peptide relationships among the different terminal proteins. We show here that DNAs from Ad12, 7, 2, 19, and 4, representing Ad groups A-E, respectively, all contain covalently bound proteins of about 55,000 daltons. To investigate the peptide relatedness among the terminal proteins, we prepared microgram quantities of covalently bound protein from Ads in groups A-E and compared their chymotryptic and tryptic
125
I-labeled peptide maps. We find that the covalently bound protein maps of the five Ad groups are highly related and possibly identical. On the other hand, the tryptic and chymotryptic peptide maps of the major virion protein II and the core proteins V and VII of groups B, C, and E Ads show considerable heterology. Assuming that the covalently bound protein is virally coded, the conserved primary sequence of these proteins suggests a major functional role for the protein in Ad replication. Because the genetic origin of the Ad covalently bound proteins is not established, our data are also consistent with the possibility that the protein is coded by a cellular gene.
Genetics of type II glycogenosis: Assignment of the human gene for acid α-glucosidase to chromosome 17
Authors: D'Ancona Gian G. , Wurm James , Croce Carlo M.
Published: May 2006

We have studied somatic cell hybrids between thymidine kinase (EC 2.7.1.75) deficient mouse cells and human diploid fibroblasts for the expression of human acid α-glucosidase (EC 3.2.1.20). A deficiency in this enzyme is associated with the type II glycogenosis or Pompe disease. All 30 somatic cell hybrids selected in hypoxanthine/aminopterin/thymidine medium expressed human acid α-glucosidase and galactokinase (EC 2.7.1.6) and retained human chromosome 17; counterselection of the same hybrids in medium containing 5-bromodeoxyuridine resulted in the growth of hybrids that concordantly lost the expression of human acid α-glucosidase and galactokinase as well as human chromosome 17. Hybrids between thymidine kinase-deficient mouse cells and fibroblasts from a patient with Pompe disease that contained human chromosome 17 were found not to express human acid α-glucosidase. Because we have already shown that hybrids between mouse peritoneal macrophages and GM54VA simian virus 40-transformed human cells selectively retain human chromosome 17 and lose all other human chromosomes, we tested 13 independent mouse macrophage × GM54VA hybrid clones, including two that retained human chromosome 17 and no other human chromosomes, for the expression of human acid α-glucosidase and galactokinase. All 13 hybrid clones were found to express these human enzymes. Thus, we conclude that the gene coding for human acid α-glucosidase is located on human chromosome 17.
Lactose genes fused to exogenous promoters in one step using a Mu-lac bacteriophage: in vivo probe for transcriptional control sequences.
Authors: Casadaban M J , Cohen S N
Published: May 2006

The lactose structural genes, without the lactose promoter, have been incorporated into the bacteriophage Mu genome to form a Mu-lac specialized transducing phage. This phage also carries a gene encoding resistance to ampicillin (Ap)[Mu(Ap, lac)]. After infection and upon establishment of lysogeny, the Mu(Ap, lac) genome can integrate into apparently random sites in the Escherichia coli chromosome. When integration occurs within a gene in the orientation of its transcription, the lactose structural genes are so situated that they become expressed solely from the promoter of that gene. Thus, expression of the lactose genes of Mu(Ap, lac) can be used as an assay for transcription of that gene and for functional and mutational studies of gene regulation.
A new glnA-linked regulatory gene for glutamine synthetase in Escherichia coli.
Authors: Pahel G , Tyler B
Published: May 2006

Mutations in the glnA region of the Escherichia coli chromosome due to Mu prophage insertion result in two phenotypic classes. One class is Gln- and does not synthesize glutamine synthetase[L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2] under any growth condition. The other class produces a low level of glutamine synthetase under all growth conditions and is uncoupled from the regulatory effects of mutations in the glnF and glnD genes. Complementation analysis demonstrates that these two classes of insertions are in different cistrons. From these data we suggest that a regulatory gene, glnG, tightly linked to glnA, mediates both activation and repression of glutamine synthetase synthesis. An analysis of the evidence accumulated to date makes it unlikely that glnG is the only gene in the glnA region involved in the complex system of nitrogen regulation.
Some recent tests of the chronometric cosmology
Authors: Segal I. E.
Published: May 2006

Two papers comparing particular samples of galaxies and quasars with certain predictions of the chronometric cosmology, and reporting significant deviations, are shown not to be altogether correct in their theoretical procedures. It is shown in addition that although the data employed in these papers are in part privately held, published data on similar samples fit the chronometric predictions satisfactorily, and fail to fit nonevolutionary Friedmann models with conventional values for
q
0
. As a check on and a refinement of our statistical analysis, the magnitude bias was removed from several well-documented samples by maximum-likelihood estimation of the individual probabilities in the differential luminosity function, without constraint on its form. The same conclusions as earlier follow, both in the classic regime of bright low-redshift galaxies and that of quasars.
Sequence of picornavirus RNAs containing a radioiodinated 5'-linked peptide reveals a conserved 5' sequence.
Authors: Hewlett M J , Florkiewicz R Z
Published: May 2006

Virion RNA (vRNA) from poliovirus type 1 (PV1), poliovirus type 2 (PV2), and coxsackie virus B1 (Cox B1) were treated with proteinase K to remove all but a small peptide of the covalently attached 5' genome-linked virion protein (VPg). The peptide on these RNA molecules was then treated with Bolton-Hunter 125I reagent, which iodinates primary amine groups, in order to obtain specific 5'-terminal radioactive labeling. Sequences of 125I-labeled vRNAs were determined by using a set of base-specific RNases and a partial alkaline hydrolysis "ladder." The first 20 positions of these RNAs show a remarkable conservation of sequence. The initial 10 nucleotides are identical in PV1, PV2, and Cox B1, with the sequence VPg-pU-U-A-A-A-A-C-A-G-C. The next 10 nucleotides show a one-base difference between PV1 and PV2 and 50% homology between PV1 and Cox B1. This conserved 5' region may provide a recognition site for interaction between the viral mRNA and the host translation system.
cis-trans
photoisomerization of 1,3,5,7-octatetraene in
n
-hexane at 4.2 K
Authors: Granville Mark F. , Holtom Gary R. , Kohler Bryan E.
Published: May 2006

Photoisomerization of the linear polyene 1,3,5,7-octatetraene has been observed in an
n
-hexane matrix maintained at the boiling point of helium. To a good approximation, only the
trans,trans
and
cis,trans
isomers participate in the photochemistry. These compounds have been unambiguously identified by comparing the observed high-resolution fluorescence spectra to those of chromatographically purified reference compounds. Although the quantum yield of this process is probably low, its microscopic rate seems to compete favorably with vibrational deactivation.
Triplet phase invariants: Formula for acentric case from fourth-order determinantal joint probability distributions
Authors: Karle Jerome
Published: May 2006

A conditional probability distribution for triplet invariants is derived for noncentrosymmetric crystals from fourth-order determinantal joint probability distributions. The formula makes use of the entire data set in the computations for each invariant. Test calculations indicate that the formula can be used to help select invariants whose values are distributed close to zero and also to evaluate special invariants associated with seminvariant phases.
Isolation and sequence of the gene for iso-2-cytochrome c in Saccharomyces cerevisiae.
Authors: Montgomery D L , Leung D W , Smith M , Shalit P , Faye G , Hall B D
Published: May 2006

The two apocytochrome c proteins of yeast are coded for by separate genes. Iso-2-cytochrome c differs from the iso-1 protein at 17 positions within a homologous sequence of 108 amino acids. The previously cloned iso-1-cytochrome c coding sequence has been used to identify lambda-yeast recombinant phage containing the gene for iso-2-cytochrome c. The latter protein contains the dipeptide Ala-Ala which is coded for by the nucleic acid sequence G-C-N-G-C-N. The recognition specificity of restriction endonuclease Fnu4HI for G-C-N-G-C provided a rapid means of locating the region of the cloned fragment which codes for iso-2-cytochrome c. The DNA sequence of this gene has been determined and compared with that of the iso-1-cytochrome c locus. There is no intervening sequence within the gene for iso-2-cytochrome c. At 45 of the 91 positions for which iso-1- and iso-2-cytochrome c have the same amino acid, the codons differ. Such third position variation does not occur within the region coding for amino acids 70-80, the protein sequence that is also most conserved among all eukaryotic cytochromes c.
[Phe4]somatostatin: a potent, selective inhibitor of growth hormone release.
Authors: Meyers C A , Coy D H , Murphy W A , Redding T W , Arimura A , Schally A V
Published: May 2006

[Phe4]Somatostatin was twice as active as somatostatin (SS) in suppressing rat growth hormone release in vitro but had only weak activity toward inhibition of insulin and glucagon release in vivo. The ability of this analogue to inhibit growth hormone release more actively than SS was confirmed in vivo by two separately designed bioassays. Further structure/activity studies of position 4 were carried out with [Glu4]SS, [Thr4]SS, and des-Lys4-SS, all of which had negligible inhibiting activity in the pituitary and pancreas. In this context the strikingly selective activity of [Phe4]SS suggests a fundamental difference in the SS receptors of pituitary and pancreas and the normal side-chain basicity of position 4 appears to be more important for action in pancreas than in pituitary. [Phe4]SS has properties that may be useful in the development of agents for the treatment of acromegaly or other disorders associated with increased growth hormone levels.
Demonstration of a specific mitochondrial isovaleryl-CoA dehydrogenase deficiency in fibroblasts from patients with isovaleric acidemia.
Authors: Rhead W J , Tanaka K
Published: May 2006

To study the enzymatic basis of isovaleric acidemia, we have developed assay methods for isovaleryl-CoA and butyryl-CoA dehydrogenases that measure the amount of tritium released from the respective [2,3-3H]acyl CoAs. Because assay of these enzymes in human fibroblast homogenates was subject to interference by nonspecific reactions, we have isolated mitochondria from cultured skin fibroblasts by protease treatment, homogenization, and differential centrifugation. By using this assay method with these isolated mitochondria, we have demonstrated a specific deficiency of isovaleryl-CoA dehydrogenase [isovaleryl-CoA: (acceptor) oxidoreductase, EC 1.3.99.10] activity in cultured skin fibroblasts from five patients with isovaleric acidemia. In contrast, mitochondrial butyryl-CoA dehydrogenase [butyryl-CoA: (acceptor) oxidoreductase, EC 1.3.99.2] activity in these cells was preserved at normal levels. These results have been reproduced by using the conventional dye reduction assays. These observations give further support to the hypothesis that isovaleryl CoA is dehydrogenated by a specific enzyme and that isovaleric acidemia is due to a deficiency of this enzyme.
Theoretical prediction of the vibrational spectra of group IB trimers
Authors: Richtsmeier Steven C. , Gole James L. , Dixon David A.
Published: May 2006

The molecular structures of the group IB trimers, Cu
3
, Ag
3
, and Au
3
, have been determined by using the semi-empirical diatomics-in-molecules theory. The trimers are found to have C
2v
symmetry with bond angles between 65° and 80°. The trimers are bound with respect to dissociation to the asymptotic limit of an atom plus a diatom. The binding energies per atom for Cu
3
, Ag
3
, and Au
3
are 1.08, 0.75, and 1.16 eV, respectively. The vibrational frequencies of the trimers have been determined for comparison with experimental results. The vibrational frequencies are characterized by low values for the bending and asymmetric stretch modes. The frequency of the symmetric stretch of the trimer is higher than the stretching frequency of the corresponding diatomic. A detailed comparison of the theoretical results with the previously measured Raman spectra of matrix isolated Ag
3
is presented.
Reiteration frequency mapping: analysis of repetitive sequence organization within cloned DNA fragments containing the human initiator methionine tRNA gene.
Authors: Zasloff M , Santos T
Published: May 2006

The organization of repetitive sequences within three cloned chromosomal segments from human fetal liver DNA containing the initiator methionine tRNA gene was studied. The procedure developed for this study involves the contact hybridization of an electrophoretically separated 5'-32P-labeled restriction endonuclease digest of the cloned segment with total human genomic DNA covalently bound to aminobenzyloxymethyl-paper. The extent of hybridization of each labeled fragment to the area of paper with which it is in contact is proportional to the representation of the sequence within the human genome. We show that sequences with a wide range of genomic repetitition are present in the neighborhoods of the three dispersed initiator tRNA loci, each characterized by a different overall organization pattern.
Pentaribonucleotides of mixed sequence are synthesized and efficiently prime de novo DNA chain starts in the T4 bacteriophage DNA replication system.
Authors: Liu C C , Alberts B M
Published: May 2006

In the presence of single-stranded DNA, the bacteriophage T4 gene 41 and gene 61 proteins catalyze the synthesis of a group of pentaribonucleotides which are homogeneous in chain length but heterogeneous in nucleotide sequence. When single-stranded T4 DNA is used as template, a unique dinucleoside sequence, pppApC, is found at the 5' end of these pentaribonucleotides with the general sequence pppApCpNpNpN. In the presence of the remaining five T4 replication proteins, the pentaribonucleotides can be utilized with high efficiency to prime de novo DNA chain starts; as a result, the vast majority of them can be detected at the 5' end of newly made DNA molecules in an unaltered form. There are multiple, but specific, sites at which new DNA chains are primed in this way on a natural single-stranded DNA. Because identical RNA primers have been isolated from the 5' end of the Okazaki fragments made in T4-infected cells, we suggest that the T4 gene 41 and gene 61 proteins also make the pentaribonucleotides that prime de novo T4 DNA chain starts in vivo during lagging strand DNA synthesis.
Untranslated mRNA for a chorion protein of Drosophila melanogaster accumulates transiently at the onset of specific gene amplification.
Authors: Thireos G , Griffin-Shea R , Kafatos F C
Published: May 2006

In the cytoplasm of follicular cells of female fruitflies, a messenger RNA for one of the chorion proteins accumulates prematurely (i.e, before in vivo synthesis of the protein) but is not associated with polysomes. Subsequently, this mRNA is rapidly degraded and, thus, is not stored for later use. At a later stage in choriogenesis, the same mRNA reappears, accumulates, associates with polysomes, and is translated into a chorion protein. The transient, premature accumulation of the mRNA occurs in concert with the onset of amplification of its specific gene, a finding suggestive of a functional coupling between the two events.
Topographic studies of Torpedo acetylcholine receptor subunits as a transmembrane complex.
Authors: Strader C D , Raftery M A
Published: May 2006

The exposure of the four subunits of the acetylcholine receptor from Torpedo californica on both the extracellular and cytoplasmic faces of the postsynaptic membranes of the electroplaque cells has been investigated. Sealed membrane vesicles containing no protein components other than the receptor were isolated and were shown to have 95% of their synaptic surfaces facing the medium. The susceptibility of the four receptor subunits in these preparations to hydrolysis by trypsin both from the external and from the internal medium was used to investigate the exposure of the subunits on the synaptic and cytoplasmic surfaces of the membrane. It was shown by sodium dodecyl sulfate gel electrophoresis of the tryptic products that all four subunits are exposed on the extracellular surface to a similar degree. All four subunits are also exposed on the internal surface of the membrane, but the apparent degree of exposure varies with the subunit size, the larger subunits being more exposed. The results are discussed in terms of a possible topographic model of the receptor as a transmembrane protein complex.
Characterization of a receptor-like protein for 1,25-dihydroxyvitamin D3 in rat skin.
Authors: Simpson R U , DeLuca H F
Published: May 2006

Isolated rat epidermis possesses a cytosolic 3.5 S receptor-like protein for 1,25-dihydroxyvitamin D3. This 3.5S binder has a high affinity (Kd = 1.4 X 10(-10) M) for 1,25-dihydroxyvitamin D3 and is present in low concentrations (31 fmol of binding sites per mg of cytosol protein). Analog competition for receptor binding revealed the following potency order: 1,25-dihydroxyvitamin D3 > 25-hydroxyvitamin D3 > 1 alpha-hydroxyvitamin D3 > 24 (R),25-dihydroxyvitamin D3 > vitamin D3. The receptor has a molecular weight of 60,000, has affinity for DNA-cellulose, and aggregates in the presence of low potassium concentrations. The 1,25-dihydroxyvitamin D3 binder is stabilized by sodium molybdate (10 mM). Addition of phenylmethylsulfonyl fluoride (3 mM) was found to yield more reproducible receptor preparations. The presence of a 1,25-dihydroxyvitamin D3 binding macromolecule with properties similar to those of the bone and intestinal receptor suggests that skin is an additional target organ for this hormone.
An activation factor of liver phosphofructokinase.
Authors: Furuya E , Uyeda K
Published: May 2006

Pure phosphofructokinase (ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) from liver is strongly inhibited by ATP, whereas crude phosphofructokinase is only slightly inhibited by ATP. A factor that is removed from the enzyme during purification and can prevent the inhibition of phosphofructokinase by ATP has been isolated. The factor can be resolved into three components that differ in molecular weights, as shown by gel filtration on Sephadex G-25. These factors overcome the ATP inhibition but have no effect on the catalytic activity under the optimum assay conditions. Furthermore, AMP acts syngeristically with the activation factor in reversing ATP inhibition. It is proposed that the activation of phosphofructokinase by the activation factor and AMP is sufficient to account for the glycolytic flux in the liver.
Priming and inhibitory activities of RNAs for the influenza viral transcriptase do not require base pairing with the virion template RNA.
Authors: Krug R M , Broni B A , LaFiandra A J , Morgan M A , Shatkin A J
Published: May 2006

Capped ribopolymers lacking a sequence complementary to the common 3' end of the influenza virion RNA segments effectively stimulated transcription of these RNAs by the virion-associated transcriptase. Thus, stimulation of transcription results not from hydrogen bonding between the capped RNA and the 3' end of the virion RNA but presumably from a specific interaction of the capped RNA with protein(s) in the transcriptase complex. Although no specific nucleotide sequence was required for priming activity, capped mRNAs with diminished secondary structure were preferred as primers. Inosine-substituted or bisulfite-modified capped reovirus mRNAs were at least 3- to 5-fold more effective as primers than were the native capped mRNAs. On the other hand, inosine substitution or bisulfite treatment of the uncapped form of reovirus mRNAs converted them from essentially inactive species to potent inhibitors of the transcriptase reaction primed by either ApG or globin mRNA. These effects of reduced secondary structure also most probably reflect an interaction of the exogenous RNAs with transcriptase protein(s). The results obtained from screening a series of native uncapped ribopolymers were consistent with inhibitory activity requiring the absence of most hydrogen bonding in the ribopolymer and also suggested that specific structural feature(s) of the nucleotides in the chain were important.
Oligosaccharide motion in erythrocyte membranes investigated by picosecond fluorescence polarization and microsecond dichroism of an optical probe.
Authors: Cherry R J , Nigg E A , Beddard G S
Published: May 2006

Oligosaccharide chains on the surfce of human erythrocytes were labeled with the probe eosin 5-thiosemicarbazide. The probe was conjugated to aldehydes produced by oxidation of sialic acid and galactose residues. The probe is associated mostly with glycophorin A after sialic acid labeling, whereas multiple components, including band 3 and lipids, are labeled after galactose oxidation. Fast molecular motion was studied by measuring steady-state and picosecond time-resolved fluorescence depolarization. Slower motions were investigated by observing flash-induced transient dichroism. It was found that both eosin-labeled sialic acid and galactose residues exhibit a rapid motion with correlation time of approximately 3 nsec. This motion is assigned to independent motion of the probe, possibly in conjunction with a short segment of the oligosaccharide chain. The order parameter of the fast motion is 0.8.-0.9, demonstrating that its angular amplitude is highly restricted. For eosin-labeled sialic acid, the order parameter in the microsecond time range is 0.2-0.3. It is deduced that a second, slower rotational motion is present, which is assigned to a cooperative motion of the oligosaccharide chains. The correlation time of this motion is in the range 10(-7)-(10-5) sec. Some eosin-labeled galactose residues may have a similar slow motion, but most appear to be remarkably immobile over the time range 10(-8)-10(-3) sec.
Immunoglobulin V/J recombination is accompanied by deletion of joining site and variable region segments.
Authors: Seidman J G , Nau M M , Norman B , Kwan S P , Scharff M , Leder P
Published: May 2006

A site-specific recombination event is responsible for the somatic activation of immunoglobulin genes and for generating a major share of immunoglobulin gene diversity. Although several possible mechanisms can be proposed to account for this process, recombinatio accompanied by deletion is a particularly attractive mechanism because it might utilize inverted repeat sequences noted on the 3' side of all variable regions and on the 5' side of all joining site segments thus far studied. Testing this model is complicated by the fact that antibody cells are at least diploid and gene segments on the inactive chromosome can obscure deletions occurring within the active gene. Accordingly, we have screened several immunoglobulin-producing plasmacytoma lines to select those in which both chromosomes are rearranged. By using appropriate cell lines and variable and joining region probes in in situ hybridization experiments, we show that recombination is accompanied by the deletion of both variable and joining region genes. These experiments also allow us to map the site of V/J recombination of several active immunoglobulin genes and suggest an order and orientation for variable, joining, and constant region sequences.
Cytotypically specific transfecting activity of DNA from C57BL/Ka mouse cells producing thymotropic in contrast to nonthymotropic retroviruses.
Authors: Kopecka H , Declève A , Lieberman M , Fry K , Kaplan H S
Published: May 2006

A comparative study has been made of the susceptibility of fibroblastic cells to transfection by DNA from C57BL/Ka mouse lines producing either fibrotropic or thymotropic retroviruses. DNA isolated from fibroblasts that release a B-ecotropic, fibrotropic virus, BL/Ka(B), was found to transfect fibroblasts of Fv-1bb genotype with release of virus similar to BL/Ka(B). Fv-1nn fibroblasts were also susceptible but expression was delayed, and xenotypic mink lung cells were refractory. In contrast, DNA prepared from a murine T-cell lymphoma line producing a B-ecotropic, thymotropic virus failed to transfect mouse fibroblasts though it transfected a nonproducer T-cell lymphoma line. The data suggest that the Fv-1 and differentiation-specific restriction mechanisms operate at different molecular levels.
Statistical invalidation of the Hubble law
Authors: Nicoll J. F. , Johnson D. , Segal I. E. , Segal W.
Published: May 2006

An optimal nonparametric technique for elimination of the observation cutoff bias, on the assumption of a given theoretical cosmology, is applied to the redshift-magnitude and redshift-angular diameter relationships in objectively specified large galaxy samples. The estimates obtained on the assumptions of linear and square redshift-distance laws are uniformly and strongly favorable to the square law. The question of whether the relative inferiority of the linear law can scientifically be ascribed to ancillary extragalactic phenomena is addressed by nonparametric crosstesting of the alternative hypotheses. Each law is used to predict the results of a statistical analysis based on the alternative law by using the given data and computer simulations. The result is that the square law predicts with statistical exactitude the results of the analyses of the linear law; but the linear law predicts with near certainty that the fit of the square law will be much worse than is observed. In the absence of independent validation of a variety of ancillary hypotheses that have been adduced in connection with the linear law, it seems necessary to conclude that the Hubble law lacks an objective statistical foundation.
Use of an indicator sequence of human DNA to study DNA damage by methylbis(2-chloroethyl)amine.
Authors: Grunberg S M , Haseltine W A
Published: May 2006

A highly reiterated sequence of human DNA was used to determine the sites of modification of DNA caused by the anti-tumor drug methylbis(2-chloroethyl)amine (HN2, mechlorethamine, nitrogen mustard) upon treatment of cells in culture and of purified DNA. The lengths of the breakage products of the DNA treated with HN2 were compared to the lengths of DNA scission products produced by chemical reactions used for DNA sequence determination. HN2 was found to create alkali-labile lesions at positions of guanine. The distribution of the guanine modifications was the same for DNA extracted from cells treated with HN2 and for purified DNA treated with HN2. However, the extent of damage was at least 2-fold greater when purified DNA was used as the substrate. Several nitrogen mustard analogues also produced alkali-labile lesions at positions of guanine.
Mutant of avian erythroblastosis virus defective for erythroblast transformation: deletion in the erb portion of p75 suggests function of the protein in leukemogenesis.
Authors: Beug H , Kitchener G , Doederlein G , Graf T , Hayman M J
Published: May 2006

Previous studies have shown that td359 AEV, a mutant of avian erythroblastosis virus (AEV), is unable to transform erythroblasts in vitro or in vivo but is capable of transforming fibroblasts in vitro and of causing sarcomas in chicks. In this paper we show that the mutant synthesizes a gag-gene related protein (delta p75) which is about 1000 daltons smaller than the protein, p75, induced by wild-type AEV. The mutant protein lacks 3 of the approximately 53 lysine-arginine tryptic peptides resolved in p75 and also contains an additional peptide. By cleavage of delta p75 with p15 protease and analysis of the fragments for size and peptide composition, the deletion in delta p75 could be located in the non-gag region of the molecule. In contrast, with p40 AEV, a second AEV-specific protein synthesized in in vitro translation experiments, there is no change in size of translation products obtained from td359 AEV RNA. Our data provide direct evidence that p75 is required for erythroblast transformation.
Anti-gamete monoclonal antibodies synergistically block transmission of malaria by preventing fertilization in the mosquito.
Authors: Rener J , Carter R , Rosenberg Y , Miller L H
Published: May 2006

Experiments from our laboratory previously demonstrated that infected chickens immunized with gametes of the avian malaria parasite Plasmodium gallinaceum were no longer infectious to the mosquito vector Aedes aegypti and that this transmission-blocking immunity was mediated by antibody. To identify those antigens that are the targets of transmission-blocking immunity, hybrid mouse cell lines secreting monospecific antibodies to surface antigens on male and female gametes of P. gallinaceum have been produced. We describe two such anti-gamete antibodies, 10G3 and 11C7, which act synergistically both to agglutinate male gametes in vitro and to suppress infectivity of parasitized blood fed to mosquitoes. In the presence of a mixture of these antibodies, the male gametes became agglutinated during gametogenesis and failed to detach from the residual body of the gametocyte. In the presence of either antibody alone, the male gametes readily detached during gametogenesis. Neither antibody alone mediated more than a slight reduction in infectivity of gametocytes to mosquitoes. Although both 10G3 and 11C7 recognize surface antigens on both male and female gametes, agglutination and prevention of detachment of the male gametes from the residual body appears to be the primary mechanism by which the mixture of these antibodies prevents fertilization.
Gaseous isotope separation using solar wind phenomena
Authors: Wang Chia-Gee
Published: May 2006

A large evacuated drum-like chamber fitted with supersonic nozzles in the center, with the chamber and the nozzles corotating, can separate gaseous fluids according to their molecular weights. The principle of separation is essentially the same as that of the solar wind propagation, in which components of the plasma fluid are separated due to their difference in the time-of-flight. The process can inherently be very efficient, serving as a pump as well as a separator, and producing well over 10
5
separative work units (kg/year) for the hydrogen/deuterium mixture at high-velocity flows.
Regulation of herpesvirus macromolecular synthesis: transcription-initiation sites and domains of alpha genes.
Authors: Mackem S , Roizman B
Published: May 2006

Herpes simplex virus 1 (HSV-1) specifies in the infected cell a set of polypeptides (alpha) whose mRNAs are made in the absence of protein synthesis. The individual mRNAs specifying alpha polypeptides 0, 4, 22, and 27 were purified by hybridization to strand-separated or total HSV-1 DNA fragments cloned in pBR322 plasmids, translated in vitro to verify their specificity, then mapped by hybridization to separated strands and digests of cloned DNA fragments. To map the transcription initiation sites, chemically decapped individual mRNAs were recapped with [alpha-32P]GTP and vaccinia virus guanylyltransferase and hybridized to digests of the cloned DNA fragments. Each of the labeled 5' termini hybridized to a specific site, two on one strand, and two on the other. The 5' ends of the transcripts do not share sequence homology, suggesting that they are transcribed from independent promoters.
Unusual sequence homology at the 5-ends of the developmentally regulated beta A-, beta C-, and gamma-globin genes of the goat.
Authors: Haynes J R , Rosteck P , Lingrel J B
Published: May 2006

We have constructed a recombinant library of goat DNA and have isolated clones containing the beta A-, beta C-, and gamma-globin genes and a presumptive embryonic globin gene. These genes are switched on and off during development and, thus, provide a model system for the study of gene regulation. To identify regions that may be involved in this switch, we determined the sequence of the areas surrounding the 5' ends of the beta A-, beta C- and gamma-globin genes. Surprisingly, the sequences of the beta A-, and beta C-globin genes are identical, beginning with the translation initiation codon and extending 131 base pairs (bp) in the 5' direction. At this point, two nucleotide differences are seen and only six additional differences are encountered when the sequences are extended 144 bp further in the 5' direction. Furthermore, the nucleotide sequence of the 5' end of the gamma-globin gene is very similar to those of the beta A-0, and beta C-globin genes. Only three nucleotide differences are found in the gamma-globin gene within the 131-bp region in which the beta A- and beta C-globin genes are identical. We conclude that this identical region cannot contain regulatory signals that mediate the switch from beta C to beta A expression.
Specific disruption of vimentin filament organization in monkey kidney CV-1 cells by diphtheria toxin, exotoxin A, and cycloheximide.
Authors: Sharpe A H , Chen L B , Murphy J R , Fields B N
Published: May 2006

We have examined the effect of diphtheria toxin, Pseudomonas aeruginosa exotoxin A, and cycloheximide on the CV-1 cell cytoskeleton. Within a few hours after producing an inhibition of cellular protein synthesis, all these agents specifically disrupted the organization of the vimentin filament system with no discernable effect on microtubules or microfilaments during the period of observation. Furthermore, just as the inhibition of protein synthesis by cycloheximide is reversible, so was the disruption of vimentin filaments by cycloheximide.
Nucleation and the kinetics of microtubule assembly.
Authors: Jackson M B , Berkowitz S A
Published: May 2006

A kinetic model was developed for the purpose of interpreting scanning calorimetric data of microtubule assembly. The model consists of two steps. The first step is a highly exothermic nucleation with a strong dependence upon temperature and concentration. The second step is the elongation of the nuclei or microtubules by the addition of tubulin dimer to growing ends. Computer fits to the data provided the values of the parameters of the model. The model successfully simulated various experiments.
[3H]Phencyclidine: a probe for the ionic channel of the nicotinic receptor.
Authors: Eldefrawi M E , Eldefrawi A T , Aronstam R S , Maleque M A , Warnick J E , Albuquerque E X
Published: May 2006

To evaluate [3H]phencyclidine ([3H]PCP)as a probe for the ionic channel of the nicotinic receptor, the characteristics of its binding to electric organ membranes od Torpedo ocellata and its effects on frog sartorius muscle were studied. Similar to PCP, [3H]PCP depressed the peak amplitude of endplate current, caused nonlinearity in the voltage-current relationship at negative potentials, accelerated the decay time of the end-plate current, and shortened the channel lifetime. Thus, [3H]PCP interacted with the ionic channel of the nicotinic receptor, although there were a few differences between its effect and that of PCP. Binding of [3H]PCP to Torpedo membranes was to sites on the ionic channel of acetylcholine (AcCho) receptor because it was saturable, dependent upon protein concentration, and inhibited by drugs that interact with the ionic channel, and the initial rate of binding was potentiated by receptor agonists. Equilibrium binding of [3H]PCP to Torpedo membranes was with two affinities, but in the presence of AcCho, [3H]PCP binding was with a single affinity. The affinities of channel drugs obtained by inhibition of binding of [3H]PCP and [3H[perhydrohistrionicotoxin to Torpedo membranes were different, with correlation coefficients of 0.52 and 0.82 in the absence and presence of a receptor agonist, respectively; this suggests differences in their binding sites on the ionic channel of the AcCho receptor.
Current recorded from a cut-open giant axon under voltage clamp.
Authors: Llano I , Bezanilla F
Published: May 2006

Squid giant axons were cut open and the resulting membrane sheet was positioned in a chamber separating two compartments. Under voltage clamp, normal sodium, potassium, and gating currents could be recorded for several hours. This preparation allows direct access to the internal side of the axonal membrane and should prove useful for recording of ionic currents, gating currents, and channel-induced current fluctuations in the same membrane sheet.
Intracellular injection of t he catalytic subunit of cyclic AMP-dependent protein kinase simulates facilitation of transmitter release underlying behavioral sensitization in Aplysia.
Authors: Castellucci V F , Kandel E R , Schwartz J H , Wilson F D , Nairn A C , Greengard P
Published: May 2006

It has been difficult to establish whether cyclic AMP-mediated protein phosphorylation in nerve cells plays a specific role in synaptic transmission. This difficulty can be overcome in higher invertebrates because their large neurons allow the injection of protein molecules into the cell. We have used intracellular injection to study whether protein phosphorylation is involved in the mechanism of sensitization, a simple form of learning. Sensitization of the gill-withdrawal reflex in Aplysia involves enhancement of transmitter release by presynaptic facilitation at a particular set of synaptic connections between identified sensory neurons and their follower cells. We have found that injection of the catalytic subunit of cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) purified from bovine heart mimics the action of the natural transmitter and of serotonin, the putative transmitter, by simulating the physiological changes that accompany presynaptic facilitation. Intracellular injection of the kinase into a sensory cell (i) broadens the action potential in the presence of tetraethylammonium, indicating an increase in Ca2+ current, (ii) decreases the input conductance of the cell, presumably as a result of a decrease in the K+ current, and (iii) increases the amount of transmitter released by terminals of the sensory cell onto follower neurons.
Effect of phenotypic variation on kin selection
Authors: Boyd Robert , Richerson Peter J.
Published: May 2006

An expression for the equilibrium of the mean phenotypic value of a quantitative character is derived for a model in which the fitness of an individual depends on its own phenotype and the mean phenotypic value of a group of related individuals. When selection is weak the equilibrium mean is well predicted by Hamilton's
k
> 1/
r
rule (
k
is the ratio of mean fitness gained by recipient of altruistic behavior to mean fitness lost by donor;
r
is mean coefficient of relationship between donor and recipient). When selection is strong, however, the equilibrium mean depends on the heritability of the character. Low heritability can lead to substantially more “altruism” than predicted by the
k
> 1/
r
rule.