bluuebunny/crossref_metadata_2025 huggingface dataset:
Site-specific recombination functions of bacteriophage λ: DNA sequence of regulatory regions and overlapping structural genes for Int and Xis
Authors: Hoess Ronald H. , Foeller Carl , Bidwell Karen , Landy Arthur
Published: May 2006

Site-specific recombination in bacteriophage λ is mediated by two phage-encoded proteins, Int and Xis. The structural genes encoding these proteins are located immediately to the right of their site of action, the phage
att
site. The DNA sequence for both the structural and regulatory regions of these genes has been determined. The location and reading frame of the
xis
gene were ascertained by sequence comparisons with the
b
538 deletion (that ends within
xis
) and with the
xis
6 amber mutation. From the DNA sequence Xis has a molecular weight of 8630; it is rich in basic amino acids with lysine and arginine comprising 25% of the 72 amino acids. Identification of the
int
reading frame was also unambiguous. From the DNA sequence, Int has a molecular weight of 40,330; of the 356 amino acids, 69 are basic and 46 are acidic. In the NH
2
-terminal portion of Int, 35% of the first 20 amino acids are basic. The site-specific recombination functions form a very tight cluster (
att-int-xis
) on the λ chromosome. The combined protein-encoding sequences of
xis
and
int
start 1347 base pairs, and terminate 84 base pairs, from the center of the phage
att
site. The two genes overlap one another by 20 base pairs (
xis
is upstream of
int
) and a possible means of controlling the relative synthesis rates of Int and Xis at the level of translation is proposed. Control at the level of transcription is also considered. The mutation
intc
226 leads to constitutive production of Int, independent of cII/cIII activator proteins normally required for transcription from the
p
I
promoter. It is shown that this mutation is the result of a single base change (in the fMet codon of the
xis
gene) that generates an improved promoter heptamer sequence. This result, in conjunction with comparisons with other promoter sequences and other sequences responding to cII/cIII action, leads to a tentative identification of the
p
I
promoter and site of cII/cIII action.
Increased ATP inhibition of liver phosphofructokinase from genetically diabetic mice.
Authors: Hosey M M , Chatterjee T , Cohen A J , Stein A L , Kemp R G , Marcus F
Published: May 2006

Phosphofructokinase (ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) was partially purified from the livers of genetically diabetic mice (C57BL/KsJ-db) and their lean littermates (C57BL/KsJ). These genetically diabetic mice have been shown to be hyperglucagonemic and to exhibit symptoms resembling those of maturity-onset diabetes in humans. Two isoenzymes of phosphofructokinase were obtained after DEAE-Sephadex chromatography of extracts of livers from either normal or diabetic animals. One of these isozymes, peak II, from the genetically diabetic mice was shown to be more sensitive to ATP inhibition at physiological pH than the peak II isozyme from the normal animals. In addition, the peak II isozyme from the diabetic mice exhibited decreased affinity for fructose 6-phosphate. The altered kinetic properties of phosphofructokinase from diabetic animals are markedly similar to those recently reported for liver phosphofructokinase isolated from normal animals after glucagon treatment. Our results suggest that increased glucagon levels in diabetes may lead to altered regulation of phosphofructokinase in this disease.
Cooperative binding of myosin subfragment-1 to the actin-troponin-tropomyosin complex.
Authors: Greene L E , Eisenberg E
Published: May 2006

The binding of myosin subfragment-1 (S-1) to the F-actin-troponin-tropomyosin complex (regulated F-actin) was examined in the presence of ADP (ionic strength, 0.23 M; 22 degrees C) by using the ultracentrifuge and S-1 blocked at SH1 with iodo[14C]acetamide. S-1 . ADP binds with positive cooperativity to regulated F-actin, both in the presence and absence of calcium; it binds independently to unregulated actin. With and without Ca2+ at very low levels of occupancy of the regulated actin by S-1 . ADP, S-1 . ADP binds to the regulated actin with less than 1% of the strength that it binds to unregulated actin, whereas at high levels of occupancy of the regulated actin by S-1 . ADP, S-1 . ADP binds about 3-fold more strongly to the regulated actin than it does to unregulated actin. The major difference between the results obtained in the presence and absence of Ca2+ with regulated actin is that, in the absence of Ca2+, the binding of S-1 . ADP remains weak until a higher free S-1 . ADP concentration is reached and the transition to strong binding is much more cooperative. These results are consistent with a model that is basically similar to the cooperative binding model of Hill[Hill, T.L. (1952) J. Chem. Phys. 20, 1259-1273] and of Monod et al. [Monod, J., Wyman, J. & Changeux, J. (1965) J. Mol. Biol. 12, 88-118]: The regulated actin filament can exist in two forms, a weak-binding and a strong-binding form; and Ca2+ and S-1 . ADP, acting as allosteric effectors, shift the equilibrium between the two forms.
Acetate kinase: a triple-displacement enzyme.
Authors: Spector L B
Published: May 2006

Facts relating to the mechanism of phosphoryl transfer by acetate kinase (ATP:acetate phosphotransferase, EC 2.7.2.1) are reviewed. They point to the existence of at least one experimentally established phosphoenzyme (E-P) intermediate on the reaction pathway. Sterically, the phosphoryl transfer occurs with a net inversion of the configuration of the phosphorus atom. These facts are best in accord with a triple-displacement mode of action for acetate kinase, with two E-P intermediates and three steric inversions on phosphorus. It follows that a second E-P for acetate kinase must exist.
Steady-state properties of coupled systems in mitochondrial oxidative phosphorylation.
Authors: Hill T L
Published: May 2006

At steady state there is effective coupling among various otherwise independent membrane and internal mitochondrial systems that share the same substrates or ligands (e.g., H+, Ca2+, Pi, ADP, ATP). The number of different systems, coupled through shared substrates or ligands, is no doubt very large. But, just as an infinite series can be approximated by a finite number of terms, here the number of systems included in the analysis can be limited, as an approximation. In two previous papers, the basic but oversimplified set of four tightly coupled systems was studied. These are: respiratory chain; reverse ATPase; proton-phosphate cotransport; and ADP-ATP exchange. Essentially as illustrations of the methodology required for a more realistic analysis, two much more complicated examples are formulated here: eight tightly coupled systems, and the original four systems but with the tight coupling relaxed in two of these four.
Detection of epidermal growth factor-urogastrone and its receptor during fetal mouse development
Authors: Nexø Ebba , Hollenberg Morley D. , Figueroa Alvaro , Pratt Robert M.
Published: May 2006

Using both a radioimmunoassay and a radioreceptor assay, we have estimated the content of mouse epidermal growth factor-urogastrone (EGF-URO) in fetal mice at 11½ to 17½ days of gestation. Concurrently, the amount of specific EGF-URO receptor binding was determined in crude membrane fractions from the embryos. EGF-URO receptor binding is readily detected in membranes from the youngest embryos (day 11½) and rises steadily up to parturition (18 days); the rise is more marked in embryo membranes derived from a potential target tissue, such as the maxilla and secondary palate. In the embryonic extracts, EGF-URO proved to be labile, requiring the presence of soybean trypsin inhibitor and sodium azide to stabilize the recovery of added EGF-URO in test samples. Even with added stabilizing agents, immunoreactive EGF-URO was barely detectable before day 14½ (less than 20 fmol per embryo), whereas a substantial increase was observed from day 15½ to 17½ (from 70 to 200 fmol per embryo). In contrast, the radioreceptor assay detected appreciable amounts of an EGF-URO-like substance at 11½ days (50 fmol per embryo); the values estimated by radioreceptor assay (about 10-fold higher than by radioimmunoassay) also increase markedly between days 15½ and 17½ (on average from 500 to 3000 fmol per embryo). We conclude that during fetal mouse development there is an increase both in the receptors for EGF-URO and in a substance (presumably a fetal growth factor) that can occupy the receptor. The differences between the radioreceptor and radioimmunoassay estimates for the EGF-URO content suggest that the fetal form of mouse EGF-URO differs from the adult molecule.
Bounds for the
r
th characteristic frequency of a beaded string or of an electrical filter
Authors: Barnsley Michael F. , Duffin Richard J.
Published: May 2006

The fundamental mode of vibration of a beaded string has a shape without change of sign. The
r
th higher normal mode of vibration has
r
changes of sign. Given any virtual shape of the string with
r
changes of sign, an algorithm is found that gives upper and lower bounds for the
r
th characteristic frequency as a function of the virtual shape. By making a certain transformation it is found that this algorithm holds for the characteristic frequencies of an inductor-capacitor network. Other transformations show that it applies to the
r
th eigenvalue of a Hermitian matrix.
Transformation-related antigens identified by monoclonal antibodies.
Authors: Strand M
Published: May 2006

Tumor-cell proteins that were antigenic in a syngeneic animal were identified by immunoprecipitation with monoclonal antibodies. Spleen cells of BALB/c mice immunized with plasma membranes of Kirsten RNA sarcoma virus-transformed BALB/3T3 cells were fused with NS-1 myeloma cells. Antibodies secreted into the culture fluid from these hybridomas were distinguished by their reactivity against proteins of different target cells. A total of 191 cultures were established; 143 produced antibodies that bound to BALB/3T3 cells transformed by the RNA sarcoma virus, of which antibodies from 82 bound to BALB/3T3 transformed with simian virus 40, and antibodies from 56 bound to BALB/3T3 cells. Thus, more than 50% of the cultures produced antibodies that possibly were specific to antigens of the transformed cell. Twenty different hybridomas have been cloned, and antibodies, from eight of these were found to immunoprecipitate five different proteins. A protein of approximately 32,000 daltons was precipitated from BALB/3T3 cells transformed by the RNA sarcoma virus, simian virus 40, or methylcholanthrene but not from untransformed BALB/3T3 cells. A protein of about 300,000 daltons was precipitated from all four cell lines; precipitation was enhanced in the viral transformed cells. Proteins of approximately 57,000, 54,000, and 8500 daltons were immunoprecipitated from all four cell lines.
Receptor-mediated uptake of 3,3',5-triiodo-L-thyronine by cultured fibroblasts.
Authors: Cheng S Y , Maxfield F R , Robbins J , Willingham M C , Pastan I H
Published: May 2006

Using video intensification fluorescence microscopy and tetramethylrhodamine (Rho)-labeled 3,3',5-triiodo-L-thyronine (T3), we studied the uptake of T3 by cultured mouse fibroblasts. After incubation of cells with Rho-T3 for 30 min at 37 degrees C the fluorescent hormone was concentrated in many small bright accumulations. With a 1000-fold excess of unlabeled T3, only weak background fluorescence was seen. Furthermore, when cells were incubated with Rho or Rho-thyronine only background fluorescence was detected. These results indicate that the cellular uptake of Rho-T3 occurred through a T3-specific receptor-mediated process. Most of these accumulations underwent saltatory motion in living cells, indicating that the T3 was contained within endocytic vesicles. When cultured cells were incubated with Rho-T3 for 60 min at 4 degrees C, only diffuse fluorescence was observed, Rho-T3 became concentrated in vesicles upon warming of the cells to either 23 degrees C or 37 degrees C. Simultaneous incubation of cells with fluorescein-labeled alpha 2-macroglobulin and Rho-T3 showed that Rho-T3 was internalized in the same vesicles as alpha 2-macroglobulin. Furthermore, as previously reported for alpha 2-macroglobulin in the presence of methylamine, dansylcadaverine, or bacitracin, clustering and internalization were inhibited but the overall fluorescence intensity of the cells did not appear to be affected. Because it has been previously shown that receptor-mediated endocytosis of alpha 2-macroglobulin occurs through clustering of ligands in coated pits on the cell surface, these results indicate that Rho-T3 follows the same pathway. Thus it has now been demonstrated that a low-molecular weight hormone enters cells by this pathway.
Passive immunotherapy prevents expression of endogenous Moloney virus and amplification of proviral DNA in BALB/Mo mice.
Authors: Nobis P , Jaenisch R
Published: May 2006

BALB/Mo mice carrying the Moloney murine leukemia virus (M-MuLV) as an endogenous virus become viremic soon after birth and develop leukemia at a later age. M-MuLV-specific gene expression and an increase of virus-specific DNA copies in lymphatic target organs are characteristics of the preleukemic phase. Passive immunotherapy of new born BALB/Mo mice with anti-gp70 glycoprotein or anti-M-MuLV serum prevented viremia and delayed significantly the subsequent development of leukemia. Molecular hybridization experiments showed that both virus-specific genome transcription and virus-specific DNA amplification could be completely suppressed by antiserum treatment. Thus virus-specific RNA concentrations in target organs of immunized BALB/Mo mice of 6 months or older were as low as in normal BALB/c mice. This is an age at which untreated BALB/Mo mice have already developed malignant lymphoma. Our experiments demonstrate that treatment with antiserum interferes with the early events of virus expression and thus prevents the subsequent steps leading to leukemia.
Application of the Eyring-Stover survival theory to soil-related functions
Authors: Wullstein L. H. , Bjorklund R. , Eyring Henry
Published: May 2006

The fit of the Eyring-Stover statistical survival theory was found to be precise when applied to diverse soil-related functions.
Comparison of the iron proteins from the nitrogen fixation complexes of
Azotobacter vinelandii, Clostridium pasteurianum
, and
Klebsiella pneumoniae
Authors: Hausinger Robert P. , Howard James Bryant
Published: May 2006

The molecular weights, amino acid compositions, amino- and carboxyl-terminal sequences, and ion-exchange peptide maps of the cysteine-containing tryptic peptides were determined for the iron proteins from the nitrogen fixation complexes of
Azotobacter vinelandii
(Av2) and
Klebsiella pneumoniae
(Kp2). Our results are compared to the known amino acid sequence of the iron protein from
Clostridium pasteurianum
(Cp2) [Tanaka, M., Haniu, M., Yasunobu, K. & Mortenson, L. E. (1977)
J. Biol. Chem.
252, 7093-7100]. Previous studies have shown the iron proteins to have similar enzymatic functions and spectroscopic properties. Furthermore, the DNAs coding for the iron protein from many different species cross-hybridize [Ruvkun, G. B. & Ausubel, F. M. (1980)
Proc. Natl. Acad. Sci. USA
77, 191-195]. Our results indicate that the protein structures are similar yet have significant differences. The amino-terminal sequences of Av2 and Kp2 are extended compared to the amino-terminal methionine of Cp2 and may indicate a different initiation site in these proteins. The aminoterminal sequences for Av2 and Kp2 are more homologous with each other than either of these are with Cp2. The carboxyl-terminal sequences are extended in Av2(14 residues) and Kp2 (≈30 residues) compared to Cp2. The amino- and carboxyl-terminal sequences establish that either the structural gene sizes are different in the three organisms or extensive posttranslational modification must occur in some species. Because cysteinyl residues are involved at the active site of the iron protein, a sensitive peptide mapping technique was used to compare cysteinyl peptides of the iron protein from the three species. Av2 and Kp2 have a redistribution of cysteinyl residues when compared to Cp2. Three important differences in the cysteine distributions were found, namely, residue 4 is valine and residue 148 is alanine in Cp2, but cysteinyl residues occupy these positions in Av2, whereas residue 231 is cysteine in Cp2 but alanine in Av2. The peptide mapping technique provides a method for the investigation of selective chemical modification of cysteinyl residues.
Deletions covering the putative promoter region of early mRNAs of simian virus 40 do not abolish T-antigen expression.
Authors: Benoist C , Chambon P
Published: May 2006

A recombinant plasmid was constructed by insertion of the early genes of simian virus 40 (SV40) into pBR322. When it was introduced into eukaryotic cells, the SV40 early genes were expressed. We have made deletion mutants of this plasmid, from which the major cap sites of SV40 early mRNAs have been removed along with some of the sequences upstream. The deleted sequences appear to be dispensable for early gene expression, but this does not necessarily imply that they serve no function in the initiation of transcription on wild-type SV40.
An antiserum to the rat liver glucocorticoid receptor.
Authors: Eisen H J
Published: May 2006

A rabbit immunized with a highly purified preparation of rat liver [3H]triamcinolone-receptor complex developed antibodies to the receptor. Although precipitating reactions were not detected, complexes formed between IgG and the receptor could be detected by Staphylococcus aureus protein A-Sepharose and gel permeation chromatography. IgG was purified and covalently immobilized on Sepharose CL-4B; this affinity matrix adsorbed the ligand-free receptor and both activated and nonactivated forms of the [3H]triamcinolone-receptor complex. Rat liver cytosol proteins adsorbed by control and immune immunoglobulin-Sepharoses were eluted with 0.1 M acetic acid and analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. A protein with molecular weight 78,000 was the major species eluted from immune immunglobulin-Sepharose, and it was not present in eluates from control columns. Rat transcortin, glucocorticoid binder IB, and an estrogen-binding protein from rat liver were not adsorbed by immune IgG-Sepharose. Mouse and hamster liver glucocorticoid receptors showed only limited adsorption. Thus, the antiserum does not crossreact with other major glucocorticoid-binding proteins and demonstrates species specificity.
Synthesis in vitro of the full-length complement of defective-interfering particle RNA of vesicular stomatitis virus.
Authors: Chanda P K , Kang C Y , Banerjee A K
Published: May 2006

Under appropriate reaction conditions in vitro, four different defective-interfering particles of vesicular stomatitis virus have been shown to synthesize the full-length complement of their RNAs. The reaction involved preinitiation of the core particles with ATP and CTP, followed by RNA chain elongation in the presence of the beta, gamma-imido analogue of ATP, AdoPP[NH]P, and the three normal ribonucleoside triphosphates. By hybridization of the in vitro synthesized plus strand with the standard genome RNA followed by RNase treatment of the heteroduplexes, we have shown that the RNA of a defective-interfering particle derived from the 3' end of the genome RNA has evolved by an internal deletion of the standard genome.
Mevinolin: a highly potent competitive inhibitor of hydroxymethylglutaryl-coenzyme A reductase and a cholesterol-lowering agent.
Authors: Alberts A W , Chen J , Kuron G , Hunt V , Huff J , Hoffman C , Rothrock J , Lopez M , Joshua H , Harris E , Patchett A , Monaghan R , Currie S , Stapley E , Albers-Schonberg G , Hensens O , Hirshfield J , Hoogsteen K , Liesch J , Springer J
Published: May 2006

Mevinolin, a fungal metabolite, was isolated from cultures of Aspergillus terreus. The structure and absolute configuration of mevinolini and its open acid form, mevinolinic acid, were determined by a combination of physical techniques. Mevinolin was shown to be 1,2,6,7,8,8a-hexahydro-beta, delta-dihydroxy-2,6-dimethyl-8-(2-methyl-1-oxobutoxy)-1-naphthalene-hepatanoic acid delta-lactone. Mevinolin in the hydroxy-acid form, mevinolinic acid, is a potent competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase [mevalonate: NADP+ oxidoreductase (CoA-acylating), EC 1.1.1.34]; its Ki of 0.6 nM can be compared to 1.4 nM for the hydroxy acid form of the previously described related inhibitor, ML-236B (compactin, 6-demethylmevinolin). In the rat, orally administered sodium mevinolinate was an active inhibitor of cholesterol synthesis in an acute assay (50% inhibitory dose = 46 microgram/kg). Furthermore, it was shown that mevinolin was an orally active cholesterol-lowering agent in the dog. Treatment of dogs for 3 weeks with mevinolin at 8 mg/kg per day resulted in a 29.3 +/- 2.5% lowering of plasma cholesterol.
Molecular cloning of human interferon cDNA.
Authors: Taniguchi T , Fujii-Kuriyama Y , Muramatsu M
Published: May 2006

A hybrid plasmid, TpIF319, has been shown to contain the sequence for human fibroblast interferon mRNA [Taniguchi, T., Sakai, M., Fujii-Kuriyama, Y., Muramatsu, M., Kobayashi, S. & Sudo, T. (1979) Proc. Jpn. Acad. 55, Ser. B, 464-469]. This conclusion was confirmed by a hybridization-translation assay, using rabbit globin mRNA and its cDNA-containing plasmid as a control. Plasmid TpIF319 was used as probe and another recombinant plasmid, TpIF319-13, whose cDNA insert consists of about 800 base pairs, was isolated. Nucleotide sequence analysis of the cDNA revealed that the DNA in fact codes for human fibroblast interferon.
Expression of the human argininosuccinate synthetase gene in hamster transferents.
Authors: Hudson L D , Erbe R W , Jacoby L B
Published: May 2006

The structural gene for human argininosuccinate synthetase [L-citrulline:L-aspartate ligase (AMP-forming), EC 6.3.4.5] was transferred to argininosuccinate synthetase-deficient Chinese hamster cells via metaphase chromosomes isolated from human lymphoblast line MGL8D1, a constitutive overproducer of argininosuccinate synthetase, and from its repressible parent, MGL8B2. Argininosuccinate synthetase expression was selected for in citrulline-containing medium, and the human origin of the argininosuccinate synthetase expressed by seven transferents was identified by isoelectric focusing. Stable transferents expressing MGL8D1 argininosuccinate synthetase fell into two classes: (i) those whose argininosuccinate synthetase activity was reduced to 10-50% by arginine, similar to the repression of argininosuccinate synthetase synthesis observed in normal human lymphoblasts, and (ii) those that constitutively expressed argininosuccinate synthetase when grown in the presence of arginine or citrulline. Two transferents from the MGL8B2 donor constitutively expressed human arginonosuccinate synthetase. Three hamster revertants were isolated that constitutively expressed hamster argininosuccinate synthetase. Transferents and revertants exhibited growth-dependent changes in argininosuccinate synthetase activity, in contrast to the constant synthetase activity levels in donor lymphoblasts during growth. The isolation of stable transferents that constitutively or repressibly express argininosuccinate synthetase makes possible the analysis of regulatory signals influencing expression of the argininosuccinate synthetase gene.
Mapping of anion binding sites on cytochrome c by differential chemical modification of lysine residues.
Authors: Osheroff N , Brautigan D L , Margoliash E
Published: May 2006

The carbonate binding site on horse cytochrome c was mapped by comparing the yields of carboxydinitrophenyl-cytochromes c, each with a single carboxydinitrophenyl-substituted lysine residue per molecule, when the modification reaction was carried out in the presence and absence of carbonate. The site is located on the "left surface" of the protein and consists of lysine residues 72 and/or 73 as well as 86 and/or 87 (Carbonate Site). Although one of the binding sites for phosphate on cytochrome c (Phosphat Site I) is located near the carbonate site, the sites are distinctly different since carbonate does not displace bound phosphate, as monitored by 31P NMR. Furthermore, citrate interacts with Phosphate Site I with high affinity, whereas chloride, acetate, borate, and cacodylate have a much lower affinity for this site, if they bind to it at all. The affinity of phosphate for Phosphate Site I (KD = 2 X 10(-4) M) is at least 1 order of magnitude higher than it is for other sites of interaction.
Molecular dissection of Rauscher virus gp70 by using monoclonal antibodies: localization of acquired sequences of related envelope gene recombinants.
Authors: Niman H L , Elder J H
Published: May 2006

Using hybridoma-specific immune precipitations of fragments derived from Rauscher virus gp70, coupled with peptide patterns (fingerprinting) and partial amino acid sequence analyses, we have generated a linear map of Rauscher gp70. We used a panel of 56 hybridomas derived from the fusion of the drug-selected SP-2 myeloma line with spleen cells from either a 129 GIX+ or a GIX- mouse immunized with purified Rauscher virus gp70. The results showed that by "natural" breakdown, gp70 splits into predominant fragments, with Mr 45,000 (P45), 34,000 (P34), and 32,000 (P32). Peptide fingerprinting of these as well as overlapping fragments coupled with partial amino acid sequence analyses allowed us to align the fragments into the linear arrangement NH2-P45-P32-COOH, with P34 being an NH2-terminal degradation product of P45. Of the 56 hybridomas, 20 immunoprecipitated both P45 and P34; 18 immunoprecipitated only P45; and 18 immunoprecipitated only P32. The hybridomas thus define three domains of the molecule as NH2-P45/P34, P45 only, and P32-COOH. Allowing these hybridomas to react with two Rauscher-derived envelope gene recombinant viruses yielded the following results: (i) all 20 P45/34 reactors bound to the two Rauscher recombinants; (ii) of 18 P45-only hybridomas, 10 reacted; and (iii) only 1 of 18 P32 reactors bound to the Rauscher recombinants. This last hybridoma reacted with various murine retroviruses, indicating that it was directed at conserved determinants of gp70. Peptide fingerprinting of R-gp70, the recombinant gp70s, and their respective breakdown products confirmed the homologies and nonhomologies defined by the hybridomas. Furthermore, peptide patterns showed that these acquired sequences on the COOH-terminal portion of the recombinant gp70s are related to xenotropic virus gp70s.
Induction of ornithine decarboxylase by renin-free nerve growth factor.
Authors: Guroff G , Montgomery P , Tolson N , Lewis M E , End D
Published: May 2006

Renin-free nerve growth factor causes the induction of ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) in superior cervical ganglia from neonatal rats but not in the brain of mature rats. Less pure preparations of nerve growth factor induce the enzyme in both brain and ganglia. The induction of ornithine decarboxylase in the central nervous system appears to be due to renin, not to nerve growth factor itself.
Differential processing of subunits of human chorionic gonadotropin by granulosa cells in vivo.
Authors: Campbell K L , Landefeld T D , Midgley A R
Published: May 2006

The question of whether the two subunits of the glycoprotein hormone human chorionic gonadotropin (hCG) are handled separately or as a unit by target cells was addressed by using a dual-labeling procedure. The individual alpha and beta subunits of hCG were labeled with 131I or 125I, recombined, chromatographed, and injected intravenously into hormonally primed immature rats. The ovaries of these rats contained large numbers of antral follicles, the granulosa cells of which possess high concentrations of receptor for hCG. Comparisons of the distribution of the different radioisotopic labels in various tissues over time indicated the activity associated with the beta subunit was preferentially retained by the ovarian granulosa cells in a hormone-specific manner, while the activity associated with the alpha subunit was preferentially lost. This contrasted with other tissues, including other ovarian cells with receptor for hCG, in which both radiolabels were either handled nondifferentially or handled differentially in a hormonally nonspecific manner.
Selection of viability at loci controlling protein polymorphisms in Drosophila melanogaster is very weak at most.
Authors: Mukai T , Tachida H , Ichinose M
Published: May 2006

In an isolated Drosophila population the frequency of chromsomes carrying the second chromosome inversion In(2L)t is about 60%. Three isozyme loci are nearly monomorphic in the inversion-carrying chromosomes but are highly polymorphic in other chromosomes. From known recombination frequencies and the slight polymorphism, it is estimated that the inversion-carrying chromosomes are descended from one or a few identical chromosomes introduced about 1000 generations previously. This is long enougn for lethal and mildly deleterious mutants to reach equilibrium frequencies but not long enough for very weakly selected mutants. Because the difference in viability between homozygous and heterozygous chromosomes is the same, it is inferred that there is at most very weak selection of isozyme loci. This method is sensitive enough to detect selective differences of 0.0005 per locus or less.
Fecalase: a model for activation of dietary glycosides to mutagens by intestinal flora.
Authors: Tamura G , Gold C , Ferro-Luzzi A , Ames B N
Published: May 2006

Many substances in the plant kingdom and in man's diet occur as glycosides. Recent studies have indicated that many glycosides that are not mutagenic in tests such as the Salmonella test become mutagenic upon hydrolysis of the glycosidic linkages. The Salmonella test utilizes a liver homogenate to approximate mammalian metabolism but does not provide a source of the enzymes present in intestinal bacterial flora that hydrolyze the wide variety of glycosides present in nature. We describe a stable cell-free extract of human feces, fecalase, which is shown to contain various glycosidases that allow the in vitro activation of many natural glycosides to mutagens in the Salmonella/liver homogenate test. Many beverages, such as red wine (but apparently not white wine) and tea, contain glycosides of the mutagne quercetin. Red wine, red grape juice, and tea were mutagenic in the test when fecalase was added, and red wine contained considerable direct mutagenic activity in the absence of fecalase. The implications of quercetin mutagenicity and carcinogenicity are discussed.
Coordination environment and fluoride binding of type 2 copper in the blue copper protein ascorbate oxidase
Authors: Dawson John H. , Dooley David M. , Gray Harry B.
Published: May 2006

The coordination environment of the type 2 (nonblue) copper in native ascorbate oxidase (L-ascorbate:oxygen oxidoreductase, EC 1.10.3.3) and of a derivative of the enzyme having the type 1 (blue) copper reversibly bleached has been examined by electron paramagnetic resonance (EPR) spectroscopy. In the g[unk] region of the spectrum of bleached ascorbate oxidase, a seven-line superhyperfine pattern is seen that is attributed to the presence of three nitrogen-donor ligands to a type 2 copper having tetragonal geometry. The superhyperfine splitting patterns in the g∥ region of the EPR spectra of native and bleached ascorbate oxidase show that as many as two fluorides may bind to type 2 copper. Because fluoride inhibits the enzyme competitively with respect to ascorbic acid, it is proposed that the type 2 copper is part of the ascorbate binding site.
Photochemically induced dynamic nuclear polarization investigation of complex formation of the NH2-terminal DNA-binding domain of lac repressor with poly[d(AT)].
Authors: Buck F , Rüterjans H , Kaptein R , Beyreuther K
Published: May 2006

The interaction of the NH2-terminal DNA-binding domain of lac repressor with synthetic oligo[d(AT)] was studied by a photo-CIDNP technique (CIDNP is chemically induced dynamic nuclear polarization). Three of the four tyrosines of the NH2-terminal region were found to be accessible to the photosensitive dye. The corresponding ring proton resonances were enhanced in the photo-CIDNP 1H NMR spectrum, and the only histidine (histidine 29) was located at the surface of the domain, which is supposed to be linked to the core protein of lac repressor by a flexible hinge region. After complex formation of the NH2-terminal region with oligo[d(AT)], two of the three tyrosine residues were no longer accessible to solvent or to photosensitive dye, which is strong evidence that the two tyrosines are part of the contact region.
Reversible translocation of cytoplasmic actin into the nucleus caused by dimethyl sulfoxide.
Authors: Sanger J W , Sanger J M , Kreis T E , Jockusch B M
Published: May 2006

The addition of 10% dimethyl sulfoxide (Me2SO) to PtK2 and WI-38 cells caused stress fibers to disappear from the cytoplasm and numerous elongated inclusions to appear in the nucleus. When Me2SO was removed, the stress fibers reformed and the nuclear inclusions disappeared. These nuclear inclusions reacted with fluorescent heavy meromyosin, phalloidin, and actin antibody. In the electron microscope, needle-like structures were seen to be composed of wavy filaments that bound heavy meromyosin. Antibodies against other components of stress fibers--tropomyosin, alpha-actinin, and myosin--did not react with the inclusions. When fluorescently labeled actin was microinjected into living PtK2 and WI-38 cells, the fluorescent actin was incorporated into stress fibers. Subsequent exposure of the same cells to Me2SO led to breakdown of the fluorescent stress fibers and the appearance of fluorescent inclusions in the nucleus. Removal of Me2SO caused reversion to the normal interphase structure. These results indicate that under the influence of Me2SO, dissolution of stress fiber releases actin in a form which allows it to diffuse into the nucleus where it then becomes organized into filamentous bundles.
Putative actin genes in the macronucleus of Oxytricha fallax.
Authors: Kaine B P , Spear B B
Published: May 2006

Previous work has shown that the macronuclear DNA of the hypotrichous ciliate Oxytricha fallax is arranged as short achromosomal pieces, 22 to 0.5 kilobase pairs (kb) in length. Micronuclear DNA has a typical chromosomal organization. Macronuclear DNA is derived from micronuclear DNA through a process of polytene chromosome fragmentation with a resultant decrease in DNA sequence complexity. Three putative actin genes have been identified in macronuclear DNA by using a cloned yeast actin gene as a hybridization probe. A restriction fragment of the yeast gene containing both actin coding and noncoding DNA hybridizes strongly to two macronuclear DNA pieces, 1.6 and 1.4 kb in length, and weakly to a 1.2-kb piece. The entire 1.6-kb piece has been cloned in plasmid pBR322 and the resulting recombinant plasmid has been designated pOfACT(1.6). The 1.6-kb pOfACT(1.6) insert hybridizes only to those restriction fragments of the yeast actin gene containing actin coding sequences. When hybridized to macronuclear DNA under conditions that allow the yeast probe to hybridize to all three macronuclear pieces, the pOfACT(1.6) insert hybridizes only to the 1.6-kb piece. Under less stringent conditions the insert also hybridizes to the 1.4-kb piece, but it shows no hybridization to the 1.2-kb DNA. The three macronuclear pieces homologous to the yeast actin gene thus differ in sequence and are interpreted as a related family of actin genes. Each of these pieces could accommodate an actin coding sequence, which in yeast, Dictyostelium discoideum, and Drosophila melanogaster is 1.1 kb, and an additional 0.1-0.5 kb of noncoding DNA.
Interaction between I region loci influences the expression of a cell surface Ia antigen.
Authors: Murphy D B , Jones P P , Loken M R , McDevitt H O
Published: May 2006

Loci clustered in the I region of the murine H-2 gene complex control the capacity to generate an immune response against foreign antigens (Ir loci) and control differentiation antigens which appear to serve as structures used by cells to interact with and regulate one another (Ia loci). Both genetic and functional studies suggest that Ia antigens may be products of Ir loci. Recent studies have shown that interaction between closely linked Ir loci is required for generating immune responses to certain foreign antigens, and that interaction between H-2-linked loci determines the appearance of an Ia glycoprotein (the Ae chain) on lymphocyte cell surfaces. In this report, we show that one Ia locus regulates the quantitative expression of the product (the E alpha chain) of a second Ia locus. This regulatory locus is dominantly expressed and exerts its effects in either the cis or trans chromosomal position. Thus, the quantitative as well as the qualitative expression of some Ia products is dependent on interaction between tightly linked loci. Our results suggest a possible molecular basis for this regulation: the synthesis and intracellular association of Ae and E alpha chains may be an absolute requirement for the expression of normal levels of either polypeptide chain on the lymphocyte cell surface. The implications these findings have for I region control of immune responses and study of human HLA-D antigens are discussed.
Adenosine receptors in brain membranes: binding of N6-cyclohexyl[3H]adenosine and 1,3-diethyl-8-[3H]phenylxanthine.
Authors: Bruns R F , Daly J W , Snyder S H
Published: May 2006

N6-Cyclohexyl[3H]adenosine ([3H]CHA) and 1,3-diethyl-8-[3H]phenylxanthine ([3H]DPX) to bind to adenosine receptors in brain membranes. The agonist [3H]CHA has high affinity in both bovine and guinea pig brain (Kd, 0.7 nM and 6 nM, respectively). [3H]CHA binding kinetics are slow (dissociation t1/2;60 min); binding is much higher at 25 degrees C than at 0 degrees C and is inhibited by guanine nucleotides. Potencies of nucleosides and xanthines in competing for [3H]CHA sites indicate that specific binding is entirely to A1 adenosine receptors. In bovine brain, the antagonist [3H]DPX exhibits high-affinity binding (Kd, 5 nM) to the same A1 receptors that bind [3H]CHA. Binding kinetics are rapid (dissociation t1/2, 1 min), and binding is moderately higher at 0 degrees C than at 25 degrees C. In guinea pig brain, [3H]DPX binding has only moderate affintiy (Kd 50 nM), and about 60% of specific binding is to sites that resemble A2 adenosine receptors.
Magnetic order and energetics of dipolar coupling in magnetic superconductors
Authors: Redi Martha , Anderson P. W.
Published: May 2006

The exact (not just nearest-neighbor) dipolar coupling energy densities for the observed structures of the rare earth Chevrel compounds are calculated by the method of Luttinger and Tisza. The dipolar coupling energy density for the most probable spin configuration is comparable to the observed magnetic transition temperature,
T
M
, but the most probable ground state is not found experimentally. The discrepancy between the observed magnetic ground state and that predicted from dipole coupling may arise from conduction electron effects or possibly from some strong crystal field effect and should be included in any electronic theory of the superconductive state below
T
M
.
Polarity of some motility-related microtubules.
Authors: Euteneuer U , McIntosh J R
Published: May 2006

We have investigated the structural polarity of microtubules from several systems in which these fibers are thought to contribute to cell motility. By using a method for displaying microtubule polarity in the electron microscope, we find that both the A and B subfibers of Tetrahymena ciliary outer doublets and the inner pair of single microtubules are all oriented with their plus ends (i.e., their fast-growing ends) distal to the basal body. All of the microtubules in the axopodia of the heliozoan Actinosphaerium and all of the microtubules in the processes of melanophores from the angelfish Pterophyllum are likewise oriented with their plus ends distal to the cell centers. These results suggest that cellular systems for motility, and even those capable of bidirectional motility, can be constructed from microtubules of a single polarity.
Three-state, steady-state Ising systems: Monte Carlo and Bragg-Williams treatments
Authors: Hill Terrell L. , Chen Yi-Der
Published: May 2006

In two earlier papers, the steady-state critical and phase-transition properties of a lattice of three-state enzyme molecules were studied by using the “closed” Bragg-Williams (BW), or mean field, approximation. The “open” BW and Monte Carlo methods are applied to the same problem in this paper by using finite lattices. The open BW treatment provides a way of locating the cut across a van der Waals type of loop encountered in a phase transition in the closed BW system. Thermodynamic-like methods cannot be used for this purpose as they can with two-state, steady-state systems.
Leaf folding in a sensitive plant: A defensive thorn-exposure mechanism?
Authors: Eisner Thomas
Published: May 2006

Quantitative photographic evidence is presented indicating that in the sensitive plant
Schrankia microphylla
the leaf-folding response that accompanies the sensitive reaction results in a pronounced increase in thorn exposure. It is argued that in sensitive plants that are thorny, including other species of
Schrankia
, as well as
Mimosa pudica
, the plant in which the sensitive reaction is traditionally demonstrated, leaf folding may be a defensive adaptation.
lambda altSF: a phage variant that acquired the ability to substitute specific sets of genes at high frequency.
Authors: Friedman D , Tomich P , Parsons C , Olson E , Deans R , Flamm E
Published: May 2006

We report the isolation of lambda altSF, a variant of Escherichia coli phage lambda that substitutes sets of genes at high frequency. Two forms of the variant phage have been studied: lambda altSF lambda, which exhibits the immunity (repressor recognition) of phage lambda, and lambda altSF22, which exhibits the immunity of Salmonella phage P22. Lysates made from single plaques of lambda altSF lambda contain 10-30% phage of the P22 form. Similarly, lysates from single plaques of lambda altSF22 contain as much as 1% phage of the lambda form. Heteroduplex analyses reveal the following features of the lambda altSF chromosomes: (i) each form has the immunity genes appropriate to its immune phenotype, (ii) the substituted segments include genes involved in regulation and replication, and (iii) the alt phages have unusual additions and substitutions of DNA not normally found associated with either immunity region. In the case of lambda altSF lambda, there is a small insertion in the region of the cI gene. Because revertants that lose this inserted DNA concomitantly lose the ability to substitute, we conclude that the insertion plays a role in the substitution process. In the case of change from lambda altSF lambda to lambda altSF22, the substituting P22 genes are derived from the E. coli host. We have identified a set of Salmonella phage P22 genes in a standard nonlysogenic strain of E. coli K-12 that is apparently carried in a silent form. The reason for this lack of expression is not obvious, because this P22 material includes structural genes and associated promoters and is potentially active. When this set of genes substitutes for the analogous set of genetic material on the genome of lambda altSF lambda, the P22 genes are expressed in a normal manner.
Gene conversion at the var1 locus on yeast mitochondrial DNA.
Authors: Strausberg R L , Butow R A
Published: May 2006

Alleles of the var1 locus on yeast mtDNA determine the apparent size of the mitochondrial translation product, var1 polypeptide. We have analyzed most of the different var1 alleles in our collection, which number at least 15, and have developed procedures and a genetic rationale for determining their origin and predicting their behavior in crosses. The var1 alleles are characterized by two genetically defined segments, designated a and b, which can move from one var1 allele to another by asymmetric gene conversion. We show that the a segment behaves as an entity in recombination; it is either present in or absent from different var1 alleles. The b segment usually, but not always, recombines as an entity; in some cases, only portions of the b segment recombine by gene conversion. Thus, the total number of electrophoretically resolvable var1 species we observe is explained by the assortment of a, b, and partial b segments. Each segment recombines at a characteristic frequency; however, one example is presented which shows that the recipient can modulate the frequency of gene conversion. Finally, we show that, like the 21S rDNA region (omega), there is polarity of gene conversion within var1.
Tumor remission in Yoshida sarcoma-bearing rts by selective targeting of magnetic albumin microspheres containing doxorubicin.
Authors: Widder K J , Morris R M , Poore G , Howard D P , Senyei A E
Published: May 2006

Magnetically responsive albumin microspheres containing doxorubicin and magnetite (Fe3O4) were selectively targeted to Yoshida sarcoma tumors in rats by utilizing an extracorporeal magnet. Tumor cells were inoculated subcutaneously in the tail of rats, and the tumors were allowed to grow to an average size of 9 X 45 mm prior to initiating treatment. Drug-bearing microspheres (0.5 mg of doxorubicin per kg of body weight) were infused proximal to the tumor through the ventral caudal artery while the tumor was exposed to an external magnetic field of 5500 Oe for 30 min. Control animals received free doxorubicin administered either intravenously (5 mg/kg) or infused intraarterially (5 and 0.5 mg/kg), drug-bearing microspheres infused intraarterially (0.5mg/kg), without the external magnet, or placebo microspheres with magnetic localization. Of the 12 animals treated with a single dose in the experimental group, 9 exhibited total remission of the tumor, representing a disappearance of tumors as large as 60 mm in length. Marked tumor regression was observed in the remaining three rats, and no deaths or metastases occurred in the experimental group. In contrast, significant increases in tumor size with widespread metastases occurred in all control groups and most rats died. These experiments indicate that targeting of oncolytic agents to solid neoplasms by magnetic microspheres may be a means of increasing the efficacy and decreasing the toxicity of antitumor agents.
Steric control of CO binding in a totally synthetic heme protein model
Authors: Busch Daryle H. , Zimmer L. Lawrence , Grzybowski Joseph J. , Olszanski Dennis J. , Jackels Susan C. , Callahan Robert C. , Christoph Gary G.
Published: May 2006

A family of totally synthetic models for the carbon monoxide adducts of heme proteins has been synthesized and applied to the elucidation of the role of steric effects in the relative detoxification of carbon monoxide. The complexes are designed such that a sheltered void of controllable dimensions encompasses the CO binding site. Systematic variations in the available space for the iron-bound CO produce a wide range of equilibrium binding constants (
K
CO
). An x-ray structure determination of a CO adduct complex having a crowded CO site reveals that the Fe—C≡O linkage is bent, and further, the distortion involves both displacement of the Fe—C vector from the normal to the N
4
plane and bending of the Fe—C—O angle.