bluuebunny/crossref_metadata_2025 huggingface dataset:
Activation of a chicken embryonic globin gene in adult erythroid cells by 5-azacytidine and sodium butyrate.
Authors: Ginder G D , Whitters M J , Pohlman J K
Published: May 2006

Adult White Leghorn chickens were rendered anemic by injection with 1-acetyl-2-phenylhydrazine and then treated with parenteral 5-azacytidine, and levels of embryonic globin RNA in circulating reticulocytes were measured. A very small but detectable amount of correctly initiated embryonic p-type globin RNA was detected in reticulocytes from birds treated with 5-azacytidine, while none was detected in reticulocytes from those receiving only phenylhydrazine or phenylhydrazine plus 1-beta-D-arabinofuranosylcytosine (cytosine arabinonucleoside). An attempt to increase embryonic globin RNA induction by treatment with parenteral sodium butyrate after 7 days of 5-azacytidine administration resulted in a 5- to 10-fold increase in the level of embryonic globin RNA. However, sodium butyrate did not induce embryonic gene expression when given alone or after treatment with cytosine arabinonucleoside. Sodium butyrate treatment also caused a DNase I-hypersensitive site to be exposed at the 5' end of the rho-globin gene only after 5-azacytidine induced demethylation of several CpG sites in and around the gene. The implications of this model of gene activation in vivo are discussed in the context of multistep gene regulation.
Regulation of bacterial DNA supercoiling: plasmid linking numbers vary with growth temperature.
Authors: Goldstein E , Drlica K
Published: May 2006

The level of DNA supercoiling can be altered either by breaking-rejoining reactions that change the DNA linking number or by environmental changes that alter the helical pitch of DNA. In vitro, temperature changes alter helical pitch and, thus, supercoiling. We find that plasmids isolated from bacteria grown at different temperatures exhibit differences in DNA linking numbers. The differences in plasmid linking numbers offset the effect temperature is expected to have on supercoiling. These results are consistent with the hypothesis that fine control of DNA topology in bacterial cells is brought about by changes in linking number to maintain a constant value for supercoiling.
Molecular cloning and characterization of a cDNA for the beta subunit of human alcohol dehydrogenase.
Authors: Duester G , Hatfield G W , Bühler R , Hempel J , Jörnvall H , Smith M
Published: May 2006

Human alcohol dehydrogenase (ADH) is encoded by at least five genes that fall into three classes. The class I ADH genes encode the three closely related alpha, beta, and gamma polypeptides. Molecular genetic analysis of class I ADH genes has been initiated by isolating a cDNA clone from a human adult liver cDNA library. A synthetic oligonucleotide mixture encoding a portion of the beta subunit of ADH was used as an in situ hybridization probe for the cDNA library. One positively hybridizing clone, pADH12, which contained an 1100-base-pair cDNA insert, was subjected to DNA sequence analysis. The sequence indicated that the cDNA encoded information for the carboxyl-terminal 91 amino acids of a class I ADH and a 3' untranslated region of 593 nucleotides. Comparisons with the carboxyl terminus of the human ADH beta subunit indicated that the cDNA encoded the beta polypeptide. This probe may facilitate genetic studies of various human alcohol-related syndromes, as well as enable basic molecular studies on human ADH gene expression.
Teratogens induce a subset of small heat shock proteins in Drosophila primary embryonic cell cultures.
Authors: Buzin C H , Bournias-Vardiabasis N
Published: May 2006

Drosophila embryonic cells placed into culture just after gastrulation differentiate in vitro over the next 24 hr. A number of drugs that are teratogenic in mammalian systems have been found to inhibit muscle or neuron differentiation (or both) in these developing cultures. We have examined, by two-dimensional gel electrophoresis, the effects of these drugs on protein synthesis in embryonic cells. For nine teratogens tested, cells treated for 20 hr with the drug show a dramatic induction of three proteins of about 20 kilodaltons, in addition to the normal proteins synthesized by untreated cells. Three teratogens as well as all eight nonteratogens tested did not show this induction. The induced proteins appear to be identical to three of the heat shock proteins (hsp 23, 22a, and 22b), as shown by electrophoretic mobilities and peptide mapping by partial proteolysis. A 37 degrees C heat shock of the embryonic cells produces the full complement of heat shock proteins, whereas drug-treated cells induce only the subset hsp 23, 22a, and 22b but not hsp 26 or 27. beta-Ecdysterone, the Drosophila molting hormone, also inhibits embryonic differentiation and induces hsp 23, 22a, and 22b, a partial subset of the heat shock proteins (hsp 22, 23, 26, and 27) induced by the hormone in imaginal discs and some Drosophila continuous cell lines. Dose-response studies of several drugs show a correlation between the degree of inhibition of differentiation and the level of induction of hsp 23, 22a, and 22b. The induction of heat shock proteins by drugs may reflect specific types of stress that can also give rise to teratogenesis.
A structural model of human erythrocyte band 2.1: alignment of chemical and functional domains.
Authors: Wallin R , Culp E N , Coleman D B , Goodman S R
Published: May 2006

Protein 2.1 is a 210-kilodalton protein that connects erythrocyte spectrin to the NH2-terminal cytoplasmic domain of band 3 and thereby functions as the essential linkage between the membrane skeleton and the bilayer. We cleaved this protein into specific chemical domains by limited digestion with trypsin and alpha-chymotrypsin at 0 degrees C. Intermediate-sized peptides were separated by two-dimensional isoelectric focusing/NaDodSO4/polyacrylamide gel electrophoresis and characterized by high resolution peptide mapping. We have established a provisional structural model of protein 2.1 by comparing the peptide maps of these chemical domains to maps obtained from larger overlapping chymotryptic fragments as well as fragments obtained from 2-nitro-5-thiocyanobenzoic acid cleavage. In addition to providing a provisional structural map of protein 2.1, we have identified two functional domains of protein 2.1, an 83-kilodalton tryptic peptide (T-83) which binds band 3 and a 65-kilodalton tryptic peptide (T-65) which binds spectrin. We have therefore localized the functional domains along our linear map of protein 2.1.
Trophic links of community food webs.
Authors: Cohen J E , Briand F
Published: May 2006

This report describes and explains regularities in the numbers and kinds of trophic links in community food webs. To a first approximation, the mean number of trophic links in a community food web is proportional to the total number of trophic species. The mean number of trophic links between any two categories of trophic species (basal, intermediate, and top) is proportional to the geometric mean number of species in the categories joined. These linear relationships, and scale-invariance in the proportions of basal, intermediate, and top species, make it possible to predict with remarkable precision the proportions of each kind of trophic link among all community food webs. The differences between food webs in constant and in fluctuating environments reflect apparently greater constraints on the trophic organization of food webs in fluctuating environments.
Construction of mutants of Moloney murine leukemia virus by suppressor-linker insertional mutagenesis: positions of viable insertion mutations.
Authors: Lobel L I , Goff S P
Published: May 2006

A highly efficient method for the generation of insertion mutations is described. The procedure involves the use of a 220-base-pair (bp) EcoRI fragment bearing the SuIII+ suppressor tRNA gene as an insertional mutagen. The plasmid DNA to be mutagenized is linearized by a variety of means, and the suppressor fragment is ligated into the site of cleavage. Successful insertion mutants can be readily detected in Escherichia coli carrying lac- amber mutations on MacConkey lactose plates; virtually 100% of the red colonies contain insertions of the fragment. Subsequent removal of the SuIII+ gene and recyclization leaves a 12-bp insertion if the original cleavage was blunt-ended and a 9-bp insertion if the original cleavage generated 3-bp cohesive termini. This technique, as well as conventional linker mutagenesis with decamer and dodecamer linkers, was used to generate a large library of insertion mutations in cloned DNA copies of the genome of Moloney murine leukemia virus. A number of viable mutants were isolated bearing 9-, 10-, and 12-bp insertions in various domains of the genome. The map positions of the viable mutations suggest that the viral long terminal repeats and portions of the gag and env genes are quite insensitive to alteration. Although most of the mutations were stable for many passages, some of the mutants lost the inserted DNA; we presume that the insertion was somewhat deleterious in these mutants and that continued passage of the virus selected for overgrowth by a revertant.
Cholesterol epoxide is a direct-acting mutagen.
Authors: Sevanian A , Peterson A R
Published: May 2006

A 24-hr treatment of V79 Chinese hamster lung fibroblasts with 12.4 microM cholesterol 5 alpha, 6 alpha-epoxide induced 8-azaguanine-resistant mutants at frequencies 4.6- to 11.8-fold higher than the spontaneous mutation rate. We show that cholesterol epoxide, which is produced by in vivo cholesterol oxidation, is a weak direct-acting mutagen. Cholesterol epoxide was found to be accumulated by cells and transformed to cholestane-3 beta, 5 alpha, 6 beta-triol, which was more toxic and a more potent inhibitor of DNA synthesis than the epoxide but, at concentrations less than 17.8 microM, was not significantly mutagenic. Consideration of the rates of cholesterol epoxide conversion to cholestane triol shows that this conversion can result in abolition of the mutagenicity of the epoxide. Conditions under which conversion of the epoxide to the triol is low, as in the case of low epoxide hydrolase activity, favor mutagenicity whereas rapid conversion to triol favors cytotoxicity.
On the amino acid sequence of cytochrome P-450 isozyme 4 from rabbit liver microsomes.
Authors: Fujita V S , Black S D , Tarr G E , Koop D R , Coon M J
Published: May 2006

Isozyme 4 of rabbit liver microsomal cytochrome P-450 was shown earlier in this laboratory to contain multiple NH2-terminal residues, whereas isozymes 2, 3a, 3b, and 3c have single, unique NH2-terminal sequences. Similar results were obtained with isozyme 4 obtained from animals that were untreated, treated with phenobarbital (which does not induce this isozyme), or induced with beta-naphthoflavone or isosafrole. With the use of selective chemical blocking at seryl or at nonprolyl residues, the complexity of the NH2-terminal sequence has now been shown to be due to the presence of three forms of the cytochrome differing only in the absence of the first or the first two residues: NH2-Ala-Met-Ser-Pro-Ala-Ala-Pro-, NH2-Met-Ser-Pro-Ala-Ala-Pro-, and NH2-Ser-Pro-Ala-Ala-Pro-. These forms may result from variable biological processing. Peptides containing the seven cysteine residues were sequenced and compared with similar peptides reported for other P-450 cytochromes; homology was extensive with respect to two of the cysteine regions in isozyme 4, and a third cysteine region showed partial identity. The sequence of peptides representing about two-thirds of the amino acids in isosafrole-induced cytochrome P-450 isozyme 4 was determined. Comparison with phenobarbital-induced rabbit cytochrome P-450 isozyme 2 indicated about 25% homology. In contrast, comparison of isozyme 4 with rat cytochrome P-450d, which is also induced by isosafrole and for which the sequence has recently been deduced from cDNA [Kawajiri, K., Gotoh, O., Sogawa, K., Tagashira, Y., Muramatsu, M. & Fujii-Kuriyama, Y. (1984) Proc. Natl. Acad. Sci. USA 81, 1649-1653], showed about 70% homology.
Ribonuclease T: new exoribonuclease possibly involved in end-turnover of tRNA.
Authors: Deutscher M P , Marlor C W , Zaniewski R
Published: May 2006

Examination of double mutants lacking one of the exoribonucleases, RNase II, RNase D, RNase BN, or RNase R, and also devoid of tRNA nucleotidyltransferase has suggested that none of these RNases participates in the end-turnover of tRNA. This prompted a search for and identification of a new exoribonuclease, termed RNase T. RNase T could be detected in mutant Escherichia coli strains lacking as many as three of the known exoribonucleases, and it could be separated from each of the four previously described RNases. RNase T is optimally active at pH 8-9 and requires a divalent cation for activity. The enzyme is sensitive to ionic strengths greater than 50 mM and is rapidly inactivated by heating at 45 degrees C. Its preferred substrate is tRNA-C-C-[14C]A, with much less activity shown against tRNA-C-C. RNase T is an exoribonuclease that initiates attack at the 3' hydroxyl terminus of tRNA and releases AMP in a random mode of hydrolysis. The possible involvement of RNase T in end-turnover of tRNA and in RNA metabolism in general are discussed.
Cloning of cDNAs specifying vitamin A-responsive human keratins.
Authors: Eckert R L , Green H
Published: May 2006

In human cultured epidermal and conjunctival keratinocytes, vitamin A promotes the synthesis of keratins 13 and 19 of the catalog of Moll et al. [Moll, R., Franke, W.W., Schiller, D.L., Geiger, B. & Krepler, R. (1982) Cell 31, 11-24] but does not alter the synthesis of keratins 5 and 6. To study this effect of the vitamin, cDNAs specifying each of these keratins were cloned in pBR322. Characterization of the clones by hybrid selection of mRNA and by hybridization of size-fractionated mRNA indicated that each was specific for a single mRNA. Treatment of epidermal cells with arotinoid Ro 13-6298, a potent synthetic analog of retinoic acid, increased the abundance of mRNA for keratin 13 by 25-fold and for keratin 19 by greater than 40-fold but had no effect on the abundance of mRNA for keratins 5 and 6.
Catalase: a tetrameric enzyme with four tightly bound molecules of NADPH.
Authors: Kirkman H N , Gaetani G F
Published: May 2006

Catalases (H2O2:H2O2 oxidoreductase, EC 1.11.1.6) from many species are known to be tetramers of 60,000-dalton subunits, with four heme groups per tetramer. Previous authors have determined the amino acid sequence and three-dimensional structure of bovine liver catalase. Studies of the regulation of the pentose phosphate pathway led the present authors to a search for proteins that bind NADP+ and NADPH in human erythrocytes. An unexpected result of that search was the finding that a major reservoir of bound NADPH in human erythrocytes is catalase. Each tetrameric molecule of human or bovine catalase contains four molecules of tightly bound NADPH. The binding sites have the relative affinities NADPH greater than NADH greater than NADP+ greater than NAD+. NADPH does not seem to be essential for the enzymic conversion of H2O2 to O2 and water but does provide protection of catalase against inactivation by H2O2.
Individual products of the adenovirus 12S and 13S EIa mRNAs stimulate viral EIIa and EIII expression at the transcriptional level.
Authors: Leff T , Elkaim R , Goding C R , Jalinot P , Sassone-Corsi P , Perricaudet M , Kédinger C , Chambon P
Published: May 2006

Recombinant plasmids containing mutant or wild-type adenovirus serotype 2 EIa genes that produce the 12S mRNA alone, the 13S mRNA alone, or both mRNAs were cotransfected into HeLa cells with plasmids containing the viral EIIa or EIII transcription units. The amount of RNA produced from the EIIa and EIII promoters was increased by the products of both the 13S and the 12S RNAs. By measuring the level of specific transcription in nuclei isolated from transfected cells we directly demonstrate that the increased amount of EIIa RNA is due to stimulation of the rate of transcription.
Transitions between oscillatory modes in a glycolytic model system
Authors: Markus Mario , Hess Benno
Published: May 2006

A glycolytic model system consisting of the enzymes phosphofructokinase (EC 2.7.1.11) and pyruvate kinase (EC 2.7.1.40) is analyzed when subject to periodic substrate addition. The calculations are performed by using detailed rate laws that have been derived for the enzymes of
Escherichia coli
. Due to linear relationships between the metabolite concentrations, the numerical solutions can be displayed inside a trapezium, so that the concentrations of four different metabolites are indicated along the trapezium edges. The analysis reveals a rich variety of time patterns, corresponding to different periodic, quasiperiodic, and chaotic attractors. These patterns undergo complex hysteresis loops when bifurcation parameters are slowly changed—for example, by modulating the input amplitude. By using this technique up to four attractors coexisting in phase space are found. The time patterns corresponding to coexisting attractors can be switched into one another by triggering the system with short substrate pulses. Furthermore, conditions exist at which the triggering is autonomous—i.e., self-sustained (intermittent) switchings occur. The time between these switchings can be set externally by the value of the input amplitude. For conditions in which the periods of the oscillations are in the order of minutes, the self-sustained switching—which modulates these oscillations—can be in the order of hours.
Genetic basis of male sterility in hybrids between two closely related species of Drosophila.
Authors: Coyne J A
Published: May 2006

Drosophila simulans and Drosophila mauritiana are closely related sibling species, the former cosmopolitan and the latter restricted to the small oceanic island of Mauritius. Genetic analysis of male sterility in hybrids between these species shows that at least five loci (one on each chromosome arm) are responsible for this reproductive isolation. This is the most loci that could have been detected with the techniques used and implies that the true genetic divergence for sterility is even greater. The effects of chromosome segments on the character are roughly additive, with the X-linked segment making the largest contribution to sterility. The large effect of X chromosomes on male-limited reproductive isolation and the frequent limitation of hybrid sterility to males may be attributable to fertility interactions between X and Y chromosomes. These results parallel what has been found in other Drosophila species and relate to recent theories of how reproductive isolation evolves in small founder populations.
Spontaneous and mutagen-induced deletions: mechanistic studies in Salmonella tester strain TA102.
Authors: Levin D E , Marnett L J , Ames B N
Published: May 2006

Salmonella tester strain TA102 carries the hisG428 ochre mutation on the multicopy plasmid pAQ1. DNA sequence analysis of 45 spontaneous revertants of hisG428 on the chromosome in the presence of pKM101 (strain TA103) indicates that hisG428 revertants fall into three major categories: (i) small, in-frame deletions (3 or 6 base pairs) that remove part or all of the ochre triplet; (ii) base substitution mutations at the ochre site; (iii) extragenic ochre suppressors. Deletion revertants are identified in a simple phenotypic screen by their resistance to the inhibitory histidine analog thiazolealanine, which feedback inhibits the wild-type hisG enzyme but not the enzyme resulting from the deletions. The effect of various genetic backgrounds on the generation of spontaneous deletion revertants was examined. The error-prone repair system encoded in the pKM101 plasmid markedly increased the frequency of total spontaneous reversion events in all genetic backgrounds except recA but did not affect the frequency of spontaneous deletion revertants in any background except polA. The presence of a polA mutation increased the frequency of spontaneous deletion revertants by 2-fold in the absence of pKM101 and by 20-fold with pKM101. The presence of a uvrB mutation or a recA mutation suppressed the generation of spontaneous deletion revertants to approximately 1/2.5. When hisG428 was in multiple copies on pAQ1, the frequency of spontaneous deletion revertants increased by 40-fold, which is the approximate copy number of pAQ1. Mutagenic agents that induce single-strand breaks in DNA (e.g., x-rays, bleomycin, and nalidixic acid) induced deletion revertants in TA102. These agents induced deletion revertants only in hisG428 on pAQ1 and only in the presence of pKM101. Deletion revertants were not induced by frameshift mutagens (i.e., ICR-191 and 9-aminoacridine). These results indicate that different pathways exist for the generation of spontaneous and mutagen-induced deletion revertants of hisG428.
Portage of various compounds into bacteria by attachment to glycine residues in peptides
Authors: Kingsbury William D. , Boehm Jeffrey C. , Perry David , Gilvarg Charles
Published: May 2006

Synthetic di- and oligopeptides are described that contain nucleophilic moieties attached to the α carbon of a glycine residue. These peptides are accepted by the peptide transport systems of
Escherichia coli
(and other microorganisms) and are capable of being hydrolyzed by intracellular peptidases. After liberation of its amino group the α-substituted glycine is chemically unstable (although it is stable in peptide form) and decomposes, releasing the nucleophilic moiety. Thus, the combined result of peptide transport and peptidase action is the intracellular release of the nucleophile. Peptides containing glycine residues α-substituted with thiophenol, aniline, or phenol are used as models for this type of peptide-assisted entry and their metabolism by
E. coli
is described. Peptides of this type have broad applicability to the study of microbial physiology and the development of an additional class of antimicrobial agents.
Local structure involving histidine-12 in reduced S-sulfonated ribonuclease A detected by proton NMR spectroscopy under folding conditions.
Authors: Swadesh J K , Montelione G T , Thannhauser T W , Scheraga H A
Published: May 2006

The C epsilon H proton resonance of His-12 of reduced cysteine S-sulfonated bovine pancreatic ribonuclease A exhibits a nonlinear temperature dependence of the chemical shift in its 1H-NMR spectrum at an apparent pH of 3.0. At temperatures below ca. 35 degrees C, the temperature dependence of the chemical shift of the His-12 C epsilon H resonance is opposite in sign to those of His-48, His-105, and His-119. At temperatures above ca. 35 degrees C, the temperature dependence of the chemical shift of the His-12 C epsilon H resonance is similar to those of the other three His C epsilon H resonances. These data indicate the existence of an equilibrium between locally ordered and locally disordered environments of His-12 in the sulfonated protein at temperatures below ca. 35 degrees C. The ordered and disordered conformations interconvert at a rate that is fast relative to the 1H-NMR chemical shift time scale--i.e., the locally ordered structure has a lifetime of much less than 7 msec. These results demonstrate that short- and medium-range interactions can define short-lived local structures under conditions of temperature and solution composition at which the native protein structure is stable. Furthermore, they demonstrate the utility of reduced derivatives of disulfide-containing proteins as model systems for the identification of local structures that may play a role as early-forming chain-folding initiation structures.
Evidence for the existence of stable curvature of DNA in solution.
Authors: Hagerman P J
Published: May 2006

A 121-base-pair DNA restriction fragment derived from the kinetoplast minicircle, Lt19, of Leishmania tarentolae displays substantially abnormal electrophoretic behavior on polyacrylamide gels. The electrophoretic behavior of a series of palindromic dimers containing all or part of the 121-base-pair fragment has been used to establish that curvature of the DNA helix is the basis of the abnormal behavior. One of the palindromic dimers, KP242, has been examined in more detail by using the technique of differential decay of birefringence (DDB). The technique consists of analyzing the difference in the rates of decay of birefringence for two DNA fragments, each consisting of an identical number of base pairs, and is capable of resolving differences in length as small as 1%. This approach has yielded an estimate for the apparent curvature of the dimer which, when represented as an equivalent rod with a single bend at its center, equals approximately 52 degrees. DDB measurements made at several ionic strengths indicate that a substantial portion of the curvature is static, rather than a simple consequence of increased flexibility.
Antibodies against a synthetic peptide identify the Epstein-Barr virus-determined nuclear antigen.
Authors: Dillner J , Sternås L , Kallin B , Alexander H , Ehlin-Henriksson B , Jörnvall H , Klein G , Lerner R
Published: May 2006

Five peptides corresponding to amino acid sequences predicted from all three reading frames of the nucleotide sequence of the third internal repeat array (IR3) of the Epstein-Barr virus (EBV) genome were synthesized chemically. All five peptides elicited antipeptide antibodies in rabbits. The antiserum raised against a 14-residue copolymer of glycine and alanine gave brilliant EBV-specific nuclear staining in the anticomplement immunofluorescence (ACIF) assay, in line with the original definition of the EBV-determined nuclear antigen (EBNA) [Reedman, B. M. & Klein, G. (1973) Int. J. Cancer 11, 499-520]. Eight EBNA and EBV DNA-carrying lines showed nuclear staining with the antipeptide antibody, whereas five EBV DNA negative lines failed to stain. The staining pattern was more discretely punctate than the finely dispersed diffuse EBNA staining obtained with human antisera. Human EBV antibody-positive but not EBV-negative sera reacted with the synthetic peptide in an ELISA test. The peptide-specific antibodies were purified from the sera of healthy EBV-seropositive persons by affinity chromatography with the peptide. They gave an EBV-specific, brilliant punctate nuclear ACIF staining similar to that of the rabbit antipeptide antibodies. It was concluded that the glycine-alanine structure encoded by the IR3 region contains a native determinant of EBNA, detected by the ACIF test. Immunoblotting with the rabbit and human peptide-specific antibodies identified poly-peptides that varied between 70 and 92 kilodaltons in size in different EBV-positive cell lines, corresponding closely to a previously identified variation pattern in the size of EBNA. In addition, rabbit antipeptide antibodies identified two cellular polypeptides, 44 and 49 kilodaltons in size.
Cell-specified expression of a selectable hybrid gene.
Authors: Episkopou V , Murphy A J , Efstratiadis A
Published: May 2006

We have inserted into a retroviral vector the structural information encoding the selectable bacterial genes neo and gpt linked, respectively, to the promoters of the herpesvirus thymidine kinase gene and the rat preproinsulin II gene. We have used this recombinant retrovirus construction to transduce insulinoma cell lines that are positive or negative for insulin expression. Selection of the transductants for neo yielded resistant colonies from all of the cell lines, while selection for gpt yielded resistant transductants in relatively high frequency only from insulin-producing cells. The 5' end of the gpt transcripts maps to the authentic preproinsulin capping site of the construction.
Isolation and characterization of a cDNA clone for human ferritin heavy chain.
Authors: Boyd D , Jain S K , Crampton J , Barrett K J , Drysdale J
Published: May 2006

Ferritin, the main iron-storage protein, is composed of two partially homologous subunits, heavy (H) and light (L), with MrS of 21,000 and 19,000, respectively. We have isolated a cDNA clone for human ferritin H chains by screening a human lymphocyte cDNA library with synthetic oligodeoxyribonucleotides. The oligonucleotide sequences were derived from two pentapeptides found in human spleen ferritin. The selected clone hybridized to both probes and selected H-chain mRNA, but not L-chain mRNA, when hybridized to HeLa cell mRNA. These results indicate that the cloned DNA codes for a H chain of human ferritin. Since the amino acid sequence derived from the cloned DNA was almost identical to the partial amino acid sequence of a minor component found in human spleen ferritin, we conclude that the minor sequence found in human spleen ferritin must be a H subunit. Genomic analysis gives a complex pattern that suggests that ferritin H chains are encoded by a multigene family or have an unusually large number of exons.
Calcium-binding protein, parvalbumin, is reduced in mutant mammalian muscle with abnormal contractile properties.
Authors: Stuhlfauth I , Reininghaus J , Jockusch H , Heizmann C W
Published: May 2006

To elucidate the biochemical basis of hereditary muscle diseases in an experimental mammal, we performed polypeptide analyses on skeletal muscles of neuromuscular mutants of the mouse. In one of these, "arrested development of righting response" (adr), the concentration of the soluble Ca2+-binding protein parvalbumin was drastically reduced in comparison to wild type. This reduction was not an unspecific consequence of muscle disease, as it was not observed in two other neuromuscular mouse mutants, "wobbler" (wr) and "motor endplate disease" (med or medjo). Isometric twitches of adr muscle had only slightly prolonged contraction and half-relaxation times, yet long-lasting after-contractions were observed upon repeated (20-100 Hz) direct stimulation. Thus, parvalbumin may be mainly involved in the relaxation after tetanic contraction of fast-twitch fibers.
Dihydropyridine derivatives prolong the open state of Ca channels in cultured cardiac cells.
Authors: Kokubun S , Reuter H
Published: May 2006

The dihydropyridine derivatives CGP 28392 and BAY K 8644 exert a strong positive inotropic effect in mammalian cardiac muscle, presumably by increasing Ca influx during the action potential. Analysis of the drug effects at the level of single Ca channels by means of the patch-clamp method revealed complicated changes in the kinetics of channel gating. The prevailing effect is a prolongation of the mean open time of Ca channels. In addition, the intervals between channel openings can be slightly prolonged. Ensemble averages of single-channel traces showed a concentration-dependent increase in the mean current amplitude by the drugs. In contrast to beta-adrenoceptor agonists, the increase in Ca current by the dihydropyridine derivatives is not associated with an increase in the intracellular cyclic AMP level.
Regulation of Cat1 gene expression in the scutellum of maize during early sporophytic development.
Authors: Chandlee J M , Scandalios J G
Published: May 2006

A regulatory element has been identified in maize that appears to exert an effect specifically on Cat1 gene expression in the scutellum of maize during early sporophytic development. Cat1 encodes CAT-1 catalase, one of two forms of catalase expressed in the scutellum during this developmental time period. Density-labeling experiments indicate that the regulatory element influences the overall levels of CAT-1 protein synthesis in the scutellum but has no effect on CAT-2 protein synthesis. Immunoprecipitation experiments of in vitro translation products suggest that this element has an effect on the level of translatable Cat1 mRNA associated with the scutellar polysomes. The element exhibits additive inheritance and is tissue and time specific in its action. This element, therefore, meets all the criteria of a regulatory gene and has been designated Car2. The element acts to regulate the temporal expression of the Cat1 structural locus in maize.
A species of human alpha interferon that lacks the ability to boost human natural killer activity.
Authors: Ortaldo J R , Herberman R B , Harvey C , Osheroff P , Pan Y C , Kelder B , Pestka S
Published: May 2006

Most species of recombinant leukocyte interferons (IFN-alpha A, -alpha B, -alpha C, -alpha D, -alpha F, -alpha I, and -alpha K) were capable of boosting human natural killer (NK) activity after a 2-hr treatment of cells at a concentration of 1-80 units/ml. In contrast, recombinant human IFN-alpha J was found to be incapable of augmenting NK activity after exposure of cells for 2 hr to concentrations as high as 10,000 units/ml. This inability of IFN-alpha J to boost NK activity was not complete because, after exposure of cells to a high concentration of IFN-alpha J (10,000 units/ml) for 18 hr, boosting of cytolysis was observed. IFN-alpha J appeared to interact with receptors for IFN on NK cells since it was found to interfere with the boosting of NK activity by other species of IFN-alpha. In contrast to its deficient ability to augment NK activity, IFN-alpha J has potent antiviral and antiproliferative activities. Such extensive dissociation of these biological activities has not been observed previously with any other natural or recombinant IFN species. Thus, this IFN species may be useful for evaluating the relative importance of various biological activities on the therapeutic effects of IFN, for understanding structure-function relationships, and for determining the biochemical pathways related to the various biological effects of IFN.
In vivo, cAMP stimulates growth and morphogenesis of mouse mammary ducts.
Authors: Silberstein G B , Strickland P , Trumpbour V , Coleman S , Daniel C W
Published: May 2006

In culture, cAMP is known to be mitogenic for mammary cells and several other epithelia, but evidence for a similar role in vivo has been only correlative. We have used plastic implants to cause slow release of cholera toxin and other cAMP-active agents to local areas of mammary glands in ovariectomized mice. Elevated levels of intracellular cAMP around the implants promoted vigorous growth and normal ductal morphogenesis, while distant sites were unaffected. Local effects of cAMP included restoration of normal ductal caliber, formation of new end buds, and reinitiation of DNA synthesis in both epithelium and surrounding stroma. Thus, cAMP is both a mitogenic and a morphogenetic factor in this tissue.
Monensin-induced inhibition of cell spreading in normal and dystrophic human fibroblasts.
Authors: Pizzey J , Witkowski J , Jones G
Published: May 2006

Cultured skin fibroblasts from normal individuals and from patients with Duchenne muscular dystrophy spread equally rapidly when seeded on a glass substratum. Exposure to the ionophore monensin substantially suppresses normal and dystrophic fibroblast spreading in serum-free media for up to at least 100 min. Preincubation of normal fibroblasts with monensin causes a further reduction in cell spreading. Dystrophic fibroblasts fail to spread as well as normal cells after monensin preincubation. Such findings indicate that there is a delay in the secretion of functional adhesive surface proteins in monensin-preincubated normal fibroblasts and that this lag period is significantly longer in dystrophic fibroblasts. These data are consistent with findings of altered adhesive and secretory properties of fibroblasts from patients with Duchenne muscular dystrophy.
Structure and molecular arrangement of proteolipid protein of central nervous system myelin.
Authors: Stoffel W , Hillen H , Giersiefen H
Published: May 2006

Proteolipid protein (PLP) of central nervous system myelin is one of the most hydrophobic integral membrane proteins. It consists of a 276-residue-long polypeptide chain with five strongly hydrophobic sequences of 26, 30, 39, 12, and 36 residues, respectively, linked by highly charged hydrophilic sequences. Hyposmotically dissociated bovine myelin membranes were treated with trypsin. PLP was completely cleaved into smaller fragments, whereas basic myelin protein remained essentially unaltered. The proteins and tryptic peptides of myelin were separated after the removal of the short, water-soluble peptides into three large fragments of 11, 7.3, and 9.0 kDA, respectively. They were characterized by their molecular mass and NH2-terminal amino acid sequences, which proved that trypsin cleaved predominantly at Arg-97 yielding the 11-kDa fragment from Gly-1 through Arg-97, at Arg-126 releasing the 7.3-kDa fragment from Gly-127 through Lys-191, and at Lys-191 releasing the 9-kDa fragment from Thr-192 through Phe-276. We propose that PLP is integrated into the lipid bilayer of myelin with the NH2 terminus and three positively charged hydrophilic loops oriented toward the extracytosolic side of the membrane, whereas one strongly negative hydrophilic loop and the positively charged COOH terminus cover the cytosolic side of the lipid bilayer. Basic myelin protein remains protected against tryptic cleavage, which indicates its apposition to the cytosolic side of the membrane. These cleavage sites of trypsin support the suggested orientation of PLP in the myelin membrane and thereby extend our knowledge about the molecular arrangement of the components of this membrane. In demyelinating processes membrane desintegration could be initiated by proteolysis at the external surfaces of proteolipid protein in a similar way as described here.
Guinea pig preproinsulin gene: an evolutionary compromise?
Authors: Chan S J , Episkopou V , Zeitlin S , Karathanasis S K , MacKrell A , Steiner D F , Efstratiadis A
Published: May 2006

We characterized a clone carrying the guinea pig preproinsulin gene, which, in contrast to other mammalian preproinsulin genes, is highly divergent in its regions encoding the B and A chains of mature insulin. Blot hybridization analysis indicates that this gene is present in only one copy in the guinea pig genome and that other normal or mutated preproinsulin genes do not exist in this animal. Moreover, the position of introns in this gene and the homology of its 3' flanking region to the corresponding regions of other sequenced mammalian genes show that it has been derived from the common mammalian stock. The rapid evolution of the region encoding the B and A chains can be interpreted, according to our sequence-divergence analysis, as due to the fixation of both neutral and adaptive mutations.
A single rat fibronectin gene generates three different mRNAs by alternative splicing of a complex exon.
Authors: Tamkun J W , Schwarzbauer J E , Hynes R O
Published: May 2006

Three fibronectin mRNAs exist in rat liver, differing by the presence or absence of segments of 285 or 360 bases at a point within the coding region. We previously proposed that the three mRNAs are encoded by a single gene and arise via alternative splicing of a common transcript. In order to test this hypothesis, we have isolated clones spanning approximately half of the fibronectin gene from a Fisher rat genomic library; blot hybridization analyses reveal the presence of only one fibronectin gene in the haploid rat genome. We determined the sequence of a portion (1221 nucleotides) of this gene. This sequence shows clearly that the three fibronectin mRNAs encoded by this gene are generated by a pattern of alternative splicing in which one 5' splice site can be paired with any one of three 3' splice sites, one at the beginning of, and two within, a single complex exon.
Receptors for human gamma interferon: binding and crosslinking of 125I-labeled recombinant human gamma interferon to receptors on WISH cells.
Authors: Sarkar F H , Gupta S L
Published: May 2006

Purified recombinant human gamma interferon (HuIFN-gamma), labeled with 125I (125I-HuIFN-gamma), was used to study receptors for HuIFN-gamma on human WISH cells. 125I-HuIFN-gamma was bound to WISH cells, and this binding was displaced by unlabeled HuIFN-gamma but not by unlabeled recombinant HuIFN-alpha 2 or [Ser17]HuIFN-beta (HuIFN-beta with serine substituted for cysteine at position 17), indicating the presence of specific binding sites for HuIFN-gamma. The cell-bound 125I-HuIFN-gamma was crosslinked with disuccinimidyl suberate or ethylene glycol bis(succinimidyl succinate), which yielded a complex of Mr approximately 105,000 +/- 5000 as analyzed by NaDodSO4/PAGE. The formation of this complex was prevented by preincubation of cells with unlabeled HuIFN-gamma but not with HuIFN-alpha 2 or [Ser17]HuIFN-beta, indicating that HuIFN-gamma binds to a specific receptor molecule and that HuIFN-alpha 2 or HuIFN-beta do not interact with this receptor. Experiments were carried out with 125I-labeled recombinant [Ser17]HuIFN-beta (125I-[Ser17]HuIFN-beta) to verify this conclusion. Binding and crosslinking of 125I-[Ser17]HuIFN-beta to human WISH cells and Daudi cells yielded a complex of Mr approximately 150,000 similar to that obtained with 125I-HuIFN-alpha 2 as described earlier. The formation of this Mr 150,000 complex with 125I-[Ser17]HuIFN-beta was displaced by unlabeled [Ser17]HuIFN-beta and by HuIFN-alpha 2 but not by HuIFN-gamma, indicating that [Ser17]HuIFN-beta binds to the same receptor as does HuIFN-alpha 2, identified earlier, and that HuIFN-gamma does not compete with 125I-[Ser17]HuIFN-beta for this receptor. We conclude that HuIFN-gamma interacts with specific receptors that are distinctly different from the receptors recognized by HuIFN-alpha and HuIFN-beta.
Specific olfactory receptor populations projecting to identified glomeruli in the rat olfactory bulb.
Authors: Jastreboff P J , Pedersen P E , Greer C A , Stewart W B , Kauer J S , Benson T E , Shepherd G M
Published: May 2006

A critical gap exists in our knowledge of the topographical relationship between the olfactory epithelium and olfactory bulb. The present report describes the application to this problem of a method involving horseradish peroxidase conjugated to wheat germ agglutinin. This material was iontophoretically delivered to circumscribed glomeruli in the olfactory bulb and the characteristics and distribution of retrogradely labeled receptor cells were assessed. After discrete injections into small glomerular groups in the caudomedial bulb, topographically defined populations of receptor cells were labeled. Labeled receptor cell somata appeared at several levels within the epithelium. The receptor cell apical dendrites followed a tight helical course towards the surface of the epithelium. The data thus far demonstrate that functional units within the olfactory system may include not only glomeruli as previously suggested but, in addition, a corresponding matrix of receptor cells possessing functional and topographical specificity.
The restricted simple Lie algebras are of classical or Cartan type
Authors: Block Richard E. , Wilson Robert Lee
Published: May 2006

The classification of the finite-dimensional restricted simple Lie algebras over an algebraically closed field
F
of prime characteristic
p
> 7 is announced. Such an algebra is either of classical type (an analogue over
F
of a finite-dimensional simple Lie algebra over the complex numbers) or of Cartan type (an analogue over
F
of one of the infinite Lie algebras of Cartan over the complex numbers).
Sulfation of lutropin oligosaccharides with a cell-free system.
Authors: Green E D , Gruenebaum J , Bielinska M , Baenziger J U , Boime I
Published: May 2006

Sulfate is covalently linked to the oligosaccharides on the alpha and beta subunits of bovine lutropin (luteinizing hormone; LH) but not to those on human chorionic gonadotropin (hCG). Since the amino acid sequences of the pituitary and placental alpha subunits are homologous, comparison of their asparagine-linked sugars can provide information regarding tissue specificity of oligosaccharide maturation. To characterize this post-translational modification, we have developed a reconstituted cell-free sulfation system. Sulfate is incorporated into exogenously added glycoproteins by sulfotransferases from Triton X-100-lysed Golgi membranes in the presence of 3'-phosphoadenosine 5'-phospho[35S]sulfate, which is generated from [35S]sulfate by a ribosome-free supernate from Krebs ascites tumor cells. LH is sulfated by pituitary and liver membranes but not by those from placenta. Desialylated hCG (AshCG) is sulfated by membranes from placenta and pituitary, but not liver, while hCG is not sulfated by any of these membranes. Endoglycosidase F releases all the incorporated sulfate from LH in the form of a heterogeneous mixture of mono- and disulfated oligosaccharides. In contrast, the sulfate added to AshCG is apparently attached to peptide rather than oligosaccharide. As found with the cell-free system, sulfate metabolically incorporated into LH by pituitary cells is present on a heterogeneous population of mono- and disulfated oligosaccharides. Thus the cell-free sulfation system accurately duplicates the in vivo process.
Specific hepatitis B virus integration in hepatocellular carcinoma DNA through a viral 11-base-pair direct repeat.
Authors: Dejean A , Sonigo P , Wain-Hobson S , Tiollais P
Published: May 2006

Integrated hepatitis B virus (HBV) DNA sequences have been cloned from cellular DNA of two human liver tumors. The structure of the clones was determined by restriction mapping, and the host-viral DNA junctions were sequenced. In each clone one junction mapped to within an 11-base-pair sequence, 5' T-T-C-A-C-C-T-C-T-G-C, which is directly repeated near the extremities of the cohesive-end region of the free viral genome. The two copies of this sequence are termed DR1 and DR2. While one clone carried a host-viral junction within DR1, the second one carried a host-viral junction within DR2. The first 1 or 2 base pairs of the repeat were deleted upon recombination with the host genome, leaving at the junctions a common 9-base-pair segment of HBV DNA, 5' C-A-C-C-T-C-T-G-C. The other two host-viral junctions mapped to the pre-S region and to the core region of the viral genome, showing no peculiar feature. These results show that HBV DNA can integrate via a specific viral DNA sequence.
Synergistic effects of antigen and soluble T-cell factors in B-lymphocyte activation.
Authors: Jelachich M L , Grusby M J , Clark D , Tasch D , Margoliash E , Pierce S K
Published: May 2006

Supernatants from phorbol 12-myristate 13-acetate-activated cultures of the mouse EL4 thymoma, or of several mouse T-cell hybridomas stimulated either by their specific antigen or by concanavalin A, induced primary splenic B cells to proliferate and differentiate to antibody-secreting cells. This effect was not due to interleukin 2 and did not require the presence of macrophages. The antibody response was polyclonal, including antibodies specific for 2,4-dinitrophenyl and pigeon cytochrome c, present in amounts of 1% or less of the total immunoglobulin produced. The addition of either of these antigens increased the amount of the corresponding specific antibody. At very high concentrations of dinitrophenyl-hemocyanin the specific response could be depressed. These observations were taken to demonstrate that soluble T-cell factors are sufficient to activate a portion of naive B cells to antibody secretion and that under these conditions in vitro the presence of antigen merely enhances the specific response.