bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein Ia and the lamB protein can replace each other in the constitution of an active receptor for the same coliphage.
Authors: Wandersman C , Schwartz M
Published: May 2006

Protein Ia and the lamB protein are both located in the outer membrane of Escherichia coli K-12. The lamB protein is known to be the receptor for phage lambda. Datta et al. [Datta, D. B., Arden, B. & Henning, U. (1977) J. Bacteriol. 131, 821--829] recently isolated a phage called TuIa that uses protein Ia for its adsorption. While phage TuIa fails to grow on ompB mutants, which lack protein Ia, we show here that host-range mutants of TuIa can be isolated that do grow on ompB strains. These host-range mutants fail to grow on ompB lamB double mutants, but retain the ability of the parental phage to grow on ompB+ lamB strains. They are therefore apparently able to use either protein Ia or the lamB protein for their adsorption. Genetic evidence suggests that essentially the same site on the lamB protein may be interacting with phage lambda or the host-range mutants of phage TuIa.
Reversal of renovascular hypertension by antibodies specific for angiotensin-converting enzyme.
Authors: Markle R A , Sonnenblick E H , Conroy J M , Soffer R L
Published: May 2006

Goat antibodies developed against pure rabbit pulmonary angiotensin-converting enzyme (peptidyl dipeptidase, EC 3.4.15.1) were administered intravenously to rats with two-kidney Goldblatt hypertension and to normotensive animals. In the hypertensive model these antibodies were associated with a sustained, immune-dependent decrease of blood pressure to normal values. A smaller, but also immune-specific, reduction of blood pressure was observed in the normotensive group. The data suggest that heterologous antibody directed against angiotensin-converting enzyme may provide a biologically specific probe for examining the contribution of the renin-angiotensin system to normal and pathologic circulatory states.
Evidence for mediation of a neuronal interaction by a behaviorally active peptide.
Authors: Branton W D , Arch S , Smock T , Mayeri E
Published: May 2006

Egg laying hormone, a peptide neurohormone with an approximate molecular weight of 6000, was isolated from the region of the abdominal ganglion of Aplysia that contains the neuroendocrine bag cells and purified by gel filtration chromatography, isoelectric focusing, and dialysis. A 1-min local application of egg laying hormone to the identified neuron R15 produced prolonged (greater than 1 hr) augmentation of impulse activity in this neuron. The distinctive quality and prolonged duration of the response are apparently identical to the previously described response to electrically elicited bag cell activity. The results provide evidence that egg laying hormone is the mediator of this prolonged neuronal interaction.
Recombination between viral and cellular sequences generates transforming sarcoma virus
Authors: Wang L.-H. , Halpern C. C. , Nadel M. , Hanafusa H.
Published: May 2006

A series of sarcoma viruses has been obtained from tumors induced by transformation-defective (td) mutants of the Schmidt-Ruppin strain of Rous sarcoma virus, subgroup A (SR-A). The RNA sequences of these “recovered avian sarcoma viruses” (rASVs) were compared with those of td mutants and of SR-A by oligonucleotide fingerprinting. Of six sarcoma-specific oligonucleotides present in SR-A RNA, three to six were missing in the RNAs of the four td mutants examined. All six isolates of rASV examined have regained these six oligonucleotides. In addition, most rASV RNAs have three new oligonucleotides not present in the RNA either of td mutants or of SR-A. The newly obtained oligonucleotides are located between 800 and 2600 nucleotides from the 3′ end of rASV RNA, which corresponds to the
src
region of SR-A RNA mapped previously. Furthermore, viral RNAs of two td mutants isolated from a clone of rASV lack most
src
-specific oligonucleotides, including the three new ones. No differences were found among RNAs of td, SR-A, and rASV in the regions outside of
src
. Our results indicate that RNA sequences that rASVs have acquired from cells in the process of conversion from td virus to transforming virus are mapped within the
src
region and segregate with the transforming function. Some of the sequences are new and some are identical with those in SR-A RNA.
Correlation of albumin production rates and albumin mRNA levels in livers of normal, diabetic, and insulin-treated diabetic rats.
Authors: Peavy D E , Taylor J M , Jefferson L S
Published: May 2006

We have studied the effects of alloxan-induced diabetes and subsequent insulin replacement on albumin and total hepatic protein synthesis. Diabetes resulted in a reduction to approximately 20% of normal in albumin synthesis relative to the rate of total protein synthesis in vivo and a reduction to 10% in the absolute rate of albumin secretion by perfused livers. In contrast, the synthesis of total secretory protein and retained hepatic protein was affected to a lesser extent by diabetes. Treatment of diabetic rats with insulin restored rates of albumin and total hepatic protein synthesis to normal levels. The molecular basis of these alterations in albumin synthesis was investigated by examining albumin mRNA levels in livers of normal, diabetic, and insulin-treated diabetic animals. The level of albumin mRNA, whether assayed by cell-free translation or by hybridization to a specific complementary DNA probe, was markedly decreased in livers of diabetic animals and was restored to normal by insulin treatment. These changes occurred in parallel with changes in the rates of albumin secretion observed in perfused liver, suggesting that albumin mRNA content is the primary factor responsible for altering rates of albumin synthesis under these conditions.
Interaction of secreted nascent chains with surrounding membrane in Bacillus subtilis.
Authors: Smith W P , Tai P C , Davis B D
Published: May 2006

To determine the length of secreted nascent polypeptide chain that is surrounded by membrane, we digested labeled nascent chains protruding from protoplasts of Bacillus subtilis with Pronase and isolated the residual ribosome-attached chains from the membrane-polysome fraction. Gel chromatography revealed a sharp major peak that had been protected by membrane plus bound ribosomes. The ribosomes themselves protected half as great a length. Because no free chain between the ribosome and the membrane was detected by Pronase treatment, the difference between the two protected lengths should measure the length protected by the membrane. More accurate measurements of these lengths, obtained by dansylation of the exposed NH2 terminus of the isolated fragments, yielded a difference of 21 amino acids. This value corresponds to an extended chain of 75 A, which is approximately the thickness of the bacterial cell membrane. We earlier presented evidence that bacterial ribosomes are attached to membrane solely by their secreted chain. The present results further show that after loss of the extracellular segment of the chain its attachment persists, at 37 degrees as well as 0 degrees C. These findings suggest that the chain does not slip through a passive membrane but is actively held within a channel.
Rapid conformational changes of cytochrome
P
-450: Effect of dimyristoyl lecithin
Authors: Tsong Tian Yow , Yang Chung S.
Published: May 2006

Binding of benzphetamine to purified microsomal cytochrome
P
-450 from rat liver causes a shift in the heme spin state of the protein to favor the high-spin form. This shift is strongly temperature dependent. A rapid temperature jump of a cytochrome
P
-450/ε benzphetamine mixture, monitored by changes in the Soret absorptions of the heme, reveals two relaxation processes: one in a 50-msec time range (τ
f
) and the other in a 0.3-sec time range (τ
s
). Both relaxations reflect conformational changes of the protein after the substrate binding. No bimolecular reaction of benzphetamine and the enzyme has been resolved. This indicates that there is no absorption change of the heme associated with the initial binding. In the presence of dimyristoyl lecithin, at 25°C τ
f
decreases by nearly one order of magnitude whereas τ
s
decreases to one-third. The enhancement of rates by added phospholipid is both temperature- and concentration-dependent: rates are accelerated only above the gel-liquid crystalline transition temperature, and this effect saturates near the enzyme/lipid ratio of 1:20. In contrast, the lipid does not have significant effect on the equilibrium binding curve of the substrate. These results suggest that the lipid may form an envelope around the enzyme and, depending on its crystalline state, regulates the rate of the substrate-induced conformational changes of cytochrome
P
-450.
Origin of DNA replication in papovavirus chromatin is recognized by endogenous endonuclease.
Authors: Waldeck W , Föhring B , Chowdhury K , Gruss P , Sauer G
Published: May 2006

Isolated simian virus 40 (SV40) and polyoma nucleoprotein complexes contain endonuclease that, under in vitro conditions, converts part (up to 30%) of the covalently closed superhelical DNA to full-length linear rods. The positions of the cleavage sites within the genomes of SV40 and polyoma were determined by digestion with various single-cut restriction endonucleases and subsequent agarose gel electrophoresis of the cleavage products. Both SV40 and polyoma covalently closed superhelical DNA were cleaved open at their respective origins of DNA replication (+/- 75 base pairs). The full-length linear DNA rods whose ends map adjacent to the origin of DNA replication could also be isolated by sodium dodecyl sulfate/phenol extraction both from SV40-infected permissive cells and from purified SV40 virions. These data reveal the presence of a unique structure of the papovavirus chromatin close to the initiation site of DNA replication.
Ecdysteroid receptors in imaginal discs of Drosophila melanogaster.
Authors: Yund M A , King D S , Fristrom J W
Published: May 2006

[3H]Ponasterone A (PNA) of high specific activity has been used to identify and begin characterization of ecdysteroid (formerly called ecdysone) receptors in cytoplasmic and nuclear fractions of imaginal discs of Drosophila melanogaster. The equilibrium Kd of the observed macromolecular binding, 3--4 X 10(-9) M PNA, is in good agreement with the minimal concentration required for induction of complete morphogenesis in vitro, 4.2 X 10(-9) M PNA. Binding is analog specific and has kinetics consistent with a role in hormone response. On gentle homogenization, less than 5% of the binding capacity of the cell is released as soluble receptor; the other 95% remains with the nuclear fraction. This nuclear fraction specifically binds [3H]PNA in vitro. Greater than 95% of nuclear PNA receptors are released by extraction with 0.3 M KCl. The binding properties of the nuclear receptors are indistinguishable from those of the cytosol fraction or of the whole cell.
Monovalent antibodies directed to transformation-sensitive membrane components inhibit the process of viral transformation
Authors: Lingwood C. A. , Ng A. , Hakomori S.
Published: May 2006

Monovalent antibodies (Fab) directed to two classes of transformation-sensitive cell surface components, ganglioside and galactoprotein a (Gap a), inhibit the process of oncogenic viral transformation of cells. Mouse 3T3 cells infected with murine sarcoma virus were not transformed in terms of morphology change and enhancement of sugar uptake when the infected cells were cultured in the presence of monovalent antibodies directed to GM
1
ganglioside or to Gap a. Transformation inhibitory activity of these cell surface ligands was not related to cell growth inhibition because the monovalent antibodies to globoside and divalent Con A were growth inhibitory but did not inhibit oncogenic transformation. Neither anti-GM
1
Fab nor anti-Gap a Fab inhibited virus production. The transformation inhibitory activity of antiganglioside and anti-Gap a Fab was additionally assessed by inhibiting the transformed phenotype in NRK cell lines with mutants of avian sarcoma virus that are temperature sensitive for expression of the transformation phenotype (NRK/LA25). In this cell line, the GM
3
ganglioside (not GM
1
) and Gap a were transformation-sensitive cell surface components. The expression at permissive temperature of transformed phenotypes, such as morphology change and capability of growth in 0.3% agar, was inhibited by preincubation of the cells with anti-GM
3
Fab or anti-Gap a Fab.

GM
3
labeling of NRK/LA25 cells decreased at permissive temperature, whereas preincubation of cells with anti-Gap a, which induces the inhibition of transformation after a temperature shift, prevented the decline of GM
3
label on the cell surface. The data suggest a possible correlation between GM
3
and Gap a expression. Application of monovalent antibodies to these transformation-sensitive components may prevent changes of these components on cell surfaces, and thus may result in abortion of phenotypic expression of transformation, although the transforming gene (
src
) has been set active. These results indicate that pericellular structures influence gene expression.
beta-Galactosidase is induced by hormone in Drosophila melanogaster cell cultures.
Authors: Best-Belpomme M , Courgeon A M , Rambach A
Published: May 2006

Drosophila melanogaster cell lines Kc and Ca and clones FC and RF6, cultured in vitro, have no detectable beta-galactosidase (beta-galactoside galactohydrolase, EC 3.2.1.23) activity (as measured by hydrolysis of o-nitrophenyl-beta-D-galoctoside). Ecdysterone, a hormonal steroid of critical importance in insect physiology, clearly induces beta-galactosidase activity in D. melanogaster cells cultured in vitro. Induction occurs in cell lines or clones known to be sensitive to ecdysterone (K, Ca, and Fc) and does not occur in clones known to be resistant to the hormone (RF6). Some properties of the hormone-induced beta-galactosidase activity were studied. The Km for o-nitrophenyl galactoside is 0.35 mM and the Ki for lactose is 12 mM (similar to those of Escherichia coli beta-galactosidase); the activity can be recovered after sodium dodecyl sulfate treatment; the enzyme is a tetramer (Mr of the monomer is 64,000).
Leukemia in AKR mice: A defined suppressor cell population expressing membrane-associated DNA
Authors: Russell James L. , Golub Edward S.
Published: May 2006

Leukemic AKR mouse spleen cells suppress normal AKR anti-sheep erythrocyte antibody responses
in vitro
. Treatment of leukemic spleen cells with DNase I prior to coculture with normal AKR cells abrogates their suppressive ability. Treatment of leukemic cells with a wide range of DNase I concentrations has no effect on the viability of these cells as measured by incorporation of [
3
H]thymidine or by eosin dye exclusion. When the activating divalent cations required for DNase I action are functionally removed in the enzyme treatment medium by chelation with EDTA, the ability of DNase I to abrogate suppression is abolished. Furthermore, the effects of DNase I in overcoming suppression are not able to be mimicked by trypsin, Pronase, or ribonuclease. These results are consistent with the existence of a population of cells in the leukemic spleen that expresses a form of membrane-associated DNA that functions in the suppression of normal antibody responses. The existence of such a population was shown by treating leukemic spleen cells with anti-single-stranded-DNA and then passing them through an anti-immunoglobulin immunoadsorption column. Approximately 15% of the leukemic cells are retained on the column and can be specifically eluted with the normal immunoglobulin. The cells of this enriched population when cocultured with normal spleen cells exhibit a 10-fold greater suppressive ability than unfractionated cells. Thus, there exists in the spleens of overtly leukemic AKR mice a population of cells expressing a form of DNA on their surfaces that in some manner is necessary for immunosuppression.
Cell-free ring expansion of penicillin N to deacetoxycephalosporin C by Cephalosporium acremonium CW-19 and its mutants.
Authors: Yoshida M , Konomi T , Kohsaka M , Baldwin J E , Herchen S , Singh P , Hunt N A , Demain A L
Published: May 2006

To examine microbiological ring expansion of penicillin N to a cephalosporin, we obtained five mutants of Cephalosporium acremonium blocked in beta-lactam antibiotic biosynthesis from 2500 survivors of mutagenesis. In submerged fermentation, mutants M-0198, M-0199, and M-2351 produced no beta-lactam antibiotic (type A), whereas mutants M-1443 and M-1836 formed penicillin N but not cephalosporin C (type B). Cell-free extracts of type A mutants converted penicillin N to a cephalosporin; those of type B mutants did not. The product of the cell-free reaction was identified as deacetoxycephalosporin C by thin-layer chromatography, paper chromatography, paper electrophoresis, and enzyme tests. These data strongly support our hypothesis that penicillin N is an intermediate of cephalosporin biosynthesis.
Genetic dimorphism in influenza viruses: Characterization of stably associated hemagglutinin mutants differing in antigenicity and biological properties
Authors: Kilbourne Edwin D.
Published: May 2006

Influenza virus recombinant X-53 produced for use in the 1976 National Immunization Program for swine influenza was found to comprise two types of virions differing in their antigenic, replicative, and plaque-forming characteristics. One type, characteristic of X-53 and designated “L,” was relatively low-yielding in chicken embryos, produced small clear plaques in Madin-Darby dog kidney cells, and was selectively inhibited by heterotypic antibody to the A/sw/Cam/39 strain of swine influenza virus. The other, X-53a or “H,” was high-yielding in chicken embryos, produced large turbid plaques in dog kidney cells, and was not inhibited by concentrations of A/sw/Cam/39 antisera inhibitory to X-53. It was shown that A/NJ/11/76 (HswN1) virus, from which X-53 was derived, and five other swine influenza virus isolates from humans and pigs were dimorphic mixtures of the two types of virus. Segregation of the hemagglutinin genes of L and H variants by further recombination demonstrated that their different properties were pleiotropic phenotypes of mutation in the hemagglutinin gene. Under selective conditions suppressive to the L mutant, mutation of cloned L to H virus was observed. This observation, as well as the apparent ubiquity of the two mutants in nature, suggests that this is another example of viral dimorphism—the stable association of two allelic mutants. Of special significance is the indication that antigenic variants may be selected by selection for properties other than antigenicity, and therefore may represent mutants with pathogenic effects determined by factors other than lesser modulation by host antibody.
Voltage-sensitive calcium channels regulate guanosine 3',5'-cyclic monophosphate levels in neuroblastoma cells.
Authors: Study R E , Breakefield X O , Bartfai T , Greengard P
Published: May 2006

Veratridine or high potassium concentration increased guanosine 3',5'-cyclic monophosphate (cGMP) levels in neuroblastoma cells of clone N1E-115 without affecting levels of adenosine 3',5'-cyclic monophosphate (cAMP). The increases in cGMP appear to be a direct result of the depolarizing action of these agents and not due to the action of substances released from the cells upon depolarization. The increase in cGMP produced by depolarization was dependent upon extracellular calcium and could be prevented by the calcium channel blockers D600 and cobalt. Carbachol, acting on muscarinic acetylcholine receptors, also caused a calcium-dependent increase in cGMP in these cells. The carbachol and potassium effects were additive from 5 to 100 mM potassium and from 1 to 3 mM calcium. The carbachol response was nearly as sensitive as the potassium response to inhibition by D600 but was much less sensitive to inhibition by cobalt. The results suggest that depolarization increases cGMP levels in these cells by opening voltage-sensitive calcium channels and that activation of muscarinic receptors opens separate, voltage-insensitive calcium channels.
Electrophysiological analysis reinnervation of transplants in the anterior chamber of the eye by the autonomic ground plexus of the iris.
Authors: Taylor D , Seiger A , Freedman R , Olson L , Hoffer B
Published: May 2006

Fetal rat hippocampus, cerebellum, and heart were homologously transplanted to the anterior chamber of the eye of adult female recipients. After the grafts were allowed to mature in oculo, ingrowing adrenergic and cholinergic fibers from the iris were activated by changing the illumination of the retina. Electrophysiological recordings from all three types of transplants showed changes similar to those reported for effects of adrenergic and and cholinergic inputs in situ. Pharmacological studies with the transplants indicated that these electrophysiological changes were caused by activation of local muscarinic cholinergic and beta-adrenergic synapses. These data suggest that the intraocular graft is able to induce functional adrenergic and cholinergic inputs from the ground plexus of the iris and support the hypothesis that target organ influences play an important role in synaptogenesis.
Bond angles in transition metal tetracarbonyl compounds: A further test of the theory of hybrid bond orbitals
Authors: Pauling Linus
Published: May 2006

An equation for the bond angles OC—M—CO for tetracarbonyl groups in which the transition metal atom M is enneacovalent, derived from the simple theory of hybrid
sp
3
d
5
bond orbitals, is tested by comparison of the calculated values of the angles with the experimental values reported for many compounds containing M(CO)
4
groups, especially those with M = Fe, Mn, Re, Cr, or Mo. The importance of the energy of resonance of single bonds and double bonds in stabilizing octahedral complexes of chromium and manganese with carbonyl, phosphine, arsine, and thio groups is also discussed.
Identification of precursor molecules to individual tRNA species from Bombyx mori.
Authors: Garber R L , Siddiqui M A , Altman S
Published: May 2006

Short-labeled 4.5S RNA molecules isolated from the posterior silk gland of Bombyx mori can be separated by two-dimensional polyacrylamide gel electrophoresis into many discrete species, some of which are radiochemically pure by the criteria of RNA fingerprinting. One region of the gel contains two precursor RNAs, one to each of the known alanine transfer RNAs. Each precursor tRNAAla molecule contains all of the internal oligonucleotides present in the corresponding tRNAAla species plus new 5'-and 3'-terminal sequences. Precursor molecules to tRNA1Gly (which differ from each other in size) are contained in two other gel regions, and a fourth region contains a precursor to tRNA2Gly. Both of the transcription initiator purine tetraphosphate nucleosides are present in unfractionated tRNA precursor mixtures, with pppA- predominating over pppG-. Minor nucleotides are also present in B. mori tRNA precursors. No polycistronic tRNA gene transcripts were observed.
Interaction of human chorionic gonadotropin with membrane components of rat testes
Authors: Pacuszka Tadeusz , Osborne James C. , Brady Roscoe O. , Fishman Peter H.
Published: May 2006

Previous studies demonstrating that gangliosides interacted with thyrotropin and human chorionic gonadotropin (hCG) suggested that gangliosides participate in the transduction of the hormonal message across the target cell membrane. As a continuation of these investigations, we examined the effects of down-regulation of hCG receptors on the interaction of hCG with rat testis membrane components. Rat testes contained a complex ganglioside pattern that did not appear to change qualitatively or quantitatively after the injection of hCG into the animals, although testis membranes from hCG-treated rats lost their capacity to bind
125
I-labeled hCG (
125
I-hCG). Gangliosides extracted from the testes of control and treated animals were equally effective inhibitors of
125
I-hCG binding to testis membranes. However, inhibition of binding was observed only under conditions (pH 6.0, low ionic strength) such that unlabeled hCG (>2500-fold excess) did not block
125
I-hCG binding, and
125
I-hCG bound similarly to testis membranes from control and treated rats. Under conditions such that hCG binding was specific (blocked by 250-fold excess of unlabeled hCG), testis gangliosides were noninhibitory. Liposomes containing gangliosides from the testes of control or hCG-treated rats bound similar small amounts of
125
I-hCG. These same liposomes bound 50 and 1000 times more thyrotropin and cholera toxin, respectively, than hCG. Oligosaccharides derived from gangliosides did not inhibit
125
I-hCG binding to testis membranes nor did they alter the fluorescence of hCG conjugated with fluorescent probes, whereas the gangliosides themselves were inhibitory and enhanced the fluorescence intensity of the hCG derivatives. Exposure of testis membranes from hCG-treated rats to 4 M MgCl
2
, which displaces bound hCG [Chen, Y.-D. I. & Payne, A. H. (1977)
Biochem. Biophys. Res. Commun.
74, 1589-1596], did not restore their ability to bind
125
I-hCG. When membranes were solubilized with Triton X-100, a solubilized receptor was detected from testis membranes of control but not hCG-treated rats.

These findings and the absence of demonstrable changes in the composition or quantity of rat testis gangliosides when hCG receptors are down-regulated suggest that gangliosides do not represent the primary binding determinants of hCG receptors.
Effect of hemin on site-specific phosphorylation of eukaryotic initiation factor 2.
Authors: Tahara S M , Traugh J A , Sharp S B , Lundak T S , Safer B , Merrick W C
Published: May 2006

Initiation factor 2 (eIF-2) is phosphorylated in vitro by two different cyclic nucleotide-independent protein kinases. As previously shown, a protein kinase activity that comigrates with the major casein kinase activity from rabbit reticulocytes phosphorylates eIF-2beta. In addition, a second protein kinase that specifically phosphorylates eIF-2alpha has been identified. Both protein kinase activities demonstrate cyclic nucleotide-independent activity and are not inhibited by the inhibitor protein diagnostic for cyclic AMP-regulated protein kinase activities. Phosphorylation of eIF-2alpha is almost completely inhibited by 20--35 muM hemin, whereas phosphorylation of eIF-2beta is only partially inhibited. Hemin acts by decreasing the rate of incorporation of phosphate into eIF-2alpha. The protein kinase activity that modifies eIF-2alpha has been shown to have inhibitory activity in the cell-free protein-synthesizing system, whereas the protein kinase for eIF-2beta has no effect. The identity of the former enzyme with the hemin-controlled repressor and role of hemin in the control of initiation are discussed.
Drug-nucleic acid interactions: conformational flexibility at the intercalation site.
Authors: Berman H M , Neidle S , Stodola R K
Published: May 2006

The conformational features of the intercalation site in polynucleotides were examined. We found that, for all the crystal structures of drug-dinucleoside complexes studied thus far, two torsion angles differ from those found in A RNA (phi and chi) and that alternate sugar puckering is not a prerequisite for intercalation. This intercalation geometry, which is the basis of helix axis displacement in a polymer, would necessitate conformational changes in the adjacent nucleotides. The base-turn angle is less sensitive to the conformation of the backbone than it is to small alterations in the base-pairing geometry. We postulate that this angle is dependent on the nature of the intercalating drug.
Comutagenic effect of norharman and harman with 2-acetylaminofluorene derivatives.
Authors: Umezawa K , Shirai A , Matsushima T , Sugimura T
Published: May 2006

Norharman enhanced the known mutagenicity of 2-acetylaminofluorene derivatives in the Salmonella test system. The mutagenicities of 2-acetylaminofluorene, 2-aminofluorene, and N-hydroxy-2-acetylaminofluorene were enhanced by norharman only when rat liver microsomal enzymes were added, whereas the mutagenicity of N-acetoxy-2-acetylaminofluorene was increased in the absence of microsomal enzymes. Harman also increased mutagenesis, althouth less so than norharman.
Assignment of genes to regions of mouse chromosomes.
Authors: Eicher E M , Washburn L L
Published: May 2006

A genetic mapping procedure, called the duplication-deficiency method, is described. This method permits the genetic location of a translocation to be determined within a linkage group without the use of recombination. By utilizing the duplication-deficiency method to define the genetic breakpoints for a series of translocations involving a given chromosome and integrating this information with their cytological breakpoints, obtained by Giemsa banding, a genetic map of the chromosomes is constructed whereby groups of loci are assigned to banded regions. Duplication-deficiency mapping and Giemsa banding analysis of the T(X;7)1Ct and T(7;19)145H translocations together with information from the c25H deletion have permitted mouse chromosome 7 to be divided into six and chromosome 19 into two definable genetic regions.
Potato spindle tuber and citrus exocortis viroids undergo no major sequence changes during replication in two different hosts
Authors: Dickson Elizabeth , Diener T. O. , Robertson Hugh D.
Published: May 2006

Potato spindle tuber viroid and citrus exocortis viroid, each purified from tomato (
Lycopersicon esculentum
) and from
Gynura aurantiaca
, were iodinated
in vitro
with
125
I, digested with ribonuclease T1, and subjected to two-dimensional RNA fingerprinting analysis. With the exception of minor variations, each viroid retained its distinctive fingerprint pattern irrespective of the host species from which it was isolated. We conclude that the nucleotide sequences of these viroids are principally determined by the infecting viroid and not by the host.
Erythroid colony formation from human fetal liver.
Authors: Rowley P T , Ohlsson-Wilhelm B M , Farley B A
Published: May 2006

The liver of the human fetus, induced to abort by prostaglandin or by hypertonic saline, contains cells that form colonies in methylcellulose in vitro. The colonies are erythroid as identified by cellular staining of hemoglobin by benzidine. Colony formation is generally similar, with regard to number, size and time of development, to that observed in cultures of nonadherent cells from human adult marrow. The number of colonies observed increases with the concentration of erythropoietin used and with the concentration of cells plated and decreases with the time interval between intra-amniotic instillation of the inducing agent and culture. Colong number is not greatly influenced by fetal age in the period 16-20 weeks or by whether the inducing agent is prostaglandin or hypertonic saline. Prostaglandin- and hypertonic saline-induced abortuses thus provide an abundant source of human fetal erythroid tissue for morphologic and biochemical studies of erythroid development.
Cooperativity in O2 binding to iron porphyrins.
Authors: Collman J P , Brauman J I , Rose E , Suslick K S
Published: May 2006

The solid-gas O2 binding equilibrium has been studied for for ferrous "picket fence" porphyrinates with sterically hindered axial imidazoles. Such systems show significant cooperativity in their binding of O2: at low O2 pressures a low O2 affinity form exists, and at high O2 pressures a higher O2 affinity form develops. Direct analogies are drawn to the cooperativity shown in O2 binding by hemoglobin. These model systems mimic hemoglobin quantitatively.
Specific binding of tRNAMet to 23S rRNA of Escherichia coli.
Authors: Dahlberg J E , Kintner C , Lund E
Published: May 2006

tRNAMetf binds to 23S rRNA of Escherichia coli, forming a complex with a melting temperature of 75 degrees (in 0.6 M NaCl). The regions within the RNAs that bind to each other have been isolated and their nucleotide sequences have been determined. The interacting region in tRNAMetf is 17 nucleotides long, extending from G5 in the acceptor stem to D21 (D = 5.6-dihydrouridine) in the D loop. The sequence in 23S rRNA is complementary to that sequence except for an extra Up in the middle and allowing a Gp.D base pair. We propose that association of these two sequences may play a role in initiation of protein synthesis by tRNAMetf. In addition, part of this sequence in 23S rRNA may also stabilize tRNA binding to the ribosome during elongation of nascent polypeptides.
Cardiolipin: a stereospecifically spin-labeled analogue and its specific enzymic hydrolysis.
Authors: Cable M B , Jacobus J , Powell G L
Published: May 2006

The spin-labeled cardiolipin 1-(3-sn-phosphatidyl)-3-[1-acyl-2-(16-doxylstearoyl)glycero(3)phosphol]-sn-glycerol has been prepared. The stereoselective synthesis makes use of the monolysocardiolipin 1-(3-sn-phosphatidyl)-3-[1-acyl-2-lyso-sn-glycero(3)phospho]-sn-glycerol, available from the stereospecific hydrolysis of cardiolipin by phospholipase A2 (phosphatide 2-acylhydrolase, EC 3.1.1.4) of Trimeresurus flavoviridis. The results of treatment of the spin-labeled cardiolipin with the cardiolipin-specific phospholipase D (phosphatidylcholine phosphatidohydrolase, EC 3.1.4.4) (Hemophilus parainfluenzae) of known specificity and with phospholipase C (phosphatidylcholine cholinephosphohydrolase, EC 3.1.4.3) of Bacillus cereus are consistent with the assigned structure. The spin-labeled cardiolipin is further characterized and the unique features of this diastereomer are discussed in the context of the unusual stereochemistry of the natural phospholipid.
Defective regulation of cholesterol biosynthesis and plasma membrane fluidity in a Chinese hamster ovary cell mutant.
Authors: Sinensky M
Published: May 2006

A Chinese hamster ovary cell mutant resistant to killing by 25-hydroxycholesterol is shown to be defective in the regulation of cholesterol synthesis by exogenous cholesterol. When grown with various cholesterol supplements in delipidized serum, the mutant cell exhibits a variation in cholesterol content and plasma membrane fluidity that is not observed in the parental cell type.
Evidence for unaltered structure and in vivo assembly of microtubules in transformed cells.
Authors: De Mey J , Joniau M , De Brabander M , Moens W , Geuens G
Published: May 2006

By using immunoperoxidase cytochemistry at the light and electron microscopic level, microtubles were visualized in a number of "normal" nontumorigenic and transformed tumorigenic cell lines. A well-defined cytoplasmic microtubule complex exists in both normal and transformed interphase cells. The distribution of this complex closely correlates with the cell shape and the degree of cell spreading. Our data support the idea that these properties determine the pattern of the cytoplasmic microtubule complex, rather than the reverse. Ultrastructural observations of immunoperoxidase-stained tumor cells showed characteristic microtubules in cells in which the microtubules were poorly resolved at the light microscopic level. The results suggest that microtubule assembly and structure are unaltered in transformed cells. However, this conclusion does not exclude the possibility that some of the microtubules' functions might be impaired in a yet-unknown way.
Cell adhesion to substrates containing adsorbed or attached IgG.
Authors: Giaever I , Ward E
Published: May 2006

When most mammalian cells are propagated in tissue culture, they are attached to a solid surface. This surface is commonly covered with a layer of serum protein. In this study we looked at the effect of the protein layer on the interaction between the cells and the surface by precoating the surface with various pure protein molecules. We found no differences between surfaces covered with pure protein layers and those covered with serum proteins except when antibody molecules were used. In all cases the cell types used avoided surfaces covered with antibody molecules. Previously, other investigators have established that some cells belonging to the immunology system are attracted to such surfaces.
Construction and properties of chimeric plasmids in Bacillus subtilis.
Authors: Gryczan T J , Dubnau D
Published: May 2006

Antibiotic resistance chimeric plasmids have been constructed by in vitro enzymatic manipulation and introduced into Bacillus subtilis by transformation. The parental plasmids used had been introduced into B. subtilis from Staphylococcus aureus by transformation. Of the seven recombinant plasmids constructed using restriction endonucleases, one was made using EcoRI, another using Hpa II, and five with Xba I (from Xanthomonas badrii), demonstrating the utility of the latter enzyme for molecular cloning experiments. Although all of the recombinant plasmids we have made replicate and express their antibiotic resistance characters, three of them have suffered a loss of DNA, either in vitro or, more likely, in vivo. The deletion event in all cases involved one of the two termini used to join the parental plasmids. The plasmid chimeras reported in this paper should prove useful for the study of plasmid replication, incompatibility, and recombination. In addition, the utility of the B. subtilis system for molecular cloning has been clearly illustrated.
Probability of founder effect in a tribal population.
Authors: Thompson E A , Neel J V
Published: May 2006

When an unusually high frequency of an allele is encountered in a population, "founder effect" is often invoked as an explanation. As usually used, the term implies the disproportionate increase through chance (rather than selection) of an allele contributed to the population by a particular ancestor. While genetic theory leaves no doubt this is a possible explanation, problems arise when we try to determine how likely this explanation is for any specific finding in any specific, finite population, i.e., just how rare is this rare event? In this communication we consider the question in the context of Amerindian tribal populations, deriving specific probabilities under defined conditions. Our interest in the question has been whetted by the finding to date of some eight possible examples of a founder effect in studies of twelve different tribes.
Sequence of a mouse germ-line gene for a variable region of an immunoglobulin light chain.
Authors: Tonegawa S , Maxam A M , Tizard R , Bernard O , Gilbert W
Published: May 2006

We have determined the sequence of the DNA of a germ-line gene for the variable region of a mouse immunoglobulin light chain, the VlambdaII gene. The sequence confirms that the variable region gene lies on the DNA separated from the constant region. Hypervariable region codons appear in the germ-line sequence. A sequence for the hydrophobic leader, 19 amino acids that are cleaved from the amino terminus of the protein, appears near, but not continuous with, the light chain structural sequence: most of the leader sequence is separated from the rest of the gene by 93 bases of untranslated DNA.
mRNA-dependent synthesis of a glycosylated subunit of human chorionic gonadotropin in cell-free extracts derived from ascites tumor cells
Authors: Bielinska Malgorzata , Boime Irving
Published: May 2006

Protein synthesized in ascites cell-free extracts in response to first trimester placental mRNA was immunoprecipitated with antisera directed against the α subunit of human chorionic gonadotropin. The immunoprecipitable proteins were resolved on sodium dodecyl sulfate/polyacrylamide slab gels. In membrane-depleted extracts placental mRNA directed the synthesis of the “preprotein” form of the α subunit. However, when membranes were added to the cell-free extracts a protein migrating more slowly than pre-α subunit was observed. This protein was specifically adsorbed to a concanavalin A column, and its migration on sodium dodecyl sulfate gels was enhanced after treatment with α-mannosidase (EC 3.2.1.24) or endo-β-
N
-acetylglucosaminidase C
II
or H. Similar results were obtained when mRNA was translated in lysates derived from first trimester placenta instead of in ascites cell extracts. Kinetic studies of the glycosylation reaction revealed that sugar attachment can occur just prior to release of the protein. These data show that the apoprotein of the α subunit can be glycosylated
in vitro
. The data also suggest that the glycosylated protein contains a sugar core consisting of di-
N
-acetylchitobiose and at least four mannose residues, some of which are α-linked. In addition, it appears that this carbohydrate unit is present in homologous placental membranes as well as in the ascites tumor membranes.
Growth state-dependent phenotypes of adult hepatocytes in primary monolayer culture.
Authors: Leffert H , Moran T , Sell S , Skelly H , Ibsen K , Mueller M , Arias I
Published: May 2006

A proliferation-competent adult rat liver cell monolayer system has been analyzed for tissue-specific functions during its growth cycle. High levels of the adult (L type) form of pyruvate kinase (EC 2.7.1.40) and glutathione S-transferase B ("ligand," EC 2.5.1.18) are observed during the early lag phase; they decline markedly during the logarithmic phase and reappear during the stationary phase. By contrast, elevated levels of the fetal (K type) form of pyruvate kinase and alpha1-fetoprotein production appear only after proliferation begins; this pattern diminishes slightly during stationary phase as the adult phenotype is restored. Albumin production continues throughout the entire growth cycle. These in vitro findings simulate those observed during hepatoproliferative transitions in the intact animal and, as such, constitute a developmental program for normal epithelial cells in primary culture.
Proteases induce secretion of collagenase and plasminogen activator by fibroblasts
Authors: Werb Zena , Aggeler Judith
Published: May 2006

We have observed that treatment of rabbit synovial fibroblasts with proteolytic enzymes can induce secretion of collagenase (EC 3.4.24.7) and plasminogen activator (EC 3.4.21.-). Cells treated for 2-24 hr with plasmin, trypsin, chymotrypsin, pancreatic elastase, papain, bromelain, thermolysin, or α-protease but not with thrombin or neuraminidase secreted detectable amounts of collagenase within 16-48 hr. Treatment of fibroblasts with trypsin also induced secretion of plasminogen activator. Proteases initiated secretion of collagenase (up to 20 units per 10
6
cells per 24 hr) only when treatment produced decreased cell adhesion. Collagenase production did not depend on continued presence of proteolytic activity or on subsequent cell adhesion, spreading, or proliferation. Routine subculturing with crude trypsin also induced collagenase secretion by cells. Secretion of collagenase was prevented and normal spreading was obtained if the trypsinized cells were placed into medium containing fetal calf serum. Soybean trypsin inhibitor, α
1
-antitrypsin, bovine serum albumin, collagen, and fibronectin did not inhibit collagenase production. Although proteases that induced collagenase secretion also removed surface glycoprotein, the kinetics of induction of cell protease secretion were different from those for removal of fibronectin. Physiological inducers of secretion of collagenase and plasminogen activator by cells have not been identified. These results suggest that extracellular proteases in conjunction with plasma proteins may govern protease secretion by cells.
Electrophoretic shift mutants in Chinese hamster ovary cells: evidence for genetic diploidy.
Authors: Siciliano M J , Siciliano J , Humphrey R M
Published: May 2006

Electrophoretic shift mutants induced in Chinese hamster ovary (CHO) cells indicate that these cells not extensively functionally hemizygotic. Therefore, effective haploidy is unsatisfactory as a general theory to explain the frequency of recessive mutants in this cell line. CHO cells were screened for electrophoretic shift variants of enzymes coded by approximately 40 genetic loci. Clones isolated after exposure to ultraviolet radiation were examined by starch gel and Cellogel electrophoresis. Shift variants were recovered for enzymes representing 11 different loci. Variant clones were subcloned to demonstrate the heritability of the variations Mutants at nine loci produced multiple-banded patterns consistent with the patterns expected of genes at loci represented twice (diploid). Chromosome localization of these diploid loci in other mammalian species where they have been mapped, suggests that they represent a random sample of CHO genes. Chromosome analysis of mutant subclones indicated that the variation did not take place in tetraploid cells. The data indicate that the quasi-diploid CHO cells appear only as functionally hemizygous as would be expected of a slightly hypodiploid cell line derived from an organism in which the haploid number is 11.
Adenovirus DNA-directed transcription of 5.5S RNA in vitro.
Authors: Wu G J
Published: May 2006

A cell-free system developed from human KB cells was used to transcribe 5.5S RNA from deproteinized adenovirus DNA in vitro. The cell-free RNA synthesis is dependent upon exogenous templates, ribonucleoside triphosphates, and cell-free postmitochondrial supernatant of human KB cells. The synthesis of 5.5S RNA is inhibited only by high levels of alpha-amanitin; therefore it is carried out by RNA polymerase III. The rate of synthesis was linear for at least 2 hr, indicating reinitiation. The 5.5S RNA synthesized in vitro is similar to the corresponding in vivo RNA in size, sequence, and coding region on adenovirus type 2 DNA. In this report is demonstrated in vitro synthesis of a facsimile of an in vivo transcript directed by deproteinized DNA in a mammalian cell-free postmitochondrial supernatant system.
Butyrate suppression of histone deacetylation leads to accumulation of multiacetylated forms of histones H3 and H4 and increased DNase I sensitivity of the associated DNA sequences.
Authors: Vidali G , Boffa L C , Bradbury E M , Allfrey V G
Published: May 2006

Exposure of HeLa cells to Na butyrate leads to an accumulation of multiacetylated forms of histones H3 and H4. Our studies of histone acetylation in HeLa S-3 cells show that 7 mM butyrate suppresses the deacetylation of histones without influencing the rate of radioactive acetate incorporation. An alteration in nucleosome structure in highly acetylated chromatin is indicated by an increased rate of DNA degradation by DNase I. A close association of acetylated histones with the DNase I-sensitive sequences is confirmed by the finding that histones remaining after limited DNase I digestion are depleted in the multiacetylated forms of histones H3 and H4. DNase I treatment has also been found to selectively release [3H]acetyl-labeled H3 and H4 from avian erythrocyte nuclei under conditions previously shown to preferentially degrade the globlin genes in erthyrocyte chromatin. Our results are consistent with the view that histone acetylation provides a key to the mechanism for altering chromatin structure at the nucleosomal level, and that this may explain the selective DNase I sensitivity of transcriptionally active DNA sequences in different cell types.
Nucleotide sequence of the recognition site for the restriction-modification enzyme of Escherichia coli B.
Authors: Ravetch J V , Horiuchi K , Zinder N D
Published: May 2006

The nucleotide sequence of the recognition site for the restriction-modification enzyme of Escherichia coli B (SB site) has been determined. The recognition site is a 15-nucleotide sequence consisting of the trimer 5'TGA3', followed by an 8-nucleotide domain of variable sequence, which in turn is followed by tetramer 5'TGCT3'. The sequence has no 2-fold rotational symmetry. Single base changes in the constant nucleotide domains result in the loss of sensitivity to both restriction and modification. Our data are also consistent with modification occurring by methylation of two adenine residues per SB site: one on the adenine of the trimer 5'TGA3' and the other on the complementary strand on the adenine complementary to the first thymine of the tetramer 5'TGCT3'. All nine independently isolated spontaneous mutants at the SB1 site of bacteriophage f1 are caused by a G-to-T transversion. Mutations at the SB2 site are caused by various single base changes.