bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytoplasmic microtubules in normal and transformed cells in culture: analysis by tubulin antibody immunofluorescence.
Authors: Brinkley B R , Fuller E M , Highfield D P
Published: May 2006

Monospecific antibody directed against bovine brain tubulin was used as an immunofluorescent probe to evaluate the distribution of microtubules in normal and transformed cells grown in tissue culture. The fluorescent staining pattern of transformed and nontransformed cells is significantly different and may be used in conjunction with other morphological features to identify transformants in mixed cell populations. Normal cells are flattened, elongated, and fibroblastic; they display numerous Colcemid-sensitive fluorescent cytoplasmic filaments, presumably microtubules. Transformed cells, however, are smaller, more polygonal in shape, and contain very few cytoplasmic tubules. During mistosis the cytoplasmic microtubule complex of normal cells completely disappears, but reappears after cell division. Treatment of transformed cells with dibutyry-adenosine 3':5'-cyclic monophosphate plus testosterone or theophylline restores the normal fibroblastic appearance of the cells and stimulates the assembly of numerous cytoplasmic microtubules. This study provides further evidence for two separate microtubule entities in cycling nontransformed cells: a cytoplasmic microtubule complex and the microtubules of the mitotic spindle. Although an interchange of tubulin dimers seems to exist between microtubules in the two systems, control of tubule assembly may be under separate constraints. Stimulation of cytoplasmic microtuble assembly in transformed cells by derivatives of adenosine 3':5'-cycle monophosphate suggests that impairment of the cytoplasmic microtubule complex in these cells may be due to suboptimal levels of adenosine 3':5'-cyclic monophosphate.
Virus-specific neutralization by a soluble non-immunoglobulin factor found naturally in normal mouse sera.
Authors: Levy J A , Ihle J N , Oleszko O , Barnes R D
Published: May 2006

A low-molecular-weight substance found naturally in mouse serum neutralizes mouse xenotropic C-type virus. It has no effect on endogenous ecotropic viruses. This neutralizing factor does not belong to the known immunogloblin classes, and its activity is not associated with the antivirus immunoglobulins that can be detected by radioimmunoprecipitation. Preparations of xenotropic virus absorb out this neutralizing activity in mouse sera. The specificity of this factor for X-tropic virus suggests that it represents a newly recognized type of response of the host to an endogenous virus. Its possible role in the regulation of endogenous C-type viruses is considered.
H-2 gene complex restricts transfer of delayed-type hypersensitivity in mice.
Authors: Miller J F , Vadas M A , Whitelaw A , Gamble J
Published: May 2006

Sensitized lymphocytes can transfer a state of delayed-type hypersensitivity to soluble protein antigens to naive mice only if donor and recipient share the I-A region of the H-2 gene complex. Identity at the K or D region is not essential. The restriction is unlikely to result from ineffective homing of the injected cells or from their early destruction. It is thought to reflect a requirement for an Ir-gene controlled mechanism which governs effective interaction between sensitized T lymphocytes and antigen presented on the surface of macrophages.
Activation of antibody Fc function by antigen-induced conformational changes.
Authors: Brown J C , Koshland M E
Published: May 2006

IgM antibody directed against the pheny-beta-lactoside hapten was examined for its capacity to fix complement in the presence of the hapten, monohapten-substituted antigen, and multihapten-substituted antigen. Hapten was found to have no effect; monovalent antigen induced an excellent response which could be inhibited by hapten; and multivalent antigen also induced an excellent response which was related to the number of determinants added and not to the formation of antigen-antibody aggregates. The difference between the activities of hapten and monovalent antigen was reflected in their affinities for the IgM antibody. The monovalent antigen had a lower Ka, indicating that energy from binding was used to activate the Fc complement binding sites. These data show that the expression of IgM Fc function depends on a change in Fc conformation produced by the binding of antigen at the distant Fab combining sites.
Porphyria variegata and porphyria cutanea tarda in siblings: chemical and genetic aspects.
Authors: Watson C J , Cardinal R A , Bossenmaier I , Petryka Z J
Published: May 2006

A woman aged 54 was studied because of a severe acute porphyric (neurologic) relapse with clinical and chemical findings characteristic of porphyria variegata. During a family survey, her brother, aged 59, was found to have chemical abnormalities typical of porphyria cutanea tarda, without suggestion of neurologic manifestations. He had mild skin changes compatible with either of these forms of porphyria. The sister exhibited the protocoproporphyria of porphyria variegata, together with a large amount of fecal "x" porphyrin fraction, without demonstrable isocoproporphyrins. The brother had a uro-isocopro-type of porphyria in accord with the diagnosis of porphyria cutanea tarda, and quite at variance with the sister's findings. This occurrence of porphyria variegata and porphyria cutanea tarda in siblings is thus far unique. Certain hypotheses are considered in respect to genetic aspects of the differing prophyrias in this sibling pair.
Separation of 1-acylglycerolphosphate acyltransferase and 1-acylglycerolphosphorylcholine acyltransferase of rat liver microsomes.
Authors: Yamashita S , Nakaya N , Miki Y , Numa S
Published: May 2006

1-Acylglycerolphosphate acyltransferase (Ec 2.3.1-) and 1-acylglycerolphosphorylcholine acyltransferase (EC 2.3.1.23) of rat liver microsomes were separated from each other. The separation was achieved by sucrose density gradient centrifugation of the enzyme preparation that was obtained by solubilizing microsomes with a nonionic detergent, Triton X-100, and subjecting the solubilized microsomes to molecular-sieve chromatography. The two acyltransferases are distinguishable from each other also with respect to their stabilities to heat and to Triton X-100. Hence, it is concluded that these acyltransferases are distinct enzymes. These results, together with our previous finding that glycerolphosphate acyltransferase is also a separate enzyme, demonstrate the presence of distinct acyltransferases responsible for the acylation of the different acyl acceptors. Furthermore, the acyl-donor specificities of these acyltransferases provide the enzymatic basis for the nonrandom distribution of fatty acids in naturally occurring glycerolipids.
Quantitation of the sensory response in bacterial chemotaxis.
Authors: Spudich J L , Koshland D E
Published: May 2006

A quantitative assay for the stimulus-response relationship in bacterial chemotaxis has been developed by measurement of tumble frequency. Application of the assay has shown an additive relationship between changes in receptor occupancy and recovery times. Tumble suppression is related to the change in receptor occupancy and not to its rate of change. The results can be explained in terms of varying levels of a tumble regulator.
Preferential and cooperative binding of histone I to chromosomal mammalian DNA.
Authors: Renz M
Published: May 2006

There is a strong preferential binding of histone I to lymphocyte DNA as compared to Escherichia coli DNA when large DNA fragments (2 times 10-6 daltons) are used. The binding of histone I to lymphocyte DNA and to E. coli DNA is cooperative. The distribution of preferential binding sites has been investigated on fragmented DNA. Most of the 2 times 10-6 dalton fragments were found to have at least one preferential histone I binding site, whereas most of the 2 times 10-5 dalton fragments have none.
Isolation of nuclear pore complexes in association with a lamina.
Authors: Aaronson R P , Blobel G
Published: May 2006

Nuclear pore complexes have been isolated in association with a 150 A thick lamina by detergent and salt fractionation of nuclear envelopes from rat liver. The pore complexes exhibit characteristic morphology and appear to be attached in a highly specific orientation to the lamina, which extends over relatively large areas. The pore complex-lamina fraction is composed of three major and several minor polypeptides with little or no DNA, RNA, or phospholipid. It is suggested that the association of the pore complexes and the lamina reflects the structural arrangement of the nuclear periphery in vivo.
Host induced alteration of avian sarcoma virus B-77 genome.
Authors: Shoyab M , Markham P D , Baluda M A
Published: May 2006

The genome of an avian oncornavirus was altered after infection of a heterologous host. This was studied with avian sarcoma virus B-77 in duck embryonic fibroblasts (DEF) and chicken embryonic fibroblasts (CEF). To detect alteration of the viral genome, we hybridized 35S B-77 RNA with normal duck DNA by either one of two techniques:when viral RNA was in excess and when DNA was in excess. The RNA of B-77 passaged only in gs minus chf minus CEF does not have homology with duck DNA. However, after several passages of B-77 through DEF the viral genome acquired duck specific RNA sequences. After 4 and 10 passages, B-77 RNA acquired 2.2 and 6.6%, respectively, complementarity to normal duck DNA. The duck specific RNA sequences were found to be covalently linked to the B-77 RNA genome. Also, the host specific sequences acquired by the virus appear to be from a region of the duck DNA which is repeated four to six times per cell. After 5 back passages in CEF some of the duck specific RNA sequences in the viral genome were lost.
Interspecies brain antigen detected by naturally occurring mouse anti-brain autoantibody.
Authors: Martin S E , Martin W J
Published: May 2006

Normal mouse sera contain naturally occurring antibodies that are cytotoxic in the presence of rabbit complement for NB1, a cell line derived from a neuroblastoma adrenal metastasis of a spontaneous ovarian teratoma. The anti-NB1 antibodies can be specifically removed from normal mouse sera by absorption of the sera with homogenized brain tissue of mouse, rat, guinea pig, chicken, and man and by homogenized kidney tissue of mouse and man. The antigen recognized by anti-NB1 naturally occurring autoantibodies, designated mouse brain antigen-2 (MBA-2), is not present on other normal tissues or tumor cell lines tested. MBA-2 is distinct from previously described mouse brain antigens.
Integrative recombination of bacteriophage lambda DNA in vitro.
Authors: Nash H A
Published: May 2006

An in vitro system for the production of integrative recombinant DNA of bacteriophage lambda is described. The in vitro recombination mimics the in vivo integration of viral DNA into host DNA in its requirement for int gene product, for the presence of a thermolabile component, and for the limitation of the recombination to a pair of specialized sites (attachment sites) on the DNA. The enzymes are extracted from Escherichia coli containing phage lambda gene products. The substrate is the DNA from lambda-attB-attP, a phage variant that contains two attachment sites on the same chromosome. The product is a recombinant phage chromosome that has lost the DNA between the attachment sites. The parental and recombinant DNA are distinguished following transfection to mature phage in spheroplasts. The reaction requires ATP, Mg++, spermidine, and a monovalent cation. Recombination occurs preferentially between attachment sites on the same molecule. The enzymatic activity is completely inhibited by extracts containing xis gene product.
RNA-directed DNA polymerase from human leukemic blood cells and from primate type-C virus-producing cells: high- and low-molecular-weight forms with variant biochemical and immunological properties.
Authors: Mondal H , Gallagher R E , Gallo R C
Published: May 2006

RNA-directed DNA polymerase (reverse transcriptase) from leukocytes of individual leukemic patients can be grouped by velocity gradient analyses into two distinct classes, a low-molecular-weight (LMW) class of approximately 70,000 and a high-molecular-weight (HMW) class of 130,000 to 140,000. The reverse transcriptases from mammalian type-C viruses have with one exception (see text) been isolated as enzymes with molecular weights of 70,000. In this study, the reverse transcriptase from extracellular gibbon ape leukemia virus was also isolated only as the LMW class. However, the enzyme from gibbon virus-producing cells was isolated partially in the HMW form; this form was converted completely to the LMW form by treatment with 0.5 M KC1 and 0.5% Triton X-100 and could be re-converted to the HMW form by lowering the KC1 and Triton X-100 concentrations. A similar conversion from a HMW form to a LMW form was demonstrated with enzyme from human leukemic cells. The LMW form of the human and gibbon ape cellular enzymes utilized synthetic primer-templates in a similar fashion to viral enzyme, and this form was strongly inhibited by antisera (IgG) to reverse transcriptase from simian (woolly monkey) type-C virus. The HMW form of both enzymes utilized synthetic primer-templates less efficiently than the LMW form, and was resistant to inhibition by antipolymerase IgG of simian type-C virus. The HMW form of the cellular reverse transcriptases transcribed viral 70S RNA in the absence of synthetic primer relatively more efficiently than did the extracellular viral form. These data suggest that the HMW form is due in part to aggregation of the LMW form and in part to a cellular factor(s) which may affect both the form and function of intracellular reverse transciptase.
Definitive evidence that the murine C-type virus inducing locus Akv-1 is viral genetic material.
Authors: Chattopadhyay S K , Rowe W P , Teich N M , Lowy D R
Published: May 2006

DNA of the AKR mouse contains a set of murine leukemia virus sequences that are not present in DNA of the NIH Swiss mouse. NIH mice partially congenic for the AKR murine-leukemia-virus-inducing locus Akv-1 contain this set of sequences, and, in a three-point cross segregating for Akv-1 on an NIH background, the sequences segregated with Akv-1. It is concluded that the Akv-1 locus contains viral sequences.
Inhibition of Balbiani ring RNA synthesis at the initiation level.
Authors: Egyházi E
Published: May 2006

The nucleoside analogue 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, a selective inhibitor of heterogeneous chromosomal RNA synthesis in salivary gland cells of the midge Chironomus tentans, blocks the initiation of transcription in Balbiani rings 1 and 2. The analogue seems to be without appreciable effect on the elongation of growing RNA chains and allows finished molecules to be detached from the chromosomal sites. The RNA chain growth rate, based on measurements of the time required for completion of synthesis of Balbiani ring 1 and 2 RNA molecules after addition of the inhibitor, was estimated to be around 25 nucleotides per second at 18 degrees.
Immunoreactive somatostatin is present in discrete cells of the endocrine pancreas.
Authors: Dubois M P
Published: May 2006

A discrete population of cells of the endocrine pancreas contains immunoreactive somatostatin as shown by immunofluorescence. These cells are different from those containing glucagon or insulin. This unexpected observation may be of physiopathological significance in the regulatory mechanisms involved in the secretion of glucagon and insulin.
Phenylalanyl-tRNA synthetase from baker's yeast: role of 3'-terminal adenosine of tRNA-Phe in enzyme-substrate interaction studied with 3'-modified tRNA-Phe species.
Authors: Von Der Haar F , Gaertner E
Published: May 2006

TRNA-Phe species from baker's yeast modified at the 3'-terminus in many cases are phenylalanylatable substrates. Out of several tRNA-Phe species possessing a modified 3'-end that cannot be phenylalanylated, only two, tRNA-Phe-C-C-2'dA and the tRNA-Phe-C-C-formycin-oxi-red, are strong competitive inhibitors for tRNA-Phe-C-C-A during phenylalanylation. In the ATP/PPi exchange, both these inhibitors reduce Vmax to about 25%; but whereas tRNA-Phe-C-C-2dA has no influence on KmATP and Km Phe during ATP/PPi exchange, tRNA-Phe-C-C-formycin-oxi-red reduces KmATP from 1430 muM, found in the absence of tRNA-Phe, to 230 muM, and Km-Phe, from 38 to 14 muM. The values found in the presence of tRNA-Phe-C-C-formycin-oxi-red during ATP/PPi exchange are identical with those determined in the phenylalanylation of tRNA-Phe-C-C-A. All other tRNA-Phe species carrying a modified 3'end that cannot be phenylalanylated exhibit a mixed competitive-noncompetitive inhibition in the phenylalanylation reaction. In the ATP/PPi exchange, they do not influence KmATP and KmPHE and only weakly, if at all, Vmax. The results show that the 3'adenosine of tRNA-Phe cannot solely be a passive acceptor for phenylalanine, but must in addition play an active role during enzyme-substrate interaction. The data can be consistently explained by the hypothesis that the 3'-adenosine of tRNA-Phe triggers a conformational change of the enzyme.
Variants of a mouse myeloma cell line that synthesize immunoglobulin heavy chains having an altered serotype.
Authors: Preud'Homme J L , Birshtein B K , Scharff M D
Published: May 2006

Cells of the MPC-11 mouse myeloma cell line, which produces an IgG2b immunoglobulin, were subjected to mutagenesis with Melphalan or with ICR-191, after which they were cloned in soft agar. Approximately 0.5 percent of the clones produced altered heavy chains that: (i) were the same size as or larger than the parent; (ii) no longer recognized by antibody specific for the parent gamma2b subclass; (iv) were recognized by antibody against the Fab (NH2-terminal half) of the parental immunoglobulin, but lacked some of the antigenic determinants of the Fc (COOH-terminal half) of the heavy chain; (v) lacked many of the tryptic/chymotryptic peptides found in the parent; (vi) contained tryptic/chymotryptic peptides that were not present in the parent but were present in an unrelated gamma2a myeloma heavy chain; and (vii) assembled with light chains by a pathway typical of IgG2a myelomas.
Locus on human X chromosome for dihydrotestosterone receptor and androgen insensitivity.
Authors: Meyer W J , Migeon B R , Migeon C J
Published: May 2006

We have studied androgen binding characteristics of cells for androgen insensitivity from an obligate heterozygote, who is the mother of three male pseudohermaphrodites with dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one) receptor deficiency. Specific dihydrotestosterone binding by skin fibroblasts from her wrist and pubis is within the normal range and indicates that androgen insensitivity is X-linked in man and is therefore homologous to the tfm locus in the mouse. A significant population of clones from the heterozygote has deficient receptor activity, and this finding is compatible with inactivation of one X-linked allele at this locus. Our results indicate the presence of a gene on the human X chromosome that is essential for normal male sexual differentiation and provide further evidence for homology between X chromosomes of all mammals.
Localized Derepression on the Human Inactive X Chromosone in Mouse-Human Cell Hybrids.
Authors: Kahan B , DeMars R
Published: May 2006

Evidence for derepression of the gene for hypoxanthine phosphoribosyltransferase (HPRT; IMP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) on the human inactive X chromosome was obtained in hybrids of mouse and human cells. The mouse cells lacked HPRT and were also deficient in adenine phosphoribosyltransferase (APRT; AMP: pyrophosphate phosphoribosyltransferase; EC2.4.2.7). The human female fibroblasts were HPRT-deficient as a consequence of a mutation on the active X but contained a normal HPRT gene on the inactive X. The two human X chromosomes were further distinguished by differences in morphology: the inactive X was morphologically normal while the active X included most of the long arm of autosome no. 1 translocated to the distal end of the X long arm. Forty-one hybrid clones were first isolated by selection for the presence of APRT; when these clones were selected for HPRT, six of them yielded derivatives having human HPRT with incidences of about 1 in 10-6 APRT-selected hybrid cells. The HPRT-positive derivatives contained a normal-appearing X chromosome indistinguishable from the inactive X of the parental human fibroblasts. The active X with the translocation was not found in any of the HPRT-positive hybrid cells. Human phosphoglycerokinase (ATP:3-phospho-D-glycerate 1-phosphotransferase. EC 2.7.2.3) and glucose-6-phosphate dehydrogenase (D-glucose 6-phosphate: NADP 1-oxidoreductase, EC 1.1.1.49), which are specified by X-chromosomal loci, were not detected in the hybrids expressing HPRT even though they contained an apparently intact X chromosome. The observations are most simply explained by the infrequent, stable derepression of inactive X chromosome segments that include the HPRT locus but not the phosphoglycerokinase and glucose-6-phosphate dehydrogenase loci.
Immunological and chemical purity of papain-solubilized HL-A antigens.
Authors: Parham P , Terhorst C , Herrmann H , Humphreys R E , Waterfield M D , Strominger J L
Published: May 2006

Three preparations of purified papain-solublized HL-A antigens have been radiolabeled by reductive methylation using formaldehyde and potassium boro[3H]hydride, and their reaction with specific HL-A antisera has been investigated. Greater than 99 percent of the radioactivity in the [3H]HL-A2 preparation could be complexed with several HL-A2 antisera, but not with specificity controls. The other two preparations, which contained mixtures of HL-A antigenic specificities (HL-A7,12 an HL-A3,W25;12,27), showed 63 per cent and 70 per cent complex formation with mixtures of the appropriate HL-A antisera. The N-terminal amino acid of both subunits has been determined for the three HL-A antigen preparations. In all cases the only detectable N-terminal amino acids were isoleucine for the small subunits, beta-2-microblogulin, and glycine for the larger subunit.
Functional intermediates in reaction of cytochrome oxidase with oxygen.
Authors: Chance B , Saronio C , Leigh J S
Published: May 2006

The development of a low temperature kinetic method for the flash photolysis of the compounds of membrane-bound cytochrome a3 with carbon monoxide in the presence of oxygen affords evidence for three categories of functional intermediate compounds of cytochrome a3 and oxygen. The three classes are identified as follows: Compounds of Type A are considered to be "oxy" compounds of the ferrous heme. They have the composition a3-2+. O2. Compounds of Type B are considered to be peroxide compounds (CU-2+A3-3+ O-2= or CU-2+A3-3+ O2H2) or the equivalent heme Fe-Cu peroxide bridge structures. Compounds of Type C are formed from the ferricyanide pretreated oxidase and may involve higher oxidation states of the heme iron such as quadrivalent iron, and peroxide. Kinetic and equilibrium studies show these compounds to be functional in oxygen reduction in the sequence A yields B yield cytochromes a, c, c1, etc.
Assignment of gene(s) for cell transformation to human chromosome 7 carrying the simian virus 40 genome.
Authors: Croce C M , Koprowski H
Published: May 2006

Somatic cell hybrid clones between either C57BL/6 or Balb/c mouse peritoneal macrophages and two different simian virus 40 (SV40)-transformed human cell lines deficient in hypoxanthine phosphoribosyltransferase (EC 2.4.2.8; IMP:pyrophosphate phosphoribosyltransferase) were obtained in hypoxanthine-aminopterin-thymidine selective medium. All the hybrid cell clones contained the human chromosome 7, which carries the SV40 genome, and were SV40 tumor (T)-antigen positive. No hybrid cell clones studied displayed the density-dependent inhibition of cell growth characteristic of normal cells; all clones had a high saturation density and gave origin to cell colonies when plated in soft agar. Since the expression of the transformed phenotype was always associated with the presence of the human chromosome 7, which carries the SV40 genome, it is concluded that this chromosome contains gene(s) [Tr gene(s)] coding for "transforming factor(s)."
Human gene expression in rodent cells after uptake of isolated metaphase chromosomes.
Authors: Burch J W , McBride O W
Published: May 2006

Permanent transfer of genetic information from chromosomes isolated from human diploid cells to recipient cells has been demonstrated. Human metaphase chromosomes were incubated with mouse A9 fibroblasts deficient in hypoxanthine phosphoribosyltransferase (IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) and adenine phosphoribosyltransferase (AMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.7). Colonies of cells containing hypoxanthine phosphoribosyltransferase appeared during growth in a selective medium. The hypoxanthine phosphoribosyltransferase gene product in four independent colonies was identified as human donor species by both gel electrophoresis and isoelectric focusing; hence these colonies did not result from reversion of ta9 parental cells. Other X-linked human genes, glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate:NAD(+) 1-oxidoreductase, EC 1.1.1.49) and phosphoglycerate kinase (ATP:3-phospho-D-glycerate 1-phosphotransferase, EC 2.7.2.3), were not expressed in these same colonies. Dissociation of expression of these X-linked genes probably results from chromosomal fragmentation during uptake, but other mechanisms have not been excluded.
Reversible, coenzyme-A-mediated inactivation of biosynthetic condensing enzymes in yeast: a possible regulatory mechanism.
Authors: Tracy J W , Kohlhaw G B
Published: May 2006

alpha-Isopropylmalate synthase [3-hydroxy-4-methyl-3-carboxyvalerate 2-oxo-3-methylbutyrate-lyase (CoA-acetylating); EC 4.1.3.12], the enzyme catalyzing the first committed step in leucine biosynthesis, and homocitrate synthase [3-hydroxy-3-carboxyadipate 2-oxoglutarate-lyase (CoA-acetylating); EC 4.1.3.21], the first enzyme in lysine biosynthesis in yeast, are rapidly inactivated in the presence of low concentrations of coenzyme A, a product of both reactions. Closely related compounds like 3-dephospho-coenzyme A or oxidized coenzyme A are almost without effect, as are other sulfhydryl compounds. Citrate (si)-synthase [citrate oxaloacetate-lyase (pro-3S-CH2-COO-minus leads to acetyl-CoA); EC 4.1.3.7] appears to be completely resistant against inactivation by coenzyme A. Inactivated alpha-isopropylmalate and homocitrate synthases can be reactivated by dialysis, but not by adding excess substrate. Protection against coenzyme-A-mediated inactivation is provided by relatively high concentrations of the alpha-ketoacid substrate or the specific end product inhibitor of each of the two enzymes. The coenzyme-A-mediated inactivation of alpha-isopropylmalate synthase has been more closely investigated. It requires the presence of divalent metal ions, with Zn++being most effective. The inactivation does not require molecular oxygen. It occurs in the presence of low concentrations of substrates and is observed in toluene-treated cells. These results, together with evidence that alpha-isopropylmalate synthase and homocitrate synthase are located in the mitochondria, suggest a mechanism by which increasing intra-mitochondrial coenzyme A concentrations might serve as a signal of decreasing acetyl-coenzyme A levels, triggering a temporary inactivation of biosynthetic acetyl-coenzyme A-consuming reactions in order to channel the available acetyl-coenzyme A into the citrate cycle.
Simian virus 40 DNA directs synthesis of authentic viral polypeptides in a linked transcription-translation cell-free system.
Authors: Roberts B E , Gorecki M , Mulligan R C , Danna K J , Rozenblatt S , Rich A
Published: May 2006

A linked cell-free system has been developed which is capable of transcribing and translating mamalian viral DNA, and its characteristics and requirements are outlined. In this system, simian virus 40 (SV40) DNA Form I (supercoiled) directed the synthesis of discrete polypeptides up to 85,000 daltons in size. One of these products was indistingusihable from authentic major virus capsid protein VPI, as judged by mobility on sodium dodecyl sulfate/polyacrylamide gels, antibody predipitation, and peptide analyses. The cell-free products larger than VPI comprised a number of polypeptides ranging in molecular weight from 50,000 to 85,000. These polypeptides demonstrated no immunological relationship whatsoever to the structural protein VPI. However, two of these products, along with one of approximately 25,000 dlatons, were precipitated with antiserum to SV40 tumor antigen. Linear SV40 DNA generated by the cleavage of Form I DNA with the restriction endonuclease EcoR1 was an efficient template in this system and also directed the synthesis of a polypeptide migrating with VPI on polyacrylamide gels. The potential of this system for defining a functional map of a DNA genome is discussed.
Increased particulate and decreased soluble guanylate cyclase activity in regenerating liver, fetal liver, and hepatoma.
Authors: Kimura H , Murad F
Published: May 2006

We determined the activities of soluble and particulate guanylate cyclase [GTP pyrophosphatelyase (cyclizing); ?EC 4.6.1.2] IN REGENERATING RAT LIVER, FETAL AND NEONATAL RAT LIVER, AND HEPATOMA. TIn these tissues we found increased particulate and decreased soluble enzyme activities compared to normal adult rat liver. The particulate activity increased 12 hr after partial hepatectomy, reached maximal activity at 48 hr, and then declined. The soluble enzyme activity decreased within 8 hr and continued to decline. The activity of homogenates did not change. Guanylate cyclase activity was increased in plasma membrane and microsome fractions from regenerating liver. The increase in particulate activity was prevented with cycloheximide. Decreased soluble and increased particulate enzyme activities were found in fetal liver. After birth the soluble activity increased and the particulate activity decreased. Seven to 14 days after birth the activities of soluble and particulate fractions were similar to those of adult rat liver. In hepatoma 3924A, the activity of particulate guanylate cyclase was 9-fold greater and that of the soluble enzyme was 50% that of normal liver. These studies suggest that guanylate cyclase activity and its subcellular distribution may be related to liver growth through some unknown mechanism.
Proposed mechanism of bacteriophage lambda induction: acquisition of binding sites for lambda repressor by DNA of the host.
Authors: Sussman R , Zeev H B
Published: May 2006

Interference with the in vitro binding of lambda phage repressor to lambda operator DNA was observed when Escherichia coli DNA containing the following lesions was present in the reaction mixture: (a) DNA with single-strand breaks from pancreatic DNase (nicked DNA); (B) DNA isolated from thymine-straved cells; (c) DNA from ultraviolet-treated cells; (d) DNA of mitomycin-treated cells; and (e) DNA from a temperature-sensitive ligase mutant after 1 hr at 42 degrees. Normal E. coli DNA did not interfere. Binding of lambda cIing-minus repressor to operator DNA was not affected by E. coli DNA with lesions. DNAs from cells treated with increasing doses of mitomycin were proportionately more effective in competition for repressor, suggesting increasing binding sites per unit of DNA. A general model of virus induction is proposed, based on binding affinity of ultraviolet-sensitive repressors for single-strand breaks in the host DNA. The model is extended also to the presumptive repressor of cell division.
Kinetics of steroid induction and deinduction of tyrosine aminotransferase synthesis in cultured hepatoma cells.
Authors: Steinberg R A , Levinson B B , Tomkins G M
Published: May 2006

The specific rate of synthesis of tyrosine aminotransferase (EC 2.6.1.5; L-tyrosine:2-oxoglutarate aminotransferase) is used as a measure of the level of functional, cytoplasmic, tyrosine aminotransferase-specific mRNA in cultured rat hepatoma cells. An analysis of the kinetics of change in this rate after the addition or withdrawal of glucocorticosteroids sets an upper limit on the half-life of the enzyme-specific mRNA of 1-1.5 hr, whether or not steroid is present. The inactivation rate of the enzyme mRNA is independent of the growth condition of the cells, occuring equally rapidly in the presence or absence of serum or insulin, both of which induce tyrosine aminotransferase in these cells. The implications of these results for the mechanism of steroid induction are discussed.
Mucopolysaccharides associated with nuclei of cultured mammalian cells.
Authors: Bhavanandan V P , Davidson E A
Published: May 2006

Mucopolysaccharides have been isolated, fractionated, and characterized from the nuclei of cultured B16 mouse melanoma cells grown in the presence of (3-H)-glucosamine and (35-S)sulfate. Digestion of the nuclei with DNase followed by Pronase gave a mixture of complex carbohydrates from which the mucopolysaccharides were isolated by precipitation with cetylpyridinium chloride. After fractionation by differential salt extraction and chromatography on controlled pore glass bead columns, the components were identified by chemical and enzymatic methods. The major polysaccharide components were a family of high-molecular-weight chondroitin sulfates with different degrees of sulfation; a minor component has been characterized as heparan sulfate.
Somatic rearrangement of chromosome 14 in human lymphocytes.
Authors: McCaw B K , Hecht F , Harnden D G , Teplitz R L
Published: May 2006

Ataxia-telangiectasia is a rare genetic disorder associated with immune deficiency, chromosome instability, and a predisposition to lymphoid malignancy. We have detected chromosomally anomalous clones of lymphocytes in eight patients with this disorder. Chromosome banding disclosed that the clones are consistently marked by structural rearrangement of the long arm (q) of chromosome 14. A translocation involving 14q was found in clones obtained from seven of the eight patients whereas a ring 14 chromosome was found in a clone obtained from the other. These findings as well as data obtained by others for patients with ataxia-telangiectasia suggest that structural rearrangement of 14q is the initial chromosomal change in lymphocyte clones of patients with this disorder. Chromosomes of lymphocytes from one of the patients were studied before and after the onset of chronic lymphocytic leukemia. Before leukemia was diagnosed, the patient had a lymphocyte clone with a 14q translocation. This clone appears to have given rise to the leukemic cells. We hypothesize that structural rearrangement of 14q is directly related to abnormal growth of lymphocytes and that it may be a step toward the development of lymphoid malignancies. Increasing evidence, provided by others, for the nonrandom involvement of 14q in African-type Burkitt's lymphoma and other lymphoid neoplasms further strengthens this hypothesis.
DNA synthesis involving a complexes form of DNA polymerase I in extracts of Escherichia coli.
Authors: Hendler R W , Pereira M , Scharff R
Published: May 2006

DNA polymerase I (EC 2.7.7.7; deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase) has been recovered as a complex of about 390,000 molecular weight. The complex displays an ATP-stimulated DNA-synthesizing activity that prefers native to heat-denatured DNA. Genetic evidence indicates that the recBC enzyme is associated with the polymerase in the complex. Preliminary evidence for complexes involving DNA polymerases II and III is also presented.
Use of the adenylate energy charge ratio to measure growth state of natural microbial communities.
Authors: Wiebe W J , Bancroft K
Published: May 2006

Measurement of the adenylate energy charge ratio is proposed as a means of determining the growth state of natural microbial communities and the effect of environmental changes on them. Observations on microbial cultures and on natural microbial populations from the Western North Atlantic Ocean water and from sediments of a costal salt marsh show that energy charge measurements do show the metabolic state of communities as well as species populations.
Conversion of Bacillus subtilis RNA polymerase activity in vitro by a protein induced by phage SP01.
Authors: Duffy J J , Petrusek R L , Geiduschek E P
Published: May 2006

A protein fraction from B. subtilis infected with phage SP01 (fraction LGG) stimulates the activity of RNA polymerase (EC 2.7.7.6; nucleosidetriphosphate:RNA nucleotidyltransferase) core from uninfected bacteria. Fraction LGG contains a protein (P-28, molecular weight 28,000) that is labeled after phage infection and binds tightly to RNA polymerase core at a relatively high ionic strength. B. subtilis RNA polymerase core with bound P-28 has the transcription specificity of the previously purified, phage-modified B-P RNA polymerase; the latter contains two subunits, v-28 and v-13 (molecular weights 28,000 and 13,000, respectively) that are synthesized after phage infection. Both enzymes transcribe SP01 DNA preferentially and direct the asymmetric synthesis of viral middle RNA. P-28, like v-28, binds more tightly to B. subtilis RNA polymerase core than the B. subtilis initiation factor, sigma, at higher ionic strength. We propose that P-28 and v-28 are the same protein. P-28 and, by implication, v-28 suffice to endow the bacterial RNA polymerase core with a novel transcription specificity.
Immunosuppressive Effect of Syngeneic Thymus Cells on Allograft Rejection
Authors: Droege Wulf
Published: May 2006

Transfer of thymus cells from young chickens to syngeneic recipients suppresses the allograft rejection between strains differing at the major histocompatibility (B) locus. Thymus cell transfer in combination with a light whole body irradiation (360 R) prolongs significantly the mean rejection time of skin allografts and leads in a proportion of recipients to long-lasting graft survival (>200 days). Three weeks after the cell transfer, the suppression appears to be antigen specific, as judged by the normal reactivity against third-party skin grafts. From the types of thymus cell preparations that are effective in these experiments, it is inferred that the suppressor cell is a bursa-dependent lymphocyte, which is predominantly found in the young chicken thymus and which is different from B-lymphocytes, B-precursor cells, or graft-versus-host-reactive T-cells.
Dissociation of bovine 6S procarboxypeptidase A by reversible condensation with 2,3-dimethyl maleic anhydride: application to the partial characterization of subunit III.
Authors: Puigserver A , Desnuelle P
Published: May 2006

Bovine 6S procarboxypeptidase A can be dissociated into its three subunits by acylation with dimethyl maleic anhydride. The deacylated subunits are obtained in a largely native form due to instability of the bonds to dimethyl maleate at pH values near neutrality. The seven first residues of subunit III are identical to residues 18-24 of bovine chymotrypsinogen B and very similar with the same residues in bovine chymotrypsinogen A and C (subunit II) and also in proelastase A of the African lungfish. Therefore, this subunit is likely to be a chymotrypsinogen or proelastase-A-like zymogen which has lost the ability to be activated on account of a deletion of the N-terminal residues from half-cystine 1 to valine 17. Like other pancreatic zymogens, subunit III appears to possess a weakly functional active site.
Antigen mobility in membranes and complement-medical immune attack.
Authors: Humphires G M , McConnell H M
Published: May 2006

The complement fixing activity of liposomes containing cholesterol, dimyristoylphosphatidylcholine (or dipalmitoylphosphatidylcholine), and 3 mol % of cardiolipin has been studied as a function of cholesterol concentration by use of human syphilitic serum containing cardiolipin-specific (Wasserman) antibodies. It is found that complement fixation increases rapidly for cholesterol concentrations above 35 mol %. Spin label studies have been used to study the incorporation of cardiolipin in the relatively rigid phase of binary mixtures of cholesterol and dimyristolphosphatidycholine (or dipalmitoylphosphatidylcholine). It is concluded that cardiolipin is included in such a phase of these lipids for cholesterol concentrations above 35 mol %. These results indicate that a relatively rigid lateral distribution of this monovalent antigen in the plane of the membrane facilitates complement fixation and concomitant complement-mediated membrane damage.
Extraction of Renilla-type luciferin from the calcium-activated photoproteins aequorin, mnemiopsin, and berovin.
Authors: Ward W W , Cormier M J
Published: May 2006

Photoproteins, which emit light in an oxygen-independent intramolecular reaction initiated by calcium ions, have been isolated from several bioluminescent organisms, including the hydrozoan jellyfish Aequorea and the ctenophore Mnemiopsis. The system of a related anthozoan coelenterate, the sea pansy Renilla reniformis, however, is oxygen dependent, requiring two organic components, luciferin and luciferase. Previously published indirect evidence indicates that photoproteins may contain a Renilla-type luciferin. We have now extracted in high yield a Renilla-type luciferin from three photoproteins, aequorin (45% yield), mnemiopsin (98% yield), and berovin (85% yield). Photoprotein luciferin, released from the holoprotein by mercaptoethanol treatment and separated from apo-photoprotein by gel filtration, no longer responds to calcium but now requires luciferase and O2 for light production. Photoprotein luciferin is identical to Renilla luciferin with respect to reaction kinetics and bioluminescence spectral distribution. In view of these results, the generally accepted hypothesis that the photoprotein chromophore is a protein-stabilized hydroperoxide of luciferin must be modified. We believe, instead, that the chromophore is free luciferin and that oxygen is bound as an oxygenated derivative of an amino-acid side chain of the protein. We propose the general term "coelenterate luciferin" to describe the light-producing chromophore from all bioluminescent coelenterates and ctenophores.
Absence of histone F1 in a mitotically dividing, genetically inactive nucleus.
Authors: Gorovsky M A , Keevert J B
Published: May 2006

Histones were extracted from macro- and micronuclear chromatin of the ciliated protozoan Tetrahymena pyriformis. Conditions that resulted in macronuclear chromatin containing large amounts of histone F1 yielded micronuclear chromatin in which this histone was absent. Evidence is presented indicating that the absence of F1 from micronuclei is not a preparative artifact and that histone F1 is replaced by other histone fractions. Since micronuclei divide mitotically, while macronuclei divide amitotically, these results suggest that histone F1 and its phosphorylation do not play an indispensable role in the process of mitotic chromosome condensation, in chromosome replication, or in the separation of newly synthesized chromatids.
Association of high-molecular-weight proteins with microtubules and their role in microtubule assembly in vitro.
Authors: Murphy D B , Borisy G G
Published: May 2006

High-molecular-weight components (HMW) specifically associated with microtubule protein purified from porcine brain tissue were separated from tubulin by DEAE-Sephadex ion exchange chromatography. Analysis by viscometry, sedimentation, and electron microscopy of the unfractionated microtubule protein, separated HMW and tubulin fractions, and reconstituted mixtures showed that HMW promoted formation of ring structures at 5 degrees and tubule polymerization at 37 degrees. The HMW reassociated with tubulin and was identified in thin sections as 18.9 x 5.6 nm projections attached to the microtubules with a longitudinal periodicity of 32.5 nm. These studies: (1) indicate that the HMW fraction stimulates microtubule assembly by facilitating the formation of ring structures which are apparently intermediates in polymerization, and (2) demonstrate that the HMW associates with microtubules as a structural component projecting from the surface of the microtubule wall.
New histones found in mature mammalian testes.
Authors: Shires A , Carpenter M P , Chalkley R
Published: May 2006

Two new histones have been found in sexually mature testes of several mammals. The new histones have been identified as a new F1 (TF1) and F2b (TF2b) on the basis of their behavior upon chemical fractionation procedures and electrophoresis at several urea concentrations. The new testis-specific histones are absent in very immature animals and in somatic tissues. However, by day 20, in the rat, the histone pattern is that of the adult, displaying nearly a full complement of TF1 and TF2b. The new histone complement evidently is characteristic of prespermatid germ cells. The degree of evolutionary variations in these histones and in other basic sperm proteins, as detected by change in electrophoretic mobility, appears to be much greater than that seen in somatic histones.
Interaction of lymphocytes with lipid bilayer membranes: a model for lymphocyte-mediated lysis of target cells.
Authors: Henkart P , Blumenthal R
Published: May 2006

Horizontal lipid bilayer membranes were used as a model system to study lymphocyte-mediated killing of target cells. Dinitrophenylated lipid bilayers can physically support dozens of lymphocytes for periods of over one hour without breakage or increasing the electrical conductance of the membrane. However, in the presence of antibody against Dnp, human lymphocytes rapidly induced increases in membrane conductance of several orders of magnitude without membrane breakage. Such ionic permeability increases occurred only when the membrane voluage was positive on the lymphocyte side, as would be the case with a target cell membrane. The lymphocyte and antibody dependence of this conductance increase parallels that observed for lymphocyte killing of antibody-coated target cells. The results are interpreted as evidence that the primary event in lymphocyte killing of antibody-coated target cells is the creation of ion-conducting channels in the target membrane.
Slow growth rate of a deep-sea clam determined by 228Ra chronology.
Authors: Turekian K K , Cochran J K , Kharkar D P , Cerrato R M , Vaisnys J R , Sanders H L , Grassle J F , Allen J A
Published: May 2006

The age of a deep-sea clam, Tindaria callistiformis, from 3803 m depth has been determined by 228Ra (6.7 year half-life) chronology of separated size fractions of a captured population. A length of 8.4 mm is attained in about 100 years. Shells of this size fraction show about 100 regularly spaced bands, indicating that the growth feature may be an annual one.
A topological theorem for nonlinear dynamics in chemical and ecological networks
Authors: Glass Leon
Published: May 2006

A topological theorem is given which places restrictions on the numbers and types of critical points in nonlinear chemical and ecological systems, provided certain stringent conditions on the flows on the boundary of the concentration space are satisfied. The sets of critical points that are found for stable and unstable oscillations, and for competitive exclusion, represent the simplest sets of critical points that satisfy the topological theorem. The restrictions that are imposed on bifurcations of the dynamics are discussed.
The disjunction property implies the numerical existence property
Authors: Friedman Harvey
Published: May 2006

Any recursively enumerable extension of intuitionistic arithmetic which obeys the disjunction property obeys the numerical existence property. Any recursively enumerable extension of intuitionistic arithmetic proves its own disjunction property if and only if it proves its own inconsistency.