bluuebunny/crossref_metadata_2025 huggingface dataset:
Slow reacting substances of anaphylaxis: Identification of leukotrienes C-1 and D from human and rat sources
Authors: Lewis Robert A. , Austen K. Frank , Drazen Jeffrey M. , Clark David A. , Marfat Anthony , Corey E. J.
Published: May 2006

Slow reacting substance(s) of anaphylaxis (SRS-A) was isolated from both human (lung) and rat sources and compared with three synthetic SRS-As of known structure—leukotrienes (LTs) C-1, C-2, and D. Reversed-phase liquid chromatography was used both as a final purification step and a means of comparison of biologically derived and synthetic substances. Two major peaks of SRS-A activity of both rat and human origin corresponded chromatographically with LTC-1 and LTD, respectively, and had equivalent specific activities on the guinea pig ileum. With guinea pig ileum, the specific activities (units/pmol) for synthetic leukotrienes and anaphylactic peaks were (mean ± SEM): synthetic LTC-1, 1.93 ± 0.13; SRS-A
rat
peak I, 1.69 ± 0.43; synthetic LTD, 6.10 ± 1.15; SRS-A
rat
peak II, 7.14 ± 0.51; and SRS-A
hu
peak II, 1.90. Both synthetic LTC-1 and LTD and their SRS-A natural counterparts had a preferential contractile activity on guinea pig peripheral airway compared to central airways and were at least 200 times more active than histamine on peripheral airways on a molar basis. Leukotriene D is the major SRS-A of human lung and accounts for almost all of the biological activity. It likely is formed from leukotriene C-1
in vivo
by an enzymic process of the well-known γ-glutamyltransferase type.
Transport of vesicular stomatitis virus glycoprotein in a cell-free extract.
Authors: Fries E , Rothman J E
Published: May 2006

We describe a cell-free system in which the membrane glycoprotein of vesicular stomatitis virus is rapidly and efficiently transported to membranes of the Golgi complex by a process resembling intracellular protein transport. Transport in vitro is energy-dependent and is accompanied by terminal glycosylation of the membrane glycoprotein (dependent upon UDP-GlcNAc and resulting in resistance to endo-beta-N-acetylglucosaminidase H).
Nucleotide sequence of the bacterial transposon Tn1681 encoding a heat-stable (ST) toxin and its identification in enterotoxigenic Escherichia coli strains.
Authors: So M , McCarthy B J
Published: May 2006

the Escherichia coli heat-stable toxin (ST I) is encoded within a transposon (Tn1681) flanked by inverted repeats of insertion sequence 1 (IS1) [So, M., Heffron, F. & McCarthy, B. J. (1979) Nature (London) 277, 453-456]. By subcloning restriction fragments and by insertion mutagenesis, we located precisely the gene for ST I within the transposon. We determined the complete nucleotide sequence of the central portion of Tn1681 (i.e., that part flanked by IS1) and identified the coding sequence of the toxin. From the nucleotide sequence, we deduced a probable amino acid sequence for ST I. The NH2-terminal portion of the amino acid sequence is extremely hydrophobic and bears a striking resemblance to the signal sequence of the fd phage minor coat protein. By using a subcloned restriction fragment containing the gene for ST I but no IS1 sequences, we determined (i) that the ST toxin with activity assayable in suckling mice (ST I) is genetically distinct from the St toxin assayable in ligated ileal loops (ST II) and (ii) that ST I can be responsible for diarrheal disease in different animals.
Platelet-derived growth factor stimulates activity of low density lipoprotein receptors.
Authors: Chait A , Ross R , Albers J J , Bierman E L
Published: May 2006

Partially purified platelet-derived growth factor stimulates low density lipoprotein binding and degradation in cultured aortic smooth muscle cells of monkeys by increasing the number of available low density lipoprotein receptors. When platelet-derived growth factor was added to quiescent cells, low density lipoprotein binding increased within 4-8 hr. Stimulation of low density lipoprotein receptor activity preceded stimulation of DNA synthesis by platelet-derived growth factor by 8-12 hr. Enhancement of endogenous cholesterol synthesis by platelet-derived growth factor preceded stimulation of low density lipoprotein receptor activity. These findings suggest that the platelet-derived growth factor can increase both the exogenous and endogenous supplies of cholesterol to the cell for its use during cell proliferation.
A specific transcription factor that can bind either the 5S RNA gene or 5S RNA.
Authors: Pelham H R , Brown D D
Published: May 2006

5S ribosomal RNA specifically inhibits transcription of cloned repeating units of 5S DNA in a nuclear extract of Xenopus oocytes. The inhibition can be explained by the interaction of 5S RNA with a transcription factor that binds specifically to a control region located within the 5S RNA gene. This transcription factor is identical to an abundant cytoplasmic protein that is known to be complexed with 5S RNA in immature Xenopus oocytes. Thus the presence of large amounts of this protein in these cells can account for both the high rate of synthesis and the subsequent storage of 5S RNA to ribosome synthesis.
Gamma ray-induced loss of expression of HLA and glyoxalase I alleles in lymphoblastoid cells.
Authors: Kavathas P , Bach F H , DeMars R
Published: May 2006

Gamma rays from a cesium source were used to generate human lymphoblastoid cell line variants that had lost expression of all major histocompatibility complex antigens coded for by a single haplotype. The cell line was heterozygous at the glyoxalase I locus and had the HLA haplotypes HLA-A1, B8, DRw3, and HLA-A2, B5, DRw1. We selected with anti-HLA-B8 antiserum in a population of cells that had been irradiated with 300 R. The incidence of B8-loss variants was 4.1 X 10(-5) on day 5 after irradiation. Analysis of variants showed that expressions of HLA and GLO alleles trans to B8 were retained. However, expression of additional cis-linked HLA and GLO gene products was lost in 12 of 17 variants. Variants that had lost expression of (i) HLA-B8, (ii) HLA-B8, A1, (iii) HLA-B8, A1, DRw3, or (iv) HLA-B8, A1, DRw3 and the cis-linked glyoxalase I allele were obtained. Karyotype analysis was performed on eight variants that had lost expression of two or more cis-linked alleles. Three variants had two normal appearing no. 6 chromosomes, four variants had a deletion that included the region coding for HLA genes on the short arm of one no. 6 chromosome, and one variant had an inversion or translocation involving the short arm of one no. 6.
Genetic control of murine IgD structural heterogeneity.
Authors: Pollock R R , Dorf M E , Mescher M F
Published: May 2006

Murine B lymphocytes express two native forms of surface IgD: IgDI consists of two delta heavy chains and two light chains; IgDII consists of one heavy chain and one light chain. The relative amounts of IgDI and IgDII present on spleen cells were found to vary significantly among different strains of mice. Genetic evidence demonstrated that the IgDI/IgDII ratio is linked to the Igh-5 allotype. (The delta heavy chain is the product of the Igh-5 locus). Mice bearing the Igh-5e allotype have a low ratio, and mice bearing the Igh-5a or Igh-5b allotype have a high ratio. The Igh-5 locus and the gene controlling the IgDI/IgDII ratio appear to map to the region between the Igh-6 and Igh-V loci.
Switching on the macrophage-mediated suppressor mechanism by tumor cells to evade host immune surveillance.
Authors: Ting C C , Rodrigues D
Published: May 2006

The present study demonstrates a unique mechanism for tumor cell-induced immunosuppression. In the presence of a nonsuppressive dose of tumor cells, generation of cytotoxic T cells in the mixed lymphocyte culture (MLC) is completely suppressed by adding exogenous (peritoneal) macrophages (PM phi) after the initiation of the MLC. This indicates that tumor cells can switch on a suppressor mechanism through host macrophages. It has further been determined that suppression can be induced only if resident (splenic) macrophages (SM phi) are exposed to tumor cells prior to addition of PM phi. If SM phi and PM phi are simultaneously present with the tumor cells, induction of suppression is completely precluded. These findings indicate that switching on of the suppressor mechanism by tumor cells has a critical requirement for the collaboration of two populations of macrophages, SM phi and PM phi, and their presence in a specific sequence (SM phi preceding PM phi). This may represent one of the mechanisms by which tumor cells evade host immune surveillance.
Abnormal net Na+ and K+ fluxes in erythrocytes of three varieties of genetically hypertensive rats.
Authors: De Mendonca M , Grichois M L , Garay R P , Sassard J , Ben-Ishay D , Meyer P
Published: May 2006

Net Na+ and K+ fluxes were measured in Na+-loaded and K+-depleted erythrocytes of three varieties of genetically hypertensive rats. In Okamoto spontaneously hypertensive rats (4 and 10-12 weeks of age), Na+ extrusion was reduced as compared to normotensive controls (Wistar/Kyoto). Na+ extrusion was also reduced in the hypertension-prone substrain of the Hebrew University Sabra rats as compared to the Na+-resistant substrain. K+ fluxes were similar in both groups. In both Okamoto spontaneously hypertensive rats and the hypertension-prone substrain, hypertension was severe and developed rapidly. In the Lyon spontaneously hypertensive rats, in which the blood pressure elevation is less severe than in other genetically hypertensive rats, erythrocyte net Na+ extrusion was the same as in normotensive controls, but net K+ gain was slightly increased. These erythrocyte abnormalities, observed in three varieties of genetically transmitted hypertension of the rat, are in several aspects similar to those previously described in accelerated and benign human essential hypertension. Erythrocyte Na+ and K+ net flux alterations may thus represent biochemical markers of primary hypertension.
Radioimmunoassay of tuberculoprotein derived from Mycobacterium tuberculosis.
Authors: Straus E , Wu N
Published: May 2006

A radioimmunoassay was developed for constituent of the purified-protein derivative obtained from cultures of Mycobacterium tuberculosis. Crossreacting immunoreactive material was detected in cultures of other mycobacterial species, but no immunoreactivity was present in cultures of various fungal and bacterial species. The development of specific radioimmunoassays for tuberculoproteins offers a new research and diagnostic approach.
Correlation between spontaneous metastatic potential, platelet-aggregating activity of cell surface extracts, and cell surface sialylation in 10 metastatic-variant derivatives of a rat renal sarcoma cell line.
Authors: Pearlstein E , Salk P L , Yogeeswaran G , Karpatkin S
Published: May 2006

Several properties of 10 cell lines derived from the polyoma-induced PW20 Wistar-Furth rat renal sarcoma have been examined, including the ability of the tumor cells to metastasize spontaneously from subcutaneous sites in syngeneic hosts, the platelet-aggregating activity of material extracted by urea from the surface of cultured cells, the sialic acid content of the platelet-aggregating material, and the degree of sialylation of cell surface glycoconjugates in cultured cells. A correlation has been observed among all of these parameters. The results suggest a possible link between the degree of cell surface sialylation of tumor cells, their ability to aggregate platelets, and their ability to metastasize.
Comparative airway and vascular activities of leukotrienes C-1 and D in vivo and in vitro.
Authors: Drazen J M , Austen K F , Lewis R A , Clark D A , Goto G , Marfat A , Corey E J
Published: May 2006

The pharmacologic activities of leukotrienes C-1 and D(LTC-1 and LTD), constituents of slow reacting substance of anaphylaxis (SRS-A), were evaluated in vitro on airway contractile tissues and in vivo on pulmonary mechanical function, mean systemic arterial pressure, and cutaneous microcirculation. In vitro both LTC-1 and LTD were potent and selective peripheral airway agonists, being more active than histamine; furthermore, LTD was active on peripheral airways at concentrations 1/100th those of LTC-1. The concentration-effect relationship for LTD and the profile of antagonism by FPL 55712 are consistent with the activity of this molecule at two separate peripheral airway receptors. In vivo, LTC-1 and LTD were nearly equally active in their effects on pulmonary mechanics, and the pattern of alterations was consistent with the predominant site of action being in the lung periphery. Furthermore, both agents had a direct systemic arterial hypotensive effect and were vasoactive on the cutaneous microcirculation. Thus, these compounds are likely to be major mediators of the pathologic alterations in immediate type hypersensitivity reactions in which peripheral airway constriction and hypotension are prominent features.
Genetic control of number of midbrain dopaminergic neurons in inbred strains of mice: relationship to size and neuronal density of the striatum.
Authors: Baker H , Joh T H , Reis D J
Published: May 2006

The activity of tyrosine hydroxylase [TyrHase; tyrosine-3-monooxygenase; L-tyrosine, tetrahydropteridine: oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2] is 20% less in whole midbrain of CBA/J mice than BALB/cJ mice and is paralleled by a comparable difference in the number of dopaminergic neurons in which the enzyme can be detected immunocytochemically. The strain-dependent difference in numbers of TyrHase-containing neurons and of TyrHase activity is not homogeneous in the midbrain but is restricted (along the rostral-caudal axis) to the medial one-third, where almost 2-fold variations are found. The volume of the striatum, a major projection field of midbrain dopamine neurons, is 20% smaller in CBA/J than in BALB/cJ mice; the difference is regional and is concentrated in the caudal half. Because the packing density of intrinsic neurons of the striatum is similar in both strains, CBA/J mice contain 20% fewer neurons than do BALB/cJ mice. The activities of TryHase and of choline acetyltransferase (ChoAcTase; acetyl-CoA:choline-O-acetyltransferase, EC 2.3.1.6) in the whole striatum of CBA/J mice are less than in BALB/cJ. The strain-dependent differences in midbrain TyrHase activity are due to variations in the number of dopamine neurons and directly correlate with differences in the number of striatal cholinergic neurons. There is genetic control of the number of neurons of a neurochemically specific class in the mammalian brain.
Uptake of free choline by isolated perfused rat liver.
Authors: Zeisel S H , Story D L , Wurtman R J , Brunengraber H
Published: May 2006

The uptake of free choline by isolated perfused rat liver was characterized. A saturable uptake mechanism [Ka = 0.17 +/- 0.07 mM (SD); Vmax = 0.84 +/- 0.16 mumol/min X g dry weight] and a nonsaturable mechanism (through which uptake is proportional to choline concentration in the perfusate) were identified. Most of the choline transported into hepatocytes was converted to betaine, phosphorylcholine, or lecithin. Free choline also accumulated within the intracellular space, suggesting that choline oxidase activity does not always limit choline's uptake by the liver.
Targeting of lipid vesicles: specificity of carbohydrate receptor analogues for leukocytes in mice.
Authors: Mauk M R , Gamble R C , Baldeschwieler J D
Published: May 2006

The presence of particular surface carbohydrate modifications is shown to affect dramatically the stability and tissue specificity of unilamellar distearoyl phosphatidylcholine vesicles in mice. Use of the gamma-ray probe 111In3+ permits analysis of tissue distributions by standard gamma counting techniques and determination of the structural integrity of the vesicles by perturbed angular correlation spectroscopy. Addition of a 6-aminomannose derivative of cholesterol to the lipid bilayer produces initial retention of high levels of intact vesicles in the lung after intravenous injection followed by concentration of intact vesicles in the liver and spleen. Vesicles bearing 6-aminosugar residues are found to concentrate in the axillary space in aggregates of polymorphonuclear leukocytes when administered subcutaneously. The in vivo stability of 6-aminomannose-labeled vesicles is substantially greater after intravenous or subcutaneous administration than that observed for any other system examined. The dose-response effects observed with surface modifications indicate that a particular receptor topography is important in the mechanism leading to transport and destruction of these vesicles.
Identification of folate binding protein of mitochondria as dimethylglycine dehydrogenase.
Authors: Wittwer A J , Wagner C
Published: May 2006

The folate-binding protein of rat liver mitochondria [Zamierowski, M. & Wagner, C. (1977) J. Biol. Chem. 252, 933-938] has been purified to homogeneity by a combination of gel filtration, DEAE-cellulose, and affinity chromatography. This protein was assayed by its ability to bind tetrahydro[3H]folic acid in vitro. the purified protein contains tightly bound flavin and has a molecular weight of about 90,000 as determined by sodium dodecyl sulfate electrophoresis. This protein also displays dimethylglycine dehydrogenase [N,N-dimethylglycine: (acceptor) oxidoreductase (demethylating), EC 1.5.99.2] activity which copurifies with the folate-binding activity. It is suggested that the role of the tetrahydrofolic acid is to accept the formaldehyde produced during the course of the reaction.
Primary structure of major outer membrane protein II (ompA protein) of Escherichia coli K-12.
Authors: Chen R , Schmidmayr W , Krämer C , Chen-Schmeisser U , Henning U
Published: May 2006

The amino acid sequence of major outer membrane protein II (ompA protein) from Escherichia coli K-12 has been determined. The transmembrane polypeptide consists of 325 residues, resulting in a molecular weight of 35,159. The transmembrane part of the protein is located between residues 1 and 177. In this part of the protein a predominantly lipophilic 27-residue segment exists that perhaps spans the membrane in a mostly alpha-helical conformation, or a 19-residue stretch of this segment might traverse the membrane linearly. Inside the outer membrane a sequence -Ala-Pro-Ala-Pro-Ala-Pro-Ala-Pro- exists that, analogous to the -Cys-Pro-Pro-Cys-Pro- sequence in the hinge region of immunoglobulin, could assume the conformation of a polyproline helix. Computer analysis did not reveal a clear overall pattern of internal homology in the protein; besides the -Ala-Pro- repeat, only one local area (two adjacent dodecapeptide segments) shows some repetitiveness. The same analysis did not produce evidence for internal homology in the previously determined sequence of outer membrane protein I (porin) nor was any marked resemblance detected between transmembrane proteins I and II.
Hydrophobic basis of packing in globular proteins.
Authors: Rose G D , Roy S
Published: May 2006

The self-assembly of globular proteins is often portrayed as a nucleation process in which the hydrogen bonding in segments of secondary structure is the precondition for further folding. We show here that this concept is unlikely because both the buried interior regions and the peptide chain turns of the folded protein (i.e., inside and outside) are predicted solely by the hydrophobicity of the residues, taken in sequential order along the chain. The helices and strands span the protein, and this observed secondary structure is seen to coincide with the regions predicted to be buried from hydrophobicity considerations alone. Our evidence suggests that linear chain regions rich in hydrophobic residues serve as small clusters that fold against each other, with concomitant or even later fixation of secondary structure. A helix or strand would arise in this folding process as one of a few energetically favorable alternatives for a given cluster, followed by a shift in the equilibrium between secondary structure conformers upon cluster association. the linera chain hydrophobicity alternates between locally maximal and minimal values, and these extrema partition the polypeptide chain into structural segments. This partitioning is seen in the x-ray structure as isodirectional segments bracketed between peptide chain-turns, with the segments expressed most often as helices and strands. the segment interactions define the geometry of the molecular interior and the chain-turns describe the predominant features of the molecular coastline. The segmentation of the molecule by linear chain hydrophobicity imposes a major geometric constraint upon possible folding events.
Cytokinin inhibition of respiration in mitochondria from six plant species
Authors: Miller Carlos O.
Published: May 2006

The influence of 6-benzylaminopurine (BAP) on the respiration by mitochondria from bush bean (
Phaseolus vulgaris
L.), mung bean (
P. aureus
Roxburgh), soybean [
Glycine max
(L.) Merrill], maize (
Zea mays
L.), pea (
Pisum sativum
L.), and wheat (
Triticum aestivum
L.) was examined. BAP, a synthetic cytokinin, consistently inhibited oxygen uptake by mitochondria from all species when malate was used as the substrate. The decrease in respiration was especially evident in the presence of ADP or an uncoupler of oxidative phosphorylation. 6-Isopentenylaminopurine and 6-furfurylaminopurine also inhibited malate oxidation, but zeatin and adenine did not. In certain instances, BAP reduced succinate and NADH oxidation. With succinate as the substrate and with antimycin A present, inhibition by BAP paralleled that caused by salicylhydroxamic acid, an inhibitor of alternative respiration. A suggested scheme features a cytokinin-inhibited point located between NADH dehydrogenase and cytochrome
b
of the electron transport system. Electrons from the NADH generated by malate oxidation are assumed to flow through this point, with electrons from externally supplied or cytosolic NADH and succinate doing so only under certain conditions such as when alternative respiration is occurring. Cytokinin effects on respiration and perhaps on other phenomena may be mediated by this mechanism.
Desensitization of enucleated cells to hormones and role of cytoskeleton in control of normal hormonal response.
Authors: Simantov R , Shkolnik T , Sachs L
Published: May 2006

Prostaglandin E1 and the beta-adrenergic hormone l-isoproterenol stimulated cyclic AMP formation in both nucleated and enucleated myeloid leukemic cells that could be induced to differentiate normally to mature cells by the macrophage- and granulocyte-inducing protein MGI (MGI+D+ cells). Enucleated as well as nucleated MGI+D+ cells also desensitized to these hormones, indicating that this desensitization is an extranuclear process. Nucleated or enucleated mutant myeloid leukemic cells that are not induced to differentiate (MGI-D- cells) were not desensitized to these hormones. The antitubulin alkaloids colchicine and vinblastine, but not the antimicrofilament compound cytochalasin B, increased the maximal hormone-induced formation of cyclic AMP in nucleated MGI+D+ cells but not in the MGI-D- cells. These alkaloids also inhibited the development of desensitization to l-isoproterenol and prostaglandin E1 in enucleated MGI+D+ cells. The results indicate that in MGI+D+ cells the cytoskeletal system puts constraints on the cells' ability to respond to these hormones and that these constraints are absent in the mutant MGI-D- cells. Because MGI+D+ but not MGI-D- cells can be induced to differentiate by the macrophage- and granulocyte-inducing protein, cytoskeletal constraints, which are also found in normal myeloid cells, may be necessary for cell competence to differentiate. The results support the suggestion that membrane cytoskeletal constraints generate may control the normal response and desensitization to membrane-mediated cell inducers.
Cycle-related toxicity and transformation in 10T1/2 cells treated with N-methyl-N'-nitro-N-nitrosoguanidine.
Authors: Grisham J W , Greenberg D S , Kaufman D G , Smith G J
Published: May 2006

Exposure of C3H 10T1/2 Cl 8 cells, synchronized by release from confluence-induced arest of proliferation, to different concentrations of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) for 30 min at various points during the cell cycle causes dose-dependent toxicity (decrease in relative colony-forming efficiency or "survival") that increases linearly during the first G1 phase, reaches a maximum in early to middle S phase, and decreases during late S. In the course of the second S phase, toxicity again becomes maximal. The transformation rate (type III foci) increases and decreases with a similar pattern, increasing during the first G1 phase to a maximum during early S phase, subsequently decreasing, and then increasing again during the second S phase. Although periods of maximal toxicity and transformation roughly coincide with some portion of the S phase, the mechanisms underlying these phenomena appear to differ for the following reasons: (a) toxicity is linearly related to dose of MNNG, whereas the latter is linearly related to the logarithm of transformation rate, and (b) the ratio between toxicity and transformation varies with the cycle phase and the dose of MNNG.
Inactive X chromosome DNA does not function in DNA-mediated cell transformation for the hypoxanthine phosphoribosyltransferase gene.
Authors: Liskay R M , Evans R J
Published: May 2006

The molecular nature of the X chromosome inactivation process has been investigated by utilizing the techniques of DNA-mediated cell transformation of the X-linked hypoxanthine phosphoribosyltransferase (HPRT) locus. The findings indicate that purified DNA from the inactive X chromosome of a near-euploid mouse cell line is not functional in transformation for HPRT, but the DNA from its "homologous" active X readily elicits transformation for HPRT in the same hamster cell recipient. These findings suggest that there is a difference between the DNA, per se, of the active and inactive X at (or near) the HPRT locus and that this difference could account, at least in part, for its inactivation.
Meridional heat flux of the North Atlantic Ocean
Authors: Wunsch Carl
Published: May 2006

Using self-consistent geostrophic general circulation estimates for the North Atlantic Ocean as determined by an inverse method, I calculate the geostrophic and total meridional heat flux. The result is to a large extent dictated by the assumption of a fixed volume flux through the Florida Straits. There is no fundamental discrepancy between oceanic heat fluxes deduced from atmospheric residuals and those estimated directly in the ocean, including the estimates made here, simply because the error bars on all calculations are very large.
Fixed points of periodic maps
Authors: Cappell Sylvain E. , Shaneson Julius L.
Published: May 2006

Let
f
be a periodic differentiable map from a sphere to itself. A well-known conjecture of Smith asserts that in many cases (e.g., when the fixed points are isolated) the derivatives of
f
at its fixed points, regarded as Jacobian matrices, are linearly similar. Here we give counterexamples to this conjecture. The results show that, in many cases, these Jacobian matrices are only nonlinearly similar. This uses our recent discovery of orthogonal matrices which are nonlinearly similar without being linearly similar. Some results on general smooth actions of finite groups on differentiable manifolds are presented; the topological equivalence of their tangential representations at the fixed points is studied.
A colchicine-sensitive uptake system in Morris hepatomas.
Authors: Tauber R , Reutter W
Published: May 2006

The interference of microtubular disruptors with the uptake of amino acids and other low molecular weight substrates has been studied in Morris hepatomas, host liver, and regenerating liver. Colchicine inhibits amino acid transport (alpha-aminoisobutyric acid, L-methionine, and L-leucine) in hepatomas by 59-98% whereas transport in host and regenerating liver is not impeded but increased. In hepatomas, treatment urea, and carbonate. Vinblastine, but not lumicolchicine or cytochalasin B, is an effective inhibitor. The inhibition of uptake is not linked to a decrease of cellular ATP and UTP. The data suggest that the transport of low molecular weight substrates in hepatomas is related to microtubules or other colchicine-binding structures, e.g., of the plasma membrane. This colchicine-sensitive uptake system in hepatomas may be due to the malignant transformation of hepatocytes.
Local anesthetics inhibit induction of ornithine decarboxylase by the tumor promoter 12-O-tetradecanoylphorbol 13-acetate.
Authors: Yuspa S H , Lichti U , Ben T
Published: May 2006

The induction of ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) activity in mouse epidermal cells in vivo and in vitro occurs rapidly after exposure to the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA). This induction has characteristics of a cell surface receptor-mediated process. Local anesthetics modify a variety of cellular responses mediated by membrane receptors. When cultured mouse epidermal cells were exposed to the local anesthetics lidocaine, tetracaine, or procaine (0.1-1 mM), induction of the decarboxylase by TPA was inhibited by more than 90%. In vivo, lidocaine essentially abolishes the decarboxylase response of mouse epidermis when applied shortly after TPA. In contrast, local anesthetics have no effect on the enzyme's activity when added directly to the assay mixture and, in concert with TPA, have only a minimal effect on overall protein synthesis relative to controls. However, lidocaine has no effect on TPA-stimulated DNA synthesis in vitro (12-fold with or without lidocaine). Local anesthetics also markedly inhibit induction of the decarboxylase by ultraviolet light, which is probably not membrane mediated. Furthermore, in culture, lidocaine has only a small inhibitory effect on ornithine decarboxylase when given before TPA but is an effective inhibitor even when given up to 4-5 hr after the promoter, a time when decarboxylase activity has already increased. These findings suggest that local anesthetics, which are tertiary amines, do not act at the site of interaction of TPA and its putative receptor but may be acting specifically on polyamine biosynthesis. These drugs could be useful agents to determine the role of the polyamine pathway in tumor promotion.
Regulation of stromal cell collagenase production in adult rabbit cornea: in vitro stimulation and inhibition by epithelial cell products.
Authors: Johnson-Wint B
Published: May 2006

Media conditioned by epithelial cells from the adult rabbit cornea were capable of both stimulating and inhibiting production of latent collagenase by stromal cells from the same source. Cytochalasin B was required in this in vitro system for both secretion of stimulators by epithelial cells and production of collagenase by stromal cells in response. Optimal production of collagenase by stromal cells in response. Optimal production of stimulators occurred in low-density epithelial cell cultures. Chromatographed conditioned medium from such cultures contained three stimulator fractions with apparent molecular weights of 19,000, 54,000, and greater than or equal to 90,000. High-density epithelial cell cultures secreted inhibitors of stromal cell collagenase production with apparent molecular weights of 7000 and 19,000. Cytochalasin B was not required for production of inhibitors. Inhibitory conditioned medium blocked the effect of the 19,000-dalton and 54,000-dalton stimulator on stromal cells. The data suggest that epithelial cells, in ways depending on their density, may modulate collagen degradation in the integument.
Action of granulocyte-macrophage colony-stimulating factors: studies using a human leukemia cell line.
Authors: Lusis A J , Koeffler H P
Published: May 2006

Granulocyte-macrophage colony-stimulating factors (CSFs) have previously been shown to stimulate colony formation in soft agar culture by a human myelogenous leukemia cell line known as KG-1. We have used KG-1 cells as a model system to investigate the interaction of CSF with myeloid cells. We now report that exposure of KG-1 cells to human CSFs in liquid culture results in a rapid (within 3 hr) burst of RNA synthesis and, after a lag of about 10 hr, a stimulation of DNA and protein synthesis. RNA and protein synthesis were maximally stimulated about 2-fold and DNA synthesis was stimulated about 2.5-fold. The stimulation was specific; various growth factors, hormones, and mouse CSFs had no effect on KG-1 macromolecular synthesis. Treatment with CSF did not discernibly alter the morphological appearance of the KG-1 cells (primarily myeloblasts) nor did it qualitatively affect the pattern of newly synthesized proteins separable by one- and two-dimensional electrophoresis. Several myeloid leukemia cell lines that were not responsive to CSF in agar culture, including a dedifferentiated variant of KG-1, showed little or no stimulation of macromolecular synthesis upon exposure to CSF. We have used the CSF-dependent stimulation of macromolecular synthesis of KG-1 to develop a rapid, sensitive microassay for human CSFs. The assay, involving thymidine incorporation by the cells, should be useful for characterization and purification of human CSFs.
Activation of cellular genes by avian RNA tumor viruses.
Authors: Groudine M , Weintraub H
Published: May 2006

We demonstrated previously that chicken embryo fibroblasts accumulate approximately 100 copies of embryonic globin RNA after transformation by Rous sarcoma virus. Here we demonstrate that the globin gene in chicken embryo fibroblasts is activated by infection with two other oncogenic retroviruses, avian erythroblastosis virus and strain MC-29 of avian myeloblastosis virus, which contain transforming genes unrelated in nucleotide sequence content to each other or to the Rous sarcoma virus src gene. In addition, we have measured the genetic complexity of transformation by using established techniques for determining the number of different RNA sequences in specific populations of cells. Our results indicate that transformation of chicken embryo fibroblasts by Rous sarcoma virus results in the accumulation of RNA from approximately 1000 average-sized new transcription units.
Origins of metabolic diversity: substitution of homologous sequences into genes for enzymes with different catalytic activities.
Authors: Yeh W K , Ornston L N
Published: May 2006

Similar amino acid sequences were found in portions of bacterial enzymes that mediate different biochemical transformations. Reaction catalyzed by the enzymes include oxygenation, decarboxylation, isomerization, and hydrolysis. The proteins share a common evolutionary history because they participate in an overall catabolic process known as the beta-ketoadipate pathway. One interpretation of the sequence similarities might be that duplication of a single gene gave rise to ancestral genes for the enzymes with different catalytic activities. According to this view, homologous sequences from the ancestral gene were conserved as the proteins diverged to assume different functions. This hypothesis is vitiated by comparison of the NH2-terminal amino acid sequences of sets of enzymes that mediate identical or analogous metabolic reactions within an organism. Gene duplications giving rise to the enzymes within each set must have followed duplication of a putative ancestral gene for all the sets. Yet the amino acid sequences of the proteins within each set have diverged widely, and against this background of divergence the conservation of sequences from an ancestor common to all the enzymes is unlikely. Rather, it appears that most regions of sequence similarity shared by enzymes from different sets were acquired subsequent to their divergence from any common ancestor. In some cases it appears that relatively short regions of sequence homology were achieved by mutations causing the transfer of sequence information from one set of structural genes to structural genes in another set. Alignment of homologous amino acid sequences within any single set requires the introduction of few gaps. Because gaps are required to align sequences that have been altered by the insertion of genetic material, the evidence indicates that copies of oligonucleotides were exchanged by genetic substitution among different structural genes as they coevolved.
Transfer of Epstein-Barr virus receptors to receptor-negative cells permits virus penetration and antigen expression.
Authors: Volsky D J , Shapiro I M , Klein G
Published: May 2006

Epstein-Barr virus (EBV) receptors were implanted into the membranes of receptor-negative cells, using Sendai virus envelopes as vehicles. The presence of the receptors in the target cell membrane was demonstrated by monitoring the fate of radioiodinated donor membranes. Receptors could be detected for at least 36 hr after implantation. [3H]Thymidine-labeled EBV bound efficiently to receptor-implanted cells but not to control cells. Binding was inhibited by an excess of nonlabeled virus. Of the [3H]thymidine-labeled EBV DNA, 50-75% was found inside the receptor-implanted, EBV-exposed cells 24 hr after the infection. The viral genome was functionally active in B lymphocyte-derived cell lines of human, murine, and baboon origin; in T lymphocyte-derived lines of human and murine origin; in mouse fibroblasts; and in freshly explanted mouse lymphocytes, as shown by the expression of EBV-determined nuclear, early, and viral capsid antigens.
Generation of an electrochemical proton gradient in Streptococcus cremoris by lactate efflux.
Authors: Otto R , Sonnenberg A S , Veldkamp H , Konings W N
Published: May 2006

Recently an energy-recycling model was proposed that postulates the generation of an electrochemical gradient in fermentative bacteria by carrier-mediated excretion of metabolic end products in symport with protons. In this paper experimental support for this model is given. In batch cultures of Streptococcus cremoris with glucose as the sole energy source the maximal specific growth rate decreased by 30% when the external lactate concentration was decreased from 50 to 90 mM. In the same range of external lactate concentrations the molar growth yield Y for glucose as measured in energy-limited chemostat cultures also showed a 30% drop. From Y max lactose values of S. cremoris grown in the presence and absence of added lactate it was calculated that the net energy gain from the lactate efflux system was at least 12%. Lactate efflux from de-energized cells loaded with lactate could drive the uptake of leucine. This uptake was sensitive to carbonylcyanide p-trifluoromethoxyphenylhydrazone and was only partly inhibited by dicyclohexylcarbodiimide (DCCD). The limited inhibition by DCCD of lactate-induced leucine uptake indicates that ATP hydrolysis was not the driving force for transport of leucine. Uptake studies with the lipophilic cation tetraphenylphosphonium demonstrated that lactate efflux increased the electrical potential across the membrane by 51 mV. The generation of an electrical potential by lactate efflux and the demonstration of a potassium efflux-induced uptake of lactate indicates that lactate is translocated across the membrane by a symport system with more than one proton.
Analgesic activity of the naturally occurring heptapeptide [Met]enkephalin-Arg6-Phe7.
Authors: Inturrisi C E , Umans J G , Wolff D , Stern A S , Lewis R V , Stein S , Udenfriend S
Published: May 2006

[Met]Enkephalin-Arg6-Phe7 is an opiate-like peptide normally found in the the adrenal gland and brain that has analgesic (antinociceptive) activity when administered directly into the cerebral ventricles of mice. On a molar basis, [Met]-enkephalin-Arg6-Phe7, with a median effective dose (ED50) of 38.5 nmol/mouse, is 8 times more potent than [Met]enkephalin. As with [Met]enkephalin, analgesic activity is blocked by naloxone and intravenous administration does not produce characteristic opiate effects in tests for analgesic, antidiuretic, or antidiarrheal activity. These findings suggest that [Met]enkephalin-Arg6-Phe7 may be at least as important as the enkephalins in the postulated enkephalin system mediating pain and analgesia.
Morphine and opioid peptides reduce paraventricular neuronal activity: studies on the rat hypothalamic slice preparation.
Authors: Pittman Q J , Hatton J D , Bloom F E
Published: May 2006

Extracellular discharges of neurons in the paraventricular nucleus (PVN) were recorded from slices of rat hypothalamus in vitro. PVN neurons (n = 14) were identified by the criteria of (i) phasic activity patterns and (ii) antidromic invasion from the neurohypophysial tract. Neurons not displaying either of these features were considered unidentified with respect to physiological function (n = 85). The majority of unidentified neurons responded to bath application of morphine (1 microM), [D-Ala2,Met5]enkephalin (1 microM) or beta-endorphin (0.01-1 microM) with a prompt, reversible, dose-related reduction in spike discharge frequency. Naloxone (1 microM) antagonized the opioid-induced depressions in some, but not all, cases. At the concentrations tested, no tachyphylaxis to the effects of the opioids was observed. The opioid effects on putative neurohypophysial neurons were less pronounced; while 2 were depressed, the remaining 12 displayed no change in frequency or pattern of discharge to micromolar concentrations of morphine, [D-Ala2,Met5]enkephalin, or beta-endorphin. Our results indicate that opioids depress neuronal activity in the rat PVN via an interaction with a specific opiate receptor but that this effect is more pronounced on unidentified neurons than on putative neurohypophysial neurons in the slice.
Similar luteinizing hormone-releasing hormone binding sites in rat anterior pituitary and ovary.
Authors: Reeves J J , Séguin C , Lefebvre F A , Kelly P A , Labrie F
Published: May 2006

To study the luteinizing hormone-releasing hormone (LH-RH; luliberin) receptors in the rat anterior pituitary gland and ovary, 125I-labeled [D-Ser(TBU)6des-Gly-NH2(10)]LH-RH ethylamide was used as a labeled ligand. The binding characteristics were assessed by Scatchard analysis of labeled ligand binding and by potency displacement with unlabeled peptides. Similar Kd values, ranging from 0.1 to 0.3 nM, were found for the labeled and unlabeled peptides in both tissues. A similar order of potency was observed between the finding affinity of 15 peptides in anterior pituitary and ovarian homogenates and their biological activity on luteinizing hormone release in rat anterior pituitary cells in culture. These data demonstrate that the LH-RH receptors present in the rat ovary have a specificity similar to that of the anterior pituitary LH-RH receptor controlling secretion of luteinizing hormone and follicle-stimulating hormone. Moreover, the binding affinities of the LH-RH agonists and antagonists can account, at least up to a large extent, for their relative biological potencies. Although there definitely are specific LH-RH receptors in the ovary which may play a role in the antifertility effects observed after administration of LH-RH agonists, the possible physiological significance of these ovarian receptors is still unknown and of great biological interest.
Isolation of functional human coagulation factor V by using a hybridoma antibody.
Authors: Katzmann J A , Nesheim M E , Hibbard L S , Mann K G
Published: May 2006

Spleen cells obtained from mice immunized with partially purified human coagulation Factor V were fused with NS-1 mouse myeloma cells, and hybrids were selected. Culture media were screened for anti-Factor V activity, and an antibody-positive clone was obtained and passaged as an ascites tumor in mice. The ascitic fluid from the hybridoma-bearing mouse could be diluted 1:10(6) before losing reactivity in an anti-Factor V radioimmunoassay. When immobilized on agarose, the monoclonal antibody quantitatively removed Factor V activity from human plasma. Factor V activity could be eluted with 1.2 M NaCl at pH 6.5. Homogeneous Factor V was isolated by chromatography of barium citrate-adsorbed, polyethylene glycol 6000 precipitated plasma on the antibody column followed by chromatography on phenyl-Sepharose. The isolated Factor V exhibited a single band upon gel electrophoresis in sodium dodecyl sulfate with an apparent Mr comparable to that of bovine Factor V (330,000). Upon exposure to thrombin, the activity of Factor V increased 53-fold when measured in Factor V-deficient plasma. This increased activity was associated with discrete proteolytic cleavages of the parent molecule.
Purification of thymus mRNA coding for a 16,000-dalton polypeptide containing the thymosin alpha 1 sequence.
Authors: Freire M , Hannappel E , Rey M , Freire J M , Kido H , Horecker B L
Published: May 2006

A mRNA fraction purified by preparative polyacrylamide disc gel electrophoresis from calf thymus polysomes codes for a polypeptide(s) having a mass of 16,000-17,000 daltons. This polypeptide contains amino acid sequences corresponding to residues 11-18 and 19-25 of thymosin alpha 1. The yield of the octapeptide indicates that the 16,000-dalton peptide is the major product formed in the cell-free synthesis system containing the purified mRNA.
Organization and expression of immunoglobulin genes in fetal liver hybridomas.
Authors: Perry R P , Kelley D E , Coleclough C , Kearney J F
Published: May 2006

The organization and expression of immunoglobulin genes were studied in a series of six hybridomas derived from the fusion of a nonproducing myeloma cell with cells from mouse fetal liver. These hybridomas, which exhibit several phenotypic characteristics of immature B lymphocytes, all have productively rearranged mu heavy chain genes and produce both the membrane and secreted forms of mu mRNA in a ratio of about 1:10. Significantly, none of the hybridomas has an unrearranged (germ line) allelic mu gene. Examination of the kappa light chain genes revealed that all six of the hybridomas contain unrearranged kappa loci and produce 8.4-kilobase transcripts containing kappa constant region sequences. None of the five hybridomas that exhibit a mu-only phenotype contains a rearranged kappa gene other than that derived from the myeloma parent. One hybridoma, which actively secretes kappa immunoglobulin, contains a rearranged kappa gene of fetal liver origin and synthesizes a distinctive kappa mRNA precursor in addition to the 8.4-kilobase transcript. These results demonstrate that rearrangement of heavy chain immunoglobulin genes normally occurs prior to that of light chain genes and further indicate that the transcriptional competence of the kappa constant region locus is established prior to the time of its rearrangement.
Some heat engine cycles in which liquids can work
Authors: Allen P. C. , Paulson D. N. , Wheatley J. C.
Published: May 2006

Liquids can work in heat engine cycles that employ regeneration. Four such cycles are discussed: Stirling, Malone, Stirling-Malone, and Brayton. Both regeneration and the role of the second thermodynamic medium are treated, and the principles are verified by quantitative measurements with propylene in a Stirling-Malone cycle.
Neoplastic transformation of chimpanzee cells induced by adenovirus type 12--simian virus 40 hybrid virus.
Authors: Rhim J S , Trimmer R , Arnstein P , Huebner R J
Published: May 2006

The adenovirus 12--simian virus 40 hybrid virus produced neoplastic transformation of chimpanzee skin fibroblasts in vitro. The transformed fibroblasts showed morphological alteration and became permanent lines. The transformed cells contained both adenovirus 12 and simian virus 40 large tumor antigens and were virus producers. However at passage 9, one line (WES) was found to be a nonproducer, producing neither infectious virus nor virus-specific antigen detectable by the complement fixation test. Virus particles were not detected nor could infectious hybrid virus be rescued from this line by cocultivation with Vero cells. The transformed cells formed large cell aggregates and grew in liquid growth medium above an agar base, formed colonies in soft agar, and grew to high saturation densities; the normal chimpanzee skin fibroblasts did not. One transformed WES line produced tumors when transplanted subcutaneously into newborn nude mice, thus providing an important tool for studying tumor immunity in the chimpanzee.