bluuebunny/crossref_metadata_2025 huggingface dataset:
Location of envelope-specific and sarcoma-specific oligonucleotides on RNA of Schmidt-Ruppin Rous sarcoma virus.
Authors: Wang L H , Duesberg P H , Kawai S , Hanafusa H
Published: May 2006

Envelope-specific and sarcoma-specific nucleotide sequences have been located within the 10,000 nucleotides of the RNA of nondefective Schmidt-Ruppin Rous sarcoma virus (nd SR). For this purpose, about 30 RNase-T1-resistant oligonucleotides were ordered relative to the 3'-poly(A) terminus of the RNA, to construct an oligonucleotide map of the nd SR RNA. A cluster of seven envelope-specific oligonucleotides, identified by their absence from an otherwise very similar oligonucleotide map of an envelop-defective deletion mutant (which lacks the major viral glycoprotein), mapped at a distance of 2800-5000 nucleotides from the poly(A) end of nd SR RNA. A cluster of two sarcoma-specific oligonucleotides, identified by their absence from an otherwise nearly identical oligonucleotide map of a transformation-defective deletion mutant, mapped at a distance of 1000-2000 nucleotides from the poly(A) end of nd SR RNA. The oligonucleotide maps of nd SR and of the two deletion mutants were the same from the poly(A) end up to 650 nucleotides and included one terminal oligonucleotid, termed C, which is found in all avian tumor viruses tested so far. A possible gene order consistent with our data suggests that sarcoma-specific nucleotide sequences map between envelope-specific nucleotide sequences and the poly(A) end of the RNA.
The mucopolysaccharidoses (a review).
Authors: Dorfman A , Matalon R
Published: May 2006

The mucopolysaccharidoses are a group of genetic diseases characterized by storage of incompletely degraded glycosaminoglycans. Such storage causes marked distortion of many tissues with consequent severe somatic changes and mental retardation. Storage of glycosaminoglycans results from markedly diminished activity of specific hydrolases requisite for the normal degradation of glycosaminoglycans. The specific enzymic defects have been identified in nine different diseases. In some cases evidence has been obtained indicating the existence of additional allelic diseases based on the same enzyme. The knowledge obtained from these studies has made prenatal diagnosis possible and has led to the possibility that therapy may be undertaken utilizing enzyme replacement.
Concatemers of alternating plus and minus strands are intermediates in adenovirus-associated virus DNA synthesis.
Authors: Straus S E , Sebring E D , Rose J A
Published: May 2006

Replicating DNA molecules of adenovirus-associated virus (AAV) were selectively extracted from KB cells coinfected at 39.5 detrees with a DNA minus, temperature-sensitive mutant of adenovirus 5 (ts125) as helper. Under these conditions AAV DNA replication proceeds normally, but there is little, if any, adenovirus DNA synthesis. An analysis of the replicating molecules in sucrose density gradients reveals that there are AAV DNA intermediates which consist of covalently linked plus and minus DNA strands. Under denaturing conditions, these concatemers are linear single strands whose lengths can reach at least four times the size of the AAV genome. The most abundant concatemeric species is a dimer which presumably exists in vivo as a unit length hairpin. Unit length linear duplexes appear to be immediate precursors of plus and minus progeny strands. These findings are compatible with a self-priming mechanism for the synthesis of AAV DNA.
Sherpas living permanently at high altitutde: a new pattern of adaptation.
Authors: Morpurgo G , Arese P , Bosia A , Pescarmona G P , Luzzana M , Modiano G , Krishna ranjit S
Published: May 2006

Adaptation of Sherpas to high altitude has been studied and compared with that of Caucasians acclimatized to high altitude. Sherpas living permanently at 4000 m above sea level do not have increased hematological parameters (i.e., red cell number, hematocrit, hemoglobin content, and 2,3-diphosphoglycerate/hemoglobin ratio) and have a higher affinity of blood for oxygen as compared with acclimatized Caucasians. Sherpas permanently living at low altitude, on the contrary, have lower affinity of blood for oxygen than do Caucasians living at comparable altitude and are mildly "anemic,". Various other red cell biochemical parameters (possibly related to adaptation to altitude) have also been studied in the same population. We suggest that Sherpas are genetically better adapted to high altitude than are Amerindians living on the Peruvian highlands, possibly as a consequence of a much more prolonged exposure to such an ecological factor of selection as high altitude.
Linearity of the hemoglobin oxidation bohr effect.
Authors: Hoffman B M , Bull C
Published: May 2006

The hemoglobin oxidation Bohr effect below pH 7 is essentially proportional to the fraction of hemes oxidized, just as the ligation Bohr effect is proportional to fractional heme ligation. The reported nonlinear proton release during oxidation [(1965) J. Biol. Chem. 240, 3317-3324] is shown to be an artifact resulting from the use of ferricyanide as oxidant. Published forms of the two-state allosteric transition model for hemoglobin function have used several proton linkage schemes, and none are compatible with a linear proton release upon oxidation.
Sequence-specific recognition of double helical nucleic acids by proteins.
Authors: Seeman N C , Rosenberg J M , Rich A
Published: May 2006

The base pairs in double helical nucleic acids have been compared to see how they can be recognized by proteins. We conclude that a single hydrogen bond is inadequate for uniquely identifying any particular base pair, as this leads to numerous degeneracies. However, using two hydrogen bonds, fidelity of base pair recognition may be achieved. We propose specific amino-acid side chain interactions involving two hydrogen bonds as a component of the recognition system for base pairs. In the major groove we suggest that asparagine or glutamine binds to adenine of the base pair or arginine binds to guanine. In the minor groove, we suggest an interaction between asparagine or glutamine with guanine of the base pair. We also discuss the role that ions and other amino-acid side chains may play in recognition interactions.
X-ray diffraction of actively shortening muscle.
Authors: Podolsky R J , St Onge H , Yu L , Lymn R W
Published: May 2006

Low angle x-ray diffraction patterns were obtained from resting and activated frog sartorius muscles by means of a position-sensitive detector. Although the intensity ratio I10/I11 decreased many-fold upon activation, it was nearly the same during isometric and isotonic contraction. Thus, motion has a much smaller effect on the low order equatorial pattern than the transition from rest to activity. Analysis of the 10 and 11 reflections separately showed that I10 and I11 change reciprocally upon activation, and that they both increase by a small amount in the transition from isometric to isotonic contraction. If the intensity ratio can be taken as a measure of cross-bridge number, the results provide evidence that the drop in force in an actively shortening muscle is due primarily to the influence of motion on the configuration, rather than the number, of cross-bridges.
Cytoplasmic microtubules in tissue culture cells appear to grow from an organizing structure towards the plasma membrane.
Authors: Osborn M , Weber K
Published: May 2006

A structure which appears to organize cytoplasmic microtubules in interphase mouse 3T3 cells can be visualized by immunofluorescence microscopy. Purified monospecific antibody against homogeneous tubulin from brain visualizes, in addition to cytoplasmic microtubules, a cytoplasmic polar structure as the focal point from which the microtubules seem to radiate. The structure is preserved after treatments that depolymerize cytoplasmic microtubules, i.e., exposure of cells to mitotic drugs or to low temperature. When cells recover from these treatments one end of each microtubule organizing structure acts as a nucleating center from which cytoplasmic microtubules grow toward the plasma membrane. Thus cytoplasmic microtubules assemble in vivo in an ordered unidirectional manner, and therefore the cell must be able to avoid the assembly of unwanted, unoriented, and disconnected microtubules. These results suggest that the assembly of tubulin into microtubules is regulated in vivo.
Secretion of macrophage neutral proteinase is enhanced by colchicine.
Authors: Gordon S , Werb Z
Published: May 2006

We have studied the effect of colchicine and related compounds on secretion of enzymes by thioglycollated-elicited mouse peritoneal macrophages in culture. Colchicine stimulated secretion of inducible neutral proteinase activities of elastase (EC 3.4.21.11), collagenase (EC 3.4.24.3), gelatinase (pepsin B; EC 3.4.23.2), and azocaseinase 2- to 6-fold for a period of several days, but inhibited the production and release of lysozyme (mucopeptide N-acetylmuramoylhydrolase; EC 3.2.1.17), a noninducible macrophage secretory product. Parallel changes were observed in cell morphology and secretion after treatment with colchicine, Colcemid, and vinblastine, but not with lumicolchicine, and these effects could be gradually reversed by withdrawal of colchicine. Cytochalasin B also stimulated secretion of elastase 2- to 3-fold but did not influence release of lysozyme. These results demonstrate that tubulin-binding drugs may have opposite effects in macrophages than those usually reported for other experimental systems and also provide evidence for the nonparallel discharge of different macrophage secretion products.
Production of collagenase and prostaglandins by isolated adherent rheumatoid synovial cells.
Authors: Dayer J M , Krane S M , Russell R G , Robinson D R
Published: May 2006

We have studied cells dispersed with proteolytic enzymes from rheumatoid arthritic synovectomy specimens to determine the cell type(s) responsible for joint destruction. Initially 10-50% of these cells adhered to culture dishes within 24 hr and were of two main types: small, round cells and larger, stellate cells. During 1-4 days of culture, 5-25% had Fc receptors and 25-50% showed brisk phagocytosis. Daily producition, per 10(6) cells of collagenase (EC 3.4.24.3) (after trypsin pretreatment) was up to 70 mug of collagen fibrils lysed per min at 37 degrees (70 units), of prostaglandin (PGE2), up to about 1200 ng, and of lysozyme, up to about 100 mug. Under identical conditions of assay, fibroblasts grown from explants of synovium produced no detectable collagenase or lysozyme, and PGE2 was only 2-4 ng. With the dispersed cell preparations, macrophage markers (Fc receptors and lysozyme) were undetectable after 4 days and PGE2 decreased rapidly after about 7 more days. However, collagenase production continued for 3-25 weeks, and in some cultures, after cell passage. At these later stages, large, slow-growing stellate cells were predominant and could phagocytose carbon particles if incubated for greater than 6-8 hr. Indomethacin (14 muM) inhibited PGE2 but stimulated collagenase production whereas dexamethasone (10 nM) inhibited both. Production of PGE2 and collagenase in large amounts in vitro by these cells suggests that they may be involved in joint destruction in vivo. The precise origin of these synovial cells and the mechanisms responsible for the sustained production of collagenase at a high rate remain unidentified.
Mouse amyloid protein AA: Homology with nonimmunoglobulin protein of human and monkey amyloid substance.
Authors: Eriksen N , Ericsson L H , Pearsall N , Lagunoff D , Benditt E P
Published: May 2006

The major protein extracted from anyloid deposits induced in mice by injection of either Candida albicans cells or sodium caseinate was found to have chromatographic and electrophoretic properties and an amino-acid compostiion characteristic of the AA class of amyloid proteins. The homology of the mouse protein with protein AA from man and monkey was established by determination of the sequence of the first 28 amino-acid residues.
Hydrolytic stability of helical RNA: a selective advantage for the natural 3',5'-bond.
Authors: Usher D A , McHale A H
Published: May 2006

Dodecaadenylic acid containing a single 2', 5'-linkage at a defined position was formed by the coupling of two hexamers on a poly(U) template at 2 degrees. The rate of hydrolysis of this dodecamer was compared with that of a dodecamer that contained only the natural 3', 5'-linkages. At 40 degrees, in 1 M aqueous ethylenediamine at pH 8 in the absence of poly(U), both dodecamers hydrolyzed at comparable rates, but the addition of two equivalents of poly(U) caused a 7-fold increase in the initial rate of hydrolysis of the oligomer containing the 2', 5'-bond, and a 5-fold decrease in the initial rate of hydrolysis of the natural oligomer. When the oligomers are fully constrained in helical form, the ratio of the rates of cleavage of one 2', 5'-bond to one 3', 5'-bond under these conditions is probably about 900:1. The use of the 3', 5'-bond, in combination with a right-handed helix, appears to have had a large selective advantage over the use of the 2', 5'-bond for the storage of genetic information.
Erythroid cell differentiation: murine erythroleukemia cell variant with unique pattern of induction by polar compounds.
Authors: Ohta Y , Tanaka M , Terada M , Miller O J , Bank A , Marks P , Rifkind R A
Published: May 2006

The murine-virus-infected erythroleukemia cell system provides an opportunity to examine regulatory mechanisms controlling cytodifferentiation. A cloned cell line (DR10c3) resistant to the erythropoiesis-inducing effect of dimethylsulfoxide (Me2SO) was isolated from the Me2SO-sensitive line DS19. DR10c3 is characterized as follows: (1) the uptake of [3H]Me2SO is similar to that in DS19; (2) cell growth with and without Me2SO is similar to that of DS19; (3) resistance is relatively stable; (4) the karyotype of DR10c3 reveals an average loss of five chromosomes per cell, but is otherwise similar to that of DS19; (5) total protein and globin synthesis by cells cultured 4 days with or without Me2SO is similar to these syntheses in DS19 cultured without Me2SO; (6) virtually no globin mRNA is detectable after 3 days in Me2SO, as assayed both by RNA-complementary DNA hybridization and by the heterologous cell-free protein-synthesizing system; (7) other polar compounds, N-methylpyrrolidinone, 1-methyl-2-piperidone, N, N-dimethylacetamide, and N-methylacetamide, induce erythroid differentiation in DR10c3, and the accumulation of alpha- and beta-globin chains is indistinguishable from that in DS19; and (8) the concentration optima for induction of differentiation by all these compounds are identical for DR10c3 and DS19.
Influence of diet on survival of mice.
Authors: Fernandes G , Yunis E J , Good R A
Published: May 2006

The longevity of mice of the (NZB X NZW)F1 (B/W) strain and the DBA/2f strain of mice is dramatically prolonged by dietary restriction. B/W mice are susceptible to, and die at an early age from, immunocomplex nephritis. Mice of the DBA/2f strain are also relatively short-lived. Restriction of caloric intake prolonged life of B/W mice more than did protein restriction. DBA/2f mice showed prolongation of life when the diet was restricted only with respect to protein. Caloric restriction alone prolonged life less in DBA/2f mice than in B/W mice. These observations show that dietary manipulations have profound effects on immunity functions, including inhibition of the development of life-shortening autoimmune disease.
beta-adrenergic receptors in rat liver: effects of adrenalectomy.
Authors: Wolfe B B , Harden T K , Molinoff P B
Published: May 2006

The response of rat liver adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] to catecholamines is enhanced after adrenalectomy. To investigate this phenomenon, we developed an in vitro assay for beta-adrenergic receptors of plasma membranes derived from livers of control and adrenalectomized rats, using [125I]iodohydroxybenzylpindolol (IHYP), a potent beta-adrenergic receptor antagonist. Binding of IHYP reached equilibrium within 30 min and dissociation occurred with a half-time of approximately 60 min. The l-isomers of isoproterenol and propranolol were at least 50 times more potent as inhibitors of IHYP binding than were the corresponding d-isomers. Adrenalectomy did not affect the rates of association or dissociation of IHYP or the dissociation constants of several ligands that are active at beta-adrenergic receptors. The number of binding sites for IHYP was determined in homogenates and in purified membranes of livers from control and adrenalectomized rats. The number of sites increased 3- to 5-fold after adrenalectomy. A similar increase in hormone stimulation of adenylate cyclase was observed. These changes were reversed by the administration of cortisone. The increase in the number of binding sites for IHYP may be a compensatory response to the impairments in gluconeogenesis and glycogenolysis which occur after adrenalectomy.
Pharmacologic characterization of the Na+ ionophores in L6 myotubes.
Authors: Sastre A , Podleski T R
Published: May 2006

We present a pharmacologic characterization of the Na+ ionophores present in L6 myotubes in vitro. Action potentials are abolished by replacement of the external Na+ by Tris. The amplitude of the action potential is generally resistant to high concentrations of tetrodotoxin (10(-5) M) and saxitoxin (10(-6 M), but the effect of these agents is highly variable. Veratridine (10(-4 M) consistently induces, as a short-term effect, a marked prolongation of the falling phase of the action potential. As a long-term effect, veratridine consistently induces a Na+-dependent reduction in the resting potential of the cell. The effects of veratridine on the action potential are not antagonized by tetrodotoxin or saxitoxin. However, the effects of veratridine on the resting potential are strongly antagonized by tetrodotoxin (10(-5) M) and fully inhibited by saxitoxin (10(-6) M). Significantly, under conditions where saxitoxin has fully inhibited the effects of veratridine on the resting potential, the myotubes are capable of generating overshooting action potentials. In contrast to their sensitivity to veratridine, L6 myotubes are insensitive to 10(-5) M alpha-dihydro-grayanotoxin-II. These results are discussed in the contexts of developmental significance and current views about Na+ ionophores.
Viscosity of liquid metals: An interpretation
Authors: Hildebrand J. H. , Lamoreaux R. H.
Published: May 2006

The fluidity of liquid metals, like that of simple nonmetallic liquids, is a linear function of the ratio of unoccupied volume to intrinsic volume over long ranges as expressed by the equation ϕ =
B
[(
V
/
V
0
) - 1]. Values of
V
0
obtained by extrapolating to ϕ = 0 agree well with molal volumes of compact crystals at 20°C calculated from densities.

Values of the ratio ϕ/[(
V
/
V
0
) - 1] range from 27.0 for Na to 1.55 reciprocal centipoise for Ni. Viscosities at ratios of expansion
V
/
V
0
= 1.10 vary linearly with squares of solubility parameters Δ

E
v

/
V
0
, where Δ

E
v

is molal energy of vaporization at the melting point. Viscosities at 10% expansion range from 0.037 cP for Na to 5.38 cP for Co, with some divergence for metals with values of η in the neighborhood of unity. The good agreement in the case of the transition metals Cu, Fe, Co, and Ni we attribute to distribution of vector momentum among quasi-chemical bonds between d-electrons and vacant orbitals.
Observations and interpretation of x-ray absorption edges in iron compounds and proteins.
Authors: Shulman G R , Yafet Y , Eisenberger P , Blumberg W E
Published: May 2006

X-ray absorption spectra near the Kalpha edge have been measured in various iron group compounds using the intense synchrotron radiation at the Stanford Synchrotron Research Project. In the cubic compounds KMF3 where M = Mn+2, Fe+2, Co+2, Ni+2, and Zn+2, well resolved lines were observed and assigned to the 1s leads to 3d, 1s leads to 4s, and 1s leads to 4p transitions. The observed energies agreed rather well with the spectroscopic energy levels of the Z + 1 ion and the intensities are shown to agree with those expected on the basis of one electron transitions of the form Z 1s2dn(L,S) leads to (Z + 1)1s2dnn'l'(L",S). The energies of the intense 1s leads to 4p transition increase by about 5 V going from KFeF3 to K2NaFeF6, but only by about 1 V from K4Fe(CN)6 to K3Fe(CN)6. The transitions confirm that upon oxidation of the hexacyanides the iron electronic structure barely changes. In the iron sulfur protein rubredoxin, where the iron is bound to a tetrahedron of sulfurs, the 1s leads to 3d transition was about seven times more intense than the same transition in an octahedrally coordinated compound. These intensities parallel those observed in the d-d transitions of optical spectra, because in both types of spectra the intensities depend upon 4p admixture. In the heme protein cytochrome c, upon oxidation the 1s leads to 4p transition shifts only about 1 V to higher energies similar to the iron hexacyanides. These results are discussed in terms of covalent bonding.
The development of the action potential mechanism of amphibian neurons isolated in culture.
Authors: Spitzer N C , Lamborghini J E
Published: May 2006

Nerve and muscle cells differentiated morphologically, in cultures of dissociated cells prepared from amphibian neural plate and underlying mesoderm (Xenopus laevis, Nieuwkoop and Faber stage 15). Cultures were grown in a defined medium containing sterile Steinberg's salt solution and 0.1% bovine serum albumin, and maintained for periods up to 5 days.
Resting state in normal and simian virus 40 transformed Chinese hamster lung cells.
Authors: Martin R G , Stein S
Published: May 2006

Normal cell deprived of amino acids or serum factors enter a resting state, whereas cells transformed by wild-type simian virus 40 do not. The ability to enter a resting state is temperature-sensitive (ts) in cells transformed by a tsA mutant of simian virus 40. We shown further: (i) that when complete medium is added to resting cells, the length of time until the onset of DNA synthesis often exceeds the length of G1 in growing cells; (ii) that the length of this interval depends upon the conditions used to arrest cell growth; but (iii) that transferring cultures from medium depleted for one factor to medium depleted in a second factor never leads to a round of DNA synthesis; and (iv) that DNA synthesis does not resume rapidly when a resting culture of cells transformed by the tsA mutant is transferred to the permissive temperature in suboptimal medium. A model proposing that in suboptimal conditions cells leave the cell cycle and traverse a branch pathway to enter the resting state is consistent with these findings.
Changes in type of collagen synthesized as clones of chick chondrocytes grow and eventually lose division capacity.
Authors: Mayne R , Vail M S , Mayne P M , Miller E J
Published: May 2006

Clones of embryonic chick chondrocytes have been isolated and collagen biosynthesis has been followed as the clones grow and eventually lose division capacity. Analysis of collagen type at each successive subculture until the time of cellular senescence has shown that a change in synthesis occurs from the cartilage-specific Type II collagen (chain composition [alpha1(II)]3) to a mixture of Type I collagen (chain composition [alpha1(I)2alpha2) and the Type I trimer (chain composition[alpha1(I)]3). The results demonstrate unequivocally that the expression of the chick chondrocyte phenotype is unstable in vitro, and that previous experiments with mass cultures of chondrocytes cannot be accounted for by overgrowth of fibroblasts. Since similar morphological changes and a similar "switching" in collagen biosynthesis have been observed after growth of chondrocytes for a few days in 5-bromo-2'-deoxyuridine, it is proposed that growth in this analog accelerates those changes that eventually lead to cellular senescence.
Effect of Fv-1 gene product on proviral DNA formation and integration in cells infected with murine leukemia viruses.
Authors: Jolicoeur P , Baltimore D
Published: May 2006

The amounts of unintegrated murine leukemia virus-specific DNA detected by molecular hybridization in extracts of Fv-ln/n (strains NIH/3T3, SIM) or Fv-lb/b (strains JLS-V9, SIM.R) mouse cells after infection with N- or B-tropic viruses were found to be the same in both permissive and resistant cells. Therefore, formation of DNA products from the viral RNA template does not appear to be grossly affected by the Fv-l gene product. Integration of virus-specific DNA into chromosomal cellular DNA was assayed by hybridization of radioactive complementary DNA to DNA from infected cells.With either NIH/3T3 or SIM.R cells infected with N- or B-tropic viruses, integration of proviral DNA could be detected in permissive cells but not in nonpermissive cells. The Fv-l gene product therefore appears to prevent integration of proviral DNA.
Elevated serum ribonuclease in patients with pancreatic cancer.
Authors: Reddi K K , Holland J F
Published: May 2006

Serum RNase (ribonuclease) of normal persons and of patients with pancreatitis, carcinoma of pancreas, or other neoplasms was determined with poly(C) as substrate. Strikingly abnormal elevations occur in the serum RNase of patients with pancreatic cancer. There is no elevation in the serum RNase level of patients with pancreatitis. Average serum RNase values of 52 normal persons, 10 patients with pancreatitis, 30 patients with pancreatic cancer, 28 patients with breast cancer, 11 patients with lung cancer, 20 patients with colon cancer, six patients with stomach cancer, and four patients with liver cancer, respectively, were 104, 120, 383, 131, 173, 197, 194, and 152 units/ml of serum. Ninety percent of the patients with pancreatic cancer were above the level of 250 units of serum and 90% of all patients with varied cancers were below this level. In the presence of severe renal insufficiency, marked elevation of serum RNase was also observed. Serum RNase, because of its unique specificity, pancreatic origin, and its abnormal elevation in sera of patients with pancreatic cancer, serves as a reliable biochemical marker of carcinoma of the pancreas in the presence of normal renal function.
Chemical characterization of the selenoprotein component of clostridial glycine reductase: identification of selenocysteine as the organoselenium moiety.
Authors: Cone J E , Del Río R M , Davis J N , Stadtman T C
Published: May 2006

A small, heat-stable selenoprotein, one of the components of the glycine reductase complex, was labeled with 75Se by growth of Clostridium sticklandii in the presence of Na2 75SeO3. The selenium-containing moiety, which is essential for the biological activity of the protein, was shown to be a selenocysteine residue. It was isolated as its Se-carboxymethyl, Se-carboxyethyl, and Se-aminoethyl derivatives from digests of the pure 75Se-labeled protein that had been reduced and treated with the various alkylating agents prior to hydrolysis. In each instance the 75Se-labeled moiety obtained from an alkylated protein sample and the corresponding alkyl derivative of authentic selenocysteine were indistinguishable. Several studies of the native selenoprotein detected a chromophore (UVmax 238nm) that appeared upon reduction of the protein with KBH4 and rapidly disappeared upon exposure to oxygen. This oxygen-labile chromophore is thought to be the ionized -SeH group of the selenocysteine residue.
Nonsuppressible insulin-like activity and thyroid hormones: major pituitary-dependent sulfation factors for chick embryo cartilage.
Authors: Froesch E R , Zapf J , Audhya T K , Ben-Porath E , Segen B J , Gibson K D
Published: May 2006

Serum from hypothyroid hypophysectomized rats did not stimulate sulfation or incorporation of amino acids into chick embryo sterna. When such rats were treated for a short time with growth hormone (somatotropin), their serum stimulated incorporation both of sulfate and of amino acids. The different actions of the two types of sera were not due to changes in thyroid state. The results support the existence in serum of a sulfation factor for chick embryo cartilage that is dependent upon growth hormone. Highly purified preparations of nonsuppressible insulin-like activity from human serum stimulated incorporation of amino acids, and of uridine into RNA, in chick embryo sterna in vitro; chondrocytes prepared from this tissue had specific high-affinity binding sites for this insulin-like activity. However, sulfate incorporation was stimulated very little, unless serum from hypothyroid hypophysectomized rats was also present. When L-3,5,3'-triiodothyronine was added as well, the stimulation was enhanced further. From these and other experiments, we conclude that (i) nonsuppressible insulin-like activity or a closely related peptide is the growth-hormone-dependent growth and sulfation factor for chick embryo cartilage: (ii) a second, unidentified factor must be present for the insulin-like activity to stimulate sulfation; and (iii) stimulation of sulfation by thyroid hormones in vitro is additive to that of nonsuppressible insulin-like activity.
Diphenylhydantoin (dilantin) gingival hyperplasia: drug-induced abnormality of connective tissue.
Authors: Hassell T M , Page R C , Narayanan A S , Cooper C G
Published: May 2006

Various degrees of gingival overgrowth may occur in individuals taking diphenylhydantoin, a drug used widely in the treatment of epilepsy. The tissue overgrowth is made up predominantly of collagen, and may therefore be a useful model for analysis of fibrosis and some other connective tissue abnormalities. Fibroblasts derived from the overgrown tissue exhibit a level of protein synthetic activity approximately twice that of comparable cells obtained from nonepileptic control individuals and from the gingiva of age-matched epileptics taking the drug but not exhibiting gingival enlargement. In addition, 20% of the protein synthesized by cells from the affected tissue is collagen, whereas collagen accounts for only about 11% of the total protein produced by control cells of both types. The drug appears to induce or select for fibroblasts characterized by enhanced levels of protein synthesis and collagen production. This alteration persists through several cell replications in vitro in the absence of drug.
Presynaptic calcium currents and their relation to synaptic transmission: Voltage clamp study in squid giant synapse and theoretical model for the calcium gate
Authors: Llinás Rodolfo , Steinberg Izchak Z. , Walton Kerry
Published: May 2006

A voltage clamp study of the presynaptic terminal in squid stellate ganglion has given quantitative results relating inward Ca
2+
current to presynaptic membrane potential and postsynaptic response to inward Ca
2+
current. The results indicate an
S
-shaped curve for the relationship between presynaptic potential and Ca
2+
current and a linear relationship between Ca
2+
current and postsynaptic potential. A similar
S
-shaped curve was found for the time-dependent properties of the Ca
2+
conductance. Based on these results a mathematical model was developed which accounts for the experimental results in this and previously published papers by other authors. The model suggests that five subunits are involved in the Ca
2+
gate and that the subunits change noncooperatively from an inactive to an active form upon membrane depolarization.
Degradation of cationized low density lipoprotein and regulation of cholesterol metabolism in homozygous familial hypercholesterolemia fibroblasts.
Authors: Basu S K , Goldstein J L , Anderson G W , Brown M S
Published: May 2006

Cultured fibroblasts derived from patients with homozygous familial hypercholesterolemia, which lack functional low density lipoprotein (LDL) receptors, fail to bind, take up, or degrade the lipoprotein with high affinity; therefore LDL-cholesterol is not made available for suppression of cholesterol synthesis or activation of cholesteryl ester formation. When LDL was given a positive charge by reaction with N,N-dimethyl-1,3-propanediamine (cationized LDL), the rate of degradation of the lipoprotein was increased by more than 100-fold in the homozygous familial hypercholesterolemia fibroblasts. Degradation of cationized LDL was inhibited by chloroquine, suggesting that it occurred in cellular lysosomes. Although the cationized LDL entered the cell through a mechanism independent of the LDL receptor, the cholesterol liberated from the degradation of the lipoprotein became available for suppression of cholesterol synthesis and stimulation of cholesteryl ester formation in the homozygous familial hypercholesterolemia fibroblasts. The rate of degradation of albumin by fibroblasts was also increased by more than 100-fold when this protein was coupled to N,N-dimethyl-1,3-propanediamine. The ability to deliver a protein to lysosomes by giving it a strong positive charge may have potential relevance not only to familial hypercholesterolemia, but also to inborn errors of metabolism that involve deficiencies in lysosomal enzymes.
Abnormalities in the glycosphingolipid content of human Pk and p erythrocytes.
Authors: Marcus D M , Naiki M , Kundu S K
Published: May 2006

Erythrocytes of the rare Pk phenotype lack the blood group P antigen, and p erythrocytes lack both P and Pk antigens. On the basis of immunological data we suggested previously that the P and Pk antigens are the glycosphingolipids globoside and trihexosyl ceramide, respectively, and we have now confirmed these designations by chemical analysis of erythrocytes lacking these antigens. The Pk erythrocytes contain only traces of globoside and have a marked excess of trihexosyl ceramide in comparison with normal erythrocytes. The p erythrocytes lack globoside and trihexosyl ceramide and contain an excess of lactosyl ceramide and other complex glycolipids. Our analyses of normal erythrocytes also revealed complex gangliosides with the approximate chromatographic mobilities of GD1b and GT1, and several gangliosides containing N-acetylglucosamine.
Identification of virion polypeptides in hamster cells transformed by herpes simplex virus type 1.
Authors: Gupta P , Rapp F
Published: May 2006

Ten polypeptides were detected on the surface of the virion of herpes simplex virus type 1. Of these ten polypeptides, three were detected in hamster cells transformed by herpes simplex type 1.
Synthesis of two collagen types by embryonic chick corneal epithelium in vitro.
Authors: Linsenmayer T F , Smith G N , Hay E D
Published: May 2006

To better understand the mechanisms involved in matrix development, we have analyzed the collagen synthesized by embryonic corneal epithelium, the tissue known to produce the collagenous component of the primary corneal stroma. Isolated epithelia were cultured in vitro in medium containing [oH]proline and the newly synthesized, labeled collagen was extracted, fractionally salt precipitated, and analyzed by carboxymethyl-cellulose chromatography and peptide mapping after cleavage with cyanogen bromide. The data show that the cornela epithelium produces at least two different types of collagen, one similar, if not identical, to the type I molecule of skin, and a second similar, if not identical, to the type II molecule of cartilage. Type II, heretofore, had been thought to be characteristic of cartilage extracellular matrix.
Release of ovoperoxidase from sea urchin eggs hardens the fertilization membrane with tyrosine crosslinks
Authors: Foerder Charles A. , Shapiro Bennett M.
Published: May 2006

One feature of fertilization is the alteration of the vitelline layer, by components released from the egg, to produce an elevated, covalently crosslinked, hard, insoluble, fertilization membrane. The following evidence indicates that crosslinking and hardening are caused by the production of diand trityrosyl residues, by oxidation of protein-bound tyrosyl residues in the presence of a peroxidase. Hardening of the fertilization membrane, as evidenced by its loss of solubility in 50 mM dithiothreitol, is inhibited by compounds known to inhibit many peroxidases. A peroxidase, here called the ovoperoxidase, is released from eggs at fertilization. This enzyme is inhibited by the same compounds that inhibit hardening and at similar concentrations. Inhibitors of the ovoperoxidase and the hardening reaction include KCN, 3-amino-1,2,4-triazole, NaN
3
, phenylhydrazine, K
4
Fe(CN)
6
, sodium sulfite, and glycine ethyl ester. In addition, tyramine and
N
-acetyltyrosine both inhibit hardening, but
O
-methyltyrosine does not. Dityrosyl and trityrosyl residues are found in acid hydrolysates of isolated, hardened fertilization membranes. These residues have been identified by cellulose phosphate column chromatography, thin-layer chromatography, and amino acid analysis. The amino acid data have been used to estimate that there is one dityrosine crosslink per 55,000 daltons of protein.

We suggest that, by catalyzing the crosslinking of tyrosyl residues, the ovoperoxidase leads to the production of a hard fertilization membrane that blocks the entry of additional sperm. Because peroxidases are spermicidal, a secondary function of the enzyme could be to kill sperm in the vicinity of the fertilized egg.
Amino acid sequence of a myosin fragment that contains SH-1, SH-2, and Ntau-methylhistidine.
Authors: Elzinga M , Collins J H
Published: May 2006

A peptide having 92 amino acid residues and a calculated molecular weight of 10,478 was isolated from a cyanogen bromide digest of rabbit skeletal muscle myosin. It contained both proline and Ntau-methylhistidine, indicating that it arose from the portion of the heavy chain that folds to form most of the globular head of the myosin molecule. The amino acid sequence of the peptide included the two sulfhydryl groups whose alkylation modifies myosin's catalytic properties: SH-2 at position 11 in the peptide, and SH-1 at position 21. This proximity in the sequence means that SH-1 and SH-2 must be relatively close together in myosin, and several lines of evidence suggest that this region is near the catalytic or actin binding site(s) of myosin.
Oligomycin-dependent ionophoric protein subunit of mitochondrial adenosinetriphosphatase.
Authors: Criddle R S , Packer L , Shieh P
Published: May 2006

A proteolipid isolated from yeast mitochondrial adenosinetriphosphatase (subunit 9) (ATP phosphohydrolase; EC 3.6.1.3) by chloroform/methanol extraction has been shown to discharge photo-induced potentials across a planar phospholipid membrane containing bacteriorhodopsin. Oligomycin, a specific inhibitor of oxidative phosphorylation which binds to this protein, allows the potential gradient to be reestablished. When proteolipid was isolated from an oligomycin-resistant strain, ionophoric activity was still obtained but the effect was not reversed by oligomycin. These studies suggest that the hydrophobic subunit-9 polypeptide is the ionophoric component linking ATP synthesis (hydrolysis) with proton translocation.
Helper factor(s) for growth of adeno-associated virus in cells transformed by adenovirus 12.
Authors: Handa H , Shiroki K , Shimojo H
Published: May 2006

Evidence is presented that a helper factor(s) for growth of adeno-associated virus (AAV) is present in cells transformed by adenovirus type 12 (Ad12). The growth of AAV was observed in heterokaryons formed by fusion of human KB and Ad12-transformed rodent cells by using ultraviolet-inactivated Sendai virus without coinfection of cells with adenovirus. The presence of the helper factor(s) for AAV growth in rat cells transformed by the EcoRI-C fragment or the HindIII-G fragment of Ad12DNA suggests that the helper factor(s) induced by infection with adenovirus is the Ad12-specific T antigen.
In vivo site-specific genetic recombination promoted by the EcoRI restriction endonuclease.
Authors: Chang S , Cohen S N
Published: May 2006

Site-specific genetic recombinations promoted in vivo by the EcoRI endonuclease has been demonstrated by using constructed hybrid plasmids in which the chloramphenicol resistance gene was inactivated by insertion of DNA fragments at an EcoRI site within the gene. Such recombination can involve either the joining of intracellularly generated cohesive termini of the same DNA fragment or intermolecular ligation of different DNA fragments. DNA cleavage and ligation in vivo are precise: recombinant DNA molecules show functional continuity of the gene sequence cleaved by the enzyme and regeneration of nucleotide recognition sites for both the EcoRI endonuclease and the EcoRI DNA methylase. In other experiments, EcoRI-generated fragments of eukaryotic DNA that had not been modified by the Escherichia coli K methylase were shown to be taken up by bacterial cells and to undergo intracellular ligation to segments of bacterial plasmid DNA.
Stimulus-secretion coupling in chromaffin cells isolated from bovine adrenal medulla
Authors: Schneider Allan S. , Herz Ruth , Rosenheck Kurt
Published: May 2006

Bovine adrenal chromaffin cells were isolated by removal of the cortex and sequential collagenase digestion of the medulla. The catecholamine secretory function of these cells was characterized with respect to acetylcholine stimulation, cation requirements, and cytoskeletal elements. The dose-response curve for stimulated release had its half-maximum value at 10
-5
M acetylcholine, and maximum secretion was on the average 7 times that of control basal secretion. The differential release of epinephrine versus norepinephrine after stimulation with 0.1 mM acetylcholine occurred in proportion to their distribution in the cell suspension. The cholinergic receptors were found to be predominantly nicotinic. The kinetics of catecholamine release were rapid, with significant secretion occurring in less than 60 sec and 85% of maximum secretion within 5 min. A critical requirement for calcium in the extracellular medium was demonstrated, and 80% of maximum secretion was achieved at physiologic calcium concentrations. Stimulation by excess potassium (65 mM KCl) also induced catecholamine secretion which differed from acetylcholine stimulation in being less potent, in having a different dependence on calcium concentration, and in its response to the local anesthetic tetracaine. Tetracaine, which is thought to inhibit membrane cation permeability, was able to block acetylcholine-stimulated but not KCl-stimulated secretion. The microtubule disrupting agent vinblastine was able to block catecholamine release whereas the microfilament disrupter cytochalasin B had little effect. The results show the isolated bovine chromaffin cells to be viable, functioning, and available in large quantity. These cells now provide an excellent system for studying cell surface regulation of hormone and neurotransmitter release.
Luminal membrane retrieved after exocytosis reaches most Golgi cisternae in secretory cells
Authors: Herzog Volker , Farquhar Marilyn G.
Published: May 2006

Dextran was used to trace membrane retrieved from the luminal surface after induced exocytosis in secretory cells of rat lacrimal and parotid glands. Two different approaches were used: (
a
) isolated acini were incubated
in vitro
with dextran followed by stimulation with carbamylcholine (lacrimal) or isoproterenol (parotid) and (
b
) rats were injected with isoproterenol followed by dextran infusion into the parotid duct
in vivo
. The main findings were the same regardless of the gland source or experimental approach. Dextran was taken up initially via coated pits into smooth-surfaced apical vesicles. Shortly thereafter it was found in multiple cell compartments: within the stacked Golgi cisternae, in condensing vacuoles, and in lysosomes. Uptake was more rapid and uniform
in vivo
; dextran was seen in multiple cisternae of numerous Golgi complexes within 5 min after infusion. In acini incubated
in vitro
uptake into Golgi cisternae was more delayed and occurred with increasing frequency up to 60 min; also, more dextran was taken up into lysosomes, which were more numerous
in vitro
than
in vivo
. The results demonstrate that, after exocytosis, membrane is removed from the cell surface via vesicles that fuse with multiple cell compartments. The two novel findings are: (
a
) the demonstration that the tracer can reach most of the Golgi cisternae in a given stack and (
b
) the demonstration of the rapidity with which the process takes place (i.e., within 5 min). The findings imply that at least some membrane retrieved from the cell surface after exocytosis fuses with the stacked Golgi cisternae.
Cell--cell interactions in conjugating Escherichia coli: role of traT protein in surface exclusion.
Authors: Achtman M , Kennedy N , Skurray R
Published: May 2006

Escherichia coli cells carrying the F sex factor are poor recipients in conjugation. This phenomenon is called surface exclusion. Two F cistrons, traS and traT, are independently responsible for part of the whole mechanism. The traS gene product reduces DNA transfer within stable mating aggregates. The traT gene product, pTraT, results in a greatly reduced ability to form stable mating aggregates, and thus also leads to reduced DNA transfer within the cell population. pTraT is a 25,000-dalton protein incorporated into the cell envelope outer membrane. It is found in 29,000-84,000 copies per cell, depending on the plasmid expressing it. There is a parallel variation in recipient ability. Models for surface exclusion are discussed.
Gyrate atrophy of the choroid and retina: deficiency of ornithine aminotransferase in transformed lymphocytes.
Authors: Valle D , Kaiser-Kupfer M I , Del Valle L A
Published: May 2006

Gyrate atrophy of the choroid and retina is an inherited form of chorioretinal degeneration associated with hyperornithinemia. We measured the activity of ornithine aminotransferase (L-ornithine:2-oxo-acid aminotransferase, EC 2.6.1.13) in phytohemagglutinin-stimulated lymphocytes of a patient with gyrate atrophy and her daughter. The patient's cells had no detectable ornithine aminotransferase activity, and the activity in the heterozygote's cells was 44% of normal values. Measurements of [3H]thymidine incorporation and other transformation-affected enzymes verified that the patient's cells were transformed. These results demonstrate an enzyme deficiency in gyrate atrophy.
High resolution two-dimensional electrophoresis of human plasma proteins.
Authors: Anderson L , Anderson N G
Published: May 2006

The two-dimensional electrophoretic technique of O'Farrell has been adapted to the analysis of human plasma proteins, and 30 polypeptides have been identified in the pattern produced. Genetic variants involving charge (isoelectric point) or size (molecular weight in the presence of sodium dodecyl sulfate) changes should be routinely detectable in at least 20 proteins at once, facilitating studies of human mutation rates.
Codon specificity of UGA suppressor tRNATrp from Escherichia coli.
Authors: Buckingham R H , Kurland C G
Published: May 2006

A synthetic polyribonucleotide, poly(U5,G), was used to study the codon specificity of wild-type and UGA suppressor tRNATrp from Escherichia coli. Phe (UUU) incorporation directed by this synthetic messenger is reduced somewhat by omission from the incubation mixtures of Val (GUU), Leu (UUG), or Cys (UGU). In contrast, omission of Cys stimulates Trp incorporation, and this effect is much more pronounced with the UGA suppressor tRNATrp than with wild-type tRNA. The apparent replacement of Cys by Trp is specific, because the omission of Val or Leu slightly inhibits Trp incorporation. These data suggest that the UGA suppressor tRNATrp can translate codons of the form UGN (N is any ribonucleotide). In other words, the suppressor tRNATrp translates codons that properly match two out of the three anticodon nucleotides.