bluuebunny/crossref_metadata_2025 huggingface dataset:
Somatic cell hybrids producing antibodies specific for the tumor antigen of simian virus 40.
Authors: Martinis J , Croce C M
Published: May 2006

We have produced somatic cell hybrids between mouse myeloma cells deficient in hypoxanthine phosphoribosyltransferase IMP: pyrophosphate phosphoribosyltransferase; EC 2.4.2.8) and spleen cells derived from mice primed with either syngeneic or allogeneic cells transformed by simian virus 40. Such hybrids produced antibodies specific for simian virus 40 tumor (T) antigen. Only four of twelve independent hybrid cell cultures produced antibodies against simian virus 40 T antigen that crossreacted with the T antigen induced by BK virus, a human papovavirus isolated from patients who had undergone immunosuppressive therapy.
New region of the simian virus 40 genome required for efficient viral transformation.
Authors: Bouck N , Beales N , Shenk T , Berg P , di Mayorca G
Published: May 2006

Viable mutants of simian virus 40 with deletions in three regions of the virus genome (map coordinates 0.21-0.17, 0.59-0.54, and 0.67-0.74) have been tested for their ability to transform rat fibroblasts to anchorage independence. Only those mutants whose deletions occur between 0.59 and 0.55 in the proximal part of the early region are defective in transforming ability. The most severely defective of these transform with less than one-hundredth the efficiency of wild type. They retain their defect when tested in Chinese hamster lung cells and when infection is initiated with viral DNA instead of intact virions. Complementation for transformation can be observed between these transformation-defective deletions and a simian virus 40 temperature-sensitive A mutant.
Identification of 5,8-oxyretinoic acid isolated from small intestine of vitamin A-deficient rats dosed with retinoic acid.
Authors: Napoli J L , McCormick A M , Schnoes H K , DeLuca H F
Published: May 2006

A retinoid was isolated by a multistep procedure from the small intestines of vitamin A-deficient rats given a single dose of retinoic acid. The compound, designated 8II, was pure, as demonstrated by four high-pressure liquid chromatographic procedures. It was positively identified as 5,8-oxyretinoic acid by ultraviolet spectrophotometry, mass spectrometry, and spectral and chromatographic comparison to known compounds. It is probable that 5,8-oxyretinoic acid was produced from 5,6-epoxyretinoic acid under the acidic conditions used in the isolation. It is highly probable, therefore, that the natural product is 5,6-epoxyretinoic acid.
Synthesis of cold-insoluble globulin by cultured calf endothelial cells.
Authors: Macarak E J , Kirby E , Kirk T , Kefalides N A
Published: May 2006

Radiolabeled amino acids were incorporated into nondialyzable protein by cultures of endothelial cells derived from calf aorta. Antibody prepared against purified bovine plasma cold-insoluble globulin (CIG) formed a strong precipitin line upon immunodiffusion against 3H-labeled proteins from endothelial cell culture media. This precipitin line formed a line of identity with the precipitin line formed by anti-CIG and purified CIG. Double-antibody immunoprecipitation of 3H-labeled protein showed that 36.3% of the radioactivity was specifically precipitated by the anti-CIG antibody. Gel filtration and polyacrylamide gel electrophoresis of the immunoprecipitate indicated that it contained a single protein species whose molecular weight was consistent with that of CIG isolated from plasma. When cultured cells were examined by indirect immunofluorescence microscopy, the endothelial cells stained specifically with anti-CIG antibody. These data indicate that cultured endothelial cells derived from calf aorta synthesize and secrete a protein antigenically similar to CIG.
Conformationally restricted bicyclic analogs of somatostatin.
Authors: Veber D F , Holly F W , Paleveda W J , Nutt R F , Bergstrand S J , Torchiana M , Glitzer M S , Saperstein R , Hirschmann R
Published: May 2006

A model for a biologically active conformation of somatostatin is proposed. This model is based primarily on the biological results obtained with novel bicyclic somatostatin analogs having a covalent bridge replacing the side chains of residues 5 and 10, 6 and 11, and 5 and 12, respectively, rather than on physical measurements on the hormone in solution. The high activity of an analog in which Phe6 and Phe11 are replaced by cystine provides evidence that these phenylalanines stabilize the biologically active conformer through "hydrophobic bonding" but do not directly interact with the receptor. The synthesis of the novel bicyclic analogs of somatostatin and the effects of these on the inhibition of secretion of insulin, glucagon, growth hormone, and gastric acid are described.
Elimination of cooperativity in aspartate transcarbamylase by nitration of a single tyrosine residue.
Authors: Landfear S M , Evans D R , Lipscomb W N
Published: May 2006

In a previous report [Landfear, S. M., Lipscomb, W. N. & Evans, D.R. (1978) J. Biol. Chem. 253, 3988--3996] we demonstrated that tetranitromethane can be employed to nitrate a limited number of tyrosine residues in aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2); such modification eliminates cooperativity, feedback inhibition, and enzymatic activity, and reduces binding of the feedback inhibitor cytidine triphosphate. Cooperativity is lost more rapidly than other properties, and this loss correlates with the nitration of a single tyrosine residue. In this paper, we describe the saturation kinetics of hybrid species constructed from nitrated subunits of one type (either catalytic or regulatory) and native subunits of the other type. We conclude that the modification responsible for loss of cooperativity is on the catalytic subunit. The tryptic peptide containing this modification has been isolated and identified.
Inhibition of translation by poliovirus: inactivation of a specific initiation factor.
Authors: Rose J K , Trachsel H , Leong K , Baltimore D
Published: May 2006

Translation of vesicular stomatitis virus (VSV) mRNA, like host mRNA translation, is inhibited in cells infected with poliovirus. To study the mechanism of poliovirus-induced inhibition of protein synthesis, we prepared extracts from poliovirus-infected and uninfected HeLa cells. Poliovirus mRNA was translated in lysates from both infected and uninfected cells, while VSV mRNA was translated only in the lysate from uninfected cells. Addition of purified translation initiation factors to the extract from infected cells showed that one factor, eIF-4B, could restore VSV mRNA translation in the infected lysate, but did not increase poliovirus mRNA translation. Further experiments involving translation of VSV mRNA in mixed extracts from poliovirus-infected and uninfected cells showed (i) that there was not an excess of an inhibitor of VSV mRNA translation in the infected lysate, but (ii) that an acitivity that caused a slow inactivation of eIF-4B was present in the infected lysate. Inactivation of eIF-4B appears to be the mechanism by which poliovirus infection causes a selective inhibition of translation.
Mutations of bacteriophage T7 that affect initiation of synthesis of the gene
0.3
protein
Authors: Dunn John J. , Buzash-Pollert Elizabeth , Studier F. William
Published: May 2006

Two different mutations that greatly diminish the rate of synthesis of the gene
0.3
protein of bacteriophage T7 have been characterized. One is in the initiator triplet for the
0.3
protein, changing it from AUG to ACG. This mutation was found to have little effect on binding of ribosomes to the
0.3
mRNA
in vitro
, although
0.3
protein synthesis was greatly depressed
in vitro
as well as
in vivo
. A suppressor mutation that partially restores the wild-type rate of synthesis was found to lie within the
0.3
RNA but not close to the mutant ACG (more than 64 nucleotides away). The second mutation is a G-to-A transition located 11 bases to the 5′ side of the initiator AUG. This change eliminates a possible five-base pairing with a sequence near the 3′ end of 16S ribosomal RNA, an interaction previous workers have proposed to be important for initiation of protein synthesis. This mutation causes the site of ribosome binding to shift about 15 bases to the 3′ side, centering on an internal AUG, but this new site has only a poor potential interaction with 16S RNA. A suppressor mutation that restores the rate of
0.3
protein synthesis to essentially wild-type levels and also restores wild-type ribosome-binding behavior was found to lie adjacent to the original mutation, creating a new four-base complementarity with 16S RNA. These results provide strong support for the idea that a pairing interaction between mRNA and 16S RNA is involved in specific initiation of protein synthesis in
Escherichia coli
and indicate that this interaction may be important in selecting the site in mRNA at which the ribosomes bind.
Direct evidence for 6-fold symmetry of the herpesvirus hexon capsomere.
Authors: Furlong D
Published: May 2006

Rotational power spectrum analysis of scanning transmission electron micrographs of negatively stained herpesvirus capsids has given direct evidence for the 6-fold symmetry of the herpesvirus hexon capsomere. Individual hexons have been analyzed in situ without interference from other parts of the capsid because only one level of the capsid was in focus in the micrograph. This study found hexons to have 6-fold symmetry. The majority of the mass of each hexon subunit was seen to lie on a line connecting the centers of adjacent capsomeres. This agrees with analysis of conventional micrographs of capsid fragments, which are also presented, as well as with biochemical data and theoretical expectations.
Induction of murine erythroleukemia differentiation by actinomycin D
Authors: Terada Masaaki , Epner Elliot , Nudel Uri , Salmon Jane , Fibach Eitan , Rifkind Richard A. , Marks Paul A.
Published: May 2006

Murine erythroleukemia cells are induced to differentiate by 0.5-5 ng of actinomycin D per ml. Murine erythroleukemia cells cultured with actinomycin D prolong cell doubling time but achieve the same density after 5 days as cells without inducer. Actinomycin D causes over 95% of the cells to become benzidine-reactive. [
3
H]Actinomycin D uptake into DNA can be detected within 2 hr and reaches a maximum (approximately 0.1 pmol/10
6
cells) by 10-12 hr. It is estimated that about one out of 10
5
dG·dC pairs is bound to actinomycin D. Commitment to differentiation, assayed by transfer of cells to culture without inducer, was detected as early as 5 hr. Unlike Me
2
SO, which causes a transient prolongation in G
1
at about 15-20 hr, cells cultured with actinomycin D show a more sustained increase in the proportion of the cells in G
1
. Globin mRNA accumulation was detectable by 19 hr in culture. Alteration in DNA stability in alkaline sucrose gradients was detected by 19 hr. Actinomycin D induces synthesis of Hb
maj
and Hb
min
in approximately equal amounts. A decrease in rates of synthesis of RNA, DNA, and total protein occurs in cells cultured with actinomycin D, as well as in cells cultured with Me
2
SO. No evidence for an early action of actinomycin D at the plasma membrane was obtained by measurement of changes in cell volume or
86
RbCl uptake. Taken together, the present results indicate that actinomycin D is a potent inducer of differentiation of murine erythroleukemia cells and suggest that the target of its effect may be at the level of DNA.
Regulation of antibody heterogeneity by suppressor T cells: diminishing suppressor T cell activity increases the number of dinitrophenyl clones in mice immunized with dinitrophenyl-poly(Glu,Lys,Phe) or dinitrophenyl-poly(Glu,Lys,Ala).
Authors: Kipps T J , Benacerraf B , Dorf M E
Published: May 2006

The anti-hapten responses to the dinitrophenyl (Dnp) conjugate of the random linear terpolymers poly(L-Glu,LLys,LPhe), GLphi, or poly(LGlu,LLys,LAla), GLA, are of highly restricted heterogeneity. Thus, individual mice of most responder strains express an average of two to four anti-Dnp clones to Dnp-GLphi or Dnp-GLA, as measured by isoelectric focusing techniques. To explore whether suppressor T cells regulate the heterogeneity of the anti-hapten response to Dnp conjugates of these polypeptides, various procedures aimed at reducing suppressor T-cell activity were tested for their ability to alter the restricted isoelectric focusing spectrotypes. These procedures, such as adult thymectomy, administration of low doses of cyclophosphamide, and in vivo treatment with anti-I-J antisera, significantly increased the magnitude and heterogeneity of the anti-Dnp antibody response to Dnp-GLphi and Dnp-GLA in strains of mice that possessed responder Ir genes. Such methods failed to alter the nonresponder status of mice that lacked the appropriate Ir genes. Thus, in systems under Ir gene control suppressor T-cell mechanisms appear to be involved in the regulation of the heterogeneity of hapten-specific B-cell responses.
beta-Lipotropin is the major opioid-like peptide of human pituitary and rat pars distalis: lack of significant beta-endorphin.
Authors: Liotta A S , Suda T , Krieger D T
Published: May 2006

beta-Lipotropin is the predominant opioid peptide of the human pituitary and rat pars distalis and is present in concentrations essentially equimolar with corticotropin. When freshly, obtained nonfrozen rat anterior pituitaries were homogenized with 0.2 M HCl, approximately 98% of the immunoreactivity detected utilizing an antiserum that crossreacts equally with beta-lipotropin and beta-endorphin coeluted with 125I-labeled human beta-lipotropin upon molecular sieve chromatography. The remainder of the activity eluted with synthetic human beta-endorphin. Similar results were obtained for human pituitary. HCl homogenization of thawed tissue or homogenization of fresh tissue with acetic acid yielded substantially greater concentrations of beta-endorphin and decreased concentrations of beta-lipotropin. In human subjects, acute anterior pituitary stimulation using either insulin-induced hypoglycemia or vasopressin administration was associated with increased plasma beta-lipotropin and corticotropin levels. At the time of peak concentrations, no significant levels of beta-endorphin were detectable. These data indicate the lack of significant amounts of beta-endorphin in human pituitary. Additionally, there appears to be no specific intrapituitary conversion of beta-lipotropin to beta-endorphin.
Ultrastructural localization of γ-aminobutyric acid receptors in the mammalian central nervous system by means of [
3
H]muscimol binding
Authors: Chan-Palay Victoria , Palay Sanford L.
Published: May 2006

This study utilizes tritiated muscimol binding and electron microscope autoradiography (Ilford L4 emulsion and phenidone development) to localize γ-aminobutyric acid (GABA) receptor sites in the cerebellum of the rat. In the cerebellar cortex, silver grains were associated with somata and dendrites of basket and stellate cells in the molecular layer, with somata and primary and secondary dendritic shafts of Purkinje cells, axons and terminals of basket cells in the
pinceau
or basket, initial axonal segments and myelinated axons of Purkinje cells, and dendrites of granule and Golgi cells in the granular layer, and with somata and dendritic shafts of large and small cells in the cerebellar nuclei. These data correspond well to the light-microscope-autoradiographic observations in the cerebellum previously reported [Chan-Palay, V. (1978)
Proc. Natl. Acad. Sci.
75, 1024-1028]. Label over GABA receptor sites can be localized to the plasma membranes between pre- and postsynaptic elements at synaptic junctions, of which 88.9% of the samples are axodendritic and the remaining 11.1% are axosomatic. GABA receptor sites are also found along axonal membranes of the GABA-containing basket cell within the basket surrounding Purkinje cells, where true axo-axonal synapses are rare. It is speculated that GABA receptors in the basket may suggest a possibility of the basis for synchronization, either self-inhibition or facilitation within the basket formation, or presynaptic suppression of inhibitory action of basket cell on Purkinje cell.
Transposition of plasmid DNA segments specifying hydrocarbon degradation and their expression in various microorganisms
Authors: Chakrabarty A. M. , Friello D. A. , Bopp L. H.
Published: May 2006

The conjugative TOL plasmid (75 Mdal), specifying biodegradation of xylenes, toluene, and trimethylbenzene derivatives, undergoes dissociation in
Pseudomonas aeruginosa
PAO to a nonconjugative TOL
*
plasmid (28 Mdal) and a transfer plasmid termed TOLΔ (48 Mdal). The TOL
*
plasmid is rendered transmissible through introduction of a number of conjugative plasmids such as factor K, CAM, and TOLΔ but not by the FP2 derivative pR0271. Transfer of TOL
*
via factor K or TOLΔ is mediated by the formation of plasmid cointegrates; no recombination is observed with CAM. A recombinant RP4-TOL plasmid (76 Mdal), which has lost resistance to tetracycline, has been isolated. The TOL
*
segment can be transposed from this RP4-TOL recombinant plasmid to other antibiotic resistance plasmids such as R702. A segment of DNA, specifying salicylate degradation from SAL plasmid, was transposed onto pAC10, the TOL
*-
derivative of RP4-TOL recombinant plasmid, which has lost resistance to tetracycline but retains the transfer genes of RP4. Transposition of the salicylate degradative genes onto pAC10 results in the loss of kanamycin resistance. It has been possible to isolate SAL
+
segregants from pAC10[unk]SAL transposition derivatives that have lost the pAC10 plasmid. Such segregants harbor the salicylate degradative genes in the form of a nonconjugative plasmid (SAL
*
). Transfer of RP4[unk]TOL
*
or pAC10[unk]SAL
*
transposition derivatives to
Escherichia coli, Salmonella typhimurium, Agrobacterium tumefaciens
, or
Azotobacter vinelandii
results in the functional expression of the antibiotic resistance genes but not of the hydrocarbon degradative genes. Such genes, however, are fully expressed on being transferred back to
Pseudomonas
.
Evidence that two forms of bovine erythrocyte cytochrome b5 are identical to segments of microsomal cytochrome b5.
Authors: Douglas R H , Hultquist D E
Published: May 2006

Homogeneous preparations of two forms of soluble cytochrome b5 have been obtained from bovine erythrocytes by successive chromatography on DEAE-cellulose, Bio-Gel P-60, and DEAE-Sephadex. Although the two forms could be separated on disc gel electrophoresis, they appeared to have similar molecular weights of approximately 12,000 and identical visible absorbance spectra. The tryptic hemepeptides derived from the two forms of bovine erythrocyte cytochrome b5 are electrophoretically indistinguishable from each other and from the tryptic core hemepeptide derived from liver microsomal cytochrome b5. The bovine erythrocyte tryptic hemepeptide was purified to homogeneity; its amino acid composition was shown to be identical to that of tryptic hemepeptide from liver microsomal cytochrome b5. The amino acid compositions of the two isolatable forms of erythrocyte cytochrome b5 correspond well to the compositions of the 97- and 95-residue segments of native liver microsomal cytochrome b5 that begin at the NH2 terminus. These results agree with the hypothesis that soluble erythrocyte cytochrome b5 is derived from microsomal protein by proteolysis during erythroid maturation.
In vitro biosynthesis and chemical characterization of beta-lipotropin, gamma-lipotropin, and beta-endorphin in rat pars intermedia.
Authors: Seidah N G , Gianoulakis C , Crine P , Lis M , Benjannet S , Routhier R , Chrétien M
Published: May 2006

Three 3-hr incubations of pars intermedia cells from 40 rat pituitaries with [35S]methionine, [3H]lysine, and [3H]leucine sufficed for the identification and chemical characterization of biosynthesized beta-lipotropin, gamma-lipotropin, and beta-endorphin. From the molecular weight, migration on polyacrylamide gels, and sequence Met5, Lys9, Leu14,17, rat beta-endorphin was shown to be identical to its sheep homologue and no trace of Leu5 beta-endorphin could be detected. Rat beta-lipotropin differs from that of sheep in its elution properties on CM-cellulose, and its sequence shows Leu2,10,14, Lys20. Rat gamma-lipotropin shows the same NH2-terminal sequence as beta-lipotropin and is again different from its sheep homologue. The identification of rat beta-lipotropin was confirmed by its selective cleavage into beta-endorphin after trypsin digestion of the citraconylated peptide, a property not observed with rat gamma-lipotropin.
Heat-stable low molecular weight form of phosphodiesterases from bovine pineal gland.
Authors: Sankaran K , Hanbauer I , Lovenberg W
Published: May 2006

The 105,000 X g supernatant fraction of bovine pineal gland contains a phosphodiesterase activity that hydrolyzes both cyclic AMP and cyclic GMP. The rate of hydrolysis is 4-5 times greater with cyclic GMP as substrate than with cyclic AMP. Chromatography of supernatant fraction on Sephadex G-150 resolves phosphodiesterase activity into two fractions designated PDE I and PDE II. These are distinguishable on the basis of their molecular size, substrate specificity, and kinetic parameters. PDE I hydrolyzes cyclic GMP at a faster rate than cyclic AMP and has a molecular weight of 163,000. PDE II appears to be a smaller protein with a molecular weight of 24,400 and is specific for cyclic AMP. PDE I has apparent Km values of 83 and 53 micron for cyclic AMP and cyclic GMP, respectively, whereas PDE II exhibits an apparent Km value of 330 micron for cyclic AMP. With subsaturating concentrations of cyclic AMP as substrate, the phosphodiesterase activity of PDE I is inhibited by the addition of cyclic GMP. However, PDE II activity remains unaffected by cyclic GMP even at concentrations up to 125 micron. PDE II appears to be thermostable, losing only 20% of its activity on heating at 80 degrees for 2 min. Similar treatment completely abolishes the enzyme activity of PDE I.
Embryonic neural retina collagen:
In vitro
synthesis of high molecular weight forms of type II plus a new genetic type
Authors: Linsenmayer Thomas F. , Little Charles D.
Published: May 2006

Chicken neural retina cells from 6- to 7-day embryos were labeled with [
3
H]proline for 24 and 72 hr and the collagenous proteins of the medium were analyzed. Ninety percent of the collagenous proteins eluted from DEAE-cellulose columns as a peak near the middle of the gradient. Upon sodium dodecyl sulfate/polyacrylamide gel electrophoresis, this material consisted predominantly of a slowly migrating procollagen, a smaller amount of an intermediate migrating form, and some α-chain material. Limited enzymatic digestion of this DEAE peak material plus mapping of its CNBr peptides identified this material as a type II precursor. The remaining 10% of the collagenous proteins eluted from DEAE-cellulose at the end of the gradient. Electrophoresis of this fraction showed four major bands. Two migrated near the type II precursors, a third migrated somewhat more slowly, and the fourth was near β-chain dimers. In addition, there were two minor bands. Limited pepsin digestion of this DEAE peak material produced two bands: one migrated slightly more slowly than α1, and the second, considerably more slowly. The CNBr peptide pattern of this material appears to be different from any previously described. Thus, neural retina cells in culture synthesize at least two genetically distinct classes of collagenous proteins. One represents precursors to type II. The second is composed of multiple, very high molecular weight forms which may represent precursors (procollagens) of a new genetic type(s) of collagen.
Primary structure of murine major histocompatibility complex alloantigens: Amino acid sequence studies of the cyanogen bromide fragments of the H-2K
b
glycoprotein
Authors: Coligan J. E. , Kindt T. J. , Ewenstein B. M. , Uehara H. , Nisizawa T. , Nathenson S. G.
Published: May 2006

Radiochemical microtechniques have been used in the amino acid sequence analysis of five major CNBr fragments of the glycoprotein specified by the murine major histocompatibility complex gene
H-2k
b
. These fragments have been tentatively aligned and represent the NH
2
-terminal 80% of the intact molecule. All amino acids except Asp, Asn, and Gln have been assigned in 128 out of 149 possible positions in the NH
2
-terminal portions of each of these fragments. These assignments, which represent approximately 50% of the total sequence from these fragments, are listed below in the order of their alignment in the intact H-2K
b
molecule: IIIn, -PHSLRYFVTAVSRP(G)L(G)(E)PRYM; IIIa, EVGYV--TEFVRF-S-AE(A)PRYEPR(A)--M; Ib, E-EGPEYWERET-KAK(G)-E-SFR--LRTLL(G)YY--TK; Ia, AALITK-KWE-AGEAERLRAYLEGTC-E-L; Ic, ELVETRPAG-GTF-KWAS-VVPLGKE-YY(T). The unassigned positions represented by dashes in the above sequences may be tentatively assigned as Asp, Asn, or Gln.

The NH
2
-terminal sequence obtained for the H-2K
b
molecule was compared to the limited sequence information available for other major histocompatibility complex gene products. An 84% homology (16 of 19 residues) to the H-2K
q
and H-2K
k
molecules, which are identical to one another in the positions compared, was observed. A similar comparison with 28 of the 31 NH
2
-terminal residues of HLA-B7 indicated 68% homology. Furthermore, significant homology was observed between H-K
b
and HLA-B7 in a region of glycosylation, which occurs between positions 85 and 100 in the two molecules.
Proteolytic activity in erythrocyte precursors
Authors: Hanash S. M. , Rucknagel D. L.
Published: May 2006

Thalassemia is characterized by unequal rates of synthesis of the α and β globin chains that are part of the hemoglobin tetramer. In the type of thalassemia due to a defect in β-chain synthesis (β-thalassemia), this imbalance results in a relative exoess of α-chains. We have studied the susceptibility of excess free α-chains to proteolysis. Incubation of isotopically labeled peripheral blood lysates from individuals with β-thalassemia trait in the presence of bone marrow or normoblast lysates from thalassemic or hematologically normal individuals resulted in a decrease in the α/β ratio and a loss of free α-chain radioactivity. Neither contamination with leukocytes nor higher ATP contents in young erythrocytes appeared to be responsible for this activity in normoblasts and bone marrow. We propose that erythroid precursor cells possess proteolytic activity that is markedly diminished in mature cells. This activity serves an important control function in the regulation of hemoglobin synthesis. It accounts at least in part for the more balanced synthesis of α- and β-chains observed in bone marrow than in peripheral blood in heterozygous β-thalassemia. It also plays a fine-tuning role in maintaining balanced synthesis in non-thalassemic erythrocytes.
Interspecies transmission of Creutzfeldt-Jakob disease to Syrian hamsters with reference to clinical syndromes and strains of agent.
Authors: Manuelidis E E , Gorgacz E J , Manuelidis L
Published: May 2006

Experimental Creutzfeldt-Jakob disease was serially transmitted from guinea pigs to Syrian hamsters with 100% incidence, morbidity, and mortality. All animals developed a subacute spongiform virus encephalopathy with neuronal destruction and concomitant astrocytic changes. In the first passage three different clinical syndromes were recorded, each with widely variant incubation times; these results suggested there may be different strains of the Creutzfeldt-Jakob agent, some of which may be partially separated when the agent is passaged from one species to another. Accumulations of neurofilaments in neuronal perikarya and processes and increased lipofuscin were suggestive of changes seen in senility and aging.
Isolation and characterization of a human serum cholesteryl ester transfer protein.
Authors: Chajek T , Fielding C J
Published: May 2006

Human plasma has been shown to contain an apolipoprotein that mediates the transport of cholesteryl ester from high density lipoprotein (HDL) to very low density lipoprotein (VLDL) or low density lipoprotein (LDL). This activity, confined to the density greater than 1.063 g/ml interval, has been isolated from HDL and appears as a single migrating species by anionic or sodium dodecyl sulfate/polyacrylamide gel electrophoresis. It is unreactive to antibodies to the major HDL apolipoproteins. Antibodies prepared against this factor and immobilized on Sepharose remove the capacity of HDL and density greater than 1.21 g/ml fractions as well as whole plasma to transport cholesteryl ester from HDL. The system shows saturation kinetics with respect to plasma LDL and VLDL concentrations, and transport of cholesteryl ester was associated with reciprocal and equimolar back-transport of triglyceride from VLDL and LDL to the HDL fraction. The possible relationship of this apoprotein to apoprotein D is discussed.
"Conjugal" transfer of plasmid DNA among oral streptococci.
Authors: LeBlanc D J , Hawley R J , Lee L N , St Martin E J
Published: May 2006

The beta plasmid from Streptococcus faecalis strain DS5, which codes for resistance to erythromycin and lincomycin, was introduced into a Lancefield group F streptococcus, strain DR1501, by transformation. This strain, DR1501 (beta), was found to be an excellent donor of the beta plasmid and readily transferred the resistance markers to various lactic acid bacteria, including certain strains of S. mutans, S. sanguis, and S. salivarius. Evidence is presented indicating that the transfer of the beta plasmid is mediated by a mechanism that requires cell-to-cell contact. The transfer of plasmid DNA during conjugation has been confirmed by the isolation of beta plasmid from transconjugant clones and by their ability to then serve as donors of the erythromycin and lincomycin resistance markers.
Siderophore electrochemistry: relation to intracellular iron release mechanism.
Authors: Cooper S R , McArdle J V , Raymond K N
Published: May 2006

Previous studies have shown that there is a major difference between the iron release mechanism of enterobactin, a catechol-based siderophore, and that of the hydroxamate-based siderophores such as ferrichrome. For ferric enterobactin there is an esterase that hydrolyzes the ligand during iron release. In contrast, iron is released by the hydroxamate-based siderophores and the ligands are reused in subsequent iron transport. It has been suggested that release of iron by hydroxamates occurs by reduction to the ferrous complex, a process that does not occur for ferric enterobactin. Cyclic voltammograms of ferrichrome A and ferrioxamine B exhibit reversible one-electron waves with pH-independent formal potentials (Ef-vs. the normal hydrogen electrode) -446 and -454 mV, respectively, within the range of physiological reductants. Ferric enterobactin also shows a reversible one-electron wave (at pH greater than 10) with Ef = -986 mV vs. the normal hydrogen electrode. From the pH dependence of this potential we estimate a reduction potential of -750 mV at pH 7. In sharp contrast to the value for the ferric hydroxamates, this value is well below the range of physiological reducing agents. The results demonstrate that the observed hydrolysis of enterobactin is a necessary prerequisite to in vivo release of iron from the siderophore via ferric ion reduction.
A protein methylesterase involved in bacterial sensing.
Authors: Stock J B , Koshland D E
Published: May 2006

A protein methylesterase has been identified in soluble extracts of Salmonella typhimurium and Escherichia coli. This enzyme catalyzes the hydrolysis of gamma-glutamyl methyl ester residues from membrane-bound 60,000-molecular weight proteins that are essential for chemotaxis. Analyses of methylesterase activity in a variety of chemotactically defective strains suggest that the methylesterase is a product of the cheX gene in Salmonella and the cheB gene in E. coli. In addition, the cheT gene product in S. typhimurium seems to play a role in expression of methylesterase activity. Mutant strains lacking the protein methylesterase tumble incessantly in the absence of attractant gradients. This behavior is the converse of that shown by mutant strains defective in methyltransferase activity, which swim smoothly in the absence of repellent gradients. This finding indicates that reversible methylation acts as a control mechanism and that both a methyltransferase and a protein methylesterase are instrumental in bacterial sensing.
Transcription patterns of amplified Dytiscus genes coding for ribosomal RNA after injection into Xenopus oocyte nuclei.
Authors: Trendelenburg M F , Zentgraf H , Franke W W , Gurdon J B
Published: May 2006

Oocytes of the frog Xenopus were injected with purified circular DNA containing amplified rRNA genes of the water beetle Dytiscus. Nuclear contents of injected oocytes were spread and examined by electron microscopy. Most of the Dytiscus DNA seen in injected nuclei contained regions indensely packed with polymerases and nascent transcripts. Apparently normal, as well as abnormal, patterns of transcription were observed. By this type of experiment, it may become possible to recognize the transcribed regions and immediate transcripts of cloned DNA molecules whose activity cannot be seen by electron microscopy of normal nuclei.
Development of parathyroid hormone- and calcitonin-activated adenylate cyclases in embryonic chicken limb and in cultured cells from embryonic chicken limb.
Authors: Zull J E , Krug S , Abel D , Caplan A I
Published: May 2006

Activation of adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] by parathyroid hormone (PTH) and calcitonin was measured as a function of stage of development in embryonic chicken limb buds. Responsiveness to both hormones develops in the tissue at the time when nascent bone is forming. In addition, a temporal sequence of development of hormone response was observed, with a PTH-activated adenylate cyclase appearing earlier than the calcitonin-activated enzyme. The responsiveness to the two hormones was additive, indicating the presence of two receptor populations. Undifferentiated cells obtained from limb buds prior to appearance of hormonal responsiveness were cultured and were found to develop a PTH-activated adenylate cyclase in vitro. However, a calcitonin-stimulated enzyme did not appear in such cultures. The PTH-activated enzyme was found to be similar to that present in bone in regard to its sensitivity to PTH. The enzyme did not respond to other hormones, and myoblast cultures did not develop a PTH-activated adenylate cyclase, indicating that a true bone adenylate cyclase was being measured.
Role of T lymphocytes in cellular immune responses during herpes simplex virus infection in humans.
Authors: Rasmussen L , Merigan T C
Published: May 2006

Lymphocyte blast transformation and interferon production in mononuclear cell culture prepared on Ficoll-Hypaque gradients from individuals with herpes simplex virus-I infection were enhanced by a disease recurrence. Responses to both herpes simplex virus-2 and phytohemagglutinin were unaltered. Transformation to herpes simplex virus-I antigen was adversely affected by depleting either thymus-derived (T) lymphocytes or bone marrow-derived (B) lymphocytes together with monocytes from cultures. The transformation response was reconstructed when the selectively depleted lymphocyte populations were recombined. X-irradiation of either T or B lymphocytes and monocytes showed that T lymphocytes incorporated [3H]thymidine with the aid of a radioresistant non-rosetting cell, probably a monocyte. Depletion of B lymphocytes and monocytes, but not of T lymphocytes, resulted in reduction in interferon production. Irradiated B lymphocytes and monocytes failed to produce significant quantities of interferon, suggesting that a radiosensitive B cell was a major interferon source.
Cells nonproductively transformed by Abelson murine leukemia virus express a high molecular weight polyprotein containing structural and nonstructural components.
Authors: Reynolds F H , Sacks T L , Deobagkar D N , Stephenson J R
Published: May 2006

Cell clones nonproductively transformed by the replication-defective Abelson strain of murine leukemia virus (AbLV) were analyzed for type C viral antigen expression by competition immunoassay. AbLV-transformed mink non-producer lines were found to express a 110,000- to 130,000-molecular weight polyprotein containing murine leukemia virus gag proteins p15 and p12 covalently linked to nonstructural AbLV-coded component(s) of around 80,000-100,000 molecular weight. This polyprotein lacked detectable antigenic cross-reactivity with other virion-coded gag gene proteins such as p30, p10, the viral reverse transcriptase (RNA-dependent DNA polymerase), or the major viral envelope glycoprotein, gp70. By analogy to earlier data on feline and avian sarcoma viruses, these results suggest that a portion of this polyprotein might represent the AbLV src gene product and that in translation it is initially linked in precursor form to gag structural proteins. Superinfection of mink cells nonproductively transformed by AbLV--with either a wild mouse amphotropic type C virus isolate, 4070-A, or with the endogenous cat virus, RD114--led to production of pseudotype virus containing high concentrations of the AbLV-coded precursor polyprotein.
Chemical determination of polypeptide hormones.
Authors: Tatemoto K , Mutt V
Published: May 2006

The presence or absence of peptide hormones in tissue extracts may in certain cases be demonstrated by exposing the extracts to conditions under which characteristic fragments of the polypeptide molecule in question are formed and then analyzing for such fragments. An approximate quantitation of the hormones may also be achieved thereby. In the present work the COOH-terminal fragments of polypeptides containing characteristic alpha-amide groups were released enzymatically and then converted into the fluorescent dansyl derivatives, which were identified by thin-layer chromatography. In this way the presence of secretin, cholecystokinin, and the vasoactive intestinal peptide in concentrates of porcine intestinal extracts were demonstrated by their COOH-terminal amide fragments: valine (or leucylvaline) amide, phenylalanine amide, and asparagine (or leucylasparagine) amide, respectively. The analytical methodology used in the present study may also be useful in devising simple and reliable chemical assay methods for the isolation of already known polypeptides and in the isolation of previously uncharacterized polypeptides from natural sources.
Direct demonstration that receptor crosslinking or aggregation is important in insulin action
Authors: Kahn C. Ronald , Baird Kathleen L. , Jarrett David B. , Flier Jeffrey S.
Published: May 2006

Exposure of adipocytes to antibodies to the insulin receptor results in a blockade of
125
I-labeled insulin binding, stimulation of glucose oxidation, and many more insulin-like effects. Allowing for differences in purity, antireceptor antibody is equipotent with insulin on a molar basis. Both the bivalent F(ab′)
2
and monovalent Fab′ fragments of the antireceptor antibody are fully active in inhibiting
125
I-labeled insulin binding. Bivalent F(ab′)
2
also retains its insulin-like effects. In contrast, the monovalent Fab′ loses almost all ability to stimulate glucose oxidation and acts as a competitive antagonist of insulin-stimulated glucose oxidation. Addition of anti-F(ab′)
2
antisera, which crosslink the Fab′-receptor complexes, results in a restoration of the insulin-like activity of the antibody. Similarly, when cells are exposed to submaximal doses of insulin, addition of anti-insulin antibodies at low concentration enhances the biological activity of insulin. These data suggest that receptor occupancy by ligand is not sufficient for signal generation and that the insulin-like effects of antireceptor antibody (and perhaps insulin itself) require receptor aggregation or clustering. This aggregation, however, appears to be independent of microfilaments or microtubules because the insulin-like effects of antireceptor antibody, and in fact, of insulin itself, are unaffected by agents that are known to disrupt these structures.
Negative control of hemoglobin production in somatic cell hybrids due to heme deficiency.
Authors: Benoff S , Bruce S A , Skoultchi A I
Published: May 2006

In somatic cell hybrids formed by the fusion of mouse erythroleukemic cells with mouse primary bone marrow cells, retention of the X chromosome contributed by the bone marrow parent is correlated with inhibition of hemoglobin accumulation in response to dimethyl sulfoxide. The inhibition of hemoglobin accumulation is not due to the absence of globin mRNA. Dimethyl sulfoxide-treated hybrid cells accumulate polyribosomal globin mRNA to levels comparable to those of the parental erythroleukemic cells under the same conditions. Heme, or its precursor delta-aminolevulinc acid, can overcome the effects of the bone marrow X chromosome and induce hemoglobin accumulation in the dimethyl sulfoxide-treated hybrid cells. The data suggest that the X chromosome contributed by the bone marrow cells inhibits hemoglobin production by inhibiting inducible heme biosynthesis, most probably at the step catalyzed by delta-aminolevulinic acid synthetase (EC 2.3.1.37).
Ultrastructural antibody localization of alpha2-macroglobulin in membrane-limited vesicles in cultured cells.
Authors: Willingham M C , Yamada S S , Pastan I
Published: May 2006

We have been developing a procedure for localizing intracellular antigens in cultured cells, by using peroxidase-labeled antibodies, that allows good morphologic preservation. Although useful, our previous technique did not preserve the morphology of membranes, and the location of the peroxidase reaction product was difficult to establish. In this paper, we report major improvements on the basic technique that markedly enhance the quality of localization and of morphology. Saponin is used to permeabilize membranes without destroying their morphology. The amount of reaction product is enhanced with a peroxidase-antiperoxidase label. The clarity of morphologic detail and contrast of reaction product density are increased by using postsectioning staining with the osmium/thiocarbohydrazide/osmium and uranyl acetate/lead citrate procedures. We have applied this technique to the ultrastructural localization of alpha2-macroglobulin and demonstrated that it is localized in membrane-limited vesicles. We have also used this method to improve the preservation of structures for localization by fluorescence microscopy.
Kinetics of desynchronization and distribution of generation times in synchronized cell populations.
Authors: Murphy J S , D'Alisa R , Gershey E L , Landsberger F R
Published: May 2006

The kinetics of the distribution of generation times in synchronized cells can be analyzed by using Fourier transform analysis. Deviations of the experimental data from the curve of completely asynchronous growth reflect the degree of synchrony at a particular time. Fourier transform analysis of these deviations yields the average generation time as well as information on the distribution of generation times characterizing a synchronized culture. A detailed analysis of synchronized cell cultures does not provide any evidence for the existence of a subcycle or a polymodal distribution in generation times. The data do indicate that cell-cell interaction occurs at cell densities as low as 2.5 X 10(3)/cm2. It is also shown that the Eyring-Stover formalism for the dynamics of survival can correctly describe the distribution of the first round of cell divisions in a synchronized culture.
Viable deletion mutants in the simian virus 40 early region.
Authors: Feunteun J , Kress M , Gardes M , Monier R
Published: May 2006

For the purpose of isolating hr-t-like mutants of simian virus 40, we have constructed variants that have lost the unique site for the restriction enzyme Taq I at 0.565. Five mutants have been isolated and characterized by restriction enzyme analysis. All of them produce a normal size T antigen. Four produce a t antigen reduced in size as well as in amount; the fifth one does not seem to make any t antigen at all. The ability of these mutants to transform mouse cells in vitro, as tested by anchorage dependence, is clearly altered; however, the defect is only partial. In the same test, the mutants can complement a tsA mutant for transformation and therefore define a second complementation group in the simian virus 40 early region.
Characterization of a feline sarcoma virus-coded antigen (FOCMA-S) by radioimmunoassay.
Authors: Sherr C J , Todaro G J , Sliski A , Essex M
Published: May 2006

A radioimmunoassay has been developed that detects a unique antigen encoded by the genome of the feline sarcoma virus (FeSV). Pseudotype viral particles containing an FeSV-specific polyprotein (p85) were used both as a source of antigen and to prepare specific antisera in rabbits. Because p85 contains antigens related to two structural proteins (p15 and p12) of feline leukemia virus (FeLV), antibodies directed to these were adsorbed with purified FeLV proteins. The adsorbed rabbit antiserum bound to antigenic determinants (designated FOCMA-S) which are also present in p85 and reacted specifically in immunofluorescence tests with rat cells transformed by FeSV and with FOCMA-positive cat lymphoid tumor cells. Competition assays detect FOCMA-S in pseudotype type C viruses rescued from FeSV-transformed mink and rat cells but not in heterologous type C helper viruses or in FeLV. A crossreactive antigen was also detected in pseudotypes of Kirsten sarcoma virus. The assay permits the quantitative measurement of an FeSV-coded protein whose expression is associated with viral transformation.
Somatostatin inhibits release of thyrotropin releasing factor from organ cultures of rat hypothalamus.
Authors: Hirooka Y , Hollander C S , Suzuki S , Ferdinand P , Juan S I
Published: May 2006

Somatostatin in concentrations of 10(-6) to 10(-8) M inhibited basal release of thyrotropin releasing factor in organ culture of rat hypothalamus. Norepinephrine in doses of 10(-4)--10(-6) M induced release of thyrotropin releasing factor which increased progressively with time and was temperature and dose dependent. This enhanced thyrotropin-releasing-factor release was inhibited by somatostatin at 10(-6)--10(-8) M.
Inhibition by Z-Pro-D-Leu of development of tolerance to and physical dependence on morphine in mice.
Authors: Walter R , Ritzmann R F , Bhargava H N , Rainbow T C , Flexner L B , Krivoy W A
Published: May 2006

The peptide-Z-Pro-D-Leu, injected daily in mice receiving morphine chronically, was found to prevent development of physical dependence as measured by changes in body temperature and body weight due either to abrupt or to naloxone-induced withdrawal. On the other hand, administration of Z-Pro-D-Leu only on the last day of morphine treatment did not alter the overt signs of withdrawal. Daily administration of Z-Pro-D-Leu was also effective in blocking the development of tolerance to the analgesic and the hypothermic effects of subsequent challenge doses of morphine. However, the peptide treatment did not alter the acute effects of a challenge dose of morphine on either analgesia or body temperature. No effects on memory were noted, as evaluated in a one-trial passive avoidance task. Clinical implications of the use of Z-Pro-D-Leu are discussed.