bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic properties of oxyhemoglobin.
Authors: Cerdonio M , Congiu-Castellano A , Mogno F , Pispisa B , Romani G L , Vitale S
Published: May 2006

When the magnetic susceptibility of frozen aqueous solutions of human oxyhemoglobin was measured in the range between 25 and 250 K, it showed a temperature-dependent behavior typical of a thermal equilibrium between a ground singlet state and an excited triplet state for two electrons per heme, the energy separation being [2J] = 146 cm-1. By contrast, within the same temperature range, carboxyhemoglobin was found to be diamagnetic, as already reported.
Chemical transformation of rat cells infected with xenotropic type-C RNA virus and its suppression by virus-specific antiserum.
Authors: Price P J , Suk W A , Peters R L , Gilden R V , Huebner R J
Published: May 2006

Fischer rat embryo cells infected with xenotropic mouse type-C RNA viruses isolated from either NIH Swiss mice or C57L inbred mice were transformed by 4-nitroquinoline oxide or 3-methylcholanthrene under conditions in which neither treatment alone sufficed to induce transformation. Transformation was dependent on the presence of actively growing virus at the time of chemical treatment. Specific antibody to xenotropic virus neutralized the virus and inhibited malignant transformation by 3-methylcholanthrene.
Pterin-6-aldehyde, a cancer cell catabolite: identification and application in diagnosis and treatment of human cancer.
Authors: Halpern R , Halpern B C , Stea B , Dunlap A , Conklin K , Clark B , Ashe H , Sperling L , Halpern J A , Hardy D , Smith R A
Published: May 2006

Active folic acid degradation with the formation pterin-6-aldehyde is a previously undescribed characteristic of cancer cells in tissue culture. Neither normal adult epithelial and fibroblastic cells nor human amniotic cells nor mouse embryonic fibroblasts degrade folic acid to a measurable degree. Twenty-nine patients whose diagnoses were not revealed until after the test of their first morning urine for pterin-6-aldehyde was completed were studied for the presence or absence of pterin-6-aldehyde by thin-layer chromatography. Pterin-6-aldehyde was found in the urine at about 300 nmol/ml or greater only in those 13 patients with a tissue diagnosis of cancer. When the cancer was totally resected, the pterin-6-aldehyde was no longer found in the urine postoperatively. Pterin-6-aldehyde is not found in the urine of healthy patients at this level of detection unless their diets are supplemented with folic acid.
Human somatotropin: restoration of full biological activity by noncovalent interaction of a natural and a synthetic fragment of the hormone.
Authors: Li C H , Bewley T A , Blake J , Hayashida T
Published: May 2006

The recombinant hormone obtained by noncovalent interaction of the natural NH2-terminal fragment (consisting of 134 amino acid residues) with a synthetic COOH-terminal fragment of 52 amino acids of the reduced-carbamidomethylated human somatotropin molecule is found to exhibit full biological activity of the native hormone as evidenced by the tibia test. Radioimmunoassay data indicate that the semisynthetic recombinant hormone possesses essentially full immunoreactivity as compared to the native one. In addition, circular dichroism and fluorescence emission spectra of the semisynthetic recombinant are identical to that of the undisociated, plasmin modified, reduced-carbamidomethylated hormone.
Nuclear magnetic resonance studies of lecithin bimolecular leaflets with incorporated fluorescent probes.
Authors: Podo F , Blasie J K
Published: May 2006

Pulse Fourier transform proton magnetic resonance techniques have been used to determine (i) the precise location of four membrane fluorescent probe molecules in lipid bilayer model membranes above the gel-to-liquid crystal transition temperature, tm; (ii) the dynamical perturbation of the host lipid molecules induced by incorporation of the probe into the bilayer. The regions of maximal perturbation induced by these probes do not necessarily coincide with their actual location in the bilayer.
Structure of ribulose-1,5-bisphosphate carboxylase-oxygenase: Form III crystals
Authors: Baker Timothy S. , Suh Se Won , Eisenberg David
Published: May 2006

A new crystal form (III) of tobacco leaf ribulosebisphosphate carboxylase [3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39] has been grown by dialysis procedures, and is suitable for structural studies at near atomic resolution. The crystals exhibit birefringence, grow as pseudo-regular rhombic dodecahedrons, and belong to the tetragonal space group P4
2
2
1
2 with a = b = 149 Å, c = 138 Å, and
V
= 3.04 × 10
6
A
3
. Each unit cell contains two molecules, with two large and two small subunits per asymmetric unit. At low resolution (>10 Å) the crystal structure is body centered belonging to space group 1422 with one large/small pair in the asymmetric unit. Thus, at low resolution the molecular symmetry is D
4
, the highest possible symmetry for an oligomer of stoichiometry large
8
small
8
. Form III crystals may be identical to crystalline inclusions found in chloroplasts.
Evolutionary consequences of parthogenesis: evidence from the Warramaba virgo complex.
Authors: Atchley W R
Published: May 2006

Comparative quantitative analyses of variability in closely related parthenogenetic and sexually reproducing species have been lacking. This paper reports results of comparative analyses of relative variability carried out on the obligate thelytokous grasshopper Warramaba virgo (Key) and three closely related sexually reproducing species. Consistent patterns of differences in variability in 14 morphometric traits were found between clones and races of the parthenogenetic species which were absent in populations and species of the related sexual forms. When variability in the parthenogenetic and sexual species was compared, the parthenogenetic taxa were shown to be at least as variable as and often more variable than the sexual species.
Partial chemical characterization of Ia antigens derived from murine thymocytes.
Authors: Schwartz B D , Kask A M , Sharrow S O , David C S , Schwartz R H
Published: May 2006

Previous chemical studies attempting to demonstrate Ia antigens on mouse thymocytes have given contradictory results. We attempted to resolve the question of whether Ia antigens exist on thymocytes (defined as thymus cells that bear a T cell marker) by isolating strain C3H thymocytes free of other contaminating cells using the fluorescence-activated cell sorter, and then chemically testing the purified populations for Ia antigens. Immunoglobulin-negative thymus cells and thymus cells selected with a rabbit antiserum to mouse brain were the two populations of thymocytes labeled with [3H]leucine after sorting. Radiolabeled proteins were solubilized with the non-ionic detergent Nonidet P-40, reacted with anti-Ia antiserum, and analyzed by electrophoresis on discontinuous sodium dodecyl sulfate/polyacrylamide gels. Ia antigens were recovered from both cell populations. These antigens were synthesized by thymocytes and were found on molecules composed of two chains of molecular weight 33,000 and 25,000, respectively, similar to Ia antigens derived from spleen cells. Assuming that all thymocytes bear similar amounts of Ia antigens, we estimated that they have approximately 1/50 the amount of Ia antigens that spleen cells do.
Partial amino-acid sequences of human and rabbit C-reactive proteins: homology with immunoglobulins and histocompatibility antigens.
Authors: Osmand A P , Gerwurz H , Friedenson B
Published: May 2006

Partial amino-acid sequence analyses of the amino terminus of rabbit C-reactive protein and of a peptide isolated from human C-reactive protein after cyanogen bromide cleavage show an extensive sequence homology between these proteins. Computer analysis detected a distant but significant homology between rabbit C-reactive protein and the CH3 domain of human IgG, In addition, an examination of the limited data available for the amino-acid sequences of human and mouse histocompatibility antigens revealed a similarity between these proteins and C-reactive protein and, therefore, immunoglobulins; These relationships are presented as evidence in support of the hypothesis that C-reactive protein and immunoglobulins share, in addition to functional similarities, a common evolutionary origin with the major histocompatibility antigens.
Specific gonadotropin binding to Pseudomonas maltophilia.
Authors: Richert N D , Ryan R J
Published: May 2006

Binding of 125I-labeled human chorionic gonadotropin to Pseudomonas maltophilia is dependent on time, temperature, and pH and the binding to this procaryotic species is hormone-specific and saturable. The equilibrium dissociation constant is 2.3 X 10(-9) M. There are no cooperative interactions between binding sites (Hill coefficient, 1.05). The number of sites is estimaated as 240 fmol/100 mug of protein. NaCl and KCl, at concentrations from 1 to 10 mM, have no effect on binding. Divalent cations (Mg2+ and Ca2+) and 1 mM EDTA inhibit hormone binding. Binding is destroyed by heat or by treatment with Pronase of alpha-chymotrypsin and is increased by phospholipase C. Binding of the labeled gonadotropin is not observed with other gram-negative organisms--e.g., Escherichia coli, Pseudomonas testosteroni, Pseudomonas aeruginosa, Enterobacter aerogenes, or Enterobacter cloacae.
Synthesis and processing of an Escherichia coli alkaline phosphatase precursor in vitro.
Authors: Inouye H , Beckwith J
Published: May 2006

Alkaline phosphatase [orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1] of E. coli was synthesized in a cell-free system, and the size of the direct translation product was analyzed. The product has a higher molecular weight than the mature alkaline phosphatase found in the periplasm. The direct translation product can be processed to the mature size by an E. coli membrane fraction; the processing activity copurifies with the outer-membrane fraction. The presumed precursor can dimerize to form active enzyme without being processed, and the resultant enzyme appears to be more hydrophobic than the mature enzyme. These findings are discussed in connection with the "signal hypothesis" proposed for the excretion of proteins across membranes.
Molecular properties of the nerve growth factor secreted by L cells.
Authors: Pantazis N J , Blanchard M H , Arnason B G , Young M
Published: May 2006

The molecular size and stability of the nerve growth factor (NGF) secreted in culture by L cells have been studied by sedimentation and gel filtration chromatography. Results indicate that L cell NGF has a molecular weight of 160,000. It contains as part of its structure a protein component that is biologically, immunologically, and electrophoretically indistinguishable from the biologically active factor purified from mouse submandibular glands. However, unlike pure gland NGF, L cell NGF is highly stable in solution, and this finding indicates that L cell NGF is a form of the factor different from that previously described.
Absence of a measurable G2 phase in two Chinese hamster cell lines.
Authors: Liskay R M
Published: May 2006

Evidence is presented that demonstrates the absence of a measurable G2 phase in the cell cycles of two sublines of the Chinese hamster lung fibroblast V79. One of the sublines, in addition, lacks a detectable G1 phase, thereby possessing a cell cycle comprised of simply two phases, DNA synthesis (S) and mitosis (M).
The product of a newly identified gene, gInF, is required for synthesis of glutamine synthetase in Salmonella.
Authors: Garcia E , Bancroft S , Rhee S G , Kustu S
Published: May 2006

The product of a newly identified gene, glnF, which is distinct from the glutamine synthetase structural gene (glnA), is required for synthesis of glutamine synthetase [L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2[ in Salmonella typhimurium and probably in Escherichia coli. Salmonella strains with ICR (2-chloro-6-methoxy-9-[3-(2-chloroethyl)aminopropylamino]acridine dihyodrochloride)-induced (frameshift) mutations in glnF are glutamine auxotrophs; they have less than 10% oof wild-type glutamine synthetase activity or antigen and are unable to derepress the synthesis of the enzyme. The mutant allele is recessive to the wild-type allele, indicating that the glnF gene encodes a diffusible product. Mutant glnF strains have normal activities of all proteins involved in covalent modification of glutamine synthetase: adenylyltransferase (EC 2.7.7.42), PII, uridylyltransferase, and uridylyl removing enzyme. In addition, they have glutamate synthase (EC 1.4.1.13) and glutamate dehydrogenase (EC 1.4.1.4) activities. Thus, glnF does not encode the structure of any of these proteins. The above evidence suggests that the product of the glnF gene is (or produces) a positive regulatory factor that is required for synthesis of glutamine synthetase; it indicates that auto-regulation cannot account for control of the synthesis of glutamine synthetase in Salmonella.
Increased resistance of cystic fibrosis fibroblasts to ouabain toxicity.
Authors: Epstein J , Breslow J L
Published: May 2006

Diploid skin fibroblasts derived from several unrelated patients with cystic fibrosis (CF) were tested for resistance to the cytotoxic effects of ouabain in comparison with cells from normal individuals. Cells from CF and normal individuals were plated at low density and exposed to ouabain at different concentrations for 24 hr. Dose-response curves showed that CF cells survived significantly better than did normal cells at all ouabain concentrations from 0.1 nM to 1 micronM in potassium-deficient medium. In medium containing the usual amount of potassium (6.25 mM), survival of the CF cells exposed to ouabain was decreased to that of the normal cells. If the glucose concentration of the potassium-deficient medium was decreased to 10% of the usual amount, the resistance of the CF cells to ouabain disappeared and their survival was identical to that of the normal cells. These findings may be useful in understanding the biochemical basis of CG and its clinical manifestations.
Cell-free synthesis of the fourth component of guinea pig complement (C4): identification of a precursor of serum C4 (pro-C4).
Authors: Hall R E , Colten H R
Published: May 2006

Polysomes (S-20) from homogenates of guinea pig liver synthesized serum albumin and a precursor of the fourth component of guinea pig complement (C4) in vitro. The C4 precursor (pro-C4) accounted for approximately 0.2% and albumin 4% of the radiolabeled protein precipitable by trichloroacetic acid and not bound to polysomes. Pro-C4 is a single polypeptide chain (molecular weight 200,000) which is then converted to C4, a three-chain (molecular weights 95,000, 78,000 and 31,000) structure linked by interchain disulfide bridges. Pro-C4 was also detected intracellularly in short-term tissue cultures of guinea pig liver. C4 was found in the medium harvested from these cultures.
A gene from Escherichia coli affecting the sigma subunit of RNA polymerase.
Authors: Harris J D , Martinez I I , Calendar R
Published: May 2006

The RNA polymerase sigma subunits of Escherichia coli K, E. coli C, and Salmonella typhimurium can be resolved by electrophoresis. Using this technique, we have analyzed Salmonella strains carrying F' plasmids from E. coli K in order to map the gene for the sigma factor. Partial diploid analyses show the location of the sigma gene at 62-66 min on the E. coli genetic map. This gene is cotransducible with toIC and dnaG, at 66 min.
Pineal protein phosphorylation during serotonin N-acetyltransferase induction.
Authors: Winters K E , Morrissey J J , Loos P J , Lovenberg W
Published: May 2006

The activity of soluble protein kinase (ATP:protein phosphotransferase,EC 2.7.1.37) and pattern of nuclear protein phosphorylation was monitored in cultured rat pineal glands during the induction of serotonin N-acetyltransferase (acetyl-CoA:serotonin N-acetyltransferase;EC 2.3.1.5)by l-isoproterenol. A nuclear protein appears to be phosphorylated during the early stages of enzyme induction but is not phosphorylated at later stages of induction. This correlates well with the need for RNA synthesis associated with the induction process. The nuclear protein was also phosphorylated when the pineal glands were treated with dibutyryl 3':5'-cyclic AMP. The soluble protein kinase activity appeared to decline during mid-to-late stages of enzyme induction, but there was no concomitant increase in the particulate protein kinase activity.
Proton spin-lattice relaxation of retinal rod outer segment membranes and liposomes of extracted phospholipids.
Authors: Brown M F , Miljanich G P , Dratz E A
Published: May 2006

A large fraction of the phospholipid protons of bovine retinal rod outer segment (ROS) disc membrane vesicles yield well-resolved nuclear magnetic resonance lines near physiological temperature. The spin-lattice (T1) relaxation rates of the resolved sharp resonance of ROS disc membranes appear biphasic above 10 degrees C. The rate of the more rapidly relaxing component of each resonance matches closely the relaxation rate of the corresponding resonances of liposomes of purified ROS phospholipids. The slowly relaxing component of each disc membrane resonance is most likely due to phospholipids whose motion is affected by rhodopsin. The primary difference in the relaxation behavior of phospholipids in the ROS membrane vesicles and ROS liposomes appears to be in T1, rather than T2, since the corresponding sharp resonances of both preparations have similar linewidths. These observations suggest that the interaction of rhodopsin with the more fluid membrane phospholipids predominantly affects relatively high frequency segmental motions, which determine T1, while having minimal effects on the lower frequency segmental motions, which influence T2. This conclusion can be rationalized by assuming that a substantial fraction of the interacting phospholipids are relatively fluid with respect to less frequent, larger amplitude segmental motions, but that the more frequent segmental motions (such as beta-coupled trans-gauche isomerizations) are significantly restricted by interaction with protein.
Nature of the antigenic complex recognized by T lymphocytes: specific sensitization by antigens associated with allogeneic macrophages.
Authors: Thomas D W , Shevach E M
Published: May 2006

Alloreactive guinea pig thymus-derived (T) cells generated in vitro were rendered unresponsive to allogeneic macrophages by treatment with bromodeoxyuridine and light. The remaining T cells were subsequently primed and rechallenged in tissue culture with trinitrophenyl (Tnp)-modified syngeneic or allogeneic macrophages. By this procedure we found that the remaining T cells primed with Tnp-modified allogeneic macrophages could be restimulated only with Tnp-modified allogeneic, not syngeneic, macrophages. Similarily, if the remaining T cells were primed with Tnp-modified syngeneic macrophages, they could be restimulated only by Tnp-modified syngeneic, and not by allogeneic, macrophages. In contrast, no T cell sensitization with Tnp-modified syngeneic or allogeneic macrophages occurred if the alloreactive T cells were treated with light alone, suggesting that an uninhibited mixed leukocyte reaction causes nonspecific suppression of antigen-specific T cell priming. These results indicate that the genetic restriction of T cell-macrophage interactions is imposed by the type of macrophage used for initial sensitization rather than by a requirement for self-recognition through cellular interaction structures.
Structure-function relations in phosphorylcholine-binding mouse myeloma proteins.
Authors: Goetze A M , Richards J H
Published: May 2006

The binding site interactions between the phosphorylcholine (phosphocholine)-binding mouse myeloma proteins TEPC 15, W3207, McPC 603, MOPC 167, and MOPC 511 and the isotopically substituted hapten phosphoryl[methyl-13C]choline have been investigated using 13C and 31P nuclear magnetic resonance (NMR) spectroscopy. Each protein exhibits a unique NMR pattern, but extensive similarities in chemical shift parameters upon binding of hapten to immunoglobulin suggest a significant degree of conservation of important hapten-binding site interactions. Moreover, independent binding studies, in conjunction with the NMR data, allow construction of a simple model of the binding sites of these antibodies, analyzed in terms of the relative strength of interaction between hapten and two main subsites. The NMR evidence supports the view that the heavy chains of these proteins dominate in interacting with bound phosphorylcholine; the various subspecificities of these proteins for phosphorylcholine analogues can be accounted for by amino acid changes in the hypervariable regions of the heavy chains.
Direct demonstration of murine thymus-dependent cell surface endogenous immunoglobin.
Authors: Szenberg A , Marchalonis J J , Warner N L
Published: May 2006

Antisera raised in mammals to murine immunoglobulin (Ig) do not detect surface Ig on thymus-dependent (T) lymphoma cells as assessed by immunofluorescence analysis. In contrast, chicken antibodies, produced against the (Fab)2 fragment of normal mouse IgG and purified by binding to and elution from IgG-Sepharose 4B, give strong indirect fluorescence with murine T cells and cultured T lymphoma cells. The surface Ig caps, is shed, and reappears, indicating that it is of endogenous origin. Nonlymphoid tumor cells of various myeloid types do not bind this reagent, even though they bear avid Fc receptors. The capacity of chicken antibodies to bind to both bone-marrow-dependent and T cell lymphomas was abolished by adsorption with myeloma-derived kappa chains coupled to Sepharose. The kappa antigenic determinant recognized by the chicken antibodies may thus be different from that seen by mammalian antibodies, and the degree of exposure of Ig on the T lymphoma surface might also affect ease of detectability with these reagents. These data provide direct evidence that T lymphocytes and T lymphoma cells express and synthesize a surface Ig containing determinants that at least 'crossreact with bone-marrow-cell-derived kappa chains.
Antigenic relatedness of the DNA polymerase of human breast cancer particles to the enzyme of the Mason-Pfizer monkey virus.
Authors: Ohno T , Spiegelman S
Published: May 2006

We have previously reported [(Ohno, T., Sweet, R.W., Hu, R., DeJak, D. & Spiegelman, S. (1977) Proc. Natl. Acad. Sci. USA 74, 764-768)] on the purification and characterization of the DNA polymerase from human breast cancer particles. Its preference for certain synthetic templates and its ability to use a viral RNA to fashion a faithful DNA transcript identify it as a reverse transcriptase similar to that found in the mouse mammary tumor virus and in the Mason-Pfizer monkey virus (MPMV). We report here that the human breast cancer enzyme crossreacts immunologically with the reverse transcriptase of MPMV. The crossreactivity was shown both by inhibition of enzyme activity and by complex formation between purified enzyme and isolated IgG against MPMV polymerase. No such interactions were observed with other oncornavirus reverse transcriptases of avian, murine, feline, or simian origin. Further, the IgG failed to neutralize the reverse transcriptases from human mesenchymal neoplasias (leukemias and lymphomas) or the activities of normal cellular DNA polymerases (alpha, beta, gamma).
Conformational basis for the activation of adenylate cyclase by adenosine
Authors: Miles D. L. , Miles D. W. , Eyring H.
Published: May 2006

The ability of adenosine to stimulate adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] and increase adenosine 3′:5′-cyclic monophosphate (cAMP) levels has important biochemical consequences. These include the suppression of immune responses and cardiovascular effects. Recent investigations involving the ability of adenosine and adenosine analogs to stimulate adenylate cyclase provided experimental data that appear to be correlated with the ability of adenosine and analogs of adenosine to exist in the glycosidic high
anti
conformation. 9-β-D-Arabinofuranosyladenine, which is not stable in the high
anti
conformation, is inactive as a stimulator of adenylate cyclase. 2′-Deoxyadenosine is also not stable in the high
anti
conformation but its instability may be significantly decreased by intramolecular adjustments promoted by receptor or active site interactions. 2′-Deoxyadenosine does not activate adenylate cyclase in lymphocytes when ATP is the substrate but is able to activate adenylate cyclase when 2-fluoro ATP is the substrate. The inability of certain analogs of adenosine, with bulky groups substituted for hydrogen at the 8 position of the adenine base, to activate adenylate cyclase and increase either lymphocyte or cardiac cell cAMP levels is consistent with the designation of the high
anti
conformation as being the conformation required for the activation of adenylate cyclase. An understanding of the glycosidic conformation required by the extracellular adenosine receptor of the adenosine molecule provides the basis for designing nucleoside analogs of adenosine that will exert a desired effect on cAMP levels. The avoidance of unwanted immunosuppressive or cardiotoxic effects can be arranged by structural changes that prohibit the high
anti
conformation.
Synthesis of 13,14-dehydroprostacyclin methyl ester: a potent inhibitor of platelet aggregation.
Authors: Fried J , Barton J
Published: May 2006

The structure of the most recently discovered, biologically highly active prostaglandin, PGI2 or prostacyclin, is correctly predicted on biogenetic grounds, and a general synthesis starting with prostaglandins of the F2alpha series is reported. Starting with the biologically active 13,14-dehydro-PGF2alpha, the synthesis involves formation of a 5-bromo-6,9alpha-epoxy derivative, followed by esterification and dehydrobromination of the methyl ester to form the prostacyclin structure. The stereochemistry at C-5 and C-6 of all reported products is assigned on the basis of experimental findings and mechanistic reasoning. 13,14-Dehydroprostacyclin methyl ester is considerably more stable at pH 7.5 than prostacyclin. It inhibits platelet aggregation induced by a variety of agents and causes an increase in renal blood flow in the dog at nanomolar levels.
Heat capacity and entropy changes in processes involving proteins.
Authors: Sturtevant J M
Published: May 2006

Six possible sources of the large heat capacity and entropy changes frequently observed for processes involving proteins are identified. Of these the conformational, hydrophobic, and vibrational effects seem likely to be of greatest importance. A method is proposed for estimating the magnitudes of the hydrophobic and vibrational contributions. Application of this method to several protein processes appears to achieve significant clarification of previously confusing and apparently contradictory data.
alpha-Fetoprotein is not a component of the estradiol receptor of the rat uterus.
Authors: Radanyi C , Mercier-Bodard C , Secco-Millet C , Baulieu E E , Richard-Foy H
Published: May 2006

In high-salt medium, cytosol from immature rat uteri displays two main high-affinity estradiol-binding peaks after ultracentrifugation in a sucrose gradient. The two components are the estradiol receptor which has a sedimentation coefficient of 5.5 S, and the alpha-fetoprotein which sediments at 4.5 S. The dissociation rate constants (k-1) of plasma alpha-fetoprotein-estradiol complexes measured at 0 degrees in the absence or presence of 0.4 M KCl were found to be 7 X 10(-5) and 8 X 10(-5) sec-1, respectively. The half-time of dissociation of these hormone-plasma protein complexes is 100-200 times more rapid than that of the estradiol-receptor complexes. These data led to the use of two "differential dissociation" methods for the measurement of the hormone-binding protein complexes. In a high-salt cytosol, the charcoal technique measured selectively the receptor binding sites; the hydroxylapatite technique measured the sum of the alpha-fetoprotein plus receptor binding sites. Under these conditions, binding specificity studies provided evidence that alpha-fetoprotein is not a subunit of the receptor. This was confirmed by binding specificity studies in high-salt medium of the receptor separated from alpha-fetoprotein by ultracentrifugation.
Translation of tobacco necrosis virus and its satellite in a cell-free wheat germ system.
Authors: Salvato M S , Fraenkel-Conrat H
Published: May 2006

Tobacco necrosis virus (TNV) and its satellite virus (STNV) each contain a single-stranded RNA genome, of about 1.4 X 10(6) and 0.4 X 10(6) daltons, respectively, which is very active in stimulating amino acid incorporation in a wheat germ cell-free system. With STNV RNA the predominant incorporation product of 22,000 daltons coelectrophoreses with viral coat protein and crossreacts with antibody to viral coat protein. A similar result is obtained with TNV RNA, the only major translation product being a 30,000-dalton protein which corresponds to the coat protein by gel sizing, serological tests, and tryptic peptide analysis. Other products appearing in smaller amounts are about 63,000, 43,000, and 26,000 daltons and smaller. The possible nature of these products is discussed, as well as the unusual feature of a large, presumably multigenic, viral RNA yielding the coat protein as the predominant translation product in a eukaryotic system. Much less STNV RNA than TNV RNA produces maximal translation. Cotranslation of both RNAs in vitro indicates that STNV RNA has a translational advantage over TNV RNA. The fact that these RNAs lack 5'-terminal capping and 3'-terminal poly(A) is discussed.
Sensitivity, polarity, and conductance change in the response of vertebrate hair cells to controlled mechanical stimuli.
Authors: Hudspeth A J , Corey D P
Published: May 2006

Hair cells, the primary receptors of the auditory, vestibular, and lateral-line sensory systems, produce electrical signals in response to mechanical stimulation of their apical hair bundles. We employed an in vitro preparation and intracellular recording to investigate the transduction mechanism of hair cells in the sacculus from the inner ear of the bullfrog (Rana catesbeiana). When stimulated directly by mechanical deflection of their hair bundles, these cells gave graded responses up to 15 mV in amplitude; the peak sensitivity was about 20 mV/micron deflection. The depolarizing component of the receptor potential corresponding to stimuli directed towards the kinocilium. Depolarizing responses were associated with a membrane resistance decrease, and hyperpolarizing responses with a resistance increase. Action potentials, possibly calcium spikes, were occasionally evoked in hair cells by mechanical or electrical stimulation.
Fidelity of synthesis of preribosomal RNA in isolated nucleoli and nucleolar chromatin.
Authors: Ballal N R , Choi Y C , Mouche R , Busche H
Published: May 2006

Comparisons were made of the T1 ribonuclease digests of 32P-labeled nucleolar 45S RNA of intact Novikoff hepatoma cells and the RNA synthesized in vitro by isolated nucleoli. Approximately 200 oligonucleotide spots were found in the two-dimensional chromatogram of 45S nucleolar RNA labeled in vivo, which includes fragments of 18S and 28S rRNA and nonconserved spacer regions; four spots containing 2'-O-methyl nucleotides were not found in the corresponding pattern of RNA labeled in vitro. This high degree of fidelity was retained in the patterns of spots from the RNA produced with nucleolar chromatin as template. This specific expression of rDNA was lost when the nucleolar chromatin was completely deproteinized. Specific spots found in the control patterns were absent and many nonspecific oligonucleotides were found to be labeled. A similar nonspecific chromatogram pattern was found when nucleolar chromatin was transcribed with RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) of Escherichia coli. These results show that specificity of genetic expression in vitro of isolated chromatin of eukaryotic systems is dependent on the chromatin-associated proteins and the type of RNA polymerase present.
Conversion of incomplete antibodies to direct agglutinins by mild reduction: evidence for segmental flexibility within the Fc fragment of immunoglobulin G.
Authors: Romans D G , Tilley C A , Crookston M C , Falk R E , Dorrington K J
Published: May 2006

Reduction of interchain disulfide bonds converted some IgG incomplete antibodies to direct hemagglutinins. This conversion occurred whether antibody was free in solution or bound to the red-cell surface. Reduced antibody permitted to reoxidize in air no longer behaved as a direct agglutinin; reversion to an incomplete antibody did not occur when reoxidation was prevented by S-alkylation. These results suggest that mild reduction of the antibody imparts sufficient freedom to permit bridging between cells and are interpreted as evidence that the interheavy-chain disulfide bonds restrict segmental flexibility within the Fc fragment of IgG.
Kinetics of cell death and disintegration in human lymphocyte cultures.
Authors: Bernheim J L , Mendelsohn J , Kelley M F , Dorian R
Published: May 2006

In order to quantitate lymphocyte proliferative responses, we explored the role of cell death in the kinetics of phytohemagglutinin-stimulated cultures. Unless the disintegration time (tDIS) of nonviable lymphocytes in culture is known, the rate of cell death cannot be calculated. To obtain tDIS, we determined the time interval between total and viable cell population decay after various killing events. Two subpopulations of lymphocytes were observed, the major (80%) with a mean (+/-SEM) tDIS of 16+/-2 hr and the minor (20%) with a tDIS of 45+/-7 hr. Kinetic balance sheets were constructed predicting total culture DNA content (cells plus medium), as calculated both from proliferation rates and from observed death and disintegration rates. In an experiment characterized by extensive cell death, the two tallies were well-matched when the above data were utilized. The large discrepancy between predicted and observed DNA contents of the medium indicates that the DNA of disintegrated lymphocytes is extensively degraded. We conclude that cell death explains proliferation deficits in stimulated lymphocyte cultures. Our approach to quantitation of cell death may have general applicability to kinetic studies of cultured cells.
Cholinergic metabolism and synapse formation by a rat nerve cell line.
Authors: Schubert D , Heinemann S , Kidokoro Y
Published: May 2006

The PC12 clone of a rat pheochromocytoma is able to synthesize acetylcholine. The amount of acetylcholine synthesized, and the specific activity of choline O-acetyltransferase (acetyl-CoA:choline O-acetyltransferase, EC 2.3.1.6), varies as a function of the culture growth curve and is dependent on cell density. The specific activity of choline acetyltransferase is increased by nerve growth factor, growth-conditioned medium from a variety of cell types, and adenosine 3':5'-monophosphate. Finally, the PC12 cell line is able to form cholinergic synapses with a clonal cell line of skeletal muscle origin.
Kinetics of hemoglobin-carbon monoxide reactions measured with a superconducting magnetometer: a new method for fast reactions in solution.
Authors: Philo J S
Published: May 2006

A new technique for measuring fast reactions in solution has been demonstrated. The changes in magnetic susceptibility during the recombination reaction of human hemoglobin with carbon monoxide after flash photolysis have been measured with a new high-sensitivity instrument using cryogenic technology. The rate constants determined at 20 degrees (pH 7.3) are in excellent agreement with those obtained by photometric techniques [Gray, R.D. (1974) J. Biol. Chem. 249, 2879-2885]. A unique capability of this new method is the determination of the magnetic susceptibilities of short-lived reaction intermediates. The magnetic moment of the intermediate species Hb4(CO)3 was found to be 4.9+/-0.1 muB in 0.1 M phosphate buffer by partial photolysis experiments. This value agrees with the predictions of two-state allosteric models of cooperativity in hemoglobin. Possible applications and improvements in this technique are discussed.
Glycophorin and the concanavalin A receptor of human erythrocytes: their receptor function in lipid bilayers.
Authors: Sharom F J , Barratt D G , Grant C W
Published: May 2006

Two integral glycoproteins from the human erythrocyte have been studied after their incorporation into lipid bilayer systems. Glycophorin (which is the M/N blood group determinant) and the concanavalin A receptor were isolated and purified prior to incorporation into model membranes by dialytic removal of detergent from lipid/protein solutions. Under the conditions described, glycoprotein receptors maintain their function in that they bind external agents specific for them, such as concanavalin A and immunoglobulins. So-called intramembranous particles are a feature of freeze-fractured preparations of lipid bilayers containing either (or both) glycoprotein(s), and to some extent each has a characteristic particle appearance. Liposomes containing the concanavalin A receptor (with or without glycophorin) are agglutinable by concanavalin A, whereas human erythrocytes are normally considered to be nonagglutinable by this lectin. Liposomes containing glycophorin alone are readily agglutinable by the appropriate glycophorin-directed M/N antiserum, as are human erythrocytes. The added presence of concanavalin A receptor in the liposomes can markedly inhibit agglutination by M/N antiserum without preventing immunoglobulin binding.
Release of Escherichia coli DNA from membrane complexes by single-strand endonucleases.
Authors: Abe M , Brown C , Hendrickson W G , Boyd D H , Clifford P , Cote R H , Schaechter M
Published: May 2006

Treatment of gently prepared lysates of Escherichia coli with single-strand-specific endonuclease (SI or from mung beans) results in the release of about 90% of the DNA from membranes, as determined by the M band technique. The released DNA has an average molecular weight of about 1.2 X 10(8). Data obtained with endonuclease S1 fit a mathematical model in which substrate sites are at or near membrane attachment sites. Data obtained with pancreatic deoxyribonuclease or x-rays fit a model for double-strand breaks at random sites along the DNA. Fitting data to these models, we estimate that there are 18+/-5 membrane attachment sites. The DNA remaining after S1 nuclease treatment is enriched for the region near the origin of chromosome replication. Therefore, attachment at this region near the origin of chromosome replication. Therefore, attachment at this region appears to be chemically different from that at the other sites along the DNA.
Extracellular labeling of nascent polypeptides traversing the membrane of Escherichia coli.
Authors: Smith W P , Tai P C , Thompson R C , Davis B D
Published: May 2006

To provide direct evidence for the hypothesis that secreted proteins may traverse membranes as growing chains, we labeled spheroplasts of Escherichia coli with a reagent (acetyl[35S]methionyl methylphosphate sulfone) that reacts with amino groups but does not cross the membrane. After fractionation, about 6% of the label in the membrane-polysome fraction was found to be attached to the polysomes. This attachment was via peptidyl-tRNA, as shown by several tests: release of most of the label from purified polysomes at low Mg2+; subsequent loss of about 25,000 daltons on cleavage by dilute alkali; release by puromycin; and release, accompanied by a marked increase in average molecular weight, on peptide chain completion. Moreover, a significant fraction of the completed chains was identified serologically and by molecular weight as a major periplasmic protein, alkaline phosphatase [orthophosphoric-monoester phosphohydrolase (alkaline optimum); EC 3.1.3.1]. This work provides direct evidence that: (i) secreted proteins thread through the membrane as growing peptide chains; and (ii) membrane-associated polysomes in bacteria are functionally attached to membrane and not merely trapped on disruption of the cell.
Control of growth by picolinic acid: Differential response of normal and transformed cells
Authors: Fernandez-Pol J. A. , Bono Vincent H. , Johnson George S.
Published: May 2006

Picolinic acid reversibly inhibits the growth of cultured cells. Fourteen other pyridine derivatives were ineffective or toxic. Untransformed normal rat kidney (NRK) cells are reversibly arrested in the G
1
stage of the growth cycle as shown by cell counts, mitotic index, [
3
H]thymidine incorporation, and flow microfluorometry. Flow microfluorometry was used to monitor the effects of picolinic acid on numerous other cell lines. Normal cells are blocked in G
1
, whereas transformed cells show responses that are dependent upon the transforming virus and independent of species or origin of the cell line. Kirsten sarcoma virus-transformed cells are blocked in G
1
. Simian virus 40-transformed cells progress to a G
2
block. Cells transformed by polyoma or Harvey sarcoma virus with Moloney virus coat have flow microfluorometry profiles that indicate blocks in both G
1
and G
2
. Cells transformed with Moloney sarcoma virus are not blocked in a specific phase of the cell cycle. Picolinic acid does not change the levels of NAD
+
plus NADH; however, the growth inhibition by picolinic acid is partially overcome by nicotinamide. These results suggest that picolinic acid interacts with a specific growth control mechanism that may involve NAD
+
and that this control mechanism is altered by different transforming viruses in different manners.
Suppressor cell regulation of immune response to tumors: Abrogation by adult thymectomy
Authors: Reinisch Carol L. , Andrew Susan L. , Schlossman Stuart F.
Published: May 2006

The regulatory role of the adult thymus on the appearance of cytotoxic and suppressor T cells (thymus-derived lymphocytes) to allogeneic and autochthonous virus-induced tumors in mice was investigated. It was demonstrated that C57BL/6 mice challenged with allogeneic P815 mastocytoma cells and complete Freund's adjuvant failed to develop cytotoxic cells but instead developed suppressor T cells which inhibited cytotoxic T cell function. Further, adjuvant-induced suppressor cells prevented the primary
in vitro
induction of cytotoxic T cells to P815 mastocytoma cells. In contrast, adult thymectomized animals, when challenged with adjuvant and allogeneic cells, had a normal cytotoxic response
in vivo
and their cells could not inhibit the generation of cytotoxic T cells
in vitro
. These studies suggested that the intact adult thymus was necessary for the induction of suppressor cells. Moreover, suppressor cells regulated cytotoxic T cell activity both
in vivo
and
in vitro
. Further, it was shown that adjuvant could prevent the normal immune response to virus-induced tumors. BALB/c mice treated with murine sarcoma virus developed tumors which reached a maximal size by day 14 and then regressed. Sham thymectomized animals treated with virus and complete Freund's adjuvant to generate suppressor cells died from progressive tumor growth. In contrast, thymectomized animals similarly treated had normal regression of tumor and survived. These studies lead to the conclusion that the adult thymus may regulate immune responsiveness by the export of suppressor T cells which regulate other T cell responses to both allogeneic and tumor antigens.
Authentic beta-globin mRNA sequences in homozygous betaO-thalassemia.
Authors: Temple G F , Chang J C , Kan Y W
Published: May 2006

In a patient with homozygous betaO-thalassemia in whom studies of reticulocyte hemoglobin synthesis showed no beta-globin chain synthesis in vivo and in vitro, molecular hybridization studies revealed RNA sequences complementary to beta-globin cDNA. The fact that these sequences were authentic beta-globin mRNA was shown by fingerprint analysis of T1 ribonuclease-digested mRNA and by sequencing of oligonucleotides unique to beta-globin mRNA. The beta-mRNA that failed to direct beta-globin chain synthesis was not detectably shortened or degraded and contained poly(A) sequences.
Immunohistochemical analysis of peptide pathways possibly related to pain and analgesia: enkephalin and substance P.
Authors: Hökfelt T , Ljungdahl A , Terenius L , Elde R , Nilsson G
Published: May 2006

The distribution of Met-enkephalin- and substance P-immunoreactive neurons was studied by indirect immunofluorescence in some areas related to pain and analgesia. Met-enkephalin- and substance P-positive cell bodies and nerve terminals were observed in the periaqueductal central gray, the nucleus raphe magnus, the marginal layers and substantia gelatinosa of the spinal trigeminal nucleus, and the dorsal horn of the spinal cord. Lesion experiments suggest that Met-enkephalin neurons in the dorsal horn and possibly in the spinal trigeminal nucleus are interneurons or propriospinal neurons with nerve terminals in the laminae I and II of the cord and in the superficial layers of the spinal trigeminal nucleus, respectively. These areas are also very rich in substance P-positive nerve terminals, mainly representing central branches of primary afferent neurons. The present immunohistochemical-anatomical findings support the hypothesis that stimulation-produced analgesia is related to activation of spinal and spinal trigeminal enkephalin interneurons forming axo-axonic synapses with (substance P?) pain afferents in the superficial laminae of the dorsal horn and the spinal trigeminal nucleus. These interneurons may be activated by sensory fibers and by descending fibers from medullary stimulation sites. Transmitter substances in these descending fibers may be 5-hydroxytryptamine and substance P.
Glucocorticoid effect on the level of corticotropin messenger RNA activity in rat pituitary.
Authors: Nakanishi S , Kita T , Taii S , Imura H , Numa S
Published: May 2006

In an attempt to understand the molecular mechanism underlying the depressive effect of glucocorticoids on corticotropin production, the level of corticotropin messenger RNA activity in rat pituitaries was measured with the use of the cell-free protein-synthesizing system derived from wheat germ. The large translation product of corticotropin messenger RNA was identified and quantitated by indirect immunoprecipitation with antibody against corticotropin. The level of corticotropin messenger RNA activity was increased 3- to 6-fold by adrenalectomy. Dexamethasone administration to adrenalectomized rats resulted in a marked suppression of corticotropin messenger RNA activity. Cortisol and corticosterone also exhibited a suppressive effect but were less effective than dexamethasone. In contrast, nonglucocorticoids such as progesterone and aldosterone had no suppressive effect. These results indicate that at least part of the glucocorticoid effect on corticotropin production in the pituitary is exerted at the pretranslational level.
Mechanism of translational control by hemin in reticulocyte lysates.
Authors: Datta A , de Haro C , Sierra J M , Ochoa S
Published: May 2006

The formation of translational inhibitor (active eIF-2 kinase) from proinhibitor (inactive eIF-2 kinase) in reticulocyte lysates, known to be controlled by hemin, can, as we recently reported, be induced by 3':5'-cyclic AMP(cAMP)-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) or its catalytic subunit. We find that in crude preparations from rabbit reticulocyte lysates, hemin inhibits the conversion of proinhibitor to inhibitor catalyzed by endogenous cAMP-dependent protein kinase upon addition of cAMP, but not that caused by the addition of free protein kinase catalytic subunit. Hemin prevents the binding of cAMP to the regulatory subunit of cAMP-dependent protein kinase and blocks the cAMP-induced dissociation of regulatory and catalytic subunits of the enzyme whereby the enzyme is inactivated. The mechanism by which hemin prevents the formation of the inhibitor and maintains protein synthesis in reticulocyte lysates is thus explained.