bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic control of enhanced mutability of mitochondrial DNA and gamma-ray sensitivity in Saccharomyces cerevisiae.
Authors: Foury F , Goffeau A
Published: May 2006

Five nuclear mutants enhancing the spontaneous mutation rate of mtDNA have been isolated in Saccharomyces cerevisiae. These mutators fall into five complementation groups and are located at five genetic loci different from rad50 to rad57 loci. Three mutants (gam1, gam2, and gam4), insensitive or weakly sensitive to gamma-rays, exhibit increased frequency of spontaneous production of mutants with large deletions of the mtDNA (p-) and of all tested mitochondrial drug-resistant mutants. Two other mutants (gam3 and gam5), highly sensitive to gamma-rays, increase only the mutation rate of particular alleles of the mtDNA. The mutant gam5 enhances only the production of p- and erythromycin-resistant clones. The mutant gam3 exhibits an enhanced rate of oligomycin-resistant clones as well as a collateral increase of nuclear mutability. The existence of gam3 and gam5 mutants indicates that at least two common steps control both nuclear DNA repair and the mutability of particular alleles of the mtDNA. However, the general spontaneous mutability of the mtDNA includes at least three steps not involved in the repair of nuclear DNA, as revealed by the gam1, gam2, and gam4 mutations.
Analysis of HLA-D region-associated molecules with monoclonal antibody.
Authors: Charron D J , McDevitt H O
Published: May 2006

A group of monoclonal antibodies directed against nonpolymorphic HLA-D antigens (human Ia antigens) was produced by somatic cell hybridization. One of these antibodies was used to analyze the two-dimensional polyacrylamide gel electrophoretic pattern of the HLA-D alloantigens from different HLA-D homozygous B-cell lines. Two-dimensional gels of [35S]methionine-labeled cell extracts immunoprecipitated by a monoclonal antibody directed against HLA-D antigens showed a complex set of spots whose electrophoretic pattern varied according to the HLA-D type. The major HLA-D-related electrophoretic polymorphism was found in the basic and smaller (26,000-28,000 daltons) HLA-D polypeptides. These patterns represent allele-specific "fingerprints" of different HLA-D genotypes. There are striking similarities with respect to number, size, and charge spectrum among HLA-D polypeptides and the murine I-A and I-E subregion polypeptides, suggesting a similar genetic organization and molecular complexity in both species.
Differential effects of colchicine and cytochalasins on the shedding of murine B cell membrane IgM and IgD.
Authors: Emerson S G , Cone R E
Published: May 2006

Lactoperoxidase (EC 1.11.1.7) catalyzed cell surface radioiodination was employed to monitor the fate of murine B cell membrane (mem) IgM and IgD on radiolabeled cells in short-term culture. Both mem-IgM and mem-IgD were shed from the cell surface with biphasic kinetics. The rapid phase of mem-IgD shedding was somewhat slower (half-time = 12 hr) than that of mem-IgM shedding (half-time = 7-8 hr). The effect of temperature, colchicine, and cytochalasin on the shedding of the two membrane immunoglobulin isotypes was determined. The shedding of mem-IgD was more energy dependent than that of mem-IgM and was sensitive to colchicine but not cytochalasin. Conversely, the shedding of mem-IgM was sensitive to cytochalasin but not colchicine. The results suggest that the mechanisms of shedding of mem-IgM and mem-IgD are qualitatively distinct and may be regulated by microfilaments or microtubules, respectively.
Analysis of human tonsil and cancer DNAs and RNAs for DNA sequences of group C (serotypes 1, 2, 5, and 6) human adenoviruses
Authors: Green Maurice , Wold William S. M. , Mackey Jesse K. , Rigden Patricia
Published: May 2006

Group C human adenoviruses (Ads) of serotypes 1, 2, 5, and 6 infect most children and commonly cause latent infections of lymphoid tissues. Ads transform cells into a malignant-like phenotype; the oncogenic genetic information is in the left 8% of the viral genome, in the
Hin
dIII-G DNA fragment. We have investigated the molecular basis for group C Ad latent infections in human tonsils as well as whether these viruses are linked to human cancer. Tonsil or cancer DNAs and RNAs were assayed for Ad sequences by liquid-phase saturation-hybridization with
in vitro
-labeled Ad5
Hin
dIII-G fragment. About 25% of the 52 tonsils analyzed contained DNA or RNA sequences specific to
Hin
dIII-G, indicating that Ad transforming sequences are expressed as RNA in tonsils. Southern blotting analysis of four tonsil DNAs revealed multiple copies of the complete Ad genome in a free state and provided evidence for an unusual form of the Ad genome, possibly Ad DNA integrated into cellular DNA. In assays of human cancers, no Ad sequences were detected in DNAs from 26 squamous cell carcinomas (Cas), 3 adenocarcinomas, 4 oat cell Cas, 5 stomach Cas, 5 small intestine Cas, 15 colon Cas, 6 rectum Cas, 5 Hodgkin and 6 non-Hodgkin lymphomas, and 2 breast Cas. Reconstruction experiments indicated that the
Hin
dIII-G probe could detect 1 copy per cell of 0.2-0.3% of the viral genome. No
Hin
dIII-G-specific sequences were detected in RNAs from 21 squamous cell Cas, 3 oat cell Cas, 2 stomach Cas, or 18 colon Cas. In six other experiments using the complete Ad2 genome as probe, no Ad sequences were found in DNAs from 6 lung Cas, 12 normal lung tissues, 33 gastrointestinal Cas, 19 normal gastrointestinal tissues, 6 Hodgkin lymphomas, 3 breast Cas, or 4 kidney Cas, at a sensitivity of about 1 copy per tumor cell of 5-10% of the Ad2 genome. All Ad-induced cancer cells should contain at least 1 copy of 1-6% of the viral genome, the minimal size of the transforming region, and probably should contain multiple copies of more of the genome. Therefore, our data are definitive evidence against group C Ads being the cause of the cancers tested, which represent about 50% of the cancer incidence in the United States. Of additional interest, we did not detect Ad2 sequences in RNAs from 7 human placentas, 12 normal lungs, or 19 normal gastrointestinal tissues (nor in 44 cancer or 23 tonsil RNAs). Thus, we did not confirm a recent report of the presence of Ad2 RNA in RNAs from human placentas; the possibility that a small population of cells in placenta expresses group C “related” sequences is not ruled out.
Estrogenic activity of the insecticide chlordecone (Kepone) and interaction with uterine estrogen receptors.
Authors: Hammond B , Katzenellenbogen B S , Krauthammer N , McConnell J
Published: May 2006

The chlorinated insecticide chlordecone (Kepone) interacts with the estrogen receptor system in the rat uterus in vitro and in vivo. It competes with estradiol for binding to the cytoplasmic receptor in vitro and also induces nuclear accumulation of estrogen receptor sites in uteri in vitro. When injected into immature rats, chlordecone translocates estrogen receptor sites to the uterine nucleus, increases uterine weight, and stimulates the synthesis of the progesterone receptor, an estrogen receptor-mediated process. Its slow onset of action but prolonged duration of interaction with estrogen receptor and stimulation of uterine weight gain and progesterone receptor synthesis indicates that, although it has an affinity for receptor only 0.01-0.04% that of estradiol, its considerable estrogenic activity may likely be derived from its long half-life and bioaccumulative character.
Polyamine-pyridoxal Schiff bases in urine.
Authors: Aigner-Held R , Campbell R A , Daves G D
Published: May 2006

Schiff bases of the diamines 1,3-diaminopropane, putrescine, and cadaverine and the polyamines spermidine and spermine with pyridoxal or pyridoxal phosphate occur in human urine, as shown by gas chromatographic/mass spectrometric selected ion-monitoring techniques. By use of synthetic standards, procedures were devised for conversion of the Schiff bases to stable derivatives amenable to gas chromatographic/mass spectrometric analysis. These procedures involve borohydride reduction of the C = N double bond, hydrolytic removal of the phosphate group, chromatographic separation from the bulk of urinary constituents, and trifluoroacetylation of polar functional groups. The levels of the polyamine-pyridoxal Schiff bases were estimated to be in the range of pmol/ml or urine.
Rich ependymal investment of luliberin (LHRH) fibers revealed immunocytochemically in an image like that from Golgi stain.
Authors: Burchanowski B J , Knigge K M , Sternberger L A
Published: May 2006

Immunospecific staining in 100-micron-thick Vibratome section by the unlabeled antibody method resembles Golgi staining and reveals an abundance of luliberin- (luteinizing hormone releasing hormone, LHRH) positive cells and fibers in close contact with the surface of the third ventricle. The polarity of LHRH cells can be seen and processes can be traced for several millimeters. In the medial preoptic and suprachiasmatic areas bipolar LHRH neurons send short stout processes to the ventricular surface and long processes toward the organum vasculosum laminae terminalis. These cells resemble the receptor cells contacting the cerebrospinal fluid that have been described by Vigh and Vigh-Teichmann [Vigh, B. & Vigh-Teichmann, I. (1973) Int. Rev. Cytol. 35, 189-251]. In the septal region some bipolar neurons send both of their processes towards the ventricular surface. LHRH neurons in the nucleus of the anterior commissure and the bed nucleus of the stria terminalis project over the anterior commissure to form a dense plexus of fibers in the subfornical organ. The proximity of LHRH perikarya and fibers to the ventricular surface supports the hypothesis [Knigge, K.M., Joseph, S.A., Scott, D.E. & Jacobs, J.J. (1971) in The Neuroendocrinology of Human Reproduction, eds. Mack, H.C. & Sherman, A.J., (Thomas, Springfield, IL), pp. 6-22.] that the cerebrospinal fluid functions in neuroendocrine control mechanisms.
Isolation of the opioid heptapeptide Met-enkephalin [Arg6,Phe7] from bovine adrenal medullary granules and striatum.
Authors: Stern A S , Lewis R V , Kimura S , Rossier J , Gerber L D , Brink L , Stein S , Udenfriend S
Published: May 2006

Bovine adrenal chromaffin granules have been shown to contain, in addition to Met-enkephalin and Leu-enkephalin, at least three small peptides with opiate receptor activity. One of these adrenal peptides has been purified to homogeneity and its sequence was shown to be Met-enkephalin-[Arg6,Phe&]. This heptapeptide was also found in beef striatal extracts in amounts comparable to those of Leu-enkephalin.
Cryoenzymology in aqueous media: Micellar solubilized water clusters
Authors: Douzou Pierre , Keh Erlend , Balny Claude
Published: May 2006

Amphiphilic compounds dissolved in nonpolar organic solvents form inverted micelles whose aqueous centers can solubilize relatively large amounts of enzymes. The solutions are homogeneous and optically transparent and have low viscosity and freezing points; they provide unique and favorable systems to perform the main cryoenzymologic studies previously carried out in mixed solvents. The preparation and properties of such micelles are described. The absorbance spectra of cytochrome
c
at various temperatures from -38°C to 20°C are given. The pH dependence of trypsin-catalyzed hydrolysis of benzoylarginine ethyl ester in inverted micelles, as well as kinetic properties and activation energy, is described. Some problems are analyzed.
Spectral and kinetic evidence for two early electron acceptors in photosystem I
Authors: Shuvalov Vladimir A. , Dolan Ed , Ke Bacon
Published: May 2006

Triton-fractionated photosystem-I particles poised at -625 mV, where the two bound iron-sulfur proteins are reduced, have been studied by optical and electron paramagnetic resonance spectroscopies from 293 to 5 K. At 5-9 K, these particles exhibit two decay components with lifetimes of 1.3 and 130 msec in the laser pulse-induced absorption and electron paramagnetic resonance signal changes. Spectral properties of the 130-msec decay component reflect the charge separation between
P
-700 and some iron-sulfur center having a broad optical absorbance in the 400- to 550-nm region and a previously reported electron paramagnetic resonance signal with
g
= 1.78, 1.88, and 2.08. Spectral properties of the 1-msec decay component indicate photoinduced charge separation between
P
-700 and a chlorophyll
a
dimer having absorption bands at 420, 450, and 700 nm. It is assumed that these two acceptors participate in the electron transfer from
P
-700
*
to the bound iron-sulfur proteins.
Chemical carcinogens produce mutations to ouabain resistance in transformable C3H/10T1/2 Cl 8 mouse fibroblasts.
Authors: Landolph J R , Heidelberger C
Published: May 2006

Chemical carcinogens induce mutations to ouabain resistance in the transformable mouse fibroblast cell line C3H/10T1/2 Cl 8. The mutant phenotype is stable and heritable in the absence of selective agent, and dose--response curves for mutant frequency were obtained with N-menthyl-N'-nitro-N-nitrosoguanidine, 3-methylcholanthrene, benzo[a]-pyrene, N-acetoxy-N-2-acetylaminofluorene, and the anti-7,8-diol-9,10-epoxide of benzo[a]pyrene. The ratio of the malignant transformation frequency to the mutation frequency was 12 for benzo[a]pyrene and 21 for N-acetoxy-N-2-acetylaminofluorene. The development of the mutational assay reported here allows the use of this permanent cell line for comparison of mutation and transfomration frequencies and as a screening system for xenobiotics that pose mutagenic or carcinogenic hazards to mammalian cells.
Action of black widow spider venom on quantized release of acetylcholine at the frog neuromuscular junction: dependence upon external Mg2+.
Authors: Misler S , Hurlbut W P
Published: May 2006

Black widow spider (Latrodectus tredecimguttatus) venom (BWSV) increases several hundredfold the frequency of occurrance of minature end-plate potentials (Fmepp) at frog neuromuscular junctions bathed in Ringer's solutions containing either Ca2+ of Mg2+, but it has little effect on Fmepp at junctions bathed in modified Ringer's solution containing 1--2 mM ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) but no Ca2+ or Mg2+. When Mg2+ is added to preparations that have been treated with BWSV in the modified solution, Fmepp increases exponentially with time. Fmepp falls again to low values when the Mg2+ is removed. The rate constant of the exponential rise is proportional to [Mg2+]o in the range 1--4 mM, and the threshold [Mg2+]o is 0.1--0.5 mM. Increasing the K+ concentration of the bathing solution decreases the ability of Mg2+ to increase Fmepp. Addition of Ca2+, Co2+, Mn2+, or Zn2+ also leads to a large increase in Fmepp. These results are consistent with the possibility that BWSV increases the permeability of the nerve terminal to divalent cations. BWSV can, however, increase Fmepp in hypertonic solutions in the absence of external divalent cations. This result suggests that the effects of BWSV on the nerve terminal may not be confined to increasing the permeability of the plasma-lemma.
Semihistone protein A24 replaces H2A as an integral component of the nucleosome histone core.
Authors: Martinson H G , True R , Burch J B , Kunkel G
Published: May 2006

The semihistone protein, A24, was shown to be a stable minor component of purified salt-washed nucleosome core particles. A24 was also shown to become integrated into nucleohistone during reconstitution in a manner characteristic of the core histones. Purified A24 in solution was shown to exhibit the same specificity of interaction with histone H2B as is exhibited by histone H2A. We conclude that A24 in chromatin replaces H2A as a stable integral component of certain nucleosome histone cores.
Correlation between structure and function of heparin
Authors: Rosenberg Robert D. , Lam Lun
Published: May 2006

We have fractionated crude porcine heparin to obtain highly active as well as relatively inactive species of molecular weight ≈7000 with specific anticoagulant activities of 360 and 12 units/mg, respectively. Nitrous acid degradation of both of these polymers yielded a tetrasaccharide fraction, 1β, that contained equimolar amounts of iduronic and glucuronic acids, possessed an internal
N
-acetylated glucosamine, and carried anhydromannitol at the reducing end position. The 1β tetrasaccharide derived from the highly active heparin, 1β
a
, was recovered in a yield of 1.1 mol/7000 daltons. Our analyses indicate that at least 95% of the 1β
a
is a single structure that consists of the following unique monosaccharide sequence: L-iduronic acid →
N
-acetylated D-glucosamine-6-sulfate → D-glucuronic acid →
N
-sulfate D-glucosamine-6-sulfate. The 1β tetrasaccharide fraction from relatively inactive mucopolysaccharide, 1β
i
, was recovered in a yield of 0.3 mol/7000 daltons and was a mixture of several components. Only 8.5% of the 1β
i
tetrasaccharide fraction exhibited the same uronic acid placement and sulfate group position found in 1β
a
. Thus, 2.6% of relatively inactive mucopolysaccharide molecules contain the unique tetrasaccharide sequence found within each molecule of highly active heparin. Given the correlation between abundance of this unique 1β
a
tetrasaccharide sequence and biologic potency, we suggest that this structure represents the critical site responsible for anticoagulant activity.
Separate roles for calcium and magnesium in their synergistic effect on uridine uptake by cultured cells: Significance for growth control
Authors: Bowen-Pope D. F. , Vidair C. , Sanui H. , Rubin A. H.
Published: May 2006

The uptake of uridine by BALB/c3T3 cells is markedly inhibited by reducing the concentration of Mg
2+
in medium containing only traces of Ca
2+
. When physiological [Ca
2+
] is present in the medium, omission of Mg
2+
has no effect on uridine uptake, and when Mg
2+
is present, omission of Ca
2+
has only a slight inhibitory effect. When both Ca
2+
and Mg
2+
are omitted, the concentration of Ca
2+
in the cells is not reduced, but that of Mg
2+
is reduced to about one-half in 3 hr. The concentration of K
+
is also reduced, and that of Na
+
is increased, suggesting increased membrane permeability to cations. The rate of diffusion of the nontransported hexose, L-glucose, into the cells is greatly increased. Changes in intracellular Na
+
and K
+
concentrations do not in themselves affect uridine uptake. When Ca
2+
alone is restored to the medium of cells that had been deprived of both Ca
2+
and Mg
2+
, there is no increase in the greatly depressed rate of uridine uptake, but when Mg
2+
alone is restored, the rate of uridine uptake returns to control values. We conclude that the omission of Ca
2+
from the medium has no direct effect on uridine uptake, but acts by increasing the exchange of Mg
2+
between cells and medium and by otherwise altering the availability of Mg
2+
for this reaction. A similar conclusion is reached in considering the role of these ions in the regulation of other reactions of the coordinate response, including the initiation of DNA synthesis and the control growth.
Measurement of mutagenesis in mammalian cells.
Authors: Waldren C , Jones C , Puck T T
Published: May 2006

A method using mammalian cells in vitro for detection and quantitation of mutagenic actions that appears to be useful for screening for carcinogenesis and genetic damage by environmental agents is presented. The method involves use of stable human--Chinese hamster ovary hybrid cells that have retained a single human chromosome not necessary for cell reproduction. Forward mutations are detected in genes necessary for production of specific human cell surface antigens. Such mutants form colonies in the presence of specific antisera and complement that destroy the unmutagenized cells. Use of the method is illustrated for the action of x-irradiation, N-methyl-N'-nitro-N-nitrosoguanidine, and caffeine. The method appears to be unique in that it permits assessment of lesions that cause loss of all or most of the chromosome as well as various localized gene mutations. The former action is particularly important because of the major involvement of chromosomal lesions in an extremely important class of human genetic disease.
Molecular reorganization of lipid bilayers by complement: a possible mechanism for membranolysis.
Authors: Esser A F , Kolb W P , Podack E R , Müller-Eberhard H J
Published: May 2006

The interaction between the membrane attack complex (MAC) of complement and flat lipid bilayers was investigated. Using spin-labeled derivatives of phospholipids and cholesterol and electron paramagnetic resonance spectroscopy, we measured the penetration of the MAC into bilayers and its influence on the order of bilayers. The MAC precursor components C5b--6, C7, C8, and C9 did not exert any measurable influence on lipid membranes. Functional C5b--7 was shown to interact strongly with the bilayer surface without deep penetration into the bilayer. Formation of C5b--8 and especially C5b--9 caused a marked change in the anisotropy of spectra from probes located within the hydrocarbon phase. The spectral changes are not caused by changes in probe rotation and, in the case of the cholesterol probes, are not due to direct probe--protein interactions. For these reasons we interpret the spectral changes to be the result of reorientation of ordered bilayer lipids effected by strong binding of phospholipids to MAC proteins.
Hemoglobin synthesis in cultures of hepatic erythroid cells from the human fetus
Authors: Rowley Peter T. , Ohlsson-Wilhelm Betsy , Farley Barbara A. , Kosciolek Barbara
Published: May 2006

A recent theory of the control of human fetal hemoglobin synthesis, based on studies in cultured adult marrow, proposes that the phenotypic expression of fetal hemoglobin is largely dependent on the level of differentiation of the parental stem cells; that is, the earlier the progenitor, the greater the ability of its progeny to express fetal hemoglobin [Papayannopoulou, Th., Brice, M. & Stamatoyannopoulos, G. (1977)
Proc. Natl. Acad. Sci. USA
74, 2923-2927]. To test this relationship with fetal tissue, we have studied hemoglobin synthesis in cultured human fetal liver, comparing γ chain synthesis in the descendants of the early progenitors (“bursts”) with that in the descendants of the later progenitors (“colonies”). Cells from the livers of midtrimester fetuses were cultured in methylcellulose with erythropoietin. The β/(β + γ) globin synthetic ratio on days 5 to 7, when colonies predominated, was 0.09-0.11, a value characteristic of fetal reticulocytes, and on days 11 and 12, when bursts predominated, was 0.15-0.17. Thus, in fetal liver, the descendants of the earlier progenitor, the burst-forming unit, may be making more β chains rather than more γ chains, compared to descendants of the later progenitor, the colonyforming unit. Our data on fetal liver, taken together with the data on adult marrow by others, suggest that the erythroid colonies express the gene characteristic of the age of the organism to a greater degree than bursts, which express β and γ genes less specifically. Thus, the capacity for highly selective gene expression characteristic of differentiated cells appears to be less well developed in the burst-forming unit than in the colony-forming unit.
Sparing of metabolic stress in Purkinje cells after maximal electroshock
Authors: McCandless David W. , Feussner Gretchen K. , Lust W. David , Passonneau Janet V.
Published: May 2006

Experimental seizures were induced in mice by application of 50 mA for 0.2 sec via corneal electrodes. The reproducible conclusive behavior was characterized by a sequence of 2 sec of tonic flexion, 13 sec of tonic extension, and 8 sec of clonus followed by a postictal depressive stage. The animals were frozen and tissues were prepared for analysis according to Lowry and Passonneau [Lowry, O. H. & Passonneau, J. V. (1972)
A Flexible System of Enzymatic Analysis
(Academic, New York)]. Freeze-dried samples (1-10 ng) of pyramidal cell bodies and adjacent neuropil from the parietal cortex and of Purkinje cell bodies and adjacent neuropil from the cerebellum were analyzed for glucose, ATP, and
P
-creatine (0.01-0.05 pmol). There were marked decreases in these energy stores after the maximal electroshock in three of the areas examined. In the Purkinje cell bodies, however, the metabolic stress was dampened; glucose concentrations decreased, but the levels of ATP were maintained and, to a lesser extent, those of
P
-creatine. The results indicate that the output from the Purkinje cells is less than in the other regions examined in the excitable stages of the convulsion. The lesser energy debt probably reflects lower energy demand as well as a lower discharge intensity. The fact that Purkinje cells are spared from the metabolic stress imposed on other regions may be a partial explanation of the seizure activity. A diminished output from the Purkinje cells could be a situation that permits cortical convulsive activity.
Inosine, an endogenous ligand of the brain benzodiazepine receptor, antagonizes pentylenetetrazole-evoked seizures.
Authors: Skolnick P , Syapin P J , Paugh B A , Moncada V , Marangos P J , Paul S M
Published: May 2006

Partially purified extracts of bovine brain were previously found to inhibit competitively the binding of [3H]-diazepam to rat brain synaptosomal membranes. The purines inosine and hypoxanthine were subsequently identified as the compounds responsible for this inhibitory activity. Intracerebroventricular administration of inosine to mice of the C3H/HEN and NIH general purpose strains caused a dose- and time-dependent increase in the latency to clonicotonic seizures produced by intraperitoneal administration of the convulsant pentylenetetrazole. Intracerebroventricular administration of equimolar doses of 2'-deoxyinosine, which is more potent than inosine in inhibiting the binding of [3H]diazepam in vitro, significantly increased pentylenetetrazole-evoked seizure latency. In contrast, both 7-methylinosine and thymidine were ineffective in inhibiting the in vitro binding of [3H]diazepam and increasing the latency to pentylenetetrazole-induced seizures in vivo. These results suggest that endogenously occurring purines such as inosine exhibit diazepam like effects when administered intracerebroventricularly, and these effects may be related to the interaction of inosine and related compounds with benzodiazepine receptors in the central nervous system.
Secular change in the variability of temperature
Authors: Waggoner Paul E.
Published: May 2006

The mean temperatures for January, April, summer and October at New Haven, Connecticut, for 1781-1970 were analyzed for evidence of a secular change in several indices of variability. The January—July difference decreased significantly. Although the standard deviation (SD) of the summer temperature within decades decreased significantly, the SDs of January, April, and October did not, and none of the SDs were correlated with means. The SD about trends within decades was not correlated with the magnitude of the trends except in April. There was no significant trend in the January-to-January persistence during the 19 decades.
Isolation of maxicircle component of kinetoplast DNA from hemoflagellate protozoa.
Authors: Simpson L
Published: May 2006

Maxicircle DNA has been isolated from the kinetoplast DNA of Leishmania tarentolae culture forms by bouyant separation in CsCl in the presence of the A + T-binding dye Hoechst 33258, after liberation from the kinetoplast DNA network by cleavage with the single-hit restriction endonuclease EcoRI. The purified linearized maxicircle DNA has a density in CsCl of 1.681 g/cm3 (79% A + T) and a molecular weight of approximately 18-20 x 10(6). The maxicircle molecule exhibited intramolecular base composition heterogeneity ranging from 85% A + T to 74% A + T.
Nucleotide sequence of the mitochondrial structural gene for subunit 9 of yeast ATPase complex.
Authors: Hensgens L A , Grivell L A , Borst P , Bos J L
Published: May 2006

We have determined the nucleotide sequence of a segment of Saccharomyces mtDNA that contains the structural gene for one of the subunits (the dicyclohexylcarbodiimide-binding protein) of the mitochondrial ATPase complex. The sequence fits the known amino acid sequence of this protein with the exception of one amino acid. Codon usage is biased in favor of A + T-rich codons. On both sides of the gene, the nucleotide sequence contains less than 4% (mol/mol) G + C for at least 180 nucleotides; these A + T sequences show no evidence of internal repetition. The gene and all the A + T-rich sequence preceding the gene are present in a 12S RNA that is the major transcript of this segment of mtDNA. The nature of the sequences responsible for binding ribosomes to mitochondrial mRNA and for termination of RNA synthesis is considered.
Tumor promoter-mediated inhibition of cell differentiation: suppression of the expression of erythroid functions in murine erythroleukemia cells.
Authors: Fibach E , Gambari R , Shaw P A , Maniatis G , Reuben R C , Sassa S , Rifkind R A , Marks P A
Published: May 2006

Previous studies demonstrated that 12-O-tetradecanoyl-phorbol-13-acetate (TPA), a tumor promoter, is a potent inhibitor of inducer-mediated differentiation of murine erythroleukemia cells. Inhibition of cell differentiation was associated with inhibition of cell growth. The present studies, employing a cell line adapted for growth in TPA, demonstrate that inhibition of differentiation is not dependent upon inhibition of cell growth or a change in the cell division cycle; neither is inhibition of differentiation accompanied by detectable effect on cell uptake of [3H]hexamethylene bisacetamide, the inducer used in these studies. TPA causes an inhibition of expression of all hexamethylene bisacetamide-inducible erythroid characteristics measured, including commitment to terminal cell division, accumulation of globin mRNA, and synthesis of globins, spectrin, heme synthetic enzymes (delta-aminolevulinic acid dehydratase and uroporphyrinogen-I synthase) and heme. A hypothetical model for the inhibitory action of tumor promoters on terminal cell differentiation is discussed.
Triplet phase invariants: Formula for centric case from fourth-order determinantal joint probability distributions
Authors: Karle Jerome
Published: May 2006

A formula is derived for centrosymmetric crystals from fourth-order determinantal joint probability distributions that provides, for the triplet invariants, values of
P
+
/
P
-
, the ratio of the probability that an invariant has a plus sign associated with it to the probability that it has a minus sign. The formula makes use of the entire data set in the computations for each invariant. Test calculations indicate that many hundreds of invariants can be selected by use of the formula with essential certainty that their value is equal to zero. Several invariants whose value is equal to π can also be selected on occasion with very high reliability.
Numerical analysis of weakly nonlinear wave turbulence
Authors: Meiss James D. , Pomphrey Neil , Watson Kenneth M.
Published: May 2006

We consider the propagation of weakly nonlinear waves such as plasma waves, surface water waves, the interaction of laser beams with matter, particle accelerators, etc. Specifically, we study internal waves in the ocean. Hamilton's principle is used to write the fluid equations in Hamiltonian form in terms of linear eigenmode amplitudes. Numerical studies are made of the effect of Fourier grid size and resonance widths. Statistical information is generated from an ensemble of initial states of the random wave field.
Reaction of nucleosome DNA with dimethyl sulfate.
Authors: McGhee J D , Felsenfeld G
Published: May 2006

We have measured the effect of the histones in the nucleosome core particle on methylation of purines in nucleosome DNA by dimethyl sulfate. By using 32P terminally labeled nucleosome cores, we have examined the pattern of strand cleavage at methylated sites in the nucleosome DNA and compared it to the pattern observed in histone-free DNA. We are unable to detect any significant difference between the reactivity of N7 of guanines in nucleosome DNA and of that in naked DNA, with the exception of a single site of enhanced reactivity at approximately nucleotide 62 from the 5' end of the nucleosome. Contrary to our expectation, there is no detectable periodic modulation of reactivity corresponding to the twist of the DNA on the nucleosome surface. We are able to place a low upper limit on the extent to which the histones of the nucleosome can protect N7 of guanine in the large groove. With somewhat less precision, we also conclude that the N3 of adenine in the small groove is largely unprotected. These results indicate that in nucleosome DNA the bases are nearly as accessible to solvent as they are in DNA free of protein.
Glutathione-dependent hydrogen donor system for calf thymus ribonucleoside-diphosphate reductase.
Authors: Luthman M , Eriksson S , Holmgren A , Thelander L
Published: May 2006

Purified calf thymus ribonucleoside-diphosphate reductase (2'-deoxyribonucleoside-diphosphate:oxidized-thioredoxin 2'-oxidoreductase, EC 1.17.4.1), showed an absolute requirement for a dithiol as hydrogen donor, whereas the natural monothiol glutathione (GSH) was inactive per se. However, a protein partially purified from thymus coupled the oxidation of GSH to the formation of deoxyribonucleotides by ribonucleotide reductase. In analogy with the ribonucleotide reductase system of Escherichia coli this protein was called glutaredoxin [Holmgren, A. (1976) Proc. Natl. Acad. Sci. USA 73, 2275-2279]. Thymus glutaredoxin had the following properties: (i) its molecular weight determined by gel chromatography was about 12,000; (ii) it was active iwth ribonucleotide reductase in the presence of GSH, NADPH, and glutathione reductase but had no activity with NADPH and thioredoxin reductase; and (iii) it was immunologically different from thioredoxin because it did not bind to antithioredoxin immunoadsorbents. Experiments on the crossreactivity of thymus and E. coli ribonucleotide reductases and the corresponding thioredoxin and glutaredoxin systems showed essentially no specificity for the homologous thioredoxin but a high species specificity for the homologous glutaredoxin.
Cell-free translation of the mRNAs for the heavy and light chains of HLA-A and HLA-B antigens.
Authors: Ploegh H L , Cannon L E , Strominger J L
Published: May 2006

Cell-free translation of poly(A)-containing RNA from the JY lymphoblastoid cell line followed by immunoprecipitation has indicated the presence of mRNAs for both the heavy and light chains of HLA-A and HLA-B antigens in these preparations. Both chains are synthesized with an NH2-terminal extension, approximately 20 residues in length for the light chain, and 20 or 24 residues for the heavy chains. The precursors can be processed by dog pancreatic microsomes to products similar to those obtained in vivo. Immunoprecipitation of the cell-free products has been employed as an assay for partial purification of the mRNAs. Investigation of the Daudi cell line, which cannot synthesize the small subunit, beta 2-microglobin, has indicated that the heavy chains of HLA-A and HLA-B antigens are synthesized intracellularly in vivo and can also be translated from their cognate RNAs in vitro. The implications of these findings for biosynthesis of membrane proteins in general and multimeric membrane proteins in particular, as well as the role of beta 2-microglobulin in expression of HLA-A and HLA-B antigens, are discussed.
Complexity transmission during replication
Authors: Davis Brian K.
Published: May 2006

The transmission of complexity during DNA replication has been investigated to clarify the significance of this molecular property in a deterministic process. Complexity was equated with the amount of randomness within an ordered molecular structure and measured by the entropy of
a posteriori
probabilities for discrete (monomer sequences, atomic bonds) and continuous (torsion angle sequences) structural parameters in polynucleotides, proteins, and ligand molecules. A theoretical analysis revealed that sequence complexity decreases during transmission from DNA to protein. It was also found that sequence complexity limits the attainable complexity in the folding of a polypeptide chain and that a protein cannot interact with a ligand moiety of higher complexity. The analysis indicated, furthermore, that in any deterministic molecular process a cause possesses more complexity than its effect. This outcome broadly complies with Curie's symmetry principle. Results from an analysis of an extensive set of experimental data are presented; they corroborate these findings. It is suggested, therefore, that complexity governs the direction of order—order molecular transformations. Two biological implications are (
i
) replication of DNA in a stepwise, repetitive manner by a polymerase appears to be a necessary consequence of structural constraints imposed by complexity, and (
ii
) during evolution, increases in complexity had to involve a nondeterministic mechanism. This latter requirement apparently applied also to development of the first replicating system on earth.
Immunosuppression by Friend leukemia virus is H-2 restricted by alloreactive T lymphocytes.
Authors: Kumar V , Bennett M
Published: May 2006

Friend leukemia virus suppresses mitogen-responsive cells in vitro by activating thymus-dependent suppressor cells. The interaction between T suppressor and mitogen-responsive cells is H-2D restricted by a third cell type, called an interfering cell. The interfering cells could be characterized as alloreactive T cells that functionally mature in the spleen at 2 weeks of age and that can be functionally inhibited by mitomycin C, irradiation, and cortisol. Interfering cells are stimulated by H-2D (and not H-2L) alloantigens of the mitogen-responsive cells. H-2D differences between interfering and T suppressor cells are unimportant. Induction of "tolerance" to H-2 alloantigens in semi-allogeneic radiation marrow chimeras resulted in the specific loss of interfering cell function. It is possible that interfering or similar cells participate in other forms of H-2 restriction.
Asymmetric and globular forms of acetylcholinesterase in mammals and birds.
Authors: Bon S , Vigny M , Massoulié J
Published: May 2006

We have identified six molecular forms of acetylcholinesterase (AcChoE: acetylcholine hydrolase, EC 3.1.1.7) in extracts from bovine superior cervical ganglia. We show that three of them resemble the collagen-tailed forms of Electrophorus AcChoE in their hydrodynamic parameters, low-salt aggregation properties, and collagenase sensitivity. The six molecular forms of bovine AcChoE appear structurally homologous to the six forms of electric fish AcChoE that have previously been characterized. They include globular molecules (monomers, dimers, and tetramers) and asymmetric aggregating molecules that possess a collagen-like tail associated with one, two, and three tetramers. We propose to call the globular forms G1, G2, and G4 and the asymmetric forms A4, A8, and A12, the subscripts indicating the number of catalytic subunits. In spite of quantitative differences in their molecular parameters, the AcChoE forms from rat and chicken are clearly homologous to those of bovine AcChoE. Thus the nomenclature we introduce is very probably valid for the main AcChoE molecular forms, at least in vertebrates, and should help to clarify structural relationships and homologies among them. This model, however, does not claim to represent entirely the complex polymorphism of AcChoE, because more or less hydrophobic variants of the G forms have been observed, and because other molecular associations cannot be excluded. We discuss the significance of the globular and collagen-tailed structure for the molecular localization of AcChoE.
Serum RNase in the diagnosis of pancreatic carcinoma.
Authors: Peterson L M
Published: May 2006

Serum RNase (RNase I; ribonuclease 3'-pyrimidino-oligonucleotidohydrolase, EC 3.1.4.22) activity (mean +/- SD) with polycytidine as substrate was determined in normal individuals (24.9 +/- 3.0 units/ml) and in patients with pancreatic cancer (37.3 +/- 14.8), pancreatitis (38.5 +/- 12.6), nonpancreatic diseases (48.7 +/- 14.8), or renal failure (175.8 +/- 92.8). Patients with pancreatic cancer could not be distinguished from those with pancreatitis or with nonpancreatic disease, although the RNase activities in all of these differed from the activity in normal individuals. The serum RNase activities of four patients with resectable "curable") pancreatic carcinoma and two others with advanced pancreatic cancer without obstructive jaundice were normal. After total pancreatectomy, serum RNase activity remained in the high-normal range. The data presented here and data in the literature show that serum RNase cannot be of primarily pancreatic origin. The present study also demonstrates that measurement of its activity is not useful in early detection of pancreatic cancer.
Chromosomal assignment of the mouse kappa light chain genes.
Authors: Swan D , D'Eustachio P , Leinwand L , Seidman J , Keithley D , Ruddle F H
Published: May 2006

Mouse-hamster somatic cell hybrids containing a variable number of mouse chromosomes have been used in experiments to determine which mouse chromosome carries the immunoglobulin kappa light chain genes. It has been shown by nucleic acid hybridization that the kappa constant gene and the genes for at least one variable region subgroup are on mouse chromosome 6. This somatic cell genetic mapping procedure appears to be general and can be applied to any expressed or silent gene for which an appropriate nucleic acid probe exists.
Electron flow through plastoquinone and cytochromes b6 and f in chloroplasts.
Authors: Velthuys B R
Published: May 2006

With dark-adapted chloroplasts in which the plastoquinone was oxidized, a partial reduction of cytochrome b6 was obtained upon illumination with a pair of short saturating flashes. The second flash of the pair was much more effective than the first, and the reduction was inhibited by the system II inhibitor diuron. When the plastoquinone pool was reduced, both the reduction and the oxidation of cytochrome b6 were accelerated. The cytochrome b6 oxidation appeared to proceed in association with the reduction of cytochrome f, although these cytochromes are not simply connected in series. From these observations it is inferred that electron flow to the secondary donors of system I alternately caused the reduction and the oxidation of cytochrome b6. An interpretation is offered that also accounts for the transmembrane proton translocation that is associated with the oxidation of plastohydroquinone.
Mitotic factors from mammalian cells induce germinal vesicle breakdown and chromosome condensation in amphibian oocytes.
Authors: Sunkara P S , Wright D A , Rao P N
Published: May 2006

Cytoplasmic extracts of HeLa cells synchronized in various phases of the cell cycle were injected into fully grown Xenopus laevis oocytes to monitor the presence of factors that can induce meiotic maturation: i.e., germinal vesicle breakdown and chromosome condensation. Extracts from GI and S phase cells had no activity. The maturation-inducing activity, which was found to be low during early and mid G2 phases, increased rapidly during late G2 and reached a peak in mitosis. The results of this study suggest that the factors that regulate the breakdown of nuclear membrane and chromosome condensation during mitosis, meiosis, and premature chromosome condensation appear to be very similar, if not identical, throughout the animal kingdom.
Familial hyperproinsulinemia: partial characterization of circulating proinsulin-like material.
Authors: Gabbay K H , Bergenstal R M , Wolff J , Mako M E , Rubenstein A H
Published: May 2006

Familial hyperproinsulinemia is an autosomal dominant defect that is associated with strikingly elevated levels of serum proinsulin-like material. Our studies show that trypsin converts familial hyperproinsulinemia proinsulin to insulin more slowly than it converts a 131I-labeled porcine proinsulin marker. Molar yields of insulin indicated that the material may be an intermediate proinsulin. Studies with two human C-peptide antisera that differ in their relative immunoreactivity with human C-peptide and proinsulin showed that the two antisera reacted equally with familial hyperproinsulinemia proinsulin, suggesting that it is a partially cleaved proinsulin intermediate. Sulfitolysis of highly purified material to break the inter- and intra-chain disulfide bridges and subsequent adsorption on a specific B-chain antibody covalently bound to Sepharose beads showed that the C-peptide was still connected to the B-chain. These data indicate that familial hyperproinsulinemia proinsulin is normally cleaved at the C-peptide-A-chain linkage site. A structural abnormality appears to underlie familial hyperproinsulinemia proinsulin, which impairs its cleavage at the B-chain-C-peptide linkage site.
Association of HLA antigens and total serum immunoglobulin E level with allergic response and failure to respond to ragweed allergen Ra3.
Authors: Marsh D G , Chase G A , Freidhoff L R , Meyers D A , Bias W B
Published: May 2006

We have applied rigorous statistical analysis to human immune response and HLA data in allergic subjects having varying sensitivity to the minor ragweed allergen, Ra3. By using regression analysis on a series of subsets of Ra3 responders and nonresponders, we obtained data supporting the concept of discrete "responder" and "nonresponder" phenotypes. We found significant positive associations between Ra3 response and total serum IgE and the presence of HLA antigens of the A2 crossreacting group (A2 and A28), and significant negative associations with antigens of the A3 crossreacting group (A3 and A11). Our results suggest that alleles of the HLA-A locus may function either as immune response or immune suppressor genes or that such alleles are epistatic to the response or suppressor genes. Our data add further support to previous findings that HLA-associated specific IgE response is strongly influenced by genetic regulation of basal IgE level.
Idiotypic analysis of monoclonal antibodies to poly(Glu60Ala30Tyr10).
Authors: Ju S T , Pierres M , Waltenbaugh C , Germain R N , Benacerraf B , Dorf M E
Published: May 2006

Fifteen hybridoma anti-poly(Glu60Ala30Tyr10) (anti-GAT) antibodies were analyzed for the presence of a common set of idiotypic specificities associated with murine anti-GAT antibodies, termed CGAT idiotype, which are present on the anti-GAT antibodies of all mouse strains. Thirteen of these monoclonal anti-GAT antibodies expressed a major fraction of CGAT idiotypic specificities. However, the remaining fraction of CGAT idiotypic specificities were not detected in individual or pooled hybridoma anti-GAT antibodies. Anti-idiotypic antisera made against each of the 15 hybridoma anti-GAT antibodies preferentially bound homologous ligand and showed minimal binding activity to specifically purified serum anti-GAT antibodies. Furthermore, the diversity of the hybridoma anti-GAT antibodies was demonstrated by the presence of individual idiotypic specificities on each of the hybridoma anti-GAT antibodies. However, relatedness among some of the hybridoma antibodies was also apparent since idiotypic analysis revealed that some hybridoma anti-GAT antibodies shared cross-reactive idiotypic specificities not associated with CGAT idiotype. The genetic mechanisms which could account for the generation of such antibody diversity are discussed.