bluuebunny/crossref_metadata_2025 huggingface dataset:
Chromosome Assignment of the Human Gene for Galactose-1-phosphate Uridyltransferase
Authors: Sun N. C. , Chang C. C. , Chu E. H. Y.
Published: May 2006

Somatic cell hybrids formed between galactose-negative mutant Chinese hamster cells and human lymphocytes were selected in galactose medium and analyzed for the concurrent presence of specific human chromosome(s) and human galactose-1-phosphate uridyltransferase. In one of the hybrid clones only a single human chromosome, A2, was consistently present when the hybrid cells were maintained in the selective medium, suggesting that the location of the structural gene for galactose-1-phosphate uridyltransferase is on this chromosome. Among subclones derived from this cell hybrid in the absence of selection, a complete concordance was demonstrated between the ability or inability to utilize galactose and the concomitant presence or absence of the human transferase and the A2 chromosome.
Metabolism of 25-Hydroxyvitamin D
3
in Anephric Rats: A New Active Metabolite
Authors: Garabedian M. , Pavlovitch H. , Fellot C. , Balsan S.
Published: May 2006

After the injection of radioactive 25-hydroxyvitamin D
3
into rats given a normal diet, two metabolites can be detected on Sephadex LH-20 chromatography modified to reveal polar metabolites. The first is designated peak Va, which by means of periodate cleavage has been identified as 24,25-dihydroxyvitamin D
3
. The second more polar metabolite has been designated peak X
1
and is only partially sensitive to periodate. This metabolite appears in serum, bone, intestine, and liver and does not chromatograph on any system like any of the previously identified metabolites. Nephrectomy, especially in the animals given large doses of 25-hydroxyvitamin D
3
, does not abolish production of either peak Va or X
1
, revealing that both metabolites can be made in extra-renal tissue. Peak X
1
has marked ability to elevate serum calcium of rats on a vitamin D-deficient, low calcium diet, but requires the presence of kidneys to carry out this function.
Identification of Discrete Polyadenylate-containing RNA Components Transcribed from HeLa Cell Mitochondrial DNA
Authors: Ojala Deanna , Attardi Giuseppe
Published: May 2006

Polyacrylamide gel electrophoresis and sedimentation analysis under denaturing conditions of poly(A)-containing RNA from the polysome region of the sedimentation pattern of a HeLa-cell mitochondrial lysate has revealed the occurrence of a discrete RNA component, which sediments in the native state with a sedimentation constant of about 7 S. From the sedimentation behavior under native and denaturing conditions and the poly(A) content, a molecular weight of about 9 × 10
4
has been estimated for this component. RNA·DNA hybridization experiments have indicated that this component is coded for by the light strand of mitochondrial DNA. Evidence for the occurrence of a poly(A)-containing RNA component sedimenting at about 9 S and coded for by the heavy strand has also been obtained.
Reconstitution of a Calcium Pump Using Defined Membrane Components
Authors: Warren G. B. , Toon Penelope A. , Birdsall N. J. M. , Lee A. G. , Metcalfe J. C.
Published: May 2006

A (Mg
2+
+ Ca
2+
)ATPase (ATP phosphohydrolase, EC 3.6.1.3) has been purified from sarcoplasmic reticulum using a single step centrifugation procedure. The preparation is >95% pure by weight and contains only 25-30% of the lipid associated with the enzyme in native sarcoplasmic reticulum. The purified enzyme is unable to accumulate Ca
2+
. Using a sedimentation-substitution technique, >98% of the lipid associated with the purified enzyme can be replaced by dioleoyl lecithin without grossly affecting the ATPase activity of the enzyme. The Ca
2+
pump can be restored to this dioleoyl lecithin-substituted enzyme by addition of excess sarcoplasmic reticulum lipids in the presence of cholate. Removal of the cholate by dialysis generates a system which accumulates Ca
2+
at a rate and to a level comparable to native sarcoplasmic reticulum. Significant reconstitution of the Ca
2+
pump can also be achieved using excess dioleoyl lecithin, but since the full expression of the capacity to accumulate Ca
2+
requires the presence of oxalate, these vesicles would appear to be more leaky than those reconstituted with an excess of sarcoplasmic reticulum lipids. Of about 90 lipid molecules which are associated with one molecule of ATPase in native sarcoplasmic reticulum, an average of less than one lipid molecule remains in these reconstituted systems. We have therefore achieved a fully functional Ca
2+
pump containing essentially a single protein and exogenous lipid.
Reversion of a Chinese Hamster Cell Auxotrophic Mutant
Authors: Chasin Lawrence A. , Feldman Aileen , Konstam Marvin , Urlaub Gail
Published: May 2006

A mutant cell strain derived from a Chinese hamster line by mutagenesis with ethylmethane sulfonate requires glycine for growth. In the wild type, glycine synthesis is catalyzed by serine hydroxymethyltransferase (EC 2.1.2.1). Cell fractionation by differential centrifugation and isopycnic sucrose gradient analysis reveals that the enzyme activity is found in both the mitochondrial and cytosol fractions. The specific activity in the mitochondrial fraction is about 20 times higher than in the cytosol, and is much more stable to thermal inactivation. The glycine-requiring mutant has lost all of the mitochondrial enzyme activity, while retaining the cytosol activity. The mutant is very stable but can be induced to revert by several chemical mutagens. One glycine-independent revertant induced by ethyl methane sulfonate was studied in detail. Serine hydroxymethyltransferase activity is again present in the mitochondrial fraction, at about [unk] of the wild-type level. However, the revertant mitochondrial enzyme exhibits an altered thermal sensitivity, with a half-life at 45° of 55 min as compared to 180 min in the wild type. The half-life for the cytosol enzyme in all three strains is 7 min. Mixing experiments demonstrate that the heat lability of the revertant enzyme is not due to a dissociable factor in the extract. The data are consistent with the idea that the original mutation occurred in the structural gene for one isozyme of the enzyme and that the revertant has undergone a second mutation in this gene, partially restoring enzyme activity.
Four Peroxidase Loci in Red-Fruited Tomato Species: Genetics and Geographic Distribution
Authors: Rick Charles M. , Zobel Richard W. , Fobes Jon F.
Published: May 2006

The banding patterns of certain anodal peroxidase variants of red-fruited tomato species are governed by alleles at four loci—two alleles per locus. Alleles at three loci code for modified enzyme migration patterns and are codominant in heterozygotes; those at the fourth locus code for presence or absence of a band. No evidence of linkage was detected in preliminary tests between four of the six possible combinations of loci. All variant alleles—i.e., those not represented in the standard genotype of
Lycopersicon esculentum
—exist in the wild
L. pimpinellifolium
from coastal Peru; all but

Prx-3
n

are also known in
L. esculentum
from the sympatric region but are rare or absent elsewhere. Between the distributions of alleles of
Prx-1
and those of
Ge
, the gamete-eliminator locus, a significant association exists, which probably does not owe to genetic linkage. The tendency of alleles of
Prx
loci, as well as those of
cm, Ge, h
, and
Od
, to be shared between wild and cultivated taxa in the sympatric region but seldom elsewhere, in addition to published correlated evidence, suggests that the wild alleles tend to substitute in cultivated forms as a result of introgression. In respect to the number of common alleles, cultivated tomatoes more closely resemble the wild
L. esculentum
var.
cerasiforme
than
L. pimpinellifolium
.
Antimalarial Quinones for Prophylaxis Based on a Rationale of Inhibition of Electron Transfer in
Plasmodium
Authors: Wan Yieh-Ping , Porter Thomas H. , Folkers Karl
Published: May 2006

Knowledge of the biochemistry of
Plasmodium
is emerging as a new field. Previous studies showed that the parasite apparently requires electron transfer for energy, and techniques to study such energy mechanisms are available. The discovery of the existence of coenzyme Q
8
in
Plasmodium
implies an indispensable functionality for this redox entity in the electron transfer of the parasite, as coenzyme Q
n
similarily functions in other forms of life.

Effective antimalarial activity in prophylaxis has been demonstrated in sporozoite-induced infections by
Plasmodium gallinaceum
in chicks by several representatives of 7-alkylmercapto-6-hydroxy-5,8-quinolinequinones. The absence of toxicity in this assay even at greatly elevated dosage underscores the achievement of selectivity and safety to the host for the potential utilization of antimetabolites of coenzyme Q
n
as medicinals.

Seven new 7-alkylmercapto-6-hydroxy-5,8-quinoline-quinones were synthesized. The structural variations of the 7-alkylmercapto group in relationship to the antimalarial activities reveal substantial differences in biological activities, which can reflect molecular specificities of enzyme sites and which are not evident from the deceptively minor structural differences in the alkylmercapto groups.

These analogs of coenzyme Q
8
having effective antimalarial activity are known to inhibit mammalian coenzyme Q
n
enzymes, and could be useful in elucidation of the basic electron transfer mechanisms of
Plasmodium
.
The Effect of Replacement of Methionine by Homocystine on Survival of Malignant and Normal Adult Mammalian Cells in Culture
Authors: Halpern Barbara C. , Clark Brian R. , Hardy Dorothy N. , Halpern Richard M. , Smith Roberts A.
Published: May 2006

In tissue cultures of normal adult and malignant mammalian cells, homocystine has been substituted for methionine in a medium rich in folic acid and cyanocobalamin. Normal adult cells thrive. Three highly malignant cell types from three different species, including man, die.
Analysis of Interphase Chromosome Damage by Means of Premature Chromosome Condensation after X- and Ultraviolet-Irradiation
Authors: Waldren Charles A. , Johnson Robert T.
Published: May 2006

Sendai virus-mediated fusion between mitotic and interphase mammalian cells causes the rapid condensation of the interphase chromosomes into distinct structures, a process termed premature chromosome condensation. This phenomenon has been used to assess the immediate action of x-rays and ultraviolet light on the chromosomes of HeLa cells irradiated in the G1 phase of the life cycle. X-irradiation produces fragmented chromosomes; but even the most finely chopped fragments retain the condensed morphology characteristic of the premature chromosome condensation of unirradiated G1 cells. For doses up to about 1800 rads, the increase in the number of fragments is linearly related to the dose. One mean lethal dose (about 100 rads) yields a net increase of 10-15 fragments per G1 cell, which is considerably larger than previous estimates based on scoring of mitotic chromosomes. Incubation of irradiated cells produces a rapid (within 2 hr) reduction in the number of fragments, indicative of a rejoining process. The decrease in the number of pieces is not accompanied by unscheduled DNA synthesis detectable by radioautography. G1 chromosomes of cells irradiated with UV light in G1 phase are not appreciably fragmented but are elongated and attenuated so that they resemble the premature-chromosome-condensation chromosomes of unirradiated S-phase cells. Both the degree of “S-like” character attained by the G1 chromosomes in a cell and the percentage of the cell population displaying the G1 → S transition increase with the dose and incubation time after irradiation. Thus, in contrast to the immediate manifestation of damage from x-rays, the maximum induction of the “S-like” state does not occur until about 2 hr after irradiation. The “S-like” chromosomes are capable of unscheduled DNA synthesis. We suggest that the difference in chromosome morphology found after UV- and x-irradiation underlies the reason why the former, but not the latter, induces unscheduled DNA synthesis in G1 cells.
Adriamycin and Daunorubicin Inhibition of Mutant T4 DNA Polymerases
Authors: Goodman Myron F. , Bessman Maurice J. , Bachur Nicholas R.
Published: May 2006

The anticancer drugs, adriamycin and daunorubicin, as well as two other DNA reagents, ethidium bromide and 9-aminoacridine, all exert a differential inhibitory effect on nucleotide incorporation for purified DNA polymerases induced by mutant and wild-type bacteriophage T4. When compared with DNA polymerase of wild-type phage, antimutator enzymes are inhibited to a far greater extent and mutator enzymes to a lesser extent. In contrast, the polymerase-associated 3′-exonuclease activities of wild type and mutants are also inhibited by the compounds but nondifferentially.
Temporal Stimulation of Chemotaxis in
Escherichia coli
Authors: Brown Douglas A. , Berg Howard C.
Published: May 2006

We used the tracking microscope to study the chemotactic responses of
E. coli
to temporal gradients of L-glutamate generated in isotropic solutions by the action of the enzyme alanine aminotransferase. Positive gradients suppress directional changes which occur spontaneously in the absence of a stimulus. Negative gradients have little effect. The data can be fit with a model in which the suppression is proportional to the time rate of change of the fractional amount of chemoreceptor bound. The model accounts for the behavior of individual cells and populations of cells in spatial gradients. A computer simulation of the motion in spatial gradients indicates that if the bacteria have a “memory,” its decay time cannot be much longer than a few seconds. The relationship between the responses observed in these experiments and in experiments in which solutions of an attractant at different concentrations are mixed is discussed.
On the Existence of a Mono-Vinyl
d
-Urobilin
Authors: Chedekel M. , Bovey F. A. , Brewster A. I. R. , Petryka Z. J. , Weimer M. , Watson C. J. , Moscowitz Albert , Lightner D. A.
Published: May 2006

Chromic acid degradation of a
d
-urobilin, obtained after incubation of bilirubin in fecal bacterial cultures, gave methylvinylmaleimide and methylethylmaleimide. The
d
-urobilin, molecular weight 588, C
33
H
40
-N
4
O
6
, clearly showed the presence of both vinyl and ethyl resonances in the nuclear magnetic resonance spectrum. These results point unambiguously to a urobilin structure with one vinyl and one ethyl
beta
-substituent.
Contact-Mediated Myogenesis and Increased Acetylcholinesterase Activity in Primary Cultures of Mouse Teratocarcinoma Cells
Authors: Gearhart John D. , Mintz Beatrice
Published: May 2006

Transplantable mouse teratomas are known to contain multipotential teratocarcinoma stem cells analogous to early embryo cells and capable of giving rise to a wide variety of specialized cell types
in vivo
when they attach to a substratum; if they are grown instead in suspension in the body cavity, they form multicellular embryoid bodies which proliferate with little or no cell specialization. Thus, changes initiated at the cell surface may play some role in promoting early cell differentiation. In order to establish an
in vitro
system for experimental investigation of this hypothesis, embryoid body cells were explanted under conditions of cell attachment versus suspension and maintained in primary culture. Because cell differentiation in previous reports was relatively limited
in vitro
, the two cellular populations were first compared for genesis of a quantifiable macromolecular phenotype, acetylcholinesterase (AChE) activity, which characterizes several of the cell types most commonly formed in the attached tumors
in vivo
. The attached cells produced markedly increased levels of AChE activity within a few weeks, while cells in suspension retained basal levels. AChE was histochemically visualized and was found to occur chiefly in cells undergoing myogenesis, especially during myotube formation. Aberrant muscle fibers formed and became predominant in the cultures. When embryoid bodies were first fractionated by increasing size, which reflects their progressive differentiation, the smallest ones, with relatively more multipotential cells and no apparent muscle cells, also showed AChE increase in attached cultures. The results are consistent with the view that attachment of the cell surface to a substratum may play a critical role in initiating some cellular developmental commitments, as well as in sustaining differentiation of cells whose specialization has already been determined. Further experimental modifications of this primary culture system of teratocarcinoma cells should be useful in analyzing cell-substratum relations and cell-surface changes in early mammalian development.
Reconstruction of Mammalian Cells from Nuclear and Cytoplasmic Components Separated by Treatment with Cytochalasin B
Authors: Veomett George , Prescott D. M. , Shay Jerry , Porter K. R.
Published: May 2006

Mouse L929 cells were separated into enucleated cytoplasmic components (cytoplasts) and nucleated subcellular fractions (karyoplasts) in the presence of cytochalasin B. Karyoplasts from cells containing tritiated nuclei were fused, using inactivated Sendai virus, to cytoplasts from cells containing large (1.0-μm diameter) latex spheres in the cytoplasm. Mononucleated cells containing radioactive nuclei and large latex spheres in the cytoplasm were observed among the products of the fusion reaction. Some of these cells were in mitotic configurations. The results indicate that cells capable of undergoing mitosis can be reconstructed from the products of cellular enucleation in the presence of cytochalasin B.
Niche Overlap and Diffuse Competition
Authors: Pianka Eric R.
Published: May 2006

Current theory predicts a distinct upper limit on the permissible degree of niche overlap; moreover, theory suggests that maximal tolerable overlap should be relatively insensitive to environmental variability. Data presented here demonstrate that, within the lizard subset of natural desert communities, niche overlap decreases both with increasing environmental variability and with increasing numbers of lizard species. The latter two factors are themselves positively correlated. A partial correlation analysis is interpreted as indicating that the extent of tolerable niche overlap does not necessarily decrease due to environmental variability, but rather that overlap is probably more closely related to the number of potential interspecific competitors in a community, or what has been termed “diffuse competition.” This result lends support to the “niche overlap hypothesis,” which asserts that maximal tolerable overlap should vary inversely with the intensity of competition. Moreover, this empirical discovery indicates that niche overlap theory could be profitably expanded to incorporate the number of competing species. Although the average amount of overlap between pairs of species decreases with the intensity of diffuse competition, the overall degree of competitive inhibition tolerated by individuals comprising an average species could nevertheless remain relatively constant, provided that extensive niche overlap with a few competitors is roughly equivalent to lower average overlap with a greater number of competitors.
Lectin Binding and Perturbation of the Outer Surface of the Cell Membrane Induces a Transmembrane Organizational Alteration at the Inner Surface
Authors: Ji Tae H. , Nicolson Garth L.
Published: May 2006

Binding of
Ricinus communis I
agglutinin to the outer surface of resealed human erythrocyte ghosts results in an organizational perturbation that is translated to the inner membrane surface. The organizational change was detected by an enhancement in the chemical cross-linking of several erythrocyte membrane components by the bifunctional reagent, dimethyl malonimidate, resulting in their loss or reduction after sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the solubilized erythrocyte components. Of the components that failed to appear, or are reduced in amount, on the gels (protein bands Ia, Ib, IVa, and VII), two are known to be the subunits of spectrin (bands Ia and Ib), an inner-surface peripheral protein. A new band, which was identified as
R. communis
lectin, appeared on the polyacrylamide gels of lectin-treated ghosts with or without crosslinking. The loss of spectrin and other bands after lectin treatment and chemical crosslinking was due to a specific transmembrane event because: (
a
) β-lactose, an inhibitor of
R. communis
agglutinin, prevented labeling of ghosts by the lectin and loss of spectrin and other erythrocyte components on gels after crosslinking; (
b
) use of inactive bifunctional or active monofunctional crosslinking reagents did not result in loss of spectrin or other components from lectin-treated ghosts; (
c
) the loss of spectrin and other components after lectin treatment and crosslinking was sensitive to temperature and lectin concentration; (
d
) no new bands appeared on the gels except for the band identified as
R. communis
agglutinin; (
e
)
R. communis
agglutinin does not interact with purified spectrin; and (
f
) previously published data indicate the
R. communis
lectin binds exclusively to the outer membrane surface while spectrin is located on the inner membrane surface. Perturbation of components of the outer membrane surface that can be translated to the cell interior by transmembrane linkages may provide a structural means of membrane communication that could be important in a variety of cellular control processes.
Glucose Inhibition of Adenylate Cyclase in Intact Cells of
Escherichia coli
B
Authors: Peterkofsky Alan , Gazdar Celia
Published: May 2006

Previous studies in
E. coli
B have demonstrated an inverse correlation between the presence of glucose in the medium and the accumulation of cyclic AMP in the medium. This observation could not be explained by the action of glucose as a repressor of adenylate cyclase (EC 4.6.1.1) synthesis, as a stabilizer of cyclic AMP phosphodiesterase (EC 3.1.4.17) activity, or as a direct inhibitor of adenylate cyclase activity in cell-free preparations. The recent development of an
in vivo
assay for adenylate cyclase has provided a basis for further exploring the inhibitory action of glucose in intact cells. With this assay it has been possible to show that, while glucose does not affect adenylate cyclase
in vitro
, it rapidly inhibits the enzyme activity in intact cells. Extensive metabolism of glucose is not required, since α-methylglucoside also inhibits adenylate cyclase
in vivo
. When cells are grown on glucose as carbon source, some sugars (mannose, glucosamine) substitute for glucose as adenylate cyclase inhibitors while others (e.g., fructose) do not. Dose-response studies indicate that low concentrations of glucose lead to essentially complete inhibition of adenylate cyclase activity while only moderately decreasing intracellular cyclic AMP concentrations. The evidence presented suggests that the decreased cellular cyclic AMP levels resulting from glucose addition can be accounted for by inhibition of adenylate cyclase without any significant effect on cyclic AMP phosphodiesterase or the transport of cyclic AMP from the cells to the medium.
The Role of a Dolichol-Oligosaccharide as an Intermediate in Glycoprotein Biosynthesis
Authors: Hsu An-Fei , Baynes John W. , Heath Edward C.
Published: May 2006

Incubation of mouse myeloma microsomes with GDP-[
14
C]mannose results in the biosynthesis of [
14
C]mannose phosphoryl dolichol [Baynes, J. W., Hsu, A.-F. & Heath, E. C. (1973)
J. Biol. Chem.
248, 5693-5704] and a [
14
C]mannose- and
N
-acetylglucosamine (GlcNAc)-containing oligosaccharide derivative of dolichol. Thus, [
14
C]mannose phosphoryl dolichol and [
14
C]mannose-labeled oligosaccharide pyrophosphoryl dolichol were isolated from incubation mixtures by solubilization in 2% (w/v) Triton X-100 and the lipids were separated from small molecules by gel filtration fractionation. After removal of radioactive protein from the preparation, the two lipid derivatives were separated quantitatively by fractionation on a concanavalin A-Sepharose column; [
14
C]mannose phosphoryl dolichol was not retained by the affinity resin but [
14
C]mannose-oligosaccharide pyrophosphoryl dolichol adsorbed to the gel and was eluted with α-methylmannoside.[
14
C]Mannose-oligosaccharide pyrophosphoryl dolichol appeared to be homogeneous when fractionated on DEAE-cellulose and in several thin-layer chromatographic systems. Treatment of [
14
C]mannose oligosaccharide pyrophosphoryl dolichol with 10% (w/v) NH
4
OH at 100° for 1 hr resulted in the formation of a water-soluble radioactive oligosaccharide phosphate which was isolated and characterized as [Man]
5
→ [GlcNAc → GlcNAc → P. Incubation of [
14
C]mannose-oligosaccharide pyrophosphoryl dolichol with myeloma microsomal preparations results in the transfer, presumably, of the entire oligosaccharide to endogenous protein. Kinetic studies indicate that the dolichol derivatives serve as intermediates in the glycosylation of protein as follows: [Formula: see text]
Phosphate Metabolism in Intact Human Erythrocytes: Determination by Phosphorus-31 Nuclear Magnetic Resonance Spectroscopy
Authors: Henderson Thomas O. , Costello Anthony J. R. , Omachi Akira
Published: May 2006

Whole human blood was examined by
31
P nuclear magnetic resonance spectroscopy. Individual phosphates (α,β,γ) of ATP were identifiable, and two microenvironments appeared to be present for this molecule. When sequential recordings of freshly collected blood were made, 2,3-diphosphoglycerate was observed to decrease in association with a concomitant increase in inorganic orthophosphate. When aged cells containing little 2,3-diphosphoglycerate were incubated in the presence of inosine and pyruvate, 2,3-diphosphoglycerate formation could be demonstrated. These results show that cellular metabolism can be recorded directly in intact cells by
31
P nuclear magnetic resonance.
Monoamine Oxidase and Cerebral Uptake of Dopaminergic Drugs
Authors: Cotzias George C. , Tang Lily C. , Ginos James Z.
Published: May 2006

The brain uptake of amines that do not enter the brain or enter it poorly was promoted by noncompetitive inhibitors of monoamine oxidase, as shown by behavioral and chemical criteria. Mice pretreated with water or enzyme inhibitors other than those mentioned were placid after receiving dopamine (3,4-dihydroxyphenethylamine). Mice pretreated with monoamine oxidase inhibitors (nialamide or iproniazid) showed upon treatment with dopamine the brisk motor responses characteristic of treatment with its precursor, L-dopa (3,4-dihydroxyphenylalanine). After receiving dopamine, intact nialamide-pretreated mice showed marked increases of brain dopamine, in contrast to water-pretreated test mice or water-treated controls. In unilaterally caudectomized, nialamide-pretreated mice, dopamine induced marked lateral curving of the body toward the lesion followed by running in that direction. Noradrenaline or adrenaline induced curving in caudectomized mice, whereas intact ones remained placid.

These catecholamines are bound and inactivated by monoamine oxidase. The cerebral uptakes of chemicals that are bound but not inactivated by monoamine oxidase were thereafter tested. Nialamide induced increased behavioral responses to apomorphine and to
N
-propyl noraporphine, increased cerebral concentrations of both, and a deep coloration of the brain from methylene blue (bound by monoamine oxidase) but not Evans blue (bound by albumin). Even large doses of nialamide, however, failed to affect the behavioral responses to oxotremorine, which has cholinergic rather than adrenergic or dopaminergic properties. Mitochondrial monoamine oxidase seems therefore to play a specific regulatory role in the transport of substances that it binds, either to inactivate or to release them.
The Binding Characteristics and Number of β-Adrenergic Receptors on the Turkey Erythrocyte
Authors: Levitzki Alexander , Atlas Daphne , Steer Michael L.
Published: May 2006

Turkey erythrocyte ghosts (empty membranes) possess a class of receptors that can bind both L-[
3
H]isoproterenol and DL-[
3
H]propranolol. The binding of [
3
H]isoproterenol to these receptors occurs with a dissociation constant of 0.15 μM and can be fully inhibited by 1 μM propranolol. The binding of [
3
H]propranolol occurs with a dissociation constant of 2.5 nM and can be fully inhibited by 0.2 mM DL-isoproterenol. Ligand binding is sensitive to sonication, boiling, and 8 M urea. The cells possess 500 to 1000 β-adrenergic receptors per cell. Binding of propranolol to the β-receptor was found to be stereospecific for the L stereoisomer. If one assumed a 1:1 relationship between β-adrenergic receptors and adenylate cyclase, the turnover number of this adenylate cyclase would be close to 100 min
-1
.
Interaction of Phalloidin with Actin
Authors: Lengsfeld Anneliese M. , Löw Irmentraut , Wieland Theodor , Dancker Peter , Hasselbach Wilhelm
Published: May 2006

Phalloidin, a toxic bicyclic peptide of rapid action from the toadstool,
Amanita phalloides
, gives rise to polymerization of G-actin to filamentous structures (Ph-actin) in a medium of low ionic strength. Ph-actin closely resembles the microfilaments found in liver membrane fractions (Ph-filaments) after
in vivo
or
in vitro
poisoning. Both phalloidin induced filaments are resistant to 0.6 M KI in contrast to F-actin, and become decorated by heavy meromyosin. After preincubation with cytochalasin B significantly fewer actin filaments are observed.
Empirical Correlation Between Hydrophobic Free Energy and Aqueous Cavity Surface Area
Authors: Reynolds Jacqueline A. , Gilbert David B. , Tanford Charles
Published: May 2006

The unitary free energy of transfer of a hydrocarbon molecule from a hydrocarbon solvent to an aqueous medium is a measure of the hydrophobic interaction in the aqueous medium. We have reexamined available data on this phenomenon and have confirmed that the free energy for saturated hydrocarbons is proportional to the surface area of the cavity created by the solute in the aqueous solution, with the same proportionality constant for linear, branched, and cyclic hydrocarbon molecules. The numerical value of the proportionality constant is uncertain because absolute and self-consistent area measurements are not available. We estimate that it falls between 20 and 25 cal/mole per Å
2
at 25° (for areas measured at the distance of closest approach of water molecules), which is significantly less than the figure of 33 cal/mole per Å
2
that has been assigned to the same parameter by Hermann [
J. Phys. Chem.
76, 2754-2759 (1972)]. A small discrepancy exists when similar data for homologous series of alkyl derivatives are compared with results based on hydrocarbons themselves, and possible reasons for it are discussed.
Structural Chemistry of 1,2 Dilauroyl-DL-phosphatidylethanolamine: Molecular Conformation and Intermolecular Packing of Phospholipids
Authors: Hitchcock Peter B. , Mason Ronald , Thomas K. Mark , Shipley G. Graham
Published: May 2006

Crystals of 1,2 dilauroyl-DL-phosphatidyl-ethanolamine:acetic acid are monoclinic with
a
= 46.2,
b
= 7.77,
c
= 9.95 Å, β = 92.0°; space group
P
2
1
/c. The structural analysis, based on the visual estimates of 1467 reflection intensities, was achieved by direct methods, and least squares analysis convergence was to
R
1
= 0.28. There are marked differences between the observed molecular conformation and those that have been predicted theoretically. The mean planes containing the lipid chains are essentially parallel to one another; the phosphodiester moiety has a double
gauche
conformation, while intermolecular hydrogen bonding modifies the conformation that could be anticipated for an isolated phosphatidylethanolamine molecule. The intermolecular packing produces the classical lipid bilayer structure, adjacent lipid bilayers being separated by acetic acid molecules of crystallization. The hydrocarbon chain packing can be considered either as a quasi-hexagonal type or as a complex orthorhombic subcell arrangement. One-dimensional electron density profiles across the lipid bilayer at increasing resolution clearly demonstrate the origin of features present on the low resolution profiles of both model and natural membranes.
The Significant Structure Theory Applied to Amorphous and Crystalline Polyethylene
Authors: Ma Shao-Mu , Eyring Henry , Jhon Mu Shik
Published: May 2006

The significant structure theory of liquids has been applied to amorphous and crystalline polyethylene. In this theory the amorphous state, like liquids in general, is assumed to have solid-like structure, gaslike structure, and positional degeneracy which arises from the motion of kinetic segments and from the libration of CH
2
units. This concept leads to a partition function giving the Helmholtz free energy in terms of volume, temperature, and composition.

Thermodynamic and transport properties are calculated for amorphous polyethylene. The thermodynamic properties are also calculated for the crystalline solid. The calculated results are in reasonable agreement with the experimental values. No such detailed calculations of polymer properties from a partition function, depending on both volume and temperature, have been previously attempted.
Differentiation of Cell Membranes in Cultures of Embryonic Chick Breast Muscle
Authors: Prives Joav M. , Paterson Bruce M.
Published: May 2006

Three components of differentiated muscle membrane, the acetylcholine receptor, acetylcholinesterase (EC 3.1.1.7; acetylcholine hydrolase), and adenylate cyclase [EC 4.6.1.1; ATP pyrophosphate-lyase (cyclizing)], appear simultaneously during myogenesis in cultures of embryonic chick muscle, after the main period of rapid cell fusion. However, unlike the cytoplasmic proteins of differentiated muscle, the elaboration of these membrane components is unaltered when fusion is blocked by lowering the calcium concentration in the medium. These results suggest that membrane differentiation and cytoplasmic differentiation are regulated independently during muscle development.
Simian Virus 40 T Antigen Binds to DNA
Authors: Carroll R. B. , Hager L. , Dulbecco R.
Published: May 2006

The T antigen of simian virus 40, which may play a role in the control of viral DNA replication, is recovered from nuclei of cells transformed by simian virus 40 in several forms sedimenting at different rates. The large molecular weight forms are converted to the smallest (5 S) form by high salt, suggesting that they differ in the degree of aggregation. All the forms of the antigen bind efficiently to double-stranded DNA-cellulose columns at pH 6.2 and low salt, and elute in two fractions: one at pH 8.0 and low salt, the other at pH 8.0 and high salt. The antigen has little affinity for single-stranded DNA.
Proteolytic cleavage of bacteriophage lambda repressor in induction.
Authors: Roberts J W , Roberts C W
Published: May 2006

The bacteriophage lambda repressor, a protein that maintains the lysogenic state of a bacterium containing a lambda prophage, is cleaved when the lysogen is induced by mitomycin C or ultraviolet light. This cleavage does not occur when induction is prevented by mutational alteration either of the phage repressor or of the host recA gene product. Proteolytic cleavage may be the primary mechanism of repressor inactivation in this induction pathway, or it may follow a different event which causes the initial inactivation.
Natural occurrence of poly(ADP-ribosyl) histones in rat liver.
Authors: Ueda K , Omachi A , Kawaichi M , Hayaishi O
Published: May 2006

Poly(ADP-ribose) bound to histones has been isolated from rat liver. When [14C]ribose was administered intraperitoneally to rats at a dosage of 300-750 mug (100-250 muCi)/10o g, approximately 1% of the radioactivity was recovered in the acid (5% CLCCCOOH)-INSOLUBLE MATERIAL OF THE LIVER NUCLEI 2 HR AFTER INJECTION. Of the acid-insoluble radioactivity, 4.5-9% was extractable with 0.25 N HCL. Carboxymethyl-cellulose column chromatography of the HCl-extracted material revealed that the radioactivity cochromatographed with histone subfractions f1 and, to a lesser extent, f2 and f3. Part of the protein-bound radioactivity was rendered acid-soluble by treatment with either snake venom phosphodiesterase or neutral NH2OH. From the enzyme digest, 5'-AMP and psiADP-ribose [2'-(5"-phosphoribosyl)-5'-AMP] were recovered, while the NH2OH treatment yielded ADP-ribose monomer and, presumably, oligomer. These observations indicate that ADP-ribose is attached to histones in vivo and is present both as a monomer and a polymer.
Demonstration of the rapid action of pure crystalline 1 alpha-hydroxy vitamin D3 and 1 alpha,25-dihydroxy vitamin D3 on intestinal calcium uptake.
Authors: Toffolon E P , Pechet M M , Isselbacher K
Published: May 2006

The biological effects of crystalline 1alpha-hydroxyvitamin D3 and crystalline 1alpha,25-dihydroxyvitamin D3 have been compared on the intestinal uptake of calcium-45 by everted duodenal gut sacs from rachitic rats. Peak calcium-45 uptake was observed 1 hr after intravenous administration and both crystalline vitamin D2 analogs were of comparable potency. The rapid onset of calcium-45 uptake and the rapid attainment of maximal calcium-45 transport suggests a direct effect of these crystalline analogs on the mucosal membranes of the intestinal cell.
A cycle of deprotonation and reprotonation energizing amino-acid transport?
Authors: Christensen H N , Handlogten M E
Published: May 2006

Although lowering the pK2 of neutral amino acids only weakens their concentrative uptake by Ehrlich cells, the same change greatly enhances uptake of diamino acids. This effect does not arise merely from putting the distal amino group in its uncharged form, but depends on an enhanced deprotonation of the alpha-amino group. Parallel effects are seen for the transport system for basic amino acids, for which the assignment of pK values within the membrane is less ambiguous. To explain the paradoxical advantages of having the alpha-amino group protonated yet readily deprotonated, we propose that a proton withdrawn from that group is pumped over an intramembrane interval to energize amino-acid transport.
Breaking of seed dormancy by catalase inhibition.
Authors: Hendricks S B , Taylorson R B
Published: May 2006

Germination of some dormant seeds is promoted by solutions of thiourea, sodium nitrite, and hydroxylamine salts. The promotions are accompanied by irreversible inhibition of catalase (EC 1.11.1.6) in extracts from the seeds. The seeds are also promoted in germination by catechol and pyrogallol solutions. These effects are recorded for lettuce (Lactuca sativa L. cv. Grand Rapids) and pigweed (Amaranthus albus L.) seeds. The results indicae that metabolically derived hydrogen peroxide, spared from decomposition by catalase inhibition, oxidizes reduced NADPH required as the oxidant in the pentose pathway of glucose use. The metabolic system for such use of H2O2 involves the enzymes, peroxidase (EC 1.11.1.7) and pyridine nucleotide quinone oxidoreductase (EC 1.6.99.2), which are present in the dormant seed prior to imbibition of water.
Regulation of proline catabolism by leucyl,phenylalanyl-tRNA-protein transferase.
Authors: Deutch C E , Soffer R L
Published: May 2006

A mutant of Escherichia coli lacking leucyl,phenylalanyl-tRNA:protein leucyltransferase, EC 2.3.2.6) exhibited several abnormal growth characteristics relative to the wild type or a revertant when grown with glycerol as a carbon source. All three strains were auxotrophic for proline. The mutant required higher levels of this amino acid than did the other strains to attain a normal growth yield and metabolized exogenous [14C]proline more rapidly. The greater rate of proline utilization was associated with a 4-fold increase in specific activity of proline oxidase. When glucose rather than glycerol was employed as a carbon source, proline oxidase activity was reduced by catabolite repression and the growth ccharacteristics of the mutant were similar to those of the parental and revertant strains. These results suggest that the mutant growth phenotype is due to an altered rate of proline catabolism and constitue evidence for regulation of a specific metabolic pathway by leucyl,phenylalanyl-tRNA-protein transferase.
Chitin synthetase zymogen is attached to the yeast plasma membrane.
Authors: Durán A , Bowers B , Cabib E
Published: May 2006

Pretreatment of yeast protoplasts with concanavalin A, according to the method used by G. A. Scarborough for Neurospora (J. Biol. Chem. 250, 1106-1111, 1975), reinforced the plasma membranes, and helped to maintain their integrity during subsequent lysis of the protoplasts. After purification by centrifuging on a Renografin density gradient, practically intact membranes were obtained. Previous labeling of the protoplasts with 125I or with [3H]concanavalin A resulted in recovery of the radioactivity in the membrane fraction. The bulk of the chitin synthetase (chitin synthase; UDP-2-acetamido-2-deoxy-D-glucose:chitin 4-beta-acetamidodeoxyglucosyltransferase; EC 2.4.1.16) recovered in the gradient was also found In this fraction; in the zymogen form. About 20% of the activity sedimented in a plasma-membrane-free fraction at lower density. Glutaraldehyde inactivated chitin synthetase when it was added to a lysate, but not when applied to intact protoplasts. It is concluded that chitin synthetase is so oriented in the membrane that it is only accessible from the inside of the cell. These results confirm our previous hypothesis that the chitin synthetase zymogen is associated with the plasma membrane, a basic assumption for the explanation of localized activation of the enzyme and initiation of septum formation.
Mechanism of action of penicillin: triggering of the pneumococcal autolytic enzyme by inhibitors of cell wall synthesis.
Authors: Tomasz A , Waks S
Published: May 2006

During penicillin treatment of an autolysin defective mutant pneumococcus we have observed three novel phenomena: (i) Growth of the mutant cultures is inhibited by the same concentrations of penicillin that induce lysis in the wild type. (ii) Mutant bacteria treated with the minimum growth inhibitory concentration of penicillin will lyse upon the addition of wild-type autolysin to the growth medium. Chloramphenicol and other inhibitors of protein synthesis protect the cells against lysis by exogenous enzyme. Sensitivity of the cells to exogenous autolysin requires treatment with penicillin or other inhibitors of cell wall synthesis (e.g., D-cycloserine or fosfonomycin) since exogenous autolysin alone has no effect on bacterial growth. (iii) Treatment with penicillin (or other inhibitors of cell wall synthesis) causes the escape into the medium of a choline-containing macromolecule that has properties suggesting that it contains pneumococcal lipoteichoic acid (Forssman antigen). Each one of these three phenomena (growth inhibition, sensitization to exogenous autolysin, and leakage of lipoteichoic acid) shows the same dose response as that of the penicillin-induced lysis of wild-type pneumococci. On the basis of these findings we propose a new hypothesis for the mechanism of penicillin-induced lysis of bacteria. It is suggested that inhibition of cell wall synthesis by any means triggers bacterial autolytic enzymes by destabilizing the endogenous complex of an autolysin inhibitor (lipoteichoic acid) and autolytic enzyme. Escape of lipoteichoic acid-like material to the growth medium is a consequence of this labilization. Chloramphenicol protects bacteria against penicillin-induced lysis by interfering with the activity of the autolytic enzyme, rather than by depleting the concentration of the enzyme at the cell surface.
Chemoreceptors and feeding in calanoid copepods (Arthropoda: Crustacea).
Authors: Friedman M M , Strickler J R
Published: May 2006

Ultrastructural studies of the mouthparts of the calanoid copepod Diaptomus pallidus have revealed the presence of numerous chemoreceptors, and the apparent absence of mechanoreceptors. The setae contain no muscles, and the setules are noncellular extensions of their chitin wall. This allows a new insight into the selective feeding of zooplankters.
Biochemical construction and selection of hybrid plasmids containing specific segments of the Escherichia coli genome.
Authors: Clarke L , Carbon J
Published: May 2006

Using a poly(dA-dT) "connector" method, a population of annealed hybrid circular DNAs was constructed in vitro; each hybrid DNA circle containing one full-length molecule of poly(dT)-tailed DNA from E1 colicinogenic factor (Col E1) fragmented by EcoRI endonuclease annealed to any one of a collection of poly(dA)-tailed linear DNA fragments of the entire E. coli genome. This annealed, but unligated, hybrid DNA was used to transform several different auxotrophic mutants of E. coli, and by direct selection, bacterial clones were isolated which contained specific hybrid plasmids. In this manner, bacterial strains containing Col E1 hybrid plasmids carrying the entire tryptophan operon or the arabinsoe and leucine operons were isolated. The methods described should allow the molecular cloning of any portion of the E. coli genome by selection from a pool of DNA molecules containing at least several hundred different hybrids representing the entire bacterial genome.
Colchicine permeation is required for inhibition of concanavalin A capping in Chinese hamster ovary cells.
Authors: Aubin J E , Carlsen S A , Ling V
Published: May 2006

Several antimitotic, tubulin-binding agents, such as colchicine, colcemid, and podophyllotoxin, inhibit the capping of fluorescent-labeled concanavalin A in Chinese hamster ovary cells. By comparing the effects of these agents on parental cell lines on several independently selected colchicine-resistant mutants with decreased drug permeability, we have demonstrated that permeation of these drugs in required for inhibition of capping. These data support the hypothesis that these antimitotic agents interact with an intracellular component, probably microtubules, to prevent the directional movement of concanavalin A receptors on the surface membranes of Chinese hamster ovary cells.
Structural features of double-stranded polyribonucleotides required for immunological specificity and interferon induction.
Authors: Johnston M I , Stollar B D , Torrence P F , Witkop B
Published: May 2006

Purified antibody to poly(adenylic acid)-poly(uridylic acid) was used in quantitative microcomplement fixation assays to detect conformational variations among several double-helical polyribonucleotide analogs of poly(adenylic acid)-poly(uridylic acid) or poly(inosinic acid)-poly(cytidylic acid) that had been previously evaluated for their ability to induce interferon. Modification at the furanose 2'-position of one or both strands resulted in a dramatic decrease in serological reactivity. Most modifications of the bases caused smaller serological changes, and no base modification caused complete loss of reactivity. The reaction patterns support the conclusion that the structure of the furanose and the overall conformation of the helix are critical in the formation of antigenic determinants. The backbones of both strands appear to be involved in forming a single antigenic site, and base modifications may alter the steric relationship between the backbones. In addition, the same structural changes that substantially alter recognition by antibody also lead to large changes in the interferon-inducing ability of the nucleic acid.