bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and Functional Similarities Between Mitochondrial Malate Dehydrogenase and L-3-Hydroxyacyl CoA Dehydrogenase
Authors: Noyes Barbara E. , Glatthaar Beat E. , Garavelli John S. , Bradshaw Ralpha A.
Published: May 2006

Pig heart mitochondrial malate dehydrogenase (EC 1.1.1.37), which has been obtained free of electrophoretic subforms, has been shown to have a molecular weight of 67,000 and to be composed of two polypeptide chains. Comparison of these and other properties, such as amino-acid composition, isoelectric point, and keto-substrate inhibition, with those of
L
-3-hydroxyaeyl CoA dehydrogenase (EC 1.1.1.35), another NAD
+
-dependent dehydrogenase of mitochondrial origin, suggests structural similarities of the type associated with proteins possessing common evolutionary origins. This conclusion is supported by immunological crossreactivity. In view of these observations, the dissimilarity in the stereospecificity of hydrogen transfer from cofactor to substrate catalyzed by the two enzymes is attributed to 180° rotation in the binding orientation of the nicotinamide moiety of the NAD
+
, rather than to gross differences in the geometry of the active site of the two enzymes.
In Vitro
Synthesis of Mouse Neuroblastoma Tubulin
Authors: Wiche Gerhard , Zomzely-Neurath Claire , Blume Arthur J.
Published: May 2006

Polyribosomes were isolated from a clonal line of mouse neuroblastoma grown in culture. In a heterologous
in vitro
system containing rat brain components, these polyribosomes were shown to direct the synthesis of neuroblastoma tubulin. Identification of the tubulin synthesized
in vitro
was achieved by coelectrophoresis with native neuroblastoma tubulin on sodium dodecyl sulfate polyacrylamide gels, immunoprecipitation, and demonstration of specific aggregation. Tubulin accounted for 2% of the total proteins synthesized. This
in vitro
protein synthesizing system offers a model for studying possible translational control mechanisms regulating the synthesis of proteins involved in nerve cell function.
The Phenotypic Complexity of Myogenic Clones
Authors: Abbott J. , Schiltz J. , Dienstman S. , Holtzer H.
Published: May 2006

A single cell isolated from cultured 8-day leg muscle may, when subcultured, yield a myogenic clone. A myogenic clone consists of myotubes and mononucleated cells. When such a myogenic clone is subcultured, large numbers of mononucleated cells are recovered. These mononucleated cells histologically and biochemically are indistinguishable from authentic fibroblasts cultured under the same conditions: they synthesize (α1)
2
α2 chains of collagen, large amounts of hyaluronic acid, and modest amounts of chondroitin sulfate. These mononucleated cells, however, will not chondrify when grown under culture conditions known to permit presumptive chondroblasts to differentiate terminally. These findings demonstrate that there is a population of single cells in 8-day muscle that is neither a myoblast nor a fibroblast, but is the common progenitor for cells in the myogenic
and
fibrogenic lineages: this progenitor, however, is beyond the point of readily yielding chondrogenic cells. These findings are discussed in terms of the limited number of phenotypic options open to differentiating cells in each of the successive compartments of their respective lineages.
Role of Phosphate and Other Proton-Donating Anions in Respiration-Coupled Transport of Ca
2+
by Mitochondria
Authors: Lehninger Albert L.
Published: May 2006

Measurements of extra oxygen consumption,
45
Ca
2+
uptake, and the osmotic expansion of the matrix compartment show that not all permeant anions are capable of supporting and accompanying the energy-dependent transport of Ca
2+
from the medium into the matrix in respiring rat-liver mitochondria. Phosphate, arsenate, acetate, butyrate, β-hydroxybutyrate, lactate, and bicarbonate + CO
2
supported Ca
2+
uptake, whereas the permeant anions, nitrate, thiocyanate, chlorate, and perchlorate, did not. The active anions share a common denominator, the potential ability to donate a proton to the mitochondrial matrix; the inactive anions lack this capacity. Phosphate and the other active permeant anions move into the matrix in response to the alkaline-inside electrochemical gradient of protons generated across the mitochondrial membrane by electron transport, thus forming a negative-inside anion gradient. It is postulated that the latter gradient is the immediate “pulling” force for the influx of Ca
2+
on the electrogenic Ca
2+
carrier in respiring mitochondria under intracellular conditions. Since mitochondria in the cell are normally exposed to an excess of phosphate (and the bicarbonate-CO
2
system), particularly in state 4, inward transport of these proton-yielding anions probably precedes and is necessary for inward transport of Ca
2+
and other cations under biological conditions. These observations indicate that a negative-inside gradient of phosphate generated by electron transport is a common step and provides the immediate motive power not only for (
a
) the inward transport of dicarboxylates and tricarboxylates and (
b
) the energy-dependent exchange of external ADP
3-
for internal ATP
4-
during oxidative phosphorylation, as has already been established, but also for (
c
) the inward transport of Ca
2+
, K
+
, and other cations.
Directionality of Brain Microtubule Assembly
In Vitro
Authors: Dentler W. L. , Granett S. , Witman G. B. , Rosenbaum J. L.
Published: May 2006

Chicks were injected intra-cerebrally with [
3
H]leucine, and
3
H-labeled microtubules were assembled
in vitro
in the brain supernatants. Pieces of these
3
H-labeled microtubules were then incubated with unlabeled brain tubulin subunits under conditions where the subunits assembled onto the labeled pieces. Electron microscopic autoradiography of the negatively-stained microtubules showed all of the radioactivity at one end of the tubules as they increased in length. This clearly demonstrated that the microtubules of brain in this
in vitro
system were being assembled unidirectionally.
Presence of a Mouse Embryonic Antigen on Human Spermatozoa
Authors: Buc-Caron Marie-Hélène , Gachelin Gabriel , Hofnung Maurice , Jacob François
Published: May 2006

A cell-surface antigen common to mouse primitive teratocarcinoma cells, morulae, and spermatozoa and specified by the +

t
12

allele at the T-locus of the mouse has been shown by serological methods to be present on the surface of human spermatozoa, but not of human lymphocytes, fibroblasts, or erythrocytes.
Synthesis of Bacteriophage Lambda DNA
In Vitro:
Requirement for
O
and
P
Gene Products
Authors: Shizuya Hiroaki , Richardson Charles C.
Published: May 2006

We have developed a cell-free system to study bacteriophage λ DNA replication. Maximal DNA synthesis
in vitro
requires the four deoxynucleoside triphosphates, ATP, and exogenous λ DNA. DNA synthesis requires the products of the phage
O
and
P
genes but is not inhibited by λ repressor. The kinetics of synthesis is linear for 10-15 min; however, the product of synthesis amounts to only 0.5-1% of the added template DNA. As judged by isopycnic analysis, extensive regions of the template are copied. Sedimentation analysis indicates that all of the product consists of short (11S) DNA chains. Fractions partially purified from λ
O
+
P
+
-infected cell extracts will complement extracts prepared from λ
O
-
or λ
P
-
-infected cells.
The Sites of Transcription and Translation for
Euglena
Chloroplastic Aminoacyl-tRNA Synthetases
Authors: Hecker L. I. , Egan J. , Reynolds R. J. , Nix C. E. , Schiff J. A. , Barnett W. Edgar
Published: May 2006

We find that cycloheximide completely blocks the light-induced apearance of
Euglena
chloroplastic aminoacyl-tRNA synthetases in dark-grown cells of
Euglena gracilis
var.
bacillaris
. Streptomycin, on the other hand, has no effect on the light-induction of these organellar enzymes. These observations, together with the finding that an aplastidic mutant (strain W
3
BUL, which has neither significant plastid structure nor detectable chloroplast DNA) contains low levels of the chloroplastic synthetases, indicate that the chloroplastic synthetases are transcriptional products of nuclear genes and are translated on cytoplasmic ribosomes prior to compartmentalization within the chloroplasts.
Depolarization of the Plasma Membrane of
Neurospora
During Active Transport of Glucose: Evidence for a Proton-Dependent Cotransport System
Authors: Slayman Clifford L. , Slayman Carolyn W.
Published: May 2006

Intracellular microelectrodes were used to measure the effects of glucose transport on membrane voltage and membrane resistance in
Neurospora crassa
. Sudden activation of glucose uptake, via the high-affinity, derepressible system II, results in a very large depolarization of the plasma membrane. At saturating concentrations of glucose, the depolarization averages 120 mV; it is diphasic in time, with an initial shift at rates of 100-200 mV/sec followed by a slow, spontaneous, partial repolarization. Changes in intracellular ATP concentration are small and could account for only 10 mV of the initial depolarization, while the rest appears to depend upon the transport process itself. A plot of peak depolarization against the extracellular glucose concentration gives a saturation curve which is half-maximal at 42 μM, in good agreement with the
K
1/2
reported for glucose transport via system II. The nonmetabolized analogue 3-
O
-methyl-D-glucose also causes depolarization, and in addition leads to a pulsed alkalinization of the medium occurring at approximately the same rate as 3-
O
-methyl-D-glucose uptake. The membrane resistance falls only slightly during glucose depolarization, a fact which requires the transport system itself to have a high internal resistance, or the membrane current-voltage relationship in glucose-starved cells to be quite nonlinear. All of the data support Mitchell's notion that sugar and hydrogen ions are contransported under the influence of the membrane potential, and lead to values for H
+
:glucose stoichiometry of 0.8 to 1.4.
Are Recommended Daily Allowances for Vitamin C Adequate?
Authors: Jukes Thomas H.
Published: May 2006

Recommended daily allowances, U.S.A., for ascorbic acid are several times the minimum daily requirement of about 10 mg to prevent clinical symptoms in adults. The recommended daily allowances reflect the levels of ascorbic acid required to produce tissue saturation in human beings, so that higher doses are promptly excreted in the urine. In various investigations, responses to ascorbic acid were not obtained under conditions where the intake was considerably lower than the recommended daily allowances, but higher than the level needed to prevent clinical symptoms of ascorbic acid deficiency. The human ascorbic acid requirement cannot be calculated by a linear extrapolation from guinea pigs per kg of body weight because guinea pigs are much smaller than human beings and, hence, their metabolism is more rapid per unit of body weight. Evolutionary loss of ascorbic-acid-synthesizing ability may be a neutral change that was incorporated by genetic drift.
Noise-Induced Threshold Shift in the Parakeet (
Melopsittacus undulatus
)
Authors: Saunders James , Dooling Robert
Published: May 2006

Parakeets exposed for 72 hr to a 1/3-octave band of noise centered at 2.0 kHz have a maximum threshold shift at 2.0 kHz with little or no spread of threshold shift to lower or higher frequencies. These results differ from those observed in mammals and suggest significant differences between avian and mammalian peripheral auditory processing.
Accumulation of an Intermediate in DNA Synthesis by HEp.2 Cells Treated with Methyl Methanesulfonate
Authors: Kato Karen , Strauss B.
Published: May 2006

A portion of the DNA synthesized by HEp.2 cells after short incubation in the presence of BrdU bands in a CsCl gradient at a distinct peak of density 1.715-1.718 g/cm
3
. Inhibition of DNA synthesis by methyl methanesulfonate results in an increased proportion of this “intermediate density” DNA. Cells labeled and subsequently chased in nonradioactive BrdU yield only hybrid DNA. Treatment with single-strand-specific deoxyribonuclease converts a portion of the intermediate density material to molecules of hybrid density (1.755 g/cm
3
). The data suggest an intermediate in DNA replication that contains a single-stranded region in the parental strand and that accumulates when DNA synthesis is blocked by an alkylation-induced lesion.
Analysis of a Simple Prototypal Muscle Model Near to and Far from Equilibrium
Authors: Chen Yi-Der , Hill Terrell L.
Published: May 2006

Accurate calculations of force generated and of ATP flux, in steady isotonic contractions, are made on a simple, two-state muscle model of the sliding filament type. The objective is to illustrate the proper formulation and use of a complete and self-consistent molecular model of muscle. Otherwise, the model is not meant to be realistic. Calculations were made near equilibrium, including linear and quadratic terms in a power series expansion, and arbitrarily far from equilibrium by direct numerical solution of the appropriate differential equation in the probability of cross-bridge attachment. The results obtained from the two different methods agree where they overlap near equilibrium. The efficiency of free energy conversion is emphasized, and the relation to linear irreversible thermodynamics is pointed out.
Cyclic-AMP-Controlled Oscillations in Suspended
Dictyostelium
Cells: Their Relation to Morphogenetic Cell Interactions
Authors: Gerisch Günther , Hess Benno
Published: May 2006

Periodic spikes of decreased optical density were recorded in cell suspensions of
Dictyostelium discoideum
. Spike formation as well as changes in the redox state of cytochrome
b
are facultatively and independently coupled to an oscillating system which is under developmental control and presumably underlies signal transmission in aggregating cells.

Cyclic AMP triggers a double response, the slow component resembling the spikes formed during spontaneous oscillations. The fast component shows characteristics of the chemotactic response to cyclic AMP. The receptor system is suggested to sense changes of cyclic AMP concentration in time. Cyclic AMP pulses interact with the oscillating system, resulting in phase shift or suppression of spike formation, and in the induction of oscillations in an early stage of development before the onset of spontaneous oscillations. Continuous flow application of cyclic AMP does not change frequency up to flow rates which extinguish oscillations.
Role of a Deoxyribonuclease in the Genetic Transformation of
Diplococcus pneumoniae
Authors: Lacks Sanford , Greenberg Bill , Neuberger Marjorie
Published: May 2006

Two steps in the uptake of DNA by
Diplococcus pneumoniae
were characterized by analyzing mutants defective in transformation. A strain deficient in the two major deoxyribonucleases of
D. pneumoniae
takes up DNA normally and converts it to single strands within the cell and oligonucleotide fragments outside the cell. Extracts of this strain contain a residual deoxyribonuclease that produces similar oligonucleotide fragments
in vitro
. This enzyme is missing in transformation-defective mutants blocked in the second or entry step. Cells of this mutant class bind large amounts of DNA to their surface in a form accessible to external agents. Another class of nontransformable mutants fails to bind DNA at all. Their deoxyribonuclease content is unchanged, and they are apparently blocked in the first or binding step of DNA uptake. The binding step requires a source of energy and prior activation of the cells by competence factor. Entry may be independent of these requirements and may come about by action of the deoxyribonuclease on one strand of DNA with energy for the transport of the intact strand deriving from hydrolysis of the degraded strand. The enzyme may thus act as a DNA translocase.
Further Analysis of a Simple Prototypal Muscle Model Near to and Far from Equilibrium
Authors: Hill Terrell L. , Chen Yi-der
Published: May 2006

The same prototypal model used in a previous paper to illustrate proper construction of a muscle model is modified here with the much more realistic choice
e

Δ
p

= 10
8
rather than
e

Δ
p

= 100, where
e

Δ
p

is the ratio of physiological ATP activity to equilibrium ATP activity. For steady isotonic contractions, the range 1 ≤
e
Δ
≤ 10
4
can be approximated quite well by use of linear terms only in expansions of
F̄
(force) and
J̄
(ATP flux) in powers of
e
Δ
- 1 and
v
(velocity). This will presumably also be true in most cases of much more complicated models. However, this region is of theoretical interest only (irreversible thermodynamics, etc.) because
F̄
and
J̄
are very small. In addition, numerical calculations of
F̄
and
J̄
were made in the region 10
4
≤
e
Δ
≤ 10
8
. The optimal efficiency η
*
is larger under physiological conditions (about 1%) than at equilibrium by a factor of 2.1 × 10
4
. The rate of entropy production is discussed in this connection.
Protection of Lethally Irradiated Mice by Spleen Cells from Neonatally Thymectomized Mice
Authors: Yunis E. J. , Good R. A. , Smith J. , Stutman O.
Published: May 2006

Long-lived, immunologically vigorous (C3H
f
× A
f
)F
1
hybrids were produced after lethal irradiation by administration of spleen cells from C3H
f
or syngeneic donors. Further, neonatally thymectomized C3H
f
or A
f
strain donors reconstituted irradiated C3H
f
or (C3H
f
× A
f
)F
1
hosts. In addition, C3H
f
spleen cells from nonthymectomized 10- to 15-day-old donors protected irradiated hybrid mice, but A
f
cells of young mice as well as of older mice produced graft-versus-host reaction and early death in irradiated C3H
f
or (C3H
f
× A
f
)F
1
hybrids.

Abrogation of secondary disease by treatment of irradiated mice with spleen cells from allogeneic neonatally thymectomized mice is possibly attributable to diminished immunologic competence of the cells grafted, followed by the development of immunological tolerance of the donor cells. Donor cells, receiving thymus influence in the recipient host after transplantation, could explain the long-lived immunologically vigorous radiation chimeras that did not experience graft-versus-host reactions. The findings of this study help to understand the differential susceptibility of A
f
and C3H
f
mice to development of tolerance to one another's antigens observed in prior investigations.

It appears that, in these mice, the host thymus influences the maturation of the spleen cells from young mice or from neonatally thymectomized mice. However, this influence was often greater in mice given 767 rads than in those given 1046 rads. This differential influence is possibly attributable to irradiation damage to the thymus produced by the higher dose of irradiation. Spleen cells from neonatally thymectomized mice can be differentiated and expanded by the thymus of the host. The differential susceptibility of T
1
, early differentiation stages, of thymus-dependent lymphocytes and T
2
, late differentiation stages, of thymus-dependent lymphocytes to tolerance induction and immunostimulation, respectively, are proposed as the bases for these otherwise paradoxical influences.
Growth Control in Cultured Mouse Fibroblasts: Induction of the Pleiotypic and Mitogenic Responses by a Purified Growth Factor
Authors: Rudland P. S. , Seifert W. , Gospondarowicz D.
Published: May 2006

Addition of serum to quiescent mouse fibroblasts induces a series of macromolecular changes (a pleiotypic response) followed by DNA synthesis and cell division. A new pituitary hormone, fibroblast growth factor, and hydrocortisone acting at physiological concentrations can completely replace exogenously added serum for the induction of these events in lines of BALB/c 3T3 cells. The induction of cell growth is specific for cultured fibroblasts; no stimulation is observed for mouse epithelial cells or virally transformed fibroblasts.
Hepatitis B Antigen: Antigenic Sites Related to Human Serum Proteins Revealed by Affinity Chromatography
Authors: Neurath A. Robert , Prince Alfred M. , Lippin Arnold
Published: May 2006

Hepatitis B antigen-associated particles, isolated from sera of antigen carriers, were submitted to affinity chromatography on columns of insolubilized antibodies to normal human plasma. The particles adsorbed to the immunosorbent at pH 7.2 and were subsequently eluted at pH 2.2. Exposure of the particles to 8 M urea, 5 M KI, pH 2.2, detergents, organic solvents, or proteolytic enzymes failed to prevent their subsequent adsorption to the immunosorbent. This suggests that antigenic determinants related to human plasma proteins are constituent components of hepatitis B antigen-associated particles. These determinants are distinct from the group-specific (
a
) and subtype-specific (
d
or
y
) sites of the hepatitis B antigen and appear to be related to antigenic specificities on prealbumin, albumin, apolipoproteins C and D, and the γ-chain of immunoglobulin G.
A Possible Effect of Heterochromatin on Chromosome Pairing
Authors: Thomas J. B. , Kaltsikes P. J.
Published: May 2006

Rye chromosomes were selectively stained in the meiosis of triticale by means of heterochromatin banding techniques. Compared to wheat chromosomes, rye chromosomes showed reduced pairing at first meiotic metaphase. Within the rye genome this pairing failure was associated with the presence of large, terminal heterochromatic bands. Since these terminal bands of rye chromosomes are late replicating, the effect of heterochromatin could arise from an overlap between the processes of chromosome replication and chromosome pairing.
The Pairwise Correlated Generalized Valence Bond Model of Electronic Structure I; The Estimation of Pair Energies from Orbital Overlaps
Authors: Petersson G. A.
Published: May 2006

A new method for the accurate
a priori
calculation of atomic and molecular energies is proposed. The new method agrees with experiment to within less than 1 kcal/mole in all cases examined thus far, and is applicable to excited states and to transition states for chemical reactions. Since the new method corrects the results of generalized valence bond calculations for the effects of electron pair correlations, we call the new method the pairwise correlated generalized valence bond method.
A Dynamical Model for Human Population
Authors: Yellin Joel , Samuelson P. A.
Published: May 2006

We analyze a simple, deterministic model of the dynamics of population changes in a bisexual, reproductive system based on marriage. Our model is one of a general class, special cases of which have been previously discussed within the framework of population biology by D. G. Kendall, L. A. Goodman, J. H. Pollard, and others. Here, we extend and complete previous analyses of systems characterized by first-degree homogeneous, unbounded marriage functions, allowing for arbitrary birth and death rates.

The dynamics of the model is determined by three coupled first-order, nonlinear differential equations, similar to those used in the description of chemical reactions and of radioactive decay chains. Solutions of the differential equation system are classified according to the associated patterns of birth and death rates of the two sexes, and growth and stability properties are discussed.

This preliminary report gives conditions sufficient to insure the existence of a unique, exponential mode of population growth or decay, with a finite ratio of the sexes. We also exhibit other conditions which, in contrast to the standard, linear demographic analysis of Lotka, guarantee that the sex ratio asymptotically becomes infinite.

The model manifests a delicate balance between the vital parameters that alerts one to the possibility of selfaggravating distortions of the sex ratio, once a monogamous society's fertility falls below the replacement value.
The Density of Acetylcholine Receptors and Their Sensitivity in the Postsynaptic Membrane of Muscle Endplates
Authors: Albuquerque Edson X. , Barnard Eric A. , Porter Carl W. , Warnick Jordan E.
Published: May 2006

In various skeletal muscles, the
mean
density of acetylcholine receptors in the muscle postsynaptic membrane is constant at about 8700 per μm
2
, even though the overall size of an endplate ranged from 400 μm
2
to 1300 μm
2
in these muscles. This measurement was by electron microscope autoradiography of α-[
3
H]bungarotoxin binding sites; only one-half of these, however, appear to be true active centers of the acetylcholine receptor. The highest density of these receptors is on the juxtaneuronal regions of the postsynaptic membrane, and their density in the depths of the fold is less than one quarter of that at the tips. A maximum sensitivity to externally applied acetylcholine, about 3000-5000 mV/nC, is found in diverse types of endplates when truly focal recording is achieved. This acetylcholine sensitivity appears to be determined by the local density of receptors in the membrane, and not by their total number at the endplate. A quantal efficiency term is also disclosed. The maximal sensitivity per molecule obtainable by microiontophoresis of acetylcholine is 5-10% of that operative when a quantum reacts. When acetylcholine is released from a vesicle, in contrast to its application from outside, geometric factors are more favorable. Consideration of the local packing density, acetylcholine molecule numbers, and the current flow when one quantum of acetylcholine interacts at the membrane suggests that one, or possibly two, activated receptor active centers are linked to one open gate of the ionic conductance modulator.
The Effects of Hemin and Double-Stranded RNA on α and β Globin Synthesis in Reticulocyte and Krebs II Ascites Cell-Free Systems and the Relationship of These Effects to an Initiation Factor Preparation
Authors: Beuzard Yves , London Irving M.
Published: May 2006

Protein synthesis in reticulocyte lysates ceases abruptly in the absence of added hemin or in the presence of double-stranded RNA. A similar effect of double-stranded RNA is observed in Krebs II ascites cell-free systems translating exogenous globin mRNA. The shut-off of protein synthesis is due to inhibition of initiation and can be prevented or reversed by addition of the initiation factor preparation M
3
. Preparations of M
1
, M
2
, and dissociation factor are ineffective under these conditions. The effects of added hemin, M
3
, and globin mRNA on the synthesis of α and β globin chains have been studied in the reticulocyte and ascites cell extracts. When the concentration of M
3
is rate limiting, the synthesis of β chains exceeds that of α chains. When the concentration of mRNA is rate limiting, synthesis of α and β chains is more nearly equal.
Alkaline Isomerization of Ferricytochrome
c:
Identification of the Lysine Ligand
Authors: Wilgus Harvey , Stellwagen Earle
Published: May 2006

Changes in the visible absorbance spectra of complexes of horse heart cytochrome
c
hemopeptide 1-65, peptide 66-104, and their guanidinated counterparts are compared with those characteristic of native and fully guanidinated ferricytochrome
c
over the pH range 7 to 11. Upon raising the pH, the methionine ligand in the guanidinated hemopeptide 1-65·peptide 66-104 complex is replaced by a strong field ligand. By contrast, the methionine ligand in the hemopeptide 1-65·guanidinated peptide 66-104 is replaced by a weak field ligand. These results demonstrate that lysine 13 does not ligate with the heme iron upon isomerization of ferricytochrome
c
and that the ligand in the horse heart protein is one of the eight lysine residues in the 66-104 segment of the polypeptide, most likely lysine 79.
Inhibition of Polypeptide Chain Initiation in
Escherichia coli
by Elongation Factor G
Authors: Lee-Huang Sylvia , Lee Henry , Ochoa Severo
Published: May 2006

We have previously reported the isolation from
E. coli
of a specific inhibitor of polypeptide chain initiation that is rendered ineffective when active aminoacylation of transfer RNA is taking place; this is normally the case during natural messenger RNA translation. Surprisingly, the inhibitory activity appears to be a hitherto unrecognized property of the chain elongation factor G. The following hold for preparations purified for either translocase or inhibitor activity: (
1
) equal electrophoretic mobility on polyacrylamide gels; (
2
) equal specific activities for (
a
) inhibition of initiation, (
b
) translocation, and (
c
) ribosome-dependent, uncoupled GTPase; and (
3
) similar heat sensitivity of translocase and inhibitor activities in a temperature-sensitive
E. coli
mutant with an altered elongation factor G. Different sites are apparently involved in translocation and inhibition because the former, but not the latter, is sensitive to
p
-chloromercuribenzoate and fusidic acid.
Failure of Lymphocytes to Reexpress Antigen Receptors after Brief Interaction with a Tolerogenic D-Amino Acid Copolymer
Authors: Ault Kenneth A. , Unanue Emil R. , Katz David H. , Benacerraf Baruj
Published: May 2006

We present data concerning a strongly tolerogenic molecule made of a copolymer of D-amino acids that is not metabolizable poly(D-glutamic acid-D-lysine). The dinitrophenyl conjugate of this molecule induces profound tolerance in dinitrophenyl-specific B lymphocytes both
in vivo
and
in vitro
. We show that dinitrophenyl-poly(D-glutamic acid-D-lysine) binds to a population of lymphocytes including those specific for dinitrophenyl, that it persists for long periods on these lymphocytes and is poorly internalized by them, and that these lymphocytes are prevented from binding other dinitrophenyl compounds. Despite prolonged culture, they do not reexpress receptors for dinitrophenyl. This behavior of dinitrophenyl-poly(D-glutamic acid-D-lysine) is contrasted to that of metabolizable antigens. This finding indicates that one mechanism of tolerance induced by nonmetabolizable antigens involves the prolonged loss of B lymphocyte receptor function.
Studies on the Carbohydrate Moiety of Dopamine β-Hydroxylase: Interaction of the Enzyme with Concanavalin A
Authors: Wallace Ellen F. , Lovenberg Walter
Published: May 2006

Dopamine β-hydroxylase [EC 1.14.17.1; 3,4-dihydroxyphenylethylamine, ascorbate:oxygen oxidoreductase (β-hydroxylating)], a glycoprotein, was found to interact strongly with the plant lectin, concanavalin A. This interaction did not appear to alter the catalytic properties of the enzyme and did not prevent interaction of the protein with specific antibodies. Dopamine-β-hydroxylase is adsorbed to concanavalin A covalently bound to Sepharose and can be eluted with α-methylmannoside. The enzyme is catalytically active when it is immobilized on a concanavalin A-Sepharose column. Enzymic removal of four of seven mannose residues present in the monomer does not result in the loss of any catalytic activity. It is concluded that the active site is not near the point of carbohydrate attachment on the molecule and that this may be of significance in orienting the enzyme on the vesicular membrane.
Carbon-13 Magnetic Resonance Evaluation of Polypeptide Secondary Structure and Correlation with Proton Magnetic Resonance Studies
Authors: Urry D. W. , Mitchell L. W. , Ohnishi T.
Published: May 2006

With the use of appropriately chosen solvent pairs it is demonstrated that solvent dependence of peptide carbonyl carbon resonances can be correlated with polypeptide secondary structure. Solvent titrations show the peptide carbonyl which is intramolecularly hydrogen bonded to exhibit less chemical shift on going from a dimethylsulfoxide solution to a solution containing a solvent which is a good proton (or deuteron) donor. Effective solvent systems are dimethylsulfoxide paired with water, trifluoroethanol, or methanol. This approach is demonstrated with the pentapeptide of elastin.
Study of Vibronic and Born-Oppenheimer Couplings
Authors: Lin S. H. , Eyring H.
Published: May 2006

The purpose of this paper has been to develop a systematic approach for classifying and distinguishing the relative orders of approximation of various types of couplings like the vibronic (Herzberg-Teller) couplings and Born-Oppenheimer couplings, and for studying the importance of the anharmonicity in the quantitative calculation of the spectral intensity and electronic relaxation. It will be shown that the perturbation parameter introduced by Born and Oppenheimer in separating the electronic and nuclear motion involved in the molecular Schrödinger equation, λ = (
m
/
M
)¼, can be used for this purpose by expanding wavefunctions and energies in power series of λ.
A Neuroblastoma × Glioma Hybrid Cell Line with Morphine Receptors
Authors: Klee Werner A. , Nirenberg Marshall
Published: May 2006

A neuroblastoma × glioma hybrid cell line with well-developed neural properties was found that has high-affinity morphine receptors. The average cell contains approximately 3 × 10
6
receptors. In contrast, parent cells and other neuroblastoma or hybrid cell lines tested had few or no morphine receptors.
Variants of Mouse Myeloma Cells That Produce Short Immunoglobulin Heavy Chains
Authors: Birshtein Barbara K. , Preud'Homme Jean-Louis , Scharff Matthew D.
Published: May 2006

After mutagenesis of cultured mouse myeloma cells with ICR 191 or Melphalan, variant clones were isolated that synthesized immunoglobulin heavy chains shorter than those produced by the parent. These variants fell into two phenotypes, based on the size, serology, and pattern of assembly of the heavy chain. Variant chains of both types no longer reacted with antisera directed either against the Fc (C-terminal half of the heavy chains) or subclass-specific IgG
2b
determinants. Comparative ion exchange chromatography of tryptic-chymotryptic peptides confirmed that the variant heavy chains differed structurally from those of the parent and from each other. A conversion from one phenotype to the other has been observed.
Bioregulation of lysosomal enzyme secretion from human neutrophils: roles of guanosine 3':5'-monophosphate and calcium in stimulus-secretion coupling.
Authors: Smith R J , Ignarro L J
Published: May 2006

The biologic role of calcium and guanosine 3':5'-monophosphate (cyclic GMP) in the immunologic secretion of lysosomal enzymes from human neutrophils was studied. Contact of neutrophils with zymosan-treated serum or the divalent cation ionophore A-23187, in the presence of extracellular calcium, resulted in beta-glucuronidase (beta-D-glucuronide glucuronosohydrolase, EC 3.2.1.31) secretion and a concomitant accumulation of cyclic GMP without any loss of cell viability. Acetylcholine (0.1 muM), in the presence of calcium, enhanced the immunologic stimulation of cyclic GMP accumulation and lysosomal enzyme discharge. A marked and rapid association of 45CaCl2 with neutrophils occurred during cell surface contact with zymosan-treated serum, and this effect on calcium association was enhanced with 0.1 muM acetylcholine. The precise mechanism of the neutrophil-calcium interaction is presently not well understood. However, the finding that 0.5-1.0 muM A-23187 also provoked a rapid association of extracellular calcium with neutrophils suggests that calcium mobilization into the intracellular environment may account, at least in part, for this association between cells and calcium. The close temporal relationship between beta-glucuronidase secretion, cyclic GMP accumulation, and calcium mobilization during cell contact with membrane active agents such as immune reactants, acetylcholine, and ionophores suggests that these three cellular events bear a cause and effect relationship. On the basis of our findings to date, we propose that the immunologic secretion of lysosomal contents from human neutrophils is signaled by intracellular cyclic GMP and that extracellular calcium, by gaining access to the intracellular processes responsible for cyclic GMP accumulation, serves as the link to stimulus-secretion coupling.
Nonrandom chromosomal abnormalities in hematologic disorders of man.
Authors: Rowley J D
Published: May 2006

A nonrandom pattern of chromosomal abnormalities occurs in bone marrow cells obtained from patients with hematologic disorders who have an abnormal karyotype involving a C group chromosome. An additional number 8 chromosome is the most common abnormality, found in more than one-half of the patients studies. An additional number 9 chromosome and the loss of all or part of a number 7 are abnormalities that occur more often than might be expected by chance. It is proposed that specific human chromosomal abnormalities may be related to different specific etiologic agents.
Bovine factor X1 (Stuart factor). Primary structure of the light chain.
Authors: Enfield D L , Ericsson L H , Walsh K A , Neurath H , Titani K
Published: May 2006

The amino-acid sequence of the light chain of bovine factor X1 is presented. The sequence of 112 of the 140 residues was determined automatically on fragments produced by specific cleavage of arginyl, glutamyl, tryptophanyl, and asparaginyl-glycine bonds. The remainder was determined by conventional procedures. The amino-terminal sequence of the light chain is homologous with the amino-terminal region of bovine prothrombin and, like the latter, appears to contain several residues of a recently discovered unusual amino acid, lambda-carboxy-glutamic acid. The role of this amino acid in the calcium-binding ability of factor X and prothrombin is discussed.
Chromatin as a template for RNA synthesis in vitro.
Authors: Groner Y , Monroy G , Jacquet M , Hurwitz J
Published: May 2006

RNA transcribed in vitro from myeloblast chromatin by exogenously added RNA polymerase B predominantly consists of short chains that remain in hybrid structure with the template; the remainder of the product is free RNA of heterogeneous size. Addition of polyanions during synthesis caused an increase in the size and amount of free RNA with a concomitant decrease in the proportion of small RNA. The large molecular weight RNA is derived from the short RNA chains, which are synthesized de novo during the reaction in vitro. The effect of polyanions on the size and nature of the product may be related to structural changes induced in the template rather than to an inhibition of nuclease activity.
Re-evaluation of Sepharose-insulin as a tool for the study of insulin action.
Authors: Kolb H J , Renner R , Hepp K D , Weiss L , Wieland O H
Published: May 2006

The biological activity of Sepharose-insulin in different assays in vitro, e.g., stimulation of glucose oxidation, lipogenesis, and antilipolysis and activation of pyruvate dehydrogenase (EC 1.2.4.1) activity, has been investigated. According to amino acid analysis, between 270 and 330 mug (6.9-8.2 U) of insulin were coupled per ml of packed beads. Related to the total insulin content, 0.2-0.7% of the insulin was biologically active. Comparable biological activity was observed with isolated fat cells and fat pad pieces. After incubation with tissue or cells, Sepharose-insulin particles were separated by centrifugation from the medium. The clear supernatant was assayed for biologically and immunologically reactive insulin and contained soluble insulin activity. A quantitative evaluation of the soluble biological and immunological insulin activity in the supernatant accounted for the total insulin activity of Sepharose-insulin.
Reovirus messenger RNA contains a methylated, blocked 5'-terminal structure: m-7G(5')ppp(5')G-MpCp-.
Authors: Furuichi Y , Morgan M , Muthukrishnan S , Shatkin A J
Published: May 2006

Reovirus mRNA synthesized in vitro by the virus-associated RNA polymerase in the presence of S-adenosylmethionine contains blocked, methylated 5'-termini with the structure, m-7G(5')ppp(5')G-MpCp. The functional significance and possible mechanism of formation of this novel 5'-5' terminal nucleotide linkage are discussed.
Apocytochrome P-450: reconstitution of functional cytochrome with hemin in vitro.
Authors: Correia M A , Meyer U A
Published: May 2006

Synthesis of microsomal cytochrome P-450 in rat liver requires synthesis of apoprotein in rough endoplasmic reticulum and of heme in mitochondria. Dissociation of apoprotein and heme synthesis by concomitant treatment of rats with inducers of cytochrome P-450 (i.e., phenobarbital) and inhibitors of heme synthesis (i.e., cobalt) resulted in a relative excess of apocytochrome P-450. Under these circumstances, it was possible to reconstitute the holocytochrome by addition of hemin in vitro. The holocytochrome was detected spectrophotometrically by its CO-binding properties and functionally by its increased oxidative activity. Heme-mediated reconstitution was most efficient in cell fractions rich in mitochondria-rough endoplasmic reticulum complexes (640 times g fraction), suggesting that the structural association of these two organelles may represent a functional unit essential for the synthesis of holocytochrome P-450. These findings indicate that phenobarbital-mediated induction of apocytochrome P-450 is independent of heme synthesis. It is suggested that synthesis of the apocytochrome may be the primary and rate-limiting event in the formation of cytochrome P-450.
Dimethyl adipimidate: a new antisickling agent.
Authors: Lubin B H , Pena V , Mentzer W C , Bymun E , Bradley T B , Packer L
Published: May 2006

A new approach to the prevention of sickling in vitro by use of the bifunctional crosslinking reagent, dimethyl adipimidate, is described. Prior treatment of sickle erythrocytes with dimethyl adipimidate will inhibit sickling in completely deoxygenated erythrocytes. Treated erythrocytes do not demonstrate the potassium loss and viscosity increase that usually accompany sickling. The oxygen affinity of hemoglobin in these cells is increased independently from changes in the concentration of 2,3-diphosphoglycerate. The hemoglobin obtained from treated erythrocytes contains a high-molecular-weight component as well as additional positively charged components. The relative degree to which chemical modification and/or crosslinking is an essential part of the antisickling properties of the material is not known.
Specialized transducing phages for ribosomal protein genes of Escherichia coli.
Authors: Jaskunas S R , Lindahl L , Nomura M
Published: May 2006

Specialized lambda transducing phages have been isolated carrying approximately half the ribosomal protein genes of E. coli. These phages carry regions of the bacterial chromosome between aroE and fus. The ribosomal protein genes on these phages have been identified by the stimulation of ribosomal protein synthesis in ultraviolet-irradiated bacteria following infection by the transducing phage, and by the in vitro synthesis of ribosomal proteins in a DNA-dependent protein synthesizing system. The results indicate lambdadspcl probably carries at least 22 ribosomal protein genes and lambdadspc2 at least 26 genes. All these genes are clustered between trkA and strA. At least 13 of them have not been previously mapped.
Adiabatic evolution of plasma equilibrium
Authors: Grad H. , Hu P. N. , Stevens D. C.
Published: May 2006

A new theory of plasma equilibrium is introduced in which adiabatic constraints are specified. This leads to a mathematically nonstandard structure, as compared to the usual equilibrium theory, in which prescription of pressure and current profiles leads to an elliptic partial differential equation. Topologically complex configurations require further generalization of the concept of adiabaticity to allow irreversible mixing of plasma and magnetic flux among islands. Matching conditions across a boundary layer at the separatrix are obtained from appropriate conservation laws. Applications are made to configurations with planned islands (as in Doublet) and accidental islands (as in Tokamaks). Two-dimensional, axially symmetric, helically symmetric, and closed line equilibria are included.
Partial purification of a glucocorticoid receptor.
Authors: Failla D , Tomkins G M , Santi D V
Published: May 2006

A simple method for purification of the glucocorticoid receptor from hepatoma tissue culture cells has been developed. The procedure, which requires only about 24 hr, involves biospecific adsorption of the receptor to deoxycorticosterone derivatized agarose, elution with a glucocorticoid, and gel filtration. The receptor-steroid complex is obtained in 35-40% yield and is about 2000-fold purified. It possesses properties similar to those reported in crude extracts, including sedimentation coefficient in glycerol gradients and activation-dependent binding to nuclei.
Human pituitary growth hormone: a biologically active hendekakaihekaton peptide fragment corresponding to amino-acid residues 15-125 in the hormone molecule.
Authors: Li C H
Published: May 2006

A hendekakaihekaton peptide fragment has been prepared by cyanogen bromide cleavage of the NH2-terminal 134-residue fragment of human pituitary growth hormone. It was characterized by amino-acid and end-group analyses, exclusion chromatography, disc electrophoresis, circular dichroism, and ultracentrifugation. The fragment, corresponding to amino-acid residues 15-125 in the hormone molecule, possesses hepatic ornithine decarboxylase (EC 4.1.1.17; L-ornithine carboxy-lyase) stimulating, lactogenic, and somatotrophic activity. It has immunoreactivity in the microcomplement-fixation and radioimmunoassay experiments. The circular dichroism data indicate that the hendekakaihekaton peptide fragment is devoid of secondary and tertiary structure.
Position-specific oxygenation of benzo(a)pyrene by different forms of purified cytochrome P-450 from rabbit liver.
Authors: Wiebel F J , Selkirk J K , Gelboin H V , Haugen D A , van der Hoeven T A , Coon M J
Published: May 2006

High-pressure liquid chromatography was used to detect oxygenated products of benzo[a]pyrene formed in a reconstituted microsomal mixed-function oxidase system containing cytochrome P-450 (P-450LM), phospholipid, and NADPH-cytochrome P-450 reductase (NADPH: ferricytochrome oxidoreductase, EC 1.6.2.4). Three cytochrome fractions purified from a single source, hepatic microsomes from phenobarbital-treated rabbits, were studied; the various forms of the cytochrome are designated by their relative electrophoretic mobilities. The total benzo[a]pyrene oxygenation rate was greatest for P-450LM1,7, intermediate for P-450LM2, and least for P-450LM4. The phenolic products were eluted in two peaks, A and B, that contained primarily 9-hydroxy- and 3-hydroxybenzo[a]pyrene, respectively. The ratio of peak A to peak B phenols was 0.11 for P-450LM2 and 0.45 for P-450LM4. Thus, the relative amounts of the various phenols formed by these two cytochrome fractions differ markedly. The positional specificity of the hydroxylation is also indicated by large differences in the fluorescence spectra of the phenolic products formed by the two cytochromes. P-450LM2 and P-450LM4 did not form benzo[a]pyrene dihydrodiols, thereby showing that benzo[a]pyrene oxide hydratase activity was absent from these purified preparations. Ninety percent of the phenols formed by P-450LM1,7 were eluted in peak B; the metabolites produced by this preparation also included dihydrodiols, thus indicating the presence of hydratase activity. The positional specificities of different forms of cytochrome P-450 may channel polycyclic aromatic hydrocarbon metabolism into the various activation and detoxification pathways and thereby help determine the cytotoxic and carcinogenic activity of these compounds.