bluuebunny/crossref_metadata_2025 huggingface dataset:
Bent Fatty Acid Chains in Lecithin Bilayers
Authors: McFarland Betty Gaffney , McConnell Harden M.
Published: May 2006

An analysis of the paramagnetic resonance spectra of a number of phospholipid spin labels in multi-lamellar arrays of lecithin bilayers has been carried out in terms of a distribution of label orientations, and the amplitude and time dependence of high-frequency random motions about these orientations. This analysis indicates that there is a long-lived (>10
-8
sec) average bending of the fatty acid chains such that near the polar head groups the chains are comparatively rigid and tilted at about 30° relative to a normal to the bilayer plane, whereas near the terminal methyl groups the chains are flexible and on the average parallel to this normal. This bent conformation of the chains permits the packing of chains into planar lamellar arrays even when different segments of the chain have different motional freedom.
Restoration of Contact-Inhibited Growth to Transformed Cells by Dibutyryl Adenosine 3′:5′-Cyclic Monophosphate
Authors: Sheppard J. R.
Published: May 2006

Spontaneously transformed and virally-transformed cells are restored to contact-inhibited growth by the addition of dibutyryl cyclic AMP to the nutrient medium. Theophylline, an inhibitor of the phosphodiesterase that degrades cyclic nucleotides, must also be present for maximal effect. Once the transformed cells reach a saturation density in the presence of the additives, release from the contact-inhibited state occurs upon removal of the dibutyryl cyclic AMP and theophylline from the medium. Agglutinability of the transformed cells by wheat-germ agglutinin (a monitor of architectural changes in the plasma membrane) is decreased by dibutyryl cyclic AMP-theophylline treatment, but increases again upon removal of the additives.
Polyadenylic Acid Sequences in the Heterogeneous Nuclear RNA and Rapidly-Labeled Polyribosomal RNA of HeLa Cells: Possible Evidence for a Precursor Relationship
Authors: Edmonds Mary , Vaughan Maurice H. , Nakazato Hiroshi
Published: May 2006

Polyadenylate sequences have been found covalently linked in heterogeneous DNA-like nuclear RNA of HeLa cells. This poly(A) material seems homogeneous in size and accounts for about 0.5% of such RNA. Similar poly(A) sequences were found in rapidly-labeled polyribosomal RNA, thought to be messenger RNA. A possible model for mRNA synthesis from large heterogeneous nuclear RNA precursor molecules is discussed.
Turnover of Genetically Defined Catalase Isozymes in Maize
Authors: Quail Peter H. , Scandalios John G.
Published: May 2006

The turnover of two homotetramers of catalase, V
4
and Z
4
, specified by genes at two separate loci, has been studied during germination of maize seed by the techniques of density labeling and starch-gel electrophoresis. Both isozymes were shown to be turning over during this time. However, Z
4
accumulates because the rate of synthesis exceeds the rate of degradation, whereas V
4
slowly disappears because the rate of degradation exceeds the rate of synthesis. Evidence is also presented that the rate of synthesis of Z
4
exceeds that of V
4
, which suggests that this may be a major factor in the differential expression of the two catalase genes.
Spontaneous Precipitation of Brushite in Urine: Evidence that Brushite Is the Nidus of Renal Stones Originating as Calcium Phosphate
Authors: Pak Charles Y. C. , Eanes Edward D. , Ruskin Belle
Published: May 2006

Further evidence that brushite plays a regulatory role in renal stone formation was provided by the identification of brushite as the first precipitate that appears in supersaturated urine by spontaneous precipitation. Calcium chloride was added to induce supersaturation in urine specimens from twelve subjects with and twelve subjects without nephrolithiasis.

The first precipitate in all specimens with pH below 6.9 was identified as brushite by x-ray diffraction and shown to have a calcium-phosphorus ratio of approximately 1.0.

The activity product of [Ca
2+
] × [HPO
4
2-
] necessary to produce a precipitate ranged from 2.2 to 3.5 times the solubility product of brushite, but the range and mean were the same for both groups of subjects.

The activity product of [Ca
2+
] × [HPO
4
2-
] in the supernatant (after spontaneous precipitation) was not significantly different from that obtained after incubation of the same urine specimen with synthetic brushite.

These results provide conclusive evidence that brushite constitutes the solid phase formed by spontaneous precipitation from acidic urine supersaturated with respect to calcium and phosphorus; they suggest that the nidus for calcium-containing renal stones is brushite as well.
Acyclic Ketones in the Defensive Secretion of a “Daddy Longlegs” (
Leiobunum vittatum
)
Authors: Meinwald J. , Kluge A. F. , Carrel J. E. , Eisner T.
Published: May 2006

The defensive secretion of the “daddy longlegs”
Leiobunum vittatum
was analyzed and found to contain the acyclic ketones 4-methylheptan-3-one and E-4,6-dimethyl-6-octen-3-one as its major organic components. Although 4-methylheptan-3-one has been found previously as an alarm substance in certain ant genera, the second component, whose structure is confirmed by synthesis, is new.
Hearing in the Crocodilia
Authors: Wever Ernest Glen
Published: May 2006

Measurements of auditory sensitivity in terms of the cochlear potentials were made in young specimens of three species of crocodilians,
Caiman crocodilus
and
Alligator mississipiensis
of the subfamily Alligatorinae and
Crocodylus acutus
of the subfamily
Crocodylinae
. These species show considerable similarity in their capabilities for sound reception. All have the best sensitivity in a fairly broad middle range, and fall off for lower tones and particularly rapidly for the high tones. The level of sensitivity in the middle range is of high degree in comparison with other reptiles and with many birds and mammals.
Biological Roles of the Two Components of Crotoxin
Authors: Hendon R. A. , Fraenkel-Conrat H.
Published: May 2006

Crotoxin, the Brazilian rattlesnake neurotoxin, generally behaves as a homogeneous protein; however, it is a molecular complex of an acidic and a basic protein. These can be separated after alkylation or acylation of the amino groups, or on carboxymethyl cellulose at pH 4, or on DEAE-cellulose in 6 M urea. The two proteins differ greatly in composition, but one or both may exist in the form of closely related variants. Their molecular weights appear to be about 8400 and 13,000.

The acidic protein lacks the hemolytic and neurotoxic activity of crotoxin and the basic protein shows only the high, indirect hemolytic activity; a mixture of the two components shows the high neurotoxicity of crotoxin.
Attenuation of Seismic Waves by Grain Boundary Relaxation
Authors: Jackson David D.
Published: May 2006

Experimental observations of the attenuation of elastic waves in polycrystalline ceramics and rocks reveal an attenuation mechanism, called grain boundary relaxation, which is likely to be predominant cause of seismic attenuation in the earth's mantle. For this mechanism, the internal friction (the reciprocal of the “intrinsic
Q
” of the material) depends strongly upon frequency and is in good agreement with Walsh's theory of attenuation (
J. Geophys. Res.
, 74, 4333, 1969) in partially melted rock. When Walsh's theory is extended to provide a model of the anelasticity of the earth, using the experimental values of physical parameters reported here, the results are in excellent agreement with seismic observations.
Selective Induction by Nerve Growth Factor of Tyrosine Hydroxylase and Dopamine-β-Hydroxylase in the Rat Superior Cervical Ganglia
Authors: Thoenen H. , Angeletti P. U. , Levi-Montalcini R. , Kettler R.
Published: May 2006

Treatment of newborn rats with 10 μg/g of nerve growth factor for 10 days enhanced not only the growth but also the differentiation of neuroblasts in superior cervical ganglia. These morphological changes were accompanied by selective induction of tyrosine hydroxylase and dopamine β-hydroxylase (EC 1.14.2.1), whereas the total and specific activities of other enzymes involved in biosynthesis or metabolic degradation of norepinephrine rose only in proportion to the increase in volume of the sympathetic ganglia. There are remarkable similarities between this effect of nerve growth factor and the induction of trans-synaptic enzymes by increased activity of the sympathetic nervous system.
Mechanism of Oxidative Carbon Dioxide Production during
Renilla reniformis
Bioluminescence
Authors: DeLuca Marlene , Dempsey Mary E. , Hori Kazuo , Wampler John E. , Cormier Milton J.
Published: May 2006

The oxidation of luciferin catalyzed by sea pansy luciferase results in the emission of light. Molecular oxygen is required and carbon dioxide is produced. When the reaction occurs in the presence of H
2
18
O, both of the oxygens of the carbon dioxide are labeled. One of the oxygens arises from the nonenzymic exchange of the ketone group of the substrate; the other oxygen is incorporated during the enzymic oxidation of the luciferin. When the reaction is carried out in the presence of
18
O
2
, neither of the oxygens of the carbon dioxide is labeled. Thus the source of oxygen in the carbon dioxide is water. A mechanism for the oxidative reaction is proposed.
Neurohypophyseal Hormone-Responsive Adenylate Cyclase from Mammalian Kidney
Authors: Douša Thomas , Hechter Oscar , Schwartz Irving L. , Walter Roderich
Published: May 2006

The investigation was undertaken to evaluate the direct stimulatory effects of neurohypophyseal hormones upon adenylate cyclase activity in a cell-free, particulate fraction derived from the kidney medulla of various mammalian species. The relative affinity of neurohypophyseal hormones for the receptor component of the adenylate cyclase system (as defined by the concentration of hormone required for half-maximal stimulation) had the order [8-arginine]-vasopressin > [8-lysine]-vasopressin ≫ oxytocin (AVP > LVP ≫ OT) for rat, mouse, rabbit, and ox; in the pig, the order was LVP > AVP ≫ OT. The relative affinities of the three hormones in rat and pig cyclase systems were found to correspond with the relative antidiuretic potencies of these hormones in the intact rat and pig. These findings show that the renal receptor for neurohypophyseal hormones in a particular species exhibits the highest affinity for the specific antidiuretic hormone that occurs naturally in that species.

Some of the molecular requirements for the stimulation of rabbit adenylate cyclase were defined by studies of several neurohypophyseal analogs possessing structural changes in positions 1, 2, 3, 4, 5, 8, and 9.

This investigation introduces the particulate preparation of renal medullary adenylate cyclase as a tool for the analysis of neurohypophyseal hormone-receptor interactions and indicates that this preparation can be adapted to serve as an
in vitro
bioassay system for antidiuretic hormonal activity.
X-Irradiation Enhancement of Transformation by Benzo(a)Pyrene in Hamster Embryo Cells
Authors: DrPaolo J. A. , Donovan P. J. , Nelson R. L.
Published: May 2006

The addition of benzo(a)pyrene to cells obtained from Syrian hamster embryo cultures that had been plated to produce discrete colonies resulted in transformation. Altered colonies were not seen in controls. Prior irradiation of hamster embryo cells increased the transformation by benzo(a)pyrene, both per cell and per total colony. Maximum enhancement occurred when benzo(a)pyrene was added 48 hr after irradiation. Enhancement was greatest after 250-500 R, and decreased with higher doses of radiation. The addition of benzo(a)pyrene 72 hr after irradiation resulted in very little enhancement. Although transformation increased with benzo(a)pyrene concentration, enhancement was independent of concentration within the range used. No colony with transformed morphology was recognized among the colonies of normal cells that survived irradiation.
Suppressive Effect of Immunization with Mouse Fetal Antigens on Growth of Cells Infected with Rauscher Leukemia Virus and on Plasma-Cell Tumors
Authors: Hanna M. G. , Tennant R. W. , Coggin J. H.
Published: May 2006

The recovery of spleen cells infected with Rauscher leukemia virus (RLV) and grown in Millipore diffusion chambers, the development of RLV-induced splenomegaly, and the cumulative mortality from a transplanted ascites plasma-cell tumor were all suppressed in young adult BALB/c male mice previously primed at 3-weekly intervals with x-irradiated, syngeneic embryo cells. RLV-induced splenomegaly was also suppressed by adoptive transfer of postpartal spleen cells, as well as spleen cells for animals primed with syngeneic embryo cells. Similar suppressions were not observed in mice primed with neonatal or normal syngeneic cells. Further, injection of fetal cells was not effective in suppressing the immune function of normal spleen cells, as measured by ability to elaborate a primary immunoglobulin M response to heterologous erythrocyte antigen. The results of this study add to the broad spectrum of tumors of experimental animals and man known to contain neoantigens common to fetal cells.
Stimulation of RNA Transcription from Pea and Corn DNA by Protein Retained on Sepharose Coupled to 2,4-Dichlorophenoxyacetic Acid
Authors: Venis Michael A.
Published: May 2006

When crude extracts from pea or corn shoots are passed through a column of agarose coupled to a derivative of the synthetic plant hormone 2,4-dichlorophenoxyacetic acid, certain protein fractions are retained, whereas unmodified agarose adsorbs no protein. Appropriate elution yields a protein factor that stimulates DNA-dependent RNA synthesis (supported by
Escherichia coli
polymerase) by 40-200%. Preliminary evidence suggests that the factor may be influencing initiation of RNA chains.
Biochemical Differentiation in Reaggregating Brain Cell Culture
Authors: Seeds Nicholas W.
Published: May 2006

Dissociated cells from embryonic mouse brain reassociate in rotation culture to form aggregates. During cell culture the specific activities of choline acetyl-transferase (EC 2.3.1.6), acetylcholinesterase (EC 3.1.1.7), and glutamate decarboxylase (EC 4.1.1.15) in the aggregates increase up to twenty-fold, a phenomenon that approximates some of the biochemical events in the development of the mouse brain.
Histrionicotoxins: Roentgen-Ray Analysis of the Novel Allenic and Acetylenic Spiroalkaloids Isolated from a Colombian Frog,
Dendrobates histrionicus
Authors: Daly John W. , Karle Isabella , Myers Charles W. , Tokuyama Takashi , Waters James A. , Witkop Bernhard
Published: May 2006

The structures and absolute configuration of two unique alkaloids isolated from the Colombian frog,
Dendrobates histrionicus
, have been elucidated by Roentgen-ray (x-ray) crystallography. Histrionicotoxin is (2
p
R, 6S, 7
p
S, 8
a
S)-7-(
cis
-1-buten-3-ynyl)-8-hydroxy-2-(
cis
-2-penten-4- ynyl)-1-azaspiro[5.5] undecane, while in dihydro-isohistrionicotoxin the acetylenic 2-pentenynyl side chain is replaced by an allenic 2-(3,4 pentadienyl) substituent.
Dendrobates histrionicus
exhibits remarkable interpopulational variations in amounts and composition of skin toxins, in behavior, and in phenotypic characters, aspects of which are illustrated in a color plate. The histrionico-toxins are the third class of alkaloids isolated from the defensive skin secretions of Neotropical (Dendrobatidae) frogs.
Kinetic Studies on
Klebsiella pneumoniae
Nitrogenase
Authors: Parejko R. A. , Wilson P. W.
Published: May 2006

Purified cell-free extracts of
Klebsiella pneumoniae
reduce N
2
, N
3
-
, CN
-
, or C
2
H
2
in the absence of an ATP-generating system when substrate concentrations of ATP are used. The optimum Mg
++
/ATP ratio is 0.5. Michaelis constants for the reduction of substrates calculated from kinetic studies of
K. pneumoniae
nitrogenase were similar to those that have been reported for
Azotobacter vinelandii
and
Clostridium pasteurianum
. Hill plots of the kinetic data are consistent with the view that there is a single binding site for each of the substrates N
2
, C
2
H
2
, CN
-
, N
3
-
, and ATP. Inhibition studies of
K. pneumoniae
nitrogenase indicate that ADP competitively inhibits C
2
H
2
reduction. Also, the reducible substrates, N
3
-
and CN
-
, inhibit C
2
H
2
reduction. The inhibition by azide is noncompetitive, that by cyanide is mixed.
Modification of Severe Coxsackievirus B
3
Infection in Marasmic Mice by Transfer of Immune Lymphoid Cells
Authors: Woodruff Jack F. , Woodruff Judith J.
Published: May 2006

Coxsackievirus causes severe disease in adult mice subjected to sustained post-weaning undernutrition (marasmus). Virus-infected marasmic mice have an increased incidence of mortality, severe lesions, and elevated and persistent viral in target organs. Transfer of immune lymphoid cells 30 min or 24 hr after viral challenge significantly reduced the incidence of death and lesions. The protective capacity of immune cells was further manifested by reduced titers of virus in the target organs. Since lymphoid tissues are severely atrophic in marasmic mice, these results indicate that this deficiency contributed significantly to the impaired ability of these hosts to recover from viral disease. These observations support the idea that the acquisition of lymphocyte-mediated defense mechanisms is essential for normal recovery from certain primary viral infections.
Decrease of the 3,4-Dihydroxyphenylalanine (DOPA) Decarboxylase Activities in Human Erythrocytes and Mouse Tissues after Administration of DOPA
Authors: Tate Suresh S. , Sweet Richard , McDowell Fletcher H. , Meister Alton
Published: May 2006

Human erythrocytes have been found to contain appreciable amounts of DOPA decarboxylase (EC 4.1.1.26) activity. The enzyme activity in erythrocytes from patients with Parkinson's disease who were treated with DOPA was significantly lower than that of untreated patients and of normal individuals. Administration of the drug to mice led to a marked decrease of DOPA decarboxylase in liver and kidney, but not of the brain enzyme. The findings thus indicate that administration of DOPA leads to a decrease in peripheral DOPA decarboxylase, an effect that is expected to be of benefit in DOPA therapy of patients with Parkinson's disease. Peripheral DOPA decarboxylase concentration also decreases in mice after short periods of fasting; the findings suggest that the peripheral enzyme activities may be affected by various nutritional and perhaps hormonal influences, which may be partially responsible for the observed fluctuations in the motor abilities of Parkinsonian patients receiving constant doses of the drug. Study of DOPA decarboxylase activity in erythrocytes may be useful in following changes in patients receiving DOPA therapy and may also be of general interest and value in investigations of catecholamine metabolism in man.
Purification of the
araC
Protein
Authors: Wilcox Gary , Clemetson Kenneth J. , Santi Daniel V. , Englesberg Ellis
Published: May 2006

The
araC
gene product, a regulatory protein required for expression of the L-arabinose operon, has been purified by affinity chromatography on Sepharose 4B to which 4-aminophenyl-β-D-6-deoxygalactopyranoside (an anti-inducer of the L-arabinose operon) had been covalently attached by means of a 4-aminophenylbutanamido side chain. Evidence is presented showing that the protein binds specifically to
ara
DNA.
Three-dimensional Reconstruction from Radiographs and Electron Micrographs: Application of Convolutions instead of Fourier Transforms
Authors: Ramachandran G. N. , Lakshminarayanan A. V.
Published: May 2006

A new technique is proposed for the mathematical process of reconstruction of a three-dimensional object from its transmission shadowgraphs; it uses convolutions with functions defined in the real space of the object, without using Fourier transforms. The object is rotated about an axis at right angles to the direction of a parallel beam of radiation, and sections of it normal to the axis are reconstructed from data obtained by scanning the corresponding linear strips in the shadowgraphs at different angular settings.

Since the formulae in the convolution method involve only summations over one variable at a time, while a two-dimensional reconstruction with the Fourier transform technique requires double summations, the convolution method is much faster (typically by a factor of 30); the relative increase in speed is larger where greater resolution is required. Tests of the convolution method with computer-simulated shadowgraphs show that it is also more accurate than the Fourier transform method. It has good potentialities for application in electron microscopy and x-radiography. A new method of reconstructing helical structures by this technique is also suggested.
Comparison of the Microtubule Proteins of Neuroblastoma Cells, Brain, and
Chlamydomonas
Flagella
Authors: Olmsted J. B. , Witman G. B. , Carlson K. , Rosenbaum Joel L.
Published: May 2006

Intact A microtubules isolated from outer doublet microtubules of
Chlamydomonas
flagella contain two separable proteins (tubulins) that differ in molecular weight and in amino-acid composition. The microtubule protein isolated from brain or neuroblastoma cells also has two electrophoretically distinct tubulins. Although the two tubulins of brain and neuroblastoma cells are electrophoretically similar to each other, only one of these tubulins migrates with the flagellar tubulins. This is the first evidence that (
a
) isolated, morphologically intact, single microtubules from flagella contain at least two different tubulins, and (
b
) at least one of these tubulins differs from tubulins that are isolated from other sources.
Sequence Differences of
Escherichia coli
30S Ribosomal Proteins as Determined by Immunochemical Methods
Authors: Stöffler G. , Wittmann H. G.
Published: May 2006

Antisera specific for each of the 21 homogenous ribosomal proteins from 30S subunits of
Escherichia coli
were used to investigate, by immunodiffusion and immunoprecipitation, whether there are any extensive sequence homologies among these proteins.

No immunological crossreactions were detected between any of the proteins. Therefore, we conclude that no significant common sequences exist among any of the 21 30S ribosomal proteins of
E. coli
.
Folding of Polypeptide Chains in Proteins: A Proposed Mechanism for Folding
Authors: Lewis Peter N. , Momany Frank A. , Scheraga Harold A.
Published: May 2006

A mechanism is proposed for the folding of protein chains. On the basis of short-range interactions, certain aminoacid sequences have a high propensity to be, say, α-helical. However, these short helical (or other ordered) regions can be stabilized only by long-range interactions arising from the proximity of two such ordered regions. These regions are brought near each other by the directing influence of certain other aminoacid sequences that have a high probability of forming β-bends or variants thereof, also on the basis of short-range interactions. An analysis is made of the tendency of various amino acids to occur in β-bends, and it is possible to predict the regions of a chain in which a β-bend will occur with a high degree of reliability.
Changes in Macromolecular Synthesis Associated with the Induction of Glutamine Synthetase in Embryonic Retina
Authors: Sarkar P. K. , Moscona A. A.
Published: May 2006

The hydrocortisone-mediated induction of glutamine synthetase in the neural retina of chicken embryo
in vitro
is correlated with enhanced incorporation into protein of [
14
C]aspartic acid, an amino acid abundant in this enzyme. In the induced retina labeled with [
14
C]aspartic acid, a peak of radioactivity was detected in the region of the polysomal profile corresponding to polysomes comprising 12-14 ribosomes. In retinas labeled with [
3
H]uridine, an increased amount of radioactivity was also detected in the same polysomal region of the hydrocortisone-induced retina. If we assume a monocistronic messenger RNA for retinal glutamine synthetase, this region corresponds to the estimated size of the polysomes necessary for the translation of this enzyme. The evidence presented demonstrates a correlation between these changes in incorporation and the induction of glutamine synthetase.
Macromolecules from Lobster Axon Membranes That Bind Cholinergic Ligands and Local Anesthetics
Authors: Denburg Jeffrey L. , Eldefrawi Mohyee E. , O'Brien Richard D.
Published: May 2006

The technique of reversible equilibrium dialysis has been applied to the study of macromolecules that are essential for axonal conduction. A binding component from a preparation of an axon-plasma membrane has been characterized and shown to bind nicotine with a

K
D

= 0.42 ± 0.04 μM and to the extent of 0.7 nmol/g of wet nerve. This binding was competitively blocked by acetylcholine (

K
i

= 43 ± 7 μM) and procaine (

K
i

= 2.9 ± 0.2 μM). This axonal macromolecule exhibits several of the properties of cholinergic postsynaptic receptors including its concentration in the tissue, blockade of its binding of nicotine by cholinergic drugs and α-bungarotoxin, and its phospholipoprotein nature. Some important differences are a lower affinity for acetylcholine and its binding of procaine. It is suggested that this nicotine receptor is on the internal surface of the axon plasma membrane and is a component common to both the Na
+
and K
+
gates.
Primary Structure of the Ovine Hypothalamic Luteinizing Hormone-Releasing Factor (LRF)
Authors: Burgus Roger , Butcher Madalyn , Amoss Max , Ling Nicholas , Monahan Michael , Rivier Jean , Fellows Robert , Blackwell Richard , Vale Wylie , Guillemin Roger
Published: May 2006

The primary structure of ovine hypothalamic hypophysiotropic luteinizing hormone-releasing factor, LRF, has been established as pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH
2
by hydrolysis of the peptide with chymotrypsin or pyrrolidone-carboxylylpeptidase and by analysis of the products by an Edman-dansylation sequencing technique, as well as by mass spectrometry of the derived phenylthiohydantoins. A decapeptide with the proposed primary structure, prepared by total synthesis, gave the same result on sequencing. The synthetic decapeptide possesses the same biological activities as the native ovine LRF. The amino-acid sequence of ovine LRF is identical to that already published for porcine LRF.
Aerobic Reduction of Cytochrome
b
566
in Pigeon-Heart Mitochondria
Authors: Erecińska M. , Chance B. , Wilson D. F. , Dutton P. L.
Published: May 2006

In anaerobic, uncoupled pigeon-heart mitochondria treated with oxidizable substrate, the cytochrome
b
566
remains largely oxidized. In the presence of antimycin A, addition of oxygen induces a reduction of this cytochrome. The rate of cytochrome
b
566
reduction is comparable to and dependent on the rate of cytochrome
c
1
oxidation. Kinetic data suggest that either ubiquinone or another donor of similar potential provides electrons for the reduction of cytochrome
b
566
. It is postulated that the aerobic reduction of cytochrome
b
566
is directly related to the energy conservation at site II.
Early Contact Interactions between Mammalian Gametes
In Vitro:
Evidence That the Vitellus Influences Adherence between Sperm and Zona Pellucida
Authors: Hartmann John F. , Gwatkin Ralph B. L. , Hutchison Cameron F.
Published: May 2006

A study
in vitro
of interactions between gametes of the golden hamster showed that the spermatozoon associates with the zona pellucida, or outer coat of the ovum, by two successive steps termed
attachment
and
binding
. Attachment, apparently the first step in fertilization, is not species-specific; it is insensitive to temperature (2°) and is reversible. Binding, on the other hand, is species-specific, temperature-sensitive, and irreversible. Experiments with isolated zonae pellucidae indicated that the vitellus (cellular portion of the ovum) influences the interaction between the sperm and the zona pellucida by increasing the time required for the sperm to bind. This effect is exerted on the sperm while they are attached to the zona pellucida.
Formation and Decay of Prelumirhodopsin at Room Temperatures
Authors: Busch G. E. , Applebury M. L. , Lamola A. A. , Rentzepis P. M.
Published: May 2006

We have excited detergent-solubilized bovine rhodopsin at room temperature with 530-nm light pulses from a mode locked laser, and have observed the appearance and decay of a transient species that absorbs more strongly at 560 nm than does ground-state rhodopsin. Our data show that the absorbing intermediate appears in a time that is at least as short as the experimental resolution (about 6 psec) and decays with a life time of about 30 nsec. The extremely fast risetime supports the hypothesis that prelumirhodopsin is the product of the primary photoprocess.
Cytochalasin B: Lack of Effect on Mucopolysaccharide Synthesis and Selective Alterations in Precursor Uptake
Authors: Cohn Ronald H. , Banerjee Shib D. , Shelton Earl R. , Bernfield Merton R.
Published: May 2006

Synthesis and secretion of mucopolysaccharide in mouse 3T3 fibroblasts and in embryonic submandibular glands are unaffected by amounts of cytochalasin B that alter the morphology of these cells and tissues. The drug markedly and reversibly inhibits incorporation of [
3
H]glucosamine into mucopolysaccharide by preventing cellular uptake of the precursor, but does not affect incorporation of radiosulfate. Cytochalasin does not alter DNA, RNA, or protein synthesis, but stimulates the uptake of orotic acid and markedly inhibits the uptake of glucose. These selective effects on the transport of small molecules suggest that the primary action of the drug may be on cell membranes. Since processes unrelated to microfilament disruption may be altered by cytochalasin, great caution must be exercised in interpreting studies with the drug.
Dog Homologue of Human β
2
-Microglobulin
Authors: Smithies O. , Poulik M. D.
Published: May 2006

The amino-acid sequence of human β
2
-microglobulin, a protein of 100 residues, is related to parts of the constant region of IgG heavy chain. The dog homologue of human β
2
-microglobulin has now been isolated and its amino-acid sequence has been partially determined. The two proteins (human and dog β
2
-microglobulins) are demonstrably different at only 6 or 7 of the 42 positions examined. Use of the dog should permit experimental investigation of the functional relationships of β
2
-microglobulin to immunoglobulins and the immune system. β
2
-Microglobulin has also been detected in serum from a chimpanzee. The gene for β
2
-microglobulin may correspond to the end portion of an immunoglobulin heavy chain gene.
A Mechanism of Action for Carboxypeptidase A
Authors: Barber Anna K. , Fisher James R.
Published: May 2006

In an attempt to gain a better understanding of the mechanism of action of carboxypeptidase A (EC 3.4.2.1), many kinetic studies have been undertaken using numerous substrates—both esters and peptides—that have exhibited substrate linearity, inhibition, activation, and sigmoid-shaped rate plots. Numerous interpretations of the kinetic data have been proposed, none of which are fully in accord both with kinetic data and x-ray crystallographic studies. Much of the kinetic data has been interpreted using multisite binding while the x-ray information seems to severely restrict these possibilities.

We have examined the feasibility of a simple model with a single active site, without modifier sites, that allows only one substrate molecule to bind the enzyme at a time. A random-pathway model was identified that simultaneously accounts for the nonlinear kinetic data and meets the restrictions imposed by the x-ray crystallographic studies.
Is There a Discriminator Site in Transfer RNA?
Authors: Crothers D. M. , Seno T. , Söll D. G.
Published: May 2006

We determined the nature of the fourth nucleotide from the 3′-end of several
Escherichia coli
tRNAs, and tabulated these results with the same data for all known tRNA sequences. We find a striking constancy of the fourth nucleotide in tRNAs specific for a given amino acid. Furthermore, tRNAs specific for chemically related amino acids are very likely to have the same nucleotide at the fourth position.

One possible explanation for these regularities is the “discriminator” hypothesis: The code by which tRNA is recognized by its cognate aminoacyl-tRNA synthetase is logically hierarchical, with the fourth nucleotide serving as a primary “discriminator” site to subdivide the tRNAs into groups for recognition purposes. Each such group could have its own recognition code, or could be further subdivided by a secondary discriminator site. According to this hypothesis, chemically similar amino acids have the same discriminator nucleotide because they evolved from a single set of related amino acids indistinguishable to a primitive system.

There are other possible explanations for the observed regularities at the fourth nucleotide. For example, it is conceivable that the position is used for a direct physical interaction with the amino acid in the charging process, and chemically similar amino acids naturally select the same nucleotide. Further experiments can be expected to clarify this question.
Processing of Adenovirus RNA Before Release from Isolated Nuclei
Authors: Brunner Michael , Raskas Heschel J.
Published: May 2006

Nuclei isolated from cultured human cells (KB) infected with adenovirus type-2 were used to study events occurring during the adenosine triphosphate-dependent release of viral RNA. When cells were labeled with [
3
H]uridine for 50 min beginning 18 hr after infection, most nuclear viral messenger RNA was in the form of high molecular weight precursors with sedimentation coefficients greater than 28 S. When nuclei were incubated in the presence of ATP and an ATP-generating system, labeled RNA the size of viral mRNA (10-29 S) was released. Cleavage of viral RNA precursor molecules of high molecular weight occurred during incubation of nuclei. The change in size of viral RNA did not require exogenous ATP and occurred before release of RNA from nuclei. This RNA cleavage seems comparable to processing of mRNA
in vivo
, for discrete viral species were produced. Cleavage was completed after 10 min of incubation but was not the rate-limiting step in the release reaction, which required about 20 min for completion.
Quantum Statistical Theory of Rate Processes
Authors: Lin S. H. , Eyring H.
Published: May 2006

A general quantum mechanical approach for treating a great number of rate processes is developed and the temperature dependence of the rate constants is discussed.
Genetics of Somatic Mammalian Cells: Demonstration of a Human Esterase Activator Gene Linked to the AdeB Gene
Authors: Kao Fa-Ten , Puck Theodore T.
Published: May 2006

Prototrophic hybrids formed from an adenine-requiring Chinese hamster cell and human fibroblasts uniformly display new esterase activity that differs from that of either parental cell in electrophoretic mobility and substrate specificity. The hybrids that grew in the selective medium and possessed the new esterase activity had a single extra chromosome that resembled a B-group human chromosome. When clones of such hybrid cells were cultured in nonselective medium, they rapidly reverted to inability to synthesize adenine, disappearance of the new esterase activity, and simultaneous loss of the extra human chromosome. Esterase activity like that of the hybrid is present in cells of various Chinese hamster, but not human, tissues. It is postulated that particular Chinese hamster esterase genes became inactive after longterm cultivation, and that, in the hybrid cell, a human activator gene linked to the adeB gene and located on a human B-group chromosome reactivated expression of these Chinese hamster esterase genes.
Covalent Structure of Bovine Neurophysin-II: Localization of the Disulfide Bonds
Authors: Schlesinger D. H. , Frangione Blas , Walter Roderich
Published: May 2006

The completed amino-acid sequence of bovine neurophysin-II, a major neurohypophyseal hormone-binding protein in the hypothalamo-neurohypophyseal complex of cows, set the stage for the localization of the disulfide bonds of this sulfur-rich molecule. Neurophysin-II was digested with subtilisin or a pepsin-trypsin mixture. The resulting peptides were subjected to first-dimensional electrophoresis at pH 6.5, oxidized with performic acid, and subjected to second-dimensional electrophoresis under identical conditions as the first-dimensional separation, but in a perpendicular direction. Cysteic acid peptides were eluted (several after additional electrophoretic purification at pH 3.5) for amino-acid composition and NH
2
- and COOH-terminal analyses. Our assignment of the seven disulfide bridges present in neurophysin-II is as follows: Cys
10
-Cys
93
; Cys
13
-Cys
95
; Cys
21
-Cys
27
; Cys
28
-Cys
44
; Cys
54
-Cys
61
; Cys
67
-Cys
73
; Cys
74
-Cys
79
. The assignment of disulfide bridges associated with Cys
27
and Cys
28
is tentative as it is derived from evolutionary consideration. The high disulfide content reduces drastically the allowed number of biofunctional conformers of neurophysin-II. It is suggested that neurophysin-II possesses a globular topography with minimal α-helix structure.
Circulation on the Continental Shelf
Authors: Stommel Henry , Leetmaa Ants
Published: May 2006

A simple analysis is presented of a hypothetical shelf-circulation that could apply to the eastcoast continental shelf of North America under winter conditions.
On the Monoheme Character of Cytochromes
c
′
Authors: Kennel S. J. , Meyer T. E. , Kamen M. D. , Bartsch R. G.
Published: May 2006

Interpretations of data bearing on structures of cytochromes
cc
′—a class of variant
c
-type heme proteins from bacteria—in support of a diheme-bearing single chain as a basic structural unit, appear to be invalid in the light of recent studies. These reveal that nearly all members of this class exist as dimers that can be dissociated into, if they do not already exist as, monoheme-bearing monomers. The particular case of the
Chromatium
protein, held to be the source of a peptic-“core” peptide containing two covalently-bonded heme groups, has been re-examined by preparation of tryptic and chymotryptic peptides derived from the heme-bearing region of the protein, as well as by repetition of experiments on peptic digestion, with more rigorous purification of the resultant peptides than was previously done. It is shown that this protein can also be dissociated into identical subunits, bearing a single heme prosthetic group, and accounting essentially for all its heme content. Thus, the previous terminology—cytochromes
cc
′—based on supposition of heme group heterogeneity, is inconsistent with these findings and should be replaced by
cytochromes c
′.
Rapid Axoplasmic Transport of Tyrosine Hydroxylase in Relation to Other Cytoplasmic Constituents
Authors: Jarrott Bevyn , Geffen Laurence B.
Published: May 2006

The transport of norepinephrine and two key enzymes involved in its synthesis, tyrosine hydroxylase (EC 1.14.3a) and dopamine β-hydroxylase (EC 1.14.2.1), has been studied in relation to other axonal constituents in ligated chicken sciatic nerves. Norepinephrine, tyrosine hydroxylase, and dopamine β-hydroxylase activity all increased proximal to the constriction over a 20-hr period. The rate of transport of norepinephrine, tyrosine hydroxylase, and dopamine β-hydroxylase were calculated as 2.6, 1.9, and 3.4 mm/hr, respectively. The only enzyme marker to show a similar rate of accumulation was acetylcholinesterase (EC 3.1.1.7), a putative marker for endoplasmic reticulum. The rapid axoplasmic transport of tyrosine hydroxylase from the cell bodies to the terminals of sympathetic neurons may be adequate to account for the elevated amounts of this enzyme in chronically active axon terminals, without the necessity to invoke peripheral axonal synthesis of the enzyme to explain such elevated amounts.
Induction of Auxotrophic Mutations by Treatment of Chinese Hamster Cells with 5-Bromodeoxyuridine and Black Light
Authors: Chu E. H. Y. , Sun N. C. , Chang C. C.
Published: May 2006

Treatment of an aneuploid Chinese hamster cell line (V79) in tissue culture with 5-bromodeoxyuridine and black light, with or without prior exposure of cells to another mutagen, led to the isolation of auxotrophic mutants, each of which exhibits a specific nutritional requirement for glycine, uridine, purine, or for a combination of glycine, hypoxanthine, and thymidine. 61 mutants that could not use exogenous galactose were also isolated. Thus, this treatment functions as an inductive, but not as a selective, procedure for mutations in mammalian cells.
Stereochemical Control of Valence and Its Application to the Reduction of Coordinated NO and N
2
Authors: Enemark John H. , Feltham Robert D.
Published: May 2006

The electronic structures of transition metal complexes of NO are controlled by the stereochemistry about the metal atom (stereochemical control of valence). The six-coordinate complex,
trans
-[CoNO(NCS)-(C
6
H
4
[As(CH
3
)
2
]
2
)
2
]
+
, consists of [Co(III)-(N=O
-
)]
2+
(angle
Co-N-O
= 135°), while the pentacoordinate trigonal bipyramidal complex, [CoNO(C
6
H
4
[As(CH
3
)
2
]
2
)
2
]
2+
, is best formulated as [Co(I)-(N≡O
+
]
2+
(angle
Co-N-O
= 179°). Evidence indicates that complexes of (NO)
+
and N
2
are electronically similar. Hence, the principles of stereochemical control of valence may be applied to metal complexes of N
2
. In a linearly coordinated M
n
˜m(N≡N) complex, valence electrons can be transferred from the metal to the N
2
ligand producing a bent, protonated, and/or metallated M
n+2
-(N=N
2-
) complex. This reduction of N
2
can be effected by the addition of an appropriate ligand to M or by a change in the coordination geometry about M. Stereo-chemical control of valence leads to the rejection of one of the previously proposed mechanisms for reduction by nitrogenase.
Erythropoietin Production in Cultures of Goat Renal Glomeruli
Authors: Burlington H. , Cronkite Eugene P. , Reincke Ursula , Zanjani Esmail D.
Published: May 2006

Cultures initiated with isolated goat-kidney glomeruli produce erythropoietin over periods of 7 months. Production seems dependent upon a minimum interval of about 30 days between changes of medium. Experiments distinguishing between erythropoietin, renal activator, and serum substrate support the conclusion that the factor released to the medium of long-term glomerular cultures is erythropoietin itself. The system offers promising opportunities for studying regulation of erythropoietin production, and possibly could be developed as a source of significant quantities of the hormone.
Hydrocortisone Induction of Rat-Liver Leucyl-Transfer RNA and Its Synthetases
Authors: Altman Kurt , Southren A. Louis , Uretsky Stanley C. , Zabos Peter , Acs George
Published: May 2006

Within 3 hr after the intraperitoneal administration of hydrocortisone to female rats, a new leucine-accepting tRNA and a new leucyl-tRNA synthetase activity appear in the liver cytosol. The new isoaccepting tRNA can be acylated only with the synthetase derived from livers of hormone-treated animals. Both components are transient; by 12 hr after hydrocortisone administration, the isoaccepting tRNA and its synthetase disappear from livers of treated animals.
Purification and Properties of D Protein: A Transcription Factor of
Escherichia coli
Authors: Ghosh Sudhamoy , Echols Harrison
Published: May 2006

D factor is protein that stimulates DNA transcription
in vitro
by RNA polymerase. For DNA from bacteriophage λ, we present evidence that D protein interacts with DNA to increase the frequency and improve the specificity of initiation by RNA polymerase.
Hilbert Transforms in Yukawan Potential Theory
Authors: Duffin R. J.
Published: May 2006

If
H
denotes the classical Hilbert transform and
Hu
(
x
) =
v
(
x
), then the functions
u
(
x
) and
v
(
x
) are the values on the real axis of a pair of conjugate functions, harmonic in the upper half-plane. This note gives a generalization of the above concepts in which the Laplace equation Δ
u
= 0 is replaced by the Yukawa equation Δ
u
= μ
2
u
and in which the Cauchy-Riemann equations have a corresponding generalization. This leads to a generalized Hilbert transform
H
μ
. The kernel function of this new transform is expressable in terms of the Bessel function
K
0
. The transform is of convolution type.
Occurrence of Uridylate-Rich Oligonucleotide Regions in Heterogeneous Nuclear RNA of HeLa Cells
Authors: Molloy G. R. , Thomas W. L. , Darnell J. E.
Published: May 2006

Heterogeneous nuclear RNA molecules from HeLa cells contain a specific segment of about 30 nucleotides length that is largely (about 80%) uridylic acid. This oligo(U) segment is located predominantly in the larger (70S-90S) heterogeneous nuclear RNA molecules, and is essentially absent in messenger RNA and 45S ribosomal precursor RNA molecules. The oligo(U) hybridizes rapidly to cellular DNA, suggesting that it is transcribed from the repeated regions of the DNA.
Isolation by Covalent Affinity Chromatography of the Penicillin-Binding Components from Membranes of
Bacillus subtilis
Authors: Blumberg Peter M. , Strominger Jack L.
Published: May 2006

An affinity chromatography technique was developed to isolate the five penicillin-binding components present in
Bacillus subtilis
membranes. The proteins were solubilized by the detergent Nonidet P-40, bound covalently to penicillin-substituted Sepharose, and subsequently eluted from the matrix with neutral hydroxylamine, which cleaves the penicilloyl-enzyme bond. Penicillin binding-component V, the D-alanine carboxypeptidase, makes up 1% of the total membrane protein. A modification of the above procedure enabled this enzyme to be obtained from the membrane in pure form in a single step with 50% overall recovery of enzymatic activity.
Molecular Buoyancy and Osmotic Equilibrium
Authors: Perez M. , Scholander P. F.
Published: May 2006

Measurements of osmotic equilibrium of colloidal solutions, ranging from 170,000 to 20,000 in molecular weight, show that the negative buoyancy of the solute molecules is additive to the osmotic pressure. Seen together with earlier measurements of positive buoyancy of oil suspensions, these data confirm that the osmotic interaction between solute and solvent at equilibrium is purely a force-coupling at the free surface.
The Maintenance of Transferrin Polymorphism in Pigeons
Authors: Frelinger Jeffrey A.
Published: May 2006

Transferrin, a nonheme iron-binding protein, is polymorphic in most vertebrate species that have been examined. In pigeons, it is controlled by an autosomal gene, with two known codominant alleles,
Tf
A
and
Tf
B
. The two alleles are found in nearly equal frequencies and the three genotypes are at Hardy-Weinberg equilibrium in all populations studied. This report shows that ovotransferrins from heterozygous females inhibit microbial growth, by use of yeast as an assay organism, better than ovotransferrins from either of the homozygous types, or those from a mixture of homozygous types. Heterozygous females hatch a larger percentage of their eggs than homozygous females. This difference is probably accounted for by the transferrin effect. The failure of the mixture of the homozygous types to act like the heterozygous type calls into question the currently accepted structure of transferrin as a monomeric protein. The greater fecundity of heterozygous females can account for the maintenance of transferrin polymorphism in pigeons.
Human Placental 15-Hydroxyprostaglandin Dehydrogenase
Authors: Jarabak Joseph
Published: May 2006

Normal, term, human placentas are a rich source of a 15-hydroxyprostaglandin dehydrogenase. The enzyme is extremely labile, and partial purification could be achieved only after stabilization with glycerol. The instability of the enzyme and its
K
m
for NAD are indications that it is different from the 15-hydroxyprostaglandin dehydrogenase isolated from swine lung. Human placental tissue should provide a very useful source from which large amounts of highly purified 15-hydroxyprostaglandin dehydrogenase may be obtained.