bluuebunny/crossref_metadata_2025 huggingface dataset:
Interrupting Reperfusion as a Stroke Therapy: Ischemic Postconditioning Reduces Infarct Size after Focal Ischemia in Rats
Authors: Zhao Heng , Sapolsky Robert M , Steinberg Gary K
Published: May 2006

Cerebral ischemic preconditioning protects against stroke, but is clinically feasible only when the occurrence of stroke is predictable. Reperfusion plays a critical role in cerebral injury after stroke; we tested the hypothesis that interrupting reperfusion lessens ischemic injury. We found for the first time that such postconditioning with a series of mechanical interruptions of reperfusion significantly reduces ischemic damage. Focal ischemia was generated by permanent distal middle cerebral artery (MCA) occlusion plus transient bilateral common carotid artery (CCA) occlusion. After 30 secs of CCA reperfusion, ischemic postconditioning was performed by occluding CCAs for 10 secs, and then allowing for another two cycles of 30 secs of reperfusion and 10 secs of CCA occlusion. Infarct size was measured 2 days later. Cerebral blood flow (CBF) was measured in animals subjected to permanent MCA occlusion plus 15mins of bilateral CCA occlusion, which demonstrates that postconditioning disturbed the early hyperemia immediately after reperfusion. Postconditioning dose dependently reduced infarct size in animals subjected to permanent MCA occlusion combined with 15, 30, and 60 mins of bilateral CCA occlusion, by reducing infarct size approximately 80%, 51%, and 17%, respectively. In addition, postconditioning blocked terminal deoxynucleotidyl transferase-mediated uridine 5′-triphosphate-biotin nick end labeling-positive staining, a marker of apoptosis, in the penumbra 2 days after stroke. Furthermore, in situ superoxide detection using hydroethidine suggested that postconditioning attenuated superoxide products during early reperfusion after stroke. In conclusion, postconditioning reduced infarct size, most plausibly by blocking apoptosis and free radical generation. With further study it may eventually be clinically applicable for stroke treatment.
Ellipsometric identification of collective optical properties of silver nanocrystal arrays
Authors: Wormeester Herbert , Henry Anne-Isabelle , Kooij E. Stefan , Poelsema Bene , Pileni Marie-Paule
Published: May 2006

The optical properties of silver nanocrystal arrays are investigated using spectroscopic ellipsometry in combination with polarized reflection measurements. Analysis of the ellipsometry and reflectometry spectra in terms of the “thin island film” theory enables a transparent identification of the contribution of collective effects to the optical response. Negligible image charge effects imply that only dipole contributions have to be considered. The interactions between the hexagonally ordered silver nanocrystals give rise to an effective modification of the spherical response to oblate entities with different polarizabilities parallel and perpendicular to the substrate, expressed in terms of corresponding depolarization factors. The effect of nanocrystal ordering, nearest-neighbor distance, size distribution, surrounding ambient, and the optical properties of the single nanocrystals on the optical response are analyzed. The extent of plasmon resonance peak splitting as a function of surface coverage is discussed.
Probabilistic analysis of tetrahedral carbon hybridization in amorphous carbon films
Authors: Wan D. , Komvopoulos K.
Published: May 2006

An energetic particle collision analysis of the effect of Ar+ ion bombardment on tetrahedral carbon hybridization (sp3) in amorphous carbon (a-C) thin films is presented for nonmagnetron radio-frequency sputtering. The analysis is based on sequential surface events involving the collision of Ar+ ions with carbon atoms on the surface of the growing film and subsequent collision cascades between excited carbon atoms and other surface carbon atoms, which promote the formation of sp3 carbon bonding. The model is validated by transmission electron and electron energy loss spectroscopy results that confirm the existence of a two-layer film structure consisting of an ultrathin interface layer and a continuous a-C film. Analytical results for the sp3 carbon content are shown to be in good agreement with similar experimental results obtained from the analysis of the C1s core level spectra of the sputtered a-C films.
Realization of freestanding InP membranes on Si by low-temperature wafer bonding and stress analysis using micro-Raman spectroscopy
Authors: Arokiaraj J. , Tripathy S. , Vicknesh S. , Ramam A.
Published: May 2006

We present a method to realize freestanding InP membranes on Si substrate by combination of low-temperature wafer bonding, layer transfer, and wet chemical release processes. The removal of InP substrate and sacrificial etching of an InGaAs layer defines the 2.0μm InP thin layer bonded to Si. The InP membranes are subsequently released by a two-step wet etching process and the surface stress profiling in these freestanding membranes has been carried out by high spectral resolution micro-Raman measurements. Realization of such micromechanical structures on Si platform would be suitable for the integration of InP-based photonic devices on large area Si-based microelectronic systems.
Experimental demonstration of negative index of refraction
Authors: Zhou Jiangfeng , Koschny Thomas , Zhang Lei , Tuttle Gary , Soukoulis Costas M.
Published: May 2006

We introduce an improved and simplified structure made of periodic arrays of pairs of H-shaped metallic wires that offer a potentially simpler approach in building negative-index materials. Using simulations and microwave experiments, we have investigated the negative-index n properties of these structures. We have measured experimentally both the transmittance and the reflectance properties and found unambiguously that a negative refractive index with Re(n)<0 and Im(n)<Re(n). The same is true for ε and μ. Our results show that H-shaped wire pairs can be used very effectively in producing materials with negative refractive indices.
Trapping of Pd, Au, and Cu by implantation-induced nanocavities and dislocations in Si
Authors: Brett D. A. , Llewellyn D. J. , Ridgway M. C.
Published: May 2006

The gettering of metallic impurities by nanocavities formed in Si is a topic of both scientific importance and technological significance. Metallic precipitates observed in the regions where nanocavities were formed have been considered the result of the metal filling the nanocavities, either as elemental metal or a silicide phase. However, our transmission electron microscopy observations demonstrate that many of these precipitates are concentrated along dislocations, rather than randomly distributed as expected for precipitates formed by the filling of nanocavities. Consequently, the gettering contribution of dislocations in the lattice caused by nanocavity formation must be considered. For Pd, dislocations are the preferred sites for the precipitation of the metal silicide. We compare results of gettering by nanocavities and dislocations for Pd, Au, and Cu to determine which structure is the dominant influence for the formation of precipitates of these metals and/or their silicides.
Simultaneous determination of apparent tortuosity and microstructure length scale and shape: Application to rigid open cell foams
Authors: Gómez Álvarez-Arenas T. E. , de la Fuente S. , González Gómez I.
Published: May 2006

A novel experimental technique based on phase spectroscopy and through transmission of high-frequency airborne ultrasonic pulses is used to study rigid open cell foams. Phase velocity shows an anomalous relaxation like behavior which is attributed to a frequency variation of the apparent tortuosity. An explanation is proposed in terms of the relationship between the different length scales involved: microstructure and macroscopic behavior. The experimental technique together with the proposed apparent tortuosity scheme provides a novel and unique procedure to determine simultaneously tortuosity and characteristic length dimension and shape of the solid constituent of foams and porous materials in general.
INSULIN BIOSYNTHESIS IN THE RAT: DEMONSTRATION OF TWO PROINSULINS
Authors: Clark Jeffrey L. , Steiner Donald F.
Published: May 2006

Proinsulin, a single-chain precursor of insulin, has been detected in biosynthetic studies
in vitro
,
1-4
and in crystalline preparations of insulin from several species.
1, 5-7
It appears that proinsulin normally serves neither as a major storage nor secretory form of the hormone.
8
Its primary functions seems to be to facilitate the efficient formation of the disulfide bonds of insulin.
9

Although several species of fish have two insulins differing slightly in primary structure,
10-12
the rat is the only mammal where this is known to be the case.
13, 14
As the two rat insulins are nonallelic
14
and presumably coded by two distinct genes, a separate proinsulin would be expected to precede each insulin. We have demonstrated the biosynthesis of both insulins
15
and of a proinsulin corresponding to each in isolated islets of Langerhans, and have detected probable intermediates in the conversion of these proinsulins to insulin. Labeled peptide material corresponding to the free connecting segment of proinsulin (C-peptide) was detected in insulin-containing fractions isolated from incubated rat islets.

It was noted that islets incubated
in vitro
secreted small amounts of
newly synthesized
proinsulin as well as the two insulins and essentially equivalent amounts of C-peptide. Increasing the glucose content of the medium selectively enhanced the incorporation of radioactivity into proinsulin and insulin and also seemed to increase the relative proportion of labeled proinsulin appearing in the medium.
THE EFFECT OF PRESSURE ON THE OXIDATION STATE OF IRON, IV. THIOCYANATE AND ISOTHIOCYANATE LIGANDS
Authors: Fung S. C. , Drickamer H. G.
Published: May 2006

The effect of pressure on the Mössbauer resonance spectra of Fe(III) with thiocyanate (M-SCN) and isothiocyanate (M-NCS) ligands has been studied. Fe(NCS)
3
·6H
2
O, which has the isothiocyanate structure, reduces with increasing pressure, reversibly, and with a pressure dependence for the conversion very similar to that shown by a wide variety of ionic ferric compounds. K
3
Fe(SCN)
6
has the thiocyanate structure. At low pressures, it exhibits a significantly larger reduction than the Fe(NCS)
3
. With increasing pressure the thiocyanate complexes isomerize, each complex apparently exhibiting about the same degree of conversion at a given pressure. At 150 kb the isomerization is essentially complete. The reduction of the Fe(III) to Fe(II) is reversible but the isomerization is not, and the sample, when powdered and reloaded in the high-pressure cell, exhibits the isomer shift, quadrupole splitting, and Fe(III) to Fe(II) conversion characteristic of an isothiocyanate. Heating the thiocyanate to 110°C at 5 kb yields a mixture of thiocyanate and isothiocyanate that converts with pressure completely to the isothiocyanate.
FATIGUE CRACK NUCLEATION IN METALS
Authors: Lin T. H. , Ito Y. M.
Published: May 2006

One of the unanswered questions in the study of fatigue is how cracks nucleate at stresses far below the static fracture strength. Previous theories show possible qualitative mechanisms that may operate in a crystal at room and low temperatures but none provides a quantitiative theory of this phenomenon. We show here a quantitative mechanism of fatigue crack initiation.

With a small initial stress field, two closely located thin slices slide in opposite directions under cyclic loading. The increase of the local plastic strain with cycles of loading is calculated. The local plastic shear strain, positive in one slice and negative in the other, reaches 100 per cent at the free surface in a few hundred cycles. These large strains clearly cause the start of an extrusion or intrusion and fatigue crack nucleation.
SYNTHESIS OF PHAGE-SPECIFIC α- AND β-GLUCOSYL TRANSFERASES DIRECTED BY T-EVEN DNA
in vitro
Authors: Gold Lawrence M. , Schweiger Manfred
Published: May 2006

—Bacteriophage T4 DNA, when added to a ribonucleic acid- and protein-synthesizing system from uninfected
Escherichia coli
, directed the
in vitro
synthesis of virus-specific glucosyl transferases.

The T4-specific α- and β-glucosyl transferases are synthesized
in vivo
early after infection, and function to glucosylate the hydroxymethylcytosine residues of phage DNA. The
in vitro
glucosyl transferase synthesis was dependent upon transcription of T4 DNA, as well as upon protein synthesis. DNA from T4 mutants unable to induce glucosyl transerases failed to induce enzyme formation
in vitro
, although protein synthesis was unimpaired.
SUPERCOILED CIRCULAR DNA-PROTEIN COMPLEX IN
Escherichia coli
: PURIFICATION AND INDUCED CONVERSION TO AN OPEN CIRCULAR DNA FORM
Authors: Clewell Don B. , Helinski Donald R.
Published: May 2006

The 23
S
twisted circular form of
Col
E
1
DNA has been isolated from
Escherichia coli
as a tightly associated DNA-protein complex with a sedimentation coefficient of approximately 24
S
. Treatment of this complex with pronase, trypsin, sodium dodecyl sulfate, Sarkosyl, or heat results in a conversion to a slower sedimenting form of 17
S
or 18
S
, as determined by centrifugation in neutral sucrose gradients. These treatments do not alter the sedimentation properties of noncomplexes supercoiled
Col
E
1
DNA even in the presence of the
Col
E
1
-protein complex. Electron microscopic analyses indicate that the decrease in sedimentation rate of the
Col
E
1
-protein complex after treatment with these various agents is largely owing to an induced transition of
Col
E
1
DNA from the supercoiled to the open circular state.
CALORIMETRIC EVIDENCE FOR THE LIQUID-CRYSTALLINE STATE OF LIPIDS IN A BIOMEMBRANE
Authors: Steim Joseph M. , Tourtellotte Mark E. , Reinert Joe C. , McElhaney Ronald N. , Rader Richard L.
Published: May 2006

Both membranes of
Mycoplasma laidlawii
and water dispersions of protein-free membrane lipids exhibit thermal phase transitions that can be detected by differential scanning calorimetry. The transition temperatures are lowered by increased unsaturation in the fatty acid residues, but in each case they are the same for membranes and lipids. The transitions resemble those observed for synthetic lipids in the lamellar phase in water, which arise from melting of the hydrocarbon chains within the phospholipid bilayers. Such melts are cooperative phenomena and would be greatly perturbed by apolar binding to protein. Thus the identity of membrane and lipid transition temperatures suggests that in the membranes, as in water, the lipids are in the bilayer conformation in which the hydrocarbon chains associate with each other rather than with proteins. Observations of morphological changes indicate that osmotic imbalance occurs when the membrane transition temperature exceeds the growth temperature, and that for transport processes to function properly the hydrocarbon chains must be in a liquid-like state.
ON THE DECOMPOSITION OF STRESS AND STRAIN TENSORS INTO SPHERICAL AND DEVIATORIC PARTS
Authors: Augusti G. , Martin J. B. , Prager W.
Published: May 2006

It is well known that Hooke's law for a linearly elastic, isotropic solid may be written in the form of two relations that involve only the spherical or only the deviatoric parts of the tensors of stress and strain. The example of the linearly elastic, transversely isotropic solid is used to show that this decomposition is not, in general, feasible for linearly elastic, anisotropic solids. The discussion is extended to a large class of work-hardening rigid, plastic solids, and it is shown that the considered decomposition can only be achieved for the incompressible solids of this class.
ON THE BEHAVIOR OF A CAPILLARY SURFACE IN A WEDGE
Authors: Concus Paul , Finn Robert
Published: May 2006

Estimates above and below are obtained for the height of the equilibrium free surface of a liquid when the liquid partially fills a cylindrical container whose cross section contains a corner with interior angle 2α. The surface is characterized by the condition that its mean curvature be proportional to its height above a reference plane (or, in the case of zero gravity, that the mean curvature be constant), and by the requirement that it meet the container wall with prescribed contact angle γ. It turns out that the qualitative behavior of such a surface near the vertex changes markedly, according as α + γ < ½π, or α + γ ≥ ½π. In the former case, the surface is either unbounded or fails to exist, while in the latter case every such surface is bounded. Some experimental comparisons are indicated, and an application to the problem of describing the mechanism of water rise in trees is discussed.

The above results describe a limiting case among corresponding properties that hold for surfaces defined over domains with smooth boundaries. This extension is indicated, as well as a formal extension to
n
-dimensional surfaces; here the interest centers on the fact that it is the mean curvature of an (
n
-1)-dimensional boundary element that controls the local behavior of the
n
-dimensional solution surface.
XERODERMA PIGMENTOSUM: A HUMAN DISEASE IN WHICH AN INITIAL STAGE OF DNA REPAIR IS DEFECTIVE
Authors: Cleaver J. E.
Published: May 2006

Homozygous xeroderma pigmentosum fibroblasts cannot repair damage to DNA bases, but can repair damage that involves chain breaks. In xeroderma pigmentosum, therefore, there is a defect in an early step in repair at which base damage is recognized and the polynucleotide chain broken enzymatically (by an endonuclease). Heterozygous fibroblasts repair base damage to normal extents. Carcinogenesis in xeroderma pigmentosum, and perhaps in some normal individuals, may be the result of somatic mutations caused by unrepaired damage.
ON THE MECHANISM OF ACTION OF ADRENOCORTICOTROPIC HORMONE: THE BINDING OF CYCLIC-3′,5′-ADENOSINE MONOPHOSPHATE TO AN ADRENAL CORTICAL PROTEIN
Authors: Gill Gordon N. , Garren Leonard D.
Published: May 2006

The binding of cyclic 3′,5′-adenosine monophosphate (cyclic AMP) within the adrenal cortical cell was studied. Cyclic AMP binds specifically to a protein which is associated predominantly with the microsomal fraction of the cell.

The binding protein was purified approximately 100-fold.
ADAPTIVE SIGNIFICANCE OF PIGMENT POLYMORPHISMS IN COLIAS BUTTERFLIES, II. THERMOREGULATION AND PHOTOPERIODICALLY CONTROLLED MELANIN VARIATION IN
Colias eurytheme
Authors: Watt Ward B.
Published: May 2006

The butterfly
Colias eurytheme
requires body temperatures above 30°C for flight. When cold, it orients its exposed wing undersides to present maximum surface area to sunlight; when too warm, it orients for minimum exposure. Dark-winged color forms heat faster in sunlight than light ones. The seasonal color polymorphism of
Colias
appears to have been evolved to maximize solar heating in cold seasons and minimize overheating in warm seasons.
AMINO ACID SEQUENCE RESTRICTION IN RABBIT ANTIBODY LIGHT CHAINS
Authors: Hood Leroy , Lackland Henry , Eichman Klaus , Kindt Thomas J. , Braun Dietmar G. , Krause Richard M.
Published: May 2006

Light chains were obtained from IgG rabbit antibodies to the group-specific carbohydrates of groups A and C streptococci. An analysis of the amino acid alternatives which exist at the first three positions of the N-terminus in both light-chain preparations shows a marked restriction in amino acid sequence heterogeneity when compared with preimmune light chains. Both of these related, but immunologically distinct, antigenic determinants select the same uncommon subpopulation of rabbit light chains.
Na
+
-FACILITATED REACTIONS OF NEUTRAL AMINO ACIDS WITH A CATIONIC AMINO ACID TRANSPORT SYSTEM
Authors: Christensen Halvor N. , Handlogten Mary E. , Thomas Edwin L.
Published: May 2006

The predominant basis for transport interactions between neutral and cationic amino acids in the Ehrlich ascites-tumor cell and the rabbit reticulocyte has been identified as a reaction of the neutral amino acid plus Na
+
with the cationic amino acid transport system. This reaction is revealed both by a Na
+
-dependent transport inhibition by the neutral amino acid, and by mutual flux accelerations whereby the neutral amino acid and Na
+
exchange for the cationic amino acid.
A MOLECULAR TIME SCALE FOR HUMAN EVOLUTION
Authors: Wilson A. C. , Sarich V. M.
Published: May 2006

We discuss published molecular evidence concerning the relationship of man to African apes and Old World monkeys. Quantitative comparisons of their serum albumins, transferrins, hemoglobins, and DNA show that man is genetically much more similar to the African apes than to the Old World monkeys.

The amino acid sequences of hemoglobins from humans, chimpanzees, gorillas, and rhesus monkeys are consistent with the hypothesis that the probability of an amino acid substitution occurring in a given interval of time is the same for every hemoglobin lineage. This allows the use of these data as a hemoglobin evolutionary clock, just as we have previously done with the albumins. It is shown that concordance exists between the hemoglobin and albumin results and that both support the suggestion that the human lineage diverged from that leading to the African apes far more recently than is generally supposed. Considering both the albumin and hemoglobin data, we would set the most probable date at 4 to 5 million years.
THE EFFECTS OF CENTRALLY ACTING DRUGS ON TREMOR IN MONKEYS WITH MESENCEPHALIC LESIONS
Authors: Goldstein M. , Battista A. F. , Nakatani S. , Anagnoste B.
Published: May 2006

The effects of centrally acting drugs on tremor were investigated in monkeys with ventromedial tegmental lesions exhibiting hypokinesia or hypokinesia and tremor. In monkeys with resting tremor, the administration of DL-5-HTP (5-hydroxytryptophan) or of DL-DOPA (3,4-dihydroxyphenylalanine) relieves the tremor, but the simultaneous administration of DL-5-HTP or DL-DOPA and atropine results in a much more pronounced relief. These results point to an imbalance between the cholinergic and adrenergic-serotonergic systems in parkinsonism.

In monkeys exhibiting hypokinesia, the administration of harmaline evokes a marked resting tremor of the extremities contralateral to the tegmental lesion. The production of tremor by harmaline is not abolished by lowering the striatal amine levels with specific inhibitors of amine synthesis. Administration of DL-5-HTP protects monkeys from tremors induced by harmaline, which might affect the functions of the central nervous system by interaction with receptors for serotonin. The present results further demonstrate the apparent role of biogenic amines in the extrapyramidal dysfunctions.
OXIDATIVE PHOSPHORYLATION: THERMODYNAMIC CRITERIA FOR THE CHEMICAL AND CHEMIOSMOTIC HYPOTHESES
Authors: Caplan S. R. , Essig A.
Published: May 2006

Oxidative phosphorylation is analyzed by means of nonequilibrium thermodynamics. It is shown that a mitochondrial system may be characterized in terms of the externally fixed affinities (negative free energies) for oxidation and phosphorylation

A
o
ex

and

A
p
ex

, without knowledge of internal activities. If the electrochemical potential difference of H
+
is also fixed, a decision can be made between the chemiosmotic and chemical hypotheses. The chemiosmotic hypothesis is shown to be a limiting case of the chemical hypothesis. In general the
P
/
O
ratio cannot be expected to be constant, but will vary with

A
p
ex

/

A
o
ex

; for certain ranges the variation may be marked.
ON THE BIOSYNTHESIS AND STRUCTURE OF DOUBLE-STRANDED RNA IN VACCINIA VIRUS-INFECTED CELLS
Authors: Duesberg P. H. , Colby C.
Published: May 2006

The virus-specific, RNase-resistant RNA appearing in vaccinia virus-infected cells was directly shown to be an RNA duplex. After its melting and subsequent banding on Cs
2
SO
4
or incubation with DNase, the RNA could be reannealed and then hybridized with vaccinia virus DNA.

The double-stranded virus-specific RNA appears to exist in the cell in the form of heterogeneous partially double-stranded RNA's sedimenting between 9 and 22
S
. The kinetics of the appearance of the double-stranded RNA in the cell show a dependence on the multiplicity of infection and suggest that the double-stranded RNA is a “late” product of viral intracellular biosynthesis. The synthesis of the double-stranded RNA is inhibited by actinomycin D.
CONTROL OF GENE ACTIVITIES IN THE POLYTENE CHROMOSOMES OF
Chironomus tentans
BY ECDYSONE AND JUVENILE HORMONE
Authors: Lezzi Markus , Gilbert Lawrence I.
Published: May 2006

The injection of ecdysone (molting hormone) into chironomid larvae is known to result in the stimulation of specific gene activities (increased RNA synthesis). The morphological manifestation of this gene activation is the formation of a puff. Cytological and autoradiographic analysis of several regions of the salivary gland chromosomes of
Chironomus tentans
revealed that ecdysone also stimulates Balbiani ring 1. In contradistinction to the puffs, the Balbiani rings are tissue specific and account for a significant percentage of the cell's non-nucleolar RNA.

The application of juvenile hormone results in a decreased activity of Balbiani ring 1, suggesting that the two hormones may act antagonistically. In addition, juvenile hormone induces a puff at chromosome region I-19-A and this puff becomes less active after a short-term treatment with ecdysone. These data demonstrate an effect of juvenile hormone on puffing and are the first to demonstrate activation of a Balbiani ring by ecdysone.
STUDIES ON THE PROTEINS OF ΦX174, II. THE PROTEIN COMPOSITION OF THE ΦX COAT
Authors: Burgess Ann B.
Published: May 2006

In order to determine the composition of the ΦX174 coat, ΦX particles labeled in most of the amino acids have been dissociated, and the proteins separated by electrophoresis on polyacrylamide gels. The molar ratios of the four proteins calculated from the fraction of radioactivity in each peak and the molecular weights of the individual proteins suggest that the capsid is composed of 60 molecules of the 48,000 daltons protein and that each of the 12 spikes is composed of one molecule of the 36,000 daltons protein and five each of the 19,000 and 5,000 daltons proteins.
AMINO ACID SEQUENCE OF SALMON ULTIMOBRANCHIAL CALCITONIN
Authors: Niall H. D. , Keutmann H. T. , Copp D. H. , Potts J. T.
Published: May 2006

Salmon ultimobranchial calcitonin has been isolated and rendered pure, as demonstrated by several chemical criteria. Its amino acid sequence was determined by means of manual Edman degradation of the intact molecule and of several peptide subfragments. Results of automated degradation provided confirmation of the structure. The salmon molecule possesses, in common with other calcitonins, a 32-amino acid peptide chain terminating in prolinamide and containing half-cystine residues at positions 1 and 7. Although the sequence of the salmon hormone differs considerably from that of the porcine, bovine and human calcitonins, the four hormones are homologous in 9 of 32 positions. The much higher biological potency possessed by the salmon calcitonin makes it of particular interest for future structure function studies.
SPECIES PACKING, AND WHAT COMPETITION MINIMIZES
Authors: Arthur Robert Mac
Published: May 2006

Species competing exclusively for renewing resources are shown to obey simultaneous differential equations equivalent to the conditions for minimizing a certain quadratic form. In this sense competition acts to select species abundances giving the best least-squares fit in an expression [Formula: see text] Thus the number of species which can coexist competitively is limited mostly by the inequality of the interspecies competition coefficients and not appreciably by their magnitude. Seasonality and number of resources become the main factors limiting the number of coexisting species.
Nuclear Magnetic Resonance Spectroscopy:
13
C Spectra of Some Common Nucleotides
Authors: Dorman Douglas E. , Roberts John D.
Published: May 2006

Natural-abundance
13
C nuclear magnetic resonance spectra of ten common nucleotides in neutral, aqueous solutions have been determined and interpreted. The spectra of two of these substances were also determined in acidic solutions, and several of the carbon chemical shifts were found to depend markedly on pH. Within the limited range of concentrations employed, there were observed no carbon chemical-shift changes which could be ascribed to base-stacking or base-pairing phenomena.
Hemizygous Expression of Glucose-6-Phosphate Dehydrogenase in Erythrocytes of Heterozygotes for the Lesch-Nyhan Syndrome
Authors: Nyhan William L. , Bakay Bohdan , Connor James D. , Marks James F. , Keele Doman K.
Published: May 2006

In women heterozygous for hypoxanthine guanine phosphoribosyl trasferase deficiency, the activity of this enzyme in the erythrocyte is usually normal. In a key kindred two such obligate heterozygotes were also heterozygous for glucose-6-phosphate dehydrogenase types
A
and
B
. The
AB
genotype was confirmed in one by assay of skin fibroblasts. Erythrocytes were exclusively of type
B
. These observations suggest the clonal origin of the hematopoietic system in these women from a primordial cell line with a single active
X
chromosome.
Oxygen-Collagen Priority and the Early Metazoan Fossil Record
Authors: Towe Kenneth M.
Published: May 2006

The thesis is developed that a low oxygen level Precambrian atmosphere presented early-evolving metazoan organisms with physiological connective tissue priorities resulting from the important molecular oxygen requirements in the biosynthesis of collagen hydroxyproline. Shells, cuticles, and carapaces which are not mandatory metazoan prerequisites but which directly or indirectly demand substantial connective tissue collagen are oxygen expensive, low priority features. A marked increase in atmospheric oxygen level near the beginning of the Paleozoic would eliminate oxygen-collagen priorities simultaneously and on a world-wide basis in all metazoan stocks providing evolutionary pressure for enlarged musculatures and associated „hard parts.” This could explain the sudden presence in the fossil record of the early Cambrian of advanced and diversified metazoans, the earlier forms of which were essentially unpreservable.
Dynamics of Systems with Large Number of Degrees of Freedom and Generalized Transformation Theory
Authors: Prigogine I. , George C. , Henin F.
Published: May 2006

A generalized transformation theory which leads to a non-Hamiltonian description of dynamics is introduced. The transformation is such that all averages of observables remain invariant. However, the time evolution of the density matrix can no longer be expressed in terms of a commutator with the Hamiltonian. Therefore such transformations are not canonical in the usual sense. An explicit „two components” representation of the equations of motion is given which has the following properties: (
a
) each of the components satisfies a separate equation of motion, and (
b
) one component satisfies a kinetic equation of a generalized Boltzmann type.

We obtain, therefore, the most remarkable result that the relation between dynamics and statistical mechanics (or thermodynamics) takes a specially transparent and simple form: thermodynamics appears in a precise sense as the random phase approximation of dynamics.

Other problems such as the meaning of diagonalization of the Hamiltonian and definition of excitations will be treated in a forthcoming paper.
Retrograde Amnesia Gradients by Subconvulsive and High Convulsive Transcranial Currents in Chicks
Authors: Lee-Teng Evelyn
Published: May 2006

Either a subconvulsive or a high convulsive current was delivered transcranially at various intervals after a learning trial to independent groups of newly hatched chicks. The one-trial learning involves suppression of the chicks' predilection to peck at a small shiny bead. The effect of current on retention was measured one day later. Results indicate a current-sensitive memory consolidation period of about 30 seconds that cannot be appreciably prolonged by a tenfold increase in current intensity and a simultaneous twofold increase in current duration. On the other hand, at comparable trial-to-current intervals within this brief consolidation period, more retention deficit was caused by the higher current. Beyond this critical period, both currents still effected some retention deficit, but it did not seem to vary with the trial-to-current interval from one minute to 24 hours. Overt muscular convulsion was unnecessary for the retrograde amnesia effect. The subconvulsive current may be a more pure agent for consolidation studies because the high, convulsive current may affect test performance in ways other than disrupting the consolidation processes.
Brain-Cell Protein Synthesis Specifically Related to Learning
Authors: Hydén H. , Lange P. W.
Published: May 2006

The study takes up the problem whether synthesis of certain protein fractions in nerve cells of the hippocampus in rats during the transfer of handedness may be specific for this learning process. Electrophoretic separation of protein was carried out on polyacrylamide gels at the microscale. The investigation encompasses the brain-specific, acidic protein S100 and two protein fractions moving close to the S100 protein during electrophoresis. The protein synthesis was studied during one month of intermittent training of the animals.

The temporal link between behavior and an increase in the synthesis of nerve-cell protein indicates that the protein response is specific for the processes occurring in the hippocampus during learning.
Unified Theory for Gel Electrophoresis and Gel Filtration
Authors: Rodbard David , Chrambach Andreas
Published: May 2006

Unified theory for gel electrophoresis and gel filtration:
The behavior of macromolecules in gel filtration and gel electrophoresis may be predicted from Ogston's model for a random meshwork of fibers. This model has been generalized to apply to nonspherical molecules and to several gel types. The model provides equations for inter-relationships between mobility, partition coefficient, gel concentration, and molecular radius; it gives a non-Gaussian distribution of pore sizes as a function of gel concentration. The theory defines conditions for optimal separation and optimal resolution in gel filtration and gel electrophoresis. The difference in resolving power between the two fractionation methods is accounted for by the fact that gel filtration is a form of partition chromatography.
Immunochemical Measurement of Double-stranded RNA of Uninfected and Arbovirus-Infected Mammalian Cells
Authors: Stollar Victor , Stollar B. David
Published: May 2006

A quantitative complement fixation assay which specifically measures double-stranded RNA has been used to study this RNA extracted from uninfected and arbovirus-infected cells. The double-straned RNA of the uninfected BHK-21 cells sedimented in the 12
S
region in sucrose gradients. The double-stranded RNA of Sinbis virus-infected cells, as measured immunochemically, included a predominant peak at 12
S
, a smaller 18
S
peak, and polydisperse material extending into the 26-30
S
region. All classes of this RNA detected immunochemically showed a sharp thermal denaturation curve, and increased in amount progressively during infection, with the 12
S
peak predominant at all times.
Globoid Cell Leucodystrophy (Krabbe's Disease): Deficiency of Galactocerebroside β-Galactosidase
Authors: Suzuki Kunihiko , Suzuki Yoshiyuki
Published: May 2006

Profound deficiency of a specific enzyme, galactocerebroside β-galactosidase, has been demonstrated in the brains, liver, and spleen of three patients with Krabbe's globoid cell leucodystrophy. The activity of this enzyme was normal in a variety of other cerebral diseases, including those with similarly devasted white matter. The lack of enzyme activity was not due to an inhibitor in the tissue, nor is it due to a shift in the pH optimum. The deficiency of galactocerebroside β-galactosidase as the primary enzymatic defect can account for the morphological and biochemical characteristics of this disease better than the previously reported deficiency of cerebroside-sulfatide sulfotransferase.
Isolation, Characterization, and Location of a Donor-Acceptor Unit from Cross-Linked Fibrin
Authors: Chen Renné , Doolittle Russell F.
Published: May 2006

The cross-linking systems of bovine and human fibrins were studied by the introduction of a radioactive substitute donor as an inhibitor of fibrin cross-linking, separation of the constituent polypeptide chains after sulfitolysis, and tryptic digestion of the labeled γ-chains. The information gathered from this approach enabled us to isolate and characterize the complete donor-acceptor unit in tryptic digests of fibrin γ-γ cross-linked systems. In both bovine and human fibrin, this kind of cross-linking is accomplished by reciprocal bridging between overlapping carboxy-terminal segments of neighboring γ-chains. The amino acid sequence of the carboxy-terminal heptadecapeptide of the bovine γ-chain was determined and an alignment of the corresponding region of the human γ-chain established.
Studies on the Formation of Transfer Ribonucleic Acid-Ribosome Complexes, XII. Phenylalanyl-Oligonucleotide Binding to
E. coli
Ribosomes: Necessity for a Free Amino Group
Authors: Hishizawa Tokutaro , Lessard James L. , Pestka Sidney
Published: May 2006

The binding of phenylalanyl-oligonucleotide, C-A-C-C-A-(Phe), to ribosomes requires the presence of a free amino group on the amino acid. Acetylation of the amino acid reduces the binding to ribosomes to about 1/20 of the binding observed with the intact Phe-oligonucleotide. Deacylation of the phenylalanyl-oligonucleotide eliminates binding of the free amino acid and markedly reduces the binding of the oligonucleotide (C-A-C-C-A). Neither 30S nor 50S subunits alone are sufficient for binding of the phenylalanyl-oligonucleotide; the presence of both subunits is necessary. The data suggest that phenylalanyl-oligonucleotide binding to ribosomes represents the binding of the aminoacyl-terminus of phenylalanyl-tRNA and that the presence of an amino acid with an unsubstituted amino group attached to the oligonucleotide (C-A-C-C-A) is required for binding to this potassium-dependent site. Furthermore, the ribosome itself has the capability of distinguishing between aminoacyl-oligonucleotides with
N
-substituted and unsubstituted amino acids-
Ribonucleic Acid Synthesis of Vesicular Stomatitis Virus, II. An RNA Polymerase in the Virion
Authors: Baltimore David , Huang Alice S. , Stampfer Martha
Published: May 2006

The virions of vesicular stomatitis virus contain an enzyme that catalyzes the incorporation of ribonucleotides into RNA. The product of the reaction is mainly RNA complementary in base sequence to that of vesicular stomatitis virus RNA.
Controlled Deamidation of Peptides and Proteins: An Experimental Hazard and a Possible Biological Timer
Authors: Robinson Arthur B. , McKerrow James H. , Cary Paul
Published: May 2006

Experiments on model peptides show that the rate of deamidation of asparaginyl residues depends strongly on the nature of neighboring residues. The natural distribution of glutaminyl and asparaginyl residues is ordered with respect to the biological lifetime of the peptides and the functional groups of the residues neighboring to glutaminyl and asparaginyl residues. The rates of deamidation of such amide peptides under physiological conditions could serve as useful timers of development and aging.
Biological Electron Transport Systems
Authors: Cowan Dwaine O. , Pasternak Gavril , Kaufman Frank
Published: May 2006

The solid-state electrical conductivities of a number of ferredoxin model compounds are reported. For one of these compounds, (KFeS
2
)

n

, an electron transfer rate for a 25 Å unit is shown to be at least 1 × 10
8
electrons sec
-1
. The rate becomes proportionally larger for smaller molecular units. This rapid rate is consistant with a short pipe model for electron transport between two reaction sites. Some of the factors leading to this rapid transfer rate are considered.
Photoregulation of Biological Activity by Photochromic Reagents, IV. A Model for Diurnal Variation of Enzymic Activity
Authors: Bieth Joseph , Wassermann Norbert , Vratsanos Spyros M. , Erlanger Bernard F.
Published: May 2006

Levels of acetylcholinesterase activity can be made to vary in response to the presence or absence of sunlight in a system that can be considered as a model for photoperiodic processes found in nature. The enzyme is rendered photosensitive by the presence of a photochromic inhibitor,
N-p
-phenylazophenylcarbamyl choline, which changes from a
trans
to a
cis
isomer under the influence of the light of the sun and reverts back to the
trans
isomer in the dark. The two isomers differ in their ability acetylcholinesterase, thus rendering the enzyme system responsive to sunlight. The relationship of this system to photoresponsive processes in nature is discussed, and a possible role in photoregulation is suggested for naturally occurring carotenoids.
Regulation of Repressor Expression in λ
Authors: Eisen H. , Brachet P. , Silva L. Pereira da , Jacob F.
Published: May 2006

A new gene in bacteriophage λ is described. The product of this gene
cro
prevents expression of immunity and regulates the expression of those genes to the left of the immunity region.
cro
-
mutants have been isolated and characterized.
A New Approach to Isoelectric Focusing and Fractionation of Proteins in a pH Gradient
Authors: Luner Stephen J. , Kolin Alexander
Published: May 2006

This paper describes a new method of condensation (focusing) of extended volumes of mixtures of proteins (or other ampholytes) into an isoelectric spectrum of discrete zones located at points of a pH gradient corresponding to the pI value of the individual proteins. In contradistinction to the currently practiced isoelectric focusing in „natural” pH gradients which may require as much as 96 hours for completion, the present method yields clear-cut condensations marking the isoelectric pH within about five minutes and complete fractionation within about 15 minutes. No „Ampholines” or other special buffers are required and establishment of the pH gradient requires only about 10 seconds rather than days as is common in natural pH gradient focusing. The pH gradient is generated by utilization of the temperature dependence of pH. By establishing a temperature gradient between 0° and 50°C in an electrophoretic column, a stable pH gradient extending over 1 pH unit can be maintained in the absence as well as the presence of a current. The pH gradient can be easily controlled by variation of the temperature limits so that high resolving power can be achieved in shallow pH gradients. The pI of the focused fractions is determined by measurement (by a thermistor or resistance thermometer) of the local temperature within each of the isoelectric zones that determine the local pH. The individual zones can be pipetted out. The method is illustrated by simultaneous condensation and evacuation of hemoglobin in two pH gradients traversed by opposite currents and by separation of hemoglobins A and S in 16 minutes in a pH gradient where the current passes in the direction of increasing pH in Tris buffer solutions stabilized by a sucrose density gradient.
THEORETICAL INVESTIGATIONS OF AUTOMIMICRY, I. SINGLE TRIAL LEARNING
Authors: Brower Lincoln P. , Pough F. Harvey , Meck H. R.
Published: May 2006

The theory of automimicry is explored mathematically on the assumption that predators can learn to avoid noxious prey by sight for some finite period after a single noxious experience. Automimetic advantage is an inevitable consequence of the evolution of an unpalatability dimorphism. An established automimetic situation is analogous to an established perfect Batesian mimicry situation, although the evolutionary bases of the two phenomena are different. In both situations, the mimetic advantage depends upon the proportion of unpalatable prey, the memory span of the predators, and the abundance of the prey relative to the predators. Automimetic advantage is maximal when the prey are neither too common nor too rare. Remarkably low proportions of unpalatable prey can confer very substantial immunity to the population. A surprising prediction of the model is that the evolution of unpalatability will not occur in rare prey species unless they first become Batesian mimics. This in turn could lead to the evolution of mimicry complexes containing many species forming a whole spectrum of unpalatability.
IMMUNOASSAY OF PLASMA VASOPRESSIN IN MAN
Authors: Robertson Gary L. , Klein Lester A. , Roth Jesse , Gorden Phillip
Published: May 2006

A radioimmunoassay for arginine vasopressin has been developed that is sensitive to the hormone at 1 pg/ml. When plasma was filtered on G-25 Sephadex, immunoreactivity was detected in three regions. Endogenous arginine vasopressin was the third and smallest of the peaks and was recovered just after the salt. By combining gel filtration with immunoassay, we have made precise measurements of arginine vasopressin in a few milliliters of plasma.
Increase in Preexisting Cellular Antigen-Combining Groups at Different Times after Infection with Different Viruses
Authors: Tarro Giulio , Sabin Albert B.
Published: May 2006

During the course of experiments designed to determine whether infection of normal cells with certain strains of
Herpesvirus hominis
(HSV) gives rise to a specific neoantigen, presumably characteristic for human malignant cells („HeLa G”), it was found that the seeming appearance of such a new antigen actually represents only an increase in concentration of previously existing normal antigen groups. The complement fixation tests for this antigen were carried out with antibody prepared by McKenna against a fraction, purified with the fluorocarbon genetron, from HeLa cells. This antibody reacted with extracts of tissue culture cells derived from various human malignant tumors and from the spontaneously transformed WISH cell line, originally derived from normal human amnion, but not with cells derived from early-passage cultures of normal human kidney, or from primary cultures of young rabbit kidney or new-born guinea pig kidney.

Infection of rabbit and guinea pig kidney tissue culture cells with HSV strains derived from brain or lip lesions at a high input multiplicity of virus failed to yield the „G” antigen. Infection of human kidney tissue culture cells with the same HSV strains yielded two units of the „G” antigen at 6 hr and 32 units at 24 hr. The conclusion that this was, nevertheless, not a new antigen, but only an increase in amount of preexisting antigen, was based on the demonstration that absorption of the anti-„HeLa G” globulin with uninfected human kidney tissue culture cells completely removed the antibody for the „G” antigen formed during the course of infection with HSV and also that present in uninfected WISH and HEp2 cells.

Infection by the same HSV strains of the human WISH cells which have a small amount of preexisting „G” antigen resulted in an increase which was maximal at 24 hr. Infection of WISH cells with vaccinia virus resulted in a rapid increase of „G” antigen, which was demonstrable at 10 min but not at 3, 6, and 24 hr. Absorption of the anti-„HeLa G” globulin with uninfected WISH cells removed the antibody for the G antigen present in the WISH cells before infection as well as after infection with the herpes and vaccinia viruses, and also the antigen present in human tissue culture cells of malignant origin.
Evaluation of the Effects of Chemical Mutagens on Man: The Long Road Ahead
Authors: Neel James V.
Published: May 2006

By analogy with the problem of evaluating the genetic risks of radiation, it appears that it will be extremely difficult to assess the mutagenicity for man of the wide range of chemicals to which human populations are currently exposed. Nevertheless, the potential significance of this problem calls for a major effort at such an evaluation.