bluuebunny/crossref_metadata_2025 huggingface dataset:
Life problems and physical illness as risk factors for suicide in older people: a descriptive and case-control study
Authors: HARWOOD DANIEL MICHAEL JAMES , HAWTON KEITH , HOPE TONY , HARRISS LOUISE , JACOBY ROBIN
Published: May 2006

Background. The role of physical illness and life problems in contributing to suicide in older people is potentially important with regard to suicide prevention.

Method. The aim of the study was to determine the life problems other than psychiatric illness contributing to suicide in older people. Semi-structured psychological autopsy interviews, covering life problems and physical illness prior to death, were conducted with informants for 100 people aged 60 years old and over who died through suicide in five English counties. Interviews were completed with informants for 54 age- and sex-matched control subjects who died through natural causes.

Results. The three most frequent life problems associated with suicide were physical illness, interpersonal problems, and bereavement. Physical health problems were present in 82% and felt to be contributory to death in 62%. Pain, breathlessness and functional limitation were the most frequent symptoms. Interpersonal problems were present in 55% of the sample and contributory in 31%. The corresponding figures for bereavement-related problems were 47% and 25%. In the case-control analysis, the problems found to be risk factors for suicide were problems related to a bereavement over 1 year before death (OR 3·5, 95% CI 1·2–10·6), and problems with accommodation (OR 5·0, 95% CI 1·1–22·8), finances (p=0·01), and retirement (p=0·02).

Conclusion. Physical illness, interpersonal problems and bereavement are commonly associated with suicide in older people, but financial, accommodation, retirement and long- term bereavement-related problems may be more specific risk factors.
From Homogeneous to Fractal Normal and Tumorous Microvascular Networks in the Brain
Authors: Risser Laurent , Plouraboué Franck , Steyer Alexandre , Cloetens Peter , Le Duc Géraldine , Fonta Caroline
Published: May 2006

We studied normal and tumorous three-dimensional (3D) microvascular networks in primate and rat brain. Tissues were prepared following a new preparation technique intended for high-resolution synchrotron tomography of microvascular networks. The resulting 3D images with a spatial resolution of less than the minimum capillary diameter permit a complete description of the entire vascular network for volumes as large as tens of cubic millimeters. The structural properties of the vascular networks were investigated by several multiscale methods such as fractal and power-spectrum analysis. These investigations gave a new coherent picture of normal and pathological complex vascular structures. They showed that normal cortical vascular networks have scale-invariant fractal properties on a small scale from 1.4 μm up to 40 to 65 μm. Above this threshold, vascular networks can be considered as homogeneous. Tumor vascular networks show similar characteristics, but the validity range of the fractal regime extend to much larger spatial dimensions. These 3D results shed new light on previous two dimensional analyses giving for the first time a direct measurement of vascular modules associated with vessel-tissue surface exchange.
Crossed-beam radical-radical reaction dynamics of O(P3)+C3H3→H(S2)+C3H2O
Authors: Kwon Lee-Kyoung , Nam Mi-Ja , Youn Sung-Eui , Joo Sun-Kyu , Lee Hohjai , Choi Jong-Ho
Published: May 2006

The radical-radical oxidation reaction, O(P3)+C3H3(propargyl)→H(S2)+C3H2O (propynal), was investigated using vacuum-ultraviolet laser-induced fluorescence spectroscopy in a crossed-beam configuration, together with ab initio and statistical calculations. The barrierless addition of O(P3) to C3H3 is calculated to form energy-rich addition complexes on the lowest doublet potential energy surface, which subsequently undergo direct decomposition steps leading to the major reaction products, H+C3H2O (propynal). According to the nascent H-atom Doppler-profile analysis, the average translational energy of the products and the fraction of the average transitional energy to the total available energy were determined to be 5.09±0.36kcal∕mol and 0.077, respectively. On the basis of a comparison with statistical prior calculations, the reaction mechanism and the significant internal excitation of the polyatomic propynal product can be rationalized in terms of the formation of highly activated, short-lived addition-complex intermediates and the adiabaticity of the excess available energy along the reaction coordinate.
Adaptive targeting of chaotic response in periodically stimulated neural systems
Authors: Gupta Kopal , Singh Harinder P. , Biswal B. , Ramaswamy R.
Published: May 2006

We demonstrate a technique for the enhancement of chaos in a computational model of a periodically stimulated excitable neuron. “Anticontrol” of chaos is achieved through intermittent adaptive intervention, which is based on finite-time Lyapunov exponents measured from the time series. Our results suggest that an adaptive strategy for chaos anticontrol is viable for increasing the complexity in physiological systems that are typically both noisy and nonstationary.
Performance enhancement of composition-graded-base type-II InP∕GaAsSb double-heterojunction bipolar transistors with fT>500GHz
Authors: Snodgrass William , Wu Bing-Ruey , Hafez Walid , Cheng K. Y. , Feng Milton
Published: May 2006

The high frequency performance of type-II InP∕GaAsSb double heterojunction bipolar transistors (DHBTs) with compositionally graded and uniform 25nm base layers and 65nm InP collectors is investigated. The graded base DHBT achieves a peak current gain of 20.5 compared to 14.9 for the uniform base DHBT at current densities near 15mA∕μm2. The peak fT of a graded base device with 0.38×8μm2 emitter dimensions improves from 505GHz at 25°C to 535GHz at −55°C as determined by −20dB∕decade extrapolation. The base grading has reduced the total transit time by 25% compared to the uniform base type-II DHBT.
Evolution of Schottky barrier heights at Ni∕HfO2 interfaces
Authors: Li Q. , Dong Y. F. , Wang S. J. , Chai J. W. , Huan A. C. H. , Feng Y. P. , Ong C. K.
Published: May 2006

The evolution of Schottky barrier heights (SBHs) at Ni∕HfO2∕n-Si stacks was studied by in situ x-ray photoemission. It was found that the n-SBH (or the effective work function) increases with thickness of the Ni overlayer and approaches 2.4eV (or 4.9eV) when metallic behavior of Ni overlayer is recovered. This is in good agreement with results of first-principles calculations. The effective work function of Ni in contact with HfO2 was found different from that in vacuum by 0.3eV. The interface dipole was induced by the weak interaction of Ni thin film and HfO2 dielectric.
Magnetic and transport properties of multilayer nanoscale antidot arrays
Authors: Wang C. C. , Adeyeye A. O. , Singh N.
Published: May 2006

The magnetic and transport properties of multilayer antidot nanostructure have been systematically investigated. The structures consisting of Co (30nm)∕Cu (tCunm)∕Ni80Fe20 (30nm) were fabricated using deep ultraviolet lithography followed by lift-off process. We observed that the magnetization reversal processes are markedly dependent on tCu due to the interplay of different interlayer coupling mechanisms. The transport properties of the antidot arrays typically show a superposition of anisotropic and giant magnetoresistance effects, and the relative magnitude of the two effects is strongly sensitive to tCu. This is completely different from the observations in the corresponding continuous films.
Viewpoint: Isotopic fractionation by plant nitrate reductase, twenty years later
Authors: Tcherkez Guillaume , Farquhar Graham D.
Published: May 2006

Plant nitrate reductase, the enzyme that reduces nitrate (NO3–) to nitrite (NO2–), is known to fractionate N isotopes, depleting nitrite in 15N compared with substrate nitrate. Nearly 20 years ago, the nitrogen isotope effect associated with this reaction was found to be around 1.015. However, the relationships between the isotope effect and the mechanism of the reaction have not yet been examined in the light of recent advances regarding the catalytic cycle and enzyme structure. We thus give here the mathematical bases of the 14N / 15N and also the 16O / 18O isotope effects as a function of reaction rates. Enzymatic nitrate reduction involves steps other than NO3– reduction itself, in which the oxidation number of N changes from +V (nitrate) to +III (nitrite). Using some approximations, we give numerical estimates of the intrinsic N and O isotope effects and this leads us to challenge the assumptions of nitrate reduction itself as being a rate-limiting step within the nitrate reductase reaction, and of the formation of a bridging oxygen as a reaction intermediate.
Summer survey of dugong distribution and abundance in Shark Bay reveals additional key habitat area
Authors: Holley David K. , Lawler Ivan R. , Gales Nicholas J.
Published: May 2006

The first standardised summer aerial survey of dugongs within Shark Bay in Western Australia, and the fourth in a series of surveys of this area, was undertaken during February 2002. This survey returned a population estimate of 11 021 ± 1357 (s.e.), a result similar to the first two winter surveys in 1989 and 1994 but considerably lower than the 1999 survey. Distribution was markedly different in this survey compared with all previous surveys, which were conducted during winter, confirming that dugongs within Shark Bay undertake a seasonal migration driven by changes in sea surface temperature. In addition to this distribution pattern it was identified that 24% of the population during summer occurred within an area known as Henri Freycinet Harbour. That is, while dugongs have been reported in this south-western region of the bay previously in summer, this is the first time that the substantial size (2629 ± 780, s.e.) of the summer dugong population has been quantified. Differences in the population estimate between the 1999 survey and this survey may be explained through large-scale movement patterns of dugongs between Shark Bay and Ningaloo Reef and Exmouth Gulf to the north, patterns that should be considered in the management of dugongs for the entire region.
Thionein can serve as a reducing agent for the methionine sulfoxide reductases
Authors: Sagher Daphna , Brunell David , Hejtmancik J. Fielding , Kantorow Marc , Brot Nathan , Weissbach Herbert
Published: May 2006

It has been generally accepted, primarily from studies on methionine sulfoxide reductase (Msr) A, that the biological reducing agent for the members of the Msr family is reduced thioredoxin (Trx), although high levels of DTT can be used as the reductant
in vitro
. Preliminary experiments using both human recombinant MsrB2 (hMsrB2) and MsrB3 (hMsrB3) showed that although DTT can function
in vitro
as the reducing agent, Trx works very poorly, prompting a more careful comparison of the ability of DTT and Trx to function as reducing agents with the various members of the Msr family.
Escherichia coli
MsrA and MsrB and bovine MsrA efficiently use either Trx or DTT as reducing agents. In contrast, hMsrB2 and hMsrB3 show <10% of the activity with Trx as compared with DTT, raising the possibility that, in animal cells, Trx may not be the direct hydrogen donor or that there may be a Trx-independent reducing system required for MsrB2 and MsrB3 activity. A heat-stable protein has been detected in bovine liver that, in the presence of EDTA, can support the Msr reaction in the absence of either Trx or DTT. This protein has been identified as a zinc-containing metallothionein (Zn-MT). The results indicate that thionein (T), which is formed when the zinc is removed from Zn-MT, can function as a reducing system for the Msr proteins because of its high content of cysteine residues and that Trx can reduce oxidized T.
GENE EXPRESSION IN INTERSPECIFIC HYBRIDS, I. DNA SYNTHESIS IN THE LETHAL CROSS ARBACIA LIXULA [unk] × PARACENTROTUS LIVIDUS [unk]
Authors: Denis H. , Brachet J.
Published: May 2006

The technique of molecular hybridization has been used to determine in what proportion the DNA's of paternal and maternal origin are present in the lethal hybrid obtained by fertilizing the eggs of the sea urchin
Paracentrotus lividus
with the sperm of another sea urchin species,
Arbacia lixula
.

The ability of the hybridization technique to recognize DNA molecules from
A. lixula
and
P. lividus
was examined and proved to be satisfactory. Labeled DNA's from
A. lixula
and
P. lividus
were found to hybridize respectively ten and seven times as well with DNA of their own species as with DNA of the other species. Labeled DNA from arrested hybrid embryos hybridized 1.7 times to twice as well with
P. lividus
as with
A. lixula
DNA. We conclude that the interspecific hybrid contains about 2.5 times as much DNA of maternal origin as DNA of paternal origin. The lower content of
A. lixula
DNA probably results from a partial elimination of the paternal chromosomes during the late cleavage stages.
TEMPERATURE OF COMPENSATION: SIGNIFICANCE FOR VIRUS INACTIVATION
Authors: Barnes Richard , Vogel Helmut , Gordon Irving
Published: May 2006

The purpose of this report is to call attention to the probable biological utility of a physical constant, the temperature of compensation (

T
c

) or isokinetic temperature.

T
c

has hitherto not been used in biological research. It is defined as the temperature at which a series of Arrhenius plots, related by variation of a single parameter, pass through a common point. Such systems demonstrate the so-called compensation effect and show linear variation of change in enthalpy with change in entropy; the slope [unk]
H/[unk]S
is

T
c

. Related reactions in which, for example, solvent change or structural change of the reactants does not change the mechanism of the reaction or the nature of the transition state exhibit an identical

T
c

. The system used in this study was a complex one, i.e., protection against thermal inactivation of Sindbis virus by HPO
4
=
and SO
4
=
. The time-rate constant of loss of infectivity was determined at different temperatures for virus suspended in different salt concentrations at constant pH. The compensation effect was demonstrated and

T
c

was found to be approximately 57°C for virus inactivation in both Na
2
HPO
4
and MgSO
4
solutions. The intercept of a Δ
S
‡/Δ
H
‡ plot, defined as the constant
B
, also was the same for the two salts.

We suggest that determination of

T
c

in biological systems might be of value in (1) establishment of whether an observed phenomenon results from the same process or mechanism as another observed phenomenon; (2) prediction of rates or other behavior under relevant conditions; and (3) classification.
HYBRIDIZATION OF HAMSTER CELLS WITH HIGH AND LOW FOLATE REDUCTASE ACTIVITY
Authors: Littlefield John W.
Published: May 2006

These studies concern the question whether diffusible repressors control the syntheses of enzymes in mammalian cells. First, clonal sublines of baby hamster kidney (BHK 21/13) cells in culture were selected in stepwise fashion for resistance to aminopterin. These sublines survived in concentrations of aminopterin that were up to 10
4
times higher than those tolerated by wild-type cells because they contained up to 125 times as much folate reductase, probably due to overproduction of the enzyme. When five resistant sublines were hybridized to wild-type lines, 32 of 35 hybrid clones contained intermediate levels of reductase activity. This suggests that overproduction of reductase is not due to loss of a diffusible repressor.
INFORMATIONAL TRANSFER IN MEIOTIC GENE CONVERSION
Authors: Fogel S. , Mortimer R. K.
Published: May 2006

Aberrant meiotic segregations attributable to intragenic events have been analyzed in an unselected sample of 1611 tetrads from three heteroallelic diploids of
Saccharomyces cerevisiae
. Reciprocal recombination between alleles accounts for only a minor fraction of the total aberrant tetrads, while the majority component is represented by single- and double-site conversions. The frequency of double-site conversion is inversely related to the physical length of the interallelic interval. Since double-site conversions do not yield prototrophs, their occurrence leads to biased estimates of intragenic distances. Conversion is viewed as a process of informational transfer distinct from conventional crossing-over. The implications of the findings for genetic fine structure mapping and evolutionary theory are discussed briefly.
CELL KINETIC STUDIES IN MIXED LEUKOCYTE CULTURES: AN
in vitro
MODEL OF HOMOGRAFT REACTIVITY
Authors: Bach Fritz H. , Bock Harvey , Graupner Kenneth , Day Elizabeth , Klostermann Heidi
Published: May 2006

The recognition phase of homograft immunity can be studied
in vitro
in the mixed leukocyte culture reaction. In this reaction, at the end of seven days, up to 30 per cent of the lymphocytes in culture “respond” to a single allogeneic cell stimulus. This paper presents evidence that the lymphocytes responding in culture divide with the generation time of 18-21 hours, with some asynchrony, and that a large percentage of the cells found at the end of the culture period may be the products by division of a small number of cells initially responding. Two estimates are made of the frequency of the initially responding unit (the cell(s) responsible for initiating the response). These are probably minimum estimates and are in the range of 1 in 200 to 1 in 2000 cells which can initially respond. This very high frequency of responding units as compared with the responding units in immediate type hypersensitivity (antibody production) is discussed.
TRANSLOCATION OF MRNA CODONS, I. THE PREPARATION AND CHARACTERISTICS OF A HOMOGENEOUS ENZYME
Authors: Leder Philip , Skogerson Lawrence E. , Nau Marion M.
Published: May 2006

This report describes a convenient scheme for the further purification of an
E. coli
enzyme which is required for the translocation step in protein biosynthesis. The homogeneous enzyme translocase appears to be a relatively large monomeric protein, having a molecular weight of approximately 72,000, and acts in a catalytic fashion during protein synthesis. It is also one of the major soluble macromolecular constituents of rapidly growing
E. coli
, comprising more than 2 per cent of the protein in ribosome-free extracts. Further, the rate of
in vitro
protein synthesis is linearly dependent upon the concentration of the pure enzyme until approximately one molecule of translocase is present per ribosome in reaction mixtures.
COMPARATIVE HYBRIDIZATION OF MITOCHONDRIAL AND CYTOPLASMIC AMINOACYL TRANSFER RNA WITH MITOCHONDRIAL DNA FROM RAT LIVER
Authors: Nass Margit M. K. , Buck Clayton A.
Published: May 2006

We have tested the specificity of hybridization of mitochondrial tRNA with mitochondrial DNA. Techniques are now available for performing RNA-DNA hybridization at low temperatures in the presence of 50 per cent formamide. With this technique, specific aminoacyl-tRNA-DNA hybridization can be followed in the presence of other species of RNA if the tRNA is acylated with radioactive amino acids. With this technique, mitochondrial leucyl-tRNA from rat liver has been found to anneal to mitochondrial DNA. Competitive hybridization between mitochondrial leucyl-tRNA and mitochondrial or cytoplasmic aminoacyl-tRNA shows that mitochondrial tRNA competes much more efficiently than cytoplasmic tRNA for sites of annealing to mitochondrial DNA. These results show that mitochondrial leucyl-tRNA differs from cytoplasmic leucyl-tRNA in its primary base sequence. They also imply that mitochondrial DNA may be the template from which mitochondrial tRNA is transcribed.
STIMULATION OF C
14
-MELATONIN SYNTHESIS FROM C
14
-TRYPTOPHAN BY NORADRENALINE IN RAT PINEAL IN ORGAN CULTURE
Authors: Axelrod Julius , Shein Harvey M. , Wurtman Richard J.
Published: May 2006

Previous work has shown that the activity of the melatonin-forming enzyme in the rat pineal gland is elevated in rats kept in continuous darkness as compared to those kept in continuous light. Information about environmental lighting reaches the pineal gland via nerves that liberate noradrenaline. Rat pineal glands in organ culture can form C
14
-melatonin from C
14
-tryptophan as follows: tryptophan → 5-hydroxytryptophan → serotonin → melatonin.

Noradrenaline was found to stimulate the synthesis of C
14
-melatonin from C
14
-tryptophan in rat pineals in organ culture. Other compounds related in structure to noradrenaline increase melatonin and serotonin synthesis and inhibit the formation of the deaminated product of serotonin, 5-hydroxyindole acetic acid. Cycloheximide, a compound that inhibits protein synthesis, also prevents the formation of serotonin, melatonin, and 5-hydroxyindole acetic acid from tryptophan in pineal organ culture. These observations suggest that noradrenaline liberated from sympathetic nerves stimulates the formation of melatonin either by increasing the formation of new melatonin-forming enzyme, by increasing transport of tryptophan into the pineal cell, or by inhibiting the metabolism of serotonin by the alternate deaminating pathway.
PROTON MAGNETIC RESONANCE STUDIES OF PORPHYRIN IRON (III) CYANIDES
Authors: Wüthrich K. , Shulman R. G. , Wyluda B. J. , Caughey W. S.
Published: May 2006

The nuclear magnetic resonance (NMR) spectra at 220 Mc of cyanodeuteroporphyrin IX dimethyl ester iron (III), cyanoprotoporphyrin IX diethyl ester iron (III), and cyanoprotoporphyrin IX iron (III) in a mixed solvent of 80 per cent d
5
-pyridine and 20 per cent D
2
O have been measured. The resonances are assigned and, except for the ester alkoxy groups, are shown to be shifted by temperature-dependent hyperfine interactions with Fe (III). From the experiments, upper limits are placed upon the pseudocontact contributions, and values of the contact interactions are derived. Spin densities in carbon π-orbitals are calculated from the contact shifts and discussed in terms of preliminary Hückel calculations.
INCORPORATION OF
14
C-TRYPTOPHAN INTO
14
C-PROTEIN BY CULTURED RAT PINEALS: STIMULATION BY
l
-NOREPINEPHRINE
Authors: Wurtman Richard J. , Shein Harvey M. , Axelrod Julius , Laren Frances
Published: May 2006

Organ cultures of individual rat pineals incorporate
14
C-tryptophan into proteins at a nearly constant rate for at least 48 hours. Previous studies have shown that these cultures also convert
14
C-tryptophan to serotonin, melatonin, and 5-hydroxyindoleacetic acid, and release these indoles into the media. The formation of
14
C-protein from
14
C-tryptophan is accelerated by the addition to the culture medium of
l
-norepinephrine or related catecholamines but is not modified by serotonin, melatonin, or 5-hydroxyindoleacetic acid.

One mechanism by which norepinephrine stimulates the synthesis of
14
C-protein from
14
C-tryptophan involves increasing the uptake of the
14
C-tryptophan into pineal parenchymal cells, inasmuch as (1) norepinephrine increases the intracellular content of
14
C-tryptophan as well as its conversion to its major products,
14
C-protein and
14
C-indoles; (2) norepinephrine does not stimulate
14
C-protein synthesis in pineal organs which contain a previously fixed amount of
14
C-tryptophan; and (3) norepinephrine does not stimulate
14
C-protein synthesis from
14
C-methionine or
14
C-leucine.

The finding that norepinephrine, but not serotonin, can stimulate the incorporation of
14
C-tryptophan into pineal proteins is consistent with the hypothesis that norepinephrine is the neurotransmitter substance utilized by pineal sympathetic nerve endings.
THE ISOLATION OF TWO ENZYME-RIBONUCLEIC ACID COMPLEXES INVOLVED IN THE SYNTHESIS OF FOOT-AND-MOUTH DISEASE VIRUS RIBONUCLEIC ACID
Authors: Arlinghaus Ralph B. , Polatnick Jerome
Published: May 2006

The foot-and-mouth disease virus-RNA polymerase complex was released from membrane particulates present in the cytoplasm of infected baby hamster kidney cells. The soluble polymerase complex was fractionated by zonal centrifugation in sucrose gradients. Two polymerase complexes (RNA and protein complex) active in the cell-free system were isolated and had
S
-rate ranges of 20-70
S
and 100-300
S
, respectively. The light polymerase complex contained 20
S
double-stranded RNA; and the heavy polymerase complex contained a polydisperse, partially RNase-resistant RNA. The cell-free product of these two polymerase complexes was analyzed by zonal centrifugation in sucrose gradients. The light polymerase complex synthesized only 20
S
double-stranded RNA. The product of the heavy polymerase complex contained no detectable 20
S
double-stranded RNA and only a peak of single-stranded RNA with
S
-rate corresponding to 37
S
viral RNA. A third polymerase complex was isolated with
S
-rate greater than 300
S
, and it contained a polydisperse, partially RNase-resistant RNA. This third polymerase complex synthesized both 37
S
viral RNA and 20
S
double-stranded RNA in the cell-free system, and it is probably the native polymerase complex still bound to cellular particulates.
ALTERATION IN MICROSOMAL PROTEIN SYNTHESIS DURING EARLY DEVELOPMENT OF MOUSE BRAIN
Authors: Johnson Terry C. , Belytschko Gail
Published: May 2006

The loss of protein synthesis during early mouse-brain development was shown to be the result, at least in part, of the inability of microsomes obtained from more mature neural tissue to participate in rapid polypeptide synthesis. The loss of brain microsomal activity was observed shortly after birth and continued until the animals were approximately ten days old. Despite the difference in synthetic activity, sucrose gradient profiles of microsomes and polyribosomes from young and more mature brain tissue were quite similar. The loss in protein synthesis was shown to be independent of available mRNA and not attributable to aminoacyl-RNA synthetases and tRNA binding activity.
THE STRUCTURE OF MOUSE-ELBERFELD VIRUS: A MODEL
Authors: Rueckert Roland R. , Dunker A. Keith , Stoltzfus C. Martin
Published: May 2006

It is proposed that the capsid structure of mouse-Elberfeld (ME) virus, a small icosahedral ribonucleic acid containing picornavirus, is determined by 60 identical protein subunits; each of the latter is composed of several non-identical polypeptide chains. Icosahedral symmetry in a 60-subunit shell allows three types of specific intersubunit bonding contacts which establish its axes of two-, three-, and fivefold symmetry, respectively. Of these three bonding types, two are sufficient to specify a complete shell. We interpret the possible identity of some discrete supramolecular structures involved in the biosynthesis of poliovirus and in the degradation of ME virus in the context of stepwise formation or disruption of two different types of specific intersubunit bonding contacts.
REVERSIBLE TRANSFORMATION OF FIBROUS COLLAGEN TO A SOLUBLE STATE
in vivo
Authors: Klein LeRoy
Published: May 2006

Metabolic pathways of pre-existing and newly synthesized collagen fractions from skin and induced connective tissue were studied in rats that had been labeled with
3
H-L-proline 6 and 20 weeks previously. The distribution of specific radioactivity was determined for soluble and insoluble collagens. Multiple extractions of neutral salt-soluble and citrate-soluble collagen demonstrated constant specific radioactivities which indicated the achievement of an isotopic steady state. Citrate-soluble collagen was four times more radioactive than neutral salt-soluble collagen, which indicated a large difference in biological age (months) between fractions.

Different levels of specific radioactivity in collagen fractions from implanted sponge indicated that both pre-existing (citrate-soluble) and newly synthesized collagen (salt-soluble) contributed to the insoluble collagen of induced connective tissue in normal and hypophysectomized rats. The isotopic data indicated that pre-existing fibrous collagen could be solubilized
in vivo
and translocated from skin to sponge via citrate-soluble collagen.
SCHWARZ'S LEMMA IN NORMED LINEAR SPACES
Authors: Harris Lawrence A.
Published: May 2006

In this paper we show that any Fréchet holomorphic function mapping the open unit ball of one normed linear space into the closed unit ball of another must be a linear mapping if the Fréchet derivative of the function at zero is a surjective isometry. From this fact we deduce a Banach-Stone theorem for operator algebras which generalizes that of R. V. Kadison.
CYTOKININS: SYNTHESIS, MASS SPECTRA, AND BIOLOGICAL ACTIVITY OF COMPOUNDS RELATED TO ZEATIN
Authors: Leonard Nelson J. , Hecht Sidney M. , Skoog Folke , Schmitz Ruth Y.
Published: May 2006

Compounds related to dihydrozeatin that define the influence of the location of the hydroxyl group along the side chain have been synthesized and tested for cytokinin activity. The compounds compared are in the series: 6-(X-hydroxy-3-methylbutylamino)purines and their ribosides, where X = 2, 3, and 4.

Hydroxy substitution on the 4-position of the side chain enhances, but in the 2-, 3-, or 2- and 3- positions, decreases cytokinin activity as compared with the unsubstituted isopentyl (or isopentenyl) chains. This differential influence of the position of the hydroxyl group in the N
6
-chain holds also for the similarly related 9-β-D-ribofuranosides. The relatively higher activity of 3,4-dihydroxy as compared with 2,3-dihydroxy derivatives is consistent with this position effect.

Compounds related to zeatin possessing side-chain ester moieties have also been synthesized and tested comparatively. Among these, 6-(4-acetoxy-3-methyl-
trans
-2-butenylamino)purine is at least as active as zeatin, the most active presently known cytokinin in the tobacco bioassay, whereas the analog, methyl 2-methyl-4-(purin-6-ylamino)-
trans
-crotonate, with the ester function effectively reversed, has vastly lower activity, and its riboside is practically inactive.
RAPID TRANSFORMATION OF CELLS BY ROUS SARCOMA VIRUS
Authors: Hanafusa Hidesaburo
Published: May 2006

The conditions for synchronous transformation of chick embryo cells by infection with Rous sarcoma virus are studied. Two factors, the treatment of cells with DEAE-dextran and the use of cells which grow rapidly following virus infection, are found to be most important. Under the conditions described, the Schmidt-Ruppin strain of Rous sarcoma virus at a multiplicity of higher than 5 induces morphological alteration in about 90 per cent of the cell population within 24 hours after infection. The alteration in the morphology is accompanied by acquisition of the ability of cells to grow in agar medium and by the increased rate of incorporation of thymidine and uridine into nucleic acids.
STRUCTURE AND FUNCTION OF
E. coli
RIBOSOMES, VIII. COLD-SENSITIVE MUTANTS DEFECTIVE IN RIBOSOME ASSEMBLY
Authors: Guthrie Christine , Nashimoto Hiroko , Nomura Masayasu
Published: May 2006

E. coli
mutants that fail to grow at 20°C were isolated, and three such mutants were studied in detail. Two of these are defective in 50
S
ribosome biosynthesis at low temperatures and accumulate 43
S
and 32
S
particles, respectively. The third mutant produces reduced amounts of 50
S
ribosomes and accumulates 21
S
particles at low temperatures. The 43
S
and 32
S
particles contain 23
S
RNA and appear to be precursors of 50
S
ribosomes. The 21
S
particles contain 16
S
RNA. The mutation that causes accumulation of 32
S
particles is linked to the
spc
locus. Isolation and characterization of coldsensitive mutants should provide a fruitful approach to the study of
in vivo
ribosomal assembly.
BIOSYNTHESIS OF INSULIN IN BOVINE FETAL PANCREATIC SLICES: THE INCORPORATION OF TRITIATED LEUCINE INTO A SINGLE-CHAIN PROINSULIN, A DOUBLE-CHAIN INTERMEDIATE, AND INSULIN IN SUBCELLULAR FRACTIONS
Authors: Tung A. K. , Yip C. C.
Published: May 2006

This communication reports the biosynthesis of insulin in the bovine fetal pancreatic slices
in vitro
. Double-chain proinsulin and insulin were found as major components in the mitochondrial-granule fraction of bovine fetal pancreas. Tritiated leucine was incorporated into a single-chain proinsulin, a double-chain proinsulin, and insulin. Subcellular fractionation of the slices incubated with tritiated leucine showed that radioactive single-chain proinsulin was present in the deoxycholate-soluble microsomal fraction, deoxycholate-insoluble microsomal fraction, and mitochondrial-granule fraction. Labeled double-chain proinsulin and insulin were present in the deoxycholate-soluble microsomal and mitochondrial-granule fractions. These results are consistent with the hypothesis that insulin is synthesized as a single-chain polypeptide on the ribosomes, and that intracellular proteolysis in the subcellular membranous organelles and beta-granules converts the single-chain proinsulin to insulin via a double-chain intermediate.
ADP KINASE AND ATPASE IN CHLOROPLASTS
Authors: Lynn W. S. , Straub K. D.
Published: May 2006

Treatment of chloroplasts with trypsin activates a light-requiring ATPase whose properties are strikingly similar to those of the light-requiring ADP kinase of chloroplasts. The observations here presented suggest that there exists, in chloroplasts, a reducible enzyme which, in its reduced state, catalyzes the reversible reaction: P
i
-2
+ ADP
-3
+ H
+
⇌ ATP
-4
+ H
2
O. By reduction and protonation of the catalytic site of this enzyme, light-driven electron flow in the chloroplast drives the reaction to the right. Hydrolysis of ATP proceeds only when the enzyme is reduced and when the proton concentration within the chloroplast is kept at low levels, viz., in the absence of light, in the presence of uncoupling agents which decrease the concentration of internal H
+
, or in the presence of electron acceptors which by oxidizing the internal electron acceptors also decrease the proton potential. Activation of the enzyme requires light; it remains active only in the presence of ATP. Hydrolysis of all the ATP results in inactivation of the ATPase. The membrane-bound protein
CF
2
limits the reversibility of the reaction by excluding ATP and H
2
O from the enzyme site. It also facilitates the ability of the chloroplasts to accumulate and to maintain high internal concentrations of such ions as ADP, P
i
, PMS
+
, and imidazole.
ON THE FLUCTUATIONS OF SUMS OF INDEPENDENT RANDOM VARIABLES
Authors: Feller William
Published: May 2006

If
X
1
,
X
2
,... are independent random variables with zero expectation and finite variances, the cumulative sums

S
n

are, on the average, of the order of magnitude

S
n

, where

S
n
2

=
E
(

S
n
2

). The occasional maxima of the ratios

S
n
/S
n

are surprisingly large and the problem is to estimate the extent of their probable fluctuations.

Specifically, let

S
n

*
= (

S
n
- b
n

)/

a
n

, where {

a
n

} and {

b
n

}, two numerical sequences. For any interval
I
, denote by
p
(
I
) the probability that the event

S
n

*
ε
I
occurs for infinitely many
n
. Under mild conditions on {

a
n

} and {

b
n

}, it is shown that
p
(
I
) equals 0 or 1 according as a certain series converges or diverges. To obtain the upper limit of

S
n
/a
n

, one has to set

b
n

= ± ε

a
n

, but finer results are obtained with smaller

b
n

. No assumptions concerning the under-lying distributions are made; the criteria explain structurally which features of {

X
n

} affect the fluctuations, but for concrete results something about
P
{

S
n

>

a
n

} must be known. For example, a complete solution is possible when the

X
n

are normal, replacing the classical law of the iterated logarithm. Further concrete estimates may be obtained by combining the new criteria with some recently developed limit theorems.
GENE LOSS IN HUMAN TERATOMAS
Authors: Linder David
Published: May 2006

If benign cystic teratomas (dermoid cysts) of the ovary arise from a germ cell that has undergone meiosis, they should be missing genes which are present in the person. Three independently segregating allelic isozymes in 11 benign cystic teratomas of the human female ovary were compared with normal tissue of the same case. Dermoid cysts from persons heterozygous for these isozymes are frequently homozygous for that particular gene product. One of two dermoid cysts is homozygous for glucose-6-phosphate dehydrogenase, two of four tumors are homozygous for phosphoglucomutase at the PGM
1
locus, and two (or more) of eight tumors are homozygous for phosphoglucomutase at the PGM
3
locus in women heterozygous for these allelic isozymes. These findings are consistent with the hypothesis that these tumors arise from a germ cell which has undergone meiosis with varying degrees of crossing-over.
MICROELECTRODE STUDIES ON THE MEMBRANE PROPERTIES OF ISOLATED MITOCHONDRIA, II. ABSENCE OF A METABOLIC DEPENDENCE
Authors: Tupper Joseph T. , Tedeschi Henry
Published: May 2006

Mitochondrial membrane potentials and resistances have been determined under various metabolic conditions by the use of piezoelectric-driven microelectrodes. The mean state 3 potentials (about +19 mv) are higher than the potentials in state 4 (about +9 mv). DNP in uncoupling concentrations or KCN have no significant effect on membrane resistance or potential. Previous experiments have shown the potential to be sensitive to mitochondrial swelling and have suggested that it depends predominantly on anionic distribution.
THE ENZYMATIC TERMINATION OF POLYDEOXYNUCLEOTIDES BY 2′,3′-DIDEOXYADENOSINE TRIPHOSPHATE
Authors: Toji Lorraine , Cohen Seymour S.
Published: May 2006

The nucleoside 2′,3′-dideoxyadenosine is lethal to
E. coli
and blocks DNA synthesis irreversibly. The hypothesis that a derived dideoxynucleoside triphosphate is incorporated terminally into the cellular DNA has been tested in an
in vitro
system. The triphosphate of dideoxyadenosine was synthesized and shown to inhibit the
in vitro
synthesis of DNA by purified
E. coli
DNA polymerase. The kinetics of inhibition of nucleotide incorporation and pyrophosphate exchange were studied. Early in synthesis the dideoxynucleotide is a competitive inhibitor of the enzyme. Subsequently, synthesis is almost completely arrested.

Radioactive dideoxyadenosine triphosphate was prepared. The compound was shown to be incorporated enzymatically into dAT copolymer to the extent of about one molecule per molecule of template. It is released from such templates by DNA polymerase at less than 1 per cent of the rate of release of other natural nucleotides. The label is released by snake venom phosphodiesterase far more rapidly than total nucleotides. This nucleoside triphosphate has thus been shown to be a competitive inhibitor of DNA polymerase and a terminator of polydeoxynucleotide chains.
THE USE OF
N
-METHYLNICOTINAMINDE CHLORIDE AS A CONFORMATIONAL PROBE FOR CHICKEN EGG-WHITE LYSOZYME
Authors: Deranleau David A. , Bradshaw Ralph A. , Schwyzer Robert
Published: May 2006

Chicken egg-white lysozyme forms a yellow complex with
N
-methylnicotinamide chloride. Titration studies utilizing the appearance of the yellow color as a measure of complex formation indicate that the weak complex (association constant
k
= 3.2 liter mole
-1
) involves a single class of binding sites on the lysozyme molecule. By analogy with similar titration studies on model compounds containing the indole moiety, the site for
N
-methylnicotinamide binding is probably the indole ring of a single, solvent-available tryptophan residue. The yellow color itself apparently arises from a charge transfer transition, with the indole ring system serving as the donor and
N
-methylnicotinamide as the acceptor. Complete resolution of the charge transfer spectrum of the lysozyme-
N
-methylnicotinamide complex was not achieved due to the very high absorbance of the protein near the short-wavelength absorption edge of the band. However, it is possible to consider the spectrum as the sum of two Gaussian bands whose positions and relative intensities agree remarkably well with the positions and relative intensities obtained by Gaussian fitting of the charge transfer spectra of several model complexes between substituted indoles and
N
-methylnicotinamide. The geometry for such complex formation requires that the ring faces of both donor and acceptor be more or less completely available for complexation. The possible use of
N
-methylnicotinamide as a molecular probe for tryptophan residues having at least one indole ring face freely available to the solvent is discussed.
PARTIALLY PURIFIED PHOTOSYNTHETIC REACTION CENTERS FROM PLANT TISSUES
Authors: Vernon Leo P. , Yamamoto Harry Y. , Ogawa Teruo
Published: May 2006

The prior removal of carotenoids from photosynthetic membranes of plants by means of organic extraction allows Triton X-100 to remove and solubilize small particles that are greatly enriched in reaction center Chl, P700. Four plant species have been examined: spinach, bush bean (
Phaseolus vulgaris
), the blue-green alga
Anabaena variabilis
, and
Euglena
. The particles obtained are generally similar and have a ratio of one P700 to approximately 30 chlorophylls (in spinach the ratio is 1 to 28). Exposure of such particles to light or to ferrycyanide causes absorbance changes that are maximal in the vicinity of 700 and 680 nm. The former represents a bleaching (oxidation) of P700, and the latter appears to be caused by a red shift of some Chl closely associated with P700 in the reaction center. The kinetics of P700 oxidation and the fluorescent properties of such preparations indicate a decreased efficiency of energy transfer to the reaction center from the bulk Chl found on the particle.
ANTIBODIES TO RIBONUCLEIC ACID IN SYSTEMIC LUPUS ERYTHEMATOSUS
Authors: Schur Peter H. , Monroe Margaret
Published: May 2006

Sera of 16 of 89 patients with systemic lupus erythematosus contained precipitating antibodies to RNA. These antibodies were found infrequently in patients with rheumatoid arthritis and Sjögren's syndrome, and not at all in patients with juvenile rheumatoid arthritis, myeloma, nor in normal individuals. These studies present evidence for the presence of antibodies to double-stranded RNA (both synthetic and viral). The fact that mammalian RNA's are probably single-stranded nucleotides suggests that these anti-RNA antibodies are directed primarily to a foreign, double-stranded RNA antigen.
EMBRYONIC CELL ADHESIVENESS: DO SPECIES DIFFERENCES EXIST AMONG WARM-BLOODED VERTEBRATES?
Authors: Burdick Morton L. , Steinberg Malcolm S.
Published: May 2006

Mouse and chick embryonic myocardial cells sort out from each other in aggregates of heart ventricle cells. This result invalidates the generalization that embryonic cells of a given tissue from different warm-blooded vertebrate species possess identical cell-sorting properties.
INTRAMOLECULAR LOCALIZATION OF THE ACCEPTOR CROSS-LINKING SITES IN FIBRIN
Authors: Lorand L. , Chenoweth D.
Published: May 2006

Using 1-
14
C-glycine ethyl ester to titrate and label the acceptor cross-linking sites in fibrin, it was possible to localize and characterize the reactivity of these sites. In terms of sulfitolyzed chain fragments, both α and γ chains were shown to act as amine-acceptors, the site in γ being more reactive. Identification and isolation of the acceptor loci were also achieved after cyanogen bromide fragmentation. It is interesting that the “N-terminal disulfide knot” portion of fibrin does not seem to contain acceptor functions.
BASE PAIRING IN 5-CHLOROURIDINE
Authors: Coulter Charles L. , Hawkinson Stuart W.
Published: May 2006

5-Chlorouridine has been found to crystallize from water with the molecules of the nucleoside arranged in a base-paired, parallel-stranded ribbon. This type of polymer structure has not been previously considered for nucleic acids. We have constructed a model of polyuridylic acid based upon the 5-chlorouridine crystal structure and wish to suggest it as a plausible molecular complex for this and perhaps other polynucleotides.

The crystals are monoclinic, space group P2
1
, with
a
= 7.536 A,
b
= 5.790 A,
c
= 13.219 A, and β = 99.89°. There are two 5-chlorouridine molecules per cell. The nucleoside bases are linked across a 2
1
axis with hydrogen bonds between N(3) and O(4). The hydrogen bond length is 2.85 A. The conformation of the base with the ribose about the β-glycosidic bond is
anti
, with a torsion angle relative to O (1′) of -59.8°. The sugar puckering is C(2′)-
endo
, and the conformation about the C(4′)—C(5′) bond is
gauche-gauche
. To build the polymer model, the C(4′)—C(5′) bond was rotated 100° and the sugar-base torsion angle adjusted to -30°. This brought O(3′) and O(5′) of adjacent sugars close enough to make the phosphate ester linkage found in polynucleotides.
THE MODIFICATION OF SOME BIOCHEMICAL PROPERTIES OF MUSCLE BY CROSS-INNERVATION
Authors: Mommaerts W. F. H. M. , Buller A. J. , Seraydarian K.
Published: May 2006

Crossing of the nerves leading to muscles with different contraction characteristics leads to biochemical changes related to the modification of the functional properties. Such changes affect the calcium-transporting activity of isolated sarcotubular vesicles, and the amount and isozyme composition of lactic dehydrogenase.
POLYMORPHISM RESULTING FROM THE MATING ADVANTAGE OF RARE MALE GENOTYPES
Authors: Anderson Wyatt W.
Published: May 2006

An algebraic model is presented for selection by the mating advantage of rare genotypes. In accordance with the results of recent experiments, the selective advantage is formulated as inversely proportional to genotype frequency. The model applies to any number of alleles at an autosomal locus or at a sex-linked locus, and it provides for a different intensity of selection for each genotype in each sex. The frequency of an allele under this selection proceeds to a stable, nontrivial equilibrium when any one of the genotypes carrying the allele
and
any one of those carrying another allele possess some degree of the advantage which varies inversely with genotype frequency. The changes in gene frequency are not affected by the mating system, being, for instance, the same with random mating as with inbreeding. With low values for the selection parameters, genetic polymorphisms could be maintained with little selection apparent except at rather low or rather high gene frequencies. The rare genotype advantage may be a significant element among the mechanisms which maintain the extensive genetic polymorphisms of natural populations.
INDUCTION OF INTERFERON BY PREPARATIONS OF SYNTHETIC SINGLE-STRANDED RNA
Authors: Baron Samuel , Bogomolova N. N. , Billiau Alfons , Levy Hilton B. , Buckler Charles E. , Stern Robert , Naylor Robert
Published: May 2006

A study was undertaken to help determine whether synthetic nonbase-paired, single-stranded RNA as well as synthetic base-paired, double-stranded RNA could induce interferon. Synthetic polyriboinosinic acid and polyribocytidylic acid induced interferon and interferon-like resistance in several different cell culture systems. However, in the intact rabbit only the most active preparations of single-stranded RNA induced circulating interferon when injected intravenously. The induced interferon and antiviral effect in tissue culture and animals was shown to have characteristics of the interferon system. Contamination of the single-stranded synthetic RNA materials by small amounts of base-paired, double-stranded RNA was ruled out by failure to find sufficient heterologous nucleic acid bases by differential activities of single-stranded and double-stranded RNA's in different cell systems and by failure to detect double-stranded RNA in poly-rI upon chromatography on benzoylated DEAE-cellulose.
AUDITORY SENSITIVITY IN THE BULLHEAD CATFISH (
Ictalurus nebulosis
)
Authors: Weiss Burton A. , Strother William F. , Hartig George M.
Published: May 2006

The auditory sensitivity of 4 specimens of the bullhead catfish (
Ictalurus nebulosis
) was determined by shock-avoidance training in an aquatic shuttle box. The range of hearing extended from 100 to 4000 cycles per second, with the maximum sensitivity around 600 to 700 cycles per second.