bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of second-harmonic generation of Lamb waves propagating in layered planar structures with imperfect interfaces
Authors: Deng Mingxi
Published: May 2006

Under second-order perturbation the modal analysis approach for waveguide excitation is used to investigate the generation of second harmonics of Lamb waves propagating in layered planar structures with imperfect interfaces. The imperfect interfaces of layered structures are characterized by the well-known finite interfacial stiffness technique. The analytical results clearly indicate that the efficiency of generation of second harmonics by Lamb wave propagation is strongly dependent on the interfacial stiffness constants. This letter shows a potential that the interfacial properties of layered planar structures can sensitively be evaluated by the effect of second-harmonic generation of Lamb wave propagation.
Pancharatnam-Berry phase optical elements for wave front shaping in the visible domain: Switchable helical mode generation
Authors: Marrucci L. , Manzo C. , Paparo D.
Published: May 2006

We report the realization of a Pancharatnam-Berry phase optical element [Z. Bomzon, G. Biener, V. Kleiner, and E. Hasman, Opt. Lett. 27, 1141 (2002)], for wave front shaping working in the visible spectral domain, based on patterned liquid crystal technology. This device generates helical modes of visible light with the possibility of electro-optically switching between opposite helicities by controlling the handedness of the input circular polarization. By cascading this approach, fast switching among multiple wave front helicities can be achieved, with potential applications to multistate optical information encoding. The approach demonstrated here can be generalized to other polarization-controlled devices for wave front shaping, such as switchable lenses, beam splitters, and holographic elements.
Two color plasmon excitation in an electron-hole bilayer structure controlled by the spin-orbit interaction
Authors: Yang C. H. , Wright A. , Gao F. , Zhang C. , Zeng Z. , Xu W.
Published: May 2006

The dispersion and intensity of coupled plasma excitation in an electron-hole bilayer with Rashba spin-orbit coupling is calculated. We propose to use the spin-orbit coupling in individual layers to tune the intensity of two plasmons. The mechanism can be used to develop a two color terahertz source with tunable intensities.
Conversion efficiency of 10.8% by a dye-sensitized solar cell using a TiO2 electrode with high haze
Authors: Chiba Yasuo , Islam Ashraful , Komiya Ryoichi , Koide Naoki , Han Liyuan
Published: May 2006

We have investigated the effects of titanium dioxide (TiO2) electrodes with high haze on dye-sensitized solar cells (DSCs). The incident photon to current conversion efficiency of the DSCs was greatly improved using TiO2 electrodes with high haze. It was found that haze of the TiO2 electrodes in the infrared region is important for advancing the conversion efficiency of DSCs. A DSC using a high haze TiO2 electrode showed a conversion efficiency of 10.8%, as measured by a public testing center in Japan.
Spatial distribution of ignitions in Mediterranean periurban and rural areas: the case of Catalonia
Authors: Badia-Perpinyá Anna , Pallares-Barbera Montserrat
Published: May 2006

Fire prevention requires a specific treatment subject to the innate characteristics of a territory and to the social interaction that takes place there. The present article deals with very different fire behaviors in two neighboring environments, in which unequal ignitory patterns have been identified. The analyzed environments constitute two prototypes of Mediterranean landscape in the region of Catalonia (Spain). The periurban-fire pattern is identified with the Metropolitan Area of Barcelona. The rural-fire pattern is observed in the county of Bages, with a far more sparse population structure. Sample observations were drawn from databases containing a compilation of ignitions occurring in these two environments during the period from 1987 to 1998. Analysis shows that the distribution of ignitions in the more urban areas is much more concentrated, whereas ignitions in rural areas are far more dispersed, and therefore more difficult to detect. The importance of the present article lies in the identification of the factors determining the patterns of development of ignitions in two very different territories, affected by diverse external pressures. Finally, guidelines for preventive policies adapted to these situations are given, taking into account the specific and differentiated characteristics relevant to each case.
Remote sensing of fire severity in the Blue Mountains: influence of vegetation type and inferring fire intensity
Authors: Hammill Kate A. , Bradstock Ross A.
Published: May 2006

Fire intensity affects ecological and geophysical processes in fire-prone landscapes. We examined the potential for satellite imagery (Satellite Pour l’Observation de la Terre [SPOT2] and Landsat7) to detect and map fire severity patterns in a rugged landscape with variable vegetation near Sydney, Australia. A post-fire, vegetation-based indicator of fire intensity (burnt shrub branch tip diameters, representing the size of fuel consumed) was also used to explore whether fire severity patterns can be used to retrospectively infer patterns of fire intensity. Six severity classes (ranging from unburnt to complete crown consumption) were defined using aerial photograph interpretation and a field assessment across five vegetation types of varying height and complexity (sedge-swamp, heath, woodland, open forest, and tall forest). Using established Normalised Difference Vegetation Index (NDVI) differencing methodology, SPOT2 and Landsat7 imagery yielded similar broad-scale severity patterns across the study area. This was despite differences in image resolution (10 m and 30 m, respectively) and capture dates (2 months and 9 months apart, respectively). However, differences in the total areas mapped for some severity classes were found. In particular, there was reduced differentiation between unburnt and low-severity areas and between crown-scorched and crown-consumed areas when using the Landsat7 data. These differences were caused by fine-scale classification anomalies and were most likely associated with seasonal differences in vegetation condition (associated with time of image capture), post-fire movement of ash, resprouting of vegetation, and low sun elevation. Relationships between field severity class and NDVIdifference values revealed that vegetation type does influence the detection of fire severity using these types of satellite data: regression slopes were greater for woodland, forest, and tall forest data than for sedge-swamp and heath data. The effect of vegetation type on areas mapped in each fire severity class was examined but found to be minimal in the present study due to the uneven distribution of vegetation types in the study area (woodland and open forest cover 86% of the landscape). Field observations of burnt shrub branch tips, which were used as a surrogate for fire intensity, revealed that relationships between fire severity and fire intensity are confounded by vegetation type (mainly height). A method for inferring fire intensity from remotely sensed patterns of fire severity was proposed in which patterns of fire severity and vegetation type are combined.
A process-based model of fine fuel moisture
Authors: Matthews Stuart
Published: May 2006

This paper presents the first complete process-based model for fuel moisture in the litter layer. The model predicts fuel moisture by modelling the energy and water budgets of the litter, intercepted precipitation, and air spaces in the litter. The model was tested against measurements of fuel moisture from two sets of field observations, one made in Eucalyptus mallee-heath under dry conditions and the other during a rainy period in Eucalyptus obliqua forest. The model correctly predicted minimum and maximum fuel moisture content and the timing of minima and maxima in the mallee-heath. Under wet conditions, wetting and drying of the litter profile were correctly predicted but wetting of the surface litter was over-predicted. The structure of the model and the dependence of predictions on model parameters were examined using sensitivity and parameter estimation studies. The results indicated that it should be possible to adapt the model to any forest type by specifying a limited number of parameters. A need for further experimental research on the wetting of litter during rain was also identified.
Clinical signs and duration of cyanide toxicosis delivered by the M-44 ejector in wild dogs
Authors: Hooke Amber L. , Allen Lee , Leung Luke K.-P.
Published: May 2006

Sodium cyanide poison is potentially a more humane method to control wild dogs than sodium fluoroacetate (1080) poison. This study quantified the clinical signs and duration of cyanide toxicosis delivered by the M-44 ejector. The device delivered a nominal 0.88 g of sodium cyanide, which caused the animal to loose the menace reflex in a mean of 43 s, and the animal was assumed to have undergone cerebral hypoxia after the last visible breath. The mean time to cerebral hypoxia was 156 s for a vertical pull and 434 s for a side pull. The difference was possibly because some cyanide may be lost in a side pull. There were three distinct phases of cyanide toxicosis: the initial phase was characterised by head shaking, panting and salivation; the immobilisation phase by incontinence, ataxia and loss of the righting reflex; and the cerebral hypoxia phase by a tetanic seizure. Clinical signs that were exhibited in more than one phase of cyanide toxicosis included retching, agonal breathing, vocalisation, vomiting, altered levels of ocular reflex, leg paddling, tonic muscular spasms, respiratory distress and muscle fasciculations of the muzzle.
Variation in population dynamics and movement patterns between two geographically isolated populations of the dusky hopping mouse (Notomys fuscus)
Authors: Moseby K. E. , Owens H. , Brandle R. , Bice J. K. , Gates J.
Published: May 2006

The ecology of the dusky hopping mouse (Notomys fuscus) was studied at Pelican Waterhole in south-west Queensland and Montecollina Bore in north-east South Australia over an eight-year period. Population parameters of N. fuscus differed markedly between the two study sites. Whilst the population at Montecollina Bore exhibited large fluctuations in size, captures at Pelican Waterhole were lower but more consistent. Recaptures between sessions at Montecollina Bore peaked at 60% but no individuals were recaptured at Pelican Waterhole. No evidence of seasonal breeding was recorded at either site. Male N. fuscus captured at Montecollina Bore were significantly heavier (average 31.4 g) than Pelican Waterhole animals (average 26.6 g). Over a 1–4-night period, the maximum linear distance moved by radio-collared individuals was 1.5 km (average 481 m) at Pelican Waterhole and 400 m (average 199 m) at Montecollina Bore. Differences in population dynamics between the two sites are ascribed to food availability and habitat quality. Whilst Pelican Waterhole may constitute a more stable, less degraded environment, Montecollina Bore appears to be defined by periods of either very high or very low resource availability depending on rainfall. The abundance of dingoes and low cat and fox activity may contribute to the persistence of N. fuscus at the two study sites.
EFFECT OF SEX HORMONES ON THE SERUM-INDUCED THROMBOSIS PHENOMENON
Authors: Amos Solange , Odake K. , Ambrus Clara M. , Ambrus J. L.
Published: May 2006

The renal veins of Sprague-Dawley rats were ligated following intravenous infusion of various dilutions of pooled dog sera. Ten minutes later, the occluded venous segment in each animal was opened, and the presence or absence of a clot was observed. After injection of saline, no clot developed. For each pool of dog sera, a „minimal thrombosis-inducing dose” (MTD) was established. This dose was about ten times higher in females than in males; castration of females reduced it to approximately the male level. Treatment of castrated females with Premarin (a conjugated estrogen preparation) returned the dose to the normal female range. Testosterone treatment of normal females reduced the dose, but to a somewhat less extent than did castration. Endocrine manipulation had little effect on the minimal thrombosis-inducing dose of males. The results obtained in this study appear to be relevant to epidemiological data in human populations, an indication that primary artery thrombosis (coronary occlusion, cerebrovascular accident) is less common in women during the reproductive ages than in men; but after the menopause, the incidence rapidly increases in the female population.
REVERSIBLE THERMAL CONFORMATION CHANGES IN HUMAN SERUM LOW-DENSITY LIPOPROTEIN
Authors: Dearborn Dorr G. , Wetlaufer D. B.
Published: May 2006

Human serum β
1
(LDL
2
) lipoprotein was preparatively divided into three subfractions on the basis of density, and the protein conformation was investigated by optical rotatory dispersion and circular dichroism. The protein conformation was found to vary substantially as a function of lipid composition and temperature in a gradual and reversible manner. Surprisingly, the reversible temperature range includes physiological temperature. From the character of the spectra, it appears that alpha-helix, disordered, and beta conformations can be present in the protein moiety. The presence of these conformations and their distribution appears to depend upon both lipid content and temperature. The importance of this conformational flexibility in its relation to the role of the lipoprotein in lipid transport is discussed.
DIFFERENCES IN LEUCYL-TRANSFER RNA'S AND SYNTHETASE IN SOYBEAN SEEDLINGS
Authors: Anderson Marianne Bieniek , Cherry Joe H.
Published: May 2006

Charged leucyl-transfer RNA (leucyl-tRNA) of soybean cotyledons can be fractionated into six radioactive peaks on a Freon column. Four leucyl-tRNA peaks are observed with the homologous hypocotyl system. Hypocotyl synthetase preparations only slightly acylate the other two leucyl-tRNA's (species 5 and 6). Further, leucyl-tRNA
5 and 6
of the hypocotyl are present in small amounts in comparison to the cotyledon. Therefore, the rate-limiting quantities of synthetase and tRNA
5 and 6
obtained from the hypocotyl prevent the detection of these two species of tRNA when a homologous hypocotyl system is used. To measure the relative amounts of hypocotyl tRNA's, the cotyledon synthetase preparation is employed. Preliminary results show that 6-benzyladenine increases the acylation of leucyl-tRNA
5 and 6
and decreases acylation of tRNA
1
in the hypocotyl. Synthetase preparations from cytokinin-treated plants are not significantly affected.
α-KETO ACID DEHYDROGENASE COMPLEXES, X. REGULATION OF THE ACTIVITY OF THE PYRUVATE DEHYDROGENASE COMPLEX FROM BEEF KIDNEY MITOCHONDRIA BY PHOSPHORYLATION AND DEPHOSPHORYLATION
Authors: Linn Tracy C. , Pettit Flora H. , Reed Lester J.
Published: May 2006

This paper reports the discovery that the activity of the multienzyme pyruvate dehydrogenase complex from beef kidney mitochondria is regulated by a phosphorylation-dephosphorylation reaction sequence. The site of this regulation is the pyruvate dehydrogenase component of the complex. Phosphorylation and concomitant inactivation of pyruvate dehydrogenase are catalyzed by an ATP-specific kinase (i.e., a pyruvate dehydrogenase kinase), and dephosphorylation and concomitant reactivation are catalyzed by a phosphatase (i.e., a pyruvate dehydrogenase phosphatase). The kinase and the phosphatase appear to be regulatory subunits of the pyruvate dehydrogenase complex.
TEMPERATURE-SENSITIVE MUTATIONS IN
Drosophila melanogaster
, III. DOMINANT LETHALS AND SEMILETHALS ON CHROMOSOME 2
Authors: Suzuki David T. , Procunier Douglas
Published: May 2006

Dominant temperature-sensitive lethal and semilethal (
DTS-L
) mutations induced by ethyl methanesulfonate have been recovered in chromosome 2 of
Drosophila melanogaster
. The 19 (0.39% of the chromosomes screened) characterized had greater than 65 per cent viability at 22° ± 2°C and less than 5 per cent at 29° ± 0.5°C. Fifteen of the
DTS-L
's map genetically as point mutants, one appears to be a synthetic lethal, and the remaining three yielded sterile females. Ten different
DTS
mutants had a high survival in triploid females at 29°C. Eleven
DTS-L
's were found to map in the same genetic region (
dp-b
). All behaved as recessive lethals at 22°C and failed to survive at 22°C when combined with mutants
3
and
12
. Crosses of the 11 mutants in all possible pairwise combinations yielded a circular complementation map with a side branch. The effective lethal phases and temperature-sensitive periods during development were determined for 15 of the mutants.
Azotobacter vinelandii
RNA POLYMERASE, VII. ENZYME TRANSITIONS DURING UNPRIMED r[I-C] SYNTHESIS
Authors: Krakow J. S. , Daley K. , Karstadt M.
Published: May 2006

Transitions in the state of RNA polymerase were demonstrated during the unprimed synthesis of the r[I-C] copolymer. No detectable change in the usual dimer-monomer pattern was noted during the lag phase (0-25 min at 37°) after analysis of the reaction mixture by acrylamide gel electrophoresis. At the end of the lag phase, a major alteration in the electrophoretic pattern occurred, marked by the disappearance of the dimer-monomer bands and the concomitant appearance of a series of monomer-r[I-C] copolymer complexes. As these complexes of r[I-C] copolymer with one or more polymerase monomer were formed, an enzymatically inactive component (γ protein) of the polymerase was displaced. During the phase of rapid r[I-C] copolymer synthesis, the active form of the
A. vinelandii
RNA polymerase was the r[I-C] monomer lacking the γ protein.
RELATIONSHIP BETWEEN NUCLEAR GIANT-SIZE DRNA AND MICROSOMAL DRNA OF RAT BRAIN
Authors: Stévenin James , Mandel Paul , Jacob Monique
Published: May 2006

(1) Among the DNA-like RNA (dRNA) species of rat brain, 35 per cent remain nuclear, whereas 65 per cent are found in the microsomes and may represent functional messenger RNA. It was estimated that 30,000-300,000 cistrons would thus code for messenger RNA in rat brain.

(2) No nuclear-specific dRNA with sedimentation characteristics similar to microsomal dRNA are detected.

(3) The nuclear large dRNA contain all the dRNA species of the brain.

(4) The presence of microsomal dRNA precursors and of nuclear restricted dRNA in large dRNA suggests the existence of a limited cleavage process and of a selection among the fragments for their transport from the nucleus to the cytoplasm. Such a selective mechanism could represent an important regulation step in the transfer of genetic information.
THE PURINE REQUIREMENT OF CELLS CULTURED FROM HUMANS AFFECTED WITH THE LESCH-NYHAN SYNDROME (HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE DEFICIENCY)
Authors: Felix Jeanette S. , DeMars Robert
Published: May 2006

Humans with the Lesch-Nyhan syndrome have an X-chromosomal mutant gene that causes severe neurological and developmental abnormalities. The patients are deficient in hypoxanthine-guanine phosphoribosyltransferase, which converts hypoxanthine to inosinic acid, a major precursor of adenine and guanine nucleotides. Paradoxically, the enzyme defect causes hypernormal
de novo
synthesis of inosinic acid, which manifests itself as excesses of hypoxanthine, xanthine, and uric acid. The first step in the
de novo
pathway is thought to be rate-limiting, due to feedback repression by adenine and guanine nucleotides. The derepressed rate of purine production in mutants and their failure to thrive could result from reduction in the amounts of nucleotides derived from inosinic acid to levels that are inadequate for normal feedback control and for nucleic acid synthesis needed in growth. Studies with cultured cells, reported here, support the interpretation that mutants are, in effect, nucleotide-deficient. Skin fibroblasts from patients fail to proliferate in media that do not contain supplementary adenine or folic acid, a participant in two stages of purine biosynthesis. The folic acid requirement of mutant cells is at least 50-fold greater than that of normal cells, which can synthesize all the nucleotides needed for growth without exogenous adenine. Both folic acid and adenine supplements are thought to provide mutant cells with the means of making more inosinic acid available for conversion to adenine and guanine nucleotides. It is not clear why the availability of inosinate or its conversion to other nucleotides is impaired. Therapy with adenine or folic acid begun at the time of birth may avert development of the disease in mutant males.

The relevant gene is X-linked and shows clonal, single-allele-expression: phenotypically normal and phenotypically mutant clones have been derived from females heterozygous for the mutant gene. The phenotypically mutant heterozygous clones have the same requirement for adenine or folic acid as cells from hemizygous mutant males, an indication that the normal allele is repressed in these clones. The adenine-folic acid requirement of mutant cells provides a method of direct, clonal selection for rare, phenotypically normal cells in mutant populations, which is applicable to the single-active-X problem and other
in vitro
genetic studies.
THE EFFECT OF TRNA CONCENTRATION ON THE RATE OF PROTEIN SYNTHESIS
Authors: Anderson W. French
Published: May 2006

Two
in vitro
protein-synthesizing systems derived from
E. coli
have been utilized to demonstrate that the concentration of a tRNA species can regulate the rate of translation of a messenger RNA. (
a
) The rate of poly-U-directed C
14
-phenylalanine incorporation into protein is stimulated by concentrations of tRNA

Phe

from 1.5 × 10
-8
M to 3.0 × 10
-6
M, the latter representing a tRNA

Phe

/70
S
ribosome ratio of 7. (
b
) The rate of translation of poly A,G in a S-30 protein-synthesizing system derived from
E. coli
is limited by the amount of tRNA

Arg

recognizing the codewords AGA and AGG present in the extract. Polypeptide synthesis can be stimulated in direct proportion to the amount of this tRNA

Arg

species added to the reaction mixture. A mechanism for regulating the rate of protein synthesis at the translational level may be the slowing of polypeptide chain propagation at certain codons due to the presence of rate-limiting tRNA species.
CYTOCHROME OXIDASE DEFICIENCY IN WILSON'S DISEASE: A SUGGESTED CERULOPLASMIN FUNCTION
Authors: Shokeir M. H. K. , Shreffler D. C.
Published: May 2006

The hypothesis is advanced that ceruloplasmin functions in enzymatic transfer of copper to copper-containing enzymes, such as cytochrome oxidase. To test this hypothesis, leucocytes from Wilson's disease patients, heterozygous carriers, and normal subjects were assayed for cytochrome-oxidase activity. The data reported here show markedly reduced levels of activity in Wilson's disease cases and moderate reductions in heterozygous individuals relative to normal controls. These observations and a close correlation between the level of cytochrome-oxidase activity in the leucocytes and ceruloplasmin in the serum tend to support the hypothesis.
DEHYDROALANYLLYSINE: IDENTICAL COOH-TERMINAL STRUCTURES IN THE PEPTIDE ANTIBIOTICS NISIN AND SUBTILIN
Authors: Gross Erhard , Morell John L. , Craig Lyman C.
Published: May 2006

The recent finding of α,β-unsaturated amino acid residues by Gross and Morrel in the polypeptide antibiotic nisin has stimulated a wider investigation of other antibiotic peptides, particularly those known to contain lanthionine. Subtilin is similar to nisin in that it polymerizes easily and contains lanthionine and β-methyl lanthionine. Like nisin it was found to contain a carboxyl terminal dehydroalanyllysine sequence and to be split by the enzyme nisinase. An additional α,β-unsaturated amino acid residue was shown to be present in subtilin by reaction with excess methyl mercaptoacetate and subsequent hydrolysis and amino acid analysis. Nisin contains three dehydropeptide residues.
AGE AND FLUORESCENCE CHARACTERISTICS IN SOME SPECIES OF ATHIORHODACEAE
Authors: Klerk H. De , Govindjee  , Kamen M. D. , Lavorel J.
Published: May 2006

Nonsulfur photosynthetic bacteria (Athiorhodaceae) exhibit a time-variable fluorescence in addition to a constant fluorescence. All species examined show upon aging a remarkable gain in the variable component at the expense of the constant component while the total fluorescence remains essentially invariant. This result can be rationalized by supposing a change in distribution of bacteriochlorophyll in photosynthetic units as cells age. Alternatively, one may assume operation of two photochemical systems—one cyclic and predominant in young cells, the other noncyclic and predominant in old cells. It is also noted that a hitherto unreported minor fluorescence with maximum emission at ∼ 860 nm exists in addition to the well-known main fluorescence band at ∼ 890 nm. The rise in variable fluorescence is associated with the main band, a result in accord with the notion that the bacteriochlorophyll component responsible and absorbing at 870 nm is directly in contact with the energy trap.
A DIFFERENCE IN THE ARCHITECTURE OF THE SURFACE MEMBRANE OF NORMAL AND VIRALLY TRANSFORMED CELLS
Authors: Burger Max M.
Published: May 2006

Several tissue culture cell lines that were transformed by a tumor virus have been found to react with an agglutinin, while under identical conditions their untransformed parent cell lines did not agglutinate. Since a short treatment of the parent cell line with low concentrations of proteases exposed the same agglutinin receptor sites in a fashion indistinguishable from the transformed cells, it is proposed that both viral and chemical transformation produce changes in the architecture of the membrane, identical to those of the proteases.
DEVELOPMENTAL PHASES OF THE BIOCOENOSIS
Authors: Goulden Clyde E.
Published: May 2006

Species number and diversity increase log-linearly with time during the early development of a biocoenosis. This period may be divided into three phases. In the first phase, diversity increases with the rapid immigration of species into the newly established habitat. In the second phase, diversity increases as common species become less common and rare species less rare. This period ends with the attainment of a maximum diversity pattern. In the third phase, rare species continue to invade the habitat until it is saturated. In each phase there is a maximal number of species that can invade the habitat.
THE INTERACTION OF RNA POLYMERASE WITH HISTONES
Authors: Spelsberg Thomas C. , Tankersley Sharon , Hnilica Lubomir S.
Published: May 2006

Arginine-rich histones (F3) interact with both the bacterial and mammalian RNA polymerase and inhibit the
in vitro
RNA synthesis to a much greater extent than when associated with the DNA template. The lysine-rich histones (F1) inhibit the RNA synthesis mainly through template inhibition. Neither histone fraction displayed such an interaction with DNA polymerase. The RNA polymerase-F3 histone interaction takes place at ionic strength equal to or greater than those occurring in living cells, suggesting a possible role of arginine-rich histones in the regulation of RNA synthesis.
SOLUBLE HEPATIC δ-AMINOLEVULINIC ACID SYNTHETASE: END-PRODUCT INHIBITION OF THE PARTIALLY PURIFIED ENZYME
Authors: Scholnick Perry L. , Hammaker Lydia E. , Marver Harvey S.
Published: May 2006

The present study confirms the existence of hepatic δ-aminolevulinic acid synthetase in the cytosol of the liver, suggests that this enzyme may be in transit to the mitochondria, and defines some of the characteristics of the partially purified enzyme. The substrate and cofactor requirements are similar to those of mitochondrial δ-aminolevulinic acid synthetase. Heme strongly inhibits the partially purified enzyme. A number of proteins that bind heme block this inhibition, which explains previous failures to demonstrate heme inhibition in crude systems. End-product inhibition of δ-aminolevulinic acid synthetase in the mitochondria may play an important role in the regulation of heme biosynthesis in eukaryotic cells.
RELEASE OF TRANSFER RNA DURING PEPTIDE CHAIN ELONGATION
Authors: Lucas-Lenard Jean , Haenni Anne-Lise
Published: May 2006

In amino acid polymerization, the tRNA donating its peptidyl moiety to the neighboring aminoacyl-tRNA must be released from the ribosome for further growth of the polypeptide chain. It was not known at what stage of peptide elongation this tRNA is released. To study this question, we prepared ac-C
14
-Phe-H
3
-tRNA using H
3
-tRNA isolated from
E. coli
strain 15THU grown in the presence of H
3
-uracil, and followed the fate of the H
3
-tRNA during chain growth. Our results indicate that donor tRNA is released during the translocation step, mediated by the soluble factor G and GTP.
X-RAY ANALYSIS OF RETINAL PHOTORECEPTORS
Authors: Gras W. J. , Worthington C. R.
Published: May 2006

A series of low-angle X-ray reflections have been recorded from photoreceptors in four types of intact untreated retinae. The retinae were maintained in a living condition during the X-ray exposure. The X-ray reflections arise from the regular arrangement of disk membranes within the photoreceptors. The recorded X-ray intensities contain information on the onedimensional electron-density distribution of the photoreceptors. An electrondensity model which is in good agreement with the low-angle X-ray data has been derived.
PURIFICATION OF MITOGENIC PROTEINS DERIVED FROM
Phaseolus vulgaris
: ISOLATION OF POTENT AND WEAK PHYTOHEMAGGLUTININS POSSESSING MITOGENIC ACTIVITY
Authors: Allen Lawrence W. , Svenson Robert H. , Yachnin Stanley
Published: May 2006

Commercially obtained phytohemagglutinin (PHAP) derived from
Phaseolus vulgaris
contains 17 different protein bands when analyzed by acrylamide gel electrophoresis. When it is subjected to CM-Sephadex chromatography followed by molecular sieving on Sephadex G150, several species of potent mitogenic proteins, which differ greatly in their hemagglutinating capacity, are obtained. A low hemagglutinating mitogen (L-PHAP), homogeneous by several different criteria, is the most potent mitogen isolated, and also possesses potent leukoagglutinating activity. It is a glycoprotein with a molecular weight of 115,000, containing glucosamine, mannose, xylose, and fucose or arabinose. Also isolated is a mixture of at least two closely related proteins possessing high hemagglutinating capacity, with hemagglutination titers 250 times more potent than L-PHAP. This material is a slightly less potent mitogen than L-PHAP and also possesses leukoagglutinating capacity, although of a lower order of magnitude. Its amino acid and carbohydrate composition are similar to L-PHAP, but it contains approximately twice as much carbohydrate and is slightly larger as determined by molecular sieving.
TRANSFORMATION AND CHROMOSOME CHANGES INDUCED BY EPSTEIN-BARR VIRUS IN NORMAL HUMAN LEUKOCYTE CULTURES
Authors: Gerber Paul , Whang-Peng Jacqueline , Monroe James H.
Published: May 2006

Three separate attempts to establish long-term leukocyte cultures from the peripheral blood of a healthy adult who had no evidence of previous infection with Epstein-Barr virus were consistently unsuccessful. On the other hand,
in vitro
infection of buffy-coat cells of this donor with Epstein-Barr virus resulted in blastoid transformation of the lymphocytes and long-term growth potential. The transformation was accompanied by major chromosome changes. The significance of these findings in relation to lymphoproliferative diseases in man remains to be determined.
REPLICATION AND PROPERTIES OF DNA IN NICOTINAMIDE ADENINE DINUCLEOTIDE DEFICIENCY OF
Escherichia coli
CELLS
Authors: Nozawa Ryushi , Mizuno Den'ichi
Published: May 2006

When niacin-requiring
E. coli
was starved of niacin, a precursor of nicotinamide adenine dinucleotide (NAD), the cells elongated and synthesis of DNA was inhibited while syntheses of RNA and protein continued. The cellular NAD concentration decreased to less than one tenth of the normal level in niacin deficiency, but no change in DNA ligase level was detected. The apparent inhibition of DNA synthesis can be explained as due to reduction in the activity of the cofactor, NAD, for the enzyme.

The DNA synthesized in this state was small in an alkaline sucrose gradient but of normal size in a neutral sucrose gradient. The molecules had a double-stranded structure, as judged by hydroxyapatite chromatography. The small pieces of DNA were integrated into normal-size DNA molecules on addition of niacin, when the cellular NAD concentration was restored to the normal level but DNA synthesis was not. It is suggested that this small DNA is an intermediate in DNA replication.
LIGHT-INDUCED OXIDATION OF A CHLOROPLAST B-TYPE CYTOCHROME AT -189°C
Authors: Knaff David B. , Arnon Daniel I.
Published: May 2006

The
b
-type cytochromes of chloroplasts have heretofore been viewed as photosynthetic electron carriers that probably occupy an intermediate position in a light-induced electron flow. The oxidation-reduction of such intermediate electron carriers, being removed from the primary photochemical reaction linked to photon capture by chlorophyll, would be expected to show a temperature dependence. Evidence has now been obtained that cytochrome
b
559
is photooxidized at -189°C and that this photooxidation can be induced only by “short-wavelength” monochromatic light which activates the oxygen-evolving system in chloroplasts (photosystem II). In appears, therefore, that photooxidation of cytochrome b
559
is closely linked with photon capture by the chlorophyll pigments characteristic of photosystem II.
HIGH-RESOLUTION PROTON NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY OF CYTOCHROME
c
Authors: Wüthrich Kurt
Published: May 2006

In cytochrome
c
the axial positions of the heme iron are occupied by two amino acid residues, one of which is known from X-ray studies to be histidyl. Nuclear magnetic resonance spectroscopy provides strong evidence that the sixth ligand is a methionyl residue in both the ferric and ferrous oxidation states. It is further shown that in cyanoferricytochrome
c
cyanide ion replaces methionyl in the first coordination sphere of the heme iron. Additional data are obtained on the protein conformation and on the electronic structure of the heme group in ferricytochrome
c
. As in other heme proteins, the interactions with the polypeptide chain greatly affect the unpaired electron distribution in the heme group of cytochrome
c
. In particular, from a comparison of ferricytochrome
c
and cyanoferricytochrome
c
, the importance of the coordination of the sixth ligand is apparent.
THE ACTION SPECTRUM FOR BREAKING DIAPAUSE IN THE CODLING MOTH,
Laspeyresia pomonella
(L.), AND THE OAK SILKWORM,
Antheraea pernyi
GUER
Authors: Norris K. H. , Howell F. , Hayes D. K. , Adler V. E. , Sullivan W. N. , Schechter M. S.
Published: May 2006

The action spectrum for breaking diapause in the oak silkworm,
Antheraea pernyi
Guer., and the codling moth,
Laspeyresia pomonella
(L.), was determined from 400 to 700 nm with a wedge-interference spectrograph. Insects were exposed to ten hours of white light, followed by six hours of spectral light each day for 45 days. The portion of the spectrum between 400 and 500 nm was found to be the most effective in terminating diapause. Diapause was broken for both insects with energy levels as low as 0.02 μw/cm
2
.
MECHANISM OF PROFLAVIN MUTAGENESIS
Authors: Sarabhai Anand , Lamfrom Hildegard
Published: May 2006

The mutagenic action of proflavin on bacteriophage T4 is greater in the presence of defective T4 ligase than in the presence of normal T4 ligase. This suggests that the persistence of single-strand breaks in DNA enhances proflavin mutagenesis.
PENICILLINASE PLASMID DNA FROM
Staphylococcus aureus
Authors: Rush Mark G. , Gordon C. N. , Novick Richard P. , Warner Robert C.
Published: May 2006

A penicillinase plasmid from
Staphylococcus aureus
and three of its derivatives, all previously identified as extrachromosomal genetic elements, have been isolated in high yield as circular duplex DNA molecules. The wild-type plasmid was found by contour-length measurements of electron micrographs to have a molecular weight of 18.6 × 10
6
daltons. Two plasmids with deletions encompassing six and eight of the eleven known plasmid cistrons had molecular weights of 16.4 × 10
6
and 15.3 × 10
6
daltons, respectively. This information was used to establish approximate physical distances for the genetic map. A high-frequency transducing element also derived from the plasmid had a molecular weight of approximately 24 × 10
6
daltons. Although each plasmid preparation appeared homogeneous by ultracentrifugal analysis, electron micrographs always revealed the presence of a low percentage of complex oligomeric forms, particularly circular and catenated dimers.
INHIBITION OF HUMAN BRAIN PYRUVATE KINASE AND HEXOKINASE BY PHENYLALANINE AND PHENYLPYRUVATE: POSSIBLE RELEVANCE TO PHENYLKETONURIC BRAIN DAMAGE
Authors: Weber George
Published: May 2006

In phenylketonuria high levels of L-phenylalanine are present along with increased levels of phenylpyruvic acid. The present work shows that L-phenylalanine is a competitive inhibitor of human brain pyruvate kinase and phenylpyruvic acid is an inhibitor of human brain hexokinase. The enzymes have approximately the same

K
i

for these inhibitors in adult and in fetal human brain. However, in the fetal human brain the absolute activities for both enzymes are less than 10 per cent of those found in the adult. Thus, the fetal brain enzymes may be more vulnerable to inhibition by these compounds in the phenylketonurics. The inhibition of human brain pyruvate kinase and hexokinase by L-phenylalanine and phenylpyruvic acid may have a role in the brain damage in phenylketonurics.
EVIDENCE FOR A ROLE OF CYCLIC AMP IN NEUROMUSCULAR TRANSMISSION
Authors: Goldberg Alfred L. , Singer Joshua J.
Published: May 2006

Experiments were undertaken to determine if the effects of epinephrine in promoting neuromuscular transmission were mediated by adenosine 3′:5′-cyclic phosphate (cyclic AMP). Dibutyryl cyclic AMP and the methyl xanthines, theophylline and caffeine (which inhibit cyclic AMP hydrolysis), were found to increase the amplitude of the end plate potential in the isolated rat diaphragm. Like epinephrine (which is known to promote cyclic AMP synthesis), these agents appear to facilitate the release of acetylcholine from the motor neuron. This interpretation is supported by the observation that theophylline and dibutyryl cyclic AMP markedly increased the frequency but not the amplitude of the spontaneous miniature end plate potentials. In addition, these drugs increased the number of transmitter packets released in response to nerve stimulation. These results are consistent with the view that cyclic AMP plays a role in the release of acetylcholine and in the “defatiguing effect” of epinephrine.
THE RADIOIMMUNOASSAY OF CIRCULATING CARCINOEMBRYONIC ANTIGEN OF THE HUMAN DIGESTIVE SYSTEM
Authors: Thomson D. M. P. , Krupey J. , Freedman S. O. , Gold P.
Published: May 2006

A radioimmunoassay has been developed for determining the serum levels of carcinoembryonic antigen of the human digestive system in patients with cancer of the colon and rectum. The assay is simple to perform and has a high degree of reproducibility and specificity. The test detects a concentration of 2.5 ng of carcinoembryonic antigen per ml of serum and this has provided the first demonstration of a circulating tumor-specific antigen in the sera of cancer patients.
THE DEFECT IN HURLER AND HUNTER SYNDROMES, II. DEFICIENCY OF SPECIFIC FACTORS INVOLVED IN MUCOPOLYSACCHARIDE DEGRADATION
Authors: Fratantoni Joseph C. , Hall Clara W. , Neufeld Elizabeth F.
Published: May 2006

Cultured fibroblasts, derived from patients with the Hurler and Hunter syndromes, show defective degradation of sulfated mucopolysaccharide. The aberrant metabolism of Hurler cells can be corrected by secretions of fibroblasts of genotype other than Hurler, and similarly, the defect of Hunter cells can be corrected by secretions of fibroblasts of genotype other than Hunter. The active factors in these secretions, which are heat labile and associated with macromolecules, accelerate the degradation of mucopolysaccharide.
SOLID PHASE SYNTHESIS OF A 42-RESIDUE FRAGMENT OF STAPHYLOCOCCAL NUCLEASE: PROPERTIES OF A SEMISYNTHETIC ENZYME
Authors: Ontjes David A. , Anfinsen Christian B.
Published: May 2006

The polypeptide corresponding to the amino acid sequence from residue 6 through 47 in staphylococcal nuclease has been synthesized by the solid-phase method. The synthetic product closely resembles the corresponding native polypeptide in both physical and chemical properties. The synthetic peptide may be recombined with the complimentary native peptide comprising residues 49 through 149 to form an active, semisynthetic enzyme. The “functional purification” of the crude, synthetic polypeptide by affinity chromatography was found to yield a synthetic fraction of greatly enhanced specific activity. This purification was accomplished on a column of Sepharose to which the complimentary native peptide had been covalently bound.
NONPERMISSIVE INFECTIONS OF MAMMALIAN CELLS: SYNTHESIS OF INFLUENZA VIRUS GENOME IN HeLa CELLS
Authors: Lerner R. A. , Hodge L. D.
Published: May 2006

The RNA synthesis of a single-stranded, multisegmented viral genome has been investigated in nonpermissive host cells. In HeLa cells, both single- and double-stranded influenza viral RNA were made and accumulated, and synthesis was completed by 15 hours. The evidence indicated that all pieces of the genome were synthesized. At least as much viral RNA was synthesized in HeLa cells as in permissive chick embryo fibroblasts cells. Explanations for this nonpermissive infection based on reduced synthesis of viral RNA or rapid destruction of newly synthesized RNA, uncontrolled synthesis of RNA, or partial synthesis of the genome appear to have been ruled out by this investigation. The persistently high amounts of double-stranded RNA, combined with the reported lack of dispersion of nucleocapsid protein from the nuclear region of the HeLa cell are consistent with a failure of assembly of the virion in this host. This nonpermissive infection of HeLa cells with influenza virus may offer a unique system for the accumulation of the intermediates involved in the assembly of a complex RNA viral genome.
THE GENETIC CODE AND ERROR TRANSMISSION
Authors: Alff-Steinberger C.
Published: May 2006

The amino acid substitutions resulting from single-base substitution in the natural genetic code have been compared with those resulting from single-base substitutions in computer-generated random codes. Considering the amino acid properties of molecular weight, polar requirement, number of dissociating groups, pK
1
′, isoelectric point, and α-helix forming ability, it is concluded that, for the natural code, single-base substitution in the first position of the codon tends to result in the substitution of an amino acid more similar to the original amino acid than would be expected from a random code. In the natural code, the second position of the codon plays the largest role in determining the properties of the amino acid.
ABNORMAL CIRCULAR DNA MOLECULES INDUCED BY ETHIDIUM BROMIDE IN THE KINETOPLAST OF
Trypanosoma cruzi
Authors: Riou Guy , Delain Etienne
Published: May 2006

The trypanocidal drug ethidium bromide induced abnormal circular DNA molecules with high frequency in the kinetoplast of
Trypanosoma cruzi
. These molecules are circular dimers, trimers, or higher circular forms with a contour length which is a multiple of the monomer length usually found in the kinetoplastic DNA of normal trypanosomes. These abnormal molecules represent more than 30 per cent of the kinetoplastic DNA, while in normal kinetoplastic DNA we only observed three circular dimers out of several thousand molecules measured.
DAILY RHYTHMS IN HEPATIC POLYSOME PROFILES AND TYROSINE TRANSAMINASE ACTIVITY: ROLE OF DIETARY PROTEIN
Authors: Fishman Bette , Wurtman Richard J. , Munro Hamish N.
Published: May 2006

Hepatic polysome profiles vary in untreated rats as a function of time of day. The ratio of polysomes to total ribosomes increases from 50 to 73 per cent in darkness. There is also a daily rhythm in tyrosine transaminase activity which resembles but does not coincide with the polysome rhythm. Both rhythms are dependent on the cyclic ingestion of dietary protein, and disappear in rats given a protein-free diet.
THE NERVE GROWTH FACTOR: PURIFICATION AS A 30,000-MOLECULAR-WEIGHT PROTEIN
Authors: Bocchini Vincenzo , Angeletti Pietro U.
Published: May 2006

The nerve growth factor protein was purified over 100-fold from adult mouse salivary glands. The first step was a gel filtration on Sephadex G-100 at pH 7.5 of the aqueous gland extract. After gel filtration, most of the NGF activity was eluted in the 80,000-90,000-molecular-weight region (G-100 pool). The G-100 pool was dialyzed at pH 5.0 and fractionated by CM52 cellulose chromatography at pH 5.0. Recovery from CM52 cellulose columns was quantitative for protein and ranged 80-100 per cent for the nerve growth factor activity; the latter was almost completely carried by a protein which did not show any heterogeneity when examined by several analytical tests. The purified nerve growth factor showed an
S

20,
w

= 2.43, a
D

20,
w

= 7.30 and a 30,000 molecular weight. The over-all recovery was about 45 per cent.
THE UNEXTRACTABLE ORGANIC FRACTION OF THE PUEBLITO DE ALLENDE METEORITE: EVIDENCE FOR ITS INDIGENOUS NATURE
Authors: Simmonds P. G. , Bauman A. J. , Bollin E. M. , Gelpi E. , Oró J.
Published: May 2006

The Pueblito de Allende meteorite contains only 0.1-0.5 ppm of solvent-extractable carbon, most or all of which is due to terrestrial contamination. Determinations of the total carbon content gives values from 0.23 to 0.35 per cent. The presumed indigenous insoluble carbon is thus present in a ratio of 2300:1 relative to contaminant carbon. A sample of the meteorite was extracted with a deuterated solvent containing benzene:methanol (4:1 w/w) to remove contaminants and then was subjected to pyrolysis-gas chromatography-mass spectrometry to investigate the nature of the remaining carbon. The pyrolysis products (about 20 ppm) consisted chiefly of aromatic and substituted aromatic hydrocarbons. The pyrolysis results were confirmed by oxidative thermal analysis which showed that the bulk of the carbon present was a macromolecular structure and not graphite. This suggests that an insoluble nongraphitic condensed aromatic polymer is indigenous to the meteorite. The origin and precise chemical structure of this material has not been determined, but it bears a superficial resemblance to coal-like structures.
CONTROL OF FATTY ACID COMPOSITION IN PHOSPHOLIPIDS OF
Escherichia coli
: RESPONSE TO FATTY ACID SUPPLEMENTS IN A FATTY ACID AUXOTROPH
Authors: Esfahani Mojtaba , Barnes Eugene M. , Wakil Salih J.
Published: May 2006

The effect of exogenous unsaturated fatty acids on the fatty acid composition of phospholipids of a mutant of
E. coli
has been examined. These exogenous acids serve as growth factors for an auxotroph requiring unsaturated fatty acids. When each member of a structurally homologous series of
cis
-unsaturated fatty acids serves as a growth factor, the percentage of unsaturated fatty acid present in phospholipids increases with increasing chain length or decreasing number of double bonds in the apolar chain of the supplement. At 37°,
trans
-octadecenoic acids support growth and are incorporated into phospholipids at levels higher than the corresponding
cis
-acids. However, a temperature shift to 27° with
trans
-acids results in loss of viability and lysis. Utilization of
cis
-acids as supplements at decreasing temperatures between 42° and 27° results in increasing amounts of unsaturated fatty acids in phospholipids with decreasing temperature. These observations suggest the operation of a regulatory mechanism which controls the composition of saturated versus unsaturated acids in order to maintain the physical properties of phospholipids within narrow limits.