bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Pressure Spectral Studies of Mixed Valence Compounds of Antimony
Authors: Chiu V. C. K. , Drickamer H. G.
Published: May 2006

In Cs
2
SbCl
6
and related compounds antimony appears as Sb(III) and Sb(V) in alternate halide octahedra. The optical spectrum contains “mixed valence” peaks assigned to Sb(III) → Sb(V) transfer near 18 and 27 kK (cm
-1
). In addition there is a peak near 31 kK assigned to an internal transition on Sb(III) and one near 37 kK assigned to Sb(V), mixed with the absorption edge of the crystal. The mixed valence peaks shift strongly to lower energy with pressure (about 5 kK in 120 kbar), and decrease rapidly in integrated intensity, as does the Sb(III) peak near 31 kK. A new peak appears near 33-34 kK, tentatively assigned to Sb(IV). The ground state apparently transforms from Sb(III)-Sb(V) to Sb(IV)-Sb(IV) at high pressure. Similar behavior is observed for Cs
2
Sb
0.3
Sn
0.7
Cl
6
and (CH
3
CH
2
NH
3
)
2
Sb
0.5
Sn
0.5
Cl
6
.
Reinitiation of a
lac
Repressor Fragment at a Codon Other Than AUG
Authors: Ganem Donald , Miller Jeffrey H. , Files James G. , Platt Terry , Weber Klaus
Published: May 2006

52 Spontaneous nonsense mutants in the
lac i
gene of
Escherichia coli
were isolated and characterized. All mutants located early in the gene show negative complementation
in vivo
with a wild-type
i
gene in a
recA
diploid strain.
In vitro
studies show that those mutants that display negative complementing activity
in vivo
also make
lac
repressor fragments retaining inducer binding and immunological crossreactivity with wild-type repressor. Amino-acid sequence analysis of these fragments shows that they arise by reinitiation at internal sities of the
i
message after chain termination at a prior amber or ochre codon.

There are at least two different internal reinitiation sites in the first 200 nucleotides of the translated part of the
i
message. The first site corresponds to the first internal in phase AUG codon, which specifies the methionine residue at position 42 of the repressor protein. This site can be activated by an amber codon, 45 nucleotides before the AUG codon. The second site is only 60 nucleotides past the first site and can be activated by an amber mutation derived from residue 60 of the protein. The second initiation codon specifies the amino-acid leucine in the wild-type repressor, but the reinitiated fragment shows an amino-terminal methionine residue at this position. Therefore, the second initiation site seems to involve an
in vivo
ambiguity of the genetic code in that the same codon can be translated into two different amino acids depending on the recognition of this codon during initiation (when methionine is inserted) or elongation of protein synthesis (when leucine is inserted). The possibility that a codon other than AUG can act as an initiation codon
in vivo
is discussed.
Primate RNA Tumor Virus-Like DNA Synthesized Endogenously by RNA-Dependent DNA Polymerase in Virus-Like Particles from Fresh Human Acute Leukemic Blood Cells
Authors: Gallo R. C. , Miller N. R. , Saxinger W. C. , Gillespie D.
Published: May 2006

A particle of discrete biochemical composition was purified from fresh, unfrozen peripheral blood leukocytes of human patients with acute myeloblastic leukemia. This particle endogenously synthesized DNA by use of an RNA primer and template. About half of the DNA sequences synthesized in the presence of actinomycin D hybridized to RNA isolated from type-C sarcoma viruses of primates or mice; lower annealing values were obtained with RNA isolated from other sarcoma or leukemia viruses. The results confirm and extend previous results from molecular hybridization experiments related to the existence in human leukemia of components of RNA tumor viruses.
Magnetofluid-Dynamic Spectrum and Low Shear Stability
Authors: Grad Harold
Published: May 2006

For a perfectly conducting, cylindrical plasma equilibrium (“screw-pinch”), the spectrum contains four distinct continua, three of which can extend to the origin. This implies the existence of irreversible damping and heating in the nondissipative model. The continuum becomes (Suydam) unstable by instantly shedding an infinite number of point eigenvalues. More generally, any
local
instability implies an infinity of unstable eigenvalues. Spectral analysis of a new class of low shear,
semilocal
unstable modes provides a connection between Suydam modes, found only in sheared systems, and interchanges, found only in closed line (shearless) systems, and gives rise to the concept of an
effective
marginal stability threshold. Study of the spectrum should also provide a unified picture of many other plasma phenomena.
Regulation of Hepatic Glycogen Synthesis During Fetal Development: Roles of Hydrocortisone, Insulin, and Insulin Receptors
Authors: Eisen Howard J. , Goldfine Ira D. , Glinsmann Walter H.
Published: May 2006

In fetal rat liver
in utero
, an increase in glycogen and the glycogen synthetic enzyme glycogen synthetase (EC 2.4.1.11) occurs between gestational days 17 and 19. We used an organ culture system for finding the stimulus for increased enzyme activity and defining the relationship of this increase to glycogen synthesis. In fetal-liver explants from an earlier period (gestational day 16), hydrocortisone causes an elevation in total glycogen synthetase activity. This effect, which can be blocked by actinomycin D, is strikingly similar in time course and magnitude to the normal increase
in utero
. However, in order for glycogen synthesis to proceed after hydrocortisone increases glycogen synthetase levels, insulin is required. Unlike hydrocortisone, insulin does not increase total glycogen synthetase; it appears to act by converting the
b
or phospho form of synthetase to the
a
or dephospho form. Insulin alone does not stimulate glycogen synthesis in explants from 16-day fetal liver, although no defect in insulin binding was demonstrable. These findings support the hypothesis that the increase in liver-glycogen synthesis during the last trimester requires glucocorticoids for the developmental induction of glycogen synthetase and insulin for activation of the enzyme.
Requirement of a Phage-Induced 5′-Exonuclease for the Expression of Late Genes of Bacteriophage T5
Authors: Chinnadurai G. , McCorquodale D. J.
Published: May 2006

Amber mutants of bacteriophage T5 defective in gene
D15
, which codes for a 5′-exonuclease, do not express late genes. Electrophoretic separation in sodium dodecyl sulfate-polyacrylamide gels of the proteins induced by this mutant in nonpermissive
Escherichia coli
show a virtual absence of late proteins. Synthesis of lysozyme and serum-blocking power is very low whereas the extent of synthesis of an early enzyme, deoxyribonucleoside monophosphokinase, is similar to that in wild-type infections. It is proposed that one requirement for the expression of late T5 genes is the introduction of gaps or nicks in the T5 DNA so that late transcription can occur.
Identification of a Disulfide-Linked Procollagen as the Biosynthetic Precursor of Chick-Bone Collagen
Authors: Monson Janet M. , Bornstein Paul
Published: May 2006

Chick cranial-bone procollagen, extracted at neutral pH in the presence of inhibitors of proteolytic enzymes, exists as a triple-stranded protein with disulfide bonds linking all three chains. The biosynthetic precursor function of this procollagen was demonstrated by pulsechase experiments. The ratio of radioactive hydroxyproline to proline in proα chains obtained by reduction and alkylation of the disulfide-bonded precursor was similar to the value determined for proα1 from acid-extracted procollagen. However, the molecular weight of these chains was higher than that previously determined for proα1 and proα2, suggesting that extraction of tissue at low pH results in a selective loss of disulfide-bonded regions from procollagen. These findings reconcile several apparently conflicting reports on the nature of procollagen identified in bone and in the medium of cultured fibroblasts and indicate that in both systems procollagen is synthesized as a disulfidelinked protein.
Triplet-Triplet Energy Transfer in α-Trypsin
Authors: Ghiron C. A. , Longworth J. W. , Ramachandran N.
Published: May 2006

Experiments are reported that demonstrate that light absorbed by ionized tyrosinyl sensitizes the phosphorescence of tryptophanyl residues of native α-trypsin. The sensitization effect is abolished when α-trypsin is unfolded in guanidine hydrochloride. Under the experimental conditions used, the tryptophan phosphorescence could only have been induced by an electron-exchange interaction. These results, therefore, require that there be at least one ionized tyrosinyl-tryptophanyl pair in the native enzyme and that the distance between the two side chains be sufficiently short to permit electron exchange.
Alteration in DNA Synthetic Response of Thymocytes from NZB Mice of Different Ages
Authors: Dauphinee Michael J. , Talal Norman
Published: May 2006

Thymocytes from NZB and DBA/2 mice were injected into lethally irradiated C57 B1/6 recipients. DNA synthesis in spleen and lymph node was measured as the incorporation of radioactive 5-iodo-2-deoxyuridine. The generation of cytotoxic effector cells was also studied in an
in vitro
cytotoxicity assay, with EL-4 lymphoma target cells. The kinetics of DNA synthesis were similar for 2- and 8-week-old DBA/2 donors and for 2-week-old NZB donors with a peak on day 4. Thymocytes from 8-week-old and 9-month-old NZB donors showed a delayed onset of DNA synthesis which was still increasing on day 6. When NZB donor thymocytes from 2- and 8-week-old mice were mixed together before injections, as few as 25% of 8-week-old cells gave a DNA synthetic response characteristic of this aged population. These results suggest an abnormal thymocyte development in NZB mice which may relate to the subsequent emergence of autoimmune disease.
Suppression of DNA Synthesis in Hepatoma Cells Exposed to Glucocorticoid Hormone
In Vitro
Authors: Loeb John N. , Borek Carmia , Yeung Lucy L.
Published: May 2006

Glucocorticoid hormone is shown to markedly suppress DNA synthesis in a line of rat hepatoma cells
in vitro
. In the presence of 300 nM hydrocortisone or 30 nM dexamethasone the incorporation of radioactive thymidine falls to 50% of control levels by 36 hr, and at higher concentrations of hormone inhibition can be noted as early as 12 hr and is nearly complete by 24 hr. This inhibition of radioactive thymidine incorporation reflects a true suppression of DNA synthesis, is accompanied by a corresponding inhibition of cell proliferation, and is readily reversible upon subsequent removal of hormone. In contrast to previously described effects of the glucocorticoid hormones on various cells of lymphoid origin, the inhibition of DNA synthesis in these hepatoma cells is not accompanied by appreciable cell lysis or by degradation of preformed DNA, and even when [
3
H]thymidine incorporation into DNA is inhibited by 90% or more, incorporation of [
14
C]uridine into RNA proceeds with little change. These findings all parallel previous observations on the effects of glucocorticoid hormone on the livers of intact animals and suggest that studies on the mechanism of the inhibition of DNA synthesis in the present more isolated system may lead to a better understanding of the means by which these compounds inhibit liver growth
in vivo
.

Despite the ready suppressibility of DNA synthesis in these hepatoma cells and in two other cell lines of liver origin, none of these cell lines was found to be inducible for tyrosine aminotransferase. The apparent dissociation between two “steroid-sensitive” phenomena is of interest and warrants further investigation.
Non-Mendelian Inheritance of DNA-Induced Inositol Independence in
Neurospora
Authors: Mishra N. C. , Tatum E. L.
Published: May 2006

Inositol-independent (
inos
+
) revertants of
Neurospora
induced in inositol-requiring mutants by treatment with wild-type DNA in previous studies were found to be stable and to grow well in the absence of inositol. Genetic data presented in this paper show that a major proportion of these induced revertants rarely transmitted the inositol independence character (
inos
+
) to their sexual progeny. Non-Mendelian transmission of the transformed character (
inos
+
) was also found to occur in some of the sexual progeny in subsequent generations. These genetic data support the idea that the transforming DNA pieces carrying the genetic information (called exosomes) are not readily integrated into the host genome. It is suggested that elimination of most exosomes during meiosis causes a loss of the genetic information and leads to non-Mendelian transmission of the induced revertant character (
inos
+
).
Alkaline Phosphatase Activity in Mouse Teratoma
Authors: Bernstine Edward G. , Hooper Martin L. , Grandchamp Simone , Ephrussi Boris
Published: May 2006

In tumors and embryoid bodies of mouse teratoma a correlation has been established between specific activity of alkaline phosphatase (EC 3.1.3.1) and content of embryonal carcinoma, the stem cell of the tumor. A histochemical study of embryoid bodies has shown that high levels of the enzyme are confined to embryonal carcinoma. Fifteen tissue culture lines could be classified into three groups: (
a
) lines identifiable as pluripotential embryonal carcinoma by their morphology, tumorigenicity, and capacity to differentiate
in vivo
; (
b
) nullipotential embryonal carcinoma, resembling pluripotential embryonal carcinoma in morphology and malignancy but giving rise to undifferentiated tumors; and (
c
) lines of apparently nonmalignant somatic cells. Both types of embryonal carcinoma possess levels of alkaline phosphatase 5- to a 100-fold higher than the somatic cell lines. The embryonal carcinoma enzyme resembles the enzymes from kidney and placenta in kinetics of thermal inactivation and sensitivity to the inhibitor L-phenylalanine, but is distinguishable from the alkaline phosphatases of liver and intestine. These findings are discussed in relation to the use of teratoma for the study of cell differentiation.
Poly(Inosinic Acid)·Poly(Cytidylic Acid) Inhibition of DNA Synthesis in Synchronized HeLa Cells
Authors: Teng C. T. , Chen M. C. , Hamilton L. D.
Published: May 2006

Inhibition by double-stranded polyribonucleotides of DNA synthesis in synchronized HeLa cultures is dose- and time-dependent. Inhibition by poly(I·C) primarily affected late G
1
and early S phases of the cell cycle. Single-stranded polynucleotides, native calf-thymus DNA, and yeast RNA had no effect. Radioautography showed that after 2-hr exposure the synthetic polyribonucleotides were predominantly inside the nucleus. The results extend the spectrum of action of double-stranded RNA.
Translation of Bacteriophage Qβ RNA by Cytoplasmic Extracts of Mammalian Cells
Authors: Morrison Trudy G. , Lodish Harvey F.
Published: May 2006

Cytoplasmic extracts from Krebs II mouse ascites cells and from L cells translate messenger RNA from coliphage Qβ with fidelity to produce products that migrate on polyacrylamide gels with those products directed by Qβ RNA in an
Escherichia coli
cell-free system. The mammalian cell extracts correctly initiate and terminate Qβ coat protein synthesis, as shown by: (
i
) [
3
H]lysine-and [
3
H]arginine-labeled tryptic peptides derived from the coat-sized product resemble these from authentic Qβ coat protein, (
ii
) Qβ coat (which contains methionine only at the N-terminal end) can be radioactively labeled with methionine only if the methionine is formylated, and (
iii
) L cell extracts directed by Qβ
am
-
11 (an amber mutant in the coat protein) RNA make no completed coat-sized material, but do make a peptide the size of the authentic amber coat fragment.
In Vitro
Repression of the Transcription of
gal
Operon by Purified
gal
Repressor
Authors: Nakanishi Shigetada , Adhya Sankar , Gottesman M. E. , Pastan Ira
Published: May 2006

We have studied the
in vitro
repression of
gal
mRNA synthesis by the
gal
repressor from
Escherichia coli
. By use of a four-step purification procedure involving chromatography on phosphocellulose, DEAE-cellulose, and an affinity resin, the
gal
repressor has been purified about 1600-fold from a crude cell extract. The purification was aided by use of a cell extract made after prophage induction of cells lysogenic for bacteriophage λ that carries the
gal
repressor gene (
galR
). The highly purified
gal
repressor is an effective and specific repressor of
in vitro
synthesis of
gal
mRNA with λ
gal
DNA as template. Both D-fucose and D-galactose overcome the action of
gal
repressor; the half-maximal concentrations of D-fucose and D-galactose for overcoming the action of repressor are 1 mM and 0.5 mM, respectively. The repressor fails to repress
gal
-specific transcription when the
gal
DNA contains a cis-dominant operator constitutive (
O
c
) mutation. We conclude that the
gal
repressor recognizes the
gal
operator site and acts by preventing
gal
transcription.
Regulation of Macromolecular Biosynthesis in a Mutant of
Escherichia coli
Defective in Membrane Phospholipid Biosynthesis
Authors: Glaser Michael , Bayer William H. , Robert  , Bell M. , Vagelos P. Roy
Published: May 2006

Nucleic acid and protein synthesis were studied in temperature-sensitive mutants defective in phospholipid synthesis. The defect is due to a single mutation in glycerol 3-phosphate acyltransferase (EC 2.3.1.15). The results show that at the restrictive temperature not only does phospholipid synthesis cease, but DNA, RNA, and protein synthesis also cease. Active transport continues, however, indicating that the cells do not become leaky or lose their energy supply. These results suggest that phospholipid synthesis is coupled to DNA, RNA, and protein synthesis.
Cytoplasmic Adenylation and Processing of Maternal RNA
Authors: Slater Isabel , Gillespie David , Slater D. W.
Published: May 2006

Molecular hybridization between [
3
H]-poly(U) and unlabeled RNA prepared from sea urchin eggs and embryos has been used to contrast the subcellular localization as well as the size distribution of adenylylated maternal RNA preexisting in the unfertilized egg with that adenylylated as a function of fertilization. Evidence reported establishes that such preadenylylated genetic messages are predominantly located in the ovum's subribosomal fraction and that fertilization elicits a rapid reallocation of these latent transcripts into the zygote's ribosomal fraction. Examination of the size distribution of the adenylylated RNA further demonstrates that the unfertilized egg contains a substantial population of RNA transcripts of exceptionally high molecular weight that are used as primers for the 2-fold net synthesis of poly(A) that follows fertilization. The poly(A)-rich tracts are shown to be covalently bonded to RNA. Assessment of the poly(A) content of nuclear and cytoplasmic fractions suggests that the function of poly(A) is not confined to the transport of genetic messages from the nucleus.
Purification of 14S Messenger RNA of Immunoglobulin Light Chain That Codes for a Possible Light-Chain Precursor
Authors: Mach B. , Faust C. , Vassalli P.
Published: May 2006

Polysomes released from microsomes of MOPC 41 mouse myeloma were used to prepare a poly(A)-containing fraction of RNA by chromatography on poly-(dT)-cellulose. From that fraction, a 14S RNA species was purified to a single peak by successive sucrose gradient centrifugations, followed by acrylamide gel electrophoresis. The RNA has an apparent molecular weight of 380,000 (1100 nucleotides), as estimated from the electrophoretic analyses. In a reticulocyte lysate this RNA directs the synthesis of a protein that migrates more slowly in sodium dodecylsulfate-acrylamide gels than does the light chain secreted by the same tumor. This difference in migration corresponds to a size difference appropriate for polypeptide chain about 20 amino acids longer than the light chain. The tryptic peptides of this protein correspond to those of the secreted light chain, except for the presence of two additional peptides from the product synthesized
in vitro
and for the absence of one light-chain peptide. The purified RNA is, therefore, the mRNA of the light chain, and it seems to code for a precursor protein slightly larger than the light chain. From the estimated size of the 14S mRNA, it appears that only 65% of the RNA is translated.
A Proposal for the Structure of the
Drosophila
Genome
Authors: Bonner James , Wu Jung-Rung
Published: May 2006

We propose a structure for the genome of
Drosophila melanogaster
in which each chromatid of each chromomere (band) consists on the average of about 30-35 different sequences of single-copy (unique) DNA, each on the average about 750 base pairs in length. These are separated from one another by stretches of the middle repetitive (reiterated) DNA, which in
D. melanogaster
makes up about 15% of the genome. These stretches are about 100-150 base pairs in length and are all of the same sequence or family in each individual chromomere and of a different family (sequence) in each different chromomere. Our proposed structure of the
Drosophila
genome is in accord with all of the known facts concerning the physical chemistry and molecular biology of
Drosophila
DNA.
Temporal Frequency Changes of Enzyme and Chromosomal Polymorphisms in Natural Populations of
Drosophila
Authors: Dobzhansky Theodosius , Ayala Francisco J.
Published: May 2006

A comparative study of chromosomal and enzyme polymorphisms in
Drosophila pseudoobscura
and in
D. persimilis
was conducted from April 1971 to October 1972 by taking samples at monthly intervals in two different localities. Seasonal cyclic changes occur in the chromosomal polymorphisms. Significant changes occur in the frequencies of the enzyme polymorphisms; preliminary evidence indicates that some of these changes may also be cyclic. Natural selection is the main process responsible for the changes in both kinds of polymorphisms.
Factor-Promoted Dissociation of Free Ribosomes in a Rabbit Reticulocyte Lysate System: Inhibition and Requirement for an Energy Source
Authors: Mizuno S. , Rabinovitz M.
Published: May 2006

A factor that promoted the dissociation of ribosomes into ribosomal subunits in a complete globin-synthesizing system was isolated from rabbit reticulocyte ribosomes. The factor stimulated both globin synthesis and the association of the small ribosomal subunit with polyribosomes. The dissociation of free ribosomes by the factor could be followed as an independent reaction in the presence of a high concentration of cycloheximide, which inhibited translation and the resulting accumulation of runoff subunits. This reaction required an energy source and was inhibited by
P
-(5′-guanylyl)-methylenebisphosphonate. These data suggest that energy generated by hydrolysis of GTP may be a requirement for the dissociation reaction. Aurintricarboxylic acid inhibited the factor-mediated dissociation of free ribosomes but not the factor-mediated preservation of subunits formed on peptide-chain termination.
Chemotaxis by the Nematode
Caenorhabditis elegans:
Identification of Attractants and Analysis of the Response by Use of Mutants
Authors: Ward Samuel
Published: May 2006

The nematode
Caenorhabditis elegans
is attracted by at least four classes of attractants: by cyclic nucleotides, cAMP and cGMP; by anions, Cl
-
, Br
-
, I
-
; by cations, Na
+
, Li
+
, K
+
, Mg
+
; and by alkaline pH values. The nematode's behavioral response to gradients of these attractants involves orientation and movement up the gradient, accumulation, and then habitutation. Comparison of the tracks of wild-type and mutant animals responding to gradients of attractants indicates that sensory receptors in the head alone mediate the orientation response and that the direction of orientation is determined by the lateral motion of the head. Therefore, the orientation response is a klinotaxis.
Synaptic Differentiation in a Regenerating Crab-Limb Muscle
Authors: Govind C. K. , Atwood H. L. , Lang Fred
Published: May 2006

Properties of synapses on regenerating nerve terminals of the single excitatory axon to the stretcher muscle were studied in the regenerating second walking leg of the shore crab,
Grapsus
. In the adult condition these synapses vary in physiological properties, ranging from high release, poorly facilitating types to low release, highly facilitating types. Synapses on regenerating stretcher-muscle fibers show a distinct temporal pattern of differentiation. In early limb buds, a characteristic fluctuating, excitatory postsynaptic potential, punctuated by failures of transmission, is seen, indicating a developmentally “naive” synapse with low quantal content. In these early stages proportionately more synapses are of the poorly facilitating type; the highly facilitating synapses appear increasingly in later stages. Thus, the type of synapse that will form seems likely to be related to the time of innervation. Synapses of early developmental stages found by electron microscopy are significantly smaller than those seen in adult muscles; thus, the synaptic contact area must increase during development. We postulate that contacts formed by the primary branches of the axon early in development differentiate into relatively large, poorly facilitating synapses, while contacts formed by secondary branches slightly later in development differentiate into smaller, highly facilitating synapses.
Population Analysis of the Deinduction Kinetics of Galactose Long-Term Adaptation Mutants of Yeast
Authors: Tsuyumu Shinji , Adams Bruce G.
Published: May 2006

By use of a selective galactose agar medium containing ethidium bromide, a population analysis of the deinduction kinetics of yeast galactose long-term adaptation mutants (
gal
3) has been done. It was first determined that the
gal
3 mutation is specific to the yeast galactose system and that induced cultures of
gal
3 strains are capable of growth on galactose agar medium containing ethidium bromide, whereas noninduced cultures are not. Population analyses of induced
gal
3 strains under going deinduction in the absence of galactose demonstrate that a minimum number of five induction units per cell are required for induction of the galactose system. It is concluded that: these induction units are actively synthesized only in the presence of inducer and are diluted out through cell division; they are stable under nongrowing conditions; they are heterogeneous in nature; at most two of the five minimum units are products of the
gal
2 locus; and the other units may be three of one type, one of one type and two of another, or one each of three different types.
Flavin 1,
N
6
-Ethenoadenine Dinucleotide: Dynamic and Static Quenching of Fluorescence
Authors: Barrio Jorge R. , Tolman Glen L. , Leonard Nelson J. , Spencer Richard D. , Weber Gregorio
Published: May 2006

Flavin 1,
N
6
-ethenoadenine dinucleotide (εFAD) was prepared by the action of chloroacetaldehyde on flavin adenine dinucleotide. This compound, which has two potential fluorophores, ε-adenine and isoalloxazine, shows extremely efficient energy transfer from the former to the latter. The fluorescences of both moieties are greatly diminished in the intact molecule. Determination of the fluorescence yields and lifetimes leads to the conclusion that at 20° in neutral aqueous solution εFAD exists mainly (90%) as an internally complexed or stacked form.
Absence of the Sequence G-T-Ψ-C-G(A)- in Several Eukaryotic Cytoplasmic Initiator Transfer RNAs
Authors: Simsek Mehmet , Ziegenmeyer James , Heckman Joyce , Rajbhandary Uttam L.
Published: May 2006

The nucleotide sequence G-T-Ψ-C-G(A)- has previously been found in every tRNA of known sequence that is active in protein biosynthesis. An exception to this generalization is the recently sequenced initiator tRNA from yeast cytoplasm. It is now reported that cytoplasmic initiator tRNAs from wheat germ, rabbit liver, and sheep mammary gland also lack the G-T-Ψ-C-G(A)- sequence. Thus: (
i
) nucleoside composition analyses show the absence of T in all these tRNAs; (
ii
) analyses of oligonucleotide fragments produced by T1 ribonuclease show the absence not only of the T-Ψ-C-G(A)- sequence, but also of U-Ψ-C-G(A)- or U-U-C-G(A)- sequences in such digests. The absence of G-T-Ψ-C-G(A)- in the eukaryotic cytoplasmic initator tRNAs is, therefore, not simply due to lack of enzymatic modification of U to T.
Evidence for the Absence of the G-T-Ψ-C Sequence From Two Mammalian Initiator Transfer RNAs
Authors: Petrissant Guy
Published: May 2006

Analyses were performed on the purified initiator tRNA from rabbit liver to test for the presence of Ψp and Tp in this molecule. Neither of these nucleotides could be detected after hydrolysis by piperidine, NaOH, or T2 RNase. Similarly digestion with venom phosphodiesterase plus phosphatase failed to release any pseudourdine or ribothymidine. Identical results were obtained with the initiator tRNA from sheep mammary gland. The absence of these nucleosides was confirmed by pancreatic and T1 RNase digestion of the rabbit-liver initiator tRNA. The classical G-T-Ψ-C sequence was not detected in this molecule. An A-U-C-G sequence has been identified; it may possibly replace the G-T-Ψ-C sequence.
Replication of DNA in Mammalian Chromosomes: Isolation of Replicating Segments
Authors: Taylor J. Herbert
Published: May 2006

From Chinese hamster cells, blocked at the beginning of the S phase by treatment with fluorodeoxyuridine and pulse-labeled with [
3
H]thymidine, one can release segments of native DNA containing template polyuncleotide chains and the most recently replicated DNA. The segments, which can be released without shear by lysis at temperatures below the melting point for the double helix, can be separated from both the nascent single chains (Okazaki pieces) and the long strands of native DNA in sodium perchlorate gradients. These 26S segments are equivalent to about 6 μm of native DNA, but may be replication forks rather than linear pieces.
Chromosomal Abnormalities in Spleens of New Zealand Black Mice, A Strain Characterized by Autoimmunity and Malignancy
Authors: Fialkow Philip J. , Paton Gillian R. , East June
Published: May 2006

Mosaicism of normal and chromosomally aberrant cells was detected in 14 of 20 spleens from adult New Zealand Black (NZB) mice reared under conventional conditions, a strain that spontaneously develops autoimmunity and lymphoreticular malignancy. No abnormalities were found in marrows from these same animals or in spleens from NZB mice younger than 3 months. The prevalence of chromosomal aberrations was significantly higher in spleens from NZB mice than in spleens from the two other strains studied—SJL/J, which has high frequency of reticulum cell neoplasia and paraproteinemia but no autoimmunity, and BALB/c, which has essentially no autoimmunity and only a low incidence of generalized lymphoid neoplasms and plasmacytomas in ageing animals. Causes for the chromosomal abnormalities in NZB mice are considered in terms of other features in these mice—immunoproliferation, autoimmunity, and the presence of murine leukemia (“C”-type) virus particles.
Aspartate Transcarbamoylase from
Escherichia coli
: Electron Density at 5.5 Å Resolution
Authors: Warren Stephen G. , Edwards Brian F. P. , Evans David R. , Wiley Don C. , Lipscomb William N.
Published: May 2006

The allosteric enzyme, aspartate transcarbamoylase (EC 2.1.3.2), has previously been shown in our x-ray diffraction studies to have D
3
-32 symmetry. There are six catalytic (C) and six regulatory (R) chains in the molecular complex (R
6
C
6
). Our three-dimensional x-ray diffraction study of this enzyme (R32,
a
= 131 Å,
c
= 200 Å) at 5.5 Å resolution shows a spatial arrangement of the two catalytic trimers C
3
above and below an equatorial belt of three regulatory dimers R
2
. The molecule is about 110 × 110 × 90 Å in largest dimensions, and is shown here to contain a large central aqueous cavity about 50 × 50 × 25 Å in size. Location of the single sulfhydryl of each catalytic chain, and correlation of its reactivity with enzymatic activity in the molecule, suggests that the nearby active sites are most probably accessible from the central cavity, but probably not directly from the external solution. The most obvious access to the central cavity consists of six channels, each about 15 Å in diameter, near the regulatory region. A component of the regulatory mechanism may be modulation of access of substrates through these channels.
Transcription of Rat-Liver Chromatin with Homologous Enzyme
Authors: Maryanka Daphne , Gould Hannah
Published: May 2006

The product of transcription of rat-liver chromatin with homologous rat-liver Form-B polymerase
in vitro
is high molecular weight RNA with sedimentation coefficients principally in the range of 18-45 S. The average size is somewhat smaller than that of the heterogeneous high molecular weight RNA synthesized by the endogenous enzyme
in vivo
(or in isolated nuclei). We have excluded the possibility that this difference can be attributed to degradation of the nascent RNA occurring under the conditions of our experiments. The size of the RNA produced by the homologous enzyme nevertheless approaches that of the natural transcripts much more closely than does that of the RNA produced by bacterial RNA polymerases, which we, in addition to other authors, have found to sediment around 10 S.
Inhibition of Cellular Protein Synthesis by Double-Stranded RNA: Inactivation of an Initiation Factor
Authors: Kaempfer Raymond , Kaufman Jennifer
Published: May 2006

Inhibition of protein synthesis in rabbit reticulocyte lysates by double-stranded RNA is caused by the inactivation of IF-3, an initiation factor required for the recycling of ribosomes and for their binding to messenger RNA. The evidence for this is that (
i
) the inhibition can be overcome by addition of exogenous If-3; (
ii
) double-stranded RNA inactivates stoichiometric amounts of IF-3; (
iii
) double-stranded RNA forms a complex with IF-3; and (
iv
) double-stranded DNA, which lacks inhibitory activity, also binds to IF-3, but with a much lower affinity than double-stranded RNA. It is concluded that double-stranded RNA inhibits cellular protein synthesis by tightly complexing with IF-3. It is suggested that IF-3 normally recognizes a double-stranded region in messenger RNA.
Primer Requirement and Template Specificity of a DNA Polymerase of Chick Embryo
Authors: Rougeon François , Brun Gilbert , da Costa Maia Jose Carlos , Chapeville François
Published: May 2006

A DNA polymerase purified from extracts of chick embryo catalyzes the synthesis of poly(dT) in the presence of poly(rA) or poly(dA) as template and poly(dT) or oligo(dT) as primer. Oligo- or polyribonucleotides are relatively ineffective initiators of polydeoxynucleotide polymerization. Using activated DNA as template, the enzyme catalyzes a repair-like reaction that resembles that catalyzed by RNA-directed DNA polymerase of RNA tumor viruses and
Escherichia coli
DNA polymerase II. With natural templates containing poly(rA) sequences, such as avian myeloblastosis virus RNA or rabbit globin mRNA, and oligo(dT) as initiator, principally poly(dT) is synthesized. Consequently, the enzyme differs from the RNA-directed DNA polymerase associated with RNA tumor viruses by its incapacity to transcribe heteropolymeric regions of RNA templates. The possible role of the enzyme in repair of DNA during transcription is discussed.
A 5′-Adenosine Monophosphate-Dependent Adenylate Cyclase and an Adenosine 3′:5′-Cyclic Monophosphate-Dependent Adenosine Triphosphate Pyrophosphohydrolase in
Dictyostelium discoideum
Authors: Rossomando Edward F. , Sussman Maurice
Published: May 2006

Cell aggregation in
Dictyostelium discoideum
appears to involve the production and detection of 3′:5′-cyclic AMP. Two pertinent catalytic activities have been studied in concentrates from
D. discoideum
purified 50- to 100-fold. They are (
i
) adenylate cyclase and (
ii
) ATP pyrophosphohydrolase. ATP pyrophosphohydrolase activity converts ATP to 5′-AMP and pyrophosphate. The presence of 5′-AMP is an absolute requirement for adenylate cyclase activity. The presence of 3′:5′-cyclic AMP is an absolute requirement for ATP pyrophosphohydrolase activity. Both activations, particularly that of ATP pyrophosphohydrolase, show narrow ranges of specificity and display significant cooperativities.
Genetic Model for the Rh Blood-Group System
Authors: Rosenfield Richard E. , Allen Fred H. , Rubinstein Pablo
Published: May 2006

Inherited quantitative aspects of the Rh blood-group system and susceptibility of Rh to the effects of independently segregating suppressor genes can be accounted for with a conjugated operon model. This assumes the existence of four operator or promotor (control) genes for these functions, while closely linked structural regions determine the qualitative characteristics of Rh antigens. Observed restriction of antigenic crossreactivity to the products of adjacent genetic regions and data from blood typing of nonhuman primates both suggest that Rh complexity arose from a series of gene duplications and independent mutations.
Polychlorinated Biphenyls: A New Type of Inducer of Cytochrome P-448 in the Liver
Authors: Alvares Alvito P. , Bickers David R. , Kappas Attallah
Published: May 2006

The CO-difference spectrum of microsomes from rats treated with the polychlorinated biphenyls mixture, Aroclor 1254, has an absorption maximum at 448 nm. With ethylisocyananide as the ligand for reduced microsomes, Aroclor 1254 treatment causes a shift in the 455-nm peak to 453 nm and increases the ratio of absorbance of 455 nm to that at 430 nm from 0.53, obtained with untreated rats, to 1.24. These findings are similar to those seen in rats treated with the polycyclic hydrocarbon, 3-methylcholanthrene, but differ from those that characterize cytochrome P-450 in control or phenobarbital-treated rats. Aroclor 1254 treatment results in a tripling of cytochrome P-448 content and a 10-fold increase in benzo-[a]pyrene hydroxylation. However—unlike 3-methylcholanthrene, but like the phenobarbital type of inducing agents—Aroclor 1254 treatment causes a significant enhancement of ethylmorphine N-demethylase. These data suggest that Aroclor 1254-induced cytochrome P-448 may be catalytically different from the 3-methylcholanthrene-induced P-448 or that the hemoprotein(s) induced by Aroclor 1254 may be a mixture of cytochromes P-448 and P-450 exhibiting catalytic properties of both cytochromes.
Membrane Intercalated Particles in Human Erythrocyte Ghosts: Sites of Preferred Passage of Water Molecules at Low Temperature
Authors: Pinto Da Silva Pedro
Published: May 2006

Although hydrophilic pores have been inferred to account for characteristics of the movement of water molecules across erythrocyte membranes, no direct evidence has associated such pores with actual structural differentiations within the membrane. Freeze-fracture and freeze-etch studies of isolated erythrocyte membranes show that they are comprised of fluid bilayer domains tranversed by protein-containing intercalations (“membrane intercalated particles”). It has previously been hypothesized that the topology of the polar and apolar spaces of the membrane-intercalated particles was not concentric the hydrophobic spaces being equatorially distributed. In consequence, axial organization of the hydrophilic regions could result in hydrophilic continuity across the membrane and might provide a structural basis for passage of hydrophilic molecules. The present experiments support this hypothesis. It is shown that sublimation at -100° of erythrocyte membrane suspensions (that had been incubated at pH 5.5 to cause aggregation of the membrane particles) results in progressive and selective sinking of the membrane regions comprised of aggregates of intercalated particles, i.e., that sublimation of water molecules occurs preferentially across these membrane regions. These results indicate that, under these experimental conditions, the membrane-intercalated particles provide a preferential structural pathway for passage of water molecules across erythrocyte ghost membranes.
Countercurrent Separation: A New Method for Studying Behavior of Small Aquatic Organisms
Authors: Dusenbery David B.
Published: May 2006

A new method for the analysis of behavior in small free-swimming aquatic organisms is described. In this procedure, called countercurrent separation, a dense solution flows down along the bottom of an inclined chamber while a light solution flows in the opposite direction, upward along the top of the chamber. The attraction of animals (injected into the center of the chamber) to one solution or the other is then determined by observing the proportion of animals that emerges from the chamber in that solution. When used with the nematode
Caenorhabditis elegans
, it is estimated that the apparatus is equivalent to at least nine theoretical plates.
Independent Control of Ribosomal Gene Replication in Polytene Chromosomes of
Drosophila melanogaster
Authors: Spear Brian B. , Gall Joseph G.
Published: May 2006

The saturation values for ribosomal RNA hybridization have been determined for DNA from diploid and polytene tissues of
Drosophila melanogaster
. These values have been measured in XO and XX larvae which have, respectively, one and two nucleolus organizers in the diploid chromosome set. The results show that (
1
) in diploid cells the ribosomal (r)DNA is present in amounts proportional to the number of nucleolus organizers, (
2
) in polytene cells the rDNA is under-replicated with respect to the euchromatic DNA, and (
3
) in polytene cells the amount of rDNA is independent of the diploid number of nucleolus organizers. These observations suggest that somatic variations in rDNA content may involve independent polytenization of the nucleolus organizer without change in the number of ribosomal cistrons per organizer. The independent polytenization of rDNA is proposed as the chromosomal explanation for the relative increase in rDNA in flies of the XO constitution.
Interaction of
13
CO
2
and Bicarbonate with Human Hemoglobin Preparations
Authors: Morrow Jon S. , Keim Philip , Visscher Ronald B. , Marshall Robert C. , Gurd Frank R. N.
Published: May 2006

Formation of
13
C-resonances attributable to carbamino derivatives has been observed in human erythrocyte hemolysate preparations equilibrated with
13
CO
2
at 33°. Carbamino formation is most marked in deoxyhemoglobin and at alkaline pH, and is very largely inhibited by the addition of 2,3-diphosphoglycerate or conversion to oxyhemoglobin. The prominent carbamino resonance at 30.0 ppm upfield of CS
2
is visible in the spectrum of packed, deoxygenated erythrocytes equilibrated in
13
CO
2
. This chemical shift falls close to that observed with sperm-whale myoglobin and within 2 ppm upfield of that seen with simple amino acids and peptides. The bicarbonate-carbonate resonance near 33 ppm is broad in the hemoglobin preparations, which always contain some carbonic anhydrase, but becomes narrow in the presence of the carbonic anhydrase inhibitor, acetazolamide. The nuclear magnetic resonance condition of intermediate exchange rate with dissolved CO
2
(68.4 ppm) obtains in the absence of inhibitor. The process has marked consequences in reducing the spin-lattice relaxation time, T
1
, of the bicarbonate resonance by more than 10 times. The deoxyhemoglobin carbamino resonance has a T
1
value of 700 msec, indistinguishable from that of the protein carbonyl resonance envelope.
Determination of Natural Host Taxonomy of RNA Tumor Viruses by Molecular Hybridization: Application to RD-114, a Candidate Human Virus
Authors: Ruprecht Ruth M. , Goodman N. C. , Spiegelman S.
Published: May 2006

The lysogenic bacteriophages and the RNA tumor viruses have in common the ability to add their genetic information to the genome of their host cells. The biological similarity extends further; data summarized here indicate that they both possess homology to the DNA of their uninfected indigenous hosts. Sharing of common sequences with normal host DNA has been established with avian, murine, feline, and primate oncornaviruses. This finding provides a method for determining the taxonomic position of the natural host of any new RNA tumor virus isolated. Application of this approach to RD-114 revealed extensive hybridization to normal cat DNA and little, if any, hybridization to human DNA. We conclude that the data assign a feline origin rather than a human origin to RD-114.
Receptor Mobility and Receptor-Cytoplasmic Interactions in Lymphocytes
Authors: Edelman Gerald M. , Yahara Ichiro , Wang John L.
Published: May 2006

An analysis of the inhibition by concanavalin A of the mobility of lymphocyte surface receptors is used to construct an hypothesis on membrane receptor-cytoplasmic interactions. It is proposed that binding of multivalent lectins alters the interaction of an assembly of colchicine-binding proteins with lectin receptors and other receptors, and reciprocally that the state of the colchicine-binding assembly alters the mobility and distribution of surface receptors on the cell membrane. Observations of the effect of colchicine and related drugs on the inhibition of receptor mobility by concanavalin A lend support to this hypothesis. The proposed model has several implications for studies of the initial events of mitogenesis in lymphocytes as well as for cell-cell interactions in general.
Classes of Spatially Inhomogeneous Pseudodifferential Operators
Authors: Beals R. , Fefferman C.
Published: May 2006

One can obtain sharp information on a pseudodifferential operator
p
(x,D) by embedding the symbol
p
in a symbolic calculus specially designed to reflect the behavior of
p
. We sketch the development of symbolic calculi arising in this connection, and use our results to give simple proofs of the sharp Gårding inequality and of sufficiency of Nirenberg-Traves' condition (
P
) for local solvability of equations of principal type.
Topographical Location of H—Y Antigen on Mouse Spermatozoa by Immunoelectronmicroscopy
Authors: Koo Gloria C. , Stackpole Christopher W. , Boyse Edward A. , Hämmerling Ulrich , Lardis Michael P.
Published: May 2006

H-Y (male) antigen was visually located on mouse sperm by electron microscopy, by use of the indirect hybrid antibody method and tobacco mosaic virus as the visual marker. Labeling was achieved by centrifugation of the sperm through a discontinuous gradient consisting of alternating layers of immune reagents and wash solutions. Treated sperm were examined topographically by preparation of platinum-carbon replicas. Antigen was located mainly on the acrosomal cap of the sperm head.
Concerted Formation of the Gel of Hemoglobin S
Authors: Williams Robley C.
Published: May 2006

Apparent weight-average molecular weights of hemoglobin A and hemoglobin S were measured at high concentrations by equilibrium ultracentrifugation. Carbonmonoxy-hemoglobin S appears to exist as a solution of unassociated molecules, as do carbonmonoxy-and deoxy-hemoglobin A. Deoxy-hemoglobin S, however, exists in a gel-like state at concentrations above 14 g/dl, but no aggregates smaller than the gel were observed in solutions that were in equilibrium with the gel. Carbamoylation of hemoglobin S produced a solution of unaggregated molecules, as did cooling of uncarbamoylated hemoglobin S to 5°. It is concluded that the gel of hemoglobin S is formed in a stoichiometrically concerted manner, and that the size of the smallest stable aggregate is greater than 20 hemoglobin molecules.