bluuebunny/crossref_metadata_2025 huggingface dataset:
Tract Specificity in the Structure of Down Feathers of the Newly-Hatched Chick
Authors: Rawles Mary E.
Published: May 2006

Comparative study of completed down feathers from seven of the major tracts of newly-hatched Silver Campine chicks reveals tract-specific differences in the total length of the primary group of barbs and in the length of their barbule-free tips. Two classes of barbs can be distinguished on the basis of overall length in feathers of any one of the tracts: (
a
) those barbs that form from the first group (complement) of 9-11 barb ridges that arise in strict dorsoventral order around the circumference of the epidermal cylinder strict dorsoventral order around the circumference of the epidermal cylinder of the feather germ, and (
b
) those barbs that are added secondarily, later, either by the formation of a newly organized ridge between the bases of two of the original group of barb ridges, or by the splitting of one or more of the original complement of barb ridges. The primary (majority) group of ridges, only, are of use in gauging tract specificity. The statistical significance of measurements of total barb-length and the length of the barbule-free tips have been evaluated; differences between the feathers of each of the seven tracts examined can be distinguished statistically. The fact that the first feathers to form from the papillae are tract-specific shows, unquestionably, that specificity is present in the papillae from the very beginning of their organization, as might be inferred from their orderly pattern of origin in time and space within each of the various tracts.
Citrate Lyase: A Pantothenate-Containing Enzyme
Authors: Srere Paul A. , Böttger Brigitte , Brooks George C.
Published: May 2006

Citrate lyase from
Klebsiella aerogenes
inactivated by reaction in the presence of substrate or by treatment with hydroxylamine can be reactivated with acetic anhydride only if its sulfhydryl groups are reduced. Alkaline hydrolysis of pure citrate lyase yields about 3 mol of phosphopantothenate per mol of enzyme.
Chemical Mutagenesis at the Phosphoribosyltransferase Locus in Cultured Human Lymphoblasts
Authors: Sato Koki , Slesinski Ronald S. , Littlefield John W.
Published: May 2006

The presence of selectable genetic markers in long-term human lymphoblast cultures would facilitate cell hybridization experiments on the biosynthesis of immunoglobulins, as well as other studies. This work reports the induction with ethylmethane sulfonate of 6-thioguanine - resistant, phosphoribosyltransferase - deficient mutants in a lymphoblast line from a patient with infectious mononucleosis. These cells were unusually sensitive, with a D
0
value of 28 μg of ethylmethane sulfonate per ml; the sensitivity curve followed a biphasic pattern suggesting the presence of 3% resistant cells. Ethylmethane sulfonate increased the frequency of mutants resistant to 6-thioguanine over 100-fold, to about 2 × 10
-4
; nitrosoguanidine was less effective. Almost all the mutants contained considerably less than 1% of the hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8) activity of wild-type cells. The mutation did not appear to result from loss of an X chromosome.
The Irreversible Inhibition of Differentiation of Limb-Bud Mesenchyme by Bromodeoxyuridine
Authors: Levitt Daniel , Dorfman Albert
Published: May 2006

Growing freshly dissociated chick-limb bud cells (stage 24) over agar for 48 hr permits differentiation into cartilage upon monolayer culture even when initial plating and subculture densities are well below confluency. Addition of 5-bromodeoxyuridine (BrdU) during the initial (48-hr) period over agar irreversibly inhibits chondrogenic differentiation, as characterized by morphology, metachromasia, and sulfate incorporation into acid mucopolysaccharide. Simultaneous, but not subsequent, addition of excess thymidine will prevent the effect of the analogue. Collagen synthesis is not depressed in BrdU-treated cells. Radioautographic studies demonstrate the specific localization of BrdU in the nucleus. Treatment of trichloroacetic acid-precipitable material containing tritiated bromodeoxyuridine with deoxyribonuclease solubilizes 90% of the radioactivity. The loss of the analogue from this precipitable material upon prolonged culture of limb-bud cells is more rapid than can be expected from cell division alone. 5-Bromodeoxyuridine may affect a fraction of DNA involved in stabilization of the differentiated cell phenotype.
Photoreduction of NADP
+
Sensitized by Synthetic Pigment Systems
Authors: Greenbaum E. , Austin R. H. , Frauenfelder H. , Gunsalus I. C.
Published: May 2006

Two synthetic pigment systems capable of enzymatically photoreducing NADP
+
are described. One system contains proflavine; the other, acridine. The complete system consists of ethylene diamine tetraacetic acid (EDTA), proflavine (or acridine), ferredoxin-NADP reductase (EC 1.6.99.4), and NADP
+
. The two pigments initiate the photoreduction of NADP
+
in different portions of the electromagnetic spectrum. Proflavine photosensitizes in the visible portion; acridine, in the ultraviolet. Neither proflavine nor acridine is structurally related to chlorophyll. The acridine system has the attractive property that the enzyme, ferredoxin-NADP reductase, is the only component of the system that absorbs appreciably in the visible region of the spectrum.
Glutamate Dehydrogenase: Amino-Acid Sequence of the Bovine Enzyme and Comparison with That from Chicken Liver
Authors: Moon Kenneth , Piszkiewicz Dennis , Smith Emil L.
Published: May 2006

Further investigation of the amino-acid sequence of bovine glutamate dehydrogenase (EC 1.4.1.3) has led to the correction of an earlier tentative sequence. The presently known sequence contains 500 residues in the subunit single peptide chain. The sequence of the homologous enzyme from chicken liver indicates that it contains 503 residues. Of the presently established 485 residues in the chicken dehydrogenase, only 26 residues differ from those in the bovine enzyme. The chicken dehydrogenase also differs in having an additional three residues at the amino terminus. The amino-terminal residue of the chicken enzyme was found to be cysteic acid.
Hyaluronate in Morphogenesis: Inhibition of Chondrogenesis
In Vitro
Authors: Toole Bryan P. , Jackson Geraldine , Gross Jerome
Published: May 2006

Purified hyaluronate, at a concentration as low as 1 ng/ml, blocks the formation of colonies and cartilage nodules in stationary cultures of cells, isolated by treatment with trypsin, from embryonic chick somites and limb buds. This phenomenon
in vitro
is correlated with sequences of hyaluronate production and hyaluronidase activity during chondrogenesis in embryonic and regenerating tissues
in vivo
. An hypothesis is proposed in which hyaluronate acts as a regulator or inhibitor of mesenchymal cell aggregation in embryogenesis, its synthesis and removal being part of the mechanism of timing of migration, aggregation, and subsequent differentiation.
Messenger RNA for Globin in the Postribosomal Supernatant of Rabbit Reticulocytes
Authors: Jacobs-Lorena M. , Baglioni C.
Published: May 2006

10S RNA has been isolated from the postribosomal supernatant of rabbit reticulocyte lysate. This RNA is associated with protein in a ribonucleoprotein particle that sediments at approximately 20S. The 10S RNA extracted from this particle codes predominantly for α globin chains when it is translated by a mouse ascites cell-free extract. The product of the cell-free synthesis has been characterized by column chromatography and electrophoresis of the tryptic peptides. About 20% of the total α chain mRNA is present in the postribosomal supernatant, whereas β chain mRNA is almost exclusively associated with polyribosomes.
Temperature-Dependent Intracellular Distribution of Thyroxine in Amphibian Liver
Authors: Griswold Michael D. , Fischer Mark S. , Cohen Philip P.
Published: May 2006

Rana catesbeiana
tadpoles were injected with [
14
C]thyroxine, and the subcellular distribution of the labeled hormone was determined. At 25° the amount of isotope found in the liver was maximal after 1-2 hr and then rapidly decreased to a relatively constant value. A large percentage of the hormone was found associated with the purified nuclei isolated 24 hr after injection of [
14
C]thyroxine. Injection of [
14
C]thyroxine into tadpoles maintained at 5° resulted in a much slower but constant accumulation of isotope in the liver, with virtually no movement of thyroxine into the cell nucleus. Thyroxine was bound very tightly to the chromatin fraction of the nucleus, but extraction and chromatography revealed no chemical modification of the thyroxine itself. These results suggest the presence of two temperature-dependent processes: one concerned with the transport of thyroxine into the liver cell and a second concerned with the transport of the intracellular thyroxine into the cell nucleus. It is proposed that the latter process is involved in the low-temperature inhibition of thyroxine-induced metamorphosis.
A Novel DNA Polymerase Activity Found in Association with Intracisternal A-Type Particles
Authors: Wilson Samuel H. , Kuff Edward L.
Published: May 2006

A DNA polymerase activity that promotes the synthesis of poly(dT) has been found in association with intracisternal A-type particles isolated from several mouse tumors. The poly(dT) synthesis activity requires a DNA or RNA primer, is optimal at high salt concentration, prefers magnesium over manganese, and is stimulated by poly(rA). No significant incorporation of dAMP, dGMP, or dCMP was detected in the presence of several RNA and DNA template-primers. The enzyme activity differs in several of its properties from the poly(rA)-directed DNA polymerase activity associated with Rauscher murine leukemia virus.
Transfecting Deoxyribonucleic Acid of
Bacillus
Bacteriophage ϕ29 That Is Protease Sensitive
Authors: Hirokawa Hideo
Published: May 2006

The transfecting activity of
Bacillus
phage ϕ29 DNA, extracted either by sodium lauroyl sarcosine-phenol or by 2 M perchlorate, was destroyed by treatment with proteolytic enzymes, although these enzymes did not effect transfecting DNAs of SPP1, SPO1, and SP50. These facts suggest that a protein is associated with transfective ϕ29 DNA. Stabilization of protease-resistance during transfection appeared earlier than that of DNaseresistance, indicating that the protein associated with ϕ29 DNA is necessary for initiation of the incorporation of DNA molecules into competent cells. The physical nature of ϕ29 DNA before and after the trypsin treatment was investigated by sucrose and CsCl density gradient centrifugations. The trypsin treatment did not alter the sedimentation rate of the unit ϕ29 DNA; however, it did convert the sedimentation rate of the aggregated material in the untreated DNA to that of the unit ϕ29 DNA. The density of the trypsinized DNA was 0.009 g/cm
3
greater than that of the untreated DNA. The possible location of the protein on the DNA is discussed.
Crystallization of tRNA
Leu
-Synthetase from Baker's Yeast
Authors: Chirikjian Jack G. , Wright H. Tonie , Fresco Jacques R.
Published: May 2006

tRNA
Leu
-Synthetase from baker's yeast has been crystallized from ammonium sulfate solution. The crystals are of orthorhombic symmetry, falling into space group [unk] or [unk] with
a
= 75.5 Å,
b
= 110.7 Å, and
c
= 124.0 Å. This unit cell contains four molecules of the native (dimeric) enzyme, with eight asymmetric units, each corresponding to the enzyme subunit. Diffraction patterns obtained for the three major projections contain reflections to spacings of less than 3.5 Å, indicating that this crystal form is amenable to structure analysis to atomic resolution.
The Temporal Expression of T2r
+
Bacteriophage Genes
In Vivo
and
In Vitro
Authors: Trimble Robert B. , Galivan John , Maley Frank
Published: May 2006

The kinetic order of synthesis of deoxycytidylate deaminase (EC 3.5.4.12), deoxycytidylate hydroxymethylase (EC 2.1.2.b), dihydrofolate reductase (EC 1.5.1.3), 5-hydroxymethyldeoxycytidylate kinase (EC 2.7.4.4), and thymidylate synthetase (EC 2.1.1.b) after infection of
Escherichia coli
with T2r
+
bacteriophage was found not to correlate with their order of synthesis in an
in vitro
protein-synthesizing preparation. The
in vivo
and
in vitro
synthesis of enzyme-specific messenger RNA measured in the protein-synthesizing preparation preceded each enzyme by about 1 min. Through the use of sheared DNA, it was shown that the thymidylate synthetase gene was most susceptible to a loss in template activity, which suggests that this gene is further removed from its promoter than the other genes are from theirs. With a DNA segment of 2.5 × 10
5
daltons, the synthesis of dihydrofolate reductase alone was obtained, but at a much reduced rate. Translation of the RNA from phage-infected cells treated with chloramphenicol yielded amounts of dihydrofolate reductase and deoxycytidylate hydroxymethylase activities similar to those obtained with RNA from untreated infected cells. These results suggest that the chloramphenicol RNA, which consists primarily of immediate-early RNA, may contain most, if not all, of the information required for the synthesis of phage dihydrofolate reductase and deoxycytidylate hydroxymethylase.
Expression of Fetal Antigens in Tumor Cells
Authors: Ting Chou-Chik , Lavrin David H. , Shiu Grace , Herberman Ronald B.
Published: May 2006

The activities of sera that reacted specifically with the specific cell-surface antigens of polyoma or simian virus 40 tumors could only be inhibited by absorption of the sera with tumor cells transformed by the specific virus, and could not be removed by the absorption with cells from various fetal tissues nor with cells from other tumors. In contrasts, the antisera produced in male C3H/HeN mice by inoculation of irradiated, syngeneic fetal tissue of 1- to 2-weeks gestation, reacted with various tumor cells. The activities of these sera, when tested against cells from tumors induced by polyoma virus or simian virus 40, could also be removed by absorption with cells from tumors induced by viruses other than polyoma or simian virus 40, including leukemia cells induced by Gross virus (C58NT)D, Rauscher virus (RBL-5), and by dimethylbenzanthrene (EL. 4), and cells from mammary tumors (MM102), plasma-cell tumors (MPC-113), and fetal tissues. These results indicated that fetal antigens may be expressed in tumor cells, but they are different from tumor-specific antigens that are specific for a particular tumor or for tumors induced by a particular virus.
Radioimmunoassay of Mammalian Type-C Viral Proteins: Interspecies Antigenic Reactivities of the Major Internal Polypeptide
Authors: Parks Wade P. , Scolnick Edward M.
Published: May 2006

Mammalian type-C viruses contain a major internal polypeptide of about 30,000 daltons that is characterized by both intraspecies and interspecies antigenic reactivities. Radioimmunoprecipitation assays were used for measurement of this protein; the assay was based upon interspecies reactivities of the protein. As little as 5 ng of the group-specific antigen of murine leukemia virus can be measured by radioimmunoprecipitation assays, thus providing an approximate 10,000-fold increase in sensitivity over the standard immunodiffusion procedure. The type-C viruses that were recently isolated from a woolly monkey and gibbon ape each have an interspecies type-C antigenic reactivity. The primate viruses, however, could be distinguished from the type-C viruses of murine, rat, hamster, and feline origin that were more highly related to each other. The interspecies reactivity of the 30,000-dalton polypeptide is an immunological marker of the mammalian type-C viruses, since even with this sensitive assay other mammalian viruses with RNA-dependent DNA polymerase activity did not contain the type-C interspecies antigen.
Natural-Abundance Carbon-13 Fourier-Transform Nuclear Magnetic Resonance Spectra and Spin Lattice Relaxation Times of Unfractionated Yeast Transfer-RNA
Authors: Komoroski Richard A. , Allerhand Adam
Published: May 2006

High-resolution Fourier-transform nuclear magnetic resonance at 15.18 MHz was used to observe the proton-decoupled natural-abundance
13
C spectra of aqueous unfractionated tRNA from baker's yeast in the presence of Mg
+2
(8 ions per tRNA molecule), as a function of temperature in the range of 27-82°C. The spectrum of thermally denatured tRNA at 82°C showed numerous sharp resonances, which were assigned to specific types of carbon atoms by comparison with the
13
C spectra of mononucleotides. Only the resonance of carbon 4′ of the ribose rings was appreciably shifted (by about 1.5 ppm upfield) with its average position in the mononucleotides. This effect was also seen in the spectrum of poly(A). In the spectrum of folded tRNA (52°C), carbon 4′ was further shifted upfield by about 1.5 ppm, and carbons 2′ and 3′, which yielded a single resonance at 82°C, now showed two partly resolved peaks.

The variation of linewidths with temperature (200 mg/ml of tRNA) was gradual in the range 27-82°C, and did not reflect the expected unfolding behavior of tRNA. Moreover, dilution to 80 mg/ml at 27°C had the same effect as an increase in temperature to about 45°C. The line-width changes below 60° were ascribed to tRNA aggregation. In contrast to the behavior of the linewidths, the
13
C spin-lattice relaxation times (
T
1
) of individual ribose carbon atoms, measured by means of partially relaxed Fourier-transform spectra were practically independent of temperature up to about 60°C, and increased rapidly at higher temperatures. The
T
1
values indicated that the backbone of thermally denatured tRNA is undergoing rapid segmental motion, with an effective correlation time of (2.6 ± 0.5) × 10
-10
sec. The
T
1
values of folded tRNA yielded no evidence of segmental motion. The correlation time for overall rotational reorientation is about (3 ± 1) × 10
-8
sec in the range 35-54°C.

Within experimental error, the
T
1
values of methine carbons of the bases were equal to those of the methine carbons on the backbone at all temperatures. Only an upper limit to the rate of internal rotation of the bases could be established.
Carbamoyl Phosphate Compartmentation in
Neurospora
: Histochemical Localization of Aspartate and Ornithine Transcarbamoylases
Authors: Bernhardt Sharon A. , Davis Rowland H.
Published: May 2006

Carbamoyl phosphate is required for arginine and pyrimidine synthesis. In the arginine pathway, it is used in the ornithine transcarbamoylase (EC 2.1.2.1) reaction; in the pyrimidine pathway, it is used in the aspartate transcarbamoylase (EC 2.1.3.2) reaction. In
Neurospora crassa
, two pathway-specific enzymes catalyze the synthesis of carbamoyl phosphate, and two path-specific pools of carbamoyl phosphate are maintained. Histochemical studies show that ornithine transcarbamoylase is located in mitochondria, and, with less certainty, that aspartate transcarbamoylase is confined largely to nuclei. The enzymes that form carbamoyl phosphate are associated with the respective transcarbamoylases in the cell. Therefore, the segregation of carbamoyl phosphate pools could be accounted for by one or both organellar membranes, which demarcate two separate sites of carbamoyl phosphate metabolism in
Neurospora
. The alternative possibility that the enzyme complex that produces and consumes carbamoyl phosphate in the pyrimidine pathway could explain the channelling of carbamoyl phosphate, wholly or in part, is discussed.
Patterns of Simian Virus 40 DNA Transcription after Acute Infection of Permissive and Nonpermissive Cells
Authors: Khoury George , Byrne Janet C. , Martin Malcolm A.
Published: May 2006

Small amounts of fractionated, denatured,
32
P-labeled DNA from SV40 virus were incubated with a large excess of the complementary RNA of SV40 prepared
in vitro
with
Escherichia coli
RNA polymerase; the viral DNA strands were separated on hydroxyapatite columns. The RNA present in green monkey cells late in the lytic cycle reacted with 40-42% of the strand complementary to the
in vitro
complementary RNA (minus strand), and 60-64% of the opposite (plus) strand. “Early lytic” RNA failed to significantly interact with the plus strand, but formed stable duplex molecules with 35-39% of the minus strand. The RNA prepared from mouse embryo cells 24 hr after infection with SV40 combined with 35-38% of the minus strand and 60-62% of the plus strand. In all cases, the same regions of either the plus or minus strand appear to be transcribed in permissive and nonpermissive infections.
Demonstration That Antigen-Binding Cells Are Precursors of Antibody-Producing Cells After Purification with a Fluorescence-Activated Cell Sorter
Authors: Julius M. H. , Masuda T. , Herzenberg L. A.
Published: May 2006

We have obtained viable and functional populations of antigen-binding cells enriched up to 500-fold from primed spleen-cell suspensions by fluorescent labeling and by a new electronic cell sorter that sorts viable cells according to fluorescence. Concomitantly, populations largely depleted of antigen-binding cells were obtained. While neither population alone is capable of a full adoptive secondary response when injected into irradiated recipients, a reconstituted mixture restores the full response of the unfractionated spleen cells. Admixture of sources of unprimed thymus-derived cells (T-cells) with the purified antigen-binding cells (B-cells) restores much of the full response.
In Vitro
Conversion of Estradiol-Receptor Protein to Its Nuclear Form: Dependence on Hormone and DNA
Authors: Yamamoto Keith R. , Alberts Bruce M.
Published: May 2006

Early events in the action of 17-β-estradiol can be studied in soluble extracts of rat uterus by exposure of the estradiol-receptor protein to a DNA-cellulose matrix. After complexing with [
3
H]estradiol, the 4S receptor protein binds to the DNA, and it can be eluted with buffer of high ionic strength as a more tightly binding, 5S form. This parallels the
in vivo
situation, where migration of the receptor to the nucleus follows addition of hormone and is concomitant with a similar increase in sedimentation rate to 5 S. In both cases, the formation of a 5S receptor requires the presence of 17-β-estradiol. The rate at which 5S receptor forms is sensitive to extract concentration in a way that suggests that this receptor is a complex created by addition of a second subunit to the hormone-binding 4S component; physical studies on both
in vivo
and
in vitro
5S receptors also support this view. These results are interpreted in terms of a model for action of estrogen in which the hormone potentiates binding of receptor to DNA, and in turn, the DNA-binding process triggers the cell response.
The Effect of Various Nucleotides on the Helical Nature of a Ribosomal Protein(s) from
Escherichia coli
Authors: Brot Nathan , Boublik Miloslav , Yamasaki Edith , Weissbach Herbert
Published: May 2006

In the presence of GTP or GDP, there is a decrease in the circular dichroic absorption of ribosomal proteins L
7
and L
12
at 221-222 nm, suggesting that these nucleotides influence the helical content of these proteins.
The Attachment Site of Streptomycin to the 30S Ribosomal Subunit
Authors: Biswas Debajit K. , Gorini Luigi
Published: May 2006

The 16S RNA dissociated from 30S ribosomal subunits of
Escherichia coli
strains either sensitive or resistant to streptomycin contains the attachment sites for two streptomycin molecules, as does the undissociated particle from a streptomycin-sensitive strain. Since no streptomycin binds to undissociated 30S subunits from a streptomycin-resistant strain, it is suggested that protein P10, specified by the
strA
locus—known to be responsible for drug sensitivity—controls the availability to streptomycin of the attachment sites. These sites remain exposed in the
strA
+
wild-type, and become masked in
strA
streptomycin-resistant mutants.

The 16S RNA molecule binds streptomycin specifically; it binds two drug molecules in its native state, binds many more after its secondary structure is unfolded by melting out, and again binds two molecules after reannealing. The binding is stable to exhaustive dialysis, but it is reversed by exposure of the streptomycin-RNA complex to high-salt concentration. The complex can not be used to reconstitute functional ribosomes, but the 16S RNA reacquires this property after streptomycin elimination.

The biological significance of this stable streptomycin binding is questioned, since in
strA
mutants exhibiting phenotypic masking, exposure to streptomycin induces a modified 30S behavior that persists even after streptomycin has been dialyzed away, and is reversed only by exposure of the modified RNA to high-salt concentration.
Evaluation of the Distribution of Distances Between Energy Donors and Acceptors by Fluorescence Decay
Authors: Grinvald A. , Haas E. , Steinberg I. Z.
Published: May 2006

When transfer of electronic excitation energy occurs between a donor-acceptor pair by the Förster mechanism, the decay of fluorescence of the donor follows first-order kinetics, with a rate constant that depends on the distance from donor to acceptor. In a system that contains donor-acceptor pairs of different separations, the fluorescence decay of the donors will not be exponential, but will depend on the distribution function of donor-acceptor distances,
f
(
r
). Various approaches are outlined for the extraction of information about
f
(
r
) from the decay curve of donor fluorescence. Specifically, if a plausible expression with adjustable parameters is assumed for
f
(
r
), numerical methods can be used to evaluate the parameters that yield the closest fit between the observed decay curve and that calculated from the assumed
f
(
r
). The technique of fluorescence decay may prove to be useful for determination of distribution functions of end-to-end distances of polymers to the edges of which suitable donor-acceptor chromophore pairs have been attached.
Interactions between Native and Chemically Modified Subunits of Matrix-Bound Glycogen Phosphorylase
Authors: Feldmann Knut , Zeisel Hans , Helmreich Ernst
Published: May 2006

Phospho-dephosphohybrids of rabbit skeletal muscle phosphorylase (EC 2.4.1.1; α-1,4-glucan: orthophosphate glucosyl transferase) have been prepared and stabilized by attachment to Sepharose activated by cyanogen bromide. They can be distinguished from phosphorylase
a
by their sensitivity to inhibition by glucose-6-phosphate and activation by adenosine 5′-monophosphate. Stable hybrids have also been formed between phosphorylase subunits containing the active cofactor pyridoxal-phosphate and inactive analogs (pyridoxalphosphate monomethylester or the corresponding reduced compounds). After complete dissociation to monomers, the Sepharose-bound phosphorylase had a residual activity of less than 3% of that of the original matrix-bound dimeric enzyme. The hybrid enzyme is composed of a potentially active subunit containing pyridoxal-phosphate and an intrinsically inactive subunit carrying the analog, and it had half the activity of the original dimeric enzyme. Thus, the interaction of the inactive subunit with matrix-bound phosphorylase monomers elicited activity in the monomers.
Control of Transcription of RNA Rich in Polyadenylic Acid in Human Lymphocytes
Authors: Rosenfeld Michael G. , Abrass Itamar B. , Mendelsohn John , Roos Bernard A. , Boone Robert F. , Garren Leonard D.
Published: May 2006

Rapidly labeled polyribosomal RNA rich in poly(A) has been isolated from cultures of highly purified human peripheral blood lymphocytes. Messenger RNA function for this RNA is suggested by its ability to direct [
3
H]Met-tRNA binding to ribosomes and incorporation of amino acids into protein in a cell-free preparation. Phytohemagglutinin and low concentrations of dibutyryl cAMP (40 nM) increase poly(A)-rich RNA synthesis 40% within 2 hr, and 100-300% by 12 hr; the percent poly(A) content and the size of the poly(A)-rich portion remain constant. Higher concentrations of dibutyryl cAMP (1 nM), which prevent morphological transformation of lymphocytes by phytohemagglutinin, inhibit synthesis of poly(A)-rich RNA in phytohemagglutinin-treated lymphocytes without damaging cells. Cortisol (0.1 mM), which also prevents lymphocyte transformation, inhibits poly(A)-rich RNA synthesis by 80%. Cycloheximide (5 μg/ml), which decreases protein synthesis by 90%, decreases poly(A)-rich RNA synthesis 80% in cells stimulated by phytohemagglutinin. These studies demonstrate that, as part of the early molecular events of their action, phytohemagglutinin and cortisol regulate transcription of adenylate-rich RNA in human lymphocytes, and that similar transcriptional effects can be produced by dibutyryl cAMP.
Antigen Recognition: Early Surface-Receptor Phenomena Induced by Binding of a Tritium-Labeled Antigen
Authors: Diener E. , Paetkau V. H.
Published: May 2006

The rate of antigen binding by mouse lymphoid cells has been investigated with polymerized flagellin of
Salmonella adelaide
that had been biosynthetically labeled with tritium. Autoradiographs of lymphnode cells incubated with the tritiated antigen at 37° showed aggregation of antigen receptors to one cell pole. This was followed 4-5 hr later by the appearance of antigen receptors on the cell surface, at a density severalfold higher than at the time of first contact with the antigen. Antigen-binding cells exposed
in vitro
to antigen concentrations known to cause high zone tolerance induction failed to form polar antigen caps once they had entered the phase of increased receptor formation. The data suggest that sufficient crosslinking of receptors by the antigen to cause their aggregation triggers the cell to differentiate and to increase its density of antigen receptors. In the presence of antigen concentrations favoring high zone tolerance, receptors may become interlinked to such an extent that they are prevented from aggregation. Such a “frozen” state of the antigen recognition system would render the cell unresponsive to antigenic stimuli.
Assays for Porphyrins, δ-Aminolevulinic-Acid Dehydratase, and Porphyrinogen Synthetase in Microliter Samples of Whole Blood: Applications to Metabolic Defects Involving the Heme Pathway
Authors: Granick S. , Sassa S. , Granick J. L. , Levere R. D. , Kappas A.
Published: May 2006

Three micromethods are described for the assay of enzymes or products of the heme biosynthetic pathway in blood. A fluorometric method for the assay of protoporphyrin may be applied to the rapid screening of children for chronic lead poisoning. A colorimetric assay for δ-aminolevulinic-acid dehydratase may be applied to the detection of acute and chronic lead poisoning. A fluorometric assay for porphyrin formation from prophobilinogen is also described.
Mechanism of DNA Replication by Highly Purified DNA Polymerase of Chicken Embryo
Authors: Stavrianopoulos Jannis G. , Karkas John D. , Chargaff Erwin
Published: May 2006

Highly purified DNA polymerase of chicken embryo was used to investigate the mechanism of DNA replication. The templates used included synthetic homopolymer pairs, as well as DNA of bacteriophage f1 and DNA-RNA hybrids prepared by partial or complete transcription of f1 DNA. The evidence suggests that the DNA synthesized is complementary either to the DNA or the RNA strand of the hybrid, depending on the relative lengths of the two strands, with the longer serving as the template and the shorter as the primer. While f1 DNA itself lacks template properties, the f1 DNA-RNA hybrids are efficient templates; and composition studies show the DNA synthesized to be complementary to the DNA strand of the hybrid. These observations suggest a mechanism of DNA replication in which the initial synthesis of a stable primer by RNA polymerase plays a pivotal role.
Stimulation of Adenosine 3′:5′-Cyclic Monophosphate Accumulation in Anterior Pituitary Gland
In Vitro
by Synthetic Luteinizing Hormone-Releasing Hormone
Authors: Borgeat Pierre , Chavancy Gerard , Dupont Andre , Labrie Fernand , Arimura Akita , Schally Andrew V.
Published: May 2006

A near-maximal dose (20 ng/ml) of synthetic luteinizing hormone(LH)-releasing hormone/follicle-stimulating hormone(FSH)-releasing hormone added to incubated anterior pituitary tissue of male rats leads to concomitant increases of intracellular concentrations of adenosine 3′:5′-monophosphate and of release of both LH and FSH. The stimulatory effect of LH-releasing hormone/FSH-releasing hormone is observed after a lag period of about 90 min and is progressive at later time intervals; a 3-fold stimulation of cAMP accumulation over control is seen after 210 min of incubation. Half-maximal stimulation of cAMP accumulation is observed between 0.1 and 1.0 ng/ml (0.1-1 nM) of LH-releasing hormone/FSH-releasing hormone. In the presence of 10 mM theophylline, the stimulatory effect of LH-releasing hormone/FSH-releasing hormone on cAMP accumulation is similar to that observed in the absence of the inhibitor of cyclic nucleotide phosphodiesterase, indicating that the releasing hormone exerts its effect by specific activation of adenylate cyclase in LH- and FSH-secreting cells rather than by inhibition of cyclic nucleotide phosphodiesterase. Since the release of growth hormone, thyrotropin, prolactin, and adrenocorticotropic hormone is not affected by LH-releasing hormone/FSH-releasing hormone, and since cAMP stimulates the release of all six adenohypophyseal hormones. the observed changes of cAMP concentrations indicate specific stimulation of adenylate cyclase activity in LH-and FSH-secreting cells of the adenohypophysis.
Circadian Surfaces and the Diversity of Possible Roles of Circadian Organization in Photoperiodic Induction
Authors: Pittendrigh Colin S.
Published: May 2006

It is an established fact that circadian rhythmicity is often somehow involved in the physiology of photoperiodic induction. It is shown, however, that there are three possible ways in which such rhythmicity could be involved. For the most part available data are inadequate to discriminate among these three roles, only one of which is covered by “Bünning's Hypothesis.” Emphasis is given to a previously ignored possibility in which circadian organization is involved in photoperiodism“ut not as the clock responsible for the time-measurement. The meaning of circadian surfaces and their bearing on the interpretation of a widely used experimental protocol is developed.
Structure and Chemical Synthesis of a Biologically Active Form of
Renilla
(Sea Pansy) Luciferin
Authors: Hori Kazuo , Cormier Milton J.
Published: May 2006

The structure of a biologically active form of
Renilla
(sea pansy) luciferin has been elucidated; this structure, confirmed by total chemical synthesis, is 3,7-dihydro-2-methyl-6-(
p
-hydroxyphenyl)-8-benzylimidazo [1,2-
a
] pyrazin-3-one. In the natural compound the methyl group at the 2 position is replaced by an unknown, more complex group. For this reason the synthetic compound is 10% as active as the natural compound in producing light with
Renilla
luciferase. However, the spectral properties of the two compounds are identical. In addition the rates of the luminescent reaction with both compounds are similar, and the color of the light produced is identical in each case.

A compound isolated from the calcium-triggered photoprotein aequorin has been identified by Shimomura and Johnson [(1972)
Biochemistry
11, 1602] to be 2-amino-3-benzyl-5-(
p
-hydroxyphenyl)pyrazine. This compound forms an integral part of the structure of
Renilla
luciferin. This, and other evidence, suggests that the structure elucidated for
Renilla
luciferin is a more general one associated with the luciferins of most, if not all, bioluminescent coelenterates.
Cleavage of Adenovirus Type 2 DNA into Six Unique Fragments by Endonuclease R·RI
Authors: Pettersson Ulf , Mulder Carel , Delius Hajo , Sharp Phillip A.
Published: May 2006

The DNA of adenovirus type 2 was cleaved by restriction endonuclease R·RI into six fragments. These fragments were separated by electrophoresis on composite agarose-polyacrylamide gels. Their molecular weights ranged from 1.1 × 10
6
to 13.6 × 10
6
, as measured by electron microscopy. Each fragment represented a unique segment of adenovirus type 2 DNA since: (
i
) the fragments were obtained in equimolar amounts; (
ii
) the sum of their molecular weights was equal to the molecular weight of complete adenovirus DNA; and (
iii
) each fragment exhibited a rate of renaturation that was inversely proportional to its size.
A Model for Active Transport of Sodium and Potassium Ions as Mediated by a Tetrameric Enzyme
Authors: Stein W. D. , Lieb W. R. , Karlish S. J. D. , Eilam Y.
Published: May 2006

A new model is proposed for the system that actively transports sodium and potassium ions across animal-cell membranes. The model is based on the physical and chemical properties of transport-associated adenosine triphosphatase (EC 3.6.1.3) and on the kinetics of ion movements mediated by the system. Transport is postulated to occur by internal transfer of cations across a protein tetramer embedded in the cell membrane. The protein tetramer can exist in either of two forms of identical energy; transport occurs as a result of the sequential “flipping” from one conformation to the other. The conformation change results in the interchanging of the affinities of cation-binding sites associated with different sub-units of the tetramer, with a concomitant splitting of adenosine triphosphate.
Malignant Transformation of BHK
21
Clone 13 Cells
In Vitro
by Nitrosamines—A Conditional State
Authors: Di Mayorca Giampiero , Greenblatt Melvin , Trauthen Thomas , Soller Arthur , Giordano Roberto
Published: May 2006

All the BHK
21
Clone 13 cells transformed by dimethylnitrosamine or nitrosomethylurea, and a single “spontaneously” transformed clone obtained in our laboratory, exhibit a conditional state of the transformed phenotype. Upon growth at 38.5°, they have a transformed phenotype (clonal morphology and the ability to plate in soft agar); when grown at 32°, their phenotype is normal. The conditional state of these cells, however, does not extend to their growth characteristics; their plating efficiency at the two temperatures in liquid medium is similar. Conversion from the normal to the transformed phenotype and the reverse is possible by temperature shifts. A working hypothesis is proposed suggesting that this phenomenon may be caused by a temperature-sensitive mutation of a cellular gene whose product is responsible for maintaining the normal phenotype. The high temperature would then affect either the synthesis or the function of the protein carrying the temperature-sensitive alteration and, as a consequence, the transformed phenotype would be expressed.
Stimulation of Mitochondrial Adenosine Diphosphate Uptake by Thyroid Hormones
Authors: Babior Bernard M. , Creagan Susan , Ingbar Sidney H. , Kipnes Ruby S.
Published: May 2006

Thyroid hormone administered
in vivo
increased carrier-mediated (atractyloside-sensitive) ADP uptake by rat liver mitochondria. 3 Days after a single large dose of triiodothyronine (20 μg/100 g of body weight), mitochondrial uptake of ADP measured at 6° was 2.35 ± 0.17 nmol/min per mg of protein, compared with an uptake of 1.81 ± 0.19 nmol/min per mg of protein in mitochondria from untreated rats (
P
< 0.025). Cyanide (1.33 mM) had no effect on ADP uptake by mitochondria from either untreated or triiodothyronine-treated animals. Uptake of ADP by mitochondria from thyroidectomized rats treated with thyroxine for 7 days was 2.89 ± 0.40 nmol/min per mg in mitochondria from thyrotoxic rats (20 μg of thyroxine per 100 g per day) and 1.98 ± 0.22 nmol/min per mg in mitochondria from euthyroid rats (2 μg of thyroxine per 100 g per day) (
P
< 0.025). Mitochondria from both untreated and thyroid hormone-treated rats displayed a highly significant linear correlation between ADP uptake and ADP-dependent (i.e., state 3 minus state 4) oxygen consumption. There was, however, no difference in respiratory control ratios between mitochondria from euthyroid and thyrotoxic animals. Administration of dinitrophenol (2 mg/100 g) also stimulated carrier-mediated ADP uptake, but respiratory control of mitochondria from dinitrophenol-treated animals was virtually abolished. Triiodothyronine
in vitro
, at concentrations of 100 and 0.1 nM, appeared to inhibit rather than stimulate the uptake of mitochondrial ADP. The relationship between these observations and the clinical manifestations of thyrotoxicosis is discussed from the point of view of the possible effects of increased mitochondrial ADP transport on oxidative phosphorylation and adenosyl nucleotide metabolism.
Ribosomal Assembly Influenced by Growth in the Presence of Streptomycin
Authors: Garvin Robert T. , Rosset Roland , Gorini Luigi
Published: May 2006

Translational leakiness (i.e., nonspecific suppression) of nonsense mutants of bacteriophage T4 is increased in cells of certain streptomycin-resistant strains previously grown in the presence of streptomycin. Concomitantly, ribosomes extracted from these streptomycin-grown cells possess a high level of misreading. Increased suppression ability as well as ribosomes that highly misread accumulate with kinetics expected for a constant differential rate of synthesis of a new product induced by drug action. The misreading ribosomes do not contain appreciable amounts of streptomycin and the misreading property is lost by exposure to high salt concentrations. It is suggested that streptomycin (or dihydrostreptomycin, or paromomycin) induces a reversible modification in 30S subunit assembly without physically participating in the modified structure. The extent of this modification appears dependent upon the
strA
allele.
Secondary Structure Maps of RNA: Processing of HeLa Ribosomal RNA
Authors: Wellauer Peter K. , Dawid Igor B.
Published: May 2006

Ribosomal RNA precursors and mature 28S ribosomal RNA from HeLa cells display a highly reproducible secondary structure of hairpin loops after they are spread and examined in an electron microscope. This structure was used to map the linear arrangement of these molecules. Partial digestion with 3′-exonuclease from ascites cell nuclei established that the 28S RNA region is located at the 5′-end of the 45S precursor. A spacer sequence follows the 28S region. This is followed by the 18S RNA region, and by another spacer sequence at the 3′-end. The 41S RNA contains both 18S and 28S regions. The 32S RNA contains only 28S RNA plus spacer, and the 20S RNA contains only 18S RNA plus spacer. Several minor nucleolar RNA components were also mapped with respect to the 45S RNA. These experiments lead to a more detailed processing pathway for HeLa ribosomal RNA which is in good agreement with earlier work.
Substrate Binding to an Active Creatine Kinase with a Thiol-Bound Mercurinitrophenol Chromophoric Probe
Authors: Quiocho Florante E. , Thomson James W.
Published: May 2006

A mol of creatine kinase (EC 2.7.3.2), an enzyme with two identical subunits can be titrated very rapidly and stoichiometrically with 2 mol of 2-chloromercuri-4-nitrophenol, an environmentally sensitive chromophoric probe specific for thiols. Chemical modification does not inactivate the enzyme nor can the reaction be prevented by a dead-end quaternary complex of enzyme, magnesium, ADP, and creatine with added nitrate. Creatine kinase modified with the chromophoric reagent can be further reacted with 200-fold molar excess of iodoacetamide, resulting in loss of enzymatic activity but without release of bound mercurinitrophenol. The tightly bound chromophore has spectral properties different from free unbound mercurinitrophenol. Only addition of MgADP, or MgATP and creatine, or nitrate, to the modified though active enzyme causes further changes in the visible spectrum of the bound nitrophenol. Addition of nitrate, Mg, ADP, and creatine to the enzyme with bound reporter group, in the order indicated, caused spectral changes; each addition gave a different spectrum.
A Specific Inhibitor of Polypeptide-Chain Initiation in
Escherichia coli
Authors: Lee-Huang Sylvia , Lee Henry , Ochoa Severo
Published: May 2006

An inhibitor of polypeptide-chain initiation was isolated from
E. coli
cells. This protein inhibits formation of the 30S or 70S initiation complex with either fMet-tRNA
f
as initiator and AUG, MS2 RNA, or late T4 RNA as messenger, or acPhe-tRNA as initiator and poly(U) as messenger. Chain elongation, e.g., poly(U) translation at high Mg
2+
concentration, is not inhibited. The inhibitor is rendered ineffective when active aminoacylation of tRNA is taking place, e.g., during natural mRNA translation. This inhibitor is distinct from the so-called interference (i) factors, which interfere exclusively with the action of initiation factor 3. Since the new inhibitor can apparently be turned on and off, it may have a regulatory function in translation.
Nuclear Magnetic Resonance Study of Hydrogen-Bonded Ring Protons in Watson-Crick Base Pairs
Authors: Crothers D. M. , Hilbers C. W. , Shulman R. G.
Published: May 2006

We have studied the low-field proton magnetic resonance spectrum of the double-helical complex of d(A-A-C-A-A) with d(T-T-G-T-T). Well-resolved resonances for the thymidine N
3
and the guanosine N
1
protons are seen at 1°C, which broaden by 4°C and disappear above 9°C. The actual T
m
of the complex was found to be 28°C by measurement of UV-absorbance change. There are several factors that could limit the observed exchange broadening of the resonance lines; the model that best fits the data is one in which the rate of double-helix dissociation limits the rate of exchange of the H-bonding protons with water.
Survey of DNA Polymerase Activity During the Early Development of
Drosophila melanogaster
Authors: Margulies Lola , Chargaff Erwin
Published: May 2006

The pattern of DNA polymerase activity in developing
Drosophila melanogaster
has been studied in seven stages of embryonic development as well as in unfertilized eggs. The crude polymerase-containing extracts, most likely of cytoplasmic origin, utilize, in the following order of decreasing template efficiency, “activated” calfthymus DNA, poly(A)·oligo(dT), and poly(A)·oligo(U). The highest enzymes levels occur in unfertilized eggs; the activity remains high during the first 9 hr of embryogenesis, but shows a progressive decline in the later stages. Deoxyribonuclease exhibits a similar trend. The unfertilized eggs of two genotypically different females had nearly identical levels of DNA polymerase.
Effects of 5-Bromo-2′-Deoxyuridine on Production of Globin Messenger RNA in Dimethyl Sulfoxide-Stimulated Friend Leukemia Cells
Authors: Preisler Harvey D. , Housman David , Scher William , Friend Charlotte
Published: May 2006

Friend leukemia cells grown in the presence of dimethyl sulfoxide show enhanced erythroid differentiation and hemoglobin synthesis. The effects of dimethyl sulfoxide stimulation are inhibited by BrdU. To determine the effect of BrdU on the amount of globin mRNA present in cells treated and not treated with dimethyl sulfoxide, molecular hybridization between total cell RNA and [
3
H]DNA complementary to mouse globin mRNA was used. Cells treated with BrdU and dimethyl sulfoxide had 70% less globin mRNA than cells treated with dimethyl sulfoxide alone. The size and base sequence of the residual globin mRNA in the cultures treated with BrdU and dimethyl sulfoxide were unaltered. Cells treated with BrdU alone contained slightly more globin mRNA than did the untreated controls, suggesting that BrdU may have a dual effect in transcription of messenger RNA.
Collagen Synthesis: A Disulfide-Linked Collagen Precursor in Chick Bone
Authors: Fessler L. I. , Burgeson R. E. , Morris N. P. , Fessler J. H.
Published: May 2006

Chick calvaria labeled
in vitro
contain a triple-stranded collagen precursor that contains two pro α1 and one pro α2 chains. All chains contain cystine and are linked by S-S bonds. Ultracentrifugal analysis was used to measure the relative size of the disulfide-linked units. It is proposed that the S-S links help to determine the correct alignment of the triple-stranded structure.