bluuebunny/crossref_metadata_2025 huggingface dataset:
Two Separate Genes Controlling Stimulation in Mixed Lymphocyte Reaction in Man
Authors: Dupont Bo , Good Robert A. , Hansen Grete S. , Jersild Casper , Nielsen Lillian Staub , Park Ben H. , Svejgaard Arne , Thomsen Mogens , Yunis Edmond J.
Published: May 2006

The genetic control of strong stimulation in the mixed lymphocyte culture reaction is determined by a separate gene (
MLR-S
) closely linked to the
FOUR
-locus of the
HL-A
chromosomal region. Three additional examples of siblings with recombination between
FOUR
-locus and
MLR-S
locus are presented which confirms the independent genetic control of mixed lymphocyte reaction from the control of
HL-A
antigens. The occurrence of two recombinant children in one family with four other children representing all possible
HL-A
haplotype-combinations, strongly supports the genetic mapping of the
MLR-S
determinants outside the
HL-A
chromosomal region. The experiments presented show that additional genes located within the
HL-A
region itself contribute with a weak stimulation of allogenic mixtures. These data are discussed in relation to the marginal stimulation of the mixed lymphocyte culture reaction which can be seen between unrelated individuals. It seems that a group of relatively histocompatible individuals can be defined by identity of the
MLR-S
locus but with differences on the weak
MLC
-determinants, and that this group for the purpose of clinical transplantation behaves as histocompatible individuals.
Effects of Guanosine Tetraphosphate, Guanosine Pentaphosphate, and β-γ Methylenyl-Guanosine Pentaphosphate on Gene Expression of
Escherichia coli In Vitro
Authors: Yang Huey-Lang , Zubay Geoffrey , Urm Elo , Reiness Gary , Cashel Michael
Published: May 2006

The effects of guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), both produced by
E. coli
, were measured on the activities of several genes in a cell-free system. Gene activity is measured as gene-directed synthesis of biochemically competent protein or transfer RNA. Both ppGpp and pppGpp stimulated the activities of the
ara, lac
, and
trp
operons and inhibited the
arg
operon. Production of transfer-RNA
Tyr
was unaffected by moderate levels of either ppGpp or pppGpp and only slightly inhibited at higher levels of ppGpp. Since the cell-free reaction mixtures hydrolyze pppGpp to ppGpp, we performed similar studies with a hydrolysis-resistant analog of pppGpp, the β-γ methylenyl derivative (pcppGpp). In general, pcppGpp shows the same inhibitory potency as pppGpp for the
arg
operon, but lacks the stimulatory effects on the
ara, lac
, and
trp
operons. This result suggests that the stimulation of these gene activities is specific for ppGpp.

Under similar conditions, pppGpp and ppGpp show a slight inhibitory effect on the messenger-directed synthesis of β-galactosidase and no effect on the messenger-directed synthesis of MS2 viral-coat protein. These observations, together with the fact that in the same system these nucleotides affect coupled transcription and translation, lead us to surmise that the activities of pppGpp and ppGpp are exerted at the level of RNA polymerase activity.
Penetration of Mouse Fibroblasts by the 5′-Phosphate of 9-β-D-Arabinofuranosyladenine and Incorporation of the Nucleotide into DNA
Authors: Plunkett William , Lapi Lillie , Ortiz Priscilla J. , Cohen Seymour S.
Published: May 2006

9-β-D-Arabinofuranosyladenine 5′-monophosphate (araAMP) is more lethal to mouse fibroblasts (L cells) than the identical exogenous concentration of 9-β-D-arabinofuranosyladenine (araA) (
Cancer Res.
32, 1512, 1972). [
3
H,
32
P]AraAMP (0.1 mM) was taken into L cells for 4 hr in the presence of a large excess of
32
P
i
. The radioactivity was subsequently found mainly in the adenine nucleotides in the acid-soluble fraction and in the cell DNA. The cellular concentration of 9-β-D-arabinofuranosyladenine 5′-triphosphate (araATP) exceeded 2 μM. More than 90% of the
3
H was associated with araA in the nucleotides. After degradation of the adenine-containing triphosphates with apyrase, the adenine mononucleotides were separated by thin-layer electrophoresis and chromatography. All of the
32
P and 97% of the
3
H were associated with araAMP.

The small amounts of
3
H and
32
P in the acid-insoluble material were similar during a 4 hr incubation. The DNA fraction was degraded enzymatically to 5′-mononucleotides. Both
32
P and
3
H were associated predominantly with 5′-dAMP. Most of the
3
H was in araA, detected after dephosphorylation. Enzymatic degradation of the DNA fraction to 3′-mononucleotides and fractionation revealed
3
H primarily in the 3′-adenine nucleotide and
32
P in each of the deoxynucleoside 3′-monophosphates. After dephosphorylation of the 3′-mononucleotides, 93% of the
3
H was found in araA. These results suggest that small amounts of araAMP penetrated the cell as an intact nucleotide, were further phosphorylated to the triphosphate, and subsequently incorporated in internucleotide linkage into DNA.
A Role of the Putidaredoxin COOH-terminus in
P
-450
cam
(Cytochrome
m
) Hydroxylations
Authors: Sligar S. G. , Debrunner P. G. , Lipscomb J. D. , Namtvedt M. J. , Gunsalus I. C.
Published: May 2006

Methylene hydroxylation by cytochrome
P
-450
cam
(cytochrome
m
) can be resolved into four distinct steps: substrate addition,
m
o
→
m
os
; reduction,
m
os
→
m
rs
; dioxygen addition,
m
rs
→
m

O
2

rs
; followed by a second putidaredoxin (
Pseudomonas putida
ferredoxin)-mediated reduction and product formation. The isolated ferrous oxy-substrate complex exhibits first-order decay kinetics with the relatively slow rate constant of
k
[unk] 0.01 sec
-1
, at 25°, without product release. Putidaredoxin addition accelerates the decomposition with second-order kinetics,
k
[unk] 51,000 M
-1
sec
-1
, and initiation of product formation. Cytochrome
m
forms a complex with putidaredoxin with dissociation constant of
K
D
= 3 μM. In the complete three-protein hydroxylase system, consisting of cytochrome
m
, putidaredoxin, and the reductase (a DPNH-specific flavo-protein), camphor hydroxylation occurs with a stoichiometry of 1 mole each of DPNH and O
2
used per mole of product formed; the

K
M

for putidaredoxin is about 4.2 μM.

Putidaredoxin, on treatment with carboxypeptidase A, loses one molecule each of tryptophan and glutamine sequentially from the carboxy terminus to expose a terminal arginine. The tryptophan-free product has been separated from native putidaredoxin and other impurities, and retains the visible and electron paramagnetic resonance spectra and the redox potential of the active center of native putidaredoxin. This modified redoxin binds less tightly to cytochrome

m, K
D

[unk] 150 μM, and is 50 times less effective in stimulation of the
m

O
2

rs
decay rate. A similar decrease in specific activity is observed in the complete hydroxylase system.
Bacteriophage λ Having
Eco
RI Endonuclease Sites Only in the Nonessential Region of the Genome
Authors: Rambach Alain , Tiollais Pierre
Published: May 2006

A derivative of λ
b221
that has lost by mutation all
Eco
RI restriction sites has been isolated by alternative growth on restrictive and nonrestrictive strains. It has an efficiency of plating equal to 1 on the restrictive strain. Genetic cross of this bacteriophage with λ
plac5 imm21
gave rise to recombinants of intermediate restricting ratios. The analysis of the
Eco
RI endonuclease-cleaved DNA by polyacrylamide gel electrophoresis, compared with the genetic results, has permitted identification of
Eco
RI endonuclease cleavage sites in the recombinants. The genotypes are: λ
plac5 CI857 sRI
λ
3
0
sRI
λ
2
0
sRI
λ
1
0
and λ
plac5 CI857 sRI
λ
2
0
sRI
λ
1
0
. The remaining cleavage sites, respectively,
sRIlac sRI
λ
4
and
sRIlac sRI
λ
4 sRI
λ
3
, are all located in a region nonessential for bacteriophage multiplication. The involvement of these mutant bacteriophages as vector for foreign genes are discussed.
Heterogeneity of HL-A Antigen Preparations Is Due to Variable Sialic Acid Content
Authors: Parham Peter , Humphreys Robert E. , Turner Mervyn J. , Strominger Jack L.
Published: May 2006

Purified, papain-solubilized preparations of HL-A antigen from cultured human lymphoblastoid cells (HL-A2 and HL-A7,12 from RPMI 4265 cells and a mixture of HL-A3, W-25, HL-A12, and HL-A27 from IM-1 cells) show substantial charge heterogeneity in isoelectric focusing gels. This heterogeneity can be ascribed largely to variable numbers of sialic acid residues on each molecule. Neuraminidase (EC 3.2.1.18) treatment of the HL-A antigens as a function of time altered the band patterns in a manner demonstrating that up to three sialic acid residues are present on both first locus (“LA”) and second locus (“Four”) antigens. Neuraminidase treatment did not alter the specificity or specific activity of the purified antigens.
Differential Lectin Agglutination of Fetal, Dividing-Postnatal, and Malignant Hepatocytes
Authors: Becker F. F.
Published: May 2006

Numerous studies have reported the capacity of the lectin, concanavalin A, to agglutinate selected cell-types. The finding that cells transformed in culture, embryonic cells, and malignant cells are all agglutinated by this substance, may contribute to our understanding of the oncogenic process. The present study compared the response to concanavalin A of rat hepatocytes derived from livers of differing developmental and mitotic-status as well as those derived from malignant liver tumors (hepatomas). Fetal hepatocytes and hepatoma cells were highly susceptible to agglutination while hepatocytes from post-natal livers, whether dividing or quiescent, were not. Treatment with protease(s) did not make the interphase hepatocyte agglutinable. These data emphasize the importance of examining a wide variety of cells in attempting to understand the interaction of lectins on cell surfaces, and further, demonstrate the value of obtaining cells directly from tissue(s) during differing physiologic and pathologic states.
A Mutant of
Escherichia coli
Defective in the Coupling of Metabolic Energy to Active Transport
Authors: Lieberman Michael A. , Hong Jen-Shiang
Published: May 2006

The isolation of a temperature-sensitive mutant of
E. coli
K12 whose active transport of amino acids and sugars is not coupled to metabolic energy at 42° is described. This mutant cannot grow on succinate, fumarate, malate, or D-lactate as sole carbon source at 42° and grows on glucose at 42° with a reduced rate and yield. Efflux of accumulated substrate is also demonstrated upon heat inactivation. The defect of this mutant in both growth and transport is not due to a failure in electron transport through the respiratory chain nor the absence of Mg, Ca-ATPase activity. The mutant is thus distinct from the other energy-uncoupled mutants
uncA, uncB
, or
etc.
Analysis of spontaneous revertants indicates that the transport defect is caused by two mutations, one in the energy coupling factor gene and the other in the
metC
gene. The
ecf
ts
mutation has been mapped to be in the 54.5- to 60-min region of the
E. coli
chromosome map. Possible interactions between the
metC
mutation and the mutated energy coupling factor protein are discussed.
Competitive Inhibition of Beef Heart Cyclic AMP Phosphodiesterase by Cytokinins and Related Compounds
Authors: Hecht Sidney M. , Faulkner Robert D. , Hawrelak S. D.
Published: May 2006

Two cytokinins and four related analogs, none of which is a cyclic ribonucleotide, have been shown to act as competitive inhibitors of the high

K
m

cyclic-AMP phosphodiesterase (3′:5′-cyclic-AMP 5′-nucleotidohydrolase, EC 3.1.4.17) activity from beef heart. Weak inhibition of the low

K
m

cyclic AMP phosphodiesterase activity was also observed, suggesting a possible mechanism for regulation of intracellular cyclic AMP levels by the exogenously added compounds. In addition to the kinetic data, obtained on the six inhibitors in four different heterocyclic series, 15 other cytokinins and related compounds have been shown to inhibit the high

K
m

cyclic AMP phosphodiesterase activity at single concentrations of substrate and inhibitor. Heterocycles such as adenosine and 7-amino-3-methylpyrazolo[4,3-
d
]pyrimidine, which lack the
N
-substituent, were inactive as cyclic AMP phosphodiesterase inhibitors. The observed inhibition of cyclic AMP phophodiesterase supports prior observations which implicate exogenously added cytokinins in cyclic AMP metabolism.
The
recBC
Deoxyribonuclease of
Escherichia coli:
Isolation and Characterization of the Subunit Proteins and Reconstitution of the Enzyme
Authors: Lieberman Robert P. , Oishi Michio
Published: May 2006

After dissociation of the
E. coli recBc
DNase (ATP-dependent DNase) with concentrated NaCl, two subunit proteins were isolated by ion exchange chromatography. Combination and subsequent incubation of the subunits resulted in the appearance of the original DNase. The subunit proteins, designated α and β, have
s
20,ω
of 4.1 S and 8.1 S, respectively. The α subunit possesses neither the ATP-dependent Dnase nor the DNA-dependent ATPase of the original enzyme. The β subunit contains a low level of both enzymatic activities in a ratio markedly different from that of the original enzyme. The β subunit complemented extracts from both
recB
and
recC
mutant strains to produce
recBC
DNase, while the α subunit did not complement either extract. These results suggest that
recB
and
recC
genes are both required for the production of β subunit and that the
recBC
DNase molecule contains a protein component (α) that is not determined by either the
recB
or the
recC
gene.
Paired Moving Charges in Mitochondrial Energy Coupling
Authors: Green David E. , Reible Stanley
Published: May 2006

A model of mitochondrial energy coupling has been proposed based on the principles of paired charge separation and vectorial paired charge flow. The unique role of the electron transfer chain and ionophores in mediating charge separation is emphasized.
Unscheduled DNA Synthesis in the Germ Cells of Male Mice Exposed
In Vivo
to the Chemical Mutagen Ethyl Methanesulfonate
Authors: Sega Gary A.
Published: May 2006

An unscheduled DNA synthesis has been clearly demonstrated in meiotic and postmeiotic germ cell stages of the male mouse after
in vivo
treatment with a 250 mg/kg dose of ethyl methanesulfonate. The germ cell stages showing unscheduled DNA synthesis range from early to middle meiotic prophase stages through early to middle spermatid stages. The initiation of this synthesis, taken to be repair of chemically damaged DNA in these germ cells, is rapid, beginning within 1 hour after the injection of ethyl methanesulfonate. Unscheduled DNA synthesis has not been detected in the most mature germ cell stages, which give rise to dominant lethal mutations, nor does it occur in germ cell stages where protamine has replaced the chromosomal histones.
Chromosomal Variation and the Origin of Drug-Resistant Mutants in Mammalian Cell Lines
Authors: Terzi Mario
Published: May 2006

Drug-resistant mutants of somatic cell lines fall into two classes: one seems to correspond to classical gene mutation, the other is characterized, albeit transiently, by karyotypic instability, high reversion frequency, and low plating efficiency. An interpretation of the origin of these drug-resistant mutants is offered on the basis of chromosomal variation, which generates variation of the number of copies of each individual chromosome and, consequently, of gene dosage.
Transformation by Simian Virus 40 of Spleen Cells from a Hyperimmune Rabbit: Evidence for Synthesis of Immunoglobulin by the Transformed Cells
Authors: Collins J. J. , Black P. H. , Strosberg A. D. , Haber E. , Bloch K. J.
Published: May 2006

Spleen cells derived from a rabbit hyperimmunized with a Type III pneumococcal vaccine were exposed to simian virus 40
in vitro
. After 114 days, transformed cells growing on the surface of one culture dish were observed and a cell line was established. The transformed cells had a morphology characteristic of cells transformed by simian virus 40, contained the simian virus 40-specific T antigen, and yielded infectious simian virus 40 upon cultivation with indicator cells in the presence of Sendai fusion factor. Transformed cells incorporated labeled amino acid into protein with the antigenic properties of rabbit immunoglobulin G.
A Proposed Model for Interaction of Polypeptides with RNA
Authors: Carter Charles W. , Kraut Joseph
Published: May 2006

Pairs of antiparallel β polypeptide-chain segments in known protein structures are usually observed to form right-handed double helixes with helix parameters in the same range as those of nucleic acids. We have constructed a model containing only standard bond lengths, bond angles, and dihedral angles in which such a polypeptide double helix fits precisely into the minor groove of an RNA double helix with identical helix parameters. The geometry of the RNA portion is essentially a hybrid between those of the A and A′ forms. Hydrogen bonds can be made between the ribose 2′-hydroxyls and polypeptide carbonyl oxygens. Since such precise complementarity between the stable conformations of RNA and polypeptides is unlikely to be merely coincidental, we propose that it played a fundamental role in the initiation of precellular evolution. Specificially, we propose that the two double-helical structures are mutually catalytic for assembly of one another from activated precursors in the prebiotic soup, and moreover that they provide some degree of genetic coding.
Trinitrophenol: A Membrane-Impermeable Uncoupler of Oxidative Phosphorylation
Authors: Hanstein W. G. , Hatefi Y.
Published: May 2006

Picrate (trinitrophenol) is a unique uncoupler of oxidative phosphorylation. Unlike the commonly used uncouplers (e.g., 2,4-dinitrophenol, pentachlorophenol,
m
-chlorocarbonylcyanide phenylhydrazone, and 5-chloro-3-
t
-butyl-2′-chloro-4′-nitrosalicylanilide), picrate seems to penetrate the mitochondrial inner membrane very slowly. Consequently, it is ineffective when added to intact mitochondria or to mitochondria depleted of their outer membranes. In contrast, when added to phosphorylating submitochondrial particles prepared by sonication in which the inner membrane orientation is inside-out, picrate binds to the uncoupler-binding sites and uncouples oxidative phosphorylation. This unique property of picrate has made it possible to compare the potencies of picrate and dinitrophenol for (
a
) uncoupling and (
b
) increasing the proton permeability of submitochondrial particle vesicles. At 50% uncoupling concentration, dinitrophenol increased the proton permeability of submitochondrial particle vesicles by 9- to 12-fold. In contrast, at 100% uncoupling concentrations or higher, picrate augmented the proton permeability of the particles by only about 3-fold. These results indicate that facilitation of transmembrane proton equilibration does not determine the degree of uncoupling, and lead to the corollary conclusion that the magnitude of transmembrane proton gradient need not be the quantitative driving force for ATP synthesis.
Formation of 5-Oxoproline from Glutathione in Erythrocytes by the γ-Glutamyltranspeptidase-Cyclotransferase Pathway
Authors: Palekar Anil G. , Tate Suresh S. , Meister Alton
Published: May 2006

γ-Glutamyltranspeptidase activity was demonstrated in the membrane fraction of rabbit erythrocytes. The activity observed (with glutathione and various amino-acid acceptors) was similar in magnitude to that of the γ-glutamylcyclotransferase and γ-glutamylcysteine synthetase activities found in the soluble fraction of the cell. No transpeptidase activity was observed with either γ-glutamyl
p
-nitroanilide or oxidized glutathione in contrast to the rabbit-kidney enzyme for which these compounds and glutathione serve as substrates. Erythrocyte suspensions and hemolysates formed 5-oxoproline (pyroglutamate; pyrrolidone carboxylate); the rate of 5-oxoproline formation from glutathione by hemolysates was increased by addition of methionine. The findings indicate that 5-oxoproline is an end-product of glutathione metabolism in erythrocytes, and that 5-oxoproline passes out of the erythrocyte and is metabolized in other tissues. The observed rate of 5-oxoproline formation is consistent with the conclusion that the γ-glutamyltranspeptidase-cyclotransferase pathway, together with the synthesis of glutathione from glycine, cysteine, and glutamate, account for a large fraction of the observed amino-acid turnover of erythrocyte glutathione.
Immunoglobulin Synthesis
In Vitro
by Lymphocytes from Patients with Immune Deficiency: Requirement for a Special Serum Factor
Authors: Wernet P. , Siegal F. P. , Dickler H. , Fu S. , Kunkel H. G.
Published: May 2006

Certain patients with immune deficiency were encountered whose peripheral blood lymphocytes included no immunoglobulin-bearing cells. However, other markers of B type lymphocytes were observed; lymphocytes isolated free of macrophages showed the presence of receptors for the Fc fragment of IgG and for the third component of complement. One patient with a syndrome of thymoma and severe hypogammaglobulinemia was studied in special detail.
In vitro
the patient's cells were able to develop surface Ig in media supplemented with fetal-calf serum or normal human serum; in media supplemented with autologous serum, the cells developed no surface Ig. During culturing antigenic determinants of immunoglobulin became detectable in the medium, and both medium and cell-surface immunoglobulin underwent a shift from specific IgM determinants early in the culture period to IgG and IgA determinants later. Normal lymphocytes and thymocytes activated by concanavalin A repaired the deficiency in the patient's serum. These data support the concept that a factor possibly derived from T cells is missing from this patient's serum and that this factor is required for the maturation of the B cell for immunoglobulin synthesis.

A patient with X-linked agammaglobulinemia had a population of circulating lymphocytes with some surface characteristics that appeared similar to those of the B cells from the patient with thymoma. In contrast, however, no Ig synthesis by this patient's cultured cells could be demonstrated. The possible nature of the lymphocytes reacting with aggregated IgG in this case is discussed.
Myosin Heavy Chain Messenger RNA from Myogenic Cell Cultures
Authors: Przybyla Alan , Strohman R. C.
Published: May 2006

The appearance of messenger RNA for myosin heavy chains in chick-embryo myogenic cell cultures was investigated. Total polyribosomes were isolated from cultures at various times of development and were purified in sucrose step gradients. These polysomes were either extracted with phenol or were treated with puromycin. The ribonucleoprotein particles and ribosomal subunits released by puromycin were fractionated on sucrose gradients. RNA from polysomes or from puromycin-dissociated subunits was fractionated on oligo(dT)-cellulose columns, and the bound and unbound RNA was assayed for activity of myosin heavy chain messenger RNA in a rabbit reticulocyte cell-free system. RNA stimulating myosin heavy-chain synthesis was found predominantly in the unbound fractions of the oligo(dT)-cellulose columns. After puromycin treatment of polysomes, the myosin heavy chain messenger RNA, which sediments at 18-26 S, was associated with a ribonucleoprotein particle sedimenting between 30 and 40 S. Myosin heavy chain messenger RNA was obtained from cultures containing well-developed myotubes and from cultures undergoing myogenic cell fusion. This messenger RNA was not detectable in early, unfused cultures, or in later cultures in which myogenic cell fusion had been prevented by treatment with ethyleneglycol bis(β-aminoethyl ether)-
N,N
′-tetraacetic acid. These experiments demonstrate that messenger RNA for myosin heavy chains becomes associated with ribosomes only after myogenic cell fusion has begun.
Conditioned Behavior in
Drosophila melanogaster
Authors: Quinn William G. , Harris William A. , Benzer Seymour
Published: May 2006

Populations of
Drosophila
were trained by alternately exposing them to two odorants, one coupled with electric shock. On testing, the flies avoided the shock-associated odor. Pseudoconditioning, excitatory states, odor preference, sensitization, habituation, and subjective bias have been eliminated as explanations. The selective avoidance can be extinguished by retraining. All flies in the population have equal probability of expressing this behavior. Memory persists for 24 hr. Another paradigm has been developed in which flies learn to discriminate between light sources of different color.
A Diffusible Factor Restoring Contact Inhibition of Growth to Malignant Melanocytes
Authors: Lipkin George , Knecht Margarete E.
Published: May 2006

Contact inhibition of growth is the property
in vitro
whose loss is most closely correlated with tumorigenicity
in vivo
. A contact-inhibited melanocytic cell line produces a diffusible protein-containing factor capable of restoring contact inhibition of cell division to highly malignant hamster melanocytes. Its addition to subconfluent cultures of the malignant cells is followed by the obligatory acquisition, at confluence, of the contact-inhibited state. Cultures are flat, oriented, and fibroblast-like, and show a 55% decrease in saturation density with no loss of viability. The effect is reversible. Present in conditioned media of cultures of the contact-inhibited melanocytic cell line, isolated by column chromatography on Sephadex G-200, the factor appears to be of high molecular weight. Activity is preserved in aqueous solutions at 4° for at least 8 weeks, but is destroyed by repeated freezethawing or by treatment with Pronase.

This newly recognized contact-inhibitory factor may be a prototype for a more general and fundamental mechanism for regulation of normal cell-cell interactions. It is the first cell-elaborated factor to be isolated that is capable of restoring the capacity for contact inhibition of growth to malignant cells.
Concordance of Collagen-Based Radiocarbon and Aspartic-Acid Racemization Ages
Authors: Bada Jeffrey L. , Schroeder Roy A. , Protsch Reiner , Berger Rainer
Published: May 2006

By determining the extent of racemization of aspartic acid in a well-dated bone, it is possible to calculate the
in situ
first-order rate constant for the interconversion of the L and D enantiomers of aspartic acid. Collagen-based radiocarbon-dated bones are shown to be suitable samples for use in “calibrating” the racemization reaction. Once the aspartic-acid racemization reaction has been “calibrated” for a site, the reaction can be used to date other bones from the deposit. Ages deduced by this method are in good agreement with radiocarbon ages. These results provide evidence that the aspartic-acid racemization reaction is an important chronological tool for dating bones either too old or too small for radiocarbon dating. As an example of the potential application of the technique for dating fossil man, a piece of Rhodesian Man from Broken Hill, Zambia, was analyzed and tentatively assigned an age of about 110,000 years.
Olfactory Basis of Homing Behavior in the Giant Garden Slug,
Limax maximus
Authors: Gelperin Alan
Published: May 2006

Time lapse photography of slugs living in an experimental enclosure shows that these animals can return to a homesite from over 90 cm by a direct route. Slime trail following and vision are not involved in this behavior. In the presence of a low velocity wind, homing occurs upwind. Surgical disconnection of the presumptive olfactory apparatus (digitate ganglion) from the central nervous system eliminates homing. Neurophysiological recordings from the receptor surface associated with the digitate ganglion and the olfactory nerve demonstrate the olfactory function of the digitate ganglion. The olfactory acuity and capacity for directed locomotion via olfactory cues are also relevant to studies of slug feeding behavior, ecology, and learning ability.
Transplantation of Posterior Polar Plasm in
Drosophila
. Induction of Germ Cells at the Anterior Pole of the Egg
Authors: Illmensee Karl , Mahowald Anthony P.
Published: May 2006

In
Drosophila melanogaster
the primordial germ cells are normally formed at the posterior tip of the egg during the preblastoderm stage. In order to determine whether the posterior polar plasm is capable of inducing the formation of primordial germ cells in another region of the embryo, portions of this cytoplasm were transferred from wild-type embryos of the early cleavage stage to the anterior tip of
mwh e
embryos of the same age. At various times after the injection (15-200 min), embryos were fixed for histological analysis. Alternating thick and thin sections were examined for the presence of experimentally induced pole cells. In more than half of the embryos analyzed in this way, one to six cells were found containing the polar granules as well as round nuclear structures, both of which are characteristic of normal pole cells and are not present in blastoderm cells. In order to determine whether these “pole cells” function normally, i.e., develop further into germ cells, the cells induced at the anterior tip of
mwh e
blastoderm embryos were introduced into the posterior region of
y w sn
3
hosts of the same age. The flies resulting from these embryos were mated to
y w sn
3
partners. In addition to the expected
y w sn
3
progeny, wild-type flies heterozygous for
mwh e
and, therefore, descended from the experimentally induced pole cells were found in 4% of the crosses. Such flies did not appear in the control experiments after transfer of normal anterior cells from noninjected blastoderm embryos.

These results demonstrate that the posterior polar plasm can be transferred to the anterior tip of the embryo and that in this presumptive somatic region it still retains its capacity to determine the formation of the primordial germ cells.
The Explanation for the Blockade of Glycolysis in Early Mouse Embryos
Authors: Barbehenn Elizabeth K. , Wales Raymond G. , Lowry Oliver H.
Published: May 2006

The reason for the failure of early-stage mouse embryos to grow on glucose alone was investigated by measurement of glucose-6-phosphate, fructose-1,6-bisphosphate plus triose phosphates, citrate, and malate in individual embryos during starvation and refeeding with glucose or glucose plus pyruvate. The results indicate a block at the 6-phosphofructokinase (EC 2.7.1.11) step at early stages, which is later removed. Although there seems to be no early difficulty in phosphorylation of glucose, maximum glucose-6-phosphate levels (and probably fructose-6-phosphate levels) are much lower at early stages than at later stages. The increase in fructose-6-phosphate with age may be the major cause of the increase in 6-phosphofructokinase activity. Unusually high citrate levels at all ages may help to keep this enzyme strongly inhibited until the increase in fructose-6-phosphate occurs. The changes in metabolite levels also indicate an early defect in mobilization of glycogen and a probably less important defect in the citrate cycle.
Studies on the Extended Active Sites of Acid Proteinases
Authors: Sampath-Kumar P. S. , Fruton J. S.
Published: May 2006

The kinetics of the hydrolysis of a series of peptide substrates at a single peptide bond (between L-phenylalanyl and L-phenylalanyl) by the acid proteinases gastric pepsin A (EC 3.4.23.1),
Rhizopus
pepsin (EC 3.4.23.9), and beef-spleen cathepsin D (EC 3.4.23.5) have been determined by use of the fluorescamine assay method. The results indicate that the extended active site of pepsin can accommodate a sequence of at least seven amino-acid residues. Although the other two acid proteinases appear to act at the sensitive L-phenylalanyl-L-phenylalanyl bond by a mechanism similar to that of pepsin, the influence of structural changes on either side of the sensitive dipeptidyl unit on the kinetic parameters is different from that for pepsin. These data give further evidence for the importance of secondary interactions in determining the catalytic efficiency of enzymes that act on oligomeric substrates.
Relationship of a Proton Gradient to the Active Transport of Proline with Membrane Vesicles from
Mycobacterium phlei
Authors: Hinds Thomas R. , Brodie Arnold F.
Published: May 2006

Electron transport particles prepared from
Mycobacterium phlei
were depleted of bound coupling factors by washing with water in the absence of inorganic ions. The depleted electron transport particles were void of latent ATPase activity and were capable of oxidation, but were unable to support coupled phosphorylation. Nevertheless, the depleted electron transport particles were capable of substrate-induced active transport of proline. Changes in pH in response to substrate oxidation were measured in normal and depleted electron particles with bromthymol blue. A bromthymol blue response upon substrate oxidation was not observed with depleted electron transport particles. The level of oxidative phosphorylation with succinate or NADH oxidation was not reduced in the presence of proline, and proline did not have an effect upon the proton gradients formed by the oxidation of either succinate or NADH.
Cell-Free Transcription of Mammalian Chromatin: Transcription of Globin Messenger RNA Sequences from Bone-Marrow Chromatin with Mammalian RNA Polymerase
Authors: Steggles A. W. , Wilson G. N. , Kantor J. A. , Picciano D. J. , Falvey A. K. , Anderson W. F.
Published: May 2006

A mammalian cell-free transcriptional system was developed in which mammalian RNA polymerase synthesizes globin messenger RNA sequences from bone-marrow chromatin. The messenger RNA sequences are detected by measurement of the ability of the transcribed RNA to hybridize with globin complementary DNA. The globin complementary DNA is synthesized by the enzyme from avian myeloblastosis virus, RNA-directed DNA polymerase, with purified globin messenger RNA as template. The specificity of the globin complementary DNA in annealing reactions was verified by preparing DNA complementary to liver messenger RNA and showing that the globin and liver complementary DNAs are specific for their own messenger RNAs. Both DNA-dependent RNA polymerase II from sheep liver and RNA polymerase from
Escherichia coli
can transcribe globin messenger RNA sequences from rabbit bone-marrow chromatin; however, the mammalian enzyme appears to be more specific in that globin gene sequences represent a higher proportion of the RNA synthesized. Neither polymerase can transcribe globin messenger RNA sequences from rabbit-liver chromatin. This cell-free assay system should be useful in searching for mammalian transcriptional regulatory factors.
Modulation of the Activity of an Avian Gene Transferred into a Mammalian Cell by Cell Fusion
Authors: Klinger Harold P. , Shin Seung-Il
Published: May 2006

Mouse A9 cells, deficient in hypoxanthine phosphoribosyltransferase (EC 2.4.2.8), were fused with normal chick erythrocytes and selected in hypoxanthine-aminopterin-thymidine medium for cells with hypoxanthine phosphoribosyltransferase activity. Recovered hybrid cells produced the chick hypoxanthine phosphoribosyltransferase exclusively, as demonstrated by electrophoretic mobility and immunoprecipitation tests, even though no chick chromosomes or chick cell-surface antigens could be identified in the hybrids. Surprisingly, the expression of the chick hypoxanthine phosphoribosyl-transferase activity in the mouse/chick hybrids required the presence of aminopterin in the growth medium; in its absence, enzyme synthesis decreased markedly. Because of the rapid and reversible modulation of hypoxanthine phosphoribosyltransferase activity, the hybrid cells could proliferate equally well in media containing hypoxanthine-aminopterin-thymidine or 8-azaguanine. Cellular selection was definitely ruled out as a possible cause. These results confirm previous reports that specific genetic information can be selectively transferred from one cell to another of a distant species. Furthermore, they demonstrate that an avian gene, whose activity is normally expressed constitutively, can become facultative when integrated into a mammalian cell. This seems to be the first instance where heterologous gene activity has been shown to be reversibly modulated in hybrid cells.
Study of CoQ
10
-Enzymes in Gingiva from Patients with Periodontal Disease and Evidence for a Deficiency of Coenzyme Q
10
Authors: Nakamura Ryo , Littarru Gian Paolo , Folkers Karl , Wilkinson Edward G.
Published: May 2006

The specific activities of both the succinate dehydrogenase-coenzyme Q
10
reductase and the DPNH-cytochrome
c
reductase [NADH:(acceptor)oxidoreductase, EC 1.6.99.3] were determined in mitochondria from 40 diseased gingival biopsies from patients with periodontal disease and from 24 control biopsies from nondiseased areas (clinically evaluated) of gingival tissues from the same mouths of the patients from whom the diseased gingival tissues were taken. The control tissue was taken during normal surgical procedures, such as for gingival recontouring and tuberosity removal.

The diseased gingival biopsies showed a mean specific activity for the succinate dehydrogenase-coenzyme Q
10
reductase which was higher (
P
< 0.02) than that of the control biopsies, and which increased (
P
< 0.01) when the assays utilized exogenous coenzyme Q
3
, and corresponded to an average deficiency of coenzyme Q
10
-enzyme activity of 35%. About 60% of the 40 diseased gingival tissues showed a deficiency of coenzyme Q
10
at its site in this succinate-coenzyme Q
10
enzyme. Of the 24 control tissues, 20% showed deficiencies of coenzyme Q
10
. As a group, the control tissues showed no deficiency of coenzyme Q
10
.

No deficiency of coenzyme Q
10
at its site in DPNH-cytochrome
c
reductase was observed for either the control or diseased gingival tissues, as groups or individually.
Early Stages in DNA Binding and Uptake During Genetic Transformation of Pneumococci
Authors: Seto Hiroyuki , Tomasz Alexander
Published: May 2006

Ethylenediaminetetraacetate and other divalent-cation-complexing agents greatly stimulate the cellular binding of DNA molecules to competent pneumococci, while the appearance of genetic transformants and nuclease-resistant DNA binding are completely inhibited. Based on this finding, we developed an experimental system in which three early and consecutive stages of genetic transformation can be experimentally separated: (
i
) attachment of DNA molecules to cell surface sites that are only demonstrable in the competent state; (
ii
) a divalent-cation-dependent nucleolytic splitting and release of the adsorbed molecules to the medium; and (
iii
) emergence of potential transformants accompanied by an energy-requiring and divalent-cation-dependent process in which the cell-associated DNA molecules become inaccessible to shearing forces, nucleases, anti-DNA serum, and polycations.
Chemical Modifications That Inhibit Gelation of Sickle Hemoglobin
Authors: Benesch Reinhold , Benesch Ruth E. , Yung Suzanna
Published: May 2006

Substitution of the N-terminal amino groups with pyridoxal compounds inhibits gelation and increases the solubility of deoxy sickle hemoglobin (Hb S). Pyridoxylation of the α chains has considerably more effect than that of the β chains. The increase in minimum gelling concentration of Hb S that results from modification of the α N-termini is the same as that produced by dilution of Hb S with an equal amount of Hb A.
Novel Properties of Satellite DNA from Muskmelon
Authors: Bendich Arnold J. , Anderson Robert S.
Published: May 2006

The purified dense satellite of muskmelon (
Cucumis melo
L.) represents 30% of the total DNA and forms a sharp, unimodal peak in both neutral and alkaline CsCl gradients. Spectrophotometric melting and DNA reassociation analyses revealed that one-third of the satellite is high melting and has a complexity of about 2.5 × 10
5
daltons, while the remaining two-thirds of the satellite melts 8° lower and has a complexity of about 5 × 10
8
daltons. The thermal stability of reassociated satellite DNA indicates that the multiple copies of the two melting fractions are essentially identical. The sharp, unimodal peak in Cs
2
SO
4
becomes two distinct peaks when either silver or mercuric ions are included in the Cs
2
SO
4
gradient
On the Molecular Basis of High Negative Interference
Authors: White Raymond L. , Fox Maurice S.
Published: May 2006

Two models designed to account for high negative interference phenomena have been examined. One proposal suggests that many recombination events are the result of insertion of a small single-stranded segment of DNA into a recipient molecule. An alternative explanation for the clustering of genetic exchanges is reduction to homozygosity of genetically heterozygous sites appearing within heteroduplex overlap regions. These proposals have been examined in phage λ by analyzing the structure of unduplicated recombinants arising from three-factor crosses with tightly linked markers. Double recombinants are found to have received substantial contributions of DNA from both parents. In addition, their patterns of genetic heterozygosity are not readily reconcilable with a single-strand insertion hypothesis. Reconstruction experiments with artifically constructed heteroduplex heterozygotes support the reduction to homozygosity hypothesis and specify the strand polarity of the heterozygous overlap region.
Isolation of the Tumor-Inducing RNA from Oncogenic and Nononcogenic
Agrobacterium tumefaciens
Authors: Beljanski M. , Cunha M. I. Aaron-Da , Beljanski M. S. , Manigault P. , Bourgarel P.
Published: May 2006

Two RNA fractions have been isolated and purified from both oncogenic and nononcogenic strains of
Agrobacterium tumefaciens
. Both RNAs are capable of inducing the formation of transplantable tumors when introduced at wound sites in stems of
Datura stramonium
plants. One of these RNA fractions was found to be bound to an RNA-directed DNA polymerase, while the other was associated with the bacterial DNA. Physical evidence suggests that both are single stranded and small in size; linear sucrose gradients show that their size corresponds to a value of 5-6 S. A concentration of 4-5 μg of the RNAs dissolved in 0.01 ml of water is effective in initiating the formation of transplantable tumors in
Datura
plants.
Blastic Transformation of Mouse Spleen Lymphocytes by a Water-Soluble Mitogen Extracted from Nocardia
Authors: Bona Constantin , Damais Chantal , Chedid Louis
Published: May 2006

A water-soluble extract of Nocardia markedly increased
in vitro
[
3
H]thymidine incorporation by mouse spleen lymphocytes. The blastogenic activity of the extract and lipopolysaccharide was studied comparatively on various mouse lymphocyte subpopulations. The data obtained by [
3
H]thymidine incorporation and by electron microscopy have demonstrated that this preparation stimulates selectively mouse bone-marrow-derived cortisone-sensitive lymphocytes. This stimulation is related neither to a natural infection of mice with Nocardia organisms nor to the presence in Nocardia water-soluble mitogen of a lipopolysaccharide contaminant or of a lipopolysaccharide-like material.
Isozymes of Lysozyme in Leukocytes and Egg White: Evidence for the Species-Specific Control of Egg-White Lysozyme Synthesis
Authors: Hindenburg Alexander , Spitznagel John , Arnheim Norman
Published: May 2006

Two structurally distinct forms of eggwhite lysozyme (EC 3.2.1.17) are known. The egg white of some species contains both of these forms, while the egg white of other species appears to contain only one or the other of them. We have immunological and electrophoretic evidence that the chicken, which has only one lysozyme type in its egg white, contains both types in its polymorphonuclear leukocytes. Experiments on Embden goose bone marrow showed that this tissue also contains both lysozymes, even though the egg white of this species contains only one of them. Our studies suggest that many avian species have the genetic loci that code for both forms of lysozyme, but that a species-specific regulatory mechanism controls whether one or the other or both of them are expressed during egg white production. The fact that two distinct lysozymes are present in chicken leukocytes may be of significance to the antibacterial mechanism of these cells, especially in light of the fact that they lack myeloperoxidase, an important leukocyte enzyme in mammals.
Founder Effects and Linkage Disequilibria in Experimental Populations of
Drosophila
Authors: Powell Jeffrey R. , Richmond Rollin C.
Published: May 2006

Six laboratory populations of
Drosophila paulistorum
were examined for changes in gene frequencies at an enzyme locus,
tetrazolium oxidase
(
To
). In some of the populations, the alleles were introduced on over 100 independently derived chromosomes. These populations showed considerable stability in gene frequencies although they were at widely different starting frequencies. Other populations were begun with only a few (about 6) independently derived chromosomes. These populations showed significant and somewhat erratic changes in
To
gene frequencies. The difference in behavior of the two sets of populations was almost certainly caused by linkage effects due to sample size. The implication of these studies in understanding the role of the founder effect in natural populations is briefly discussed.
The Activity-Related Ionization in Carbonic Anhydrase
Authors: Appleton David W. , Sarkar Bibudhendra
Published: May 2006

The catalytic activity of carbonic anhydrase (EC 4.2.1.1) is linked to the ionization of a group in close proximity to the essential zinc ion. Studies have been undertaken to delineate the ionizations germane to the active-site chelate system. Several imidazole ligand systems were studied in order to approach a representative chelate. The simplest involved the complexation of Zn(II) by imidazole and by
N
-methylimidazole. As well, two bidentate systems, Zn(II)-4,4′-bis-imidazoylmethane and Co(II)-cyclic-L-histidyl-L-histidine were investigated. It was found that in a species containing metal-bound water and imidazole coordinated by means of the pyridinium nitrogen, the most acidic group was the pyrrole N-H in the imidazole ring. By the use of
N
-methylimidazole, the pK
a
of a metal-bound water molecule in a tri-imidazole ligand field was found to be 9.1. Noting the preference for labilization of the pyrrole hydrogen, the catalytic features of carbonic anhydrase are reexamined assuming that the pK
enz
is associated with the N-H ionization, and not with the ionization of metal-bound water.
Characterization and Substrate Specificity of a Protein Carboxymethylase in the Pituitary Gland
Authors: Diliberto Emanuel J. , Axelrod Julius
Published: May 2006

Protein carboxymethylase, an enzyme capable of methylating proteins and polypeptides, was purified from bovine pituitary. The anterior pituitary hormones, luteinizing hormone, follicle-stimulating hormone, adrenocorticotropic hormone, growth hormone, thyroid-stimulating hormone, and prolactin, were found to be substrates for this enzyme. The posterior pituitary hormones, oxytocin and vasopressin, did not serve as substrates. With luteinizing hormone as the substrate, protein carboxymethylase had a pH optimum near pH 5.5. A limiting
K
m
of 1.47 μM for
S
-adenosyl-L-methionine was obtained with luteinizing hormone as the methyl acceptor. Possible roles of this enzyme in the posterior and anterior pituitary are discussed.
Localization of Five Antibiotic Resistances at the Subunit Level in Chloroplast Ribosomes of
Chlamydomonas
Authors: Schlanger Gladys , Sager Ruth
Published: May 2006

The chloroplast ribosomes from five antibiotic resistant strains of
Chlamydomonas
, each carrying one mutant gene mapping in chloroplast DNA, have been shown to be resistant to the corresponding antibiotic in a poly(U)-directed amino-acid incorporating assay system. The alteration conferring resistance was localized to the 30S subunit in ribosomes from streptomycin, neamine, and spectinomycin resistant strains, and to the 50S subunit in ribosomes from cleocin and carbomycin resistant strains. Spectinomycin resistant ribosomes showed no cross-resistance to any other drugs, but limited cross-resistance was noted with the other mutant ribosomes. The similarity between these findings and results reported by others with bacterial ribosomes supports our hypothesis that at least some chloroplast ribosomal proteins are coded by genes in chloroplast DNA.