bluuebunny/crossref_metadata_2025 huggingface dataset:
Higher Dimensional Mappings for Which the Area Formula Holds
Authors: Goffman Casper , Ziemer William P.
Published: May 2006

For each continuous mapping of 2 space into
n
space,
n
≥ 2, the Lebesgue area is given by the classical formula provided that the partial derivatives exist almost everywhere and belong to the class
L
2
. The analogous question for mappings of
m
space into
n
space, 2 <
m
≤
n
, has been open for a long time. We answer this question in the affirmative in a more general setting. Accordingly, as a special case, we show that if a continuous mapping of
m
space into
n
space,
m
≤
n
, has partial derivatives which belong to

L
m

then the Lebesgue area is given by the classical formula.
Mechanics of Frameshift Mutagenesis in Bacteriophage T4: Role of Chromosome Tips
Authors: Lindstrom Dona M. , Drake John W.
Published: May 2006

In contrast to observations in bacteria and fungi, frameshift mutations in bacteriophage T4 do not arise during genetic recombination. Nascent mutants, captured in the heterozygous condition, exhibit properties which indicate that the new lesions are located at the extreme tips of the chromosomes, and are segregated by a combination of recombination and replication.
Derepression of GDP-α-D-Mannose and UDP-Glucose Pyrophosphorylases by a Regulator Gene Mutation; Episomal Dominance in Partial Diploids
Authors: Lieberman Michael M. , Buchanan Christine E. , Markovitz Alvin
Published: May 2006

Mutants of
Escherichia coli
K12 at the
cap
R locus are overproduce capsular polysaccharide, and are derepressed for synthesis of several enzymes involved in capsular polysaccharide synthesis
1-3
including GDP-mannose pyrophosphorylase.
8
UDP-glucose pyrophosphorylase is also derepressed in a haploid
cap
R9 mucoid mutant. Heterozygous mucoid partial diploids with the
cap
R9 allele on the episome and the wild-type (
cap
R
+
) allele on the chromosome (F′
cap
R9/
cap
R
+
) are derepressed for UDP-glucose pyrophosphorylase and GDP-mannose pyrophosphorylase, while the reciprocal nonmucoid heterozygotes (F′
cap
R
+
/
cap
R9) are repressed for these enzymes. These results provide evidence that the episomal
cap
R allele is dominant with respect to synthesis of these two enzymes.
The Appearance and Disappearance of the Post-Transcriptional Repressor of Tyrosine Aminotransferase Synthesis during the HTC Cell Cycle
Authors: Martin David W. , Tomkins Gordon M.
Published: May 2006

The synthesis of the enzyme tyrosine aminotransferase in HTC cells (an established line of rat hepatoma cells) is inducible by glucocorticoid hormones only during the latter part of G1 phase and throughout S phase in the cell generation cycle. We have earlier shown that during the first few hours of G1 phase when the enzyme cannot be induced, its synthesis is constitutive, presumably using as template, preexisting messenger RNA. Our model for tyrosine aminotransferase gene regulation in eukaryotic cells entails a specific post-transcriptional repressor which is formed only during the periods in the cell cycle when tyrosine aminotransferase is inducible. This model predicts that during the noninducible period, G2, the tyrosine aminotransferase repressor would not be present and thus tyrosine aminotransferase synthesis would be constitutive. Data are presented which confirm this prediction in further support of the model.
Mixtures and Characteristic Functions
Authors: Klonecki Witold
Published: May 2006

Let
g
(
u
|
c
,
y
) = exp {
y
Σ

c
k

(

u
k

- 1)} with
y
> 0, Σ

k
=0

∞

c
k

= 1,|
u
| < 1, and
c
standing for {

c
k

}, be a probability generating function of a nonnegative integer-valued random variable. Let
S
be a distribution function on (0, ∞) non-degenerate at zero. The functions
g
and
S
determine another probability generating function,
G
(
u
|
S
c
) = ∫
0
∞
gdS
(
y
). One of the results obtained asserts that, if the sequence
c
is finite and the characteristic function of
S
is entire, then
G
determines uniquely both
S
and
c
. The assertion does not hold if these conditions are not satisfied. Another group of results refers to properties of characteristic functions. Let
P
(
z
) be a polynomial of degree
m
and
f
(
z
|
y
) = exp- {
yP
(
z
)}. The theorem of Marcinkiewicz asserts that with
m
> 2 the function
f
cannot be a characteristic function. It is shown that, if the characteristic function of
S
is entire, then
F
(
z
) = ∫
0
∞
f
(
z
|
y
)
dS
(
y
) can be characteristic function only if
m
≤ 2. Again the assertion need not be true if the characteristic function of
S
is not entire.
Purkinje Cells in the Cerebellum: Their Responses to Postural Stimuli in Cats
Authors: Konorski Jerzy , Tarnecki Remigiusz
Published: May 2006

The responses of Purkinje cells in the cerebellum produced by various positions of the limbs were studied in decerebrated unanesthetized cats. The majority of units located in the intermediate zone of the anterior lobe selectively reacted to definite postures of the limbs: some of them were active when a given limb was in an extended position and were silent when it was in flexion; the other ones, on the contrary, were active when the limb was flexed and silent when it was extended. The rate of discharges was in both cases the same and amounted to 40 to 80 per second. It did not change with the lapse of time, and remained the same when flaxedil was administered. These results, in connection with some other data, seem to explain the problem of how the cerebellum transforms the information about the tensions of tendons and muscles, delivered by the tendon organs and muscle spindles, respectively, into the information about movements.
Mechanism of Activation of Catabolite-Sensitive Genes: A Positive Control System
Authors: Zubay Geoffrey , Schwartz Daniele , Beckwith Jon
Published: May 2006

Catabolite repression is defined as the inhibition of enzyme induction by glucose or related substances. In the bacterium
E. coli
, the effect of glucose appears to be due to a lowering of the cyclic AMP level. A DNA-directed cell-free system for β-galactosidase synthesis has served as a model system for studying the mechanism of action of cyclic AMP. Previously, it was reported that in this system cyclic AMP is required for normal initiation of mRNA synthesis. A protein factor which acts in conjunction with the cyclic AMP has been partially purified. This protein factor has a high affinity for cyclic AMP. These and other results presented herein lead us to the conclusion that cyclic AMP and a protein factor called the catabolite gene activator protein are part of a positive control system for activating catabolite-sensitive genes.
The Dynamics of Life. I. Death from Internal Irradiation by
239
Pu and
226
Ra, Aging, Cancer, and Other Diseases
Authors: Stover Betsy J. , Eyring Henry
Published: May 2006

Early in the era of atomic energy the potential of plutonium as an industrial and an environmental hazard was recognized. Thus, the Laboratory for Radiobiology was established at this University 20 years ago to compare the effects of plutonium and radium in beagles. Sufficient data have now accrued for exacting analysis. Concurrently we have formulated the steady-state theory of mutation rates which provides the necessary formalism to assess the survival data from the
239
Pu and
226
Ra study. Although the principal biological end point for both nuclides is the osteosarcoma, the mechanisms of nonsurvival for the two nuclides appear to be different. The success of the theory in this case suggests that application to data on irradiation of more inbred and more outbred species would prove to be exceedingly valuable.
Statistical Theories of Success
Authors: Zener Clarence
Published: May 2006

The Pareto and the log-normal distributions are commonly used to describe the statistical distribution of success. A detailed comparison of these distributions is made with Lotka's extensive observations on success as measured by rate of publication. These distributions are found to adequately describe the observed distribution only for low and moderate success. Contrariwise, the flat factor analysis of performance recently developed by the author in these
Proceedings
(
59,
1078 (1968)) is shown to give an excellent agreement over the whole range of success. Lotka's data allows a determination of the number of environmental factors.

The Pareto distribution does give an excellent agreement with the tail of the success distribution where success is defined as income. An interpretation of this distribution is here presented based upon the expected behavior of entrepreneurs.
Viruslike Particles in Nuclei of Cultured Plant Cells Which Have Lost the Ability to Differentiate
Authors: Sjolund R. D. , Shih C. Y.
Published: May 2006

A line of cultured plant cells used to study cell differentiation and organ initiation over a period of several years has lost its ability to differentiate. Examination of these proliferating cells by electron microscopy reveals aggregates of 600-Å polyhedral particles in the nucleoli and heterochromatic regions of interphase nuclei. During mitosis and cell division the same particles are present on the chromosomes and are segregated into the daughter cells. Although the nucleoli and nuclear envelope are absent during mitosis, the particles remain associated with the chromosomes and do not appear in the cytoplasm. The morphological similarity of these particles to several known plant viruses suggests that the nuclear particles may represent a viral infection. The relationship between these particles and the loss of differentiation ability is discussed with reference to the production of carcinomas and the transformation of animal cells by viruses.
Characteristic Classes and Weyl Tensor: Applications to General Relativity
Authors: Avez André
Published: May 2006

In a recent paper, Chern and Simons proved that the Pontrjagin forms of a Riemannian manifold remain invariant under a conformal deformation. We show that these forms can be expressed uniquely in terms of the conformal curvature tensor: this provides a new proof of their result. Similar techniques can be applied to Euler-Poincare characteristic class, as suggested to me by A. Taub. We obtain the following: If the Weyl tensor of a compact space time is of type III of Bel-Petrov, then it cannot carry a perfect fluid + electromagnetic field.
The Dynamics of Life, II. The Steady-State Theory of Mutation Rates
Authors: Eyring Henry , Stover Betsy J.
Published: May 2006

The statistical effect of internal irradiation on the survival of beagles is similar to that of aging, with the exception that death occurs earlier. Since biological processes are close to equilibrium most of the time, the above observation suggests that death ensues when the rate of insult has exceeded the rate of recovery to a sufficient extent that the reserves are depleted and the steady state can no longer be maintained. The steady-state theory of mutation rates is derived from first principles, and, through absolute rate theory, is completely general and is not limited to a specific kind of cellular alteration. However, the nature of the cellular alterations that lead to nonsurvival are considered. The young growing system is also considered in the context of this theory.
Qβ-Replicase and
E. coli
Transcriptase: Requirements for Substrate Selection as Revealed by a Study of Base Analogs
Authors: Kapuler A. M. , Spiegelman S.
Published: May 2006

Base selection by the Qβ-replicase and
E. coli
transcriptase has been studied using substrate analogs. Six analogs with normal hydrogen-bonding sites were polymerized by both enzymes. Three analogs containing ring substitutions which affect the conformation at the glycosyl bond would not substitute for their normal congeners. The remaining analog was an excellent substrate for the transcriptase but not the replicase.

The results imply that the base selection procedure has stringent requirements for substrate conformation. Part of the restriction may derive from the requirement that template and substrates conform to the stereochemical constraints of a double helix.

In the Qβ-replicase reaction, synthesis in the presence of substrate analogs displayed abortive kinetics, implying that the replicase reaction can be uniquely curtailed by substrate analogs.
Ability of Nonenzymic Nitration or Acetylation of
E. coli
Glutamine Synthetase to Produce Effects Analogous to Enzymic Adenylylation
Authors: Cimino Filiberto , Anderson Wayne B. , Stadtman E. R.
Published: May 2006

Treatment of unadenylylated glutamine synthetase from
Escherichia coli
with tetranitromethane or with
N
-acetylimidazole produces alterations in catalytic parameters that are similar to alterations caused by the physiologically important process of adenylylation. All three modification reactions lead to a change in divalent ion requirement for biosynthetic activity; the unmodified enzyme requires Mg
2+
for activity, whereas the modified enzymes exhibit increased activity with Mn
2+
. The γ-glutamyl transferase activity of the modified enzyme is more sensitive to feedback inhibition by tryptophan, histidine, CTP, and AMP, and to inhibition by Mg
2+
or to inactivation by 5
M
urea. Finally, the pH optimum for the unmodified enzyme is 7.9, while the modified enzymes are more active at pH 6.8.

Since treatment of the enzyme with
N
-acetylimidazole results in a decrease in absorbancy at 278 mμ and treatment with tetranitromethane causes an increase in absorbancy at 428 mμ, the effects of these reagents are probably due to modification of certain tyrosyl groups on the enzyme. However, other evidence indicates that the tyrosyl residues which are susceptible to adenylylation in the adenylyltransferase-catalyzed reaction are not involved in the acetylation or nitration reactions.
Immunoglobulin Synthesis and Secretion, IV. Sites of Incorporation of Sugars as Determined by Subcellular Fractionation
Authors: Uhr Jonathan W. , Schenkein Isaac
Published: May 2006

P
3
K cells were uniformly labeled with [
14
C]leucine and also for 1 hr with [
3
H]leucine, [
3
]galactose, or [
3
H]glucosamine. Subcellular fractionation of labeled cells was performed and the amounts of radioactive immunoglobulin G in each fraction were determined. The results indicate that amino acids are incorporated in the rough endoplasmic reticulum, galactose primarily in the smooth endoplasmic reticulum, and glucosamine at both sites. A small portion of radioactivity was found in the microsomal supernatant regardless of the radioisotope employed.
ACTINOMYCIN D BEFORE AND DURING PRIMARY AND SECONDARY ANTI-FORSSMAN IMMUNOGLOBULIN HEMOLYSIN RESPONSES IN RABBITS
Authors: Taliaferro William H. , Taliaferro Lucy Graves
Published: May 2006

The effects of actinomycin D were studied on successive stages of the primary and secondary (anamnestic) anti-Forssman immunoglobulin hemolysin responses induced in rabbits by the antigen, sheep red blood cells. (Fully developed anamnestic reactivity was tested 1.5-2 months after the start of an untreated initial response.) The stages of both responses include induction by antigen, the latent period, the acute rise of hemolysin to peak titer, and the decline afterwards. This antibiotic modified both responses significantly in ways strikingly similar to those produced by large doses of x-rays. It was injected in a sublethal amount (0.08 mg/kg) at selected times before or after a test intravenous injection of 10
8.3
sheep erythrocytes/kg. Given within several days before the antigen, it delayed and depressed peak titer, whereas given during induction and the latent period, it delayed and enhanced peak titer. Given during the acute rise, its effect decreased, and given during the decline after peak titer, it only produced erratic slight rises in titer. It is suggested that delayed and depressed peak titers are associated with both known activities of sublethal doses of actinomycin D, i.e., cytotoxicity and inhibition of RNA synthesis, whereas enhanced peak titers are brought about by the presence of nucleic acid degradation products released by the cytotoxicity of actinomycin D at the critical time of active RNA synthesis in the latent period. Effects of actinomycin D differed quantitatively in the two responses. During the initial response, delayed depression was not apparent as soon and did not last as long, whereas delayed enhancement was more pronounced. In terms of the cells operating in the two responses, the data indicate that immunologically competent initial cells, as compared to memory cells, are more easily stimulated, are not injured as quickly, recover more rapidly, and overcompensate for the injury for a longer time. In addition, in untreated controls, recruitment of immunologically competent initial cells appears to be largely inhibited during induction of memory cells. Otherwise, decline of the secondary response would be less abrupt.
SEQUENTIAL TRANSLATION OF TRINUCLEOTIDE CODONS FOR PEPTIDE BOND FORMATION, TRANSLOCATION, AND TERMINATION
Authors: Tompkins Richard K.
Published: May 2006

The addition of GUA, valyl-tRNA, T factor, GTP, and ethanol to reactions containing fMet-tRNA·AUG·ribosome intermediate results in the synthesis of fMet-valyl-tRNA which can be translocated if G factor is also present. The translocated peptidyl-tRNA can interact with puromycin to form fMet-Val-puromycin. Release of fMet-valine can also take place after translocation if a terminator trinucleotide and its specific release factor are present.
ALTERATION OF GENE CONVERSION PATTERNS IN
Sordaria fimicola
BY SUPPLEMENTATION WITH DNA BASES
Authors: Kitani Y. , Olive Lindsay S.
Published: May 2006

Supplementation with DNA bases in crosses of
Sordaria fimicola
heterozygous for spore color markers (
g
1
,
h
2
) within the
gray-spore
(
g
) locus has been found to cause significant alterations in patterns of gene conversion at the two mutant sites. Each base had its own characteristic effect in altering the conversion pattern, and responses of the two mutant sites to the four bases were different in several ways. Also, the responses of the two involved chromatids of the meiotic bivalent were different.
Isolation of the Fundamental Polypeptide Subunits of Biological Membranes
Authors: Laico Marion T. , Ruoslahti Erkki I. , Papermaster David S. , Dreyer William J.
Published: May 2006

A group of peptides (some or all of them glycopeptides), of molecular weight about 5000, has been shown to be a major fraction of biological membranes. These „miniproteins” have been prepared from membranes of human and bovine red blood cells, from purified bovine liver mitochondria, and from the rhodopsin-containing membranes of the outer segments of bovine retinal rods. While the miniproteins were found in large amounts in each case, the other protein components differed markedly depending on the function of the membrane studied. This fact was particularly clear in the case of the rod membranes where the only major proteins detected were the miniproteins and rhodopsin. The large size of the miniprotein fraction in each of these membranes leads us to propose that the miniproteins play a fundamental role in the several functions which occur as common denominators in biological membranes.
DNA-Dependent RNA-Directed Protein Synthesis
In Vitro
, IV. Peptide Analysis of an
In Vitro
and
In Vivo
ϕX174 Structural Protein
Authors: Gelfand David H. , Hayashi Masaki
Published: May 2006

An antibody-precipitable structural protein from the bacteriophage ϕX174 was purified from an
in vitro
protein-synthesizing system primed with the replicative DNA of the virus. This protein was trypsin digested in the presence of the differentially labeled analogous protein that was purified from the bacteriophage. The tryptic hydrolysate was subjected to high resolution peptide chromatography which revealed essentially identical patterns for the ϕX174 proteins synthesized
in vitro
and
in vivo
.
Host Range Mutants of Polyoma Virus
Authors: Benjamin Thomas L.
Published: May 2006

A line of polyoma-transformed mouse cells has been isolated which is fully susceptible to lytic infection by polyoma virus. This line has been used to select virus mutants which have lost most or all of their ability to grow in the untransformed parental line while retaining the ability to grow in the transformed derivative. These virus mutants are also defective in their ability to transform cells of rat or hamster origin. Since the DNA extracted from the mutants has the same host range as the whole virus, the mutants appear to be blocked at some intracellular step which is required both for the completion of virus development in mouse cells and for transformation in rat or hamster cells.
Biology of the Precambrian Genus
Kakabekia:
New Observations on Living
Kakabekia barghoorniana
Authors: Siegel B. Z. , Siegel S. M.
Published: May 2006

Kakabekia barghoorniana
Siegel, living species of a fossil genus
Kakabekia
, has now been cultured from Alaskan soil samples obtained from the Mendenhall Glacier near Juneau and from the Point Barrow region above the Arctic Circle. Morphological comparisons, especially of mantle variations, show that fossil and living populations overlap in many details. Cytochemical tests demonstrate that living
Kakabekia
has no storage forms of lipid or polysaccharide and no phenoloxidase. Some individuals (19-33%) contain heme enzymes but most do not; hence they cannot utilize O
2
even in air.
Effect of Loss of Thymidine Kinase Activity on the Tumorigenicity of Clones of SV40-Transformed Hamster Cells
Authors: Rothschild Henry , Black Paul H.
Published: May 2006

Cells deficient in the enzyme thymidine kinase were derived from transplantable SV40-transformed hamster cells. The resultant cell lines were less transplantable when inoculated into hamsters. Tumors which did arise from such cells had prolonged latent periods and were found to contain a mixture of enzyme-containing and enzyme-deficient cells. Revertant cell lines obtained either spontaneously or after mutagenesis
in vitro
contained intermediate levels of thymidine kinase activity and displayed an oncogenic potential which was intermediate between the wild type and enzyme-deficient cells. It is postulated that salvage pathway enzymes may play a rate-limiting role in tumorigenesis.
Mechanism of Thyroid Calorigenesis: Role of Active Sodium Transport
Authors: Ismail-Beigi Faramarz , Edelman Isidore S.
Published: May 2006

The hypothesis that thyroid calorigenesis is mediated by stimulation of active Na
+
transport was tested by measuring the Q

o
2

of liver slices and skeletal muscle (diaphragm) from thyroxine- and triiodothyronine-injected thyroidectomized and normal rats in media fortified with ouabain (10
-3
M) and/or free of Na
+
or K
+
. In both tissues, more than 90% of the increase in Q

o
2

produced by injections of thyroid hormone in euthyroid rats was derived from increased energy utilization by the Na
+
pump. In triiodothyronine-treated thyroidectomized rats, activation of Na
+
transport accounted for 90% or more of the increment in Q

o
2

in liver and 40% or more of the increment in diaphragm. Intracellular Na
+
, K
+
, and Cl
-
concentrations were measured in euthyroid and hyperthyroid liver and diaphragm. The transmembrane Na
+
and K
+
concentration differences were significantly increased in both tissues by the administration of triiodothyronine. These results indicate that thyroid hormone activates Na
+
extrusion and K
+
accumulation either by increasing the local concentration of ATP or by direct stimulation of the Na
+
pump.
A Generating Function for Certain Coefficients Involving Several Complex Variables
Authors: Srivastava H. M.
Published: May 2006

In an attempt to unify a number of generating functions for certain classes of generalized hypergeometric polynomials, Lagrange's expansion formula is applied to prove a generating relation for an
n
-dimensional polynomial with arbitrary coefficients. It is also shown how these coefficients can be specialized to obtain the generalized Lauricella function as a generating function for a class of generalized hypergeometric polynomials of several complex variables.
Peptide Chain Termination: Effect of Protein S on Ribosomal Binding of Release Factors
Authors: Goldstein J. L. , Caskey C. T.
Published: May 2006

The protein factor S, previously shown to stimulate polypeptide chain termination in bacterial extracts, has two effects upon the complex formed between ribosomes, release factor, and terminator (trinucleotide) codon: (1) in the absence of GTP or GDP, S stimulates formation of an [R·UAA·ribosome] intermediate, and (2) in the presence of GTP or GDP, S participates in dissociation of this intermediate. Factor S can stimulate fMet release from [fMet-tRNA
f
·AUG·ribosome] intermediates in either the presence or absence of GTP or GDP. A model is proposed which relates the
in vitro
effects of S ± GTP (or GDP) on fMet release to the effects of S ± GTP (or GDP) on the binding and dissociation of R factor from ribosomes.
A Density Label for Membranes
Authors: Fox C. Fred , Law John H. , Tsukagoshi Norihiro , Wilson Golder
Published: May 2006

Bromostearic acid satisfies the essential fatty acid requirement of an unsaturated fatty acid auxotroph of
Escherichia coli
K12. Over 55% of the fatty acids derived from lipids isolated from membranes of cells grown in bromostearate-supplemented medium contained bromine, as established by gas chromatography and mass spectrometry of the methyl esters. During equilibrium centrifugation in sucrose gradients, the cytoplasmic membranes isolated from bromostearate-grown cells banded at a density approximately 0.06 g/cm
3
greater than membranes isolated from oleate- or elaidate-grown cells, affording a complete separation between membranes which contain brominated fatty acids and those which do not.
A
Saccharomyces cerevisiae
Mutant Defective in Saturated Fatty Acid Biosynthesis
Authors: Schweizer E. , Bolling H.
Published: May 2006

The isolation and biochemical characterization of a
Saccharomyces cerevisiae
mutant, which grows only when emulsified myristic, palmitic, stearic, or oleic acid is added to the growth medium, is described. The mutant contains an enzymatically inactive fatty acid synthetase complex. The gene affected, preliminarily designated by the symbol fas, exhibits a 2:2 nuclear inheritance pattern. The formation of fatty acid synthetase in yeast is constitutive and not subject to repression by long chain fatty acids. After extensive purification, the mutant fatty acid synthetase was obtained as an essentially homogeneous protein with a sedimentation constant identical to that of the wild type enzyme. A systematic study of the seven reaction steps involved in fatty acid biosynthesis revealed that the enzyme catalyzing the condensation of acetate and malonate to acetoacetate was completely inactive in the mutant. The other six component enzymes had identical specific activities in the mutant and in the wild type fatty acid synthetase complexes. It is concluded that the mutant described harbors a missense mutation in the structural genes of either the condensing enzyme of the „acyl carrier protein” component of the fatty acid synthetase complex.
220 MHz Proton Nuclear Magnetic Resonance Study of the Interaction between Chicken M
4
Lactate Dehydrogenase and Reduced Diphosphopyridine Nucleotide
Authors: Sarma Ramaswamy H. , Kaplan Nathan O.
Published: May 2006

220 MHz proton nuclear magnetic resonance investigations of reduced pyridine coenzymes and coenzyme fragments, both in the presence and absence of M
4
lactate dehydrogenase, show the following: (1) That the energy barrier between a folded and open conformation of the reduced pyridine coenzyme (in aqueous solutions) is insignificant because an unfavorable enthalpy change of 5 kcal is compensated for by a favorable entropy change of 19 entropy units. (2) The coenzyme, however, appears to maintain its intramolecularly folded conformation on contact with the enzyme. The binding of the coenzyme results in the immobilization of the adenine and pyridine moieties and there is no longer any gain in the conformational entropy as a result of unfolding as in aqueous solutions. (3) The purine moiety of the coenzyme facilitates the binding of the pyridine ring and indicates how high frequency nuclear magnetic resonance can be utilized to study binding of small molecules to enzymes.
A Short Stereoselective Synthesis of Cecropia Juvenile Hormone
Authors: Loew Peter , Siddall John B. , Spain Virginia L. , Werthemann Lucius
Published: May 2006

A very short synthesis of the racemic cecropia hormone has been realized, utilizing a Claisen reaction. Methyl 6-hydroxy-3-methyl-7-methylene-2-
trans
-nonenoate, on treatment with the dimethyl ketal of 3-chloro-3-methyl-2-pentanone and a catalytic amount of 2,4-dinitrophenol, is transformed directly into methyl 11-chloro-3,11-dimethyl-7-ethyl-10-oxo-2-
trans
, 6-
trans
-tridecadienoate. Selective reduction gives a mixture of diastereoisomeric chlorohydrins separable by chromatography. The predominant
threo
-chlorohydrin is transformed into the juvenile hormone.
Contemporaneous Disequilibrium, a New Hypothesis to Explain the „Paradox of the Plankton”
Authors: Richerson Peter , Armstrong Richard , Goldman Charles R.
Published: May 2006

The diversity of lake phytoplankton is unexpectedly high, since the epilimnion of a lake is continuously mixing and might be expected to have only one or at most a few niches for primary producers. However, a carefully replicated series of samples from Castle Lake, Calif., showed a high degree of patchiness for many phytoplankton species, indicating that the rate of mixing is slow enough relative to the reproductive rate of the algae for many different niches to exist simultaneously. Productivity per unit biomass ratios, measured at Lake Tahoe, California-Nevada, shows that the turnover times for carbon in even this ultraoligotrophic lake are often less than 1 day. High diversity is associated with high productivity per unit biomass and high zooplankton populations in this lake.

A contemporaneous disequilibrium model to explain the diversity of the lake phytoplankton is therefore highly plausible. At any one time, many patches of water exist in which one species is at a competitive advantage relative to the others. These water masses are stable enough to permit a considerable degree of patchiness to occur in phytoplankton, but are obliterated frequently enough to prevent the exclusive occupation of each niche by a single species.
Mutation and Recombination of Bacteriophage Lambda: Effect of Ultraviolet Radiation
Authors: Miura Akiko , Tomizawa Jun-ichi
Published: May 2006

Defects in the bacterial
rec
B or
rec
C or phage
red
or
int
gene did not impair ultraviolet light-induced clear mutations of λ phage. Clear mutants of
c
I and
c
II genes were not enriched among RecA-promoted UV-induced recombinants between the N and O genes which closely encompass the
c
genes. No correlation was observed between UV-induced mutation and genetic recombination.
Evidence for an Extended Active Center in Elastase
Authors: Thompson Robert C. , Blout Elkan R.
Published: May 2006

Large increases in the esterase, amidase, and peptidase activities of elastase are observed on increasing the length of peptide substrates. The results suggest that at least five contiguous peptide units of the substrate (four N-terminal and one C-terminal to the scissile bond) can interact concurrently with the enzyme. When analyzed in terms of an acyl-enzyme mechanism, the increased effectiveness of the enzyme with larger substrates appears mainly in the acylation reaction and, to a lesser extent, in the binding and deacylation steps.
Reversal of Malignant Transformation by Tumor DNA
Authors: Halpern Barbara C. , Halpern Richard M. , Chaney Suzanne Q. , Smith Roberts A.
Published: May 2006

Walker-256 carcinosarcoma cells grown in tissue culture medium containing inhibitory DNA prepared from the tumor are shown to have an unaltered growth
in vitro
, but a diminished capacity to produce malignant tumors on injection into the rat. Coincident with this change in virulence is the induction of tRNA methylase inhibitors in these malignant cells. Within days after the DNA is removed from the growth medium, the tRNA methylase inhibitors disappear and the oncogenicity reappears.
Trypanosoma lewisi
Infection in the Rat: Effect of Adenine
Authors: Taliaferro William H. , D'Alesandro Philip A.
Published: May 2006

The reproductive activity of
Trypanosoma lewisi
was strikingly enhanced and sometimes prolonged for 2 days when sublethal doses of adenine were given to rats. The drug was effective when given for 5 or 7 days in the diet and/or intraperitoneally, starting one or two days before infection through two days after infection. Peak parasitemia was also enhanced. In terms of host immunity, daily sublethal doses of adenine given to rats within two days before or after infection with
T. lewisi
significantly depressed a hitherto unrevealed natural immunity to reproduction of the trypanosomes, but only slightly modified the development of acquired immunity.
A Negative Partition Relation
Authors: Hajnal A.
Published: May 2006

If the continuum hypothesis is assumed, there is a graph
G
whose vertices form an ordered set of type ω
1
2
;
G
does not contain triangles or complete even graphs of form [[unk]
0
,[unk]
0
], and there is no independent subset of vertices of type ω
1
2
.
Analysis of the Helical Ribosome Structures of
Mycoplasma gallisepticum
Authors: Maniloff Jack
Published: May 2006

The helical ribosome structures of
Mycoplasma gallisepticum
have been analyzed by optical diffraction and the rotational symmetry technique. The helix repeat (510 Å) is composed of 10 ribosomes in 3 turns. The rotational studies show some ribosome fine structure.
Solution of the Time-Dependent Schrödinger Equation by the Laplace Transform Method
Authors: Lin S. H. , Eyring H.
Published: May 2006

The time-dependent Schrödinger equation for two quite general types of perturbation has been solved by introducing the Laplace transforms to eliminate the time variable. The resulting time-independent differential equation can then be solved by the perturbation method, the variation method, the variation-perturbation method, and other methods.
Analysis of Host Range Restriction in
Escherichia coli
Treated with Toluene
Authors: Fleischman Roger A. , Richardson Charles C.
Published: May 2006

Escherichia coli
cells treated with toluene replicate DNA when they are provided with deoxyribonucleoside 5′-triphosphates, ATP, Mg
++
, and K
+
. However, when deoxycytidine 5′-triphosphate is replaced by hydroxymethyl deoxycytidine 5′-triphosphate, incorporation of nucleotides into acid-precipitable material by toluenetreated strains restrictive to nonglucosylated T-even phage is reduced to less than 5% of that normally observed. Even when dCTP is present in the reaction mixture, a similar effect of the hydroxymethyl analogue on DNA replication is observed. In contrast, toluene-treated
E. coli
K12
r6
-
r2,4
-
, a strain permissive to the nonglucosylated T-even phage, incorporates hydroxymethyl deoxycytosine into its DNA, and replication proceeds at only a slightly reduced rate in the presence of the hydroxymethyl deoxycytidine 5′-triphosphate. The presence of the hydroxymethyl deoxycytidine 5′-triphosphate in the reaction mixture does not lead to degradation of preexisting DNA of the restrictive host, but it does lead to an irreversible inhibition of further DNA replication; the inhibition is observed only when the hydroxymethyl deoxycytidine 5′-triphosphate is present during replication. Thus phage-specific enzymes are not necessary for the incorporation of hydroxymethylcytosine into phage DNA, and the restrictive mechanism, present in the host cell before infection, can recognize hydroxymethylcytosine residues in its own DNA, as well as the DNA of the T-even phage.
Resource Specialization and Equilibrium Population Size in Patchy Environments
Authors: King Charles E.
Published: May 2006

A simple model is formulated in which the growth of a consumer population is regulated by the diversity, quantity, and quality of alternate environmental resources. Equilibrium population size is dependent not only upon these resource characteristics, but upon the pattern of resource exploitation by the consumer. It is proven that in many circumstances, an exploitation pattern in which each individual uses each of the alternate resources leads to a greater equilibrium size for the consumer population than does a pattern of resource specialization. Therefore, given a knowledge of resource qualities, it is possible to predict the exploitation pattern that will lead to the largest equilibrium population size for the consumer species.
Homotropic Cooperative Binding of the First Component of Guinea Pig Complement to Rabbit IgG-Erythrocyte Complexes: A Possible Allosteric Effect
Authors: Thompson James J. , Hoffmann Louis G.
Published: May 2006

Binding of the activated first component of guinea pig complement to immune complexes formed between dinitrophenylated erythrocytes and rabbit IgG antibody to 2,4-dinitrophenylhapten has been studied quantitatively. Cooperative binding was observed; it in volves no interactions between the domains on the erythrocyte surface that bind the activated first component of complement, or between the activated complement molecules in solution. By curve-fitting methods, we find that the data are consistent with an allosteric model, which assumes 10 binding sites per domain, a low allosteric equilibrium constant, and virtually exclusive binding to one of the isomers.
Postulational Basis of the Law of Increase of Entropy
Authors: Kittel C.
Published: May 2006

The law increase of entropy is shown to be a consequence of the central assumption, in the manner of Gibbs, for the construction of the ensemble that represents the physical system. It is no longer necessary to make two separate assumptions in the Gibbs-Tolman development of the bases of statistical mechanics.
Lactobacillus
Exonuclease Mutants: Selection of Mutants with Altered Ability to Utilize Deoxyribonucleotides
Authors: Hotchkiss Rollin D. , Nozawa Ryushi , Gabor Magda
Published: May 2006

Lactobacillus acidophilus
R-26, which requires preformed deoxyriboside for its growth, is able to grow in a basal medium supplemented with nitrophenyl esters of thymidine 3′- and 5′-phosphates. Mutants unable to grow on the thymidine phosphate esters were isolated and classified thus far into two classes.

One class of mutants that are unable to grow on the diesters have modified exonucleases, their extracts being unable to hydrolyze the specific nitrophenyl ester on which the strain did not grow. It appears therefore, that the known 3′- and 5′-exonucleases specifically hydrolyzing these esters can be used for the support of growth. A second mutagenization treatment of one of the mutants gave rise to a new strain unable to use or hydrolyze either diester for growth, although it could still grow on several deoxyribodinucleotides.

Another class of mutants does not grow on deoxyribooligonucleotides but grows on monodeoxyribo-nucleosides and -nucleotides. These mutants have normal levels of exonuclease activities, so it appears possible that they bear a mutation affecting permeability to diesters or to molecules larger than mononucleotides.
New Polarity Suppressors in
Escherichia coli:
Suppression and Messenger RNA Stability
Authors: Carter Timothy , Newton Austin
Published: May 2006

Two new polarity suppressors (Su27 and Su78) have been isolated in
Escherichia coli
. Both suppress polarity in the
trp
and
lac
operons, and neither shows codon specificity for suppression. Extreme polar mutants of the
lac z
gene that contain either Su27 or Su78 make mRNA from the entire operon; however, no active β-galactosidase is translated from the
z
-gene messenger, and the amount of distal messenger is greater than would be expected from corresponding enzyme activities. Puromycin treatment of
lac
+
strains mimics the effect of polar chain-termination mutations in destabilizing
lac
mRNA. This effect is completely reversed by Su27, and it is partially reversed by Su78. The results suggest that these suppressors act by stabilizing mRNA after premature termination of protein synthesis.
Is
Drosophila
dAT on the Y Chromosome?
Authors: Blumenfeld Martin , Forrest Hugh S.
Published: May 2006

DNA isolated from
Drosophila melanogaster
embryos contains measurable amounts of dAT, the copolymer of deoxyadenylate and deoxythymidylate. In wild-type (XX,XY) embryos, dAT constitutes 4% of the total DNA. In embryos containing extra Y chromosomes, or even extra portions of Y chromosomes, dAT constitutes as much as 7% of the total. The enrichment for dAT is dependent upon the number of extra short arms of the Y chromosome (Y
S
) or long arms (Y
L
) of the Y chromosome per individual. This enrichment of dAT dependent on the Y chromosome may be interpreted in several ways. The most straightforward interpretation is that dAT is present in high concentrations on the Y chromosome.
Purification and Base Composition Analysis of Phage Lambda Early Promoters
Authors: Talaer Jean-Yves Le , Jeanteur Ph.
Published: May 2006

RNA-polymerase of
Escherichia coli
was allowed to bind to DNA of phage lambda in the absence of precursors. The resulting complex was excised by nuclease digestion and the protected DNA was recovered by phenol-extraction and ethanol precipitation. Acrylamide gel electrophoresis of protected DNA fragments reveals the existence of two distinct oligonucleotide peaks corresponding, respectively, to 45-52 and 7-10 nucleotide residues along with species of intermediate sizes. Peak I molecules have two properties: (
a
) their existence is dependent on the presence of sigma factor during the initial binding step, and (
b
) they are considerably enriched in A-T (up to 67%). On the contrary, peak II molecules have the same base composition as DNA of phage lambda, whether obtained in the presence or absence of sigma factor. Peak I molecules are thus believed to contain DNA sequences involved in promoter recognition, whether they are the promoters themselves, adjacent, or related sequences.
Performance of an Automated Computerized Plate Scanner
Authors: Luyten Willem J.
Published: May 2006

A brief summary is given of the initial performance of an automated computerized plate-measuring machine, and it is seen that the machine is working entirely satisfactorily.
Effect of Pressure on the Electronic Structure of Ferric Hydroxamates and Ferrichrome A
Authors: Grenoble D. C. , Drickamer H. G.
Published: May 2006

The effect of pressure up to 175 kilobars on the electronic structure of three ferric hydroxamates and on ferrichrome A has been studied by optical absorption and Mössbauer resonance. The ferric ion was reduced to ferrous ion with pressure, as has been previously observed for various compounds. For the hydroxamates, the amount of reduction correlated very well with the location and shift of the metal-to-ligand charge transfer peak. This is entirely consistent with a previously presented theory. The results for ferrichrome A did not fit quantitatively into the series. Since the shape of the potential well is almost certainly different for this compound, this result is not surprising.
The Question of Histidine Content in
c
-Type Cytochromes
Authors: Cusanovich M. A. , Meyer T. , Tedro S. M. , Kamen M. D.
Published: May 2006

Reports that histidine may not occur in heme peptides derived from
c
-type cytochromes isolated from chloroplasts of
Euglena gracilis
and
Porphyra
sp. have not been substantiated in the present investigation, in which the amino acid composition and a partial sequence were determined for a heme peptide derived from the
c
-type cytochromes of a strain of
Euglena
closely related to that used in the previous studies. It is concluded that no evidence exists to challenge the generalization that histidine is always present vicinal to the hemebinding site in
c
-type cytochromes.
Chromosomal Aberrations and Mortality of X-Irradiated Mammalian Cells: Emphasis on Repair
Authors: Dewey W. C. , Miller H. H. , Leeper D. B.
Published: May 2006

Chromosomal aberrations induced by x-rays in synchronized Chinese hamster cells correlated well with mortality as the radiosensitivity was made to vary by a factor of 4 by treating the cells with colcemid or 5-bromodeoxyuridine and by irradiating the cells in different parts of the cell cycle. 37% survival was observed when the cells sustained about one aberration per cell. Furthermore, the positive correlation was observed during repair of damage. Repair was measured by the reduction in damage observed either as the incubation period between two doses was increased (repair of sublethal lesions), or as the cells were held at 20°C after a single dose of radiation (repair of potentially lethal lesions). Repair of both sublethal and potentially lethal lesions occurred with a half-time of about 12 min and was inhibited at 0°C. These correlations strongly support the hypothesis that x-ray-induced cell death results from damage in chromatin structures.
Purification of Erythropoietin
Authors: Goldwasser E. , Kung C. K.-H.
Published: May 2006

Erythropoietin, the hormone that is the primary regulator of erythrocyte production, has been purified from anemic-sheep plasma, with a purification factor of more than 1 million. Gel electrophoresis shows that the major contaminant is desialated erythropoietin.
Microtubules and Sensory Transduction
Authors: Moran David Taylor , Varela Francisco Garcia
Published: May 2006

Cockroach legs bear tactile spines equipped with campaniform sensilla—mechanoreceptors associated with the cuticle—which function by a single bipolar neuron from whose dendrite tip extends a modified cilium packed with 350-1000 parallel cytoplasmic microtubules. These microtubules, which can be chemically disassembled with colchicine and vinblastine, are intimately associated with the site of mechanical stimulation. Treatment of living sensilla with colchicine and vinblastine abolishes their ability to respond to mechanical stimulation 1-2 hr after drug application. Loss of function is accompanied by large-scale disassembly of microtubules in the modified cilium. The experimental evidence strongly suggests that microtubules play an important role in the process of sensory transduction in campaniform sensilla.
Comparative DNA Renaturation Kinetics in Amphibians
Authors: Straus Neil A.
Published: May 2006

Amphibian haploid genome sizes vary from 9 × 10
8
to 8 × 10
10
nucleotide pairs. The rate of reassociation of DNA from amphibians of different genome sizes has been employed to eliminate one of the theoretical models of chromosome structure.

Scaphiopus couchi, Bufo marinus
, and
Rana clamitans
, whose haploid genome sizes are in the ratio 2:7:10, all contain sequences of DNA represented once in the haploid genome. This indicates that their chromosomes are not composed of identical lateral strands (polynemy). The relative frequencies of repetition of DNA sequences are different for the various species of amphibians.

The observed frequencies of repetitive DNA sequences in amphibians do not show the relationships expected if amphibians form a polyneme series.
Differentiable Pseudo-Free Circle Actions
Authors: Montgomery Deane , Yang C. T.
Published: May 2006

The circle group
G
is said to act pseudofreely if it is not free and if every orbit is one-dimensional and if the isotropy group is the identity except on isolated exceptional orbits where the isotropy group is the finite cyclic group Z
k
, k > 1. We consider differentiable actions of this kind on homotopy seven spheres and classify all such actions. As a corollary, it follows that there can be any finite number of exceptional orbits, in contrast to the linear case where there can be at most four.