bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of Liver Alcohol Dehydrogenase at 2.9-Å Resolution
Authors: Brändén Carl-Ivar , Eklund Hans , Nordström Bo , Boiwe Torne , Söderlund Gustaf , Zeppezauer Eila , Ohlsson Ingrid , Åkeson Åke
Published: May 2006

The conformation of the polypeptide chain in horse liver alcohol dehydrogenase (EC 1.1.1.1), as well as the binding sites for some inhibitor molecules, have been determined from x-ray crystallographic data to a resolution of 2.9 Å. Each subunit of the dimeric molecule is organized into two parts unequal in size and separated by a wide and deep active-site cleft. The adenosine moiety of the coenzyme is bound within the smaller region. Interactions between these coenzyme-binding substructures define the subunit contact area of the molecule. The “catalytic” zinc atoms are bound at the bottom of the clefts about 20 Å from the surface of the molecule. The coenzyme binding region has a main-chain conformation very similar to a corresponding region in lactate and malate dehydrogenase. It is suggested that this substructure is a general one for binding of nucleotides and, in particular, the coenzyme NAD
+
.
Two Distinct Types of Enhancement of Galactose Uptake into Hamster Cells: Tumor-Virus Transformation and Hexose Starvation
Authors: Kalckar H. M. , Ullrey D.
Published: May 2006

Enhancement of hexose uptake seems well correlated with transformation of cell cultures by tumor viruses and the absence of contact inhibition. Enhancement of sugar uptake has also been observed as a result of hexose starvation. Both types of enhancement can clearly be demonstrated in cultures of hamster cells when uptake of
14
C-labeled galactose is monitored after 10 or 20 min. The profiles of accumulation products are strikingly different. In cultures of hamster NIL cells transformed with polyoma virus much of the
14
C is accumulated as UDPhexose. Untransformed cells accumulate galactose-l-phosphate as well as UDPhexose. Hexose-starved cells show enhanced uptake of galactose; however, this marked enhancement was only observed in NIL cultures close to contact inhibition. The novel and common feature seen in hexose-starved cells when incubated briefly with
14
C-labeled galactose is the occurrence of a marked accumulation of [
14
C]UDPglucuronic acid at the expense of UDPhexose. The ratio [
14
C]UDPglucuronic acid/UDPhexose in cultures fed glucose or galactose was invariably low (0.15-0.2) regardless of the presence or absence of contact inhibition. 20 hr of hexose starvation invariably changed this ratio by a factor of 10 or more, due to accumulation of UDPglucuronic acid. This result was also observed in cultures transformed with polyoma virus. The presence of 3-
O
-methylglucose in the growth medium did not alter the typical “sugar starvation pattern” (i.e., the UDPglucuronic acid/UDPhexose ratio averaged 1.7).

Enhancement of galactose uptake by hexose starvation was very pronounced in NIL cultures that were close to contact inhibition, but was not a prominent feature in the polyoma-transformed cultures. The transformed cells grown on glucose or galactose growth medium showed the usual enhanced rate of uptake of galactose as compared with nontransformed near-confluent cultures that had been fed hexose. The polyoma-induced enhancement showed none of the features characteristic of hexosestarved cells.
New Lymphocyte Antigen System (
Lna
) Controlled by the
Ir
Region of the Mouse
H-2
Complex
Authors: David C. S. , Shreffler Donald C. , Frelinger Jeffrey A.
Published: May 2006

A new system of lymphocyte alloantigens in mice is described. This
Lna
(lymph-node antigen) system is associated with the
Ir
region of the
H-2
(histocompatibility-2) gene complex. It has the following distinctive characteristics: (
1
) The gene or genes controlling these antigens has been mapped in the
Ir
(immune response) region between
H-2K
and
Ss-Slp
. (
2
) The antigens are most readily detectable on lymph-node cells, although they are also expressed on peripheral blood lymphocytes, splenic lymphocytes, and thymocytes. (
3
) Cytotoxicity against only about half of lymph-node cells is consistently observed. (
4
) Cytotoxic antibody titers against these antigens are strikingly high—more than 2000 by
51
Cr-release and up to 100,000 in the microcytotoxic test. (
5
) At least two, probably allelic, forms of the antigen(s) have been defined, one associated with the
H-2
k
haplotype and one with the
H-2
a
haplotype. (
6
) Antisera against
Lna
contain multiple antibody specificities that can be fractionated by absorption either with certain recombinants or with other
H-2
halotypes that have crossreactive antigens. The antisera against
Lna
may be of value for definition and characterization of the products of the
Ir
and
MLR
(mixed lymphocyte reaction stimulatory) genes associated with the
H-2
complex.
Enhancement of Dopamine-Stimulated Adenylate Cyclase Activity in Rat Caudate after Lesions in Substantia Nigra: Evidence for Denervation Supersensitivity
Authors: Mishra Ram K. , Gardner Eliot L. , Katzman Robert , Makman Maynard H.
Published: May 2006

Unilateral radiofrequency lesions or chemical lesions with 6-hydroxydopamine were produced in the substantia nigra of rat brain in order to destroy dopaminergic innervations to caudate nucleus and thereby to produce functional denervation supersensitivity. Both types of lesions resulted in enhanced stimulation of caudate adenylate cyclase (EC 4.6.1.1) activity by dopamine at all dopamine concentrations tested, with more marked enhancement at the lower concentrations. Response to another dopamine agonist, 1-(3,4-dihydroxybenzyl)-4-(20pyrimidinyl) piperazine (S584) was also enhanced. 6-Hydroxydopamine lesions resulted in selective enhancement of the dopamine-stimulated component of adenylate cyclase, whereas radiofrequency lesions resulted also in a marked decrease in basal activity. It is postulated that the basal activity of caudate represents primarily an adenylate cyclase distinct from that stimulated by dopamine and destroyed only by the less selective radiofrequency lesion. The enhancement of dopamine-sensitive adenylate cyclase after lesions serves as indirect evidence for a significant role of this system in the transmitter function of dopamine and indicates, furthermore, that it is directly involved in dopamine receptor supersensitivity
in vivo
produced by denervation.
Accelerating Gallstone Dissolution
Authors: Tao J. C. , Cussler E. L. , Evans D. F.
Published: May 2006

The dissolution rates of cholesterol in model bile salt solutions are controlled by diffusion in slowly flowing bile and by interfacial kinetics in rapidly flowing bile. At low flow, dissolution varies with the square root of bile flow and can be predicted,
a priori
, from existing correlations of mass transfer. At high bile flow, dissolution is independent of bile flow and is probably dominated by the rate of micelle adsorption. These results show that cholesterol gallstone dissolution, a potential nonsurgical therapy for cholelithiasis, can be accelerated little in slow bile, but more significantly in rapidly flowing bile.
The 5′-Terminal Nucleotide Sequences of the Double-Stranded RNA of Human Reovirus
Authors: Miura Kin-Ichiro , Watanabe Kumiko , Sugiura Masahiro , Shatkin Aaron J.
Published: May 2006

The 5′-terminal nucleotide sequences of human reovirus double-stranded RNA were determined after labeling the RNA with [
32
P]phosphate by polynucleotide kinase. The 5′ terminal were labeled to only a limited extent prior to sequential oxidation, β-elimination, and phosphomonoesterase treatment, indicating that the terminal phosphates were in a modified, blocked configuration. Each genome segment, after removing the blocking group, contained the same two 5′-terminal sequences: GpApUp in one chain and G
*
pCp in the other. G
*
p is a derivative of guanylic acid, probably 2′-
O
-methyl-Gp, which renders the 5′-terminal sequence resistant to hydrolysis by alkali. The results indicate that the transcription of reovirus double-stranded RNA strats from the 3′ end complementary to the G
*
pCp-terminal, resulting in the synthesis of single-stranded mRNA carrying the same 5′ sequence as the G
*
pCp-chain. The presence of a modified nucleotide at the 5′ terminus of the strand complementary to the mRNA template is a feature common to another double-stranded RNA virus, cytoplasmic polyhedrosis virus.
Guanosine 3′:5′-Monophosphate-Dependent Protein Kinases in Mammalian Tissues
Authors: Kuo J. F.
Published: May 2006

The mammalian protein kinase activity stimulated preferentially by low concentrations of guanosine 3′:5′-monophosphate (cyclic GMP), but not by adenosine 3′:5′-monophosphate (cyclic AMP), was readily assayed in a modified incubation system that contained a neutral phosphate buffer, protein kinase modulator, and arginine-rich histone. Cyclic GMP-dependent protein kinase activity assayed under these conditions was about two to three orders of magnitude higher than that previously detected. The enzyme activity occurred in all guinea pig and rat tissues (lung, heart, aorta, brain, liver, ileum, adipose, and pancreatic islets) examined. The activity can be separated from the cyclic AMP-dependent protein kinase activity, also present in the same tissues, by means of either Sephadex G-200 gel filtration or ammonium sulfate fractionation. The cyclic GMP-dependent enzyme preparations had
K
a
values for cyclic GMP ranging from 0.03 to 0.12 μM, compared to the
K
a
values for cyclic AMP ranging from 0.6 to 3.8 μM. The presence of phosphate and protein kinase modulator was essential for maximal cyclic GMP-dependent enzyme activity.

The occurrence of high levels of cyclic GMP-dependent protein kinase activity in mammalian tissues clearly suggests that it may serve as a “target” enzyme for cyclic GMP, mediating many biological effects of this cyclic nucleotide.
Altered Development of the Rat Brain Serotonergic System after Disruptive Neonatal Experience
Authors: Giulian Dana , McEwen Bruce S. , Pohorecky Larissa A.
Published: May 2006

A single disruptive experience, a cold treatment, on postnatal day 1 elevated open-field activity and reduced reaction to handling in rats tested more than 240 days later. Neurochemical mechanisms underlying these behavioral phenomena were examined by monitoring the development of the rat brain serotonergic system. After cold treatment, elevations in 5-hydroxytryptamine levels of a preparation of forebrain plus midbrain could be first detected on postnatal day 16 in both sexes. A more detailed regional dissection of the brain showed that such increases occurred in the cerebrum, midbrain, septum-thalamus, and hypothalamus-preoptic area. Rats treated on postnatal days 1 or 6 showed increased 5-hydroxytryptamine levels, whereas animals treated on postnatal day 10 did not, a finding that points to a possible “critical period” of sensitivity. Results of adrenalectomy and corticosterone injections suggest that the influence of the adrenal gland cannot account for the elevation in brain serotonin. Furthermore, the gonadal steroids, estradiol and testosterone, alter brain 5-hydroxytryptamine independently of early experience, as distinguished by the time of appearance, periods of sensitivity, and the direction of monoamine changes. These findings are discussed in relation to the maturation of the neuroendocrine systems governing adrenal and gonadal function.
Conversion of ϕX174 Viral DNA to Double-Stranded Form by Purified
Escherichia coli
Proteins
Authors: Wickner Sue , Hurwitz Jerard
Published: May 2006

The
E. coli
proteins that catalyze the conversion of ϕX174 single-stranded DNA to duplex DNA have now been purified extensively. The reaction depends on
dnaB, dnaC(D), dnaE
, and
dnaG
gene products, DNA elongation factors I and II,
E. coli
DNA binding protein, and two additional
E. coli
proteins, replication factors X and Y. DNA synthesis by these proteins requires ϕX174 viral DNA, dNTPs, Mg
+2
, and ATP. The product synthesized is full-length linear ϕX174 DNA. The reaction has been resolved into two steps. The first step involves the interaction of ATP and ϕX174 DNA with
dnaB
and
dnaC(D)
gene products,
E. coli
DNA binding protein, and replication factors X and Y in the absence of dNTPs. Subsequent dNMP incorporation requires the addition of DNA polymerase III, DNA elongation factors I and II,
dnaG
gene product, and dNTPs.
Myosin in a Component of the Cell Surface of Cultured Cells
Authors: Willingham Mark C. , Ostlund Richard E. , Pastan Ira
Published: May 2006

Antisera to myosin from mouse L929 cells, mouse uterus, and rabbit skeletal muscle have been prepared in goats. Each antiserum shows specific reaction by immunodiffusion only to the myosin against which it was prepared. Antiserum against L cell myosin agglutinates L929 cells and shows surface localization in unfixed cells by indirect immunofluorescence. This reaction is prevented by immunoabsorption with L cell myosin, but not by absorption with mouse uterine or rabbit skeletal muscle myosins. Elution of the antibody from L cell myosin antiserum that absorbs to fixed L cells yields antibody reactive to L cell myosin in immunodiffusion. At the ultrastructural level, surface localization is also evident with a peroxidase bridge immunocytologic method as a uniform distribution of surface label. Antiserum against L cell myosin also shows localization on the surface of other cells of rodent origin (3T3-4, NRK, MNRK, KNRK, and MEF) and HeLa cells, but not with some other cells of human origin (ALL and WI-38). The reactivity with antibody of the plasma membrane myosin is unaffected by trypsin treatment or fixation with 0.5-2.0% formalin. These results strongly suggest that myosin in cultured nonmuscle cells is a component of the plasma membrane, a finding of possible significance in studying the mechanisms regulating the motility, morphology, and growth of these cells.
Heavy Water Slows the
Gonyaulax
Clock: A Test of the Hypothesis That D
2
O Affects Circadian Oscillations by Diminishing the Apparent Temperature
Authors: McDaniel Martha , Sulzman Frank M. , Hastings J. W.
Published: May 2006

In order to test the hypothesis that deuterium oxide acts in circadian systems by simulating a lower environmental temperature, we have examined the effects of D
2
O on
Gonyaulax polyedra
, where the period of the circadian rhythm of bioluminescent glow in constant environmental conditions is shorter at 16° than at 22°, and the phase of the glow peak relative to a light-dark cycle is advanced at 16° relative to 22°. Addition of low concentrations of D
2
O to
Gonyaulax
does not produce the same effects on period and phase as lowering the temperature; the free running period is lengthened and the phase is delayed. These results show that in the
Gonyaulax
rhythm, the effect of added D
2
O is not equivalent to lowering the temperature.
Determination of Actin Messenger RNA in Cultures of Differentiating Embryonic Chick Skeletal Muscle
Authors: Paterson Bruce M. , Roberts Bryan E. , Yaffe David
Published: May 2006

Cytoplasmic polyadenylylated messenger RNA from differentiated muscle cultures, when incubated in a wheat germ cell-free system, directed the synthesis of a polypeptide indistinguishable from authentic chicken skeletal muscle actin, as judged by mobility on sodium dodecyl sulfate-polyacrylamide gels, tryptic peptide analyses, and biological activity. The synthesis of actin in the cell-free system was used to assay levels of translatable actin mRNA in cultures of fibroblasts, pre- and post-fusion myoblasts, and myoblasts grown under conditions that prevent fusion. In all cases the amount of actin polypeptide synthesized in the cell-free system was proportional to the rate of actin synthesis in the cultures from which the RNA was extracted. It is suggested that actin synthesis is regulated by the actin mRNA content of the cell and that an increase in the cytoplasmic level of translatable actin messenger RNA is mediated by cell fusion rather than by the terminal round of DNA synthesis.
Purification and Properties of Rat Liver Microsomal Stearyl Coenzyme A Desaturase
Authors: Strittmatter P. , Spatz L. , Corcoran D. , Rogers M. J. , Setlow B. , Redline R.
Published: May 2006

The terminal enzyme of the NADH-dependent stearyl coenzyme A desaturase system has been isolated from rat liver microsomes. This desaturase is a single polypeptide of 53,000 daltons containing 62% nonpolar amino-acid residues and one atom of non-heme iron. The purified protein forms high molecular weight aggregates that can be dispersed by detergent procedures. Desaturase activity requires NADH, stearyl coenzyme A, oxygen, lipid, and the three enzymes, cytochorme
b
5
reductase (EC 1.6.2.2), cytochrome
b
5
, and desaturase. Cytochrome
b
5
is the direct electron donor to the desaturase, which appears to utilize the iron in the oxidation-reduction sequence during desaturation of stearyl coenzyme A.
Effect of a Fibroblast Growth Factor, Insulin, Dexamethasone, and Serum on the Morphology of BALB/c 3T3 Cells
Authors: Gospodarowicz Denis , Moran John
Published: May 2006

The effects of serum, fibroblast growth factor, dexamethasone, and insulin on the morphology of two lines of BALB/c 3T3 cells are described and illustrated. Fibroblast growth factor, a polypeptide purified from bovine brain and pituitary glands, stimulates DNA synthesis and cell division in both sparse and confluent cultures of quiescent 3T3 cells. When cells are grown in the presence of the factor, they go through one or two cycles of division and their morphology differs from that of cells either growing in 10% serum or maintained in a quiescent state in low serum; they appear rounded with long processes and show no sign of contact inhibition. When dexamethasone is present with the growth factor, the cells grow to a high density and are not contact-inhibited; they have the appearance of transformed cells. Addition of insulin or dibutyryl cyclic AMP to the cells results in a morphology similar to that of cells growing in the presence of serum. Addition of growth factor or growth factor plus dexamethasone to cells that have reached confluency in 10% serum and that are clearly contact-inhibited results in the resumption of growth. The final cell density reached is similar to that of cells growing in the presence of 30% serum with daily fluid changes. No contact inhibition is observed in either of these situations.
Isolation of DNA-Membrane Complex in
Bacillus subtilis
Authors: Sueoka Noboru , Hammers Joan M.
Published: May 2006

A DNA-membrane complex of
Bacillus subtilis
was separated from the bulk of the membrane by CsCl-sucrose double gradient centrifugation. The complex has a CsCl-sucrose buoyant density of 1.35-1.45 g/cm
3
. Gel electrophoretic analyses show that the complex has about 5% of the whole membrane proteins and contains proteins unique to the complex as well as a small amount of membrane proteins. DNA in the complex is enriched for a genetic marker close to the origin (
pur A16
) and for one near the terminus (
metB5
). Artifactual formation of the complex during the lysate preparation was shown to be unlikely.
Cyclic Nucleotides and Growth Control in Cultured Mouse Cells: Correlation of Changes in Intracellular 3′:5′cGMP Concentration with a Specific Phase of the Cell Cycle
Authors: Seifert W. , Rudland P. S.
Published: May 2006

The commencement of cell growth following serum addition to quiescent cultures of mouse fibroblasts is preceded by transient changes in intracellular concentrations of cAMP and cGMP. By artificial depletion of the culture medium for different nutrients, cell growth can be reversibly arrested in various phases of the cell cycle. Here it is shown that the major cGMP increases are only observed when cultures which are arrested in the G
0
phase are stimulated to grow or when synchronized growing cells pass through the G
1
phase. In addition to its concomitant decrease, cAMP exhibits rhythmic changes during the cell cycle. This suggests that the increase in cGMP could act as a specific signal for movement of cells out of the G
0
or G
1
phase of the cell cycle by activating the pleiotypic and mitogenic program of the cell.
Sequence Homology Between the RNA of Mason-Pfizer Monkey Virus and the RNA of Human Malignant Breast Tumors
Authors: Colcher David , Spiegelman S. , Schlom Jeffrey
Published: May 2006

Radioactive DNA ([
3
H]cDNA) complementary to the RNA of Mason-Pfizer monkey virus was used in molecular hybridization experiments to demonstrate sequence homology between its viral RNA and RNA of human malignant breast tumors. Hybridization products were analyzed by cesium sulfate equilibrium density centrifugation and hydroxylapatite chromatography. Seven of ten human malignant breast tumors tested contained virus-related RNA when assayed by hydroxylapatite chromatography, whereas no sequence homology was found in RNA from 11 human benign breast tumors or from RNA of normal human spleen, liver, or kidney. Hybridizations between [
3
H]cDNA of the monkey virus and human breast adenocarcinoma RNA showed a C
r
t
½
of about 2 × 10
4
. The fidelity of the hybrids formed was indicated by a

T
m

of 80.5°.
Isolation and Structure of Two Prostaglandin Endoperoxides That Cause Platelet Aggregation
Authors: Hamberg Mats , Svensson Jan , Wakabayashi Toshio , Samuelsson Bengt
Published: May 2006

Incubation for a short time of arachidonic acid with the microsomal fraction of a homogenate of the vesicular gland of sheep in the presence of 1 mM
p
-mercuribenzoate followed by extraction and silicic acid chromatography yielded two prostaglandin endoperoxides. The structures of these compounds, i.e., 15-hydroperoxy-9α,11α-peroxidoprosta-5,13-dienoic acid (prostaglandin G
2
) and 15-hydroxy-9α,11α-peroxidoprosta-5,13-dienoic acid (prostaglandin H
2
), were assigned mainly by a number of chemical transformations into previously known prostaglandins. The new prostaglandins were 50-200 times (prostaglandin G
2
) and 100-450 times (prostaglandin H
2
) more active than prostaglandin E
2
on the superfused aorta strip. The half-life of the prostaglandin endoperoxides in aqueous medium (about 5 min) was significantly longer than that of “rabbit aorta-contracting substance” released from guinea pig lung, indicating that none of the prostaglandin endoperoxides is identical with this factor. Addition of 10-300 ng/ml of the endoperoxides to suspensions of washed human platelets resulted in rapid aggregation. Furthermore, platelet aggregation induced by thrombin was accompanied by release of material reducible by stannous chloride into prostaglandin F
2α
, thus indicating the involvement of endogenous prostaglandin endoperoxides in platelet aggregation.
Demonstration of Electrogenic Na
+
-dependent D-glucose Transport in Intestinal Brush Border Membranes
Authors: Murer H. , Hopfer U.
Published: May 2006

Na
+
-coupled D-glucose transport was studied in isolated membrane vesicles from intestinal brush borders. Concentration gradients of SCN
-
, K
+
, and H
+
were established between the intravesicular solution and the incubation medium and their influence on D-glucose uptake from the medium was measured. A gradient (medium > vesicle) of NaSCN, but not of KSCN, produced a transient overshoot of D-glucose uptake above the equilibrium level. Similarly, an increase of the membrane conductance with valinomycin (K
+
-conductance) or with uncoupling agents of oxidative phosphorylation (H
+
-conductance) induced an overshooting D-glucose uptake, provided a (vesicle > medium) K
+
-gradient or a H
+
-gradient, respectively, was present in each case. The transient overshoot is evidence that D-glucose was taken up against its concentration gradient (up to 10-fold). The gradients of SCN
-
, K
+
(in the presence of valinomycin), and H
+
(in the presence of uncouplers) are thought to contribute to the “driving” force for this “active” D-glucose transport by changing the electrical potential across the vesicle membrane and thus making the inside more negative (with respect to the medium). These experiments, therefore, provide evidence that the Na
+
-coupled D-glucose translocation across the brush border membrane is an electrogenic process, i.e., the positive charge associated with Na
+
is not compensated by the co-movement of an anion or the counter-movement of a cation
via
the glucose “carrier”. The results imply that an electrical potential across the brush border membrane may play an important role in determining the transport of D-glucose by intact cells.
The Juvenile Hormone Binding Protein in the Hemolymph of
Manduca sexta
Johannson (
Lepidoptera
:
Sphingidae
)
Authors: Kramer Karl J. , Sanburg Larry L. , Kézdy Ferenc J. , Law John H.
Published: May 2006

C
18
:juvenile hormone is quite soluble in water, yielding a monomeric solution greater than 10
-5
M.
In vivo
injection or addition of aqueous juvenile hormone to the hemolymph
in vitro
shows the complexation of juvenile hormone to a protein, as demonstrated by gel permeation chromatography and disc-gel electrophoresis. The protein has an apparent molecular weight of 3.4 × 10
4
and is present in the hemolymph at a concentration in the micromolar range. The binding of the hormone to the protein can be described as a simple thermodynamic equilibrium with a dissociation constant of 3 × 10
-7
M, and the protein has a much higher affinity for the hormone than for the hydrolysis products.
Interaction of Bacterial and Lambda Phage Recombination Systems in the X-Ray Sensitivity of
Escherichia coli
K-12
Authors: Trgovčević Željko , Rupp W. Dean
Published: May 2006

E. coli
cells lysogenic for the thermoinducible prophage λcI857 can be transiently induced by a brief heat treatment. Although this treatment does not kill the cells, some λ products normally formed during vegetative phage development are made that can alter the response of host cells to x-irradiation by causing an increase in radioresistance. This increased resistance is particularly striking in the recombination-deficient
recB
-strain, which is normally much more radiosensitive than its
recB
+
parent. After pulse-heating at 42°, the survival curve of
E. coli recB
-
lysogenized with λcI857 does not differ from that of the wild-type strain. Since λ
red
mutants do not increase the radioresistance of
recB
-
strains, both λ
red
gene products, λ exonuclease and β-protein, are required to compensate for the missing
recB
product. Furthermore, phage-induced radioresistance also occurs in
recB
+
lysogens even when they carry λ
red
-
, but not when the λ prophage is
gam
-
. Thus, in wild-type cells, phage-induced radioresistance requires some interaction between the bacterial
recB
gene product (exonuclease V) and the phage λ-protein.
Detection and Quantitation of Octopine in Normal Plant Tissue and in Crown Gall Tumors
Authors: Johnson Roosevelt , Guderian Ronald H. , Eden Francine , Chilton Mary-Dell , Gordon Milton P. , Nester Eugene W.
Published: May 2006

Octopine has been detected in normal tobacco leaf and stem tissue, normal sunflower stem tissue, pinto bean leaves, and normal tobacco callus tissue in culture. Octopine was identified in extracts by means of electrophoresis and chromatography in several solvent systems. Tobacco and sunflower tumor lines induced by various strains of
Agrobacterium tumefaciens
were found to contain from 1 to 240 times as much octopine as the normal plant tissues examined. Several strains of
A. tumefaciens
produce undifferentiated tobacco tumors containing high levels of octopine, but produce undifferentiated sunflower tumors containing normal levels of octopine and high levels of arginine. Further, strain CGIC of
A. tumefaciens
produces in tobacco an undifferentiated tumor which contains high levels of octopine and a teratoma which contains normal levels of octopine. This evidence shows that there is no consistent relationship between the causative strain of
A. tumefaciens
and the octopine content of the resulting crown gall tumor.
Association of DNA-dependent and -independent Ribonucleoside Triphosphatase Activities with
dnaB
Gene Product of
Escherichia coli
Authors: Wickner Sue , Wright Michel , Hurwitz Jerard
Published: May 2006

Preparations of
E. coli dnaB
gene product contain ribonucleoside triphosphatase activity that is stimulated 10-fold by DNA. The products of the triphosphatase activity are nucleoside diphosphates and P
i
. The
dnaB
complementing activity in the ϕX174 DNA-dependent system and these triphosphatase activities copurify over the last 20-fold of an extensive (about 40,000-fold) purification procedure. Acrylamide gel electrophoresis of the purified material shows a single band of protein coincident with eluted
dnaB
complementing and DNA-dependent and -independent nucleoside triphosphatase activities.
Resonance Raman Spectra of Cobalt-Substituted Hemoglobin: Cooperativity and Displacement of the Cobalt Atom upon Oxygenation
Authors: Woodruff William H. , Spiro Thomas G. , Yonetani Takashi
Published: May 2006

The resonance Raman spectra of oxy and deoxy cobalt-substituted hemoglobin (CoHb) are reported. Comparison of these spectra to those of hemoglobin, methemoglobin, cytochrome
c
, and model cobalt porphyrin complexes suggests that the displacement of the cobalt atom upon oxygenation of CoHb is no greater than the out-of-plane distance in five-coordinate Co(II) porphyrins, 0.15 Å. Combining this distance with the expected contraction of the cobalt-histidine bond, Ibers has estimated a maximum displacement of 0.37 Å for the proximal histidine with respect to the heme plane upon oxygenation, about one-third the corresponding distance estimated for iron hemoglobin. The free energy of cooperativity for cobalt hemoglobin is also estimated to be one-third that of iron hemoglobin. These results are therefore consistent with Hopfield's distributed energy model, which predicts proportionality between proximal histidine displacement and the free energy of cooperativity. By implication they support Perutz's trigger mechanism for cooperativity.
In Vitro
Properties of Leukocyte Dialysates Containing Transfer Factor
Authors: Ascher Michael S. , Schneider William J. , Valentine Fred T. , Lawrence H. Sherwood
Published: May 2006

The chief impediment to the precise biochemical identification of transfer factor and its mechanism of action has been the lack of a reproducible
in vitro
assay. We now report on a method by which dialysates containing transfer factor of proven
in vivo
potency can convert nonimmune lymphocytes to immune responsiveness
in vitro
, as reflected by antigen-triggered lymphocyte proliferation. However, “water-dialyzed transfer factor” (TF
D
) prepared for
in vivo
use by the conventional method of dialysis against large volumes of water exhibits diminished activity
in vitro
and is frequently toxic to lymphocyte cultures. This problem can be avoided by dialysis of transfer factor into tissue culture medium. When this precaution is taken, such “media-dialyzed transfer factor” (TF
DM
) causes nonimmune lymphocytes to respond to antigen by an increment of thymidine incorporation that ranges from 2 to 25 times that of such cells cultured with antigen alone. This response is generally observed only in the presence of those antigens to which the TF
DM
donor expresses delayed cutaneous reactivity and is distinguishable from nonspecific adjuvant effects.
A Hyperglycemic Peptide from Pituitary Growth Hormone: Preparation with Pepsin and Assay in ob/ob Mice
Authors: Lostroh Ardis J. , Krahl M. E.
Published: May 2006

A fragment that induces glucose intolerance in hereditarily obese mice has been prepared from pituitary growth hormone(sheep and human) by controlled digestion with pepsin in 0.05 M sodium acetate buffer, pH 3.7. The digest was purified by column chromatography on Bio-Gel P-6, followed by chromatography on Bio-Rex 70 and Bio-Gel P-2; in each successive step peptide was quantitated with the fluorescamine procedure. The fragment from sheep growth hormone has these characteristics: (
1
) It induces glucose intolerance in fasted ob/ob female mice when injected subcutaneously in a divided dose 15 min before, and concurrently with, glucose. (
2
) It is a basie peptide, as judged from its elution behavior on Bio-Rex 70, H
+
form. (
3
) It does not crossreact with antiserum to human growth hormone in radioimmunoassay. Further purification and initial sequence determinations have been undertaken.
Isolation of Heterogeneous Circular DNA from Induced Lysogens of Bacteriophage Mu-1
Authors: Waggoner Barbara T. , González Nélida S. , Taylor Austin L.
Published: May 2006

Covalently-closed circular DNA molecules are formed after induction of phage Mu
cts4
and after infection with phage Mu
cts4
. The circular molecules obtained after induction have a molecular length range from 36.5 to 156.7 kilobases as measured by electron microscopic techniques. These heterogeneous molecules have no consistent correlation to exact multiples of a Mu genome equivalent (37.3 ± 1.2 kilobases). Direct evidence is given that these molecules contain phage Mu DNA that is covalently linked to other DNA sequences.
Renal Aldosterone Receptors: Studies with [
3
H]Aldosterone and the Anti-Mineralocorticoid [
3
H]Spirolactone (SC-26304)
Authors: Marver Diana , Stewart John , Funder John W. , Feldman David , Edelman Isidore S.
Published: May 2006

In vivo
, a spirolactone (SC-26304) inhibited the effects of aldosterone on urinary K
+
:Na
+
ratios and the binding of [
3
H]aldosterone to renal cytoplasmic and nuclear receptors. Cytoplasmic binding of [
3
H]aldosterone and [
3
H]spirolactone (SC-26304) was similar in magnitude and involved the same set of sites. Under three sets of conditions—(
i
) in the intact rat, (
ii
) in kidney slices, and (
iii
) in reconstitution studies (mixing prelabeled cytoplasm with either purified renal nuclei or chromatin), [
3
H]spirolactone (SC-26304) did not yield specific nuclear complexes in contrast to the reproducible generation of these complexes with [
3
H]aldosterone. In glycerol density gradients, cytoplasmic [
3
H]aldosterone receptor complexes sedimented at 8.5 S and 4 S in low concentrations of salt and at 4.5 S in high concentrations of salt. Cytoplasmic [
3
H]spirolactone (SC-26304) receptor complexes sedimented at 3 S in low concentrations of salt and 4 S in high concentrations of salt. These results are discussed in terms of an allosteric model of the receptor system.
Cyclic 3′:5′-Adenosine Monosphate in
Escherichia coli
during Transient and Catabolite Repression
Authors: Wayne Peter K. , Rosen O. M.
Published: May 2006

Cyclic AMP concentrations were low for an adenylate cyclase-deficient mutant (
cya
-
) and abnormally high for a catabolite receptor protein-deficient mutant (
crp
-
). A fall in cellular cAMP concentration was always found when cells were subjected to transient repression. No consistent correlations were observed between catabolite repression and cellular cAMP levels.
Induction of T-Cell Differentiation
In Vitro
by Thymin, a Purified Polypeptide Hormone of the Thymus
Authors: Basch Ross S. , Goldstein Gideon
Published: May 2006

Thymin, a purified polypeptide isolated from bovine thymus, was shown to induce the expression of differentiation antigens characteristic of thymocytes [TL and Thy-1 (θ)] when incubated
in vitro
with mouse bone marrow or spleen cells. This induction occurred in 5-10% of the cells from bone marrow after a 2-hr incubation with subnanogram concentrations of thymin. The induced cells expressed more TL and Thy-1 (θ) antigens than average normal thymocytes.
Reconstitution of a Chemically Excitable Membrane
Authors: Hazelbauer Gerald L. , Changeux Jean-Pierre
Published: May 2006

Membrane fragments rich in cholinergic (nicotinic) receptor sites, purified from homogenates of
Torpedo marmorata
electric organ, are dissolved in high concentrations of Na cholate and Tris buffer in the presence of Na ethylenediaminetetraacetate, without loss of the ability to bind
Naja nigricollis
[
3
H]α-toxin. After extensive dialysis to remove cholate, the solution is supplemented with crude lipids extracted from native membrane fragments and MgCl
2
-CaCl
2
added dropwise to the mixture as a concentrated solution. The reconstituted membranes obtained retain
22
Na
+
. Release of Na from these microsacs increases in the presence of carbamylcholine and the α-toxin from
N. nigricollis
blocks this effect.
A Molecular Model of High Density Lipoproteins
Authors: Assmann Gerd , Brewer H. Bryan
Published: May 2006

Based on the analysis of recombined lipidapoprotein complexes by C-13 and P-31 nuclear magnetic resonance spectroscopy and circular dichroism [Assmann, G., Sokoloski, E. A. & Brewer, H. B., Jr. (1974)
Proc. Nat. Acad. Sci. USA
71, 549-553; Assmann, G., Highet, R. J., Sokoloski, E. A. & Brewer, H. B., Jr. (1974)
Proc. Nat. Acad. Sci. USA
71, in press; Assmann, G. & Brewer, H. B., Jr. (1974)
Proc. Nat. Acad. Sci. USA
71, 989-993] and the identification of conformational amphipathic regions in apoproteins, a new model for human high density lipoproteins is proposed. This model is analogous to membrane models proposed by Singer, in that protein “icebergs” are embedded in a “sea” of lipid.
Quantitative Analysis of Mass and Energy Balance in Non-Ideal Models of the Renal Counterflow System
Authors: Stephenson John L. , Tewarson R. P. , Mejia Raymond
Published: May 2006

A modified Newton-Raphson method for solving finite difference equations for the renal counterflow system is described. The method has proved generally stable and efficient, and has given significant computational results for a variety of models: calculations on single solute models of the coupled vasa recta nephron counterflow system have shown that for large water and solute permeabilities of the exchanging membranes, behavior of the non-ideal system approaches that of the previously described ideal central core model. Concentration by salt and urea mixing in two solute models has been analyzed and previous conclusions from central core models have been found to remain valid in non-ideal systems. The numerical solutions have set some order of magnitude bounds on permeability requirements for concentration in different types of non-ideal systems. Finally, from the detailed concentration profiles it has been possible to relate the rate of free energy creation and dissipation from transmembrane transport of solutes and water to the net rate of free energy efflux from the counterflow system, and so to compute in a given model the fraction of power used for solute concentration.
Cytoplasmic Inheritance of Chloramphenicol Resistance in Mouse Tissue Culture Cells
Authors: Bunn C. L. , Wallace Douglas C. , Eisenstadt J. M.
Published: May 2006

A chloramphenicol-resistant mutant, isolated from mouse A9 cells, was enucleated and fused with a nucleated chloramphenicol-sensitive mouse cell line. Resultant fusion products, cytoplasmic hybrids (or “cybrids”), were selected as resistant to chloramphenicol, and had the nuclear markers and chromosome complement of the chloramphenicol-sensitive parent. These cybrids appeared at the high frequency of 2-8 per 10
4
cells plated. Neither parent produced any colonies when plated under identical selective conditions. Fusion between enucleated chloramphenicol-sensitive cell fragments and the chloramphenicol-sensitive cell produced no resistant colonies, suggesting that chloramphenicol resistance is not due to an increase in the ratio of cytoplasm to nucleus. Furthermore, fusions between resistant and sensitive nucleated cells produced resistant hybrids at a frequency 100 times less than that of resistant cybrids. Thus, these stable chloramphenicol-resistant cybrids result from the fusion of a chloramphenicol-resistant cytoplasm with a chloramphenicol-sensitive cell. It is proposed, therefore, that chloramphenicol resistance is a cytoplasmically inherited characteristic in this mouse cell line.
Widespread Natural Occurrence of High Titers of Neutralizing Antibodies to a Specific Class of Endogenous Mouse Type-C Virus
Authors: Aaronson Stuart A. , Stephenson John R.
Published: May 2006

Mouse cells contain several biologically distinguishable endogenous type-C viruses. In the present studies, the immunologic response of different strains of mice to the natural expression of these viruses has been examined. High titers of neutralizing antibodies have been detected to a class of virus that lacks the ability to exogenously infect mouse cells. The expression of this virus,
in vivo
as well as
in vitro
, is shown to be vertically transmitted as a dominant genetic trait. The findings indicate the widespread occurrence of this endogenous virus and the ability of the mouse to immunologically respond to a class of type-C virus whose mode of transmission is similar to that of cellular genes.
Spontaneous Induction of Endogenous Murine Leukemia Virus-Related Antigen Expression During Short-Term
In Vitro
Incubation of Mouse Lymphocytes
Authors: Lonai Peter , Declève Alain , Kaplan Henry S.
Published: May 2006

Short-term lymphocyte cultures from mouse thymus, spleen, or lymph nodes were studied for the presence of murine leukemia virus group-specific antigens with an immunofluorescence test using rat immune sera against syngeneic cells infected with the radiation leukemia virus or its pseudotype of murine sarcoma virus and goat and rabbit antisera against purified murine leukemia virus group-specific antigen. Antigens reacting with these sera appeared in the cultured lymphocytes within 24 hr, and the proportion of immunofluorescent-positive cells increased to 25-80% by the second or third day of cultivation, concomitantly with a decrease in cell viability. The appearance of these antigens can be suppressed by inhibitors of DNA (mitomycin-C), RNA (actinomycin-D, cordycepin, and polyadenylic acid), and protein (cycloheximide) synthesis. No infectious virus could be detected by the immunofluorescence and XC-cell tests. The observed phenomenon appears to represent the spontaneous partial derepression of endogenous murine leukemia virus replication in lymphocytes during short-term
in vitro
cultivation.
Immunological Identity of the Small Subunit of HL-A Antigens and β
2
-Microglobulin and Its Turnover on the Cell Membrane
Authors: Cresswell Peter , Springer Timothy , Strominger Jack L. , Turner Mervyn J. , Grey Howard M. , Kubo Ralph T.
Published: May 2006

A number of immunological methods have been employed to show that the small subunit of HL-A antigens, isolated either after papain treatment or after solubilization with detergent, is identical to β
2
-microglobulin, a protein previously isolated from human urine and shown to be homologous in structure to constant region domains of immunoglobulins. Moreover, quantitative data indicate virtually total identity between the small subunit of HL-A antigens and β
2
-microglobulin. Studies of the turnover of labeled HL-A antigens from the lymphocyte surface indicate that the two subunits turn over at similar rates, although only the small subunit could be detected in the culture medium. The significance of these observations is discussed.
Carbon-13 Relaxation and Proton Nuclear Magnetic Resonance Studies of Prostaglandin F
2α
Authors: Conover Woodrow W. , Fried Josef
Published: May 2006

Carbon magnetic resonance T
1
relaxation and chemical shift measurements at 22.63 MHz establish hydrophobic aggregation of prostaglandin F
2α
in phosphate buffer solutions between 0.05 and 0.2 M. Analysis of the proton magnetic resonance spectra of prostaglandin F
2α
at 270 MHz by double resonance techniques yield all the proton-proton coupling constants for the five-membered ring indicating a favored half-chair conformation for the ring in which the dihedral angle for the C-8 and C-12 protons is close to 180°. Effective correlation times derived from carbon magnetic resonance T
1
values for all the carbon atoms show segmental motion for ring carbon C-10 and in the aliphatic portions of both side chains, while the double bonded portions of the side chains and the ring carbons act as a more rigidly interconnected network. Chemical shift changes in the carbon magnetic resonance and proton magnetic resonance spectra upon aggregation suggest that the 5-6 double bond, C-7, and C-9 participate in the aggregation process.
Correlation Between Deoxyribonucleic Acid Excision-Repair and Life-Span in a Number of Mammalian Species
Authors: Hart R. W. , Setlow R. B.
Published: May 2006

The ability of fibroblasts to perform unscheduled DNA synthesis (a measure of excision-repair) after UV irradiation was measured radioautographically for seven species at several times after several UV fluences. Both the initial rate and the maximum incorporation of [
3
H]dThd increased with the life-span of the species (shrew, mouse, rat, hamster, cow, elephant, man). Unscheduled DNA synthesis was approximately proportional to the logarithm of life-span.
Replication of Colicin E1 Plasmid DNA in Minicells from a Unique Replication Initiation Site
Authors: Inselburg Joseph
Published: May 2006

Replicating DNA molecules of the colicin E1 plasmid isolated from minicells are cleaved at a single site by R1 restriction endonuclease (
Eco
R1). Electron microscopic measurements of the replicating molecules treated with the endonuclease indicate that (
a
) replication is initiated at a site between 14% and 20% of the distance from the
Eco
R1 endonuclease cleavage site; and (
b
) extensive replication of most molecules occurs in one direction from the initiation site, although a limited amount of replication in the opposite direction may occur. Single-stranded regions at one or both replication forks, involving one or both DNA strands, can be frequently found in replicating molecules.
In Vitro
Repair of Apurinic Sites in DNA
Authors: Verly W. G. , Gossard F. , Crine P.
Published: May 2006

Apurinic sites disappear from DNA during an incubation of the DNA with the
Escherichia coli
endonuclease specific for apurinic sites, DNA polymerase I (EC 2.7.7.7.), and T4 ligase (EC 6.5.1.1). Omission of any one of these three enzymes and, in particular, omission of the endonuclease specific for apurinic sites prevents this
in vitro
repair.
Separation of Specific Initiation Factors Involved in the Translation of Myosin and Myoglobin Messenger RNAs and the Isolation of a New RNA Involved in Translation
Authors: Heywood Stuart M. , Kennedy Doris S. , Bester Andre J.
Published: May 2006

Two messenger specific factors, phosphocellulose fractions 3 and 4, have been isolated from the initiation factor 3 fraction of red muscle initiation factors by chromatography on phosphocellulose. When added to a reticulocyte cell-free system containing both myoglobin and myosin mRNAs, phosphocellulose fraction 3 is found to specifically stimulate the synthesis of myoglobin while phosphocellulose fraction 4 is found to specifically stimulate the synthesis of myosin. In addition, a new RNA, isolated from the initiation factor 3 fraction, is shown to specifically inhibit the translation of heterologous mRNAs.
Glutathione Synthetase Deficiency, an Inborn Error of Metabolism Involving the γ-Glutamyl Cycle in Patients with 5-Oxoprolinuria (Pyroglutamic Aciduria)
Authors: Wellner Vaira P. , Sekura Ronald , Meister Alton , Larsson Agne
Published: May 2006

Enzyme studies on placenta, cultured skin fibroblasts, and erythrocytes from two sisters with the inborn error 5-oxoprolinuria (pyroglutamic aciduria) indicate that the metabolic lesion in this disease is at the glutathione synthetase (EC 6.3.2.3) step of the γ-glutamyl cycle. Excessive urinary excretion of 5-oxoproline by these patients appears to be associated with increased synthesis of γ-glutamyl-cysteine and formation of 5-oxoproline from this dipeptide. Thus, 5-oxoproline is produced in amounts that exceed the normal capacity of 5-oxoprolinase to convert it to glutamate. The data indicate that it may be possible to identify individuals who are heterozygous for this trait by determinations of erythrocyte glutathione synthetase.