bluuebunny/crossref_metadata_2025 huggingface dataset:
Mouse Immunoglobulin Heavy Chains Are Coded by Multiple Germ Line Variable Region Genes
Authors: Barstad P. , Farnsworth V. , Weigert M. , Cohn M. , Hood L.
Published: May 2006

The N-terminal 20 residues of 13 heavy immunoglobulin chains from myeloma protein of the BALB/c mouse are compared with the same residues of 15 other heavy chains described in the literature. Sixteen of 28 sequences are different from one another. These proteins fall into four major sets, with 18 of the proteins in the largest set being further divisible into at least five subsets. This pattern of diversity suggests there are at least eight germ line genes coding for the variable regions of mouse heavy chain. Many of the immunoglobulins from which these heavy chains are derived exhibit binding activity for various haptens. The differing hapten specificities are closely correlated with distinct primary amino-acid sequences.
Cell-free Synthesis of a Specific Lipoprotein of the
Escherichia coli
Outer Membrane Directed by Purified Messenger RNA
Authors: Hirashima Akikazu , Wang Sansan , Inouye Masayori
Published: May 2006

A specific lipoprotein of the
E. coli
outer membrane has been synthesized in a cell-free system directed by purified messenger RNA. The mRNA for the lipoprotein was purified as 7S RNA about 250-fold from exponentially growing cells. Protein synthesis of the cell-free system was totally dependent upon the addition of the purified mRNA. The product of the cell-free system was identified as the specific lipoprotein by immunoprecipitation and by peptide mapping.
An Inhibitor of Cell Proliferation Released by Cultures of Macrophages
Authors: Calderon Jesus , Williams Richard T. , Unanue Emil R.
Published: May 2006

Culture fluids from mouse peritoneal exudate cells inhibited [
3
H]thymidine incorporation by, and proliferation of, EL-4 leukemia cells, 3T3 cells, and mitogen-stimulated spleen lymphocytes. Inhibited EL-4 leukemia cells recovered their normal proliferative capacity when washed and incubated in normal medium. The inhibitory activity resided in a low-molecular-weight substance that could be absorbed by incubation with the tumor cells. This substance was dialyzable and resistant to tryptic digestion and phosphodiesterase treatment. The mononuclear phagocytes in the peritoneal exudate seemed to be the source of the inhibitor. The inhibitory material was found in the same amounts in exudates of normal mice or mice injected with peptone or infected with
Listeria monocytogenes
; spleen cells adherent to plastic released the inhibitor but in lesser amount. We suggest that this inhibitor may contribute to the deleterious effects found when various cells, including neoplastic ones, are cultured in the presence of macrophages.
Regulation of Herpesvirus Macromolecular Synthesis: Nuclear Retention of Nontranslated Viral RNA Sequences
Authors: Kozak M. , Roizman B.
Published: May 2006

We report two instances of selective accumulation of herpes simplex 1 RNA transcripts in different compartments of infected HEp-2 cells. In the first, transcripts derived from about 50% of the viral DNA accumulated in the nuclei of cells 8 hr after infection. However, only 40-42% of the DNA was represented in transcripts accumulating in both cytoplasm and polyribosomes. A more striking disparity in the distribution of transcripts between nuclei and cytoplasm occurred when viral infection was initiated and maintained for several hours in the absence of protein synthesis. RNA complementary to about 50% of the viral DNA accumulated in the nuclei, while transcripts derived from only about 10% of the DNA were detectable in the cytoplasm. The transcripts that were selectively transported in the presence of cycloheximide seem to be functional messenger RNA molecules, since they were found on polysomes immediately after cycloheximide reversal. In contrast, RNA retained in the nuclei during the period of cycloheximide treatment was not mobilized when protein synthesis subsequently resumed.

The two instances of selective RNA transport observed during herpesvirus infection suggest that only viral transcripts competent to function in translation are exported from the nucleus.
Amino-Acid Sequence of NADP-Specific Glutamate Dehydrogenase of
Neurospora crassa
Authors: Wootton John C. , Chambers Geoffrey K. , Holder Anthony A. , Baron Andrew J. , Taylor John G. , Fincham John R. S. , Blumenthal Kenneth M. , Moon Kenneth , Smith Emil L.
Published: May 2006

A tentative primary structure of the NADP-specific glutamate dehydrogenase [L-glutamate: NADP oxidoreductase (deaminating), EC 1.4.1.4] from
Neurospora crassa
has been determined. The proposed sequence contains 452 amino-acid residues in each of the identical subunits of the hexameric enzyme. Comparison of the sequence with that of the bovine liver enzyme reveals considerable homology in the amino-terminal portion of the chain, including the vicinity of the reactive lysine, with only shorter stretches of homology within the carboxyl-terminal regions. The significance of this distribution of homologous regions is discussed.
A Novel Form of RNA Polymerase from
Escherichia coli
Authors: Wickner William , Kornberg Arthur
Published: May 2006

A new form of RNA polymerase, termed RNA polymerase III, has been recognized as a large fraction of the rifampicin-sensitive enzyme in
E. coli
. It is physically separable from RNA polymerase (holoenzyme, RNA polymerase I) by gel filtration and is distinguished by its capacity to discriminate between M13 and ϕX174 viral DNA templates in priming DNA synthesis. This template specificity is manifested only with saturating levels of DNA unwinding protein and characterizes the priming of DNA synthesis on viral single strands in cell-free extracts and
in vivo
. RNA polymerase III has less than 5% of the specific activity of RNA polymerase I in transcribing duplex DNA of phages λ and T4, salmon sperm DNA, and the copolymer poly[d(A-T)]. Rifampicin inactivation of RNA polymerase III releases a factor, presumably a small subunit, which can be isolated and used to confer on RNA polymerase I the properties of III, namely, discrimination between M13 and ϕX174 templates in priming DNA synthesis, and a relative inability to transcribe duplex DNA.
Gap Junction Formation Between Reaggregated Novikoff Hepatoma Cells
Authors: Johnson Ross , Hammer Marie , Sheridan Judson , Revel Jean-Paul
Published: May 2006

We have combined freeze-fracture and electrophysiological methods in a study of gap junction formation between reaggregated Novikoff hepatoma cells. Cell clumps are dissociated with EDTA, and the resulting single cells are allowed to reaggregate (5-180 min) in loose pellets in the presence of calcium at 37°. The earliest electron microscopic evidence for the genesis of new junctions is the appearance of flattened regions of the plasma membrane with a relative paucity of small intramembranous particles. These regions contain instead loosely organized groupings of 9- to 11-nm intramembranous particles, which are seen on the A face of the fractured plasma membrane, while corresponding pits occur on the membrane B face. We have termed the specialized membrane regions “formation plaques.” They are seen as early as 5 min after reaggregation and are quite numerous by 30 min. Larger plaques are observed at later times. Plaques seen at 30 min are consistently matched with other plaques on apposed cells, although the extracellular space separating these structures still exceeds 10 nm. By 60 min, some matched plaques display a reduced extracellular space, resembling that of normal gap junctions. Between 30 and 60 min, aggregates of closely packed particles on A faces and hexagonally arranged pits on B faces frequently appear in the formation plaques. The aggregates, which are indistinguishable from small gap junctions, appear to enlarge over the subsequent 2-hr period as the number of unaggregated 9- to 11-nm particles declines. Microelectrode studies demonstrate progressive increases in the percent of interfaces containing lowresistance junctions and in the degree of elctrical coupling in preparations incubated up to 2 hr. Coupling is first detected at about the same time as particle aggregates (or formation plaques with reduced extracellular spaces), and increases as aggregate sizes increase.
Direct Evidence for Fluid Membranes
Authors: Tamm Sidney L. , Tamm Signhild
Published: May 2006

We describe a new kind of cell motility that provides direct, visual evidence for the fluid nature of cell membranes. The movement involves continual, unidirectional rotation of one part of a devescovinid flagellate in relation to a neighboring part, at speeds up to one rotation/1.5 sec (room temperature). Rotation includes the plasma membrane, using the flagellar bases and ectosymbiotic bacteria embedded in pockets of the membrane as visible markers. The plasma membrane between the rotating and stationary surfaces is continuous, without fusions with other membranes, and has the typical trilaminar structure of other cell membranes. The nucleus, helical Golgi complex, and stiff central axostyle also rotate. The head of the flagellate always rotates clockwise (as viewed from the anterior end) in relation to the body, but when the head becomes stuck to debris, the body rotates counterclockwise. Evidence suggests that the microtubular axostyle generates the motive force for rotation.
Latent DNA of Epstein-Barr Virus: Separation from High-Molecular-Weight Cell DNA in a Neutral Glycerol Gradient
Authors: Tanaka Akiko , Nonoyama Meihan
Published: May 2006

Epstein-Barr virus DNA in virus non-productive cells was separated from high-molecular-weight cell DNA by sedimentation through a neutral glycerol gradient after gentle lysis of cells by Pronase and Sarkosyl. The isolated Epstein-Barr virus DNA had a density of 1.716-1.717 g/cm
3
in CsCl equilibrium centrifugation, which is very close to the virus DNA density of 1.718 g/cm
3
. The results indicated that the majority of Epstein-Barr virus DNA in virus nonproductive cells is not covalently integrated into high-molecular-weight cell DNA.
Effect of Alkylureas on the Polymerization of Hemoglobin S
Authors: Elbaum Danek , Nagel Ronald L. , Bookchin Robert M. , Herskovits Theodore T.
Published: May 2006

Alkylureas (methyl-, ethyl-, propyl-, and butyl-) can inhibit both the gelation of deoxyhemoglobin S and red cell sickling without denaturation of the hemoglobin or intrinsic alteration of its oxygen affinity. This effect is directly proportional to the length of the alkyl chain and substantiates the importance of hydrophobic interactions in the polymerization of hemoglobin S. In addition, it opens the possibility that further systematic investigations with these compounds will help quantitate the role of hydrophobic interactions in this system so as to further our understanding of the polymerization of deoxyhemoglobin S.
Isolation of a Viral Polypeptide Associated with Poliovirus RNA Polymerase
Authors: Lundquist R. E. , Ehrenfeld E. , Maizel J. V.
Published: May 2006

Poliovirus-infected HeLa cells were labeled with radioactive methionine or phenylalanine and subjected to a new purification procedure for the viral induced RNA polymerase activity. Detergent-solubilized polymerase activity was purified by precipitation with 2 M LiCl and sedimentation through sucrose gradients. Approximately 0.001% of the incorporated amino acid radio-activity sediments with the peak of polymerase activity. Gradient fractions comprising the polymerase activity peak were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and found to contain predominantly one virus-specific polypeptide. Polyacrylamide gel electrophoresis also reveals that this purified polypeptide migrates with a 58,000 molecular weight noncapsid polio-virus polypeptide.
The Effects of Increased Temperature on Electroretinograms of Temperature-Sensitive Paralysis Mutants of
Drosophila melanogaster
Authors: Kelly Leonard E. , Suzuki D. T.
Published: May 2006

Mutations within the
shibire
locus of
Drosophila melanogaster
are non-complementing alleles which result in reversible paralysis at 29° but retention of normal locomotor behavior at 22°.

Electroretinograms of six of the mutants have been recorded at various temperatures. Two changes occurred in the electroretinograms of flies carrying most of the alleles at high temperature: they lost the “on”- and “off”- transients of the normal electroretinogram, and the fast decay of the receptor potential was attenuated. For flies with four of the alleles, a base-line oscillation was also observed.

Analysis of electroretinograms of mosaic
shibire
flies indicates that the loss of the transients can be attributed to both a pre-synaptic and a post-synaptic effect.
An “External” RNA Removable from Mammalian Cells by Mild Proteolysis
Authors: Rieber Manuel , Bacalao Josefina
Published: May 2006

Brief exposure of Chinese hamster ovary cell monolayers prelabeled with [
32
P]phosphate and [
3
H]leucine to 1 μg/ml of trypsin under conditions in which cells remain fully viable causes the release of macromolecular
32
P and
3
H. Whereas ribonuclease treatment was found to affect markedly both the
32
P and
3
H radioactivity, Pronase treatment had little effect on the macromolecular
32
P. Treatment of cells prelabeled with [
3
H]glucosamine and [
32
P]phosphate with insolubilized papain also revealed a parallel release of macromolecular glucosamine together with ribonuclease-susceptible macromolecular phosphate. Lactoperoxidase-mediated radioiodination of surface components in cells prelabeled with [
32
P]phosphate revealed electrophoretic comigration between the
125
I and the
32
P that are removed from the cells by mild proteolysis. Growth of the cells in Bt
2
cAMP-testosterone altered the kinetics of release and nature of the macromolecular
32
P liberated by proteolysis.
Enzymatic Utilization of
P
1
-Di-
N
-acetylchitobiosyl
P
2
-Dolichyl Pyrophosphate and Its Chemical Synthesis
Authors: Wedgwood Josiah F. , Warren Christopher D. , Jeanloz Roger W. , Strominger Jack L.
Published: May 2006

Fully acetylated chitobiose was treated with phosphoric acid to give a mixture of products from which 2-acetamido-4-
O
-(2-acetamido-3,4,6-tri-
O
-acetyl-2-deoxy-β- D-glucopyranosyl)-3,6-di-
O
-acetyl-2-deoxy-α,β- D-glucopyranosyl phosphate (Ac
3
GlcNAc-Ac
2
GlcNAc-
P
) was isolated by preparative thin layer chromatography. Treatment of this compound with
P
1
-diphenyl
P
2
-dolichyl pyrophosphate gave an acetylated pyrophosphate diester, which was purified chromatographically and deacetylated. The product,
P
1
-di-
N
-acetylchitobiosyl
P
2
-dolichyl pyrophosphate (Dol-
P
-
P
-GlcNAc-GlcNAc), was readily separated from
P
1
-2-acetamido-2-deoxy-α-D-glucopyranosyl
P
2
-dolichyl pyrophosphate (Dol-
P
-
P
-GlcNAc) by thin layer chromatography in several solvent systems. Addition of this compound to human lymphocyte membrane preparations led to the formation of a mannose-containing derivative which appears to be an oligosaccharide phospholipid, as judged by its behavior on DEAE-cellulose chromatography and by its hydrolysis to give an oligosaccharide containing more than four monosaccharide units.
Repression by Hematin of Porphyrin Biosynthesis in Erythrocyte Precursors in Congenital Erythropoietic Porphyria
Authors: Watson C. J. , Bossenmaier I. , Cardinal R. , Petryka Z. J.
Published: May 2006

Hematin administered intravenously in a patient with congenital erythropoietic porphyria evidently entered erythrocyte precursors in the bone marrow, producing the well-known negative feedback repression of porphyrin biosynthesis with marked decline of porphyrin concentrations in urine, circulating plasma, and erythrocytes. A delay in the major segment of this effect corresponded roughly with the sum of the average transit times through the maturation compartments of the erythrocyte precursors. This delay was considerably longer than previously observed in the decline of porphyrin precursors after administration of hematin in patients with hepatic porphyria. The effect of hematin was compared with that of packed erythrocyte transfusions given at regular intervals in the same patient over a period of 2.5 years. In general, administration of hematin results in a reduction of porphyrin formation of the same order of magnitude, but of shorter duration, possibly in relation to the relatively small amounts of hematin infused.
Specific Binding of Cholera Toxin to Isolated Intestinal Microvillous Membranes
Authors: Walker W. Allan , Field Michael , Isselbacher Kurt J.
Published: May 2006

A sucrose density gradient assay was used to demonstrate the specificity and saturation of the binding of [
125
I]cholera toxin to isolated intestinal microvillous membranes from rat small intestine. When the toxin is first complexed to antitoxin and then exposed to intestinal membranes, the binding of cholera toxin is inhibited. To emphasize the physiologic importance of these observations, similar concentrations of [
125
I]cholera toxin were shown to stimulate the accumulation of cyclic AMP in mucosal homogenates and to increase the secretion of fluid into intestinal loops, whereas the same concentrations of toxin mixed with antitoxin had no effect on cyclic AMP accumulation. These studies suggest that cholera toxin attaches to brush border binding sites before exerting its biologic effect and that local intestinal antibody protection against cholera toxin may be due to inhibition of toxin attachment to these binding sites.
Size Distribution and Molecular Polarity of Newly Replicated DNA in
Escherichia coli
Authors: Louarn Jean-Michel , Bird Robert E.
Published: May 2006

Newly synthesized DNA, in
E. coli
lysogenic for the phage λ, was labeled by short pulses of [
3
H]-thymidine, isolated, and separated on the basis of size by alkaline sucrose density gradient centrifugation. The molecular polarity of this DNA was determined by hybridization with each of the separated strands of λ DNA. The results show that, in the 3′ to 5′ direction, replication proceeds by synthesis of short chains that are subsequently joined to long DNA. This is true for both a
polA
+
and a
polA
-
strain. (The
polA
locus codes for DNA polymerase I.) In the 5′ to 3′ direction, replication proceeds continuously, by addition of nucleotides to long DNA, for the
polA
+
strain. In the
polA
-
strain, however, replication in the 5′ to 3′ direction is also discontinuous, but the discontinuities are 1-40 times less frequent than in the other direction.
Actin in the Green Alga,
Nitella
Authors: Palevitz Barry A. , Ash John F. , Hepler Peter K.
Published: May 2006

Bundles of microfilaments very similar in appearance to actin are present in cytoplasmic suspensions obtained from
Nitella flexilis
. The microfilaments bind rabbit heavy meromyosin in arrowhead arrays similar to those produced on muscle actin. The arrowheads are removed with ATP. The results provide evidence that actin is present in green plants, probably in the form of microfilaments thought to be involved in cytoplasmic streaming.
Transfer RNA Biosynthesis: The Nucleotide Sequence of a Precursor to Serine and Proline Transfer RNAs
Authors: Barrell B. G. , Seidman J. G. , Guthrie Christine , McClain William H.
Published: May 2006

The nucleotide sequence of a transfer RNA precursor molecule coded by bacteriophage T4 has been determined. The molecule is a single polynucleotide chain which contains two transfer RNA species that are destined to recognize serine and proline. The 3′ -CCA
OH
termini of both mature transfer RNA species are absent in the precursor molecule; these termini must therefore be added enzymatically at a subsequent stage of maturation. Nucleotide residues unique to the precursor are located at both ends of the molecule and between the two transfer RNA sequences.
Effect of 5-Bromodeoxyuridine on Chromatin Transcription in Confluent Fibroblasts
Authors: Hill Bridget T. , Tsuboi Atsushi , Baserga Renato
Published: May 2006

3T6 mouse fibroblasts were grown in 5-bromodeoxyuridine (BrdU) so that approximately 20% of the thymine residues in DNA were replaced by BrdU. BrdU replacement caused an alteration in the relative incorporation of labeled nucleotide precursors into RNA. The RNA synthesized by cells grown in BrdU has a lower proportion of adenine and a higher guanine complement. This was shown for (
a
) nascent RNA made
in vivo
by confluent monolayers of cells in culture; (
b
) RNA synthesized
in vitro
on a chromatin template with either homologous or heterologous RNA polymerase; and (
c
) RNA synthesized
in vitro
on a DNA template with a highly purified RNA polymerase. The product was completely digested by RNase. The relative decrease in the incorporation of adenine into RNA was reserved when BrdU-treated cells were allowed to proliferate in BrdU-free medium.
Interaction of Mycoplasmas with Cell Cultures, as Visualized by Electron Microscopy
Authors: Brown Susan , Teplitz Marlyn , Revel Jean-Paul
Published: May 2006

Mycoplasmas were examined on the surfaces of tissue culture cells prepared for transmission and scanning electron microscopy. The pleomorphic bodies seen were proved to be mycoplasmas by the use of thin sections, passage of the infection from one cell line to another, and by autoradiography with [
3
H]thymidine both on the sections and the replicas. The mycoplasmas were not always evenly distributed over the cell's surface; their arrangement seemed to correlate with the activity or morphology of the cell. The use of replicas and scanning electron microscopy in routine examination of cultures for mycoplasma contamination is discussed.
The Effect of Light on Fruiting Body Formation and Adenosine 3′:5′-Cyclic Monophosphate Metabolism in
Coprinus macrorhizus
Authors: Uno Isao , Yamaguchi Mitsuyo , Ishikawa Tatsuo
Published: May 2006

The monokaryotic mycelia of a mutant strain,
fis
c
, of
Coprinus macrorhizus
, which are able to form monokaryotic fruiting bodies in the light, failed to form any fruiting bodies in darkness. A dikaryon and a mutant strain,
ds
, formed malformed fruiting bodies in darkness. Illumination for 1 day of
fis
c
mycelia grown in darkness for 4 days or longer was effective in inducing malformed fruiting bodies. The accumulation of adenosine 3′:5′-cyclic monophosphate in the illuminated mycelia of strain
fis
c
was demonstrated. The illuminated mycelia of strain
fis
c
produced high levels of adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] and phosphodiesterase (3′:5′-cyclic-AMP 5′-nucleotidohydrolase, EC 3.1.4.17), which degrades cAMP, while the dark-grown mycelia showed no or very low activities of these enzymes. Dikaryotic mycelia and monokaryotic mycelia of strain
ds
produced significant amounts of these enzymes even in darkness. When the dark-grown mycelia of strain
fis
c
were exposed to continuous light, the activities of adenylate cyclase and phosphodiesterase increased rapidly after a lag period whose length depends on the culture age of mycelia. Cycloheximide inhibited the increase in these enzyme activities stimulated by light. When the
fis
c
mycelia were exposed to continuous light, an increase in cAMP-binding activity was observed. A possible participation of cAMP in the formation of fruiting bodies in
C. macrorhizus
is discussed.
Quasilinkage Equilibrium and the Evolution of Two-Locus Systems
Authors: Nagylaki Thomas
Published: May 2006

In terms of intrinsic variables of the system, short, intermediate, transitional, and long (or asymptotic) times are defined for the evolution of a two-locus model with linkage and epistasis. It is argued that, during the first two and last periods, all quantities of genetic interest, such as the gametic frequencies, the mean fitness, the linkage disequilibrium, and the linkage disequilibrium ratio,
Z
, change with time in essentially the same manner, characteristic of the particular epoch concerned and determined in this paper, and therefore, when quasilinkage equilibrium occurs, it is a transitional phenomenon. Both continuous random births and deaths and discrete, nonoverlapping generations are considered.
The
lac
Repressor Protein: Molecular Shape, Subunit Structure, and Proposed Model for Operator Interaction Based on Structural Studies of Microcrystals
Authors: Steitz Thomas A. , Richmond Timothy J. , Wise David , Engelman Donald
Published: May 2006

Electron microscopic and powder x-ray diffraction studies of small crystals of the
lac
repressor protein provide evidence on its molecular shape and subunit structure which in turn suggests a possible mode of repressor—operator interaction. The crystals are probably orthorhombic space group P222
1
with unit cell dimensions of
a
= 140,
b
= 91,
c
= 117 Å. This tetrameric protein appears rather asymmetric, having approximate molecular dimensions of 140 Å by 60 Å by 45 Å. The dumbbell shape of the projected molecular outline observed in the electron micrographs can be explained by assuming that the subunits are related by 222 symmetry and are placed at the corners of a plane rectangle. We propose a model for repressor—operator interaction in which the DNA binds to the repressor with its long axis aligned with that of the repressor and with its 2-fold axis coincident with a twofold axis of the repressor.
Membrane Molecules Determined by the
H-2
Associated Immune Response Region: Isolation and Some Properties
Authors: Cullen S. E. , David C. S. , Shreffler D. C. , Nathenson S. G.
Published: May 2006

Membrane associated molecules that are probably glycoproteins could be specifically precipitated from NP-40 detergent solubilized extracts of radiolabeled mouse spleen or lymph node cells by antisera produced in congenic strain combinations differing only in the
Ir
gene region which is linked to the
H-2
genes. These
Ir
region products were designated Lna (lymph node antigen) to conform to previous serological work.

Sodium dodecyl sulfate—polyacrylamide gel electrophoresis of unreduced specific immune precipitates revealed the presence of a possible dimer form, while reduced samples showed only a single peak equivalent to 30,000 daltons. Thus the Lna molecules are clearly distinct from the
H-2D
and
H-2K
molecules, which are about 45,000 daltons. Anti-Lna antibodies of different specificity can be present in a single serum; there were at least two separate antigen molecules present in one haplotype tested.
Mechanism of IgM Polymerization
Authors: Chapuis Rose Marie , Koshland Marian Elliott
Published: May 2006

The stoichiometry of J chain in pentamer IgM has been determined by measuring the radiolabeled thiols in the constituent chains after complete reduction and alkylation of the polymer. One mole of J was found to be disulfide bonded to 1 mol of pentamer. The linkage of J chain in IgM has been determined by correlating the J disulfides cleaved with the subunits released after limited reduction and alkylation of the polymer. The analyses showed that: (
a
) Significant amounts of monomers, as well as small quantities of dimers, trimers, and tetramers, were generated by the reducing conditions employed. (
b
) The number of J disulfide bonds broken did not correspond to the extent of depolymerization. (
c
) No J disulfides were cleaved in the J-containing dimer products of the limited reduction. These data demonstrated that the J chain is located as a disulfide clasp between two of the IgM monomer subunits. From the observed linkage, the assembly of IgM is postulated to proceed by a series of sequential disulfide exchanges beginning with the formation of the J-containing dimer.
A Variant of Special Relativity and Long-Distance Astronomy
Authors: Segal I. E.
Published: May 2006

The redshift, microwave background, and other observable astronomical features are deduced from two theoretical assumptions: (
1
) global space-time is a certain variant of Minkowski space, locally indistinguishable in causality and covariance features but globally admitting the full conformal group as symmetries although having a spherical space component; (
2
) the true energy operator corresponds to a certain generator of this group which is not globally scale-covariant, whereas laboratory frequency measurements are inevitably such and correspond to the conventional energy operator [unk]/
i
[unk]/[unk]
t
.
Familial hypercholesterolemia: Defective binding of lipoproteins to cultured fibroblasts associated with impaired regulation of 3-hydroxy-3-methylglutaryl coenzyme a reductase activity
Authors: Brown Michael S. , Goldstein Joseph L.
Published: May 2006

Monolayers of cultured fibroblasts from normal human subjects bind
125
I-labeled low-density lipoproteins with high affinity and specificity. High affinity binding of similar magnitude was not observed in cells from five unrelated subjects with the homozygous form of familial hypercholesterolemia. In normal cells incubated at 37°, the binding sites were saturated at a low-density lipoprotein concentration of 20
μ
g/ml. A maximum of approximately 250,000 molecules could be bound to each cell. Whole serum and very-low-density lipoproteins displaced
125
I-labeled low-density lipoproteins from the binding sites, but high-density lipoproteins, the lipoprotein-deficient fraction of serum, and abetalipoproteinemic serum did not. This binding appears to be a required step in the process by which low-density lipoproteins normally suppress the synthesis of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-controlling enzyme in cholesterol biosynthesis. The demonstration of a defect in binding of low-density lipoproteins to cells from subjects with the homozygous form of familial hypercholesterolemia appears to explain the previously reported failure of lipoproteins to suppress the synthesis of this enzyme and hence may account for the overproduction of cholesterol that occurs in these cultured cells.
Complementation Studies of Lethal Alleles in the Mouse Causing Deficiencies of Glucose-6-Phosphatase, Tyrosine Aminotransferase, and Serine Dehydratase
Authors: Gluecksohn-Waelsch Salome , Schiffman Michael B. , Thorndike Janet , Cori Carl F.
Published: May 2006

The pleiotropic effects of six radiation-induced lethal alleles at the albino locus in the mouse include deficiencies of various enzymes and of serum proteins. Closely correlated with the biochemical deficiencies are severe ultrastructural abnormalities of endoplasmic reticulum membranes and the Golgi apparatus in liver and kidney cells. Complementation studies led to the distinction of four different complementation groups among the six lethal alleles. The results are compatible with the interpretation that the six lethal alleles represent overlapping deletions of various sizes at and around the albino locus in the mouse, in a region concerned with the control of biochemical and structural differentiation.
Variable Region Sequences of Five Human Immunoglobulin Heavy Chains of the V
H
III Subgroup: Definitive Identification of Four Heavy Chain Hypervariable Regions
Authors: Capra J. Donald , Kehoe J. Michael
Published: May 2006

The variable regions of five human immunoglobulin heavy chains of the V
H
III subgroup have been totally sequenced. Three of the heavy chains belonged to the IgG class and two to the IgA class. Examination of these sequences, and comparison with additional published heavy chain sequences, showed that a total of
four
hypervariable regions is characteristic of human heavy chain variable regions.

The relatively conserved character of large segments of the heavy chain variable region was very evident in these studies. The conserved segments, which are those sections located outside the hypervariable regions, comprise approximately 65% of the total heavy chain variable region. The following general structural pattern for antibody molecules emerges from this and related studies: an overall combining region superstructure is provided by the more conserved segments while the refinements of the active site specificity are a function of hypervariable regions.
Galactosyltransferase and Concanavalin A Agglutination of Cells
Authors: Podolsky Daniel K. , Weiser Milton M. , Mont J. Thomas La , Isselbacher Kurt J.
Published: May 2006

A correlation has been observed between concanavalin A agglutination of various cell types and the presence of surface membrane galactosyltransferase (1-
O
-α-D-Galactosyl-
myo
-inositol:raffinose galactosyltransferase, EC 2.4.1.67) activity. Moreover, a reduction to less than 50% of cell surface galactosyltransferase activity occurred after treatment with concanavalin A; other cell surface glycosyltransferase enzyme activities examined were unaffected by concanavalin A treatment. To confirm the participation of cell surface galactosyltransferase in concanavalin A-induced cell agglutination, the enzyme from rabbit erythrocytes was solubilized by sonication and purified by preparative polyacrylamide gel electrophoresis. It was possible to achieve a purified preparation of rabbit erythrocyte galactosyltransferase by separation on concanavalin A-Sepharose. The purified enzyme showed visible immunoprecipitation (Ouchterlony) with concanavalin A. Furthermore, human erythrocytes, which are not normally agglutinated by concanavalin A, became agglutinable by the lectin when the erythrocytes were preincubated with purified galactosyltransferase. These experiments suggest a direct and possible specific role of cell surface galactosyltransferase enzyme in the mechanism of concanavalin A agglutination of cells.
Aspartate Transcarbamoylase Molecules Lacking One Regulatory Subunit
Authors: Yang Y. R. , Syvanen J. M. , Nagel G. M. , Schachman H. K.
Published: May 2006

Reconstitution of aspartate transcarbamoylase (EC 2.1.3.2) from dilute solutions of the isolated regulatory and catalytic subunits, with the latter in large excess, led to the formation of appreciable amounts of a second, stable component in addition to the reconstituted enzyme. The purified component, designated r
4
c
6
, was found to have a molecular weight about 3 × 10
4
less than that of the native enzyme, and it combined with isolated regulatory subunit to form aspartate transcarbamoylase. It also combined with
one
succinylated regulatory subunit to form a hybrid species that was identified electrophoretically. These findings indicate that r
4
c
6
differs from the native enzyme in that only two (rather than three) regulatory subunits participate in “crosslinking” the two catalytic trimers. The “incomplete” enzyme, r
4
c
6
, exhibits the characteristic sigmoidal saturation behavior and CTP inhibition of aspartate transcarbamoylase; however these allosteric effects are reduced in extent by about one-third in comparison to the native enzyme and free catalytic subunits. The complex, which may be an intermediate in the assembly and dissociation of the native enzyme, is useful in assessing the role of the various bonding domains responsible for the stability and regulatory properties of the native enzyme.
Genetic Recombination in
Rhodopseudomonas capsulata
Authors: Marrs Barry
Published: May 2006

A system for genetic exchange in
Rhodopseudomonas capsulata
has been discovered. Each genetic marker thus far examined can be transferred, and many strains of
Rps. capsulata
can participate in genetic exchange. The mechanism of gene transfer seems unlike that of any previously described bacterial system, since genes can be transferred by cell-free filtrates, but the vector is resistant to deoxyribonuclease and has a sedimentation constant of about 70 S.
Accumulation of 5-Oxoproline in Mouse Tissues After Inhibition of 5-Oxoprolinase and Administration of Amino Acids: Evidence for Function of the γ-Glutamyl Cycle
Authors: Van Der Werf Paul , Stephani Ralph A. , Meister Alton
Published: May 2006

5-Oxoprolinase catalyzes the conversion of 5-oxo-L-proline (L-pyroglutamate, L-2-pyrrolidone-5-carboxylate) to L-glutamate with concomitant stoichiometric cleavage of ATP to ADP and inorganic orthophosphate. In this reaction, a step in the γ-glutamyl cycle, 5-oxoproline (formed by the action of γ-glutamylcyclotransferase on γ-glutamyl amino acids, which are in turn formed by transpeptidation of amino acids with glutathione), is made available for glutathione synthesis. When mice are injected with L-2-imidazolidone-4-carboxylate, a competitive inhibitor of 5-oxoprolinase, they accumulate 5-oxoproline in their tissues (kidney, liver, brain, and eye) and excrete it in the urine. Mice given the inhibitor together with one of several L-amino acids accumulate and excrete much more 5-oxoproline than when they are given the inhibitor alone. Such augmentation of 5-oxoproline accumulation offers evidence for the function of the γ-glutamyl cycle
in vivo
and supports the view that 5-oxoproline is a quantitatively significant metabolite.
Isolation of a Clone of Chinese Hamster Ovary Cells Deficient in Plant Lectin-Binding Sites
Authors: Gottlieb Charlene , Skinner Sister Ann Marie , Kornfeld Stuart
Published: May 2006

Ricin, a galactose-binding lectin with potent cytotoxic activity, was used to select a clone of Chinese hamster ovary cells with altered plant lectin-binding properties. The clone (15B) is 80-fold less sensitive to the toxic action of ricin than the parent line. In the absence of ricin, it grows both in monolayer and suspension culture with a normal generation time. Plating efficiency, however, is significantly reduced. Relative to the parent cells, its binding of the
Ricinus communis
lectins,
Phaseolus vulgaris
erythroagglutinating phytohemagglutinin,
Abrus precatorius
phytohemagglutinin, and soybean phytohemagglutinin is less than 7%, while binding of lentil phytohemagglutinin, wheat-germ agglutinin, and mushroom phytohemagglutinin is 17%, 40%, and 109%, respectively. In contrast, its concanavalin A binding is increased by 70%. Consistent with these alterations, crude membrane preparations of the 15B cells were found to contain the same sugars as the parent-cell membranes but in different proportions. The 15B membranes have 28% less sialic acid, 38% less
N
-acetylglucosamine, 49% less galactose, the same amount of
N
-acetylgalactosamine, and 53% more mannose than the membranes of the parent cells.
Tertiary Structure of H-Pro-Leu-Gly-NH
2
, the Factor That Inhibits Release of Melanocyte Stimulating Hormone, Derived by Conformational Energy Calculations
Authors: Ralston Evelyn , Coen Jean-Louis De , Walter Roderich
Published: May 2006

Conformational energy calculations were carried out on H-Pro-Leu-Gly-NH
2
, the factor that inhibits the release of melanocyte stimulating hormone, and its biologically active analog, H-Pro-Ala-Gly-NH
2
. Both peptides were found to be relatively compact molecules that retain, however, some degree of flexibility. After structure refinement, H-Pro-Leu-Gly-NH
2
possesses at least three preferred compact conformations. Two of these conformations occupy rather broad and flat energy troughs, while a third occupies a narrow and deep potential energy well. This third structure, which consists of a 10-membered β-turn closed by a (4 → 1) hydrogen bond between the proton of the
trans
carboxamide of Gly and the C=O of Pro, is the one that was proposed for H-Pro-Leu-Gly-NH
2
in dimethylsulfoxide and was also found by x-ray analysis.
Human Pituitary Growth Hormone Isolation and Properties of Two Biologically Active Fragments from Plasmin Digests
Authors: Li Choh Hao , Gráf László
Published: May 2006

Two biologically active fragments have been isolated from plasmic digests of human pituitary growth hormone. It was shown that these two fragments were derived from the cleavage of the Arg-Thr (positions 134-135) and the Lys-Gln (positions 140-141) bonds of the hormone: one has 134 amino acids and the other 51 amino acids, respectively. The two fragments were active in the rat tibia and pigeon crop-sac tests, as well as in complement fixation experiments.
Serological Crossreactivity Between H-Y (Male) Antigens of Mouse and Man
Authors: Wachtel Stephen S. , Koo Gloria C. , Zuckerman Evelyn E. , Hammerling Ulrich , Scheid Margrit P. , Boyse Edward A.
Published: May 2006

Antisera to H-Y (male-specific) antigen were prepared by immunizing female mice with spleen cells from males of the same inbred strain. These antisera were used in mixed hemadsorption and cytotoxicity tests with cells of rats, guinea pigs, rabbits, and humans. The results showed that the H-Y components of all four species are antigenically related to H-Y of the mouse.
Identification by Photo-Affinity Labeling of the Proteins in
Escherichia coli
Ribosomes Involved in Elongation Factor G-Dependent GDP Binding
Authors: Maassen J. A. , Möller W.
Published: May 2006

Guanosine diphosphate esterified at the β-phosphate group with the photolabile 4-azidophenol [1-(4-azidophenyl)-2-(5′-guanyl)pyrophosphate] was found to inhibit GDP binding to the ribosomes of
E. coli
. UV-irradiation of the fusidic acid-stabilized complex among ribosomes, elongation factor G, and the azidophenyl-GDP, results in selective attachment of the photo-affinity label to the proteins L5, L11, L13, L18, and L30. In addition, a substantial reduction of the amount of L16 present in irradiated ribosomes was found. Except for L13, no significant reaction of azidophenyl-GDP with the ribosomal proteins was observed when fusidic acid was omitted from the irradiation mixture. The results strongly suggest that L5, L11, L18, and L30 are involved in GDP binding. The possibility of a transient binding of GDP to L13 followed by migration to the actual GTPase site is discussed.
Relationship Between RNA-directed DNA Polymerase (Reverse Transcriptase) from Human Acute Leukemic Blood Cells and Primate Type-C Viruses
Authors: Gallagher R. E. , Todaro G. J. , Smith R. G. , Livingston D. M. , Gallo R. C.
Published: May 2006

An RNA-directed DNA polymerase was isolated from the peripheral blood leukocytes of a patient with acute myelomonocytic leukemia by successive purification of a particulate cytoplasmic fraction with endogenous, ribonuclease-sensitive DNA polymerase activity. Like RNA-directed DNA polymerase from mammalian type-C virus, the human leukemic cell enzyme efficiently utilized (A)
n
·(dT)
12-18
and (C)
n
·(dG)
12-18
and had an approximate molecular weight of 70,000. Further, the leukemic cell enzyme was strongly inhibited by antisera to RNA-directed DNA polymerase of primate type-C virus in a fashion similar to that noted with an extensively purified RNA-directed DNA polymerase from a person with acute myelogenous leukemia [Todaro, G.J. & Gallo, R.C. (1973),
Nature
244, 206]. By these biochemical and immunological results the leukemic cell enzyme could be differentiated from all other known cellular DNA polymerases but could not be distinguished from RNA-directed DNA polymerase of primate type-C virus. We interpret these data, combined with observations published elsewhere, to indicate that human acute myelogenous leukemia cells contain components related to primate type-C virus. The parameters used in this study may provide the specificity and sensitivity required for determining the presence or absence and (if present) the relatedness of RNA-directed DNA polymerase in other cases and types of human leukemia.
The Synthesis of Human Placental Lactogen by Ribosomes Derived from Human Placenta
Authors: Boime Irving , Boguslawski Sophie
Published: May 2006

In a very active cell-free system containing polysomes derived from human placenta and a cell-sap fraction prepared from ascites tumor cells, the synthesis of the hormone human placental lactogen (HPL) was detected. The identification was based on the following: (
a
) The
in vitro
synthesized protein labeled with [
35
S]methionine migrated at the same rate as authentic HPL on sodium dodecyl sulfate-polyacrylamide gels and (
b
) tryptic fingerprint analysis of the labeled protein yielded peptides having the same mobilities as seen with the same analysis of purified HPL.

The amount of HPL synthesized in a cell-free system containing polysomes derived from term placenta was about 10% of the total proteins synthesized and in a comparable system containing first trimester ribosomes the level of synthesis was about 5%. These data suggest the potential for quantitating the HPL mRNA activity as a function of the period of gestation and for isolating the mRNA itself.
Sexual Morphogenesis in
Achlya:
Ultrastructural Basis for the Hormonal Induction of Antheridial Hyphae
Authors: Mullins J. Thomas , Ellis E. Ann
Published: May 2006

Male strains of the water mold
Achlya ambisexualis
produce antheridial hyphae in response to the steroid hormone antheridiol. The antheridial hypha is postulated to be initiated through a localized wall softening with the enzyme cellulase. Freeze-etch studies of hormone-treated hyphae were conducted to determine if aggregates of vesicles are induced at the location of new antheridial hyphae. Localized aggregates of vesicles were found in conjunction with areas of wall thinning. These data suggest that the processes of vesiculation and secretion provide a mechanism for concentration of cellulase at the site of initiation of antheridial hyphae.
Composition of Mammalian Ribosomal Subunits: A Re-Evaluation
Authors: McConkey Edwin H.
Published: May 2006

A method for preparation of highly active mammalian ribosomal subunits is described, which yields 60S subunits containing no more than 33% protein. It is suggested that the composition of these subunits corresponds closely to that of
Escherichia coli
50S subunits. Data on the composition of bacterial and mammalian ribosomal subunits recovered from CsCl are given. It is shown that the commonly employed assumptions about the relationship between the buoyant density of a particle in CsCl and its protein content are in error. The composition of ribosomal subunits cannot ordinarily be calculated from the buoyant density in CsCl.
The Synthesis and Stability of Cytoplasmic Messenger RNA During Myoblast Differentiation in Culture
Authors: Buckingham M. E. , Caput D. , Cohen A. , Whalen R. G. , Gros F.
Published: May 2006

The synthesis of poly(A)-containing cytoplasmic RNA was examined in primary myoblast cultures prepared from skeletal muscle of fetal calves. After a period of cell division, these cells undergo fusion, with concomitant appearance of acetylcholine receptor and subsequent myosin synthesis. In the dividing myoblast there is a high level of messenger RNA synthesis, including a 26S RNA, the size of a putative messenger for the large subunit of myosin. In the transition period prior to fusion, there are quantitative changes in RNA synthesis. At this time, there is a pronounced production of 26S RNA, which diminishes during fusion. The possibility that 26S RNA is accumulated in the dividing myoblast was investigated by chase experiments. At fusion, there is a marked increase in the half-lives of a number of messenger RNA species, including 26 S, which increases from about 10 hr in the dividing cell to a value of more than 50 hr. The identity of the more rapidly turning over 26 S in the myoblasts, compared to that of the 26 S at fusion, was examined in terms of polysomal distribution, migration on gels, and hybridization with complementary DNA for the myosin message. The results of these analyses suggest that the 26S species are identical. Thus, it would appear that in a predetermined cell like the myoblast, the transition to the differentiated state of myotube that is synthesizing muscle specific proteins is effected by the stabilization of messenger already being actively transcribed: terminal differentiation, with respect to myosin synthesis, is preceded by the stabilization of 26S RNA.