bluuebunny/crossref_metadata_2025 huggingface dataset:
Chromosomal localization of human β globin gene on human chromosome 11 in somatic cell hybrids
Authors: Deisseroth Albert , Nienhuis Arthur , Lawrence Jeanne , Giles Richard , Turner Patricia , Ruddle Frank H.
Published: May 2006

We have successfully used a DNA·cDNA molecular hybridization assay to directly determine the presence or absence of human β globin gene sequences in 20 human—mouse somatic cell hybrids, each of which contained a different subset of human chromosomes. The assay is specific for the individual human globin genes and will detect the presence of a globin gene if the relevant chromosome is present in only 10% of the cells of a hybrid population. The content of human chromosomes in each hybrid clone was characterized by Giemsa 11 staining, Giemsa trypsin-Hoechst 33258 staining, and by the use of 22 independent isozyme markers for 17 different human chromosomes. All human chromosomes were present in one or more cell lines devoid of the human β globin gene except for 6, 8, 9, 11, and 13. Among these latter chromosomes, only chromosome 11 was present in the six hybrid clones that contained the human β globin gene. In fact, chromosome 11 was the only human chromosome that was present in all of the six hybrid clones found to be positive for the human β globin gene. Two sister clones, 157-BNPT-1 and 157-BNPT-4, had similar subsets of human chromosomes except that 11 was present only in 157-BNPT-4. 157-BNPT-4 contained the human β globin gene while 157-BNPT-1 did not. DNA from three hybrid lines was also annealed to purified human γ globin cDNA; two lines positive for human β globin gene sequences also contained human γ globin gene sequences while one line was negative for both β and γ gene sequences. On the basis of these results, the human β and γ globin genes have been assigned to human chromosome 11.
Detection in human breast carcinomas of an antigen immunologically related to a group-specific antigen of mouse mammary tumor virus
Authors: Mesa-Tejada R. , Keydar I. , Ramanarayanan M. , Ohno T. , Fenoglio C. , Spiegelman S.
Published: May 2006

An antigen immunologically related to a group-specific antigen (gp52, a 52,000-dalton glycoprotein) of the mouse mammary tumor virus has been identified in paraffin sections of human breast cancers by means of the indirect immunoperoxidase technique. The specificity of the reaction with antibody against mouse mammary tumor virus was examined by absorption of the IgG with the following: (
a
) purified gp52; (
b
) a number of virus preparations (mouse mammary tumor virus, Rauscher leukemia virus, simian sarcoma virus, baboon endogenous virus, and Mason—Pfizer monkey virus); (
c
) normal plasma, leukocytes, breast tissue, milk, actin, collagen, and hyaluronic acid, all of human origin; (
d
) sheep erythrocytes and mucin. Only mouse mammary tumor virus (from C
3
H or Paris RIII strains and grown in either murine or feline cells) and purified gp52 eliminated the immunohistochemical reaction in the human breast tumors.

Positive reactions were seen in 51 of 131 (39%) breast carcinomas of various histologic types, a minimal estimate in view of the limited number of sections from each tumor that could be examined. Negative reactions were obtained in all 119 benign breast lesions (cystic disease, fibroadenoma, papilloma, gynecomastia) and in all 18 normal breast tissues. With one exception, 99 carcinomas from 13 organs other than breast and 8 cystosarcomas were all negative.
Theoretical study of protein--lipid interactions in bilayer membranes.
Authors: Owicki J C , Springgate M W , McConnell H M
Published: May 2006

An analysis is given for the perturbation of the order and composition of lipid bilayers near an intrinsic membrane protein. Two cases are examined: the protein influences the lipid order (i.e., "fluidity"), and the protein associates with one component of a lipid mixture preferentially. The order perturbation is studied as a function of temperature and lateral pressure by using Landau--de Gennes theory and a variational procedure. It is concluded that, for a given lateral pressure, the greatest amount of boundary lipid is present at the lipid phase-transition temperature. A critical point for the phase transition occurs, near which the amount of boundary lipid increases dramatically. The composition perturbation is modeled in a binary lipid mixture by using a simple regular solution theory. The perturbation is found not to extent much beyond the directly bound layer of lipids unless the solution is near a critical mixing point.
A cell-free assay measuring repair DNA synthesis in human fibroblasts.
Authors: Ciarrocchi G , Linn S
Published: May 2006

Osmotic disruption of confluent cultured human fibroblasts that have been irradiated or exposed to chemical carcinogens allows the specific measurement of repair DNA synthesis using dTTP as a precursor. Fibroblasts similarly prepared from various xeroderma pigmentosum cell lines show the deficiencies of UV-induced DNA synthesis predicted from in vivo studies, while giving normal responses to methyl methanesulfonate. A pyrimidine-dimer-specific enzyme, T4 endonuclease V, stimulated the rate of UV-induced repair synthesis with normal and xeroderma pigmentosum cell lines. This system should prove useful for identifying agents that induce DNA repair, and cells that respond abnormally to such induction. It should also be applicable to an in vitro complementation assay with repair-defective cells and proteins obtained from repair-proficient cells. Finally, by using actively growing fibroblasts and thymidine in the system, DNA replication can be measured and studied in vitro.
Transformation of yeast.
Authors: Hinnen A , Hicks J B , Fink G R
Published: May 2006

A stable leu2- yeast strain has been transformed to LEU2+ by using a chimeric ColE1 plasmid carrying the yeast leu2 gene. We have used recently developed hybridization and restriction endonuclease mapping techniques to demonstrate directly the presence of the transforming DNA in the yeast genome and also to determine the arrangement of the sequences that were introduced. These studies show that ColE1 DNA together with the yeast sequences can integrate into the yeast chromosomes. This integration may be additive or substitutive. The bacterial plasmid sequences, once integrated, behave as a simple Mendelian element. In addition, we have determined the genetic linkage relationships for each newly introduced LEU2+ allele with the original leu2- allele. These studies show that the transforming squences integrate not only in the leu2 region but also in several other chromosomal locations.
Change of gene frequencies by natural selection under population number regulation.
Authors: Kimura M
Published: May 2006

By incorporating a population number regulating mechanism into the formulation of genic selection involving a pair of alleles (A1 and A2) with respective frequencies x and I-x, it is shown that the change of x in one generation is given by deltax = sx(1-x)/W, in which W is the mean absolute selective value (in Wright's sense). It is also shown that, in the process in which advantageous allele (say A1) increases from a low frequency to a high frequency, quasi-equilibrium is rapidly attained where deltaW approximately 0. In this state we have W approximately 1 + (s2/c)x(1-x) in the case of logarithmic population number regulation, and W approximately 1 + s2x(1-x)/(cN) in the case of logistic regulation. In these expressions, s is the selective advantage of A1 over A2, and c is a coefficient relating to the total population number regulation. It is pointed out that the approximation formula deltax = sx(1-x) is valid under wider circumstances than usually suggested by the conventional treatment of genic selection.
Transforming activity of Epstein-Barr virus obtained by superinfection of Raji cells.
Authors: Yajima Y , Marczynska B , Nonoyama M
Published: May 2006

Epstein-Barr virus obtained by superinfection of Raji cells with Epstein-Barr virus recovered from P3HR1 cells (HRI virus) transformed human lymphocytes, but it did not superinfect Raji cells. A human lymphoblastoid cell line, HLB, established by such transformation contained 22 Epstein-Barr virus genomes per cell and Epstein-Barr virus-associated nuclear antigen, and a few cells contained early or viral capsid antigen complexes. Chromosomal analysis revealed that HLB-cells were diploid with normal female karyotypes. Replication of Epstein-Barr virus DNA and inhibition of host cell DNA synthesis were observed in HLB cells after superinfection with HR1 virus.
Nerve extract induces increase and redistribution of acetylcholine receptors on cloned muscle cells
Authors: Podleski T. R. , Axelrod D. , Ravdin P. , Greenberg I. , Johnson M. M. , Salpeter M. M.
Published: May 2006

The effect of rat spinal cord explants and cell-free nerve extract on acetylcholine receptor site density and distribution was studied using
125
I- and rhodamine-labeled α-bungarotoxin on L
6
, a cloned rat muscle cell line. Control L
6
myotubes have a low and uniform distribution of acetylcholine receptors (20 ± 3 sites per μm
2
in the present study). The addition of spinal cord explants caused an increase in average receptor site density of about 6 times on myotubes within 2 mm of the explant, while a smaller increase of 3 times was observed at distances greater than 5 mm. The formation of high-density patches of receptors was also stimulated. These observations suggested that a diffusible substance originating from the explant was responsible for these changes. Cell-free homogenates of the central nervous system were prepared and found to produce the same effects. The effect of the homogenate was not strongly dependent on the age of the fetus from which the tissue was isolated, and fetal liver had little or no effect. The active component(s) appears to be a protein(s) with a molecular weight of about 100,000. Because the nerve homogenates make the L
6
cells resemble primary muscle cultures, we suggest that a common factor is responsible for regulating the acetylcholine receptor in the two types of muscle culture. The normally acetylcholine receptor-poor L
6
cells may provide a more sensitive assay for these factors than do primary muscle cultures.
Connectivity as an alternative to boundary integral equations: Construction of bases
Authors: Herrera Ismael , Sabina Federico J.
Published: May 2006

In previous papers Herrera developed a theory of connectivity that is applicable to the problem of connecting solutions defined in different regions, which occurs when solving partial differential equations and many problems of mechanics. In this paper we explain how complete connectivity conditions can be used to replace boundary integral equations in many situations. We show that completeness is satisfied not only in steady-state problems such as potential, reduced wave equation and static and quasi-static elasticity, but also in time-dependent problems such as heat and wave equations and dynamical elasticity. A method to obtain bases of connectivity conditions, which are independent of the regions considered, is also presented.
Uracil incorporation into nascent DNA of thymine-requiring mutant of
Bacillus subtilis
168
Authors: Tamanoi Fuyuhiko , Okazak Tuneko
Published: May 2006

A thymine-requiring mutant of
Bacillus subtilis
strain 168 accumulates short DNA chains after brief pulses with [
3
H]thymidine. Reversion of the
thy
mutation to
thy
+
abolishes the accumulation of short DNA chains, suggesting that the accumulation is related to the
thy
mutation. The reason for this accumulation has been further investigated by analysis of a mutant with a defective uracil-DNA glycosidase activity (
urg
). The accumulation of short DNA chains in
thy
-
cells is abolished by the deficiency of uracil-DNA glycosidase activity. In
thy
+
cells, the deficiency of the glycosidase activity does not change the sedimentation profile of pulse-labeled DNA. DNA isolated from
thy
-
urg
-
cells is fragmented by successive treatment with purified uracil-DNA glycosidase and alkali, indicating that uracil residues are present in this DNA. DNA isolated from
thy
+
urg
-
cells is not fragmented by the same treatment. Significant radioactivity is detected in the dUMP region, when [
3
H]uridine-labeled DNA from
thy
-
urg
-
cells is hydrolyzed and analyzed by thin-layer chromatography. Only a trace amount of radioactivity, which is not influenced by the deficiency of uracil-DNA glycosidase activity, is found in the dUMP region in DNA hydrolysates from
thy
+
cells. These results suggest that, in
thy
-
cells, uracil is incorporated into DNA and the accumulation of short DNA chains results from the excision-repair of this uracil whereas in
thy
+
cells, uracil is seldom, if ever, incorporated into DNA.
Induction of maturation in
Xenopus laevis
oocytes by a steroid linked to a polymer
Authors: Godeau J. Francois , Schorderet-Slatkine Sabine , Hubert Patrick , Baulieu Etienne-Emile
Published: May 2006

A progesterone analog has been covalently linked via an amide bond to polyethylene oxide (molecular weight, 20,000). This macromolecular steroid molecule displays the biological activity of progesterone in inducing meiotic maturation when incubated with
Xenopus laevis
oocytes (stage VI)
in vitro
. Its efficiency (half-maximum effective concentration, 30 μM) is approximately 10 times lower than that of its low molecular weight homolog (3 μM). Control experiments with polyethylene oxide and an estradiol derivative (up to 1 mM) assessed the specificity of the progesterone macromolecular analog. Uptake experiments using radioactive derivatives revealed a small (if not negligible) intake of the macromolecular progesterone analog by the oocytes compared to that of free steroids, and no parallelism was found between radioactivity incorporation and effect. The possibility of cleavage of the macromolecular derivative during the incubation was ruled out. Furthermore, injection of the polymer-linked progesterone into the oocytes did not induce maturation. These observations suggest that the macromolecular progesterone analog itself is responsible for the biological effect and that the presence of this compound inside the cell is neither necessary nor sufficient for triggering reinitiation of meiosis. These conclusions are in agreement with the proposal that interaction with the plasma membrane of the oocyte is necessary for progesterone action in this particular system, in contrast to the case of somatic cells which have intracellular steroid receptors.
Multiple glycosidase deficiencies in a case of juvenile (type 3) Gaucher disease.
Authors: Chiao Y B , Hoyson G M , Peters S P , Lee R E , Diven W , Murphy J V , Glew R H
Published: May 2006

Biochemical investigations were performed on autopsy tissues obtained from an 11-year-old girl who died with the juvenile, subacute neuropathic form of Gaucher disease. In addition to the expected deficiency of glucocerebrosidase activity, extracts of both liver and kidney from this individual displayed a profound (greater than or equal to 90%) deficiency of "soluble" beta-glucosidase, beta-xylosidase, and beta-galactosidase activities. Fibroblasts obtained from this individual also contained markedly reduced levels of beta-xylosidase activity but normal levels of beta-D-fucosidase and beta-galactosidase activity. Because the soluble beta-glucosidase, beta-xylosidase, and a portion of the beta-galactosidase activities from control human liver all cochromatographed on a gel filtration column of Sephadex G-200, it is suggested that these activities all reside in a single enzyme, analogous to the situation described in a number of nonhuman, mammalian tissues. This demonstration of multiple glycosidase deficiencies in addition to the deficiency of glucocerebrosidase in a case of subacute neuropathic Gaucher disease suggests that other biochemical aberrations, in addition to a deficiency of glucocerebrosidase, might contribute to pathology in some cases of Gaucher disease.
Myelin basic protein demonstrated immunocytochemically in oligodendroglia prior to myelin sheath formation.
Authors: Sternberger N H , Itoyama Y , Kies M W , Webster H D
Published: May 2006

A specific antibody to myelin basic protein has been used to localize the protein in developing rat oligodendroglia and myelin. Basic protein is found in the oligodendroglial cytoplasm of anterior commissures of 5- and 7-day old rats before the beginning of myelination. Staining of basic protein in oligodendroglia increases, becoming most intense during early myelination; it decreases during rapid myelination. Staining intensity of oligodendroglia is dependent upon age, brain region, and nervous tract studied. In myelin, reaction of basic protein with antibody decreases when large compact sheaths are present, unless tissue sections are first treated with alcohol.
Immunofluorescent localization of a serine protease in rat small intestine.
Authors: Woodbury R G , Gruzenski G M , Lagunoff D
Published: May 2006

An intracellular serine protease, which is believed to initiate the degradation of several intracellular pyridoxal phosphate-dependent enzymes, was localized by immunofluorescence in atypical mast cells of the lamina propria and in intraepithelial cells of the rat small intestine. Some mucus-secreting goblet cells also contained the protease antigen. Atypical mast cells containing the enzyme were present in large numbers beneath the epithelium of bronchioles. All atypical mast cells also contained low levels of the chymotrypsin-like protease of normal mast cells. Both enzymes were consistently present in normal connective tissue mast cells. Amino acid content, molecular weight, and lack of immunologic crossreactivity indicate that the two enzymes are similar but not identical. The cell-specific localization of the intestinal serine protease makes it unlikely that the enzyme has any general role in the degradation of pyridoxal phosphate-dependent enzymes. The function of the enzyme in mast cells, atypical mast cells, and intestinal goblet cells is not known.
Diabetic cataract formation: potential role of glycosylation of lens crystallins.
Authors: Stevens V J , Rouzer C A , Monnier V M , Cerami A
Published: May 2006

A high glucose concentration in vivo or an increased glucose of glucose 6-phosphate concentration in vitro has been found to lead to the glycosylation of epsilon-amino groups of lysine residues in bovine and rat lens crystallins. In vitro, this glycosylation imparts an increased susceptibility of the crystallins to sulfhydryl oxidation. Disulfide crosslinks result in the formation of high molecular weight aggregates and an opalescence in the crystallin solutions. The addition of reducing agents prevents as well as reverses the formation of high molecular weight aggregates and the opalescence of the crystallins. These phenomena suggest a new interpretation of previous results on cataract formation and a new approach for development of drugs to prevent cataracts.
Hemopoietic stem cell transplantation using mouse bone marrow and spleen cells fractionated by lectins.
Authors: Reisner Y , Itzicovitch L , Meshorer A , Sharon N
Published: May 2006

Mouse bone marrow and spleen cells were fractionated with the aid of soybean agglutinin and peanut agglutinin. A test for spleen colony-forming units in the isolated fractions showed that the hemopoietic stem cells are agglutinated by both of these lectins. The capacity of the agglutinated fractions to reconstitute lethally irradiated allogeneic mice was investigated. A sequential fractionation of splenocytes from SWR donors by soybean agglutinin and peanut agglutinin, or a single fractionation by soybean agglutinin of splenocytes from BALB/c donors, afforded a cell fraction that successfully reconstituted lethally irradiated (BALB/c X C57BL/6)F1 mice, without complications due to graft-versus-host reaction.
Clusters of intramembranous particles on cultured myotubes at sites that are highly sensitive to acetylcholine.
Authors: Yee A G , Fischbach G D , Karnovsky M J
Published: May 2006

Electrophysiological and autoradiographic studies have shown that the distribution of acetylcholine (AcCho) receptors on uninnervated cultured chicken muscle cells is not uniform. Regions of high receptor density (hot spots 10--40 times more sensitive than surrounding areas are localized as discrete patches or clusters about 10 micrometer in diameter o myotube muscle membranes. Hot spots were also found on fusion-arrested mononucleated myoblasts. We have developed a method for freeze-fracturing monolayer cultures that allows the unambiguous reidentification of membrane patches previously assayed for ACCho sensitivity. The freeze-fractured membranes at physiologically defined hot spots contain aggregates of many (10--20) small clusters of large (10--19 nm in diameter) intramembranous particles. Clusters are found on both fracture faces, but the particle density is much greater on the protoplasmic (P) face than on the extracellular (E) face (about 2000/micrometer2 vs. 700/micrometer2). Some of the particles appear to be composed of five or six "subunits" arranged cylindrically around a central dark dot. Because the aggregates are present at sites of high AcCho sensitivity, it is likely that the intramembranous particles are in some way related to the AcCho receptor molecule.
Strong consistency of least squares estimates in multiple regression
Authors: Lai T. L. , Robbins Herbert , Wei C. Z.
Published: May 2006

The strong consistency of least squares estimates in multiple regression models with independent errors is obtained under minimal assumptions on the design and weak moment conditions on the errors.
Adenosine kinase initiates the major route of ribavirin activation in a cultured human cell line.
Authors: Willis R C , Carson D A , Seegmiller J E
Published: May 2006

Inhibition of IMP dehydrogenase (EC 1.2.1.14) by ribavirin causes the normal human lymphoblast to excrete increased amounts of newly formed purine into the culture medium. In order for ribavirin to be active as an inhibitor of the dehydrogenase, this synthetic nucleoside must be phosphorylated. The effect of ribavirin on purine excretion has been determined with a normal lymphoblast line, and with lymphoblast lines deficient in hypoxanthine phosphoribosyltransferase (IMP:pyrophosphate phosphoribosyl-transferase, EC 2.4.2.8), in adenosine kinase (ATP:adenosine 5'-phosphotransferase, EC 2.7.1.20), and in both hypoxanthine phosphoribosyltransferase and adenosine kinase. Resistance to the effect of ribavirin on purine excretion was associated only with those cell lines deficient in adenosine kinase activity. These cell lines have normal deoxyadenosine kinase (ATP:deoxyadenosine 5'-phosphotransferase, EC 2.7.1.76) activity. Therefore, the nucleoside kinase activity responsible for ribavirin phosphorylation is adenosine kinase.
Use of T4 RNA ligase to construct model substrates for a ribosomal RNA maturation endonuclease
Authors: Meyhack Bernd , Pace Bernadette , Uhlenbeck Olke C. , Pace Norman R.
Published: May 2006

RNase M5 of
Bacillus subtilis
specifically cleaves a 179-nucleotide precursor 5S rRNA to yield mature 5S rRNA (116 nucleotides) and two fragments derived from the termini. Possible recognition elements for RNase M5 within the precursor structure include nucleotide sequences arranged with 2-fold rotational and translational symmetry about the substrate bonds. We have used bacteriophage T4 RNA ligase to construct, from synthetic oligonucleotides and mature or precursor 5S rRNA fragments, test substrates lacking these symmetry elements. The susceptibilities of the artificial substrates to RNase M5 demonstrate that the symmetrically arranged sequences are not used in the RNase M5 interaction with the precursor. Additionally, the synthetic protocols permitted the invention of an acid-soluble assay for RNase M5 and, potentially, other specific endoribonucleases.
ATP-induced conformational changes in the restriction endonuclease from Escherichia coli K-12.
Authors: Bickle T A , Brack C , Yuan R
Published: May 2006

ATP induces a conformational change in the Escherichia coli K-12 restriction enzyme that allows it to discriminate between unmodified and modified DNA recognition sequences. This conformational change does not require ATP hydrolysis. However, ATP hydrolysis is a requirement for DNA cleavage.
Allosteric regulation of monocyclic interconvertible enzyme cascade systems: Use of
Escherichia coli
glutamine synthetase as an experimental model
Authors: Rhee S. G. , Park R. , Chock P. B. , Stadtman E. R.
Published: May 2006

The interconversion of
Escherichia coli
glutamine synthetase [L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2] between its adenylylated and unadenylylated forms has been used to verify the prediction derived from a theoretical analysis of the steady-state functions of a model for a monocyclic interconvertible enzyme cascade system [Stadtman, E. R. & Chock, P. B. (1977)
Proc. Natl. Acad. Sci. USA
74, 2761-2770]. Because glutamine and α-ketoglutarate are multifunctional effectors and because three active enzyme complexes are involved in both adenylylation and deadenylylation of glutamine synthetase, at least 28 constants are required to describe the glutamine synthetase monocyclic cascade. Of these, 22 constants were determined experimentally and 6 were estimated via computer curve fitting. Despite the complexity, when both adenylylation and deadenylylation reactions are functioning, the number of adenylyl groups bound per mole of enzyme,
n̄
, assumes a steady-state level as is predicted by the model. This
n̄
value is determined by the mole fraction of P
IIA
—given by ([P
IIA
]/([P
IIA
] + [P
IID
])—and the ratio of glutamine to α-ketoglutarate (P
IID
and P
IID
are the unmodified and the uridylylated forms of the P
II
regulatory protein). In the presence of 0.5 mM glutamine and 2 mM α-ketoglutarate, the value of
n̄
increases as a nearly hyperbolic function in response to increasing mole fractions of P
IIA
. When the constant level of α-ketoglutarate is gradually increased to 40 μM, the hyperbolic function converts slowly to a parabolic function. When the P
IIA
mole fraction was maintained at 0.6 and α-ketoglutarate levels were varied from 1 mM to 4 μM, an 800-fold increase in signal amplification was observed with respect to glutamine activation. In addition, because glutamine activates the adenylylation and inhibits the deadenylylation reaction, a sensitivity index of 2.1 (corresponding to a Hill number of 1.5) was obtained for the variation of
n̄
values in response to increasing glutamine concentration.
Location of the genes for human heavy chain immunoglobulin to chromosome 6
Authors: Smith Moyra , Hirschhorn Kurt
Published: May 2006

Immunoglobulin synthesis was examined in 31 man-mouse hybrid clones produced by fusing RAG mouse cells with human lymphoid cells. Cells were grown in serum-free medium containing [
14
C]leucine and a
14
C-labeled amino acid mixture. Spent medium was dialyzed, concentrated, and subjected to radioimmunoelectrophoresis. Eighteen clones were found to produce material that gave a radiolabeled precipitin line with anti-human IgG (γ-chain specific). Production of material which was indistinguishable on radioimmunoelectrophoresis from human Ig γ heavy chain, was dependent on the presence in hybrid clones of human chromosome 6. The material was found to have the ion-exchange elution characteristics of human IgG. When radiolabeled spent medium from human lymphoid lines and from chromosome 6-positive hybrid clones was exposed to protein A-Sepharose and bound material eluted with 8 M urea was subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis, three radiolabeled peaks occurred with molecular weights of approximately 55,000 (coinciding with that of Ig γ heavy chain), 40,000 and 25,000 (coinciding with that of Ig light chains). No similar peaks were detected in experiments where spent medium from RAG cells was treated identically. These studies lead us to conclude that certain RAG-human lymphoid hybrid clones produce human IgG and that the structural genes for γ heavy chains are located on human chromosome 6. These results also imply that the locus coding for human α,-antitrypsin (Pi) is located on chromosome 6.
Direct determination of volume- and time-dependence of alveolar surface tension in excised lungs.
Authors: Schürch S , Goerke J , Clements J A
Published: May 2006

We measured alveolar surface tension directly by observing the spreading properties of fluid droplets placed by micropipette within individual alveoli. Alveolar surface tension in excised rat lungs at total lung capacity and 37 degrees was 29.7 +/- 1.4 mN-m-1. In lungs held at functional residual capacity, surface tension changed slowly, rising to 9 mN-m-1 at 30 min with a subsequent approximately linear rise to 16 mN-m-1 at 115 min. Thereafter it rose more rapidly (20 mN-m-1 at 140 min), suggesting that it was not asymptotically approaching an equilibrium value.
Physicochemical characterization of six monoclonal cryoimmunoglobulins: possible basis for cold-dependent insolubility.
Authors: Middaugh C R , Gerber-Jenson B , Hurvitz A , Paluszek A , Scheffel C , Litman G W
Published: May 2006

The physical and chemical properties of five human and one canine monoclonal cryoimmunoglobulin have been compared. By many criteria, the proteins cannot be distinguished from the noncryoglobulin reference proteins analyzed in parallel; however, certain hydrodynamic and spectroscopic properties of the proteins indicate that cryoimmunoglobulins differ in tertiary structure relative to their cold-soluble counterparts. These differences seem to favor low-temperature-induced association between cryoglobulin molecules as an immediate consequence of increased intermolecular ionic or van der Waals forces. No evidence was found for the formation of cold-dependent antigen-antibody complexes or the ubiquitous presence of low-temperature-dependent conformation changes as a component of cryoprecipitation. Rather, the anomalous solution behavior of monoclonal cryoimmunoglobulins can be considered a direct result of the individual solubility properties of these proteins.
Induced cell aggregation and mating in Streptococcus faecalis: evidence for a bacterial sex pheromone.
Authors: Dunny G M , Brown B L , Clewell D B
Published: May 2006

Recipient strains of Streptococcus faecalis produce a trypsin sensitive, heat resistant, nuclease resistant factor, designated clumping-inducing agent (CIA) which causes strains carrying certain conjugative plasmids to aggregate. RNA and protein synthesis but not DNA synthesis are required for aggregation to occur. Recipient filtrates that contain CIA activity also induce donors to mate at high frequencies. Introduction of a transferable plasmid into strains producing CIA dramatically reduces the amount of CIA activity produced by the strain but allows the strain to respond to exogenously added CIA. Our data suggest that CIA represents a bacterial sex hormone (pheromone).
Complementary sequences 1700 nucleotides apart form a ribonuclease III cleavage site in Escherichia coli ribosomal precursor RNA.
Authors: Young R A , Steitz J A
Published: May 2006

The nucleotide sequence of Escherichia coli DNA at both ends of the gene for 16S rRNA has been determined for two rRNA operons, rrnD and rrnX. The 400 nucleotides we have examined exhibit only one base change between rrnD and rrnX. Within the 160 nucleotides that precede mature 16S rRNA sequences are cleavage sites for several E. coli endonucleases, including RNase III. A 240-nucleotide segment encompassing the 16S 3' end contains another RNase III site and the point of presumed RNase P scission at the 5' end of tRNA1Ile, the first tRNA appearing in the 16-23S spacer region of rrnD and rrnX. Most importantly, the DNA sequences predict that regions flanking the 16S gene in the rRNA primary transcript extensively base pair to form a double-helical structure whose hairpin loop includes the entire mature 16S molecule; within this structure is a 26-base-pair stem containing the two sequences at which RNase III action generates the 5' and 3' ends of a previously characterized precursor to 16S rRNA. Although our proposed secondary structure for this RNase III site is superficially dissimilar to previously described cleavage sites in the T7 early mRNA precursor, certain common features may constitute signals for RNase III recognition. The suggestion that distant portions of an RNA molecule can form a secondary structure within which specific endonucleolytic cleavages occur may have mechanistic implications for the joining of noncontiguous portions of gene sequences evident in several eukaryotic mRNAs.
Processing of the 5' end of Escherichia coli 16S ribosomal RNA.
Authors: Dahlberg A E , Dahlberg J E , Lund E , Tokimatsu H , Rabson A B , Calvert P C , Reynolds F , Zahalak M
Published: May 2006

We have isolated and partially characterized an endonuclease involved in processing the 5' end of 16S rRNA of Escherichia coli. A mutant strain that is deficient in this enzyme accumulates a new precursor of 16S rRNA, named 16.3S rRNA. This rRNA has the 3' end of mature 16S rRNA but is about 60 nucleotides longer at the 5' end. In vitro, the enzyme preparation cleaves an RNA fragment of about 60 nucleotides from the 5' end of 16.3S rRNA in 30S ribosomal subunits, yielding the mature 5' end of 16S rRNA. In the mutant strain the 16.3S rRNA is associated with a full complement of 21 ribosomal proteins in 30S subunits. These particles, which comprise 50% of the total 30S subunits, are present on polyribosomes.
Properties of the interaction of fluoride- and guanylyl-5'-imidodiphosphate-regulatory proteins with adenylate cyclase.
Authors: Hebdon M , Le Vine H , Sahyoun N , Schmitges C J , Cuatrecasas P
Published: May 2006

The mechanism of activation of adenylate cyclase by guanylyl-5'-imidodiphosphate [Gpp(NH)p] and NaF has been investigated by studying the reconstitution of Gpp(NH)p and NaF sensitivity of an enzyme rendered insensitive to these agents by differential detergent extraction of a particulate brain enzyme. Such reconstitution can be achieved by the addition of macromolecular regulatory factors from membranes of various tissues. Trypsin digestion and thermal inactivation provide evidence for the existence of two distinct regulatory functions, one capable of restoring the Gpp(NH)p response and another the NaF response. The regulatory protein(s) seem to interact with their respective activators in an easily reversible, divalent cation-independent reaction. This appears to be followed by a high-affinity interaction between the catalytic and regulatory components of adenylate cyclase in a slow, temperature-dependent, divalent cation-dependent process tha produces the persistently activated state of the enzyme. The enzyme activation can be reversed by methods that separate catalytic from regulatory components and the resulting enzyme activity can be restimulated by the reconstitution technique.
Alteration of myoblast phenotype by dimethyl sulfoxide.
Authors: Miranda A F , Nette E G , Khan S , Brockbank K , Schonberg M
Published: May 2006

Application of dimethyl sulfoxide to proliferating L8 myoblasts (an established cell line of rat skeletal muscle) for 72 hr completely prevented fusion and induction of creatine phosphokinase (EC 2.7.3.2) activity (an indicator of muscle differentiation). The growth pattern changed from the usual sheets of randomly oriented cells to flattened, whorled monolayers of elongated fibroblast-like cells. By electron microscopy, rough endoplasmic reticulum increased and extracellular material appeared that had the morphologic and staining characteristics of collagen. After 120 hr in dimethyl sulfoxide-containing medium, the cells secreted about 6 times more collagen than untreated controls. Dimethyl sulfoxide was ineffective when applied to L8 cells just prior to fusion, and effects of dimethyl sulfoxide were not readily reversible unless treated cells were subcultured at low density.
Variation in mitochondrial translation products associated with male-sterile cytoplasms in maize
Authors: Forde Brian G. , Oliver Robin J. C. , Leaver Christopher J.
Published: May 2006

Mitochondria were isolated under sterile conditions from maize lines with normal cytoplasm and with T, C, and S sources of cytoplasmic male sterility. Protein synthesis by these mitochondria was dependent upon the presence of ADP and an oxidizable substrate or an energy generating system and displayed characteristic sensitivity towards inhibitors of protein synthesis. Approximately 20 polypeptides were detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis of the [
35
S]methionine-labeled mitochondrial translation products. Mitochondria from the T and C cytoplasms were characterized by the synthesis of a single additional or variant polypeptide.

These observations are discussed with reference to the possible mechanisms of male sterility and the susceptibility of plants with T cytoplasm to
Helminthosporium maydis
, race T. Our results also suggest a potentially rapid method of classifying sources of cytoplasmic male sterility that could be used in conjunction with existing methods, which depend on patterns of fertility restoration after an extended breeding program.
Conjugation of methotrexate to poly(L-lysine) increases drug transport and overcomes drug resistance in cultured cells
Authors: Ryser Hugues J.-P. , Shen Wei-Chiang
Published: May 2006

Methotrexate and [
3
H]methotrexate were conjugated through a carbodiimide-catalyzed reaction to a 70,000 molecular weight poly(L-lysine) in molar ratios of approximately 13 to 1. The cellular uptake of labeled conjugate was far in excess of the uptake of free drug in cells that were either proficient or deficient in methotrexate transport. The conjugate markedly inhibited the growth of PRO
-
3 Mtx
RII
5-3 Chinese hamster ovary cells, which are known to be drug resistant by virtue of a deficient methotrexate transport. The cells, however, were not inhibited by the same concentrations of free poly(Lys) and free drug. The 100-fold difference in drug concentration needed to inhibit the mutant cells and their corresponding wild type was totally abolished by exposing the methotrexate-resistant cells to methotrexate-poly(Lys). That the drug is carried into the resistant cells as intact drug-poly(Lys) is evident also from the fact that the conjugate is rendered inactive by brief trypsinization
in vitro
. Because the conjugate fails to inhibit dihydrofolate reductase (5,6,7,8-tetrahydrofolate: NADP
+
oxidoreductase; EC 1.5.1.3)
in vitro
, it must be concluded that the strong growth inhibitory effect of the conjugate is due to the intracellular hydrolysis of its polymeric backbone, followed by the release inside the cell of a pharmacologically active form of methotrexate. Our date show that in methotrexate-resistant cells the intracellular release of active drug after uptake of conjugate is of the same order of magnitude as the uptake of free drug by transport-proficient cells and, hence, that the drug resistance due to deficient transport can be totally overcome.
Multiple related immunoglobulin variable-region genes identified by cloning and sequence analysis.
Authors: Seidman J G , Leder A , Edgell M H , Polsky F , Tilghman S M , Tiemeier D C , Leder P
Published: May 2006

We have identified at least six EcoRI fragments of mouse DNA that encode variable-region gene sequences closely related to the mouse kappa light chain, MOPC-149. Two of these fragments have been cloned, and the entire nucleotide sequence of the variable-region genes encoded on each has been determined. Both genes encode closely related variable-region sequences extending from codon position 1 through position 97. Neither fragment encodes a constant-region sequence. Although both genes are closely related, they differ from one another and from the sequence expressed in the MOPC-149 cell from which they were cloned. These few differences cluster within the complementarity-determining regions although several occur in framework sequences as well. We therefore conclude that an antibody-producing cell contains genetic information corresponding to its expressed sequence and several other closely related but silent sequences. These initial results raise the possibility that similar sets of genes might exist corresponding to each of the many subgroups already identified among mouse kappa light chains. If true, this would further suggest that the mouse genome might be rich enough in variable-region genes so as to encode a major portion of the variable-region repertoire.
Molecular genetics of herpes simplex virus: Demonstration of regions of obligatory and nonobligatory identity within diploid regions of the genome by sequence replacement and insertion
Authors: Knipe David M. , Ruyechan William T. , Roizman Bernard , Halliburton Ian W.
Published: May 2006

The DNAs of herpes simplex virus (HSV) 1 and 2 consist of two components, L and S, each composed of unique sequences bracketed by inverted repeats. In this study we have probed the structure of the reiterated regions of the S component in marker rescue experiments involving transfection of cells with mixtures of intact HSV-1 mutant viral DNA and individual DNA fragments generated by restriction endonuclease digestion of wild-type HSV-1 or HSV-2 DNAs. The results were as follows: (
i
) HSV is diploid for the wild-type sequences that rescue two temperature-sensitive (
ts
) mutants. DNA fragments from both reiterated regions of the S component of HSV-1(F) DNA can rescue
ts
LB2 and
ts
D mutants. (
ii
) Identity of the entire reiterated sequence at both ends of S is not obligatory because only one end of the S component of wild phenotype virus HSV-1(1061) rescues
ts
D even though both ends rescue
ts
LB2. (
iii
) Genes in both reiterated sequences can be expressed. We produced, by marker rescue experiments, recombinants with heterotypic ends of the S component, and these specified corresponding polypeptides characteristic of both HSV-1 and HSV-2. (
iv
) The reiterated sequences of the S component may contain a region of obligatory identity. Thus, several recombinant clones produced by rescue with HSV-2 DNA contained identical HSV-2 DNA insertions within both reiterated regions of the HSV-1 S component. Consistent with this conclusion, the termini of the S component in the heterodiploids described in
iii
were identical by restriction enzyme analysis. (
v
) The observation that HSV DNA can be expanded by at least 5 × 10
6
by means of insertion in the S component suggests that it can be a vehicle for exogenous DNA.
Ontogeny of synaptic phosphoproteins in brain.
Authors: Lohmann S M , Ueda T , Greengard P
Published: May 2006

The ontogeny of two endogenous substrates for cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase; EC 2.7.1.37) has been studied in rat and guinea pig cerebrum. These endogenous substrates, referred to as proteins Ia and Ib, have been shown in other studies to be specific to nervous tissue and to be enriched in the synaptic membrane and synaptic vesicle fractions of adult brain. In the present study, proteins Ia and Ib were shown to increase markedly during the time of major synaptogenesis in rat cerebrum and guinea pig cerebrum, in which the morphological development of synapses is predominantly postnatal and prenatal, respectively. Similar results were obtained either by measuring endogenous phosphorylation of proteins Ia and Ib in the synaptic membrane fraction or by measuring phosphorylation of extracted proteins Ia and Ib with added protein kinase.
Dose-response curves and competing risks.
Authors: Groer P G
Published: May 2006

Points of the underlying dose-response curve of a lethal response or group of lethal responses induced by varying doses of a toxicant in a homogeneous population can be estimated from knowledge of the time of occurrence for all responses if the response(s) of interest is (are) statistically independent from the other competing responses (risks). In the case of statistical dependence, only tight upper and lower bounds can be established within which the points of the dose-response curve have to lie. These bounds for the response(s) of interest are far apart if the frequency of occurrence of the competing response(s) is large. In such situations, the shape of the underlying dose-response curve is only suggested by the imaginary band connecting the estimated bounds. The estimation procedures for both cases are illustrated with data from an experiment in which beagles received injections of 239Pu.
Enzymatic breakage of the cohesive end site of phage lambda DNA: terminase (ter) reaction.
Authors: Becker A , Gold M
Published: May 2006

An in vitro system is described for measuring the endonucleolytic conversion of the phage lambda cohesive end sites in concatemeric DNA to the cohesive chromosomal ends of the mature molecule. This enzymic process, known as the ter reaction, is catalyzed by purified lambda A gene protein. The reaction is markedly stimulated by ATP, Mg2+, spermidine, and one or more uncharacterized factors present in extracts of uninfected Escherichia coli cells. In vitro, the ter reaction proceeds in the absence of proheads under conditions that are similar to those previously found necessary for the formation of a DNA-A gene protein intermediate for the initiation of packaging.
Evidence that spontaneous mitotic recombination occurs at the two-strand stage.
Authors: Esposito M S
Published: May 2006

Spontaneous reciprocal mitotic recombination in the yeast Saccharomyces cerevisiae, associated with heteroallelic recombination, occurs almost exclusively at the two-strand stage and involves recombination of unduplicated chromosomes (i.e., during G1) or the unduplicated regions of chromosomes during the S phase of mitosis. The associated heteroallelic recombination frequently reflects the formation of symmetric Holliday structures, is not strongly polarized with respect to conversion at the heteroallelic trp5 sites studied, occasionally results in simultaneous conversion of widely separated genetic markers, and is positively correlated with recombination of flanking markers.
Myoinositol and phosphatidylinositol metabolism in synaptosomes from galactose-fed rats.
Authors: Warfield A S , Segal S
Published: May 2006

The effects of experimental galactose toxicity on inositol and phosphatidylinositol (PtdIns) metabolism in synaptosomes from 0- to 30-day-old rats were investigated. Galactose toxicity was induced by feeding mothers a 40% galactose diet from the 12th day of pregnancy until 19 days postpartum when the offspring were weaned onto the maternal diet. There was no decrease in myoinositol concentrations and only a small decrease in PtdIns in synaptosomes from galactose-fed rats relative to glucose-fed controls. Synaptosomes from rats on the two diets converted equivalent amounts of [U-14C]glucose to inositol and PtdIns. Acetylcholine stimulated [2-3H]inositol incorporation into PtdIns while producing a net decrease in PtdIns concentration in synaptosomes from 22- to 30-day-old rats. However, the phospholipid response to acetylcholine in synaptosomes from galactose-fed rats was impaired. Thus, the acetylcholine-stimulated labeling of PtdIns was 40--50% lower in these synaptosomes while the effect on PtdIns concentration was reduced by a maximum of 55%. The data suggest that galactose-fed rats may have either a deficiency in the number of acetylcholine receptors or a defect in some step between receptor-neurotransmitter interaction and PtdIns breakdown.