bluuebunny/crossref_metadata_2025 huggingface dataset:
Fourteen nucleotides in the second complementarity-determining region of a human heavy-chain variable region gene are identical with a sequence in a human D minigene.
Authors: Wu T T , Kabat E A
Published: May 2006

A sequence of 14 nucleotides in one human diversity (D) minigene (D2) is identical with a sequence in complementarity-determining region 2 (CDR2) of one human gene for the variable region of the heavy chain of immunoglobulin. The finding that nucleotide segments present in a D minigene can appear in CDR2 raises the possibility that other minigene segments may be involved in the generation of antibody diversity and complementarity or that nucleotide segments may move from one CDR to another by a gene conversion mechanism.
Contribution of zinc and other metals to the biological activity of the serum thymic factor.
Authors: Dardenne M , Pléau J M , Nabarra B , Lefrancier P , Derrien M , Choay J , Bach J F
Published: May 2006

The serum thymic factor (FTS) utilized in its synthetic or natural form loses its biological activity in a rosette assay after treatment with a metal ion-chelating agent, Chelex 100. This activity is restored by the addition of Zn salts and, to a lesser extent, certain other metal salts. FTS activation is secondary to the binding of the metal to the peptide. The metal-to-peptide molar ratio of 1:1 provides the best activation. These data indicate the existence of two forms of FTS. The first one lacks Zn and is biologically inactive; the second one contains Zn and is biologically active, for which we propose the name of "thymulin" (FTS-Zn). The presence of Zn in synthetic FTS was confirmed by atomic absorption spectrometry. The interaction between Zn and FTS was further suggested by microanalysis demonstrating the presence of this metal in thymic reticuloepithelial cells.
Complete nucleotide sequence of the attenuated poliovirus Sabin 1 strain genome.
Authors: Nomoto A , Omata T , Toyoda H , Kuge S , Horie H , Kataoka Y , Genba Y , Nakano Y , Imura N
Published: May 2006

The complete nucleotide sequence of the genome of the type 1 poliovirus vaccine strain (LSc,2ab) was determined by using molecular cloning and rapid sequence analysis techniques. The restriction fragments of double-stranded cDNA synthesized from the vaccine strain RNA were inserted into the adequate sites of cloning vector pBR322. Sequence analysis of the cloned DNAs revealed that the virion RNA molecule was 7,441 nucleotides long and polyadenylylated at the 3' terminus. When the nucleotide sequence was compared with that of the genome of the virulent parental strain (Mahoney), 57 base substitutions were observed to be scattered all over the genome. Of these, 21 resulted in amino acid changes in a number of viral proteins. A cluster of amino acid changes is located in the viral coat proteins, especially in the NH2-terminal half of the viral capsid protein VP1. These results may imply that the mutations in the VP1 coding region contribute to attenuation.
Role of prostaglandin D2 in the hypothermia of rats caused by bacterial lipopolysaccharide.
Authors: Ueno R , Narumiya S , Ogorochi T , Nakayama T , Ishikawa Y , Hayaishi O
Published: May 2006

The intraperitoneal administration of lipopolysaccharide from Salmonella typhimurium (1 mg/kg) caused a fall in the rat colonic temperature of about 2 degrees C at an ambient temperature of 22 +/- 3 degrees C. The hypothermia induced by the lipopolysaccharide was abated in a dose-dependent manner by the administration of indomethacin. Other inhibitors of prostaglandin synthetase such as aspirin, flufenamic acid, and phenylbutazone had effects similar to those of indomethacin. When various prostaglandins were injected intracerebroventricularly, only prostaglandin D2 caused a dose-dependent fall in the colonic temperature at doses between 1.2 and 6 nmol/kg. Microinjection of prostaglandin D2 into the preoptic area caused hypothermia of about 1 degree C. However, injection of prostaglandin D2 into the posterior hypothalamus had little effect on the colonic temperature. The hypothermia caused by prostaglandin D2 was not abated by the administration of indomethacin. The amount of prostaglandin D2 increased significantly in the preoptic/hypothalamic region of rat brain 1 hr after the intraperitoneal administration of the lipopolysaccharide, whereas such increase was not observed in rats pretreated with indomethacin. The in vitro incubation of the preoptic/hypothalamic slices with the lipopolysaccharide also increased the amount of prostaglandin D2. These results suggest that the intraperitoneal administration of the lipopolysaccharide induces the release of prostaglandin D2 in the preoptic/hypothalamic area of rat brain and that the latter compound is involved in the hypothermic response of rats to the lipopolysaccharide.
Factors determining frequency of plasmid cointegration mediated by insertion sequence IS
1
Authors: Machida Yasunori , Machida Chiyoko , Ohtsubo Hisako , Ohtsubo Eiichi
Published: May 2006

We demonstrate that mutants with deletions at either end of the insertion sequence IS
1
lose the ability to mediate cointegration of two plasmids, whereas mutants with deletions or an insertion within IS
1
can mediate cointegration at a reduced frequency. These results, together with the nucleotide sequence analysis of the IS
1
mutants, indicate that the two ends of IS
1
(
insL
and
insR
) and two genes (
insA
and
insB
) that are encoded by IS
1
are required for cointegration. Using a plasmid carrying two copies of IS
1
, we found that the individual IS
1s
mediate cointegration at different characteristic frequencies, and that each of two parts of plasmid DNA segments flanked by the two IS
1s
is a transposon, mediating plasmid cointegration at a unique frequency. When one IS
1
was replaced with a mutant IS
1
, the remaining wild-type IS
1
complemented the cointegration ability of the mutant IS
1
as well as a resulting mutant transposon that was then flanked by a wild-type IS
1
and a mutant IS
1
. The efficiency of this complementation reflected the characteristic ability of an individual IS
1
present on the plasmid to promote cointegration. The results suggest that the IS
1
-encoded proteins are produced in different amounts, depending on the location of IS
1
in the plasmid, and that these amounts determine the efficiency of complementation of the cointegration ability of a mutant IS
1
as well as a mutant transposon. However, the location of an individual IS
1
itself can also determine the frequency of cointegration in the presence of a given amount of the IS
1
proteins. On the basis of the observation that the cointegration ability of a mutant IS
1
is less efficiently complemented than is the ability of a mutant transposon, we also suggest that the IS
1
-encoded proteins can function in
trans
, but act preferentially on the IS
1
or transposon sequence from which they are produced in promoting cointegration.
Coated vesicles from human placenta carry ferritin, transferrin, and immunoglobulin G.
Authors: Pearse B M
Published: May 2006

Coated vesicles prepared by using isotonic gradients retain their contents. Ferritin, transferrin, and immunoglobulin G have been detected in human placental coated vesicles. Triton X-100 extraction of crude coated vesicles removes contaminating uncoated membranes, leaving coated particles and their associated proteins apparently intact; this provides an efficient means of preparing large quantities of coated vesicle proteins. The clathrin cages surround "cores" of structural protein containing polypeptides of 100,000 and 50,000 molecular weight.
Proliferation and differentiation of single hapten-specific B lymphocytes is promoted by T-cell factor(s) distinct from T-cell growth factor.
Authors: Pike B L , Vaux D L , Clark-Lewis I , Schrader J W , Nossal G J
Published: May 2006

Hapten-specific B lymphocytes reactive to fluorescein were prepared from mouse spleen, placed singly in 10-microliters culture wells, and stimulated with fluorescein-polymerized flagellin in the presence of conditioned media (CM) from various concanavalin A-stimulated cloned T-cell tumors or hybridomas. Antigen plus appropriate CM triggered 5-9% of the B cells into both clonal proliferation and differentiation into antibody-forming cells. Antigen alone stimulated 0.5-0.8% of B cells and CM alone stimulated less than 0.1%. This bioactivity was termed B-cell growth and differentiation factor(s) (BGDF). Four CM rich in T-cell growth factor (TCGF)--namely, CM from spleen and the lines EL4, T6, and 123--contained BGDF. The lines T19.1 and WEHI-3 lacked BGDF and TCGF. Four lines of evidence suggested that BGDF and TCGF were distinct molecules. First, the BGDF/TCGF ratios in the various CM varied. Second, on gel filtration, TCGF eluted as a sharp peak corresponding to a Mr of about 35,000, whereas BGDF eluted over a range corresponding to a Mr of 25,000-60,000. Third, the activity of TCGF in EL4-CM was markedly reduced by treatment with guanidine HCl while BGDF activity was not. Fourth, BGDF showed more heterogeneity than TCGF on hydrophobic chromatography. All CM or fractions active in promoting B-cell division also promoted differentiation to antibody-forming cells. These results provide unequivocal evidence that antigen and a T-cell product can synergize to directly activate a single B lymphocyte.
Isolation and preliminary characterization of the GAL4 gene, a positive regulator of transcription in yeast.
Authors: Laughon A , Gesteland R F
Published: May 2006

The GAL4 locus encodes a positive regulator of the inducible galactose and melibiose genes of yeast. Using the yeast plasmid vector YEp13, we have cloned GAL4 by complementation of a gal4 mutation. Restriction endonuclease mapping of subclone DNA has delimited the region sufficient for complementation to a 3.2-kilobase segment of DNA. The GAL4 mRNA is 2.8 kilobases long, sufficient to encode a protein as large as 105,000 daltons. The concentration of the GAL4 transcript is about 0.1 per cell and is almost identical in galactose-induced and noninduced cells. This result is consistent with a previously proposed model in which the activity of the GAL4 protein and not the transcription of the GAL4 gene is modulated by galactose induction.
Dimethyl sulfoxide affects colony morphology on agar and alters distribution of glycosaminoglycans and fibronectin.
Authors: Dairkee S H , Glaser D A
Published: May 2006

We have found striking changes in the morphology of colonies of Chinese hamster ovary cells grown on agar containing low doses of dimethyl sulfoxide. Effects on morphology of cells grown on plastic at the same dimethyl sulfoxide concentrations were not as pronounced. Computer-assisted analysis of darkfield photographs of growing colonies proved very useful in measuring the magnitude of morphological changes at various doses. A large decrease in total cell-bound and released glycosaminoglycans (GAGs) was observed in the presence of dimethyl sulfoxide by measuring incorporation of radiolabeled precursors into cetylpyridinium chloride-precipitable GAGs in Chinese hamster ovary cells. By contrast, dimethyl sulfoxide was found to cause an increase in the network of fibronectin (the large external transformation-sensitive protein) at the cell surface. These observations demonstrate the association of GAGs and fibronectin in processes affecting the three-dimensional growth patterns of aggregates of mammalian cells and also demonstrate the sensitivity of agargrown colonies as model systems for quantitatively measuring the morphological changes induced by exogenous agents such as drugs, hormones, growth factors, mutagens, and carcinogens. These findings might be relevant to the study and treatment of the important class of genetic diseases called mucopolysaccharidoses which result in mental, skeletal, and ocular defects as a consequence of GAG accumulation.
A theory of allelic and isotypic exclusion for immunoglobulin genes.
Authors: Wabl M , Steinberg C
Published: May 2006

Heavy (H) chain binding protein (BiP), which binds to free immunoglobulin H chain of the mu and gamma classes, can be demonstrated in pre-B-cells. It is proposed that the displacement of BiP from H chain by light (L) chain terminates the activity of the enzyme system, L-generase, which catalyzes DNA rearrangement at the L chain loci, generating the complete gene which may or may not be functional. This ensures allelic and isotypic exclusion for the L chain loci. It is further proposed that those cells that productively rearrange both alleles at the H chain locus are eliminated by the "H chain toxicity" effect.
In vivo uptake of chylomicron [3H]retinyl ester by rat liver: evidence for retinol transfer from parenchymal to nonparenchymal cells.
Authors: Blomhoff R , Helgerud P , Rasmussen M , Berg T , Norum K R
Published: May 2006

We have studied hepatic uptake of chylomicron retinyl ester. Chylomicrons were obtained from intestinal lymph of rats that were given retinol in groundnut oil by intraduodenal injection. When lymph was injected intravenously into normal rats, the radioactivity was cleared from blood with t1/2 approximately equal to 10 min. Retinyl ester was taken up initially by the liver, which, after 30 min, contained 80-90% of the radioactivity injected. Initially, most of the radioactivity was in hepatocytes, but after 30 min it disappeared from these cells and reappeared in nonparenchymal liver cells. After 2 hr these cells contained more radioactivity than the hepatocytes. When lymph was injected into vitamin A-deficient rats or rats given vitamin A in the form of retinoic acid, the plasma clearance and initial hepatic uptake of radioactivity were similar to that found in control animals. However, the nonparenchymal cells in these animals did not accumulate radioactivity. The current data suggest that vitamin A (in chylomicron remnants) is taken up initially by hepatocytes and then is released from these cells and delivered mainly to nonparenchymal liver cells in normal animals. In vitamin A-deficient rats, the vitamin is transferred from the hepatocytes to extrahepatic tissues.
Internal dialysis of Limulus ventral photoreceptors.
Authors: Stern J H , Lisman J E
Published: May 2006

The internal dialysis technique has been applied to Limulus ventral photoreceptors. This method potentially allows quantitative control of the concentration of diffusible molecules within living cells. During dialysis, Limulus photoreceptors retained their ability to respond to light. Under conditions of dim illumination, responses were normal for close to an hour. In bright light, abnormalities developed more rapidly. The reversible effects of raising the dialysate Mg2+ concentration and the entrance of rhodamine-labeled albumin into cells shows that the dialysis method is useful for assaying the effects of small or large molecules on visual transduction. This method has been used to examine the effects of nucleotide triphosphates and cyclic nucleotides. The results show that nucleotide triphosphates (5-10 mM) are required to maintain a low rate of spontaneous quantum bumps. The importance of cyclic nucleotides in transduction is less clear; the light response was reduced by either cGMP or cAMP but only at very high concentrations (10 mM).
Opiates and classical conditioning: selective abolition of conditioned responses by activation of opiate receptors within the central nervous system.
Authors: Mauk M D , Madden J , Barchas J D , Thompson R F
Published: May 2006

It has previously been shown that opiates produce selective abolition of aversively motivated classically conditioned responses in the rabbit. The experiments reported here show that these effects are mediated by specific activation of opiate receptors within the central nervous system in that this central activation is both necessary and sufficient to produce opiate-induced abolition of conditioned responding. Further characterization suggests that selective activation through opiate-mu-receptor interactions within the periaqueductal gray/periventricular region of the fourth ventricle may be critical in mediating this abolition.
Isolated-patch recording from liposomes containing functionally reconstituted chloride channels from Torpedo electroplax.
Authors: Tank D W , Miller C , Webb W W
Published: May 2006

Small unilamellar vesicles formed from purified phospholids by detergent/dialysis methods may be enlarged to 30-microns diameter by freezing and thawing. Very-high-resistance seals were formed by applying a glass micropipette to the surface of these large liposomes, and single bilayer "patches" of membrane were isolated from the liposome surface while remaining sealed to the micropipette. The exogenous channel-forming peptides gramicidin and alamethicin induced characteristic single-channel fluctuation behavior in these excised patches held under voltage-clamp conditions. Large liposomes were formed from the small unilamellar vesicles made from cholate extracts of Torpedo electroplax plasma membrane vesicles. Isolated patches formed from these reconstituted membranes displayed current fluctuations due to single voltage-gated Cl- channels from non-innervated-face membranes; the properties of these Cl- channels are identical to those observed in planar bilayer membranes after direct insertion from native membranes. This liposome-patch method combines the advantages of membrane protein incorporation into liposomes with high-resolution electrical recording methods and may provide a generally applicable approach to the study of integral membrane channel proteins after solubilization and reconstitution.
Chemosensory recognition of phenotypes determined by the Tla and H-2K regions of chromosome 17 of the mouse.
Authors: Yamazaki K , Beauchamp G K , Bard J , Thomas L , Boyse E A
Published: May 2006

It is known that mice can distinguish the H-2 haplotypes of other mice by scent and that urine is a potent source of the characteristic odors governed by H-2. It now is shown that genetic disparity confined to the Qa:Tla region of chromosome 17, adjacent to H-2, is accompanied by distinctive urinary scents that can be distinguished by trained mice in a Y maze. This was confirmed by the transfer of training procedure in which mice trained to distinguish the urine of B6 mice from the urine of recombinant congeneic B6-Tlaa mice successfully distinguished the urines of Tlaa and Tlab homozygous F2 segregants of the cross B6 X B6-Tlaa in the absence of reward, including blind trials with coded urine samples. It also is shown that genetic disparity confined to the K end of H-2 is accompanied by distinctive urinary scents recognized in the Y maze. Thus, mice trained to distinguish the urines of B10 from B10.A congeneic mice successfully distinguished various combinations of B10, B10.A, and B10.A (2R, 3R, 5R, and 18R) recombinant congeneic mice representing genetic differences limited to the K end of H-2. It is suggested that the individual scents of mice comprise several odorous components, at least some of which may be incidental to quantitative or qualitative metabolic variations arising from polymorphism of genes such as H-2.
Translocation of the c-myc gene into the immunoglobulin heavy chain locus in human Burkitt lymphoma and murine plasmacytoma cells.
Authors: Taub R , Kirsch I , Morton C , Lenoir G , Swan D , Tronick S , Aaronson S , Leder P
Published: May 2006

The consistent appearance of specific chromosomal translocations in human Burkitt lymphomas and murine plasmacytomas has suggested that these translocations might play a role in malignant transformation. Here we show that transformation of these cells is frequently accompanied by the somatic rearrangement of a cellular analogue of an avian retrovirus transforming gene, c-myc. Moreover, we map c-myc to human chromosome 8 band q24, the chromosomal segment involved in the reciprocal Burkitt translocations [t(8;14), t(8;22) and t(2;8)]. In two t(8;14) human Burkitt cell lines, c-myc appears to have been translocated directly into a DNA restriction fragment that also encodes the immunoglobulin mu chain gene. In the case of a specific cloned fragment of DNA derived from a mouse plasmacytoma, we demonstrate directly that c-myc has been translocated into the immunoglobulin alpha switch region. Our data provide a molecular basis for considering the role that specific translocations might play in malignant transformation.
Peptaibol antibiotics: a study on the helical structure of the 2-9 sequence of emerimicins III and IV.
Authors: Benedetti E , Bavoso A , Di Blasio B , Pavone V , Pedone C , Toniolo C , Bonora G M
Published: May 2006

Solution conformations of the protected 2-9 segment of the peptaibol antibiotics emerimicins III and IV [alpha-aminoisobutyric acid (Aib)]3-L-Val-Gly-L-Leu-(Aib)2 and the related short sequences benzyloxy-(Aib)3-L-Val-OMe and benzyloxy-(Aib)3-L-Val-Gly-OMe have been investigated by circular dichroism studies. For the latter two compounds the structural preferences in the solid state have been assayed by x-ray diffraction analyses. The experimental data described here, along with those previously reported, support the view that the shortest Aib-containing segments (from tri- through pentapeptides) adopt the 3(10)-helical structure both in solution and in the solid state. In contrast, the octapeptide appears to adopt the alpha-helical structure in solution. The role of peptide chain length and specific amino acid sequences in stabilizing either of the two helical structures and hence their possible implications on the nature of the channel formed by peptaibol antibiotics in the membrane are also briefly outlined.
Assembly map of the large subunit (50S) of Escherichia coli ribosomes.
Authors: Röhl R , Nierhaus K H
Published: May 2006

Stoichiometric amounts of ribosomal proteins and RNA derived from the 50S subunit reconstitute to fully active particles under the conditions of a two-step incubation procedure. After the first incubation, all components are found in a particle that is activated in the second incubation [Dohme, F. & Nierhaus, K. H. (1976) J. Mol. Biol. 107, 585-599]. Here we describe the assembly dependences of the ribosomal components in the first incubation. Assembly dependence is the requirements of one protein that, before it binds, another must be first built into the ribosome. After incubation of 23S RNA and the proteins under observation, the mixture was subjected to sucrose gradient analysis. The RNA-protein complex was precipitated with trichloroacetic acid and the proteins were identified by NaDodSO4 gel electrophoresis. The assembly dependences of 26 proteins could be elucidated. In a second series of experiments, the incorporation of 3H-labeled 5S RNA in the 23S-protein complex was analyzed. It was found that L5, L15, and L18 are absolutely required for 5S RNA incorporation. In addition, two of the three proteins L2, L3, and L4 are needed, in excellent agreement with the protein dependences. The data are summarized in an assembly map. Comparison with other data shows a structural domain at the 5' end of 23S RNA around protein L20 combining all proteins essential in the early assembly. All the proteins essential for the reconstitution of the peptidyltransferase protein form a skeleton of strong assembly dependences. Finally, L proteins whose genes are present in large transcriptional units on the chromosome depend on each other during assembly.
Determinants of the selective toxicity of alloxan to the pancreatic B cell.
Authors: Malaisse W J , Malaisse-Lagae F , Sener A , Pipeleers D G
Published: May 2006

The diabetogenic agent alloxan exerts a preferential cytotoxic effect on the pancreatic B cell. The determinants of such a tissue specificity were investigated. Alloxan accumulated rapidly in liver and pancreatic islets but much more slowly in muscle. The activity of glutathione peroxidase and the resistance to exogenous peroxide were approximately 20 times higher in liver and kidney than in islets, intermediate values being found in exocrine pancreas and muscle. These findings suggest that the selective cytotoxicity of alloxan to the pancreatic B cell is attributable to the conjunction of two features: a rapid cellular uptake of the drug and an exquisite sensitivity of the B cell to peroxide.
Quantitative model for gene regulation by lambda phage repressor.
Authors: Ackers G K , Johnson A D , Shea M A
Published: May 2006

A statistical thermodynamic model has been developed to account for the cooperative interactions of the bacteriophage lambda repressor with the lambda right operator. The model incorporates a general theory for quantitatively interpreting cooperative site-specific equilibrium binding data. Values for all interaction parameters of the model have been evaluated at 37 degrees C, 0.2 M KCl, from results of DNase protection experiments in vitro [A. D. Johnson, B. J. Meyer, & M. Ptashne, Proc. Natl. Acad. Sci. USA (1979) 76, 5061-5065]. With these values, the model predicts repression curves at the divergent promoters PR and PRM that control transcription of genes coding for the regulatory proteins cro and repressor, respectively. At physiological repressor concentrations, repression at PR is predicted to be nearly complete whereas PRM is predicted to remain highly active. The results demonstrate the importance of cooperative interactions between repressor dimers bound to the adjacent operator sites OR1 and OR2 in maintaining a stable lysogenic state and in allowing efficient switchover to the lytic state during induction.
Methane: Interhemispheric concentration gradient and atmospheric residence time
Authors: Mayer Edward W. , Blake Donald R. , Tyler Stanley C. , Makide Yoshihiro , Montague Derek C. , Rowland F. Sherwood
Published: May 2006

The ground level concentrations of methane in the atmosphere have been measured to be in the range from 1.45 to 1.62 parts per million by volume (ppmv) of dry air in remote locations between 62°N and 54°S latitudes during the time period from November 1977 to July 1979. The average (±rms) concentration for the northern hemisphere was 1.57 ± 0.02 ppmv in January 1978 and 1.59 ± 0.02 in July 1979. The average concentration in the southern hemisphere was lower—1.47 ± 0.02 in January 1978 and 1.51 ± 0.01 in July 1979. The ratio of concentrations between the two hemispheres was 1.068 ± 0.016 in January 1978 and 1.055 ± 0.013 in July 1979, for an average of 1.06 ± 0.01. The higher concentrations in the northern hemisphere require either that the sources of methane lie preferentially in the northern hemisphere or that the removal processes operate more rapidly in the southern hemisphere or both. The primary removal process for CH
4
is reaction with tropospheric OH radicals and its estimated atmospheric lifetime is 10.5 ± 1.8 yr. The observed interhemispheric gradient is consistent with this lifetime and preferential release of methane in the northern hemisphere. Measurements taken in the Amazon basin region indicate the presence of a substantial source of methane in that area.
Perturbation of the metabolism of essential fatty acids by dietary partially hydrogenated vegetable oil.
Authors: Hill E G , Johnson S B , Lawson L D , Mahfouz M M , Holman R T
Published: May 2006

Rats were fed purified diets containing (i) partially hydrogenated soybean oil as source of isomeric octadecenoic acids, (ii) hydrogenated coconut oil as source of saturated fatty acids, and (iii) a low level of corn oil as low-fat control. All diets contained 18% of the linoleate requirement. Rat liver and heart phospholipids were analyzed by gas/liquid chromatography for fatty acids, and liver, microsomes were assayed for desaturase (acyl-CoA, hydrogen-donor: oxidoreductase, EC 1.14.99.5) activities. Products of desaturation reactions measured analytically provided more information with greater statistical significance than did the enzymatic assays. Rats fed isomeric octadecenoic acids showed more severe essential fatty acid deficiency than did saturated-fat and control groups. The suppression of linoleate metabolites was largely due to decreased delta 5 and delta 6 desaturase activities. At several levels of linoleate, the deficiency was more severe at the higher level of isomeric octadecenoic acids. Increasing the intake of linoleate to 7.5% of calories did not suppress deposition of isomeric unsaturated acids in tissue lipids.
Proteins antigenically related to the human erythrocyte glucose transporter in normal and Rous sarcoma virus-transformed chicken embryo fibroblasts.
Authors: Salter D W , Baldwin S A , Lienhard G E , Weber M J
Published: May 2006

Antibody raised against the purified human erythrocyte glucose transporter specifically precipitated four proteins from normal and Rous sarcoma virus-transformed chicken embryo cells: a major protein of Mr 41,000 and minor proteins of Mr 68,000, 73,000, and 82,000. The Mr 41,000 and 82,000 proteins were found only in a membrane fraction, not in the soluble fraction, and displayed a heterogeneous mobility on NaDodSO4/polyacrylamide gel electrophoresis, suggesting glycosylation. The Mr 41,000 and 82,000 proteins were increased in amount after malignant transformation in direct proportion to the increase in hexose transport rate, and the increase was dependent on the expression of the src gene product, as revealed with a temperature-conditional src mutant. We suggest that the Mr 41,000 and 82,000 proteins are the glucose transporter of chicken embryo fibroblasts, or a component of the glucose transporter. These experiments provide direct evidence that malignant transformation increases the rate of glucose transport by increasing the number of transporters in the membrane.
Mitogenic leukoagglutinin from Phaseolus vulgaris binds to a pentasaccharide unit in N-acetyllactosamine-type glycoprotein glycans.
Authors: Hammarström S , Hammarström M L , Sundblad G , Arnarp J , Lönngren J
Published: May 2006

The carbohydrate binding specificity of leukoagglutinin (La; Phaseolus vulgaris isolectin L4) was studied by using quantitative precipitation and precipitation-inhibition. A series of purified glycopeptides and synthetic oligosaccharides were used as inhibitors. The minimal structural unit required for La binding was the disaccharide GlcNac(1 leads to beta 2)Man. Additions for this basic unit of different sugar residues gave a positive or negative contribution to binding. The most complementary structure was the pentasaccharide (formula: see text). This pentasaccharide units occurs in tetraantennary N-acetyllactosamine-type glycoprotein glycans. Glycoproteins containing such structures were accordingly precipitated by La. Selected glycopeptides and oligosaccharides were also tested as inhibitors of La-induced DNA synthesis in human lymphocytes. The pattern of inhibition was essentially the same as that obtained by precipitation-inhibition, indicating that binding to lymphocytes via the carbohydrate binding site of the lectin is an essential step in the activation process.
Kallikrein-like activity of crotalase, a snake venom enzyme that clots fibrinogen.
Authors: Markland F S , Kettner C , Schiffman S , Shaw E , Bajwa S S , Reddy K N , Kirakossian H , Patkos G B , Theodor I , Pirkle H
Published: May 2006

During the amino acid sequence determination of crotalase (EC 3.4.21.30), the thrombin-like enzyme from the venom of Crotalus adamanteus (eastern diamondback rattlesnake), we found that, in addition to the expected structural homology with bovine thrombin (EC 3.4.21.5), there was even greater homology with porcine pancreatic kallikrein (EC 3.4.21.8). In exploring further the similarities between crotalase and kallikrein, several striking observations were made. First, crotalase was rapidly and specifically inhibited by the tripeptide affinity labeling derivative prolylphenylalanylarginine chloromethyl ketone, which is known to be a specific inhibitor of kallikrein. Second, NaDodSO4/acrylamide gel electrophoresis revealed that crotalase cleaves the plasma kallikrein-susceptible bonds in human high molecular weight kininogen, producing an intermediate with procoagulant activity. Crotalase-catalyzed cleavage of high molecular weight kininogen also liberates kinin as evidenced by rat blood pressure bioassay. Finally, crotalase exhibits substrate specificity not only for the thrombin chromogenic substrate S-2238 but also for the kallikrein substrates S-2302 and S-2266. Interestingly, one of the other reactions catalyzed by plasma kallikrein, the activation of plasminogen, was not one of the activities exhibited by crotalase.
3-Methyladenine: Specific inhibitor of autophagic/lysosomal protein degradation in isolated rat hepatocytes
Authors: Seglen Per O. , Gordon Paul B.
Published: May 2006

3-Methyladenine (5 mM) inhibits endogenous protein degradation in isolated rat hepatocytes by about 60%, while having no adverse effect on the degradation of an exogenous protein (asialofetuin), on protein synthesis, or on intracellular ATP levels. 3-Methyladenine appears to act specifically upon the autophagic/lysosomal pathway of degradation, as judged from its lack of effect in the presence of amino acids or a lysosomotropic amine (propylamine). The effect of the purine is not mediated by amino acids because the inhibition of protein degradation is accompanied by a significant depression of intracellular amino acid levels. The ability of 3-methyladenine to suppress the formation of electron microscopically visible autophagosomes suggests that it may be regarded as a specific inhibitor of autophagy.
Linkage disequilibrium due to random genetic drift in finite subdivided populations
Authors: Ohta Tomoko
Published: May 2006

In order to clarify the mechanisms responsible for the observed linkage disequilibrium, such as that found between markers in the major histocompatibility complex of man and mouse, linkage disequilibrium between two linked loci was studied for a finite population with a subdivided structure. The infinite allele model was used. In analogy with the subdivision of the inbreeding coefficient, the linkage disequilibrium coefficient was subdivided, and various variance components of disequilibrium were defined. It was found that the disequilibrium components may get very large when migration is limited if the correlation of alleles at the two loci within a colony is taken relative to that of the entire population. In other words, with limited migration, random genetic drift of gamete types prevails in each colony. A possible test in which the variance components of disequilibrium are compared is suggested; the test discriminates between epistatic natural selection and limited migration, showing the former as the main cause of the observed linkage disequilibrium. It is pointed out that the major histocompatibility complex polymorphism is in accord with the population genetics model of multigene families that incorporate gene conversion or double unequal crossing-over between the loci in the supergene family.
Tangier disease: a structural defect in apolipoprotein A-I (apoA-I Tangier).
Authors: Kay L L , Ronan R , Schaefer E J , Brewer H B
Published: May 2006

Tangier disease is a familial disorder characterized by orange tonsils, cholesterol ester deposition in reticuloendothelial cells, abnormal chylomicron remnants, and a marked reduction in high density lipoproteins. Plasma concentrations of the apolipoproteins apo-A-I and apoA-II in patients with Tangier disease are approximately 1% and 7% of those in normal subjects, respectively. Previous studies have shown that the low plasma concentrations of apoA-I and apoA-II are due to increased fractional catabolism with a relatively normal apoA-I and apoA-II synthesis. Plasma apoA-I and apoA-II were isolated to electrophoretic homogeneity from delipidated plasma lipoproteins from a patient with Tangier disease. ApoA-I Tangier differed from apoA-I from control subjects in amino acid composition, electrophoretic mobility, apparent molecular weight on sodium dodecyl sulfate/polyacrylamide gel electrophoresis, and heterogeneity of isoforms on isoelectric focusing. ApoA-II Tangier, however, appeared to be identical to normal apoA-II in amino acid composition and in immunological as well as chemical properties. These results have been interpreted as indicating that apoA-I Tangier has a different covalent structure than does normal apoA-I, and apoA-II Tangier is identical to normal apoA-II. This structural change in apoA-I Tangier is associated with rapid catabolism of apoA-I Tangier-and apoA-II Tangier-containing plasma lipoproteins, and it leads to the deficiency in high density lipoproteins, abnormal chylomicron remnants, and the intracellular accumulation of cholesterol ester characteristic of Tangier disease.
Nucleotide sequence of the structural gene for colicin E1 and predicted structure of the protein.
Authors: Yamada M , Ebina Y , Miyata T , Nakazawa T , Nakazawa A
Published: May 2006

We have determined the nucleotide sequence of the structural gene for colicin E1, which consists of 1,566 base pairs. The amino acid sequence (522 residues) of the protein was derived from the DNA sequence, and the molecular weight was calculated to be 57,279. From the analysis of the predicted secondary structure, there appear to be three consecutive long alpha-helices in the NH2-terminal half of the polypeptide, spanning 40, 100, and 35 amino acid residues. In addition, there is a polypeptide region near the COOH terminus that shows homology to the NH2-terminal signal portions of outer membrane lipoprotein in Escherichia coli and beta-lactamase in Bacillus licheniformis. Most of the homologous amino acids are located in the region where either alpha-helix or beta-sheet would be expected to occur, as determined from the amino acid sequence. These characteristics of the predicted protein structure might correspond to properties of colicin E1 as an ionophore in its antimicrobial action and also as an exported protein during its induced synthesis.
Nucleotide sequence to the v-myc oncogene of avian retrovirus MC29.
Authors: Alitalo K , Bishop J M , Smith D H , Chen E Y , Colby W W , Levinson A D
Published: May 2006

Avian myelocytomatosis viruses are retroviruses whose oncogene (v-myc) induces an unusually wide variety of tumors, including carcinomas, endotheliomas, sarcomas, and myelocytomatoses. The viral gene v-myc arose by transduction of an undetermined portion of a cellular gene known as c-myc. In order to facilitate further studies of the functions of v-myc and c-myc and to permit detailed comparisons between the two genes, we have determined the nucleotide sequence of v-myc in the genome of the MC29 strain of myelocytomatosis virus. The v-myc domain in MC29 virus encodes a hydrophilic polypeptide with a molecular weight of 47,000, fused to a portion of the polyprotein encoded by the viral structural gene gag. The carboxyl-terminal half of the v-myc polypeptide is rich in basic amino acid residues. This feature may account for the DNA-binding properties of the hybrid gag-myc-encoded protein which would have a molecular weight of approximately 100,000, in accord with results from previous studies of the protein encoded by v-myc. The junctions between v-myc and the genome of the transducing virus are apparent but reveal no clues to the mechanism by which transduction might occur.
Instability of dicentric plasmids in yeast.
Authors: Mann C , Davis R W
Published: May 2006

Dicentric plasmids containing either two copies of centromere 4 or one copy of centromere 4 and one copy of centromere 3 in the yeast plasmid vector YRp17 were constructed in vitro and introduced into yeast cells by DNA transformation. The resulting colonies were heterogeneous for a mixed population of rearranged plasmids. The rearrangements always involved deletion of one or both centromere sequences originally present on the plasmid. Heterogeneity was due to the continued production of deleted plasmids from a pool of unrearranged dicentric plasmids maintained within some of the yeast cells in the colony. The RAD52 gene product is known to be required for the repair of DNA double-strand breaks in yeast. Transformation of rad52 mutant yeast cells with dicentric plasmids gave rearranged plasmids similar to those observed with RAD+ yeast cells, but the transformation frequency was only 5-10% compared to transformation with monocentric plasmids. Also, the ratio of unrearranged dicentric plasmid to deleted plasmids was greatly reduced in the rad52-transformed cells. These observations are consistent with a model in which centromeric DNA sequences can interact independently with the yeast cell spindle apparatus. Occasional movement of centromeres to opposite poles may result in mechanical breakage of plasmid sequences. Plasmids deleted for one or both centromere sequences can be obtained from these broken molecules and are resistant to further rearrangement.
Association of the lethal yellow (Ay) coat color mutation with an ecotropic murine leukemia virus genome.
Authors: Copeland N G , Jenkins N A , Lee B K
Published: May 2006

The dilute (d) coat color mutation on chromosome 9 is closely associated with an ecotropic murine leukemia virus (MuLV) genome [Jenkins, N.A., Copeland, N.G., Taylor, B.A. & Lee, B.K. (1981) Nature 293, 370-374]. DBA/2J mice homozygous for the reverse mutation to wild type at the dilute locus (d+2J) lack ecotropic virus-specific sequences, suggesting that the dilute mutation was caused by virus integration. In the experiments described here, we analyzed the ecotropic MuLV DNA content of mice that collectively carry 10 different alleles at the agouti coat color locus (of chromosome 2) to determine whether any of these alleles also are associated with ecotropic virus sequences. Of the 10 alleles analyzed, one allele, lethal yellow (Ay), which is carried congeneically and heterozygously on C57BL/6J, 129/Sv, and LT/Sv mice, was closely associated with an ecotropic MuLV provirus. The close association of this provirus with the Ay allele suggests that this mutation also may be caused by virus integration. Furthermore, this association may be useful for molecular cloning and characterizing the many alleles at this locus.
Structural features of a phased nucleosome core particle.
Authors: Simpson R T , Stafford D W
Published: May 2006

Chicken erythrocyte inner histones associate with a cloned 260-base-pair (bp) segment of Lytechinus variegatus DNA in a unique location. The fragment contains a 120-bp segment encoding 5S rRNA, a 90-bp flanking sequence to the 5' side of the transcribed segment, and a 50-bp downstream flanking sequence. Association of DNA, uniquely labeled at one end or the other and at either the 3' or the 5' terminus of a given strand, with histones at 0.1 M ionic strength leads to formation of a compact complex which sediments at about 13 S. Analysis of cutting of the complex by DNase I shows that protection from the nuclease is confined to a region beginning 20 bp from the left end of the segment and extending to about 165 bp from the left end. Within the protected region, the two DNA strands differ in their susceptibilities to the nuclease, the precise location of nuclease cutting sites and the spacing between these sites, and the relative susceptibilities of specific cutting locations. It seems that information present in DNA and the histone octomer is sufficient to create a precisely phased nucleosome in which interactions of the two DNA strands with histones are not the same. The structure of this unique nucleosome is not predicted by the intellectual model based on studies of mixed populations of nucleosome core particles.
In vitro nonsense suppression in [psi+] and [psi-] cell-free lysates of Saccharomyces cerevisiae.
Authors: Tuite M F , Cox B S , McLaughlin C S
Published: May 2006

An homologous in vitro assay for yeast nonsense suppressors was used to examine the effect of the cytoplasmically inherited genetic determinant [psi] on the efficiency of in vitro nonsense suppression. The efficiency of all three types of yeast tRNA-mediated nonsense suppressor (ochre, amber, and UGA) is much greater in cell-free lysates prepared from a sup+ [psi+] strain than in lysates prepared from an isogeneic sup+ [psi-] strain. Lysates prepared from a [psi-] strain, into which the [psi+] determinant was reintroduced by kar1-mediated cytoduction, support efficient suppression. Evidence is also presented that [psi-] lysates contain an inhibitor of in vitro nonsense suppression.
Some general principles in free energy transduction.
Authors: Hill T L
Published: May 2006

Chemical potentials or standard chemical potentials of bound ligands cannot be used to follow the step-by-step transfer of free energy from one ligand to another in a free energy transducing cycle. The basic difficulty is that, in most states of the cycle, separate ligand free energies are not even defined because, when ligands are bound on the enzyme, the interaction free energy of the complex cannot simply be assigned to ligands nor in general even be divided between two ligands if both are bound. This is a mutual, indivisible free energy among enzyme and ligands. Separate ligand free energies are well defined only at the complete cycle level, where the enzyme drops out of consideration (returns to its original state). Other types of free energy are also considered in order to discuss recent work of Tanford. In principle, the kinetics and mechanism can be followed in molecular or atomic detail through the steps of a transduction cycle, but the transfer of free energy from one ligand to another cannot be so followed.
Cytoplasmic and chloroplast synthesis of phycobilisome polypeptides
Authors: Egelhoff Thomas , Grossman Arthur
Published: May 2006

In vivo
labeling of eukaryotic phycobilisomes in the presence of inhibitors of translation on 70S and 80S ribosomes demonstrates that some of the polypeptides of this light-harvesting complex are synthesized in the cytoplasm while others are synthesized in the chloroplast. The major pigmented polypeptides, the α and β subunits of the biliproteins (molecular weights between 15,000 and 20,000) and the anchor protein (molecular weight about 90,000) are translated on 70S ribosomes. This suggests that these polypeptides are made within the algal chloroplast. Because the α and β subunits comprise a group of closely related polypeptides, the genes encoding these polypeptides may reside in the plastid genome as a multigene family. Other prominent phycobilisome polypeptides, including a nonpigmented polypeptide that may be involved in maintaining the structural integrity of the complex, are synthesized on cytoplasmic ribosomes. Because the synthesis of phycobilisomes appears to require the expression of genes in two subcellular compartments, this system may be an excellent model for: (
i
) examining interaction between nuclear and plastid genomes: (
ii
) elucidating the molecular processes involved in the evolution of plastid genes: (
iii
) clarifying the events in the synthesis and assembly of macromolecular complexes in the chloroplast.
A short 5′ flanking region containing conserved sequences is required for silkworm alanine tRNA gene activity
Authors: Larson Drena , Bradford-Wilcox Janice , Young Lisa S. , Sprague Karen U.
Published: May 2006

Using partially deleted genes, we have identified an upstream control signal required for transcription of a
Bombyx mori
(silkworm) tRNA
2
Ala
gene. The 5′ boundary of this essential region lies between 34 and 11 nucleotides preceding the transcription initiation site. Sequences in the 5′ half of the tRNA
2
Ala
coding region are also important. Both regions contain oligonucleotides that are conserved among several
Bombyx
genes transcribed by RNA polymerase III, suggesting that these sequences may have a general control function.