bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of the separated catalytic and regulatory units of brain adenylate cyclase.
Authors: Strittmatter S , Neer E J
Published: May 2006

Adenylate cyclase from bovine brain cortex was solubilized with 14 mM cholate and 1 M (NH4)2SO4. Gel filtration over a column of Sepharose 6B separated the catalytic unit (CU) from a factor (G/F) that confers responsiveness to 5'-guanylyl imidophosphate (p[NH]ppG) or fluoride. The separated CU, which elutes with a Kav, of 0.48 +/- 0.01 (n=5), is not responsive to p[NH]ppG or fluoride and is relatively inactive when Mg . ATP is the substrate but activated 8-15-fold by Mn2+. The separated G/F elutes with a Kav of 0.70 +/- 0.02 (n=4). It restores the responsiveness of the CU to p[NH]ppG and fluoride. Activation of the enzyme by p[NH]ppG before solubilization does not decrease the amount of G/F eluting with a Kav of 0.7. Therefore, the G/F is probably present in brain cortex in excess over the CU. p[NH]ppG stabilizes the G/F but not the CU against thermal inactivation, suggesting that it interacts with G/F and not with CU. Incubation of the G/F with p[NH]ppG before addition of CU markedly increases the rate of activation of the reconstituted enzyme by p[NH]ppG. We propose, therefore, that the rate-limiting step in adenylate cyclase activation is a process in G/F alone and not a slow conformational change in CU or a slow association of G/F with CU. Binding of p[NH]ppG to the isolated G/F appears to be readily reversible; the ability of fully activated G/F to stimulate CU can be blocked if GDP is added before CU. In contrast, after the CU has been activated by interaction with G/F, GDP cannot reverse the activation. This suggests that association with the CU increases the affinity of G/F for p[NH]ppG.
Anionic lipid domains: correlation with functional topography in a mammalian cell membrane.
Authors: Bearer E L , Friend D S
Published: May 2006

Polymyxin B was used to explore distribution of anionic phospholipids in sperm plasma membranes by electron microscopy of freeze-fracture replicas. After exposure to Hepes/Tris-buffered polymyxin at 4 mM, phosphatidylcholine liposomes showed no perturbations nor did they fluoresce with dansylated incubation. When phosphatidylethanolamine was included in the liposomes, they became perturbed and fluoresced. Plasma membranes of Drosophila larval cells, containing or lacking cholesterol, were also disrupted by polymyxin. The cell membranes of guinea pig sperm were likewise disrupted but in specific functional areas. Fusional membrane domains showed protrusions; the stable membrane of the flagellum revealed diffuse bubbling. Regions of well-defined particle arrays and the postacrosomal segment maintained smooth contours. By fluorescence microscopy, we detected the same heterogeneous binding of the polymyxin dansyl derivative.
Antipain inhibits N-methyl-N'-nitro-N-nitrosoguanidine-induced transformation and increases chromosomal aberrations.
Authors: DiPaolo J A , Amsbaugh S C , Popescu N C
Published: May 2006

The morphologic transformation induced in Syrian hamster embryo cells by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) (0.25 microgram/ml of medium) is inhibited by posttreatment with antipain (6-600 microgram/ml), a protease inhibitor, but is unaffected by pretreatment. DNA replication relative to untreated controls is not affected by MNNG, antipain, or the combination of the two; no synergistic lethality of antipain and MNNG occurred as reflected in the cloning efficiency. Antipain was ineffective in influencing MNNG-induced sister chromatid exchanges, but it increased frequencies of chromosomal aberration (per metaphase) at 10, 26, and 40 hr when cells were treated with MNNG at 0.25 microgram/ml of medium followed by antipain 10 min later, the procedure used in the transformation studies. Antipain also increased the average number of aberrations at the second mitosis (34 hr) when the MNNG concentration was doubled. Chromatid exchanges increased 26 hr posttreatment with the combination of MNNG and antipain used for transformation. No difference in MNNG-induced aberrations was observed when antipain preceded MNNG by 24 hr. Although the mode of actin of antipain is unknown, antipain does not inhibit transformation by suppressing chromosomal rearrangements that could convert recessive mutations to the homozygous state.
Maternal inheritance of human mitochondrial DNA.
Authors: Giles R E , Blanc H , Cann H M , Wallace D C
Published: May 2006

Human mitochondrial DNA was obtained from peripheral blood platelets donated by the members of several independent families. The samples were screened for nucleotide sequence polymorphisms between individuals within these families. In each family in which we were able to detect a distinctly different restriction endonuclease cleavage pattern between the parents, the progeny exhibited the maternal cleavage pattern. Informative polymorphisms were detected for Hae II (PuGCGCPy) in a three-generation family composed of 33 members, for HincII (GTPyPuAC) in a two-generation family composed of four members, and for Hae III(GGCC) in a two-generation family composed of four members. The Hae II polymorphism was analyzed through all three generations in both the maternal and paternal lines. The results of this study demonstrate that human mitochondrial DNA is maternally inherited. The techniques described for using peripheral blood platelets as a source of human mitochondrial DNA represent a convenient way to obtain data on mitochondrial DNA variation in both individuals and populations.
Resistance of simian virus 40-transformed hamster cells to the cytolytic effect of activated macrophages: a possible factor in species-specific viral oncogenicity.
Authors: Cook J L , Hibbs J B , Lewis A M
Published: May 2006

Simian virus 40 (SV40)-transformed hamster cells were relatively resistant to the lytic effect of activated macrophages from animals with chronic intracellular infections. Conversely, SV40-transformed mouse and rat cells and adenovirus 2-transformed hamster cells were highly susceptible to destruction by tumoricidal activated macrophages. The pattern of resistance or susceptibility of SV40-transformed rodent cells was the same whether activated macrophage effectors were obtained from mice, random-bred hamsters, or the inbred LSH hamsters from which some of the SV40-transformed hamster lines were derived. The results suggest that resistance of transformed cells to macrophage-mediated cytolysis may explain in part the species-specific oncogenicity of this DNA virus.
Simultaneous expression of mouse immunoglobulins M and D is determined by the same homolog of chromosome 12.
Authors: Wabl M R , Johnson J P , Haas I G , Tenkhoff M , Meo T , Inan R
Published: May 2006

A hamster-mouse hybrid cell line expressiong both murine IgM and murine IgD on the membrane was shown to have only one copy of mouse chromosome 12. This chromosome is known to carry the structural genes for the immunoglobulin heavy chains. Cloning of populations selected for loss of mouse membrane IgM yielded cells that had also lost expression of membrane IgD, but not the expression of hamster immunoglobulin heavy chain. Karyotype analysis of these subclones demonstrated the concurrent loss of the chromosome 12 present in the parental hybrid. Absence of this chromosome was confirmed by use of the isozyme acid phosphatase 1. The results of the genetic analysis prove that the coexpression of mu and delta immunoglobulin heavy chains is not due to long-lived immunoglobulin mRNA nor to the transcription of genes on homologous chromosomes. We conclude that the genetic information for IgM and IgD expressed by a single cell lies on the same chromosome.
Primary structure of ovine hypothalamic somatostatin-28 and somatostatin-25.
Authors: Esch F , Böhlen P , Ling N , Benoit R , Brazeau P , Guillemin R
Published: May 2006

The primary structure of the NH2-terminally extended somatostatins isolated from ovine hypothalamic extracts, one containing 28 residues and the other 25, has been determined. The structure of somatostatin-28 is Ser-Ala-Asn-Ser-Asn-Pro-Ala-Met-Ala-Pro-Arg-Glu-Arg-Lys-Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys-OH; the shorter one, somatostatin-25, has the same sequence as somatostatin-28 except that the first three NH2-terminal residues are deleted. The two peptides as isolated were found to be oxidized at the methionine residue to the methionine sulfoxide. Their structures were established by subjecting the native peptides to direct sequence analysis in a Beckman 890C sequencer and identifying the released phenylthiohydantoin derivatives by high-performance liquid chromatography. Their structures were confirmed by trypsin digestion and isolation of all the tryptic peptides, followed by amino acid analysis of the tryptic fragments. Moreover, some of the tryptic peptides were matched with their respective synthetic replicates on high-performance liquid chromatography.
Proportion of hemoglobin G Philadelphia (alpha 268 Asn leads to Lys beta 2) in heterozygotes is determined by alpha-globin gene deletions.
Authors: Sancar G B , Tatsis B , Cedeno M M , Rieder R F
Published: May 2006

In humans the alpha-globin genes are duplicated and closely linked. Whereas individuals heterozygous for most alpha-chain mutations possess approximately 25% abnormal hemoglobin, heterozygotes for the alpha-chain variant Hb G Philadelphia synthesize either 33% or 50% Hb G. Both variable gene dosage and interaction with alpha-thalassemia have been proposed to explain this observation. To differentiate between these models, we have performed restriction endonuclease mapping and hematological studies on individuals with Hb G from four families. In every case the alpha G locus was carried on an EcoRI or EcoRI + BamHI fragment approximately 4 kilobases shorter than that bearing the two linked alpha A loci of hematologically normal individuals. Bgl II digestion revealed that the alpha G gene is the only alpha locus on the affected chromosome. Erythrocyte indices and alpha/beta synthesis ratios indicated that the alpha G chromosome confers alpha-thalassemia. In addition to the alpha G gene, subjects who synthesized 33% Hb G possessed two alpha A genes on the homologous chromosome and exhibited the mild form of alpha-thalassemia trait ("silent carrier"). Subjects who synthesized 50% Hb G possessed a single alpha A gene trans to the alpha G locus and displayed the more pronounced form of alpha-thalassemia trait. One subject, who synthesized 100% alpha G chains and had Hb G-Hb H disease, was found to have a single nonfunctional alpha gene trans to the alpha G gene. Thus the proportion of Hb G synthesized by heterozygotes is determined by interaction with alpha-globin gene deletions cis and trans to the alpha G locus.
Molecular characterization, reconstitution, and "transport-specific fractionation" of the saxitoxin binding protein/Na+ gate of mammalian brain.
Authors: Goldin S M , Rhoden V , Hess E J
Published: May 2006

The saxitoxin (STX) binding protein has been solubilized by sodium cholate, both from axolemma and from synaptosomal membranes of mammalian brain. On the basis of agarose gel filtration and sedimentation properties in H2O and 2H2O, the solubilized particle has the following molecular properties: Stokes radius, 120 A; partial specific volume, 0.85 cm3/g; mass, 1,020,000 daltons; frictional ratio f/fo, 1.6. The solubilized STX binding protein was incorporated into unilamellar (approximately 550-A) artificial phosphatidylcholine vesicles. Based on the expectation that the STX binding protein contains functional monovalent cation gating activity ("action potential Na+ gate") that can be activated by veratridine and inhibited by tetrodotoxin, a strategy was devised for partial purification of the reconstituted sodium gate/STX binding protein by "transport-specific fractionation." When the entire vesicle population was preloaded with 0.4 M cesium ion, addition of veratridine allowed Cs+ efflux from specifically those vesicles containing the ion gate; the concomitant reduction in intravesicular density permitted the ion gate/STX binding protein to be fractionated on density gradients. These observations demonstrate functional reconstitution and partial (30- to 50-fold) purification of the STX binding protein/Na+ gate of mammalian brain.
Relative sea levels from tide-gauge records
Authors: Emery K. O.
Published: May 2006

Mean annual sea levels at 247 tide-gauge stations of the world exhibit a general rise of relative sea level of about 3 mm/year during the past 40 years. In contrast, general uplift of the land is typical of high northern latitudes, where unloading of the crust by melt of Pleistocene ice sheets is significant. Erratic movements are typical of belts having crustal overthrusting and active volcanism. Short-term (5- and 10-year) records reveal recent changes in rates, but such short time spans may be so influenced by climatic cycles that identification of new trends is difficult, especially with the existing poor distribution and reporting of tide-gauge data.
Structure of the body-centered cubic phase of lipid systems
Authors: Saludjian Pedro , Reiss-Husson Françoise
Published: May 2006

A new model is proposed for the structure of the body-centered cubic phase of lipid systems. Infinite rods of polar groups (and water) are arranged with axes parallel to the four cubic [unk]1 1 1[unk] directions. The hydrocarbon chains fill the space between the rods to form a continuous matrix. With this unified topology, the model explains satisfactorily the x-ray diffraction patterns of strontium soaps, lecithin, galactolipids, potassium soaps, and hexadecyltrimethylammonium bromide and explains the transition between cubic/H
II
phases. The paradoxical thermal effects on the lipid cubic phase, in particular the decrease of unit cell dimensions with increasing temperature, can be explained with the proposed model by mechanisms similar to those used for the monodimensional and bidimensional (mesomorphic) phases.
Release of 1-O-alkylglyceryl 3-phosphorylcholine, O-deacetyl platelet-activating factor, from leukocytes: chemical ionization mass spectrometry of phospholipids.
Authors: Polonsky J , Tencé M , Varenne P , Das B C , Lunel J , Benveniste J
Published: May 2006

Evidence is presented for the simultaneous release of platelet-activating factor (PAF-acether) and of its deacetylated derivative (lyso-PAF-acether) from hog leukocytes. On the basis of spectroscopy and chemical reactions, the structure of O-deacetyl-PAF is shown to be 1-O-alkylglyceryl 3-phosphorylcholine, an alkyl ether analog of lyso-phosphatidylcholine. Acetylation of lyso-PAF yields a compound with biological activity and chromatographical behavior indistinguishable from those of native PAF. Lyso-PAF may be considered to be either the precursor or the enzymatic degradation product of PAF. The usefulness of chemical ionization mass spectrometry for structural determination of phospholipids is also demonstrated.
Feedback regulation of ribosomal protein gene expression in Escherichia coli: structural homology of ribosomal RNA and ribosomal protein MRNA.
Authors: Nomura M , Yates J L , Dean D , Post L E
Published: May 2006

Certain ribosomal proteins (r proteins) in Escherichia coli, such as S4 and S7, function as feedback repressors in the regulation of r-protein synthesis. These proteins inhibit the translation of their own mRNA. The repressor r proteins so far identified are also known to bind specifically to rRNA at an initial stage in ribosome assembly. We have found structural homology between the S7 binding region on 16S rRNA and a region of the mRNA where S7 acts as a translational repressor. Similarly, there is structural homology between one of the reported S4 binding regions on 16S rRNA and the mRNA target site for S4. The observed homology supports the concept that regulation by repressor r proteins is based on competition between rRNA and mRNA for these proteins and that the same structural features and of the r proteins are used in their interactions with both rRNA and mRNA.
Biochemical characterization of human melanoma cell surfaces: dissection with monoclonal antibodies.
Authors: Mitchell K F , Fuhrer J P , Steplewski Z , Koprowski H
Published: May 2006

This report describes the structures of three distinct human melanoma surface antigens detected by monoclonal anti-melanoma antibodies. One antigen, expressed on all melanoma cells and on certain astrocytoma cells but not on any other kind of normal or tumor cell tested, has been shown to consist of our associated polypeptide chains. A second antigen expressed on many but not all melanomas has been identified as the antigenic product of the HLA-D locus, the DR antigen. A third protein antigen is not found on any normal cell tested but occurs on some, but not all, tumors of various origins.
Inversions of specific DNA segments in flagellar phase variation of Salmonella and inversion systems of bacteriophages P1 and Mu.
Authors: Kutsukake K , Iino T
Published: May 2006

Prophages P1 and Mu produces a trans-acting factor possessing the din+ activity which catalyzes the inversion of the specific DNA segment responsible for flagellar phase variation of Salmonella, din mutants were isolated from PICMclr100 phage by selecting phages that did not suppress the yh2 mutation of Salmonella in prophage state. No inversion loop structure was detected among DNA forms arising after denaturation and rehybridization of DNAs extracted from the din mutants. The DNA fragment containing C region of P1 was cloned on a plasmid vector, pCR1. The resulting hybrid plasmid, pKK2, was shown to possess the din+ activity: the vh2 mutant of Salmonella harboring the plasmid changed the flagellar phase. From analysis of the plasmid by use of BamHI and Bgl II, the din gene specifying the din+ activity was located near or within the C region of P1. It is highly plausible that the din gene of P1 was also involved in the inversion of the C region. Similarly, the DNA fragment containing the G and beta segments of Mu was cloned on pCR1. The resulting hybrid plasmid, pII101, also possessed the din+ activity.
No apparent nucleotide sequence specificity in cellular DNA juxtaposed to retrovirus proviruses.
Authors: Shimotohno K , Temin H M
Published: May 2006

The sequences of the virus-cell junctions of seven DNA clones of spleen necrosis virus provirus were analyzed to determine the nucleotide sequence specificity of the cellular integration sites. As previously reported for one provirus, all clones contain a 5-base-pair direct repeat of cellular DNA at the cell-virus junctions and a 3-base-pair inverted repeat at both ends of the provirus DNA. The sequences of the 5-base-pair direct repeats are different in each clone and have no apparent homology to viral DNA. No apparent common features and no sequences significantly homologous to the ends of the provirus DNA were found in the cellular DNAs surrounding the viral integration sites.
Transcripts of the immunoglobulin C mu gene vary in structure and splicing during lymphoid development.
Authors: Kemp D J , Harris A W , Adams J M
Published: May 2006

Two classes of transcripts of the mouse immunoglobulin mu constant region (C mu) gene can be distinguished. Whereas B cells contain mu mRNAs of 2.4 and 2.7 kilobases (kb), many T lymphoma, Abelson pre-B lymphoma, and myeloid tumor cell lines contain polyadenylylated RNA species bearing C mu sequences (C mu RNAs) of 1.9, 2.1, 2.3, and 3.0 kb. Production of C mu RNAs, unlike mu mRNAs, does not require recombination with the joining region (JH) locus. To define the structure of C mu RNAs, RNA from representative cell lines was fractionated by gel electrophoresis, transferred to diazobenzyloxymethyl paper, and tested for hybridization with 23 DNA fragments that collectively span a chromosomal mu gene, cloned from a plasmacytoma. All the C mu RNAs bear sequences derived from each of the four C mu domains, but none contain the intervening sequences separating domains; thus each represents a spliced RNA species. The 1.9-kb C mu RNA contains the 3' sequence characteristic of secreted mu chain, whereas the longer species bear that of membrane-bound mu chin. Hence C mu RNAs and mu mRNAs are equivalent throughout the C mu and 3' terminal regions. They differ markedly, however, in their 5' regions, because the 3.0-and 2.3-kb C mu RNAs bear sequences from within the conventional JH-C mu intervening sequence. Because these sequences are several kb from C mu, this region must contain at least one hitherto unsuspected splice site. C mu RNAs may not express immunological diversity, because no evidence was found that they bear variable regions. T and pre-B lymphoid and myeloid cells contain equivalent C mu RNA species, which coexist with mu mRNAs in some pre-B and B lymphoid lines. C mu RNA expression appears to reflect an activated state of the C mu gene common to cells at early stages of T, B, and myeloid development.
Insulin release, insulin sensitivity, and glucose intolerance.
Authors: Efendić S , Wajngot A , Cerasi E , Luft R
Published: May 2006

Groups of subjects with different degrees of glucose intolerance were examined in order to determine, first, the capacity of the beta cells to release insulin upon glucose stimulation and, second, sensitivity to insulin. The groups were selected on the basis of fasting blood glucose value and tolerances to oral and intravenous glucose administration. The body weights, ages, and sexes of the subjects were well matched with those of control subjects with normal tolerances to oral and intravenous glucose administration. Computer analysis of the glucose and insulin curves during a standardized glucose infusion test made possible the measurement of the initiatory (parameters KI and IP) and potentiatory (parameter KP) effects of glucose on insulin release and of the sensitivity to endogenous insulin (parameter KG). In subjects with impaired oral but normal intravenous glucose tolerance tests, KG was decreased, KP was increased, and KI and IP were normal. However, in these subjects, KI and IP were considerably lower than in a matched group of control subjects with the same decrease in KG but with normal oral and intravenous glucose tolerance tets. In subjects in which both oral and intravenous glucose tolerance tests were impaired and in subjects with mild manifest diabetes, KI, IP, and KG were decreased whereas KP was normal. These data suggest that all stages of glucose intolerance are accompanied by a decreased ability of glucose to initiate insulin release and by decreased sensitivity to insulin. These derangements seem to be partially compensated for by enhancement of the capacity of glucose to potentiate insulin release in subjects with decreased oral but normal intravenous glucose tolerance tests.
Coordinate modulation of D-glucose transport activity and bilayer fluidity in plasma membranes derived from control and insulin-treated adipocytes.
Authors: Pilch P F , Thompson P A , Czech M P
Published: May 2006

The cis-monoenoic fatty acids vaccenate and oleate stimulate D-glucose transport when partitioned into isolated plasma membranes from rat adipocytes. The magnitude of hexose transport stimulation due to these agents is equal to that observed in plasma membranes derived from insulin-treated adipocytes. Addition of cis-unsaturated fatty acids to plasma membranes derived from insulin-treated cells results in no further stimulation of glucose transport over that due to the hormone alone. In contrast, treatment of membranes exhibiting insulin-activated D-glucose transport activity with saturated fatty acids reduces transport activity to control levels. No effect of the saturated fatty acids was observed on D-glucose transport in control membranes. Because cis-unsaturated fatty acids fluidize plasma membranes under the conditions used in these experiments, these data demonstrate a positive correlation between membrane fluidity and adipocyte D-glucose transport system activity. In addition, the results suggest that enhanced bilayer fluidity or increased affinity of the glucose transporter for fluid microenvironments of the membrane may play a key role in transport regulation by insulin.
Purification of a manganese-containing protein involved in photosynthetic oxygen evolution and its use in reconstituting an active membrane
Authors: Spector Mark , Winget G. Douglas
Published: May 2006

Extraction of thylakoid membranes with cholate in the presence of ammonium sulfate inactivated oxygen evolution and liberated a managanese-containing protein. This protein could be combined with preformed liposomes containing the depleted thylakoid membranes to restore 85% of the original oxygen-evolution activity. The protein did not affect the primary photochemical events of photosystem I or photosystem II, and it was required only for electron transport in which water was the electron donor. The protein has been purified to homogeneity and has an apparent molecular weight of 65,000 (polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate). Atomic absorption revealed two atoms of manganese bound to each 65,000-dalton protein molecule. Treatment with alkaline Tris removed the bound manganese and rendered the protein incapable of restoring oxygen evolution; however, Tris treatment of the depleted membranes before reconstitution had no effect. Thus, this manganese protein is probably the site of Tris action in isolated chloroplasts and is at least part of the water-oxidation enzyme system.
Polyoma large tumor antigen is not required for tumorigenesis mediated by viral DNA.
Authors: Moore J L , Chowdhury K , Martin M A , Israel M A
Published: May 2006

The arrangement of viral DNA sequences in a hamster cell line derived from a tumor induced by a recombinant plasmid DNA preparation containing the entire polyoma virus genome was examined. In the recombinant plasmid employed, viral DNA sequences specifying the large species of polyoma tumor antigen but not the small and middle tumor antigens were interrupted by the insertion of plasmid DNA at the EcoRI restriction endonuclease site. Blot-hybridization analyses of tumor cell DNA indicated that the "joints" linking viral and plasmid DNAs in the original recombinant plasmid used in animal inoculation had been preserved. Integration into the hamster cell genome had apparently occurred within plasmid DNA sequences. These results indicate that polyoma large tumor antigen is not required for tumorigenesis mediated by viral DNA.
Crossreactivity between the light-emitting systems of distantly related organisms: Novel type of light-emitting compound
Authors: Dunlap Jay C. , Hastings J. W. , Shimomura Osamu
Published: May 2006

Dinoflagellate luciferin has been found to crossreact and emit light with euphausid photoprotein; and euphausid fluorescent substance gives luminescence with dinoflagellate luciferase. Luciferin and the fluorescent substance, both highly unstable and fluorescent compounds, are biochemically similar but not identical. Preliminary spectral and chemical data suggest that both compounds contain an open-chain polypyrrole structure, novel among compounds so far known to be involved in light emission in any biological system. The dinoflagellates and euphausids are phylogenetically distant; the possibility that the latter obtain the molecule nutritionally from the former is suggested.
Processing of precursors of 21S ribosomal RNA from yeast mitochondria.
Authors: Merten S , Synenki R M , Locker J , Christianson T , Rabinowitz M
Published: May 2006

The transcription and processing of mitochondrial 21S rRNA in a petite strain of Saccharomyces cerevisiae has been examined by electron microscopic analysis of R-loop hybrids and by hybridization of labeled mitochondrial DNA probes to RNA transferred to diazobenzyloxymethyl paper. We have shown the presence of a large [5.1- to 5.4-kilobase (kb)] transcript that appears to be a precursor of mitochondrial 21S rRNA. This transcript contains sequences homologous to those of the mature 21S rRNA, to the intervening sequence present in the gene, and to additional sequences at the 3' end of the molecule. Our data suggest that this precursor of 21S rRNA is processed in two steps. The intron sequence is usually excised first, followed by removal of the extra 3' sequences. In some cases, however, the 3' extension is first removed and the intron sequence is then excised. Both pathways appear to lead to formation of the 3.1-kb mature 21S rRNA and a stable 1.2-kb intron transcript. Similar results were obtained with grande MH41-7B mitochondrial RNA by RNA transfer hybridization. We have also observed a number of additional transcripts that may be normal processing intermediates or may result from faulty cleavage-ligation during excision of the intervening sequence.
Magnetic fields produced by steady currents in the body.
Authors: Cohen D , Palti Y , Cuffin B N , Schmid S J
Published: May 2006

The magnetic fields produced by naturally occurring steady currents in the body were measured by using a new magnetic gradiometer in a magnetically shielded room. A field of 0.1 micro G/cm with reproducible pattern was seen over the head and over the limbs, whereas the field over the torso proper was weaker (except over the abdomen). Most of the field over the head is produced by electrical sources associated with the hair follicles of the scalp; this field is produced only as a response to touching or pressing the scalp, in regions where the hair is dense. Most of the field over the limbs is produced by electrical sources associated with the muscles. The field over the forearm, studied in detail, was often present spontaneously; when absent, it could be induced by mild twisting and rubbing. On the basis of auxiliary experiments involving electrolytes, a general mechanism for generation of steady current in the body is suggested. In this mechanism, the steady current is generated by a nonclosed or a nonuniform polarized layer across an elongated semipermeable membrane such as a muscle fiber; the nonuniform polarization is due to a gradient of extracellular K+ along the membrane.
Modulation of membrane protein lateral mobility by polyphosphates and polyamines
Authors: Schindler Melvin , Koppel Dennis E. , Sheetz Michael P.
Published: May 2006

The lateral mobility of fluorescein-labeled membrane glycoproteins was measured in whole unlysed erythrocytes and erythrocyte ghosts by the technique of “fluorescence redistribution after fusion.” Measurements were made on polyethylene glycol-fused cell pairs in which only one member of the couplet was initially fluorescently labeled. Diffusion coefficients were estimated from the rate of fluorescence redistribution determined from successive scans with a focused laser beam across individual fused pairs. This technique allows for the analysis of diffusion within cell membranes without the possible damaging photochemical events caused by photobleaching. It was found that lateral mobility of erythrocyte proteins can be increased by the addition of polyphosphates (i.e., ATP and 2,3-diphosphoglycerate) and decreased by the addition of organic polyamines (i.e., neomycin and spermine). This control is exerted by these molecules only when they contact the cytoplasmic side of the membrane and is not dependent upon high-energy phosphates. Microviscosity experiments employing diphenylhexatriene demonstrated no changes in membrane lipid state as a function of these reagents. Our results, in conjunction with data on the physical interactions of cytoskeletal proteins, suggest that the diffusion effector molecules alter the lateral mobility of erythrocyte membrane proteins through modifications of interactions in the shell, which is composed of spectrin, actin, and component 4.1.
Role of the degradation process in the mitogenic effect of epidermal growth factor
Authors: Savion Naphtali , Vlodavsky Israel , Gospodarowicz Denis
Published: May 2006

The protease inhibitor leupeptin inhibits the degradation process of
125
I-labeled epidermal growth factor (
125
I-EGF) by cultured bovine granulosa cells. At 80 μg/ml, leupeptin inhibited the appearance of degradation products of
125
I-EGF in the medium by 95% during 1 hr of incubation and by 90% during 24 hr of incubation when the cells were exposed to 5 ng of
125
I-EGF per ml. In contrast, cultures exposed to either saturating (10 ng/ml) or nonsaturating (0.1 ng/ml) concentrations of EGF in the presence of leupeptin (80 μg/ml) exhibited an increase in DNA synthesis that was 70-80% that of cultures exposed to EGF alone. Cultures responded to either EGF or fibroblast growth factor with a logarithmic increase in cell number and, over a period of 8 days, the number of cells increased 10- to 18-fold. Addition of leupeptin did not diminish the growth rate of the cultures. In the presence of leupeptin,
125
I-EGF accumulated within the granulosa cells and was in a form that was precipitable with antiserum against EGF and that comigrated on isoelectric focusing with native
125
I-EGF. That a full mitogenic response can be obtained despite a 90-95% inhibition of EGF degradation at either saturating or nonsaturating concentrations of the mitogen suggests that a proteolytic degradation of a given mitogen may not be involved in the induction of a proliferative response.
Antibody directed against Friend leukemia virus stimulates DNA synthesis in a subpopulation of mouse B lymphocytes.
Authors: Moroni C , Forni L , Hunsmann G , Schumann G
Published: May 2006

Goat and rat antisera directed against Friend leukemia virus (anti-FLV) were found to be B-lymphocyte mitogens stimulating DNA synthesis in these cells but not in T lymphocytes. Membrane fluorescence microscopy showed that anti-FLV reacts with a subset of B lymphocytes of which the majority express immunoglobulin mu chains. The mitogenic effect was found with all mouse strains tested including 129 and AKR. Absorption experiments with purified viruses indicated that the mitogenic effect is specific for an antigen present in murine leukemia viruses of the FMR subgroup. In absorption experiments with viable cells, the antigen involved in mitogenicity was found to be expressed on Friend erythroleukemia cell lines (4/4) and on myelomas (2/2) but not on normal thymus T lymphomas (0/2) or on rabbit or mink cells infected with BALB/c xenotropic virus. Preincubation of spleen cells with anti-gp70 antiserum inhibited the mitogenic effect of anti-FLV but not of lipopolysaccharide.
Inability of serum from abetalipoproteinemic subjects to stimulate proliferation of human smooth muscle cells and dermal fibroblasts in vitro.
Authors: Layman D L , Jelen B J , Illingworth D R
Published: May 2006

Serum from two patients with abetalipoproteinemia, a rare disorder of lipid metabolism characterized by the absence of chylomicrons and very low density and low density lipoproteins, did not stimulate the proliferation and growth of human smooth muscle cells or dermal fibroblasts in vitro as effectively as normal serum. The growth-promoting activity of this serum was comparable to that observed for lipoprotein-deficient plasma from normolipidemic subjects. Although the mitogenic effect of abetalipoproteinemic serum was improved with supplementation of low density lipoproteins, it was still about half the activity achieved with normal serum. However, the growth-promoting activity of this serum was completely restored to normal levels after addition of a lysate of normal platelets. In contrast, the mitogenic activity of lipoprotein-deficient plasma remained unchanged after addition of a lysate from abetalipoproteinemic platelets, whereas a similar supplementation of normal platelets completely restored its growth-promoting activity to normal. Thus, the inability of abetalipoproteinemic serum to promote growth appears to be due both to a deficiency of a platelet-releasable growth factor(s) and to the absence of serum lipoproteins.
Lateral diffusion of membrane lipids and proteins during the cell cycle of neuroblastoma cells.
Authors: de Laat S W , van der Saag P T , Elson E L , Schlessinger J
Published: May 2006

The fluorescence photobleaching recovery method has been used to determine the lateral mobilities of membrane lipids and proteins during the cell cycle of synchronized C1300 mouse neuroblastoma cells (clone Neuro-2A). As probes for lipid mobility, 3,3'-dioctadecylindocarbocyanine iodide and a fluorescein-labeled analog of ganglioside GM1 were used. Membrane proteins were labeled with rhodamine-labeled rabbit antibodies against mouse E14 cells. For both lipid probes the diffusion coefficients reach a minimum in mitosis, increase 2- to 3-fold during G1, remain constant at maximal values during S, and decrease again shortly before mitosis. Membrane proteins also exhibit minimum diffusion coefficients in mitosis, followed by a similar rise in G1. However, as cells proceed through S and G2, the lateral mobility of the membrane proteins gradually decreases. It is argued that lipid mobility is controlled by the fluidity of the membrane lipid matrix whereas protein mobility is governed also by other constraints.
Nucleotide sequences associated with differences in electrophoretic mobility of envelope glycoprotein gp70 and with G
IX
antigen phenotype of certain murine leukemia viruses
Authors: Donis-Keller Helen , Rommelaere Jean , Ellis Ronald W. , Hopkins Nancy
Published: May 2006

Previous genetic and biochemical studies led to the identification of two large RNase T1-resistant oligonucleotides, designated the G
IX
+
and G
IX
-
oligonucleotides, whose presence in the genomes of closely related murine leukemia viruses is mutually exclusive and predictive of two properties of the viral envelope glycoprotein gp70. Viruses harboring the G
IX
+
oligonucleotide induce expression of the gp70-associated antigen G
IX
and possess gp70s with more rapid electrophoretic mobility on sodium dodecyl sulfate/polyacrylamide gels than viruses that possess the G
IX
-
oligonucleotide. The latter viruses fail to induce G
IX
on infected fibroblasts. The G
IX
+
and G
IX
-
oligonucleotides lie in corresponding positions in the 3′ third of the oligonucleotide maps of their respective viruses. We have determined the nucleotide sequences of the G
IX
+
and G
IX
-
oligonucleotides. The sequence of the G
IX
-
oligonucleotide is U-A-U-C-U-C-A-A-C-C-A-C-C-A-U-A-C-U-U-A-A-C-C-U-C-A-C-C-A-C-[unk]-G, and the sequence of the G
IX
+
oligonucleotide is U-A-U-C-U-C-A-A-C-C-A-C-C-A-U-A-C-U-U-G. Thus, a single base change could result in the interconversion of the two oligonucleotides. Consideration of the amino acids specified by the two oligonucleotides suggests that this single base difference may result in the presence of an additional oligosaccharide chain in the gp70s of the G
IX
-
viruses. Evidence supporting this prediction has been obtained by M. R. Rosner, J.-S. Tung, E. Fleissner, and P. W. Robbins (personal communication). It is entirely possible that the single nucleotide change that apparently results in a different electrophoretic mobility of the gp70s of the G
IX
+
and G
IX
-
viruses is also responsible for the presence or absence of the G
IX
antigenic determinant; however, the validity of this possibility awaits further investigation.
Vasoactive intestinal polypeptide in cholinergic neurons of exocrine glands: Functional significance of coexisting transmitters for vasodilation and secretion
Authors: Lundberg Jan M. , Änggärd Anders , Fahrenkrug Jan , Hökfelt Tomas , Mutt Viktor
Published: May 2006

By a combination of the indirect immunofluorescence technique with acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) staining, it was shown that vasoactive intestinal polypeptide (VIP) is present in cholinergic (acetylcholinesterase-rich) neurons involved in control of secretion and vasodilation in exocrine glands of cat. The submandibular salivary gland was used as a functional model. Preganglionic nerve stimulation induced an atropine-resistant, hexamethonium-sensitive vasodilation and release of VIP into the venous outflow from the gland and an atropine- and hexamethonium-sensitive secretion. Infusion of VIP antiserum reduced both the vasodilation and secretion. Infusion of VIP caused vasodilation only, whereas acetylcholine caused both vasodilation and secretion. Simultaneous infusion of VIP and acetylcholine in low doses resulted in a marked potentiation of both vasodilation and secretion. The present morphological and functional data support the following hypothesis for regulation of vasodilation and secretion in exocrine glands. Preganglionic cholinergic nerves activate, via nicotinic receptors, postganglionic neurons, causing concomitant release from the same nerve endings of two coexisting putative transmitters, acetylcholine and VIP. Acetylcholine produces mainly secretion by a muscarinic action and VIP causes mainly vasodilation, but the two substances seem to cooperate directly or indirectly in both types of response. Thus, the coexistence of two putative neurotransmitters, VIP and acetylcholine, in one neuron may explain the dual effector response (i.e., the cholinergic secretion and the atropine-resistant vasodilation) caused by nerve stimulation in exocrine glands.
Metabolite gene regulation of the L-arabinose operon in Escherichia coli with indoleacetic acid and other indole derivatives.
Authors: Kline E L , Brown C S , Bankaitis V , Montefiori D C , Craig K
Published: May 2006

The ability of indole derivatives to facilitate RNA polymerase transcription of the L-arabinose operon in Escherichia coli was shown to require the catabolite activator protein (CAP) as well as the araC gene product. Adenosine 3',5'-monophosphate (cAMP) was not obligatory for araBAD transcription when the cells were grown in the presence of 1 mM indole-3-acetic acid or in the presence of indole-3-acetamide, indole-3-propionic acid, indole-3-butyric acid, or 5-hydroxyindole-3-acetic acid. However, these indole derivatives were unable to circumvent the cAMP requirement for the induction of the lactose and the maltose operons. Catabolic repression occurred when glucose was added to cells grown in the presence of L-arabinose and 1 mM indoleacetic acid or 1 mM cAMP. This effect was reversed at higher concentrations of indoleacetic acid or cAMP. The induction and the catabolite repression phenomena were quantitated by measuring the differential rate of synthesis of L-arabinose isomerase (the araA gene product). These results indicated that indole metabolites from various living systems may regulate gene expression and may be involved in "metabolite gene regulation."
Molecular cloning of unintegrated Moloney mouse sarcoma virus DNA in bacteriophage lambda.
Authors: Verma I M , Lai M H , Bosselman R A , McKennett M A , Fan H , Berns A
Published: May 2006

The covalently closed circular forms of unintegrated viral DNA obtained from cells infected with Moloney mouse sarcoma virus was cloned in bacteriophage lambda. The viral DNA was cleaved with restriction endonuclease HindIII and inserted in the unique HindIII site of lambda Charon 21A DNA. Recombinant clones containing virus-reactive DNA sequences were analyzed by restriction endonuclease mapping, R-loop formation, and infectivity assays. Two of eight genome-length recombinant clones characterized contained the large terminal repeat. Only the recombinant clones containing the large terminal repeat were able to induce focus formation in uninfected mouse fibroblasts.
Reconstitution of a deoxyribonuclease I-sensitive structure on active genes.
Authors: Gazit B , Panet A , Cedar H
Published: May 2006

Chicken erythrocyte nuclei have been labeled in the active regions of the chromosome by using the nick translation reaction. In this procedure, accessible areas of the genome are preferentially nicked by the action of pancreatic DNase I and subsequently labeled by using DNA polymerase I from Escherichia coli. These nuclei were employed as a substrate for studying the factors responsible for maintaining the special chromatin conformation of the overall population of active genes. Treatment of nuclei with 0.35 M NaCl resulted in the loss of DNase I sensitivity in the active genes, but this sensitivity could be restored when nuclei were reconstituted with the NaCl eluate. Further purification of the released factors revealed that the HMG (high-mobility group) proteins HMG-14 and HMG-17 are involved in maintaining the conformation of the active regions. These factors are not tissue specific and seem to be involved in the chromosomal structure of most of the active genes.
Multiple forms of H4 histone mRNA in human cells.
Authors: Lichtler A C , Detke S , Phillips I R , Stein G S , Stein J L
Published: May 2006

Two species of H4 histone mRNA were isolated from the polysomes of S phase HeLa S3 cells. Electrophoresis under denaturing and nondenaturing conditions indicates that the two H4 mRNAs differ in size. Both mRNAs translate H4 histones in vitro, lack poly(A) at their 3' termini, and are capped at their 5' termini. Polyacrylamide gel electrophoresis and tryptic peptide analysis suggest that the polypeptides synthesized by the two mRNAs are indistinguishable.
Genes coding for sensitivity to interferon (IfRec) and soluble superoxide dismutase (SOD-1) are linked in mouse and man and map to mouse chromosome 16.
Authors: Cox D R , Epstein L B , Epstein C J
Published: May 2006

By using 12 hamster-mouse hybrids segregating a mouse T(16;17)Bnr Robertsonian translocation chromosome in conjunction with 10 similar hybrids segregating normal mouse chromosomes, we have shown that the loci that control cellular sensitivity to interferon (IfRec) and code for the soluble enzyme superoxide dismutase (SOD-1) (superoxide:superoxide oxidoreductase; EC 1.15.1.1) are syntenic in the mouse and map to mouse chromosome 16. IfRec and SOD-1 are also syntenic in man. They have previously been assigned to the distal segment of the long arm of human chromosome 21, trisomy for which causes Down syndrome. Because both IfRec and SOD-1 map to mouse chromosome 16, it will now be possible to use mice trisomic for this chromosome to determine whether certain aspects of the Down syndrome phenotype in man are caused by an altered dosage of IfRec and SOD-1.
Beta-Endorphin: dissociation of receptor binding activity from analgesic potency.
Authors: Li C H , Tseng L F , Ferrara P , Yamashiro D
Published: May 2006

Biological activities of synthetic camel beta-endorphin and human beta-endorphin (beta h-EP) have been measured by the radioreceptor binding assay, using [Tyr27-3H]-beta h-EP as the primary ligand and by the tail-flick test for analgesic potency. Four synthetic analogs of beta h-EP, namely [Gly31]-beta h-EP-Gly-NH2, [Gly31]-beta h-EP-Gly-Gly-NH2, [Gln8,Gly31]-beta h-EP-Gly-Gly-NH2, and [CH3(CH2)4NH231]-beta h-EP, have also been assayed by the same procedures. Results indicate a clear dissociation of radioreceptor binding activity from analgesic potency.
Physical mapping of primary and secondary origins of bacteriophage T7 DNA replication.
Authors: Tamanoi F , Saito H , Richardson C C
Published: May 2006

Deletion mutants of bacteriophage T7 have been used to identify and to map, by electron microscopy, the origins of T7 DNA replication. The primary origin of phage T7 DNA replication lies within a 100-base-pair region located 14.75-15.0% of the distance from the genetic left end of the DNA molecule. T7 phage whose DNA contains a deletion of this region initiate replication at secondary origins, the predominant one of which is located at a distance approximately 4% from the left end of the molecule.