bluuebunny/crossref_metadata_2025 huggingface dataset:
Opposing effects of estradiol and progesterone on oxytocin receptors in rabbit uterus
Authors: Nissenson R. , Flouret G. , Hechter O.
Published: May 2006

Estradiol-17β administration to young (10- to 12-week-old) rabbits to produce the “estrogen-dominated” uterus increased the uterine contractile response to both oxytocin and methacholine
in vitro
. In “progesterone-dominated” uteri, obtained from rabbits that received progesterone for 4 days after estrogen pretreatment, the contractile response to oxytocin
in vitro
was selectively abolished; the response to methacholine was unaffected. Parallel changes were observed in the concentration (but not affinity) of specific sites in uterine microsomal membranes that bind [
3
H]oxytocin with selectivity features expected for oxytocin receptors. Thus, estrogen-dominated uteri have an increased number of specific [
3
H]oxytocin binding sites per mg of membrane protein relative to untreated controls, whereas specific oxytocin binding sites are reduced to barely detectable levels in the progesterone-dominated uterus. Similar results are obtained when binding sites are measured in membranes from the myometrium of estrogen- or progesterone-dominated uteri. Short-term (24-hr) progesterone administration to estrogen-pretreated rabbits decreased, but did not abolish, specific [
3
H]oxytocin binding; the concentration of specific [
3
H]oxytocin binding sites was reduced without influence on the affinity of these sites. A sublethal dose of actinomycin D, administered over a 24-hr period to rabbits pretreated with estradiol for 4 days, likewise reduced specific oxytocin binding; additive effects were not observed when progesterone and actinomycin D were administered together. These results suggest that the regulatory effects of estrogens and progesterone upon the rabbit uterine contractile response to oxytocin are achieved, at least in part, by the opposing actions of these steroids in regulating the number of oxytocin receptors in smooth muscle cells. Estradiol increased the concentration of uterine oxytocin receptors; the maintenance of high receptor levels appears to depend upon the continuous
de novo
synthesis of oxytocin receptors. In contrast, progesterone, like actinomycin D, appears to act at the nuclear locus to repress synthesis of oxytocin receptors.
Mathematical aspects of divergent beam radiography
Authors: Smith K. T. , Solmon D. C. , Wagner S. L. , Hamaker C.
Published: May 2006

At the present time, largely because of a breakthrough in radiology called
computed tomography
, the attenuation of x-ray beams is measured in extremely sensitive quantitative ways, and the information from many x-ray sources is assembled and analyzed on a computer. In this situation mathematics can make significant contributions concerning the nature of the information conveyed by x-rays from many sources, the extent to which this information determines the object x-rayed, suitable configurations of sources, methods for using the data to build a detailed reconstruction of the object, etc. This article announces results on these topics for the divergent x-ray beam. The three-dimensionally divergent beam, or cone beam, presents new problems that do not appear in the two-dimensional, or fan beam, case.
Direct C-1 hydroxylation of vitamin D compounds: convenient preparation of 1alpha-hydroxyvitamin D3, 1alpha, 25-dihydroxyvitamin D3, and 1alpha-hydroxyvitamin D2.
Authors: Paaren H E , Hamer D E , Schnoes H K , DeLuca H F
Published: May 2006

An efficient procedure for the direct C-1 hydroxylation of vitamin D compounds has been developed. The method involves conversion of vitamin D3 tosylates to 3,5-cyclovitamin D derivatives, allylic oxidation with selenium dioxide, and acid-catalyzed solvolysis to the 1 alpha-hydroxyvitamin D analogs. When applied to vitamin D3,25-hydroxyvitamin D3, and vitamin D2, this sequence give the corresponding 1alpha-hydroxylated derivatives in 10-15% yield.
Asymptotic representation of conformal maps of strip domains without boundary regularity
Authors: Rodin Burton , Warschawski Stefan E.
Published: May 2006

Many parts of the subject of the boundary behavior of conformal mappings can be subsumed under the general heading of asymptotic representations of the Riemann mapping function near a boundary point. Asymptotic representations have, up to now, required that the boundary of the domain satisfy various types of regularity conditions. The results announced here give a method for obtaining asymptotic representations when the domain fails to satisfy such regularity conditions.
Hepatic receptor that specifically binds oligosaccharides containing fucosyl α1→3
N
-acetylglucosamine linkages
Authors: Prieels Jean-Paul , Pizzo Salvatore V. , Glasgow Lowrie R. , Paulson James C. , Hill Robert L.
Published: May 2006

Evidence is presented suggesting that hepatocytes contain a receptor that binds glycoproteins specifically through fucose in α1→3 linkage to
N
-acetylglucosamine. Human lactoferrin, which contains this type of linkage, is rapidly cleared from the circulation of mice after intravenous injection, and greater than 90% of the injected material is found in hepatocytes. Binding of lactoferrin is mediated through its carbohydrate groups, since its clearance is prolonged after periodate oxidation or after its oligosaccharide groups are extensively degraded with glycosidases. In addition, glycopeptides from lactoferrin inhibit lactoferrin clearance. That lactoferrin clearance is mediated through binding to its fucosyl groups is suggested for several reasons. First, transferrin and asialotransferrin, whose oligosaccharide groups are essentially structurally identical to those of lactoferrin but devoid of fucose, are not cleared on intravenous injection. Second, when fucose is incorporated into asialotransferrin by α1→3
N
-acetylglucosamine fucosyl transferase, the resulting fucosylated derivative is cleared rapidly. Neither mannan nor derivatives of orosomucoid that are cleared by binding to receptors for galactose,
N
-acetylglucosamine, or mannose, inhibit clearance of lactoferrin although clearance is inhibited by fucoidin. Finally, glycoproteins containing fucose in α1 → 2 linkage to galactose or α1 → 6 linkage to
N
-acetylglucosamine do not inhibit lactoferrin clerance by the liver. Since clearance of other glycoproteins, such as human lactoperoxidase, also appears to be mediated through binding to the same hepatocyte receptor as lactoferrin, it is concluded that the fucose-specific receptor studied here may fulfill other functions than binding lactoferrin. Preliminary studies with liver homogenates and detergent extracts of liver show binding
in vitro
.
Isolation, preliminary characterization, and interferon antagonistic effect of a mammalian lectin-like substance.
Authors: Chany-Fournier F , Pauloin A , Chany C
Published: May 2006

We have isolated from mouse costal cartilage a tissue antagonist of interferon (TAI) which accelerates the decay of an established antiviral state. The effect is reminiscent of substances previously isolated from the basement membrane of human amnion. Since we have recently shown that phytohemagglutinin can mimic the biological effect of TAI, we have explored the possibility that TAI could be an animal lectin-like material. First, TAI agglutinates mouse cells; second, this cell agglutination is inhibited by some sugars. Preliminary characterization indicates that the active molecule is a protein. After Sephadex G-100 gel filtration, TAI is found in a peak of 150,000 molecular weight. When purified by isoelectric focusing, this peak shows maximal activities corresponding to an isoelectric point of pH 8.8 TAI binds to polysaccharide residues of the cell membrane which could be its primary site of action, comparable to phytohemagglutinin.
Genetic analysis of the human cell surface: antigenic marker for the human X chromosome in human-mouse hybrids.
Authors: Dorman B P , Shimizu N , Ruddle F H
Published: May 2006

Somatic cell hybrids of human fibroblasts and mouse A9 cells, carrying only a portion of the human X chromosome in a mouse chromosome background, were injected into C3H mice. The resulting mouse anti-hybrid cell antisera contain antibodies found to be human specific and to react with only those hybrid cells carrying the human X chromosome, as confirmed by essentially perfect concordance between antibody binding assayed by indirect immunofluorescence and presence of the human X-linked enzyme hypoxanthine phosphoribosyl-transferase determined by autoradiographic assay of [3H] hypoxanthine utilization. Heterogeneous mixtures of hybrid cells may be analyzed into fluorescent (X plus) and nonfluorescent (X minus) subpopulations and fractionated viably by using a fluorescence-activated cell sorter.
Ultraviolet reactivation of herpes simplex virus is mutagenic and inducible in mammlian cells.
Authors: DasGupta U B , Summers W C
Published: May 2006

The survival of UV-irradiated herpes simplex virus on UV-irradiated Vero cells was increased over that on unirradiated cells. A time period between irradiation of the host cells and infection with virus was needed to achieve maximum reactivation. In parallel experiments in which the frequencies of occurrence of the forward mutation in the thymidine kinase gene of the virus were measured, growth of herpes simplex virus on UV-irradiated cells yielded progeny virus that had higher frequencies of TK- mutants than did progeny from infections of control cells. The time course of development of this mutagenic effect was the same as that for the development of the UV-reactivation capacity. Furthermore, development of the UV reactivation could be blocked by inhibition of protein synthesis. These results suggest that an "error prone" inducible UV-reactivation phenomenon exists in mammalian cells.
Reduction of membrane potential, an immediate effect of colicin K.
Authors: Weiss M J , Luria S E
Published: May 2006

Colicin K causes a rapid and drastic reduction of the membrane potential of Escherichia coli cells, as measured by the uptake of the lipophilic cation triphenylmethylphosphonium. The colicin causes no major changes in the pH gradient, as measured by the uptake of butyric acid. The decrease in membrane potential following addition of colicin K to the cells is a prompt response that parallels or precedes known physiological effects such as efflux of accumulated substrates. Hence the loss of membrane potential qualifies as the primary action by which the colicin uncouples membrane-associated function from respiration. Certain peculiarities of bacterial cells pretreated with EDTA in their response to uncoupling agents and lipophilic ions are described.
Proposed temperature-dependent conformational transition in D-amino acid oxidase: a differential scanning microcalorimetric study.
Authors: Sturtevant J M , Mateo P L
Published: May 2006

A number of authors have reported observations on D-amino acid oxidase [D-amino acid: O2 oxidoreductase (deaminating), EC 1.4.3.3.] that they have interpreted in terms of a temperature-dependent conformational transition having a van't Hoff enthalpy amounting to more than 1 cal per g of protein (1 cal = 4.184J). No indication of this transition is obtained by using a differential scanning calorimeter having a sensitivity considerably in excess of that required to detect such a transition. The implications of this discrepancy are discussed.
Isolation of a mutant of Escherichia coli lacking penicillin-sensitive D-alanine carboxypeptidase IA.
Authors: Matsuhashi M , Maruyama I N , Takagaki Y , Tamaki S , Nishimura Y , Hirota Y
Published: May 2006

A mutant of Escherichia coli that is deficient in D-alanine carboxypeptidase IA has been isolated. The enzyme is membrane bound and moderately sensitive to penicillin. It catalyzes in vitro both D-alanine carboxypeptidase and transpeptidase reactions. Being able to synthesize crosslinked peptidoglycan both in vivo and in vitro despite the absence of enzyme activity, the newly isolated mutant grew normally under a wide range of growth conditions. Therefore, this enzyme, like D-alanine carboxypeptidase IB, is not required for normal peptidoglycan synthesis in E. coli. The defect in the activity of D-alanine carboxypeptidase IA in the mutant however was not associated with disappearance of penicillin-binding proteins 5 and 6 (which have been shown to be D-alanine carboxypeptidase IA) or any of the other protein bands that bind [14C]penicillin G. Genetic mapping studies showed that the mutation (dacA) is located close to leuS(13.7 min) on the E. coli chromosome map. Double mutants (dacA dacB) that are deficient in both D-alanine carboxypeptidases IA and IB were obtained. These double mutants also were found to grow normally and to catalyze normal formation of crosslinked peptidoglycan.
Direct visualization of binding, aggregation, and internalization of insulin and epidermal growth factor on living fibroblastic cells
Authors: Schlessinger Joseph , Shechter Yoram , Willingham Mark C. , Pastan Ira
Published: May 2006

We have studied in detail the binding of fluorescent derivatives of insulin and epidermal growth factor to 3T3 fibroblasts. We have used two types of fluorescent analogues of insulin and epidermal growth factor:
highly fluorescent
derivatives which have seven to eight rhodamine molecules or
fluorescent
derivatives which have a single rhodamine molecule per one molecule of insulin or epidermal growth factor. Both types of analogue retained substantial binding affinity as determined by radioreceptor assays and biological activity. The cells labeled with the fluorescent analogues were visualized with a sensitive video intensification microscopic system that enabled us to directly observe the location of the fluorescent hormone on the surface and within the living fibroblasts. We found that both insulin and epidermal growth factor initially bound diffusely to the cell surface and, at 4°, remained dispersed. Within a few minutes at 23° or 37° the hormone-receptor complexes aggregated into patches that could be readily removed by trypsin but not by excess native hormone. The hormone-receptor complexes, which were initially
mobile
in the plane of the membrane, become immobilized later as the consequence of the receptor aggregation or internalization. Within ∼30 min at 37°, much of the labeled hormone was found within the cell in endocytic vesicles that moved about in the cytoplasm in a saltatory manner. The aggregation and immobilization of the hormone-receptor complexes could be due to either hormone-hormone interactions on the cell membrane or a hormone-induced conformational change in the hormone-receptor complex. Aggregation and internalization of hormone-receptor complexes could be associated with certain aspects of hormone action, hormone degradation, down regulation of receptors, or negative cooperativity of hormone binding.
Mechanism of cholera toxin action: Covalent modification of the guanyl nucleotide-binding protein of the adenylate cyclase system
Authors: Cassel Dan , Pfeuffer Thomas
Published: May 2006

Treatment of pigeon erythrocyte membranes with cholera toxin and NAD
+
enhanced the GTP stimulation and suppressed the F
-
activation of the adenylate cylase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1]. In the presence of NAD
+
labeled with
32
P in the AMP moiety the toxin catalyzed the covalent incorporation of radioactivity into membrane proteins with molecular weights (
M
r
s) of 200,000, 86,000, and 42,000. Extraction of toxin-treated membranes with Lubrol PX followed by affinity chromatography on a GTP-Sepharose column resulted in a 200-fold purification of the 42,000-
M
r
labeled protein and in its complete separation from the other labeled proteins. The fraction containing the purified GTP-binding component from toxin-treated membranes conferred an enhanced GTP-stimulated activity on adenylate cyclase solubilized from nontreated membranes. Likewise, the addition of GTP-binding fraction from nontreated membranes to an enzyme solubilized from toxin-treated membranes restored F
-
stimulation of the adenylate cyclase. The toxin-induced modification of adenylate cyclase and the incorporation of radioactivity into the 42,000-
M
r
protein were partially reversed upon incubation with toxin and nicotinamide at pH 6.1. The results indicate that cholera toxin affects the adenylate cyclase system by catalyzing an ADP-ribosylation of the 42,000-
M
r
component bearing the guanyl nucleotide regulatory site.
Pseudomonas cytochrome c551 at 2.0 A resolution: enlargement of the cytochrome c family.
Authors: Almassy R J , Dickerson R E
Published: May 2006

The structure of respiratory cytochrome c551 of Pseudomonas aeruginosa, with 82 amino acids, has been solved by x-ray analysis and refined to a crystallographic R factor of 16.2%. It has the same basic folding pattern and hydrophobic heme environment as cytochromes c, c2, and c550, except for a large deletion at the bottom of the heme crevice. This same "cytochrome fold" appears to be present in photosynthetic cytochromes c of green and purple sulfur bacteria, and algal cytochromes f, suggesting a common evolutionary origin for electron transport chains in photosynthesis and respiration.
Immunological screening method to detect specific translation products.
Authors: Broome S , Gilbert W
Published: May 2006

We describe a very sensitive method to detect as antigens the presence of specific proteins within phage plaques or bacterial colonies. We coat plastic sheets with antibody molecules, expose the sheet to lysed bacteria so that a released antigen can bind, and then label the immobilized antigen with radioiodinated antibodies. Thus, the antigen is sandwiched between the antibodies attached to the plastic sheet and those carrying the radioactive label. Autoradiography then shows the positions of antigen-containing colonies or phage plaques. A few molecules of antigen released from each bacterial cell generatean adequate signal.
Role of estrogen receptor binding and transcriptional activity in the stimulation of hyperestrogenism and nuclear bodies.
Authors: Clark J H , Hardin J W , Padykula H A , Cardasis C A
Published: May 2006

The effects of estradiol and nafoxidine on nuclear estrogen receptor binding, RNA polymerase activities, and uterine ultrastructure were studied. Animals were either injected with estradiol, implanted with estradiol/paraffin pellets, or injected with nafoxidine. Animals treated with nafoxidine or estradiol implants showed sustained long-term nuclear retention of estrogen receptor and increased nuclear RNA polymerase activities for up to 72 hr. A single injection of estradiol caused initial increases in these variables which returned to control levels by 24 hr after hormone treatment. Uterine tissue was examined by light and electron microscopy 72 hr after hormone treatments. Uteri from eith estradiol-implanted or nafoxidine-treated animals showed markedly increased hypertrophy of the luminal epithelial cells. Nuclei in sections of the uteri of these hyperestrogenized animals displayed a large number and wide array of nuclear bodies composed of a filamentous capsule and granular cores. We conclude that hyperestrogenization, a condition that eventually results in abnormal cell growth, is correlated with increased and sustained nuclear binding of the estrogen receptor, increased and sustained RNA polymerase activity, and the appearance of nuclear bodies.
Comparison of Artemia salina and Escherichia coli ribosome structure by electron microscopy.
Authors: Boulik M , Hellmann W
Published: May 2006

The structure of eukaryotic Artemia salina and prokaryotic Escherichia coli ribosomes has been compared by electron microscopy. Despite the established differences in size and in the amount and proportion of the protein and RNA moieties, both types of ribosomes appear to have substantial similarity in the overall shape and in the mutual orientation of the subunits on the monosome. The small subunit is located in the "crown" region of the large subunit lengthwise between the two side crests. However, high-resolution electron microscopy reveals distinct differences in the fine structure of both small and large subunits. The 40S A. salina subunit with three structural domains is more complex than the corresponding E. coli subunit. The 60S A. salina subunit has a less expressed "crown" region and shows a knob-like protrusion in the base. Structural asymmetry is a characteristic feature common to subunits and monosomes from both A. salina and E. coli.
Adult murine T cells activated in vitro by alpha-fetoprotein and naturally occurring T cells in newborn mice: identity in function and cell surface differentiation antigens.
Authors: Murgita R A , Goidl E A , Kontiainen S , Beverley P C , Wigzell H
Published: May 2006

Murine alpha-fetoprotein (alphaFP) has been shown to suppress T cell-dependent antibody responses in vitro but not T cell-independent responses. Our earlier preliminary findings indicated that such inhibitory effects are mediated via activated T cells. In this study, using alphaFP as the inducing agent, we have analyzed cells generated in vitro from adult spleen cells with regard to function and surface markers and compared the cells to the naturally occurring splenic T cells of newborn mice, in which there are high intrinsic concentrations of alphaFP. Both types of T lymphocytes were found to effectively inhibit T cell-dependent antibody responses in vitro but not T cell-independent responses. Moreover, both groups of T cells were found to express the identical differentiation antigen phenotype,Ly 1 + 2-. Thus alphaFP-induced inhibitory T cells from adults could be shown to have the same functional properties and Ly phenotype as splenic T lymphocytes from newborn mice. These findings support the concept that alphaFP might function as an important immunoregulatory agent in vivo during ontogenetic development.
Endorphins may function in heat adaptation.
Authors: Holaday J W , Wei E , Loh H H , Li C H
Published: May 2006

Administration of the opiate antagonist naloxone to rats after acute or chronic heat exposure precipitates an increase in colonic temperature, an increase in escape attempts, and a decrease in body weight. These changes are accompanied by signs associated with hyperthermia such as salivation, diarrhea, and an abnormal extended posture. Although brain endorphin involvement is possible, hypophysectomy diminishes the intensity and magnitude of these naloxone effects, indicating that the naloxone effect in intact animals may be due to a functional antagonism of pituitary endorphins. These observations suggest that endorphins attenuate physiological responses to thermal and noxious stimuli triggered in common neuroanatomical pathways by heat.
In vitro
isolation of stable rat sarcoma viruses
Authors: Rasheed Suraiya , Gardner Murray B. , Huebner Robert J.
Published: May 2006

A Sprague-Dawley (SD-1) rat embryo culture, at low passage level, released an endogenous ecotropic type C virus (SD-RaLV) and after about 20 further passages it underwent spontaneous transformation. The SD-RaLV, released from the transformed cells, did not cause rapid transformation of other rat embryo cells. However, when the transformed cells were repeatedly cocultivated with three different chemically transformed and serially transplanted rat tumor cell lines (sarcoma, carcinoma, and hepatoma), rapidly fibroblast-transforming “sarcoma” viruses (RaSV) were recovered after each attempt. RaSV was not recovered from one of these tumor cell lines before transplantation, nor could focus-forming virus be rescued from these same tumor cells by cocultivation with other cells releasing heterologous type C viruses. Foci were induced on normal rat kidney and several other rat embryo cell strains within 7-15 days and both productive and nonproductive NRK clones were derived. The productive clones were positive for rat specific p30 antigen and the RaSVs released were serially transmitted to other rat embryo cells. RaSV genome was rescued from the nonproductive clones by superinfection with SD-RaLV, wild rat type C virus, and several heterologous type C viruses. These observations appear to represent naturally occurring transformation-specific (
src
) genes being recovered
in vitro
in the form of stable “sarcoma” viruses. These viruses differ from the Kirsten and Harvey strains of murine sarcoma virus in that they apparently contain no MuLV sequences and are of purely rat origin.
Synthetic peptide derivatives that bind to fibrinogen and prevent the polymerization of fibrin monomers
Authors: Laudano Andrew P. , Doolittle Russell F.
Published: May 2006

A series of small peptides corresponding to the amino termini of the fibrin α- and β-chains has been synthesized. The peptides glycyl-L-prolyl-L-arginyl-L-proline and glycyl-L-prolyl-L-arginylsarcosine are potent inhibitors of fibrin polymerization. Moreover, these peptides have a natural stability stemming from their inherent resistance to proteolysis because of the involvement of amino acids in each of their peptide bonds. The peptide glycyl-L-prolyl-L-arginyl-L-proline binds to fibrinogen and to fragment D, in both cases with an association constant of approximately 5 × 10
4
; it does not bind to fragment E. The number of binding sites is two for fibrinogen and one for fragment D. The tripeptide glycyl-L-prolyl-L-arginine binds less tightly and is less than half as effective in preventing polymerization. The peptide glycyl-L-histidyl-L-arginyl-L-proline, which corresponds exactly to the amino terminus of the fibrin β-chain, does not inhibit the aggregation of fibrin monomers under the conditions used. It does bind weakly to fibrinogen, however, suggesting the involvement of sites other than those binding the α-chain analogues. Various other peptides were found not to inhibit polymerization; these included glycine-L-proline, L-prolyl-L-arginine and glycyl-L-prolyl-L-seryl-L-proline. The last-named corresponds to the serine/arginine amino acid replacement previously reported for a defective human fibrinogen.
Direct demonstration of duplicate tuf genes in enteric bacteria.
Authors: Furano A V
Published: May 2006

Radioactive tuf mRNA was used to detect the tuf gene in bacterial DNA that had been digested by various restriction endonucleases. Both the K-12 and the B strains of Escherichia coli contain two tuf genes, but no more than two. Salmonella typhimurium also contains duplicate tuf genes.
Soluble biospecific macromolecule for purification of estrogen receptor.
Authors: Hubert P , Mester J , Dellacherie E , Neel J , Baulieu E E
Published: May 2006

An alternative to affinity chromatography purification of proteins based on the use of a water-soluble biospecific polymer has been applied to the estrogen receptor from calf uterus. The receptor (4S-trypsin form) was bound to a dextran-estradiol conjugate (molecular weight approximately 500,000) and the complex was isolated by gel filtration. Highly purified receptor was subsequently released from the dextran-estradiol conjugate by exchange with [3H]estradiol.
Molecular structure of membrane vesicles from
Escherichia coli
Authors: Owen Peter , Kaback H. Ronald
Published: May 2006

The molecular architecture of membrane vesicles prepared from
Escherichia coli
ML 308-225 has been studied by using crossed immunoelectrophoresis, and a reference pattern of 52 discrete immunoprecipitates has been established. Progressive immunoadsorption experiments conducted with untreated control vesicles and with physically disrupted vesicles demonstrate that the membrane-associated immunogens fall into two categories: (
i
) those immunogens typified by ATPase (ATP phosphohydrolase, EC 3.6.1.3) and NADH dehydrogenase [NADH: (acceptor) oxidoreductase, EC 1.6.99.3] whose expression is minimal unless the vesicles are disrupted; and (
ii
) immunogens such as Braun's lipoprotein that are expressed to similar extents in untreated and in disrupted vesicles. A mathematical relationship between the peak area subtended by an immunoprecipitate in the crossed immuno-electrophoresis system and the quantity of vesicles used in the adsorption process has been derived. This relationship allows quantitation of the degree to which specific membrane immunogens partition between exposed and unexposed surfaces of the vesicle membrane. The results demonstrate conclusively that >95% of the membrane in the vesicle preparations is in the form of sealed sacculi with the same polarity as the intact cell. Moreover, the findings provide a strong indication that dislocation of immunogens from the inner to the outer surface of the membrane during vesicle preparation does not occur to an extent exceeding 11%.
Free ribosomal RNA genes in Paramecium are tandemly repeated.
Authors: Findly R C , Gall J G
Published: May 2006

The genes coding for 17S and 25S rRNA in Paramecium tetraurealia were isolated. The macronuclear ribosomal DNA (rDNA) exists as relatively small, extrachromosomal molecules with both linear and circular forms. Electron microscopy and restriction endonuclease analysis revealed that the rDNA is arranged as tandem repeats with an average repeat size of 5.5 X 10(6) daltons. Some heterogeneity of repeat lengths was found both by electron microscopy and by restriction enzyme analysis. The rDNA does not snap back after denaturation. This study provides additional evidence that extrachromosomal rDNA may be a common feature among lower eukaryotes. However, in contrast to several other cases, the rDNA of Paramecium is not palindromic, but occurs as tandem repeats as in higher eukaryotes.
Co-transfer of human X-linked markers into murine somatic cells via isolated metaphase chromosomes
Authors: Miller Carol Lynn , Ruddle Frank H.
Published: May 2006

Transformation frequencies of 4 × 10
-5
were obtained in chromosome-mediated gene transfer experiments using human cell line HeLa S3 as donor and mouse cell line A9 as recipient. This high frequency of interspecific transformation was achieved by treating the recipient cells with dimethylsulfoxide in addition to other facilitators. The high frequency of transformation correlated positively with transgenome size on the basis of both co-transfer of linked markers and chromosome analysis. The syntenic human markers glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate:NADP
+
1-oxidoreductase, EC 1.1.1.49) and phosphoglycerate kinase (ATP:3-phospho-D-glycerate 1-phosphotransferase, EC 2.7.2.3) were sometimes transferred together with the selected X-linked prototrophic marker hypoxanthine phosphoribosyltransferase (IMP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) into murine somatic cells. Donor human chromosome material could be demonstrated cytologically in some of the transformed cell lines. Transformants exhibited various rates of loss of the human hypoxanthine phosphoribosyltransferase marker when grown under nonselective conditions. These results reveal a broader range of possible interspecific transgenome sizes than has been recognized in the past. The largest transgenomes consist of cytologically detectable donor fragments and contain syntenic markers that are not closely linked to the selected marker.
Mass isolation and fertility testing of temperature-sensitive mutants in Tetrahymena.
Authors: Bruns P J , Sanford Y M
Published: May 2006

A set of 239 heat-sensitive (38 degrees) and 16 cold-sensitive (18 degrees) conditional mutants of Tetrahymena has been generated by combining techniques to manipulate large numbers of clones with a method for the selection of self-fertilized cells after mutagen treatment. A simple technique is presented for determining the fertility of individual clones; 179 of the clones in this set (71%) are fertile. The fertile conditional mutants have already been shown to have lesions in a number of diverse functions, including nucleic acid metabolism, mobility, cell cycle, and cortical pattern.
Anti-interferon globulin inhibits the development of glomerulonephritis in mice infected at birth with lymphocytic choriomeningitis virus.
Authors: Gresser J , Morel-Maroger L , Verroust P , Rivière Y , Guillon J C
Published: May 2006

Swiss mice infected at birth with lymphocytic choriomeningitis virus develop glomerulonephritis. Injection of potent anti-mouse interferon globulin at the time of viral infection inhibited the development of these renal lesions. We conclude that the production of endogenous interferon by this virus in the first few days of life plays an important role in the pathogenesis of this glomerulonephritis.
Identification of the trypanocidal factor in normal human serum: high density lipoprotein.
Authors: Rifkin M R
Published: May 2006

The differentiation of Trypanosoma brucei from T. rhodesiense, the causative agent of human sleeping sickness, depends on their relative sensitivities to the cytotoxic effects of normal human serum. The molecule responsible for the specific lysis of T. brucei has now been isolated. Serum lipoproteins were fractionated and purified by ultracentrifugal flotation and chromatography on Bio-Gel A-5m. Trypanocidal activity was recovered in the high density lipoprotein fraction (density, 1.063-1.216 g/ml). Contamination by other serum proteins was checked by crossed immunoelectrophoresis and sodium dodecyl sulfate/acrylamide gel electrophoresis. Only a trace of beta-lipoprotein was found. The trypanocidal activity of pure human high density lipoprotein was identical to that of unfractionated serum when the following were tested: (i) time course of in vitro lysis of T. bruceli; (ii) in vivo destruction of T. brucei; (iii) relative resistance of T. rhodesiense to lysis. Rat or rabbit high density lipoprotein had no trypanocidal activity. Identification of the trypanocidal factor as high density lipoprotein was confirmed by the finding that serum from patients with Tangier disease, an autosomal recessive disorder characterized by a severe deficiency of high density lipoprotein, had no trypanocidal activity.
Insulin resistance due to a defect distal to the insulin receptor: Demonstration in a patient with leprechaunism
Authors: Kobayashi Masashi , Olefsky Jerrold M. , Elders Joycelyn , Mako Mary E. , Given Bruce D. , Schedwie Heinrich K. , Fiser Robert H. , Hintz Raymond L. , Horner James A. , Rubenstein Arthur H.
Published: May 2006

We have studied a 2-year-old girl with acanthosis nigricans, glucose intolerance, marked hyperinsulinemia, and somatic features characteristic of the leprechaunism syndrome. Circulating plasma insulin levels were increased up to 50-fold and the patient showed a blunted hypoglycemic response to an injection of exogenous insulin (0.2 units/kg), indicating the presence of severe insulin resistance. Insulin purified from the patient's plasma was normal on the basis of chromatographic, electrophoretic, and immunologic criteria. Furthermore, the purified insulin competed effectively with
125
I-labeled insulin for binding to insulin receptors on cultured IM-9 lymphocytes and rat fat cells and also exhibited normal biological potency when tested on rat fat cells. Anti-insulin receptor and anti-insulin antibodies were not detected in the patient's plasma, and plasma levels of glucagon, growth hormone, and cortisol were normal. Insulin binding to the patient's circulating monuclear leukocytes was only slightly depressed into the low normal range and could not account for the severe insulin resistance. Studies on the patient's fibroblasts revealed normal levels of insulin receptors but a total absence of insulin's ability to accelerate glucose transport. Because rates of glucose transport and metabolism were normal in the basal state in the absence of insulin, we conclude that this patient's insulin resistance is due to an inherited cellular defect in the coupling mechanism between occupied insulin receptors and the plasma membrane glucose transport system.
Responses to light of solitary rod photoreceptors isolated from tiger salamander retina.
Authors: Bader C R , MacLeish P R , Schwartz E A
Published: May 2006

Single, isolated rod photoreceptors were obtained by enzymatic dissociation of the tiger salamander (Ambystoma tigrinum) retina. These solitary cells retained the morphological features of rods of the intact retina and could be maintained in culture for several days. When impaled with micropipettes for electrophysiological recording, dark-adapted solitary rods had during darkness a resting potential of approximately -45 mV and a steady-state slope resistance of 500 Momega at rest. The current-voltage relationship showed both inward- and outward-going rectification. The responses to light of solitary rods were similar to those recorded from rods in the intact retina stimulated with large-diameter spots of light. The reversal potential of the light response of solitary rods was near 0 mV when measured in either the inner or outer segment.
Group selection on a quantitative character
Authors: Slatkin M. , Wade M. J.
Published: May 2006

We derive a model of group and individual selection on a quantitative character that is similar to the single-locus “metapopulation” models of group selection. Two alternative methods for the colonization of new or vacant habitats are examined and their effects are contrasted. In one model, all populations contribute migrants to a common pool, the “migrant pool,” from which colonists are drawn at random to fill vacant sites. In the migrant pool there is complete mixing of individuals from different populations. This model of colonization is the one used in all previous models of group selection. In the other model, the “propagule pool” model, each propagule is made up of individuals derived from a single population and there is no mixing of colonists from different populations during propagule formation. The analysis shows that much more between-population genetic variance can be maintained with the propagule pool model than with the migrant pool model. Consequently, group selection can be much more effective in natural populations than is commonly supposed.
Nucleotide specificity in DNA scission by neocarzinostatin.
Authors: Hatayama T , Goldberg I H , Takeshita M , Grollman A P
Published: May 2006

Using the DNA sequencing technique of Maxam and Gilbert, we show that the protein antibiotic neocarzinostatin, cleaves double-stranded phiX174 DNA restriction fragments almost exclusively at deoxythymidylic and deoxyadenylic acid residues in a reaction requiring 2-mercaptoethanol. Overall, deoxythymidylic acid residues are attacked much more frequently than are deoxyadenylic acid residues, although there is variability in the attack rate for both nucleotides at different locations in the DNA molecule. While all deoxythymidylic acid residues are sites of scission by neocarzinostatin, not all deoxyadenylic acid residues are cleavage sites. There appears to be no clear-cut nucleotide sequence specificity in determining cleavage frequency. Single-stranded DNA is a very poor substrate for neocarzinostatin-induced scission; with one single-stranded DNA fragment, cleavage occurs at a position that is not attacked in double-stranded DNA. The possible significance for its biological activity of a drug that can attack both members of a DNA base pair is discussed.
Sequence specific cleavage of DNA by the antitumor antibiotics neocarzinostatin and bleomycin.
Authors: D'Andrea A D , Haseltine W A
Published: May 2006

We have investigated the sites of DNA damage by the antitumor antibiotics neocarzinostatin and bleomycin by using a 5'-end-labeled DNA fragment of defined sequence as a substrate. At the high drug concentrations used here, neocarzinostatin creates single-strand breaks in DNA at positions of adenine and thymine in the presence of 2-mercaptoethanol, and bleomycin cleaves DNA at GC and GT sequences and to a lesser extent at TA sequences with its degradative activity enhanced by 2-mercaptoethanol. In the presence of ferrous ions, bleomycin cleaves DNA at TT, AT, and TA, as well as at GC and GT sequences. Both antibiotics make double-strand breaks in DNA at specific sites and it is likely that these result from two independent single-strand breaks at nearby sites on opposite strands of the DNA.
Isolation of an avian erythrocyte protein possessing ADP-ribosyltransferase activity and capable of activating adenylate cyclase
Authors: Moss Joel , Vaughan Martha
Published: May 2006

An ADP-ribosyltransferase was purified ∼500-fold from the supernatant fraction of turkey erythrocytes. The enzyme hydrolyzed [
carbonyl
-
14
C]NAD to ADP-ribose and [
carbonyl
-
14
C]nicotinamide at a low rate. Nicotinamide formation from NAD was enhanced by arginine methyl ester > D-arginine ∼ L-arginine > guanidine; lysine, histidine, and citrulline were ineffective. Incubation of [
adenine-U
-
14
C]NAD and arginine methyl ester or arginine with the purified enzyme resulted in the formation of new compounds that contained
14
C, reacted with ninhydrin, and quenched background fluorescence of thin-layer plates viewed in ultraviolet light. Their mobilities on thin-layer chromatograms were indistinguishable from those of ADP-ribosylarginine methyl ester and ADP-ribosylarginine formed during incubation of choleragen with NAD and arginine methyl ester or arginine, respectively [Moss, J. & Vaughan, M. (1977)
J. Biol. Chem.
252, 2455-2457]. The purified transferase also catalyzed the incorporation of label from [
adenine
-
14
C]-NAD into lysozyme, histones and polyarginine. When the
14
C-labeled lysozyme was incubated with snake venom phosphodiesterase, the radioactivity was released and, on thin-layer chromatograms, exhibited a mobility indistinguishable from that of 5′-AMP, as would be expected of an ADP-ribosylated protein, but not of a poly(ADP-ribosylated) product. The purified transferase activated rat brain adenylate cyclase and, as is the case with choleragen, activation was absolutely dependent on NAD. The presence in the avian erythrocyte of a protein that, like choleragen and
Escherichia coli
heat-labile enterotoxin, apparently activates adenylate cyclase and possesses ADP-ribosyl transferase activity is consistent with the view that the mechanisms through which the bacterial toxins produce pathology are not entirely foreign to vertebrate cells, at least some of which may possess and employ an analogous mechanism for activation of adenylate cyclase.
Influenza virus proteins: identity, synthesis, and modification analyzed by two-dimensional gel electrophoresis.
Authors: Privalsky M L , Penhoet E E
Published: May 2006

A modification of the two-dimensional protein electrophoresis system of O'Farrell was used to resolve influenza A virus proteins from each other and from host proteins in infected cells. Viral protein spots corresponding to the hemagglutinin proteins, neuraminidase, nucleocapsid protein, and nonstructural protein, were identified on the two-dimensional electrophoretogram. Use of the two-dimensional separation has allowed us to identify glycoprotein heterogeneity, to demonstrate directly the synthesis of neuraminidase, to analyze some viral proteins early after infection, and to demonstrate that the influenza virus NP and NS proteins are phosphorylated in infected MDCK cells.
Regulation of protein synthesis in rabbit reticulocyte lysates: purification and characterization of heme-reversible translational inhibitor.
Authors: Trachsel H , Ranu R S , London I M
Published: May 2006

To define the mechanism of regulation of the protein kinase that is activated in heme deficiency and that inhibits initiation of protein synthesis, we have isolated and purified the heme-reversible form of the protein kinase from rabbit reticulocytes. The inhibitory activity is found in a single band after polyacrylamide gel electrophoresis under nondenaturing conditions. It migrates as a 95,000-dalton polypeptide in 15% sodium dodecyl sulfate/polyacrylamide gels. This purified inhibitor becomes self-phosphorylated in the presence of ATP; the phosphorylated protein and the inhibitory activity copurify. The inhibitor produces characteristic biphasic kinetics of inhibition in reticulocyte lysates and phosphorylates the 38,000-dalton subunit of eukaryotic initiation factor 2 (eIF-2); the inhibition is reversed by added eIF-2. In contrast to the heme-irreversible inhibitor, this heme-reversible inhibitor is no longer inhibitory after incubation with 20 micron hemin. Incubation with hemin also inhibits self-phosphorylation. Preincubation of the heme-reversible inhibitor in the presence of ATP potentiates the inhibition of protein synthesis in the subsequent incubation, as does treatment with N-ethylmaleimide. Phosphorylation of the heme-reversible inhibitor and inhibition of protein synthesis in the lysate due to phosphorylation of eIF-2 appear to be related. These findings suggest that hemin acts directly on the heme-reversible inhibitor.
Low molecular weight RNA species encoded by a multiple drug resistance plasmid.
Authors: De Wilde M , Davies J E , Schmidt F J
Published: May 2006

Multiple drug resistance plasmid NR1 is shown to code for at least 10 low molecular weight RNAs. These species, ranging in size from 60 to 120 nucleotides, have been purified from minicells by two-dimensional gel electrophoresis and characterized by RNase T1 fingerprinting. Hybridization of purified RNAs to restriction endonuclease digests of NR1 DNA indicates that most are derived from the resistance transfer factor region of the plasmid genome. One RNA was found to be coded by the transposable tetracycline resistance element Tn10, and several are associated with DNA fragments that contain origins of replication.
Ribonuclease P: an enzyme with an essential RNA component.
Authors: Stark B C , Kole R , Bowman E J , Altman S
Published: May 2006

The activity of ribonuclease P on precursor tRNA substrates from Escherichia coli can be abolished by pretreatment of this enzyme with micrococcal nuclease or pancreatic ribonuclease A, as well as by proteases and by thermal denaturation. Highly purified RNase P exhibits one prominent RNA and one prominent polypeptide component when examined in polyacrylamide gels containing sodium dodecyl sulfate. The buoyant density in CsCl of RNase P, 1.71 g/ml, is characteristic of a protein-RNA complex. The activity of RNase P is inhibited by various RNA molecules. The presence of a discrete RNA component in RNase P appears to be essential for enzymatic function. A model is described for enzyme-substrate recognition in which this RNA component plays an important role.
Control of microtubule assembly-disassembly by calcium-dependent regulator protein.
Authors: Marcum J M , Dedman J R , Brinkley B R , Means A R
Published: May 2006

The Ca2+-dependent regulator (CDR) protein of cyclic nucleotide phosphodiesterase is a low molecular weight, acidic, Ca2+-binding protein which has been implicated in a number of Ca2+-dependent enzymatic functions. Indirect immunofluorescence has revealed that CDR is specifically associated with the chromosome-to-pole region of the mitotic apparatus during metaphase-anaphase in a pattern distinctly different from that of similar cultured cells stained with antitubulin. This characteristic localization in the mitotic half-spindle suggested a role for CDR in the control of microtubule assembly-disassembly during mitosis. Thus, CDR was examined for its effects on microtubule polymerization in vitro. It was determined that stoichiometric concentrations of CDR and a homologous Ca2+-binding protein, skeletal muscle troponin C, both inhibited and reversed microtubule assembly in a Ca2+-dependent manner. CDR-dependent inhibition of in vitro microtubule assembly occurred at physiological Ca2+ concentrations (approximately 10 micron) that, in the absence of CDR, caused only a slight reduction in polymerization. At Ca2+ concentrations in the low physiological range (less than 1 micron), no inhibition was observed. These biochemical results, together with the immunofluorescent localization of CDR in the mitotic half-spindle, provide evidence that Ca2+ is an endogenous regulator of microtubule disassembly through the activity of CDR.