scholarly journals Biosynthesis of glucagon in isolated pancreatic islets of guinea pigs

1974 ◽  
Vol 140 (1) ◽  
pp. 13-21 ◽  
Author(s):  
Claes Hellerström ◽  
Simon L. Howell ◽  
John C. Edwards ◽  
Arne Andersson ◽  
Claes-Göran Östenson
Keyword(s):  
Molecular Weight ◽  
Biological Activity ◽  
Gel Filtration ◽  
Subcellular Fractionation ◽  
Fat Cell ◽  
Electron Microscopic ◽  
Isolated Pancreatic Islets ◽  
Isolated Islets Of Langerhans ◽  
Electron Microscopic Radioautography ◽  
Very High

1. The biosynthesis of glucagon in guinea-pig A2 cells was investigated by incubation of isolated islets of Langerhans in the presence of [3H]tryptophan for periods of up to 14 days. Proteins were extracted from islets and incubation media and analysed by gel filtration. 2. In addition to very-high-molecular-weight (100000) proteins, the principal tryptophan-containing biosynthetic product after incubation for up to 17h was a protein of minimum mol.wt. 9000, which co-eluted on gel filtration with a peak of glucagon-like immunoreactivity, but was apparently devoid of biological activity in a fat-cell assay. A discrete peak of labelled glucagon was only recovered after incubation for at least 6 days. Losses of glucagon during the extraction and rapid secretion of newly synthesized glucagon into incubation media were excluded as reasons for the lack of recovery of labelled hormone from islets after shorter incubations. 3. The 9000-mol.wt. protein was localized to A2 cells in experiments using B-cell-depleted islets, and to A2-cell granules by subcellular fractionation and electron-microscopic radioautography. Only glucagon was secreted into the incubation medium. 4. Possible relationships between the 9000-mol.wt. protein and glucagon are discussed in the light of postulated mechanisms of glucagon biosynthesis.

Rapid release of peroxidase by peanut cells in suspension culture

1973 ◽  
Vol 51 (6) ◽  
pp. 1169-1175 ◽  
Author(s):  
R. B. van Huystee ◽  
G. Turcon
Keyword(s):  
Molecular Weight ◽  
Metabolic Rate ◽  
Suspension Culture ◽  
Gel Filtration ◽  
Electron Microscopic ◽  
Rapid Release ◽  
Microscopic Studies ◽  
Very High

Peanut cells in a suspension culture were studied with regard to the process of peroxidase release and some ultrastructural features that appeared to relate to this process. By means of gel filtration on Sephadex G-200 it was established that protein released into the medium had the same molecular weight as the peroxidase found in this medium. From information gained through the electron-microscopic studies and from incorporation of labeled leucine, it may be deduced that the metabolic rate of these cells is very high. Within 2 h after incubation with radioactive leucine it was noted that newly synthesized protein was released by the cells into the medium. This protein had also the same characteristics of peroxidase and its synthesis and subsequent appearance in the medium could be reduced by incubation in the presence of cycloheximide. A possible explanation for the presence of these large quantities of peroxidase is discussed.

scholarly journals The regulatory proteins of the myofibril. Characterization and properties of the inhibitory factor (troponin B)

1971 ◽  
Vol 123 (3) ◽  
pp. 367-377 ◽  
Author(s):  
M. C. Schaub ◽  
S. V. Perry
Keyword(s):  
Molecular Weight ◽  
Biological Activity ◽  
Inhibitory Activity ◽  
Gel Filtration ◽  
Inhibitory Factor ◽  
Regulatory Proteins ◽  
Actomyosin Atpase ◽  
Troponin Complex

1. Gel-filtration results indicate that the major component of inhibitory-factor preparations isolated by dissociation of the troponin complex consisted of a protein of subunit weight 23000 daltons. By the same procedure a molecular weight of 18000 was obtained for the calcium-sensitizing factor. 2. The inhibitory factor is specific for the actomyosin type of ATPase and ITPase. It is effective on desensitized actomyosin, natural actomyosin and intact myofibrils. 3. For inhibition, the actomyosin ATPase must be stimulated by Mg2+, Ca2+ or Mn2+. The Co2+-, Cd2+- or Zn2+-stimulated ATPases are not affected. 4. Biological activity is stable to treatment with dissociating agents, heat, pH11, pH1 and carboxymethylation. 5. Increasing amounts of actin, but not myosin or tropomyosin, progressively neutralize the inhibitory activity when added to desensitized actomyosin or myofibrils.

Distribution of radioactive silver in the subcellular fractions of various tissues of the rat and its binding to low molecular weight proteins

1983 ◽  
Vol 61 (11) ◽  
pp. 1391-1395 ◽  
Author(s):  
Yousef Matuk
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Gel Filtration ◽  
Total Radioactivity ◽  
Subcellular Fractions ◽  
Low Molecular Weight ◽  
Electron Microscopic ◽  
Molecular Weight Peak

In view of the electron microscopic evidence that silver does not penetrate cellular barriers, the distribution of radioactive silver in rat blood and subcellular fractions of liver, kidneys, spleen, and forebrain was studied. It was found that 24 h after a single intraperitoneal injection high levels of radioactivity were reached which decreased at different rates in the various tissues studied. In plasma, liver, and kidneys there was an initial rapid loss of radioactivity which was followed by a slower rate of loss. In the blood, forebrain, and spleen the loss of radioactivity was linear and somewhat slower than in the other three tissues. The cytosols of the liver and kidneys contained 60% while those of the forebrain and spleen contained 30% of the total radioactivity found in the tissue homogenates. Gel filtration on Sephadex G-75 showed that all cytosols contained two peaks of radioactivity; a high molecular weight peak which eluted just after the void volume and a low molecular weight peak. The amount of radioactivity in both peaks was, however, much lower in the chromatographic peaks of the forebrain and spleen than that found in those of the liver and kidneys. Furthermore, the spleen had a comparatively very small low molecular weight radioactive peak. In vitro experiments with liver cytosol showed similar results to those found in vivo in that the high molecular weight radioactive peak could be removed by heat. It is concluded that silver does enter cells and that silver thionein exists in the cytosols of forebrain, spleen, kidney, and liver.

scholarly journals Isolation of material displaying insulin-like immunological biological activity from the brain of the blowfly Calliphora vomitoria

1979 ◽  
Vol 184 (2) ◽  
pp. 221-227 ◽  
Author(s):  
H Duve ◽  
A Thorpe ◽  
N R Lazarus
Keyword(s):  
Biological Activity ◽  
Neurosecretory Cell ◽  
Polyacrylamide Gel Electrophoresis ◽  
Gel Filtration ◽  
Insulin Receptors ◽  
Neurosecretory Cells ◽  
Bovine Insulin ◽  
Fat Cell ◽  
Median Neurosecretory Cells ◽  
The Brain

An insulin-like material from the brain of the blowfly Calliphora vomitoria was partially purified by acid alcohol extraction, gel filtration and ion-exchange cellulose chromatography. In addition, the RF value on polyacrylamide-gel electrophoresis was determined. The material was characterized by its ability to cross-react with bovine insulin antibody and by displaying diminished immunoreactivity on dilution. It displaced specifically bound 125I-labelled insulin from rat liver plasma membrane insulin receptors and displayed insulin-like biological activity on the isolated rat fat-cell. Within 30 min of injection into Calliphora, made hypertrehalocaemic and hyperglucaemic as a result of median neurosecretory cell removal, it caused the concentrations of both sugars to return to normal. The hypothesis is put forward that the median neurosecretory cells are the source of the material.

scholarly journals The heterogeneity of the lipoprotein lipase of rat epididymal adipose tissue

1978 ◽  
Vol 171 (2) ◽  
pp. 305-311 ◽  
Author(s):  
P Ashby ◽  
A M Tolson ◽  
D S Robinson
Keyword(s):  
Molecular Weight ◽  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Density Gradient Centrifugation ◽  
Gradient Centrifugation ◽  
Gel Filtration ◽  
Particulate Material ◽  
Epididymal Adipose Tissue ◽  
Fat Cell ◽  
Enzyme Preparations

Lipoprotein lipase is heterogeneous, and it was suggested that the enzyme in adipose tissue is transformed from a species of mol. wt. approx. 120000 to forms of much higher molecular weight as it is secreted from the fat-cell. This paper demonstrates that the forms of higher molecular weight are probably artifacts. Enzyme preparations were characterized by gel filtration, by density-gradient centrifugation and by affinity chromatography. The results indicate that the enzyme forms of mol. wt. greater than 120000 result from an association of the enzyme with particulate material. It is therefore necessary to reconsider schemes that have recently been proposed for the synthesis and export of lipoprotein lipase.

scholarly journals Size heterogeneity of rat pituitary prolactin

1980 ◽  
Vol 189 (3) ◽  
pp. 605-614 ◽  
Author(s):  
M Wallis ◽  
M Daniels ◽  
S A Ellis
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Gel Filtration ◽  
Paper Electrophoresis ◽  
Freezing And Thawing ◽  
Molecular Weights ◽  
Size Heterogeneity ◽  
Very High

The occurrence of multiple forms of rat prolactin with different molecular weights (size heterogeneity) was studied with anterior pituitary extracts, purified rat prolactin and 125I-labelled rat prolactin. In each case, three main forms of the hormone were detected by gel filtration on Sephadex G-100: a major one (80–90%) corresponding to monomeric prolactin (mol.wt. 22000–25000), a peak (8–20%) that could be a dimer (mol.wt. 45000–50000) and a small quantity (1–5%) of a component of much greater molecular weight. On freezing and thawing of 125I-labelled rat prolactin, there was little interconversion of monomer and ‘dimer’ peaks, but both were converted substantially to very high-molecular-weight material. All three peaks of 125I-labelled rat prolactin could be precipitated by anti-(rat prolactin) serum and all three gave similar patterns of radioactive peptides after digestion with chymotrypsin followed by high-voltage paper electrophoresis. On sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, the monomer peak of 125I-labelled prolactin migrated as a single component of mol.wt. 22000, the very high-molecular-weight peak largely dissociated to a component running in the same position as the monomer, and the ‘dimer’ peak migrated partly as a component of mol.wt. 45000 and partly as a component migrating with monomeric prolactin. No treatment was found that could dissociate the ‘dimer’ peak completely to monomeric prolactin.

scholarly journals The separation and distribution of simple and condensed leucoanthocyanins of the tea plant (Camellia sinensis L.)

1969 ◽  
Vol 113 (5) ◽  
pp. 757-763 ◽  
Author(s):  
G. I. Forrest ◽  
D S Bendall
Keyword(s):  
Molecular Weight ◽  
Gel Filtration ◽  
Inverse Correlation ◽  
Tea Plant ◽  
Degree Of Polymerization ◽  
Monomer Ratio ◽  
Lower Mobility ◽  
High Concentrations ◽  
Root Tissues ◽  
Very High

1. Leucoanthocyanin monomers of high mobilities in aqueous solvents on thinlayer chromatograms, assumed to be structurally simple, were characteristic of mature bulky tissues, whereas members of lower mobility were confined to young vegetative and floral tissues. 2. Flavylogens were separated by gel filtration on Sephadex columns into monomeric, oligomeric and polymeric fractions. 3. The polymeric fraction from young brown stems was heterogeneous, one-half having a molecular weight of about 3400, one-third a molecular weight between 3600 and 17000, and the remainder a molecular weight of over 17000. 4. Leaves had low flavylogen concentrations; only monomers were present. Stem tissues were rich in polymers, which increased with the age of the young stem and decreased inwards through the wood. The maximal flavylogen concentrations were in the phloem and cambium from mature stems, where all three fractions were richly present. The periderm tissue and, to a lesser extent, the seed coat were characterized by a very high polymer/monomer ratio, exhibiting a much higher degree of polymerization than the wood. Root tissues contained high concentrations of monomers. 5. In general, there was an inverse correlation between the extent of polymerization and the complexity of the monomers present. 6. The results are in favour of the thesis that the function of the flavanols is, after polymerization to condensed tannins, to impregnate dead structural tissues and thereby to protect them from infection and decay.

scholarly journals STUDIES ON THE PATHOGENESIS OF FEVER

1968 ◽  
Vol 127 (2) ◽  
pp. 341-357 ◽  
Author(s):  
Marilyn Sue Kozak ◽  
Helmut H. Hahn ◽  
William J. Lennarz ◽  
W. Barry Wood
Keyword(s):  
Molecular Weight ◽  
Biological Activity ◽  
Active Material ◽  
Gel Filtration ◽  
Chemical Properties ◽  
Disc Electrophoresis ◽  
Polyacrylamide Gel ◽  
Sulfhydryl Groups ◽  
Biologically Active ◽  
Exhaustive Extraction

Small quantities of highly purified granulocytic pyrogen have been separated from contaminating proteins by disc electrophoresis in polyacrylamide gel. The biologically active material thus isolated was shown to be electrophoretically homogeneous at pH 9 and pH 3.8. Earlier work on the chemical properties of the pyrogen molecule has been extended to include: (a) estimation of its molecular weight by gel filtration; (b) demonstration of free sulfhydryl groups essential for its biological activity; and (c) evidence that it is not inactivated by exhaustive extraction with ethanolether or n-heptane.

DISCREPANCIES IN PLASMA LH ACTIVITIES AS MEASURED BY RADIOIMMUNOASSAY AND AN IN VITRO BIOASSAY

1974 ◽  
Vol 77 (4) ◽  
pp. 672-685 ◽  
Author(s):  
M. H. Qazi ◽  
P. Romaní ◽  
E. Diczfalusy
Keyword(s):  
Molecular Weight ◽  
Biological Activity ◽  
Gel Filtration ◽  
Biologically Active ◽  
Plasma Samples ◽  
Elution Volume ◽  
Immunological Activity ◽  
Molecular Weight Range ◽  
Weight Range

ABSTRACT Using a highly sensitive in vitro bioassay system, luteinizing hormone activity has been measured in parallel with radioimmunoassays in postmenopausal plasma and plasma obtained from women in various phases of the menstrual cycle (follicular, mid-cycle, luteal). Biological and immunological activities were measured directly in plasma samples without any chemical manipulation. The biological activity (B) was always higher than the immunological activity (I); the B/I ratio varied from 2.1 to 14.0. Gel filtration of pooled plasma samples through Sephadex G-100 revealed major discrepancies in each physiological state when immunological and biological activities were measured in each fraction. The biological activity was eluted as a single peak behind the elution volume of bovine serum albumin, but in front of the elution volume of chymotrypsinogen. It was invariably preceded by a small hump. The immunological activity was spread all over the chromatogram. Areas of immunological activity without any biological activity were located on either side of the biologically active fractions, both in the high molecular weight range (including the void volume) and in the low molecular weight range. The biological LH activity recovered following fractionation on Sephadex G-100 was in close agreement with that loaded, whereas the immunological activity recovered following gel filtration exceeded the loaded activity by a factor of 6–8. In the various physiological states, 11 to 44 % of the total immunological activity recovered was not associated with any biological activity. Furthermore, there was a marked variation in the ratio of biological to immunological activities of those fractions which contained biological activity. It is suggested that the specificity of current RIA methods could be improved significantly by preparing antisera which react only with biologically active LH species.

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