scholarly journals ISOLATION AND PROPERTIES OF SECRETORY GRANULES FROM RAT ISLETS OF LANGERHANS

1969 ◽  
Vol 41 (1) ◽  
pp. 167-176 ◽  
Author(s):  
S. L. Howell ◽  
D. A. Young ◽  
P. E. Lacy
Keyword(s):  
Islets Of Langerhans ◽  
Secretory Granules ◽  
Sodium Deoxycholate ◽  
Rat Islets ◽  
The Matrix ◽  
Effects Of Ph ◽  
The Stability ◽  
Rat Islets Of Langerhans ◽  
Specific Insulin

A partially purified secretory granule fraction, isolated from rat islets of Langerhans by differential centrifugation, was used for investigating the stability of the beta granules during incubation in various conditions. Effects of pH, temperature, and time were studied; the granules possessed optimal stability at 4° and pH 6.0, and could be solubilized at pH 4.0 or 8.5, or in the presence of sodium deoxycholate, but not by phospholipase c, ouabain, or alloxan. Incubation with glucose or some of its metabolites, or with tolbutamide, ATP, or cyclic 3',5'-AMP did not alter the stability of the beta granules Exogenous insulin-131I was not bound by the isolated granules under the conditions used; no specific insulin-degrading activity could be detected in subcellular fractions of the islets. These findings indicate that intracellular solubilization of the granules with subsequent diffusion of the insulin into the extracellular space is not a likely mode of insulin secretion in vivo, and suggest that a crystalline zinc-insulin complex may exist in the matrix of the beta granules.

scholarly journals ISOLATION AND PROPERTIES OF SECRETORY GRANULES FROM RAT ISLETS OF LANGERHANS

1969 ◽  
Vol 41 (1) ◽  
pp. 154-161 ◽  
Author(s):  
S. L. Howell ◽  
C. J. Fink ◽  
P. E. Lacy
Keyword(s):  
Islets Of Langerhans ◽  
Secretory Granule ◽  
Islet Cells ◽  
Secretory Granules ◽  
Morphological Characterization ◽  
Differential Centrifugation ◽  
Rat Islets ◽  
Granule Fraction ◽  
Final Yield ◽  
Rat Islets Of Langerhans

A method has been devised for the isolation of a secretory granule fraction from isolated rat islets of Langerhans. The islets were homogenized in buffered sucrose, and the homogenate was separated into nuclear, mitochondrial, secretory granule, and microsomal fractions by differential centrifugation. The secretory granule fraction was purified by differential centrifugation in discontinuous sucrose density gradients. A greater degree of purification could be achieved by the use of two successive gradients of this type, although the final yield was greatly reduced. Biochemical and morphological characterization of the fractions was obtained; the secretory granule fraction contained both insulin and glucagon. The limiting membranes of the granules remained intact and the general appearance of the granules was similar to that seen within the whole islet cells.

scholarly journals ISOLATION AND PROPERTIES OF SECRETORY GRANULES FROM RAT ISLETS OF LANGERHANS

1969 ◽  
Vol 41 (1) ◽  
pp. 162-166 ◽  
Author(s):  
Marie H. Greider ◽  
S. L. Howell ◽  
P. E. Lacy
Keyword(s):  
Surface Structure ◽  
Islets Of Langerhans ◽  
Thin Section ◽  
Phosphotungstic Acid ◽  
Secretory Granules ◽  
Crystalline Material ◽  
Intact Cells ◽  
Rat Islets ◽  
Rat Islets Of Langerhans

Beta granules isolated from rat islets of Langerhans and subjected only to phosphotungstic acid had, in negatively stained images, a 50-A periodicity. This periodicity was also observed in thin-section profiles of beta granules in intact cells. In shadowed preparations, the granules were spherical in shape and had irregular edges and surface structure. The presence of such a periodicity in the beta granule indicates that its matrix may be composed of a crystalline material.

scholarly journals Direct effects of progesterone on rat islets of Langerhans in vivo and in tissue culture

Diabetologia ◽  
1977 ◽  
Vol 13 (6) ◽  
pp. 579-583 ◽  
Author(s):  
S. L. Howell ◽  
Margaret Tyhurst ◽  
Irene C. Green
Keyword(s):  
Tissue Culture ◽  
Islets Of Langerhans ◽  
Direct Effects ◽  
Rat Islets ◽  
Rat Islets Of Langerhans

Opioid peptides in rat islets of Langerhans. Immunoreactive met- and leu-enkephalins and BAM-22P

Diabetes ◽  
1986 ◽  
Vol 35 (1) ◽  
pp. 52-57 ◽  
Author(s):  
K. I. Timmers ◽  
N. R. Voyles ◽  
C. King ◽  
M. Wells ◽  
R. Fairtile ◽  
...  
Keyword(s):  
Islets Of Langerhans ◽  
Opioid Peptides ◽  
Rat Islets ◽  
Rat Islets Of Langerhans

Effects of epicatechin on rat islets of Langerhans

Diabetes ◽  
1984 ◽  
Vol 33 (3) ◽  
pp. 291-296 ◽  
Author(s):  
C. S. Hii ◽  
S. L. Howell
Keyword(s):  
Islets Of Langerhans ◽  
Rat Islets ◽  
Rat Islets Of Langerhans

scholarly journals CYTOCHEMICAL LOCALIZATION OF ADENYL CYCLASE ACTIVITY IN RAT ISLETS OF LANGERHANS

1972 ◽  
Vol 20 (11) ◽  
pp. 873-879 ◽  
Author(s):  
S. L. HOWELL ◽  
MARGARET WHITFIELD
Keyword(s):  
B Cells ◽  
Islets Of Langerhans ◽  
Adenosine Triphosphate ◽  
Adenyl Cyclase ◽  
Cyclase Activity ◽  
Cytochemical Localization ◽  
Adenyl Cyclase Activity ◽  
Rat Islets ◽  
Rat Islets Of Langerhans ◽  
A And B Cells

A cytochemical method has been used to investigate the localization of adenyl cyclase activity in A and B cells of isolated rat islets of Langerhans. Adenosine triphosphate was initially utilized as substrate, the pyrophosphate liberated being precipitated by lead ions at its site of production. The specificity of the method was increased by the use of adenylyl-imidodiphosphate as an alternative substrate; this adenosine triphosphate analogue was not hydrolyzed by adenosine triphosphatase but provided an effective substrate for adenyl cyclase. Adenyl cyclase activity, which was found to retain its glucagon and fluoride sensitivity in glutaraldehyde-fixed tissue, was found exclusively and almost uniformly in the plasma membranes of A and B cells. Storage granule membrane, incorporated into the plasma membrane during secretion of the granule content by exocytosis, appeared to be devoid of adenyl cyclase activity.

scholarly journals Stimulation of Adenylate Cyclase by Ca2+ and Calmodulin in Rat Islets of Langerhans: Explanation for the Glucose-induced Increase in Cyclic AMP Levels

Diabetes ◽  
1980 ◽  
Vol 29 (1) ◽  
pp. 74-77 ◽  
Author(s):  
G. W. G. Sharp ◽  
D. E. Wiedenkeller ◽  
D. Kaelin ◽  
E. G. Siegel ◽  
C. B. Wollheim
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Islets Of Langerhans ◽  
Rat Islets ◽  
Rat Islets Of Langerhans ◽  
Stimulation Of

Immunological characterization of the guanine-nucleotide binding proteins Gi and Go in rat islets of Langerhans

1992 ◽  
Vol 8 (2) ◽  
pp. 103-108 ◽  
Author(s):  
N. S. Berrow ◽  
G. Milligan ◽  
N. G. Morgan
Keyword(s):  
G Proteins ◽  
Islets Of Langerhans ◽  
Pertussis Toxin ◽  
Nucleotide Binding ◽  
Molecular Forms ◽  
Antigenic Determinants ◽  
Guanine Nucleotide ◽  
Rat Islets ◽  
Guanine Nucleotide Binding ◽  
Rat Islets Of Langerhans

ABSTRACT Inhibition of insulin secretion from rat islets of Langerhans is known to involve at least one pertussis toxin-sensitive guanine-nucleotide binding (G) protein. We have used antisera raised against unique antigenic determinants of different members of the family of pertussis toxin-sensitive G proteins to identify these proteins in rat islets. Antiserum SG1, which recognizes both Gi1 and Gi2, reacted with an islet protein having an approximate Mr of 40 000. Antiserum IlC (Gi1 specific) failed to recognize any islet proteins, suggesting that Gi2 is present in much greater amounts than Gi1. Indeed, Gi1 levels were below the detection limit of a sensitive immunogold/silver-staining method, indicating that it may be absent from the cells of rat islets. Two different antisera were used to identify Go-like G proteins in rat islet homogenates. Both antisera reacted with a protein band which, under appropriate conditions, could be resolved to reveal two separate proteins of Mr 39–40 000. Thus, at least two molecular forms of Go are present in rat islets. Subcellular fractionation indicated that all three G proteins identified in this study (Gi2 and two forms of Go) are localized to islet membranes. No immunoreactivity could be detected in the cytosolic fraction.

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