scholarly journals Transport of ascorbic acid and dehydroascorbic acid by pancreatic islet cells from neonatal rats

1991 ◽  
Vol 274 (3) ◽  
pp. 739-744 ◽  
Author(s):  
A Zhou ◽  
J H Nielsen ◽  
O Farver ◽  
N A Thorn
Keyword(s):  
Ascorbic Acid ◽  
Pancreatic Islet ◽  
Islet Cells ◽  
Secretory Granules ◽  
Dehydroascorbic Acid ◽  
Pancreatic Tissue ◽  
Biologically Active ◽  
Pancreatic Islet Cells ◽  
High Concentration ◽  
Old Rats

Several amidated biologically active peptides such as pancreastatin, thyrotropin-releasing hormone, pancreatic polypeptide and amylin are produced in endocrine pancreatic tissue which contains the enzyme necessary for their final processing, i.e. peptidylglycine alpha-amidating mono-oxygenase (EC 1.14.17.3). The enzyme needs ascorbic acid for activity as well as copper and molecular oxygen. The present work shows that pancreatic islet cells prepared from overnight cultures of isolated islets from 5-7-day-old rats accumulate 14C-labelled ascorbic acid by a Na(+)-dependent active transport mechanism which involves a saturable process (estimated Km 17.6 microM). Transport was inhibited by ouabain, phloridzin, cytochalasin B, amiloride and probenecid. Glucose inhibited or stimulated uptake, depending on the length of incubation time of the cells. The uptake of dehydroascorbic acid was linearly dependent on concentration. Dehydroascorbic acid was converted to ascorbic acid by an unknown mechanism after uptake. The uptake of both ascorbic acid and dehydroascorbic acid was inhibited by tri-iodothyronine, and uptake of ascorbic acid, but not of dehydroascorbic acid, was inhibited by glucocorticoids. Isolated secretory granules contained a fairly low concentration of iron but a high concentration of copper.

scholarly journals Association between Hydrogen Peroxide-Dependent Byproducts of Ascorbic Acid and Increased Hepatic Acetyl-CoA Carboxylase Activity

2005 ◽  
Vol 51 (8) ◽  
pp. 1462-1471 ◽  
Author(s):  
Laurent Knafo ◽  
Philippe Chessex ◽  
Thérèse Rouleau ◽  
Jean-Claude Lavoie
Keyword(s):  
Ascorbic Acid ◽  
Lipid Metabolism ◽  
Guinea Pig ◽  
Dehydroascorbic Acid ◽  
Biologically Active ◽  
Urinary Concentration ◽  
Acetyl Coa Carboxylase ◽  
High Concentration ◽  
Acetyl Coa ◽  
Carboxylase Activity

Abstract Background: Parenteral multivitamin preparation (MVP) induces fatty liver in neonatal guinea pig pups; this is prevented by photoprotection. Photo-excited riboflavin present in MVP generates H2O2 and molecules with masses of 136 and 208. We hypothesized that H2O2 initiates the peroxidation of ascorbic acid (AA), producing biologically active byproducts affecting hepatic lipid metabolism. Methods: Mass spectrometry (MS) documented the participation of H2O2 and photo-excited riboflavin (Ribo) in the formation of AA byproducts. Sixteen 3-day-old guinea pig pups received an intravenous solution (50 g/L dextrose + 4.5 g/L NaCl + 1 kIU/L heparin) at 240 mL · kg−1 · day−1, enriched with control or test mixtures, for 4 days. The control mixture was photo-protected AA + Ribo (without byproducts or H2O2), and the test mixture was AA + Ribo treated to generate AA byproducts without H2O2. Hepatic acetyl-CoA carboxylase (ACC) activity was determined after 4 days. Fourth-day urine samples were analyzed by MS. Data were treated by ANOVA (α = 0.05). Results: H2O2 did not influence the classic degradation of AA, as the generation of 2,3-diketogulonic acid was not affected. In contrast, the formation of molecules with masses of 136 and 208 was H2O2 and time dependent. ACC activity was higher (P <0.01) in animals receiving high concentration of these molecules; its hepatic activation correlated (P <0.01) with the urinary concentration of molecule-208. Conclusions: H2O2 at concentrations found in the clinical setting of total parenteral nutrition induce the transformation of dehydroascorbic acid into compounds that have the potential to affect lipid metabolism. These molecules have peroxide and aldehyde functions.

scholarly journals The Role of Mesenchymal Stem Cells in Regulating PDGF and VEGF during Pancreatic Islet Cells Regeneration in Diabetic Animal Model

Folia Medica ◽  
2021 ◽  
Vol 63 (6) ◽  
pp. 875-883
Author(s):  
Agung Putra ◽  
Zakariya Hadi Suwiryo ◽  
Adi Muradi Muhar ◽  
Agus Widyatmoko ◽  
Fifin Luthfia Rahmi
Keyword(s):  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
Blood Glucose ◽  
Pancreatic Islet ◽  
Islet Cells ◽  
Pancreatic Tissue ◽  
Enzyme Linked Immunosorbent Assay ◽  
Control Group ◽  
Prolonged Release ◽  
Pancreatic Islet Cells

Introduction: Diabetes is a heterogeneous group of metabolic diseases characterized by elevated blood glucose due to autoimmune disorder or a combination of insulin resistance and insulin deficiency. VEGF and PDGF are the main actors in the regeneration of damaged pancreatic tissue. However, the prolonged release of these molecules may induce fibrosis formation. Mesenchymal stem cells (MSCs) have a high potential to regenerate damaged pancreatic tissue by releasing PDGF and VEGF. Aim: This study aimed to investigate the effect of MSCs on the levels of PDGF and VEGF on days 2 and 44 in diabetic mice and determine the number of pancreatic islet cells and blood glucose levels. Materials and methods: This study used a post-control group design with animals divided into five groups: sham, control, and three treatment groups (P) which were given MSCs at doses of 1.5×105, 3×105, and 6×105 cells. The levels of PDGF, VEGF, and blood glucose were measured by enzyme-linked immunosorbent assay (ELISA), while the number of pancreatic islet cells was analyzed using H&E staining. Results: This study showed a significant increase of VEGF and PDGF levels on day 2 and a significant increase in islet cell percentages on day 44 in line with the decreased blood glucose level. However, there was no difference between VEGF and PDGF levels on day 44. Conclusions: MSCs regulate PDGF and VEGF levels in wound healing phases and remodel pancreatic islet β-cells regeneration to control blood glucose in diabetic model mice.

Monolayer cultures of pancreatic islet cells from adult rats: effect of 2-deoxyglucose

1988 ◽  
Vol 118 (2) ◽  
pp. 173-NP ◽  
Author(s):  
M. Aoki ◽  
S. Kagawa ◽  
T. Yamamura ◽  
A. Matsuoka ◽  
J. Utsunomiya
Keyword(s):  
Insulin Secretion ◽  
B Cells ◽  
Pancreatic Islet ◽  
Cell Function ◽  
Islet Cells ◽  
Pancreatic Tissue ◽  
Pancreatic Islet Cells ◽  
Adult Rats ◽  
Monolayer Cultures

ABSTRACT Techniques for the monolayer culture of pancreatic islet cells from adult rats and the responsiveness of B cells are described. Whole pancreatic tissue was enzymatically dispersed and then cultured for 30 days in tissue culture medium 199 containing 5·5 mmol glucose/l, with or without 1 mmol 2-deoxyglucose/l. In the absence of 2-deoxyglucose, the responsiveness of B cells diminished to almost zero by day 15 and islets degenerated. In contrast, addition of 2-deoxyglucose to the medium resulted in a selective degeneration of fibroblasts, yielding monolayers that consisted mostly of islet cells. In this stationary system in which monolayers of islet cells were maintained in medium with 2-deoxyglucose, insulin secretion from B cells on days 15 and 30 increased in a dose-dependent fashion in response to increasing concentrations of glucose, leucine and 2-ketoisocaproate. Similarly, when exposed to 16·7 mmol glucose/l, perifused B cells showed a biphasic pattern of insulin secretion on day 15. Addition of 10 μmol forskolin/l and 200 nmol 12-O-tetradecanoyl phorbol13-acetate/l remarkably enhanced this response. Likewise, the response to 10 mmol leucine/l or 10 mmol 2-ketoisocaproate/l was biphasic. These results suggest that these monolayer cultures retain the functional properties of the adult rat pancreas, and may be useful not only as a model for the in-vitro study of B cell function, but also for implantation. J. Endocr. (1988) 118, 173–178

scholarly journals Menin Immunoreactivity in Secretory Granules of Human Pancreatic Islet Cells

2014 ◽  
Vol 22 (10) ◽  
pp. 748-755 ◽  
Author(s):  
Larisa V. Debelenko ◽  
Sunita Agarwal ◽  
Qiang Du ◽  
Wusheng Yan ◽  
Heidi S. Erickson ◽  
...  
Keyword(s):  
Pancreatic Islet ◽  
Islet Cells ◽  
Secretory Granules ◽  
Pancreatic Islet Cells ◽  
Human Pancreatic Islet

Monolayer cultures of adult pancreatic islet cells on osmotically disrupted fibroblasts

Diabetes ◽  
1980 ◽  
Vol 29 (6) ◽  
pp. 497-500 ◽  
Author(s):  
P. Meda ◽  
E. L. Hooghe-Peters ◽  
L. Orci
Keyword(s):  
Pancreatic Islet ◽  
Islet Cells ◽  
Pancreatic Islet Cells ◽  
Monolayer Cultures

Use of liposomes to introduce substances into pancreatic islet cells

Diabetes ◽  
1988 ◽  
Vol 37 (8) ◽  
pp. 1123-1128
Author(s):  
N. Welsh ◽  
A. Hallberg ◽  
S. Sandler ◽  
C. Hellerstrom
Keyword(s):  
Pancreatic Islet ◽  
Islet Cells ◽  
Pancreatic Islet Cells

Superfusion of dissociated pancreatic islet cells attached to Cytodex beads

Diabetes ◽  
1982 ◽  
Vol 31 (3) ◽  
pp. 189-193 ◽  
Author(s):  
Y. Spiess ◽  
M. A. Smith ◽  
W. Vale
Keyword(s):  
Pancreatic Islet ◽  
Islet Cells ◽  
Pancreatic Islet Cells
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