scholarly journals Die ultrastrukturele, morfometriese evaluering van die mikrotubulere stelsel in gestimuleerde B-selle van die pankreas

1992 ◽  
Vol 11 (4) ◽  
pp. 127-135
Author(s):  
A. Crous ◽  
A. M. De Beer ◽  
E. J. Visser
Keyword(s):  
B Cells ◽  
Insulin Release ◽  
Insulin Response ◽  
High Magnification ◽  
Tissue Samples ◽  
Islet Tissue ◽  
Pancreatic B Cells ◽  
Complete Cell

The intracellular distribution of microtubules in pancreatic B-cells was studied morphometrically to elucidate the positive correlation between microtubular content and the rate of insulin release found by biochemical investigations. Rat islet tissue was glucose stimulated under in vivo and in vitro (isolated islets) conditions and tissue samples taken to represent both phases of the phasic insulin response. Electron micrographs (x40 000) of individual B-cells were assembled into montages to obtain complete cell profiles at high magnification.

scholarly journals Islet constitutive nitric oxide synthase and glucose regulation of insulin release in mice

1999 ◽  
Vol 163 (1) ◽  
pp. 39-48 ◽  
Author(s):  
B Akesson ◽  
R Henningsson ◽  
A Salehi ◽  
I Lundquist
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Insulin Release ◽  
Ex Vivo ◽  
Insulin Response ◽  
Glucose Regulation ◽  
Nos Inhibitor ◽  
Oxide Synthase

We have studied, by a combined in vitro and in vivo approach, the relation between the inhibitory action of N(G)-nitro-l-arginine methyl ester (L-NAME), a selective inhibitor of nitric oxide synthase (NOS), on the activity of islet constitutive NOS (cNOS) and glucose regulation of islet hormone release in mice. The cNOS activity in islets incubated in vitro at 20 mM glucose was not appreciably affected by 0.05 or 0.5 mM L-NAME, but was greatly suppressed (-60%) by 5 mM L-NAME. Similarly, glucose-stimulated insulin release was unaffected by the lower concentrations of L-NAME but greatly enhanced in the presence of 5 mM of the NOS inhibitor. In incubated islets inhibition of cNOS activity resulted in a modestly enhanced insulin release in the absence of glucose, did not display any effect at physiological or subphysiological glucose concentrations, but resulted in a markedly potentiated insulin release at hyperglycaemic glucose concentrations. In the absence of glucose, glucagon secretion was suppressed by L-NAME. The dynamics of glucose-induced insulin release and (45)Ca(2+) efflux from perifused islets revealed that L-NAME caused an immediate potentiation of insulin release, and a slight increase in (45)Ca(2+) efflux. In islets depolarized with 30 mM K(+) in the presence of the K(+)(ATP) channel opener, diazoxide, L-NAME still greatly potentiated glucose-induced insulin release. Finally, an i.v. injection of glucose to mice pretreated with L-NAME was followed by a markedly potentiated insulin response, and an improved glucose tolerance. In accordance, islets isolated directly ex vivo after L-NAME injection displayed a markedly reduced cNOS activity. In conclusion, we have shown here, for the first time, that biochemically verified suppression of islet cNOS activity, induced by the NOS inhibitor L-NAME, is accompanied by a marked potentiation of glucose-stimulated insulin release both in vitro and in vivo. The major action of NO to inhibit glucose-induced insulin release is probably not primarily linked to changes in Ca(2+) fluxes and is exerted mainly independently of membrane depolarization events.

scholarly journals Increase of gap junctions between pancreatic B-cells during stimulation of insulin secretion.

1979 ◽  
Vol 82 (2) ◽  
pp. 441-448 ◽  
Author(s):  
P Meda ◽  
A Perrelet ◽  
L Orci
Keyword(s):  
Insulin Secretion ◽  
B Cells ◽  
Gap Junctions ◽  
Freeze Fracture ◽  
Secretory Activity ◽  
Isolated Rat Islets ◽  
Pancreatic B Cells ◽  
Stimulation Of

The development of gap junctions between pancreatic B-cells was quantitatively assessed in freeze-fracture replicas of isolated rat islets under different conditions of insulin secretion. The results show that in resting B-cells, gap junctions are small and scarce but that these junctions increase when insulin secretion is stimulated. Both a short (90 min) stimulation by glucose in vitro and a prolonged (2.5 d) stimulation by glibenclamide in vivo raise the number of gap junctions; in addition, the glibenclamide stimulation causes an increase in the size of individual gap junctions. As a consequence, the total area occupied by gap junctions on the B-cell membrane and the ratio of this area to the cell volume were found significantly increased in the latter condition. The slight increase of these values observed after the glucose stimulation did not reach significance. These data indicate a change of gap junctions during the secretory activity of the pancreatic B-cells. The possibility that the coupling of the cells is affected by the treatment is discussed.

Glucagon-like peptide-1(7-36)-amide confers glucose sensitivity to previously glucose-incompetent beta-cells in diabetic rats: in vivo and in vitro studies

1997 ◽  
Vol 155 (2) ◽  
pp. 369-376 ◽  
Author(s):  
N Dachicourt ◽  
P Serradas ◽  
D Bailbe ◽  
M Kergoat ◽  
L Doare ◽  
...  
Keyword(s):  
Glucose Tolerance ◽  
Beta Cells ◽  
Insulin Release ◽  
Insulin Response ◽  
Diabetic Rats ◽  
Insulin Response To Glucose ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

The effects of glucagon-like peptide-1(7-36)-amide (GLP-1) on cAMP content and insulin release were studied in islets isolated from diabetic rats (n0-STZ model) which exhibited impaired glucose-induced insulin release. We first examined the possibility of re-activating the insulin response to glucose in the beta-cells of the diabetic rats using GLP-1 in vitro. In static incubation experiments, GLP-1 amplified cAMP accumulation (by 170%) and glucose-induced insulin release (by 140%) in the diabetic islets to the same extent as in control islets. Using a perifusion procedure, GLP-1 amplified the insulin response to 16.7 mM glucose by diabetic islets and generated a clear biphasic pattern of insulin release. The incremental insulin response to glucose in the presence of GLP-1, although lower than corresponding control values (1.56 +/- 0.37 and 4.53 +/- 0.60 pg/min per ng islet DNA in diabetic and control islets respectively), became similar to that of control islets exposed to 16.7 mM glucose alone (1.09 +/- 0.15 pg/min per ng islet DNA). Since in vitro GLP-1 was found to exert positive effects on the glucose competence of the residual beta-cells in the n0-STZ model. we investigated the therapeutic effect of in vivo GLP-1 administration on glucose tolerance and glucose-induced insulin release by n0-STZ rats. An infusion of GLP-1 (10 ng/min per kg; i.v.) in n0-STZ rats enhanced significantly (P < 0.01) basal plasma insulin levels, and, when combined with an i.v. glucose tolerance and insulin secretion test, it was found to improve (P < 0.05) glucose tolerance and the insulinogenic index, as compared with the respective values of these parameters before GLP-1 treatment.

Insulin Secretion and Glucose Tolerance after Islet Transplantation in Rats with Noninsulin-Dependent Diabetes Induced by Neonatal Streptozotocin

1997 ◽  
Vol 6 (1) ◽  
pp. 23-32 ◽  
Author(s):  
Maria-Angeles Tormo ◽  
Trinidad Leon-Quinto ◽  
Catherine Saulnier ◽  
Danielle Bailbe ◽  
Patricia Serradas ◽  
...  
Keyword(s):  
Glucose Tolerance ◽  
Insulin Release ◽  
Insulin Response ◽  
Tolerance Test ◽  
Oral Glucose ◽  
Β Cells ◽  
Basal Plasma

The present study was designed to identify in a model of noninsulin-dependent diabetes induced by neonatal streptozotocin (n0-STZ), the long-term consequences of an islet graft upon 1) glucose handling of the recipient and, 2) glucose response of the residual β cells in the recipient pancreas. We have examined, 4 and 8 wk after islet implantation under the kidney capsule of syngeneic diabetic n0-STZ rats, their tolerance to glucose administered in vivo, together with their insulin release in response to glucose in vivo (oral glucose tolerance test) as well as in vitro (perfused pancreas). The results in the islet-grafted n0-STZ rats, were compared to those obtained in nongrafted nondiabetic rats and nongrafted n0-STZ rats. Our study shows that transplanting a limited number (900) of adult islets under the kidney capsule reverses to normal, many parameters of the noninsulin-dependent diabetic state in the n0-STZ rat model: these include body weight, basal plasma glucose in both the nonfasted and postabsorptive states, and basal plasma insulin in the postabsorptive state. Furthermore, tolerance to oral glucose administration was greatly improved in the transplanted rats and it was correlated with restoration of a manifest glucose-induced insulin secretion in vivo as evaluated (ΔI) during an oral glucose tolerance test. Our data clearly show that the insulin response to glucose from the endogenous pancreas of n0-STZ diabetic rat was not really improved by long-term (8 wk) basal normoglycemia. More precisely, we were able to detect a slight but significant improvement of the early phase of insulin release in vitro in response to glucose; however, the overall insulin response remained 15 times lower than the normal one with no reapparance of the late phase of insulin release. After cessation of glucose stimulation in vivo, off-response of insulin, which is also a landmark of the impaired insulin release by the β cells of n0-STZ rats, was still detectable in the perfused pancreas of the transplanted n0-STZ rats. Finally, because the reactivity to glucose of the endogenous residual β cells was not regained, the insulin released in vivo during the oral glucose test in the graft-bearing n0-STZ rats can be attributed mainly to functioning of the grafted islets population. Copyright © 1997 Elsevier Science Inc.

Effect of 1,25 dihydroxyvitamin D3 on isolated islets from vitamin D3-deprived rats

1990 ◽  
Vol 258 (4) ◽  
pp. E643-E648 ◽  
Author(s):  
B. J. Billaudel ◽  
A. G. Faure ◽  
B. C. Sutter
Keyword(s):  
Insulin Release ◽  
Vitamin D3 ◽  
Insulin Response ◽  
Dihydroxyvitamin D3 ◽  
1,25 Dihydroxyvitamin D3 ◽  
Dose Dependent ◽  
Vitamin D3 Deficiency ◽  
Calcium Redistribution

Insulin release is impaired by vitamin D3 deficiency but can be restored by in vivo administration of 1,25 dihydroxyvitamin D3 [1,25(OH)2D3]. A direct influence of 1,25(OH)2D3 on the B-cell was studied in vitro with islets from 5-wk vitamin D3-deprived rats. This hormone (10(-12) to 10(-6) mol/l) added to the incubation medium had a stimulatory dose-dependent effect on insulin response to 8.3 mmol/l glucose 6 h later. Moreover, perifusion experiments performed after different times of incubation demonstrated that after 6 h 1,25(OH)2D3 increased in particular the first phase of insulin response to 16.7 mmol/l glucose. The 45Ca fluxes, followed in parallel, were never modified by 1,25(OH)2D3 in the absence of glucose but were enhanced during the glucose stimulus, whereas 86Rb fluxes were never affected by 1,25(OH)2D3. These results demonstrated that 1,25(OH)2D3 acts in vitro on B-cells, but with a 6-h delay to potentiate the glucose-induced insulin release, concomitant with intracellular calcium redistribution.

Persistent impairment of the insulin response to glucose both in vivo and in vitro after streptozotocin exposure: Studies with grafted pancreatic islets and islets maintained in culture

1989 ◽  
Vol 121 (6) ◽  
pp. 849-856 ◽  
Author(s):  
Décio L. Eizirik ◽  
Stellan Sandler ◽  
Olle Korsgren ◽  
Leif Jansson ◽  
Arne Andersson
Keyword(s):  
Pancreatic Islets ◽  
Insulin Release ◽  
Common Property ◽  
Insulin Response ◽  
Insulin Content ◽  
Functional Responses ◽  
Mouse Pancreatic Islets ◽  
Insulin Response To Glucose

Abstract. The functional responses of the pancreatic B-cells after cytotoxic damage are still largely unknown. Using in vitro models to clarify this issue, we have recently observed a preferential reduction of glucose-stimulated insulin production and release in mouse pancreatic islets maintained in culture after in vitro exposure to streptozotocin. In order to evaluate the relevance of these findings in vivo, two sets of experiments were performed. First, mouse pancreatic islets were exposed in vitro to 2.2 mmol/l streptozotocin or vehicle alone, cultured for 6 days, and finally grafted under the kidney capsule of normoglycemic nude mice. Two weeks after transplantation there was no difference in the total DNA and insulin content between the two groups of islet grafts, but the insulin concentration, as expressed per μg DNA, was decreased by 40% in the streptozotocin-treated islets. The insulin release of the grafts, during perfusion of the graft-bearing kidney in situ with 16.7 mmol/l glucose was diminished in the streptozotocin group, whilst perfusion with 16.7 mmol/l glucose plus 5 mmol/l theophylline was able partially to counteract the reduction in insulin release. In the second set of experiments, NMRI mice were injected iv with 160 mg/kg streptozotocin or vehicle alone, and their islets isolated 15 min after the injections. After 6 days in culture, there was no decrease in DNA, glucagon and somatostatin contents, but the insulin content was decreased by 40% in the streptozotocin exposed islets. These islets also showed a 60% decrease in the insulin response to glucose, which was partly counteracted by incubation with 16.7 mmol/1 glucose plus 5 mmol/l theophylline. These observations suggest that a defective response to glucose, in conjunction with a better response to non-nutrient secretagogues, may be a common property of pancreatic islets following toxin-induced disturbances.

Ginkgolic acid induces apoptosis and autophagy of endometrial carcinoma cells via inhibiting PI3K/Akt/mTOR pathway in vivo and in vitro

2021 ◽  
pp. 096032712110237
Author(s):  
L Zhou ◽  
S Li ◽  
J Sun
Keyword(s):  
Endometrial Cancer ◽  
B Cells ◽  
Western Blot ◽  
Signal Pathway ◽  
Mtor Pathway ◽  
Related Protein ◽  
Western Blot Assay ◽  
Ginkgolic Acid

Endometrial cancer (EC) is the fourth most common malignancy in women in developed countries. The prognosis of EC is extremely poor, and it is an important factor that contributes to the death of patients. Therefore, studying EC pathogenesis and therapeutic targets, and exploring effective drugs are the primary tasks to improve the prognosis of EC. In the present study, we aimed to explore the function of ginkgolic acid (GA) in EC cell apoptosis and autophagy through PI3K/Akt/mTOR signal pathway in vitro and in vivo. Firstly, MTT assay and clone formation assay were employed to analyze the Ishikawa and HEC-1-B cell viabilities and proliferation after treatment with GA. The results showed that GA inhibited endometrial cancer cell survival. Flow cytometry assay and western blot assay were applied to examine the apoptosis and apoptosis related protein Bcl-2, Bax, Cleaved caspase-3 expression levels of Ishikawa and HEC-1-B cells after treatment with GA. Next, we applied western blot assay to analyze the autophagy associated proteins LC3I, LC3II, p62 and Beclin-1 in GA treated Ishikawa and HEC-1-B cells. We found that GA promoted apoptosis and induced autophagy of endometrial cancer cells. Meanwhile, western blot assay was also used to determine the expression levels of the PI3K/Akt/mTOR signal pathway related protein and the results revealed that GA inhibited the activity of PI3K/Akt/mTOR pathway. Finally, we found that GA inhibited tumor growth in vivo through immunohistochemistry assay. In conclusion, GA induces apoptosis and autophagy of EC cells via inhibiting PI3K/Akt/mTOR pathway in vivo and vitro.

scholarly journals Novel Identified Circular Transcript of RCAN2, circ-RCAN2, Shows Deviated Expression Pattern in Pig Reperfused Infarcted Myocardium and Hypoxic Porcine Cardiac Progenitor Cells In Vitro

2021 ◽  
Vol 22 (3) ◽  
pp. 1390
Author(s):  
Julia Mester-Tonczar ◽  
Patrick Einzinger ◽  
Johannes Winkler ◽  
Nina Kastner ◽  
Andreas Spannbauer ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Progenitor Cells ◽  
Regulatory Networks ◽  
Circular Rnas ◽  
Cardiac Progenitor Cells ◽  
Tissue Samples ◽  
Healthy Myocardium ◽  
Acute Mi

Circular RNAs (circRNAs) are crucial in gene regulatory networks and disease development, yet circRNA expression in myocardial infarction (MI) is poorly understood. Here, we harvested myocardium samples from domestic pigs 3 days after closed-chest reperfused MI or sham surgery. Cardiac circRNAs were identified by RNA-sequencing of rRNA-depleted RNA from infarcted and healthy myocardium tissue samples. Bioinformatics analysis was performed using the CIRIfull and KNIFE algorithms, and circRNAs identified with both algorithms were subjected to differential expression (DE) analysis and validation by qPCR. Circ-RCAN2 and circ-C12orf29 expressions were significantly downregulated in infarcted tissue compared to healthy pig heart. Sanger sequencing was performed to identify the backsplice junctions of circular transcripts. Finally, we compared the expressions of circ-C12orf29 and circ-RCAN2 between porcine cardiac progenitor cells (pCPCs) that were incubated in a hypoxia chamber for different time periods versus normoxic pCPCs. Circ-C12orf29 did not show significant DE in vitro, whereas circ-RCAN2 exhibited significant ischemia-time-dependent upregulation in hypoxic pCPCs. Overall, our results revealed novel cardiac circRNAs with DE patterns in pCPCs, and in infarcted and healthy myocardium. Circ-RCAN2 exhibited differential regulation by myocardial infarction in vivo and by hypoxia in vitro. These results will improve our understanding of circRNA regulation during acute MI.

scholarly journals Splicing factor SRSF1 promotes breast cancer progression via oncogenic splice switching of PTPMT1

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Jun-Xian Du ◽  
Yi-Hong Luo ◽  
Si-Jia Zhang ◽  
Biao Wang ◽  
Cong Chen ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Progression ◽  
High Risk Group ◽  
Clinical Samples ◽  
Binding Motif ◽  
Ki 67 ◽  
Tissue Samples

Abstract Background Intensive evidence has highlighted the effect of aberrant alternative splicing (AS) events on cancer progression when triggered by dysregulation of the SR protein family. Nonetheless, the underlying mechanism in breast cancer (BRCA) remains elusive. Here we sought to explore the molecular function of SRSF1 and identify the key AS events regulated by SRSF1 in BRCA. Methods We conducted a comprehensive analysis of the expression and clinical correlation of SRSF1 in BRCA based on the TCGA dataset, Metabric database and clinical tissue samples. Functional analysis of SRSF1 in BRCA was conducted in vitro and in vivo. SRSF1-mediated AS events and their binding motifs were identified by RNA-seq, RNA immunoprecipitation-PCR (RIP-PCR) and in vivo crosslinking followed by immunoprecipitation (CLIP), which was further validated by the minigene reporter assay. PTPMT1 exon 3 (E3) AS was identified to partially mediate the oncogenic role of SRSF1 by the P-AKT/C-MYC axis. Finally, the expression and clinical significance of these AS events were validated in clinical samples and using the TCGA database. Results SRSF1 expression was consistently upregulated in BRCA samples, positively associated with tumor grade and the Ki-67 index, and correlated with poor prognosis in a hormone receptor-positive (HR+) cohort, which facilitated proliferation, cell migration and inhibited apoptosis in vitro and in vivo. We identified SRSF1-mediated AS events and discovered the SRSF1 binding motif in the regulation of splice switching of PTPMT1. Furthermore, PTPMT1 splice switching was regulated by SRSF1 by binding directly to its motif in E3 which partially mediated the oncogenic role of SRSF1 by the AKT/C-MYC axis. Additionally, PTPMT1 splice switching was validated in tissue samples of BRCA patients and using the TCGA database. The high-risk group, identified by AS of PTPMT1 and expression of SRSF1, possessed poorer prognosis in the stage I/II TCGA BRCA cohort. Conclusions SRSF1 exerts oncogenic roles in BRCA partially by regulating the AS of PTPMT1, which could be a therapeutic target candidate in BRCA and a prognostic factor in HR+ BRCA patient.

scholarly journals Circular RNA hsa_circ_0006401 promotes proliferation and metastasis in colorectal carcinoma

2021 ◽  
Vol 12 (5) ◽  
Author(s):  
Chenjing Zhang ◽  
Xiaolu Zhou ◽  
Xiaoge Geng ◽  
Yu Zhang ◽  
Jingya Wang ◽  
...  
Keyword(s):  
Splice Junction ◽  
Circular Rna ◽  
Host Gene ◽  
Cell Counting ◽  
Tissue Samples ◽  
Proliferation And Metastasis ◽  
And Migration ◽  
Proliferation And Migration

AbstractDysregulation of circular RNA (circRNA) expression is involved in the progression of cancer. Here, we aimed to study the potential function of hsa_circ_0006401 in colorectal cancer (CRC). CircRNA hsa_circ_0006401 expression levels in CRC and adjacent nontumor tissues were analyzed by real-time quantitative PCR (qRT-PCR) and circRNA in situ hybridization (RNA-ISH). Then, CRC cell proliferation was assessed by cell counting. Wound-healing and transwell assays were utilized to detect the effect of hsa_circ_0006401 on CRC migration. A circRNA-ORF construct was created, and a specific antibody against the splice junction of hsa_circ_0006401 was prepared. Finally, the proteins directly binding to hsa_circ_0006401 peptides were identified by immunoprecipitation combined with mass spectrometry. In our study, we found hsa_circ_0006401 was closely related to CRC metastasis and exhibited upregulated expression in metastatic CRC tissue samples. Proliferation and migration were inhibited in vitro when hsa_circ_0006401 expression was silenced. Downregulation of hsa_circ_0006401 expression decreased CRC proliferation and liver metastasis in vivo. A 198-aa peptide was encoded by sequences of the splice junction absent from col6a3. Hsa_circ_0006401 promoted CRC proliferation and migration by encoding the hsa_circ_0006401 peptide. Hsa_circ_0006401 peptides decreased the mRNA and protein level of the host gene col6a3 by promoting col6a3 mRNA stabilation. In conclusion, our study revealed that circRNAs generated from col6a3 that contain an open-reading frame (ORF) encode a novel 198-aa functional peptide and hsa_circ_0006401 peptides promote stability of the host gene col6a3 mRNA to promote CRC proliferation and metastasis.

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