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At least 19 recordsLinked to original sources
PubMed1977

[Presence of biogenic amines in the Langerhans' islets of the sand rat (Psammomys obesus) (author's transl)].

The islets of Langerhans of sand rats (Psammomys obesus) have been investigated ultrahistochemical in order to demonstrate biogenic amines. It could be found that amine containing vesicles with a diameter of 600 to 700 nm from the type of catecholamine granules exist in A-cells as well as in B-cells. Further, 2 very rare cell types not containing specific hormone granules could be found. These cells contain particles, in one case similar to catecholamine granules and in the other case representing serotonine-like granules according to their electron optical properties. It can be stated that the sand-rat belongs to the species containing amines in A- and B-cells. Moreover they contain 2 amines simultaneously. The importance of the amines for the regulation of the hormone secretion of the islets of Langerhans is discussed and the connections to the diabetes mellitus are refered to.

Animals↗
PubMed2003

Cytokine sensitivity of Langerhans' islets of diabetes-prone BB/OK rats under hypoglycemic conditions.

Islets of Langerhans isolated from diabetes-prone BB/OK rats were exposed to interleukin-1beta (IL-1beta) or to a combination of tumor necrosis factor-alpha (TNF-alpha) plus interferon-gamma (IFN-gamma) under hypoglycemia at glucose concentrations of 2.2 and 3.2 mmol/l or in the presence of stimulatory conditions at 6.0 and 11 mmol/l glucose. For estimating cytokine effects the islets were functionally assayed by measurement of glucose stimulated insulin secretion. Pancreatic islets exposed for 24 h to IL-1beta at a glucose concentration of 6.0 mmol/l exhibited a reduced insulin secretion following a 48h recovery period compared to islets which were cytokine treated at 2.2 or 3.2mmol/l glucose, respectively. Islets pre-exposed for 24h to TNF-alpha plus IFN-gamma at 2.2, 3.2 or 6.0 mmol/l glucose displayed no alterations of insulin secretion following a 48 h regeneration. A temporary (3 h) influence of IL-1beta under hyperglycemic conditions at 11 mmol/l glucose caused a reduction of the subsequent insulin secretion of Langerhans' islets prior incubated for 24 h at 6.0 mmol/l glucose without cytokines, but not of islets precultured at 2.2 mmol/l glucose. In contrast, a 3 h treatment with TNF-alpha plus IFN-gamma at 11 mmol/l glucose did not affect insulin secretion of islets prior held at 6.0 mmol/l glucose, whereas a transient exposure for 6h to IL-1beta as well as TNF-alpha plus IFN-gamma under similar conditions diminished insulin secretion of islets preincubated at 2.2 or 6.0 mmol/l glucose. In conclusion, hypoglycemia reduces the sensitivity of BB/OK rat islets to IL-1beta, whereas a slight elevation of glucose concentration to 6.0 mmol/l increases again their vulnerability. TNF-alpha plus IFN-gamma at concentrations capable to decrease insulin secretion of islets during hyperglycemia do not affect the insulin output in a range between 2.2 and 6.0 mmol/l glucose. During glucose stimulation at 11 mmol/l islets' insulin secretory machinery is protected from IL-1beta as well as TNF-alpha plus IFN-gamma for 3 h by a preceding 24 h hypoglycemia, but its vulnerability is restored within additional 3 h.

Animals↗
PubMed1990

[In vitro and in vivo studies of isolation, transplantation and function of Langerhans islets in the swine].

Limits and possibilities of the transplantation of islets of Langerhans in pigs were studied. 6 x 10(4) to 3 x 10(6) islets and insulin producing fragments per pancreas were obtained by intraductal collagenase digestion of the pancreatic gland following total pancreatectomy. Islets grafted into the spleen or liver rendered normoglycemia to the pancreatectomized animals as demonstrated by normal fasting blood sugars and normal intravenous glucose tolerance tests as compared to not operated animals permitting a survival time of up to one year. Apancreatic controls died of ketoacidosis and diabetic coma 10 to 12 days posttransplant. The number of isolated and transplanted islets correlated well to the normoglycemic state of the animal. Beyond that the in vitro challenge of the islets with glucose and resulting insulin secretion was a very important indicator for the functional status and integrity of the islets after transplantation. Thus the pig appears to be a suitable model for the preclinical studying of islet transplantation especially since immunologic, physiologic and anatomic features of the pig are similar to those in the human regarding pancreas and nutrition.

Animals↗
PubMed1991

Changes of A, B and D cells in Langerhans islets in pancreatic cancers of hamsters.

In order to clarify the effect of pancreatic hormones on the oncogenesis of pancreatic cancer, the kinetics of the B, A and D cells in the islets of Langerhans were studied in hamsters with pancreatic cancer induced by di-iso-propanol nitrosamine (DIPN). Tumors appeared histologically 8 weeks and duct adenocarcinomas became evident 12 weeks after the administration of DIPN. Although the area of the islets did not change in 8 to 16 weeks, the numbers of B cells was decreased 8 weeks after the administration of DIPN and of A and D cells was decreased at 16 weeks. The area occupied by B cells in proportion to the number of islet cells showed a significant decrease 8 weeks after the administration of DIPN. Since insulin has been reported to have a trophic effect on the exocrine pancreas, our findings suggest that pancreatic B cells start to decrease at the same time that pancreatic cancer begins to form. Thus, insulin appears to play an important role locally in the oncogenesis of pancreatic cancer in acinar cells.

Animals↗
PubMedDate not supplied

Quantitative electron-microscopic studies of langerhans islets in normoglycemic chinese hamsters of a diabetic strain.

On the basis of previous studies of the retina and the pituitary, normoglycemic Chinese hamsters from a diabetic strain were divided into two groups, depending on the thickness of their capillary basement membrane and on the number of somatotrophs. Both values were significantly lower in group I than in group II. Quantitative electron microscopy of the islets of Langerhans showed in group II a tendency to a volume increase for A-cells, to a decrease for D- and B-cells. Also the number of B-granules and the surface area of electron dense material deposited in B-cells appeared to be increased in group II. Hypotheses are offered to explain the islet changes in correlation to previous findings in the retina and pituitary.

Animals↗
PubMed1975

Synthesis of proinsulin and large glucagon immunoreactivity in isolated Langerhans islets from EMC-virus infected mice.

The protein synthesis in normal and in EMC-virus infected mouse islets of Langerhans was investigated. Mouse large glucagon immunoreactivity was determined by an immunoassay after chromatographic separation. It was characterized as a peptide of 16 000 MW with in intracellular half-life of 35-45 min. The proportional reduction of void volume proteins, large glucagon immunoreactivity and proinsulin synthesis after infection shows, that both alpha- and beta-cells are damaged by the virus. A reduction in the synthesis of the three protein fractions was already found 6 hrs after inoculation of the virus and remained nearly constant for 48 hrs. An almost complete breakdown of protein synthesis occurred 60 to 70 hrs after infection and was paralleled by the first light microscopic changes in the islets. The stimulation of proinsulin synthesis by glucose was preserved for 48 hrs after EMC-virus infection.

Animals↗
PubMed1983

[Pancreatic function after pancreatoduodenectomy--correlation between the volume ratio of parenchyma and the number of Langerhans' islets].

Correlation between the volume ratio of the pancreatic parenchyma and the volume of hydroxyproline in the pancreatic tissue was studied in 9 mongrel dogs with pancreatic-duct ligation. The volume ratio of the pancreatic parenchyma and the number of Langerhans' islets were determined in 11 normal pancreas. And the relationship between the volume ratio of the pancreatic parenchyma in the 37 resected pancreas by pancreatoduodenectomy (PD) and the functions in the remaining pancreas after PD, was examined. The following results were obtained: The method to determine the volume ratio of the pancreatic parenchyma by using a Roller-planimeter proved to be a simple and convenient to find out the extent of pancreatic fibrosis. The volume ratio of the pancreatic parenchyma in normal pancreas was almost uniform over the whole pancreas. The number of Langerhans' islets in the tail of normal pancreas was about 1.5 times as many as that at the resection line by the scheduled PD. The volume ratio of the pancreatic parenchyma and the number of Langerhans' islets after PD were about half that in normal pancreas. Positive correlation was noted between the volume ratio of the pancreatic parenchyma and the post-operative pancreatic juice secreted at the time of PD. In the cases which the volume ratio of the pancreatic parenchyma was over 80%, the pancreatic juice secretion was over 200 ml/day. In many of the cases which the volume ratio of the pancreatic parenchyma was over 70%, the exocrine function in the remaining pancreas was good even three to four years after PD. Correlation was observed between the number of Langerhans' islets at PD and the post-operative glucose tolerance. In the cases which the number of Langerhans' islets was large, more favorable insulin secretory function was observed in the remaining pancreas.

Adult↗
PubMed1975

Effect of quinaldic acid and its relatives on insulin-release from isolated Langerhans islets.

Influence of quinaldic acid on insulin release from isolated Langerhans islets of rats was studied. It was found that quinaldic acid by itself caused insulin release on the one hand and that it inhibited the second phase of glucose-induced insulin release on the other. A possible mechanism concerning the effect of quinaldic acid on beta-cells of Langerhans islets is presented.

Animals↗
PubMed1998

Offspring of streptozotocin diabetic rats: size changes in Langerhans islets with time after birth.

It has been demonstrated that, in the diabetic rat, pregnancy and lactation are severely altered: in this study, we have measured the size of Langerhans islets of rat pups, the offspring of experimental diabetic mothers and nondiabetic controls. Diabetes was induced through streptozotocin administration (dose, 60 mg/kg body wt.). This drug was injected in every animal; their blood sugar was measured 1 week later (Haemo-Glukotest, Boehringer Mannheim), and they were then separated into three groups according to their fasting blood sugar levels: (a) severe diabetics (above 16.5 mM/l); (b) mild diabetics (6.5-16.5 mM/l); and (c) nondiabetic normals. They received insulin therapy (2-4 I.U./day) as the mild diabetics exhibited a slightly higher than normal fasting blood sugar, and the diabetic ones, above 15 mM/l. The areas of Langerhans islets of pups were measured 1 and 5 days after parturition; pancreas sections were dyed (haematoxylin-eosin) and morphometry was then performed using a digitalized magnetic tabloid connected to a Zeiss Morphomat 30 (Kontron). On the first day after parturition, the pancreas section areas in pups from mildly and severely diabetic mothers were smaller than those in neonates from nondiabetic controls (P < 0.001). The areas in neonates from severely diabetic mothers showed a more intense decrease than those from mildly diabetic animals (P < 0.01). On day 5 after delivery, the areas of Langerhans islets in offspring from normal mothers decreased and those in pups from diabetic mothers tended to normalize (P < 0.01), particularly those from the severely sick group (P < 0.01). We conclude that after parturition the offspring is no longer exposed to the high blood sugar levels found in both diabetic groups of mothers, thereby no hyperinsulinemia is needed; as time elapses, then, the area of their Langerhans islets tends to normalization.

Aging↗
PubMed1981

Histological and histochemical investigations on the Langerhans' islets of the frog (Rana ridibunda).

The Langerhans' islets of the frog Rana ridibunda are built up of A, B, and D cells like other vertebrates. The phospholipids (Baker's test) are located in the capillary pole of the B-Cells, where also beta-granules are present. In the cells of the endocrine pancreas there is found also some quantity of glycogen, but the reaction for zink is negative. The quantity of RNA in the cytoplasme of the islet's cells is minimum.

Animals↗
PubMed1980

Prolactin binding in rat Langerhans islets.

Membrane preparations of collagenase-dispersed Langerhans islets of female Wistar rats exhibit specific binding sites for 125I-labelled ovine prolactin (125I-oPrl). Almost negligible binding was detected in islets of male animals. The binding is a saturable and time-temperature dependent process, equilibrium being reached after 16 h incubation at 0 degrees C. The bound oPrl is not displaceable by hFSH, hLH, bGH or hGH. In contrast with other cell fractions, the 12,000 g pellet accounts for more than 80% of the specific binding of 125I-oPrl. Scatchard plots of data obtained in saturation studies indicate a single class of binding sites with Ka = 0.21 x 10(10)M-1. Protein and phospholipid moieties are essential for the receptor activity, since after trypsin or phospholipase C digestions marked loss of binding was verified. In islets of streptozotocin diabetic rats a marked reduction in the number of binding sites was observed. These findings may suggest that some of the actions of prolactin on endocrine pancreas could be explained by its specific interaction with islet cell membranes.

Animals↗
PubMed1998

Constitutive nitric oxide synthase (cNOS) activity in Langerhans islets from streptozotocin diabetic rats.

Nitric oxide synthase activity was measured in Langerhans islets isolated from control and streptozotocin diabetic rats. The activity of the enzyme was linear up to 150 micrograms of protein from control rats and was optimal at 0.1 microM calcium, when it was measured after 45 min of incubation at 37 degrees C in the presence of 200 microM arginine. Specific activity of the enzyme was 25 x 10(-4) nmol [3H]citrulline 45 min-1 mg protein-1. Streptozotocin diabetic rats exhibited less enzyme activity both in total pancreas homogenate and in isolated Langerhans islets when compared to control animals. Nitric oxide synthase activity measured in control and diabetic rats 15 days after the last streptozotocin injection in the second group of animals corresponded only to a constitutive enzyme since it was not inhibited by aminoguanidine in any of the mentioned groups. Hyperglycemia in diabetic rats may be the consequence of impaired insulin release caused at least in part by reduced positive modulation mediated by constitutive nitric oxide synthase activity, which was dramatically reduced in islets severely damaged after streptozotocin treatment.

Analysis of Variance↗
PubMed1995

Quantitation of insulin stores in Langerhans islets by combined immunohistochemistry and computerized microspectrophotometric analysis.

Histology, size, and insulin content of Langerhans islets from normal and recent experimental hyperthyroid (REH) dogs were studied. Insulin localization in the islets was revealed by immunohistochemistry, and the remaining two variables were analyzed by computerized microspectrophotometry according to an original technique described here. Observed under the light microscope, the REH dog pancreas section shows larger than normal islets whose scarce beta-granules are mainly located near B-cell borders and grouped along capillaries. The brown areas occupied by insulin in Langerhans islets from REH and normal dogs (mean +/- SEM) are 5182 +/- 311 and 4236 +/- 287 microns2, the total mean insulin amount per respective islet section-as expressed in absorbance arbitrary units-is 1108 and 1846, and the light absorbances per such area units are 0.214 +/- 0.070 and 0.436 +/- 0.060, respectively. Measuring these variables in dog and human (large) pancreases by the conventional methods successfully used for small pancreases would have been technically impossible.

Animals↗
PubMed2006

Podocyte-associated proteins FAT, alpha-actinin-4 and filtrin are expressed in Langerhans islets of the pancreas.

Nephrin is a crucial podocyte molecule in the kidney glomerular filtration barrier and it is also expressed in Langerhans islet beta cells of the pancreas. Recently, genetic mapping of proteinuric kidney disease genes and animal models have revealed further important molecules for the kidney filtration function including alpha-actinin-4, podocin, FAT, and NEPH1. This study was addressed to explore the pancreatic expression of the podocyte molecules podocin, FAT, alpha-actinin-4, NEPH1, NEPH2, filtrin/NEPH3, synaptopodin and CD2 associated protein (CD2AP). The mRNA and protein expressions were studied by RT-PCR and immunoblotting, and localization in the pancreas was investigated by immunofluorescence. Of the nephrin-associated podocyte proteins, filtrin/NEPH3, FAT, and alpha-actinin-4 were found to be expressed in the pancreas at the gene and protein level and localized to Langerhans islets. Immunoreactivity with the podocin antibody was detected mostly in the exocrine pancreas. NEPH1 and synaptopodin expression was detected only at the mRNA level. Further studies are needed to unravel the functional role of these podocyte-associated molecules in the pancreatic Langerhans islets.

Actinin↗
PubMed1994

In vitro and in vivo evaluation of protamine-heparin membrane for microencapsulation of rat Langerhans islets.

Rat pancreatic islets were microencapsulated with multilayer protamine-heparin (PH) membrane. Basal and stimulatory insulin secretion of microencapsulated islets was similar to the controlled free islets in vitro. During the long-term culture (up to 2 weeks) mean insulin release of encapsulated islets did not significantly differ from the mean of free ones (the ratio of mentioned means was 54-167%). Empty PH microcapsules transplanted into Wistar rats intraperitoneally and under the kidney capsule were generally harmless up to 4 months. In only a few cases traces of fibrotic tissue around capsules entrapped in the omentum were found. No damage of microcapsules structure was observed. The worst results were obtained in the instance of retroperitoneal transplantation. We conclude, therefore, that PH membrane was proved to be highly biocompatible, nontoxic for islets, and did not impair viability and glucose-dependent insulin secretion of Langerhans islets in in vitro culture.

Animals↗
PubMed1992

Diffusion properties of an artificial membrane used for Langerhans islets encapsulation: an in vitro test.

Glucose and insulin permeability of an artificial membrane (AN69, HOSPAL, Sweden) used for Langerhans islets encapsulation were investigated. In vivo, a 1 and 7 d intraperitoneal implantation of the AN69 membrane in rats induced a loss of permeability towards glucose and insulin probably due to a protein-coating performed after implantation. In vitro, a protein-coating of the AN69 membrane with fetal calf serum solution reproduced similar results. Thus this in vitro test which mimicks in vivo conditions should be proposed to evaluate rapidly the physicochemical properties of a membrane suitable for pancreatic islets encapsulation.

Acrylic Resins↗
PubMed2001

[The blood drainage of Langerhans islets with special reference to the functional and clinical significance of pancreatic exocrine part].

OBJECTIVE: This study sought to gain an insight into the blood drainage of Langerhans islets with special reference to the functional and clinical significance of pancreatic exocrine part. METHODS: Observations were carried out in 11 human dead bodies, 40 monkeys, 24 dogs, 62 rats and 24 rabbits by scanning electron microscopy and light microscopy with the technique of retaining microcirculatory dynamic and tissular information in the static specimens, microvascular serial reconstruction, and/or by intravital fluorecence microscopy with FITC-labeled erythrocytes. RESULTS: Three patterns of islet drainage channels drained into different acinar regions with different features and insulo-insular drainage channels observed in the primates were found in this study. The authors suggest that these patterns might be termed as follows: 1. Continuous drainage vessels. All islets possessed these capillary-sized portal vessels which ran a short distance, and then drained into the peri-islet acinar region. 2. Convergent drainage vessels. Some islets possessed one or two, occasionally more, of these portal vessels, which were relatively long and/or thick and drained into the acinar region far away from the islet in the lobule. 3. Translobular drainage vessels. These portal vessels crossed the interlobular septum into an adjacent lobule where sometimes no islet existed, and then drained into the exocrine acinar region 4. Insulo-insular drainage vessels. Some islets in the monkey and human, possessed these vessels which drained into an adjacent small islet through the insulo-insular drainage vessels. CONCLUSION: Langerhans islets possessed the consummate drainage system which drained into different exocrine acinar regions, suggesting that the release of islet hormones is in some way necessary for the exocrine secreting function, and that the reduction of local insular hormone levels in insuloacinar portal circulation and the impairment of insular drainage vessels would be the morphological basis of the pancreatic exocrine pathologic lesion in human diabetes.

Adult↗
PubMed1986

The size and number of Langerhans islets correlated with their endocrine function: a morphometry on immunostained serial sections of adult human pancreases.

Surgical and autopsy specimens of normal pancreas from three human adults were submitted to morphometry of Langerhans islets and so-called extra insular islet cells, by measuring the islet radii on serial sections immunostained for either insulin or glucagon. All the islets contained in a test volume were measured including single cells, and the distribution of their radial sizes was studied. It was found that the distribution of islets was strongly skewed and continuous, with the majority of islets having radial values near to the minimum. From the fact that only one peak was found in the distribution curve, it is concluded that in spite of the distinction previously made between islets of Langerhans and so-called extra-islet cells, they are in fact both part of a continuous distribution. Moreover, the Weibull function, assumed as the theoretical distribution, fit well with the empirical histograms, giving support for the contention of continuous distribution with a single peak. Although the small islets account for a majority of the number of islets, they account for only a very small percentage of the islet volume. This is thought to indicate that the bulk of the endocrine functions of the pancreas are carried out by large islets, whereas the so-called extra-islet cells are likely to be their precursors. With regard to the cellular structure of the islets, it was found that the smaller the islet, the smaller the percentage of islets containing A cells, with the vast majority of cells in the smallest islets (often single cells) being B cells.

Adult↗