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  • 1996  (21)
  • Insulin
  • 1
    ISSN: 1420-9071
    Schlagwort(e): Insulin ; insulin-like growth factor ; Bombyx mori ; ovary ; neurosecretory peptide ; Oligotex reverse transcription-polymerase chain reaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Bombyxin is a 5 kDa insulin-related peptide produced in four pairs of medial neurosecretory cells in the brain of the silkmothBombyx mori. We demonstrate here the presence of bombyxin mRNA in tissues other than brain: ganglia, epidermis, testis, ovary, fat body, silk gland, Malpighian tubule, midgut, and hindgut of theBombyx fifth instar larvae. Bombyxin mRNA was detected by Oligotex reverse transcription-polymerase chain reaction (RT-PCR), a rapid and simple procedure of reverse transcription-PCR, and in situ hybridization. The Oligotex RT-PCR method effectively eliminated the contaminating DNA in RNA samples and amplified bombyxin mRNA efficiently. In situ hybridization of theBombyx ovary clearly demonstrated the localization of the bombyxin mRNA in the ovariole. The present study is the first demonstration of expression of brain neurosecretory peptide in tissues other than the central nervous system in insects at RNA level.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 428 (1996), S. 177-185 
    ISSN: 1432-2307
    Schlagwort(e): Diabetic Chinese hamster ; Pancreatic beta cell ; Immunocytochemistry ; Insulin ; GLUT2 glucose transporter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The diabetic Chinese hamster is a well-established animal model for NIDDM with a defective glucose-induced insulin secretory response. In the pancreas of nondiabetic hamsters, the GLUT2 glucose transporter was localized in the plasma membrane of insulin-positive beta cells. At variance with the rat, immunoreactivity was also detected in the cytoplasm. Other islet cell types were not GLUT2 positive. GLUT2 immunoreactivity was already significantly reduced in beta cells from mildly diabetic animals in spite of a normal insulin immunoreactivity. In severely diabetic animals the majority of the beta cells had lost GLUT2 immunostaining. This observation was confirmed in a Western blot analysis of the GLUT2 protein in isolated pancreatic islets. Only beta cells that were densely immunostained for insulin were still GLUT2 positive. However, around 40% of the beta cells devoid of GLUT2 immunoreactivity were still insulin immunoreactive. Thus, the loss of GLUT2 immunoreactivity, which is an important component of the glucose recognition apparatus of the pancreatic beta cell, is an early indicator of beta cell dysfunction before the development of degenerative lesions or the loss of insulin immunoreactivity. GLUT2 loss may be important in the deterioration of glucose-induced insulin secretion in the diabetic Chinese hamster.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1432-0568
    Schlagwort(e): Key words Gastro-entero-endocrine cells ; Enteric nerve fibers ; Insulin ; Glucagon ; Somatostatin ; Pancreatic polypeptide ; Neuropeptide Y ; Insulin-like growth factor I ; Pancreastatin ; Neurotensin ; Substance P ; Gastrin ; Cholecystokinin ; Vasoactive intetinal polypeptide ; Serotonin ; Development ; Scophthalmus maximus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  The ontogeny of endocrine cells and nerve fibers containing immunoreactivities for 12 regulatory peptides and serotonin was studied in the digestive tract of a flatfish, the turbot (Scophthalmus maximus), using antisera specific for mammalian and teleostean hormones. Transient insulin-immunoreactive (-IR) endocrine cells were detected from day 5 to day 10 in stomach and intestine I. Somatostatin (SOM)-IR cells appeared at day 8 in the stomach anlage and intestine I. In contrast to the islet cells, they reacted with antisera against mammalian (m) SOM-14 and salmon (s) SOM-25. Infrequent nerve fibers reacting only with anti-mSOM-14 appeared around day 24. Thus, different forms of SOM seem to be present in the gastro-entero-pancreatic system and the enteric nervous system. Neuropeptide Y (NPY)-, salmon pancreatic polypeptide (sPP)- and mPP-immunoreactivities coexisted thoughout development. In entero-endocrine cells, NPY/PP-immunoreactivity was first observed at day 8 and around day 24 in enteric nerve fibers. Glucagon (GLUC)-IR entero-endocrine cells appeared at day 5. No coexistence of NPY/PP- and GLUC-immunoreactivities was observed. The first insulin-like growth factor I (IGF-I)-IR cells were identified around day 8. They seemed to contain none of the other peptides. Their number and distribution exhibited great interindividual differences. Vasoactive intestinal polypeptide (VIP)-IR entero-endocrine cells appeared as late as around day 24. The first VIP-IR nerve fibers, however, were identified at day 5. Infrequent neurotensin (NT)-IR cells appeared along the intestine around day 10 and NT-IR nerve fibers at day 17. The first serotonin (SER)-IR cells were observed in the stomach anlage around day 10 and SER-IR nerve fibers at day 15 thoughout the gastro-intestinal tract. Gastrin (GAS)/cholecystokinin (CCK)-IR cells appeared around day 11 in stomach and intestine I. The first substance P (SP)-IR enteric nerve fibers were detected around day 8 and SP-IR endocrine cells at day 11. Pancreastatin (PST)-IR cells were identified in the stomach anlage and intestine I around day 8 and contained NT-, GAS/CCK- and SER-immunoreactivities in coexistence. Thus, several developmental phases can be distinguished: (1) at the onset of exogenous feeding only transient INS-IR cells and VIP-IR nerve fibers are present; (2) a differentiated entero-endocrine system establishes during the early phase of exogenous feeding; (3) before the final differentiation of stomach and gut GAS/CCK-IR cells appear; (4) after metamorphosis most of the different types of regulatory peptide-containing nerve fibers develop, probably setting up the fine regulation of gastro-intestinal blood flow and motility.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-0428
    Schlagwort(e): Insulin ; small GTPases ; GLUT4 ; translocation ; adipocytes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The small guanosine 5′-triphosphate (GTP)ase Rab4 has been suggested to play a role in insulin-induced GLUT4 translocation. Under insulin stimulation, GLUT4 translocates to the plasma membranes, while Rab4 leaves the GLUT4-containing vesicles and becomes cytosolic. Rab proteins cycle between a GTP-bound active form and a guanosine 5′-diphosphate (GDP)-bound inactive form. The intrinsic GTPase activity of Rab proteins is low and the interconversion between the two forms is dependent on accessory factors. In the present work, we searched for a GTPase activating protein (GAP) for Rab4 in 3T3-L1 adipocytes. We used a glutathione-S-transferase (GST)-Rab4 protein which possesses the properties of a small GTPase (ability to bind GDP and GTP and to hydrolyse GTP) and can be isolated in a rapid and efficient way. This GAP activity was observed in 3T3-L1 adipocyte lysates, and was able to accelerate the hydrolysis of the [α-32P]GTP bound to GST-Rab4 into [α-32P]GDP. This activity, tentatively called Rab4-GAP, was also present in 3T3-L1 fibroblasts. The Rab4-GAP activity was present in total membrane fractions and nearly undetectable in cytosol. Following subcellular fractionation, Rab4-GAP was found to be enriched in plasma membranes when compared to internal microsomes. Insulin treatment of the cells had no effect on the total Rab4-GAP activity or on its subcellular localization. Taking our results together with the accepted model of Rab cycling in intracellular traffic, we propose that Rab4-GAP activity plays a role in the cycling between the GTP- and GDP-bound forms of Rab4, and thus possibly in the traffic of GLUT4-containing vesicles.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1432-0428
    Schlagwort(e): Insulin ; insulin receptor substrate-1 ; phosphoinositide 3-kinase ; signal transduction ; phosphotyrosine ; enzyme activation ; conformational change ; Fao cells
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Phosphoinositide 3-kinase (PI3-kinase) plays a crucial role in insulin signal transduction. We studied the molecular mechanism of the insulin-induced activation of PI3-kinase in rat hepatoma Fao cells using an antibody against the 110-kDa catalytic subunit (p110) and two against the 85-kDa regulatory subunit (p85α). PI3-kinase activity increased 1.6-fold in anti-p85 immunoprecipitates after insulin stimulation, whereas it did not increase when cell lysates were first immunoprecipitated with anti-phosphotyrosine or anti-insulin receptor substrate-1 (IRS-1), then with anti-p85, suggesting that the PI3-kinase which associates with tyrosyl phosphoproteins including IRS-1 is responsible for the increase in kinase activity. The activated PI3-kinase molecules constituted 4–6% of the total PI3-kinase, and their specific activity was 11–14 times higher than that of the basal state. Anti-p110 recognized the catalytically active form of p110, and immunoprecipitated p110 only after exposure to insulin. Hence, the epitope of anti-p110, P200-C215, seems to be included in the portion of p110, the conformation of which is changed by insulin stimulation. We conclude that, in response to insulin stimulation, only a small fraction of p85 in the PI3-kinase pool associates with tyrosyl phosphoproteins including IRS-1, and that the specific activity of p110 is increased presumably through a conformational change including the P200-C215 region.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1423-0127
    Schlagwort(e): Endothelin-1 ; Insulin ; Protein Kinase FA/GSK-3α ; MAP kinase signaling pathway ; Rat adipocytes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract In this study, we investigate the effects of endothelin-1 (ET-1) and insulin on the cellular activity of protein kinase FA/glycogen synthase kinase-3α (kinase FA/GSK-3α) in rat adipocytes. The cellular activity of kinase FA/GSK-3α is inhibited to ∼ 50% of control within 30 min when cells are treated with 1 nM ET-1 at 37°C; in addition, significant inhibition to ∼ 60% of control is observed at as low as 1 pM ET-1. Conversely, ET-1 at concentrations up to 1 nM has no direct effect on purified kinase FA/GSK-3α in vitro. Immunoblotting analysis further reveals that the protein level of this kinase is not significantly changed when treated with 1 nM ET-1 for 30 min. Similar to ET-1, insulin as low as 10 nM can also induce inactivation of kinase FA/GSK-3α to ∼ 50% of control in adipocytes when processed under identical conditions. Most importantly, when treated with both insulin and ET-1, the activity of kinase FA/GSK-3α can be decreased only to ∼ 50% of control. Taken together, the results provide initial evidence that ET-1 and insulin may regulate this important multisubstrate/multifunctional protein kinase in a common signaling pathway in cells.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-0428
    Schlagwort(e): Insulin ; mediator ; d-chiro-inositol ; euglycaemia ; manganese
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We compared the effects of infusing a chemically defined chiro-inositol glycan putative insulin mediator with an equivalent dose of insulin in low-dose (45 mg/kg) streptozotocin diabetic rats. Insulin decreased plasma glucose levels from 17.32±0.17 to 3.96±0.064 mmol/l (p〈0.0002) in 120 min, a decrease of 77.13%, while the putative mediator promoted a decrease in plasma glucose from 14.85±0.084 to 7.22±0.13 mmol/l (p〈0.007) in 60 min. The putative mediator maintained euglycaemia over the ensuing 60 min with a plasma glucose level of 7.01±0.10 mmol/l at 120 min. Thus, insulin further reduced the plasma glucose from euglycaemia at 60 min to produce hypoglycaemia at 120 min. The lack of production of hypoglycaemia by the putative mediator can be explained by its inhibition of glucose-stimulated insulin secretion by the islet beta cells, thus providing a potential negative feedback regulatory mechanism; or by its selective action on muscle to increase glycogen synthesis. The significance of these results in terms of future directions in drug design is herein considered.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 52 (1996), S. 421-425 
    ISSN: 1420-9071
    Schlagwort(e): Insulin ; fatty acids ; insulin-like growth factors ; Cori cycle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Insulin can influence rates of glucose utilization by muscle and possibly other tissues via both direct and indirect effects. It can control the rate of fatty acid mobilization from adipose tissue and the rate of fatty acid oxidation in muscle, and the latter inhibits glucose utilization and oxidation. Insulin may influence the levels of insulin-like growth factors I and II, both of which have effects on rates of glucose utilization by muscle. The intertissue cycle between glucose and lactate — the Cori cycle, which is influenced by insulin — may provide another novel mechanism for control of blood glucose. How far other anti-insulin hormones affect these processes is not clear.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1432-041X
    Schlagwort(e): Key words Hydra ; Insulin ; Development ; Receptor ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  A gene encoding a receptor protein-tyrosine kinase closely related to the vertebrate insulin receptor has been identified in the Cnidarian Hydra vulgaris. The gene is expressed in both epithelial layers of the adult polyp. A particularly high level of expression is seen in the ectoderm of the proximal portions of the tentacles and in a ring of ectodermal cells at the border between the foot basal disk and body column. The expression pattern of the gene in asexual buds is dynamic; expression is high throughout the newly emerging bud but the area of high expression becomes restricted to the apex as the bud lengthens. When the bud begins hypostome and tentacle formation, a high level of expression appears at the bases of the emerging tentacles. Finally, a ring of high expression appears just above the foot of the bud, completing the pattern seen in the adult polyp. The presence of this receptor and its pattern of expression suggested that an endogenous molecule related to insulin plays a role in regulating cell division in the body column and in differentiation of the tentacle and foot cells in Hydra, with the switch between the two being determined by the level of the receptor. Treatment of Hydra polyps with mammalian insulin caused an increase in the number of ectodermal and endodermal cells undergoing DNA synthesis.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 52 (1996), S. 769-773 
    ISSN: 1420-9071
    Schlagwort(e): Insulin ; imprinting ; Tetrahymena ; phagocytosis ; insulin receptor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Receptor-mediated endocytosis byTetrahvmena pyriformis was studied using tetramethylrhodamine isothiocyanate-labeled concanavalin A (TRITC-Con A) with fluorescence and confocal microscopy. In the presence of insulin, or 24 h after insulin pretreatment (hormonal imprinting), the binding and uptake of TRITC-Con A increased when compared to controls, owing to the binding of TRITC-Con A to sugar oligomers of insulin recptors. Mannose inhibited the binding of Con A, thus demonstrating the specificity of binding. Histamine, a phagocytosis-promoting factor in mammals andTetrahymena, and galactose, did not influence the uptake of TRITC-Con A.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 52 (1996), S. 426-432 
    ISSN: 1420-9071
    Schlagwort(e): Insulin ; proinsulin ; insulin resistance ; metabolic syndrome ; triglycerides ; free fatty acids ; fat intake ; galanin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract For better comprehension of the metabolic syndrome, it is necessary to differentiate the effect of insulin on glucose metabolism on the one hand, and on other metabolic activities on the other hand. Whereas glucose utilization is affected by insulin resistance, the effect of insulin on lipid metabolism, ion and aminoacid transport does not seem to be diminished. Lipid metabolism, however, seems to play a crucial role in the induction of the vicious cycle. Increased energy and fat ingestion may be due to an increased number of galanin secreting cells in the hypothalamus. The excessive fat intake results in an increased rate of release of insulin and increased influx of triglycerides into the blood. From these triglycerides an excess of free fatty acids is released by the action of lipoprotein lipase. The increased plasma free fatty acid level then results in insulin resistance affecting glucose metabolism. Also, these free fatty acids may impair the secretion of insulin. Induction of insulin resistance results in higher glucose levels, which may cause hyperinsulinemia. Hyperinsulinemia maintains the elevation of triglycerides. When diabetes becomes overt and elevated glucose levels prevail, the hyperinsulinism acts on the metabolic pathways which are still sensitive to insulin, namely lipid metabolism, aminoacid transport and ion transport.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 59 (1996), S. 492-495 
    ISSN: 1432-0827
    Schlagwort(e): Insulin ; Osteoblasts ; In vivo ; Calvariae ; Histomorphometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract Recent clinical studies have established that bone density is related to both fat mass and circulating insulin levels. A direct action of insulin on the osteoblast may contribute to these relationships. Osteoblast-like cells have insulin receptors, and insulin has been shown to stimulate proliferation of these cells in vitro. However, it has not been possible to study the effects of insulin administration on bone in vivo because of the metabolic effects of insulin, particularly hypoglycemia. A model involving the local injection of insulin over one hemicalvaria of an adult mouse overcomes these difficulties and permits the histomorphometric study of insulin's action on bone. Insulin or vehicle was injected daily for 5 days over the right hemicalvariae of adult mice, and the animals were sacrificed 1 week later. All indices of bone formation were significantly increased in imsulin-treated hemicalvariae compared with the noninjected hemicalvariae. There was a 2.73±0.50-fold increase in osteoid area (P=0.0005), a 2.20±0.37-fold increase in osteoblast surface (P=0.021) and a 2.04±0.29-fold increase in osteoblast number (P=0.021). Indices of bone resorption tended to decline and mineralized bone area tended to increase in insulin-treated animals. The direct action of insulin on bone may contribute to the increased bone density seen in obesity and to the osteopenia of type I diabets, conditions associated with insulin excess and deficiency, respectively.
    Materialart: Digitale Medien
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  • 13
    ISSN: 1432-2013
    Schlagwort(e): Propionyl-l-carnitine ; Insulin ; Streptozotocin-induced diabetic rat ; Motor nerve ; conduction velocity ; Sciatic nerve blood flow ; Electroretinogram ; Sorbitol ; myo-Inositol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effect of an analogue ofl-carnitine, propionyl-l-carnitine, on the electroretinogram, motor nerve conduction velocity and nerve blood flow was determined in rats with streptozotocin-induced diabetes, and was compared with the effects of insulin alone or combined therapy. Oral administration of propionyl-l-carnitine (3 g/kg daily for 4 weeks) significantly increased caudal nerve motor conduction velocity and sciatic nerve blood flow in diabetic rats. There were no differences in the effects of insulin (8–10 U daily for 4 weeks), propionyl-l-carnitine and combined therapy. Although propionyl-l-carnitine significantly shortened the peak latency of the electroretinogram b-wave in diabetic rats, its effect was far weaker than that of insulin or combined therapy, with combined therapy producing the greatest improvement. These effects of propionyl-l-carnitine were accompanied by a decrease of serum lipid levels, an increase of the sciatic nerve carnitine content, and no changes of the tissue (nerve and retinal) sorbitol andmyo-inositol concentrations. In contrast, insulin significantly reduced the tissue sorbitol content and markedly increasedmyo-inositol. These findings suggest that propionyl-l-carnitine may improve diabetic neuropathy and retinopathy without influencing the polyol pathway, and that this beneficial effect may be mediated through the amelioration of microcirculation and tissue carnitine content, thus probably increasing fatty acid oxidation.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 156 (1996), S. 1-2 
    ISSN: 1432-1076
    Schlagwort(e): Key words Neonatal diabetes mellitus ; Intra-uterine dystrophy ; Insulin ; Insulin-like growth factor␣I ; Fetal growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    European biophysics journal 24 (1996), S. 354-357 
    ISSN: 1432-1017
    Schlagwort(e): Cyclodextrin ; Insulin ; Dimer Dissociation ; Microcalorimetry ; Thermodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Abstract The energetics of dissociation of bovine insulin in aqueous solution have been investigated by sensitive dilution microcalorimetry. Cyclodextrins increase dissociation of insulin oligomers in a manner consistent with their interaction with protein side chains. For example, assuming monomer-dimer equilibrium, in the absence of cyclo-dextrins the calorimetric dilution data (25 °C, pH 2.5) indicate a dimer dissociation constant (Kdiss) of about 12 µM and an endothermic dissociation enthalpy (ΔHdiss) of +41 kJ mol−1. Addition of methyl-β-cyclodextrin (up to 200 mm) makes dissociation significantly more endothermic (ΔHdiss = 79 kJ mol−1) and reduces the apparent dimer dissociation constant by more than two orders of magnitude (Kdiss ≈ 1.7 mm). Qualitatively similar results are observed with α-cyclodextrin and other β-cyclodextrin derivatives. Cyclodextrin-induced insulin dissociation is also observed at pH 7.4.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 431 (1996), S. 748-756 
    ISSN: 1432-2013
    Schlagwort(e): Benzamil ; Insulin ; Nonselective cation channel ; Na+ channel ; Alveolar cells ; Type II ; Single-channel recording
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The Na+ transport function of alveolar epithelium represents an important mechanism for clearance of fluid in air space at birth. I observed the activity of two types of amiloride-blockable Na+-permeant cation channels in the apical membrane of fetal distal lung epithelium cultured on permeable filters for 2 days after harvesting of the cells from Wistar rats of 20 days' gestation (term = 22 days). One type was a nonselective cation (NSC) channel and had a linear current/voltage (I/V) relationship with a single-channel conductance of 26.9 ± 0.8 pS (n = 5). The other type was highly Na+ selective (i.e. Na+ channel) and had an inwardly rectifyingI/V relationship with a single-channel conductance of 11.8 ± 0.2 pS (n = 5) around resting membrane potential. The NSC channel was more frequently observed (1.37 ± 0.15 per patch membrane;n = 73) than the Na+ channel (0.15 ± 0.40 per patch membrane;n = 73). However, the open probability of the NSC channel was smaller than that of the Na+ channel. Both types of the channels were activated by cytosolic Ca2+, however the sensitivity to cytosolic Ca2+ was much higher in the Na+ channel than in the NSC channel. Furthermore, both types of the channels were blocked by amiloride or benzamil. The half-maximal inhibitory concentration (IC50) of amiloride or benzamil of the Na+ channel was 1–2 μM, while that of NSC channel was less than 1 μM. Both channels were activated by insulin.
    Materialart: Digitale Medien
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  • 17
    ISSN: 1432-2013
    Schlagwort(e): Key words Propionyl-L-carnitine ; Insulin ; Streptozotocin-induced diabetic rat ; Motor nerve conduction velocity ; Sciatic nerve blood flow ; Electroretinogram ; Sorbitol ; myo-Inositol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effect of an analogue of L-carnitine, propionyl-L-carnitine, on the electroretinogram, motor nerve conduction velocity and nerve blood flow was determined in rats with streptozotocin-induced diabetes, and was compared with the effects of insulin alone or combined therapy. Oral administration of propionyl-L-carnitine (3 g/kg daily for 4 weeks) significantly increased caudal nerve motor conduction velocity and sciatic nerve blood flow in diabetic rats. There were no differences in the effects of insulin (8–10 U daily for 4 weeks), propionyl-L-carnitine and combined therapy. Although propionyl-L-carnitine significantly shortened the peak latency of the electroretinogram b-wave in diabetic rats, its effect was far weaker than that of insulin or combined therapy, with combined therapy producing the greatest improvement. These effects of propionyl-L-carnitine were accompanied by a decrease of serum lipid levels, an increase of the sciatic nerve carnitine content, and no changes of the tissue (nerve and retinal) sorbitol and myo-inositol concentrations. In contrast, insulin significantly reduced the tissue sorbitol content and markedly increased myo-inositol. These findings suggest that propionyl-L-carnitine may improve diabetic neuropathy and retinopathy without influencing the polyol pathway, and that this beneficial effect may be mediated through the amelioration of microcirculation and tissue carnitine content, thus probably increasing fatty acid oxidation.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 432 (1996), S. 685-691 
    ISSN: 1432-2013
    Schlagwort(e): Key words Aldosterone ; Insulin ; IGF1 ; ADH ; Vasopressin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The Madin-Darby canine kidney (MDCK) cell line forms an epithelial monolayer which expresses many of the morphological and functional properties of the renal collecting duct. The C7 subclone of the parent line forms an epithelium which expresses many of the characteristics of principal cells. The MDCK-C7 subclone forms a high-resistance epithelium that is capable of vectorial ion transport. We have found that this epithelium responds to aldosterone, antidiuretic hormone (ADH) and insulin like growth factor 1 (IGF1) with increases in amiloride-sensitive Na+ transport. The responses to aldosterone and ADH follow time-courses that are consistent with the action of these hormones in vivo. This is the first demonstration of IGF1-induced Na+ reabsorption in a mammalian model system. Interestingly, a maximal response to any one of these natriferic factors does not inhibit a subsequent response to another hormone. These studies indicate that the C7 subclone retains many of the natriferic responses of the native principal cells and is an ideal model for studying hormonal modulation of Na+ transport.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 431 (1996), S. 748-756 
    ISSN: 1432-2013
    Schlagwort(e): Key words Benzamil ; Insulin ; Nonselective cation channel ; Na+ channel ; Alveolar cells ; Type II ; Single-channel recording
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The Na+ transport function of alveolar epithelium represents an important mechanism for clearance of fluid in air space at birth. I observed the activity of two types of amiloride-blockable Na+-permeant cation channels in the apical membrane of fetal distal lung epithelium cultured on permeable filters for 2 days after harvesting of the cells from Wistar rats of 20 days’ gestation (term = 22 days). One type was a nonselective cation (NSC) channel and had a linear current/voltage (I/V) relationship with a single-channel conductance of 26.9 ± 0.8 pS (n = 5). The other type was highly Na+ selective (i.e. Na+ channel) and had an inwardly rectifying I/V relationship with a single-channel conductance of 11.8 ± 0.2 pS (n = 5) around resting membrane potential. The NSC channel was more frequently observed (1.37 ± 0.15 per patch membrane; n = 73) than the Na+ channel (0.15 ± 0.40 per patch membrane; n = 73). However, the open probability of the NSC channel was smaller than that of the Na+ channel. Both types of the channels were activated by cytosolic Ca2+, however the sensitivity to cytosolic Ca2+ was much higher in the Na+ channel than in the NSC channel. Furthermore, both types of the channels were blocked by amiloride or benzamil. The half-maximal inhibitory concentration (IC50) of amiloride or benzamil of the Na+ channel was 1–2 μM, while that of NSC channel was less than 1 μM. Both channels were activated by insulin.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 20
    ISSN: 1040-0397
    Schlagwort(e): Insulin ; Myoglobin ; Protein ; Potentiometric stripping analysis ; Carbon paste electrode ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A potentiometric stripping method for trace measurements of insulin at carbon paste electrodes is described. The method is based on the controlled adsorptive accumulation of this polypeptide hormone at the anodically pretreated carbon surface followed by constant-current chronopotentiometric measurements of the surface species. A well-defined peak, associated with the oxidation of the tyrosine residues, is observed over the flat baseline of the potentiometric stripping operation. Variables of the pretreatment and measurement steps are optimized to offer a detection limit of 2 × 10-9M after 5 min preconcentration. Excess of nunierous potential interferences does not influence the response observed after transferring the electrode (with the accumulated insulin) to a blank electrolyte solution. A similar protocol is described for trace measurements of the protein myoglobin.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 21
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 49-54 
    ISSN: 1040-0397
    Schlagwort(e): Insulin ; Potentiometric stripping analysis ; Constant current stripping analysis ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Porcine insulin was analyzed in the presence of dissolved oxygen by constant current stripping analysis (CCSA) and potentiometric stripping analysis (PSA). The CCSA analysis involves the constant current reduction of mercuric insulin thiolate following its potentiostatic accumulation on a hanging mercury drop electrode. The CCSA response was quantitatively enhanced in the presence of dissolved oxygen. The PSA analysis involves the oxidation, by dissolved oxygen, of sulfhydryl groups in reduced insulin following its accumulation on the HMDE at -900mV (vs. SCE).
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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