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  • 1
    ISSN: 1432-0428
    Schlagwort(e): Dihydroxyacetone ; ATP-sensitive K+ channels ; GK rat ; glycerol phosphate shuttle ; pancreatic beta cell
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In the GK (Goto-Kakizaki) rat, a genetic model of non-insulin-dependent diabetes mellitus, glucose-induced insulin secretion is selectively impaired. In addition, it has been suggested by previous studies that impaired glucose metabolism in beta cells of the GK rat results in insufficient closure of ATP-sensitive K+ channels (KATP channels) and a consequent decrease in depolarization, leading to a decreased insulin release. We have recently reported that the site of disturbed glucose metabolism is probably located in the early stages of glycolysis or in the glycerol phosphate shuttle. In the present study, in order to identify the impaired metabolic step in diabetic beta cells, we have investigated insulin secretory capacity by stimulation with dihydroxyacetone (DHA), which is known to be directly converted to DHA-phosphate and to preferentially enter the glycerol phosphate shuttle. In addition, using the patch-clamp technique, we also have studied the sensitivity of DHA on the KATP channels of beta cells in GK rats. The insulin secretion in response to 5 mmol/l DHA with 2.8 mmol/l glucose was impaired, and DHA sensitivity of the KATP channels was reduced in beta cells of GK rats. From these results, we suggest that the intracellular site responsible for impaired glucose metabolism in pancreatic beta cells of GK rats is located in the glycerol phosphate shuttle.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-0428
    Schlagwort(e): Key words Insulin release ; intracellular calcium ; exocytosis ; GK rat ; permeabilized islets.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In spontaneously diabetic GK rats, insulin secretion from pancreatic beta cells in response to glucose is selectively impaired, probably due to deficient intracellular metabolism of glucose and impaired closure of KATP channels during glucose stimulation. By using electrically permeabilized islets of GK rats, we explored the functional modulations in exocytotic steps distal to the rise in [Ca2 + ]i in the diabetic condition. At 30 nmol/l Ca2 + (basal conditions) insulin release was similar between GK and non-diabetic control Wistar rats. In response to 3.0 μmol/l Ca2 + (maximum stimulatory conditions), insulin release was significantly augmented in permeabilized GK islets (p 〈 0.01). Raising glucose concentrations from 2.8 to 16.7 mmol/l further augmented insulin release induced by 3.0 μmol/l Ca2 + from permeabilized control islets(p 〈 0.001), but had no effect on that from permeabilized GK islets. The stimulatory effect of glucose on insulin release from permeabilized control islets was partly inhibited by 2,4-dinitrophenol, an inhibitor of mitochondrial oxidative phosphorylation (p 〈 0.01). The hyperresponse to Ca2 + in GK islets may play a physiologically compensatory role on the putative functional impairment both in [Ca2 + ]i rise and energy state in response to glucose in diabetic β cells, and may explain the relative preservation of insulin release induced by non-glucose depolarizing stimuli, such as arginine, from pancreatic islets in non-insulin-dependent diabetes mellitus. [Diabetologia (1995) 38: 772–778]
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1432-0428
    Schlagwort(e): Key words Dihydroxyacetone ; ATP-sensitive K+ channels ; GK rat ; glycerol phosphate shuttle ; pancreatic beta cell.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In the GK (Goto-Kakizaki) rat, a genetic model of non-insulin-dependent diabetes mellitus, glucose-induced insulin secretion is selectively impaired. In addition, it has been suggested by previous studies that impaired glucose metabolism in beta cells of the GK rat results in insufficient closure of ATP-sensitive K+ channels (KATP channels) and a consequent decrease in depolarization, leading to a decreased insulin release. We have recently reported that the site of disturbed glucose metabolism is probably located in the early stages of glycolysis or in the glycerol phosphate shuttle. In the present study, in order to identify the impaired metabolic step in diabetic beta cells, we have investigated insulin secretory capacity by stimulation with dihydroxyacetone (DHA), which is known to be directly converted to DHA-phosphate and to preferentially enter the glycerol phosphate shuttle. In addition, using the patch-clamp technique, we also have studied the sensitivity of DHA on the KATP channels of beta cells in GK rats. The insulin secretion in response to 5 mmol/l DHA with 2.8 mmol/l glucose was impaired, and DHA sensitivity of the KATP channels was reduced in beta cells of GK rats. From these results, we suggest that the intracellular site responsible for impaired glucose metabolism in pancreatic beta cells of GK rats is located in the glycerol phosphate shuttle. [Diabetologia (1994) 37: 1082–1087]
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    ISSN: 1432-0428
    Schlagwort(e): Keywords Pioglitazone ; muscle TNF-α ; sphingomyelinase ; insulin resistance ; Wistar fatty rat.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In order to evaluate the relationship between tumour necrosis factor-α (TNF-α) level in muscle and metabolic abnormalities in obesity and diabetes mellitus, pioglitazone, a novel insulin-sensitizing agent, was administered to Wistar fatty rats and time-dependent changes in muscle TNF-α content and plasma indicators of diabetes and obesity were measured. Wistar fatty rats were hyperglycaemic, hyperlipidaemic and hyperinsulinaemic, and their plasma and muscle TNF-α levels were two or more times higher than those in normal lean rats at 16 weeks of age. When pioglitazone was administered to fatty rats at a dose of 3 mg · kg–1· day–1, the plasma triglyceride level and TNF-α levels in plasma and muscle decreased time-dependently, and reached the levels of lean rats within 4 days. Plasma glucose and insulin levels also decreased time-dependently with pioglitazone, but on day 4, these levels were still much higher than the levels in lean rats. Neutral sphingomyelinase (SMase) activity in muscle of fatty rats was two times higher than that in lean rats and was lowered to the level of that in lean rats by 4 days' pioglitazone administration. The plasma leptin level in fatty rats was 8 times higher than that in lean rats, but pioglitazone did not affect the level during the 4-day administration period. These results suggest that an increase in TNF-α production and subsequent activation of SMase in muscle leads to metabolic abnormalities in obesity and diabetes and that antidiabetic activity of pioglitazone is deeply associated with the suppression of TNF-α production. [Diabetologia (1998) 41: 257–264]
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 1432-0533
    Schlagwort(e): Pituitary adenoma ; Plurihormonal adenoma ; Immunohistochemistry ; Acromegaly ; Rathke's cleft cyst
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A case of multiple large Rathke's cleft cyst within a pituitary adenoma presenting with acromegaly is reported. Rathke's cleft cyst within a pituitary adenoma is rare condition, and this is the first report of such a case presenting with acromegaly. An electron microscopic and an immunohistochemical analysis proved that the cyst within the pituitary adenoma of this case differs from cysts found in the embryonic stage of the pituitary gland.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 83 (1992), S. 361-364 
    ISSN: 1432-0533
    Schlagwort(e): c-myc protein ; Bromodeoxyuridine ; Pituitary adenoma ; Malignancy ; Labeling index
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary To clarify the relationship between the percentage of c-myc protein-labeled cells, the bromodeo-xyuridine (BrdUrd) labeling index (LI) and clinical malignancy in pituitary adenomas, we studied 31 cases of pituitary adenomas. Tumor invasiveness, recurrence, tumor size and the length of illness were evaluated from operative findings, magnetic resonance imaging findings, and the clinical course. Each pituitary adenoma was scored to represent the degree of clinical malignancy. An hour before excision of the tumor, we administered BrdUrd intravenously. Surgical materials were fixed in 70% alcohol and embedded in paraffin. Both hematoxylin and eosin staining and immunohistochemical staining were performed using a monoclonal antibody for both anti-BrdUrd and anti-c-myc protein. Among pituitary adenomas, there was a significantly low percentage of c-myc protein-labeled cells in cases with acromegaly. The percentage of c-myc protein-labeled cells in the pituitary adenomas tended to increase with increase with the total scores of clinical malignancy. The BrdUrd LI was lower than 1% in almost all cases of pituitary adenomas, and it showed no correlation with their clinical malignancy. In conclusion, determination of the percentage of c-myc protein-labeled cells in pituitary adenomas proved to be useful for evaluating their clinical malignancy.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 77 (1988), S. 33-38 
    ISSN: 1432-0533
    Schlagwort(e): Rathke's cleft cyst ; Immunohistochemistry ; Pituitary hormones ; Intermediate filament ; Squamous metaplasia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary An immunohistochemical study was made of ten cases of asymptomatic and three cases of symptomatic Rathke's cleft cyst. The cysts in the asymptomatic cases had monolayer columnar or cuboidal epithelium. Within the epithelium, cells which were positive for at least one of the pituitary hormones were found. The rate of positive reactions for these six pituitary hormones was between 70% and 100%. In contrast, the cysts in the symptomatic cases had an epithelium which was partly stratified squamous and partly squamous epithelium, and none of the pituitary hormones were found in them. Therefore, when a Rathke's cleft cyst enlarges to the extent that clinical symptoms are produced, we consider that changes have already occurred in structure and function of the cyst epithelium. In addition, we believe there is a tendency for monolayer epithelia to undergo squamous metaplasia and for cells which are positive for pituitary hormones to change into non-granulated cells.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Abdominal imaging 24 (1999), S. 196-199 
    ISSN: 1432-0509
    Schlagwort(e): Key words: Computed tomography (CT), helical—Kidney, CT—Kidney, abnormalities.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract. Background: The term “junctional parenchyma” (JP) has been used to represent many renal anomalies including lobar dysmorphism; however, it has not been evaluated with modalities other than ultrasound (US). Methods: Twenty-two kidneys with lobar dysmorphism incidentally found on helical computed tomography (CT) were studied. In all cases, axial, multiplanar reformation, and three-dimensional images on corticomedullary phase scans were analyzed. Fifteen additional kidneys were prospectively examined with US, and we compared those sonograms with helical CT findings. Results: Comparison of the US and helical CT findings showed that the JP defect and the JP line corresponded anatomically to the upper aspect of the renal sinus and to the thick mural cortex originating from that point, extending inferiorly, respectively. The lesions of lobar dysmorphism were situated deep in the medulla, adjacent to the cortex; however, findings on helical CT did not indicate JP. Conclusions: Although JP may have been seen on US in this study, it did not show fusion remnants of subkidneys but a combination of the upper aspect of the renal sinus, the mural cortex, and the lesion of lobar dysmorphism.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    ISSN: 1432-1211
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    ISSN: 1432-1211
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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