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  • Articles: DFG German National Licenses  (6)
  • ATP-sensitive K+ channels  (2)
  • Contrast sensitivity  (2)
  • Pituitary hormones  (2)
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  • Articles: DFG German National Licenses  (6)
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  • 1
    ISSN: 1432-1920
    Keywords: Pituitary adenoma ; MRI ; Immunohistochemistry ; Pituitary hormones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Our aim was to elucidate the factors which determine the MRI signal intensities of pituitary adenomas. We examined 51 patients with surgically-confirmed pituitary adenomas. Using a spin-echo pulse sequence (SE 500/15), coronal and sagittal images (3 mm slices) were obtained. Signal intensities on T1-weighted images were measured in the parenchyma of the adenoma and in normal grey matter. The relative intensity of the adenoma was assessed by calculating the ratio of its signal intensity to that of the normal grey matter of the same patient. Parafin-embedded sections were used for haematoxylin and eosin staining. The number of cells in a prescribed area was counted, and the mean of five such counts was taken as the cell density. Immunohistochemically stained sections using antibodies for various pituitary hormones were similarly examined; the ratio of the total number of hormone-positive cells to the overall total number of adenoma cells was calculated. Four independent variables were used in the analysis: the age of the patient, the maximum diameter of the adenoma, the cell density and the proportion of hormone-positive cells in the adenoma and, with the signal intensity ratio as the dependent variable, a multiple regression analysis was performed. This revealed that the the greatest influence upon the signal intensities on T1-weighted images was the proportion of hormone positive cells.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 77 (1988), S. 33-38 
    ISSN: 1432-0533
    Keywords: Rathke's cleft cyst ; Immunohistochemistry ; Pituitary hormones ; Intermediate filament ; Squamous metaplasia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0428
    Keywords: Dihydroxyacetone ; ATP-sensitive K+ channels ; GK rat ; glycerol phosphate shuttle ; pancreatic beta cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0428
    Keywords: Key words Dihydroxyacetone ; ATP-sensitive K+ channels ; GK rat ; glycerol phosphate shuttle ; pancreatic beta cell.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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]
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 35 (1979), S. 559-582 
    ISSN: 1432-1106
    Keywords: Strabismus ; Amblyopia ; Retinal ganglion cells ; Visual acuity ; Contrast sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The spatial resolving power, contrast sensitivity, and receptive field properties of retinal ganglion cells were studied in cats reared with either convergent or divergent squint in one eye. Sustained-X cells in the area centralis of the squinting eye of the cats with esotropia without alternating fixation showed significantly poorer spatial resolution, and reduced contrast sensitivity compared with cells in the area centralis of the normal eye. These amblyopic sustained-X cells in the area centralis of the squinting eye had receptive field characteristics similar to those found in immature cells of young kittens. They had a shallow sensitivity gradient within a relatively widespread centre zone and a weak and widespread inhibitory surround. In contrast, the sustained cells in the area centralis of the normal eye revealed a typical, well defined, small centre zone with its sensitivity gradient extremely steep and its inhibitory surround strong and confined. A minor degree of amblyopia was also found in transient Y-cells in the area centralis of the squinting eye of these cats. However, no loss of resolving power was found in the cells in the area centralis of the squinting eye of the cats with esotropia or exotropia which showed alternating fixation. Thus, amblyopia occurs in those eyes which have lost the use of the area centralis as the normal visual axis during early postnatal development, and its organic lesion is already apparent in the retinal ganglion cells — the third order neurone in the afferent visual system. It is suggested that the loss of the ability to fixate results in inadequate stimulation of the central retinal ganglion cells due to the habitual presence of blurred images at the area centralis which prevents their full development during the critical period.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 34 (1979), S. 11-26 
    ISSN: 1432-1106
    Keywords: Convergent squint ; Amblyopia ; Spatial vision in cat ; Contrast sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Visual acuity and contrast sensitivity were measured behaviourally in normal adult cats and cats reared with monocular convergent squint from 3, 6, 8, 12, and 24 weeks of age. The visual acuity of the squinting eye was significantly lower than that of the non-squinting eye in cats with squint from 3, 6, and 8 weeks of age. No significant difference in acuity between eyes was found in the 12- and 24-week squinting cats and in the controls. Contrast thresholds at all spatial frequencies tested (range 0.13–2.0 c/ °) were higher in the squinting eye than in the non-squinting eye of cats with squint from 3 and 6 weeks of age, but differences were greater at the higher spatial frequencies. In the 8-week squinting cat, contrast thresholds were increased only at higher spatial frequencies. No significant differences in contrast sensitivity were found in the cat with squint from 24 weeks of age and in the controls. The degree of disturbance of spatial vision in squinting cats was most related to the age at onset of the squint, i.e., the earlier the onset, the more profound the amblyopia. The period of susceptibility extended from about 3 to 12 weeks of age. When compared with data on the development of visual acuity in kittens, the pattern of results from the present study suggests that convergent squint can arrest the development of spatial vision.
    Type of Medium: Electronic Resource
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