Biomedical subjects

H Geiger

Publications and source records attributed to H Geiger.

149 records · Page 9Linked to original sources

PubMedDate not supplied

Transdifferentiation of distal but not proximal tubular epithelial cells from human kidney in culture.

Human renal proximal and distal (thick ascending limb and early distal convoluted tubule) epithelial cells have been isolated according to their specific antigen expression. The cells were well characterized by flow cytometry, enzyme cytochemistry and electron microscopy and cultured for up to 3 months. Cultured tubular cells coexpressed cytokeratin and vimentin as intermediate filament proteins. While primary isolated cells, proximal as well as distal, revealed the phenotypic characteristics of their nephron origin, cultured distal cells showed the tendency to dedifferentiate/transdifferentiate. Distal cells lost their characteristic expression of Tamm-Horsfall glycoprotein and started de novo expression of the proximal marker proteins aminopeptidase M, gamma-glutamyl transferase and dipeptidyl peptidase IV. The expression of these antigens by distal cells could be shown by flow-cytometric analysis and fluorescence microscopy. Enzyme activity assays revealed the activity of aminopeptidase M, gamma-glutamyl transferase and dipeptidyl peptidase IV, but not of the proximal marker enzyme alkaline phosphatase. This antigenic shift could not be prevented in different culture media, and the original phenotype could not be restored. Cultured cells displayed characteristic hormonal stimulation patterns indicative of their proximal and distal origins, as shown by activation of adenylate cyclase by different peptide hormones. These results indicate that distal tubular cells possibly transdifferentiate to a more proximal phenotype in view of loss of the distal marker enzyme Tamm-Horsfall protein and de novo expression of proximal marker enzymes like dipeptidyl peptidase IV and aminopeptidase M.

Alkaline Phosphatase↗

PubMedDate not supplied

The cooccurrence of different biflavonoid types in Pilotrichella flexilis.

From Pilotrichella flexilis various flavonoids have been isolated. This species contains in contrast to P. cuspidata not only 3',3'''-binaringenin and related compounds, but also some hitherto unknown biflavonoids based on eriodictyol and aureusidin. The structures of two new compounds are elucidated spectroscopically. Possible causes for the differences of the flavonoid patterns between the two species of the genus Pilotrichella are discussed.

Benzofurans↗

PubMedDate not supplied

Triflavones and a biflavone from the moss Rhizogonium distichum.

From gametophytes of Rhizogonium distichum have been isolated the biflavone dicranolomin and five triluteolins. Two of the triluteolins, which were named rhizogoniumtriluteolin and distichumtriluteolin, were new compounds; their structures have been elucidated spectroscopically.

Bryopsida↗

PubMedDate not supplied

Neurotransmitters and neuropeptides in the baroreceptor reflex arc: connections between the nucleus of the solitary tract and the ventrolateral medulla oblongata in the rat.

The primary baroreceptor area (nucleus of the solitary tract-NTS) is anatomically interconnected with the rostral ("vasomotor area") and the caudal ("vasodepressor area") ventrolateral medulla by a well-defined arc of neuronal pathways. The chemical character and the direction of these pathways have been investigated with immunohistochemical and neurochemical techniques in intact and brainstem-operated rats. The transection of the neuronal arc resulted in an accumulation of tyrosine hydroxylase immunoreactivity in a small group of cells in the NTS adjacent to the area postrema, ipsilateral to the knife cut. Decreased angiotensinogen mRNA and atrial natriuretic peptide concentrations were measured in the ventrolateral medulla after the cut, and an accumulation of angiotensin II-immunoreactivity was found in neuronal perikarya in the ipsilateral NTS. Intracranial vagotomy caused marked depletions in glutamate levels in the subcommissural portion of the NTS and in the caudal ventrolateral medulla but nowhere else in the brainstem investigated including the rostral ventrolateral medulla.

Angiotensin II↗

PubMedDate not supplied

Adenylate cyclase-cyclic AMP-phosphodiesterase system in microdissected brain areas of normotensive and spontaneously hypertensive rats.

The topographical distribution of the adenylate-cyclase-cyclic adenosine monophosphate-phosphodiesterase system was investigated in specific brain areas of rats, and compared with spontaneously hypertensive rats. In normotensive animals, brain cyclic adenosine monophosphate levels were quite uniform (between 7.14 and 13.04 pmol/mg protein) with highest concentrations in catecholamine-containing cell groups. In contrast, the distribution of basal adenylate cyclase and phosphodiesterase activity is not uniform. The unstimulated adenylate cyclase activity was very low in the striatum and catecholamine-containing cell groups in the medulla oblongata (A1C1-cell groups) and very high in the central gray matter and the cerebellum, where the lowest phosphodiesterase activities were measured. In spontaneously hypertensive rats, altered cyclic adenosine monophosphate levels were found in 17 of 36 brain areas investigated in comparison to those of normotensive rats. Increased concentrations were found in regions which are known to participate in the central regulation of blood pressure (nucleus of the solitary tract, A1C1 catecholaminergic cell groups in the ventrolateral medulla oblongata, locus coeruleus) and in the periaqueductal central gray matter, the hippocampus and the cingulate cortex. Lower levels were measured only in hypothalamic nuclei, especially in the paraventricular and dorsomedial nucleus. No significant differences in basal adenylate cyclase activity were found in spontaneously hypertensive rats compared with Wistar-Kyoto control rats, while phosphodiesterase activity was generally higher in spontaneously hypertensive rats, most significantly in the medulla oblongata. Present data show that characterization of the adenylate cyclase-cyclic adenosine monophosphate-phosphodiesterase system helps to localize structural and/or functional differences between the spontaneously hypertensive rat and its normotensive control rat and indicate that more than one functional system is affected in spontaneous hypertension.

3',5'-Cyclic-AMP Phosphodiesterases↗