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Biomedical subjects

H Winkler

Publications and source records attributed to H Winkler.

At least 217 records · Page 12Linked to original sources
PubMed1988

Image interpretation of metal shadowed specimens with the aid of Monte Carlo simulation of the shadowing process.

Rotary shadowing is investigated by means of an adapted shadowing model, which has been used for relief reconstruction of unidirectionally shadowed specimens. The metal layer geometry is calculated for a simple geometric object. In order to elucidate the metal accumulation process on the surface, a Monte Carlo simulation of shadowing is applied to synthetic reliefs and to experimental relief reconstruction data of a paracrystalline membrane. For rotary shadowed specimens, no linear relationship between local metal thickness and surface height can be established as in the unidirectional case. Low spatial frequencies of the surface relief contribute very little to the information content of the observed metal film. Contrast produced by rotary shadowed films is lower compared to unidirectionally shadowed ones. The main effects are due to the steep slopes which give rise to the considerable amount of metal viewed in the normal projection, and due to the shadow casts. A further contrast enhancing effect is self-shadowing, an artifact introduced primarily by rotating the specimen during evaporation. The Monte Carlo simulation shows that low elevation angles favor self-shadowing effects. This results in a pronounced granularity that is caused by the random incidence of the atoms and the accumulation at previously deposited atoms or grown clusters. On real surfaces, small decorating clusters can be enlarged by self-shadowing. This explains the increased decoration tendency of rotary shadowed specimens. The Monte Carlo method can be used as a means to differentiate shadowing information from these effects.

Image Processing, Computer-Assisted↗
PubMed1987

Cholinergic nerve terminals in the rat diaphragm are chromogranin A immunoreactive.

Cholinergic nerve terminals in the rat diaphragm contain binding activity for antisera raised against either bovine or rat adrenal medulla chromogranin A. This was shown using indirect FITC immunofluorescence and rhodamine-labelled alpha-bungarotoxin to mark the endplates. No immunoreactivity was found for chromogranin B and secretogranin II.

Animals↗
PubMed1987

Synthesis, structure and spectroscopic properties of two models for the active site of the oxygenated state of cytochrome P450 [corrected].

Two dioxygen adducts of thiolato-iron(II) porphyrins, [K(222)][Fe(TPpivP)(SC6HF4)(O2)] 1a and [Na(18c.6)][Fe(TPpivP)(SC6HF4)(O2)] 2 were synthesized by reaction of O2 with five-coordinate, high-spin, cryptated alkali metal thiolato-iron(II) 'picket fence' porphyrinate. They were characterized by visible and infrared spectroscopy: lambda max (log epsilon) = 360 nm (4), 427 nm (4.69), 560 nm (3.69), 610 nm (3.40) for both compounds; v(16O-16O) = 1139 cm-1 in chlorobenzene and fluorobenzene for 1a and 2. Single crystals of composition [K(222)][Fe(TPpivP)(SC6HF4)(O2)].[K(222)](SC6HF4)(C 6H5Cl)(H2O) 1b were obtained by diffusion of pentane/xylene mixtures into chlorobenzene solutions of 1a at -5 degrees C. Single crystals of composition [Na(18c.6)][Fe(TPpivP)(SC6HF4)(O2)] were obtained by slow diffusion of pentane into benzene solutions of 2. Structures of 1b and 2 were studied at 20 degrees C (1b) and -100 degrees C (1b and 2). 1b: space group P2(1)/c (monoclinic), a = 16.806(5) A (1.6806 nm), b = 14.331(4) A (1.4331 nm), c = 52.000(15) A (5.2000 nm), beta = 92.95(2) degrees, V = 12.507 A3 (12.507 nm3), Z = 4, Dcal = 1.28 g.cm-3 (t = 20 degrees C). The final R1 factor was 0.085 for 5238 reflections having I greater than 3 sigma(I). 2: space group P2(1)/c (monoclinic), a = 13.107(3) A (1.3107 nm), b = 27.055(4) A (2.7055 nm), c = 25.029(4) A (2.5029 nm), beta = 96.84(2) degrees, V = 8812 A3 (8.812 nm3), Z = 4, Dcal = 1.18 g.cm-3 (t = -100 degrees C). The final R1 factor was 0.088 for 6587 reflections having I greater than 3 sigma(I). The iron atom is, in both compounds, bonded to the four porphyrinato nitrogens (Np), the sulfur atom of the axial thiolate and one oxygen atom of the axially end-on bonded dioxygen molecule. The average Fe-Np distance found in 1b [1.994(4) A, 0.1994 nm] is not significantly different from that found in 2 [1.993(3) A, 0.1993 nm]. The Fe-S bond length is 2.367(3) A (0.2367 nm) in 1b and 2.365(2) A (0.2365 nm) in 2. The Fe-O1 distances with the oxygen atom of O2 bonded to iron are respectively 1.837(9) A (0.1837 nm) and 1.850(4) A (0.1850 nm). The end-on bonded O2 molecule is disordered in both complexes 1b and 2.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding Sites↗
PubMed1987

Immunological characterization of chromogranins A and B and secretogranin II in the bovine pancreatic islet.

Antisera against chromogranin A and B and secretogranin II were used for analysing the bovine pancreas by immunoblotting and immunohistochemistry. All three antigens were found in extracts of fetal pancreas by one dimensional immunoblotting. A comparison with the soluble proteins of chromaffin granules revealed that in adrenal medulla and in pancreas antigens which migrated identically in electrophoresis were present. In immunohistochemistry, chromogranin A was found in all pancreatic endocrine cell types with the exception of most pancreatic polypeptide-(PP-) producing cells. For chromogranin B, only a faint immunostaining was obtained. For secretogranin II, A- and B-cells were faintly positive, whereas the majority of PP-cells exhibited a strong immunostaining for this antigen. These results establish that chromogranins A and B and secretogranin II are present in the endocrine pancreas, but that they exhibit a distinct cellular localization.

Adrenal Medulla↗
PubMed1987

Chromogranin A and B and secretogranin II in bronchial and intestinal carcinoids.

Carcinoid tumours (bronchial and intestinal) were analyzed by immunoblotting for the presence of chromogranin A, B and secretogranin II. In all tumours an antigen corresponding in electrophoretic behaviour to adrenal chromogranin A was present. Lung carcinoids (3 out of 5) contained a relatively high concentration of a proteoglycan form of this antigen in addition. Chromogranin B was found in all tumours. In one and two dimensional immunoblotting it appeared identical to the corresponding adrenal antigen. Secretogranin II was also present, however concentrations (especially in intestinal carcinoids) were low and variable. Furthermore, in intestinal tumours it differed from the adrenal antigen by having a slightly higher molecular size and a more alkaline pI. Immunohistochemistry revealed that the tumour tissues stained positively for all three antigens. For secretogranin II the staining in intestinal tumours was relatively weak and quite variable. These results should provide a defined basis for immunohistochemical screening of carcinoids for the chromogranin/secretogranin antigens.

Bronchial Neoplasms↗
PubMed1987

Rat adrenal medulla: levels of chromogranins, enkephalins, dopamine beta-hydroxylase and of the amine transporter are changed by nervous activity and hypophysectomy.

The levels of several constituents of chromaffin granules were determined in rat adrenal medulla after treatment with insulin or reserpine and after hypophysectomy. Insulin treatment induced increased levels of enkephalins, dopamine beta-hydroxylase, the amine carrier and of chromogranin B whereas catecholamines, cytochrome b-561 and chromagranin A remained slightly below control levels. Administration of reserpine led to similar changes with the exception of the enkephalins which increased much less. After hypophysectomy, chromogranin A was reduced to low levels; dopamine beta-hydroxylase, the amine carrier and catecholamines showed an intermediate reduction, whereas the other components remained at control levels. We can conclude that nervous stimulation of the adrenal medulla (by insulin and reserpine) induces the synthesis of enkephalins, dopamine beta-hydroxylase, the amine carrier and chromogranin B whereas the level of chromogranin A apparently depends on corticosteroids. Thus, major components of the secretory content and the membranes of chromaffin granules are regulated separately, which allows the biogenesis of chromaffin granules with a significantly altered composition.

Adrenal Medulla↗
PubMed1987

Chromogranin A and B and secretogranin II in medullary carcinomas of the thyroid.

We have studied the presence of chromogranins A and B and secretogranin II in medullary carcinomas of the thyroid using the methods of immunoblotting and immunohistochemistry. All three antigens were identified by immunoblotting. Chromogranin A and secretogranin II behaved identically to the adrenal antigens in electrophoresis, whereas the molecular size of chromogranin B in the thyroid tissue appeared slightly smaller, possibly due to a higher degree of proteolytic processing. In immunohistochemistry, positive staining was obtained with all three antigens throughout the tumor tissue. All three antigens, as well as the hormone calcitonin, were apparently present in the same cells. Our study suggests that in addition to chromogranin A, the other two antigens (chromogranin B and secretogranin II) may also be useful markers for tumors arising from endocrine tissues.

Carcinoma↗
PubMed1987

Comparison of chromogranins A, B, and secretogranin II in human adrenal medulla and pheochromocytoma.

Human phenochromocytomas were analyzed for the presence of chromogranins A and B and secretogranin II (chromogranin C). In immunohistochemistry, a positive staining of the tumor cells was observed for all three antigens. For immunoblotting, a method had to be developed which prevented proteolytic degradation of the antigens. Boiling homogenates of freeze-dried tissues achieved this and in addition, led to a significant enrichment of these secretory proteins. All three antigens could be identified in the tumor by immunoblotting. Chromogranin A and B were the major components present in about equal amounts. The relative concentration of all these antigens in the tumors was similar to those in adrenal medulla. A method involving high pressure liquid chromatography is presented which allows the separation of the human chromogranins/secretogranins.

Adrenal Gland Neoplasms↗
PubMed1986

Chromogranin A, B and C: immunohistochemical localization in ovine pituitary and the relationship with hormone-containing cells.

Chromogranins A, B and C, three distinct groups of proteins found in bovine chromaffin granules, were also found to be present in the pituitary using immunoblotting techniques. Their distribution was therefore studied in the normal ram pituitary using an immunoperoxidase technique applied to semithin serial sections and compared with that of some of the hormones of the anterior pituitary. Chromogranin-immunoreactivity was found in gonadotrophs (all three), thyrotrophs (A with some positive for C) and corticotrophs (a fraction with A and fewer with B and C). The mammotrophs and somatotrophs were negative. Chromogranin C was the only one of the three to be located in the pars nervosa, whilst chromogranin B was rarely found in the pars intermedia. The results suggest that chromogranins A, B and C are not always stored together, some hormone-containing cells do not contain immunohistologically detectable levels of the chromogranins.

Adrenocorticotropic Hormone↗
PubMed1986

Identification of two glycoproteins of chromaffin granules as the carboxypeptidase H.

An antiserum against carboxypeptidase H, an enzyme involved in the biosynthesis of neuropeptides such as the enkephalins, was used to identify the enzyme proteins in bovine chromaffin granules. Two-dimensional immuno- and lectin-blots revealed that two closely migrating glycoproteins which have been previously named J and K represented the enzyme. The same protein doublet was present in the membrane preparation and the soluble lysate of bovine chromaffin granules; however, the membrane contained significantly more enzyme protein.

Animals↗
PubMed1986

An immunological characterization of five common antigens of chromaffin granules and of large dense-cored vesicles of sympathetic nerve.

Bovine chromaffin granules and large dense-cored vesicles of bovine splenic nerve were compared by one- and two-dimensional immunoblotting. Both types of vesicles contain chromogranin A, B and C. However, the proteolytic processing of these chromogranins within these vesicles is apparently different. Chromogranin B in chromaffin granules is processed by more than 80% whereas in nerve vesicles only 15% has been broken down to smaller proteins. In addition both types of vesicles contain dopamine beta-hydroxylase and cytochrome b-561.

Animals↗