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Biomedical subjects

K Braun

Publications and source records attributed to K Braun.

At least 109 records · Page 6Linked to original sources
PubMed1991

[Dosage reduction of d-phe-6-GnRH for the regulation of ovulation by complexation with polyglycine].

The gonadotropin-releasing-hormone analogue D-Phe6-GnRH was complexed with polyglycine under non-denaturing conditions. The liberation behaviour of these complexes was investigated in vitro in dependence of hormone content. The "effective dose 50" (ED 50) could be decreased by factor 34 in vivo in mouse ovulation test by reason of protection effect of polyglycine for the hormone against untimely proteolytical degradation.

Animals↗
PubMed1990

[Radio-ulnar bridge callus following osteosynthesis of forearm fractures].

137 patients with forearm fractures and internal plate fixation were investigated for postoperative radio-ulnar synostosis. 10 patients (7.3%) developed such a complication, 7 after complete, 3 after either ulnar or radial lesion. Of 73 patients with complete forearm fractures, 50 had separate incisions, and developed radio-ulnar synostosis only secondary to severe soft tissue injury. Of 12 other patients, by contrast, who were operated on for radial and ulnar plate fixation via one common incision (Boyd's approach), synostosis occurred in 5. After isolated ulnar fractures in 32 cases, synostosis was seen in two cases - in one after severe soft tissue injury, in the other after a modified Boyd's approach. Only one patient with isolated and open fracture of the radius presented later with radio-ulnar synostosis.

Adolescent↗
PubMed1989

System-specific distribution of zinc in the chick brain. A light- and electron-microscopic study using the Timm method.

The brain of young domestic chicks was investigated using a Timm sulfide silver method. Serial Vibratome sections were analyzed under the light microscope, and the localization of zinc-positive structures in selected areas was determined at the ultrastructural level. Both strong and differential staining was visible in the avian telencephalon whereas most subtelencephalic structures showed a pale reaction. The highest staining intensity was found in the nonprimary sensory regions of the telencephalon such as the hyperstriatum dorsale, hyperstriatum ventrale, hippocampus, palaeostriatum augmentatum, lobus parolfactorius and caudal parts of neostriatum. There was an overall gradient of staining intensity in neostriatal areas from rostral to caudal with the heaviest zinc deposits in the caudal neostriatum. Primary sensory projection areas, such as the ectostriatum (visual), hyperstriatum intercalatum superius (visual), nucleus basalis (beak representation), the input layer L2 of the auditory field L and the somatosensory area rostral to field L were selectively left unstained. Fiber tracts throughout the brain were free of zinc deposits except for glial cells. In electron micrographs of stained regions, silver grains were localized in some presynaptic boutons of asymmetric synpases (Gray type I), within the cytoplasm of neuronal somata and sporadically in the nucleus. The possible involvement of zinc in synaptic transmission and other processes is discussed.

Animals↗
PubMed1989

[The MTT-dye test for the in vitro vitality control of fresh as opposed to cryopreserved rat pancreatic islets for syngeneic intraportal islet transplantation].

The vitality of freshly isolated and of cryopreserved (-1 degree C/min, 10% DMSO) islets of the rat pancreas was determined by means of the colorimetric MTT-test. The recover rate of vital islet cells amounted to 35% after cryopreservation. The in vitro results were confirmed by the effects after syngeneic intraportal transplantation. The transplantation of freshly isolated islets of Langerhans leads to a permanent normoglycemia in Streptozotocin diabetic rats (n = 5). Cryopreserved islets after transplantation (n = 5) led in contrary to it to no influence of the metabolism. The hepatic insulin content of livers with implanted cryopreserved islets amounted only 43% in face of livers with transplantation of freshly isolated islets. The MTT-assay allows accordingly a prompt judgement of the quality of islet allotransplants and this should make its way in the clinical practice.

Animals↗
PubMed1989

Reorganization of the subplasmalemmal cytoskeleton in association with exocytosis in rat mast cells.

The subplasmalemmal cytoskeleton in mast cells has been studied by scanning electron microscopy of the internal side of the plasma membrane. Rearrangement of the dense subplasmalemmal network of actin filaments took place following cell activation by compound 48/80 and secretion of histamine. The rearrangement was a withdrawal of the subplasmalemmal cytoskeleton from the exocytotic sites and the development of bare, filament-free areas around the sites. In calcium-depleted mast cells we demonstrated a dense network that was difficult to break. Activation of the calcium-depleted cells by compound 48/80 did not induce rearrangement of the network, and in parallel there was no secretion of histamine.

Animals↗
PubMed1988

Postnatal development of parvalbumin-, calbindin- and adult GABA-immunoreactivity in two visual nuclei of zebra finches.

The characterization of neuron populations by their immunoreactivity against parvalbumin- and calbindin (28-kDa)-antisera has been used to study the postnatal development of the visual diencephalic nucleus rotundus and the mesencephalic nucleus isthmi complex in zebra finches. In nucleus rotundus, parvalbumin-immunoreactivity was restricted to the neuropil during the first 10 days and appears additionally in somata around day 12 where it remains until adulthood. Calbindin-immunoreactivity of the very scarce neuropil and the few somata, which can be observed during the first two weeks, disappears until adulthood. Thus, the adult nucleus rotundus shows an almost complementary distribution of calbindin- and parvalbumin-immunoreactive structures: the numerous, heavily parvalbumin-positive somata, which are surrounded by dense immunoreactive neuropil are in sharp contrast to the complete absence of calbindin-immunoreactive somata. Only a thin rim surrounding this nucleus contains punctate calbindin-positive neuropil. In the nucleus isthmi complex, parvalbumin and calbindin staining patterns show markedly different developmental profiles. While the density of parvalbumin-immunoreactive neuropil in the parvocellular part of the nucleus isthmi continuously increases and the somata remain unstained, the initially heavily calbindin-positive somata gradually lose their immunoreactivity during the first two weeks. In the adult nucleus isthmi complex, parvalbumin- and calbindin show nearly identical staining patterns. A comparison between the two calcium-binding proteins and GABA-immunoreactivity in adult brains revealed different relationships in the two nuclei: while in nucleus rotundus GABA-staining pattern neither resembles that of parvalbumin nor of calbindin, in the nucleus isthmi complex all three staining patterns coincide.

Animals↗
PubMed1988

Syngeneic transplantation of thyroid tissue encapsulated in a cellulose sulphate membrane.

A new, simple encapsulation method, the precipitation of a polyelectrolyte complex membrane of cellulose sulphate and poly(dimethyldiallylammoniumchloride) was investigated in syngeneic thyroid transplantation. Half a thyroid gland was placed beneath the kidney capsule either after being encapsulated or as a non-encapsulated control graft. In normo-thyroid as well as hypothyroid recipients, the grafted tissue was viable for up to 12 weeks. Furthermore, the hypothyroid state, which was characterized by a markedly diminished 125iodine incorporation into the thyroid, no body weight gain and undetectable serum thyroxin concentrations, was compensated by the grafted tissue. The encapsulated grafts showed lower iodine incorporation, T4 secretion and body weight gain when compared with non-encapsulated control grafts. This may be due to a partial restriction of TSH by the capsule membrane. It was concluded that the cellulose sulphate membrane is biocompatible and enables the functional survival of syngeneic grafted tissue.

Animals↗
PubMed1987

Prevention of complement-mediated cytotoxicity against rat islets by encapsulation in a cellulose sulphate membrane.

The immuno-isolation by semipermeable membranes should prevent the immunological destruction of the transplanted tissue. The polyelectrolyte complex membrane from cellulose sulphate and poly(dimethyldiallylammoniumchloride), which does not alter the viability of the encapsulated rat islets, can prevent complement-mediated cytotoxicity. The 51Cr release from prelabelled islets, which was induced by either unspecific cytotoxicity of rabbit sera against the rat islets or by an anti-MHC rat serum in presence of complement, was prevented. The diffusion of immunoglobulins as well as of factors of the complement system was inhibited by encapsulation. The capsule membrane also prevents the beta-cell destruction in cytotoxic sera from newly diagnosed type-I diabetics measured as insulin leakage after blocking the active hormone secretion. In conclusion, the cellulose sulphate membrane seems to be useful for the transplantation of encapsulated islets.

Animals↗
PubMed1986

The long-term culture of encapsulated pancreatic islets.

A new encapsulation technique, the formation of a polyelectrolyte complex membrane from sodium cellulose sulphate and a polycationic solution (polydimethyldiallylammoniumchloride) can be used for culturing pancreatic islets. After 5 weeks of culture, such encapsulated islets were morphologically well preserved, and parameters of cell viability and functionality such as DNA content and DNA synthesis, insulin content and stimulated insulin release were not different between the encapsulated and non-encapsulated control islets. A lower insulin secretion into the medium of the encapsulated islets during the first 3 weeks of culture can probably be explained by the capsule diameter (4-5 mm) and should be improved using microcapsules with a diameter of less than 1 mm.

1-Methyl-3-isobutylxanthine↗
PubMed1986

New approaches for the detection of early activation products in thrombotic states.

The occurrence of a consumption coagulopathy as well as prethrombotic and thrombotic states are connected with the formation of thrombin. The proteinase acts upon physiological substrates leading to activation products, e.g. fibrinopeptides, platelet factors or thrombin-antithrombin III-complex. For the determination of such products we have developed immunochemical assays, which detect parameters of a direct or indirect action of thrombin in a specific and sensitive manner: 1. ELISA for determination of platelet factor 4; 2. Latex-test for determination of D-Dimer; 3. ELISA for determination of thrombin-antithrombin III complex. Preliminary results from clinical investigations indicate that the determination of these parameters can be valuable for the diagnosis of activation processes of the clotting system.

Blood Coagulation Disorders↗
PubMed1985

Anaerobic degradation of 2-fluorobenzoate by benzoate-degrading, denitrifying bacteria.

Three strains of anaerobically benzoate-degrading, denitrifying bacteria of the genus Pseudomonas were able to grow on 2-fluorobenzoate as the sole carbon and energy source. Fluoride ion release was stoichiometric, and the reduction of dissolved organic carbon indicated total degradation. Cells grown anaerobically with benzoate were adapted for immediate growth with 2-fluorobenzoate, and both compounds were substrates for an inducible benzoyl-coenzyme A synthetase, the initial enzyme of anaerobic degradation. It is proposed that fluoride is eliminated gratuitously by a regioselective reaction in a sequence common to both carbon sources. Benzoate, but not 2-fluorobenzoate, was oxidized by aerobically grown cells.

Acetate-CoA Ligase↗
PubMed1985

The encapsulation of pancreatic islets. Investigation of insulin secretion and content in vitro.

Polyelectrolyte complex capsules from cellulose sulphate can be formed by precipitation in a polycation bath. The application of this new method for encapsulation of pancreatic islets requires investigations whether and to what extent cellulose sulphate injures viability and functionality of the pancreatic islets. Islets cultures in the presence of 2% cellulose sulphate for up to 3 weeks are characterized by unchanged insulin content, secretion and biosynthesis when compared to appropriate controls.

Animals↗
PubMed1984

Anaerobic degradation of 2-aminobenzoate (anthranilic acid) by denitrifying bacteria.

In the presence of oxygen many aminoaromatic compounds polymerize to form recalcitrant macromolecules. To circumvent undesirable oxidation reactions, the anaerobic biodegradation of a simple member of this class of compounds was investigated. Two strains of bacteria were isolated which degrade 2-aminobenzoate anaerobically under denitrifying conditions, with nitrate as the terminal electron acceptor. Both organisms, which were assigned to the genus Pseudomonas, oxidized 2-aminobenzoate completely to CO2 and NH4+. Nitrate was reduced to nitrite. When nitrate was deplete from the growth medium the accumulated nitrite was reduced to nitrogen. The results establish a model system for the anaerobic, rapid, and complete oxidation of an aminoaromatic compound.

Anaerobiosis↗