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Biomedical subjects

S Stocker

Publications and source records attributed to S Stocker.

At least 37 records · Page 2Linked to original sources
PubMed1996

Pharmacokinetics of 5-aminolevulinic-acid-induced porphyrins in tumour-bearing mice.

Photodynamic therapy and photodynamic diagnosis help to support efficient treatment of superficial and early-stage cancer. During the last few years, 5-aminolevulinic acid (5-ALA), a precursor of haemoglobin in the haem biosynthetic pathway, was used to stimulate endogenous porphyrin production. In the following the time dependence of 5-ALA-induced porphyrin concentration will be investigated on several tissues in an in-vivo tumour model. 5-ALA was administered intravenously at a concentration of 50 mg-1 body weight. According to a certain time schedule the animals were sacrificed and 12 different organs as well as the tumour were removed. During excitation with the violet light of a Kr+ laser, porphyrin fluorescence spectra in the range 550-750 nm could be detected on the tissue samples. The intensity of the emission spectra at lambda = 635 +/- 2 nm was taken as a measure of the porphyrin concentration. All tissues showed porphyrin fluorescence. Brightest fluorescence was found on the tumour. A maximum contrast of the fluorescence intensity between the tumour and the non-malignant organs of up to 30 was observed at 4-6 h post-injection. The kinetics of the porphyrin concentration depend on the organ. Simple mathematical models will be derived and discussed.

Aminolevulinic Acid↗
PubMed1995

Stress-induced tyrosine phosphorylation of actin in Dictyostelium cells and localization of the phosphorylation site to tyrosine-53 adjacent to the DNase I binding loop.

Actin is known to be phosphorylated at tyrosine, serine, or threonine residues in various cells. In cells of Dictyostelium discoideum, a rise in the tyrosine phosphorylation of actin is observed in response to ATP depletion. An actin fraction rich in phosphotyrosine was obtained by chromatography on the weak anion exchanger Mono-P. Mass spectrometry and amino acid sequencing of protease cleavage products indicated that a single tyrosine residue was phosphorylated. Localization of this residue to position 53 of the actin sequence attributed the modification to a site that is critical for the capability of actin to polymerize. Induction of the tyrosine phosphorylation by heat shock and Cd2+ ions indicates that this modification of actin is implicated in the response of Dictyostelium cells to stress.

Actins↗
PubMed1995

alpha-D-glucuronidases from the xylanolytic thermophiles Clostridium stercorarium and Thermoanaerobacterium saccharolyticum.

alpha-D-Glucuronidases were purified from the xylanolytic thermophiles Clostridium stercorarium and Thermoanaerobacterium saccharolyticum. This enzyme activity was found to be intracellular in each organism, with T. saccharolyticum producing much greater total activity. The specific activities of the purified enzymes (10 U mg-1 T. saccharolyticum; 1.7 U mg-1 C. stercorarium) differed by a factor of approximately 5. For the determination of enzyme activities, 4-O-methyl-alpha-D-glucuronosyl-xylotriose was used as a substrate and the glucuronic acid released by alpha-D-glucuronidase action was quantified by a colorimetric procedure. 4-O-Methyl-alpha-D-glucuronosyl-xylotriose was the hydrolysis product that accumulated after exhaustive degradation of 4-O-methyl-alpha-D-glucuronoxylan with xylanases of C. stercorarium. Hydrolysis of side chains in high-molecular-mass glucuronoxylan could not be detected. Neither of the enzymes was able to hydrolyse the chromogenic aryl-substrate p-nitrophenyl-alpha-D-glucuronoside. Both alpha-D-glucuronidases have a dimeric structure, with monomeric molecular masses of 72 and 76 kDa for C. stercorarium and of 71 kDa for T. saccharolyticum. The pI was estimated to be 4.3 for each enzyme. While both enzymes exhibited a similar pH optimum (pH 5.5-6.5) they differed in their thermostabilities. At 60 degrees C, half-lives of 14 and 2.5 h, respectively, were determined for the alpha-D-glucuronidases of C. stercorarium and T. saccharolyticum. This description of alpha-D-glucuronidase activity in thermophilic anaerobic bacteria extends our knowledge of these enzymes, previously purified and characterized only in fungi.

Bacterial Proteins↗
PubMed1994

Exogenous testosterone differentially affects myelination and neurone soma sizes in the brain of canaries.

We assessed the temporal and functional relationship of myelin maturation and of neuronal development in the telencephalic song motor centres of the canary at different developmental stages. Brain differentiation was modulated by exogenous testosterone, its effects on song quality were also monitored. Myelin maturation was studied by using computer aided analysis of silver impregnated brain sections, whereas the differentiation of neurones was determined by measuring neuronal soma sizes. At an early developmental stage, testosterone triggers growth of neurones but does not affect myelination. At a later developmental stage, both neurone soma sizes and myelination are enhanced by testosterone.

Animals↗
PubMed1993

Antioestrogen inhibits myelination in brains of juvenile Zebra finches.

The effects of the antioestrogen Keoxifene on the ontogenetic process of myelination, on the differentiation of neurones of telencephalic song motor centres, on cerebellar structures and on behaviour were studied in male Zebra finches. Brain differentiation was studied by using computer aided analysis of silver impregnated brain sections and by measuring soma sizes of neurones after Nissl staining. An antioestrogen induced inhibition of myelination could be detected in the song motor centre robust nucleus of the archistriatum (RA) and in the cerebellum, whereas the region magnocellular nucleus of the anterior neostriatum (MAN) showed no difference between treated birds and controls.

Animals↗
PubMed1992

Improving the diet of under fives in a deprived inner city practice.

This paper reports the introduction of a programme of dietary education to a selected group of young mothers living in a deprived inner city area. The programme was devised by a general practitioner and practice health visitors in collaboration with two hospital dietitians. A diary was used to provide data on diet, food choice, shopping habits, eating together, and planning and frequency of meals. These were included in a list of twelve 'desirable' food groups and three organisational skills, thus providing an individual syllabus for teaching, and a means of assessing the intervention. At the start of the study milk, fruit, vegetables and protein containing iron were common dietary omissions. However, the results show that these foods were an established part of the children's diets following the intervention. The dietary diaries provided a successful means of analysis, and the teaching programme is continuing in this practice. The limitations of such a small study are acknowledged, and a long-term controlled study is suggested.

Adult↗
PubMed1984

Immunolocalization of collagen types, laminin and fibronectin in the normal human pancreas.

In order to define the connective matrix organization of the normal human pancreas collagen types I, III, pro-III and IV, laminin and fibronectin were labeled using specific, antihuman antibodies. Visualization was by indirect immunofluorescence. Collagen types I, III and pro-III were present within lobules: around acini, ducts and small vessels. Their immunofluorescence reaction was particularly obvious in septa and it also outlined interlobular vessels and ducts. The type III and pro-III fractions possessed a characteristic, branched appearance in many situations, when compared to the more linear type I reaction. Collagen type IV, laminin and fibronectin were closely applied to acini, ducts and vessels, but in contrast to the other collagen types were absent from septa.

Antibodies↗
PubMed1983

Distribution of immunoreactive fibronectin and collagen (type I, III, IV) in mouse joints. Fibronectin, an essential component of the synovial cavity border.

Hyaluronic acid traditionally has been held to play a major role in the control of transsynovial exchanges and in the biomechanical properties of synovial fluid and cartilage surfaces. As with previous ultrastructural observations, immunohistochemical data show that a more complex differentiation must be envisaged for interstitial tissues bordering the synovial cavity. In particular, the elective concentration of fibronectin in the lining layer of the synovial membrane and its presence as a fine layer at the articular cartilage surfaces indicate that this glycoprotein, along with hyaluronic acid, may play an important role in joint physiology. Only immunoreactivity for type III procollagen is diffusely distributed in the entire synovial membrane and, in addition, is found associated with fibronectin immunoreactivity at the articular cartilage surfaces.

Animals↗
PubMed1983

[Immunologic distribution of collagens during the embryogenesis of the secondary palate in the Fauve de Bourgogne rabbit].

The distribution of collagens during development of the palate in the Rabbit embryo is studied using the technique of indirect immunofluorescence. During the phase prior to epithelial contact, only types II and III are found in the mesenchyme. Type I, which is abundant on the free surface of apical epithelial cells, becomes even denser at the time when the palatine projections unite. Type IV fluorescence clearly outlines the basement membrane. When epithelial development regresses, fluorescence in type I and IV decreases in a way such that, in the areas where mesenchymal coalescence is apparent, no immunofluorescent labeling is observed.

Animals↗