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Biomedical subjects

P Stoll

Publications and source records attributed to P Stoll.

At least 55 records · Page 3Linked to original sources
PubMed1990

The use of computer-assisted video image analysis in the enumeration of immuno-stained cells in tissue sections.

A novel method of computer-assisted video image analysis (VIA) was used to determine the number of immunostained cells in tissue sections. This method permitted an accurate and objective quantification of cells of a particular phenotype. This enumeration was achieved by measuring the area stained by a test monoclonal antibody (such as the T cell marker, CD3) and comparing it with the area stained by a leukocyte common (LCA) monoclonal antibody (CD45). The proportion of T cells within the total leukocyte population in a particular tissue was then calculated. The differentiation of positive (stained) and negative (unstained) cells was uniformly maintained by setting the computer to detect a threshold for staining intensity. This enabled consistency to be maintained within a tissue section as well as between sections stained with the same antibody. In the present study, we determined the phenotype of leukocytes in colonic carcinomas by VIA and compared this with results obtained by normal visual analysis. The VIA method showed distinct advantages over normal visual analysis especially in sections which contained moderate numbers of stained cells.

Antibodies, Monoclonal↗
PubMed1990

Radiation and osteosynthesis. Dosimetry on an irradiation phantom.

An irradiation phantom was used to measure dose increases using the backscatter of different materials (titanium, steel, lead, aluminium). Telecobalt-60 and 8-MV photons were used for the irradiation. The irradiation dose was measured by means of a defined X-ray film blackening. The most important parameter was to find out whether under simulated conditions, undesirable hot spots occur. We were able to demonstrate that a 12.5 to 16% increase in the radiation dose can be observed for titanium and steel at a distance of 0.45 mm from the metal specimen. A comparison between titanium and steel did not demonstrate a relevant advantage for titanium. Therefore, adjuvant percutaneous radiation therapy should not have any influence on the life of the implant, if the soft tissue layer is of sufficient thickness. The available literature is reviewed and presented in tables.

Aluminum↗
PubMed1990

Gas supply across membranes in bioreactors for hepatocyte culture.

The conditions required for hepatocyte cultures is a main topic in the development of bioreactors for hybrid liver support systems. The detoxification of ammonia and the synthesis of urea due to primary isolated hepatocytes was measured in order to compare two different models of gas supply in bioreactors: (a) indirect medium oxygenation and (b) direct membrane-contact oxygenation of the hepatocytes using polypropylene membranes. Increasing oxygen pressure promoted cell function. At day 6 of culture, urea synthesis was 0.8 +/- 0.3 mM in 21% of O2 cultures and 1.5 +/- 0.1 mM in oxygenated cultures. Alkalosis due to CO2 loss decreased ammonia metabolism. The direct membrane-contact oxygenation resulted in enhanced cell metabolism in comparison to medium oxygenation: urea synthesis at day six was 1.42 +/- 0.2 mM in 21% O2 cultures. Polypropylene oxygenation membranes proved to be sufficient for hepatocyte adhesion. Two functions can be integrated in one element in liver support systems using the investigated polypropylene membrane and the direct membrane-contact oxygenation: oxygenation with physiological oxygen pressure in bioreactors due to gas supply across the membrane and adhesion of hepatocytes in bioreactors on the membrane.

Animals↗
PubMed1990

[The use of osteosynthesis screws in child mandibles. Anatomical and mechanical considerations].

Thirty seven child mandibular skeletons were analysed radiographically and computer tomographically to establish if there is enough room for osteosynthesis screws. The study demonstrated that in the primary and early mixed dentition there is not enough room in the canine or post-canine region to allow the installation of an osteosynthesis screw without damaging the inferior dental nerve or teeth buds. However, in the later stage of permanent tooth eruption the entire caudal portion of the mandibular body seems to provide sufficient room for osteosynthesis screws. SEM examinations of implant beds of 100 2 mm AO miniscrews inserted into the mandibles of eight fresh cadavers aged eight to twelve years showed cracks, as well as signs of squashing, crushing and shearing stress, regardless of whether the screws were pretapped or not. When, during screw insertion, the axis of the screw deviated by at least 10 degrees from the axis of the tap, two crossing thread courses resulted.

Bone Screws↗
PubMed1990

Membranes as substrates for hepatocyte adhesion in liver support bioreactors.

Fourteen membranes out of cellulose (CuprophanR), polyamide and polypropylene were compared in a cytocompatibility test using the cytokinetics and cytomorphology of primary hepatatocytes as parameters. Additionally, the impact of coating the membranes with collagen or fibronectin was investigated. Hepatocytes were not able to attach in acceptable amounts on investigated cellulose membranes. On polyamide and polypropylene membranes a sufficient cell seeding was possible. Coating with collagen or fibronectin improves the attachment and spreading on all membranes. Differences between collagen and fibronectin were detected, observing the morphology of the cells: on collagen, most of the cells spread, whilst on fibronectin, most of the cells spread and flattened polygonally. If the adhesion of hepatocytes prolongs their metabolic function, a large adhesion surface in bioreactors is necessary. To reach a high surface area for cell adhesion in bioreactors one possibility is the use of polyamide and polypropylene membranes.

Animals↗
PubMed1987

Effect of prophylactic intravenous ceftriaxone in maxillofacial surgery.

Cephalosporins are commonly used in maxillofacial surgery because they achieve high concentrations in bone. Prophylactic antibiotic therapy was given to 65 patients undergoing diverse surgical procedures. 20 patients received cefotiam in 2 doses of 2 g for 5 days; 15 patients received cefotiam in 2 doses of 2 g only perioperatively. No difference was found between these two groups with respect to prophylactic protection against infection. A further 15 patients received ceftriaxone in a single dose of 2 g preoperatively. Since we found that local infection and febrile morbidity was not significantly different even in the 'one-shot' group, we investigated the effect of 'low-dose' prophylaxis with only 1 g ceftriaxone preoperatively in another 15 patients. We found that this dose was sufficient to prevent infection in patients.

Adolescent↗
PubMed1986

Adrenocortical function and suicidal behavior in depressive disorders.

In order to examine the hypothesis that abnormal adrenocortical function is associated with suicidal behavior, morning and afternoon plasma cortisols and 1-mg dexamethasone suppression tests (DSTs) were performed in 65 patients with primary major depressive disorder. Patients with recent suicide attempts (within 28 days before DST) were compared to patients who had made past attempts and those who had never made suicide attempts with respect to age, gender, severity of depression, and plasma cortisol levels. Plasma cortisol levels did not differ significantly among the three groups. Nonsuppression on the DST was associated with presence of delusions, increasing age, and global severity of depression, but not with suicide attempts.

Adrenal Cortex↗