Biomedical subjects

H Mayer

Publications and source records attributed to H Mayer.

389 records · Page 22Linked to original sources

PubMedDate not supplied

Characterization and reduction of ischemia/reperfusion injury after experimental pancreas transplantation.

Reperfusion injury after pancreas transplantation is a cause of early graft pancreatitis. The aim of this study was to quantify pancreatic microcirculation after pancreas transplantation in correlation with cold ischemia time. In a second step the effect of N-acetylcysteine on reperfusion damage was tested. Pancreas transplantation was performed in three different groups of male Lewis rats. Groups 1 and 2 received no special treatment. Cold ischemia time was 1.5 hours in group 1 and 16 hours in groups 2 and 3. In group 3 donor and recipient were both treated with N-acetylcysteine (300 mg/kg) 1.5 hours after reperfusion graft microcirculation was quantified by means of intravital microscopy. Rhodamine-labeled leukocytes, fluoroscein isothiocyanate-labeled erythrocytes, and fluoroscein isothiocyanate-albumin were used as fluorochromes. After a cold ischemia time of 16 hours, functional capillary density, erythrocyte velocity, and leukocyte-endothelium interaction were reduced significantly compared to a cold ischemia time of 1.5 hours (P<0.05). After 16 hours of cold ischemia, treatment with N-acetylcysteine improved all of these parameters (P</=0.05). Ischemia/reperfusion injury after experimental pancreas transplantation is characterized by a disturbance of the pancreatic microcirculation exhibiting a correlation with the duration of cold ischemia. Treatment of donor and recipient with N-acetylcysteine resulted in prevention of cold ischemia-induced microcirculatory disturbance.

Animals↗

PubMedDate not supplied

[Differentiation of osteogenetic cells: systems and regulators].

Bone formation comprises a complex but ordered sequence of events, beginning with the proliferation of chondrogenic and osteogenic precursor cells followed by their subsequent differentiation, ultimately leading to extracellular matrix maturation and mineralisation. Several models have been established which recreate discrete elements of this network. Factors induce ectopic bone formation, when implanted into muscle pouches, have been characterized as members of the TGF-beta-superfamily. Detailed information about the course of OB-differentiation has been obtained from an in vitro model system. The process of mineralisation was found to consist of three distinct time periods: a proliferative phase, a period of extracellular matrix maturation and mineralisation. The development of each states depends on each other. This model is not as complex as the whole organ and cannot of course lead to any conclusion about the kinetic differentiation path of a cell in its normal spatial environment. Different organ culture systems are described and through the application of sensitive methods the differentiation can be studied in the normal spatial environment. The cascade of events in the differentiation process must be strictly regulated. Hormones and growth factors in many cases show a bone-forming and/or bone-resorbing action. The effects of the classical calcium regulating hormones Vitamin D and PTH on OB-differentiation are reviewed. A large number of growth factors have been shown to effect OB. Growth factors, that have been isolated from the bone matrix are of particular interest to bone formation.

Animals↗

PubMedDate not supplied

Unusual lipid A types in phototrophic bacteria and related species.

Photosynthetic bacteria of the Rhodospirillaceae family (sulfur-free purple bacteria) possess lipopolysaccharides (LPS) that deviate markedly from the Salmonella lipopolysaccharides in the chemical makeup of the lipid A component and in their biologic properties. LPS of Rhodopseudomonas gelatinosa is highly toxic and pyrogenic, while that of Rhodospirillum tenue shows cryptic toxicity. Two LPS types are completely non-toxic. The Rhodopseudomonas sphaeroides lipid A has the same backbone as that of Salmonella, but a part of the amide-linked fatty acids has the unusual 3-oxo structure (3-oxo-14:0). The lipid A's of Rhodopseudomonas viridis and Rhodopseudomonas palustris have 2,3-diamino-2,3-dideoxy-D-glucose as the backbone sugar. This is the first demonstration of this sugar in nature. In recent studies using 16S rRNA sequencing, the nonphotosynthetic Nitrobacter strains were shown to be phylogenetically closely related to R. palustris. The R. palustris lipid A type has been identified in three Nitrobacter species, including Nitrobacter winogradskyi, the type strain. The data demonstrate the taxonomic significance of lipid A constituents and structures.

Bacteria↗

PubMedDate not supplied

Objective assessment of spine function following industrial injury. A prospective study with comparison group and one-year follow-up.

Objective functional capacity measurement techniques were used to guide a treatment program for a group of 66 chronic back pain patients. These patients were compared with a group of 38 chronic patients who were not administered the treatment program. Outcome data were collected by telephone survey at an average 1 year follow-up. In addition, functional capacity measures were collected for treatment group patients on admission and follow-up evaluations. Results demonstrated that the functional capacity measures collected for the treatment group improved in approximately 80% of the patients. These changes were also accompanied by positive changes in psychologic measures. In addition, at 1 year follow-up, the treatment group had approximately twice the rate of patients who returned to work, relative to the comparison group. Additional surgery rates were comparable for both groups (6% in the treatment and 7% in the comparison group), but the frequency of additional health-care professional visits was substantially higher in the comparison group. The findings suggest that quantitative functional capacity measures can give objective evidence of patient physical abilities and degree of effort and can significantly guide the clinician in administering an effective treatment program.

Adult↗

PubMedDate not supplied

Different lipid A types in lipopolysaccharides of phototrophic and related non-phototrophic bacteria.

Lipid A analyses confirm not only the present taxa of the purple nonsulfur bacteria (formerly Rhodospirillaceae), but also phylogenetical relatedness of distinct phototrophic to distinct non-phototrophic bacteria, as was suggested by cataloguing 16S rRNA. For example, lipid A with ester-bound 3-OH-10:0 and the rare amide-linked 3-oxo-14:0 is common to the phototrophic Rhodobacter capsulatus and Rhodobacter sphaeroides and also to Paracoccus denitrificans and Thiobacillus versutus. 'Lipid ADAG' (lipid A with 2,3-diamino-D-glucose (DAG)) occurs in the phototrophic Rhodopseudomonas viridis and Rhodopseudomonas palustris and also in the related non-phototrophic species, e.g., Nitrobacter winogradskyi, Pseudomonas diminuta, or Thiobacillus ferrooxidans. The phylogenetically more coherent purple sulfur bacteria (Chromatiaceae) uniformly contain D-mannose in their phosphate-free lipid A. Among the green bacteria, only the Chlorobiaceae but not the likewise chlorosome-containing Chloroflexaceae contain lipopolysaccharide. Lipid ADAG from R. viridis is a structural analogue of a biosynthetic precursor (lipid X) of enterobacterial lipid A. Lipid A synthase from Salmonella accepts not only lipid X but also the synthetic di-N-acyl-2,3-diamino-D-glucose analogue as substrate (Raetz, C.R.H., unpublished results). More and more naturally occurring lipid A's with both, 2,3-diaminoglucose and glucosamine ('mixed' lipid A, with 2,3-diaminoglucose or glucosamine dominating) are being found. Newly recognized lipid A and lipid ADAG types might offer the possibility of differentially stimulating desired biological activities in animals without also having the undesired endotoxic activities. The non-toxic lipid A from Rhodopseudomonas viridis for example is able to stimulate prostaglandin secretion in peritoneal macrophages and can be used as an antagonist to the endotoxic shock caused by Salmonella lipopolysaccharide.

Bacteria↗

PubMedDate not supplied