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Biomedical subjects

C Wiedemann

Publications and source records attributed to C Wiedemann.

12 recordsLinked to original sources
PubMed2001

Species of flea (siphonaptera) infesting pets and hedgehogs in Germany.

The species of flea infesting pets and hedgehogs in Germany were investigated through a survey of small animal practitioners throughout the country who were asked to collect specimens at their veterinary practices. A total of 625 veterinarians/veterinary practices responded and provided 2445 intact anti identifiable flea specimens. These fleas originated from 294 dogs (795 fleas), 334 cats (1152 fleas), 76 hedgehogs (481 fleas), five domestic rabbits (10 fleas), one golden hamster (four fleas) and one ferret (three fleas). Dogs were found to be infested with Archaeopsylla erinacei, Chaetopsylla globiceps, Ctenocephalides canis, Ctenocephalides felis, Hystrichopsylla talpae, Nosopsyllus fasciatus, Paraceras melis and Pulex irritans. From cats, Archaeopsylla erinacei, Ceratophyllus gallinae, Ceratophyllus garei, Ctenocephalides felis, Ctenophthalmus assimilis, Hystrichopsylla talpae, Monopsyllus sciurorum, Nosopsyllus fasciatus, Spilopsyllus cuniculi and Typhloceras poppei were collected. In both dogs and cats the most prevalent species were Ctenocephalides felis (78.9% and 91.6%, respectively) and Archaeopsylla erinacei (21.1% and 12.6%, respectively) followed by Ctenocephalides canis in dogs (5.8%) and Hystrichopsylla talpae in cats (1.2%). The fleas isolated from rabbits were Ctenocephalides felis, Hystrichopsylla talpae and Spilopsyllus cuniculi. Nosopsyllus fasciatus and Ctenocephalides felis were recovered from the golden hamster and the ferret, respectively. The hedgehogs were found to be infested with Archaeopsylla erinacei, Ceratophyllus gallinae and Ctenocephalides felis.

Animals↗
PubMed2001

[Object-related action: use of recall in anticipation and performance].

Consideration of the course of everyday actions during which real objects are manipulated would suggest that the sequence of individual activities should be represented in the memory not as a chain but as a network with specific characteristics. These characteristics would appear to indicate that activities which directly change parts of the environment are more memorable than shifts of attention during the performance of the action. The results of Experiment 1 support this view. Furthermore, it may be supposed that complex actions are not anticipated in their entirety before being performed, but only partially. Hypotheses concerning the temporal order of the parts of the anticipation process were tested in Experiment 2, the results supporting the hypotheses. Altogether, the results obtained confirm certain basic assumptions relating to the memory model Net of Recallable Action.

Activities of Daily Living↗
PubMed1999

Resynthesis of phosphatidylinositol in permeabilized neutrophils following phospholipase Cbeta activation: transport of the intermediate, phosphatidic acid, from the plasma membrane to the endoplasmic reticulum for phosphatidylinositol resynthesis is not dependent on soluble lipid carriers or vesicular transport.

Receptor-mediated phospholipase C (PLC) hydrolysis of phosphoinositides is accompanied by the resynthesis of phosphatidylinositol (PI). Hydrolysis of phosphoinositides occurs at the plasma membrane, and the resulting diacylglycerol (DG) is converted into phosphatidate (PA). Two enzymes located at the endoplasmic reticulum (ER) function sequentially to convert PA back into PI. We have established an assay whereby the resynthesis of PI could be followed in permeabilized cells. In the presence of [gamma-32P]ATP, DG generated by PLC activation accumulates label when converted into PA. The 32P-labelled PA is subsequently converted into labelled PI. The formation of labelled PI reports the arrival of labelled PA from the plasma membrane to the ER. Cytosol-depleted, permeabilized human neutrophils are capable of PI resynthesis following stimulation of PLCbeta (in the presence of phosphatidylinositol-transfer protein), provided that CTP and inositol are also present. We also found that wortmannin, an inhibitor of endocytosis, or cooling the cells to 15 degrees C did not stop PI resynthesis. We conclude that PI resynthesis is dependent neither on vesicular transport mechanisms nor on freely diffusible, soluble transport proteins. Phosphatidylcholine-derived PA generated by the ADP-ribosylation-factor-stimulated phospholipase D pathway was found to accumulate label, reflecting the rapid cycling of PA to DG, and back. This labelled PA was not converted into PI. We conclude that PA derived from the PLC pathway is selected for PI resynthesis, and its transfer to the ER could be membrane-protein-mediated at sites of close membrane contact.

Biological Transport↗
PubMed1998

An essential role for a small synaptic vesicle-associated phosphatidylinositol 4-kinase in neurotransmitter release.

Glutamate release from nerve terminals is the consequence of Ca2+-triggered fusion of small synaptic vesicles with the presynaptic plasma membrane. ATP dependence of neurotransmitter release has been suggested to be founded, in part, on phosphorylation steps preceding membrane fusion. Here we present evidence for an essential role of phosphatidylinositol phosphorylation in stimulated release of neurotransmitter glutamate from isolated nerve terminals (synaptosomes). Specifically, we show that a phosphatidylinositol 4-kinase (PtdIns 4-kinase) activity resides on nerve terminal-derived small synaptic vesicles (SSVs) and that inhibition of the PtdIns 4-kinase activity in intact synaptosomes leads to attenuation of the evoked release of glutamate. The attenuation of transmitter release is reversible and correlates with respective changes in intrasynaptosomal PtdIns 4-kinase activity. Because only the Ca2+-dependent release of glutamate is affected, regulation appears to be at the level of exocytosis. Taken together, our data imply a mandatory role for PtdIns 4-kinase and phosphoinositide products in the regulated exocytosis of SSV in mammalian nerve terminals.

1-Phosphatidylinositol 4-Kinase↗
PubMed1996

Chromaffin granule-associated phosphatidylinositol 4-kinase activity is required for stimulated secretion.

Permeabilized bovine adrenal chromaffin cells have been used to characterize the MgATP requirement of processes preceding exocytosis. Incubation of primary cultures with the membrane-permeable phenylarsine oxide (PAO) at 20 microM inhibited the phosphorylation of phosphatidylinositol (PtdIns) and completely blocked secretion. This block could be reversed by addition of 2,3-dimercaptopropanol to the permeabilized cells. Simultaneous addition of [gamma32P]ATP and 2,3-dimercaptopropanol permitted a comparison between recovery of secretion and phosphorylation of intracellular components. Recovery of secretion closely correlated with phosphorylation of PtdIns and PtdIns4P. Subcellular fractionation of permeabilized cells after recovery of secretion revealed that the majority of newly phosphorylated PtdIns4P was localized on the chromaffin granules. In accordance with these results, PtdIns 4-kinase activity was found in protein extracts of permeabilized cells as well as associated with purified chromaffin granules, sensitive in both cases to PAO. Additionally, PtdIns 4-kinase activity in these two assays was inhibited by quercetin. In permeabilized cells, quercetin decreased the levels of labeled PtdIns4P and Ptdlns(4,5)P2 and inhibited secretion. Our data suggest that a chromaffin granule-associated PtdIns 4-kinase acts in the priming of exocytosis.

1-Phosphatidylinositol 4-Kinase↗
PubMed1992

The role of matrix molecules in regeneration of leech CNS.

Extracellular matrix (ECM) molecules extracted from the leech central nervous system (CNS) provide substrates that induce extensive growth of processes of identified leech nerve cells in culture. Two ECM molecules, laminin and tenascin, have been identified. The laminin-like molecule has been purified and shown to be a cross-shaped molecule similar to vertebrate laminin with subunits of 340, 220, 180, and 160 kD. Purified laminin as a substrate induces rapid outgrowth of Retzius (R) and Anterior Pagoda (AP) cells in culture. The tenascin molecule has been partially purified. In electronmicrographs, leech tenascin, like vertebrate tenascin, has six arms of equal size joined in a central globule. Highly enriched fractions of leech tenascin induce rapid and extensive outgrowth of Retzius and AP cells in culture. Substrate molecules not only induce outgrowth of processes but also affect the growth patterns of individual nerve cells. Neurites are straight with few branches in laminin, but curved with profuse branches on tenascin. During regeneration of the CNS in the animal, laminin appears at new sites associated with growth cones. The appearance of laminin correlates with the accumulation of microglial cells. Thus, ECM molecules with growth-promoting activity for leech nerve cells in vitro appear to be involved in inducing regeneration and allowing the neurites to reconnect with former targets.

Animals↗
PubMed1990

[The effectiveness and safety of an immunization against parvovirus and rabies in anesthetized puppies].

The efficacy and safety of a vaccination during anaesthesia was examined in 20 puppies from 8 litters of one kennel. The animals were vaccinated in a state of reflex-free anaesthesia (neuroleptanalgesia in combination with halothane, nitrous oxide and oxygen). 20 puppies from the same litters were used as controls. A parvovirus living vaccine (Canimed) and a rabies vaccine from inactivated viruses (Rabisin) were used for the vaccinations. The titers of neutralizing antibodies against rabies virus were significantly lower in the group of anaesthetized animals compared to the control group on the 10th and 20th day p.vacc. The average titers of antibodies against parvovirus of both groups, however, do not allow any statistically significant statements. It is nevertheless remarkable that 6 of the anaesthetized puppies (three different litters) showed no increase in antibodies. The results of the investigations lead to the recommendation not to vaccinate anaesthetized puppies. The risk of reducing the efficacy of vaccinations with vaccines from inactivated agents is greater than with living vaccines.

Anesthesia↗
PubMed1988

An elementary approach to cell cycle analysis.

An elementary semistochastic model for cell cycle analysis is presented. Various independently generated experimental data sets are compared with the theory in which for the first time, a consistent consideration of non-proliferating cells has also been taken into account.

Animals↗
PubMed1988

An elementary approach to cell cycle analysis.

An elementary semistochastic model for cell cycle analysis is presented. Various independently generated experimental data sets are compared with the theory in which for the first time, a consistent consideration of non-proliferating cells has also been taken into account.

Animals↗