Search PubMed⌕ Search

Biomedical subjects

D Walter

Publications and source records attributed to D Walter.

44 records · Page 3Linked to original sources
PubMed1977

Neural repetitive firing: modifications of the Hodgkin-Huxley axon suggested by experimental results from crustacean axons.

The Hodgkin-Huxley equations for space-clamped squid axon (18 degrees C) have been modified to approximate voltage clamp data from repetitive-firing crustacean walking leg axons and activity in response to constant current stimulation has been computed. The m infinity and h infinity parameters of the sodium conductance system were shifted along the voltage axis in opposite directions so that their relative overlap was increased approximately 7 mV. Time constants tau m and tau h, were moved in a similar manner. Voltage-dependent parameters of delayed potassium conductance, n infinity and tau n, were shifted 4.3 mV in the positive direction and tau n was uniformly increased by a factor of 2. Leakage conductance and capacitance were unchanged. Repetitive activity of this modified circuit was qualitatively similar to that of the standard model. A fifth branch was added to the circuit representing a transient potassium conductance system present in the repetitive walking leg axons and in other repetitive neurons. This model, with various parameter choices, fired repetitively down to approximately 2 spikes/s and up to 350/s. The frequency vs. stimulus current plot could be fit well by a straight line over a decade of the low frequency range and the general appearance of the spike trains was similar to that of other repetitive neurons. Stimulus intensities were of the same order as those which produce repetitive activity in the standard Hodgkin-Huxley axon. The repetitive firing rate and first spike latency (utilization time) were found to be most strongly influenced by the inactivation time constant of the transient potassium conductance (tau b), the delayed potassium conductance (tau n), and the value of leakage conductance (gL). The model presents a mechanism by which stable low frequency discharge can be generated by millisecond-order membrane conductance changes.

Action Potentials↗
PubMedDate not supplied

Insulin changeover.

Explore the source record for details and available documents.

Drug Labeling↗
PubMedDate not supplied

[The importance of the common cancer registry for the identification of cancer cases in the EPIC Potsdam-study -- results of the first record linkage].

AIM: The follow-up of the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study has been identifying cancer diagnoses by an active follow-up through participant's self-report which is then confirmed by pathology registries or medical doctors. To utilise another source of information, a record linkage was performed with the Common Cancer Registry (CCR) of the states of Berlin, Brandenburg, Mecklenburg-Western Pomerania, Saxony-Anhalt and of the free states Saxony and Thuringia in November 2001, using the EPIC-Potsdam database of compliant study participants at that point in time (n = 27 087). This methodological study compares data of identified cancer cases in the EPIC-Potsdam study with those generated through the record linkage. METHODS: The GKR identified 1468 study participants of the EPIC-Potsdam study. Cases (n = 108) with non-melanoma skin cancer were excluded. A separate analysis was done for prevalent (date of cancer diagnosis before baseline examination) and incident cancers (date of diagnosis after baseline examination). We examined how many subjects with at least one cancer were known to EPIC-Potsdam and the CCR, how many had been known only to the CCR and how many only to the EPIC-Potsdam study. Of incident cancer cases each diagnosis was counted. It was analyzed whether the diagnoses as they had been collected by EPIC-Potsdam were identified by the record linkage. Focus was on the diagnoses that had been unknown in EPIC-Potsdam before. The concordance of information from both sources was also considered. RESULTS: According to the record linkage, 1298 subjects with at least one prevalent cancer were identified in the EPIC-Potsdam cohort, 593 (46 %) of whom were identified in both data sources, 241 (19 %) were newly identified, and 464 (36 %) participants self-reported at least one prevalent tumour which was not identified through the record linkage. Seven tumours were diagnosed before 1961 (the CCR's computerised data are only available since 1961). Fifty-seven percent (n = 187) of all tumours which could not be identified in the cancer registry dated from 1990 - 1995. After completion of the record linkage a total of 582 medically verified incident cancer cases were identified. These comprised 397 medically verified cases that were identified in the EPIC-cohort study prior to the record linkage, 18 self-reported cases where the medical verification was pending, and 167 newly identified cases. Eighty-five of the latter cases have not been identified by other sources in the two following years after record linkage indicating that 15 % of the medically verified cases have been found solely through the linkage. CONCLUSION: The EPIC-Potsdam study had a significant benefit of the record linkage due to both the additional identification and verification of prevalent and incident cancer cases, as well as a timely advanced identification of incident diagnoses. The record linkage with the cancer registry improved the quality of the endpoint data of the EPIC-Potsdam study.

Adult↗
PubMedDate not supplied

Efficacy of ceftizoxime in the treatment of incubating syphilis in rabbits.

While ceftizoxime given as a single intramuscular shot cures uncomplicated gonorrhoea in almost every case, its efficacy against Treponema pallidum in cases of concomitant incubating syphilis is less clear. To analyse this question, the rabbit orchitis model was used. After initial experiments defining appropriate inocula and doses, ceftizoxime was compared to penicillin G with its well-known activity against the organism in vitro and in vivo. According to the final experiment, ceftizoxime applied in doses corresponding to the ones used in humans for uncomplicated gonorrhoea cures rabbit orchitis due to T. pallidum about as effectively as penicillin. Hence there seems to be no need to refrain from using the third-generation cephalosporin ceftizoxime to cure gonorrhoea for fear of masking concomitant syphilis.

Animals↗