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Biomedical subjects

H J Koch

Publications and source records attributed to H J Koch.

At least 55 records · Page 3Linked to original sources
PubMed2000

Isoluminant monochromatic and polychromatic visual backgrounds alter response characteristics of cat visual neurons after stimulation with stationary and moving light bars.

The role of colour vision in night-active cats has not been elucidated completely hitherto. In order to assess the colour sensitivity in cat cortical neurons we used large isoluminant computer-generated monochromatic and polychromatic background stimuli which were superimposed on moving and stationary (on/off) light bars. Background stimuli were moved at different speeds either inphase or antiphase. The modulatory effect of the visual noise on the neuronal bar was the primary objective of the study. The maximum PSTH peaks of some 40% of the neurons tested was influenced by both moving and stationary bars. About 2 thirds of maximum peak-sensitive cells showed also altered direction selectivity. Latencies and field widths, on the other hand, turned out to be rather stable. The retino-cortical conduction time was not influenced either. In conclusion, a large portion of cat cortical visual neurons is remarkably sensitive to the spectral composition of the visual noise process surrounding the stimulating light bar.

Animals↗
PubMed2000

Monochromatic and polychromatic visual backgrounds influence the response of area 17 and 18 neurons after stimulation with stationary and moving light bars.

The role of colour vision in night-active cats has not been elucidated completely hitherto. In order to assess the colour sensitivity in cat cortical neurons we used large isoluminant computer-generated monochromatic and polychromatic background stimuli which were superimposed on moving and stationary (on/off) light bars. Background stimuli were moved at different speeds either inphase or antiphase. The modulatory effect of the visual noise on the neuronal bar was the primary objective of the study. The maximum amplitudes of some 40% of the neurons tested was influenced by both moving and stationary bars. About two thirds of amplitude-sensitive cells showed aldo altered direction selectivity. Latencies and field widths, on the other hand, turned out to be rather stable. The retino-cortical conduction time was not influenced either. In conclusion, a large portion of cat cortical visual neurons is remarkably sensitive to the spectral composition of the visual noise process surrounding the stimulating light bar.

Animals↗
PubMed2000

Bioequivalence of two oral immediate release formulations of pindolol in healthy volunteers assessed by ratio analysis.

The objective of this study was to test bioequivalence and therapeutic equivalence of two oral formulations of pindolol (ViskenR = Vs = Ref.; Nonspi 5R = Np = Test). Twenty one healthy volunteers (11 females; 10 males; aged 18-55 years) participated in the single-dose (10 mg), single-blind, randomised crossover study. Blood samples were taken up to 24 hs after intake and pindolol in serum was determined using HPLC. Key criteria for ratio analysis to assess bioequivalence were log-transformed AUC (0, last) and Cmax. Blood pressure and heart rate vs. time data were subjected to ANOVA according to Friedman. Vital signs did not show significant differences. Ratios of log-transformed data and 90%-confidence intervals were within the predefined limits of 0.8 to 1.25 or 0.7 and 1.43, respectively. We conclude that both formulations of pindolol are equivalent with regard to extent and rate of absorption as well as pharmacodynamic effect.

Adrenergic beta-Antagonists↗
PubMed1999

Longterm treatment of psoriasis using fumaric acid preparations can be associated with severe proximal tubular damage.

Fumaric acid preparations are used as longterm and effective treatment of psoriasis. Apart from gastrointestinal, dermatological and hematological side-effects, transient renal damage was observed during treatment with fumaric acid. The case of a 38 year old woman who was treated with fumaric acid (420 mg bid) for 5 years before she complained of fatigue and weakness. According to clinical laboratory she had developed severe proximal tubular damage. Hypophosphatemia, glycosuria and proteinuria persisted although medication was stopped immediately.

Adult↗
PubMed1999

Diurnal variation of ECG intervals and R or T amplitudes in healthy male subjects assessed by means of spectral and cosinor analysis.

Twelve lead standard ECGs 35 healthy male volunteers, recorded from 08.00 H up to 01.00 H, were analysed retrospectively in order to investigate primarily the diurnal changes in vital sign measurements, ECG interval durations (PQ, QRS, QTc) and R wave as well as T wave amplitudes. Data were analysed descriptively and by means of ANOVA, spectral analysis and cosinor models. ANOVA revealed significant variations for vital sign parameters and the QTc interval, although remarkable variation in all ECG parameters was observed. T wave amplitudes in particular showed marked alterations, with changes up to 40%. Transient maxima of median T wave amplitudes and QTc interval duration were found at 12.00 H and 14.00 H, respectively. R wave amplitudes and PQ duration revealed lower values in the afternoon. Although there was remarkable interindividual variability, ultradian rhythmic activity of ECG parameters was confirmed by spectral analysis and cosinor models based on population data.

Adult↗
PubMed1999

Is there seasonal periodicity in the prevalence of Helicobacter pylori?

The objective of the present study was to evaluate seasonal periodicity in the prevalence of Helicobacter pylori. A prospective study was performed on 1076 consecutive patients who were investigated in our hospital over a 3-year span because of epigastric complaints. Our findings indicate a significant accumulation of positive Helicobacter pylori tests in October. Gastric acidity, gender, and age did not influence Helicobacter pylori infection significantly. There was no significant correlation between potential seasonal influence on the diagnosis of ulcer disease and the seasonal fluctuation of Helicobacter pylori infection. The seasonality was confirmed by cosinor analysis for the absolute frequencies of H. pylori infections and also for the number of cases positive for H. pylori per number of presenting patients per month. A seasonal concept of a sensitivity threshold for positive Helicobacter pylori testing is introduced, taking into account such factors as immune system, nutrition, and medication status.

Age Factors↗
PubMed1998

Graft-versus-host-like mucocutaneous eruptions with serological features of paraneoplastic pemphigus and systemic lupus erythematosus in a patient with non-Hodgkin's lymphoma.

A 63-year-old male patient spontaneously developed severe erosive orogenital mucositis, palmoplantar and gluteal inflammatory lesions resistant to therapy. The skin lesions clinically and histologically resembled lichen-planus-like graft-versus-host disease. Investigation for an underlying autoimmune or malignant disorder revealed a centrocytic-centroblastic low-grade non-Hodgkin's lymphoma (according to the Kiel classification) in the bone marrow, mesenterial and iliacal lymphoma. Serological titers were intermittently positive for ANA, anti-Sm/U1RNP, anti-Ro and anti-dsDNA. Immunoprecipitation of lysates from radiolabeled human keratinocytes with the patient's serum revealed circulating antibodies against 210-kD (desmoplakin II), 190- and 170-kD antigens but none against the 230-kD antigen or 250-kD desmoplakin I. Under cytostatic chemotherapy the lymphomas showed complete and long-lasting remission, whereas the mucocutaneous lesions persisted. Six years after diagnosis, the mucocutaneous lesions are sufficiently controlled by immunosuppressive therapy. In the presented case, several features of lymphoma-associated dysimmunoreactivity are assumed that bring about the intrinsic production of various autoantibodies typical of paraneoplastic pemphigus and systemic lupus erythematosus.

Diagnosis, Differential↗
PubMed1998

Altered response characteristics of cat visual neurons after systemic administration of the dihydropyridine calcium antagonist nimodipine.

Nimodipine, a cerebrovasotropic dihydropyridine calcium antagonist, has gained increasing interest in geriatric research during last years and is discussed with regard to its possible involvement in restoration and preservation of brain plasticity. Single unit responses were recorded by microelectrodes in the visual cortex of anaesthetized adult cats. Receptive fields were stimulated with light bars moved forward and backward or flashed On/Off. Neuronal activity was recorded before and 5 and 30 min after i.v. administration of 0.1 mg/kg nimodipine. On the basis of penstimulus-time-histograms (PSTH) the response was analysed. There was a marked variability of the response after stimulation with both stationary and moving bars. Median firing rate was reduced 5 min after injection following On-stimulation but generally rose 30 min both after stimulation with light bars flashed On or Off Following stimulation with moving light bars about 60% of neurons showed decreased firing rates and 40% of neurons increased firing rates after injection of the calcium antagonist. The latency following On/Off-stimulation was rather constant, whereas the median latency following stimulation with moving light bars increased by about 15O ms after administration of nimodipine. In conclusion, nimodipine alters neuronal response characteristics in the visual cortex of the cat.

Action Potentials↗
PubMed1997

Treatment of canine pyoderma with co-amoxyclav: a comparison of two dose rates.

The efficacy of oral co-amoxyclav, administered twice daily for up to 12 weeks either at the manufacturer's dose rate of 12.5 mg/kg or at 25.0 mg/kg, in curing the lesions of canine folliculitis, furunculosis and cellulitis was compared in a blind study. A total of 97 dogs entered the trial and 67 completed it. There was no significant difference in the rate of cure or the duration of therapy. The lesions of folliculitis were cured in 91.5 per cent of cases, in a mean period of 25.3 days. Furunculosis and cellulitis were cured respectively in 87.5 per cent and 60.0 per cent of the dogs, in mean periods of 37.6 and 44.7 days. The standard dose rate was very effective in folliculitis and furunculosis and there was no benefit in doubling the dose. Too few cases of cellulitis were treated to provide a reliable dose comparison.

Amoxicillin↗