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Biomedical subjects

Horst J Koch

Publications and source records attributed to Horst J Koch.

At least 19 recordsLinked to original sources
PubMed2005

ROC analysis as an additional method to characterize time to event data.

The receiver operating characteristic (ROC) is predominantly used to assess the discriminant power of diagnostic tests. The present paper proposes this method as an additional alternative to compare survival data of in oncology or related fields. Survival data of brain tumors were analysed with conventional Kaplan-Meier method and ROC. The Area und the Curve (ROC-curve) gives additional illustrative information to distinguish between two therapeutic approaches and low or high grade brain tumors.

Adult↗
PubMed2005

[Spinal and cerebral leptomeningeal seeding from a melanocytoma of the cerebello-pontine angle].

Meningeal melanocytoma refers to the uncommon clinical appearance of a generally benign tumour deriving from leptomeningeal melanocytes. Meningeal spread of this tumour is very rarely observed. We present the case of a 38-year-old man with meningeal melanocytoma of the cerebello-pontine angle, who showed a biphasic course of this disease, with a stable period followed by a steady progress within few months. After surgical resection of the melancytoma in the left skull base and of a first local recurrence five years later, a second local recurrence occurred 6 years after diagnosis, with intracerebral and spinal meningeal seeding. This tumor did not respond to a combined radiochemotherapy including oral temozolomide, and the patient died 5 months after starting treatment for this relapse. Secondary malignisation of the melancytoma is suggested.

Administration, Oral↗
PubMed2005

Memantine: a therapeutic approach in treating Alzheimer's and vascular dementia.

Memantine has been clinically used in the treatment of organic disorders in Germany for over ten years and has now been approved in Europe and also in the US for moderate to severe Alzheimer's disease. The rationale for this indication is strongly related to the physiological and pathological role of glutamate in neurotransmission. Glutamate is an agonist of NMDA, kainate and AMPA (ionotropic) receptors, where its influence on NMDA receptors plays an important role with regard to neuronal plasticity effecting memory and learning. Excessive levels of glutamate result in neurotoxicity, in part by overactivation of NMDA receptors. Memantine acts as an uncompetitive antagonist of NMDA receptors and therefore compensates for this overactivation. Furthermore, memantine is a neuroprotective agent in various animal models based on both neurodegenerative and vascular processes, as it ameliorates cognitive and memory deficits. Memantine was effective and safe in several clinical studies, particularly in Alzheimer's disease. The compound is completely absorbed after oral intake and undergoes little metabolism. Having a low probability for drug-drug interactions, memantine, in principle, is suited for elderly patients exposed to multiple therapeutic therapies.

Alzheimer Disease↗
PubMed2004

[Diurnal variation of pain perception and heart rate in the human tourniquet pain model in healthy volunteers].

The diurnal variation of pain threshold was studied in 13 healthy volunteers (age: 21 - 27 ys) using the tourniquet pain model. A tourniquet was inflated above systolic blood pressure for 1 minute and pain scores and heart rate were recorded at 0.5, 1.0, 1.5 and 2.0 minutes. The test was repeated during a study day at 6.00 h, 12.00 h, 18.00 h and 24.00 h. Significant differences of pain scores between clocktimes were found 1 minutes after inflation and after 1.5 minutes with regard to heart rate. Generally, the highest pain scores were found at 24.00 h.

Adult↗
PubMed2004

NMDA-antagonism (memantine): an alternative pharmacological therapeutic principle in Alzheimer's and vascular dementia.

Memantine, a non-competitive NMDA antagonist, has been clinically used in the treatment of dementia in Germany for over ten years. The rationale for this indication is strongly related to the physiological and to the pathological role of glutamate in neurotransmission. Physiologically, NMDA receptors mediate synaptic plasticity by acting as a coincidence detector. Only those synapses that show temporally and spatially discrete activation of NMDA receptors undergo plastic changes secondary to Ca++ influx after rapid unblocking of Mg++, thus crucially contributing to memory and learning processes. The voltage-dependency of Mg++ is so pronounced that under pathological conditions it leaves the NMDA channel upon moderate depolarisation, thus interrupting memory and learning. Its pharmacological properties allow memantine to rapidly leave the NMDA channel upon transient physiological activation by synaptic glutamate (restoring significant signal transmission), but to block the sustained activation of low glutamate concentration under pathological conditions, i.e. to protect against excitotoxicity as a pathomechanism of neurodegenerative disorders. Memantine acts as a neuroprotective agent in various animal models based on both neurodegenerative and vascular processes as it ameliorates cognitive and memory deficits. Memantine has shown to be effective and safe in the treatment of dementia, particularly Alzheimer's disease, in controlled clinical trials. Provided that the dose is slowly increased it is generally well tolerated and safe up to 20 and 30 mg per day, with intake preferably in the morning. The compound is completely absorbed after oral intake with Cmax values after 6 hours, undergoes little metabolism and has a terminal elimination half life between 60 and 100 hours. Due to its low potential of interaction, memantine can be combined with acetylcholinesterase inhibitors, the mainstay of current symptomatic treatment of Alzheimer's disease and it is suited in elderly patients receiving multiple drug therapy.

Alzheimer Disease↗
PubMed2003

[Determination of reliability of psychometric tests in psychiatry using canonical correlation].

Test results (raw scores) are composed of an unknown true score and an error term. The error term can be estimated by means of test reliability which is defined by the ratio of true variance and obtained variance. Different estimates of reliability either based on single measurements (e.g. Cronbach's coefficient, split half reliability, Kuder Richardson method) or two measurements (test/retest, inter- or intrarater reliability) are available. Parallel test reliability depends on the correlation of two different tests obtained in one session. Canonical correlation methods allow an extension of the parallel test situation and split half technique. Two or more tests are performed in a sample of subjects. Randomized subsets are correlated using canonical correlation technique. The objective of this study is to estimate the homogeneity of test batteries. 94 patients (64 f, 30 m; age: 54-89 ys.) supposed to have dementia were tested using the clocktest (CT, scores: 1-5), MMSE (mini mental state examination) and SKT (Syndrom Kurztest). Four (i, j: 1-4) subsets of 20 patients each were determined by random and the following characteristics were calculated: Empiric correlation coefficient for n = 94 (R), canonical correlation coefficient (Rcan), eigenvalues (EV) and redundancy (Rnd) of corresponding variable sets. The results of canonical analysis showed canonical correlation coefficients in order of 0.8 to 0.9 (p-values < 0.001). This high internal consistency can be interpreted as a measure of reliability of the test batteries. In conclusion, canonical correlation based on parallel tests splitted in subsets gives information on consistency, i.e. reliability, of test batteries in addition to conventional correlation methods.

Adult↗
PubMed2003

[Circannual rhythm of drug use by a psychiatric clinic].

The total number per month of prescribed antibiotics or psychiatric drugs during one year (1998) was assessed by means of sine wave models [Y(t) = M + A x sin(2 x pi x t/tau + phi)]. M (no. of prescriptions per month) denotes mean frequency over one period, A (no. per month) denotes amplitude, tau (month) corresponds to the period and phi (month) to the phase of the fitted curve. Data were evaluated descriptively and chronograms including 95%-confidence limits were given. Significant nonlinear regression models could be calculated for amoxicillin, paroxetine, citalopram, amitriptyline and buspirone prescription behaviour. Both circannual and ultra-annual (period shorter than one year) rhythms of prescription were found. Peak values for antibiotic drug prescription during fall and winter is probably associated with higher incidence of infectious diseases. Antidepressant drug prescription has maxima in spring and fall, which is in keeping with the epidemiology of depressive disorders. The seasonality of buspirone prescription may reflect a basic periodicity of anxiety disorders. In conclusion, the chronopharmaco-epidemiological data of antibiotic and antidepressant drug prescription with circannual and ultra-annual rhythms may reflect the periodicity of infectious and psychiatric diseases.

Anti-Bacterial Agents↗