Biomedical subjects

Christian Holzapfel

Publications and source records attributed to Christian Holzapfel.

7 recordsLinked to original sources

PubMed2007

Macroporous ultramicroelectrodes for improved electroanalytical measurements.

Recent work on the preparation of highly organized macroporous electrodes and nanoporous ultramicroelectrodes has been combined and extended to elaborate macroporous ultramicroelectrodes (UMEs) by template synthesis using colloidal crystals and following two different and complementary methods. On the one hand, arched porous UMEs were prepared, and on the other hand, cylindrical porous UMEs were obtained by using cavity UMEs. These macroporous UMEs have an active surface area which is up to 2 orders of magnitude higher compared to that of a classical disk UME as characterized by cyclic voltammetry. To study their analytical performance, the macroporous UMEs have been modified with a redox-active thiol and also a model bioelectrocatalytical system containing a redox mediator, a cofactor, and glucose-dehydrogenase. In both cases the electrochemical signal is amplified by up to 2 orders of magnitude, which increases significantly the analytical performance of such electrodes and therefore opens up new applications for this kind of miniaturized electrochemical system.

Journal Article↗

PubMed2006

Prevalence of typus melancholicus in healthy germans.

BACKGROUND: There have been few studies concerning the prevalence of Typus melancholicus (TM) in healthy volunteers based on age or sex. To our knowledge, no such studies have been performed in healthy Germans, but several in healthy Japanese people. Therefore, it is necessary to also determine the prevalence of TM in healthy Germans, in order to know whether the prevalence of TM is cross-culturally constant. SUBJECTS AND METHODS: We examined the prevalence of TM in 121 healthy German volunteers (62 men and 59 women with a mean age +/- SD of 43.9 +/- 16.8 years and 47.4 +/- 15.9 years, respectively). Kasahara's Inventory for the Melancholic Type Personality (KIMTP) and von Zerssen's F-List (F-List) were used to identify TM. The subjects were divided by age into three groups: those aged 40 years or less (group A), those aged 41-60 years (group B), and those aged 61 years or more (group C). Mean total KIMTP and F-List scores were calculated. In addition, we also calculated mean scores of the two KIMTP TM factors ['harmony in personal relationships' (factor 1) and 'social norms' (factor 2)]. Differences in scores between men and women were analyzed by Student's t test. Differences in scores between the three age groups were evaluated by one-way analysis of variance and Scheffé's test. RESULTS: The KIMTP and F-List scores increased with age in both men and women. In the women, the KIMTP and F-List scores were significantly higher in groups B and C than in group A. In the women, the group C KIMTP factor 1 score was significantly higher than the group A KIMTP factor 1 score. The KIMTP and F-List scores tended to be higher for the women than for the men. Within groups B and C, the KIMTP and F-List scores and the KIMTP factor 1 score were significantly higher for the women than for the men. CONCLUSION: Overall, the sex and age distributions of scores for both questionnaires were similar to those obtained in previous studies in Japanese people. It is of note that our German subjects and previous Japanese subjects were not demographically controlled and, clearly, cultural backgrounds differed. Thus, KIMTP and the F-List may discriminate the TM personality with some degree of universality despite cultural differences and might be useful in cross-cultural comparisons of TM.

Adult↗

PubMed2005

Fe-Mg interdiffusion in (Mg,Fe)SiO3 Perovskite and lower mantle reequilibration.

Fe-Mg interdiffusion coefficients for (Mg,Fe)SiO3 perovskite have been measured at pressures of 22 to 26 gigapascals and temperatures between 1973 and 2273 kelvin. Perovskite Fe-Mg interdiffusion is as slow as Si self-diffusion and is orders of magnitude slower than Fe-Mg diffusion in other mantle minerals. Length scales over which chemical heterogeneities can homogenize, throughout the depth range of the lower mantle, are limited to a few meters even on time scales equivalent to the age of Earth. Heterogeneities can therefore only equilibrate chemically when they are stretched and thinned by intense deformation.

Journal Article↗

PubMed2004

Dimension of Typus melancholicus on Kasahara's Inventory for the Melancholic Type Personality.

BACKGROUND: Traditionally, Typus melancholicus (TM) was considered, a priori, to represent unidimensionality. Recent studies have suggested that TM is not a personality trait, but rather a constellation of personality traits. The purpose of this study was to examine whether TM on Kasahara's Inventory for the Melancholic Type Personality (KIMTP), considered to represent one of the valid TM questionnaires, is comprised of personality dimensions, and if so, which dimension is essential for distinguishing depressive subjects from control subjects. SUBJECTS AND METHODS: To clarify the dimensionality of TM scores on KIMTP, factor analysis of the TM scores was conducted using principal factor analysis followed by varimax rotation. Comparisons were then made between endogenous depressive patients (n = 38), nonendogenous depressive patients (n = 20), and healthy volunteers (n = 81) for total KIMTP score and factor scores using analysis of covariance, adjusting for sex and age. RESULTS: Factor analysis of KIMTP revealed 2 distinct clusters of items, i.e. 'harmony in personal relationships' (factor 1) and 'social norms' (factor 2). Endogenous and nonendogenous depressive patients showed significantly higher KIMTP total and factor 1 scores than did control subjects. However, no significant differences were observed for KIMTP total score and scores of individual factors between endogenous and nonendogenous depressive patients. CONCLUSIONS: The present results indicate that TM on KIMTP represents a constellation of personality traits, and that the factor 'harmony in personal relationship' possesses the essential meaning for assessing TM.

Adult↗

PubMed2003

[Ocular complications of the virostatic drug cidofovir].

Cidofovir, a nucleotide analogue virostatic drug is effective in the treatment of herpes virus infections. However, cytomegaly infection is the prime indication due to its adverse effects. There is growing evidence suggesting cidofovir's effectiveness against progressive multifocal leukoencephalopathy (PML) caused by a reactivation of JC-virus. Chronic ocular hypotension which seems to be therapy refractory and anterior uveitis are considered to be the most serious ocular complications of cidofovir. Secondary side effects such as macular folds, retinal or choroidal detachment can result in a permanent loss of vision. Little is known about the pathology of reduced intraocular pressure and only few reports deal with therapeutical attempts to compensate this complication. Abandoning cidofovir presently remains the only therapeutic option. To avoid serious damage it is of utmost importance to monitor all patients undergoing cidofovir administration for signs of anterior uveitis and ocular hypotension.

AIDS-Related Opportunistic Infections↗

PubMed2002

Late onset postpartum eclampsia: a rare and difficult diagnosis.

Late postpartum eclampsia without the classical pre-eclamptic signs oedema, proteinuria and hypertension is a rarely noticed complication of pregnancy. In three patients eclampsia started no earlier than 6, 8 and 11 days postpartum. Seizures were preceded by headache, vomiting, visual disturbance or impaired level of consciousness. One patient suffered a series of seizures making neurointensive care necessary. In another patient the clinical course was complicated by an additional Guillain-Barré syndrome. Aside from the typical parieto-occipital lesions brain MRI showed cerebellar hyperintensities on T2 weighted sequences as well as abnormalities on diffusion weighted images in one patient. In all patients neurological deficits and MRI findings were reversible.

Adolescent↗

PubMed2002

Concordance between self- and observer-ratings on Kasahara's Inventory for the Melancholic Type Personality.

The concordance between self- and observer-ratings was investigated for items on Kasahara's Inventory for the Melancholic Type Personality (KIMTP). Subjects consisted of 44 patients diagnosed with an ICD-10 diagnostic criteria for research (DCR) depressive episode (F32) or recurrent depressive disorder (F33) unipolar affective disorder, and 44 observers. Thirty-one of the 44 patients were diagnosed with endogenous depression. The observers consisted of five parents, eight children, thre siblings, 25 spouses, and three partners. Concordance was tested with Student's paired t-test and one-way analysis of variance intraclass correlation coefficient (ANOVA ICC). There was no statistical difference between the mean total self-rating score and the mean total observer-rating score in the endogenous depression group, but the mean total self-rating score was significantly higher than the mean total observer-rating score in the non-endogenous depression group. When the self and observer tests in this non-endogenous depression group were compared on an item-by-item basis, most items tended to receive higher scores from the self-raters than from the observer-raters. The ICC had good concordance for mean total self- and observer-ratings in the endogenous depression group but not the non-endogenous depression group. On an item-by-item basis, concordance was high between self- and observer-raters for more items in the endogenous depression group than in the non-endogenous depression group. There were some important differences between self- and observer-ratings for certain items in the non-endogenous depression group. Patients in this group tended to give higher scores to items representing Typus melancholicus in relation to scores given by observers.

Adult↗