Biomedical subjects

I Grunwald

Publications and source records attributed to I Grunwald.

23 records · Page 2Linked to original sources

PubMed1997

[Cementless fixation of the endoprosthesis using trabecular, 3-dimensional interconnected surface structures].

While the principle of enlarging the surface area has been recognized and used in different ways for some time, there is often no schematic, detailed description or fundamental research. Taking a surface structure consisting of trabecular three-dimensional connecting elements, essential parameters are shown, making it clear that the flexible dynamic reaction of the effective "anchoring space" with a suitable specified shape (construction height, alignment, network) can be reproducibly shaped and used. This has led to a hip endoprosthesis with a graduated surface structure. The construction height of the trabecular structure varies, decreasing from proximal to distal.

Biocompatible Materials↗

PubMed1993

Malignant tumour of the psoas: another cause of meralgia paraesthetica.

Contrasting the more benign causes known for meralgia paraesthetica we report a case due to a malignant tumour of the psoas muscle. We discuss the use of sensory nerve conduction study and somatosensory evoked potentials of the lateral femoral cutaneous nerve as well as needle EMG and diagnostic nerve block to detect the site of the lesion along its course. This appears of major importance, as causes located above the inguinal ligament can bear a more serious prognosis than the ones below.

Action Potentials↗

PubMed1990

Reading with fixed and variable character pitch.

We compared the effects of fixed and variable (proportional) spacing on reading speeds and found variable pitch to yield better performance at medium and large character sizes and fixed pitch to be superior for character sizes approaching the acuity limit. The data indicate at least two crowding effects at the smallest sizes: one that interferes with individual character identification and one that interferes with word identification. A control experiment using rapid serial visual presentation suggests that it is the greater horizontal compression and consequently reduced eye-movement requirements of variable pitch that are responsible for its superiority at medium and large character sizes.

Eye Movements↗

PubMed1988

Effect of aging on kinetic parameters of 5 alpha-reductase in epithelium and stroma of normal and hyperplastic human prostate.

Altered 5 alpha-dihydrotestosterone (DHT) metabolism and stromal-epithelial cell interactions are two factors hypothesized to explain the development of benign prostatic hyperplasia (BPH). Furthermore, the development of BPH is clearly age dependent. Therefore, we studied the age-dependent alteration of 5 alpha-reductase, the enzyme that catalyzes the irreversible conversion of testosterone to DHT in epithelium and stroma of the human prostate. For this purpose kinetic parameters [Km Vmax] of 5 alpha-reductase were determined separately in epithelium and stroma of normal prostatic tissue (NPR) from 5 and BPH tissue from 20 men, and the results were correlated with the age of the donors (15-86 yr). The mean Km in epithelium [NPR, 14.3 +/- 1.8 (+/- SE); BPH, 29.5 +/- 2.7 nmol/L] was significantly (P less than 0.0001) lower than that in stroma (NPR, 78.4 +/- 8.5; BPH, 185.8 +/- 13.6 nmol/L). The mean Vmax in epithelium [NPR, 23.8 +/- 3.9 (+/- SE); BPH, 27.9 +/- 3.0 pmol/mg protein.h] was significantly (P less than 0.0001) lower than that in stroma (NPR, 68.3 +/- 4.4; BPH, 173.8 +/- 12.2 pmol/mg protein.h). The DHT-forming index (Vmax/Km) in NPR epithelium [1.6 +/- 0.2 (+/- SE)] was significantly (P less than 0.01) higher than that in NPR stroma (0.9 +/- 0.1), while in BPH the DHT-forming index was nearly identical in epithelium (1.1 +/- 0.1) and stroma (1.0 +/- 0.1). The Km values in epithelium and stroma both correlated positively (P less than 0.01) with age, but the Vmax values correlated positively with age (P less than 0.0001) only in stroma. The DHT-forming index decreased significantly with age in epithelium (P less than 0.01), but remained constant in stroma. These results indicate that there is a nonuniform age-dependent alteration of Km and Vmax in epithelium and stroma of the human prostate independent of the presence of BPH, which might have an impact on the conversion rate of testosterone to DHT with advancing age.

Adult↗

PubMedDate not supplied

[Comparative static biomechanical studies of tripod surface structures of cementless endoprostheses].

AIM: While the importance of stability of endoprosthetic surface structures has been recognized for some time there is a lack of comparative surveys and assessment indices that would permit comparison and improvement of surfaces on cementless endoprostheses. METHOD: Using separately produced, systematically mounted specimen pieces of endoprosthetic surfaces with isolated non-linked elements of varying shapes and sizes, stability parameters and stability behaviour are described. Results of tripode-structures are compared to spherical surfaces. RESULT: These investigations show clearly that geometrical attributes, the orientation and the contact of surface elements to the endoprosthetic stem influence the stability considerably more than the size of these surface elements. CONCLUSION: Using tripode-elements with different orientation, size and density, a differentiated formation of cementless endoprosthetic surfaces is possible.

Biomechanical Phenomena↗