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Biomedical subjects

H Sick

Publications and source records attributed to H Sick.

At least 91 records · Page 5Linked to original sources
PubMedDate not supplied

The role of the zygomatic arch in the statics of the skull and its adaptive shape.

The zygomatic arch of mammals is usually considered a phylogenetic relic of the fenestrations of the skull roof which may be observed in morphological sequences of primitive vertebrate skulls. If this concept is correct, the element is comparable (though not homologous) to the jugal arches of diapsid reptiles. Two major questions then remain unanswered: why different elements are maintained in reptiles and mammals during evolution, and why the arches are maintained as relics of ancestral forms. It is tempting to respond to the latter question with a very simple answer, namely that the elements function in order to sustain mechanical stresses. In this paper, we raise the questions which quality of stresses occurs in a primate skull within the zygomatic arches and what relationship these stresses hold to the morphology of these bony elements. An answer has been sought by means of finite element stress analysis. We found that the zygomatic arch in primate skulls represents a structure which carries, under all biologically relevant conditions, either compressive or tensile stresses. In a very simple model of the human skull under bite forces, a strip of stresses occurs lateral to the orbits, which seems roughly comparable to the zygomatic arch. Once such a structure exists and is used as an insertion of adductor muscles, it will be exposed to bending stress in side view and in frontal view. Morphological details of the zygomatic arch (curvature, profile, suture) are well suited to sustain the evoked stresses by a minimum of material.

Adaptation, Biological↗
PubMedDate not supplied

Ammonia production from hippurate by the rat kidney in vitro.

Hippurate is known to be synthesized from benzoate and glycine in the liver and kidney. It takes part in renal ammoniagenesis by modulating the activity of gamma-glutamyl transpeptidase (gamma GT). Due to its chemical structure, however, hippurate might also serve as a substrate of renal ammoniagenesis. Hippurate may yield ammonia either having been cleaved by hippuricase or by Erlenmeyer's reaction after condensation with an aldehyde. In order to elucidate the possibility of hippurate being a substrate of renal ammoniagenesis, experiments were carried out on cortical kidney slices and on isolated tubular segments of the rat. The incubation medium (pH 7.1) was enriched with 10 mmol/l hippurate spiked with 15N-hippurate, some of the known competitive inhibitors of hippuricase, acivicin and different aldehydes. Factors known to affect hippuricase or gamma GT did not interfere with renal ammonia production. Glyceraldehyde (up to 1.0 mmol/l) but not glycerate had a stimulating effect, especially on the ammoniagenesis from hippurate. In normal rats fed a vegetarian diet, 1% of the added 15N moiety was found to be 15NH3. Renal 15NH3 production was significantly greater if, prior to the experiments, the animals were either acidotic or had a reduced renal mass or were fed animal proteins. These results indicate that hippurate may, to a certain extent, serve as substrate for ammoniagenesis.

Acidosis, Renal Tubular↗
PubMedDate not supplied

[Medullary microcirculation in human primary and secondary myeloscloroses].

There are histological and experimental evidence for bone marrow microcirculation to play a role in histogenesis of myelosclerosis. Human sternal bone marrow microcirculation was studied after death using ink injection in two cases of primary myelofibrosis, two cases of secondary meylofibrosis (Hodgkin's disease) an one case of osteomyelosclerosis. Control material consisted of 30 previously studied normal human sternums. In all cases interadipocytic sinusoidal network has completely disappeared. Medullary vascularization is anarchic with a vascular and hypervascular areas. The significance of these modifications is discussed.

Aged↗
PubMedDate not supplied

[Methods for the anthropologic and teleradiographic study of the pterygoid process].

The relationships of the external pterygoid plate with the other components of the craniofacial building has hardly been explored because of recording difficulties. A method to accurately identify in a reproducible way the main axis of the pterygoid process with the help of two small iron balls was contrasted with other methods seen in the literature. The iron balls technique was shown to be the method of choice with regard to biostatistical consistency.

Adult↗