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Biomedical subjects

K Jahnke

Publications and source records attributed to K Jahnke.

At least 127 records · Page 7Linked to original sources
PubMed1981

[Obliteration of the mastoid air cell system with porous tricalcium phosphate ceramic. An animal experiment of the bulla tympanica of the pig (author's transl)].

The paper reports on an animal experiment on the obliteration of mastoid cavities with tricalcium phosphate ceramic. The pneumatic air cell system of the bulla tympanica of pigs of 11-12 weeks of age was totally removed in one group of animals and partially removed in the second group. In this second group, apical part of the bulla was left intact. The operation cavity was then obliterated with adjacent layers of porous tricalcium phosphate ceramic. Histological sections wee evaluated for both groups of animals after survival time of 1, 3 and 6 months. Initially, an ingrowth of granulated tissue between the ceramic layers and into the porous surface can be observed. This dissolves the ceramic material, which is substituted by bony tissue. Pneumatic cells in the apical part of the bulla, which were left intact in the second group of animals, do not obliterate after the air supply has been cut off by sealing the basal part. Cystic cavities remain which contain a serous exudate. After 6 months, the mucous membrane of such cells shows signs of "sclerosis". Formation of spongy bony tissue with marrow spaces can be seen in most of the apical areas of the growing bulla. There is no formation of air-containing cells. It appears from our preliminary results obtained from animal experiments that porous tricalcium phosphate ceramic may be a suitable material for the obliteration of mastoid cavities.

Animals↗
PubMed1980

[Permeability barriers of the inner ear. Fine structure and function].

This paper summarizes the own electronmicroscopic studies on the inner ear fine structure (guinea pig) with the peroxidase tracer technique and mainly with the freeze-etch-technique. New findings are presented concerning the blood-perilymph-barrier, perilymph-endolymph-barrier as well as cell membrane differentiations of the stria vacularis cells and the sensory epithelia. The physiological and pathophysiological meaning is discussed in detail.

Animals↗
PubMed1980

The fine structure of the cochlear plexus.

Ultrathin sections and freeze-fracture replicas of the guinea pig cochlear plexus were studied under the electron microscope. Generally, the capillaries possess a continuous endothelial cell layer. The endothelial cells are connected by tight junctions. Occasionally, fenestrated capillaries can be found. Nonmyelinated nerves are intimately related to smooth muscle cells of arterioles as well as pericytes and endothelial cells of capillaries. The axonal varicosities contain clear synaptic-type vesicles. The cochlear plexus cells are connected by desmosomes, gap junctions, and tight junctions. The latter are thought to be part of the blood-perilymph-barrier in this region. There is evidence that the cochlear plexus derives from the meninges.

Animals↗
PubMed1980

The blood-perilymph barrier.

Freeze fracture replicas of the guinea pig inner ear were studied under the electron microscope to define the blood-perilymph barrier morphologically. This barrier is represented basically by the continuous endothelium of the inner ear capillaries. The endothelial cells contain only a few micropinocytotic vesicles in contrast to those of the stria vascularis vessels. The cochlear plexus also exhibits some special differences. Tight junctions of the continuous mesothelial type connect the endothelial cells of the inner ear capillaries. Cell membranes of these cells possess a lower particle density than those of the stria vascularis vessels. In general, the blood-perilymph barrier is morphologically similar to the blood-brain barrier.

Animals↗
PubMed1980

[Reconstruction of the frontal base with ceramic materials (author's transl)].

Frontal base reconstruction presents significant problems, expecially during initial handling of injuries involving comminuted fractures. The main goal is the immediate application of effective surgical techniques to reestablish a functonally and aesthetically acceptable state with a minimum of additional stress to the patient, who is usually in a polytraumtic, critical condition. The use of ceramic in such situations offers several particularly advantageous features: a) There is no additional surgical stress from obtaining autogenic transplants. b) The ceramic exhibits excellent biocompatibility. c) It can be utilized during surgery in areas compromised by septic exposure.-Our first clinical experiences and preliminary results are described.

Adolescent↗
PubMed1980

[Ceramic implants in middle ear surgery (author's transl)].

Several different ceramic materials have recently been used in middle ear surgery: bio-inert aluminum oxide, bio-active glass and bio-active tri- and tetra-calcium phosphate. We have compared these materials with regard to their physical properties as well as various characteristic biological reactions when used in implantation. All of these materials were found to exhibit excellent biocompatibility. Other advantages relate to specific applications of the material and depend on the particular qualities of the individual ceramic. However, we conclude that caution is needed against the uncritical application of these materials in middle ear surgery and consider some still open question for their use.

Animals↗
PubMed1979

Freeze-fracture study of taste bud pores in the foliate papillae of the rabbit.

In freeze-fractured specimens of taste buds from the foliate papillae of rabbits, the intercellular spaces are separated from the pore of the taste bud by zonulae occludentes of the "tight-type". Below these tight junctions numerous desmosomes are found at irregular intervals. The epithelial cells adjacent to the pore are also joined by single strands of fusion. The microvilli arising from the neck of the type I cells have a high particle density. The microvilli of type II cells and especially the short microvilli of peripherally situated cells have a lower intramembranous particle density. The single microvillus of type III cells has a very large diameter and is longer than the other microvilli. It contains a few larger intramembranous particles and vesicle-like protrusions of the membrane facing the cytoplasm. Transverse fracturing reveals a filamentous fine structure in all microvilli. The physiological implications of these observations are discussed.

Animals↗
PubMed1979

[Carotid body and glomus vagale tumours (author's transl)].

Twentyfour chemodectomas (non-chromaffin paragangliomas) of the neck seen in 20 patients are presented. The investigation including angiography and the surgery in respect to risk factors and preoperative assessment is discussed. The long term results are also presented. Special note is made of the familial incidence since two twin brothers who had bilateral tumours are included.

Adolescent↗
PubMed1979

[Hypacusis in acquired hypothyroidism (author's transl)].

We examined 56 patients with latent or clinical hypothyroidism and a control group of 18 patients with acute hypothyroidism. We were especially interested in the localization and extent of hearing abnormalities. 45% of the patients with chronic hypothyroidism showed a hearing loss. 2 of these patients had a pure conductive loss, 7 a combined hearing loss and 16 a sensorineural hearing loss. We demonstrated hair cell damage in 13 of the patients with chronic hypothyroidism. This loss was mild to moderate in over 90% of the cases. Although several patients had basilar-cochlear hearing losses, no characteristic audiograms could be found. 50% of the patients showed a small improvement in hearing after thyroid substitution therapy. The results of our examinations are discussed in detail.

Adolescent↗
PubMed1978

[Hypacusis in acquired hypothyroidism (author's transl)].

We examined 56 patients with latent or clinically manifest hypothyroidism and 18 patients with acute athyreosis as a control group. We were especially interested in the localization and extent of hearing abnormalities. 45% of the patients with chronic hypothyroidism showed a hearing loss. Of these, two patients had a pure conductive loss, seven a combined hearing loss and 16 a sensori-neural hearing loss. We demonstrated hair cell damage in 13 of the patients with chronic hypothyroidism. The hearing loss was mild to moderate in over 90% of the cases. Although several patients had a basocochlear hearing loss, no characteristic audiogram was found. There was a correlation between the conductive loss and the severity of the hypothyroidism. 50% of the patients showed a significant improvement in hearing after substitution therapy. The results of our examinations are discussed in detail.

Adolescent↗
PubMed1977

[The pathogenesis of the acute symptoms of Menière's disease (author's transl)].

The pathogenesis of vertigo attacks and hearing fluctuations in Menière's disease is discussed on the basis of new electronmicroscopic observations on the perilymph endolymph barrier. The zonulae occludentes (z.o.) of the epithelial cells lining the endolymphatic space are the main sealing elements which control the passive ion transport. They consist of parallel running intramembranous fibrils (cell membrane fusion lines). Recent investigations demonstrated conditions which partially destruct some of such fibrils (e.g. increased osmotic pressure, endocrine disorders). This also may be true in Menière's attacks: tight z.o. are transformed to leaky z.o. such that a high transepithelial ion exchange developes. This would result in reduced generation of the receptor potentials as well as in decreased activities of the first order afferent neurons as it was supposed earlier by other authors. This mechanism may be combined with a decompensation of active ion transport processes due to microcirculation disturbances. Finally it will be pointed out that true ruptures of the endolymphatic walls cannot be the usual mode of reversible lesions in Menières disease but a diffuse leakage of the perilymph-endolymph barrier.

Acute Disease↗
PubMed1976

[Regeneration capacity of B-cell function in obese diabetics after weight reduction (author's transl)].

Glucose and tolbutamide-stimulated endogenous insulin secretion were measured in 12 patients with partial B-cell insufficiency (diabetes of the adult type) before and after dietary weight reduction (average reduction 6.7 kg = 8.1% of average initial weight). In three patients there was complete restoration of normal B-cell function with complete remission of the diabetes, in four there was incomplete regeneration of endogenous insulin secretion and of effective insulin reserve. In five patients with less weight reduction there was no response. The mechanism of B-cell function regeneration remains unknown. But weight reduction must be considered as causal treatment in maturity-onset diabetes associated with obesity.

Adult↗