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Biomedical subjects

W Kuijpers

Publications and source records attributed to W Kuijpers.

At least 55 records · Page 3Linked to original sources
PubMed1986

Experimental endolymphatic hydrops in the rat.

In the rat, the epithelial lining of the endolymphatic duct and sac, and the contents of the sac, showed remarkable differences in comparison with these structures in the guinea pig and man. Obliteration of the endolymphatic duct resulted in endolymphatic hydrops of varying severity in 55% of the rats, after survival times varying from one to five months. The presence of a positive periodic acid-Schiff-stain for coagulum accumulating in the endolymphatic duct after prolonged saccus obliteration suggests active involvement of the endolymphatic duct in the migration of endolymph toward the endolymphatic sac.

Animals↗
PubMed1986

Cholinergic receptors in the upper respiratory system of the rat.

Radioligand receptor binding might give more detailed information on the innervation pattern of the nasal mucosa and the character of the various neuroreceptors involved. With respect to the cholinergic receptors, this technique reveals that specific binding of tritiated I-quinuclidinyl benzilate to rat nasal mucosa homogenates occurs to a homogeneous class of binding sites, with a dissociation constant of 0.06 +/- 0.02 nM and a receptor density of 8 +/- 2 pmole/g of tissue. Binding is stereoselectively inhibited by benzetimide hydrochloride enantiomers. Pirenzepine displacement (inhibition constant = 0.5 X 10(-6) M) classifies tritiated I-quinuclidinyl benzilate binding sites as M2-muscarinic receptors. Methylfurthrethonium inhibits tritiated I-quinuclidinyl benzilate binding at high concentrations, pointing to the presence of low-affinity agonist binding sites, probably admixed with a small proportion of high-affinity agonist binding sites. These data obtained in the rat open new perspectives for studying muscarinic receptors in the human nose to elucidate the supposed disturbance of autonomic nerve regulation in nasal hyperreactivity.

Animals↗
PubMed1986

The biological performance of calcium phosphate ceramics in an infected implantation site: I. Biological performance of hydroxyapatite during Staphylococcus aureus infection.

In the present study the biological performance of macroporous and dense hydroxyapatite after implantation in the rat middle ear was evaluated during an induced Staphylococcus aureus middle ear infection. The course of the infection was similar to that in the absence of an implant. Hydroxyapatite was frequently integrated with fibrous ingrowths in the middle ear lumen, originating solely from the infection. Good epithelial covering of the implant with all types of epithelial cells of importance for middle ear defence, was found. Increase of the exudate in the pores due to the infection was relatively small, and most of the exudate was restricted to pores on the implant surface. The bony tissue in the pores was not influenced significantly by the induced infection. Degradation of hydroxyapatite was consistent with earlier results obtained in the non-infected middle ear. The results obtained so far suggest that hydroxyapatite is highly suitable for middle ear implantation.

Animals↗
PubMed1986

The biological performance of calcium phosphate ceramics in an infected implantation site. III: Biological performance of beta-whitlockite in the noninfected and infected rat middle ear.

The biological performance of macroporous beta-whitlockite implanted in the rat middle ear was evaluated. The material was studied in the non-infected middle ear and in middle ears infected by Staphylococcus aureus. beta-whitlockite was quickly covered by a normal mucosa. One week post-operatively the macropores were filled with exudate, fibrous tissue, and a small quantity of bone. Six months after the operation the greater part of the macropore area was filled with bone (74%); fibrous tissue accounted for 20%, and exudate for 5%. In histological sections, the macropore area of beta-whitlockite had increased by 68% after six months, indicating biodegradation. Macrophages and multinucleated cells were present in the vicinity of the implant and played a role in this biodegradation. Besides cytoplasmic vacuoles containing calcium phosphate, the cells showed smaller granules containing trace elements originally present in the implant material, such as silicon, titanium, aluminum, iron, and magnesium.

Animals↗
PubMed1986

The secretory activity of rat nasal glands and the effect of cholinergic drugs.

The secretory behaviour of rat nasal glands, under normal conditions and after the application of cholinergic drugs, has been studied using morphological and radiobiochemical techniques. Autoradiography and electrophoresis provide evidence for the selective incorporation of 3H-arginine into the glycoprotein-containing fraction of the nasal glandular secretion. Radiobiochemical experiments show that labelled arginine is rapidly incorporated into the acinar cells of unstimulated glands, although it takes approximately 4 h before the labelled secretory proteins leave the cells. The secretion of proteins is stimulated by the parasympathetic agonist pilocarpine, whose main action is to promote discharge. Histological sections show a depletion of secretory granules after pilocarpine treatment. The cholinergic antagonist atropine inhibits the secretion; the acinar cells are completely filled with secretory granules following this treatment. The time course of the events following atropine administration suggests that there is no feed-back system controlling glycoprotein synthesis. The techniques employed here therefore appear to be useful for studying the effects of drugs that interfere with the secretory activity of the nasal glands.

Animals↗
PubMed1986

Macropore tissue ingrowth: a quantitative and qualitative study on hydroxyapatite ceramic.

The aim of this study was to obtain more information about macropore tissue ingrowth into the pores of sintered hydroxyapatite implanted in the rat middle ear, for the assessment of the usefulness of this material in reconstructive middle-ear surgery. The exudate filing the pores during the early post-operative period was gradually replaced by equal amounts of fibrous tissue and bone. The percentage of the macropore area occupied by bone was directly correlated with the macropore size. Bone was deposited not only from the pore wall towards the pore centre, but also in the opposite direction. Bonding osteogenesis was demonstrated. At sites of mechanical irritation, the presence of multinucleated cells and proliferatively active mononuclear phagocytes persisted for as long as a year. Under appropriate conditions hydroxyapatite seems to be a promising material for bone substitution in reconstructive middle-ear surgery.

Animals↗
PubMed1986

Growth characteristics of head and neck squamous cell carcinoma in nude mice.

Growth behaviour of human squamous cell carcinoma from the head and neck region was studied in nude mice. Tumour growth was observed in 10 out of 13 tumours transplanted with a primary take rate of 77 and 100% for serial passaging. The take rate percentage related to the number of tumour inocula used, varied from 10 to 90% in the first passage and from 70 to 100% in the subsequent passages. No significant difference could be established in the growth character, except from the first to the second passage. Histological studies demonstrated preservation of the original histopathological features, micro- and macroinvasion of two tumour lines into the fibrous capsule and cyst formation. Comparison of growth curves with histological features demonstrated that growth curves are not a reliable measure for the number of vital tumour cells present.

Animals↗
PubMed1986

Developmental aspects of glycoprotein secretion and migration in the endolymphatic space.

Secretion and migration of sulphated glycoproteins during the early postnatal development of the rat inner ear was studied autoradiographically with the use of 35SO4. This isotope was found to be selectively incorporated into the embryonal sulcus cells and subsequently expelled into the tectorial membrane. This process decreased simultaneously with the replacement of the tall sulcus cells by cuboidal cells and the detachment of the tectorial membrane from these cells. A two stage development of the tectorial membrane is postulated: formation of filaments followed by incorporation of glycoproteins. Incorporation of isotope was also observed in the sensory epithelium of the vestibular part of the labyrinth, followed by migration into the cupulae and otolithic membranes. The accumulation of labelled material in the lumen of the endolymphatic sac 6 hours after isotope administration, suggests the existence of endolymph flow towards the endolymphatic sac in the early postnatal period.

Animals↗
PubMed1985

Muscarinic receptors in rat nasal mucosa are predominantly of the low affinity agonist type.

Specific [3H]l-quinuclidinyl benzilate binding to rat nasal mucosa homogenates occurs to a homogeneous class of binding sites with Kd = 60 +/- 2 10(-12) M and Bmax = 8.1 +/- 2 pmol/g tissue. Binding is stereoselectively inhibited by benzetimide enantiomers. Pirenzepine inhibits [3H]l-quinuclidinyl benzilate binding with low affinity (Ki = 5.0 10(-7) M), classifying the binding sites as muscarinic M2-receptors. Methylfurtrethonium and methacholine inhibit [3H]l-quinuclidinyl benzilate binding following an almost sigmoid curve at high concentrations pointing to the presence of mainly low affinity agonist binding sites.

Animals↗
PubMed1985

Proximal symphalangia and stapes ankylosis.

A father and his two sons had an autosomal-dominant syndrome of proximal symphalangia and conductive hearing loss. Exploratory tympanotomy revealed a congenitally fixed stapes and incus in the oldest boy. Surgical intervention resulted in normal hearing. To our knowledge, this is the first such histologic report of a stapes in this syndrome.

Adolescent↗
PubMed1985

The influence of neuropharmaca on the nasal glands. Preliminary report.

Contributions from various sources to the nasal fluid are a serious complicating factor for investigating the isolated role of the nasal glands in the production of this fluid. This study is an attempt to obtain a better insight in the secretory behaviour of the nasal glands and its neural regulation. Radioligand binding strongly suggests that rat nasal glands contain muscarinic receptors. Parasympathomimetic drugs mainly promote the discharge of the secretory proteins from the glandular cells. However, histological sections do not show any change in the number of secretory granules after parasympatholytic drug application. These observations refer to a complex nature of the parasympathetic regulation of the glandular secretory activity.

Animals↗
PubMed1984

The structure of the middle ear epithelium of the rat and the effect of Eustachian tube obstruction.

The middle ear cavity of the rat is lined with ciliated and squamous epithelium. The arrangement of the ciliated cells, interspersed with secretory cells, in distinct tracts and their continuity with the ciliated epithelium of the Eustachian tube, suggests the existence of a mucociliary transport system for cleaning the middle ear cleft. The secretory cells produce either neutral or sulphated glycoproteins, dependent on their location. In addition to these secretions, the epithelium of the lower part of the Eustachian tube is bathed with secretory products of seromucous glands. Also in the areas with squamous epithelium, numerous small secretory cells, the character of which is only identifiable with the electronmicroscope, are present. It is concluded that the middle ear lining can be considered as a locally modified respiratory epithelium. Blockade of the mucociliary transport system, supposedly a crucial aetiological factor in secretory otitis media, by obstruction of the Eustachian tube, induces pathogenic behaviour of microorganisms normally present in the middle ear. This results in either a transient or a longstanding infective middle ear disease, associated with a large variety of changes of the mucosa, especially with respect to the secretory activity. The data obtained indicate that the increased secretory activity encountered in secretory otitis media cannot be attributed to the isolated effect of tubal occlusion, but rather to an infective process.

Animals↗
PubMed1984

The mucoperiosteum of the middle ear in experimentally induced sterile otitis media.

The effect of Eustachian tube obstruction has been studied in germ-free rats. This model proved to be a reliable approach by which to study the isolated effect of tubal occlusion without the interference of infection. The effects on the middle ear structures are characterized mainly by stratification and hyperplasia of the epithelium, a transient increase in the periosteal activity, tympanosclerotic-like changes and accumulation of cholesterol in the middle ear fluid. No increase in the number of secretory elements could be registered during an observation period of 2 years.

Animals↗
PubMed1983

Effect of tubal occlusion on bone formation in the middle ear of the rat.

The effect of experimental occlusion of the Eustachian tube in rats have been studied. Only in germ-free animals it has been possible to eliminate infection as a complicating factor. The formation of new bone in the wall of middle ear and bulla was apparent soon after occlusion, even in the absence of infection. These findings suggest that tubal occlusion causing serous otitis media can lead to extensive changes in the bone lining the middle ear cavity and this could explain the condensation of bone found in ears without any apparent sign of infection.

Animals↗