Cation transport and cochlear function.
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Adenosine Triphosphatases↗
Biomedical subjects
W Kuijpers
Publications and source records attributed to W Kuijpers.
Biological considerations for the use of homograft tympanic membranes and ossicles.
This report deals with some biological aspects of transplantation and preservation of tympanic membrane and ossicular grafts. The structure and behaviour of tympanic membrane grafts depends largely on the reaction of the preservatives with the tissue proteins. Due to these properties no observable change in the microscopical structure of the membranes and ossicles was found up to 3 years after alcohol and formaldehyde preservation. Preservation in cialit showed gradual disappearance of nuclei and an increasing disintegration of the fibrous structures. Irrespective of the mode of preservation, the fibrous tissue appeared to persist virtually unaffected for long periods. The monocellular reaction found around the grafts preserved in formaldehyde after heterolopie transplantation suggests that tissue antigens are not completely destroyed. A reaction to transplantation in the middle ear is only found around fresh heterologous grafts and around the fresh homologous grafts after previous sensitisation. As observed in rats, ossicles preserved in alcohol or cialit, obtained from revision operations in humans showed partial remodelling. Moreover in some cases these ossicular and especially the cartilaginous grafts showed areas of frank erosion.
Animals↗
Dentine as an ossicular substitute. Experimental results in animals.
The fate of dentine grafts of autogenous, allogeneic and xenogeneic origin has been studied in rats both in muscle and in the middle ear. The dentine has been implanted fresh, autoclaved, Cialit-preserved and demineralised. Xenogeneic material tends to extrude from the ear and not to form a functional union with the structures it contacts. Fresh or Cialit-preserved, autogenous or allogeneic material, eventually stimulate new bone formation and usually become incorporated into the host ossicular chain; however, continuing resorptive activity is present. Autoclaved material does not result in new bone formation; demineralised allogeneic material stimulates very active new bone formation in the ossicular chain. It is concluded that non-demineralised dentine, on account of resorption, is inferior to ossicular grafts as a tympanoplastic material. Demineralised dentine, by virtue of its bone-inductive potential, may be of value in tympanoplasty.
Animals↗
Epithelial migration on the tympanic membrane. An experimental study.
The existence of an epidermal migration pattern was studied in mice using a whole-mount autoradiographical technique. The mitotic activity appeared to be confined to an area close to the annulus tympanicus. A very slow migratory activity of the labelled cells, was observed, situated in the basal cell layer. Perforation of the tympanic membrane showed no effect on the position of the labelled cells. This slow migration described by several authors. The latter migration was suggested to represent a mechanism for cleaning the tympanic membrane.
Animals↗
The effect of experimental tubal obstruction on the middle ear. Preliminary report.
The rat was used as a model for studying the effect of tubal obstruction on the middle ear. Animals raised under conventional conditions, SPF- and germ-free animals were used. The predominant findings were: (1) Tubal occlusion causes an effusion of serous fluid into the middle ear cavity and promotes the pathological behaviour of pathogen and non-pathogen symbionts of the middle ear cavity. (2) The germ-free animal is an excellent model for studying the isolated effect of tubal obstruction without the interference of infectious disease. (3) The middle ear reacts towards tubal obstruction by a tendency to resorb and to organize the fluid by phagocytosis and fibrosis of the cavity. Transformation of the epithelium into mucus-producing cells was observed only in those animals which developed a middle ear infection after occlusion. (4) The final result shows a near-totally obliterated middle ear cavity resembling the atelectatic middle ear in humans.
Animals↗
Flash-induced nystagmus (FIN) and the vestibular system in the rabbit.
Flash-induced nystagmus (FIN) was found more often in albino than in pigmented rabbits. Incremental and decremental phase mainly showed exponential change in SPV, but linear change was seen as well with apparent time constant of 5-40 sec. FIN was unaltered by rendering the stimulated eye akinetic. Lesioning the nucleus of the optic tract (NOT) on one side abolished FIN and OKN responses from the other side. Bilateral labyrinthectomy led to a diminished response and after-responses were lost. Algebraic addition was shown if FIN was combined with vestibular reflex eye movements. The gain of these reflexes was enhanced. FIN may be specified as a type of nystagmus that is evoked by monocular essentially open-loop stimulation of the crossed ('subcortical') optic pathway. Direction-selective elements in the retina may play a specific role in that their predominant orientation gives rise to abduction nystagmus during on/off stimulation by flashes.
Animals↗
Secretory characteristics of the rat nasal glands.
The distribution of the secretory elements in the nasal mucosa and the nature of their secretory products were studied with the use of light- and electronmicroscopical techniques and radioisotopes. Unicellular glands showed a varying density at different sites of the nasal cavity and their distribution appeared to depend on environmental conditions. In contrast to the human nose, the multicellular glands are concentrated in two large glandular masses, which appeared to consist of various glands. They differed in producing either a glycoprotein or a nonglycoprotein containing secretion, in the character of the secretory granules and in the nature of the glycoproteins. The secretions are drained at different sites in the nasal cavity. Uptake and release of radioisotopes suggest a rather high activity of the glandular tissue.
Animals↗
The vestibular functions of the manganese-deficient rat.
Vestibular functions were examined in 25 animals of the second generation of rats raised on a manganese-deficient diet; 9 animals appeared to be normal and 16 showed behavioural abnormalities, characterized by inability to swim and lack of tonic eye deviations. The nystagmic responses elicited by rotatory stimulation appeared to be normal. Histological studies showed that the only defect was the absence of both utricular and saccular otoconia. These rats' swimming disability was similar to that of bilabyrinthectomized rats in normogravic condition and to that of normal rats immersed in water during weightlessness. It is concluded that the observed anomalies must be attributed solely to the lack of normal otolith function.
Animals↗
Epithelial reactions to hydroxyapatite. An in vivo and in vitro study.
The intention of this study was to investigate the epithelial reactions to hydroxyapatite ceramic in vivo and in vitro. Shortly after implantation in the rat middle ear, hydroxyapatite was found covered by a mucosal layer. In the early postoperative period the implant was almost completely covered by epithelial cells, which were found to proliferate and also showed migratory activity. After longer intervals the implant was completely covered by epithelium, which was composed predominantly of flat polygonal cells and a relatively small number of ciliated epithelium and goblet cells. All cells showed normal morphology. In vitro experiments showed preservation of the morphology of rat middle-ear mucosa explants with good outgrowth of epithelial cells. In these outgrows, the majority of the cells were flat polygonal, but ciliated epithelium was also seen. No difference was found between the absence and presence of hydroxyapatite. Serially cultured cells displayed normal polygonal morphology, but no ciliated cells were found. Ciliated cells were also absent in control experiments without hydroxyapatite. Growth curves obtained in the absence and presence of hydroxyapatite did not differ significantly from each other.
Animals↗
An experimental model for tympanosclerosis. A preliminary report.
This study deals with an animal model where tympanosclerosis could be evoked with high reproducibility during the course of a sterile otitis media, induced by Eustachian tube obstruction. The histopathological features of this induced lesion were very similar to those reported in human specimens. It was concluded that this process is most probably triggered by a mechanical deformation of the tympanic membrane.
Animals↗
Chemosensitivity testing of xenografted squamous cell carcinomas of the head and neck region.
Eight squamous cell carcinomas from the head and neck region were established as xenograft lines in nude mice and tested for their sensitivity to the antineoplastic drugs bleomycin and cisplatin. Tumor volume, histology, DNA flow cytometry and mitotic activity were used as parameters. One out of the 8 tumours appeared to be highly sensitive to bleomycin, while three other tumours were sensitive to both bleomycin and cisplatin. These observations are in good correlation with the reported data in patients. All chemosensitive tumours showed regrowth after the cytotoxic drug treatment had been completed. No change was seen in the chemosensitivity of other features of the regrown tumours, not even after repeated exposure to the drugs. Comparison of the tumour volume with the other parameters applied indicated that the tumour volume of squamous cell carcinomas was not always a reliable parameter for testing chemosensitivity, because of the important contribution of keratin to the tumour volume. It is concluded that additional parameters such as histological examination, DNA flow cytometry or mitotic activity are necessary in order to draw reliable conclusion on xenografts with a large avital component. In addition, DNA flow cytometry has proved to be very useful for the rapid screening of drug sensitivity.
Animals↗
DNA--cytometric studies on xenografts of squamous cell carcinomas of the head and neck.
The primary tumors of four human head and neck carcinomas and their xenografts in nude mice were analysed with respect to their histological features and DNA-ploidy level using DNA-flow and DNA-image cytometry. The histological characteristics of the xenografts and the DNA-index did not differ from those of the parent tumors, whereas the growth rate remained unchanged during serial passaging. DNA-flow cytometric analysis revealed the presence of both aneuploid and euploid cells in both parent tumors and their xenografts. During passaging the proportion of aneuploid cells increased. Analysis of the different cell populations by DNA-image cytometry revealed the presence of aneuploid tumor cells and euploid host cells. This study demonstrates that the characteristics of the original tumors in terms of histological features and DNA-ploidy are retained after xenografting.
Animals↗
In vitro chemosensitivity testing of squamous cell carcinoma of the head and neck. A preliminary report.
This study deals with in vitro chemosensitivity testing of squamous cell carcinoma of the head and neck by measuring the drug-induced inhibition of [3H]thymidine incorporation. Cell suspensions and tumour slices obtained from four human tumour xenografts were used. These were grown in nude mice and tested in this animal for their sensitivity to bleomycin and cis-platinum. No reliable data could be obtained with the use of cell suspensions because of the rapid decrease in cell viability during incubation. The incubation of 400-microns-thick tumour slices using hyperbaric O2 revealed a stable control level of [3H]thymidine incorporation which persisted for more than 24 h. Cytotoxic drugs only demonstrated a significant and reproducible decrease in the incorporation of [3H]thymidine in those tumours which were found to be sensitive to these drugs in nude mice. This technique seems to be very promising but needs further evaluation of its application on tumour specimens obtained directly from patients.
Animals↗
Cytotoxic drug sensitivity of squamous cell carcinoma as predicted by an in vitro testing model.
An in vitro technique for testing the chemosensitivity of squamous cell carcinoma from the head and neck is described. Single-cell suspensions and tumor slices obtained from human xenografts were used. The sensitivity to cisplatin and bleomycin was quantified using the incorporation of (3H) thymidine as a parameter. The in vitro assays were compared with in vivo tests in mice. No reliable data could be obtained with cell suspensions of these tumors due to a rapid decrease in cell viability during incubation, while tumor slices revealed a stable control level of (3H) thymidine incorporation for up to 30 hours. In 6 out of 7 cases close agreement was found between the effect of the cytotoxic drug on the tissue slices and on the same tumors in nude mice.
Animals↗