Demonstration of the Fine Structure of Stereocilia in the Organ of Corti of the Guinea Pig by Field Emission Scanning Electron Microscopy

A combined perfusion- and immersion prefixation with glutaraldehyde followed by a tannic acid/arginine/osmium tetroxide (TAO) treatment of the guinea pig cochlea is described for field-emission gun scanning electron microscopy (FEG-SEM) observation of the fine structure of the stereocilia of the organ of Corti. Conventional osmium tetroxide postfixation methods in combination with a thin conductive coating failed to show the fine structure of the glycocalyx of the epithelial lining in the endolymphatic compartment of the cochlea, in particular, on the stereocilia surface. The antennulae-like glycocalyx covering of the stereocilia surface of the more pronounced rows of outer hair cells has been demonstrated only in ultrathin sections by means of cationic markers. The side- and tip-links connecting the stereocilia have been demonstrated both in scanning and transmission electron microscopy, although at that time these structures often were considered as artificial. However, they can be visualized with FEG-SEM at low accelerating voltage (2-3 kV), and at appropriate working distance and probe current, in combination with a glutaraldehyde perfusion/immersion prefixation and TAO postfixation. Stereo images enhance considerably the three-dimensional appreciation of the stereocilia with glycocalyx lining and side- and tip-links, proving that these connections are a structural part of the hair cell

Loss of ubiquitin E2 Ube2w rescues hypersensitivity of Rnf4 mutant cells to DNA damage

SUMO and ubiquitin play important roles in the response of cells to DNA damage. These pathways are linked by the SUMO Targeted ubiquitin Ligase Rnf4 that catalyses transfer of ubiquitin from a ubiquitin loaded E2 conjugating enzyme to a polySUMO modified substrate. Rnf4 can functionally interact with multiple E2s, including Ube2w, in vitro. Chicken cells lacking Rnf4 are hypersensitive to hyroxyurea, DNA alkylating drugs and DNA crosslinking agents, but this sensitivity is suppressed by simultaneous depletion of Ube2w. Cells depleted of Ube2w alone are not hypersensitive to the same DNA damaging agents. Similar results were also obtained in human cells. These data indicate that Ube2w does not have an essential role in the DNA damage response, but is deleterious in the absence of Rnf4. Thus, although Rnf4 and Ube2w functionally interact in vitro, our genetic experiments indicate that in response to DNA damage Ube2w and Rnf4 function in distinct pathways

Bolaang Mongondowsch-Nederlandsch woordenboek, met Nederlandsch-Bolaang Mongondowsch register

xii, 635 p.; 231/2 cm

Two-phaseEndolymphatic hydrops : a dynamic model for maniere's disease

+163hlm.;23c

Two-phase endolymphatic hydrops:a dynamic model for Menière's disease

In 1861, Prosper Menière described the classical triadic symptomatology of hearing loss, vertigo and tinnitus, which he attributed for the first time to a labyrinthine disorder. The underlying pathophysiology of this disabling inner ear disease was not known, but since Hallpike and Cairns, and also Yamakawa in 1938 discovered hydrops of the endolymphatic system in the temporal bones of patients with Menière’s disease, endolymphatic hydrops has been generally accepted as the basic histopathological substrate of Menière’s disease. Endolymphatic hydrops may arise as a result of the destabilization of natural regulation through overproduction of endolymph and/or reduced absorption of endolymph. Total destruction of the endolymphatic sac, which is considered to be responsible for the absorption of endolymph, and obliteration of the vestibular aqueduct, resulted in endolymphatic hydrops in the guinea pig, and has been established as the classical guinea pig model for Menière’s disease (Kimura, 1965). However, obliteration of the vestibular aqueduct is regarded as a non-physiological model for Menière’s disease. In patients with Menière’s disease, endolymphatic sac tissue still remains present, although the size of the endolymphatic sac is reduced, suggesting a reduction in resorptive capacity. The production of endolymph is thought to be regulated by Na/K-ATPase in the marginal cells of the stria vascularis of the cochlea, as well as in the dark cells of the utricle and the cristae ampullares of the semicircular canals. In recent experiments, a relationship between circulating adrenal steroids and Na/K-ATPase activity in the inner ear was observed. Emotional stress leads to the activation of neuroendocrine effector systems, including the production of adrenal steroids such as aldosterone, and could thus increase the production of endolymph. A borderline capacity of the ES, in combination with a periodic increase of endolymph production caused by stressful situations may be responsible for the development of Menière’s disease. Indeed, manifestations of Menière’s disease frequently occur during stressful experiences in patients with physiological systems under challenge due to a neurasthenic psychological profile. We developed the two-phase endolymphatic hydrops model in guinea pigs which was based on two compromising fators; mild chronic endolymphatic sac dysfunction has been established by dissection of the distal part of the endolymphatic sac from the sigmoid sinus, in combination with periodic increase of endolymph production by stimulation of the Na/K-ATPase pumps in the stria vascularis by administration of aldosterone. This model, which seemed to represent a functional model combining multiple etiologies, and may resemble the fluctuant characteristics of Menière’s disease.

Experimental and modeling study of subsea releases of oil and gas. - Oil behavior and effects in a cold or Arctic marine environment as a function of release conditions, oil chemistry and dispersant injection.

Abstract With oil exploration going into deeper waters and more extreme environments, more detailed knowledge is needed about the fate of oil in case of a release. This thesis focuses on initial droplet formation, secondary breakup and fate of oil in a subsurface release and the effect of subsurface injection of dispersants. The objectives were to study initial droplet formation, the effectiveness of different surfactant blends when injected in warm oil, secondary droplet breakup and to model hypothetical oil releases in the Barents Sea. The effectiveness of tested surfactant combinations increased when the temperature of Troll B oil increased. However, a decrease was observed when the commercially available dispersant Corexit 9500A was injected in Kobbe oil at increasing temperatures. This observed change in behavior and effectivity could be related to surfactant and/or oil chemistry. The secondary breakup mechanism tip-streaming, where small droplets shed of the parent droplet due to deformation after surfactant treatment, has been studied and observed to be finished within 10 minutes after the release at different dispersant-to-oil ratios. After one hour in very turbulent conditions, the droplets were stable and spherical in shape. Simulations with the OSCAR model have shown how a reduction in droplet size due to dispersant injection can change the environmental fate of the released oil. Further research could be of interest to see whether the change in dispersant effectiveness is a result of oil or surfactant chemistry and to study tip-streaming at higher oil temperatures