15 research outputs found
Osmotic blistering in enamel bonded with one-step self-etch adhesives
One-step self-etch adhesives behave as permeable membranes after polymerization, permitting water to move through the cured adhesives. We hypothesize that osmotic blistering occurs in bonded enamel when these adhesives are used without composite coupling. Tooth surfaces from extracted human premolars were bonded with 5 one-step self-etch adhesives. They were immersed in distilled water or 4.8 M CaCl2, and examined by stereomicroscopy, field-emission/environmental SEM, and TEM. Water blisters were observed in bonded enamel but not in bonded dentin when specimens were immersed in water. They collapsed when water was subsequently replaced with CaCl2. Blisters were absent from enamel in specimens that were immersed in CaCl 2 only. Water trees were identified from adhesive-enamel interfaces. Osmotic blistering in enamel is probably caused by the low water permeability of enamel. This creates an osmotic gradient between the bonded enamel and the external environment, causing water sorption into the interface.published_or_final_versio
Bonding of some self-etch adhesives to unground enamel
Abstract no. 0027published_or_final_versio
Developmental Expression of Fos Protein in Horizontal Canal-Related Vestibular Nuclear Neurons of Postnatal Rats following Angular Acceleration
To investigate the postnatal distribution of horizontal canalrelated
neurons within the vestibular nucleus, conscious young
(1–21 days) and adult Sprague-Dawley rats were subjected to constant
angular acceleration on the horizontal plane for 60 minutes.
This stimulation paradigm, composed of alternate modes of angular
acceleration (at 50–200º/s 2 ) in the clockwise (8s) and counterclockwise
direction (8s), activates hair cells in both horizontal
canals. Neuronal activation within brainstem nuclei was defined
by the expression of Fos protein. Labyrinthectomized controls
and normal stationary controls showed only a few sporadically
scattered Fos-labeled eurons. In P1–4 rats, no Fos-labeled neurons
were found in the vestibular nucleus and prepositus hypoglossal
nucleus (PrH). In the vestibular nucleus, significant Fos
labelling was identified in the medial (MV), spinal (SpV) nuclei
and group ! subnucleus as early as P5. From P5 to P14, Fos expression
in both the MV and SpV progressively increased, reaching
an adult level at P21. In P5–7 rats, Fos-labeled neurons, though
few in number, were evenly distributed throughout the entire rostrocaudal
length of the MV and SpV. In P21 and adult rats, however,
the number of Fos-labeled neurons tended to cluster in the
caudal end of the MV and SpV. In the PrH, an area related to vestibulo-ocular functions, an age-dependent increase in the number
of Fos-labeled neurons was observed from P7 onwards. These
were mainly distributed in the rostral PrH. The present results
provide evidence that functional connectivity between canal receptors
and central vestibular neurons is established during the
first postnatal week.
Acknowledgement: Supported by HK RGC.link_to_subscribed_fulltex
Postnatal development of canal-related brainstem neurons responsive to three-dimensional rotations in rats
Conference Theme: Improving the Health of an Aging Populatio
Developmental expression of c-fos in canal-related brainstem neurons of rats following horizontal angular acceleration
Session: 392. Vestibular System: Neurophysiology of VOR and Spatial Orientation PosterTo investigate the distribution of functionally activated canal-related brainstem neurons during postnatal development, conscious Sprague-Dawley rats (P1-adult) were subjected to constant horizontal angular acceleration for 60 min. This stimulation paradigm composed of alternate modes of angular acceleration (at 150o/s2) in the clockwise (8s) and counterclockwise direction (8s), activating all hair cells of the two horizontal canals. Neuronal activation within brainstem nuclei was defined by immuno-/hybridization histochemical expression of c-fos. Labyrinthectomized controls and normal stationary controls showed only sporadic c-fos-expressing neurons. In P1-4 rats, no Fos-labeled neurons were found in the vestibular nucleus. By P5, significant Fos labeling in the medial (MV), spinal (SpV), superior (SuV) vestibular nuclei, group x and group y was identifiable. From P5-14, Fos expression increased significantly, reaching adult level at P21. In P5 rats, Fos-labeled neurons were evenly distributed throughout the entire rostrocaudal length of the MV, SpV and SuV while in adult rats Fos-labeled neurons were clustered in the caudal end of MV and SpV as well as the rostral end of SuV. In each age group, no Fos-labeling was observed in the whole lateral vestibular nucleus. In other canal-related brainstem areas such as the prepositus hypoglossal nucleus and locus coerulus, there was also an age-dependent increase in the number of Fos-labeled neurons from P5 onwards. Our findings suggest that functional connectivity between canal afferents and central vestibular neurons is established during the first postnatal week
Postnatal development of canal-related brainstem neurons responsive to vertical head rotation in rats
Developmental responsiveness of canal-related brainstem neurons to vertical head rotation
Developmental responsiveness of vestibular-related brainstem neurons to horizontal rotational and translational motions
To investigate the distribution of functionally activated vestibular-related
brainstem neurons during postnatal development,
combined immuno-/hybridization histochemistry for c-fos expression
was performed in Sprague-Dawley rats (P1–21; adult).
Conscious animals were subjected to rotational or translational
stimulus which activates hair cells on the horizontal semicircular
canals or utricle, respectively. Neuronal activation within brainstem
nuclei was defined by the expression of c-fos . Labyrinthectomized
controls and normal stationary controls showed only a few
sporadically scattered Fos-expressing neurons. During postnatal
development, Fos-labeled vestibular nuclear (VN) neurons activated
by cycles of constant angular acceleration and deceleration
were observed by P4 while those by sinusoidal translational movement
were not identifiable until P7. In both stimulation paradigms,
an age-dependent increase in Fos-labeled neurons was observed
in the VN and prepositus hypoglossal nucleus (PrH), the
latter being a downstream area related to vestibulo-oculomotor
function. In P7–9 rats, Fos-labeled neurons activated by canal or
utricle input were evenly distributed throughout the rostro-caudal
length of the VN complex (except the dorsal part of lateral VN) as
well as groups x and y. At this age, PrH neurons were only activated
with rotational stimulus and those activated with translational
stimulus were not found until P11. In P21 and adult rats, the
overlapping distribution of canal- and utricle-related Fos-labeled
neurons was limited to the middle part of medial VN and caudal
part of spinal VN. The rostral part of spinal VN was found to be
constituted with neurons activated by translational motion. In the
medial VN and PrH, a vast majority of the neurons was activated
by rotational stimulus and only a small proportion was by translational
stimulus. Taken together, we have demonstrated that canal-
and otolith-related brainstem neurons that encode horizontal
rotational and translational movements are histologically segregated
and exhibit different developmental time frame.
Acknowledgement: Supported by HKRGC.link_to_subscribed_fulltex
Functional maturation of vestibular-related brainstem neurons: Postsynaptic currents and responsiveness to horizontal rotational-/translational head movements
Maturation of canal-related brainstem neurons in the detection of horizontal angular acceleration in rats
We examined the functional maturation of canal-related brainstem neurons in Sprague-Dawley rats at postnatal day (P) 1 to adult. Conscious animals were subjected to cycles of angular acceleration and deceleration so as to selectively activate hair cells of the horizontal semicircular canals. Brainstem neurons were monitored for c-fos expression by immune-hybridization histochemistry as an indicator of neuronal activation. Fos-immunoreactive canalrelated neurons were identifiable from P4 onwards in the vestibular nucleus and downstream vestibular relay stations, propositus hypoglossal nucleus, and inferior olive. In the vestibular nucleus and prepositus hypoglossal nucleus, the number of canal-related neurons increased progressively with age, reaching the adult level by P21. Those in the inferior olive increased in number from P4to P14 but decreased significantly afterwards until adulthood. The topography was not clear in the vestibular nucleus and pre-positus hypoglossal nucleus. Canal-related neurons in P4 -7 rats were spread throughout the rostrocaudal length of each subnucleus but clusters of canal-related neurons tended to form within specific subnuclei by P21. These were concentrated in the caudal halves of medial and spinal vestibular nuclei and the rostral parts of superior vestibular nucleus and prepositus hypoglossal nucleus. In the inferior olive, the topography was evident early in the course of development. Canal-related neurons were exclusively located in four subnuclei: dorsal medial cell column, dorsal cap, subnucleus A, and subnucleus C, but not in other subnuclei. Taken together, our data revealed the developmental profile of neuronal subpopulations within the horizontal canal system, thus providing an internal neural representation for postnatal coding of horizontal head rotations in spatial perception. © 2009 Wiley-Liss, Inc.link_to_subscribed_fulltex