Biomedical subjects

M Hultcrantz

Publications and source records attributed to M Hultcrantz.

65 records · Page 4Linked to original sources

PubMedDate not supplied

Vestibular hair cell pathology following low-dose irradiation during embryonic development.

Pregnant CBA/CBA mice (total gestational age 20-21 days) were whole-body irradiated on the 12th, 13th and 16th gestational days with single doses of 1 and 2 Gy using a 60Co source. Litters were taken for morphological analysis 14-21 days after birth. Irradiation on the 12th and 13th gestational days was thus performed prior to morphologic inner ear organogenesis and cytodifferentiation. In approximately 20% of the total postnatal vestibular hair cell population cytological alterations were evident: giant cytoplasmic protrusions, sensory hair fusion and disintegration of the cuticular plate. The other parts of the hair cells remained intact, including nerve endings. Morphometry was not performed. Hair cells type I are more vulnerable to ionizing irradiation during cytodifferentiation than hair cells of type II. All investigated animals showed clinically a normal balance and a normal righting reflex.

Animals↗

PubMedDate not supplied

Malformations of vestibular organs following low dose gamma irradiation during embryonic development.

Pregnant mice were whole-body irradiated on the 12th, 13th and 16th gestational day with single doses of 0.5, 1, 2, 3, 4, 10 and 20 Gy, using a 60Co source. No surviving litters occurred in groups exposed to more than 2 Gy. Below this dose, irradiation can cause malformation of the cristae ampullares and the maculae. Malformations were more severe and more frequent in fetuses exposed on the 12th than on the 13th gestational day, indicating that, prior to or the earlier during morphogenesis irradiation takes place, the more vulnerable is the developing tissue. Inner ears exposed to irradiation on the 16th gestational day did not reveal severe malformations.

Animals↗

PubMedDate not supplied

Low-dose gamma irradiation effects on labyrinthine development in vitro.

The 13th and 16th gestational day inner ear anlagen, respectively, were exposed after explantation to an organ culture system to low-dose gamma irradiation with a 2 Gy single dose. The explants were thereafter cultured in vitro for 8 vs. 5 days to an age corresponding to birth in vivo. The explants were analysed with regard to gross morphology and at the light and electron microscopic levels. The 13th gestational day inner ear anlage showed malformations of the gross shape. The gross morphology of the 16th gestational day inner ear explant was unaffected. Irradiated specimens showed a delayed development in general as compared with controls. A defective cytodifferentiation of hair cells was observed at the ultrastructural level. Sensory hair fusion occurred, the sensory hair rootlets were poorly developed as also was the cuticle. Nerve terminals were not identified. The observations in the present in vitro study are in agreement with corresponding earlier published in vivo investigations. The organ culture model can thus be used for irradiation induced selective effects on labyrinthine development.

Animals↗

PubMedDate not supplied

The development of the endolymphatic duct and sac. A light microscopical study.

The development and maturation of the endolymphatic sac were studied in the CBA/CBA mouse. The otocyst is developed at gestational day 10 and the primitive endolymphatic sac is present as a large slit-like appendage at day 12 of gestation. At day 18 the endolymphatic sac is clearly detached from the rest of the otocyst, forming a true sac. The epithelial lining consists of only one layer of immature cells containing large vesicles. The endolymphatic sac is surrounded by a rich network of vessels. One day before birth, the epithelial lining is uneven and the first signs of differentiation into light and dark cells is visible. This situation is more pronounced 2 days post partum when the sac also seems to be filled with a stainable material. At day 6 post partum the otic capsule fuses around the sac, forming the vestibular aqueduct. At 14 days post partum the sac is mature, with clearly developed light and dark cells and widened lateral intercellular spaces, constituting the rugose epithelium. The lumen is filled with a stainable precipitate and a few free-floating cells.

Animals↗

PubMedDate not supplied

The pre- and postnatal maturation of the epithelium in the endolymphatic sac. An electron microscopic survey.

The cellular development of the endolymphatic sac was studied in the CBA/CBA mouse, starting from day 10 of gestation following the different stages of maturation up to an adult age of one month. The first immature cylindrical cells lining the future sac in several cell layers are seen at day 12 of gestation. At day 18 of gestation, a true sac appears and a floccular precipitate is frequently found in its lumen together with signs of increased activity in the still immature epithelial cells. Approximately one day before birth the first signs of the future light and dark cells can be distinguished. At day 4 post partum the cells are more differentiated with some showing signs of secretory activity indicating that these cells start to function at this stage. Eight days after birth differentiation into distinguishable almost mature light and dark cells is seen. Two days later these epithelial cells have obtained a fully mature appearance. At 14 days after birth widened lateral intercellular spaces separating the epithelial cells can be visualized and a few free floating cells are found in the sac lumen. The sac epithelium is thus considered to have completed its maturation process at this stage.

Animals↗

PubMedDate not supplied

Prenatal low-dose gamma irradiation of the inner ear induces changes in the expression of intermediate filaments.

The expression of intermediate filaments (1F) was analysed in the inner ear in normally developed adult CBA/CBA mice and in mice of the same age which had been gamma irradiated in utero with a low dose 1-2 Gy single exposure. Well characterized monoclonal antibodies (mAbs) against all classes of intermediate filament proteins (cytokeratins-Cks, vimentin, neurofilaments, desmin and glial fibrillar acidic protein) were used. With the exception of neurofilament proteins, the expression of intermediate filament proteins was the same in adult normal and irradiated inner ears, irrespective of gestational age at exposure. A complex Ck pattern occurred in the various cell types comprising the membranous labyrinth. In spite of the differences in cell shape and internal organization of organelles, epithelia actively involved in inner ear fluid homeostasis (stria vascularis, dark cell epithelium, endolymphatic duct and sac) revealed, according to our mAbs, the same expression of Cks, except for the mouse counterpart of human Ck 7, which was found exclusively in the stria vascularis and the endolymphatic duct and sac. The pattern of intermediate filament composition in the labyrinth was the same in the mouse as in man. Irradiation on gestational days 12 or 13 (the otocyst stage)--but not at more advanced embryonic age--induced immunoreactivity for neurofilament proteins in vestibular hair cells (HC) and to a minor extent also in cochlear HC. No such positivity was found in the control material.

Abnormalities, Radiation-Induced↗

PubMedDate not supplied

The influence of prenatal gamma irradiation on the ageing of the cochlea.

Pregnant CBA/Ca mice were subjected to whole-body irradiation on the 12th, 13th or 16th day of gestation with 0.5, 1 or 2 Gy, respectively. Auditory brainstem response (ABR) thresholds in the offspring at one month of age were significantly elevated. The irradiated mice were raised to an age of between 25 and 36 months. Before the animals were killed, the ABR thresholds were again determined and compared with those in age-matched controls. The most pronounced ABR threshold loss at a high age occurred in those animals irradiated on gestation day 12. There was a significant (up to p less than 0.001) potentiation of the age-related loss of ABR threshold in the old irradiated mice. In the scanning electron microscope, both inner and outer hair cells were missing in large numbers in exposed animals, irrespective of irradiation dose. Remaining hair cells and also the pillar cells showed signs of degeneration. In particular, damage observed in the mid-cochlear region was significantly more pronounced in the old irradiated mice than in the old control mice. It is concluded 1) that elevation of ABR thresholds in ageing irradiated animals is due to damage to cells and nerve endings in the peripheral receptor organ, and 2) that prenatal irradiation significantly potentiates age-related hearing loss. Exposure to gamma rays seems to function as a sensitizer causing premature ageing.

Aging↗

PubMedDate not supplied

Murine endolymphatic sac development in tissue culture: an in vitro model for sac function.

Numerous studies have attempted to elucidate the function of the mammalian endolymphatic sac (ELS). All of these studies have been performed on in vivo specimens and are thus influenced by humoral and tissue factors extraneous to the sac. In contrast, an in vitro model would provide an opportunity to study ELS cells in a carefully controlled environment. This report presents our experience with tissue culturing the murine endolymphatic sac removed from 16 and 18 gestational day fetuses. Light (LM) and transmission electron microscopical (TEM) evaluations of the developing endolymphatic sac were performed over periods of one, four, and seven days in tissue culture. In order to confirm growth and maturation, three-dimensional reconstructions from serial sections of the cultured ELS were made and compared with published accounts of in vivo murine ELS development for equivalent periods of time. Both whole and dissected otocysts were grown in tissue culture and compared with one another. Two different tissue culture medias were investigated, each with and without the addition of collagenase, used to soften the dense fibrous capsule of the otocyst and thus facilitate dissection and histological preparation. The impact of collagenase and the tissue culture medias on endolymphatic sac growth were studied. Results demonstrated that murine ELS cells were able to differentiate and mature in tissue culture, as confirmed by LM, TEM, and three-dimensional reconstructions. After an initial delay, in vitro maturation of cells in tissue culture paralleled normal in vivo growth and in some specimens appeared to show accelerated maturation. This in vitro model should prove useful in efforts to define ELS function and in providing a technique for tissue culturing human ELS from normal and diseased ears.

Animals↗

PubMedDate not supplied

In vitro fluid and particle transport in the murine endolymphatic sac.

The murine endolymphatic sac (ELS) can survive for several weeks in tissue culture. The epithelial cells mature in vitro and demonstrate functional activity under these artificial conditions. The goal of the present study was to investigate fluid and particle transport between the ELS cells, the ELS lumen, and the surrounding tissue culture medium. A series of tracers, including anti-mouse IgG-labelled colloidal gold, horseradish peroxidase (HRP), and ruthenium red (RR) were used to elucidate different aspects of ELS transport. Results indicated that both light and dark cells of the ELS took up HRP from both the luminal and the basal side of the epithelial cells, forming coated vesicles. Only luminal uptake occurred when the HRP was injected into the lumen, and only basal uptake was observed when the HRP was placed in the culture media. HRP introduced into the tissue culture media never entered the lumen of the ELS. Anti-mouse IgG labelled with gold showed no uptake at all from either side of the epithelial cells. Gold could be found only in membrane-bound vesicles in the cytoplasm of reticuloendothelial (RES) cells in the ELS lumen and lateral intercellular spaces (LIS) of the sac. This suggests that there are no IgG sites in sac cells and that the circulating RES cells seen in the lumen of the ELS come from the surrounding connective tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Functional aspects of murine endolymphatic sac in tissue culture.

A recent report from our laboratory describes techniques for growing fetal murine endolymphatic sac (ELS) in vitro in tissue culture. The purpose of the present study is twofold: first, to determine whether the in vitro endolymphatic cells function in their artificial environment; and second, to begin to understand the nature of luminal cell function in vitro when separated from subepithelial connective tissue and blood. The endolymphatic sac was dissected from 18th gestational day fetal mouse otocysts and grown in DME tissue culture media for 7 days. Light microscopic sections of the endolymphatic sac were stained with Periodic Acid Schiff (PAS) reagent, alcian blue, Verhoff's elastin stain, and van Gieson's collagen stain to reveal deposits of glycogen as well as mucopolysaccharides, elastic fibers, and collagen. Controls for glycogen staining were prepared using the amylase enzyme. For electron microscopical evaluation, 'en bloc' staining was used, to confirm the location of cellular glycogen. Results indicate that in vitro luminal cells of the murine ELS are viable and show signs of functional activity with the markers used. The luminal substance and apical cytoplasm shows distinct purple metachromasia with toluidine blue and PAS-positive staining that disappears with amylase digestion. The ELS cells and luminal substance were negative for alcian blue at pH 1.0 and pH 2.5. These findings are similar to those seen in in vivo murine control sac specimens and demonstrate the ability of cultured sac cells to store glycogen and produce complex carbohydrates. The similarity in staining between the luminal substance and the cytoplasm of sac cells in all in vitro specimens suggests some secretory function by sac cells.

Animals↗

PubMedDate not supplied

Influence of age on noise-induced permanent threshold shifts in CBA/Ca and C57BL/6J mice.

Two inbred strains of mice, CBA/Ca (showing a moderate hearing loss with onset late in life) and C57BL/6J (undergoing spontaneous auditory degeneration with onset during young adulthood), were exposed to a broad-band noise of 120 dB SPL (2-7 kHz) for 5 min at 1,2,3,6 or 12 (only for CBA) months of age. Permanent threshold shifts (PTS) were determined by recording auditory brainstem response (ABR) 1 month after exposure. C57 mice were more severely affected by acoustic trauma than age-matched CBA mice. With increasing age, susceptibility to PTS decreased in CBA mice but remained constant in C57 mice. Results indicate that the auditory system of CBA mice undergoes a progressive resistance to noise damage, whereas the persistent high susceptibility to acoustic trauma in C57 mice may be related to their genetic predisposition to rapid auditory degeneration.

Acoustic Stimulation↗