To understand the development of the gustatory structures necessitates a reliable marker for both immature and mature taste buds. It has been reported that the intragemmal cells within the taste buds of adult rats were bound to Ulex europaeus agglutinin-I (UEA-I), a specific lectin for α-linked fucose, but it has not been determined whether immature taste buds, i.e. taste buds without an apparent taste pore, are labeled with UEA-I. The present study was conducted to examine the UEA-I binding pattern during the development of the rat gustatory epithelium. In adult animals, UEA-I bound to the membrane of taste buds in all examined regions of the gustatory epithelium. Within the individual taste buds, UEA-I labeled almost all intragemmal cells. The binding of UEA-I was occasionally detected below the keratinized layer of the trench wall epithelium but could not be found in the lingual epithelium of the adult animal. During the development of circumvallate papilla, some cells within the immature taste buds were also labeled with UEA-I. The developmental changes in the UEA-I binding pattern in fungiform papillae were almost identical to those in the circumvallate papilla: both immature and mature taste buds were labeled with UEA-I. The present results indicate that UEA-I is a specific lectin for the intragemmal cells of both immature and mature taste buds and, thus, UEA-I can be used as a reliable marker for all taste buds in the rat.

抄録全体を表示

We investigated the rat laryngeal taste buds and their innervation by electron microscopy and immunohistochemical methods. Taste buds were densely arranged in the surface facing the laryngeal cavity of the epiglottis, the aryepiglottic fold, and the cuneiform process of the arytenoid cartilages. The cells of the buds were classified into types I, II, III, and basal cells, the ultrastucture of which was almost the same as that previously reported in lingual taste buds. The type III cells that had synaptic contacts with nerve fibers were considered to be sensory cells. Immunohistochemical analysis revealed thick calbindin D28k-immunoreactive fibers and thin varicose fibers immunoreactive for calcitonin gene-related peptide or substance P in and around the taste bud. Serotonin-immunoreactive cells were also observed here. The results revealed the innervation pattern of laryngeal taste buds to be the same as that in lingual taste buds. Carbonic anhydrase (CA) is known to catalyze the hydration of CO₂ and dehydration of H₂CO₃, and seems to be essential in CO₂ reception. Immunoreactivity for CAI was detected in slender cells and that for CAIII was observed in barrel-like cells in the laryngeal taste buds. The pH-sensitive inward rectifier K⁺ (Kir) channel in the cell membrane may be involved in CO₂ reception as well. CAII-reactive cells were also reactive to Kir4.1, PGP 9.5 and serotonin. Our results indicated that CAII and Kir4.1 are located in type III cells of the laryngeal taste buds, and supported the idea that the buds may be involved in the recognition of CO₂.

抄録全体を表示

The biocompatibility of dental materials is a topic of increasing importance for dentists. We investigated the effects of alloys for ceramic crowns and removable prostheses on the skin and lymphoid organs of rats. We used three groups of Sprague Dawley rats: group I as the control, with groups II and III implanted with different biomaterials into subcutaneous pockets. After sacrifice, the rat skin around the implant and the lymph nodes was studied. The tissues of implanted rats were morphologically different from the control animals as they showed a number of mast cells that increased 7 days after the implant with both alloys. These cells decreased 14 days after the implant with alloy for ceramic crowns whereas they were still high 28 days after the implant with alloy for removable prostheses. The findings suggest that both alloys induced different and time-dependent inflammatory reactions. Our findings have importance in the future rational design of biocompatible implantable and blood-contact biomaterials.

抄録全体を表示

The localization of the epidermal hyaluronan in the digital foot pads of the North American raccoon (Procyon lotor) was examined by light and electron microscopic histochemical methods. The thick epidermis contained five epidermal layers composed of typical keratinocytes. In the stratum basale and stratum spinosum, hyaluronic acid was clearly detectable at cytoplasmic processes, in close vicinity to the surface coat of the plasma membrane, and/or in the intercellular space between the basal and spinous cells.
The results suggest that epidermal hyaluronan that fills the intercellular space may particularly control water maintenance in the epidermis of the raccoon digital pads to guarantee the optimal mechanoreceptive function of the very specific and sensitive sensoric subepidermal equipment in this mammalian species.

抄録全体を表示

Afferent signals from jaw muscle spindles contribute to the feedback mechanism that regulates mastication. The integrity and adaptability of this proprioceptor to age-related changes of the surrounding structures are therefore essential to maintain an appropriate masticatory function throughout life. In this study, we examined muscle spindles obtained from temporal and masseter muscles of 10-week-, 12-, 18-, and 24-month-old Wistar rats, employing immunohistochemistry for protein gene product 9.5 (PGP 9.5) or growth-associated protein (GAP-43) in addition to transmission electron microscopy, in order to investigate their morphological changes in relation to the effect of aging on the adaptive potential of the receptors.
Immunohistochemistry for PGP 9.5 showed virtually similar reactions at sensory nerve terminals in all age groups. On the other hand, immunoreactivity for GAP-43 in the sensory nerve ending of the muscle spindles was found 2 and 3 weeks after birth but became almost undetectable by 10 weeks. However GAP-43 immunoreactions occasionally reappeared in those of spindles in 12- and 18-month old animals, and vanished again by 24 months of age. Electron microscopic observations also revealed age-related morphological changes in the intrafusal muscle fibers of the rats in 12-month and older groups. The extent of degenerative and/or atrophic alterations of intrafusal fibers increased with age and involved the nerve elements of spindles by 24 months. These findings indicate that the adaptation potential of rat jaw muscle spindles is well preserved until middle age, but diminishes in elderly animals. Structural changes of muscle spindles in elderly animals probably contribute to the deterioration of the muscular function.

抄録全体を表示

The present study examined whether the development in rats of behavioral sensitization to methamphetamine (MAP) is related to the development of neurotoxic morphological changes presumably induced in the medial prefrontal cortex (MFC). Male rats were intraperitoneally injected with MAP (5 mg/kg) once a day for 12 days (day 1-day 12), and then the drug was withdrawn for 7-42 days (WD7-WD42). The MAP- treatment caused hypersensitivity of a successive head-movement stereotypy, which reached a basic plateau level on day 4, and rose successively to a higher level by day 12. Morphological changes were histochemically and morphometrically examined in the MFC. In the strata covering layers II and III, the densities of tyrosine hydroxylase (TH)-immunoreactive axons decreased on a daily basis to 50% of the control on day 4 and then to 40% on days 6 and 12. The densities of dopamine-β-hydroxylase (DBH)-immunoreactive axons did not change during the injection period. A few TUNEL-positive cells were observed in a unit area (0.25mm²) covering layers II-V on day 6 and they increased to 19 and 16 on day 12 and WD7, respectively. These observations demonstrate a role for the neurotoxic changes in the MFC in the processes of behavioral sensitization of a stereotypy to a low dose of MAP.

抄録全体を表示

The microvasculature in the brain plays a vital role in the maintenance of brain perfusion, and fulfills the dynamic requirements of normal brain functions. It is well known that collateral circulation can be induced by ischemia in cerebral infarctions, but it is not known whether cerebral ischemia affects microvasculatures in the ischemic region. In the present study, we examined quantitatively serial changes in capillaries following bilateral common carotid artery ligation in Wistar rats. After the animals were perfused with tetramethylrhodamine isothiocyanate-labeled gelatin 3 h (n=9), 1 day (n=9), 7 days (n=9) and 28 days (n=9) after the ligation, capillary diameters in the brain sections were measured with a confocal laser-scanning microscope. Capillary diameters of the cerebellum did not differ among all groups, while those in the ischemic regions decreased significantly 3 h after the ligation (p<0.01), thereafter gradually returned toward the baseline level, and became significantly larger (168% of the control) 28 days after the ligation (p< 0.01). The density of capillaries in the frontal and parietal cortices increased approximately to 1.3-fold of those of the control level 28 days after the ligation. Transmission electron microscopy showed that the mean ratio of the inner diameter to the outer diameter of capillaries in the frontal cortex became significantly greater 28 days after the ligation (p<0.05). Our data indicate that capillaries dilate in the ischemic brain region in the chronic phase of cerebral ischemia. It is also suggested that neovascularization occurs in the ischemic brain region.

抄録全体を表示

Cathodoluminescence (CL) is the light that is emitted from a material irradiated by an electron beam. The present study was undertaken to show the applicability to biological studies of a scanning electron microscope (SEM) equipped with a high-sensitive cathodoluminescence detection system. For this purpose, we injected inorganic fluorescent powders (P43) suspended in phosphate buffered saline into rat blood circulation, fixed the animals with glutaraldehyde within a day, and observed the hepatic tissues with a SEM. Our instrument enabled the simultaneous collection of both secondary electron (SE) and CL images of these tissues. Backscattered electron (BSE) images of the same portion were also able to be obtained with this microscope. SE and BSE images clearly showed the three-dimensional structure of the hepatic tissues including hepatocytes, Kupffer cells, Ito cells, and sinusoidal epithelial cells, while CL images visualized cathodoluminescence signals emitted from P43 as bright spots. We observed non-coated tissues under a low-vacuum condition and metal-coated tissues under a high-vacuum condition, and found that the high-vacuum observation of metal-coated tissues provided high quality CL images of P43 in the Kupffer cells. The superimposition of the CL images onto the corresponding SE or BSE images revealed that bright spots in the CL images were produced by the fluorescent powders uptaken by Kupffer cells. These findings indicate that the detection of CL as well as SE or BSE signals by SEM all provide us with useful information on the distribution of fluorescent tracers in tissues and cells in three-dimensional images.

抄録全体を表示