Ultrastructural features of adrenomedullary adrenaline (A) cells in golden hamsters and rats were investigated qualitatively and quantitatively with special reference to the Golgi apparatus. The A cells displayed a characteristic follicular arrangement, with each cell showing structural polarity in hamsters, but not apparently in rats. In hamsters, the Golgi apparatus of A cells was larger (t-test: P<0.001) and more frequently showed large and complexly organized structures (χ²-test: P<0.005) compared with that of rats. Quantitative analysis of the Golgi apparatus revealed differences in the size and numerical density of Golgi vesicles in relation to the animal species and region. Two-way analysis of variance (ANOVA) confirmed species difference in the size of coated vesicles (P<0.005) and interaction between species and region concerning the size of smooth-clear vesicles (P<0.01) and numerical density of granular vesicles (P<0.05). One-way ANOVA revealed regional differences in the size and numerical density of smooth-clear vesicles in rats and hamsters (P<0.01∼0.001), and in the numerical density of coated vesicles in hamsters (P<0.05). Data were further analyzed by Tukey-Kramer's method. These and other reported results suggest that, in hamster A cells, the Golgi apparatus has different structural, molecular, and functional mechanisms which are at least partly related to the distinct cellular polarity and higher concentration of peptide hormones in secretory vesicles, and that in rat A cells, in contrast, loading secretory vesicles with A during the post-Golgi stage is predominant. In conclusion, the Golgi apparatus in hamster A cells shows markedly different ultrastructural features compared with that in rat A cells.

抄録全体を表示

Interstitial cells of Cajal (ICC) are important regulatory cells generating electrical rhythmicity and transducing neural signals in the gastrointestinal musculature. ICC express the proto-oncogene c-kit, a receptor tyrosine kinase, and can be examined morphologically using the c-Kit antibody. The c-kit gene is allelic with the murine white-spotting locus W, and the c-kit mutation (W mutation) affects various aspects of hematopoietic cells, germ cells, melanocytes, mast cells, and ICC. Heterozygous W/W ^v mutant mice lack a specific type of ICC and have been used to reveal its function. To search for a new model that lacks a specific type of ICC, we examined homozygous W ^v/W ^v black-eyed-white mice that are viable with anemia. Results showed the principal patterns of ICC deficiency were the same between the W/W ^v and W ^v/W ^v mutants. In the stomach of both mice, intramuscular ICC (ICC-IM) were missing and myenteric ICC (ICC-MY) were reduced in number. In the small intestine, the number of ICC-MY was severely reduced in spite of a normal distribution of deep muscular plexus ICC (ICC-DMP). The cecum also exhibited fewer reduced. ICC-IM in the colon were almost entirely missing, whereas ICC-MY were reduced only in the distal colon. In the small intestine and colon, the number of remaining ICC-MY in W ^v/W ^v mice was greater than that in W/W ^v mice. The enteric nervous system of the two mutant mice showed normal characteristics. From these findings, we conclude that W ^v/W ^v mice represent a new genotype that lacks a part of the ICC in its gastrointestinal musculature.

抄録全体を表示

The microarchitecture of collagen fibrils in the articular disc of the temporomandibular joint (TMJ) plays an important role in dissipating the mechanical load during jaw movement. However, little information is available on its adaptations to the biomechanical environment during development. To address this issue, we analyzed the diameter of collagen fibrils of the articular disc of the rat TMJ with quantitative ultrastructural analysis during postnatal development.
  The mean diameter of the collagen fibrils significantly increased and the arrangement of the collagen fiber networks became compact during development. Articular discs of suckling rat pups were composed of thin, uniformly sized collagen fibrils (range: 30-60 nm, peak: 40-50 nm). At the age of 4 weeks, thicker collagen fibrils began to appear in articular discs, shortly after weaning (range: 20-70 nm, peak: 40-50 nm). In articular discs of adult rats, collagen fibrils varied widely in diameter, with thick fibrils predominating (range: 10-120 nm, peak: 40-70 nm).
  These age-related changes in the microarchitecture of collagen fibrils in articular discs may reflect changes in their biomechanical environment during development.

抄録全体を表示

The distribution of substance P (SP) immunoreactivity and the colocalization of SP with other bioactive substances in chromaffin cells and nerve fibers were investigated in the rat adrenal gland at the light microscopic level. In the capsule and cortex, SP immunoreactivity was seen in some nerve fibers around blood vessels and in thick nerve bundles passing through the cortex directly into the medulla. In the medulla, the SP immunoreactivity was observed in a small number of chromaffin cells; these SP-immunoreactive chromaffin cells were either phenylethanolamine N-methyltransferase (PNMT) immunoreactive or immunonegative, indicating that they were either adrenaline cells or noradrenaline (NA) cells. SP-immunoreactive varicose nerve fibers were also found in the medulla and were in contact with a cluster of the NA cells showing catecholamine fluorescence, which suggests that SP from medullary nerve fibers may regulate the secretory activity of the NA cells. Because no SP-immunoreactive ganglion cell was present in the rat adrenal gland, the intra-adrenal nerve fibers were considered to be extrinsic in origin. The double-immunostaining method further revealed that the SP-immunoreactive chromaffin cells also exhibit immunoreactivities for calcitonin gene-related peptide (CGRP), and neuropeptide tyrosine (NPY), suggesting that these peptides can also be released from the chromaffin cells by certain stimuli. The intra-adrenal nerve fibers in the medulla were composed of SP-single immunoreactive, and SP/CGRP-, SP/choline acetyltransferase (ChAT)-, SP/nitric oxide synthase (NOS)-, SP/pituitary adenylate cyclase activating polypeptide (PACAP)-, ChAT/NOS-, and ChAT/PACAP-immunoreactive nerve fibers, which may affect the secretory activity of the NA cells. In the adrenal capsule, the nerve fibers were present around blood vessels and showed immunoreactivities for SP/ CGRP, SP/NPY, SP/NOS, and SP/vasoactive intestinal polypeptide, suggesting that the origin of nerve fibers in the capsule may differ from those in the medulla.

抄録全体を表示

We investigated cyclooxygenase-2 (Cox-2) immunoreactive cells in the hippocampus and dentate gyrus of Sprague-Dawley rats at 4 h after the induction of normothermic and hypothermic ischemia and reperfusion. Under the normothermic condition, Cox-2 immunoreactive cells showed more intense staining and clearer proximal dendrite configurations as compared with the control animals, whereas the numbers of immunoreactive cells in the hippocampus and dentate gyrus were not remarkably increased. In contrast to the normothermic condition, long-term (pre- and intra-ischemic) and short-term (exclusively intra-ischemic) hypothermic conditions caused a drastic increase in immunoreactive cells in the dentate gyrus. Nearly all granule cells were immuno-positive for Cox-2, whereas the CA3 and hilus sectors showed no remarkable increase in immunoreactive cell numbers. In sham-operated animals exposed to long-term hypothermia - but not ischemia, Cox-2 staining profiles were similar to those in the control animals. These results suggest that, for a drastic increase in Cox-2 immunoreactive granule cells to occur within a short time period (4 h), at a minimum, both hypothermia and ischemia, are required. Considering the neuroprotective roles of the hypothermia, a rapid increase in Cox-2 in the dentate gyrus might be associated with this temperature-sensitive phenomenon.

抄録全体を表示

The thalamic lateral posterior nucleus (LP) of the hooded rat is regarded as a relay nucleus for the transmission of information from visuomotor-related structures such as the superior colliculus, pedunculopontine tegmental nucleus (PPT) and substantia nigra, pars reticulata, to visual cortical areas as well as the striatum. The aim of the present study was to examine the relationships of the thalamo-striatal projection neurons with the LP afferent fibers derived from the PPT, using injections of the anterograde tracer biotinylated dextran amine (BDA) and the retrograde tracer cholera toxin-B (CTB) into the PPT and the striatum, respectively. Findings showed that the location of terminals derived from PPT and LP neurons projecting to the striatum overlapped considerably in the ventral portion of the LP. Ultrastructural observations within this overlapped LP region showed that BDA-labeled terminals make synaptic contacts with dendrites of CTB-labeled neurons. The present results thus provide morphological support for the contention that information from the PPT neurons is relayed to the striatum through by the LP.

抄録全体を表示