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Biomedical subjects

A Tamada

Publications and source records attributed to A Tamada.

At least 37 records · Page 2Linked to original sources
PubMed1998

Ultrastructure of the parathyroid gland of the young golden hamster after short-term treatment with ethanol.

We studied the ultrastructure of the parathyroid gland of young golden hamsters after short-term treatment with ethanol (1.5 g/kg bw or 6.0 g/kg bw). We did not find any ultrastructural changes of the parathyroid gland after administration of 1.5 g/kg ethanol. In the hamsters, 3 hours after administration of 6.0 g/kg ethanol, the mean serum calcium concentration was significantly low as compared to that of the control animals. In the parathyroid gland 1 hour after administration of 6.0 g/kg ethanol, the Golgi complexes associated with a few prosecretory granules and the volume density occupied by the Golgi complexes decreased compared with that of the control animals. In the parathyroid glands 3 hours after administration of 6.0 g/kg ethanol, the Golgi complexes decreased as compared with those of the control animals, while the large vacuolar bodies increased. These findings suggest that the cellular activity of the parathyroid gland is suppressed after short-term treatment with ethanol. Intracellular lumen was found in the parathyroid chief cells 3 hours after administration of 6.0 g/kg ethanol, and the significance of this structure is discussed.

Animals↗
PubMed1998

Effect of immobilization on the ultrastructure of the golden hamster parathyroid gland.

To investigate the morphological changes of the parathyroid gland of the immobilized hamsters, we studied the ultrastructure of the parathyroid gland of golden hamsters kept in special small cage (Ballman cage II). All hamsters of the control group were kept in one ordinary cage. Each hamster of the isolated group was kept in ordinary cage individually. Each hamster of the immobilized group was kept in Ballman cage II individually. All hamsters were kept for 5 days. On the first and fifth day of the experiment, bone mineral content (BMC) and bone mineral density (BMD) of whole body were measured by dual energy X-ray absorptiometry (DXA). In the control and isolated groups, BMD of the fifth day was significantly increased as compared to that of the first day. In the immobilized group BMC and body weight were significantly decreased. There was no significant difference among 3 groups concerning the mean serum calcium level. Volume density of the cell organelles and inclusions was estimated and compared among 3 groups. Volume density of the lysosomes and large vacuolar bodies of the isolated and immobilized groups was significantly higher than that of the control group. Much more lipid droplets were observed in the immobilized group than the control and isolated groups. No particular differences were observed as to the Golgi complex in the isolated and the immobilized groups compared to the control group. These findings suggest that the cellular activity of the parathyroid gland is suppressed with immobilization.

Absorptiometry, Photon↗
PubMed1998

Fine structure of the parathyroid and ultimobranchial glands of the snake, Elaphe quadrivirgata.

The ultrastructure of the parathyroid gland and ultimobranchial gland of the snake, Elaphe quadrivirgata, was studied. The parenchyma of the parathyroid gland was consisted of chief cells arranged in cords. Oxyphil cells and water-clear cells were not recognized. The chief cells contained irregular shaped nucleus, moderately-developed mitochondria, granular endoplasmic reticulum and Golgi complexes. A few secretory granules of 100-300 nm in diameter distributed in the cytoplasm. Small aggregations of glycogen particles and lipid droplets were dispersed widely in the cytoplasm. The ultimobranchial glands consisted of follicles and interfollicular aggregates of C-cells. Follicles were invaginated and composed of C-cells, goblet cells and ciliated cells. C-cells were located in the basal position of the follicle and possessed variety of secretory granules of 100-300 nm in diameter in the basal region of the cell. C-cells presented various secretory cycles. Goblet cells projected microvilli into follicular lumen. At the apical region the goblet cells had large granules of 300-1,200 nm in diameter. Ciliated cells projected cilia intermixed with micovilli from the apical surface of the cell into the follicular lumen.

Animals↗
PubMed1997

OCAM: A new member of the neural cell adhesion molecule family related to zone-to-zone projection of olfactory and vomeronasal axons.

Zone-to-zone projection of olfactory and vomeronasal sensory axons underlies the topographic and functional mapping of chemoreceptor expression zones of the sensory epithelia onto zonally arranged glomeruli in the main and accessory olfactory bulbs. Here we identified OCAM (R4B12 antigen), an axonal surface glycoprotein expressed by subsets of both olfactory and vomeronasal axons in a zone-specific manner. OCAM is a novel homophilic adhesion molecule belonging to the immunoglobulin superfamily with striking structural homology to neural cell adhesion molecule. In both the main and accessory olfactory systems, OCAM mRNA is expressed by sensory neurons in restricted chemoreceptor expression zones, and OCAM protein-expressing axons project to the glomeruli in the corresponding zones of the main and accessory bulbs. OCAM protein is expressed on subsets of growing sensory axons in explant cultures even in the absence of the target bulb. These results demonstrate a precisely coordinated zonal expression of chemoreceptors and OCAM and suggest that OCAM may play important roles in selective fasciculation and zone-to-zone projection of the primary olfactory axons.

Amino Acid Sequence↗
PubMed1997

A procedure for in situ hybridization combined with retrograde labeling of neurons: application to the study of cell adhesion molecule expression in Dil-labeled rat pyramidal neurons.

We have devised a simple method that combines retrograde labeling of projecting neurons and in situ hybridization histochemistry to examine mRNA expression in the retrogradely labeled neurons. First, projecting neurons were retrogradely labeled in vivo by injection of the lipophilic neuronal tracer Dil. The fluorescence of the labeled neurons in the brain slices was photoconverted into stable DAB precipitate by green light illumination. The slices were cut into thinner sections and processed for detection of specific mRNA by in situ hybridization. Using this highly sensitive method, we demonstrate here that the corticospinal tract neurons in newborn rats express mRNA for the cell adhesion molecule L1. TAG-1 mRNA was not detected in these neurons. Therefore, the present method provides an important tool to study the molecular expression of projection neurons during the development of neuronal circuitry.

Affinity Labels↗
PubMed1997

Nuclear bodies of the human lung in psittacosis.

Lung piece obtained from a female patient with psittacosis by biopsy. A nuclear bodies of five different types were observed, depending on their degree of ultrastructural development. First type showed fibrillary nuclear bodies surrounded by a clear halo. Type II resembled the nuclear body of type I but showed heterogeneously electron density. Type III comprised nuclear bodies with a fibrillary cortex containing a central granular component. These bodies were separated from the nucleoplasm by a clear halo. Type IV was characterized by a more complex structure and resembled the nuclear body of type III but with dense osmiophilic granules. Nuclear bodies of type V were comprised of numerous osmiophilic granules.

Cell Nucleus↗
PubMed1997

Effects of short-term treatment with CaCl2 or EDTA on the parathyroid glands in pregnant golden hamsters, with special reference to large vacuolar bodies.

The large vacuolar bodies in the parathyroid glands of pregnant golden hamsters after administration of CaCl2 or EDTA were investigated. In the parathyroid glands of the pregnant animals 15 min after administration of CaCl2, the mean serum calcium concentration was significantly high when compared to that of the control animals. In the parathyroid glands of the pregnant animals 15, 30 and 60 min after administration of EDTA, the mean serum calcium concentration was significantly low when compared to that of the control animals. In the parathyroid glands of the pregnant animals 15 min after administration of CaCl2, the percentage area occupied by large vacuolar bodies was significantly increased when compared to that of the control animals. In the parathyroid glands of the pregnant animals 15 min after administration of EDTA, the percentage area occupied by large vacuolar bodies was significantly decreased when compared to that of the control animals.

Animals↗
PubMed1996

Ultrastructural changes in water-clear cells of the golden hamster parathyroid gland after streptozotocin treatment.

The effects of streptozotocin treatment on parathyroid water-clear cells in golden hamsters were investigated. In the cytoplasm of the water-clear cells, lipid droplets were increased as compared to that of the control animals. This finding suggests that treatment of streptozotocin affects functional activity in the parathyroid water-clear cells of the golden hamsters.

Animals↗
PubMed1995

Overlapping and differential expression of BIG-2, BIG-1, TAG-1, and F3: four members of an axon-associated cell adhesion molecule subgroup of the immunoglobulin superfamily.

Axon-associated cell adhesion molecules (AxCAMs) play crucial roles in the formation, maintenance, and plasticity of functional neuronal networks. We report here a molecular cloning of a novel AxCAM, BIG-2. BIG-2 is a member of TAG-1/F3 subgroup of the immunoglobulin (Ig) superfamily, with six Ig-like domains, four fibronectin type III-like repeats, and a glycosyl phosphatidylinositol-anchoring domain. Recombinant BIG-2 protein had a neurite outgrowth-promoting activity when used as a substrate for neurons in vitro. To survey the spatial expression pattern of BIG-2 in comparison with other TAG-1/F3 subgroup members, an in situ hybridization analysis was performed in adult and developing rat brain sections with riboprobes specific for BIG-2, BIG-1, TAG-1, and F3. The four AxCAM transcripts displayed cell type-specific expression patterns with overlapping and distinct profiles. In adult hippocampus, for example, we observed BIG-1 mRNA specifically in granule cells of the dentate gyrus, BIG-2 mRNA highly in the CA1 pyramidal cells, TAG-1 mRNA predominantly in the CA3 pyramidal cells, and F3 mRNA in neurons in all of these fields. These results suggest that BIG-2, BIG-1, TAG-1, and F3 may play important roles in the formation and maintenance of specific neuronal networks in the brain.

Amino Acid Sequence↗
PubMed1995

Guidance of cerebellofugal axons in the rat embryo: directed growth toward the floor plate and subsequent elongation along the longitudinal axis.

To elucidate guidance mechanisms of brain commissural axons, we examined the navigation of cerebellofugal axons. Axons were labeled by implantation of the fluorescent tracer Dil into the cerebellar plate (CP) of fixed, flat whole-mount embryonic rat brain. Axons initially grew straight toward the ventral midline floor plate (FP) in the rostral hindbrain and then, after crossing it, made a right-angled turn to grow either caudally or rostrally along the longitudinal axis. In collagen gel culture, CP axons showed directed growth toward both FP explants and heterologous cells expressing netrin-1, a FP-derived chemoattractant for spinal commissural axons. These results suggest that CP axons are guided to the midline by FP-derived chemoattractant(s) and then reoriented, possibly by another guidance cue, for longitudinal extension. Considering that the basic structures of the neural tube, including the FP, extend up to the caudal diencephalon, these results suggest that common guidance mechanisms operate for ventrally decussating commissural axons in both the brain and spinal cord.

Animals↗
PubMed1995

Floor plate chemoattracts crossed axons and chemorepels uncrossed axons in the vertebrate brain.

In the bilaterally symmetrical vertebrate CNS, all developing axons must choose between remaining on the same side of the midline or growing across it. The mechanism underlying this axonal pathfinding is, however, poorly understood. Here we demonstrate that the ventral midline floor plate (FP) chemorepels two types of ipsilaterally projecting axons, one from the alar plate and another from the basal plate in the mesencephalon. We further demonstrate that the FP chemoattracts contralaterally projecting myelencephalic as well as metencephalic axons. The FP at all axial levels displayed both chemoattractive and chemorepellent activities, suggesting that FP chemoattraction and chemorepulsion may be at work throughout the neuraxis. Chemotropic guidance by the FP may therefore play a key role in the establishment of neuronal projection laterality.

Animals↗
PubMed1995

Effects of progesterone on the ultrastructure of the golden hamster parathyroid gland.

The ultrastructure of the parathyroid glands in golden hamsters after administration of progesterone was investigated. In the parathyroid glands of the female hamsters after administration of progesterone, the mean serum calcium concentration was significantly higher when compared to that of the control hamsters. In the male experimental hamsters, the percentage area occupied by Golgi complexes and lipid droplets was significantly increased when compared to that of the control hamsters, respectively. In the female hamsters after administration of progesterone, the percentage area occupied by large vacuolar bodies was significantly decreased when compared to that of the control hamsters. In the male and female experimental hamsters, the mean number of secretory granules per 100 microns2 of cytoplasm showed a significant increase compared with that of the male and female control hamsters, respectively. These findings suggest that the secretory activity of the parathyroid glands may be stimulated in response to hypocalcemia induced by progesterone.

Animals↗
PubMed1994

BIG-1: a new TAG-1/F3-related member of the immunoglobulin superfamily with neurite outgrowth-promoting activity.

We have cloned a rat cDNA for a novel brain-derived immunoglobulin (Ig) superfamily molecule, BIG-1, by using PCR based on the amino acid sequences of the two closely related and well-known Ig superfamily members, rat TAG-1 and mouse F3. BIG-1 is a glycosylphosphatidylinositol-anchored membrane protein with six Ig-like domains and four fibronectin type III repeats, belonging to the TAG-1/F3 subgroup. The expression of BIG-1 mRNA is developmentally regulated with the highest level in the adult brain. It is restricted to subsets of neurons such as Purkinje cells of the cerebellum, granule cells of the dentate gyrus, and neurons in the superficial layers of the cerebral cortex. Recombinant BIG-1 protein has a neurite outgrowth-promoting activity when used as a substrate for neurons in vitro. These results suggest that BIG-1 may be involved in the formation and maintenance of neuron type-specific networks in the brain.

Amino Acid Sequence↗
PubMed1994

Effects of prostaglandin E2 on the ultrastructure of the golden hamster parathyroid gland.

The effects of different ages on large vacuolar bodies in the parathyroid glands of golden hamsters after administration of prostaglandin E2 (PGE2) were investigated. In the parathyroid glands of the young and senile animals 15 min and the senile animals 60 min after administration of PGE2, the mean serum calcium concentration was significantly higher when compared to that of the young and senile control animals, respectively. In the experimental adult animals 60 min after administration of PGE2, the serum calcium concentration was seen to increase. In the parathyroid glands of the young animals 15 min and the adult and senile animals 60 min after administration of PGE2, the percent area occupied by large vacuolar bodies was significantly increased when compared to that of the young, adult and senile control animals, respectively. These findings suggest that the percent area occupied by large vacuolar bodies is increased in response to hypercalcemia induced by PGE2. It is thought that in the parathyroid glands suppressed by hypercalcemia there is a relationship between the percent area occupied by large vacuolar bodies and aging.

Aging↗
PubMed1993

Individual corticorubral neurons project bilaterally during postnatal development and following early contralateral cortical lesions.

The corticorubral projections in adult cats are primarily uncrossed. However, early in development and after early unilateral lesions of the sensorimotor cortex, crossed corticorubral projections are also observed. The present study was performed to disclose (1) whether the crossed projections originate from neuronal subpopulations different from those producing uncrossed ones and (2) how the neurons that give rise to the crossed projections in the lesioned animals are related to those occurring in normal development. We injected fluorescent latex microspheres into the red nucleus of two groups of animals: (1) intact kittens at postnatal week 3 and (2) kittens that had received unilateral ablation of the cerebral cortex at this stage and were then allowed to survive for at least 4 weeks. Red fluorescing microspheres were injected on one side and green ones on the other. In both normal and lesioned kittens, a number of cells in the cortex were labeled as a result of the contralateral as well as the ipsilateral injections, and no difference in size or distribution was found between the cells labeled from contralateral and ipsilateral injections. More than half of the cells labeled from contralateral injections were double-labeled in both groups of animals. These results indicate that individual corticorubral cells project bilaterally in normal development as well as following unilateral lesions of the cortex. With respect to the cells producing crossed projections, they were similar in both laminar and regional distributions between the intact and lesioned animal, suggesting that the crossed projections arise from the same neuronal subpopulation before and after cortical lesions. This view was supported by sequential injections of the tracers, which indicated that cells normally projecting contralaterally maintained the crossed projection after the lesions. Taking into account our previous observations that growth and proliferation of crossed corticorubral axons took place in the red nucleus (Murakami et al. 1991a), it is likely that growth and proliferation of the axons in denervated targets play a major role in lesion-induced establishment of aberrant projections.

Aging↗