Kunshige Hamasaki

Cadmium toxicity in the thyroid gland of pregnant rats

The toxic effects of cadmium on the thyroid gland of pregnant rats were studied with an electron microscope and an X-ray microanalyzer. Serum levels of thyroid hormones (T3 and T4) were also analyzed. Deterioration of the rough-surfaced endoplasmic reticulum occurred in the thyroid follicular epithelium on the fifth day of cadmium treatment. Large intracellular vacuoles, which arose from dilated cisternae of the rough-surfaced endoplasmic reticulum, were fused together, and marked swelling of the mitochondria was also noted. Thyroglobulin-secreting granules at the apical cytoplasm were decreased in number. By energy dispersive X-ray microanalysis, cadmium peaks were preferentially obtained from swollen mitochondria in the follicular epithelial cells. Serum levels of T3 and T4 were significantly decreased in cadmium-treated rats dams when compared to those of controls. In the present experiment, cycloheximide also caused degenerative changes in the rough-surfaced endoplasmic reticulum and the disappearance of thyroglobulin-secreting granules. Cycloheximide is a known inhibitor of protein synthesis on cytosolic ribosomes. These results indicated that accumulated cadmium in the mitochondria of thyroid follicular epithelial cells might disturb the oxidative phosphorylation of this organelle and the loss of energy supply possibly caused the inhibition of the synthesis and release of thyroid hormones.

Histamine Disposition in Endothelial Specific Granules of the Toad Aorta

High-performance liquid chromatography revealed that toad aorta delivered appreciable concentrations of histamine into the perfusate when perfused by Ringers solution containing the histamine liberator. Electron micrographs of this vessel after the perfusion showed an expulsion of the endothelial specific granules into the vascular lumen. These results support to our previous hypothesis that the granules are a reservoir site of histamine and might take an important role in the regulation of vascular tone.

Expression of α-calcitonin gene-related peptide in the enteric nervous system of rat small intestine

Abstract We first detected α-calcitonin gene-related peptide (α-CGRP) precursor mRNA in the enteric nervous system (ENS) of rat small intestine by reverse transcriptase polymerase chain reaction (RT-PCR). The nucleotide sequence of the RT-PCR product was completely identical to that found in other organs. By in situ hybridization using digoxygenin-labeled α-CGRP precursor cRNA probe, we found that antisense probes detected a signal on nerve cell bodies of both submucosal and myenteric plexuses. Our findings indicate that the rat ENS participates in synthesis of α-CGRP precursor.

Immunocytochemistry of human chorionic gonadotropin in human chorionic villi

The immunocytochemical localization of human chorionic gonadotropin was investigated in chorionic villi from the seventh to twelfth week of gestation. By the light microscopic peroxidase-antiperoxidase technique, positive reactions of human chorionic gonadotropin were found exclusively in the syncytiotrophoblast. Immunoelectron microscopy by means of the protein A-gold technique reveals localization of the immunoreactive gold particles in two kinds of membrane-bound granular inclusions in this cell; one type is granules of 200 to 300 nm in diameter with moderate electron density and the other is large electron-dense bodies of 500 to 1000 nm. The former seems to be Golgi-derived secretory granules that play a role in the release of human chorionic gonadotropin from the syncytiotrophoblast. Although the origin of the latter is still uncertain, a certain amount of this hormone might be stored or treated by lysosomal digestion in the large bodies during these stages.

Iron-Containing Granules in the Syncytiotrophoblast of the Human Chorionic Villi

The syncytiotrophoblast of the human chorionic villi during earlier stages of gestation contains abundant granules derived from Golgi complexes. The granules often include very electron-dense lamellae in their interior, and X-ray microanalysis revealed the presence of iron in these lamellae. It is, therefore, supposed that iron particles absorbed into the syncytiotrophoblast are transported to Golgi complexes and integrated into these lamellae. No evidences that the granules are released from the cells by exocytosis have been proved. Thus, one possibility to their nature might be considered, that is they play a role in lysosomal storage of iron during earlier stages when the capillaries in the chorionic stroma are undeveloped and so have little ability to transport iron into the fetal circulation.

Immunocytochemistry of Fibronectin and Endothelin-1 in the Cavernous Body of Postnatal Rabbit Penises

The differentiating cavernous body (CB) of postnatal rabbit penises was examined with a special reference to immunolocalizations for fibronectin (FN) and endothelin-1 (ET-1). At postnatal day 1, the CBs were embedded by an abundance of mesenchymal cells (MCs), and some of them were closely associated with endothelial cells of preexisting capillaries. Our electron micrographs indicated that such MCs are successively incorporated into the capillary endothelium as vasoformative cells. At this period, vascular sprouts of the helicine artery (HA), which were associated with the MCs, arose from the deep penile artery, and the transformation of such cells to endothelial and medial muscle ones was also indicated, and some MCs appeared to differentiate to epithelioid cells in the media. Immunoreactions for FN were preferentially localized in the rough endoplasmic reticulum (rER) and along the plasma membrane of such vasoformative MCs, and on the extracellular matrix components which connect these MCs with sprouts of both growing capillaries and HA. These findings suggest that FN, which is produced in the rER of the MCs, plays a crucial role in the mechanical linkage during the incorporation of vasoformative MCs into these penile vessels. Immunoreactions for ET-1 were preferentially localized on Weibel-Palade bodies in endothelial cells of the HA, implying the involvement of this peptide in the regulation of the local blood flow in this vessel.

Protein-Secretory Patterns of Normal and Abnormal Human Placentas with Special Reference to Human Chorionic Gonadotropin

[35S]Methionine-labeled protein-secretory patterns resolved by two-dimensional polyacrylamide gel electrophoresis in abnormal hydatidiform-mole placentas were compared with those in normal full-term placentas with special reference to human chorionic gonadotropin (hCG) by means of immunoblotting and immunoelectron-microscopic techniques. Although basic protein-secretory patterns of both placentas were similar to each other, four polypeptide spots appeared and one spot disappeared in the hydatidiform-mole samples. Among four newly synthesized and secreted spots, three were immunoreacted with anti-hCG serum by an immunoblotting experiment. Ultrastructural localization of hCG showed that the labeling intensity of anti-hCG serum in hydatidiform-mole placentas was much heavier than that in full-terms ones. Particularly, the Golgi apparatus, middle-sized granules and large bodies were highly immunoreactive. The present study reveals that hydatidiform-mole placentas have different protein-secretory functions especially in hCG synthesis and secretion from those of normal pregnancy.

Immunoelectron microscopy of human chorionic gonadotropin (hCG) and human placental lactogen (hPL) in the syncytiotrophoblast of human placenta, clarifying the nature of the So-called large dense bodies

The synthetic and secretory processes of human chorionic gonadotropin (hCG) and human placental lactogen (hPL) were investigated by immunoelectron microscopy which included the use of the double immunolabeling technique. The syncytiotrophoblast contains three kinds of granules: Small-sized granules (SG), middle-sized granules (MG), and large dense bodies (LB). Immunoreactions of hCG are localized in the MG and LB, while those of hPL are in the SG and LB. The double immunolabeling method proved without a doubt that hCG and hPL do not co-exist in the same SG or MG, but they are co-localized in the LB. This means that hCG and hPL are separately sorted into different secretory granules in the Golgi apparatus, but the LB are a kind of cytolysosome which are involved in the uptake and storage of both hPL and hCG.