Masahiko Hiramatsu

Influence of age on epidermal growth factor receptor level in the rat brain

The influence of age on125I-epidermal growth factor (EGF) binding to rat brain plasma membranes was investigated. The specific binding of EGF to membranes decreased gradually with age in both male and female rats. There was no significant difference in the specific binding between males and females. Scatchard analysis of the binding data showed that the decrease in EGF binding with age was due to a decrease in the number of EGF receptors.

Effect of streptozotocin-induced diabetes on epidermal growth factor receptors in rat liver plasma membrane.

The effect of streptozotocin-induced diabetes on 125I-labeled epidermal growth factor (EGF) binding was studied in microsomal membranes from rat liver. The binding of EGF in membranes from diabetic animals was significantly low, the value being about 60% of the control level. Scatchard analysis of the binding data clearly showed that the decrease in EGF binding was due to a decrease in the number of receptors. Treatment of diabetic animals with insulin restored EGF receptors to control levels, whereas the treatment with triiodothyronine had no effect. Serum EGF concentrations measured were almost the same among the control, diabetic, and insulin-treated diabetic groups. These results suggest that insulin deficiency in vivo causes a decrease in hepatic EGF receptors.

Epidermal growth factor stimulates collagen synthesis in liver-derived epithelial clone cells

Abstract The effect of epidermal growth factor (EGF) on collagen fiber formation in clone RLC-18(4) epithelial cells obtained from rat liver was investigated by silver impregnation and assay of hydroxyproline content. EGF caused dose-related stimulation of collagen fiber formation and was effective at as low as concentration as 0.5 ng/ml. Actinomycin D suppressed collagen fiber formation increased by EGF, suggesting that this factor stimulates de novo collagen synthesis in the cells.

Age-related changes in the content of non-reducible crosslinks in rat mandibular bone

Age-related changes in the content of non-reducible crosslink amino acids, pyridinoline and histidinoalanine, in rat mandibular bone were studied. The pyridinoline content markedly increased up to 12 months of age and thereafter slightly increased. The histidinoalanine content was low until 3 months of age, but thereafter increased significantly up to 24 months. Total collagen content remained constant throughout the experiment. From these results, pyridinoline and histidinoalanine may serve as markers for the maturation and senescence, respectively, of mandibular bone.

Immunohistochemical analysis of EGF in epiphyseal growth plate from normal, hypophysectomized, and growth hormone-treated hypophysectomized rats.

Epiphyseal growth plate cartilages from the proximal tibia of normal, hypophysectomized, and growth hormone (GH)-treated hypophysectomized rats were subjected to immunohistochemistry for detection of epidermal growth factor (EGF). In the normal growth plate, EGF was distributed mainly in the proliferative zone. Hypophysectomy resulted in considerable atrophy of the chondrocytes and the cartilage matrix (a decreased number of mature-type chondrocytes and a decreased ratio of proliferating to hypertrophic chondrocytes) and a significant diminution of EGF immunoreactivity. Treatment with GH reversed these effects of hypophysectomy, causing an increased thickness of the growth plate and EGF-reactive sites in all chondrocyte layers. The most intense immunostaining for EGF, however, was frequently seen in the nuclei of chondrocytes with flattened appearance. It appears that EGF could be incorporated or synthesized in chondrocytes having marked mitogenic activity. The present results, taken with previous data on EGF involvement in growth of cartilaginous tissue in vivo and in vitro, strongly suggest that EGF-immunoreactive chondrocytes are involved in cartilage proliferation and growth under the specific influence of GH.

Male mouse submaxillary gland secretes highly toxic proteins

Submaxillary gland saliva induced by phenylephrine from male mice was highly toxic to guinea-pigs, rats and hamsters, whereas the toxicity was relatively low to mice. One of the toxic components in the saliva was isolated as a kallikrein-like enzyme.

Influences of the submaxillary gland of male mice on the immune response to sheep red blood cells.

Removal of the submaxillary gland (SMG) from male but not female mice caused a suppressed immune response to sheep red blood cells. Administration of a SMG saline extract from male mice to SMG-ectomized males restored the suppressed response to control levels. This suggests that the male mouse SMG contains a factor(s), possibly of an endocrine nature, capable of influencing cells involved in an immune response.

Genetic variation in esteroproteases in the mouse submandibular gland.

9 isozymes of esteroproteases were detected by column isoelectric focusing of submandibular gland extracts from four inbred strains of male mice. A marked strain variance in the esteroprotease isozymes was found among the strains.

Effect of Autonomic Agents on the Secretion of N-Acetyl-β-Glucosaminidase of Mouse Submaxillary Gland

The secretion of N-acetyl-β-glucosaminidase of mouse submaxillary gland into saliva was stimulated by norepinephrine and phenylephrine but not by pilocarpine and isoproterenol. The stimulative effects of the α-adrenergic agents were inhibited by α-blockers, phentolamine, and phenoxybenzamine. These results suggest that the secretion of the enzyme is regulated through α-adrenergic receptors.

Peroxidase activity in salivary glands and saliva of beige (Chediak-Higashi) mice

Peroxidase activity was lower in the submandibular and parotid glands of beige mice than in controls. A lower level of activity was also observed in the isoproterenol-elicited saliva of beige mice.