[Extraction and Separation of Sinapine from Rapeseed Cake and the Mode of Action of Melanin Production Inhibition].

Brassica campestris L. is the important oil-bearing crop in China. Rapeseed cake is the main byproduct of rapeseed oil extraction. As the main active ingredient in rapeseed cake, sinapine has several important biological activities. Therefore, the inhibitory activity of sinapine on tyrosinase in vitro and its free radical-scavenging rate were determined. Tyrosinase activity in A-375 human melanocytes was also investigated and the effects of sinapine on the melanin content and its antioxidant effects on melanin biosynthesis were studied. The results showed that sinapine had significant antioxidant activity. Sinapine significantly inhibited A-375 human melanocytes in a dose-dependent manner. Sinapine inhibited melanin synthesis in A-375 cells by downregulating the mRNA and protein expression of TRP-1, TRP-2, and MITF factors. The results showed that rapeseed cake sinapine inhibited melanin production and could be used as a potential active ingredient in the development of whitening agents.

The role of central arginine vasopressin in corticotropin releasing hormone-induced fever in rats.

The purpose of the present study was to investigate the role of central arginine vasopressin (AVP) in corticotropin releasing hormone (CRH) induced fever in the rat. Guide cannulae were inserted into the third ventricle and placed over the ventral septal area (VSA). The content of arginine vasopressin in the VSA of the brain was determined by radioimmunoassay. Colon temperature was monitored in lightly restrained rats by insertion of a catheter mounted thermistor probe 5 cm in the rectum. The results demonstrated that intracerebroventricular (icv) injection of CRH increased AVP level in the VSA and the colonic temperature of the rats. Microinjection of AVP V(1) antagonist into the VSA 10 min before CRH administration significantly enhanced CRH-induced febrile response, while AVP V(1) antagonist itself did not have a significant effect on the colonic temperature. Furthermore, injection of AVP into the VSA 5 min before CRH administration (icv) suppressed the fever evoked by CRH. These findings suggest that CRH is an important factor that stimulates the release of AVP in the VSA during fever, and endogenous AVP in the VSA has an antipyretic action on the CRH-induced fever.

[Antipyretic action of dexamethasone on egtazic acid-induced fever in rabbits].

The purpose of the present study was to investigate whether the antipyretic effect of dexamethasone (DEX) delivered by intravenous injection (i.v.) on intracerebroventricularly (icv) administered egtazic acid-induced febrile response is relevant to the changes in cytosolic free calcium concentration of the hypothalamus. The colon temperatures were measured by a thermistor and the cytosolic free calcium concentration ([Ca2+]i) in dissociated brain cells was measured by Fura 2-AM. The results demonstrated that the pyretic action of egtazic acid (0.6 mumol, icv) was markedly inhibited by DEX (5 mg/kg, i.v.), but DEX (60-120 mumol/L) did't affect [Ca2+]i in dissociated hypothalamus cells. Actinomycin D, which interferes with gene transcription (3 nmol, icv), completely abolished the antipyretic action of DEX on egtazic acid-induced fever. These findings suggest that the antipyretic action of DEX on egtazic acid-induced fever is related to the activation of certain gene expression in the brain, but not to the changes of transmembrane calcium ion current in hypothalamus neurons.

Quantitative study of the effects of long-term denervation on the extensor digitorum longus muscle of the rat.

BACKGROUND: In order to understand the cellular basis underlying the progressively poorer restorative capacity of long-term denervated muscle, we determined the effects of long-term denervation on the muscle fibers and satellite cell population of the rat extensor digitorum longus (EDL) muscle. METHODS: In 36 male rats, the right hind legs were denervated, and EDL muscles were removed 2, 4, 7, 12, and 18 months later. Muscles were either fixed for electron microscopic analysis or were dissociated into individual muscle fibers for direct fiber counting or for confocal microscopic analysis. RESULTS: The percentage of satellite cells rose from the 2.8% control value to 9.1% at 2 months of denervation; thereafter the percentage decreased to 1.1% at 18 months of denervation. The number of myonuclei per muscle fiber steadily declined from 410 in 4 month control muscle to 158 in 7 month denervated muscle. Up to 7 months of denervation, the total number of muscle fibers per muscle remained relatively constant at somewhat over 5,000. The calculated total satellite cell population in 4 month denervated EDL muscle was the same as that of controls at 65,000, but by 7 months of denervation it had declined to 21,000. With increasing time of denervation, the number of cross-sectional profiles of muscle fibers not containing nuclei rose from 14% in control muscle to 49% in 12 month denervated muscle. This was correlated with a pronounced regular clumping of the nuclei, with pronounced nonnucleated segments between nuclear clumps. CONCLUSIONS: Increasing times of denervation are accompanied by a pronounced decline in the number of myonuclei per muscle fiber and an initial rise and subsequent fall in satellite cell number. These changes are correlated with a decreasing restorative ability of these muscles over the same periods of denervation. Further work on the proliferative capacity of the remaining satellite cells is necessary before firm quantitative conclusions can be made.

Electron microscopic study of long-term denervated rat skeletal muscle.

BACKGROUND: This study describes the ultrastructure of long-term denervated rat extensor digitorum longus and tibialis anterior muscles, with particular emphasis on understanding the cellular basis for the reduced restorative capacity of long-term denervated muscle. METHODS: In 30 male WI/HicksCar rats, the right hindleg was denervated for periods of 1, 2, 4, 5.5, 6, 7, 12, 14, and 18 months before tissues were prepared for electron microscopy. RESULTS: Atrophy of muscle fibers was prominent by the second month post-denervation. At this time, type II fibers showed greater atrophy than type I fibers. At further periods of denervation, atrophy of all fibers was seen; and with increasing times of denervation the muscle fibers became surrounded by dense mats of collagen fibers. Muscle spindles persisted for the duration of this study. At two and four months, satellite cells showed signs of activation, such as elongated cytoplasmic processes and an increased concentration of cytoplasmic organelles. As denervation progressed, activated satellite cells became more widely separated from their associated muscle fibers, and basal lamina material was deposited between the satellite cells and muscle fibers. Some satellite cells broke free from their muscle fibers, and others acted as bridges between two muscle fibers. Evidence was seen of both muscle fiber degeneration and the regeneration of new muscle fibers, often more than one regenerating fiber beneath a single basal lamina. Loose folds of basal lamina were often present around atrophic muscle fibers. As denervation progressed, the morphology of individual muscle fibers varied. Some contained well-ordered lattice arrays of myofilaments, whereas in others considerable sarcomeric disorganization was evident. Mitochondria became smaller and rounded; elements of the sarcoplasmic reticulum proliferated and became more disorganized; lipid droplets, glycogen deposits, and autophagic vesicles were all present in the cytoplasm of atrophic muscle fibers. CONCLUSIONS: In addition to muscle fiber atrophy, long-term denervated muscles show evidence of myofiber and capillary death, as well as the deposition of massive amounts of interstitial collagen. These changes, all of which would appear to reduce the restorative capacity of the denervated muscle, take place concurrently with the morphological activation of satellite cells. The latter indicates that even in the denervated condition, restorative processes occur concurrently with regressive processes.

The occurrence of post-denervation hypertrophy in chick slow muscle fibres after complete elimination of stretch and tension.

With the slow muscle fibres in the pure slow muscle ALD as well as in two mixed muscles, flexor metacarpi ulnaris and sartorius, it is demonstrated that the phenomenon of postdenervation hypertrophy still occurs under conditions preventing stretch of muscle after denervation or even in tenotomized muscles in shortened state relieved of tension. Striking differences between the slow fibres of the ALD and those of the mixed muscles are seen, both with respect to their histochemical property and to the degree of development of post-denervation hypertrophy. The slow fibres in the mixed muscles show the phenomenon of post-denervation hypertrophy in a much more striking form than the ALD fibres and should be made more use of in further studies on the phenomenon.

Of post-denervation hypertrophy in chick slow muscle fibres after complete elimination of stretch and tension.

For the slow muscle fibres in the pure slow muscle ALD as well as in two mixed muscles, flexor metacarpi ulnaris and sartorius, it is demonstrated that the phenomenon of post-denervation hypertrophy still occurs under conditions preventing stretch of muscle after denervation or even in tenotomized muscles in shortened state relieved of tension. Striking differences between the slow fibres of the ALD and those of the mixed muscles are seen, both with respect to their histochemical property and to the degree of development of post-denervation hypertrophy. The slow fibres in mixed muscles show the phenomenon of post-denervation hypertrophy in a much more striking form than do the ALD fibres, and should be used in further studies of the phenomenon.