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Biomedical subjects

Y C Yang

Publications and source records attributed to Y C Yang.

At least 271 records · Page 15Linked to original sources
PubMed1982

Radiation control through licensing and intensive training.

Various types of intensive training courses to suit radiation workers in different fields were sponsored by both the Atomic Energy Council of Executive Yuan and the National Health Administration of Executive Yuan, Republic of China during the past seven years. During the years 1974-79, the number of radiation workers attending each training course, their age, sex and educational background are presented in detail. The typical course contents for both medical and non-medical radiation workers are given. A summary of the percentage of passes and failures of the final examination given at the end of each training course is also given. The present status of licensing for radiation facilities and workers is described, and its results are indicated. The successful control of ionizing radiation through this kind of intensive training and licensing is evidenced in the film badge records given by a centralized service laboratory located at the National Tsing Hua University.

Adult↗
PubMed1981

Biological actions of melanocyte-stimulating hormone.

Melanocyte-stimulating hormone (alpha-melanotropin, MSH) may function in a number of diverse physiological roles. MSH stimulates (1) rapid translocation of melanosomes (melanin granules) in dermal melanophores to effect rapid colour change and (2) melanogenesis in normal and abnormal (melanoma) epidermal melanocytes. Both actions involve (1) initial binding of the peptide on the melanocyte membrane, (2) transduction of signal to adenylate cyclase, and (3) increased cytosolic levels of cyclic AMP. Efforts to prepare radioiodinated MSH and analogues for radioreceptor studies using melanoma membranes and intact cells reveal that conventional iodination procedures inactivate the hormone because of oxidative and iodination effects on specific structural components of the peptide. These effects can be circumvented by the use of synthetically tailored MSH analogues. Transduction of signal from receptor to adenylate cyclase requires calcium, but prostaglandin or beta-adrenoceptor stimulation of melanophores does not. The nucleotide and metal ion requirements for mouse melanoma adenylate cyclase activity have been characterized. There is both a transcriptional and translational requirement for MSH stimulation of tyrosinase activity and melanin production in melanoma cells. Melanosome translocation within melanophores is enhanced in the absence of extracellular calcium. A model for the MSH control of melanosome movements suggests a bifunctional, but compartmentalized, role for calcium in the action of MSH.

Adenylyl Cyclases↗
PubMed1981

Multiple sclerosis. A clinical study of 70 cases.

70 cases of multiple sclerosis were seen at the Department of Neurology of the Capital Hospital in 1949--1977. There were 25 males and 45 females averaging 30.6 years of age. The most frequent sites of the lesions based on the clinical symptomatology were the spinal cord and optic nerve, the cerebellum was much less frequently involved. The onset of the disease was acute or subacute in 63 cases. Remission and relapse were observed in 62 cases. There were 9 deaths. The survival times of these 9 cases after onset of illness was 1/4--4 years, 5 surviving less than 2 years. The clinical manifestations and pathologic findings noted in the present series support the opinion that optic neuromyelitis is but a variant of multiple sclerosis.

Adolescent↗
PubMed1981

Racemization effects on melanocyte-stimulating hormones and related peptides.

Heat-alkali treatment of synthetic alpha- and beta-melanocyte-stimulating hormones (MSH), known to cause racemization of amino acids within the peptides, results in prolongation of the darkening (melanophore dispersion) effect of these hormones on frog and lizard skins in vitro. Skins remain darkened for hours or even days if supramaximal concentrations of the racemized hormones are used. This response can be partially reversed by melatonin or noradrenaline. Heat-alkali treatment of alpha-MSH at either 60 or 97 degrees C results in a retardation of the response of the skins to the racemized peptides. In contrast, the response of frog skins to heat-alkali-treated beta-MSH is immediately enhanced and potentiated. Heat-alkali treatment also prolongs and potentiates the activity of synthetic [des-acetyl]-alpha-MSH (in contrast to the retardation effect on the natural acetylated peptide). These data suggest a role for the N-acetyl group in the retardation phenomenon. The activity of synthetic [2-D-tyrosine]-alpha-MSh is much lower than that of alpha-MSH itself, indicating that heat-alkali treatment of the hormone may produce either potentiation or partial inactivation of the peptide, depending on the site of racemization.

Animals↗
PubMed1980

Synthesis and structure-function studies of melanocyte stimulating hormone analogues modified in the 2 and 4(7) positions: comparison of activities on frog skin melanophores and melanoma adenylate cyclase.

The synthesis and purification of several analogues of the melanotropins with amino acid substitutions at the tyrosine-2 and methionine-4(7) positions are reported. The compounds synthesized included [4-norleucine]-alpha-MSH, [7-norleucine]-beta p-MSH, [2-3',5'-diiodotyrosine]-alpha-MSH, [2-D-tyrosine]-alpha-MSH, and [2-phenylalanine,4-norleucine]-alpha-MSH. The biological activities of these derivatives were measured and compared on normal melanocytes (frog skins) and on transformed melanocytes (mouse melanoma adenylate cyclase), over the entire dose-response range. All compounds tested were full agonists in both assay systems but varied considerably in potency. The relative potencies in the frog skin assay (alpha-MSH = 1.0) were as follows: [Nle7]-beta p-MSH (5.2) > [Nle4]-alpha-MSH (2.3) > alpha-MSH (1.0) > [Phe2,Nle4]-alpha-MSH (0.80) > beta p-MSH (0.55) > [I2-Tyr2]-alpha-MSH (0.12) > [D-Tyr2]-alpha-MSH (0.04). The relative potencies in the melanoma adenylate cyclase system were [Nle7]-beta p-MSH (4.2) > beta p-MSH (2.2) > [Nle4]-alpha-MSH (2.0) > alpha-MSH (1.0) approximately equal to [Phe2,Nle4]-alpha-MSH (0.9) > [I2-Tyr2]-alpha-MSH (0.40) > [D-Tyr2]-alpha-MSH (0.20). There appears to be some differences in structural specificity at the melanotropin receptors of the two cell systems.

Adenylyl Cyclases↗