THE MELANOGENIC RESPONSE TO TESTOSTERONE IN SCROTAL EPIDERMIS: EFFECTS ON TYROSINASE ACTIVITY AND PROTEIN SYNTHESIS

1976 ◽  
Vol 81 (2) ◽  
pp. 435-448 ◽  
Author(s):  
Michael J. Wilson ◽  
Eugene Spaziani
Keyword(s):  
Protein Synthesis ◽  
Specific Protein ◽  
Tyrosinase Activity ◽  
Melanin Synthesis ◽  
Testosterone Treatment ◽  
Pre Treatment ◽  
Inhibitor Of Protein Synthesis ◽  
Rate Limiting

ABSTRACT Pigmentation of the scrotum of the black-pelted rat, as expressed through melanocyte melanogenic activity, is controlled by androgens. Castration decreased in vitro incorporation of [14C] tyrosine into melanin. Testosterone pre-treatment for 4 days increased melanin radioactivity over castrate controls; the increment in vitro was prevented by an inhibitor of protein synthesis (cycloheximide) added to the incubation. However, cycloheximide only partially blocked melanin synthesis when added to tissue from animals hormone treated for 6 days in vivo, and was ineffective in tissue from intacts. Bulk protein synthesis in vitro (incorporation of [14C] tyrosine or -leucine) was not affected by castration or testosterone treatment but was uniformly inhibited by cycloheximide. The data suggest that new synthesis of specific protein in vitro was necessary for initial hormone-stimulation of melanogenesis, but with longer exposure to hormone sufficient protein was pre-synthetized in vivo to permit melanogenesis during incubation with the inhibitor. Radioautographs of epidermis incubated with [14C] tyrosine showed grains concentrated over macromolecular aggregates in melanocytes, a pattern not altered by cycloheximide. Though available for incorporation into general tissue protein. [14C] tyrosine was apparently incorporated preferentially into melanin by melanocytes. DOPA (3,4-dihydroxyphenylalanine) added to incubations in cofactor amounts did not affect decreased melanin synthesis after castration and appears, therefore, not to be rate limiting in that decrease. Tissue uptake of free [14C] tyrosine or — leucine during incubation was lower than normal in castrate epidermis; uptake was elevated by testosterone treatment. Concentrations appeared sufficient in all preparations to suggest that availability is not rate limiting for synthesis of melanin or protein; however, a possible influence on amino acid permeability for melanocytes remains undetermined. Tyrosinase activity was present in both particulate and cytosol fractions of epidermis but decreased significantly after castration only in the cytosol. Testosterone increased particulate activity after 4 days and soluble activity after 9 days of treatment. These and findings above are consistent with a model that tyrosinase is synthesized and incorporated into melanosome structure within 4 days testosterone treatment; with longer treatment synthesis may then exceed that required for melanosome assembly and tyrosinase appears in the soluble milieu.

scholarly journals The rate-limiting step of protein synthesis in vivo and in vitro and the distribution of growing peptides between the puromycinlabile and puromycin-non-labile sites on polyribosomes

1971 ◽  
Vol 122 (3) ◽  
pp. 267-276 ◽  
Author(s):  
D. C. N. Earl ◽  
Susan T. Hindley
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Donor Site ◽  
Peptide Bond ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Donor And Acceptor ◽  
Rate Limiting

1. At 3 min after an intravenous injection of radioactive amino acids into the rat, the bulk of radioactivity associated with liver polyribosomes can be interpreted as growing peptides. 2. In an attempt to identify the rate-limiting step of protein synthesis in vivo and in vitro, use was made of the action of puromycin at 0°C, in releasing growing peptides only from the donor site, to study the distribution of growing peptides between the donor and acceptor sites. 3. Evidence is presented that all growing peptides in a population of liver polyribosomes labelled in vivo are similarly distributed between the donor and acceptor sites, and that the proportion released by puromycin is not an artifact of methodology. 4. The proportion released by puromycin is about 50% for both liver and muscle polyribosomes labelled in vivo, suggesting that neither the availability nor binding of aminoacyl-tRNA nor peptide bond synthesis nor translocation can limit the rate of protein synthesis in vivo. Attempts to alter this by starvation, hypophysectomy, growth hormone, alloxan, insulin and partial hepatectomy were unsuccessful. 5. Growing peptides on liver polyribosomes labelled in a cell-free system in vitro or by incubating hemidiaphragms in vitro were largely in the donor site, suggesting that either the availability or binding of aminoacyl-tRNA, or peptide bond synthesis, must be rate limiting in vitro and that the rate-limiting step differs from that in vivo. 6. Neither in vivo nor in the hemidiaphragm system in vitro was a correlation found between the proportion of growing peptides in the donor site and changes in the rate of incorporation of radioactivity into protein. This could indicate that the intracellular concentration of amino acids or aminoacyl-tRNA limits the rate of protein synthesis and that the increased incorporation results from a rise to a higher but still suboptimum concentration.

Attenuation of In Vitro and In Vivo Melanin Synthesis using a Chinese Herbal Medicine through the Inhibition of Tyrosinase Activity

Phytomedicine ◽  
2021 ◽  
pp. 153876
Author(s):  
Shu-Chun Liu ◽  
Meei-Ling Sheu ◽  
Yi-Ching Tsai ◽  
Yu-Chin Lin ◽  
Ching-Wen Chang ◽  
...  
Keyword(s):  
Herbal Medicine ◽  
Chinese Herbal Medicine ◽  
Tyrosinase Activity ◽  
Melanin Synthesis ◽  
Chinese Herbal

scholarly journals SPECIFIC PROTEIN SYNTHESIS IN CELLULAR DIFFERENTIATION

1972 ◽  
Vol 55 (3) ◽  
pp. 653-680 ◽  
Author(s):  
M. Paul ◽  
M. R. Goldsmith ◽  
J. R. Hunsley ◽  
F. C. Kafatos
Keyword(s):  
Protein Synthesis ◽  
Messenger Rna ◽  
Developmental Stages ◽  
Specific Protein ◽  
Chain Elongation ◽  
Synthetic Activity ◽  
Translational Efficiency ◽  
Kinetics Of

Silkmoth follicles, arranged in a precise developmental sequence within the ovariole, yield pure and uniform populations of follicular epithelial cells highly differentiated for synthesis of the proteinaceous eggshell (chorion). These cells can be maintained and labeled efficiently in organ culture; their in vitro (and cell free) protein synthetic activity reflects their activity in vivo. During differentiation the cells undergo dramatic changes in protein synthesis. For 2 days the cells are devoted almost exclusively to production of distinctive chorion proteins of low molecular weight and of unusual amino acid composition. Each protein has its own characteristic developmental kinetics of synthesis. Each is synthesized as a separate polypeptide, apparently on monocistronic messenger RNA (mRNA), and thus reflects the expression of a distinct gene. The rapid changes in this tissue do not result from corresponding changes in translational efficiency. Thus, the peptide chain elongation rate is comparable for chorion and for proteins synthesized at earlier developmental stages (1.3–1.9 amino acids/sec); moreover, the spacing of ribosomes on chorion mRNA (30–37 codons per ribosome) is similar to that encountered in other eukaryotic systems.

ADRENAL RESPONSES TO CORTICOTROPHIN IN THE PRESENCE OF AN INHIBITOR OF PROTEIN SYNTHESIS

1968 ◽  
Vol 58 (4) ◽  
pp. 619-629 ◽  
Author(s):  
René Maier ◽  
Matthys Staehelin
Keyword(s):  
Fatty Acids ◽  
Blood Flow ◽  
Protein Synthesis ◽  
Unsaturated Fatty Acids ◽  
Cholesterol Esters ◽  
Acth Stimulation ◽  
Inhibitor Of Protein Synthesis ◽  
Primary Action

ABSTRACT The effect of cycloheximide, an inhibitor of protein synthesis, on the response of the rat adrenal to ACTH was studied. Cycloheximide blocks corticosteroidogenesis in vivo and in vitro, but does not affect the increase in adrenal blood flow in vivo. When the corticosterone production of adrenal slices was studied after ACTH stimulation in vivo, it was found that adrenal slices from rats pre-treated with cycloheximide, secreted corticosterone just as efficiently as adrenal slices from control animals. It is concluded that cycloheximide does not block the primary action of ACTH but that it inhibits subsequent enzymatic processes taking place in the mitochondria. The hypothesis is put forward that the increase in adrenal blood flow induced by ACTH might be due to prostaglandins which could be formed from unsaturated fatty acids released by the cleavage of cholesterol esters.

DISSOCIATION OF STIMULATORY EFFECTS OF CORTICOTROPHIN ON ADRENAL CORTICOSTERONE AND PROTEIN SYNTHESIS FOLLOWING HYPOPHYSECTOMY

1968 ◽  
Vol 59 (3) ◽  
pp. 475-478
Author(s):  
P. C. Scriba ◽  
F. Kluge
Keyword(s):  
Protein Synthesis ◽  
Acth Treatment ◽  
Rate Limiting ◽  
Adrenal Corticosterone

ABSTRACT At various intervals after hypophysectomy some dissociation of stimulation by corticotrophin (ACTH) treatment of the activity of a factor in adrenal homogenates, previously shown to be rate limiting for in vitro 14C-glycine incorporation into adrenal proteins, from stimulation by ACTH of the in vivo secretion of corticosterone, was found.

Thyroid hormone regulation of translation in tadpole tail muscle

1980 ◽  
Vol 58 (6) ◽  
pp. 461-468 ◽  
Author(s):  
Mohammed Saleem ◽  
Burr G. Atkinson
Keyword(s):  
Protein Synthesis ◽  
Synthetic Activity ◽  
Translational Efficiency ◽  
Hormone Regulation ◽  
Tadpole Tail ◽  
Inhibitor Of Protein Synthesis ◽  
Tail Muscle ◽  
Translational Level

Recent in vivo and in vitro studies with polyribosomes from the tail muscle of T3-treated tadpoles establish that this hormone initiates a regulating effect on tadpole tail muscle which operates at the translational level and results in an overall decreased rate of protein synthesis (Saleem, M. &Atkinson, B. G. (1978) J. Biol. Chem. 253, 1378–1384). This hormone-induced decrease in the rate of protein synthesis is partially, if not wholly, due to the presence of a sarcoplasmic factor(s) inhibiting ribosomal translational efficiency. This research employs the use of a reconstituted, cell-free polypeptide synthesizing system as a means to substantiate the presence of an inhibitor and further elucidate the mechanism by which this inhibitory factor(s) depresses protein synthesis. The results of this study further demonstrate the presence of an inhibitor of protein synthesis in the tail muscle sarcoplasm of T3-treated tadpoles and suggest that this depressed synthetic activity results from an interaction of the inhibitor with ribosomal or polyribosomal constituents.

The Milk Mononuclear Phagocyte

PEDIATRICS ◽  
1979 ◽  
Vol 64 (5) ◽  
pp. 745-749
Author(s):  
Jane Pitt
Keyword(s):  
Protein Synthesis ◽  
Smooth Endoplasmic Reticulum ◽  
Mononuclear Phagocyte ◽  
Mononuclear Phagocytes ◽  
Human Colostrum ◽  
The One ◽  
Inhibitor Of Protein Synthesis ◽  
Glass Surfaces

A large number of mononuclear phagocytes are present in human colostrum and milk and are transferred from mother to baby. Although one can only speculate on their role in vivo, there is a modest amount of information about their characteristics in vitro which will be reviewed in this paper. About 80% of the one to two million leukocytes in colostrum and early human milk are mononuclear phagocytes1,2 as determined by esterase staining,3 latex ingestion, and glass adherence. While See Table in the PDF Document their concentration diminishes with longer lactation, the number of macrophages secreted daily is large (Table 1). The milk mononuclear phagocyte spreads avidly onto glass surfaces extending long filamentous processes into the environment (Fig 1). Trypan blue is rapidly taken up into the lysozomes of living cells (Fig 2) as is acridine orange. These cells are lipid laden (Fig 3) and on ultrastructural analysis one sees that the lipid inclusions are not always membrane bound (Fig 4). Mitochondria, an indication of oxidative metabolism, and rough and smooth endoplasmic reticulum, suggesting active protein synthesis, are plentiful. Comparisons between milk and blood mononuclear phagocytes are listed in Table 2. Lysozyme is one of the proteins synthesized and secreted by the milk mononuclear phagocyte. By competitive binding, radioimmunoassay milk macrophages can be shown to release 100 ± 8 ng lysozyme/ 5 x 105 cells into the supernatant; the level is reduced to 20 ± 4 ng when these cells are cultured in the presence of 10 µg/ml of cyclohexamide, an inhibitor of protein synthesis. Moreover, it appears that these cells make C3 and C4.

scholarly journals Control of cell protein catabolism in rat liver. Effects of starvation and administration of cycloheximide

1982 ◽  
Vol 206 (2) ◽  
pp. 395-405 ◽  
Author(s):  
F M Baccino ◽  
L Tessitore ◽  
G Cecchini ◽  
M Messina ◽  
M F Zuretti ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Osmotic Fragility ◽  
Total Activity ◽  
Cell Protein ◽  
Liver Protein ◽  
Lysosomal Hydrolases ◽  
Protein Mass ◽  
Inhibitor Of Protein Synthesis

1. The loss of liver protein occurring in rats starved for 24 h was largely prevented by the administration of repeated doses of cycloheximide, an inhibitor of protein synthesis. Similar effects were produced on tubulin, a ‘fixed’ liver protein. 2. Starvation accelerated, whereas cycloheximide markedly lowered, the rate of protein radioactivity decay after labelling with [3H]valine or [14C]bicarbonate, indicating that changes in catabolic rates played an important role in the above regulations of liver protein mass. 3. The total activity of several lysosomal hydrolases showed little change in livers of starved rats, but a marked progressive decline developed after the administration of cycloheximide, particularly in the activities of cathepsins B, D and L as well as acid ribonuclease. There was no evidence that these changes might be due to endogenous inhibitors (at least for cathepsin B activity, which fell to less than 30% of the control values) or enzyme leakage into the bloodstream; rather, plasma beta-galactosidase and beta-N-acetylglucosaminidase activities fell progressively during the cycloheximide treatment. 4. Endogenous proteolytic rates, measured in vitro by incubating subcellular preparations from livers prelabelled in vivo with [3H]valine, were markedly decreased in cycloheximide-treated animals. 5. The osmotic fragility of hepatic lysosomes, appreciably enhanced in starved animals, after cycloheximide treatment was found to be even lower than in fed controls. 6. The present data are consistent with the view that in starved animals the loss of liver protein is mostly accounted for by increased breakdown, due, in part at least, to enhanced autophagocytosis. 7. Cycloheximide largely counteracted these effects of starvation, altering the liver from being ‘poised’ in a proteolytic direction to a protein-sparing condition. The present data suggest that, besides suppression of the autophagic processes, a decrease in the lysosomal proteolytic enzyme system may also play a role in this regulation, and they seem to provide further circumstantial evidence for the existence of co-ordinating mechanisms between protein synthesis and degradation.

Specific Labeling of Protein Domains with Antibody Fragments

1981 ◽  
Vol 39 ◽  
pp. 416-417
Author(s):  
U. Aebi ◽  
L.E. Buhle ◽  
W.E. Fowler
Keyword(s):  
Image Processing ◽  
Specific Protein ◽  
Antibody Fragments ◽  
Supramolecular Organization ◽  
Two Dimensional ◽  
Ordered Structures ◽  
Virus Capsids ◽  
Processing Techniques

Many important supramolecular structures such as filaments, microtubules, virus capsids and certain membrane proteins and bacterial cell walls exist as ordered polymers or two-dimensional crystalline arrays in vivo. In several instances it has been possible to induce soluble proteins to form ordered polymers or two-dimensional crystalline arrays in vitro. In both cases a combination of electron microscopy of negatively stained specimens with analog or digital image processing techniques has proven extremely useful for elucidating the molecular and supramolecular organization of the constituent proteins. However from the reconstructed stain exclusion patterns it is often difficult to identify distinct stain excluding regions with specific protein subunits. To this end it has been demonstrated that in some cases this ambiguity can be resolved by a combination of stoichiometric labeling of the ordered structures with subunit-specific antibody fragments (e.g. Fab) and image processing of the electron micrographs recorded from labeled and unlabeled structures.

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