Inhibitory effects of dibutyryl cyclic AMP and theophylline on the melanosome transformation in the embryonic chick pigmented retina cultured in vitro

1976 ◽  
Vol 53 (2) ◽  
pp. 178-189 ◽  
Author(s):  
Yoshiko K. Takeuchi ◽  
Takao Kajishima
1979 ◽  
Vol 44 (5) ◽  
pp. 1651-1656 ◽  
Author(s):  
Sixtus Hynie ◽  
Jiří Smrt

3'-Oleolyl-2,3-dihydroxypropyl-AMP, 3'-stearoyl-2,3-dihydroxypropyl-AMP, octadecyl-AMP and palmitamidoethyl-AMP inhibited in comparison with adenosine or fatty acids much stronger the lipolysis in rat epididymal fat pads in vitro stimulated by isoproterenol, theophylline and dibutyryl cyclic AMP. The inhibition of the effects of the two latter drugs suggest that the described effect is caused not only by the inhibition of the cyclic AMP production but also by the inhibition of its effect on the following steps in process of lipolysis.


1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.


1976 ◽  
Vol 71 (2) ◽  
pp. 231-238 ◽  
Author(s):  
RÉGINE PICON

SUMMARY Testosterone secretion by foetal rat testes (13½–21½ days of gestation) explanted for 3 days in a synthetic medium was measured every 24 h by radioimmunoassay. During the first day of explantation, the foetal testis produced, respectively, 1013 ± 132, 8734 ± 1118, 9179 ± 2185 and 3886 ± 309 (s.e.m.) pg/testis when explanted at 14½, 16½, 18½ and 21½ days respectively. Testosterone production by 13½-day-old testes was not detectable on the first day of culture, but appeared on subsequent days. Daily testosterone secretion increased on the 2nd and 3rd days of culture in 14½-day-old testes and decreased in older stages. These results suggest that the functional differentiation of the testis is independent of stimulatory factors like gonadotrophins. Dibutyryl cyclic AMP was found to stimulate testosterone production significantly from 14½ days of gestation onwards.


Reproduction ◽  
1989 ◽  
Vol 86 (1) ◽  
pp. 373-381 ◽  
Author(s):  
B. K. Tsang ◽  
D. F. Mattice ◽  
M. Li ◽  
E. K. Asem

1984 ◽  
Vol 4 (10) ◽  
pp. 2142-2150 ◽  
Author(s):  
R A Levine ◽  
G J LaRosa ◽  
L J Gudas

In the absence of retinoic acid, PSA-G teratocarcinoma stem cells spontaneously differentiate at a moderate frequency into fibroblast-like cells. In the presence of retinoic acid and dibutyryl cyclic AMP, PSA-G stem cells differentiate into parietal endoderm cells. We prepared a cDNA library from undifferentiated PSA-G teratocarcinoma stem cells; this cDNA library was then screened for gene sequences which exhibit a reduction in expression during the differentiation of these stem cells. From ca. 1,000 clones screened, eight independent sequences were isolated. The level of expression of these cloned genes decreases by 3.0-fold to more than 10-fold after differentiation of PSA-G cells into fibroblast-like cells. After treatment of either PSA-G or F9 teratocarcinoma cells with retinoic acid and dibutyryl cyclic AMP for 72 h, the expression of seven genes is inhibited by two- to fourfold. This decrease of clone-specific transcripts can be detected within 12 h after the addition of retinoic acid. Hybridization-selection and in vitro translation experiments identified the proteins encoded by three of the cloned genes: pST 6-23 codes for a 89,000-dalton protein, pST 7-105 codes for a 41,000-dalton protein, and pST 9-31 codes for a 34,000-dalton protein. The 89,000-dalton protein encoded by pST 6-23 is a heat shock protein. In vitro transcription experiments demonstrate that the retinoic acid-mediated decrease in pST 6-135- and pST 1-68-specific RNA occurs at the transcriptional level and that dibutyryl cyclic AMP acts posttranscriptionally to further depress the levels of these RNAs.


1988 ◽  
Vol 118 (3) ◽  
pp. 485-489 ◽  
Author(s):  
J.-P. Weniger ◽  
A. Zeis

ABSTRACT The effect of dibutyryl cyclic AMP and FSH on oestrogen biosynthesis was investigated in testes from 18- to 21-day-old fetal rats cultured in vitro in the presence of tritiated testosterone. Oestrone and oestradiol concentrations were measured by determination of constant specific activity after isotopic dilution. Dibutyryl cyclic AMP and FSH markedly stimulated the conversion of testosterone into both oestrone and oestradiol at all stages studied. Oestradiol synthesis was stimulated by two- to sevenfold, while stimulation of oestrone synthesis was even greater. The results demonstrate that the aromatase enzyme system of the fetal rat testis responds to cyclic AMP and FSH. J. Endocr. (1988) 118, 485–489


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