The Effects of Isoflavones on Androgens and Glucocorticoids During Puberty on Male Wistar Rats     

S Caceres  G Silvan  L Martinez‐Fernandez  MJ Illera  P Millan  B Monsalve  L Peña  JC Illera 《Reproduction in domestic animals》2014,49(4):611-617

Isoflavones are the most common phytoestrogens found in human diets. However, it is still not clear whether isoflavones have effects on the reproductive and the endocrine systems under normal dietary intake and overdose. The aim of this study was to determine how the most important isoflavones, genistein and daidzein, affect androgen and glucorticoid levels on male prepuberal rats. A hundred and seventy‐five 30‐day‐old male Wistar rats were dosed orally by stomach tube every day for 35 days, with saline solution, low and high doses of genistein, daidzein and a mixture of both. Serum samples were analysed by an enzyme immunoassay for hormone determinations. In control group, there was a peak of testosterone (T) and dihydrotestosterone levels associated to the onset of puberty, at the third week. However, in low‐dose groups, the same peak was found at the fourth week (p < 0.05), indicating a delay in the onset of puberty in these groups. Moreover, high doses groups serum androgen levels were significantly lower (p < 0.05) than the control group from the first week until fifth week. This fact was supported by a epididymal histological analysis that indicate in low doses there were several content of spermatozoa at fourth week and in high doses there were few content of spermatozoa. Besides, corticosterone levels followed the same pattern of androgens in all groups. We can conclude that oral administration of isoflavones in male rats decreased the secretion of androgens and glucocorticoids causing a delay in the onset of puberty and may cause physiological and developmental problems.  相似文献   

Economic growth, carrying capacity, and the environment   总被引：11，自引：0，他引：11  

Arrow K  Bolin B  Costanza R  Dasgupta P  Folke C  Holling CS  Jansson BO  Levin S  Mäler KG  Perrings C  Pimentel D 《Science (New York, N.Y.)》1995,268(5210):520-521

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Binding of benzo[a]pyrene 7,8-diol-9,10-epoxides to DNA, RNA, and protein of mouse skin occurs with high stereoselectivity   总被引：7，自引：0，他引：7  

M Koreeda  P D Moore  P G Wislocki  W Levin  H Yagi  D M Jerina 《Science (New York, N.Y.)》1978,199(4330):778-781

The formation, stereostructure, and cellular reactions of the 7,8-diol-9,10-epoxide metabolites of the carcinogen benzo[a]pyrene have been examined after topical application of benzo[a]pyrene to the skin of mice. In this known target tissue, polymer adducts from diastereomeric diol epoxides, (+)-(7S, 8R, 9R, 10R) and (+)-(7R, 8S, 9R, 10R), were formed stereospecifically from their corresponding 7,8-dihydrodiols. Both diol epoxides bind with proteins, RNA, and DNA in vivo. For the nucleic acids, binding occurs preferentially at the 2-amino group of guanine in cellular RNA and DNA in vivo. Methods for establishing the structure of the cellular adducts as well as the possible biological implications of their formation are discussed.  相似文献   

Prolactin in the postpartum rat: synthesis and release in the absence of suckling stimulation     

H Moltz  R Levin  M Leon 《Science (New York, N.Y.)》1969,163(871):1083-1084

Postpartum female rats deprived of suckling stimulation while being kept continuously with pups nonetheless suspended ovarian cyclicity for an average of 16 days and responded to uterine trauma by forming deciduomata. These results show that the extramammary stimulation afforded by young is alone capable of sustaining prolactin output from the adenohypophysis of the postpartum rat.  相似文献   

Detection and Characterization of the Cumulene Carbenes H2C5 and H2C6     

MC McCarthy  MJ Travers  A Kovacs  W Chen  SE Novick  CA Gottlieb  P Thaddeus 《Science (New York, N.Y.)》1997,275(5299):518-520

Two cumulene carbenes, H2C5 and H2C6, were detected in a supersonic molecular beam by Fourier transform microwave spectroscopy. Their rotational and leading centrifugal distortion constants were determined with high accuracy, such that the entire radio spectrum can now be calculated. Like the known carbenes H2C3 and H2C4, both molecules have singlet electronic ground states and linear carbon-chain backbones. They can be produced in sufficiently high concentrations in the laboratory that their electronic spectra, expected to lie in the visible, should be readily detectable by laser spectroscopy. The microwave spectra of other, more exotic isomers may be detectable as well.  相似文献   

Cerebrospinal fluid production by the choroid plexus and brain   总被引：7，自引：0，他引：7  

T H Milhorat  M K Hammock  J D Fenstermacher  V A Levin 《Science (New York, N.Y.)》1971,173(994):330-332

The production of cerebrospinal fluid and the transport of (24)Na from the blood to the cerebrospinal fluid were studied simultaneously in normal and choroid plexectomized rhesus monkeys. Choroid plexectomy reduced the production of cerebrospinal fluid by an average of 33 to 40 percent and the rate of appearance of (24)Na in the cerebrospinal fluid and its final concentration were proportionately reduced. In both normal and plexectomized animals, (24)Na levels were found to be markedly greater in the gray matter surrounding the ventricles and in the gray matter bordering the subarachnoid space. That sodium exchanges in these two general areas of the brain may be linked to the formation of the cerebrospinal fluid is discussed here.  相似文献   

Beta-1C-globulin: metabolism in glomerulonephritis   总被引：9，自引：0，他引：9  

C A Alper  A S Levin  F S Rosen 《Science (New York, N.Y.)》1966,153(732):180-182

The metabolism of beta(1C)-globulin labeled with iodine-131 was studied in six normal individuals and in three individuals with glomerulonephritis who exhibited markedly reduced serum concentrations of this protein. Fractional of serum beta(1C)-globulin in glomerulonephritis appears to be chiefly secondary to decreased synthesis.  相似文献   

Global air pollution crossroads over the Mediterranean   总被引：3，自引：0，他引：3  

Lelieveld J  Berresheim H  Borrmann S  Crutzen PJ  Dentener FJ  Fischer H  Feichter J  Flatau PJ  Heland J  Holzinger R  Korrmann R  Lawrence MG  Levin Z  Markowicz KM  Mihalopoulos N  Minikin A  Ramanathan V  De Reus M  Roelofs GJ  Scheeren HA  Sciare J  Schlager H  Schultz M  Siegmund P  Steil B  Stephanou EG  Stier P  Traub M  Warneke C  Williams J  Ziereis H 《Science (New York, N.Y.)》2002,298(5594):794-799

The Mediterranean Intensive Oxidant Study, performed in the summer of 2001, uncovered air pollution layers from the surface to an altitude of 15 kilometers. In the boundary layer, air pollution standards are exceeded throughout the region, caused by West and East European pollution from the north. Aerosol particles also reduce solar radiation penetration to the surface, which can suppress precipitation. In the middle troposphere, Asian and to a lesser extent North American pollution is transported from the west. Additional Asian pollution from the east, transported from the monsoon in the upper troposphere, crosses the Mediterranean tropopause, which pollutes the lower stratosphere at middle latitudes.  相似文献   

The global extent and determinants of savanna and forest as alternative biome states   总被引：4，自引：0，他引：4  

Staver AC  Archibald S  Levin SA 《Science (New York, N.Y.)》2011,334(6053):230-232

Theoretically, fire-tree cover feedbacks can maintain savanna and forest as alternative stable states. However, the global extent of fire-driven discontinuities in tree cover is unknown, especially accounting for seasonality and soils. We use tree cover, climate, fire, and soils data sets to show that tree cover is globally discontinuous. Climate influences tree cover globally but, at intermediate rainfall (1000 to 2500 millimeters) with mild seasonality (less than 7 months), tree cover is bimodal, and only fire differentiates between savanna and forest. These may be alternative states over large areas, including parts of Amazonia and the Congo. Changes in biome distributions, whether at the cost of savanna (due to fragmentation) or forest (due to climate), will be neither smooth nor easily reversible.  相似文献   

O2- ions and the Mars labeled release response     

Levin GV 《Science (New York, N.Y.)》2001,291(5511):2041

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