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  • 1
    ISSN: 1573-4919
    Keywords: aging ; AR phosphorylation ; AR synthesis ; brain cortex ; sex steroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract To examine the synthesis and phosphorylation of androgen receptor (AR) and their regulation by sex steroids, adult (24 weeks) and old (65 weeks) male and female mice were gonadectomized and administered with testosterone and estradiol. AR amount, synthesis and phosphorylation were measured in the brain cortex by immunoblotting and immunoprecipitation using antibody raised against rat AR transactivation domain (TAD) which was expressed in E. coli as a fusion protein. We found that the amount of AR was high in adult and declined in old mice of both sexes. Administration of testosterone and estradiol significantly down-regulated the level of AR in old male and adult female. Similarly, the rate of AR synthesis also declined with age. Exogenous treatment of gonadectomized mice with testosterone and estradiol reduced the extent of synthesis significantly in all groups except in old female. No sex-dependent variation was noticed either in the level or synthesis of AR. In contrast, the extent of phosphorylation was higher in old mice of both sexes as compared to their adult counterparts. Testosterone and estradiol supplementation resulted in remarkable increase in AR phosphorylation in all groups. Thus it is evident from our findings that the amount and synthesis of AR decrease but phosphorylation of AR increases in the brain cortex with advancing age of mice and they are regulated by testosterone and estradiol in age and sex-specific manner.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Molecular biology reports 26 (1999), S. 179-184 
    ISSN: 1573-4978
    Keywords: aging ; amyloid precursor protein degradation ; lysosomal proteases ; mouse brain cortex ; post-mortem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have examined the degradation of amyloid precursor protein (APP) in the brain cortex of adult (24±2) and old (58±2) mice at different post-mortem time intervals (0, 1.5, 3, 6, 12 and 24 h). The brain cortex extract was prepared and processed for immunoblotting using antibodies against N-terminal 47–62 amino acids (Asp29) and central 301–316 amino acids containing Kunitz protease inhibitor (KPI) domain (Asp45) of APP. Asp29 (N-terminal) recognizes two bands of 140 and 112 kDa. The amount of 140 kDa is relatively higher in adult than old. The level of 112 kDa is 1.6 times lower in adult than old. It shows no remarkable change with varying post-mortem time. On the other hand, Asp45 (KPI) detects two bands of 110 and 116 kDa. While 116 kDa disappears rapidly after death of the animal, 110 kDa shows no remarkable change with different post-mortem periods. Further incubation of the disrupted tissue at 4 °C for 24 h and immunoblot analysis with Asp29 (N-terminal) shows 112 kDa in both ages but 58.5 kDa in adult and 70 kDa in old only. Analysis with Asp45 (KPI) shows only 54 kDa which increases after 3 h in adult but decreases significantly after 1.5 h and becomes undetectable at 24 h in old. Thus the present findings indicate that APP is degraded in a precise pattern and it depends on cellular intactness, post-mortem period and age of the animal.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-6768
    Keywords: aging ; androgen receptor ; gene amplification ; mouse brain ; sex steroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have investigated the effect of testosterone on theamplification of androgen receptor (AR) gene in the brain cortex ofaging female mice. For this purpose, high molecular weight (HMW) DNApurified from the brain cortex of intact, gonadectomized, testosterone-and estradiol-treated adult and old female mice was digested withdifferent restriction enzymes and used for Southern hybridization with32P-labeled AR cDNA fragments representing different domainsof AR. The results reveal that only exons 4 and 5 corresponding toamino-terminal part of the hormone binding domain of AR are amplified intestosterone-treated old female but not in adult mice. Densitometricanalysis further shows that testosterone increases the copy number ofexons 4 and 5 of mouse AR gene by four-fold. Reprobing of slot blotswith estrogen receptor and cathepsin D cDNA as probes supports theobservation that amplification occurs only in AR gene. The tissuespecificity is also confirmed when the slot blot hybridization of mouseliver HMW DNA with AR cDNA fails to show similar amplification. As therestriction map analysis of Southern blots does not show restrictionfragment length polymorphism, the possibility of structuralrearrangement leading to amplification of AR gene is ruled out. Thus ourresults suggest that the in vivo induction of mouse AR geneamplification by testosterone is tissue- and age-specific, and mightcontribute to the progress of genetic instability in the brain of agedfemale mice.
    Type of Medium: Electronic Resource
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