PubMed · 10141455
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A Majeed, A Pollock. 1995-03-16. Contract data. Set piece.. https://pubmed.ncbi.nlm.nih.gov/10141455/
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The biochemical mechanisms by which regular exercise significantly benefits health and well being, including improved cognitive function, are not well understood. Four-week-old (young) and 14-month-old (middle aged) Wistar rats were randomly assigned to young control and young exercised, middle-aged control and middle-aged exercised groups. Exercise groups were exposed to a swimming regime of 1 h a day, 5 days a week for 9 weeks. The passive avoidance test showed that middle-aged exercised rats had significantly (P<0.05) better short- (24 h) and long-term (72 h) memory than aged-matched control rats. Conditioned pole-jumping avoidance learning was improved markedly in both age groups by exercise. Brain thiobarbituric acid-reactive substances and 8-hydroxy-2'deoxyguanosine content in the DNA did not change significantly, while the protein carbonyl levels decreased significantly (P<0.05) in both exercised groups. This decrease was accompanied by an increase in the chymotrypsin-like activity of proteasome complex in the exercised groups, whereas trypsin-like activity did not differ significantly between all groups. The DT-diaphorase activity increased significantly (P<0.05) in the brain of young exercised animals. These data show that swimming training improves some cognitive functions in rats, with parallel attenuation of the accumulation of oxidatively damaged proteins.
Aggrecan degradation involves proteolytic cleavage of the core protein within the interglobular domain. Because aggrecan is highly glycosylated with chondroitin sulfate (CS) and keratan sulfate (KS), we investigated whether glycosylation affects digestion by aggrecanase at the Glu(373)-Ala(374) bond. Treatment of bovine aggrecan monomers to remove CS and KS resulted in loss of cleavage at this site, suggesting that glycosaminoglycans (GAGs) play a role in cleavage at the Glu(373)-Ala(374) bond. In contrast, MMP-3 cleavage at the Ser(341)-Phe(342) bond was not affected by glycosidase treatment of aggrecan. Removal of KS, but not CS, prevented cleavage at the Glu(373)-Ala(374) bond. Thus, KS residues may be important for recognition of this cleavage site by aggrecanase. KS glycosylation has been observed at sites adjacent to the Glu(373)-Ala(374) bond in steer aggrecan, but not in calf aggrecan (Barry, F. P., Rosenberg, L. C., Gaw, J. U., Gaw, J. U., Koob, T. J., and Neame, P. J. (1995) J. Biol. Chem. 270, 20516-20524). Interestingly, although we found that aggrecanase degraded both calf and steer cartilage aggrecan, the proportion of fragments generated by cleavage at the Glu(373)-Ala(374) bond was higher in steer than in calf, consistent with our observations using aggrecan treated to remove KS. We conclude that the GAG content of aggrecan influences the specificity of aggrecanase for cleavage at the Glu(373)-Ala(374) bond and suggest that age may be a factor in aggrecanase degradation of cartilage.
The aim of the present study was to retrospectively analyze causes of the variation in age at first mating in Swedish Landrace (L) and Swedish Yorkshire (Y) gilts. Production traits including growth rate from birth to 100kg body weight and backfat thickness at 100kg body weight were also studied. Data analyzed were obtained from 11 L and 11 Y nucleus herds and included gilts born during a 5-year-period from October 1993 until September 1998. The complete data set included information on 14,761 gilts (6997 L and 7764 Y). Traits analyzed included age of gilt at first mating, growth rate and backfat thickness. Seven statistical models were used for analyzing the data. Factors included were gilt breed, birth month, parity number and size of the litter in which the gilt was born as well as their interactions. Compared with Y gilts, L gilts grew faster (571 versus 556 g/day; P<0.001), had a thinner backfat (11.9 versus 12. 3mm; P<0.001) at 100kg body weight and were 12 days younger at first mating (237 versus 249 days; P<0.001). Birth month significantly (P<0.001) influenced age at first mating, growth rate and backfat thickness. Gilts born from smaller litters were mated at younger age than gilts born from larger litters even when age at first mating was adjusted for the effect of growth rate and backfat thickness. Growth rate of the gilts decreased when 'birth litter size' increased. Gilts born from primiparous sows grew slower, had a thinner backfat at 100kg body weight and were older at first mating compared with gilts born from multiparous sows. Gilts with a higher growth rate were younger at first mating than those with a lower growth rate. Gilts with a thicker backfat at 100kg body weight were mated earlier than the thin ones. However, the effect of growth rate on age at first mating was more pronounced in the gilts with a thinner backfat rather than the ones with a thicker backfat.