Masatoshi Nakano

AGE-RELATED CHANGES IN THE LIPOFUSCIN ACCUMULATION OF BRAIN AND HEART

Lipofuscin is the end-product of intracellular lipid peroxidation and the accumulation results from the cellular metabolism during aging (life stage). We suggested that the accumulation of cardiac lipofuscin was dependent on the specific metabolic rate of mammals. Slower rate of cardiac lipofuscin accumulation (against absolute lifespan) was observed in the animals of larger body size. The rate of cardiac lipofuscin accumulation was correlated with the specific metabolic rate, and inversely correlated with the brain weight of mammals. The first appearance of lipofuscin granules was 8 weeks of age in the hippocampus and in the thalamus. In the case of cerebral cortex (laminae III), lipofuscin granules were first found at 3-month-old rats. The rate of lipofuscin accumulation was the highest in the hippocampus (y = 0.286x - 0.099, r = 0.963) among the three regions examined. In the case of cerebral cortex and thalamus, the slower rate of lipofuscin accumulation was observed (y = 0.072x - 0.14, r = 0.797 for cerebral cortex; y = 0.067X - 0.14, r = 0.953 for thalamus). It is noticed that the most abundant accumulation and the highest rate of lipofuscin accumulation are the hippocampus. Even the hippocampus, the rate and the magnitude of lipofuscin accumulation was low as compared with cardiac muscles. From these results, it is suggested that brains have better protective system against oxidative stress than other organs do.

Antiviral properties of a mangrove plant, Rhizophora apiculata Blume, against human immunodeficiency virus.

A polysaccharide extracted from the leaf of Rhizophora apiculata (RAP) was assessed in cell culture systems, for its activity against human and simian immunodeficiency viruses. RAP inhibited HIV-1 or HIV-2 or SIV strains in various cell cultures and assay systems. It blocked the expression of HIV-1 antigen in MT-4 cells and abolished the production of HIV-1 p24 antigen in peripheral blood mononuclear cells (PBMC); the 50% effective concentration (EC50) of RAP in HIV-1 infected MT-4 cells and in PBMC was 10.7 and 25.9 microg/ml, respectively. RAP (100 microg/ml) completely blocked the binding of HIV-1 virions to MT-4 cells. RAP also reduced the production of viral mRNA when added before virus adsorption. RAP inhibited syncytium formation in cocultures of MOLT-4 cells and MOLT-4/HIV-1(IIIB) cells. RAP did not prolong activated partial thromboplastin time (APTT) up to 500 microg/ml. These properties may be advantageous should RAP be considered for further development.

Effects of long-term dietary supplement of tea polyphenols on lipid peroxide levels in rats

We examined the effects of tea polyphenols (TP) on the body weight gain and contents of lipids and lipid peroxides in rat plasma, kidney and liver. The supplementation of TP (0.5% and 1.0%) in the diet was performed from weanling (3 weeks of age) to 19 months old. A significant suppression of body weight gain was observed only at 7–11 weeks of age, but there were no significant changes in liver and kidney weight between control group and TP-feeding group (TP group). Daily food intake of animals in two TP groups was almost the same as the control group.In the older rats (13–19 months of age), thiobarbituric acid reactive substances (TBARS) in the plasma in 1.0% TP group were significantly lower than that of the control g roup (p<0.01). The contents of plasma lipids (triglyceride, total cholesterol, and phospholipid) in 1.0% TP group at 19 months old were significantly lower as compared with the control group (p<0.05). There was a positive correlation in an age group 13–19 months old between these lipid contents and TBARS.These results suggest that long-term dietary supplementation of TP caused the decrease of plasma TBARS, mainly due to the hypolipidemic activity and antioxidative effect of TP in vivo.

Age-related changes in the metabolism of neurotransmitters in rat striatum: a microdialysis study.

Rats from one month to 22 months of age were subjected to in vivo brain microdialysis under a free-moving condition. The 3,4-dihydroxyphenylacetic acid level in the striatum reached a maximum at 3 months old. However, both basal and potassium-induced dopamine release were maximal at 1.5 months, which represents sexual maturation (puberty). The inhibitory effect of monoamine oxidase (MAO) activity by pargyline was maximal at 1.5 months. The delayed maximum level of the metabolites may be due to different age-related changes in MAO-A and MAO-B. From these results, it is suggested that in the rat striatum, the release of dopamine is maximal at the age of sexual maturation, and that the whole synaptic function of the dopaminergic neurons is at its highest during late adolescence.

Age-related accumulation of lipofuscin in three different regions of rat brain

The rate of accumulation of auto-fluorescent granules (lipofuscin) in three different regions of rat brain was investigated at various ages from very young to old animals (1, 2, 3, 6, 12 and 30-34 months of age. The accumulation of lipofuscin increased with age in the three brain regions. The first appearance of lipofuscin granules was at 8 weeks of age in the hippocampus and in the thalamus. In the case of cerebral cortex (laminae III), lipofuscin granules were first found in 3-month-old rats. The rate of lipofuscin accumulation was the highest in the hippocampus (y = 0.286x - 0.099, r = 0.963) among the three regions examined. In the case of cerebral cortex and thalamus, a slower rate of lipofuscin accumulation was observed (y = 0.072x - 0.14, r = 0.797 for cerebral cortex; y = 0.067x - 0.14, r = 0.953 for thalamus). It was noted that the most abundant accumulation and the highest rate of lipofuscin accumulation was in the hippocampus. But the rate and magnitude of lipofuscin accumulation in the hippocampus were low compared with cardiac muscles. From these results, it is suggested that brains have better protective system against oxidative stress than other organs.

Accumulation of cardiac lipofuscin in crab-eating monkeys (Macaca fasicularis): The same rate of lipofuscin accumulation in several species of primates

Previously, we have reported that the aging process begins at sexual maturation (Nakano, M. et al., Mech. Ageing Dev., 52 (1990) 93-106). In this paper, we reported the cardiac lipofuscin accumulation of crab-eating monkeys. The first appearance of cardiac lipofuscin was around sexual maturation, and the rate of accumulation in crab-eating monkey was 0.45. Several primates which have different life spans show the same rate of lipofuscin accumulation in the life stage. Namely, even in a different life span, the amount of lipofuscin accumulation in a given period of life such as puberty, middle age, old age was the same. From these results, it is suggested that the amount of lipofuscin accumulation is the same in the life span of primates having different life spans.

Renal trehalase: two subsites at the substrate-binding site

Phlorizin, phloretin, Tris and beta-methylglucoside are competitive inhibitors, with respect to the substrate trehalose, of purified renal trehalase. Mercuric chloride is a noncompetitive inhibitor. The active site of trehalase was examined further by multi-inhibition kinetic studies involving combinations of inhibitors. Phlorizin vs. phloretin and phlorizin vs. Tris were mutually non-competitive. In contrast, phloretin vs. Tris was mutually competitive. These findings suggest that the binding site of phlorizin to the enzyme differed from that of phloretin or Tris, and that phloretin and Tris might bind at a common site. These findings suggest a model in which trehalase has two binding sites at the substrate-binding site, a phlorizin (glucosyl) and a phloretin (phenyl) binding site, analogous to the model proposed previously for the glucose carrier. In addition, mercuric chloride vs. beta-methylglucoside was mutually competitive, although mercuric chloride and beta-methylglucoside, respectively, were noncompetitive and competitive inhibitors with respect to the substrate. Thus, it is suggested that the substrate binding and the SH-inhibitor binding sites are located very close to each other.

Age-related accumulation of lipofuscin in myocardium of Japanese monkey (Macaca fuscata)

Deposition of lipofuscin autofluorescent granules, is an important phenomenon in the aging process. Cardiac lipofuscin in Japanese monkey (Macaca fuscata) first appears at approximately two years of age. Thereafter, the amount of cardiac lipofuscin increases with increasing age. The first appearance of cardiac lipofuscin shows a good correlation with the maximum life span of animals. Moreover, the rate of lipofuscin accumulation is inversely correlated with life span energy potential (LEP) of animals. From these results, it is suggested that the rate of lipofuscin accumulation depends on the total life span energy expenditure of the tissue.

Age-related change in brush borders of rat kidney cortex

Age-related change of rat renal brush borders was examined with electron microscopy and biochemical procedures. Total activity of renal brush border enzymes, such as alkaline phosphatase and leucine aminopeptidase in the homogenate, was significantly decreased with age. Acid phosphatase activity and protein content were not significantly changed with age. Specific activity of leucine aminopeptidase in brush border fraction was significantly decreased at a later stage of age. Protein content of brush border fraction was decreased significantly with age. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, some of the proteins disappeared during aging. Electron microscopic observations of kidney cortex showed that microvilli of renal brush borders from old rats were observed to be fewer than those from the young; epithelial cells in young rats have more densely packed brush border projections than those in old rats. From these results, it is suggested that during aging renal brush borders are degraded, and that protein components of the brush borders were different between old and young.

Accumulation of cardiac lipofuscin in mammals: correlation between sexual maturation and the first appearance of lipofuscin

Accumulation of lipofuscin is an important phenomenon of the cellular aging process. The first appearance of cardiac lipofuscin showed a good correlation with sexual maturation, which was correlated with maximum life-span of mammals. Large metabolic changes occurred at sexual maturation. From these results, it is suggested that sexual maturation of mammals is the initiation period of the aging process. Correlation between sexual maturation and longevity was re-evaluated using many mammals. Domestic and laboratory animals showed an earlier sexual maturation than other mammals, including rodents.