Lipofuscin--does it affect cellular performance?

Piperine and curcumin exhibit synergism in attenuating D-galactose induced senescence in rats

Aging is associated with progressive decline in mental abilities and functional capacities. Postmitotic tissues are most vulnerable to alteration due to oxidative damage leading to behavioral and biochemical changes. We hypothesized that the anatomical and functional facets of the brain could be protected with powerful antioxidants such as piperine and curcumin by examining their effects individually and in combination in delaying senescence induced by d-galactose. Young adult male Wistar rats were treated with piperine (12 mg/kg) alone, and curcumin (40 mg/kg) alone; and in combination for a period of 49 days by the oral route with treatment being initiated a week prior to d-galactose (60 mg/kg, i.p.). A control group, d-galactose alone and naturally aged control were also evaluated. Behavioral tests, hippocampal volume, CA1 neuron number, oxidative parameters, formation of lipofuscin like autofluorescent substances, neurochemical estimation, and histopathological changes in CA1 region of hippocampus were established. Our results suggest that the combination exerted a superior response compared to monotherapy as evidenced by improved spatial memory, reduced oxidative burden, reduced accumulation of lipofuscin; improvement in signaling, increase in hippocampal volume and protection of hippocampal neurons. We speculate that the powerful antioxidant nature of both, augmented response of curcumin in the presence of piperine and enhanced serotoninergic signaling was responsible for improved cognition and prevention in senescence.

Species-Specific Ultrastructure of Neuronal Lipofuscin in Hippocampus and Neocortex of Subhuman Mammals and Humans

Lipofuscin represents an integral part of neurons and glial cells in mammals and in submammalian species. It is a special lysosomal organelle, takes part of cellular metabolism, and is a structural expression of catabolic pathways. Species-specific differences of lipofuscin indicate metabolic differences of the relevant neurons. The authors have studied the ultrastructure of neuronal lipofuscin in the hippocampus and cerebral neocortex of dogs, horses, cows, elephants, rats, mice, apes, and humans to answer the question of species-specific differences of this organelle. Paraffin sections of formalin-fixed material were investigated by hematoxylin-eosin and PAS staining, by fluorescence microscopy for autofluorescence, with a laser scanning confocal microscope and by electron microscopy. In the animals studied and in humans the lipofuscin displayed, in addition to the general trilaminar substructure, species-specific appearances. No differences were found in the lipofuscin structure between neocortical and hippocampal neurons of the separate animal species. In contrast, in humans, neurons of the hippocampus showed a particular lipofuscin structure, not only different from the neocortical one, but also with differences between CA1 and CA3/4 sectors. Interestingly, in apes a transitional situation was found with slight differences between neocortical and hippocampal lipofuscin, especially in the rhesus monkey. This peculiarity was corroborated by the distribution of special pentilaminar linear structures in the lipofuscin pigment in all animals, only sparsely in the rhesus monkey and not in humans. The results indicate that lipofuscin ultrastructure of neocortical and hippocampal neurons is species specific and that lipofuscin in the human hippocampal neurons displays structures characteristic of man differing from the neocortical neuronal lipofuscin. The neuronal lipofuscin of apes, especially of the rhesus monkey displays structures in between humans and lower mammals. Nothing is known about the functional significance of these findings. They may indicate metabolic and/or functional characteristics of the relevant neurons.

Potential role of retinal pigment epithelial lipofuscin accumulation in age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of severe visual impairment in developed countries. The vision loss associated with AMD is the result of degenerative changes in the central region of the retina called the macula. Maintenance of normal structure and function of the macular retina, and of the remainder of the retina as well, is critically dependent on the supporting role of the adjacent retinal pigment epithelium (RPE). Impairment of normal RPE functions is known to result in retinal degeneration and loss of visual function. Thus, it has been hypothesized that the retinal degeneration that characterizes AMD is secondary to age-related deterioration in RPE support functions. Like many other postmitotic cell types, the RPE accumulates autofluorescent lysosomal storage bodies (lipofuscin) during senescence. In human eyes, lipofuscin comes to occupy a substantial fraction of the RPE cytoplasmic volume in the elderly. Does this lipofuscin accumulation contribute to the development of AMD? This question is a specific case of the broader question of whether lipofuscin accumulation in general is detrimental to cells. Unfortunately, definitive data do not exist to allow these questions to be answered. Although a correlation between RPE lipofuscin content and AMD has been reported, a cause-and-effect relationship between RPE lipofuscin accumulation and the development of this disease has not been established. It has been reported that a mutation in a gene encoding a photoreceptor-specific protein results in massive RPE lipofuscin accumulation and early-onset macular degeneration. However, again the accelerated RPE lipofuscin accumulation has not been shown to be the cause of the accompanying macular degeneration. The lack of a definitive link between RPE lipofuscin accumulation and AMD illustrates one of the biggest challenges remaining in lipofuscin research-determining whether lipofuscin accumulation per se has an impact on cell function.

Age-related decline in multiple unit action potentials of CA3 region of rat hippocampus: correlation with lipid peroxidation and lipofuscin concentration and the effect of centrophenoxine

Changes in lipid peroxidation, lipofuscin concentration, and multiple unit activity (MUA recorded in conscious animals) in the CA3 region were studied in the hippocampus of male Wistar rats aged 4, 8, 16, and 24 months. The lipid peroxidation and lipofuscin concentration were increased with age. The MUA, however, declined with age. Correlational analyses were performed for the four age groups to determine the relationship between the age-associated decline in MUA with the age-related alterations in lipid peroxidation and lipofuscin concentrations. The age-related increase in lipid peroxidation correlated positively with the age-associated increase in lipofuscin concentration. The age-related increases in lipid peroxidation and lipofuscin concentration correlated negatively with the changes in MUA. Since lipid peroxidation may affect neuronal electrophysiology, our data suggested that age-related increase in lipid peroxidation may contribute to an age-associated decline in neuronal electrical activity. Centrophenoxine effects were studied on the three above-mentioned age-associated changes in the hippocampus. The drug had no effect on all three parameters in 4- and 8-month-old rats. In 16- and 24-month-old rats, however, the drug significantly increased the MUA but concomitantly decreased lipofuscin concentration and lipid peroxidation. Correlational analyses of the data on MUA, lipid peroxidation and lipofuscin concentration from the centrophenoxine-treated animals showed that the drug-induced diminution in both lipofuscin and lipid peroxidation was significantly correlated with the drug-induced increase in MUA. The differential effect of the drug in younger (4-8 months) and older (16-24 months) animals indicated that the stimulation of MUA was clearly associated with concomitant decrease in lipid peroxidation and lipofuscin concentration.

The lysosomal system in neuronal cell death: a review

The lysosomal system has often been considered a prominent morphologic marker of distressed or dying neurons. Lysosomes or their constituent hydrolases have been viewed in different neuropathologic states as either initiators and direct agents of cell death, agents of cellular repair and recompensation, effectors of end-stage cellular dissolution, or autolytic scavengers of cellular debris. Limited data and limitations of methodology often do not allow these potential roles to be discriminated. In all forms of neurodegeneration, it may be presumed that lysosomes ultimately rupture and release various hydrolases that promote cell autolysis during the final stages of cellular disintegration. Beyond this perhaps universal contribution to cell death, the degree to which the lysosomal system may be involved in neurodegenerative states varies considerably. In many conditions, morphologic evidence for activation of the lysosomal system is minimal or undetectable. In other cases, lysosomal activation is evident only when other morphologic signs of cell injury are also present. This level of participation may be viewed as either an attempt by the neuron to compensate for or repair the injury or a late-stage event leading to cell dissolution. The early involvement of the lysosomal system in neurodegeneration occurs most commonly in the form of intraneuronal accumulations of abnormal storage profiles or residual bodies (tertiary lysosomes). Very often the lysosomal involvement can be traced to a primary defect or dysfunction of lysosomal components or to accelerated or abnormal membrane breakdown that leads to the buildup of modified digestion-resistant substrates within lysosomes. Because they are often striking, changes in the lysosomal system are a sensitive morphologic indicator of certain types of metabolic distress; however, whether they reflect a salutary response of a compromised neuron or a mechanism to promote cell death and removal of debris from the brain remains to be established for most conditions. Factors that may influence the lysosomal response during lethal neuronal injury include species differences, stage of neuronal development, duration of injury and pace of cell death. The lysosomal system may be more closely coupled to certain forms of neuronal cell death in lower vertebrate or invertebrate systems than in mammalian systems.

The biochemistry of mammalian senescence

Senescence is a process which, until quite recently, has been the subject of little scientific investigation. Even the word "senescence" is difficult to define, and complex methodological pitfalls have impeded progress. In the past few years, there have been exciting advances in understanding the physiological, cell biological, biochemical, and molecular biological nature of senescence. Changes in membrane function, protein synthesis, DNA structure (including glycosylation, altered tertiary structure, free-radical effects, and loss of telomeric DNA), and changes in gene regulation with age are reviewed. Recent work on changes in responses to transcriptional regulatory proteins and cellular senescence factors, some of which have been identified, is particularly promising and leads to the conclusion that senescence, at least in part, is a programmed process. Despite these advances, the fundamental cause of senescence remains elusive but might, as in the case of other biological processes which are phylogenetically widespread, turn out to be quite simple, and perhaps, even modifiable.

Comments on review by Swaab--brain aging and Alzheimer's disease. "Wear and tear" versus "use it or lose it"

This review discusses a new hypothesis about cellular ageing in the context of current experimental observations and other well-known ideas, particularly "wear and tear," the relationship between metabolic rate and life span, and "free radical" reactions. However, even though these concepts are frequently used in the literature it is clear from the data discussed by Swaab that there are fundamental disagreements between the theories and experimental observations.

Effect of vitamin E on the accumulation of fluorescent material in cultured cerebral cortical cells of mice

The effect of vitamin E on the accumulation of lipofuscin-containing fluorescent material in the mouse cerebral cortical cells in primary culture was studied. Fluorescent material was extracted in ethanol:diethylether (3:1) and autofluorescence intensity of the extracts was measured by a spectrofluorophotometer. Although vitamin E at the concentration of 0.005 IU/ml was not effective, 0.01 IU/ml vitamin E inhibited the accumulation of fluorescent material. Fluorescent material accumulation was reduced to 76.3-86.4% of the control level in 6-, 12-, or 18-day treatment of 0.01 IU/ml vitamin E. High doses of vitamin E (0.05 or 0.1 IU/ml) were toxic for cultured cells. Ethanol, the vehicle of vitamin E, at the final concentration of 0.005% was also effective on the reduction of fluorescent material accumulation (81.0% of the control level at 18 days). The inhibitory effects of vitamin E as well as ethanol on the accumulation of fluorescent material in cultured cells are explained by their nature as free radical scavengers.

Age-related changes in Schwann cells of the internal branch of the rat superior laryngeal nerve

While previous studies have examined the role of neurons in age-related changes of laryngeal sensory nerve function, investigators have not focused on the significant role of Schwann cells in the aging process. This investigation used an electron microscopic morphometric technique to systematically study Schwann cells of the internal branch of the superior laryngeal nerve of three Wistar rat age groups: young = 3 to 5 months; old = 25 months; very old = 29 to 31 months. In Schwann cells of myelinated axons, a substantial and significant reduction (p = 0.0127) in mitochondrial volume fraction was found between the young and old groups, and also between the young and very old groups (young = 0.0034, old = 0.00175, very old = 0.0019). The volume fraction of compact myelin also showed a trend (p = 0.0683) toward decreasing with age. The volume fractions of cytoplasm, nuclei, and lipofuscin granules showed no significant age-related changes (lipofuscin in myelinating Schwann cells: young = 0.0025, old = 0.0020, very old = 0.0051; lipofuscin in non-myelinating Schwann cells: young = 0.012, old = 0.0061, very old = 0.0051). Our observations on mitochondria lead to two possible conclusions regarding energy availability in aged Schwann cells. One possibility is that aged cells have a decreased energy requirement, which is reflected in the decreased mitochondrial densities in old and very old specimens. The other possibility is the reduced mitochondrial volume fractions are independent of cellular energy requirements and are indicative of some aging or pathologic process.(ABSTRACT TRUNCATED AT 250 WORDS)

Schwann cells associated with vestibular ganglion cells in the aging rat

The purpose of this study was to quantify any age-related change in the components of Schwann cells associated with vestibular ganglion cells: adperikaryonal Schwann cell cytoplasm, myelin bubbles, compact myelin, Schwann cell lipofuscin, or mitochondria in addition to extracellular intraganglionic space. Studies were carried out in young (Y, 3 to 5 months of age, N = 6), old (0, 24 to 26 months of age, N = 3), and very old (VO, 28 to 31 months of age, N = 6) female Wistar rats using point counting stereologic techniques. Recent reports have demonstrated age-related increases in the peripheral nerve counterparts to the following entities: adaxonal Schwann cell cytoplasm, myelin bubble, endoneurial space, and a decrease in Schwann cell mitochondria. Our results indicate no age-related change in the volume fraction of extracellular intraganglionic space (Y, 0.179 +/- 0.04; O, 0.174 +/- 0.049; VO, 0.205 +/- 0.043), adperikaryonal Schwann cell cytoplasm (Y, 0.026 +/- 0.008; O, 0.019 +/- 0.003; VO; 0.028 +/- 0.007), myelin bubble (Y, 0.004 +/- 0.003; O, 0.011 +/- 0.009; VO, 0.006 +/- 0.002), Schwann cell lipofuscin (Y, 0.002 +/- 0.001; O, 0.004 +/- 0.003; VO, 0.002 +/- 0.001), or mitochondria (Y, 0.194 +/- 0.019; O, 0.208 +/- 0.024; VO, 0.205 +/- 0.04). The only age-related change was an increase in compact myelin (Y, 0.006 +/- 0.001; O, 0.008 +/- 0.006; VO, 0.011 +/- 0.004). These findings differ from those of the peripheral nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Volume fraction and ultrastructure of age pigment in the saccular epithelium of old mice

Age pigment in the sensory and supporting cells was a prominent characteristic distinguishing old saccules from young. However, the pigment was not distributed uniformly throughout the sensory epithelium but displayed cell-specific patterns of accumulation. The highest cytoplasmic volume density was in the old supporting cells followed by type I hair cells and then type II hair cells. The most common form of pigmented inclusion seen in old type I hair cells was a cluster of granules resembling melanin. This form was never seen in type II hair cells or supporting cells where a form containing a lipid-like droplet was prevalent. The differences in the amount of age pigment and the forms accumulated probably reflects metabolic differences between the three cell types.

The waste-product theory of aging: transformation to unlimited growth in cell cultures

A differential equation governing intracellular waste content is solved numerically to determine the circumstances under which the growth of an in vitro cell population is limited. Parameter values derived from data on human glial cell cultures are employed. It is assumed that a) waste accumulation depresses the rate of cellular reproduction and b) intracellular waste is diluted by cell division, but is not otherwise eliminated. Population size depends upon two parameters: the rate of waste production and the rate of cell division in the absence of waste. If the rate of waste production is sufficient, the population size approaches an asymptote as in phase III growth in vitro. If a lower rate of waste production allows the cells to outmultiply the waste, growth is unlimited as in a transformed cell population. The asymptotic population size and the threshold for unlimited growth are remarkably sensitive to small changes in the values of the two rate parameters unless the ratio of their values is constant. This suggests that there may be a cellular mechanism that relates the waste production and cell division rates.

Quantification of age pigments (lipofuscin)

1. Three methods have hitherto been applied for age pigment quantification: (a) numerically from micrographs; (b) fluorimetrically from histological sections; (c) spectrofluorimetrically from dissolved age pigments. 2. The spectrofluorimetric method is at present the most commonly used technique for quantification of age pigments. 3. By comparing the related publications since introduction of the spectrofluorimetric method, it has become apparent that few authors specify fluorimetrically significant factors, such as temperature and pH which influence the sample fluorescence during measurement. 4. Recent developments in fluorimetrical age pigment quantification using chloroform/methanol as solvent have additionally revealed the necessity to measure and present the age pigments dissolved in both phases: the polar and non-polar solvents.

Redistribution of lipofuscin in aged neurons induced by colchicine

The effect of a single, 40 micrograms, intracerebroventricular injection of colchicine on the distribution of neuronal lysosomes and lipofuscin granules in aged mice was studied. At the light microscope level we observed that colchicine induced a redistribution of dipeptidyl aminopeptidase II (Dpp II), a lysosomal and lipofuscin granule marker enzyme, from the cell bodies of neurons to the dendrites; cell bodies became depleted of Dpp II while dendrites became enriched with this enzyme. Quantitation of this phenomenon at the electron microscope level demonstrated that colchicine induced a rapid and significant decrease in the density of lysosomes and lipofuscin granules from the somata of neurons whereas in dendrites we observed a significant increase in the density of these organelles.

Morphometric analysis and fine structure of the vestibular epithelium of aged C57BL/6NNia mice

The vestibular organs of young and very old C57BL/6NNia (B6) mice were compared by light and electron microscopy. Hair cell density decreased an average of 14% in the utricle, 19% in the saccule and posterior crista, 23% in the horizontal crista, and 24% in the anterior crista. Hair cell size remained the same throughout the mouse's life span as did the ratio of Type I to Type II hair cells. The most apparent sign of advanced age was dense inclusions found in sensory and supporting cells. Although small inclusions were present at five weeks, by 29 months, additional, larger forms appeared. An unusual melanin-like form was characteristic of old Type I hair cells. Synaptic morphology and synaptic bodies were well preserved even in very old B6 mice. Elongated bars were common in Type I hair cells and spheroid synaptic bodies were the most common form in Type II hair cells. Large clusters of synaptic bodies occurring in both young and old mice were seen only in Type I hair cells. Although the B6 strain suffers from genetically determined early cochlear degeneration, it does not experience early degeneration of the peripheral vestibular organs.

The effect of vitamin E deficiency on the induction of age pigment in various tissues of the mouse

The effect of a dietary deficiency of vitamin E on the concentrations of lipofuscin in the hippocampus and the supraoptic nucleus (SON) of the hypothalamus, and in adrenal cortical cells was assessed in male mice. The animals were fed either a control diet or the vitamin E deficient diet after 2 months of age for a period of 6 months. There was no significant difference in the growth curves of the 2 groups of animals over the period studied. Fluorescence microscopy and transmission electron microscopy were used to assess the effect of the diet on lipofuscin in the different tissues. Quantitative morphological techniques were used to determine the relative volumes of lipofuscin in the neurons from the SON and in the adrenal cortical cells. There was no significant difference in the concentration of lipofuscin in the SON neurons after vitamin E deficiency but there was a significant increase in the adrenal cortical cells. There was a clear difference in the effect of the deficiency on mitotic and fixed post-mitotic cells over the period investigated but further studies would be necessary to determine whether or not there was a critical period in the life span where vitamin E deficiency may induce changes in all cell types.

The waste-product theory of aging: cell division rate as a function of waste volume

The rate of cell division is calculated as a function of waste product volume in U-787CG human diploid glial cells grown in vitro. The calculation is based on two earlier mathematical models. One is a compartmental analysis in which cell division rate is obtained from data on the fraction of cells which become sterile as the passage level increases. A second model is used to calculate the amount of waste per cell from the observed rate of waste accumulation in a non-dividing population and from the division rate calculated with the use of the first model. Results from the two models are correlated to obtain the desired function relating cell division rate to waste volume. If cellular aging is taken to mean loss of the ability of cells to divide, and if, as in the waste-product theory, this loss is attributed to waste accumulation, the calculated results show that aging is evident at waste levels well below those at which non-dividing populations can survive. Thus the process of cell division may be much more sensitive to waste accumulation than other cellular processes needed for the maintenance of life.

Azathioprine hypersensitivity manifesting as acute focal hepatocellular necrosis

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Prevention of lipofuscin development in neurons by anti-oxidants

It was documented that ageing is associated with a progressive and highly significant proliferation of the total number of light microscopically visible lipofuscin granules in the grey substance of sections of the cervical spinal cord of Balb/c mice. The mean total numbers (+/- standard errors) of lipofuscin granules in standard sections of the glutaraldehyde-osmium fixed, epon embedded spinal cords that were examined with a phase contrast light microscope in 1 week, 1 month, 8 months and 18 months old mice were 0, 269 +/- 56, 1101 +/- 82 and 2464 +/- 318, respectively. The population densities of multiglobular lipofuscin units as seen with the electron microscope in random spinal cord neurons of the same 4 age groups corresponded well with the above quantitative, light microscopic data. Continuous treatment for 8 months with either the natural anti-oxidant Vitamin E (alpha-tocopherol) at 40 mg/mouse/week or the synthetic anti-oxidant butylated hydroxytoluene at about 100 mg/mouse/week diminished significantly the proliferation of lipofuscin granules in spinal cord neurons that developed during that period of ageing. No toxicity of any sort was caused by these two treatments. These results provide support for the peroxide theory of lipofuscin biogenesis and encourage further exploration of the possibilities of obtaining greater anti-lipofuscin effects with less molecular bulk of antioxidants.

The effect of osmotic challenge and subsequent rehydration on the aging hypothalamo-neurohypophyseal system. A quantitative morphological study of the supraoptic nucleus

The neurons of the supraoptic nucleus (SON) of male C57BL/Icrfat mice at 6 or 28 months of age were examined from normally hydrated, osmotically loaded and osmotically loaded/rehydrated animals. Using quantitative morphological techniques it was shown that the majority of the ultrastructural variables investigated were controlled in the same way in the SON neurons of young and old mice. The major exception was the mitochondrial compartment which although maintaining a constant proportion of the volume of the SON cell did show a significant reduction in the number of mitochondria in the old group, particularly during the osmotic challenge period of the experiment. The "lipid" body compartment of the SON neuron also behaved differently in the cells from the older age group. This study when viewed in conjunction with previous investigations suggests that these SON neuroendocrine neurons from old animals are able to produce hormone until late in the life-span. However, other aspects of cellular activity appeared to be altered when judged by morphological criteria. It is concluded that the SON neurons from these old mice are able to synthesize hormone-containing organelles to the same concentration as the cells from a younger animal. However, the efficiency of the process, or at least the efficiency of concomitant cellular processes, must be questioned in view of the alterations in the rough endoplasmic reticulum, mitochondrial and lysosomal systems.

Changes in the secretory acinar cells of the rat parotid gland during aging

The secretory acinar cells of parotid glands from rats of varying ages have been examined by electron microscopy to determine what age-related changes occur in these cells. The most prominent change noted in these cells is the progressive increase in the amount of lipofuscin granules with age. Lipofuscin granules are membrane-bound structures consisting of lipids, other subcomponents, and a matrix. In addition, these cells contain lipid droplets that are not associated with any other components and tend to accumulate at the base of the cells in older rats. Also, many acinar cells in the glands of old rats contain altered secretory granules which appear to be in the process of degeneration. The accumulation of lipid and degenerating secretory granules appears to be related to the reduced level of cellular secretory activity in the glands of older rats. It is possible that these two types of inclusions contribute to the formation of lipofuscin granules. Lipofuscin and degenerating secretory granules are associated with acid phosphatase, which is demonstrated cytochemically, indicating that these granules are lysosomal structures.

Influence of oxygen tension, pro-oxidants and antioxidants on the formation of lipid peroxidation products (lipofuscin) in individual cultivated human glial cells

Cultivated human glial cells, kept in a state of density-dependent inhibition of growth, accumulate age pigment (lipofuscin) within their lysosomal vacuomes which has the same characteristics as the age pigment observed in vivo. The rate of formation and accumulation of lipofuscin is greatly accelerated under the conditions of routine cell culture in comparison to the in vivo event. Lipofuscin is generally considered to be composed of products of lipid peroxidation and thus it would be reasonable to suggest that factors which influence lipid peroxidation would also alter the rate of lipofuscin formation and accumulation. Human glial cells were grown in the presence of various oxygen concentrations (5%, 10%, 20%, 40%) or exposed to pro-oxidants (vitamin C/Fe) or antioxidants (vitamin E/Se, dimethylsulfoxide, reduced glutathione) treatments in the presence of normal oxygen concentration (20%). It was found that these factors can modulate (accelerate or decrease) the rate of formation of lipofuscin. This study thus provides: (1) important supportive evidence for the lipid peroxidation origin of lipofuscin, (2) a useful model system for studying the effect of lipofuscin accumulation on lysosomal function and cell growth kinetics, (3) evidence that our culture conditions are far from ideal: oxygen concentration may drastically alter rates of lipofuscin formation and accumulation. Cell culture technique, as we know it today, may benefit from more closely controlled oxygen tensions, i.e. by reducing oxygen to levels that more closely approximate conditions in vivo.

Aging changes in the optic tectum of the guppy Poecilia (Lebistes) reticulatus

Histological surveys of the brains of guppies throughout their lifespan showed no overall loss of tissue with advancing age. Brain and body increased in size at a similar rate throughout adult life in male fish. In old females after the age of two years, brain growth apparently ceased, although body growth continued at a low rate. In both sexes there was a loss of neurones from the stratum griseum periventriculare in the midbrain roof in old age; the decrease in size was significant. The midbrain is a major correlative center concerned with spatial orientation. How far neuronal loss may contribute to functional behavioral disorder in old age is unknown, but a loss of orientation could render the older fish more susceptible to predation.

The measurement of lipid peroxidation products (lipofuscin) in individual cultivated human glial cells

The natural fluorescence (autofluorescence) of the age pigment lipofuscin has been quantitated and related to the dry mass and DNA content (after Feulgen staining) of individual cultivated human glial cells which were density-dependent growth-inhibited for 3 and 18 months, subcultivated and kept in log growth phase for a period of up to 3 weeks. Stereological measurements at the ultrastructural level were performed in parallel to determine the volume density of secondary lysosomes of the residual body type (containing lipofuscin). The autofluorescence/dry mass/cell and the volume density of residual bodies showed a positive correlation. Cells in S-phase following subcultivation demonstrated similar autofluorescence values to cells in G1-phase. These results demonstrate that (1) multiparametric measurements of this type can be utilized to correlate many parameters which may be indicative of differing cell functions in individual cells, (2) there is a positive correlation between the ultrastructural and the autofluorescence techniques to measure lipofuscin, and (3) despite the limited data, even high cellular lipofuscin content does not appear to be detrimental to the ability of cells surviving subcultivation to re-enter the cell cycle.

The effect of lipofuscin on cellular function

The neurons of the supraoptic nucleus of male C57BL/Icrfat mice at 6 or 28 months of age were examined from normally hydrated, osmotically loaded and osmotically loaded-rehydrated animals. Using quantitative morphological techniques, a reduction in the concentration of lipofuscin in the neurons was observed in osmotically loaded mice at both ages, and these levels were restored to control values during rehydration. In addition, there was a significant difference in the pattern of response of lipofuscin levels between the two age groups during the experiment. The concentration of hormone containing neurosecretory granules in the neurons of the supraoptic nucleus did not differ significantly between the two age groups during the experiment. However, the surface area of rough endoplasmic reticulum per unit volume of the supraoptic nucleus cell did differ significantly between the two age groups over the course of the experiment. It is concluded that increasing concentrations of lipofuscin do not affect the ability of the cell to control the concentration of neurosecretory granules or rough endoplasmic reticulum. The simplistic view that lipofuscin accumulates with age to the detriment of cell function must be revised.

Reduction of lipofuscin by centrophenoxine and chlorpromazine in the neurons of rat cerebral hemisphere in primary culture

Cells from neonatal rat cerebral hemispheres were dispersed by trypsin and cultured for 32 days. Histochemical, fluorescence, and electron microscopic analyses demonstrated that lipofuscin pigments increased in neuronal and non-neuronal cells in primary culture according to the lapse of time. When centrophenoxine (10(-4) or 5 X 10(-4) M) or chlorpromazine (10(-6) or 10(-5) M) was added to the medium, the accumulation of lipofuscin pigments in neurons was significantly reduced. However, the effects of these agents were not detected in non-neuronal cells.

Uptake and transport of horseradish peroxidase by cochlear spiral ganglion neurons

Cochlear spiral ganglion neurons in the cat have been classified as type I and type II. The type II neurons are of special interest since they are reported to provide the afferent innervation to three-quarters of the cochlear hair cells, and also because of a recent assertion that they do not project to the brain. In the present study the neuronal marker horseradish peroxidase (HRP) was utilized to re-examine these issues. HRP was injected into the intranuclear cochlear nerve root of adult cats. 18 to 48 h post-injection HRP reaction product was observed in both type I and type II neurons. The majority of labeled cells were characterized by granular reaction product, while a smaller number of cells were also diffusely filled with HRP, resulting in intense staining of the cell soma and its processes. These data indicate that the central axons of type II neurons are constituents of the cochlear nerve root at the level of the brainstem and thus do project centrally. In the organ of Corti HRP-filled fibers to both inner and outer hair cells were observed and demonstrated in electron microscopy to be afferent neurons. This intra-axonal accumulation of the HRP by outer hair cell afferents constitutes direct evidence of the functional projection of these neurons to the cochlear nucleus.