Lipofuscin formation in the developing nervous system of squirrel monkeys consequent to maternal dietary protein deficiency during gestation

A Sequential Study of Age-Related Lipofuscin Accumulation in Hippocampus and Striate Cortex of Rats

Background

The age-pigment, lipofuscin that accumulates in cells intrinsically and progressively with age is considered as the hallmark of aging. This accumulation is more prominent in post-mitotic cells like neurons and also appears in glia.

Purpose

The aim of the present study was to assess the age-associated occurrence and distribution pattern of lipofuscin both in neurons and microglia in various regions of hippocampus and striate cortex.

Methods

The accumulation pattern of lipofuscin in hippocampus and striate cortex was observed in the female Wistar rats of 6 age groups, that is, 3, 6, 12, 18, 24, and 30 months using the autofluorescent property of lipofuscin and its specific localization in neurons and microglia by dual immunolabeling with NeuN and Iba-1 antibodies respectively. Cytoarchitectural and the morphological age-related changes were observed with cresyl violet staining.

Results

Lipofuscin pigments accumulate progressively through the normal aging process in hippocampus and striate cortex. However, in hippocampus, lipofuscin accumulates in a region-specific manner with the highest accumulation observed in cornu ammonis (CA) 1 and 3 subregions. Furthermore, the lipofuscin accumulation was also observed in microglia in the senile brains both in the hippocampus and striate cortex.

Conclusion

The progressive deposition of lipofuscin could result in cellular dysfunction. This encouraged us to forward the idea that microglia not only participate in the removal of the pigment from the neurons but also accumulate these waste products in itself. Such senescent microglia may contribute to age- related neurodegeneration as they lose the neuroprotective potential due to oxidative stress and thus may be unable to effectively phagocytose the age pigment.

Evidence for cellular aging in long-term confluent cultures: heritable impairment of proliferation, accumulation of age pigments and their loss in neoplastic transformation

Previous experiments had shown that repeated rounds of prolonged growth constraint at confluence of NIH 3T3 sublines result in persistent changes in the growth behavior that are characteristic of cellular aging. These changes, which include an enduring decrease in the rate of proliferation in low density subcultures and a marked increase in neoplastic transformation, are here reproduced cumulatively over a 6 week period during which cultures are maintained in a single, continuous round of constraint at confluence. By testing multiple cultures at weekly intervals we show that the persistent reduction in exponential growth in low density subcultures is a property of the entire treated cell population that is first demonstrable in the cell population used here within a few days after the constraint of confluence is imposed. There is also a reduction in saturation density of cells subcultured from this early confluence which is reversed in longer term confluence when the cells become transformed. The reduction in exponential growth rate in serial subcultures becomes more pronounced in cells after longer periods of confluence. It is strongly manifest at 6 weeks when most of the cells have undergone neoplastic transformation. The transformation initially involves only a very small fraction of cells in a confluent culture, and is only detectable after 3 weeks of confluence. Beyond that time there is selective overgrowth of the transformed cells so they become the dominant element at 6 weeks. The very same cells from the 6 week cultures that have a reduced rate of growth when subcultured at low density, grow to higher saturation densities at confluence. The reduced growth rates are heterogeneously distributed among clones derived from the 6 week confluent cultures. Typical age pigment bodies appear in the cytoplasm of the cells after 3-4 days of confluence, and fill the cytoplasm at 2 weeks. They tend to enlarge into residual bodies at 3 weeks but largely disappear at 6 weeks when most of the cells are transformed. The results reinforce the conclusion that the prolonged constraint of confluence of these cells reproduces the major growth and morphological effects of cellular aging in the body.

Carotenoids: recent progress, problems and prospects

1. This is a review of the current state of research on the structure and functions of carotenoids, a common group of natural pigments. 2. Discussed in this paper are recent advances in carotenoid studies and problems that still await elucidation. 3. A new natural nomenclature is proposed to rationalize investigation of biological functions of carotenoids. 4. Data included in the paper are taken from the book, "Biological Functions of Carotenoids" (Karnaukhov, 1988).

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.

The potential intermediate role of lysosomes in oxygen free radical pathology. Review article

The term "free radical" refers to atoms or groups of atoms containing a single unpaired electron occupying an outer orbital. This unpaired electron lends the molecule distinct chemical and physical properties such as its high reactivity and magnetic moment, respectively. Some relevant advances in medical research have encompassed O2 radicals and other toxic derivatives of O2. These reactive O2 species were shown to play a significant role in a wide spectrum of pathological states (see Halliwell & Gutteridge, 1985; Flohé 1986; Kensler & Taffe, 1986; McCord, 1986), though the measurement of free radical activity in clinically-accesible material has been unsatisfactory (Dormandy, 1986). This overview provides only a framework of information to assist the reader on some relevant topics on free radical pathology, which by no means can cover the multiple aspects of the medical literature in this context. The reader is referred to several articles which cover particular features of free radical biology and medicine (Chance et al., 1979; Pryor, 1976-1984; Fridovich, 1983; Jamieson et al., 1986; Kensler & Taffe, 1986; McCord, 1986; Weiss, 1986).

Lipofuscin and lipofuscin-like substances

Lipofuscin is defined as being a yellowish brown, lipid-rich, heterogeneous, cytoplasmic granular pigment emitting an intense yellow autofluorescence when excited with ultraviolet light, which accumulates in various tissues of animals during their aging. It is believed that the pigments are derived from the reaction of some of reactive secondary products including malonaldehyde, formed during membranous lipid peroxidation, with amino groups of phospholipids and proteins, etc., and that these formations are accompanied by alteration of the membrane structure and inactivation of the enzymes. The fluorescence measurement of the pigments is widely used as a parameter of lipid peroxidation in vivo as well as in vitro. However, their origin, chemical structure, biological significance or fate has not as yet been fully elucidated. This article introduces and discusses the recent studies on these problems.

Neuronal lipofuscin accumulation in ageing and alzheimer dementia: a pathogenic mechanism?

The amount of intraneuronal lipofuscin in the parietal cortex and in the inferior olivary nucleus was measured in post-mortem tissue affected by Alzheimer dementia and in specimens from non-demented individuals. The results indicate that there is a liner relationship between the accumulation of cell body lipofuscin and advancing age, both in neuronal populations of the non-demented groups, and in the olivary neurones of the demented group. However, in the demented group, the lipofuscin fluorescence intensity of the parietal neurons was not significantly correlated with age. The estimated amount of lipofuscin in the olivary neurons in the demented group was significantly higher than in the non-demented group, when age has been taken into account (P less than 0.01). The possible pathogenic role of lipofuscin accumulation in ageing and Alzheimer dementia is discussed.

A comparative study on the effects of ageing and training on the levels of lipofuscin in various tissues of the rat

1. A modified procedure, based on the autofluorescent properties of the age pigment, lipofuscin, has been applied to obtain quantitative data on the accumulation of the proteolipid fraction of the pigment in a variety of tissues of the rat (Rattus norvegicus). The tissues investigated included muscle (fast-twitch white and red fibers), heart, brain and spleen. 2. The effects of a life-long treadmill training program on the concentration of lipofuscin in the different tissues, was determined in a cross-sectional study at various ages between 41/2 and 19 months. 3. All the tissues investigated revealed an increase in the concentration of lipofuscin with training. The increase exceeded the increment observed in ageing control animals. 4. It is postulated that the elevated lipofuscin levels observed with physical training reflect an ultrastructural adaptive change in the cells. A relative deficiency of oxygen in the tissues could be the important metabolic factor triggering this mechanism.

"Aging" pigments in term human placenta

First-, second-, and third-trimester placentas were examined with fluorescent microscopy for the presence of lipofuscin pigments. Prior to 32 weeks' gestation these were not seen, but they were routinely found in the trophoblast of the term placenta. These pigments may or may not represent "aging" of the placenta.

Effects of hypophysectomy on age-related changes in the rat kidney glomerulus: observations by scanning and transmission electron microscopy

The kidney glomeruli of 9-month-old intact, 23-month-old intact, and 23-month-old hypophysectomized female rats were examined by scanning and transmission electron microscopy. With increasing age, the glomeruli increased in diameter and more podocyte microvilli were found. Hypophysectomy (4 months before sacrifice) reduced these values to levels approaching values seen in the 9-month intact controls. Transmission electron microscopy revealed that increased numbers of podocytes and endothelial cells had cytoplasmic dense bodies with advancing age. Granular cytoplasmic material, seen in podocytes, did not alter in frequency with age. Hypophysectomy reduced the number of cells containing the dense bodies as well as the number of podocytes containing granular material. Basal laminar thickness, while increasing with age, was unaffected by hypophysectomy. The results show that hypophysectomy can return some structural age-related changes to values seen in younger subjects. The effects are similar in some respects to the effects of dietary restriction.

Lipofuscin accumulation in squirrel monkey spinal cord consequent to protein malnutrition during gestation

The formation of lipofuscin pigment in the anterior horn cells of the cervical spinal cord has shown in the fetuses and neonates under the extrinsic influence of maternal protein deprivation during the gestation period in the squirrel monkeys.