Microspectrofluorometric quantitation of autofluorescent lipopigment in the human sympathetic ganglia

Age-related structural and neurochemical changes of the human superior cervical ganglion

The aim of this study was to investigate age-related morphological and neurochemical changes in the human superior cervical ganglion (SCG). Thirty-seven superior sympathetic human cervical ganglia of young, adult, and aged subjects were examined using morphometric analysis, biotin-streptavidin immunohistochemistry for detecting neurofilament, myelin protein, protein gene product 9.5, nerve growth factor receptor p75 in sympathetic neurons and nerve fibers. Morphometric parameters of neurons (area, long and short axis, shape factor of the neuron body, nucleus, cytoplasm, and lipofuscin) were investigated in every sixth serial section of the ganglion. Seven hundred neurons with clearly visible nuclei were measured in each studied group. The present study showed that human SCG of older subjects had larger areas of neuron body, cytoplasm and nucleus, a lower shape factor, an increased amount of lipofuscin, and a greater number of large-size neurons, as compared to SCG obtained from young subjects. Neuronal cytoskeletal alterations manifested themselves through a decreased number of neurofilament-positive neurons were detected in old human SCG. The amount of myelinated fibers decreased with age, although the amount of myelinated fibers in the young and the adult subjects varied from few to a moderate number. PGP 9.5 immunoreactivity varied in different age groups. A marked reduction of nerve growth factor receptor p75 in old human sympathetic neurons was detected. In conclusion, the findings of this study confirm age-related morphological changes in the human SCG. Structural neuronal changes may influence the deterioration of neuronal functional capacity, neuronal plasticity, and regenerative characteristics.

A Note on Age-Related Biomarkers

Forty-eight randomly selected age-related human biological functions were analyzed in order to establish whether or not their (linear) regressions were modified by age-related standard errors. Possible reasons for this are advanced. Statistically significant multiple regressions were obtained in 25%, and 21% of the functions yielded statistically significant changes in the correlations between data and age when partial correlation coefficients were calculated. The conclusion is that age-related data need to be subjected to the above tests in order to minimize confounding factors.

Ultrastructural differences of hippocampal lipofuscin in human development

The lipofuscin of pyramidal cells in each hippocampal subfield of each of seven human autopsy cases without brain disease at the age of 3-12 months (infants) and of 17-23 years (young adults) was comparatively investigated at the electron microscopic level. In infant pyramidal neurons of the hippocampal subfields CA 1, CA 2, CA 3 and CA 4 O-2, very small lipofuscin particles were observed. The lipofuscin composition showed a slightly larger granular component compared to the vacuolar component with one or two small lipid droplets. No obvious ultrastructural variability of lipofuscin granules was observed. The CA 1 lipofuscin in young adults consists of larger particles than in infants, but no obvious difference in the composition of granular and vacuolar components from the infant lipofuscin was seen. The amount of lipofuscin in CA 1 strongly increased in young adults compared to infants and appeared in a perinuclear distribution. In young adults, in contrast to the infant group, the amount of lipofuscin in the subfields CA 2, CA 3 and CA 4 was significantly higher than in CA 1. In CA 2, CA 3 and CA 4 pyramidal neurons, the vacuolar component was significantly larger than the granular component. The similarity of infant hippocampal lipofuscin patterns in all subfields is discussed as a state of immaturity. To explain the observed differences between the CA 1 and the other subfields during neuronal development, as shown in the young adult group, several factors are discussed: the effects of cell specific metabolism, cellular functional activity, cytoprotective mechanisms and effects of efferent and afferent pathways connected with the subfields.

Ultrastructural morphometric analysis of lipofuscin in pyramidal cells of the human Ammon's horn

Lipofuscin is a waste product of autolysosomal metabolism. The amount of lipofuscin in the cytoplasm depends on cell type, cell function and age. In most studies, either the fluorescent or the stained component of lipofuscin was investigated. Quantitative morphological investigations of the lipofuscin composition separated into the vacuolar and granular component were missing. For the hippocampal pyramidal cells we have determined the lipofuscin quantity and, separately, the vacuolar and granular component at the ultrastructural level. The hippocampal subfields CA 1, CA 2, CA 3 and CA 4 were observed at the ages 20, 40, 60 and 80 years (+/-3 years). Quantitative determinations of the vacuolar and granular component of neuronal lipofuscin in pyramidal cells were performed with a semi-automatic image analysis system. In CA 1 pyramidal cells the lipofuscin content was significantly lower than in the other sectors, which did not differ significantly in their lipofuscin content. The amount of the granular component in relation to the vacuolar component in CA 1 was larger than in the other sectors. With advancing age the lipofuscin content per cell increased. The vacuolar component of all hippocampal subfields experienced a larger increase than the granular component. Consequently the relation of the vacuolar and granular component changed; the relative amount of the vacuolar component increased, while that of the granular component decreased with age. The differences between sector CA 1 and the other hippocampal subfields were discussed with reference to differences of metabolic and functional activity of the neurons. Cytoprotective factors like Calbindin D28k were discussed for CA 1.

Fine structure of presynaptic axonal terminals in sympathetic autonomic ganglia of aging and diabetic human subjects

The neuropathologic changes that may underlie autonomic nervous system dysfunction in nondiabetic elderly human subjects or as a complication of diabetes have been systematically examined in sympathetic ganglia of a series of autopsied human subjects. As in animal models of aging and diabetes, enormously swollen terminal axons were found closely apposed to the perikarya of principal sympathetic neurons in prevertebral superior mesenteric sympathetic ganglia of aged and diabetic human subjects. Dystrophic axons consisted of two stereotyped forms: the first was composed of large numbers of misaligned aggregates of neurofilaments surrounded by variable numbers of small dense core vesicles; the second was characterized by large numbers of mitochondria, vacuoles, and dense and multivesicular bodies. The fine structural characteristics of neuroaxonal dystrophy, its predilection for prevertebral rather than paravertebral sympathetic ganglia, and the tendency for multiple dystrophic axons to cluster preferentially around selected neurons were identical in aged and diabetic human ganglia and were similar to changes seen in animal models of aging and diabetes. Neither diabetic nor aging ganglia demonstrated evidence of neuronal degeneration. Such structural changes may represent a degenerative influence of diabetes and aging on the normal remodeling of nerve terminals in autonomic ganglia, i.e., the continually ongoing process of turnover and replacement of axonal terminals. Similarity of lesions in human diabetes and aging suggests the possibility of pathogenetic mechanisms that are common to diabetes and the aging process. The substantial parallels between humans and animal models provide support for the validity of testing some proposed pathogenetic mechanisms directly in animal models.

Lifelong ethanol consumption enhances the age-related changes in rat sympathetic neurons

The effects of aging and chronic ethanol administration on the histochemical and morphometric features of rat superior cervical ganglion were studied in a rat strain selected for voluntary alcohol consumption. Ethanol was administered to the experimental group ad libitum (10% v/v in drinking water) from 3 months to 28 months of age, the average ethanol intake being 6.4-5.4 g/kg per day. The sympathetic neurons of the ethanol consuming rats showed several signs of enhanced degeneration, e.g. decreased neuronal packing density, increased amount of age-pigment and decreased intensity of catecholamine histofluorescence and tyrosine hydroxylase immunoreactivity. The results may indicate a selective vulnerability of peripheral sympathetic neurons rather than a universal accelerated aging due to chronic ethanol exposure.

Suramin-induced changes in sympathetic neurons: correlation between catecholamine fluorescence, tyrosine hydroxylase immunoreactivity and accumulation of pigment bodies

The effect of suramin, a strong inhibitor of lysosomal enzymes, was studied in rat superior cervical (SCG) and dorsal root ganglia (DRG). Ten days after administration both types of ganglion showed increased intraneuronal pigment fluorescence; in DRG there were also accumulated pigments in Schwann cells. Ultrastructurally the pigment bodies were membranous or lamellar inclusion bodies. In SCG suramin-induced inclusion bodies were associated with decreased catecholamine fluorescence and tyrosine hydroxylase immunoreactivity, suggesting that altered activity of lysosomal enzymes and the formation of lysosomal inclusion bodies may be coupled with decreased synthesis of neurotransmitters in rat sympathetic neurons.

Age pigments in different populations of peripheral neurons in vivo and in vitro

The distribution and ultrastructure of lipopigments in the rat sympathetic, vagus and spinal ganglion neurons were studied in vivo and in vitro using fluorescence and electron microscopy. Newborn, 3-6 mo and 24-30 mo-old male Wistar rats were used. In vivo, the age pigments in the sympathetic neurons showed a tendency to form unipolar or bipolar caps, whereas in the vagus and spinal ganglion neurons pigment granules were packed in the peripheral area of the perikarya during aging. Ultrastructurally, lipid-like vacuoles and a rather homogeneous matrix were the components shared by pigment bodies of all types of peripheral neurons. However, pigment granules in sympathetic neurons frequently had a third, osmiophilic component, which likely represents neuromelanin. In vitro, the cytoplasmic area occupied by autofluorescent pigments was increased in most of the neurons. Some neurons, however, showed the same amount of lipopigments as in vivo. In electron microscopy, age pigment granules typical of each type of neuron were found, and their number and intracellular distribution seemed to be comparable with those in vivo. In most of the neurons cultured from all ages and of all types of ganglion, there appeared to be accumulations of another, very homogeneous and large type of pigment body. In some cases, they were structurally connected with classical pigment bodies or they had a finger print-like substructure. Large homogeneous pigment bodies were also seen in surrounding satellite cells. All these changes were most frequently seen in cultures of spinal ganglia from old animals. It is concluded that although classical age pigments maintain their characteristics in cultured peripheral neurons, there is, in addition, a rapid accumulation of ceroid-like pigments, which may be caused by the inability of the cultured neurons to cope with increased peroxidative damage.

Effect of vitamin E and selenium supplement on the aging peripheral neurons of the male Sprague-Dawley rat

The effect of life-long diets containing different concentrations of selenium and vitamin E on the age pigment accumulation in the rat superior cervical ganglion, vagal ganglion and dorsal root ganglion, was studied using microspectrofluorometry. All types of ganglia showed unchanged amounts of age pigments at low or high concentrations of selenium, whereas dietary concentration of vitamin E regulated age pigment content in the dorsal root ganglion, but not in the superior cervical and vagal ganglion. Vitamin E deficiency induced a three-fold increase in age pigment content in dorsal root ganglion at 8 months of age, whereas high vitamin E concentration was associated with a lesser amount of pigments at 18 months of age. Emission spectra of age pigment recorded from the dorsal root ganglion and vagal ganglion were different from that from the superior cervical ganglion, but were independent of dietary concentrations of selenium or vitamin E. The results suggest that exogenous antioxidants may play a more crucial role in lipid peroxidation and accumulation of age pigment in dorsal root ganglion than in autonomic ganglia.

Neuronal degeneration and lipopigment formation in rat sympathetic ganglion after treatment with high-dose guanethidine

Degenerative changes in the rat superior cervical ganglion (SCG) were studied 3 months after treatment with a high-dose of guanethidine using microspectrofluorometry and electron microscopy. The density of the SCG neurons was decreased by 30% and by 60% following 1 and 2 weeks treatment respectively with guanethidine. Intraneuronal lipopigments were increased after the treatment, whereas cytoplasmic catecholamines were decreased. Electron microscopy revealed swollen mitochondria and a novel type of lipo-pigment in surviving neurons. The number and structure of small intensely fluorescent (SIF) cells remained unchanged after the treatment. The results suggest that accelerated lipid peroxidation processes might be involved in guanethidine neurotoxicity and that intraneuronal concentrations of catecholamines may be related to this toxicity.

The effect of bleaching on the lipopigments in the human sympathetic neurons

The effect of exposure to H2O2 on the lipopigments of the human sympathetic neurons was investigated by fluorescence and electron microscopy. In intact ganglia two subtypes of the lipopigment were seen: the yellow fluorescent pigment (emission maximum at 510 nm), which under the electron microscope had two components (vacuoles and osmiophilic matrix) and the orange fluorescent pigment (emission maximum at 535 nm), which in electron microscopy showed a third, highly osmiophilic component. Bleaching did not change the emission spectrum of the yellow pigment, while that of orange pigment shifted from 535 nm to 485 nm. Under electron microscopy the highly osmiophilic component disappeared in bleached orange pigment bodies. The characteristics of orange autofluorescent lipopigment are similar to those described for neuromelanin in the substantia nigra. The results suggest that neuromelanin accumulates in aging sympathetic neurons.