Extracellular edema and glial response to it in the cerebellum of suckling rats with low-dose lead encephalopathy. An electron microscopic and immunohistochemical study

The 14th International Symposium on Brain Edema and Brain Tissue Injury

The 14th International Symposium on Brain Edema and Brain Tissue Injury, 2008 was held in a highly productive academy environment in Warsaw, Poland, in the premises of the prestigious Polish Academy of Sciences, under the able guidance of Professor Dr Zbigniew Czernicki on June 11–14, 2008.

Evidence of toxicity, oxidative stress, and neuronal insult in autism

According to the Autism Society of America, autism is now considered to be an epidemic. The increase in the rate of autism revealed by epidemiological studies and government reports implicates the importance of external or environmental factors that may be changing. This article discusses the evidence for the case that some children with autism may become autistic from neuronal cell death or brain damage sometime after birth as result of insult; and addresses the hypotheses that toxicity and oxidative stress may be a cause of neuronal insult in autism. The article first describes the Purkinje cell loss found in autism, Purkinje cell physiology and vulnerability, and the evidence for postnatal cell loss. Second, the article describes the increased brain volume in autism and how it may be related to the Purkinje cell loss. Third, the evidence for toxicity and oxidative stress is covered and the possible involvement of glutathione is discussed. Finally, the article discusses what may be happening over the course of development and the multiple factors that may interplay and make these children more vulnerable to toxicity, oxidative stress, and neuronal insult.

Changes of local cerebral blood flow concomitant to lead-exposure in adult rabbits

Lead is considered a pathogenic factor of atherosclerosis and arterial hypertension, which are main risk factors of cerebrovascular disease. The brain microvasculature preferentially accumulates lead and its function is sensitive to its toxic effect. Influence of inorganic lead-exposure (20 mg/kg-I group, 40 mg/kg II group) for 10 days on local cerebral blood flow (lCBF) in hypothalamus (HYP) and cerebral cortex (CTX) of rabbits was studied by means of the hydrogen clearance method. Corresponding results were compared to sham operated group (III group). During lead-exposure lCBF was reduced in both investigated regions. The reduction of lCBF in HYP was reduced in both investigated regions. The reduction of lCBF in HYP was 12.9% (P < 0.05) in I and 19.9% (P < 0.001) in II group; corresponding changes in CTX were -16.9% (statistically non-significant -N) in I and 1.4% (NS) in II group. Present finding suggest that inorganic lead induces cerebral microvascular dysfunction with following changes in lCBF. These alteration have a biphasic character Although these disturbances reveal a tendency towards normalization, it is possible to presume that higher concentrations of ingested lead cause more severe injury to endothelium of brain microvasculature.

Astroglial alterations in rat hippocampus during chronic lead exposure

The present study was performed in order to follow the response of astroglial cells in the rat hippocampus to chronic low-level lead exposure. The experiments combined immunohistochemistry using anti-glial fibrillary acidic protein (GFAP) antibody and conventional transmission electron microscopy (EM). Chronic administration with drinking water [1 g% w/v (subclinical dose) of lead acetate dissolved in distilled water] was started through the mother's milk when pups were 7 days old. Following weaning, experimental offspring were treated for 3 months with the same concentration of adulterated water. The group of intoxicated animals and their controls were sacrificed by perfusion-fixation at 30, 60, and 90 days of exposure. After 60 days of lead treatment, staining of GFAP-positive cells demonstrated an astroglial transformation from the quiescent to the reactive state, characterized by an increase in GFAP. In control rats no changes in GFAP immunostaining were observed. The intensity of the astroglial response was enhanced after 90 days of lead intoxication, showing an increment of GFAP immunoreactivity. Quantification of these changes was made by computerized image analysis, confirming that the sectional areas of the astroglia in lead-exposed animals were larger than those in controls. These results are consistent with the ultrastructural alterations. Simultaneously with the increment in gliofilaments, intranuclear inclusions were seen in some astrocytes. The mechanisms by which lead affects astrocytes are unknown. Probably the astroglial changes induced by lead intoxication produce microenvironmental modifications that may disturb the neuronal function.

Decreased nerve conduction velocity in optic nerve following early post-natal low-dose lead exposure

A study was made on nerve conduction velocity of the optic nerve in rats subjected to lead exposure during the first 2 weeks of post-natal life. The rats were given intraperitoneal injections with a calculated daily exposure of 7.6 micrograms (low-dose) or 15.8 micrograms (high-dose) lead g-1 body weight. Growth retardation at 30 days was seen only with the higher dose. Littermates of low-dose exposed rat were injected with vehicle only and served as controls. Lead concentrations in blood and brain were measured in rats of 20 days of age in order to ascertain that exposure was adequate in the present litters. Nerve conduction velocity of the optic nerve was examined in 14 rats of 30 days of age taken from 10 different litters. The optic nerve(s) was prepared in anaesthetized rats and placed in a flow-through incubation chamber. One stimulating and two recording tungsten electrodes were used. In all rats, three positive-negative waves, regarded as representing three functional groups of optic nerve axons, could be recorded. The last one often had a long duration and a small amplitude without distinct peaks and hence was omitted from further analysis. The mean conduction velocities for the two faster axonal groups were 16.8 and 5.4 m s-1 in control rats, 10.3 and 5.8 m s-1 in low-dose rats and 9.4 and 5.2 m s-1 in high-dose rats. The difference in conduction velocity for the fastest axons was significant for controls versus low-dose and high-dose but not for low-dose versus high-dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of lead in the cerebellum of suckling rats following low and high dose lead exposure. A micro-PIXE analysis

The distribution of lead in the cerebellum of suckling Sprague-Dawley rats was examined using a nuclear microprobe for elemental mapping of tissue sections (particle-induced X-ray emission, 3-microns beam of 2.5 MeV protons; micro-PIXE). The rats were injected intraperitoneally with a lead-containing vehicle or vehicle only from ages 1 to 14 days. The calculated doses were 7.8 (low-dose) and 15.6 (high-dose) micrograms lead/g body weight. The rats were killed at 20 days of age. The vascular system was rinsed quickly with 0.15 M ammonium acetate to obtain determinations of intra-parenchymal lead with minimal influence of lead bound to erythrocytes and plasma proteins. Brains were frozen in propane/propylene in liquid nitrogen. Cryostat sections, 15 microns thick, were air dried on formvar coats that covered a hole, 15 mm in diameter, in a plastic disc, and were used for lead analysis by micro-PIXE. Very low concentrations of lead were found in the brain of controls. Lead levels in homogenates from cerebrum and cerebellum measured by atomic absorption spectrometry (AAS) were: low-dose 1.2-2.2 micrograms/g wet weight and high-dose 1.4-2.4 micrograms/g wet weight. The lead levels measured with the micro-PIXE method were in good agreement with the levels found with AAS. Lead was present in the cerebellar white matter in two to three times higher amounts than in the cortical grey (low-dose white matter 11-18 micrograms/g dry weight, grey matter 2.0-5.5 micrograms/g dry weight). This was true for both low and high dose exposed rats.(ABSTRACT TRUNCATED AT 250 WORDS)