The effect of lead exposure and serum deprivation on mesencephalic primary cultures

The effect of Pb2+ was studied in embryonic mesencephalic primary cultures that contain neurons and glia. Pb2+ exposure in absence of serum, damaged more efficaciously the cultured cells than Pb2+ exposure in presence of serum. In serum-free medium, Pb2+ elicited mainly necrosis and apoptosis in maximally 13% of the cells in culture. The glial fibrillary acidic protein (GFAP) content was decreased by Pb2+ exposure in serum-containing medium. The abundance of GFAP was also decreased by serum deprivation that was augmented by the addition of 12.5 microM Pb2+ in serum-free medium. A 6h exposure to 6 microM Pb2+ in serum-free medium also lowered the low affinity 3H-D-aspartate uptake. A 6h exposure of mesencephalic cells to 3-25 microM Pb2+ in serum-free medium failed to alter the number of tyrosine hydroxylase- and calretinin-immunoreactive cells, whereas, 50 microM Pb2+ obliterated both cell types. A 6h exposure of cells to 3 microM Pb2+ in serum-free medium decreased 3H-dopamine uptake by 50 % and 12.5 microM Pb2+ obliterated it. Addition of albumin to serum-free medium failed to prevent the Pb2+ -elicited inhibition of [3H]-dopamine uptake suggesting that the serum-afforded delay of cell death may not be due to a removal of reactive Pb2+ by protein/chelate formation but rather to the Pb2+ -scavenging function of glial cells. Serum deprivation may exacerbate the Pb2+ -induced neurotoxicity presumably by impairing the metal scavenging function of astrocytes.

Lead-induced abnormalities in blood-brain barrier permeability in experimental chronic toxicity

The aim of this paper was to determine whether prolonged drinking of lead acetate-containing water by adult rats, which imitates environmental exposure to lead (Pb), affects some morphological and biochemical properties of rat brain microvessels. We noted a significant increase of lead level in capillaries and synaptosomes obtained from brains of rats under chronic toxicity conditions. Intravenously injected horseradish peroxidase (HRP) was used to evaluate the functional state of the blood-brain barrier (BBB). The results indicate that, systematically administered at low doses, lead induces BBB dysfunction. The changes, revealed in light microscopy and confirmed by electron microscopic studies, are typical for "leaky" microvessels, reported for variety of neuropathological conditions associated with BBB damage. Enhanced pinocytotic activity of the endothelial cells and the opening of interendothelial tight junctions, together with enormous phagocytizing action of the pericytes, are the most characteristic ultrastructural features noted. The presence of specific type of perivascular cells containing droplets of lipids in the cytoplasm, together with changes in phospholipid profile in brain capillaries, suggest that altered lipid composition of membranes may, at least in part, be responsible for changes in observed membrane permeability.

Acute arsenic toxicosis in five horses

Five adult horses presented with acute clinical signs of watery diarrhea, excessive salivation, muscle tremors, ataxia, and depression. Four died within 24 hours and the fifth was euthanatized approximately 48 hours after onset of clinical signs. Necropsy finds in two of the horses included hyperemia of gastric mucosa, intestines filled with green to black watery fluid, and multifocal to coalescing, hemorrhagic 1.0-2.0-cm-diameter ulcers of the mucosa of the cecum and large colon. Histopathologic changes in the cecum and large colon consisted of mucosal necrosis and ulceration, vascular thrombosis, necrosis of submucosal blood vessels, and infiltration by mixed mononuclear inflammatory cells and neutrophils. Arsenic toxicosis was suspected. The owner had not been feeding the horses any grain; however, a mixture of grain and pink powder was found in the pasture. Liver arsenic concentrations in the two horses were 14.0 and 11.0 ppm, a sample of renal cortex contained 108 ppm arsenic, and the grain/powder mixture found in the pasture was positive for arsenic at > 3,000 ppm. kidney lead concentrations were 6.5 and 4.2 ppm. Results were consistent with lead arsenate or lead arsenite poisoning.

Intracranial vascular calcifications, glioblastoma multiforme, and lead poisoning

A 72-year-man with previous lead poisoning presented with raised intracranial pressure and localizing neurologic signs. CT scans showed a high-grade glioma and extensive intracranial calcifications, which proved to be vascular in distribution on postmortem examination. The latter findings support the concept of dystrophic calcification following lead-induced cerebrovascular injury. Lead poisoning should be considered in the differential diagnosis of unexplained intracranial calcifications. There is also evidence from previous studies to suggest a causative relationship between lead poisoning and development of glioma.

An epizootic of lead poisoning in greater flamingos (Phoenicopterus ruber roseus) in Spain

During November 1992 to March 1993, and November 1993 to February 1994, 106 greater flamingos (Phoenicopterus ruber) were collected dead or moribund in the wetlands of El Fondo and Salinas de Santa Pola, eastern Spain. Birds still alive were emaciated and had a bile-stained diarrhea. On necropsy, they had liquid in the upper digestive tract and the walls of their gizzards were stained dark green. Fifty-three (93%) of 57 gizzards examined contained lead shot (range one to 277 shot), and fifty-five (96%) of 57 livers contained levels of lead greater than 5 micrograms/g dry weight (DW) (median = 192.3 micrograms/g DW, range < 2.5 to 992.2 micrograms/g DW).

Lead toxicosis in a captive bottlenose dolphin (Tursiops truncatus) consequent to ingestion of air gun pellets

A captive bottlenose dolphin (Tursiops truncatus) in a dolphinarium in Tel Aviv, Israel, had signs of anorexia, weight loss and a reluctance to train over a 4-week period in June 1995 and died shortly thereafter. On necropsy, it had an enlarged, yellow discolored liver, and about 55 air gun pellets in the second stomach. The pellets were composed of 40% lead. Samples of liver and kidney cortex contained 3.6 and 4.2 micrograms/g lead, respectively. There was hemosiderosis in the liver and kidneys, status spongiosus in the brain, and vacuolization in the optic nerve; acid-fast intranuclear inclusion bodies were seen in the kidneys. We propose that chronic lead toxicosis had been induced after the gradual dissolution of the lead-based pellets in the acid environment of the stomach.

Effects of chelation therapy on hepatic glutathione, lipid peroxidation and phospholipid contents in lead-poisoned rats

Hepatic lipid peroxidation, glutathione and phospholipid contents of homogenate prepared from the liver of lead-intoxicated male rats treated with 0.3 m mol/kg CaNa2EDTA and DMSA for 8 weeks, either alone or in combination, were investigated. A significant increase in hepatic malondialdehyde (MDA) and a reduction in glutathione levels was noticed. While a marginal decrease in phosphatidyl choline (PC) level was noticed, no effect on phospholipid contents was seen. Treatment with all the three chelating agents elicited decrease in PC level. DMSA alone was partially effective in restoring lead-induced altered hepatic glutathione and MDA levels. Combined treatment may have an adverse effects on hepatic tissue and does not seem to produce immediate recoveries in the lead-induced hepatic damage.

Cholinergic denervation-like changes in rat hippocampus following developmental lead exposure

We investigated the effects of developmental lead exposure from embryonic day 16 (E16) through postnatal day 28 (PN28), on cholinergic and catecholaminergic markers in the septohippocampal pathway in rats through fourth month of age. Lead exposure resulted in a persistent 30-40% reduction of [3H]hemicholinium-3 ([3H]HC-3) binding in the hippocampus through PN120, and 20-30% reduction of septal and hippocampal choline acetyltransferase (ChAT) activity which persisted through PN84 but returned to control levels in both septum and hippocampus at PN112. The muscarinic ligand [3H]quinuclidinyl benzylate ([3H]QNB) binding was reduced in the septum at PN28 but did not differ significantly from controls at PN56-PN112. Neither short- nor long-term effects of Pb exposure on [3H]QNB binding were seen in the hippocampus. Similar to the effects of fimbria-fornix transection, Pb exposure resulted in a long-term 50-90% increase of tyrosine hydroxylase(TH) activity in the hippocampus, although neither treatment affected TH activity in the septum. The lead-induced increase in hippocampal TH was significantly attenuated by superior cervical ganglionectomy. It is concluded that the effects of perinatal lead exposure resemble in several respects those seen following surgical disruption of the septohippocampal pathway in adult animals. The denervation-like effects in the hippocampus may be an important factor in long-term learning and cognitive impairments following developmental exposure to low-levels of lead.

Dendritic alterations of cortical pyramidal neurons in postnatally lead-exposed kittens: a Golgi-Cox study

Cortical pyramidal cell development was studied in postnatally lead-exposed kittens by light microscopic and Golgi staining methods. The most evident finding was an elevation of spine density on the distal apical dendritic branches of lead-treated kittens. Also, the branching pattern of the apical dendrites in lead-treated animals was different from control, but there was no overall change in total branch number of the dendritic arbor. Pyramidal cell height and cortical thickness were unaffected. No evidence of vascular damage or other pathologies were found in hematoxylin and eosin-stained sections. The results are discussed with reference to dendritic spine development and function and to other reports of hyperspiny dendrites. Evidence of hyperspiny dendrites in the present study indicates this represents a useful protocol for investigating dendritic spine development and differentiation.

Lead as an inductor of some morphological and functional changes in synaptosomes from rat brain

1. The effect of lead (in vivo) on the uptake of GABA, dopamine, and histidine as a precursor of histamine in synaptosomes obtained from chronically lead-treated rats was studied. 2. Lead decreased the uptake of GABA, increased the uptake of dopamine, and did not change the uptake of histidine. These effects were independent of calcium concentration. 3. Lead administration to the rat changed the morphology of the synaptosomes, as manifested in the decreased number of synaptic vesicles and disturbed mitochondrial structure. 4. The results suggest the existence of several mechanisms of lead toxicity on uptake, related to individual neurotransmitters, which are not necessarily connected with a Pb2+/Ca2+ interaction.

Ultrastructural evaluation of the rat parotid gland after six-week-intoxication with lead acetate

Clinical and experimental data point to the unfavorable effect of lead compounds on the oral cavity condition. The aim of this study was to analyse ultrastructural changes in the parotid gland of rats subjected to intoxication with lead acetate. The experiment was carried out on 24 Wistar rats divided into 4 groups, 6 animals in each. Group I animals were given aqueous solution of lead acetate of lead concentration 50 mg/dm3(50ppm), group II-500 mg/dm3(500ppm), group III-1,000 mg/dm3(1,000ppm). Control animals drank tap water. All the rats were sacrificed after six weeks of the experiment and material was collected for ultrastructural studies and evaluation of lead level in the tissue dry mass. A three fold increase in lead levels in the parotid gland was observed in group I and a tenfold increase in groups II and III. In all experimental ultrastructural examinations revealed groups in which lead impaired secretion of alveolar cells, damaged mitochondria and disturbed the lipid balance. The greatest destructive changes were observed in group III.

Ultrastructure of the hypothalamo-neurohypophysial system in rats exposed to lead. II. Neurohypophysis

Ultrastructure of neurohypophysis was examined in rats allowed to drink for 6 weeks only solution of lead acetate. It was found the increased number of neurosecretory granules in axonal terminals, the signs of granulolysis in Herring bodies and the presence of axonal terminals with atypical, heterogeneous contents. The possible mechanisms of alterations observed in the whole hypothalamoneurohypophysial system affected by lead were discussed.

Pathomorphologic findings of lead poisoning in white-fronted geese (Anser albifrons)

Nineteen lead-poisoned white-fronted geese (Anser albifrons), including nine immature birds, were examined pathologically. Subacute lead poisoning due to ingestion of spent lead shots was diagnosed pathologically and confirmed by demonstrating high lead concentration in the liver. The liver lead concentration ranged from 6.9 to 67.7 mg/kg wet weight. The most suggestive gross lesions were mottled bile-stained liver in eight geese and proventricular impaction and/or the presence of lead pellets in the gizzard. Histologic lesions of the liver consisted of Kupffer cell hemosiderosis, large bile plugs in dilated canaliculi, bile pigmentation in hepatocytes, and bile extravasation and associated hepatic necrosis. Seven geese of the remaining 11 birds also had hepatic necrosis in the liver, the greenish discoloration of which was obscure macroscopically. The liver discoloration was considered a jaundice due to both rapid overproduction of bile from increased breakdown of erythrocytes and intrahepatic impaired excretion of bile. The severity of lesions was not correlated to the liver lead concentrations. All examined geese had hemosiderosis of mononuclear phagocytic system cells in the spleen and hypoplasia or edema of the bone marrow with increased numbers of polychromatic erythroblasts. These prominent changes probably resulted from excess breakdown of erythrocytes, hypercholia followed by intrahepatic cholestasis, and disrupted erythropoiesis in bone marrow caused by lead.

Chronic lead exposure induces ultrastructural alterations in the monkey testis

The purpose of this study was to establish the effects of lead on the non-human primate testis. Sixteen cynomolgus monkeys maintained in environmentally controlled conditions were administered 1500 micrograms lead acetate/kg bw/day in gelatin capsules. Monkeys were randomly assigned to the following groups: control (n = 3), which received 95% glycerol and 5% distilled water (vehicle) over their lifetime for 9 years; infancy group (n = 4), exposure limited to the first 400 days of life; post-infancy group (n = 5), dosed following 300 days of life to 9 years of age; lifetime group (n = 4), dosed for nine years. All the animals were treated with lead or vehicle for the entire duration of the experiment. The organs from animals in the control group consisted of seminiferous epithelium comprised of typical Sertoli cells containing nuclei with numerous infoldings and longitudinally-oriented profiles of endoplasmic reticulum, microtubules, mitochondria, and lipid droplets that were scarce. Spermatogenic cell types at different developmental stages were observed. Seminiferous epithelium from animals of the treated groups exhibited distortion in the general architecture of the epithelium such that a marked decrease in its height was revealed. In particular, Sertoli cells contained heightened number of lipid droplets and lysosomal elements, and the basal lamina was usually stratified. The magnitude of alterations in the seminiferous tubules was indistinguishable among the three treated groups. These findings support the conclusion that lead is a potent testicular toxin.

Alterations in the hepatic enzymes following experimental lead poisoning

An investigation on the influence of lead toxicity on some of the hepatic enzymes was studied in rats both after a shorter interval of 15 d and after longer intervals of 60 and 90 d. Three different doses of lead as 5, 10, and 50 mg/kg body wt were administered orally on every alternate day. Whereas significant inhibition of succinic dehydrogenase was seen following lead poisoning, the activity acid and alkaline phosphatase increased with lead intoxication. The histoarchitecture of the liver was grossly intact. Liver accumulated less lead compared to kidney at 60 and 90 d.

Mechanisms of kidney cell injury from metals

The most environmentally abundant toxic metals/metalloids (arsenic, cadmium, lead, and mercury) are each known to produce cell injury in the kidney but the molecular mechanisms underlying these events are now being elucidated. It is clear that the nephrotoxicity of these agents is due, in part, to the fact that urinary elimination is a major route of excretion from the body. The role(s) of molecular factors such as metal-binding proteins, inclusion bodies, and cell-specific receptorlike proteins that appear to influence renal tubule cell expression, have attracted increased interest as determinants that modulate cell populations as special risk for toxicity and renal cancer. The future of mechanistic toxicology studies with regard to how and why only certain renal cell populations become targets for toxicity from these metals/metalloids and other less common inorganic nephrotoxicants must focus on the molecular handling of these agents by target cell populations.

[Light and electron microscopic studies of calf kidneys after exposure to subtoxic lead levels]

Eight calves were fed from the fourth to the twentieth week of age a milk powder diet containing 40 mg lead acetate per kg dry substance. This is twice the lead concentration legally permitted. In average, each animal has daily taken up 0.834 mg lead per kg body weight. Eight calves were used as controls. The animals gained the usual fattening weights and did not show clinical symptoms. Beginning with week 14, increased levels of blood urea were encountered in the animals which received lead in their diet. Morphologically, severe renal lesions were found in these calves. The kidneys were increased in weight, pale and of firm consistency. Histologically, fibrosis and periglomerular interstitial non-purulent nephritis were found. Light- and electronmicroscopically, numerous intranuclear inclusion-bodies typical for lead poisoning were demonstrated in epithelial cells of proximal tubules. The results show, that daily uptake of less than 1 mg lead per kg body weight must be considered as a toxic dose for calves, and not 5-7 mg as stated in literature.

Histomorphological and cytochemical changes induced in the liver of goldfish Carassius carassius var. auratus by short-term exposure to lead

The cellular and molecular effects of experimental lead intoxication (5 mg l-1/24 h and 48 h) were studied in hepatocytes of Carassius carassius var. auratus. Significant lead storage was not detected by atomic absorbance spectroscopy after treatment. Cell morphology appeared only poorly impaired. A decrease of glycogen content was observed. Glycolysis, Krebs cycle and pentose shunt were altered in their enzymatic activities. Lysosomal activities were strongly increased. All enzymatic activities tested were altered 24 h after lead treatment.

Experimental model of lead nephropathy. I. Continuous high-dose lead administration

This study followed the progression of lead nephropathy in male Sprague-Dawley rats (E) administered lead acetate (0.5%) continuously in drinking water for periods ranging from 1 to 12 months. Control animals (C) were pair-fed. Observations included renal pathology by light and electron microscopy, wet and dry kidney weights, and glomerular filtration rate (GFR) to assess renal function. Urinary excretion of lead, the enzymes N-acetyl-beta-D-glucosaminidase (NAG) and glutathione-S-transferase (GST), and brush border antigens (BB50, CG9, and HF5) were utilized to explore possible markers of kidney injury. GFR was increased significantly after three months of lead exposure, but was decreased significantly after 12 months. Kidney wet weights were significantly greater in E than C from three months on. Kidney dry weight/wet weight ratio was constant up to three months, but decreased in E at 12 months. Glomerular diameters were normal at all time periods; the nephromegaly was related primarily to hypertrophy of proximal tubules. Lead inclusion bodies were found in nuclei of proximal convoluted tubules and pars recta at all times. Tubular atrophy and interstitial fibrosis first appeared at six months, and increased in severity thereafter. Brush borders of proximal tubules were disrupted at one and three months, but recovered thereafter. Focal and segmental glomerulosclerosis was observed in 2 of 10 rats at 12 months. Arteries and arterioles remained normal at all time periods. Urinary NAG was elevated in E above C after three months of lead exposure. However, urinary NAG in C also increased with age, obscuring changes in the 12 month E rats. GST was elevated after three months of lead administration in E, not without an attendant age-related increase in C rats. In three-month E rats, urinary brush border antigens were increased above C, but were decreased at six and 12 months, correlating with the morphologic changes in brush border. We conclude that a high dose of lead in rats may initially stimulate both renal cortical hypertrophy and an increase in GFR. Later, the adverse effects of lead on the tubulointerstitium predominate, and GFR falls. The urinary marker, NAG, was abnormal in the early stages of the disease, but age-related changes obscured its utility at later stages; urinary GST appeared to be a more consistent marker of injury.

Pathological study of lead poisoning in whooper swans (Cygnus cygnus) in Japan

During spring 1989, thirty-three whooper swans (Cygnus cygnus) died at Lake Miyajima in Hokkaido, Japan; 15 were examined. The birds were diagnosed as having subacute lead poisoning due to ingestion of spent lead shot. The main gross findings were bile-stained liver, edematous or gelatinous bone marrow, bile-stained lining with hyperkeratosis and lead pellets in the gizzard, and proventricular impaction. Histopathologically, there was lead-hemolytic jaundice of the liver, hemosiderosis in the liver and spleen, and hypoplasia of the bone marrow with increased numbers of polychromatic erythroblasts. Acid-fast intranuclear inclusion bodies were seen in kidneys of seven swans. Under electron microscopy, inclusion bodies had frayed contours and consisted of high-electron-dense fine granules. The lead concentration of the liver ranged from 5.5 to 44.3 mg/kg wet weight. It was suggested that these changes resulted from excess breakdown of erythrocytes, inhibition of heme synthesis, and impaired erythropoiesis caused by lead shot.