Chronic copper poisoning and changes in the central nervous system of sheep

Copper Toxicity in Animals: A Review

Copper is an essential trace element in animals and humans. However, excessive intake of copper can cause copper ions to accumulate in tissues and organs of animals, leading to copper toxicity. Copper ions induce apoptosis and autophagy through oxidative stress-mediated mitochondrial dysfunction. In addition, copper induces cell death by targeting lipoylated tricarboxylic acid (TCA) cycling proteins, termed cuproptosis. In recent years, copper cytotoxicity studies have attracted attention. In addition, the number of cases of copper toxicity in animals has been increasing over the past years due to environmental pollution and overdose from copper feed supplements. Therefore, a comprehensive understanding of copper toxicity and the metabolism of copper ions can aid in devising strategies for preventing copper toxicity. This review introduces the tissue and organ toxicity and cytotoxicity caused by copper toxicity and reviews the metabolism of copper ions in tissues, organs, and cells. The paper also reviews the clinical cases and animal experiments of copper toxicity in recent years. Finally, the preventive and curative measures for copper toxicity and the future challenges are also discussed. The general objective of this paper is to provide a reliable reference for copper toxicity prevention.

Copper Poisoning, a Deadly Hazard for Sheep

Simple Summary

Sheep are very susceptible to copper intoxication, a deadly disease that causes significant economic losses worldwide. Two types of copper poisoning can occur depending on the chronic or acute exposure to copper. Chronic toxicosis is the most common form and is developed after a long subclinical period of copper accumulation in the liver. When the capacity of the liver for copper storage is exceeded, a sudden release of copper into the blood causes severe haemolysis and the death of the animals. Acute copper poisoning is much less frequent and appears following the accidental administration or ingestion of toxic amounts of copper. Collapse and death occur shortly after parenteral administration, whereas acute oral exposure to copper causes severe gastroenteritis followed by shock and death. In this review, we summarise the available information on the aetiology, epidemiology, pathogenesis, clinical features, diagnosis, treatment and prevention of sheep copper poisoning.

Abstract

Copper (Cu) is an essential microelement for animals. However, sheep are particularly susceptible to Cu intoxication, a deadly disease reported worldwide. The risk of developing this poisoning is higher in vulnerable breeds and in intensively managed lambs or milk sheep. Two types of Cu intoxication can occur depending on the chronic or acute exposure to Cu. In chronic Cu poisoning (CCP), the most common form, Cu is accumulated in the liver during a subclinical period. A low intake of Cu antagonists (molybdenum, sulphur, iron, or zinc) favours Cu accumulation. The sudden release of Cu into the blood causes acute haemolysis with anaemia, haemoglobinuria, jaundice and death within 1–2 days. Acute Cu poisoning is related to the accidental administration or ingestion of toxic amounts of Cu. Acute oral exposure to Cu causes severe gastroenteritis, shock and death. Collapse and death occur shortly after parenteral administration. The diagnosis is based on history, clinical, gross pathological, histological and toxicological findings. Treatment of sheep with severe clinical signs often has poor success but is very effective during the Cu accumulation phase. Different therapies, based on either chelating agents or Cu antagonists, have been used to treat and prevent CCP.

Atypical chronic copper poisoning in a sheep secondary to copper wire ingestion - case report

ABSTRACT A 14-month-old female Texel sheep that came from a herd made up of 19 animals showed haemoglobinuria, apathy, and anorexia, and died two days after the start of the clinical signals. The sheep remained in a natural grassland, where trailers were repaired, and multiple copper wires were deposited on the pasture. The animal had tachycardia, tachypnoea, pale mucous membranes, groaning pain on abdominal palpation, circling, head pressing, intensely hemolyzed plasma, and intense azotaemia. The necropsy showed focally extensive oedema in the inguinal and medial region of pelvic limbs, kidneys dark brown, and liver diffusely yellow with an evident moderate diffuse lobular pattern. The abomasum had a considerable amount of enameled material of thickness, firm to the cut, with 1-5 mm (copper wires). Histopathological examination showed marked diffuse tubular and glomerular coagulative necrosis in the kidneys, in addition to neutrophils, macrophages, lymphocytes, and plasma cells with moderate multifocal nephritis. The liver showed centrilobular necrosis, moderate hepatocellular edema, multifocal cholestasis, and in the lungs and brain mild to moderate diffuse edema. Copper content in the frozen liver (in natura) reached 1,598 mg/kg. Copper mesh ingestion led to sheep poisoning, which in this case was considered an atypical form of chronic primary copper poisoning.

Chronic copper poisoning in beef cattle in the state of Mato Grosso, Brazil

ABSTRACT: Copper is an essential micromineral in animal feed; however, when consumed in excess, it can cause liver necrosis, hemolytic crisis, hemoglobinuric nephrosis and death in cattle. Although uncommon in this species, copper poisoning occurs as a result of exacerbated supplementation, deficiency of antagonist microminerals, or previous liver lesions. An outbreak of chronic copper poisoning is reported in semi-confined cattle after supplementation with 50 mg/Kg of dry matter copper. The cattle showed clinical signs characterized by anorexia, motor incoordination, loss of balance, jaundice, brownish or black urine, diarrhea and death, or were found dead, 10 to 302 days after consumption. Of the 35 cattle that died, 20 underwent necropsy, whose frequent findings were jaundice, enlarged liver with evident lobular pattern, black kidneys, and urinary bladder with brownish to blackish content. Microscopically, the liver showed vacuolar degeneration and/or zonal hepatocellular centrilobular or paracentral coagulative necrosis, in addition to cholestasis, mild periacinal fibrosis, apoptotic bodies, and mild to moderate mononuclear inflammation. Degeneration and necrosis of the tubular epithelium and intratubular hemoglobin cylinders were observed in the kidneys. Copper levels in the liver and kidneys ranged from 5,901.24 to 28,373.14 μmol/kg and from 303.72 to 14,021 μmol/kg, respectively. In conclusion, copper poisoning due to excessive nutritional supplementation is an important cause of jaundice, hemoglobinuria, and death in semi-confined cattle.

Effects of aging on the myelination of the optic nerve in rats

AIM OF THE STUDY

Cognitive decline due to aging is most probably the result of changes in the white matter in the central nervous system (CNS) and/or demyelination.

MATERIAL AND METHODS

We used electron microscopic analysis of the morphological changes in aging rats' optic nerves as an easily accessible part of the CNS.

RESULTS

Several age changes were observed in aging rats (36 months) vs. young adult rats (6 months), namely degeneration of axons, decreased packing density and morphological alterations of myelination, including the ballooning of some myelin sheaths, separation of myelin lamellae and degenerative changes in the oligodendrocytes population.

CONCLUSION

Cognitive decline related to aging may occur in part due to the disturbed myelination of axons in CNS white matter.

Spongiform Leukoencephalopathy Induced in Mice by Oral Benzidine Administration

Small foci of spongy change, often bilaterally symmetric, were observed in the brains of mice exposed to benzidine dihydrochloride. These vacuoles were most frequent in the superior thalamic radiation of the internal capsule. They possibly represent swollen glial cells and intramyelinic vacuoles. No consistent relationship was observed between the presence of vacuoles in the brain and hepatic lesions in these mice, and this change may be attributable to benzidine treatment unrelated to toxic effects of the liver.

The effects of normal aging on myelinated nerve fibers in monkey central nervous system

The effects of aging on myelinated nerve fibers of the central nervous system are complex. Many myelinated nerve fibers in white matter degenerate and are lost, leading to some disconnections between various parts of the central nervous system. Other myelinated nerve fibers are affected differently, because only their sheaths degenerate, leaving the axons intact. Such axons are remyelinated by a series of internodes that are much shorter than the original ones and are composed of thinner sheaths. Thus the myelin-forming cells of the central nervous system, the oligodendrocytes, remain active during aging. Indeed, not only do these neuroglial cell remyelinate axons, with age they also continue to add lamellae to the myelin sheaths of intact nerve fibers, so that sheaths become thicker. It is presumed that the degeneration of myelin sheaths is due to the degeneration of the parent oligodendrocyte, and that the production of increased numbers of internodes as a consequence of remyelination requires additional oligodendrocytes. Whether there is a turnover of oligodendrocytes during life has not been studied in primates, but it has been established that over the life span of the monkey, there is a substantial increase in the numbers of oligodendrocytes. While the loss of some myelinated nerve fibers leads to some disconnections, the degeneration of other myelin sheaths and the subsequent remyelination of axons by shorter internodes slow down the rate conduction along nerve fibers. These changes affect the integrity and timing in neuronal circuits, and there is evidence that they contribute to cognitive decline.

Brain copper elevation and neurological changes in north ronaldsay sheep: a model for neurodegenerative disease?

This study in North Ronaldsay (NR) sheep showed that copper was elevated in both the liver and brain of older animals and that the elevation in these two sites was highly correlated. The accumulation of copper in the liver culminated in chronic active hepatitis. Evidence of tissue damage in the brain was equivocal, but the astrocytes showed strong immunoreactivity for metallothionein. The study suggested that the blood-brain barrier of NR sheep possesses unusual features in respect of the import of copper into the brain, and that NR sheep may provide a useful animal model for the investigation of brain copper homeostasis.

Molybdenum-associated Pituitary Endocrinopathy in Sheep Treated with Ammonium Tetrathiomolybdate

Ammonium tetrathiomolybdate (TTM) has hitherto been the treatment of choice for chronic copper poisoning in sheep, but the long-term consequences have not been evaluated. This study was based on a flock of copper-poisoned sheep which, after apparently successful treatment with TTM, became infertile and progressively unthrifty and eventually died 2-3 years later. The last five surviving animals were subjected to euthanasia and detailed study. Necropsy revealed marked wasting together with depletion of the pituitary and adrenal glands, testicular atrophy and ovarian cystic follicles. Histopathological examination revealed a non-inflammatory atrophy or degeneration of the adenohypophysis with loss of trophic cells; adrenocortical and testicular atrophy and ovarian degeneration. The regressive changes in the anterior lobe of the pituitary were confirmed by immunocytochemical labelling, which revealed a marked depletion of adrenocorticotrophic hormone (ACTH), follicle stimulating hormone (FSH) and luteinizing hormone (LH) in the affected pituitaries by comparison with healthy controls. Excess molybdenum (Mo) retention (P<0.02) was identified by inductively coupled plasma mass spectrometry (ICPMS) in the pituitaries and atomic absorption spectrometry (AAS) in the adrenals and brains of affected sheep. It was concluded that molybdenum introduced systemically as TTM is retained within the brain, pituitary and adrenal glands and is associated with a toxic endocrinopathy. It is postulated that Mo administered as thiomolybdate adversely affects the hypothalamo-adenohypophyseal system by interfering with trophic hormone release, leading to the cessation of reproductive activity and ultimately the failure of intermediary metabolism. Whether Mo exerts its effect centrally or directly on the pituitary was not established.

Early, middle, and late stages of neural cells from ovine embryo in primary cultures

The utilization of neural cells in culture has importantly increased the knowledge of the nervous system biology. In most studies, the investigations are performed on biological materials coming from common laboratory animals and the extrapolation of the results to other animals is not easy. For some studies, such as developmental biology of the nervous system, prion disease investigations, or agronomical production, the utilization of ovine neural cell cultures presents many advantages. Unfortunately, there are few data on the conditions of culture of such cells. In the present work, we investigated simple ways to obtain neurons and astrocytes from sheep brain. Viable neuronal cell cultures were obtained from 40 to 50 day old fetuses. Their morphologies were quite similar to that of neurons from rodent or chick brain and they were labeled by antineurofilament antibodies. Stages older than 50 days of pregnancy were unable to give viable culture of neurons. The stages of 40 day old fetus to newborn lamb were able to give viable astrocyte cultures. The common protoplasmic astrocytes were obtained and they were labeled by antiglial fibrillary acidic protein antibodies. The astrocytes contained glycogen, thus looking like the common astrocytes from rodents. Neuronal or astroglial cultures can be derived from 26 day old embryos, but the cultures contained contaminating cells. Among the latter cells, there were undifferentiated cells which were flat and epitheloid and which were grouped as islets. These cells could be maintained in culture for a time duration over 7 months, even after two passages. They differentiated principally in astrocytes with a radial configuration. This work shows how some neural cells can be simply and easily cultured from sheep brain. For the first time, neurons were cultured from the sheep embryonic brain. Moreover, stem cells were cultured for more than 7 months and, finally, glycogen accumulation in sheep astrocytes was shown to be the same as that in rodent astrocytes. The oligodendrocyte culture was already documented. Thus, sheep can easily be used as well as other models for neural cell studies.

Clinical and pathological studies in cattle with hepatic disease

In cattle with hepatic lipidosis, hepatic abscessation, leptospirosis, biliary calculi or fasciolosis, the progression of the disease was studied by serial measurements of serum total bile acid concentrations, plasma glutamate dehydrogenase, gamma-glutamyltransferase, 5'-nucleotidase and leucine aminopeptidase activities Terminalia avicennioides and by liver biopsy. Regardless of the cause of the hepatic disease, weight loss, anorexia, dullness and depression were consistent features. Signs of hepatic encephalopathy, such as blindness, head pressing, excitability, ataxia and weakness were less common and, together with pyrexia and jaundice, were grave prognostic signs. Plasma ammonia concentrations were significantly elevated compared to clinically normal cattle, but such changes were not always accompanied by a decline in plasma urea concentrations. In normal, healthy cattle, the plasma ammonia:urea concentration ratio is 9:1 and the plasma ammonia:glucose concentration is 11:1. In hepatic disease, a plasma ammonia:glucose ratio > 40:1 or plasma ammonia:urea ratio > 30:1, particularly with a rising total ketone body concentration and a declining glucose concentration, carried a guarded prognosis. The study suggested that other factors, such as hypokalaemia, alkalosis, short-chain volatile fatty acids, and false and true neuro-transmitters, may be important in the pathogenesis of hepatic coma in cattle.

Spongiform central nervous system myelinopathy in African dwarf goats

A novel spongiform myelinopathy of the central nervous system (CNS) of eleven African dwarf goats was examined by light and electron microscopy. Histological lesions consisted of extensive vacuolation predominantly of the white matter of the diencephalon, midbrain and cerebellar peduncles, as well as of spinal white matter. Ultrastructurally, vacuoles were shown to be intramyelinic, resulting from the splitting of the outer myelin lamellae at the intraperiod line. A few oligodendrocytes showed vacuolar degeneration of cell bodies and processes. Inflammatory reactions were absent. The observed lesions point to an unknown primary damage of oligodendroglia and central myelin. A hereditary background of the disorder is suspected as all investigated dwarf goats were half-brothers or -sisters and partly descended from the mating of adult females with their own sire.

Wilson's disease-like lesion in a calf

Wilson's disease-like lesion was seen in a 2-month-old calf. Fibrosis was apparent in the liver, but there was no cholestasis or icterus. Marked spongy degeneration was seen in the central nervous system. Hepatic and brain copper values were significantly higher than normal: 1970 and 113 ppm dry matter, respectively. Serum ceruloplasmin was lower than normal: 17.5 U/liter. Etiology of this disease was unknown, but there is no evidence that the calf ingested a large quantity of copper.

Ultrastructural findings in spongy degeneration of white matter in silver foxes (Vulpes vulpes). A naturally occurring demyelinating disease with oligodendrocyte vacuolation

Spongy degeneration of white matter in silver foxes is a naturally occurring, hereditary disorder. We report ultrastructural findings in the upper cervical cord of five perfusion-fixed foxes that were examined between 5 weeks and 2 1/4 years after the onset of clinical signs. Large cytoplasmic vacuoles in oligodendrocytes were present in the foxes examined 5, 12 and 20 weeks after the onset. Other early features of the disease were severe vacuolation of myelin sheaths, demyelination, expansion of extracellular spaces and hypertrophy of astrocytes. Evidence of partial demyelination as well as demyelination of entire internodes was found. In the later stages of the disease, the vacuolation was largely resolved but a marked astrogliosis persisted and numerous remyelinated axons were present in the gliotic areas. Vacuolation of oligodendrocytes and partial demyelination has not previously been seen together in a single disease process. The relationship between oligodendrocyte vacuolation, myelin sheath vacuolation and demyelination is discussed. It is concluded that the present condition is due to a primary damage to oligodendrocytes; however, the underlying biochemical lesion is not known.

Death in sheep following dosing with copper diethylamine oxyquinoline sulphonate as a commercial injectable copper preparation

Death occurred in sheep following diethylamine oxyquinoline sulphonate (DOS) copper injections given at recommended dose rates. The copper content in unused portions of DOS copper packs was normal and free of bacterial contamination. Liver and blood copper levels in dead and sick sheep were not high. Sick sheep showed signs of hepatic encephalopathy and dead sheep were generally piled against fences and scrub. Deaths were associated with acute, severe, generalised, centrilobular, hepatocellular necrosis and live sheep had elevated circulating levels of liver enzymes consistent with liver damage. In recovered sheep there were no residual complications. It would appear that even at 0.5 mg/kg of DOS copper the safety threshold may sometimes be exceeded in some sheep.

Acute nicotinamide deficiency in the pig induced by 6-aminonicotinamide

Pigs given intraperitoneal injections of 6-aminonicotinamide developed a syndrome similar to a natural disease found in Queensland. Focal lesions, involving mainly destruction of glial cells, developed in the intermediate grey matter of the cervical and lumbar enlargement of the spinal cord. There was widespread vacuolation of spinal cord white matter. The glial cell loss was repaired. We suggest that natural acute nicotinamide deficiency can occur if a threshold dose of an antimetabolite of nicotinamide is absorbed over a short period of time.

Glial changes in pigs with porto-caval anastomosis and temporary or total hepatic artery clamping

The number and size of astrocyte, oligodendrocyte, and neurone nuclie were determined in cortex and corpus striatum (putamen) of pigs with porto-caval anastomosis (PCA) and total or temporary clamping of the hepatic artery. Animals with PCA and total clamping became comatose and died on average 18 1/2 hours postoperatively. Their brains showed slight oedema but no changes in the glial and neurone nuclear numbers. Animals with PCA and temporary clamping of the hepatic artery (30-60 min.) all survived without clinical symptoms of encephalopathy. However, the brains showed vacuolization of the deeper cortical layers, diffuse occurrence of Alzheimer type II astrocytes, and the counts revealed an increased number of astrocytic nuclei. The total number of glial cells decreased due to loss of oligodendrocytes, but the number of neurones was unchanged. The findings indicate that the neuropathological changes after PCA and temporary hepatic artery clamping are concerned primarily with changes of the glial cells.

Heavy metal pollution among autoworkers. II. Cadmium, chromium, copper, manganese, and nickel

Garages and auto-repair workshops may be polluted with other heavy metals besides lead. Blood of autoworkers with high lead content was analysed for cadmium, chromium, copper manganese, nickel, ALAD activity and carboxyhaemoglobin level. Cadmium and copper levels in blood of autoworkers were comparable with those of the control subjects while chroimium and nickel levels were significantly higher (P less than 0-01 for both metals), and scattered raised values of manganese were found. There was no significant mutual correlation between levels of various heavy metals determined in whole blood. High copper levels were slightly related to decreasing ALAD activity (P less than 0-1). Nineteen per cent of autoworkers were found to have an abnormally blood level of carboxyhaemoglobin. The amount of particulate heavy metal in autoworkshop air was not related to biochemical abnormalities found in the autoworkers. Various sources of pollution of these heavy metals in autoworkshops are discussed.

Glial cell reactions in rats with hyperammoniemia induced by urease or porto-caval anastomosis

The density and size of astrocyte, oligodendrocyte and neurone nuclei were determined in the corpus striatum of rats with urease-induced hyperammoniemia (plasma NH4+-concentration about 800 micronmol/1). No changes in the number of neurone nuclei were found. After 4 days the density of astrocyte nuclei increased from 13 to 23 per cent of the glial nuclei. However, the number of oligodendroxyte nuclei decreased correspondingly and the total glial nuclear number remained constant. The number of astrocyte nuclei was normalized 1 week after the 4-day period of hyperammoniemia. Moreover, intracerebral injections of colchicine at different times of the experimental period revealed no mitoses, indicating that no astrocyte divisions took place in pure hyperammoniemia. The astrocyte nuclei were of normal size in the urease animals in contrast to the animals with porto-caval anastomosis (PCA) which showed enlarged astrocyte nuclei. Thus, hyperammoniemia caused a reversible transformation of glial nuclei, but no real proliferation. A comparison of the glial reactions 4 days after a brain lesion showed the same frequency of astrocyte mitoses in control and urease animlas but a higher incidence of mitoses in the PCA animals. The number of Alzheimer type I astrocytes was the same in control and PCA animals, whereas no such cells were found in the urease animals, indicating that this form of hyperammoniemia did not lead to arrest of astrocyte metaphases with subsequent formation of Alzheimer type 1 cells.