The effects of zinc deficiency on pancreatic carboxypeptidase activity and protein digestion and absorption in the rat

1. Proteolytic enzyme activities were examined in the pancreas of zinc-deficient and control rats. 2. No change was detected in trypsin-plus-chymotrypsin activity. 3. Carboxypeptidase activity was appreciably lowered in zinc deficiency and returned rapidly to normal on zinc therapy. 4. In experiments in which U-(14)C-labelled Chlorella protein was fed no evidence was obtained which suggested that the reduction in carboxypeptidase activity had limited the rate of protein digestion or absorption. 5. The specific activity of pancreatic protein synthesized during these experiments was appreciably lower in zinc-deficient than in control rats. 6. A higher proportion of the total activity present, in each organ examined, was in the non-protein fraction in zinc-deficient rats.

Metabolic interactions of copper with other trace elements

Metabolic interactions between copper and other trace elements influence not only the susceptibility of animals and humans to deficiency or toxicity of copper but also the biochemical and pathological consequences of these states. Antagonistic trace elements affect the utilization of copper by reducing its solubility within the intestinal lumen, by competing with copper during its absorption or transport, or by modifying its distribution between receptors in body tissues. The derangement of iron-dependent functions during the development of copper deficiency provides a further example of such interactions which, in this instance, arise from the involvement of copper in processes that apparently regulate the flux of iron between plasma and cellular pools. This paper deals with recent studies of the mechanisms of the interactions between copper and zinc, cadmium molybdenum and iron.

[The Médicins sans Frontières HIV/AIDS programme in Ukraine]

In 1999, Médicins sans Frontières started an HIV/AIDS programme in Ukraine, a country with an estimated 410,000 people with HIV (1.4% prevalence), including 53,000 in urgent need of antiretroviral therapy. Between 1999 and 2004, a comprehensive HIV/AIDS programme was implemented in close collaboration with the Ministry of Health in AIDS centres in Odessa, Mikolaev and Simferopol. Initial activities included prevention and treatment advocacy campaigns, which were later followed by prevention of mother-to-child transmission, treatment of opportunistic infections, antiretroviral therapy for infants and adults and palliative care. This programme has served as a model and has led to meaningful improvements in HIV/AIDS care in Ukraine. It demonstrates that adequate care for patients with HIV or AIDS is possible in countries like Ukraine.

An evaluation of germinating beans as a source of vitamin C in refugee foods

OBJECTIVE

To assess whether germinating pulses and beans are a potential source of vitamin C in rations for refugee communities with poor vitamin C status.

DESIGN

High pressure liquid chromatographic assessment of vitamin C content of a range of legumes following germination in light and dark and after cooking.

RESULTS

Many species of pulses produced significant quantities of vitamin C up to five days following germination in both light and dark although cooking caused a marked loss of ascorbate.

CONCLUSION

Germination of approximately half of the seeds of the pulse constituents of many basic rations would be likely to generate, within a 3-5 d germination period, sufficient ascorbate to provide the 10 mg needed to protect adults against the development of scurvy.

Micronutrient status of the besieged residents of Sarajevo: May 1993

OBJECTIVE

To assess micronutrient status indices in blood and plasma of subjects subjected to siege conditions.

DESIGN

Whole blood and serum samples were taken from subjects, sampled from 30 clusters in four Municipal Areas of Sarajevo. The blood samples were flown, under appropriate refrigeration, to the UK for analysis.

SETTING

The study was conducted in besieged Sarajevo and laboratory analyses were carried out at Department of Clinical Chemistry, Aberdeen Royal Infirmary and at Rowett Research Institute, Aberdeen, Scotland.

SUBJECTS

202 subjects, aged from 1 to 82 years were included in the sample.

INTERVENTIONS

Serum folate, ferritin, transferrin, retinol, retinol-binding protein, beta-carotene, alpha-tocopherol, 25-hydroxycholecalciferol, C-reactive protein, haemoglobin and mean corpuscular volume of blood were determined. Micronutrient status was assessed by comparison with a range of values derived from multinational data sets from both pathologically malnourished and normal subjects.

RESULTS

Haemoglobin, ferritin, folate, retinol and 25-hydroxycholecalciferol levels were lower in the Sarajevan sample than in normal reference populations. Serum alpha-tocopherol was low in children and adolescents while a low beta-carotene level probably reflected the scarcity of green vegetables. No consistent evidence of protein/energy deficits were detected.

CONCLUSIONS

Data for retinol binding protein and transferrin, when considered in association with BMI and Z-score data, provided no significant evidence of protein-energy undernutrition. However, the prevailing food aid rations failed to maintain adequate reserves of several micronutrients, particularly iron, folate and vitamin D. The significance of low values for serum retinol and beta-carotene and of low serum alpha-tocopherol in children must be investigated further.

Reduction of radiocaesium absorption by sheep consuming feed contaminated with fallout from Chernobyl

Two compounds, a zeolite, clinoptilolite, and a ferrocyanide, potassium hexacyanocobalt (II) ferrate (II), were found to be the most effective adsorbers of caesium in vitro. When used in vivo they significantly reduced the absorption of caesium by sheep fed contaminated herbage. These compounds did not alter the rate of excretion of pre-absorbed caesium, which varied with the time from cessation of contamination.

Copper deficiency and tissue glutathione concentration in the rat

Copper deficiency in rats increased renal vein and arterial (heart) plasma GSH concentration by approximately 50%. There was no change in plasma GSSG concentration. Renal vein plasma GSSG/GSH ratio was decreased in copper deficiency, which is consistent with previous reports showing a copper-dependent thiol oxidase activity in the renal basement membrane. No change occurred in arterial plasma GSSG/GSH ratio. Hepatic GSH concentrations were also elevated by 50% in copper deficiency, GSSG concentrations were unaffected, but GSSG/GSH ratio was depressed. Renal and cardiac tissue GSH and GSSG were unaffected by copper deficiency. The decreased SOD activity and GSH-Px activity observed in copper deficiency may contribute to increased hepatic and plasma GSH concentrations.

Biochemical and physiological indicators of mineral status in animals: copper, cobalt and zinc

The value of estimates of trace element requirements or of data on tissue trace element content for identifying and controlling trace element-related disorders is often limited by inadequate data on the relationships of such criteria to physiological performance. Investigations of metabolic events initiating early pathological responses to deficiency are beginning to suggest more effective indicators of physiologically relevant abnormalities in trace element intake or status. Progress in studies of metabolic responses to deficiencies of copper, cobalt and zinc is reviewed.

Stimulation of peroxidation in rat liver microsomes by (copper, zinc)-metallothioneins

The abilities of pig liver (copper, zinc) metallothionein I and rat liver zinc metallothionein II to modify lipid peroxidation in incubations of liver microsomes have been compared with the activities of reduced glutathione, mannitol, quinacrine, EDTA, dimethyl-pyrroline-N-oxide and phenyl-butyl-nitrone. Lipid peroxidation was determined by assay of thiobarbituric acid reactive substance formation in incubations of microsomes with iron/ADP or a mixture of xanthine and xanthine oxidase. Zinc metallothionein II had no effect on the extent of peroxidation in either system but (copper, zinc) metallothionein I caused a stimulation of peroxidation initiated by xanthine and xanthine oxidase, all other compounds tested were inhibitory. Gel exclusion chromatography of incubations of (copper, zinc) metallothionein I with xanthine and xanthine oxidase revealed aggregation of the metalloprotein. This may have exposed copper in a form capable of initiating peroxidation.

Tissue damage in vitamin E deficient rats is not detected by expired ethane and pentane

Despite evidence for tissue damage in vitamin E deficient rats, no discernible difference in ethane and pentane production was apparent compared with controls. It is suggested that other sources of hydrocarbons may mask hydrocarbon production from peroxidation of polyunsaturated fatty acid components of cell membranes, or that tissue damage occurs before peroxidation of the polyunsaturated fatty acids.

Use of ammonium tetrathiomolybdate in the treatment of copper poisoning in sheep

Intravenous administration of ammonium tetrathiomolybdate (three doses on alternate days) appeared to be an effective means of containing the acute phase of copper toxicity in sheep, whether this arose from continuous ingestion of high copper feeds or by injudicious use of copper preparations for the control of copper deficiency. No adverse effects were recorded on lamb numbers, birth weight or survival of lambs born to ewes of normal to low copper status when the treatment was applied at sensitive periods of the reproductive cycle. Decreases in 'available' plasma copper and in liver damage occurred rapidly in response to intravenous tetrathiomolybdate and it is suggested that all animals at risk be treated.

Effects of dietary copper, cadmium, iron, molybdenum and manganese on selenium utilization by the rat

The possible antagonistic effects of different dietary concentrations of copper (1.3-200 mg/kg), cadmium (1-5 mg/kg), iron (20-500 mg/kg), molybdenum (0.3-50 mg/kg) and manganese (0.2-200 mg/kg) on selenium utilization by the rat were studied by the measurement of the absorption and organ distribution of dietary selenium as [75Se]selenite and by effects on organ glutathione peroxidase (GSH-Px: EC 1.11.1.9) activity. Although a high concentration of copper (200 mg/kg) in the diet did not alter the percentage absorption and total-body retention of doses of 75SeO3(2)- by rats, after such treatment tissue 75Se distribution was changed and was lower total selenium in some tissues. After copper treatment (200 mg/kg diet) GSH-Px activity of liver, testis, kidney and whole blood was also lower. Dietary cadmium, iron, molybdenum and manganese at the concentrations investigated had no significant effects on selenium metabolism. Thus it is unlikely that copper, cadmium, iron, molybdenum and manganese at normal dietary concentrations will have a major effect on selenium metabolism in the rat, especially if adequate amounts of selenium are being consumed.

Studies on the effects of copper deficiency on rat liver mitochondria. II. Effects on oxidative phosphorylation

Effects of dietary copper deficiency in rats on respiratory enzymes of isolated rat liver mitochondria have been studied. After 2 weeks of Cu-depletion, cytochrome c oxidase (EC 1.9.3.1) activity had declined by 42% and between 4 and 8 weeks exhibited between 20 and 25% of the activity of control mitochondria. Activities of NADH cytochrome c reductase (EC 1.6.99.3) and succinate cytochrome c reductase (EC 1.3.99.1), were unaffected initially but declined by 32 and 46%, respectively, after 8 weeks of Cu-depletion. After 4 weeks there was a significant (34%) decline in succinate supported state 3 respiration with only a modest (18%) decline in state 4 respiration. The ADP:O ratio was unaffected by Cu-depletion after 6 and 8 weeks of dietary Cu-restriction. State 3 respiration was significantly reduced after 6 weeks when glutamate/malate or beta-hydroxybutyrate were used as substrates, whereas state 4 respiration and ADP:O ratios were unaffected. The fall in state 3 respiration was of sufficient magnitude at 8 weeks to cause a significant decline in the respiratory control ratio with all substrates. Comparisons between the relative activities of cytochrome c oxidase and reductase activities in Cu-deficient preparations, the relatively specific effect of the deficiency on state 3 respiration with all substrates tested and the ability to increase significantly oxygen consumption in excess of maximal state 3 respiration by the uncoupler 2,4-dinitrophenol suggest that the defect in Cu-deficient mitochondria cannot be attributed solely to the decreased activity of cytochrome c oxidase.

Studies on the effects of copper deficiency on rat liver mitochondria. I. Changes in mitochondrial composition

As part of an investigation of the lesions of copper (Cu) deficiency a study was undertaken of the copper, iron, cytochrome and fatty acid composition of liver mitochondria from Cu deficient and Cu-adequate control rats. Cu concentrations were significantly decreased in whole liver, liver mitochondria and in blood plasma. Total iron was significantly increased in whole liver but remained at the normal level in mitochondria. Cytochrome c oxidase (EC 1.9.3.1) and its component cytochromes a and a3 were significantly reduced in liver mitochondria from Cu-deficient rats, whereas there was no effect on the concentration of cytochromes b, c1 and c. Evidence from comparisons between cytochrome c oxidase activity and the amount of enzyme present, as assessed from the mitochondrial cytochrome a and a3 content, suggests that in addition to an absolute loss of enzyme, Cu-deficiency adversely affects the efficiency of the residual enzyme. Severe Cu deficiency had no effect on 'ageing' or 'swelling' properties of liver mitochondria, indicating no marked effects on fatty acid composition. Fatty acid analyses demonstrated a slight but significant increase in docosapentenoic acid (22:5) of Cu-deficient mitochondria, but since this represents a minor component there was no change observed in the 'unsaturation index'. It was concluded that, in contrast to previous reports, Cu deficiency of the severity reported did not have a deleterious effect on the integrity and permeability of the inner mitochondrial membrane as exemplified by any qualitative modification of fatty acid constitution per se.

Selenium utilization by sheep given diets differing in sulfur and molybdenum content

The effects of differing dietary concentrations of sulfur (0.4, 1.8, and 3.9 g/kg diet) or Mo (0.3, 3, and 5 mg/kg diet) on Se utilization, were studied in Suffolk × Finn-Dorset ewes. Se concentrations and glutathione peroxidase (E.C.1.11.1.9) activity were measured in tissues of the ewes being repleted with Se or depleted of Se in the presence of the proposed antagonists. Evidence for an antagonism between dietary S and Se was found with an inverse relationship between dietary S concentrations and the Se concentrations of liver and wool, and glutathione peroxidase activity in the liver. Molybdenum (0.3, 3, or 5 mg) in diets of the sheep (0.01 or 0.03 mg Se/kg dry matter) had no significant effects on tissue Se concentrations or glutathione peroxidase activities. With an adequate supply of Se in the diet, there are probably no major effects of S on Se availability and metabolism in the sheep. Within dietary concentrations tested, dietary Mo does not influence utilization of Se by the sheep.

The effects of dietary sulfur on selenium utilization by the rat

The antagonistic effects of S on Se utilization were studied by measurement of tissue Se concentrations and glutathione peroxidase (GSHpx, E.C.1.11.1.9) activities in rats offered Torula yeast-based diets supplemented with sodium sulfate to provide 1.5, 3, or 5 g S/kg diet. Increasing sulfur concentrations in the diet caused small but significant decreases in GSHpx activity of liver, spleen, heart, lung small intestine, and skeletal muscle. Also significantly decreased were Se concentrations in liver and hair. Dietary sulfur content had no significant effect on body weight gain of the rats. With an adequate supply of Se in the diet, there are probably no major deleterious effects of dietary S on Se metabolism in the rat.

Zinc absorption in celiac disease and dermatitis herpetiformis: a test of small intestinal function

The increments in plasma zinc concentrations after an oral dose of elemental zinc (50 mg) as the sulphate were used to assess the intestinal absorption of the metal in 11 patients with dermatitis herpetiformis (DH) before starting a gluten-free diet, 12 patients with newly diagnosed celiac disease (CD), 10 patients known to have CD, and 15 healthy volunteers. The areas under the plasma zinc increment curve plotted against time were determined for 3 (AUC3) and 6 (AUC6) h. The AUC3 in healthy volunteers was 401 +/- 48 mumol 1(-1) 3 h (mean +/- SD); it was reduced in newly diagnosed CD 187 +/- 76 mumol 1(-1) 3 h (p less than 0.001), and in dermatitis herpetiformis 206 +/- 87 mumol 1(-1) 3 h (p less than 0.01); but it was normal in the known CD 396 +/- 204 mumol 1(-1) 3 h, the wide variation reflecting the variable compliance with a previously instituted gluten-free diet. The AUC6 was similarly affected, healthy volunteers 700 +/- 111 mumol 1(-1) 6 h, new CD 380 +/- 169 mumol 1(-1) 6 h (p less than 0.01); dermatitis herpetiformis 471 +/- 107 mumol 1(-1) 6 h (p less than 0.01); known CD 725 +/- 380 mumol 1(-1) 6 h. The AUC3 was more consistently abnormal than conventional tests of small intestinal function. In a prospective study the AUC3 and AUC6 improved and reflected compliance with a gluten-free diet.

Thiomolybdates in rumen contents and rumen cultures

Examination of direct and (Cu)-difference spectra of i) the aqueous supernatants of in vitro cultures of bovine rumen contents incubated with MoO42- and potential sources of S2- and ii) samples drawn directly from the rumen of animals receiving high Mo diets yielded evidence of the presence of thiomolybdates. Only MoS42- was detected in the soluble phase of in vitro cultures. Although intense and variable background absorbance precluded full characterization of thiomolybdate species in samples drawn directly from the rumen, both spectral data and the biochemical and clinical responses of animals given high Mo diets were consistent with the conclusion that MoS42- rather than MoOS32- was the predominant thiomolybdate species present in the aqueous phase. Addition of Ca2+ either to rumen cultures before incubation or as a supplement to diets high in MoO42- content inhibited the appearance of MoS42- in the aqueous phase. Evidence of the sequestration of MoS42- and MoOS32- by particulate or microbial fractions of rumen contents is considered in relation to the inhibitory action of Mo upon Cu absorption by ruminants.

Uteroplacental dysfunction and prostaglandin metabolism in zinc deficient pregnant rats

Relationships between perinatal mortality, disrupted utero-placental function and prostaglandin metabolism have been studied in Zn-deficient rats. Uterine contractility in vitro, placental blood flow in vivo, and uterine and placental prostaglandin synthesis from [1-14C] arachidonic acid in vitro were investigated at day 22 of pregnancy. High amplitude uterine contractions were almost completely eliminated and utero-placental blood flow was decreased by 85% by Zn deficiency. Synthesis of [1-14C]-prostaglandin E2, F2 alpha and 6-keto-F1 alpha from [1-14C] arachidonic acid decreased significantly in uterine tissue but increased in placentae. These possibly inter-related effects may contribute to the high perinatal mortality observed in Zn deficiency.

Studies on the role of zinc in parturition in the rat

1. Pregnant rats were fed either low (less than 1 p.p.m.) Zn or control (40 p.p.m. Zn) diets from day 10 of gestation. They were killed at intervals during the last 96 h preceding the normal time for onset of parturition, and differences in plasma progesterone, oestradiol-17 beta and ovarian 20 alpha-hydroxysteroid dehydrogenase were assessed. 2. Gestation was prolonged in Zn-deficient rats. 3. Although the preparturient decline in plasma progesterone began at the same time in all groups, at term, plasma progesterone concentration in Zn-deficient rats remained significantly higher than in normal females. 4. Induction of ovarian 20 alpha-hydroxysteroid dehydrogenase activity was delayed by about 8 h by Zn deficiency. This delay was not observed if prostaglandin F2 alpha was injected previously. 5. The results suggest a Zn-dependent step(s) in uterine synthesis and/or release of prostanoids.

Effects of tetrathiotungstate and dithiotungstate on copper metabolism in rats

The effects of dietary supplementation with ammonium tetrathiotungstate and dithiotungstate on copper metabolism in young rats have been investigated. The addition of WS4(2-) (4-32 mg W/kg diet) decreased growth rates and induced clinical and biochemical signs of Cu deficiency. These were overcome by increasing the dietary content of Cu. The intestinal absorption of 64Cu was impaired and the tissue distribution of absorbed Cu modified by the administration of WS4(2-). No clinical or biochemical defects indicative of Cu deficiency developed in rats receiving WO2S2(2-) in their diet at concentrations up to 32 mg W/kg. In contrast, this oxythioanion enhanced the content of Cu in plasma liver and kidney, especially when dietary Cu was increased. Most of the additional Cu retained by plasma and kidney was associated with albumin and metallothionein, respectively. The effects of these W sources are compared with those caused by their thio- and oxythiomolybdate analogs and are discussed in relation to the mechanisms whereby Mo induces Cy deficiency in ruminants.

Copper metabolism in rats given di- or trithiomolybdates

As one of a series of studies on the influence of S substitution of MoO4(2-) on the action of Mo as an antagonist of Cu, the effects of MoO2S2(2-) and MoOS3(2-) on the metabolism of Cu by rats have been investigated. Administration of either oxythiomolybdate increased both plasma Cu concentration and the retention of Cu by the albumin fraction of plasma. In contrast to the effects of MoS4(2-), described previously, neither oxythiomolybdate inhibited 64Cu absorption from the digestive tract or induced biochemical or clinical signs of Cu deficiency. Evidence is discussed suggesting that the potency of the thio- and oxythiomolybdates as inhibitors of Cu utilization is directly proportional to the degree of thio substitution within the series series MoO4- chi S chi 2-.

Noradrenaline concentrations in gut muscle and mucosa of the copper-deficient steer and rat

1. Noradrenaline (NA) concentrations in the duodenum and colon of copper-deficient and Cu-adequate steers and rats were determined. 2. In Cu-deficient steers exhibiting diarrhoea, there were significant decreases (P less than 0.05) in duodenal and colonic muscle NA concentrations. Duodenal and colonic mucosal NA concentrations in the steer were also diminished by Cu deficiency but this effect was not statistically significant. 3. Rat intestinal musculature had a higher NA concentration than that of the steer. Rat duodenal muscle NA was not influenced by Cu deficiency, but increased markedly with age. 4. It is suggested that the decline in NA concentration of cattle musculature in copper deficiency may have a role to play in the aetiology of diarrhoea in such animals.

Glutathione peroxidase activity and erythrocyte stability in calves differing in selenium and vitamin E status

1. Glutatione peroxidase activity (EC 1.11.1.9) and erythrocyte stability were measured in Friesian bull calves which were given for 36 weeks semi-purified diets either adequate or low in selenium or vitamin E or both. 2. Dietary Se or vitamin E content had no effect on growth rate and haematlogical values. None of the calves exhibited clinical deficiency symptoms and serum aspartate amino transferase (EC 2.6.1.1) and creatine phosphokinase (EC 2.7.3.2) activities remained normal. Heart and skeletal muscles of all calves appeared macroscopically and microscopically normal ato autopsy. 3. Glutathione peroxidase activity in plasma, blood and other tissues, except the testis, was significantly lower in calves receiving low dietary Se but was independent of dietary vitamin E content. 4. Plasma vitamin E levels decreased rapidly and to very low levels in calves given low vitamin E diets irrespective of the Se content of the diet. 5. A low dietary vitamin E intake increased the susceptibility of erythrocytes to auto- and peroxidative haemolysis whereas a low Se intake in the presence of adequate vitamin E did not. However, erythrocytes from calves receiving low Se and low vitamin E were more susceptible to peroxidative haemolysis than erythrocytes from calves receiving low vitamin E and adequate Se. The effect of dietary vitamin E content on osmotic haemolysis induced by hypotonic saline was variable. 6. The results suggest that measurement of blood glutathione peroxidase activity and the susceptibility of erythrocytes to auto- or peroxidative haemolysis could be used for the differential diagnosis of subclinical Se and vitamin E deficiency in ruminants.

Some outstanding problems in the detection of trace element deficiency diseases

Knowledge of the functional roles of many essential trace elements has grown rapidly. Despite this, it is rarely possible to relate this information to observed pathological consequences of deficiency. Few studies of the effect of deficiency upon enzyme activity have attempted to determine whether such changes influence substrate-product relations and thus may have pathological significance. Evidence that the differing susceptibility of tissues to deficiency may reflect metabolic activity or the lifespan of cells and their organelles is considered. The need is growing for more effective biochemical diagnostic techniques for the early detection of covert pathological changes in trace element deficient subjects. Progress towards satisfying this need will reflect the future availability of information from which to predict the nature of rate-limiting metabolic defects in sensitive populations of cells.

Absorption, transport and tissue storage of essential trace elements

Intestinal absorption of many essential trace elements probably occurs by saturable and carrier-mediated processes. The nature and efficiency of these are influenced by a range of physiological, nutritional and genetic variables. Special emphasis is given to the influence of exogenous and endogenous ligands of small molecular mass in the intestinal lumen on absorptive efficiency. The effect of enterocyte proteins such as metallothionein which, by sequestering metals, influence their fate during absorption is also considered. Changes in the metabolic activity of the intestinal mucosa induced by copper or zinc deficiencies influence the fate of other nutrients, either by inhibiting intracellular transport or by preventing the degradation of potential antagonists of absorption. Conflicting evidence of roles for plasma albumin, transferrin and caeruloplasmin in the transport of zinc and copper is considered. The extent, location and form in which trace elements are stored in tissues differs between elements and between species. Retention and utilization are also influenced by pregnancy, lactation, stage of foetal development and by genetic variables. Better definition of the effects of these variables would improve the validity of estimates of the trace element requirements of man and other animals.

Effects of molybdate, sulfide, and tetrathiomolybdate on copper metabolism in rats

Species differences in the response to dietary MoO4(2)- as a metabolic antagonist of Cu are considered briefly. Suggestions that (i) the potency of MoO4(2)- as a Cu antagonist is enhanced by normally innocuous dietary concentrations of S20 and (ii) that MoS4(2)- may be a more effective antagonist than either MoO4(2)- or S2- were investigated in a series of studies with rats. Diets including MoS4(2)- but not of MoO4(2)- or S2- alone promoted a decline in hepatic Cu and ceruloplasmin activity and induced clinical signs of Cu deficiency. Evidence of concurrent anomalies in the partition of Cu between tissues and in the distribution of Cu between proteins of plasma and kidney cytosol suggested that such effects were partly attributable to the development of systemic defects in Cu metabolism. The relationship of such findings to the suggested involvement of MoS4(2)- or its derivatives in the etiology of Mo-induced Cu deficiency in ruminant animals is considered.

Trace elements in animals

Trace element deficiency and toxicity in animals induces a wide variety of clinical effects although few are sufficiently specific to permit diagnosis without supporting investigation of changes in tissue trace element content or of the activity of metabolic processes influenced by trace element supply. Study of such trace element dependent processes has shown that extensive changes often arise before overt signs of disease appear. Some of these subclinical effects have pathological consequences and thus cannot be ignored when seeking correlations between geochemical anomalies and disease incidence. Many past estimates of the quantitative requirements of animals for the essential trace elements are imprecise. Although recent work is providing clearer definition of requirements, many common dietary components have a marked influence upon the efficiency with which such elements can be utilized from the diet. Recent evidence indicates that such antagonists influence both the absorption and the subsequent fate of essential and toxic elements in body tissues and these processes have to be taken into account when investigating the aetiology of disorders believed to be attributable to anomalies in trace element supply. Their existence is not always detectable if attention is confined to the trace element analysis of body tissues or to the nature of clinical lesions. Provided the complexity of soil-plant-animal relations with respect to trace element supply is fully recognized in the interpretation of data, the geochemical approach to the initial recognition of areas associated with a high risk of anomalies in trace element supply to animals and man has considerable potential value. This is already apparent from investigations upon the incidence of trace element problems in animals. As yet, its validity for similar purposes in man is less fully established.

Increased hepatic copper concentration in Indian childhood cirrhosis

19 Indian children with liver disease were studied. 5 in whom a clinical and histological diagnosis of Indian Childhood Cirrhosis was made had massive orcein-staining deposits in liver cells. The hepatic copper content in these 5 cases was strikingly high (1389 microgram/g dry tissue, range 1045--2303) the normal range being 15--55 microgram/g. Of the other 14 cases, only 2 had hepatic copper levels above normal (170 and 262 microgram/g.) This high hepatic copper concentration may be caused by excessive copper ingestion or an abnormality of copper metabolism.

Observations on the selenium status of cattle in the north-east of Scotland

Cattle on 18 of 21 farms in north-east Scotland were found to have low whole blood activities of the selenium-containing enzyme, glutathione peroxidase (less than 5 units per ml whole blood), and a low blood concentration of selenium (less than 0.05 mg per litre). These cattle had all been fed on locally produced feedstuffs without any mineral supplementation. The low selenium status in cattle occurred on farms with soils derived from a range of parent material, no one particular type predominating.

Perinatal changes in the absorption of trace elements

Fetal demands for many of the essential trace elements change markedly during the terminal stages of development. Susceptibility to deficiency during early postnatal life is influenced by the extent of fetal trace element reserves, by inadequacies in the supply of some elements in maternal milk and by postnatal changes in the efficiency of trace element absorption. The efficiency with which essential and some toxic trace elements are absorbed after birth is a function both of age and of diet. Homeostatic mechanisms for the control of iron absorption are poorly developed in the newborn. There are indications that pinocytotic absorption of iron, copper, lead and cadmium may occur at this stage and account for the high efficiency with which these elements are absorbed from a liquid diet. Evidence of developmental changes in the enterohepatic recirculation of such metals is considered and an account is given of our very inadequate understanding of the processes of trace metal absorption in the weaned animal.

Protective effect of zinc supplementation against copper toxicosis in sheep

1. A study has been made of the effects of dietary zinc supplementation on the development of copper toxicosis in three groups each of eight 12-week-old lambs. 2. None of the lambs receiving 420 mg Zn/kg diet developed Cu toxicosis in the 24-week experimental period, compared with three in the control group receiving 43 mg Zn/kg and possibly one in the group receiving 220 mg Zn/kg. 3. Liver Cu concentrations were reduced by up to 40% in the Zn-supplemented animals, with concomitant reductions, especially in the early stages of the experiment, in the extent of liver damage, as assessed by measurement of plasma aspartate aminotransferase (EC 2.6.1.1) and arginase (EC 3.5.3.1) activities. 4. Plasma and liver Zn concentrations were increased only slightly in the lambs receiving the Zn-supplemented diets, and the only indication of possible toxic effects of the Zn supplements was the development of a slight anaemia in those animals receiving 420 mg Zn/kg diet. 5. The results suggest that the incidence of Cu toxicosis in sheep may be controlled by increasing their dietary Zn intake.

Biochemical and pathological changes in tissues of Friesian cattle during the experimental induction of copper deficiency

1. Copper deficiency was induced in five Friesian cattle offered a semi-synthetic diet containing less than 1 mgCu/kg. Changes in blood and liver Cu contents and in the Cu-containing enzymes, ferroxidase I (caeruloplasmin; EC 1.16.3.1) and monoamine oxidase (EC 1.4.3.4) of plasma and cytochrome oxidase (EC 1.9.3.1) of liver and skeletal muscle were monitored during Cu depletion. 2. Rapid decreases in blood and liver Cu and plasma ferroxidase I activity were found at least 80 d before the first appearance of overt clinical signs of deficiency. Plasma monoamine oxidase and liver cytochrome oxidase activities decreased less rapidly and thus may provide useful indices of chronic Cu depletion.

Changes in enterocyte mitochondria associated with deficiency of copper in cattle

Comparisons were made between specimens of intestinal mucosa from three young Friesian steers, killed when showing clinical signs associated with copper deficiency, and three controls that had received supplementary copper. Copper deficiency was associated with marked depletion of cytochrome oxidase in the epithelium of the duodenum, jejunum and ileum, and with partial villus atrophy in the duodenum and jejunum. Enterocytes from the duodenum, jejunum and ileum showed mitochondrial abnormalities ranging from slight swelling to marked localised dilation. Many of the mitochondria not affected by swelling had a distinctly condensed appearance. These changes are discussed in relation to the copper-responsive diarrhoea that affects a proportion of cattle suffering from copper deficiency.