Mutagenicity, carcinogenicity and teratogenicity of zinc

Pregnancy Outcomes in Wilson's Disease Women: Single-Center Case Series

OBJECTIVES

To evaluate and compare pregnancy outcomes in women with Wilson's disease (WD) undergoing different therapies during pregnancy.

MATERIAL AND METHODS

Retrospective review of medication in WD patients during pregnancy and the outcomes.

RESULTS

Of 26 pregnancies, zinc was used in 14 (53.8%), D-penicillamine in 4 (15.4%) patients, and 8 (30.8%) were untreated. Spontaneous abortion was observed in 8 (30.8%) pregnancies - untreated patients (4/8 pregnancies), zinc (2/14 pregnancies) and D-penicillamine (2/4 pregnancies) -, healthy outcome in 12 (46.1%) and birth defects in 6 (23.1%). All cases of birth defects occurred in patients using zinc therapy (6/14 pregnancies).

CONCLUSIONS

A remarkably high frequency of fetal complications shed lights on the potentially harmful effect of WD drugs during childbearing age. Zinc's safety profile may have to be better evaluated during pregnancy, as all of birth defects occurred with zinc therapy.

Chemical sterilization with intratesticular administration of zinc gluconate in adult dogs: a preliminary report

BACKGROUND

Chemical sterilization with zinc gluconate is being developed due to its permanent contraceptive effect in prepubertal dogs. In this study, five healthy adult dogs were selected randomly. Semen samples were collected and analyzed before the study to confirm normal testicular function. Under general anesthesia, pH neutralized zinc gluconate was injected directly into their testes. Testes diameter, ultrasonographic appearance, changes in the percentage of white blood cells, and testosterone concentration were monitored twice a week before and 1 month after the injection. At the end of the study, the dogs were castrated and their testes were removed for histopathological evaluation.

RESULTS

The general health of all dogs was normal after the injection. The appearance of testicular swelling was limited within 2 days of treatment. The average diameter of left and right testes was 2.48 and 2.03 cm before the injection and reached to diameter 2.12 and 2.15 cm, respectively, at the end of the study. Serum testosterone concentration was 4.2 ng/ml at the start and 4 ng/ml at the end of the study. The percentage of white blood cells at the start and end of the study were within normal ranges reported for dogs. Histopathological analyses indicate a degeneration of germ cells in seminiferous tubules, but Leydig cells retained their structure.

CONCLUSIONS

Therefore, It is inferred that the injection of pH neutralized zinc gluconate into the adult dogs' testes resulted in the loss of sperm-producing tissue without affecting the production of testosterone and the general health of adult dogs.

Genomics of Adaptation Depends on the Rate of Environmental Change in Experimental Yeast Populations

The rate of directional environmental change may have profound consequences for evolutionary dynamics and outcomes. Yet, most evolution experiments impose a sudden large change in the environment, after which the environment is kept constant. We previously cultured replicate Saccharomyces cerevisiae populations for 500 generations in the presence of either gradually increasing or constant high concentrations of the heavy metals cadmium, nickel, and zinc. Here, we investigate how each of these treatments affected genomic evolution. Whole-genome sequencing of evolved clones revealed that adaptation occurred via a combination of SNPs, small indels, and whole-genome duplications and other large-scale structural changes. In contrast to some theoretical predictions, gradual and abrupt environmental change caused similar numbers of genomic changes. For cadmium, which is toxic already at comparatively low concentrations, mutations in the same genes were used for adaptation to both gradual and abrupt increase in concentration. Conversely, for nickel and zinc, which are toxic at high concentrations only, mutations in different genes were used for adaptation depending on the rate of change. Moreover, evolution was more repeatable following a sudden change in the environment, particularly for nickel and zinc. Our results show that the rate of environmental change and the nature of the selection pressure are important drivers of evolutionary dynamics and outcomes, which has implications for a better understanding of societal problems such as climate change and pollution.

Zinc as an adjunct treatment for reducing case fatality due to clinical severe infection in young infants: study protocol for a randomized controlled trial

Background

An estimated 2.7 of the 5.9 million deaths in children under 5 years of age occur in the neonatal period. Severe infections contribute to almost a quarter of these deaths. Mortality due to severe infections in developing country settings is substantial despite antibiotic therapy. Effective interventions that can be added to standard therapy for severe infections are required to reduce case fatality.

Methods/Design

This is a double-blind randomized placebo-controlled parallel group superiority trial to investigate the effect of zinc administered orally as an adjunct to standard therapy to infants aged 3 days up to 2 months (59 days) hospitalized with clinical severe infection, that will be undertaken in seven hospitals in Delhi, India and Kathmandu, Nepal. In a 1:1 ratio, we will randomly assign young infants to receive 10 mg of elemental zinc or placebo orally in addition to the standard therapy for a total of 14 days. The primary outcomes hospital case fatality, which is death due to any cause and at any time after enrolment while hospitalized for the illness episode, and extended case fatality, which encompasses the period until 12 weeks after enrolment.

Discussion

A previous study showed a beneficial effect of zinc in reducing the risk of treatment failure, as well as a non-significant effect on case fatality. This study was not powered to detect an effect on case fatality, which this current study is. If the results are consistent with this earlier trial, we would have provided strong evidence for recommending zinc as an adjunct to standard therapy for clinical severe infection in young infants.

Trial registration

Universal Trial Number: U1111-1187-6479, Clinical Trials Registry – India: CTRI/2017/02/007966: Registered on February 27, 2017.

Antioxidant and anti-inflammatory effects of zinc. Zinc-dependent NF-κB signaling

Zinc is a nutritionally fundamental trace element, essential to the structure and function of numerous macromolecules, including enzymes regulating cellular processes and cellular signaling pathways. The mineral modulates immune response and exhibits antioxidant and anti-inflammatory activity. Zinc retards oxidative processes on a long-term basis by inducing the expression of metallothioneins. These metal-binding cysteine-rich proteins are responsible for maintaining zinc-related cell homeostasis and act as potent electrophilic scavengers and cytoprotective agents. Furthermore, zinc increases the activation of antioxidant proteins and enzymes, such as glutathione and catalase. On the other hand, zinc exerts its antioxidant effect via two acute mechanisms, one of which is the stabilization of protein sulfhydryls against oxidation. The second mechanism consists in antagonizing transition metal-catalyzed reactions. Zinc can exchange redox active metals, such as copper and iron, in certain binding sites and attenuate cellular site-specific oxidative injury. Studies have demonstrated that physiological reconstitution of zinc restrains immune activation, whereas zinc deficiency, in the setting of severe infection, provokes a systemic increase in NF-κB activation. In vitro studies have shown that zinc decreases NF-κB activation and its target genes, such as TNF-α and IL-1β, and increases the gene expression of A20 and PPAR-α, the two zinc finger proteins with anti-inflammatory properties. Alternative NF-κB inhibitory mechanism is initiated by the inhibition of cyclic nucleotide phosphodiesterase, whereas another presumed mechanism consists in inhibition of IκB kinase in response to infection by zinc ions that have been imported into cells by ZIP8.

Zinc Toxicity: Does It Exist?

Zinc is an indispensable trace element and is a constituent of more than 200 enzymes. It can assure the stability of biological molecules such as DNA, or biological structures such as membranes or ribosomes. It is not surprising, therefore, that, compared with zinc toxicity, zinc deficiency is a much more frequent risk. Few acute toxic effects have been ascribed to zinc and no long-term effects were found after single or prolonged exposure at doses below 1 g/kg of food. Zinc is neither mutagenic nor carcinogenic, although its levels may influence tumor growth. Zinc appears not to be teratogenic but, on the contrary, deleterious action on zinc deficiency on the developing organisms is well documented.

Studies with an immobilized metal affinity chromatography cassette system involving binuclear triazacyclononane-derived ligands: automation of batch adsorption measurements with tagged recombinant proteins

This study describes the determination of the adsorption isotherms and binding kinetics of tagged recombinant proteins using a recently developed IMAC cassette system and employing automated robotic liquid handling procedures for IMAC resin screening. These results confirm that these new IMAC resins, generated from a variety of different metal-charged binuclear 1,4,7-triaza-cyclononane (tacn) ligands, interact with recombinant proteins containing a novel N-terminal metal binding tag, NT1A, with static binding capacities similar to those obtained with conventional hexa-His tagged proteins, but with significantly increased association constants. In addition, higher kinetic binding rates were observed with these new IMAC systems, an attribute that can be positively exploited to increase process productivity. The results from this investigation demonstrate that enhancements in binding capacities and affinities were achieved with these new IMAC resins and chosen NT1A tagged protein. Further, differences in the binding performances of the bis(tacn) xylenyl-bridged ligands were consistent with the distance between the metal binding centres of the two tacn moieties, the flexibility of the ligand and the potential contribution from the aromatic ring of the xylenyl group to undergo π/π stacking interactions with the tagged proteins.

Evaluation of solubility in simulated lung fluid of metals present in the slag from a metallurgical industry to produce metallic zinc

The objective of this study was to determine the solubility parameters (rapid and slow dissolution rates, rapid and slow dissolution fractions) for nickel, cadmium, zinc and manganese compounds present in a pile of slag accumulated under exposure to weathering. This slag was generated by a metallurgical industry that produced zinc and zinc alloys from hemimorphite (Zn(4)(OH)(2)Si(2)O(7).H(2)O) and willemite (Zn(2)SiO(4)) minerals. A static dissolution test in vitro was used to determine the solubility parameters and Gamble's solution was used as the simulated lung fluid (SLF), on a time basis ranging from 10 min to 1 year. The metal concentrations in the slag samples and in the SLF were determined using Particle Induced X-rays Emission (PIXE). There are significant differences in terms of solubility parameters among the metals. The results indicated that the zinc, nickel, cadmium and manganese compounds present in the slag were moderately soluble in the SLF. The rapid dissolution fractions of these metals are associated with their sulfates. In conclusion, this study confirms the harmful effects on the neighboring population of the airborne particles containing these metals that came from the slag.

Effect of subchronic zinc toxicity on rat salivary glands and serum composition

BACKGROUND

Zinc plays an important role in a wide variety of metabolic processes in animal systems. The role of zinc in preservative treatment, fungicidal action and medicine, and addition of supplementary zinc have increased the probability of zinc toxicity, specially the chronic type. It is known that the composition and quantity of saliva influence the oral health. Regarding people's exposure to zinc in routine life and the importance of saliva, our purpose was to investigate the effects of oral zinc intoxication on secretory function in rat salivary glands and also on serum composition.

METHODS

In this study, there were five groups of female rats. Four groups received zinc acetate dehydrate through their drinking water. After 3 months of experiment, the chemical characteristics and flow rate of saliva and weight of salivary glands were determined. The effects of zinc on hematological and chemical factors of plasma were assessed too.

RESULTS

Flow rate of submandibular glands was significantly lower in experimental groups and there were significant changes in Na(+), Ca(2+) and K(+) concentration both in saliva and in plasma. The serum glutamate oxaloacetate transaminase, serum glutamate pyruvate transaminase, glucose levels in the plasma and urine creatinine levels were also altered in experimental groups in comparison with the control group.

CONCLUSION

Our results show that zinc toxicity will affect the quantity and quality of saliva probably through changes in the various neurologic pathways to the salivary glands or effects on acinar cells of the salivary glands. Furthermore, our results showed that zinc toxicity will affect the liver and renal function.

Intratesticular injection of a zinc-based solution as a contraceptive for dogs

The objective of the present study was to evaluate, by light and transmission electron microscopy, the efficacy of a single intratesticular injection of a novel zinc-based solution, as a contraceptive for male dogs. Fifteen mongrel dogs were assigned to three groups (five dogs/group). Group 1, the control group, which consisted of animals ranging from 8 mo to 4 yr, was injected with saline solution. Group 2, which consisted of animals ranging from 8 mo to 1 yr old and Group 3, animals ranging from 2 to 4 yr old, were injected with a zinc-based solution (0.2-1.0mL; volume based on testicular width). There were no histopathological changes detected in testes from control dogs. Histological examination of treated groups revealed degeneration, vacuolation, fewer germ cells, formation of multinucleated giant cells, and a lack of elongated spermatids in atrophic seminiferous tubules. Leydig cells had varying degrees of lipid degeneration and necrosis. The majority of seminiferous tubules in all zinc-treated dogs were lined only by Sertoli cells, which were vacuolated. Ultrastructure of testis of treated groups had degenerate Sertoli and Leydig cells, characterized by numerous mitochondria with the lack of a matrix and agglomeration of lysosomal bodies. The cytoplasm of elongated spermatids was characterized by tubules of hyperplastic and hypertrophic smooth endoplasmic reticulum and numerous Golgi apparati. Round spermatids in Golgi phase had lysis of acrosomal vesicles. The degree of histological changes suggested irreversibility. In conclusion, intratesticular injection of a zinc-based solution effectively impaired spermatogenesis.

Effects of Se and Zn supplementation on the antagonism against Pb and Cd in vegetables

The antagonistic effects of supplementation of Zn and Se to the soil on vegetables were studied in this work. In the pot experiment, Se (Se4+) and Zn (Zn2+) were applied, respectively, to the soil, in which the Chinese cabbage (Brassica rapa) and the lettuce (Lactuca sativa L.) were planted. As a result, Se and Zn were enriched evidently in the two vegetables. The contents of Pb and Cd in the two vegetables were decreased markedly while contents of some healthy mineral elements, like Mn and Mg, were increased to some extent when Se and Zn were applied. The antagonism of Se and Zn against Pb and Cd in plants was suggested. The farmland experiment on the lettuce was conducted to explore further the effect of supplementation of Zn and Se under the actual field conditions. Result came out to be that the enrichment of Zn and Se restrained the accumulation of Pb and Cd in the lettuce remarkably, as well as enhanced the absorption of some other nutritional elements, like Fe, Mn, Cu, Ca and Mg. Therefore, application of Se and Zn was proved to be an effective and feasible method to improve trace elements nutrition in the vegetables.

ZnCl2 induces Syrian hamster embryo (SHE) cell transformation

In order to test the hypothesis of a relationship between apoptosis and neoplastic transformation, we studied the transforming potency of zinc, known for its antiapoptotic effects. In this study, zinc chloride (100 microM) was shown to induce morphological transformation (MT) in Syrian hamster embryo (SHE) cells. It was also tested in combination with benzo(a)pyrene (BaP), a positive control for carcinogenicity, or fomesafen, a carcinogenic pesticide with hepatic peroxisomal proliferation properties. A co-exposure of the two carcinogens with 100 microM zinc increased cell transformation in SHE cells. These results were in agreement with the theory of a relationship between the inhibition of apoptosis and induction of cell transformation. The cloning efficiency (CE) of SHE cells seeded at clonal density was raised by zinc, fomesafen and furthermore by the mixture of the two chemicals, which could be explained by the antiapoptotic action of zinc and fomesafen on SHE cells. No change in myc and bax expressions was observed in zinc-treated SHE cells.

Changes in serum and prostatic zinc concentrations in rats after intraprostatic injection of zinc: Comparison of two forms of zinc delivery

BACKGROUND

We investigated changes in zinc concentrations in serum and prostatic tissue after an intraprostatic injection of zinc, and compared two forms of zinc delivery: solution and liposome.

METHODS

Ninety-six male Wistar rats were used in the study (24 controls, 72 test rats). The test animals were randomly divided into two groups and were injected intraprostatically with 2 mL of 0.04 mol/L zinc sulfate according to the form of zinc delivery. Nine rats in each test group were sacrificed 1 day, 7, 14 and 28 days after injection, and 24 normal rats were injected intraprostatically with 2 mL of distilled water as controls. Serum and prostatic zinc concentrations of each group were measured by inductively coupled plasma atomic emission spectrometry. Blood chemistries, routine urinalysis, urine culture and histopathologic examination were also performed.

RESULTS

Serum zinc concentrations did not change significantly after the intraprostatic injection of zinc. Prostatic zinc concentrations were found to be significantly greater (P < 0.05) in zinc-injected groups than in the control group. The intraprostatic injection of zinc solution and zinc liposome increased zinc levels in both ventral and dorsolateral lobes significantly. Prostatic zinc levels increased progressively following injection, reaching a peak level in 7 days and maintaining a high value throughout the experimental period. The prostatic zinc level of the 1-day zinc liposome group was higher than that of the 1-day zinc solution group, while no significant difference was observed between the solution and liposome group in 7, 14, 28 days. No abnormal findings were observed in any of the laboratory and histopathologic examinations; however, an acute inflammatory response was observed in the 1-day groups.

CONCLUSION

These findings suggest that an intraprostatic injection of zinc in normal rats increases and maintains the prostatic zinc level for at least 4 weeks without causing any systemic or local toxicities. These findings suggest the potentially important clinical applicability of local zinc to the treatment of chronic prostatitis.

Antibacterial effect of intraprostatic zinc injection in a rat model of chronic bacterial prostatitis

High levels of prostatic zinc are associated with prostatic antimicrobial activities and are depressed in patients with chronic prostatitis. We investigated the inhibition of bacterial growth in the rat prostate with chronic prostatitis after intraprostatic injection of zinc and compared two different types of zinc delivery. Ninety male Wistar rats were used in the study. Experimental chronic bacterial prostatitis was induced by instillation of bacterial suspension (Escherichia coli 10(8) per ml) into the prostatic urethra. Animals were followed for 4 weeks and then injected intraprostatically with either 0.2 ml of zinc liposome (ZL) or zinc solution (ZS) (0.04 M zinc sulphate) or 0.2 ml of phosphate-buffered saline (PBS) for the controls. Ten rats in each group were sacrificed 4, 6 and 8 weeks after injection. The inhibition of inflammation and its consequences were analyzed microbiologically and histologically. Prostatic zinc concentrations were measured by inductively coupled plasma atomic emission spectrometry. Microbiological culture of the prostates demonstrated bacterial growth inhibition by the intraprostatic injection of zinc. The average infection rates and mean log(10) cfu/g of the zinc-treated groups were significantly lower than those of the controls. The histopathology showed resolving prostatitis in zinc-treated groups compared with the controls. Prostatic zinc levels were higher in the zinc-treated groups than in the controls 4 and 6 weeks after zinc injection (P<0.05). However, the ZL and ZS groups were found to be effectively identical in terms of prostatic zinc levels, bacterial cfu, and histological findings throughout the experiment period. The intraprostatic injection of zinc inhibited bacterial growth by increasing zinc levels in the rat prostatitis model. Our results suggest that the local application of zinc to the prostate may be a new treatment for chronic bacterial prostatitis at the point of its pathogenesis.

Survey of some heavy metals in sediments from vehicular service stations in Jordan and their effects on social aggression in prepubertal male mice

Vehicle services create the potential for heavy metal accumulation in the working environment. This study assessed five vehicle services, namely body repair, oil exchange, mechanical repair, tire repair, electrical repair, and washing services for three types of vehicles: airplanes, buses, and cars. The results show that there are significant increases in the total contents of Fe, Cu, Pb, Zn, Ni, Mn, and Cr in ambient dust, with Fe being the highest and Cr the lowest. The main cause of the presence of these elements is due to the metals' corrosion from vehicle sources and petroleum residue. Variations in the concentrations with the type of service and within the same service at different locations were observed. In this study, the exposure of prepubertal male mice to industrial metal salts in drinking water at a concentration of 1000 ppm for 90 days was investigated. Exposure of male mice to lead acetate significantly reduced the social aggression of the resident untreated subjects. Additionally, this treatment resulted in decreasing weights of body, testes, preputial glands, and seminal vesicles. In comparison, no such effects were seen in mice given copper chloride or manganese chloride. The results show that only lead acetate produced a pattern of responses clearly indicative of altered gonadal function.

Silver electrode as a sensor for determination of zinc in cell cultivation medium

Use of the silver electrode as a sensor for the monitoring of zinc in cell growth medium is described. Zinc at silver electrodes provides specific voltammetric signal, which is affected by solution components. Signals of zinc ions in phosphate buffer solutions with and without cell growth medium were compared. Common DMEM cell culture medium was used for the cultivation of a cell line of v-myb-transformed chicken monoblasts and its variants expressing v-jun and c-jun in a zinc-dependent manner. Electrochemical results showed zinc concentrations in the medium coincide very well with the jun expression. With respect to the low toxicity of silver for eukaryotic cells, silver electrodes represent promising tools for the determination of zinc concentrations in vivo without the potential risk of a cell culture damage.

Are metals dietary carcinogens?

Humans have been in contact with metals almost since the beginning of our existence. In fact, one cannot even think on human evolution without considering the great role played by metals in mankind's development. Metals are common moieties of molecules involved in a wide variety of biological processes, and hence are found in virtually all living organisms. Some metals are essential for human nutrition; others are found as contaminants in foodstuffs. One feature of the normal human diet which is frequently found is the simultaneous presence of both essential and toxic metals. Other factors important in the risk-evaluation analysis of metals are their pharmacokinetics, interactions among them and with other major components of the diet, and, especially, the great differences in the dietary habits of different populations and in the regional distribution of metals. In attempting to understand the role which dietary metals could play in human carcinogenesis, we found that the many factors involved and the lack of specific information made it difficult to reach firm conclusions on the hazards of dietary metals. We hope that this paper will raise the interest of genetic toxicologists in the subject and will consequently facilitate a risk analysis of the carcinogenic potential of dietary metals.

Increased sister chromatid exchanges in workers exposed to occupational lead and zinc

Sister chromatid exchange (SCE) in blood lymphocytes was determined in 32 male workers occupationally exposed to lead (Pb) and zinc (Zn) and in 20 controls matched for age and smoking habits. Exposed workers have higher SCE mean values than control workers (p < 0.01). In exposed persons, blood Pb concentrations were also significantly higher than controls (p < 0.0001), but the difference between Zn levels in the blood of these groups was not found to be significant (p > 0.05). Our results indicate that Pb may be genotoxic and harmful to human health.

Cytogenetic effects of cadmium on unfertilized oocytes in short-term zinc deficiency in hamsters

Chromosomal mutagenic effects of cadmium were examined during oogenesis in hamsters fed a zinc-deficient diet in the short term. Although mild zinc deficiency per se decreased the number of oocytes recovered, other reproductive and cytogenetic effects were not observed. On the other hand, cadmium induced a high incidence of oocyte degeneration and diploidy, which did not differ between the zinc-deficient and control groups. The mutagenic activities of cadmium were not accentuated in metaphase II oocytes of zinc-deficient hamsters. However, it appears that zinc deficiency alters the effects of cadmium on the reproductive system in female hamsters.

Localization of zinc and metallothionein in the rat bladder epithelium during carcinogenesis induced by N-butyl-N-(4-hydroxybutyl) nitrosamine

This study investigated the presence of zinc and expression of metallothionein (MT) in different pathological changes of the rat bladder induced by administration of N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). Using the Timm staining method, the presence of zinc was observed in normal and benign hyperplastic epithelial cells of the rat bladder, particularly in the malignant bladder tumor, induced by the administration of BBN. Immunohistochemically, MT expression was detected only in noninvasive (30%) and invasive transitional cell carcinoma (80%) of the rat bladder where the tumor cells were rich in zinc. Our data suggest that: (1) growth and development of the rat bladder tumor, especially malignant tumors, may have a high requirement for zinc and (2) MT synthesis may be induced by a high zinc concentration in rat bladder tumor cells.

Effect of zinc deficiency on chromosomal abnormalities in mice

In the present study we investigated the effect of zinc-deficiency on chromosomal abnormalities and mitotic index, and the interaction of zinc-deficiency and methotrexate. Therefore, two zinc-deficient and two zinc-adequate diet received mouse groups were constituted. Methotrexate was injected to one of zinc-deficient and one of zinc-adequate diet groups. There were no structural and numerical abnormalities in all groups. However, mitotic index was significantly lower than other groups in zinc-deficient and methotrexate administered mice.

[Zinc--update of an essential trace element]

Since the recognition of zinc as an essential trace element in man and animals there has been a remarkable progress in our knowledge of the role of zinc in nutritional physiology, biology and medicine during the last few decades. Highlights in zinc research, mechanisms and homeostatic regulation of zinc absorption, sources of zinc intake, dietary factors and mineral interactions affecting zinc bioavailability are reviewed in the present paper. This is followed by an overview of the biochemical functions of zinc in enzymes, gene expression, endocrinology, immunology and oxidative stress. General signs and metabolic consequences of zinc deficiency as well as excessive intake and toxicity of zinc are summarized. Furthermore, national and international dietary zinc recommendations and different methods to determine the zinc status are discussed.

Wilson's disease in pregnancy

Patients with Wilson's disease contemplating pregnancy should have their hepatic function and copper status assessed. We report a case of a pregnant woman with Wilson's disease with compromised hepatic function. The medical problems and controversy of prescribing treatment are discussed.

The function of metallothionein

Since its discovery in 1957 metallothionein (MT) has remained a protein in search of a function. After 40 years of frustrating efforts, three areas of research point to its zinc cluster structure as the basis of its functional potential: (1) the regulation of MT gene expression by zinc-dependent transcription factors, (2) neuronal growth inhibition in brain, and (3) interactions with glutathione and zinc proteins.

Effects on enzymes and the genetic apparatus of sheep after administration of samples from industrial emissions

In the present work the influence of the administration of industrial emissions from a zinc and copper plant on aspartate aminotransferase (AST), alanine aminotransferase, gammaglutamyl transferase, creatine phosphokinase (CK), total bilirubin, serum zinc levels and the genetic apparatus was studied on seven ewes. Each animal was given a dose of 31.99 g of emissions per day. The first and the last animals died of zinc intoxication on days 42 and 58, respectively. Significantly increased zincemia could be observed from day 8 of the experiment (P < 0.01). In the enzymes under investigation, the most pronounced effects of the emission were seen in AST and CK activities. In comparison with the starting levels, AST values revealed significant differences on days 37 and 58 (P < 0.05 and P < 0.01, respectively), and CK on day 58 (P < 0.01). Significantly increased bilirubinemia (P < 0.01) could be observed from day 8 of the experiment. In the period prior to the first gavage of emission and day 30 of administration no significant increase of chromosome breaks per cell was observed in the experimental sheep. The genotoxic effect of the emission was also stated on the basis of recombination frequency visualized by means of the sister chromatid exchange test; on day 30, the increase of these disturbances revealed statistical significance (P < 0.01).

An elemental correlation study in cancerous and normal breast tissue with successive clinical stages by neutron activation analysis

Influence of trace elements in body metabolism and their physiological importance in various diseases have motivated their accurate and quantitative determination in biological tissues and fluids. Instrumental Neutron Activation Analysis (INAA) using short and long term irradiation has been employed to determine five minor elements (Cl, K, Na, Mg, P) and 15 trace elements (As, Br, Co, Cr, Cs, Cu, Fe, Hg, Mn, Rb, Sb, Se, Sc, Sr, and Zn) in cancerous and normal breast tissue from 30 patients of four clinical stages. Several elements show enhancement in cancerous breast tissue. Selenium shows maximum enhancement of 94.7% followed by K (81.6%), Sc (66.7%), Cu (58.2%) Na (48.5%), P (44.4%), and Zn (39.2%). Some elements, such as Fe, Cr, and Mn, are depressed by 30.8, 30.1, and 12.8%, respectively. These elements compete for binding sites in the cell, change its enzymatic activity and exert direct or indirect action on the carcinogenic process accelerating the growth of tumors. This is further evidenced by histopathological examination of cancerous cells showing poor cytological differentiation. An attempt has been made to correlate trace element concentrations of Se, Cu, Zn, Rb, Br, Hg, As, Co, Fe, Cr, and Mn and the ratios of Se/Zn, K/P, Cu/Zn, Na/K, and Se/Fe with the clinical stages of cancer. Inhibition of enzymatic activity caused by variation in trace element concentrations results in immunological breakdown of the body system.

Metal-induced developmental toxicity in mammals: a review

It is well established that certain metals are toxic to embryonic and fetal tissues and can induce teratogenicity in mammals. The main objective of this paper has been to summarize the toxic effects that excesses of certain metals may cause on mammalian development. The reviewed elements have been divided into four groups: (a) metals of greatest toxicological significance (arsenic, cadmium, lead, mercury, and uranium) that are wide-spread in the human environment, (b) essential trace metals (chromium, cobalt, manganese, selenium, and zinc), (c) other metals with evident biological interest (nickel and vanadium), and (d) metals of pharmacological interest (aluminum, gallium, and lithium). A summary of the therapeutic use of chelating agents in the prevention of metal-induced developmental toxicity has also been included. meso-2,3-Dimercaptosuccinic acid (DMSA) and sodium 2,3-dimercaptopropane-1-sulfonate (DMPS) have been reported to be effective in alleviating arsenic- and mercury-induced teratogenesis, whereas sodium 4,5-dihydroxybenzene-1,3-disulfonate (Tiron) would protect against vanadium- and uranium-induced developmental toxicity.

Zinc and copper levels in serum and urine: relationship to biological, habitual and environmental factors

Zinc and copper levels were determined in serum and urine of 434 subjects living in an industrial and an agricultural area of Tarragona Province, Spain. Zinc and copper concentrations were related to a range of factors such as sex, age, blood pressure, and drinking and smoking habits. Geometric mean serum zinc and copper concentrations were, respectively, 113.9 and 84 micrograms dl-1, while the mean values for urine zinc and copper concentrations were 698.7 and 26.6 micrograms g-1 creatinine. Serum zinc and copper levels and urine copper concentrations in men were significantly lower than in women, while there were no differences in serum or urinary zinc and copper levels with age. The consumption of alcohol significantly reduced the levels of zinc and copper in serum, whereas blood pressure had no influence on these values. The levels of zinc and copper in urine were not affected by the smoking and drinking habits, place of residence, or blood pressure. In general terms, the results of this study agree with previously reported values from different countries.

Zinc arginine, a 5 alpha-reductase inhibitor, reduces rat ventral prostate weight and DNA without affecting testicular function

Zinc has been implicated in steroid endocrinology of the prostate gland; and 5 alpha-dihydrotestosterone (DHT) is believed to express androgenic responses in the prostate. To note the effect of neutralized zinc (zinc gluconate + arginine) on the prostate, 50 sexually mature rats, weighing 325 +/- 20 g, were divided into five groups as follows: (1) control, (2) sham, (3) castrated, and injected intraprostatically with (4) 10 mg neutralized zinc, and (5) 20 mg neutralized zinc. Results indicated significant reduction (P < 0.05) of prostate weight, 5 alpha-reductase activity, and total protein and DNA concentrations in treated prostate tissue; no significant change in weight and histological structure of testes, epididymides, and seminal vesicles; and no significant effect on progeny and blood testosterone level of treated animals. These results suggest that direct application of neutralized zinc to the prostate offers a new modality for treatment of prostatitis without affecting spermatogenesis.

Sterilization of dogs with intra-epididymal injection of zinc arginine

Condoms and vasectomy are the only fertility control methods available to males. Fifty million surgical vasectomies have been performed worldwide. In spite of improvements in the surgical techniques, the widespread use of vasectomy is limited due mainly to fear of genital operation. Chemical sterilization offers a promising new approach as an alternative to surgery. Fifteen sexually mature, mixed breed, male dogs, 2-3 1/2 years of age and weighing 22 +/- 1.8 kg, were divided into two groups. Five control placebo animals were injected with 0.5 ml of saline into the cauda epididymis, and ten treated animals were injected with 0.5 ml of 50 mg of zinc arginine into the cauda epididymis. Semen analysis performed before injection showed no significant difference between control placebo and treated groups. The control placebo animals exhibited a significant reduction in sperm motility one month after injection, which returned to normal within two months, and no change in semen volume, sperm abnormalities, or sperm concentration analyzed monthly for twelve months. The zinc arginine-treated animals achieved azoospermia ninety days after injection. The dogs were sacrificed one year after injection. There was no significant reduction of reproductive organ weights of the treated group as compared to the control placebo group. Although histological examination of the testes revealed normal seminiferous tubules, there was atrophy of the rete testes of the zinc arginine-treated group and, thus, increase in connective tissue. Histological examination of epididymides of the zinc arginine-treated group indicated that none of the cells in the head, body, and tail of the epididymis and ductus deferens contained sperm; 90% of the coils were empty and 10% contained amorphous pink cell debris; the coils decreased in diameter and were lined by cuboidal to columnar epithelium; no granuloma was observed. There was no significant change in serum testosterone level of control placebo and treated groups. These results offer the possibility of a new method of permanent sterilization instead of surgery. Zinc is considered to be nonmutagenic, noncarcinogenic, and nonteratogenic.

Cytotoxicity of zinc chloride in mice in vivo

Intraperitoneal administration of zinc chloride (ZnCl2) to Swiss albino mice in vivo induced a significant (p less than or equal to 0.05) increase in the frequencies of chromosomal aberrations of the bone-marrow cells at all concentrations used following acute (7.5, 10, 15 mg/kg body weight) and chronic (2.0, 3.0 mg/kg body wt) treatment. The degree of clastogenicity was directly proportional to the concentrations (p less than or equal to 0.05, trend test) and indirectly to the period of treatment (p less than or equal to 0.05, ANOVA test). It induced a dose-dependent, statistically significant increase (Mann-Whitney U statistics, Student's t-test) in sperm-head abnormalities. The data designate ZnCl2 as a potent clastogen and as a toxic chemical at the concentrations used.

Cadmium-enhanced gene expression in suspension-culture cells of tobacco

The effects of various concentrations of cadmium on Nicotiana tabacum L. cv. Xanthi suspension cells were examined. Surprisingly, certain concentrations of Cd (100-150 μM) stimulated growth of cell cultures considerably, whereas all other concentrations were inhibitory. Synthesis of DNA was severly affected in a dose-dependent manner by Cd concentrations of 250 μM and higher. In contrast, RNA and protein synthesis were similarly stimulated by 100 μM Cd, thus indicating that enhancement of RNA synthesis was the primary cause for the observed stimulation of cell culture growth. The transient expression of a chimeric chloramphenicol-acetyltransferase gene was similarly affected by Cd. When the effects of other heavy metals (Cu, Zn, Pb, Co, Mn, Al) on these cellular processes were investigated, only Zn showed a comparable stimulation of RNA and protein synthesis, although a tenfold higher concentration of Zn compared with Cd was required. As Zn and Cd are chemically very similar, these results are discussed in view of the well-known role of Zn in the regulation of transcription.

Mechanisms in metal genotoxicity: the significance of in vitro approaches

A survey of the literature published on the ability of metal salts to produce, in vitro, gene mutations, structural chromosome aberrations, sister-chromatid exchanges, to interfere with the chromosome distribution or to induce mammalian cell transformation demonstrates that the carcinogenicity of inorganic compounds is clearly associated with their genotoxicity. The induction of structural aberrations, SCEs and forward gene mutations represents the most sensitive and specific assay to assess the carcinogenic potential of metal salts.

Studies of mutagenesis and neoplastic transformation by bivalent metal ions and ionizing radiation

We examined the influence of nontoxic concentrations of each of two essential (Zn++ and Mn++) and one nonessential (Ni++) bivalent metal ions on spontaneous and radiation-induced neoplastic transformation and specific gene mutations in mammalian cells. All three metals induced low levels of transformation in mouse BALB/3T3 cells but exerted no mutagenic effect in CHO cells (hprt locus) over a broad range of concentrations. Continuous incubation for 8 or 15 days with each of the metal ions did not enhance the frequency of cell killing, transformation, or mutations induced by acute exposure to x-rays. Zn++, however, had a small but consistent protective effect on the induction of all three endpoints by x-irradiation.

Inhibition of DNA replication and repair by cadmium in mammalian cells. Protective interaction of zinc

The effects of the treatment of cultured human and simian cells with Cadmium (Cd), a toxic and carcinogenic metal, were first assayed on macromolecular synthesis. It was observed that DNA synthesis was inhibited by Cd concentrations considerably lower than those inhibiting protein and RNA synthesis. Because of the necessary occurrence of a DNA resynthesis step during the DNA excision repair process, the consequences of the exposure of cells to Cd were ulteriorly tested on different parameters measuring DNA repair after ultraviolet (UV) damage. UV-induced unscheduled DNA synthesis (UDS) was found 2-3 times lower in Cd (4 X 10(-6) M) treated cells than in control cells for UV doses higher than 10 J/m2. DNA breaks accumulated in UV-irradiated cells during post-exposure incubation in presence of Cd, whereas they were induced only transiently in control cells irradiated with the same dose. Cd inhibited in a concentration-dependent way the recovery of RNA transcription impaired by UV-irradiation. However, at concentrations used, Cd had no significant effects on DNA size and on rRNA synthesis in unirradiated cells. Finally, Cd was shown to inhibit the repair of potentially lethal damage during a 24 h liquid holding and to increase the toxicity of UV-irradiation. The interactions between Cd and Zinc (Zn), an essential metal for many enzymatic proteins, were also analysed. Results showed that Zn, at 5 to 10 times higher concentrations, counteracts the inhibitory effects of Cd on DNA synthesis and restores, at least partially, the repair capability of cells and their survival. The possible molecular level and mechanism of action of these metals are discussed.