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Investigation of the parameters of toxicity of 8 zinc compounds revealed some differences in the degree of their risk for persons working with them. The following TSELs (tentative safe exposure levels of harmful substances) have been determined: 0.5 mg/m3 for zinc nitrate and hydrogen and dihydrogen zinc phosphates, 2 mg/m3 for zinc carbonate and zinc selenide, as well as MAC (maximum allowable concentration) for zinc sulphide equal to 5 mg/m3. No TSEL have been set for zinc caprylate and zinc stearate, but intratracheal administration of 50 mg caprylate caused 100%, of stearate 50% death of experimental animals due to pulmonary edema. Maximum tolerable doses were 10 and 1 mg, respectively. Zinc nitrate shows an expressed irritative effect on the skin and a highly expressed effect on the conjunctiva. Zinc phosphates, zinc caprylate and zinc stearate are resorbed by the skin. In all cases, working persons must be protected from the effect of the compounds under study because even though the toxicity of a compound may be rather low, highly noxious compounds may develop in the course of the technological process, e.g., in mechanical treatment of zinc selenide and zinc sulphide monocrystals, hydrogen selenide and hydrogen sulphide, respectively, can be isolated.
The antiseborrheic effect of zinc L-cysteate, a new zinc compound, was evaluated in vitro by determining the lipidic metabolic activity of rat preputial glands as measured by incorporation of 14C-sodium acetate. At 10(-3) and 10(-4) mol/l, zinc L-cysteate was more active than S-carboxymethyl L-cysteine used as reference in corresponding concentrations (p < 0.05 and p < 0.01, respectively). The pharmacologic results seem promising for clinical studies in dermatology.
It was established that industrial shops engaged in zinc compounds' processing were characterized by considerable temperature shifts, relative humidity and air motion changes. In drying and packing shops, concentrations of the final product dusts were established at 0.8-2 mg/m3. The major occupational pathology was constituted by skin and upper respiratory tract diseases, including allergic and contact dermatitis, chronic pharyngitis, tonsillitis and rhinitis. Blood tests revealed B-lymphocytes: increases, circulating immune complexes and considerable levels of lymphocytic spontaneous blastotransformations. Erythrocytic acidic hemolysis was markedly changed, which proved disbalances in the system of red blood.
Metalloporphyrin inhibitors of heme oxygenase may also have photosensitizing properties in vivo. To assess photoactivity in serum, the relative ability to mediate photooxidation of tryptophan or other oxidizable targets, presumably by singlet oxygen production, was measured for tin mesoporphyrin, zinc mesoporphyrin, and zinc deuteroporphyrin bisglycol in aqueous solution and when bound to human serum albumin. While tin mesoporphyrin sensitized at the greatest initial rate in aqueous solution, the zinc compounds sensitized at a greater initial rate in detergent micelles or when bound to albumin. There was minimal alteration of the tin mesoporphyrin during the time course of illumination in the Soret or visible absorption regions. The zinc compounds, however, proved to be extremely photolabile and were extensively destroyed by light; the photooxidized forms were found to be ineffective as inhibitors of heme oxygenase.
The absorption of zinc in different parts of the small intestine and from various Zn compounds was studied in situ, using rats. Segments of equal length from the duodenum, jejunum and ileum were ligated. Into these loops, 65Zn-ZnC12 or 65Zn-ZnC12 with an excess of histidine at a molar ratio of 1:250 and 1:2,000 was injected. The uptake of 65Zn was measured in blood, plasma and different organs after 1 h of absorption. The absorption of zinc was significantly greatest from the duodenum, followed by the jejunum and ileum. The jejunum differed only slightly from the ileum in the absorption capacity for zinc. A 250-fold excess of histidine did not alter the Zn absorption in comparison to ZnC12. There were, however, distinct interactions between the site of Zn absorption and the Zn compound at the molar ratio of zinc:histidine of 1:2,000. With this addition of excess histidine, zinc was absorbed just as well from the jejunum as from the duodenum. The 2,000-fold addition of histidine raised the Zn absorption from the jejunum by about 40% in comparison to ZnC12.
To perform a thorough risk assessment of the new antifouling compound zinc pyrithione (ZnPT2), additional information regarding the fate of the compound is needed. The present study examined the recovery and transchelation of ZnPT2 in controlled laboratory experiments, photodegradation experiments, and a fate study in a large-scale field experiment. Chemical analyses were performed using a newly developed method for simultaneous analyses of ZnPT2 and copper pyrithione (CuPT2). Furthermore, two antifouling paints containing ZnPT2 were examined for the fate of leaching biocide. Naturally occurring ligands and metals in seawater influence the stability of ZnPT2. The presence of free Cu2+, which is present naturally in the seawater or is released from copper-containing paints, results in a partial transchelation of ZnPT2 into CuPT2. A complete transchelation of ZnPT2 into CuPT2 was observed when Cu2+ was present at an equimolar concentration in the absence of interfering ligands. When ZnPT2 was leached from antifouling paints containing both ZnPT2 and Cu2O, CuPT2 was found, with no trace of ZnPT2. Photodegradation was low in natural waters and absent from 1 m or more below the surface. The results show that ZnPT2 has a low persistence in seawater when leached from antifouling paints. However, the more stable and toxic transchelation product CuPT2 is formed, which has the potential to accumulate in the sediments and, therefore, should be included in both chemical analysis and risk assessment of ZPT2.
The cytotoxicity of latex urinary catheters has been earlier documented. During the manufacturing process tens of chemicals are added to the natural rubber base. Several of the accelerators and other chemicals used have carcinogenic and acute toxic effects. Some of the accelerators are zinc compounds. In the present study, the cytotoxicity and zinc concentration of 68 latex catheter extracts were analysed. The siliconized latex catheters were the most toxic, and a correlation was seen between the IC50 values and the zinc concentration. The good manufacturing practice (GMP) has to some extent resolved the cytotoxicity problem of latex urinary catheters. There is, however, still a need to reformulate the manufacturing process and to find new catheter materials to meet the new EN standards concerning the biological safety of urinary catheters.
The objective of the present study was to examine the combined effects of zinc compounds with different acidic pH levels on the aerobic growth of a S. typhimurium poultry isolate in either rich or minimal media. When overall main effects of pH levels of medium or concentrations of Zn compounds were compared, growth rates of the S. typhimurium poultry isolate were significantly (p < 0.05) decreased by stepwise increase of pH levels of medium (pH 4, 5, 6, and 7) or concentrations (0.67, 3.35, and 6.03%) of Zn compounds (Zn acetate and Zn sulfate). In general growth rates of S. typhimurium poultry isolate appeared to be more reduced by Zn acetate than by Zn sulfate and more reduced in minimal media compared to rich media.
The partially hydrophilic and hydrophobic tripodal ligands, tris(hydroxy-2-benzimidazolylmethyl)amine L1h and tris(2-benzimidazolyl)amine L1 were used for the preparation of biomimetic complex of carbonic anhydrase. The CO(2) hydration using [L1hZn(OH)]ClO(4).1.5H(2)O provided the zinc-bound and free HCO(3)(-)s, which were formed by nucleophilic attack of Zn-OH toward CO(2) in dimethyl sulfoxide (DMSO). The phenolic OH in L1h can recognize water molecules through hydrogen bonds to facilitate the collection of the water molecules around a biomimetic zinc compound; the molecular structure of [L1hZn(OH)](+) was revealed. The packing diagram has demonstrated the all the water molecules are hydrogen bonded to each phenolic OH. The nucleophilic attack of zinc-bound OH(-) to substrate is used to catalyze the CO(2) hydration and phosphoester hydrolysis. The carbonic anhydrase model compound [L1Zn(OH(2))](2+) was applied for the hydrolysis of phosphoesters, parathion and bis(p-nitrophenyl)phosphate (BNPP(-)). The low reactivity of [L1Zn(OH)](+) for parathion hydrolysis is attributed to the stability of the intermediate [L1Zn(OP(S)(OEt)(2))](+). Since the structures of the intermediates [L1Zn(OH(2))](BNPP)(2) (1) and [L1Zn(OP(S)(OEt)(2))]ClO(4) (2) formed on the way of hydrolysis are too stable to realize the catalytic cycle and are not active for hydrolysis, carbonic anhydrase model compound [L1Zn(OH(2))](2+) was not suitable for phosphoester hydrolysis; the zinc model compound surrounded by three benzimidazolyl groups is used to have the steric hindrance for bulky substrate, such as parathion and BNPP(-).
This study aimed to investigate functional responses of natural marine planktonic communities to stress from the antifouling compound zinc pyrithione (ZPT). Isotope labelling techniques (14C) were applied to study bacterial incorporation of leucine, photosynthetic activity of phytoplankton and grazing of labelled prey by zooplankton communities for 6 days after exposures to nominal concentrations of 0, 5, 25, 50 nM ZPT in a mesocosm experiment in Isefjord, Denmark. Significant direct effects were visible on chlorophyll a concentrations, which decreased in all exposed communities, to between 48 and 36% of control concentrations on Day 3, 1 day after the last exposure. Phytoplankton activities were also significantly affected on Day 3 with activities between 9 and 26% of control levels, as was zooplankton activities in the 25 and 50 nM exposures. In the 50 nM exposure the total community zooplankton activity was reduced to 25+/-4%, and per individual to 46+/-11% of control levels. Bacterial communities showed positive indirect effects with high activities (up to 183+/-40%) due to higher amounts of available substrate from algal death. Pollution induced community tolerance analyses performed on phytoplankton and bacterial communities at the end of the experiment indicated a development of increased tolerance for phytoplankton in the 50 nM exposed communities, whereas there were no changes in tolerance in the bacterial communities. Multivariate analysis of the integrated functional response by the plankton communities revealed a significant difference (p<0.05) between exposed communities compared to controls in the first 3 days after last exposure and in the end of the experiment. The study provides evidence of diverse effects on the functions of marine plankton communities under stress from a pollutant. Direct effects lead to cascading indirect effects throughout the community, eventually causing different developments. Continuous exposure to ZPT could lead to severe long-term effects, causing more permanent changes in structure and function than observed here. The study demonstrates that it is possible to assess the functional effects of a stressor in a complex mesocosm system, and to determine effects in a complex plankton community, which were not predictable from laboratory studies.
Effects of chain-end structure and residual metal compounds on thermal degradation of poly(epsilon-caprolactone) (PCL) were investigated by means of thermogravimetric and pyrolysis-gas chromatograph mass spectrometric analyses. Four types of PCL samples with different chain-end structures (alpha-carboxylic acid-omega-hydroxyl-PCL, alpha-dodecyl ester-omega-hydroxyl-PCL, alpha-carboxylic acid-omega-acetyl-PCL, and alpha-dodecyl ester-omega-acetyl-PCL) were prepared by ring-opening polymerization of epsilon-caprolactone in the presence of zinc-based catalyst and by subsequent acetylation reaction of polymers with acetic anhydride. PCL samples with different zinc contents were obtained by washing with acetic acid in chloroform solution of polymer. Thermal degradation behaviors of these PCL samples with different chain-end structures were examined under both isothermal and nonisothermal conditions. From both the isothermal and nonisothermal experiments, the thermal degradation of PCL samples containing high amounts of residual zinc compounds from synthesis process revealed the selective unzipping depolymerization step below 300 degrees C producing epsilon-caprolactone exclusively. In contrast, zinc-free PCL samples were stable at temperatures below 300 degrees C, and the thermal degradation occurred only at temperatures above 300 degrees C regardless of the chain-end structure. From (1)H NMR analysis of the residual molecules after isothermal degradation of zinc-free PCL, it was confirmed that the omega-chain-end of residual molecules was 5-hexenoic acid unit. However, the cyclic monomer and oligomers were detected as the volatile products of zinc-free PCL samples. These results suggest that the dominant reaction of thermal degradation for PCL above 300 degrees C is a competition between the random chain scission via cis elimination reaction and the cyclic rupture via intramolecular transesterification of PCL molecules.
Taking into account the competitive action of zinc towards other ion essential for pathogenic germs metabolism, the complex erythromycin-zinc, zinc salts of sulfamethoxydiazine, sulfanilamide, sulfacetimide, sulfathiazole as well as the Mannich basis of sulfamethoxydiazine were synthetized. The antimicrobial action towards gram-positive, gram-negative pathogens and fungi was tested by the classic diffusiometric method. An increased antimicrobial action for the Mannich basis of sulfamethoxydiazine and for the zinc salt of sulfamethoxydiazine, alone or in association with metronidazole--chemotherapeutic agent used in the infections with anaerobic organisms was found. A significant antimicrobial action was also found for the complex erythromycin-zinc and zinc salts of sulfacetimide and sulfathiazole.
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This report describes how a material within the cartridge of an automatic injector contaminated its contents. On prolonged storage, a formulation that contained atropine produced lethality in mice. The toxic material originated from zinc compounds that were present in the rubber stopper and plunger of the container and that subsequently leached into the formulation. The contents of cartridges that contained greater than or equal to 0.75 mg/mL of solubilized zinc were lethal to at least 20% of the mice tested; those that contained 0.42 mg/mL showed no lethality. The problem resulted from the physicochemical properties of the rubber, not the concentration of zinc used in the vulcanization process.
The paper presents the results of study of zinc hair content in 43 Moscow schoolchildren, aged 9-11 years of both sex (May 2003 to December 2003). Significant drop of zinc hair content was established in 67% of schoolchildren. It was shown that the organic form of zinc enchanted zinc hair content. The findings will be used to implement preventive and health-promoting measures among schoolchildren.
Dietary supplementation with 6000 mg of Zn2+/kg of feed has been shown to modify the clinicopathologic expression of Brachyspira hyodysenteriae infection in a laboratory mouse model of swine dysentery. However, this concentration impaired the body weight gain of the mice. The purpose of the present study was to determine a minimal prophylactic concentration of feed-grade zinc compounds that would not affect the growth of mice challenge-exposed with B. hyodysenteriae. A total of 440, 6- to 8-week-old, C3H/HeN mice were allocated randomly to groups and fed either a defined diet or a defined diet containing either 1000, 2000 or 4000 mg/kg ZnO, ZnSO4 or zinc-methionine for 7 days before intragastric inoculation with B. hyodysenteriae. From days 7 to 35 after inoculation, mice in each group were necropsied at weekly intervals for determination of body weight, presence of B. hyodysenteriae in the cecum, and histological assessment of cecal lesions. Only ZnO fed at 2000 mg/kg had a prophylactic effect against B. hyodysenteriae infection without affecting the body weight gain of the mice. The prophylactic effect of Zn2+ against infection with B. hyodysenteriae was also affected by the relative concentration of Fe2+ and Zn2+/Fe2+ ratio of the diet.
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