Influx of zinc by channel catfish (Ictalurus punctatus): Uptake from external environmental solutions

An Overview of Scaffolds and Biomaterials for Skin Expansion and Soft Tissue Regeneration: Insights on Zinc and Magnesium as New Potential Key Elements

The utilization of materials in medical implants, serving as substitutes for non-functional biological structures, supporting damaged tissues, or reinforcing active organs, holds significant importance in modern healthcare, positively impacting the quality of life for millions of individuals worldwide. However, certain implants may only be required temporarily to aid in the healing process of diseased or injured tissues and tissue expansion. Biodegradable metals, including zinc (Zn), magnesium (Mg), iron, and others, present a new paradigm in the realm of implant materials. Ongoing research focuses on developing optimized materials that meet medical standards, encompassing controllable corrosion rates, sustained mechanical stability, and favorable biocompatibility. Achieving these objectives involves refining alloy compositions and tailoring processing techniques to carefully control microstructures and mechanical properties. Among the materials under investigation, Mg- and Zn-based biodegradable materials and their alloys demonstrate the ability to provide necessary support during tissue regeneration while gradually degrading over time. Furthermore, as essential elements in the human body, Mg and Zn offer additional benefits, including promoting wound healing, facilitating cell growth, and participating in gene generation while interacting with various vital biological functions. This review provides an overview of the physiological function and significance for human health of Mg and Zn and their usage as implants in tissue regeneration using tissue scaffolds. The scaffold qualities, such as biodegradation, mechanical characteristics, and biocompatibility, are also discussed.

Influence of water hardness on zinc toxicity in Daphnia magna

Zinc is an essential trace metal required for the maintenance of multiple physiological functions. Due to this, organisms can experience both zinc deficiency and toxicity. Hardness is recognized as one of the main modifying physiochemical factors regulating zinc bioavailability. Therefore, the present study analyzed the effect of hardness on zinc toxicity using Daphnia magna. Endpoint parameters were acute‐toxicity, development, reproduction, and expression data for genes involved in metal regulation and oxidative stress. In addition, the temporal expression profiles of genes during the initiation of reproduction and molting were investigated. Water hardness influenced the survival in response to exposures to zinc. A zinc concentration of 50 μg/l in soft water (50 mg CaCO₃/L) caused 73% mortality after 96 h exposure, whereas the same zinc concentration in the hardest water did not cause any significant mortality. Moreover, increasing water hardness from 100 to 200 mg CaCO₃/L resulted in a reduced number of offspring. Fecundity was higher at first brood for groups exposed to higher Zn concentrations. The survival data were used to assess the precision of the bioavailability models (Bio‐met) and the geochemical model (Visual MINTEQ). As the Bio‐met risk predictions overestimated the Zn toxicity, a competition‐based model to describe the effects of hardness on zinc toxicity is proposed. This approach can be used to minimize differences in setting environmental quality standards. Moreover, gene expression data showed that using the toxicogenomic approach was more sensitive than the physiological endpoints. Therefore, data presented in the study can be used to improve risk assessment for zinc toxicity.

The present study analyzed the effect of hardness on zinc toxicity using Daphnia magna for acute‐toxicity, development, reproduction, and gene expression. Results showed that hardness plays an important role for Zn toxicity by effectively changing the bioavailability of Zn. The competition between Zn, Ca, and Mg can be used to normalize hardness effect on mortality. Bioavailability models used in risk assessment could be improved by considering water hardness.

Effects of Na, Ca, and pH on the simultaneous uptake of Cd, Cu, Ni, Pb, and Zn in the zebrafish Danio rerio: a stable isotope experiment

Concentrations of major cations in the medium play an important role in metal accumulation process. Variations in Ca, Na concentrations and pH of the medium had pronounced effects on metal uptake in zebrafish simultaneously exposed to five metals at environmentally realistic concentrations. Largest effects were found in gills (the whole body for Ni). A high level of Zn homeostatic regulation was observed. Addition of 0.1-2.5 mM Ca2+ to the medium had a suppressing effect on Cd uptake. The highest Cu, Pb and the lowest Ni uptake rates were observed atthe middle 0.5 mM Ca concentration. Increase in Na concentrations from 0.5 to 8 mM decreased Cd and increased Ni uptake rates in gills. Both low and high Na concentrations in water had a suppressing effect on Pb uptake. Increase in the pH of the medium promoted Cd and Ni uptakes. Cu and Pb, in turn, exhibited highest uptakes at neutral conditions compared to acidic and alkaline pH due to changes in Cu and Pb speciation. The fact that such changes in metal uptakes occur at low, environmentally relevant concentrations, emphasizes the need for further studies of bioaccumulation and toxicity processes.

In vitro characterization of cadmium and zinc uptake via the gastro-intestinal tract of the rainbow trout (Oncorhynchus mykiss): Interactive effects and the influence of calcium

An in vitro gut sac technique was employed to study whether Cd and Zn uptake mechanisms in the gastro-intestinal tract of the rainbow trout are similar to those at the gills, where both metals are taken up via the Ca transport pathway. Metal accumulation in surface mucus, in the mucosal epithelium, and transport into the blood space were assayed using radiolabelled Cd or Zn concentrations of 50micromolL(-1) in the luminal (internal) saline. Elevated luminal Ca (10 or 100mmolL(-1)versus 1mmolL(-1)) reduced Cd uptake into all three phases by approximately 60% in the stomach, but had no effect in the anterior, mid, or posterior intestine. This finding is in accordance with recent in vivo evidence that Ca is taken up mainly via the stomach, and that high [Ca] diets inhibit Cd accumulation from the food specifically in this section of the tract. In contrast, 10mmolL(-1) luminal Ca had no effect on Zn transport in any section, whereas 100mmolL(-1) Ca stimulated Zn uptake, by approximately threefold, into all three phases in the stomach only. There was no influence of elevated luminal Zn (10mmolL(-1)) on Cd uptake in the stomach or anterior intestine, or of high Cd (10mmolL(-1)) on Zn uptake in these sections. However, high [Zn] stimulated Cd transport into the blood space but inhibited accumulation in the mucosal epithelium and/or mucus-binding in the mid and posterior intestine, whereas high [Cd] exerted a reciprocal effect in the mid-intestine only. We conclude that Cd uptake occurs via an important Ca-sensitive mechanism in the stomach which is different from that at the gills, while Cd transport mechanisms in the intestine are not directly Ca-sensitive. Zn uptake does not appear to involve Ca uptake pathways, in contrast to the gills. These results are discussed in the context of other possible Cd and Zn transport pathways, and the emerging role of the stomach as an organ of divalent metal uptake.

Alterations of organ histopathology and metallothionein mRNA expression in silver barb, Puntius gonionotus during subchronic cadmium exposure

Common silver barb, Puntius gonionotus, exposed to the nominal concentration of 0.06 mg/L Cd for 60 d, were assessed for histopathological alterations (gills, liver and kidney), metal accumulation, and metallothionein (MT) mRNA expression. Fish exhibited pathological symptoms such as hypertrophy and hyperplasia of primary and secondary gill lamellae, vacuolization in hepatocytes, and prominent tubular and glomerular damage in the kidney. In addition, kidney accumulated the highest content of cadmium, more than gills and liver. Expression of MT mRNA was increased in both liver and kidney of treated fish. Hepatic MT levels remained high after fish were removed to Cd-free water. In contrast, MT expression in kidney was peaked after 28 d of treatment and drastically dropped when fish were removed to Cd-free water. The high concentrations of Cd in hepatic tissues indicated an accumulation site or permanent damage on this tissue.

Molecular cloning and functional characterization of a high-affinity zinc importer (DrZIP1) from zebrafish (Danio rerio)

Zinc is a vital micronutrient to all organisms and a potential toxicant to aquatic animals. It is therefore of importance to understand the mechanism of zinc regulation. In the present study, we molecularly cloned and functionally characterized a zinc transporter of the SLC39A family [commonly referred to as the ZIP (Zrt- and Irt-related protein) family] from the gill of zebrafish (Danio rerio) (DrZIP1). DrZIP1 protein was found to localize at the plasma membrane and to function as a zinc uptake transporter when being expressed in either chinook salmon (Oncorhynchus tshawytscha) embryonic 214 cells or Xenopus laevis oocytes. In comparison with pufferfish transporter proteins (FrZIP2 and FrECaC) that are known to facilitate cellular zinc uptake, DrZIP1 appears to have high affinity to bind and transport zinc, suggesting that it maybe a high-affinity zinc uptake transporter (Km < 0.5 microM) in fish. Orthologues of DrZIP1 were also identified in both freshwater and seawater pufferfish (Tetraodon nigroviridis and Takifugu rubripes), indicating that these proteins may be functionally conserved among different fish species. DrZIP1 mRNA is expressed in all the tissues examined in the present study and thus DrZIP1 may be a constitutive zinc uptake transporter in many cell types of zebrafish.

Kinetic analyses of waterborne Ca and Cd transport and their interactions in the gills of rainbow trout (Oncorhynchus mykiss) and yellow perch (Perca flavescens), two species differing greatly in acute waterborne Cd sensitivity

We evaluated the differential nature of interactions between waterborne Ca and Cd transport in the gills of yellow perch (Perca flavescens) and rainbow trout (Oncorhynchus mykiss), two species with a more than 400-fold difference in acute waterborne Cd tolerance. The Jmax (maximum rate of uptake) and K(m) (inverse of affinity) for Ca uptake, in the absence of Cd, were significantly lower in yellow perch (120.48 nM g(-1) wet wt h(-1) and 92.17 microM, respectively) relative to rainbow trout (188.68 nM g(-1) wet wt h(-1) and 243.90 microM, respectively). Similarly, the Jmax for Cd uptake, at the lowest waterborne Ca level (100 microM) tested, was significantly lower in yellow perch (0.27 nM g(-1) wet wt h(-1)) relative to rainbow trout (0.40 nM g(-1) wet wt h(-1), but no significant difference was observed in the K(m) values between the two species (yellow perch: 32.47 nM; rainbow trout: 31.27 nM). Waterborne Cd (0-890 nM) as well as waterborne Ca (100-1,000 microM) competitively inhibited branchial uptake of each other in both species. However, analyses of inhibitor constants for branchial Ca uptake by waterborne Cd (Ki[Cd2+]) revealed that the inhibition was about 1.8 times more potent in rainbow trout compared to yellow perch. In contrast, analyses of inhibitor constants for branchial Cd uptake by waterborne Ca (Ki[Cd2+]) indicated that the inhibition was more than three fold more potent in yellow perch than in rainbow trout. Higher branchial Ca uptake and more potent inhibition by Cd as well as higher branchial Cd uptake and less potent inhibition by Ca were also reflected in whole-body measurements of Ca and Cd influx in trout relative to perch. Overall, whole-body effects were in accord with the branchial kinetic analyses. These results further strengthen the conclusion that branchial influxes of Ca and Cd occur through common pathways. Moreover, interspecific differences in acute waterborne Cd sensitivity can be explained, at least in part, by the differential nature of interactions between waterborne Ca and Cd transport in fish gills.

Intestinal zinc uptake in two marine teleosts, squirrelfish (Holocentrus adscensionis) and gulf toadfish (Opsanus beta)

Zinc is a vital micronutrient, yet as an environmental toxicant it can be deleterious to aquatic organisms such as fish. Consequently, the study of zinc uptake mechanisms is essential for understanding nutrition, toxicity, and metabolism of this metal. Intestinal zinc uptake was studied in two marine teleosts, using both in vitro (in vitro perfusion and intestinal sacs) and in vivo techniques (in situ bolus). Female squirrelfish (Holocentrus adscensionis) exhibited significantly increased epithelial zinc uptake associated with enhanced hepatic zinc accumulation. This confirms this zinc-hyperaccumulating teleost as a potential model of zinc absorption. Intestinal zinc uptake in the gulf toadfish (Opsanus beta) was biphasic with respect to zinc concentration (0.3-500 microM), exhibiting both saturable and passive uptake components. In both species, the passage of zinc into the postintestinal compartment was highly dependent on technique. Decreased proportions of postintestinal zinc in vivo, coupled with concentration-dependent distribution of zinc accumulation, suggested mechanisms may act to control the movement of zinc into the circulation. In addition, the results of this study were used to reinterpret previous findings of zinc uptake in freshwater fish and allowed a critique of techniques used to study intestinal metal uptake.

Nutritive metal uptake in teleost fish

Transition metals are essential for health, forming integral components of proteins involved in all aspects of biological function. However, in excess these metals are potentially toxic, and to maintain metal homeostasis organisms must tightly coordinate metal acquisition and excretion. The diet is the main source for essential metals, but in aquatic organisms an alternative uptake route is available from the water. This review will assess physiological, pharmacological and recent molecular evidence to outline possible uptake pathways in the gills and intestine of teleost fish involved in the acquisition of three of the most abundant transition metals necessary for life; iron, copper, and zinc.