Reconnaissance survey of Galveston Bay sediments for selective nonresidual trace metals

The nonresidual concentrations of five trace metals were determined for 322 sediments that were the product of a systematic sampling program of the entire Galveston Bay system. The nonresidual component of the trace metal concentration (e.g. that fraction of the metals that can be relatively easily removed from the sediments without complete destruction of the sediment particle) was considered to be more indicative of the anthropogenic metal pollution that has impacted the Galveston Bay ecosystem.^ For spatial analysis of the metal concentrations, the Galveston Bay system was divided into nine bay-areas, based on easily definable geological and geographical characteristics. Isopleth mapping analyses of these metal concentrations indicated a direct relationship with the $<$63$\mu$m fraction of the sediment (%FINE) in all of the bay areas. Covariate regression analyses indicated that position of the sediment within the Galveston Bay system (e.g. bay-area) was a better predictor of metal concentration than %FINE. Analysis of variance of the metals versus the bay-areas indicated that the five metals maintained a relatively constant order and magnitude of concentration for all the bay-areas.^ The major shipping channels of the Galveston Bay system, with their associated vessels and transported materials, are a likely source of metal pollution. However, these channels were not depositional corridors of high metal concentration. All metal concentration highs were found to be located away from the channels and associated with %FINE highs in the deeper portions of the bay-areas.^ Disturbance of the sediments, by the proposed widening and deepening of these channels, is not predicted to remobilize the trace metals. A more likely adverse effect on the health of the Galveston Bay ecosystem would come from the increase in turbidity of the water due to the dredging and in an extension of the salt water wedge farther north into the bay system. ^

A STUDY OF ZINC CONCENTRATION IN HAIR AS AN INDICATION OF ZINC IMBALANCES

Trace metal imbalances have been implicated in several disease and nutritional states. There is mounting concern to identify the nutritional balance of the trace metals needed for growth, mental acuity and physical functioning. These two factors, diseases in which trace metals show involvement and nutritional balance, have made it necessary to be able to accurately describe the trace metal balances of an individual. Although several investigators have measured the concentration of trace metals in the hair and related those observed concentrations to various disease and nutritional states, no one has satisfactorily answered the questions of whether hair is useful to determine trace metal imbalances, whether the concentrations found in hair reflect tissue or serum concentrations of the trace metals, or whether any tissue accurately reflects body status of the trace metals.^ Male mice were used to examine several tissues, heart, liver, kidney, spleen, intestine, brain, bone, hair and serum for copper and zinc concentrations. The environment and dietary intake of the animals were carefully controlled, so that environmental and physical variables were minimized. Dietary intake of zinc was varied while copper intake was held constant. Each experimental diet group was matched with a pair fed control group.^ Of the tissues examined, only the serum was indicative of an early state of zinc imbalance. Neither hair nor the other tissues examined for copper and zinc concentrations were indicative of an acute zinc imbalance in a normal mature mouse. Zinc deficiencies or excesses may manifest themself differently in the chronic imbalance state or in the weanling, aged or traumatized mouse. The tissue response to zinc imbalance may vary in these cases. ^

Interactions and structural analysis of the zinc -binding motif in decorin, a small leucine rich proteoglycan in extracellular matrix

Decorin, a dermatan/chondroitin sulfate proteoglycan, is ubiquitously distributed in the extracellular matrix (ECM) of mammals. Decorin belongs to the small leucine rich proteoglycan (SLRP) family, a proteoglycan family characterized by a core protein dominated by Leucine Rich Repeat motifs. The decorin core protein appears to mediate the binding of decorin to ECM molecules, such as collagens and fibronectin. It is believed that the interactions of decorin with these ECM molecules contribute to the regulation of ECM assembly, cell adhesions, and cell proliferation. These basic biological processes play critical roles during embryonic development and wound healing and are altered in pathological conditions such as fibrosis and tumorgenesis. ^ In this dissertation, we discover that decorin core protein can bind to Zn2+ ions with high affinity. Zinc is an essential trace element in mammals. Zn2+ ions play a catalytic role in the activation of many enzymes and a structural role in the stabilization of protein conformation. By examining purified recombinant decorin and its core protein fragments for Zn2+ binding activity using Zn2+-chelating column chromatography and Zn2+-equilibrium dialysis approaches, we have located the Zn2+ binding domain to the N-terminal sequence of the decorin core protein. The decorin N-terminal domain appears to contain two Zn2+ binding sites with similar high binding affinity. The sequence of the decorin N-terminal domain does not resemble any other reported zinc-binding motifs and, therefore, represents a novel Zn 2+ binding motif. By investigating the influence of Zn2+ ions on decorin binding interactions, we found a novel Zn2+ dependent interaction with fibrinogen, the major plasma protein in blood clots. Furthermore, a recombinant peptide (MD4) consisting of a 41 amino acid sequence of mouse decorin N-terminal domain can prolong thrombin induced fibrinogen/fibrin clot formation. This suggests that in the presence of Zn2+ the decorin N-terminal domain has an anticoagulation activity. The changed Zn2+-binding activities of the truncated MD4 peptides and site-directed mutagenesis generated mutant peptides revealed that the functional MD4 peptide might contain both a structural zinc-binding site in the cysteine cluster region and a catalytic zinc site that could be created by the flanking sequences of the cysteine cluster region. A model of a loop-like structure for MD4 peptide is proposed. ^