Thesis (Ph. D.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains viii, 147 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains viii, 135 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Copper metallothionein (Cu-MT) was extracted from the induced biomass of Aspergillus niger. The crude extract (FI), obtained by cell homogenization, was partially purified by heat treatment (FII) and ultrafiltration (FIII). Further purification of the Cu-MT extract by affinity chromatography resulted in three major fractions, FIVa, FIVb and FIVc, of which fraction FIVc was considered to be the Cu-MT extract fraction. Fraction FIVc was re-chromatography on affinity chromatography and the eluted fraction showed a single peak (FIVc'). Spectrophotometric analysis of fraction FIVc' demonstrated a maximum absorption peak at 268 nm. Native and denatured electrophoretic analysis of fraction FIVc ' showed the presence of a single band with an estimated molecular weight of 9.5 and 10.0 kDa, respectively. Inhibition of mushroom tyrosinase (PPO) by the Cu-MT extracts was investigated, using selected phenolic substrates, including catechin, chlorogenic acid, catechol, 4-methylcatechol, caffeic acid, L-3,4-dihydroxyphenylalanine, 3,4-dihydroxyphenylacetic acid, 3-( p-hydroxyphenyl) propionic acid, p-hydroxyphenylpyruvic acid, p- and m-cresol. The results showed that the inhibitory effect of the Cu-MT extract increased with the degree of purification. The results revealed that the Cu-MT extracts were effective inhibitors of PPO activity and the best inhibitory effect was demonstrated with catechin as substrate; however, PPO activity was not inhibited by the Cu-MT extract when p-hydroxyphenylpyruvic acid and p- and m-cresol were used as substrates. The results also showed that the Cu-MT extracts exhibited different types of inhibition, including mixed, competitive and uncompetitive on PPO activity. In addition, the experimental findings indicated that the nature and degree of enzymatic inhibitions by the Cu-MT extracts were dependent upon the structural nature of the substrates as well as the methods including, spectrophotometer and polarograph, used for the detection of enzyme

Two natural enzymatic browning inhibitors, copper-metallothionein (Cu-MT) and polyphenol esterase (PPE), were obtained from A. niger and investigated. Reflectance measurements, expressed as L (lightness variable) and a (red to green degree of color) were used to compare, over extended periods of time, the relative inhibitory effectiveness of Cu-MT and PPE to those observed with the use of selected chemicals including ascorbic acid (AA), citric acid (CA), ethylenediaminetetraacetic acid (EDTA), sodium bisulfite (NaHSO3) and 4-hexylresorcinol (4HR), in the prevention of browning on the cut surfaces of selected food products such as apple and potato slices as well as freshly prepared apple juice. Treatment of each food product required an optimum concentration of the selected inhibitor for the inhibition of browning. (Abstract shortened by UMI.)

A two by six factorial design was used to investigate the effect of zinc and all-trans retinoic acid (RA) on the growth of two human breast cancer cell lines differing in their expression of metallothionein (MT) and of estrogen receptors; MCF7 cells express estrogen receptors, BT-20 cells do not. Cells were treated with zinc to induce MT then treated with six concentrations of RA. Cell proliferation, lipid peroxidation, MT protein, MT mRNA and glutathione concentrations were measured. / BT-20 cells expressed higher constitutive MT concentrations than MCF7 cells. MT was significantly induced by zinc treatment in BT-20 cells but not in MCF7 cells. Low RA concentrations stimulated growth proliferation but higher concentrations inhibited cell proliferation. High RA concentrations increased lipid peroxidation. There was a significant negative correlation between lipid peroxidation and cell proliferation. Growth inhibition and lipid peroxidation were reduced by zinc in BT-20 cells but not in MCF7 cells. Glutathione did not appear to be a significant factor. / Induction of metallothionein by zinc may modulate the growth inhibitory effects of all-trans retinoic acid in human breast cancer cells. One mechanism of growth inhibition may be through increased lipid peroxidation.

Ethanol consumption during pregnancy can result in wide range of negative outcomes, including pre-and post-natal mortality, growth retardation, physical abnormalities and brain deficits, manifested as behavioural impairments. These outcomes can result from “binge-drinking” (generally defined as >5 standard drinks on a single occasion) or chronic ethanol consumption. Ethanol-induced zinc (Zn) deficiency is one of the mechanisms proposed as a cause of ethanol teratogenicity. We have previously demonstrated in mice that ethanol exposure on gestational day (GD)8 (during organogenesis) can alter Zn homeostasis by inducing the Zn-binding protein metallothionein (MT) in the maternal liver. This causes plasma Zn concentrations to decrease as Zn redistributes into the liver, and consequently decreases the fetal Zn supply and increases the risk of teratogenicity. Subcutaneous Zn treatment with ethanol on GD8 can prevent the deleterious effects of ethanol on the fetus (i.e. physical abnormalities and spatial memory impairments). The main objective of this thesis was to investigate whether a less invasive approach of giving dietary Zn supplementation throughout pregnancy could provide similar protective benefits against a range of adverse outcomes caused by prenatal binge or chronic ethanol exposure. Binge ethanol exposure in early pregnancy (i.e. where mice are injected with 25% ethanol (0.015 ml/g) intraperitoneally at 0 and 4 hours on GD8) significantly increased the incidence of birth abnormalities measured on GD18. These included craniofacial abnormalities (microphthalmia, anophthalmia) and limb defects. Ethanol also increased postnatal mortality between birth and postnatal day (PD)60. In a separate study, offspring from dams given ethanol on GD8 were subjected to a physical and behavioural screening protocol (including tests for vision, olfactory, exploratory, anxiety and motor impairments) and subsequently a cohort of phenotypically-normal offspring were randomly selected for testing in a cross-maze escape task (for spatial learning and memory) and an object recognition test (for short-term non-spatial memory). While ethanol did not affect behaviour measured during screening, it resulted in spatial memory and object recognition memory impairments in adult offspring. The most important finding was that dietary Zn supplementation throughout pregnancy significantly increased plasma Zn concentrations at the time of ethanol exposure (avoiding the “typical” ethanol-induced decrease in plasma Zn) and prevented all negative outcomes resulting from early ethanol exposure (birth abnormalities, mortality, spatial and object recognition memory impairments). In the chronic ethanol mouse model (i.e. where mice were fed a liquid diet containing 27 % v/v ethanol-derived calories from GD6-18), ethanol did not affect offspring growth between birth and PD21 or spatial memory in adult offspring, thus, the influence of Zn supplementation could not be examined for these parameters. While ethanol decreased offspring weight at PD50 and increased mortality between birth and PD40, they were not prevented by Zn supplementation throughout pregnancy. The findings from this thesis emphasise that organogenesis is a particularly vulnerable period to ethanol exposure and even a binge of ethanol during this time can result in dysmorphology, mortality and spatial and object memory impairments in adulthood. In addition, dietary Zn supplementation is protective against the deleterious effects of binge ethanol exposure in early pregnancy. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1368113 / Thesis (Ph.D.) - University of Adelaide, School of Molecular and Biomedical Sciences, 2009

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 109-122). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 109-122). Also available on the Internet.

Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xiv, 152 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Orientador: Pedro de Magalhães Padilha / Resumo: Devido a sua grande concentração de nutrientes, tais como proteínas, vitaminas e minerais, o peixe é considerado um dos alimentos mais saudáveis que se pode encontrar na natureza. No entanto, a ingestão de peixes é considerada a forma predominante de via de exposição do ser humano ao mercúrio (Hg), principalmente para as populações que vivem às margens dos rios, onde o peixe constitui a principal fonte de proteína. Na tentativa de elucidar os mecanismos de toxicidade das espécies mercuriais, o teor desse metal tem sido estudado intensamente pela comunidade científica nas últimas décadas em amostras de solo, sedimentos, humanos e peixes na Amazônia brasileira. Sabe-se que as espécies mercuriais bioacumuladas nos tecidos dos seres vivos ligam-se a metaloproteínas, e quando há uma concentração alta de metal tóxico nos organismos, esses passam a expressar proteínas de defesa, denominadas metalotioneínas (MTs) responsáveis pelo transporte e eliminação de metais tóxicos. Apesar de estudos mostrarem o aumento das metalotioneínas em animais expostos a metais potencialmente tóxicos, essas proteínas não foram caracterizadas para confirmação de sua veridicidade, são analisadas por métodos indiretos, esse fato leva a necessidade de técnicas mais precisas na identificação de metalotioneínas. Levando em consideração o exposto esse estudo teve como objetivo otimizar métodos de quantificação de mercúrio e técnica de eletroforese para identificação de possíveis metalotioneínas biomarcadoras d... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Due to its high concentration of nutrients, such as proteins, vitamins and minerals, fish is considered one of the healthiest foods that one can find in nature. However, fish intake is considered to be the predominant human exposure pathway to mercury (Hg), especially for populations living along riverbanks where fish are the main source of protein. In the attempt to elucidate the toxicity mechanisms of mercurial species, the content of this metal has been intensively studied by the scientific community in recent decades in soil, sediment, human and fish samples in the Brazilian Amazon. It is known that mercurial species bioaccumulated in the tissues of living beings bind to metalloproteins, and when there is a high concentration of toxic metal in organisms, they begin to express defense proteins, called metallothioneins (MTs) responsible for the transport and elimination of Toxic metals. Although studies have shown the increase of metallothioneins in animals exposed to potentially toxic metals, these proteins have not been characterized to confirm their veridicity, are analyzed by indirect methods, this fact leads to the need for more precise techniques in the identification of metallothioneins. Taking into account the above, this study aimed to optimize mercury quantification methods and electrophoresis technique for identification of possible mercury biomarkers metallothionein in muscular and hepatic tissue of fish of economic interest, Tucunaré (Cichla spp.), Filhote (Bra... (Complete abstract click electronic access below) / Doutor