航天对MT工程菌株的影响研究

为了探讨航天与常规诱变技术对MT工程菌株的影响,进行了HNO2.UV、γ-射线、LiCl及γ-射线 LiCl分别与航天共诱变对MT工程菌株活性的影响试验,并且就航天对MT工程菌株的致死作用及质粒的稳定性进行了研究。结果表明:MT工程菌株经航天处理后,活菌数降低,死亡率为34.59%,航天对MT工程菌株具有一定的致死作用;MT工程菌株经UV、γ-射线、LiCl及γ-射线 LiCl分别与航天共诱变处理后的生长活性没有改变,MT工程菌株经HNO2与航天共诱变处理后的生长速率减慢;在航天处理的作用下,MT工程菌株的质粒不易丢失,能够维持很好的稳定性,丢失率仅为8.26%,而置于地面的MT工程菌株的质粒易丢失,丢失率为83.51%。     

Inhibition of ischemia-induced angiogenesis by benzo[a]pyrene in a manner dependent on the aryl hydrocarbon receptor

We have investigated the effect of benzo[a]pyrene (B[a]P), a carcinogen of tobacco smoke and an agonist for the aryl hydrocarbon receptor (AHR), on hypoxia-induced angiogenesis. Ischemia was induced by femoral artery ligation in wild-type and AHR-null mice, and the animals were subjected to oral administration of B[a]P (125 mg/kg) once a week. Exposure to B[a]P up-regulated the expression of metallothionein in the ischemic hindlimb and markedly inhibited ischemia-induced angiogenesis in wild-type mice. The amounts of interleukin-6 and of vascular endothelial growth factor (VEGF) mRNA in the ischemic hindlimb of wild-type mice were reduced by exposure to B[a]P. These various effects of B[a]P were markedly attenuated in AHR-null mice. Our observations suggest that the loss of the inhibitory effect of B[a]P on ischemia-induced angiogenesis apparent in AHR-null mice may be attributable to maintenance of interleukin-6 expression and consequent promotion of angiogenesis through up-regulation of VEGF expression.     

Molecular aspects of human cellular zinc homeostasis: redox control of zinc potentials and zinc signals

Zinc(II) ions are essential for all forms of life. In humans, they have catalytic and structural functions in an estimated 3,000 zinc proteins. In addition, they interact with proteins transiently when they regulate proteins or when proteins regulate cellular zinc re-distribution. As yet, these types of zinc proteins have been explored poorly. Therefore the number of zinc/protein interactions is potentially larger than that given by the above estimate. Confronted with such a wide range of functions, which affect virtually all aspects of cellular physiology, investigators have begun to elucidate the molecular mechanisms of cellular homeostatic control of zinc, especially the functions of transporter, sensor, and trafficking proteins, such as metallothioneins, in providing the correct amounts of zinc ions for the synthesis of zinc metalloproteins. The sulfur-containing amino acid cysteine in proteins has an important role in the cellular mobility of zinc ions. Sulfur-coordination environments provide sufficiently strong interactions with zinc ions; they can undergo fast ligand-exchange; and they can serve as molecular redox switches for zinc binding and release. For the cellular functions of zinc, the free zinc ion concentrations (zinc potentials, pZn = −log[Zn²⁺]) and the zinc buffering capacity are critically important parameters that need to be defined quantitatively. In the cytoplasm, free zinc ions are kept at picomolar concentrations as a minute fraction of the few hundred micromolar concentrations of total cellular zinc. However, zinc ion concentrations can fluctuate under various conditions. Zinc ions released intracellularly from the zinc/thiolate clusters of metallothioneins or secreted from specialized organelles are potent effectors of proteins and are considered zinc signals. The cellular zinc buffering capacity determines the threshold between physiological and pathophysiological actions of zinc ions. When drugs, toxins, other transition metal ions or reactive compounds compromise zinc buffering, large zinc ion fluctuations can injure cells through effects on redox biology and interactions of zinc ions with proteins that are normally not targeted.

Prevalence of kidney dysfunction in humans – Relationship to cadmium dose, metallothionein, immunological and metabolic factors

Long term cadmium (Cd) exposure in occupational and general environments may give rise to kidney dysfunction. This effect is usually considered to be the critical effect, i. e. the effect that occurs at relatively low level of exposure. The present review focused on studies of the prevalence of cadmium-related kidney dysfunction among population groups residing in cadmium contaminated areas in China. Dose–response relationships were shown between UCd and the prevalence of increased levels of biomarkers in urine of renal tubular dysfunction such as urinary beta-2-microglobulin or N-acetyl-beta-d-glucosaminidase – NAG or urinary albumin, a biomarker of glomerular kidney dysfunction. Factors that influence these dose–response relationships include: 1) Metallothionein mRNA levels in peripheral blood lymphocytes, used as a biomarker of the ability of each person, to synthesize metallothionein (a protein known to provide intracellular protection against cadmium toxicity). 2) The occurrence of increased levels in blood plasma of autoantibodies against metallothionein. 3) Concomitant changes in glucose metabolism i e Type II diabetes. 4) Concomitant exposure to other nephrotoxic agents such as inorganic arsenic. Increased susceptibility in diabetics has been shown also in population groups in Europe. In persons with type II diabetes and increased levels of autoantibodies against metallothionein in blood plasma or in persons with concomitant exposure to environmental inorganic arsenic, indications of Cd-related kidney dysfunction was observed at UCd levels around 1 μg/g creatinine, levels found among “unexposed” population groups in many countries.     

Identification and cloning of first cadmium metallothionein like gene from locally isolated ciliate, <Emphasis Type="Italic">Paramecium </Emphasis>sp.

First cadmium metallothionein like gene PMCd1 of a ciliate, Paramecium sp., isolated from industrial wastewater has been cloned and sequenced. PMCd1 is an intronless gene, encoding 612 nucleotides, with TAA coding for glutamine. The coding region of PMCd1 comprises 203 amino acids, including 37 cysteine residues with a conserved structural pattern in the form of recurring structural motifs, arranged in 17 x-cys-x-y-cys-x, 1 x-cys-cys-x and x-cys-x contexts. Both, the deduced amino acids and nucleotide sequence differ, not only from other animal metallothioneins (MTs), but also from the previously characterized Tetrahymena Cu and Cd-MTs. The translated protein of PMCd1 contains conserved cysteine residues, peculiar characteristic of stress inducible metallothionein genes of ciliates and other groups of organisms.     

A single form of metallothionein is Present in both heavy metal induced and neonatal chicken liver

MultiPlicity of metallothionein and their genes in higher animals are documented extensively in recent literature. In contrast, chicken liver Produced aPParently a single form of metallothionein uPon heavy metal exPosure. This Protein was Purified by gel filtration and ion exchange chromatograPhy and another technique based on heat treatment and acetone fractionation, followed by ion exchange chromatograPhy. In adult uninduced chicken liver the Presence of metallothionein was below the detection limit. But, like mammalian system, chicken liver was found to contain high amount of metallothionein at neonatal stage. This naturally occurring neonatal chicken hePatic metallothionein was Purified and comPared with the heavy metal induced adult hePatic metallothionein. The biochemical and immunobiological comParative analysis of adult and neonatal hePatic metallothionein showed identical characteristics. The neonatal metaltothionein exPressed naturally was a zinc metallothionein and unlike few other mammalian neonatal metallothionein did not contain any coPPer. Metallothionein was undectable in unfertilized eggs, in early embryos, and in Postnatal chicken, from 4 weeks after birth. The highest level of this naturally occurring neonatal metallothionein was found in 1–4 day old neonatal liver, which was about 1.5% of the total cytosolic Protein. This is the first rePorted evidence for the Presence of ontogenically modulated exPression of metallothionein in avian system. Possible biological role of neonatal metallothionein and their cellular interactions has been discussed.