Heavy Metals

Heavy metals and electron microscopy

As a science, electron microscopy relies primarily on heavy metals to make specimens stable enough to withstand the electron beam. Without the heavy metals used during preparation, delicate biological specimens would be burned up under the intensity of the electrons. Heavy metal fixatives insert themselves into the membranes, providing stability to the entire structure. Heavy metal stains, such as uranyl acetate and lead citrate,10 permeate ultrathin sections and are absorbed by the tissue, thus stabilizing the sections. In SEM, the thin layer of gold, gold-palladium, plati

Preface To The Series

The assessment of safe to use starts with the harvested plant material which has to comply with an official monograph. This may require absence of, or prescribed limits of, radioactive material, heavy metals, aflatoxins, pesticide residue, as well as the required level of active principle. This analytical control is costly and tends to exclude small batches of plant material. Large scale contracted mechanised cultivation with designated seed or plantlets is now preferable.

Induction Of The Heat Shock Response

As mentioned above, a diverse array of metabolic insults, including the exposure of cells to heavy metals, various ionophores, amino acid analogues, and metabolic poisons which target ATP production, all result in similar changes in gene expression leading to the accumulation of the stress proteins. Many of these agents treatments which induce a stress response share the common property of being protein chaotropes they adversely affect the proper conformation and therefore the function of proteins. Consequently, it was proposed (1) and later demonstrated that under conditions where abnormally folded proteins might begin to accumulate in the cell, a stress response would be initiated (2). Presumably the resultant increases in the levels of the stress proteins would somehow facilitate the identification, removal, and or restoration of those proteins adversely affected by the particular stress event again a prediction which now appears correct. The intracellular accumulation of...

Nonbiogenic Toxic Substances Metals

It is a well-known fact that virtually all microorganisms are capable of accumulating heavy metals at concentrations that are several orders of magnitude higher than those present in the surrounding media. Their accumulation in algae is a relatively rapid process.35 In Spirulina, special attention has been paid to the concentration of heavy metals (lead, cadmium, mercury, and arsenic).11 To illustrate the extent of heavy metals found in algal samples, selected analytical data found in the literature are summarized in Table 2.1 and are compared to recommendations on upper limits of heavy-metal contents in different food goods.54 Estimates differ widely, depending on the origin of the algal samples as well as on the laboratories doing the analyses.11

Effects of acidity on stream ecosystems

The degree of acidification is of course very important, and depends upon both inputs and buffering capacity. Organisms evidently are harmed via diverse pathways, including metal toxicity, and taxa differ in their susceptibility. Consequently, while one can assert that anthropogenic acidification is generally harmful once pH falls much below 5.0, the details depend upon many factors.

Chaperonin Function Under Cellular Stress Conditions

Structure of a folded protein can be perturbed by various forms of cellular stress, including heat shock and exposure to heavy metals, oxygen radicals, ethanol, and UV light (Parsell and Lindquist, 1993). Not surprisingly, many molecular chaperones are stress proteins and their concentrations are increased under these conditions. Cells may respond to a particular form of stress by increasing the synthesis of a specific subset of stress proteins. Chaperone components with a general function in protein folding, such as DnaK, DnaJ, and GrpE or GroEL and GroES, are often among the induced stress proteins. As during de novo folding, these chaperones may interact with proteins that have partially unfolded under stress, preventing their aggregation and mediating their subsequent refolding. Proteins of relatively low structural stability may thus be maintained in an active form or in a soluble state competent for refolding, once more favorable conditions have been reestablished.

Metalbinding Capacities of Microbial Cell Walls and Extracellular Exopolymers

Natural microbial populations usually secrete large amounts of extracellular exopolymer (EPS), ranging from tightly structured capsules and sheaths around cells to a more loosely bound slime that forms the matrix of microbial biofilms and mats. Decho (1990) identified a wide variety of functions for EPS, including (1) buffering the microenvironment around cells against changes in pH, salinity, and the harmful effects of toxins (e.g., heavy metals) (2) protection against the harmful effects of UV radiation and desiccation during exposure (3) protection against digestion by grazers (4) adhesion of biofilms to surfaces and (5) the concentration of exoenzymes and nutrients required for growth (including dissolved carbon compounds).

The Ecophysiology Of Salvia Disorders And Adaptation

Zheljazkov and Zheljazkova (1996) investigated the simultaneous effect of soil heavy metals on the essential oil content and productivity of Salvia sclarea L. as well as the heavy metal accumulation in plant parts (roots, stems, inflorescence). As reported, the simultaneous contamination of soil (taken at a distance of 0.5 km from the source of pollution) with excessive amounts of Cd and Zn decreased the yield of fresh inflorescences by 14-19 and the yield of oil by 12-18 . There was no

Antibiotic Resistance Mechanisms

It is necessary to distinguish between destructive chemicals, antiseptics, and antibiotics. An agent that kills organisms non-selectively, such as phenols, alcohols, cationic antiseptics, and heavy metals, can be useful if their action can be directed by choices of where and how it is applied. An antiseptic is only a little different because of the topical way it may be applied. An antibiotic must have the property that it acts against the microbe, and at least much less against the human or animal that is also simultaneously exposed to it.

Protection against Irritants

Substances and bisulphite, with toxic gases and fumes being formed when diluting, transfer acid to water, not vice versa do not use together with other cleaning agents cleaning agents that contain hypochlorite release toxic gases that may harm the airways exothermic reaction with lyes risk of decomposition with impurities of any kind, particularly heavy metals B, T, F, S, cV uV Iodine compounds are available as iodophors, which are combinations of elemental

Known And Suspected Occupational Carcinogens

At present, 26 chemicals, groups of chemicals and mixtures for which exposures are mostly occupational are established human carcinogens (Table 1). Whereas some agents such as asbestos, benzene and heavy metals are currently widely used in many countries, other agents are of mainly historical interest (e.g. mustard gas and 2-naphthylamine).

Nonhereditary Idiopathic Cerebellar Ataxia

Differential Diagnosis and Evaluation. The clinical phenotype of advanced IDCA-P MSA, consisting of ataxia, parkinsonism, and autonomic failure, is highly characteristic and rarely causes confusion with other disorders. In contrast, IDCA-C and incomplete or beginning forms of IDCA-P MSA must be carefully distinguished from symptomatic cerebellar ataxia. Degeneration of the cerebellar cortex in patients with chronic cerebellar ataxia may be due to alcoholism, various toxic causes (antiepileptics, cytostatic drugs, lithium, solvents, heavy metals), remote effects of malignancy (paraneoplastic cerebellar degeneration), malabsorption with vitamin E deficiency, increased body temperature (heat stroke, neuroleptic malignant syndrome, sepsis), and hypothyreosis.

Evaluation Guidelines Table95

Thyroid function testing is important to identify patients with thyroid orbitopathy, but it must be remembered that nearly a half of patients have normal thyroid function at the time they present with orbital manifestations. Patients with lead and other heavy metal poisoning can present with elevated intracranial pressure and false-localizing cranial nerve VI palsy. Urine screen for heavy metals is an important adjunct to the workup of these patients.

Ray Crystallography [1278

The process of determining a crystal structure is too complex to discuss at length here, so the reader is referred to an excellent book by McPherson for more details 7 . Briefly, protein crystals are irradiated with x-rays this produces diffraction patterns that ultimately provide amplitudes and positions of scattered waves. But, the phases of these scattered x-ray waves must be determined before a structure can be calculated, and this is typically accomplished by comparison to a structurally similar protein (molecular replacement) or by comparison of the diffraction patterns for proteins soaked with heavy metals or with methionine residues substituted with selenomethionine residues (multiple isomorphous replacement). Once this phase problem is solved, an electron density map can be calculated from the diffraction patterns. Then, a covalent model of the protein is fitted into this electron density map. This is then subjected to rounds of refinement where small adjustments are made to...

The Composition of the Culture Medium

The culture medium used in Spirulina mass culture mimics that of the natural system. The medium that is commonly used is based on the original medium of Zarouk32 and is typically composed of water, sodium carbonate bicarbonate, a source of nitrogen, phosphorus, iron, and other trace minerals. Arthrospira platensis is cultivated in an alkaline aqueous medium rich in nutrient salts. The high pH and alkalinity of the growth medium inhibits the growth of potentially contaminating organisms, resulting in a virtual monoculture of A. platensis (Figure 1.4). Nutrients are supplied by reliable manufacturers that include specifications for heavy metals and other possible

Heavy Metal Contamination

As in other agricultural products, lead, mercury, cadmium, and arsenic are potential contaminants in algal products since they are components of industrial pollution and occur in trace amounts in certain agricultural fertilizers. It is known that certain microalgae are effective accumulators of heavy metals.37 The production of high-quality Spirulina therefore requires the use of high-grade nutrients and a meticulous and routine analysis of heavy metals in the culture medium and the product. This is particularly important in situations where food-grade Spirulina is to be produced from earthen ponds or natural lakes. The soil in certain regions may have a high content of heavy metals that can easily be accumulated by the algae. Table 1.4 shows some examples of regulatory standards for heavy metals in dietary supplements and foods.

Scope of the Problem Epidemiology

There are also occupational risk factors for head and neck cancer. Painters, construction workers, metal or plastic workers, and machine operators have all been found to have higher rates of head and neck cancer in probable association with the heavy metals and solvents to which they are exposed.

Introduction

The heat shock response, first observed in fruit fly Drosophila melanogaster over 30 years ago, provided investigators a relatively simple way to study rapid changes in gene expression. Simply raising the temperature of Drosophila above its physiological norm resulted in the decreased expression of those genes which were active prior to the temperature shock and the increased expression of genes encoding a group of proteins referred to as the heat shock proteins (hsps). Over the last 30 years, similar changes in gene expression following relevant temperature shocks have been observed in cells from all organisms, be they derived from bacteria, plants, yeasts, or mammals. Moreover, the heat shock proteins from various organisms appear highly conserved with respect to their primary structure, mode of regulation, and biochemical function. In addition to heat shock treatment, many other types of metabolic insults, including exposure to heavy metals, amino acid analogues, different...

Brain Injuries

The brain can suffer injury in diverse ways metabolic or structural abnormalities that are genetically inherited or perinatally induced trauma from civilian accidents or military combat toxicity from drugs, heavy metals, or poisonous gases malnutrition infections or diseases tumors cerebrovascular accidents (stroke) surgical removal of brain tissue for relief of epilepsy, intractable pain, or serious psychiatric symptomatology and aging-related disorders (e.g., Alzheimer's disease).

Dysplasia

The causes for morphological changes leading to dysplasias are only partially understood. Migrational abnormalities may be the consequence of altered cell-cell interactions but can also result secondarily from radiation exposure. Altered cell-cell interactions can be caused either by mutations in the genes coding for cell surface proteins or by environmental factors that change the expression of cell surface proteins. Neuronal differentiation is controlled by a plethora of factors including cell surface interactions, neurotrophins, cytokines, neurotransmitters and neuromodulators, and, last but not least, synaptic activity. Disruptions of any one, or any combination, of these factors may induce altered neuronal maturation. In addition to genetic mutations, aberrant neuronal migration and maturation may be caused by environmental factors, such as heavy metals (for example, lead) ethanol and other psychoactive drugs of abuse or gestational and perinatal insults, such as hypoxia and...

Application

It is widely held that there has been a decline in human male fertility within the past few decades.5051 The direct cause or causes of this reduction remain controversial, although, in part, it may reflect a trend toward decreased family size in the Western world. However, concurrent with the growing decrease in male infertility, there has been a corresponding increase in the incidence of testicular cancer and cryptorchidism.52 Several theories have been put forward to help explain the causes of increased male infertility, including increased environmental and systemic exposure to pesticides, herbicides, estrogenic compounds, heavy metals, and reactive oxygen species.53-55

The Nasal Route

Chemicals like lipophilic atmospheric pollutants (solvents, engine smoke, aryl hydrocarbons), or drugs of addiction like cocaine or amphetamine derivatives, may rapidly enter the brain by the nasal route (part 2 of Fig. 1), and possibly promote reversible or irreversible alterations of nervous functioning (4). Anatomical pathways may allow molecular movement in the cerebrospinal fluid (CSF) from the subepithelial olfactory space and from the olfactory bulb, to the entorhinal cortex. Another possibility involves the transport in the axons of the olfactory neurons, as demonstrated for heavy metals, which can reach easily the brain in this way (5). Nasal drug intake has appeared to be a fast and effective route of administration, suitable for drugs that must act rapidly and are taken in small amounts, like antimigraine drugs, analgesics, vitamin B-12 or apomorphine. Nasal administration also prevents gastrointestinal clearance and hepatic metabolism and seems to be a promising route for...

Acute Renal Failure

Acute tubular necrosis due to ischemia Acute tubular necrosis due to toxins (heavy metals, ethylene glycol, insecticides, poison mushrooms, carbon tetrachloride) There is a long list of renal poisons and medications that can damage the tubular epithelium and cause acute renal failure. Some of these are carbon tetrachloride, heavy metals (such as mercury and lead), ethylene glycol (which is a major component in antifreeze), various insecticides, various medications (such as tetracyclines) used as antibiotics, and cis-platinum, which is used in treating certain cancers. Each of these substances has a specific toxic action on the renal tubular epithelial cells, causing death of many of them. As a result, the epithelial cells slough away from the basement membrane and plug the tubules. In some instances, the basement membrane also is destroyed. If the basement membrane remains intact, new tubular epithelial cells can grow along the surface of the membrane, so that the tubule repairs...

The Fertility Factor

Richard Spark's review of the male fertility literature suggests that for global sperm count the persistent trend is unquestionably downward. 14 With such a wide variety of risk factors, it's not surprising that men's fertility has become increasingly compromised. For example, some diseases lead to male infertility these include cystic fibrosis, sickle cell anemia, and some sexually transmitted diseases. Environmental factors such as pesticides and herbicides (including estrogen-like chemicals), hydrocarbons (found in products like asphalt, crude oil, and roofing tar), heavy metals (used in some batteries, pigments, and plastics), and aromatic solvents (used in paint, varnish, stain, glue, and metal de-greasers) have all been suspected of lowering sperm counts and damaging morphology.15 Furthermore, men and boys may lower their sperm count through tobacco exposure, whether chewing or smoking,16 and prenatal exposure to tobacco has been shown to lower sperm counts in male offspring.17...

Other Toxicities

Lead As in drug toxicities, Spirulina or its bioactive constituent, phycocyanin, has been found to protect from heavy metal poisoning. Again, this protection seems to be mediated mostly by the prevention of oxidative damage through direct antioxidant actions and through induction of endogenous antioxidant enzymes. For example, in rats treated with lead acetate, dietary S.fusiformis (1500 mg kg) reversed the lead-induced inhibition of SOD and catalase activity in liver, lung, heart, and kidney to levels that were only slightly, but not significantly, lower than those of untreated controls.23 Lead did not induce significant decreases in the activities of these anti-oxidant enzymes in the brain, and Spirulina did not markedly alter them either. Interestingly, brain was the only tissue in which Spirulina feeding resulted in a significant reduction in lead concentrations compared to the lead-treated unsupplemented group. Dietary S. fusiformis was also associated with a pronounced decrease...