The physicochemical basis of the membrane toxicity of pentachlorophenol: An overview

The relationships between pesticide metabolites and neurobehavioral test performance in the third National Health and Nutrition Examination Survey

Regression analysis was used to estimate and test for relationships between urinary pesticide metabolites and neurobehavioral test performance in adults, 20 to 59 years old, participating in the third National Health and Nutrition Examination Survey. The 12 pesticide metabolites included 2 naphthols, 8 phenols, a phenoxyacetic acid, and a pyridinol. The 3 neurobehavioral tests included in the survey were simple reaction time, symbol-digit substitution, and serial digit learning. As the 2,4-dichlorophenol, 2,5-dichlorophenol, and the pentachlorophenol concentrations increased, performance on the serial digit learning test improved. As the 2,5-dichlorophenol concentration increased, performance on the symbol-digit substitution test improved. At low concentrations, the parent compounds of these metabolites may act at acetylcholine and γ-aminobutyric acid synapses in the central nervous system to improve neurobehavioral test performance.

Cytotoxic effects in mammalian Vero cells exposed to pentachlorophenol

The effects of pentachlorophenol have been studied on diverse biological systems both in vivo and in vitro, however the cellular basis of the pronounced cytotoxicity of this organochlorine compound is poorly understood. In this work, morphological and biochemical analyses were carried out to identify the primary targets of pentachlorophenol toxicity in mammalian cells. Our results show that pentachlorophenol is a very potent cytotoxic drug that displays an unusual and interesting mode of action in Vero cells. Although this compound is a powerful uncoupler of oxidative phosphorylation, we present the novel finding that lysosome destabilization is an early cytotoxic response that precedes the mitochondrial dysfunction. In addition, soon after exposure to moderate doses of pentachlorophenol, a significant number of cells initiate an apoptotic death process identified by the condensed and fragmented state of their nuclei. These results demonstrate that there are multiple potential targets of PCP-induced toxicity in mammalian cells, and the need to develop further experimental studies for the risk assessment of this environmental pollutant.

Pentachlorophenol Poisoning

Despite being banned in many countries and having its use severely restricted in others, pentachlorophenol (PCP) remains an important pesticide from a toxicological perspective. It is a stable and persistent compound. In humans it is readily absorbed by ingestion and inhalation but is less well absorbed dermally. Its distribution is limited, its metabolism extensive and it is eliminated only slowly. Assessment of the toxicity of PCP is confounded by the presence of contaminants known to cause effects identical to those attributed to PCP. However, severe exposure by any route may result in an acute and occasionally fatal illness that bears all the hallmarks of being mediated by uncoupling of oxidative phosphorylation. Tachycardia, tachypnoea, sweating, altered consciousness, hyperthermia, convulsions and early onset of marked rigor (if death occurs) are the most notable features. Pulmonary oedema, intravascular haemolysis, pancreatitis, jaundice and acute renal failure have been reported. There is no antidote and no adequate data to support the use of repeat-dose oral cholestyramine, forced diuresis or urine alkalinisation as effective methods of enhancing PCP elimination in poisoned humans. Supportive care and vigorous management of hyperthermia should produce a satisfactory outcome. Chronic occupational exposure to PCP may produce a syndrome similar to acute systemic poisoning, together with conjunctivitis and irritation of the upper respiratory and oral mucosae. Long-term exposure has also been reported to result in chronic fatigue or neuropsychiatric features in combination with skin infections (including chloracne), chronic respiratory symptoms, neuralgic pains in the legs, and impaired fertility and hypothyroidism secondary to endocrine disruption. PCP is a weak mutagen but the available data for humans are insufficient to classify it more strongly than as a probable carcinogen.

Biokinetic models for representing the complete inhibition of microbial activity at high substrate concentrations

This paper reintroduces the Wayman and Tseng model for representing substrate inhibition effects on specific growth rate by further documenting its potential predictive capabilities. It also introduces a modification to this model in which an Andrews inhibition function is used in place of the Monod noninhibitory substrate function. This modification better represents the relationship between specific growth rate and substrate concentration for those substrates that show Andrews type inhibition at lower substrate concentrations, rather than the Monod type noninhibitory behavior described in the model of Wayman and Tseng. Results from nonlinear, least squares regression analysis are used to evaluate the ability of these models to empirically represent experimental data (both new and from the literature). The statistical goodness of fit is evaluated by comparing the regression results against those obtained using other empirical models. Finally, possible mechanisms of toxicity responsible for the observed inhibition trends are used to further justify use of these empirical models. The dominant mechanism considered to be relevant for conceptually explaining complete inhibition at high concentrations of solvents is the deterioration of cell membrane integrity. Literature citations are used to support this argument. This work should lead to improvements in the mathematical modeling of contaminant fate and transport in the environment and in the simulation of microbial growth and organic compound biodegradation in engineered systems.

Studies on the Electrochemical Characterization of Cellulose Acetate and Dowex-50 Membranes for Uni-Univalent Electrolytes in Aqueous Solutions

Membrane potential and bi-ionic potential studies using cellulose acetate and Dowex-50 membranes and sodium chloride and potassium chloride aqueous solutions have been carried out. The results have been used to estimate solute permeability, ionic transport numbers, fixed charge density, and surface charge density of both the membranes. Both membrane potential and bi-ionic potential are affected by adsorption of ions. Adsorbed ions affect the surface potential as well as solute retention capacity of the membranes. Solute retention expressed in terms of the "maximal retention" of membranes could thus be estimated. Furthermore, a correlation between permselectivity of the membrane and effective concentration with the dielectric constant of the membrane has also been established. Copyright 1999 Academic Press.

Chlorophenols in the terrestrial environment

Chlorophenols are presently widespread in the environment. Even in the most remote natural environments, the presence of chlorophenols in both aquatic and terrestrial food chains has been recorded. These pervasive compounds have been used for a wide range of domestic, agricultural, and industrial purposes for more than 50 years. In addition to industrial production and usage, chlorophenols are produced from naturally occurring phenols as a result of chlorine bleaching of wood pulp in the paper industry and through the chlorination of domestic water supplies and swimming pools. It must be emphasized that chlorophenols, although a local problem in some areas, generally cannot be considered a major environmental problem today because their use is prohibited or restricted in many countries. Future reduction in the use of the herbicidal phenoxy acids will further minimize their levels in the terrestrial environment. Because of the long persistence and high toxicity of pentachlorophenol in particular, however, it is important that the discharge of chlorophenols to the terrestrial environment by way of sewage sludge or pulp mill effluents be maintained at their current levels or even reduced to lower levels.

Activation energy for permeation of phosphonium cations through phospholipid bilayer membrane

The conductance caused by translocation of various phosphonium cations across phospholipid (from soybean) bilayer membrane was measured. Phosphonium cations used were tetraphenylphosphonium (TPP+) and triphenylalkylphosphonium cations formulated as (Phe)3-P(+)-(CH2)nCH3 (n = 0-5). The conductance was dependent on voltage applied externally to the membrane in accordance with a theory developed by previous authors. Using the theory, values of beta K(i) were determined, where beta and k(i) are a linear partition coefficient and a rate constant of transmembrane ion transport, respectively. Since beta k(i) depended on the phosphonium ion concentration, values extrapolated to infinite dilution, (beta k(i))0, were determined. Temperature dependence of (beta k(i))0 allowed us to estimate the activation energy of transport, Ea. For TPP+ thermodynamic values obtained were consistent with values calculated by Flewelling and Hubbell [(1986) Biophys. J. 49, 541-552]. When (Phe)3-P(+)-(CH2)nCH3 (n = 0-5) were used, E(a) depended on the odd or even of n. This "odd and even" pattern was observed in a variety of phenomena such as solubility in water, equivalent ionic conductivity in water, and 31P NMR chemical shift.