Gamma-irradiation of lyophilised wound healing wafers

Lyophilised wafers are being developed as drug delivery systems that can be applied directly to the surface of suppurating wounds. They are produced by the freeze-drying of polymer solutions and gels. This study investigates the possibility of sterilising these glassy, solid dosage forms with gamma-irradiation and determining the rheological properties of rehydrated wafers post-irradiation. One series of wafers was formulated using sodium alginate (SA) modified with increasing amounts of methylcellulose (MC), the other being composed of xanthan gum (XG) and MC. Batches were divided into three lots, two of which were exposed to 25 and 40 kGrays (kGy) of Cobalt-60 gamma-irradiation, respectively, the third being retained as a non-irradiated control. Apparent viscosities of solutions/gels resulting from the volumetric addition of distilled water to individual wafers were determined using continuous shear, flow-rheometry. Flow behaviour on proprietary suppurating surfaces was also determined. Large reductions in viscosity were apparent for irradiated SA samples while those of XG appeared to be largely unaffected. In addition, an increase in the yield stress of xanthan formulations was observed. Xanthan wafers appeared to withstand large doses of irradiation with no detrimental effect on the rheology of reconstituted gels. This offers the possibility of manufacturing sterilisable delivery systems for wounds.     

Fibrin glue safety: inactivation of potential viral contaminants by pasteurization of the human plasma components

Fibrin glue has become an indispensable tool in salvaging operations of the parenchymatous organs of the abdomen, in vascular and ophthalmic plastic surgery as well as neurosurgery. Currently available glues contain clotting factors from human plasma and thus carry the potential risk of transmitting viral infections like hepatitis or acquired immunodeficiency syndrome (AIDS). Combined efforts in selection of plasma donations as well as pasteurization of the human plasma products allow the manufacturing of a product (Beriplast) with virtually no risk of transmission of viral infections as demonstrated by in vivo and in vitro experiments with a variety of human pathogenic viruses. No changes in activity or antigenicity of the clotting factors by the pasteurization procedure have been encountered.     

The Effect of Gamma-irradiation on the Antibacterial Activity of Honey

There is increasing usage of honey as a dressing on infected wounds, burns and ulcers, but there is some concern that there may be a risk of wound botulism from the clostridial spores sometimes found in honey. It is well-established that the antibacterial activity is heat-labile so would be destroyed if honey were sterilized by autoclaving, but the effect of gamma-irradiation on the antibacterial activity of honey is not known. Therefore an investigation was carried out to assess the effect on the antibacterial activity of honey when the honey was subjected to a commercial sterilization procedure using gamma-irradiation (25 kGy). Two honeys with antibacterial activity due to enzymically-generated hydrogen peroxide and three manuka honeys with non-peroxide antibacterial activity were investigated. The honeys were tested against Staphylococcus aureus in an agar well diffusion assay. There was no significant change found in either type of antibacterial activity resulting from this form of sterilization of honey, even when the radiation was doubled (to 50 kGy). Testing of honey seeded with spores of Clostridium perfringens and C. tetani (10 000 and 1000 spores g^?1 of honey, respectively) showed that 25 kGy of gamma-irradiation was sufficient to achieve sterility.     

Endotoxin inactivation by the humoral components in the tolerant rat serum

A rapid inactivation of endotoxin has shown to occur following its incubation in serum obtained from endotoxin-tolerant rats with the aid of the limulus amebocyte lysate (LAL) assay. The tolerant rat had large quantities of lipopolysaccharide inhibitor (LPSI) activity, which does not appear to be complement. Heating tolerant rat serum for 60 min at 56 degrees C or the addition of lead acetate to the tolerant serum both resulted in the loss of LPSI activity. This paper focuses on the most unique properties of LPSI, namely it's alteration of activity after heating or the addition of lead acetate, compared with those properties of inhibitors for endotoxin which have been previously demonstrated by a number of investigators.     

Hazard identification for contaminants

In recent years, the recognition of generation of large quantities of toxicants and their by-products due to the industrial and/or cultural activities and transport and their persistence in the environment and biological activities brings out the necessity and importance of their assessment of risk they pose to the ecosystems (e.g. aquatic environment-coastal waters, rivers, lakes and ground water). Indeed, understanding the impacts of contaminants on the environment, including the organisms which live in it, is rather complicated. Nevertheless, the need for protection of the scarce natural resources in the environment and wiser use of them brings the necessity and importance of focusing more attention to the issue. Accordingly the process of ecological risk assessment (ERA) has evolved rapidly since the Environmental Protection Agency (EPA) issued a framework for ecological risk assessment in 1992. The ecological risk assessment involves three stages in a continuous process: (1) problem formulation (problem identification-hazard identification), (2) the analysis of exposure and effects and (3) risk characterisation. Risk management follows the risk characterisation. Of these stages, problem identification is the most critical one which establishes the direction and scope of the ecological risk assessment. The stage involves identifying the actual environmental value(s) to be protected (assessment endpoints) and selecting ways in which these can be measured and evaluated (measurement endpoints). The accuracy of the risk estimation is largely based on the availability of the key information about the contaminant characteristics, ecosystem at risk and ecological effects and the less uncertainty associated with them. The key information required during this phase of the risk assessment process are as follows: (a) potential/actual contaminant of concern, (b) source of contaminant; current and historic use, (c) mode of action of the contaminant, (d) contaminant characteristics (e.g. physical/chemical properties and environmental behaviour, persistence in the ecosystem, transformation products and bioaccumulation), (e) ecosystem potentially at risk and (f) areas of uncertainty. Finally based on these information a conceptual model has to be developed to define the possible exposure and assessment scenarios. Herein, the aforementioned key issues concerning the problem-hazard identification stage of ecological risk assessment for contaminants have been briefly reviewed.     

Analysis of moonshine for contaminants

OBJECTIVES: In the past, some moonshine products contained potentially toxic contaminants. Although moonshine production continues in the United States, no studies have analyzed the content of moonshine since the early 1960s. We hypothesize that moonshine continues to contain potentially toxic concentrations of contaminants. METHODS: Forty-eight samples of illicitly distilled moonshine were obtained from law enforcement agencies. An independent laboratory, blinded to both the moonshine source and a control sample of ethanol, conducted the analysis. Lead content was determined using atomic absorption spectrophotometry with a graphite tube atomizer. Alcohol content, including ethanol, acetone, isopropanol, methanol, and ethylene glycol, was determined using gas liquid chromatography with flame ionization detection. RESULTS: Ethanol content ranged from 10.5% to 66.0% with a mean value of 41.2%. Lead was found in measurable quantities in 43 of 48 samples with values ranging from 5 to 599 parts per billion (ppb) with a mean value of 80.7 ppb. A total of 29 of 48 (60%) of samples contained lead concentrations above or equal to the EPA water guideline of 15 ppb. Methanol was found in only one sample at a concentration of 0.11%. No samples contained detectable concentrations of acetone, isopropanol, or ethylene glycol. CONCLUSIONS: Many moonshine samples contain detectable concentrations of lead. Extrapolations based on the described moonshine lead content suggest that chronic consumers of moonshine may develop elevated lead concentrations. Physicians should consider lead toxicity in the differential diagnosis when evaluating patients consuming moonshine.     

Data considerations for regulation of water contaminants

There are several pieces of legislation based on human health assessment that set the framework for U.S. EPA's regulation of water contaminants, such as bromate. The Safe Drinking Water Act, for example, specifies that the best available science be used in support of regulation of drinking water contaminants, and highlights that regulations must provide protection to sensitive human populations. Recent EPA guidance, including the 2005 Cancer Guidelines, emphasize analyzing data, and using defaults only in the absence of adequate data. This represents a major shift from the former practice of invoking default methodologies or values unless it was judged that there were sufficient data to depart from them. The Guidelines further present a framework for assessing data in order to determine if a mode of action (MOA) can be established, based on a modification of the Bradford-Hill criteria for causality. A similar approach is used by the International Programme on Chemical Safety (IPCS). To illustrate the application of the framework for evaluating animal tumors, three case studies are considered here. In the first example (chloroform carcinogenicity), sufficient data exist to identify the MOA in animals, and the data are used to illustrate the evaluation of the plausibility of the animal MOA in humans, taking into account toxicokinetics and toxicodynamics. In this case, the MOA was judged to be relevant to humans, and was used to determine the approach for the cancer quantitation. In the second example (naphthalene inhalation carcinogenicity), the key question is whether the weight of evidence (WOE) is sufficient to establish the MOA in animals. Atrazine-induced mammary tumors form the final example, illustrating the reasoning used to determine that the tumor MOA in animals was not considered relevant to humans; atrazine is therefore considered not likely to be a human carcinogen.     

The contribution of hepatic inactivation of testosterone to the lowering of serum testosterone levels by ketoconazole.

Hepatic biotransformation processes can be modulated by chemical exposure and these alterations can impact the biotransformation of endogenous substrates. Furthermore, chemically mediated alterations in the biotransformation of endogenous steroid hormones have been implicated as a mechanism by which steroid hormone homeostasis can be disrupted. The fungicide ketoconazole has been shown to lower serum testosterone levels and alter both gonadal synthesis and hepatic inactivation of testosterone. The present study examined whether the effects of ketoconazole on the hepatic biotransformation of testosterone contribute to its lowering of serum testosterone levels. Results also were used to validate further the use of the androgen-regulated hepatic testosterone 6alpha/15alpha-hydroxylase ratio as an indicator of androgen status. Male CD-1 mice were fed from 0 to 160 mg/kg ketoconazole in honey. Four h after the initial treatment, serum testosterone levels, gonadal testosterone secretion, and hepatic testosterone hydroxylase activity decreased, and the hepatic testosterone 6alpha/15alpha-hydroxylase ratio increased in a dose-dependent manner. Immunoblot analysis indicated that the transient decline in hepatic biotransformation was not due to reduced P450 protein levels. Rather, hepatic testosterone biotransformation activities were found to be differentially susceptible to direct inhibition by ketoconazole. Differential inhibition was also responsible for the increase seen in the 6alpha/15alpha-hydroxylase ratio. The changes in serum testosterone levels could be explained by decreased gonadal synthesis of testosterone and were not impacted by decreased hepatic biotransformation of testosterone. These results demonstrate that changes in the hepatic hydroxylation of testosterone by ketoconazole, and perhaps other chemicals, have little or no influence serum testosterone levels.     

Pharmacological inactivation of MYC for the treatment of cancer

The overexpression of the MYC proto-oncogene has been implicated in the pathogenesis of most types of human cancer. Recent experimental observations indicate that the inactivation of MYC may be effective in the treatment of neoplasia. Several different strategies have been employed to develop novel drugs that may be effective to target the inactivation of MYC for the treatment of cancer. Some of these strategies are discussed.     

Mechanism for inactivation of polyene antibiotics

The process of complete and partial oxidation of nystatin by potassium permanganate in an acid medium is studied. With complete oxidation of the antibiotic, the main reaction product is succinic acid, and with partial, a mixture of succinic, oxalic, malonic, and lactic acids, identified by the methods of paper and gas-liquid chromatography. These same acids are formed on inactivation of nystatin during storage. On inactivation of nystatin under moist chamber conditions, acetone and acetaldehyde are included in the mixture of low-molecular dehydration products.Translated from Khimiko-Farmatsevticheskii Zhurnal, No. 4, pp. 42–47, April, 1967.     

A kinetic method for the detection of inhibitory contaminants in radioactive substrates

A simple kinetic test is proposed that will detect the presence of contaminating inhibitors in the radioactive substrate solutions used in the radiochemical assays of enzymes. Double-reciprocal plots are constructed from initial velocity data obtained from assays conducted under conditions of constant specific radioactivity and of constant radioactivity. A significant difference between the K_m values determined in this way will show the presence of an inhibitory impurity necessitating the purification of the radioactive substrate. It is possible to determine whether the contaminating inhibitor is competitive, uncompetitive or mixed by this method and to estimate the true K_m value in the first two cases.     

Evidence for lidocaine-induced enzyme inactivation

The effects of lidocaine on hepatic enzyme activity were studied using the isolated perfused rat liver. The in vivo liver activity was examined by infusing lidocaine via the jugular vein, followed by organ isolation and drug perfusion 24 h later. The liver was studied in vitro by perfusing the organ with lidocaine until steady state was reached, then allowing the drug and metabolites to wash out of the organ, followed by a second infusion of lidocaine to probe enzyme activity. In both types of experiments, pretreatment with lidocaine caused a reduction in deethylation, and led to a more rapid attainment of steady state. The experimental concentration-time profiles and literature data were successfully described by a mathematical model.     

Sensitivity ranking for freshwater invertebrates towards hydrocarbon contaminants

Hydrocarbons have an utmost economical importance but may also cause substantial ecological impacts due to accidents or inadequate transportation and use. Currently, freshwater biomonitoring methods lack an indicator that can unequivocally reflect the impacts caused by hydrocarbons while being independent from effects of other stressors. The aim of the present study was to develop a sensitivity ranking for freshwater invertebrates towards hydrocarbon contaminants, which can be used in hydrocarbon-specific bioindicators. We employed the Relative Sensitivity method and developed the sensitivity ranking S _hydrocarbons based on literature ecotoxicological data supplemented with rapid and mesocosm test results. A first validation of the sensitivity ranking based on an earlier field study has been conducted and revealed the S _hydrocarbons ranking to be promising for application in sensitivity based indicators. Thus, the first results indicate that the ranking can serve as the core component of future hydrocarbon-specific and sensitivity trait based bioindicators.     

Enhancement of the biodegradability of aromatic groundwater contaminants

Groundwater (GW) from the Bitterfeld industrial region, Central Germany, is contaminated mainly with monochlorobenzene (MCB). Accordingly, current research addresses the development of feasible in situ groundwater remediation technologies. Although easily degradable under aerobic conditions, MCB persists in the essentially anaerobic Bitterfeld aquifer. Therefore, we focused on primary oxidation of MCB and the subsequent anaerobic biodegradability of MCB oxidation products by the indigenous microbial community. In groundwater microcosms, most efficient MCB removal was observed upon treatment with Fenton's reagent (H2O2 + Fe2+), which produces the highly reactive hydroxyl radical and Fe3+ simultaneously. Phospholipid fatty acid analysis following different treatments suggested respective shifts of the microbial community compositions, and indicated that Fenton's reagent had a rather beneficial than an adverse effect on biomass development. Potential metabolites of hydroxyl radical attack on MCB such as chlorohydroquinone, hydroquinone, catechol, resorcinol, and phenol were anaerobically degraded by the groundwater microbial community under Fe3+ -reducing conditions.     

Cytochrome P450 inactivation by serum from humans with a viral infection and serum from rabbits with a turpentine-induced inflammation: the role of cytokines

Serum from humans with an acute upper respiratory viral infection and from rabbits with turpentine-induced inflammation reduce the catalytic activity of hepatic cytochrome P450 (P450). The aim of this study was to identify the serum mediators responsible for the decrease in P450 activity. Rabbit and human sera were fractionated by size exclusion chromatography and the fractions tested for their ability to reduce the activity and amount of P450 after 4 h of incubation with hepatocytes from turpentine-treated rabbits (H(INF)). Rabbit and human sera decreased P450 activity by around 40% without any change in the amount of CYP1A1 and 1A2 apoproteins. In rabbit serum, the fraction containing proteins of M(r) 23-15 kDa decreased P450 content by 41%, but did not alter the amount of the apoproteins. Anti-IL-6 antibody added to the M(r) 23-15 kDa fraction restored P450 content to 97% of control values, while anti-IL-1beta, TNF-alpha and IFN-gamma antibodies had no effect. Supporting the role of IL-6, incubation of H(INF) in the presence of IL-6 for 4 h reduced P450 content by 40%. In human serum, the fraction containing proteins of M(r) >95 kDa lowered P450 content by 43% without modifying the amounts of CYP1A1/2. Neutralization experiments showed that IFN-gamma, IL-6, and IL-1beta contributed to the decrease in P450 content. In conclusion, the present results demonstrate that IL-6, and IFN-gamma, IL-6 and IL-1beta are the serum mediators released in vivo by a turpentine-induced inflammatory reaction in the rabbit and an upper respiratory viral infection in humans, respectively, inactivating hepatic P450.     

Characterization of the human kinetic adjustment factor for the health risk assessment of environmental contaminants

A default uncertainty factor of 3.16 (√10) is applied to account for interindividual variability in toxicokinetics when performing non‐cancer risk assessments. Using relevant human data for specific chemicals, as WHO/IPCS suggests, it is possible to evaluate, and replace when appropriate, this default factor by quantifying chemical‐specific adjustment factors for interindividual variability in toxicokinetics (also referred to as the human kinetic adjustment factor, HKAF). The HKAF has been determined based on the distributions of pharmacokinetic parameters (e.g., half‐life, area under the curve, maximum blood concentration) in relevant populations. This article focuses on the current state of knowledge of the use of physiologically based algorithms and models in characterizing the HKAF for environmental contaminants. The recent modeling efforts on the computation of HKAF as a function of the characteristics of the population, chemical and its mode of action (dose metrics), as well as exposure scenario of relevance to the assessment are reviewed here. The results of these studies, taken together, suggest the HKAF varies as a function of the sensitive subpopulation and dose metrics of interest, exposure conditions considered (route, duration, and intensity), metabolic pathways involved and theoretical model underlying its computation. The HKAF seldom exceeded the default value of 3.16, except in very young children (i.e., <≈ 3 months) and when the parent compound is the toxic moiety. Overall, from a public health perspective, the current state of knowledge generally suggest that the default uncertainty factor is sufficient to account for human variability in non‐cancer risk assessments of environmental contaminants. Copyright © 2013 John Wiley & Sons, Ltd.     

乙型脑炎减毒活疫苗外源病毒因子检查法阳性对照的选择

目的 选择合适的阳性对照供乙型脑炎(乙脑)减毒活疫苗外源病毒因子检查法(细胞培养法)使用.方法 细胞病变试验中,将乙脑病毒稀释成不同浓度,分别接种3种细胞,培养2～3 d,观察培养期末细胞病变.病变较典型时对应的病毒浓度即为本试验细胞病变阳性对照浓度.血吸附试验中,将植物血凝素经0.5％鸡、豚鼠红细胞悬液稀释成不同浓度,分别加入3种细胞中,置2～8℃或20～25℃0.5h,观察血吸附情况.血吸附较典型的植物血凝素浓度即为本试验血吸附阳性对照浓度.结果 乙脑病毒浓度为3～4 lg噬斑形成单位/ml时可引起20％～50％细胞病变,植物血凝素浓度为30～40 mg/L时可导致20％～50％细胞血吸附.结论 适当浓度的乙脑病毒和植物血凝素可作为外源病毒因子检查法的试验阳性对照.     

Subclinical effects of groundwater contaminants

Toxicity of environmental pollutants may be expressed as combined effects of a chemicals. Benzene, a proven hematotoxic agent, frequently occurs with toluene in cocontaminated groundwater. Groups of CD-1 male mice were exposed continuously for 4 weeks to benzene (166 mg/l), toluene (80 and 325 mg/l), and combinations of benzene (166 mg/l) + toluene (80 mg/l or 325 mg/l) in drinking water. Benzene-induced anemia was alleviated by simultaneous toluene treatment. Leukopenia and lymphopenia were observed in the case of benzene only and benzene + toluene (80 mg/l)-treated mice. The cytopenia, however, was less severe in the benzene + toluene (325 mg/l)-treated group. Immunotoxicity induced by benzene treatment alone was characterized by involution of thymic mass and suppressions of both B- and T-cell mitogeneses, mixed lymphocyte culture response to alloantigens, the tumor lytic ability of cytotoxic T-lymphocytes as determined by 51Cr-release assay, and antibody production response to T-dependent antigen (sheep red blood cells). IL-2 secretion by Con A-stimulated mouse T-cells was decreased in the benzene-treated group. Toluene (325 mg/l) completely inhibited these adverse effects when it was coadministered with benzene, while the low dose of toluene (80 mg/l) did not protect against benzene-induced depressions of immune functions. Toluene administered alone at levels up to 325 mg/l showed no obvious immunotoxic effects. Results of this study demonstrated that toluene, in sufficient amounts, has an antagonistic effect on benzene immunotoxicity.