Toxicity and character of the effect of some zinc compounds

Investigation of the parameters of toxicity of 8 zinc compounds revealed some differences in the degree of their risk for persons working with them. The following TSELs (tentative safe exposure levels of harmful substances) have been determined: 0.5 mg/m3 for zinc nitrate and hydrogen and dihydrogen zinc phosphates, 2 mg/m3 for zinc carbonate and zinc selenide, as well as MAC (maximum allowable concentration) for zinc sulphide equal to 5 mg/m3. No TSEL have been set for zinc caprylate and zinc stearate, but intratracheal administration of 50 mg caprylate caused 100%, of stearate 50% death of experimental animals due to pulmonary edema. Maximum tolerable doses were 10 and 1 mg, respectively. Zinc nitrate shows an expressed irritative effect on the skin and a highly expressed effect on the conjunctiva. Zinc phosphates, zinc caprylate and zinc stearate are resorbed by the skin. In all cases, working persons must be protected from the effect of the compounds under study because even though the toxicity of a compound may be rather low, highly noxious compounds may develop in the course of the technological process, e.g., in mechanical treatment of zinc selenide and zinc sulphide monocrystals, hydrogen selenide and hydrogen sulphide, respectively, can be isolated.     

On the establishing of permissible relations between MACC- and MACT-values of harmful substances

The establishment of MACC (Ceiling Values) and MACT (Time Weighted Average Values) for chemical substances permits a substantial more precise evaluation of the exposure to harmful substances at the work place as if only one limit value is given without reference to a Ceiling Value or a Time Weighted Average Value, respectively. The derivation of MACC- and MACT-Values is proposed from toxicometric data that are gained during animal experiments with chemical substances. For acutely toxic substances (e.g. irritants) the quotient F = MACC/MACT ought to be = 1. For cumulative acting substances the permissible relation of both values is determined from the magnitude of the zone of chronic effect (Zch) as F = 0.4. Zch. The condition MACC less than less than Limac takes into consideration at the same time. The frequency and the duration of MACT exceedings need not to be regulated with this procedure. A method is proposed for the derivation of the length of sampling periods necessary from the toxicological point of view starting from the Zch.     

Hygienic examination of the stimulating effect on the organism of a complex of natural substances

No exhaustive hygienic studies have been conducted yet of the natural substances present in the atmosphere. A complex of natural substances was shown to affect EEG parameters, subjective perception of one's health and general perception. The concentration of the vapours of a mixture of substances was kept at 0.1 mg/m3 which is characteristic of mountainous air. The inhalation of the natural substances was shown to alter the EEG indicators and subjective perception of tested subjects, suggesting a stimulatory effect on the central nervous system. The natural substances proved to stimulate the efficiency of mental and manual work, self-perception and mood. These effects can be accounted for by the positive biological influence of the mountainous atmosphere.     

Sampling of working-zone air and biomaterials and unification of MPC values

Some points concerning the strategy of working-zone-air sampling, the sampling plan and the manner of sampling biological materials have been discussed. In drawing up an air-sampling plan, the following items should be paid attention to: production technology, organization, physicochemical properties and composition of the raw materials, intermediate and final products, potential sources of spread of harmful substances and their spread from these sources, the time picture of workers' presence, the analytical method and the concentration of the harmful substances in the working-zone atmosphere. In order to unify MPC's within the frame of CMEA, one should be informed about the norms and standardized methods in force in each country, work out and unify principles for sampling the air and biomaterials and work out a project of a unified way of evaluating analysis results.     

Anesthetic requirement of isoflurane is reduced in spontaneously hypertensive and Wistar-Kyoto rats

The isoflurane requirement to keep 50% of rats (Rattus norvegicus) unresponsive to noxious stimuli (MAC) was determined in age matched Sprague-Dawley (SD, n = 8), Spontaneously Hypertensive (SHR, n = 8) and Wistar-Kyoto (WKY, n = 8) strains. Following induction and orotracheal intubation, each rat received isoflurane (1.65% end-tidal) for 120 minutes. Physiologic parameters were similar except for expected differences in mean arterial pressure (148 +/- 13mmHg-SHR group, 101 +/- 10mmHg-SD group and 94 +/- 12mmHg-WKY group [mean +/- standard deviation]). Anesthetic equilibration was verified by infrared analysis of end-tidal gases. MAC was then determined in each rat by the tail clamp method and a group MAC calculated.     

腐殖质在环境污染物生物降解中的作用研究进展

腐殖质物质在地球的生态环境中大量存在,它不仅可以在有毒化合物的生物降解和生物转化过程中起到氧化还原中间体的作用,加速有毒物质的降解和转化。也可以作为唯一末端电子受体,接受来自一些有机酸或者甲苯等环境中有毒物质提供的电子,偶联能量的产生,支持菌体的生长,形成一种新的细菌厌氧呼吸形式——腐殖质呼吸。因此,对腐殖质在环境有毒物质的生物降解和生物转化过程中的作用进行研究,不仪对于深入理解细菌呼吸的本质具有重要的理论意义,而且对于环境有毒物质的降解和转化以及元素的生物地球化学循环具有重要的生态学意义,同时对地球表面的有毒物质进行更有效的生物降解具有重要的现实意义。     

Effect of isoflurane, atracurium, fentanyl, and noxious stimulation on bispectral index in pigs

The study reported here was done to determine the relationship between anesthesia depth and bispectral index (BIS) in stimulated pigs. Isoflurane minimal alveolar concentration (MAC) was determined using the tail-clamp method in 16 Yorkshire/Landrace-cross pigs with mean+/-SEM weight of 27.7+/-1.76 kg. One week later, BIS, ECG, heart rate, arterial blood pressure, esophageal temperature, end-tidal CO2 tension and isoflurane concentration, arterial pH, PaO2, PaCO2, plasma bicarbonate concentration, and base excess were determined at each of five isoflurane MAC-multiples: 0.8, 1.0, 1.3, 1.6, and 2.0. Six treatments were studied: isoflurane; isoflurane and atracurium; isoflurane, atracurium, and fentanyl; isoflurane with noxious stimulation; isoflurane and atracurium with noxious stimulation; and isoflurane, atracurium, and fentanyl with noxious stimulation. The noxious stimulus during BIS measurement was the same as that for MAC determination. Each pig was studied three times (n = 8), and order of MAC-multiples and treatments was randomized. Data were evaluated by use of general linear model analysis of variance and linear regression analysis, with statistical significance set at P < 0.05. Significant differences in BIS values were identified between MAC-multiples within each treatment and between treatment 3 compared with treatments 2 and 4. Significant differences also were observed within and between treatments for heart rate, arterial blood pressure, and PaO2. Use of BIS appears reliable for identification of light versus deep anesthesia, but is of limited use for discrimination between isoflurane MAC-multiples of 1 and 1.6. We conclude that, compared with other treatments, atracurium and noxious stimulation had no significant effect on BIS.     

Prediction of dysbiotic effect in toxico-hygienic assessment of antibiotics

The results of the studies showed that there was relation between the changes in the size of the typhlon and the composition of the microflora of its contents under antibiotic effect. On the basis of the analysis of the literature data and the experimental results a new toxicometric index i. e. a typhlon weight coefficient was proposed. A procedure for probabilistic estimation of the index is described. Close coincidence of the values of the threshold concentrations determined by the typhlon weight coefficient and the bacteriological methods was observed.     

Intermittent exposure to toxic compounds in the working-zone atmosphere viewed from the aspect of hygienic standardization

Four highly cumulative substances (carbon tetrachloride, 1,1,2,2-tetrachloroethane, benzene and dimethylformamide) were studied at two exposure levels under a monotonous and an intermittent exposure regimen in subacute experiments on rats. The biological effect produced by the intermittent concentrations as compared with the stable concentrations under time-weighted average concentrations depended both on the physiochemical properties and biological action of the poisons as well as on the exposure level. The intermittent concentration rises within certain limits (threefold as a rule) were injurious with some of the substances at a relatively high exposure level, but were not detrimental as compared with stable concentrations at a low exposure level. The other substances showed no difference between the effect of the monotonous and the intermittent regimens at either low or high exposure levels. The results of these studies form an experimental basis for a dual hygienic standardization: the establishment of maximum and average-shift admissible concentrations for the compounds studied as well as other highly cumulative substances.     

Reduction of isoflurane MAC with buprenorphine and morphine in rats

Preoperative analgesics are being increasingly used to provide analgesia in the intraoperative and postoperative period. Opioids reduce anaesthetic requirements, although the effect varies with the different drug and species. The aim of this work was to determine whether buprenorphine reduces the minimum alveolar concentration (MAC) of isoflurane in a dose-related fashion, and whether this effect is similar to morphine when clinical doses of both drugs are used in the rat. Thirty-six male Wistar rats were anaesthetized with isoflurane, and MAC was determined before and after the administration of either buprenorphine or morphine. MAC of isoflurane was determined from alveolar gas samples when a standard noxious stimulus, in the form of a tail clamp, was applied. The duration and degree of reduction of the MAC of isoflurane were recorded. Basic cardiovascular and respiratory measurements were also recorded. Buprenorphine (10, 30 and 100 microg/kg) and morphine (1, 3 and 10 mg/kg) reduced in a dose-dependent fashion the MAC of isoflurane by 15%, 30% and 50%, respectively. Buprenorphine resulted in less cardiovascular and respiratory depression and had a longer-lasting action than morphine. In conclusion, buprenorphine has a dose-related isoflurane sparing effect in the rat similar to that caused by morphine at clinical doses of both drugs.     

Hygienic and toxicological aspects of occupational and environmental exposure to beryllium

As the production of missile, nuclear devices and electronics grew and modern industrial technologies emerged the risk of the occupational exposure to beryllium has become increasingly common and widespread. The environmental burden of beryllium is also on the increase, not only as a result of emissions from plants producing and processing beryllium, or its alloys and compounds, but also from burning coal of higher beryllium content in some localities. This article discusses primarily the hygienic and toxicologic aspects of beryllium and its threat to human health. The following topics are included in this review: occurrence, production and uses of beryllium; its metabolism and experimental toxicology; clinical toxicology and pathogenesis of berylliosis; hygienic and epidemiologic aspects of berylliosis; berylliosis treatment and prevention. Berylliosis is here characterized as a disease combining clinical manifestations of pneumosclerosis, allergy to beryllium and, in its granulomatous form, autoimmune reactions. Importantly, the available technical means and measures can ensure that the both occupational and environmental exposure to beryllium can be kept below the established MAC values. If occasionally impossible, special preventive measures should be adopted. It is essential that all persons with allergy be prophylactically excluded from work at risk of exposure to beryllium.     

Application of toxico-kinetic criteria as a basis for toxicometric parameters

In an experiment with single exposure to benzene and styrene at a level corresponding, to the threshold of harmful effect established by functional indices the intensity of metabolism was found to decrease. Toxico-kinetic characteristics of the substance in a single experiment permit us to prognosticate the risk of developing chronic intoxication. In comparison with indices characterizing general state of the organism, toxicokinetic indices enhance the reliability of toxicometric parameters used in determining Mac's for the air of the working area.     

Relationship of feline bispectral index to multiples of isoflurane minimum alveolar concentration

The study reported here was done to determine the relationship between bispectral index (BIS) values and minimum alveolar concentration (MAC) multiples of isoflurane in cats. Isoflurane MAC was determined using the tail-clamp method in eight domestic cats. Ten days later, the cats were anesthetized a second time with isoflurane at each of five MAC multiples administered in random order. Ventilation was controlled and, after a 20-min equilibration period at each MAC multiple of isoflurane, BIS data were collected for 5 min and the median BIS value calculated. Data from each isoflurane MAC multiple were compared using analysis of variance for repeated measures, and statistical significance was set at P < 0.05. The MAC of isoflurane (mean +/- 1 standard deviation) was 1.8% +/- 0.2%. BIS values at 0.5 MAC could not be recorded due to spontaneous movement in all eight cats. BIS values at 2.0 MAC were confounded by burst suppression in seven of the eight cats. Over the range of 0.8 to 1.5 MAC, BIS values decreased significantly with increasing end-tidal isoflurane concentrations. Mean (+/- 1 standard deviation) BIS measurements were 32 +/- 3 at 0.8 MAC, 20 +/- 4 at 1.0 MAC, and 5 +/- 3 at 1.5 MAC. Therefore, BIS values are inversely and linearly related to end-tidal isoflurane concentrations in anesthetized cats. However, the consistently low BIS values recorded in this study suggest that clinical BIS endpoints used to titrate anesthetic agents in humans may not be applicable to cats.     

Potency of isoflurane and nitrous oxide in conventional swine

The minimum alveolar concentration (MAC) of isoflurane in oxygen (O2) was determined to be 1.55 +/- 0.08 (SEM) volumes % in twelve pigs (Sus scrofa). Values for isoflurane MAC in the presence of 50% (I-50%N2O) and 66% (I-66%N2O) nitrous oxide were determined in nine and six of these same animals, respectively, and equalled 1.03 +/- 0.05 vol % for I-50%N2O and 0.95 +/- 0.07 vol % for I-66%N2O. Animals respired spontaneously and arterial blood pressure (AP), heart rate (HR), rectal body temperature, and arterial blood gases (PO2, PCO2, and pH) were recorded throughout the study period. These parameters were within normal limits near MAC for all three gas combinations. The MAC for isoflurane in swine was similar to that for other animals and, man and the use of this agent was associated with rapid and uneventful anesthetic induction and recovery. The addition of 50% and 66% nitrous oxide (N2O) reduced the isoflurane MAC by 30% and 42%, respectively.     

Evolution of dietary specialization and chemical defense in poison frogs (Dendrobatidae): a comparative analysis

Defensive mechanisms, including noxious or toxic substances, are favored by predation-driven natural selection. The acquisition of noxious/toxic substances can be either endogenous, in which the substances are produced by the organism, or exogenous, in which the substances are produced by another organism and are sequestered. Evidence indicates that the defensive skin alkaloids of Neotropical poison frogs (Dendrobatidae) have an exogenous source: a diet of ants and other small alkaloid-containing arthropods, which we term the diet-toxicity hypothesis. A critical prediction of the diet-toxicity hypothesis is that independent origins of dietary specialization will be found to be correlated with independent origins of skin alkaloids. We tested this prediction in an integrated framework using comparative methods with new and published data on feeding ecology and chemical defense for 15 species of dendrobatids in five genera. We found a significant correlation between alkaloid profiles and degree of dietary specialization. This reveals a recurring association of dietary specialization and alkaloid sequestration in dendrobatids, which suggests parallel evolutionary trends in the origins of defensive mechanisms.     

肠上皮快速复原过程中的细胞信号传递: 多胺和K+通道的影响

胃肠道粘膜上皮细胞具有重要的屏障作用,可以保护次上皮组织抵御一系列的有害物质,包括过敏原、病毒以及微生物病原体。粘膜损伤后的修复有赖于上皮细胞对信号网络的调节,而这一网络系统控制着基因的表达、细胞的存活、迁移及增殖。近几年的研究结果显示,在胃肠道粘膜的修复中,多胺起到关键作用;且细胞多胺的调控是众多信号传递路径的焦点。本文简要综述了多胺在肠粘膜上皮快速复原中的功能和机制,特别是对K^ 通道活性的影响。     

On-line identification of parameters in a fermentation process

In a fermentation process, the establishment of gas mass balances provides valuable information and allows both measurements concerning the characteristics of the biomass itself and the monitoring of a cultivation process. If the quantity and oxidation level of substances excreted into the fermentation broth are known or constant, the yield factor and the dry cell-weight production are stoichiometrically related to the quantity of CO₂ evolved and to the quantity of O₂ consumed. Where frequent measurements of both yield factor and dry cell-weight production are desirable or where rapid adjustment of the parameters is necessary, on-line identification of these parameters is required, An algorithm allowing the identification of the specific growth rate is presented. Moreover, this technique allows one to estimate the percent protein in the biomass during continuous culture.     

Plantlet recruitment is the key demographic transition in invasion by Kalanchoe daigremontiana

Biological invasions have a great impact on biodiversity and ecosystem functioning worldwide. Kalanchoe daigremontiana is a noxious invasive plant in arid zones. Besides being toxic for domestic animals and wildlife, this species inhibits the growth of native plants. Its rapid proliferation in Cerro Saroche National Park (Venezuela) is of great concern because this area hosts several species endemic to the scarce arid zones in the Caribbean. The traits of K. daigremontiana that contribute to its invasive success are unknown. Based on empirical data, we derived a stage structured, stochastic and density-dependent model, to identify characteristics relevant for its establishment. Sensitivity analyses revealed that the establishment of K. daigremontiana depends exclusively on plantlet recruitment. Because asexual plantlets reproduce in less than 1 year populations are able to increase rapidly during the initial phases of invasion, when extinction risks are higher. Sexual seedlings, on the contrary, require a minimum of 3 years to reproduce. As a result, seedling recruitment contributes little to the transient dynamics of the population and therefore cannot warrant the successful establishment of the species. Simulations of various management strategies show that eradication through plant removal may only be achieved if harvest begins shortly after introduction. If a rapid response is not possible, reducing the survival and growth rates of plantlets through biological control is an alternative option. Thus, a strict control of dispersal of plantlets by humans and a continuous monitoring of new invasions should be the first priority for reducing further impact on native species.     

Physicochemical, toxicological and hygienic aspects of ethylene oxide application for the sterilization of medical products. III. Setting hygienic norms in sterilized medical products

Some of the drawbacks are discussed associated with hygienic norms for gaseous sterilizing agents in polymeric products for medical applications. A new approach is proposed for regulating ethylene oxide (EO) in such products. To this end, limiting types of biological effect and its pathways have been determined and substantiated as well as the reliability factor for establishing hygienic norms for EO in medical products. Daily threshold EO limit values were calculated for momentary and repeated exposure of humans. The duration of long-term and short-term exposure of the patient to sterilized products was evaluated on the basis of EO extraction kinetics from a variety of materials. Using daily threshold limit values, threshold residual values (TRV) of EO were calculated for different groups of polymeric products for medical applications.     

Utilization of data obtained in pilot acute experiments for practical hygienic assessment of a chemical substance

A large number of the chemical substances and preparations (compositions) that are incorporated into the national economy cannot be subjected to long-term and detailed testing for toxicity and safety. There are simple methods on the acute experimental level which can serve as a basis for working out the necessary prophylactic measures in introducing new substances into the industry. Determination of LD50 upon intragastric administration, intravenous administration (model of rapid penetration into the organism), static inhalatory treatment under saturated concentration, determination of the primary local effect of the skin and mucous membranes, together with careful observation of the behaviour of the experimental animals, signs of their intoxication and their death, as well as comparison of the physico-chemical properties of the substance and its already familiar structural analogues may serve as the ground for predicting the biological significance of the new substance even at longer terms of contact with the organism and making toxicological and hygienic assessments under concrete technological conditions.