Various toxic effects of nitrates and nitrites]

The main features of the long-term toxicity of nitrates and/or nitrites in man and experimental animals are reviewed; the possible formation of carcinogenic nitrosamines is dealt with in another paper of this series. It appears that the allowable daily intake of nitrates and nitrites for the healthy adult man has been evaluated chiefly from the no-effect levels in rats. First, the no-effect levels in rats are questionable, since some experiments have pointed out adverse effects of nitrates and nitrites with dosages near, or lower than, the so-called no-effect levels. Second, there is a risk that the allowable daily intake is outpassed in the diet of a man. Third, nutritional conditions, such as the vitamin A or C, or the iodine content of the diet, as well as other factors which are discussed, might alter theno-effect levels. From the cell metabolism viewpoint, nitrites are inhibitors of oxidative phosphorylation and of microsomal enzymes. Our present lack of knowledge does not yet allow us to explain the long-term toxicity of nitrates and nitrites in terms of cell metabolic disturbances.     

Morphological evaluation of toxic effect of kartolin-2

Lipid dystrophy, rapid reduction of RNA and glycogen content in the liver of all experimental rats, developing as a result of acute kartolin-2 poisoning testify to an expressed hepatotropic effect of the substance. Alongside with the processes of parenchymal liver cell damage the signs of intracellular regenerating processes--increase of the size of hepatocytes nuclei are detected. Liver protein metabolism disturbances are observed following exposure to kartolin-2 in the acute experiment. Chronic exposure to kartolin-2, and, specifically to its preparation form in the dose 1/100 LD50 cause lipid infiltration, reduction of histochemical indicators of liver glycogen, and RNA content. No-effect doses of kartolin-2 have been determined.     

Biological prevention of combined effects of toxic metals and organic substances

The antitoxic activity of several biological prophylactic complexes was studied in subchronic experiments on inbred albino rats exposed to a metal combination of leadchromium-arsenic-manganese-vanadium and benzo(a)pyrene, as well as phenol or naphthalene, and combinations of naphthalene-lead and phenol-naphthalene-lead. It has been shown that upon simultaneous exposure to the study combination of metals and organic poisons, it is advisable to use a biological prophylactic complex involving glutamic acid, a pectin enterosorbent, the multivitamin agent "Vitrum-Kids", calcium, vitamin C, glycine, methionine, and "Iodomarin".     

A method for evaluating effects of toxic chemicals on the productivity of freshwater ecosystems

The finding that trout apparently consumed more invertebrates than were produced in the Horokiwi stream has been described as "Allen's paradox." One explanation for this is that invertebrate sampling techniques underestimate the standing crop. If so, trout growth might be a relatively sensitive indicator of the effects of toxic chemicals on the productivity of experimental ponds. In a replicated pond experiment, methyl parathion was applied at concentrations toxic to invertebrates but not to fish. Three 50-m3 ponds were treated at 40 micrograms liter-1 and three at 10 micrograms liter-1, and there were three untreated controls. Each pond was stocked with eight small, individually marked rainbow trout. The fish were removed by electrofishing 3 weeks after treatment. Mean growth rate of fish in control ponds was 6.3% per day, 4.3% per day in ponds treated with 10 micrograms liter-1, and 3.7% per day in ponds treated with 40 micrograms liter-1. Effects were significant at the 1% level. The standing crop of invertebrates was apparently insufficient to support the growth of the fish, an indication that the active, predatory rainbow trout is more efficient at sampling invertebrates than standard limnological procedures.     

Rapid and simple method for quantitative evaluation of neurocytotoxic effects of radiation on developing medaka brain

We describe a novel method for rapid and quantitative evaluation of the degree of radiation-induced apoptosis in the developing brain of medaka (Oryzias latipes). Embryos at stage 28 were irradiated with 1, 2, 3.5, and 5 Gy x-ray. Living embryos were stained with a vital dye, acridine orange (AO), for 1-2 h, and whole-mount brains were examined under an epifluorescence microscope. From 7 to 10 h after irradiation with 5 Gy x-ray, we found two morphologically different types of AO-stained structures, namely, small single nuclei and rosette-shaped nuclear clusters. Electron microscopy revealed that these two distinct types of structures were single apoptotic cells with condensed nuclei and aggregates of apoptotic cells, respectively. From 10 to 30 h after irradiation, a similar AO-staining pattern was observed. The numbers of AO-stained rosette-shaped nuclear clusters and AO-stained single nuclei increased in a dose-dependent manner in the optic tectum. We used the number of AO-stained rosette-shaped nuclear clusters/optic tectum as an index of the degree of radiation-induced brain cell death at 20-24 h after irradiation. The results showed that the number of rosette-shaped nuclear clusters/optic tectum in irradiated embryos exposed to 2 Gy or higher doses was highly significant compared to the number in nonirradiated control embryos, whereas no difference was detected at 1 Gy. Thus, the threshold dose for brain cell death in medaka embryos was taken as being between 1-2 Gy, which may not be so extraordinarily large compared to those for rodents and humans. The results show that medaka embryos are useful for quantitative evaluation of developmental neurocytotoxic effects of radiation.     

Psychological evaluation of the emotional effects of a community toxic exposure

OBJECTIVE: We sought to assess the emotional effects of a major community toxic release while controlling the potential effects of response bias associated with litigation. METHODS: Participants included 152 exposed adult litigants and a matched unexposed comparison group (n = 76). Psychological assessment methods included: (1) Minnesota Multiphasic Personality Inventory-2; (2) Symptom Checklist-90-Revised; and (3) Impact of Event Scale-Revised. RESULTS: Ten to 40% of the exposed group demonstrated emotional distress (compared with a 5% comparison baseline) depending on indicator and cutoff score used. CONCLUSIONS: The psychological consequences of a community toxic exposure were present even when exaggeration was carefully controlled. Accounting for exaggeration in the assessment of subjective psychological complaints provides a more accurate view of the subjective emotional state of persons who have experienced toxic exposure thereby facilitating appropriate clinical management of their mental health needs.     

A comparative evaluation of acute action thresholds during the isolated and combined effects of boricid fungicide and its components (polycarbacin+sulphur)

The article contains a comparative analysis of the acute action thresholds in isolated and combined actions of boricide fungicide and its components when inhaled. To determine the predominant type of the combined action, a correlation analysis technique of dosage (concentration) dependences was used with regard both to mixtures and isolated components, as it was done in case with the lethality curves studies involving calculation of the combined action coefficient. The coefficient calculation technique used for the lethality levels can be adequately applied to the calculations of acute action thresholds of a permanent composition mixture by CE50 degrees and CE50 min.     

一种医院管理系统软件综合评审的方法

近几年来随着计算机技术的普及和医院管理水平的提高，越来越多的医院已建立或正在考虑建立一个医院内的网络系统，同时也希望买到一套适合本医院的管理信息系统软件。市场上的有关软件五花八门，使得医院决策者目不暇接，往往使决策者拿不定主意，在软件选择上花费了大量的精力和时间。在此我们介绍一种利用层次分析法进行软件质量评审的方法以供决策者们参考。　　《ＩＳＯ９００１ａｎｄＳｏｆｔｗａｒｅＱｕａｌｉｔｙＡｓｓｕｒａｎｃｅ》对于软件质量要素有如下描述，（１）、正确性（ｃｏｒｒｅｃｔｎｅｓｓ）：是指软件系统符合其需…     

应用基准剂量法探讨锰所致心脏的毒性作用

目的探讨尿锰的基准剂量(BMD)在锰所致心脏危害防治中的应用。方法选择广东省某厂电焊工人和电工为调查对象,根据工人尿锰含量将工人分为8组,分别统计各组工人的心电图异常人次和心电图异常率。结果随着工人尿锰含量的增加工人心电图异常率呈逐渐增加的趋势。根据工人尿中锰含量及其心电图异常率的剂量-反应关系计算的尿锰含量的BMD和基准剂量下限值(BMDL)为1.420和0.510μmol/L。结论根据该项BMD的计算结果可知,心电图异常率并不是制定尿锰生物接触限值敏感的生物指标。