The epidemiology of acute intestinal infections of undetermined etiology in children

Materials obtained in the study of conditions for contacting acute enteric infections of uncertain etiology, based on the analysis of the age structure of patients, the structure of clinical diagnoses and the monthly dynamics of cases registered in one of the districts of Moscow for 3 years (1984-1986), are presented. An important role of the alimentary factor in the spread acute enteric infections of uncertain etiology among the population of different age groups and everyday contacts in the spread of such infections among young children has been shown. The authors put forward a suggestion concerning the formation of natural immunity to infective agents, serving as etiological factors in the development of enteric infections of uncertain etiology, in children of preschool age.     

Estimation of Uptake of Humic Substances from Different Sources by Escherichia coli Cells under Optimum and Salt Stress Conditions by Use of Tritium-Labeled Humic Materials

The primary goal of this paper is to demonstrate potential strengths of the use of tritium-labeled humic substances (HS) to quantify their interaction with living cells under various conditions. A novel approach was taken to study the interaction between a model microorganism and the labeled humic material. The bacterium Escherichia coli was used as a model microorganism. Salt stress was used to study interactions of HS with living cells under nonoptimum conditions. Six tritium-labeled samples of HS originating from coal, peat, and soil were examined. To quantify their interaction with E. coli cells, bioconcentration factors (BCF) were calculated and the amount of HS that penetrated into the cell interior was determined, and the liquid scintillation counting technique was used as well. The BCF values under optimum conditions varied from 0.9 to 13.1 liters kg⁻¹ of cell biomass, whereas under salt stress conditions the range of corresponding values increased substantially and accounted for 0.2 to 130 liters kg⁻¹. The measured amounts of HS that penetrated into the cells were 23 to 167 mg and 25 to 465 mg HS per kg of cell biomass under optimum and salt stress conditions, respectively. This finding indicated increased penetration of HS into E. coli cells under salt stress.Humic substances (HS) are natural organic compounds comprising 50 to 90% of the organic matter of peat, coal, and sapropel (i.e., sludge that accumulates at the bottom of lakes), as well as of the nonliving organic matter of soil and water ecosystems (9, 34, 53). Being the products of stochastic synthesis, HS are characterized as polydispersed substances having elemental compositions that are nonstoichiometric and structures which are irregular and heterogeneous. Thus, it is not possible to assign an exact structure to HS. Instead, they are operationally defined using a model structure predicated on available compositional, structural, functional, and behavioral data: a model structure containing all the same basic structural units and types of reactive functional groups (46). HS have been demonstrated to contain a large amount of residues resembling the original building blocks (aromatic subunits, amino acids, carbohydrates, etc.) (51) as well as polyphenolic components with nonhydrolyzable C-C and ether bonds (51, 16). Since humic matter is a complex mixture of organic substances, HS yield extremely high polydispersity values (i.e., the ratio of weight-average molecular weight to the number-average molecular weight [M_w/M_n]), which vary within the range of 1.64 to 4.40 (38). These extremely high polydispersity values mean that even though they yield relatively high values of molecular weight, HS contain a low-molecular-weight fraction.HS are known to play important roles in protecting microorganisms and higher plants from climatic and technogenic stresses, such as pollution, draught, UV irradiation, and pathogen and viral infections (2, 22, 31). However, mechanisms underlying protective functions of these natural systems are still poorly understood. The primary reason for that is a lack of experimental tools for tracking uptake and distribution of natural organic mixtures in living cells and tissues, which makes it extremely difficult to link structure and functions in systems of such high complexity. Besides, predicting HS behavior in biological systems is extremely arduous, as HS are complex mixtures with a number of concurrent properties, such as polyanionic and polyelectrolyte character, hydrophilic and hydrophobic moieties, different functional groups, etc.The most straightforward hypothesis is that the biological activity of HS depends on both hydrophobic and hydrophilic characteristics of structural components (56). This hypothesis implies that the biological effects of HS are connected to membrane activity (12, 44, 56). Sorption of HS onto cells is the best documented phenomenon; numerous studies include phytoplankton (7, 15, 36, 57), isolated fish gill cells (7), bacteria (13, 14, 27, 57), fungi (60), and plants (12, 31, 44). This suggests that the sorption of HS onto biological membranes is a general process, but very few quantitative estimates are available (13, 36). Moreover, the penetration of HS into the living cells is still questionable, and to the best of our knowledge, only one study has reported a direct estimate of HS uptake by microorganisms (10).The main complication that arises in the study of the interactions of HS with living cells is the lack of a reliable analytical technique for determination of HS in the presence of biomolecules (e.g., proteins, lipids, and saccharides). To overcome the problem, radioactive labeling of HS is being used widely for this purpose. However, the reported studies deal predominantly with synthetic rather than with native humic materials (49, 50, 58). This is because of the approaches used for the radioactive labeling of the humics used in those studies, which involve either composting of a labeled precursor (e.g., ¹⁴C-glucose) with a soil sample (17) or the synthesis of model polymeric compounds. The polymeric compounds either are synthesized by enzyme-mediated oxidative polymerization of phenolic compounds, which is initiated by adding H₂O₂ in the presence of horseradish peroxidase (19), or proceed spontaneously in the presence of oxygen or other oxidants at an alkaline pH (48). When phenolics are polymerized with nonaromatic precursors (e.g., proteins, peptides, amino acids, carbohydrates, and amino sugars), the resulting humic-like materials are very similar to natural HS (19). These methods can be used for producing both ¹⁴C- and ¹⁵N-labeled humic-like substances. Their substantial disadvantage is that the resulting materials are similar but not identical to natural HS. Given high structural heterogeneity and irregularity inherent within HS, the availability of a broad set of labeled humic materials identical to their natural counterparts is a prerequisite for disclosing the mechanism of their interactions with living organisms on the cellular and organismal levels.The goal of this work was to study the behavior of humics in a simple microbial system using humic substances from various natural sources. For this purpose, six natural humic materials with different molecular features and properties were isolated from various natural sources and then labeled with tritium using a technique developed in previous studies (3, 4). A strain of the well-studied bacterium Escherichia coli was used as a model bacterial culture. The molecular weight of humics is quite high and is generally considered to be the leading factor restricting their uptake by living cells. In view of our study, prokaryotic bacteria seemed to be the most appropriate model, as recent evidence suggests that size differences among eukaryotic homologues of integral membrane proteins are consistently larger than their bacterial counterparts (8).To demonstrate the potential strengths of using tritium-labeled HS for biological study, uptake of HS by bacterial cells under stress conditions was also studied. One way in which bacteria respond to environmental change is to regulate cell membrane permeability. Thus, another goal of this work was to monitor changes in HS-bacterium interactions under salt stress conditions. For quantitative indicators, bioconcentration factors, maximum adsorption, and the amount of HS that penetrated into the cell interior were used.     

Effect of an alternating magnetic field of industrial frequency on the lipid composition of the rat liver

Multiple application (15 runs for 5 hours a day) of an alternative magnetic field of industrial frequency causes changes in lipid spectrum and phospholipid fractional composition of mitochondria and postmitochondrial fraction in rat liver. A decrease in the level of free fatty acids, triglycerides and cholesterol esters in mitochondria is registered, which presumably indicates an increase of the fats use in the cell's energetics. Changes in the phospholipid composition of mitochondria are negligible. In contrast to mitochondria, accumulation of lipids--triglycerides, cholesterol and its esters against a background of disbalance in phospholipid composition is established, which may presumably be one of the reasons for development of destructive infringements in the liver parenchyma during application of the alternating magnetic field.     

高温油藏内源微生物及其提高采收率潜力研究

大港孔店油田油藏特征、流体和微生物性质分析结果表明, 属于高温生态环境, 地层水矿化度较低, 氮、磷浓度低, 而且缺乏电子受体, 主要的有机物来源是油气。油田采用经过除油处理的油藏产出水回注方式开发, 油层中存在的微生物类型主要是厌氧嗜热菌, 包括发酵菌(102个/mL~105个/mL), 产甲烷菌(103个/mL); 好氧菌主要存在于注水井周围。硫酸盐还原菌(SRB)还原速率0.002 mg S2-/(L·d) ~18.9 mg S2-/(L·d), 产甲烷菌产甲烷速率0.012 mgCH4/(L·d)~16.2 mgCH4/(L·d)。好氧菌能够氧化油形成生物质, 部分氧化产物为挥发性脂肪酸和表面活性剂。产甲烷菌在油氧化菌液体培养基中产生CH4, CO2为好氧微生物和厌氧微生物的共同代谢产物。这些产物具有提高原油流动性的作用。用示踪剂研究了注入水渗流方向。通过综合分析, 油藏微生物具有较大的潜力, 基于激活油层菌的提高采收率方法在该油田是可行的。     

Prevalence of skin ulceration in cod (<Emphasis Type="Italic">Gadus morhua callarias</Emphasis> L.) under anthropogenic contamination in the southeastern part of the Baltic Sea

Data on the occurrence of skin ulceration cases and concentrations of anthropogenic contaminants (PCBs; DDT; PAN; and heavy metals Hg, Pb, As, and Cd) in Baltic cod in the Russian exclusive economic zone (EEZ) of the southeastern part of the Baltic Sea are presented and an attempt is made to analyze the relationship between the prevalence of disease and contaminant concentrations. In 2005–2009 the prevalence of skin ulcers was 0.7%. The share of skin ulceration in fish was maximal in 3- and 6-year-old cod (1.0 and 1.1%, correspondingly) and in fish of the size group 39–45 cm (0.9%). Since 2007, a reduction of skin ulceration cases has been recorded in the Russian EEZ of the southern Baltic Sea. In 2005–2009, the concentration of contaminants in cod tissues did not exceed the permissible levels accepted in the Russian Federation. The relationship between the concentration of PCBs in skin and the prevalence of ulceration cases requires further studies.     

Serum immunoglobulin levels in various forms of meningococcal infection and in meningococcus carriers

The levels of serum IgG, IgA and IgM were examined in 191 adults including 103 patients with various forms of meningococcal infection, 32 meningitis convalescents and 56 carriers, in order to elucidate the causes of different susceptibility to the meningococcal infection. The IgD level was determined in 54 meningitis patients as well as in convalescents and carriers. The amount of immunoglobulins was determined by radial immunodiffusion. The level of IgG at the beginning of the disease in patients with the generalized forms of meningococcal infection (meningitis, meningitis combined with meningococcaemia, meningococcaemia) was found to be considerably lower than in healthy subjects. The levels of all immunoglobulins, particularly of IgA and IgM, increased in the course of the disease. The levels of IgG, IgA and IgM in meningitis convalescents a year after recovery were found to be the same as in the controls. The levels of IgG, IgA and IgM in patients with meningococcal nasopharyngitis were significantly lower than in healthy subjects. The carriers showed a decreasd level of IgA and a considerably increased level of IgG while the levels of IgM and IgD did not differ from the control.     

Localization of ATPase activity, respiration and ultrastructure of wheat root cells with modulated ion conductivity of plasma membrane

Changes in the localization of ATPase activity, respiration and ultrastructure of wheat root cells with modulated ion conductivity of plasma membrane were studied. A 2 h treatment of excised root with valinomycin (20 microM), N,N-dicyclohexylcarbodiimid (100 microM), gramicidin S (20 microM) and chlorpromazine (100 microM) caused an increased loss of potassium by cells, a decreased respiration and changes in the localization of ATPase activity and in cell ultrastructure. Differences in the observed changes may be conditioned by different mechanisms of action of the membrane active compounds used. It is concluded that changes in the localization of ATPase activity and ultrastructure may indicate some early specific responses of root cells, whereas the increase in the ion conductivity and decrease in respiration under disruption of ion homeostasis caused by membrane active compounds indicate unspecific responses of cells.