Substantiation of hygienic standard of lincomycin in the air of the work area

The main parameters of lincomycin toxicometry were studied in animals. It was shown that the compound was low toxic after its oral or intraperitoneal administration in single doses, had no local irritant and skin resorptive effects and did not accumulate. The allergenic properties were slightly pronounced. The intoxication picture after a single inhalation was characterized by renal dysfunction, erythropenia, neutrophilia, lymphopenia and impairment of the normal intestinal microflora. The zone of the specific antimicrobial effect was equal to 8. On chronic inhalation, the signs of the specific antimicrobial effect were of the paramount importance: Limch am was equal to 4.7 mg/m3 and Limch exceeded 18.3 mg/m3. In the concentrations used, the substance had no embryotoxic and gonadotropic effects. The level of 0.5 mg/m3 (for Hazard Class 2) was recommended and approved as the maximum allowable concentration.     

Experimental data on hygienic norms for antibiotics of the tetracycline group]

Toxicity of tetracyclines was studied experimentally on different species of laboratory animals. It was shown that tetracycline, oxytetracycline and chlortetracycline were close by their chemical structure and physico-chemical properties, as well as by the main toxicity parameters, i.e. acute toxicity, cumulative activity, skin-irritating and sensitizing effect. Under the conditions of subacute experiments the above 3 antibiotics induced evenly pronounced one direction changes in animals. The data obtained during the experiments provided recommendation of the level of 0.1 mg/m3 as the maximum allowable concentration (MAC) of oxytetracycline and chlortetracycline, i.e. the same level as the previously recommended for tetracycline.     

Establishing of a minimal set of tests (minimal standards) to identify species included in the genus Mycobacterium

Mycobacterium genus includes over 100 species and subspecies; new species are discovered every year. Minimal standard criteria are represented by the resistance to acid-alcohol (e.g. in the Ziehl - Neelsen staining), the presence of some mycolic acids containing 60-90 carbon atoms that can be cleaved by pyrolysis in fatty acids with 22 - 26 carbon atoms and a guanine + cytosine content of the DNA of 61 to 71 mol %. The species with the highest rate of involvement are those from Mycobacterium tuberculosis complex, and tuberculosis is still one of the most widespread world diseases. The most important for a laboratory is to be able to identify the species from M. tuberculosis complex. We have done a series of experiments, their goal being to evaluate and establish a minimal set of useful tests for identification of mycobacterial species. We used strains from "Cantacuzino" Institute collection and applied a series of classical and modern methods. We appreciate that the minimal set of tests could be represented by the microscopic examination for acid-fast bacilli (AFB), the examination for the preferred growth temperature, the growth rate, the colonies morphology, pigmentation and photo reactivity, the niacin accumulation test, the test of nitrate reduction, the catalase test (in both variants), plus the susceptibility to Para-Amino Salicylic Acid, Para-Nitro-Benzoic Acid andto Tiophene-2-Carboxylic Acid Hydrazide.     

Implications of flexible work systems for work studies

The relationship between changing work systems and work study methods is discussed by focusing on a recent trend toward more flexible work systems in different countries. These systems are commonly characterized by (a) uncoupling of working hours from business hours, (b) combining different atypical work forms and (c) individualized work patterns. Increased flexibility in working patterns is demanded because business hours may be covered by different workers and because special arrangements become necessary for unpopular shifts or linking separate jobs. Changes in work systems seem more successful when they are associated with (a) multiskilled work, (b) independent task implementation, (c) networked communication, (d) balanced or adjusted workload, and (e) accommodation of workers' preferences. Special attention is drawn to safety and health concerns and work-life effects. Many intervention studies done for work improvement are paying attention to multifaceted work aspects, locally available options, and participation by people. All these elements are important because prepackaged solutions do not exist. The following three views seem especially useful for action-oriented work studies: 1) Look at multiple aspects of the work, including work content and atypical work forms; 2) Know worker preferences and available options; and 3) Take into account work elements that may not be well defined, but important from local points of view. It is envisioned that these studies can provide support for a well-informed participatory process of work system changes in each local context.     

Electronic particle counting for evaluating the quality of air in operating theatres: a potential basis for standards?

Airborne particle counting in eight size ranges (0.5 → 20 μm), by computerized electronic equipment, was compared with the numbers of bacteria-carrying particles (BCP) assessed by slit sampling in ultra-clean and turbulently ventilated operating theatres. In the ultra-clean theatre the number of particles of 5–7 μm size range correlated with BCP while peaks in the numbers of particles <3 μm and > 15 μm corresponded with activity. Comparative relationships also occurred in the turbulently ventilated theatre but the use of this equipment in that environment cannot yet replace counts of airborne bacteria. We consider that electronic particle counting in the 0–20 μm size range may be used to judge the performance of a clean air operating theatre distribution system, including efficiency and integrity of the filter/seal systems and the presence or absence of entrainment of bacteria and other particles. The sampling techniques and analysis of particle concentration results described here may be a suitable basis for standards.     

Kinetic studies on the mechanism of the penicillin amidase-catalysed synthesis of ampicillin and benzylpenicillin

Hydrophobic protein chromatography was used to prepare homogeneous fractions of penicillin amidase (EC 3.5.1.11) from E. coli. The apparent ratios of the rate constants for the deacylation of the acyl-penicillin amidase formed in the hydrolysis of phenylacetylglycine or D-phenylglycine methyl ester, by H2O and 6-aminopenicillanic acid (6-APA), were determined at different concentrations of the latter compound. The ratios were obtained from direct measurements of the initial rates of formation of phenylacetic acid and benzylpenicillin or D-phenylglycine and ampicillin. For the semisynthesis of ampicillin as well as of benzylpenicillin the ratio was found to depend on the concentration of 6-APA. This was observed for heterogeneous and homogeneous enzyme preparations. These results show that 6-APA must be bound to the acyl-enzyme before the deacylation, yielding ampicillin and benzylpenicillin, occurs. The dissociation constant KN for the formation of the complex was estimated to be approximately 10mM. This mechanism in which acyl-enzyme with and without bound nucleophile is involved, is in agreement with the principle of microscopic reversibility. Both acyl-enzymes can be deacylated by H2O. The finding that there is a specific binding site for 6-APA adjacent to the binding site for the phenylacetyl-(D-phenylglycyl-) group in the active site of the enzyme is supported by the observation that 6-APA acts as a mixed inhibitor in the hydrolysis of D-phenylglycine methyl ester. The ionic strength dependence indicates that the binding site for 6-APA of the acyl-enzyme is positively charged.     

Molecular-size standards for use in radiation-inactivation studies on proteins.

The accuracy of the radiation-inactivation technique for estimating molecular size was investigated with a range of proteins of known molecular mass. With the use of irradiation with a 16 MeV electron beam, inactivation was examined both in frozen samples at 77 K and in freeze-dried samples at room temperature. The effect of the presence of detergents and chloroplast membrane preparations was also measured. It was demonstrated that proteins added as internal standards, including malate dehydrogenase, glucose-6-phosphate dehydrogenase and cytochrome c, can provide an accurate calibration of molecular size. However, a disadvantage of the technique was that the target size of oligomeric enzymes could be that of either the monomers, dimers or higher oligomers. The detergent Triton X-100 increased the rate of inactivation of the proteins investigated.     

Evaluation of the results of animal studies with a scheme of serologic reactions according to a table of standards]

The authors suggest a method of processing of the data of examination of the animals in the system of serological reactions for the purpose of diagnosis of epizootic situations in the natural plague foci. Positive results are recorded in a table in the form of a grid whose cells correspond to all possible variants of the two reaction titres. The table is divided into 6 sections into which the results differing by the correlation and the absolute reaction titres (the standard grid) are placed. The frequency of reactions is determined by the grid sections in the regions in which the character of the epizootic development in nature was studied by bacteriological examination of the animals. The diagnostic scale is drawn by the results of such standard observations. The trial of the suggested method was carried out in the regions of plague epizootics among the Rhombomys optimus Licht. in the Lowland Kara-Kum; it was possible to differentiate the signs of epizootic situations there in greater detail than by the methods suggested earlier.     

Minimum reporting standards for plant biology context information in metabolomic studies

Plant metabolomics has matured over the past 8 years. Plant biologists routinely use comprehensive analyses of plant metabolites to discover new responses to genetic or environmental perturbation, or to validate initial hypotheses on the function and in vivo action of gene products. The wealth of scientific findings has increasingly provoked interest to share and review raw or processed data from plant metabolomics reports. We here suggest a minimum of parameters to be reported in order to define details of experimental study designs in plant metabolomics studies.     

Autogamous seed set in a critically endangered orchid in Japan: pollination studies for the conservation of Nervilia nipponica

The pollination biology of the critically endangered Nervilia nipponica was investigated at two sites on Shikoku Island, Japan, to shed light on the species' ecological strategy and to help prioritise management decisions for its conservation. Though the solitary flowers failed to attract pollinators, high rates of fruit set were observed in control plants at both sites. Comparable rates were obtained in bagged plants and following induced autogamous and xenogamous pollinations, indicating that the species is capable of outbreeding, but self-compatible and not pollinator-limited for fruit set under natural conditions; rates were significantly lower following emasculation. The number of seeds set per fruit and their fertility did not differ significantly between open-, self- and cross-pollinated treatments. Epifluorescence microscopy revealed that, in open-pollinated plants, pollen grains germinate within the anther on the first day of anthesis, and that fertilisation occurs within the following 96 hours. The position of the stigma, which overlaps the clinandrium, friable pollinia, and the absence of a rostellum ensure efficient, non-mechanical autopollination. Though this confers reproductive assurance, inbreeding depression may be limiting fitness at subsequent stages of the recruitment cycle and low genetic diversity is inferred.     

Possibility of the intrauterine sensitization to benzylpenicillin and ampicillin in Syrian hamsters]

Immunization of Syrian female hamsters with benzylpenicillin and ampicillin resulted in positive skin reactions of the retarded type and decreased titers of the blood antihistamine factor (AHF) in a part of the posterity. Penicillin allergy was in particular observed in the posterity of the female hamsters immunited before the pregnancy. The state of allergy to penicillins was found in the posterity of the female hamsters with both the positive and negative skin reactions on immunization during the 2nd half of the pregnancy.