Estimation of genome sizes of hyperthermophiles

Genomes of various hyperthermophilic and extremely thermophilic prokaryotes were analyzed with respect to size, physical organization, and 16S rDNA copy number. Our results show that all the genomes are circular, and they are in the size range of 1.6–1.8 Mb for Pyrodictium abyssi, Methanococcus igneus, Pyrobaculum aerophilum, Archaeoglobus fulgidus, Archaeoglobus lithotrophicus, and Archaeoglobus profundus (the two bacteria Fervidobacterium islandicum and Thermosipho africanus possess genomes of 1.5-Mb size). A systematic study of all validly described species of the order Sulfolobales revealed the existence of two classes of genome size for these archaea, correlating with phylogenetic analyses. The Metallosphaera–Acidianus group, plus Sulfolobus metallicus, have genomes of ca. 1.9 Mb; the other members of the order Sulfolobales group possess genomes >2.7 Mb. The special case of Stygiolobus azoricus is discussed. Received: August 10, 1997 / Accepted: January 1, 1998     

Seasonal study of the fungal biota of the fur of dogs

During a one year period, 944 dogs from the Municipal kennel of Barcelona were examined to detect animals with suspected dermatophytosis. Only a few animals (1.8%) presented skin lesions but none of them had dermatophytosis. A representative number of dogs without visible skin lesions (n=172), selected at random, were used to carry out a seasonal study of the mycobiota of their fur. Fifteen isolates belonging to the genera Microsporum and Trichophyton were isolated from 14 of the 172 (8.1%) dogs without lesions. The identity of these fungi was Microsporum gypseum (6/15), Trichophyton terrestre (4/15), M. canis (2/15), M. cookei (2/15) and Trichophyton ajelloi (1/15) (one strain each of M. gypseum and T. ajelloi were isolated from one dog). Species of Penicillium (% prevalence=89.5%), Alternaria (86.6%), Cladosporium (84.9%), Aspergillus (77.3%), Scopulariopsis (65.7%) and Chrysosporium (64.5%) were the most prevalent. No significant differences in the fungal biota were observed with respect to age, gender, hair length or between mixed and pure breed dogs. A large number of isolates, including species belonging to the genera Beauveria, Chrysosporium, Malbranchea and Scopulariopsis, that macroscopically and/or microscopically resemble dermatophytes and may be mistaken for them, produced a red color change in Dermatophyte Test Medium. No significant seasonal difference was detected among the isolates belonging to the the most frequently encountered genera, with the exception of Scopulariopsis (higher in summer and autumn) and Chrysosporium (higher in summer). Species from other genera, with lower occurrence also presented significant differences in their seasonal distribution. Arthrinium, Aureobasidium, Chaetomium and Phoma spp. presented maximum prevalence peaks in spring, Fusarium, Paecilomyces, Phoma and Rhizopus spp. in summer and Geotrichum and Mucor spp. in autumn. The Microsporum and Trichophyton species were more frequently isolated in summer.     

Ultrastructure of transitional epithelium of man

Summary Blocks of human normal renal pelvis and ureter obtained at the time of surgery were fixed in glutaraldehyde and osmium with or without ruthenium red, for electron microscopic observations. The transitional epithelium is arranged in three cell layers: basal, intermediate and superficial. All epithelial cells show numerous microvilli and contain the characteristic vesicles of transitional epithelium, bundles of cytoplasmic filaments, microtubules and numerous free ribosomes. The epithelial extracellular compartment is notably large and appears as an intricate, tridimensional network of canaliculi and cisternae which are wider in the intermediate and superficial layers and in which microvilli and cytoplasmic folds of vicinal cells are often attached or interdigitated. At these sites there are desmosomes.The surface of all transitional epithelial cells is covered by a fibrillar mucous coat which is more developed at the plasmalemma of the free border of luminal cells in which microvilli are also seen. Ruthenium red stains selectively the plasmalemma and the mucous coat of the free surface of the epithelium, indicating the presence of an acid polysaccharide. With this technic (Luft, 1965), it is observed, radiating from the plasmalemma, branching filaments which measure 100 Å in diameter forming a zone of varying density which is about 400 m wide and which corresponds, at the light microscopic level, to the luminal border of the transitional epithelial cells in which a sialomucin has been identified. The slender filaments have a beaded appearance. At the free border, superficial cells are attached by functional complexes in which tight junctions seal the epithelial intercellular space, which is opened at the level of the basement membrane where only desmosomes are observed.The ultrastructure of human transitional epithelium of urinary tract resembles the duct cells of the salt gland of certain marine birds (Fawcett, 1962) and the amphibian epidermis (Farquhar and Palade, 1965) in which there are active processes of transport. The mucous surface coat, selectively stained by the ruthenium red, contains a sialomucin (Monis and Dorfman, 1965, 1967).The ultrastructure and histochemistry of the mucous fluffy coat of man transitional epithelium and the observations of Porter and Tamm (1955), on the ultrastructure of preparations of the Tamm and Horsfall mucoprotein (1952) are bases for suggesting that transitional epithelium of urinary tract of man is the site of biosynthesis of certain urinary mucoids. Present investigations are directed to obtain evidence to substantiate this hypothesis.General Abbreviations B basal cell - E exfoliating cell - I intermediate cell - L lumen - S superficial cell - SC surface coat - bm basement membrane - ci cell infolding - d desmosome (macula adhaerens) - f fibroblast - fi cytoplasmic filaments - is intercellular space - jc junctional complex - ly lysosome - lym lymphocyte - mt microtubules - m mitochondria - mv microvilli - n nucleus - r ribosomes - rv round vesicle - zo zonula occludens - za zonula adherens Dr. Monis wishes to thank Dr. E. De Robertis for the use of the electron microscope facilities of the Instituto de Anatomía General y Embriologia, Facultad de Medicina, Universidad de Buenos Aires. — Prof. E. Trabucco and Dr. R. J. Borzone (Cátedra de Clinica Genitourinaria de la Facultad de Medicina, Universidad de Buenos Aires) generously supplied the specimens which were the bases of this study. — Thanks are due to Mrs. A. M. Novara and Mrs. Defilippi-Novoa for efficient technical help and to Miss Rosa Gentile for secretarial assistance. Photomicrography by Mr. M. A. Saenz.Dr. Zambrano is investigator (CNICT).     

Mode of Action of Lomofungin

Lomofungin inhibited the growth of some yeasts and mycelial fungi at concentrations between 5 and 10 μg/ml. At such concentrations, there was no decrease in endogenous and exogenous oxygen consumption, and even 50 μg of antibiotic per ml caused only slight decreases. The permeation of the cell membrane was changed so that leakage of ninhydrin-positive substances was reduced, and the uptake of ¹⁴C-labeled glucose, amino acids, uracil, and thymidine was decreased at concentrations as low as 4 μg/ml. Protein synthesis in whole cells of Saccharomyces cerevisiae was reduced 35% at 10 μg/ml. However, the antibiotic did not reduce the incorporation of phenylalanine-U-¹⁴C into polypeptides with cell-free systems of Rhizoctonia solani and S. cerevisiae. The synthesis of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) was inhibited even at concentrations of lomofungin of 4 μg/ml. Since RNA synthesis was inhibited at lower concentrations and earlier than DNA synthesis, the primary site of action of the antibiotic appears to be the synthesis of RNA.     

Non-Productive Binding of Substrates as One of Aspects of Substrate Specificity of Cholinesterases of Different Origin

Taking into account the phenomenon of non-productive binding of substrate, kinetic parameters of hydrolysis of acetylcholine (ACh) and its 13 derivatives with different structures of ammonium group by cholinesterase (ChE) of human erythrocytes, ChE of horse blood serum, and ChE of optic ganglia of the Pacific squid Todarodes pacificus are determined. A dependence is revealed of values of parameters of their enzymatic hydrolysis and parameters of the non-productive binding on the substrate structure and ChE nature. Effects of salts, LiCl, NaCl, KCl, MgCl₂, CaCl₂ and BaCl₂, on various kinetic parameters, including parameters of the non-productive binding of substrate, of enzymatic hydrolysis of iodides of ACh and N-acetoxyethylene-N-ethylpiperidinium under action of horse blood serum ChE are studied. Addition of the salts to the reaction mixture produced different effects on values of the catalytic center activity (a _c) and the Michaelis constant (K _M), depending on the cation nature and the substrate structure. At the same time, values of the a _c/K _M ratio that characterize to a degree the substrate affinity to the enzyme are equal to each other for two substrates differing in structure, regardless of the presence and nature of the studied cations. Parameters of the non-productive binding of N-acetoxyethylene-N-ethylpiperidinium iodide also depended on the salt nature; however, in that case, a question arises as to the correctness of the comparative analysis, when at determinations of the parameters the non-productive binding of ACh is ignored.     

Enzymatic synthesis of carotenes by cell-free preparations of fruit of several genetic selections of tomatoes

Several mutants of tomatoes are known in which the carotene content of the fruit is markedly altered qualitatively and quantitatively from that found in the standard red tomato variety. These selections are: rr (yellow flesh, low carotene); tt (tangerine, orange, proneurosporene and prolycopene); at at (apricot, low in acyclic carotenes); og^c og^c (crimson, high in lycopene); Verkerk 377-2αα (probably identical to vircscent orange vo vo, high in ζ-carotene); B B (H_i-β, high in β-carotene), and Del Del (Hi-δ, high in δ-carotenc). Studies of carotene synthesis from [1-¹⁴C]isopentenyl pyrophosphate, [¹⁴C]phytoene, and [¹⁴C]lycopcne by soluble enzyme systems obtained from fruits of these selections have shown unexpected enzyme activities. All selections evidence activity for the synthesis of phytoene. All mutants have also been found to contain an enzyme system for the synthesis of β-carotenefrom lycopene. Three of the selections analyzed (rr, at at, and og^c og^c) also contain an enzyme system for the conversion of lycopene to α-carotene and the variants rr and tt contain an enzyme for the synthesis of poly-cis-carotencs from isopentenyl pyrophosphate and phytocne.The reasons for the discrepancies that are observed between carotene composition of fruit of field-grown tomato selections and enzyme activities for carotene synthesis by cell-free preparations obtained from these fruits are not presently known. It is obvious, however, that either inhibitors are present, cofactors are missing, or there are permeability barriers to substrate or cofactor transport into plastids of selections in which enzyme activities are not expressed in field-grown fruit. Further investigations will be required for clarification of this problem.     

非计划再次手术关键环节管理与效果分析

目的 探索有效降低非计划再次手术发生率的管理方法。方法 对2012年1月—2016年12月住院并进行手术的患者进行主动监测,加强管理,发现非计划再次手术病例,统计发生率及引发原因。结果 225 944例手术共发生非计划再次手术914例,平均发生率为0.40%且五年呈显著下降趋势。引发原因以手术部位感染、切口裂开、切口疝或愈合不良,术后出血,出现漏或瘘为主,共占73.9%。结论 完善主动监测与报告系统、加强院科两级管理、注重原因分析与改进可有效降低非计划再次手术的发生率。     

医疗机构合理用药评价模型的构建研究

目的 针对医疗机构的合理用药水平进行评价研究。方法 根据医疗机构合理用药的具体要求,构建医疗机构合理用药评价指标体系,采用基于模糊群决策的方法和多指标评价分析法构建医疗机构合理用药评价模型。结果 构建了基于模糊群决策的医疗机构合理用药评价模型,并通过实例分析证明了评价模型的可行性。结论 建立的基于模糊群决策的医疗机构合理用药评价模型能够对医疗机构的合理用药水平进行科学评价,为提高医疗机构合理用药水平奠定基础。     

Effects of different batches of iodine on properties of I-hFSH and characteristics of radioligand-receptor assays

Radioiodination of highly purified human follicle-stimulating hormone (hFSH) (4000 IU/mg) was performed every other week for 23 weeks using 2 mCi carrier free Na ¹²⁵I (Amersham Corp., 15 mCi/μg I₂) in the presence of lactoperoxidase. Incorporation of ¹²⁵I into hFSH was determined by the method of [7.]Biochem. J. 89, 114). Hormone binding was studied in vitro under steady-state conditions (16 h, 20°C) using different calf testis membrane preparations having similar receptor characteristics. Each ¹²⁵I-hFSH preparation was characterized for maximum bindability, specific activity of bindable radioligand as determined by self-displacement analysis, and by determination of K_a and R_t. Incorporation of ¹²⁵I into FSH was relatively constant over the large number of experiments (62.4 ± 6.4 μCi/μg; n = 23). By comparison, however, specific radioactivity of the receptor bindable fraction of ¹²⁵I-hFSH was related to the lot of ¹²⁵I utilized, and was significantly (P ≤ 0.01) lower and more variable (28.7 ± 10.5 μCi/μg). Maximum bindability of ¹²⁵I-hFSH was not correlated to specific activity (r = 0.06) but was negatively correlated to hFSH ¹²⁵I incorporation (r = −0.47; P ≤ 0.05). These observations demonstrate the need to assess the quality of each batch of radioligand before undertaking radioligand-receptor assays and suggest that differences in Na¹²⁵I lots affect specific radioactivity of the radioligand and its receptor binding characteristics.     

Spatial distribution of brood-bearing females of limnetic species of Cladocera

In this study, the spatial distribution of brood-bearing females of five species of limnetic cladocerans (Daphnia cucullata, D. longispina, Bosmina coregoni, B. longirostris, Diaphanosoma brachyurum) in the deep mesotrophic lake in relation to the predation pressure of planktivorous fish (roach Rutilus rutilus, perch Perca fluviatilis, catfish Ictalurus nebulosus, white fish Coregonus albula, bleak Alburnus alburnus), and planktonic invertebrates (cyclopoids Mesocyclops leuckartii, Thermocyclops oithonoides, T. crassus, and cladoceran Leptodora kindtii) as well as some environmental variables was estimated. Most cladocerans showed apparent differences in horizontal distribution (ANOVA F = 0.2–0.45, P < 0.05) in the littoral zone and lack of such differences in the pelagic zone (F = 0.07–0.13, P > 0.05). Vertical distribution of most species, in turn, showed a clear pattern in the pelagic zone (F = 0.31–0.39, P < 0.05) and less regularities in the littoral zone (F = 0.15–029, P > 0.05). The differences in spatial distribution of non-predated and predated species suggest that predation pressure, but not predatory type, was an important factor structuring their distribution. Other factors that affected their distribution were conductivity, dissolved oxygen, TOC and macrophyte biomass; however, most of those variables better explained the distribution of brood-bearing cladocerans in the vertical than horizontal aspect.     

Characterization of the RpoS Status of Clinical Isolates of Salmonella enterica

The stationary-phase-inducible sigma factor, σ^S (RpoS), is the master regulator of the general stress response in Salmonella and is required for virulence in mice. rpoS mutants can frequently be isolated from highly passaged laboratory strains of Salmonella. We examined the rpoS status of 116 human clinical isolates of Salmonella, including 41 Salmonella enterica serotype Typhi strains isolated from blood, 38 S. enterica serotype Typhimurium strains isolated from blood, and 37 Salmonella serotype Typhimurium strains isolated from feces. We examined the abilities of these strains to produce the σ^S protein, to express RpoS-dependent catalase activity, and to resist to oxidative stress in the stationary phase of growth. We also carried out complementation experiments with a cloned wild-type rpoS gene. Our results showed that 15 of the 41 Salmonella serotype Typhi isolates were defective in RpoS. We sequenced the rpoS allele of 12 strains. This led to identification of small insertions, deletions, and point mutations resulting in premature stop codons or affecting regions 1 and 2 of σ^S, showing that the rpoS mutations are not clonal. Thus, mutant rpoS alleles can be found in freshly isolated clinical strains of Salmonella serotype Typhi, and they may affect virulence properties. Interestingly however, no rpoS mutants were found among the 75 Salmonella serotype Typhimurium isolates. Strains that differed in catalase activity and resistance to hydrogen peroxide were found, but the differences were not linked to the rpoS status. This suggests that Salmonella serotype Typhimurium rpoS mutants are counterselected because rpoS plays a role in the pathogenesis of Salmonella serotype Typhimurium in humans or in the transmission cycle of the disease.     

Peculiarities of Selectivity of Three Subtypes of Low-Threshold T-Type Calcium Channels

Despite the progress in studies of the properties and functions of low-threshold calcium channels (LTCCs) [1], the mechanisms of their selectivity and permeability remain unstudied in detail. We performed a comparative analysis of the selectivity of three cloned pore-forming LTCC subunits (α1G, α1H, and α1I) functionally expressed in Xenopus oocytes with respect to bivalent alkaline-earth metal cations (Ba²⁺, Ca²⁺, and Sr²⁺. The relative conductivities (G) of these channels were determined according to the amplitudes of macroscopic currents (I) and potentials of zero currents (E). The currents were recorded after preliminary intracellular injection of a fast calcium buffer, BAPTA, in order to suppress the endogenous calcium-dependent chloride conductivity. Channels formed by α1G subunits demonstrated the following ratios of the amplitudes of macroscopic currents and potentials of zero current: I _Ca:I _Ba:I _Sr = 1.00:0.75:1.12 and E _Ca ≈ E _Ba ≈ E _Sr. For channels that were formed by α1H and α1I subunits, these ratios were as follows: I _Ca:I _Ba:I _Sr = 1.00:1.20:1.17, E _Ca ≈ E _Ba ≈ E _Sr and I _Ca:I _Ba:I _Sr = 1.00:1.48: 1.45, E _Ca ≈ E _Ba ≈ E _Sr respectively. The different macroscopic conductivities and similar potentials of zero current typical of α1G and α1I channels indicate that, probably, various bivalent cations can in a differential manner influence the stochastic parameters of functioning of these channels. At the same time, channels formed by α1H subunits are characterized by more positive potentials of zero current for Ca²⁺. It seems possible that the selectivity of the above channels is determined by mechanisms that mediate the selectivity of most high-threshold calcium channels (more affine binding of Ca²⁺ inside the pore). Neirofiziologiya/Neurophysiology, Vol. 37, No. 4, pp. 319–329, July–August, 2005.     

Comparison of Vanadium-Rich Activity of Three Species Fungi of Basidiomycetes

A comparison of vanadium-rich activity of three species fungi of Basidiomycetes, Ganoderma lucidum, Coprinus comatus, and Grifola frondosa, was studied. By fermentation and atomic absorption spectroscopy analysis, the biomass of G. lucidum and G. frondosa declined rapidly when the concentration of vanadium exceeded 0.3% but the biomass of C. comatus did not decline rapidly until the concentration of vanadium exceeded 0.4% and the content of vanadium accumulated in the mycelia was 3529.3 μg/g. After the mice were administered (intragastrically) with vanadium-rich C. comatus, the blood glucose of alloxan-induced hyperglycemic mice was decreased (p < 0.05) and the body weight of the alloxan-induced hyperglycemic mice was increased gradually. Thus, we selected C. comatus to absorb vanadium and chose 0.4% as the optimal concentration of vanadium for the pharmacological works.     

Comparative estimation of the neurotropicity of trace elements in the organism of children living in industrial towns of Ukraine

In 10- to 16-year-old children, inhabitants of industrial towns of Ukraine, an X-ray fluorescence analysis of the content of some chemical elements in hair samples allowed us to find a deficiency of Zn and Cu against the background of excesses of Ca, Cr, Ni, Mo, and Cd. Comparison of the parameters of EEG frequency components and levels of Ca, Zn, Cu, Fe, Mn, Co, Cr, Mo, Ni, Sr, Pb, and Cd showed that there are significant correlations between the normalized values of spectral powers of many frequency components of the ongoing EEG recorded in different functional states (eyes closed/open, solving an arithmetic task, and phono-/photostimulation) and concentrations of ten of the above-mentioned trace elements. Comparative estimation of the neurotropicity of the elements showed the following sequence of numbers of significant correlations (shown in parentheses) from the total set of possible comparisons: Cd (35) > Ni (31) > Cr (19) > Sr (17) > Pb (16) > > Ca (10) > Cu (7) > Mo (3) > Zn (2) > Fe (1). The intensity of correlations (values of the correlation coefficients) varied from 0.26 to 0.42 at 0.05 < P < 0.001; more frequently, such correlations were observed under conditions of EEG recording with the eyes closed (39) and upon solving an arithmetic task (33).     

Intertidal zonation of prosobranch gastropods: Analysis of densities of four co-existing species

The densities of populations of Nerita atramentosa Reeve, Austrocochlea constricta Lamarck, Bembiciuin nanum (Lamarck), and Cellana tramoserica (Sowerby) were recorded in 0.25 m² quadrats on landward and seaward halves of a sheltered and a moderately exposed rock platform from June 1972 to June 1973. The data have been subjected to variance and multiple regression analysis. Differences between densities of each species on the two shores and in the two areas of each shore are discussed with respect to the regressions on littoral height. Densities of Nerita on the sheltered shore, Austrocochlea and Bembicium on both shores, and Cellana, on the exposed shore, increased with height. The density of Cellana on the sheltered shore decreased as height increased. The density differences in the landward and seaward areas on the two shores were attributable to the effect of height for Nerita and Austrocochlea. Height was the major variable affecting the density of these two species on the sheltered shore. Bembicium and Cellana densities on both shores, and Austrocochlea density on the exposed shore, are not primarily determined by height.On the sheltered shore, Nerita and Cellana increased in density with increasing cover of water in rock pools. On the exposed shore, Bembicium and Cellana became sparser with increasing water cover. Bembicium on both shores increased in density with increasing cover of the alga Peyssonelia, as did Cellana on the exposed shore. Cellana and Austrocochlea tended to increase in density with Nerita on the sheltered shore. Cellana tended to be sparse where Bembicium was dense on the exposed shore. The biological effects of substrata and other species on the densities of each species remain unexplained.Significant time effects were found for variations in the densities of Nerita and Cellana on the sheltered shore and of Austrocochlea and Cellana on the exposed shore. The seasonal change in density of Nerita was parabolic with a minimum in summer, and is consistent with the known period of recruitment of this species. The lack of significant time effects on density of Austrocochlea on the sheltered shore is consistent with the known continuous recruitment of this species. The declining density of Austrocochlea on the moderately exposed shore was found, by size-frequency analysis, to be due to reduced recruitment compared with surrounding shores. The density of Cellana on both shores showed seasonal changes, with a maximum in summer, which is consistent with the known period of recruitment in Cellana. The lack of seasonal changes in density of Bembicium is briefly discussed.This type of multifactor analysis identifies biological interactions affecting variation in density of these species. It also corroborates the results of other ecological investigations and determines the relative importance of a variety of physical and biological factors in the distribution of density of intertidal gastropods.     

Diversity of the Carbohydrate Composition of the Antigenic Polysaccharides of Proteobacteria of the Genera Pseudoalteromonasand Marinomonas

The sugar analysis of the glycans of the type strains of marine proteobacteria of the genera Pseudoalteromonasand Marinomonas—Pseudoalteromonas atlanticaIAM12927^T, P. aurantiaNCIMB 2033^T, P. citreaATCC 29719^T, P. elyakoviiKMM 162^T, P. espejianaATCC 29659^T, P. piscicidaNCIMB 645^T, P. tetraodonisIAM 14160^T, Marinomonas communisATCC 27118^T, and M. vagaATCC 27119^T—showed that they contain glucose, galactose, galactosamine, glucosamine, fucose, rhamnose, mannose, heptose, 2-keto-3-deoxyoctonate (KDO), uronic acids, colitose (3,6-dideoxy-L-xylo-hexose), and 6-deoxy-L-talose. The carbohydrate composition of the antigenic polysaccharides (PSs) of P. elyakoviiKMM 162^Tand P. espejianaATCC 29659^Tdepended on the type and the concentration of carbohydrate substrates in the nutrient media. The molar proportion between rhamnose, glucose, and galactose (ca. 1 : 0.3 : 2) in the PS of P. elyakoviiKMM 162^Twas almost the same in the media lacking carbohydrates or containing glucose or galactose at a concentration of 1 g/l. At the same time, the molar proportion between fucose, glucose, galactose, galactosamine, and glucosamine (ca. 1 : 1 : 1 : 2 : 0.5) in the PS of P. espejianaATCC 29659^Tdepended on the presence and the concentration of carbohydrate substrates in the medium. A high concentration of glucose in the medium (30 g/l) brought about a rise in the content of glucose in PSs (9-fold for the PS of P. elyakoviiKMM 162^Tand 4.6-fold for the PS of P. espejianaATCC 29659^T) and led to a decrease in the content of other carbohydrates. The cultivation of these two strains at a lactose concentration of 30 g/l resulted in their PSs containing glucose and galactose in about equal proportions (ca. 1 : 1 in the case of P. espejianaATCC 29659^Tand ca. 2.1 : 1.7 in the case of P. elyakoviiKMM 162^T).     

Metabolite regulation of the state of adenylylation of glutamine synthetase

When glutamine synthetase is incubated in a mixture containing adenylyltrans-ferase, the regulatory protein (P_II) and several effectors, including ATP, UTP, P_i, α-ketoglutarate, glutamine, and Mg²⁺ and/or Mn²⁺, it ultimately assumes a constant state of adenylylation. The final state of adenylylation (i.e., the number of adenylylated subunits per mole of enzyme) can vary from 0 to 12 and is specified by the concentrations and ratios of the various effectors and by the extent of uridylylation of P_II (i.e., the P_IIA:P_IID ratio). Under otherwise identical conditions, increasing the concentrations of either UTP, P_i, α-ketoglutarate, Mn²⁺, or P_IID decreases the state of adenylylation finally reached, whereas increasing the concentrations of either glutamine, ATP, or Pua increases the final state of adenylylation. The final state of adenylylation is independent of the concentrations of glutamine synthetase, adenylyltransferase, and P_II (but not of the P_IIA:P_IIDratio), and also of the initial average state of adenylylation of glutamine synthetase. Various lines of evidence show that the final state of adenylylation represents a dynamic steady state in which the rates of adenylylation and deadenylylation of glutamine synthetase are equal. It is concluded that the regulation of glutamine synthetase activity by the adenylylation mechanism utilizes a significant amount of ATP energy, but this amount is less than 0.1% that utilized directly by the glutamine synthetase in the synthesis of glutamine.     

Mode of Action of Lomofungin

Lomofungin inhibited the growth of some yeasts and mycelial fungi at concentrations between 5 and 10 μg/ml. At such concentrations, there was no decrease in endogenous and exogenous oxygen consumption, and even 50 μg of antibiotic per ml caused only slight decreases. The permeation of the cell membrane was changed so that leakage of ninhydrin-positive substances was reduced, and the uptake of ¹⁴C-labeled glucose, amino acids, uracil, and thymidine was decreased at concentrations as low as 4 μg/ml. Protein synthesis in whole cells of Saccharomyces cerevisiae was reduced 35% at 10 μg/ml. However, the antibiotic did not reduce the incorporation of phenylalanine-U-¹⁴C into polypeptides with cell-free systems of Rhizoctonia solani and S. cerevisiae. The synthesis of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) was inhibited even at concentrations of lomofungin of 4 μg/ml. Since RNA synthesis was inhibited at lower concentrations and earlier than DNA synthesis, the primary site of action of the antibiotic appears to be the synthesis of RNA.     

A study of the mechanism of the antiarrhythmic action of Allapinin

Allapinin (lappaconitine hydrobromide) is a drug used for the treatment of cardiac rhythm disturbances; its properties are characteristic of class IC antiarrhythmics. The mechanism of its electrophysiological action involves the blockade of Na⁺ channels with a subsequent decrease of depolarization rate leading to a slowing of impulse propagation and a decrease of excitability in the conductive system of the heart. Factors underlying the side effects of Allapinin (tachycardia, arterial hypertension, impaired coordination, etc.) are currently unknown, and therefore a study of the molecular mechanisms of its action seems relevant. The target genes of the drug were identified in rats with induced aconitine arrhythmia using the commercially available Rat Neuroscience Ion Channels & Transporters RT² Profiler? PCR Array kit (SA Biosciences). A comparison of expression levels of 84 genes in rats treated with Allapinin, after the induction of arrhythmia by aconitine (experiment) and in physiological saline-treated arrhythmic rats (control), revealed 18 mRNAs which were up- or downregulated twofold or more in the experiment relative to the control. Allapinin was shown to stimulate the expression of genes coding for various types of K⁺ channels (kcna6, kcnj1, kcnj4, kcnq2, and kcnq4), Ca²⁺ channel (cacna1g), and vesicular acetylcholine transporter (slc18a3). A decrease in mRNA levels was detected for genes coding for K⁺ channels (kcne1, kcns1), a Na⁺ channel (scn8a), and membrane transporter genes (atp4a, slc6a9). Our data shows that Allapinin administered to animals with aconitine arrhythmia modulates the expression of genes accounting for ion current conductances involved in the formation of various phases of action potential (I _Na , I _to , I _Ks , I _K1 , I _CaT ). The effect of the drug on the levels of mRNAs coding for acetylcholine and glycine transporters suggests the involvement of these neuromediators in the mechanisms underlying the antiarrhythmic effect of Allapinin.