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The low frequency noise in rectifier diodes in the breakdown region is investigated as a function of the reverse current. The results showed that two processes balance in the diode breakdown, that is, impact ionization, and microplasma switching and conducting.

A calorimetric method of obtaining directly the fragility of liquids from the fictive temperatures of variably quenched glasses, is outlined. "Steepness indexes" m, have been determined for a group of molecular liquids of diverse character, and vary in the range 50-150. The values obtained mostly agree well with those from earlier studies using dielectric relaxation, heat capacity spectroscopy, and viscosity data. In our method there is the advantage that the fragility is determined from the relaxation process that is basic to the calorimetric glass transition temperature measurement, namely, that of the enthalpy. The calorimetric measurements also yield the liquid and glass heat capacities, and entropies of fusion, permitting relationships between thermodynamic and kinetic responses to be examined simultaneously. We study glycerol, dibutylphthallate, 9-bromophenanthrene, salol, orthoterphenyl, propylene carbonate, decalin and its nitrogen derivative decahydroisoquinoline, and find the latter two to be the most fragile liquids known, m = 145 and 128 respectively. Surprisingly, of the liquids studied, decalin has the smallest increase in heat capacity at the glass transition. By contrast, the strongest liquid, glycerol, has the largest increase. However, the thermodynamic fragility of decalin, assessed from the scaled rate of increase of the excess entropy above T[SUBg], is found to be high, due to the unusually small value of the excess entropy at T[SUBg]. Conversely, the entropy-based fragility for glycerol is the lowest. Thus the correlation of kinetic and entropy-based thermodynamic fragilities reported in recent work is upheld by data from the present study, while the basis for any correlation with the jump in heat capacity itself is removed. [ABSTRACT FROM AUTHOR]

A detailed investigation of the low frequency noise in rectifier diodes in the breakdown regime showed that the noise is a nonmonotonic function of the reverse current. A dynamic "competition" between impact ionization and microplasma switching explains the nonmonotonic, repetitive, and correlated variations in the breakdown slope (change in voltage per unit change in current—dV/dI), the noise level, and the noise waveform. These variations are due to the bistable microplasma fluctuation. The theories for avalanche charge multiplication and microplasma fluctuation should be combined with the microplasma switching theory to develop a physical model for the avalanche breakdown. [ABSTRACT FROM AUTHOR]

Bacteria of the genusAgrobacteriumare capable of transferring a fragment of their Ti-plasmid T-DNA, in a complex with the proteins VirE2 and VirD2, into the nuclei of plant cells and incorporating it into the chromosome of the host. The mechanisms of T-DNA transportation through the membrane and cytoplasm of the plant cell are unknown. The aim of this work was isolation of the virulence protein VirE2 for studying its role in T-DNA transportation through the membrane and cytoplasm of eukaryotic cells. For VirE2 accumulation, thevirE2gene was cloned into plasmid pQE31. VirE2 was isolated from the cells ofE. colistrain XL1-blue, containing the recombinant plasmid pQE31-virE2. The cells were disrupted ultrasonically, and the protein, with six histidine residues at the N-end, was isolated by means of affinity chromatography on a Ni-NTA-superose column. The purified protein was tested by the immunodot method using polyclonal rabbit antibodies and anti-VirE2 miniantibodies. The ability of the recombinant protein VirE2 to bind to single-stranded DNA was judged from the formation of complexes detected by electrophoresis in agarose gel. Thus, we isolated, purified, and partially characterized theAgrobacterium tumefaciensvirulence protein VirE2, which is capable of binding to single-stranded T-DNA upon transfer to the plant cell. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the low frequency noise in rectifier diodes in the breakdown regime. Basic theories; Experimental details; Discussion.

The bacteriophage ΦAb-Sp7 was isolated from the cells of the Azospirillum brasilense Sp7. The morphology, size of the gram-negative colonies, and range of lytic activity against other strains and species of the genus Azospirillum was tested. The isolated phage DNA was examined using electrophoretic and restriction analysis, and the size of the genome were established. The electron microscopy. resuIts show that the phage (capsid) has a strand-like form. The electron microscopy study of the bacteriophage ΦAb-Sp7 adsorption on the A. brasilense Sp7 bacterial surface was performed.

Abstract-A transfer DNA (T-DNA) carrying the marker gene nptII was detected in the genomes of diploid and haploid maize plants obtained after the treatment of pistil filaments with a suspension of Agrobacterium during artificial pollination. PCR analysis of total DNA isolated from 155 canamycin-resistant diploid F1 seedlings revealed T-DNA insertions in the genomes of 111 plants (32.7% of the total number of analyzed seeds). The example of matroclinal haploids was used to demonstrate that T-DNA may be transported to the egg cell by the growing pollen tube (PT). Twelve out of 16 analyzed haploid plants contained the T-DNA insertion. The possible mechanism of the transfer of the Agrobacterium T-DNA to the maize genome during pollination is discussed.

The nucleotide sequences of mitochondrial genome fragments containing the genes coding for cytochrome oxidase subunit III (COIII) and 12S ribosomal RNA of common European viper and Nikolsky's viper from various habitats (Saratov, Samara, and Penza oblasts; Chuvash Republic; and the Republic of Mordovia) were determined. According to the sequencing data, all samples clustered into two groups except for a number of individuals carrying single mutations in the genes in question. One group comprised V. nikolskii from Saratov oblast and the other, V. berus from the Chuvash Republic, Republic of Mordovia, and Samara and Penza oblasts. These results comply with the available data on the karyotypes of the studied vipers of this region. Further genetic studies of V. nikolskii and V. berus from various parts of this area are necessary.

Integration of T-DNA into the maize genome as a result of treatment of silks with Agrobacterium cells, containing activated vir genes, was demonstrated. In planta treatment of maize (Zea mays L) was performed during flowering in field. Cell suspension of Agrobacterium tumefaiciens strain GV3101(pTd33), carrying activated vir genes, was applied onto the previously isolated silks, which were afterwards pollinated with the pollen of the same cultivar. Integration of T-DNA into maize genome was confirmed by PCR (the nptII and gus reporter genes) and hystochemical staining of the seedling tissues, obtained from the transformed seeds. Amplification of the nptII gene showed the presence of about 60.3% of PCR-positive plants out of the total number of kanamycin-resistant seedlings examined, or 6.8% of the total of number of seedlings.

The scFv miniantibodies to the recombinant protein VirE2 from Agrobacterium tumefaciens were obtained by the method of phage display. The miniantibodies were purified and tested using timmunodot method for binding to a recombinant protein from Escherichia coli and to the native protein VirE2 from A. tumefaciens. The functional activity of the miniantibodies was comparable to the activity of mouse polyclonal antibodies against the VirE2 protein.

Bacteria of the genus Agrobacterium are capable of transferring a fragment of their Ti-plasmid, T-DNA, in a complex with the proteins VirE2 and VirD2, into the nuclei of plant cells and incorporating it into the chromosome of the host. The mechanisms of T-DNA transportation through membrane and cytoplasm of the plant cell are unknown. The aim of this work was isolation of virulence protein VirE2 for studying its role in T-DNA transportation through the membrane and cytoplasm of eukaryotic cells. For VirE2 accumulation, virE2 gene was cloned into plasmid pQE31. VirE2 was isolated from the cells of E. coli strain XL1-blue, containing the recombinant plasmid pQE31-virE2. The cells were disrupted ultrasonically, and the protein with six histidine residues at the N-end was isolated by means of affinity chromatography on a Ni-NTA-superose column. The purified protein was tested by the immunodot method using polyclonal rabbit antibodies and anti-VirE2 miniantibodies. The ability of the recombinant protein VirE2 to bind to single-stranded DNA was judged from the formation of complexes detected by electrophoresis in agarose gel. Thus, we isolated, purified, and partially characterized the Agrobacterium tumefaciens virulence protein VirE2 which is capable of binding to single-stranded T-DNA upon transfer to the plant cell.

Exocellular structures containing VirB2 proteins were, for the first time, localized on the surface of Agrobacterium by transmission electron microscopy. Using colloidal gold (CG)-labeled VirB2-specific antibodies, it was shown that VirB2 proteins enter into the composition of short surface pili, which emerge at the poles of acetosyringone (AS)-inducedAgrobacterium cells. However, cells of the Ti plasmidless A. tumefaciens strain UBAPF-2 and cells not induced with AS were incapable of pilus synthesis. In suspension, mating Agrobacterium cells were connected together by short thick bridges. It was found that these bridges did not include as part of their structure CG-labeled VirB1 and VirB2 proteins. We did not find the tetracycline-resistant transconjugants after mating of A. tumefaciens donor cells harboring binary systems with plasmid-free A. tumefaciens GM-I9023 in vir-induced and vir-uninduced conditions. However, the same strains can transfer pSUP106 plasmid via a vir-dependent way. We found that activated vir genes slightly stimulate pTd33 plasmid transfer via a tra-dependent pathway to plasmid-free strain UBAPF-2. It seems, that vir-induced T-DNA/plasmid DNA transfer machinery is not essential for the conjugation process between agrobacterial cells but may participate in this process.

Skin thigh biopsies were regularly taken in 186 patients with insulin-dependent and non-insulin-dependent diabetes. Progression of diabetic microangiopathy was found in spite of hypoglycemic treatment. Development of lesions of microvessels was somewhat inhibited only by angioprotectors (ticlid, dyamicron, dipiridamol).

Femoral skin biopsies of 300 patients with insulin-dependent and non-insulin-dependent diabetes were studied immunomorphologically and the results were compared to the level of immunoglobulins in the blood serum. It is found that IgG, beta-lipoproteins, complement were registered in the arterioles and capillary walls in diabetic microangiopathy more frequently than in healthy persons. The conclusion is made that in development of diabetic microangiopathy, in both types of diabetes, immune (immunocomplex) mechanisms that damage vascular wall are involved.

The process of the transfer of the Ti-plasmid vector pGV3850 with the plasmid pBR322 inserted into the T-DNA region from Agrobacterium tumefaciens to a non-plasmid strain of Escherichia coli was studied. The transferred Ti-plasmid was found to be exposed to deletions and formed a wide range of derivatives with a size ranging from 3-4 kb to 50 kb, maintained in E. coli due to ColE1-replicon. The Ti-plasmid is also inserted into the chromosome of the recipient bacterium with at least a 100-fold lower frequency than the formation of deletional derivatives. It was shown that the induction of vir genes controlling the transfer of T-DNA into plants has no appreciable effect on the efficiency of obtaining transconjugates in mating with E. coli. The deletion of the genetic material of megaplasmids with the inserted functional site OriV ColE1, as a result of the conjugative transfer from cells of different bacteria to the cells of E. coli, was proposed for molecular cloning.

As shown by conjunctival biomicroscopy, 6-month administration of ticlid and gliclazide induced a statistically significant increase in the frequency of less severe microcirculatory disturbances compared to conventional hypoglycemic therapy. The drugs also restricted plasmatic impregnation and cell proliferation in skin biopsy microvascular wall. Following 2-year antiaggregation treatment (gliclazide, trental, dipiridomol) 48.9% of diabetes mellitus patients achieved regression of morphological manifestations of diabetic microangiopathy, 16.2% stabilization against 34.9% of progressive disease cases. Conventional sugar-reducing therapy fails to stop diabetic microangiopathy progression in 73.4-93.3% of the diabetics.

Hemocoagulation was examined in 477 diabetes mellitus patients. Whatever the disease type, severity, duration and the intensity of microvascular complications, diabetes mellitus was discovered to be marked by the development of chronic intravascular blood microcoagulation associated with primary hyperactivation of the platelet component of hemostasis. The use of the new antiaggregation agents tiklid and diabeton allows an appreciable decrease of the activity of platelet microthrombus formation whereas the administration of the common sugar-reducing antidiabetic therapy favours the maintenance of its high level.

Skin biopsies from 40 patients 17 to 75 years old with type I and II diabetes mellitus were studied morphologically. The formation of diabetic microangiopathy starts with the damage of endotheliocytes, vascular permeability disturbance, activation of pericytes and smooth muscle elements with subsequent thickening of basal membranes and capillary and arteriole hyalinosis, these lesions being directly related to the duration of diabetes. Diabetic microangiopathy is a manifestation of the disease and its morphology is similar in both type I and II diabetes.

A study was made of the immunological mechanisms implicated in the evolution of diabetic microangiopathy. For this purpose in 270 patients with type I and II diabetes mellitus, the concentration of IgA, IgM and IgG was measured and compared with morphological alterations in skin biopsy specimens. The control group was made up of 30 normal persons (donors). The sections were stained with conventional methods, which made it possible to reveal by light microscopy the correlation between the intensity of diabetic microangiopathy and the rise of the IgG level.

The biopsies of the thigh skin from 85 patients with insulin-dependent (juvenile) diabetes mellitus are studied. Diabetic microangiopathy is detected histologically in 70 patients. The degree of microangiopathy was positively correlated with the duration of diabetes (p less than 0.01) and this allowed to calculate the probability of vascular alterations development at various periods of disease. The patient age and the gravity of insulin-dependent diabetes did not influence significantly the frequency and the degree of diabetic microangiopathy (p greater than 0.05).