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PubMedDate not supplied

[Ca2+, Mg2+, Zn2+ levels in histone fractions from normal and tumor cells].

Distribution of some bivalent cations (Ca2+, Mg2+, Zn2+) in histones isolated from healthy mice liver and ascitic hepatoma 22A cells has been investigated by atomic-absorption analysis. It has been shown that the content of these cations is higher in normal and diseased H3, H2B and H1 fractions and lower--in H2A; however, in the H4 fraction these metals are not detected. A significant increase of Ca2+, Mg2+ and Zn2+ levels has been established in ascitic H3, H2B and H1 fractions. An increase of bivalent cations (Ca2+, Mg2+, Zn2+) content in some histone fractions apparently is bound with the changes of histone--histone and histone--DNA interactions.

Animals↗
PubMedDate not supplied

[The presence of cooperative structures in tryptic fragments of troponin C].

Scanning microcalorimetry has been used to study the ability of TR-1 and TR-2 tryptic fragments of troponin C to form an ordered compact structure in solution under different conditions. It has been shown that: (1) in the presence, as well as in the absence of bivalent ions both fragments have a structure which can melt with an intensive heat absorption at heating; (2) the structure of fragment TR-1 containing two Ca2+-specific domains (domains I and II) melts as a whole under all conditions studied and therefore the domains form one cooperative block. Binding of Ca2+ or Mg2+ ions stabilizes the block structure, however, significant conformational rearrangements which would lead to a change of denaturational enthalpy do not occur; (3) Ca2+Mg2+-domains of fragment TR-2 (domains III and IV) represent individual cooperative units, blocks. Stability of these cooperative blocks strongly depends on concentration of bivalent ions and in the presence of 2 mM EDTA the melting temperature of one of them is below 10 degrees. Thermodynamic melting temperature of one of them is below 10 degrees. Thermodynamic melting parameters of cooperative blocks within peptides and in the intact molecule of troponic C are compared.

Animals↗
PubMed1983

Testicular cells in hybrid water buffaloes (Bubalus bubalis).

Meiotic chromosome behaviour and testicular histology were studied in water buffaloes (Bubalus bubalis) including two river (Murrah), two swamp and three F1 (Murrah cross swamp) hybrids aged between two and two and a half years, from testicular biopsies obtained by an open surgical method. Meiotic preparations revealed spermatogonial metaphases, pachytene, diplotene, diakinesis, first and second meiotic metaphases and spermatozoa in all three types of buffalo. Chromosome sets ranging from 22 to 26 (most frequent, 24 and 25) with many cells carrying univalent, bivalent and multivalent configurations were observed in hybrids, whereas the meiotic cells in the Murrah and swamp showed chromosome sets exclusively of 25 and 24 (bivalents) respectively. Histological examination of the hybrid testis revealed a large proportion of degenerating spermatocytes and abnormal spermatids in the process of spermiogenesis suggesting that the various synaptic associations leading to unbalanced gametes may be responsible for the degenerating germ cells in the hybrids. The unbalanced meiotic products will probably lead to selection against such spermatozoa or early embryos after fertilisation. Due to a large percentage of germinal epithelial cells in F1 hybrids being wasted, the fertility of backcross and F2 generations will be subnormal.

Animals↗
PubMed1981

Aspects of immunoglobulin G structure relevant to its interaction with Fc receptors.

One unambiguous message that comes from the data obtained relates to the central role played by the hinge region, and its constituent disulfide bonds, in the functioning of the IgG molecule. Segmental flexibility allows variation in the distance between the antibody combining sites, located at the distal ends of the Fab regions, and serves the important function of allowing bivalent attachment of antibodies to antigenic determinants even if the latter form a fixed array, for example, on a cell surface (monogomous bivalency). Too much flexibility, however, seen as a consequence of cleaving the hinge-region disulfides appears to be inimicable to the expression of effector functions. The hinge region and its disulfides control the degree of flexibility, thus allowing the IgG molecule to perform its varied functions.

Animals↗
PubMed1983

[Effect of cations and protons on chloroplast and etioplast membranes].

The stacking of grana and intergrana tylakoids of chloroplast, etioplast and etiochloroplast membranes was studied at various concentrations of H+ and bivalent cations. It was demonstrated that bivalent cations and H+ cause stacking of all types of the membranes tested and is not strictly correlated with the presence of a well-formed ligh-harvesting chlorophyll a/b-protein complex. In preparations of intergrana tylakoids (in contrast to those of grana tylakoids) the effects of cations was minimal. The stacking of intergrana tylakoids is more appreciable in the presence of H+ which is probably due to the peculiarities of components located on the membrane surface.

Cations, Divalent↗
PubMedDate not supplied

[Changing characteristic viscosity of DNA interacting with Cu2+ and Mn2+ ions].

The interaction of DNA with Cu2+ and Mn2+ ions in low ionic strength solutions (10(-3) M NaCl) has been studied by the viscosimetry method. The DNA characteristic viscosity [eta] decreases sharply at low ion concentrations (addition of 10(-5) M Cu2+ leads to [eta] reduction by a factor of 1.4) and attains certain saturation at high concentrations, the saturation magnitude slightly depending on the ion type. The reduction is much lower in solutions containing bivalent ions, in concentration 2 X 10(-2) M NaCl. The experimental data for bivalent and monovalent (Na+) ions have been compared. The results are discussed in terms of equilibrium ion-DNA binding and compared with the Fixman theory. It is discussed if ion binding constants can be determined by visosimetry. It is shown that the cause of the viscosity reduction with time observed by some authors may be the action of DNAases activated by metal ions.

Animals↗
PubMed1981

Selective desensitization of neutrophils: further studies with 1-O-alkyl-sn-glycero-3-phosphocholine analogues.

Human polymorphonuclear neutrophils aggregate and degranulate in response to 2 recently described platelet-activating phospholipids: 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine and 1-O-alkyl-2-O-ethyl-sn-glycero-3-phosphocholine. Here, we find that the 2 phospholipids can also desensitize neutrophils. Thus, cells incubated with either phosphocholine for 1 to 5 min in the absence of calcium and magnesium (which are required for aggregation) did not aggregate when exposed to the bivalent cations and fresh lipid stimulus. Also, cells incubated with either lipid for 5 min in the absence of cytochalasin B (which is required for degranulation) did not degranulate when exposed to cytochalasin B and fresh lipid stimulus. However, these desensitized neutrophils aggregated and degranulated fully in response to the chemotactic oligopeptide N-formyl-methionyl-leucylphenylalanine and C5a. In relation to the aggregation response, this selective desensitization was not due to lipid inactivation; it persisted after thorough cell washing; and it was not induced by a nonaggregating analogue, 1-O-alkyl-sn-glycerol-3-phosphocholine. Furthermore, cells desensitized to the formylated oligopeptide or C5a (by preincubation with either stimulus in the absence of bivalent cations) did not aggregate when challenged with the oligopeptide or C5a, respectively, but exhibited a normal or enhanced aggregation response to the 2 active phospholipids. These data support the concept that C5a, formylated oligopeptides, and phosphocholines represent 3 distinct classes of stimulants that activate and densensitize neutrophils by at least partially independent pathways. This activation and desensitization may be mediated by 3 types of cellular receptors, each of which interacts with only 1 class of stimuli.

Animals↗
PubMed1981

The cell populations mediating natural killing-(NK) and antibody-dependent cell-mediated cytotoxicity are only partially identical.

A cold target inhibition assay has been used to investigate the relationship between the effector cells responsible for NK and ADCC activity. Two models of ADCC have been studied in parallel with NK, one involving in vivo armed effector cells and the other involving normal effector spleen cells tested on antibody-precoated target cells. Bivalent effector cells active in ADCC and NK as well as monovalent NK cells and monovalent FcR-positive ADCC killer cells appear to exist concomitantly. However, the variability from experiment to experiment of the blocking efficiency displayed by the heterologous cold targets, suggests that the proportions of monovalent to bivalent cells may vary between batches of mice depending on their immunological status at the time of the test. This should be taken into careful consideration when interpreting the results of this type of investigation.

Animals↗
PubMed1994

Effect of antibody valency on interaction with cell-surface expressed HIV-1 and viral neutralization.

F(ab) and F(ab')2 fragments of the human mAb, F105, were compared to intact IgG1 for binding to the CD4 binding site of HIV-1/gp120 on the surface of infected cells and viral neutralization. F105 IgG1 and F(ab')2 bound to IIIB, MN, and RF infected cells and neutralized these strains in an identical fashion, whereas strain-specific differences were observed in F(ab) activity. Although F105 F(ab) bound with equivalent affinity to IIIB-infected cells, there was a 4- to 10-fold decrease in the neutralization of IIIB by monovalent F(ab) compared to the bivalent molecules. F105 F(ab) demonstrated both diminished binding and neutralization of the MN strain and failed to bind or neutralize the RF strain. When cooperativity of V3 loop antibody (V3ab) with F105 IgG and fragments was examined, the binding of F105 IgG and F(ab')2 to IIIB-, MN-, or RF-infected cells was modestly enhanced by V3ab; viral neutralization was substantially enhanced by the combination of V3ab and F105 IgG and F(ab')2. The combination of F105 F(ab) with V3ab also resulted in significant cooperative neutralization of IIIB and MN, but the lack of F105 F(ab) binding and neutralization of RF was unaltered by V3ab. These results suggest that bivalent interaction may be important in binding and neutralization of virus, and support the notion that this interaction may depend on conformational changes in oligomeric gp120 on intact virions and cell surface rather than on affinity or steric effects.

Antibodies, Monoclonal↗
PubMed1995

Soluble, but not immobilized, anti-IgM antibody inhibits post-activation events leading to T-cell-dependent B-cell differentiation.

The potential for surface immunoglobulin-binding ligands to modify B-cell differentiation responses induced by activated T cells has been investigated. Activated T cells in human splenic mononuclear cells cultured on anti-CD3-coated plates induced B cells to produce large amounts of IgM and IgG. In this experimental system, cross-linking of B-cell antigen receptors by soluble, bivalent monoclonal or polyclonal anti-IgM antibodies completely inhibited IgM production, and greatly diminished IgG production, in a dose-dependent manner. Similar results were obtained using a F(ab')2 fragment of a goat anti-IgM antibody. Inhibition of B-cell differentiation by bivalent cross-linking reagents did not require the presence of antigen-presenting cells (APC), as comparable results were obtained in co-cultures of purified T and B cells. In contrast, enhanced immunoglobulin secretion was seen when surface IgM was cross-linked using anti-IgM antibody immobilized on the culture plate. Interestingly, activated T cells induced similar levels of expression on B cells of the activation antigens CD23, CD25 and CD71, and of class II molecules, irrespective of any treatment with soluble or immobilized anti-IgM antibody. This indicates that soluble anti-IgM specifically inhibits B-cell differentiation without altering initial events of T-cell-dependent B-cell activation.

Antibodies, Anti-Idiotypic↗
PubMedDate not supplied

Partial inhibition by turkey herpesvirus of serotype 2 Marek's disease virus plaque formation and in vivo infectivity.

The increased use of serotype 2 Marek's disease virus (MDV) and serotype 3 turkey herpesvirus (HVT) as components of effective bivalent vaccines against Marek's disease (MD) prompted studies on the possible interactions of these two viruses in vitro and in vivo. The replication of the SB-1 strain of MDV was compared with replication of the FC126/2 strain of HVT in chickens and cell cultures infected with one or both viruses. Replication of MDV was reduced in the presence of HVT in both in vitro and in vivo systems. MDV plaque counts in dually infected chicken embryo fibroblast cultures inoculated with tissue-culture-propagated viruses were reduced by up to 91%; however, no inhibition was noted when inocula consisted of virus-infected buffy-coat cells. Plaque formation by MDV in chicken embryo fibroblast cultures was inhibited by virus-free conditioned medium from HVT-infected cultures. This conditioned medium also inhibited growth of vesicular stomatitis virus in a standard interferon assay. In chickens inoculated with both MDV and HVT, MDV viremia titers were lower and the dose required to infect 50% of susceptible chickens was increased 13-fold compared with chickens inoculated with MDV alone. In spite of these findings, there was no evidence that high concentrations of HVT interfered with either the ability of MDV to induce protective synergism in vivo or the protective efficacy of bivalent vaccines. No reciprocal inhibitory effects of MDV on the replication of HVT in vivo or in vitro were noted.

Animals↗
PubMed1995

Granulation in amine-storage organelles of mouse megakaryocytes: X-ray microprobe analysis and radioautography.

The mechanisms and the processes of the storage of bivalent cations, ATP and 5-hydroxytryptamine (5HT) in the precursors of the amine-storage organelles of megakaryocytes were studied at the electron microscopic level. Although the precursors of the amine-storage organelles in the megakaryocytes fixed with glutaraldehyde and osmium tetroxide were empty, the electron opaque granules were observed in these organelles of the freeze-substituted megakaryocytes cut onto ethylene glycol. X-ray microprobe analysis demonstrated that they contained P, Mg and Ca. Quantitative differences in bivalent cations in the granules were not observed between megakaryocytes and blood platelets. Electron opaque uranaffin-reaction products were observed in the precursors of the amine-storage organelles of the megakaryocytes after treatment with the uranaffin reaction for ATP. However, few chromaffin positive granules were observed in the precursors of the amine-storage organelles after the chromaffin reaction for monoamines. Radioautographic analysis demonstrated that blood platelets avidly took up 3H-5HT but megakaryocytes were not able to accumulate 3H-5HT in vivo. These results indicate that megakaryocytes do not yet acquire the well developed uptake system of 5HT in vivo, while they readily accumulate cations and ATP in the precursors of the amine-storage organelles.

Adenosine Triphosphate↗
PubMed1994

[Seasonal transformations in the lampbrush chromosomes and the morphogenesis of the karyosphere capsule in Rana temporaria oocytes detectable by an analysis of the isolated nuclear structures].

A study was made of the seasonal changes in lampbrush chromosomes, accompanying structures and the karyosphere capsule, isolated from diplotene oocytes of Rana temporaria of stages 3-6 of oogenesis, as classified by Dumont (1972). The frogs were collected from their hibernation sites. The formation of fibrillar material of the karyosphere capsule was followed from stage to stage. Isolation of nuclei by hand, and dispersal of their content was carried out as described by Callan (Callan, 1986; Callan et al., 1987). A modified Miller's method (Miller, Beatty, 1969) was used for the ultrastructural analysis. The examination of lampbrush chromosomes shows that they change from season to season (summer, autumn, winter), reaching the maximum size in summer (Fig. 2). In autumn their transcriptional activity decreases, although their size remains unchanged. In this period each transcription unit of lateral loops contains about IO RNP-fibrils per 1 mkm, whereas in summer their number is 20 per 1 mkm (Fig. 4, 5). A large number (about 100 per each bivalent) of spheroidal granules about 1.8 mkm in diameter appear around the autumn bivalent (Fig. 3). They constantly accompany the chromosomes and therefore are called satellites. In winter, the satellites are of variable diameter (0.8-5.3 mkm) and still bound to lateral loops of chromosomes. The loops are notably reduced, and the association of the satellites shortened, to aggregate into knots.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Pharmacokinetics of pretargeted monoclonal antibody 2D12.5 and 88Y-Janus-2-(p-nitrobenzyl)-1,4,7,10-tetraazacyclododecanetetraacetic acid (DOTA) in BALB/c mice with KHJJ mouse adenocarcinoma: a model for 90Y radioimmunotherapy.

Three-step pretargeting for radioimmunotherapy in BALB/c mice with KHJJ tumors was done with monoclonal antibody (mAb) 2D12.5, which is specific for yttrium-1,4,7,10-tetraazacyclododecanetetraacetic acid (DOTA) but nonspecific for the tumor. Tumor uptake was by passive diffusion of mAb through leaky neovasculature in the tumor. The three steps were: (a) anti-hapten mAb 2D12.5 (0 h); (b) polyvalent haptenprotein conjugate chase (20 h); and (c) 88Y-labeled monovalent DOTA or bivalent Janus-DOTA haptens (21 h) and organ and tumor bioassay (24 h). Rapid tumor (T) uptake and high tumor:blood ratio (T:BL) was seen 3 h after injection after step c. For monovalent 88Y-DOTA, T = 1.7%/g* and T:BL = 16:1; for bivalent 88Y-Janus-DOTA, T = 4.41%/g* and T:BL = 21:1 at 3 h (*, P < 0.001). Blood and bone plus marrow were << 1%/g, and liver was < 1%/g. The 24-h whole body retention was approximately 5% of injected dose with 1% in tumor (20% of total), 1.8% in other organs, and 2.2% in carcass; the 24-h whole body retention of covalent nonspecific antibody conjugates was > 80% of injected dose. The biological half-life in the tumor of 0.9 microCi 88Y-Janus-DOTA was approximately 24 h, measured daily for 5 days. Activity in microCi/g of tumor and blood for 90Y equimolar to the amount of 88Y injected (0.9 microCi 88Y = 0.744 pmol = 36.47 microCi 90Y) was used for calculating the area under the curve of tumor and blood in microCi-h/g of 90Y. The 90Y radiation absorbed dose (RAD) from multiplying microCi-h/g x the 90Y absorbed dose constant, 1.99 RAD-g/microCi-h, gave T = 89 RAD and BL = 3.7 RAD. The therapeutic ratio from RAD T:RAD BL = 24:1. These results indicate that pretargeting 90Y hapten-specific mAb for radioimmunotherapy has considerable promise.

Acetates↗
PubMedDate not supplied

[Autoantibody formation against the antigens of the synaptonemal complex in the syngeneic immunization of male Mus musculus].

Male mice were immunized with the suspension of synaptonemal complexes (SC) isolated from mouse spermatocytes nuclei. The indirect immunofluorescent analysis showed the active binding of sera obtained from immunized mice to SC of mouse spermatocyte spreads. At early and mid-pachytene, SC can be clearly identified in 19 autosome bivalents and in sex chromosome bivalent. According to the electron microscopic analysis, all structural elements of SC bind antibodies. Metaphase chromosomes were not stained with the immune sera. Specificity of interaction between SC components and antibodies was confirmed in a series of control experiments. Analysis of sera obtained from mice after their syngeneic immunization with isolated SC fraction suggested that certain mouse SC components induce the formation of autoantibodies. This, in turn, suggests that these SC components are meiosis-specific.

Animals↗
PubMed1993

[O2 generation during neuromelanin synthesis. The action of manganese].

The oxygen uptake during the reaction of dopamine autoxidation was studied and it was found that it may occur through two distinct oxidative pathways. One involves the univalent reduction of oxygen, forming the superoxide radical, the other involves a bivalent reduction which generates hydrogen peroxide. The detection of the univalent reaction was followed by the study of oxygen consumption, in the presence of cytochrome c. The detection of the bivalent reaction was made in the presence of catalase. It was found that manganese increases the oxygen uptake of the reaction, by increasing the production of both oxygen active forms. It seems probable that the neurotoxicity of this metal may be related with the increased production of activated oxygen in dopaminergic neurons, which undergo an oxidative stress.

Dopamine↗
PubMedDate not supplied

[The morphofunctional indices of the erythrocytic link in hemopoiesis in persons constantly working in an area of intensified radioecological control].

A study of the peripheral blood indicates that persons constantly working in the zone of rigid radiation control showed a statistically valid reduction of the hemoglobin concentration, appearance of spinous and spheric erythrocyte forms, reduction of the mechanical resistance. Simultaneously 18% of males and 26% of females revealed moderate hypochromic anemia with a normal level of serum iron. The intensity of Fe-transferrin electron paramagnetic resonance was statistically reduced, that may be related to reduction of trivalent iron to bivalent and formation of a pool of free bivalent iron--a potent inductor of lipid peroxidation. Activation of oxidative processes in blood is confirmed by significant fluctuations of the blood ceruloplasmin level.

Ceruloplasmin↗
PubMed1993

[Behavior of pachytene chromosomes in male mice heterozygotic for various translocations (Rb(8,17), T(16,17)43H)].

The electron microscopic analysis of synaptonemal complexes of the Robertsonian translocation heterozygotes (Rb/T) and heterozygotes of the reciprocal translocation (Rb(8, 17)/T(16, 17) 43H revealed three types of translocation configurations (TC). The observed TC were subdivided into three types according to the manner of synapsis: 1) full synapsis of homologues forming trivalent with interstitial centromere in 15%; 2) the centromeric asynapsis (8 and 17-16 chromosomes forming trivalent with the extension region of asynapsis and breakpoint of the reciprocal translocation on chromosome 17 in 70%; 3) centromeric asynapsis (only single chromosome 17-16 of trivalent, when the break point of reciprocal translocation and the absence of centromeric asynapsis of another chromosome 8 formed trivalent in 15%). The frequency of association between trivalents and the XY bivalents is 20% and close proximity is 15% for heterozygotes Rb/T. Which are fertile, while in the sterile heterozygotes Rb(8, 17)/T(16, 17) 43H it is 45% for association and 15% close proximity (total 60%). These data show the significant differences in the contact of translocation configurations with the XY bivalents of fertile heterozygotes, in comparison with the sterile. Thus, it is shown that the chromosome pairing of fertile and sterile mice is clearly distinguished.

Animals↗