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Biomedical subjects

J Bíró

Publications and source records attributed to J Bíró.

At least 19 recordsLinked to original sources
PubMed2006

Identification and characterization of genes associated with the induction of embryogenic competence in leaf-protoplast-derived alfalfa cells.

Alfalfa leaf protoplast-derived cells can develop into somatic embryos depending on the concentration of 2,4-dichlorophenoxyacetic acid (2,4-D) in the initial culture medium. In order to reveal gene expression changes during the establishment of embryogenic competence, we compared the cell types developed in the presence of 1 and 10 microM 2,4-D, respectively, at the time of their first cell divisions (fourth day of culture) using a PCR-based cDNA subtraction approach. Although the subtraction efficiency was relatively low, applying an additional differential screening step allowed the identification of 38 10 microM 2,4-D up-regulated transcripts. The corresponding genes/proteins were annotated and representatives of various functional groups were selected for more detailed gene expression analysis. Real-time quantitative PCR (RT-QPCR) analysis was used to determine relative expression of the selected genes in 2,4-D-treated leaves as well as during the whole process of somatic embryogenesis. Gene expression patterns confirmed 2,4-D inducibility for all but one of the 11 investigated genes as well as for the positive control leafy cotyledon1 (MsLEC1) gene. The characterized genes exhibited differential expression patterns during the early induction phase and the late embryo differentiation phase of somatic embryogenesis. Genes coding for a GST-transferase, a PR10 pathogenesis-related protein, a cell division-related ribosomal (S3a) protein, an ARF-type small GTPase and the nucleosome assembly factor family SET protein exhibited higher relative expression not only during the induction of somatic embryogenesis but at the time of somatic embryo differentiation as well. This may indicate that the expression of these genes is associated with developmental transitions (differentiation as well as de-differentiation) during the process of somatic embryogenesis.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1995

Dehydroepiandrosterone modulates the spontaneous and IL-6 stimulated fibrinogen production of human hepatoma cells.

The role of an androgen, dehydroepiandrosterone (DHEA) has been studied on the constitutive and IL-6 induced fibrinogen production of HepG-2 cells. DHEA markedly augments the constitutive fibrinogen production of the hepatoma cells in a dose dependent fashion. Oppositely, for IL-6 induced fibrinogen production, DHEA is strongly inhibitory. The effectiveness of DHEA on the constitutive fibrinogen production is further potentiated if the hepatoma cells are preincubated with a glucocorticosteroid, dexamethasone. These findings demonstrate that the complex interaction between the steroid- and cytokine-directed regulation of the production of acute phase proteins is further coloured by the action of androgens on immune and hormonal systems.

Carcinoma, Hepatocellular↗
PubMed1994

[Interleukin-6: friend or enemy? Latest findings on the clinical aspects of IL-6].

The authors summarize the recent findings obtained in the field of inflammatory cytokines with particular attention on interleukin-6 (IL-6). After a short review of the molecular biology and of the cellular effects of IL-6, the most important clinical relations of IL-6 in hepatic diseases, in non-specific inflammatory bowel diseases (Crohn's disease and ulcerative colitis) and in certain autoimmune diseases are provided. The simultaneous discussion of molecular and clinical data contribute to the understanding of pathomechanisms.

Autoimmune Diseases↗
PubMed1984

Effects of hysterectomy and uterine extracts on the endocrine system of adult, nonpregnant rats.

Plasma concentration and anterior pituitary content of growth hormone (rGH), thyroid stimulating hormone (rTSH), prolactin, follicle stimulating hormone (rFSH), luteinizing hormone (rLH) as well as the plasma concentrations of triiodothyronine (T3), thyroxine (T4), corticosterone and immunoreactive somatomedin A (SM-A) have been determined in intact, ovariectomized or ovo-hysterectomized rats with and without treatment with steroid-free uterine extracts. The endocrine organs were weighed. Two weeks after hysterectomy the body weight was decreased, the weight of adrenals was increased, the plasma GH concentrations increased and the plasma TSH and T3 concentrations were decreased compared to the sham operated controls. Treatment with steroid-free uterine extracts had opposite effects; furthermore, a reduction of pituitary FSH, GH and prolactin content was observed. Plasma immunoreactive SM-A concentrations were not significantly influenced by this treatment, but there was a positive correlation between the body weight and SM-A and a negative correlation between the plasma GH and plasma SM-A concentrations regarding the individual values of hysterectomized, uterine-extract-treated and ovariectomized animals. The results suggests that uterine factors can influence the synthesis and release of several hormones and the weight of some endocrine organs in adult, nonpregnant rats.

Animals↗
PubMed1984

Effects of hysterectomy and in-vivo treatment with uterine extracts on plasma concentrations of growth hormone, thyrotrophin and thyroid hormones in rats: a kinetic study.

Plasma concentrations of GH, TSH, tri-iodothyronine (T3) and thyroxine (T4) were measured in adult rats 2 and 4 weeks after ovariectomy and and ovariohysterectomy. Two weeks after ovariohysterectomy, the concentration of GH was significantly higher, but TSH and T3 concentrations were significantly lower than in rats which had been ovariectomized only. Hysterectomy had no effect on plasma GH and TSH concentrations if it was performed 2 weeks after ovariectomy. Plasma T3 had decreased by 2 weeks after ovariectomy but returned to pretreatment levels by 4 weeks. Recovery of the plasma T3 concentration was not observed if ovariectomy was followed by hysterectomy, since a further decrease of plasma T3 occurred. Plasma T4 was not significantly influenced either by ovariectomy or by ovariohysterectomy. Steroid-free uterine extracts given i.p. to ovariohysterectomized rats reduced plasma GH within 24 h of injection. Increases in plasma TSH, T3 and T4 were achieved in ovariohysterectomized rats with injections of uterine extracts (from intact, oestrogen-treated or castrated rats), but the increases were not consistent for the three hormones either as regards time after injection, nor for which particular extracts were effective. It concluded that the uterus may contain factors which influence the GH storage and secretion and TSH-thyroid regulation in rats.

Animals↗
PubMed1983

Some theoretical questions of mechanisms of thyroid hormone action.

The effects of iodothyronines, the suggested mechanisms of their action, the methodical difficulties of determining receptors of thyroid hormones, the significance of iodothyronine formation during hormone action and some stereochemical aspects of the receptor--thyroid hormone interaction have been reviewed and a new model of the thyroid hormone action has been developed. It is suggested that the thyroid hormones may interact with more than one protein and nucleic acid at the same time and in this way "help" the interaction of macromolecules, thus catalysing and modulating biochemical processes of diverse character.

Humans↗
PubMed1983

Information transfer in biological systems. Part I: Calculation of the information content of some amino acids, lipids, and nucleic acid bases.

The Information Contents (IC) of some small molecules (amino acids, nucleic acid bases, lipids . . .) have been calculated by a newly developed method. A coordinate system, in which parallel, linear, saturated . . . -CnH2n- . . . chains in space serve the dimensions, has been postulated and its properties have been mathematically characterized. The system is suitable for the crude calculation and comparison of the IC-s of small molecules using conventional methods of information theory. A series of calculations has been presented to illustrate the use of the method. The importance of the IC calculations for understanding some biochemical processes (receptor-ligand bindings, enzymatic reactions) is discussed.

Amino Acids↗
PubMed1983

Information transfer in biological systems. Part II: Transfer of molecular information through biological membranes. The "reverse-translation".

A theory based on the fluid-mosaic-membrane model is presented to account for the transduction of extracellular molecular information into cells. Binding of a ligand to the external surface of the lipoprotein membrane leads to a specific rearrangement of the intracellular receptor-analogs or to a characteristic deformation of the inner membrane surface and these changes trigger further intracellular events. The saturated and unsaturated fatty acid chains in the membrane have important roles in transferring the extracellular molecular informations. Some similarities between the effects of monoamines, oligo- and polypeptides may be explained on the basis of this model. As a consequence of the model the possible existence of "reverse-translation" is suggested.

Amino Acids↗
PubMed1983

General theory of cell regulation.

A general theory of cell regulation has been based on a previously described concept that both DNA chains of the chromatin may be expressed, and the protein products of this type of gene expression are also complementary to each other and can specifically interact with each other and with the nucleic acids which serve the code for them. The regulation of biological processes is directed by these specifically interacting molecules which are organized in Elementary Regulatory Units (ERU). The biological information in ERUs is persisting reversibly transformable (on the basis of protein and nucleic acid complementarity), buffered, and complementary information is in balance with each other. The information transfer by macromolecules in the ERUs follows the law of mass action. Biologically active "small" molecules (nucleotide phosphates, steroids, iodothyronins) interact with the ERUs and influence their steady states. The contact inhibition of the cells and the cooperative regulation of different cells and cell functions have been explained on the basis of the theoretically explained properties of the ERUs.

Cell Physiological Phenomena↗
PubMed1983

Effects of hysterectomy and uterine extracts on growth hormone, somatomedin, prolactin, thyrotrophin and thyroid hormones in adult rats.

Plasma concentrations and anterior pituitary content of growth hormone (rGH), thyroid stimulating hormone (rTSH), and rat prolactin (rPrl) as well as the plasma concentrations of triiodothyronine (T3), thyroxine (T4) and somatomedin A (SM-A) have been determined in intact, castrated or hysterectomized adult rats with and without treatment with steroid-free, crude uterine extracts. Hysterectomy caused a significant increase in the plasma GH but decrease in the plasma TSH concentrations. Injection of crude, steroid-free uterine extracts for 14 days had the following effects: decreased plasma GH concentration of intact rat and anterior pituitary GH content of both intact and castrated animals; increased plasma TSH and T3 concentrations above the ovariectomized control; decreased pituitary content of prolactin in castrated rats. The plasma levels of immunoreactive somatomedins A were negatively correlated to the plasma GH concentrations but positively correlated to the body weight. It was concluded that the uterus is not only a target for different endocrine influences but contains biologically active, non-steroidal substances which have a complex effect on the endocrine system of adult, female rats.

Animals↗
PubMed1982

Some theoretical questions of the peptide and steroid hormone regulation. Part I.: The receptor-steroid variable complex (RSVC) hypothesis of genetic regulation.

Steroids exert their known biological and biochemical effects in connection with specific receptors. These effects are so various and complex that it is impossible to explain them on the basis of a concept supposing the presence of only one unique receptor molecule in the target organs. The heterogeneity in the function of steroids requires a heterogeneity in the molecular composition of the receptor-steroid complexes. Direct and indirect evidence is presented to support a multiplex, heterogene receptor theory. The possible origin of this complexity is analyzed and a new concept of specific gene regulation by heterogene receptor-steroid complexes is suggested. in this theory the distribution and sequence of one or more steroids on the receptor can carry and serve highly specific and unique information capable or recognizing and binding to the acceptor site of the chromatin and regulating gene expressions specific for steroids. The formation of such Receptor-Steroid Variable Complexes (RSVC) has been mathematically analyzed and the properties of a chromatin protein capable of detecting both the DNA and the steroid sequences on the receptor are discussed.

Animals↗
PubMed1982

Some theoretical questions of the peptide and steroid hormone regulation. Part II.: The second messenger system.

The "second messenger system" has been analysed regarding its possibilities for containing and transferring highly specific molecular, biological information. Very heterogeneous molecules were found behind the different - cyclase, diesterase, kinase,... - activities of the system, whereas the connection realized between them by cyclic nucleotides was very poor. So, I constructed a theoretical model mostly on the basis of real and known experimental facts to resolve this obvious contradiction and make the second messenger system adequate as a highly specific biological informational channel.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1982

Some theoretical questions of the peptide and steroid hormone regulation. Part III.: The RLVC hypothesis as a possible mode for the interaction of the peptide and steroid hormone regulation.

My previous models for peptide and steroid hormone actions, in accordance with their biological and molecular-informational requirements, suggested possible mechanisms for the subcellular interactions of the two regulatory systems. In my hypothesis the homogeneous or heterogeneous multiligand binding-proteins (receptors, characterized previously) have the ability to bind both steroids and (cyclic) nucleotide phosphates in a unique distribution and sequence. The specificity of such a Receptor-Ligand Variable Complex (RLVC), the pattern of the steroid and/or (cyclic) nucleotide phosphate ligands, is determined by the equilibrium between the actually acting steroids and peptides on the one hand and by the binding possibilities of the receptor on the other.

Animals↗
PubMed1982

Thyroid-stimulating antibodies in Grave's disease and the effect of thyrotrophin-binding globulins on their determination.

Globulin preparations from the sera of 104 untreated patients with Grave's disease have been tested for their thyroid-stimulating antibody (TSAb) activities. Eighty-one of the samples (78%) were positive in the assay for the thyrotrophin-binding inhibitory immunoglobulins, 48 samples (46%) contained human thyroid adenyl cyclase stimulators (HTACS) and 71 (68%) contained human thyroid stimulators (HTS) measured as stimulation of colloid droplet formation in human thyroid slices. All 104 samples were positive in one or other of the assays, 29 (28%) were positive in all three assays and 38 (37%) in two. All samples were tested for their specific TSH-binding characteristics, 40 (38%) possessed 'B-type' binding sites (previously characterized as TSH-binding sites with low affinity but high capacity for the ligand) but the remaining 64 samples (62%) were no different from normal control samples and had 'A-type' binding sites (high affinity but low capacity binding sites for TSH). Samples without detectable thyrotrophin-binding inhibitory immunoglobulin did not contain B-type TSH-binding globulins. Globulins exhibiting B-type binding were more active in the HTACS and HTS assays. The B-type TSH-binding globulins have a characteristic, dose-dependent reducing effect on the human thyroid adenyl cyclase stimulation by TSH whereas A-type globulins do not. Globulins exhibiting B-type TSH-binding may therefore have a significant effect on assays for TSAb activities. The method used to measure TSAb have been reviewed from this point of view.

Adenylyl Cyclases↗
PubMed1982

Specific uridine binding by some proteins.

Chemically pure or highly purified proteins have been analysed for their specific uridine binding. The peptides generally have two well distinguishable binding sites for uridine regarding their Kd and Bmax values. Uracil competed for the uridine binding sites with uridine, whereas adenine, corticosterone and testosterone did not. The adenine and the sexual steroids augmented the number of maximal binding sites in many cases. The number of specific binding sites varied from 1 to 61 per peptide (Kd: 1.1--51.7 X 10(-10) M).

Adenine↗