A mathematical model of the response of principal cells of collecting ducts to hypotonic shock

The regulatory decrease in the volume of principal cells of collecting ducts to hypoosmotic shock has been investigated experimentally and using the mathematical modeling. A mathematical model of the response of collecting duct principal cells to hypotonic shock has been constructed on the basis of the experimental time course of changes in cell volume measured by the fluorescent dye Calcein. It was shown that the regulatory decrease in volume under hypotonic conditions occurs via a marked release of osmolytes and is accompanied by a decrease in water permeability of the cell membrane. The mathematical modeling of transmembrane transport processes allowed us to quantitatively estimate the changes in membrane water permeability, which decreased tenfold, from 2 x 10(-1) cm/s to 2 x 10(-2) cm/s. It was also shown that the effective regulatory decrease in the volume of collecting duct principal cells in hypotonic medium results from a significant increase in membrane permeability for K+, Cl-, and organic anions.     

Study of the reaction of kidney collecting duct principal cells to hypotonic shock. Experiment and mathematical model

The reaction of rat kidney collecting duct principal cells to hypotonic shock was studied. The changes in cell relative volume were measured using fluorescent dye calcein, and a mathematical model based on our experimental results was developed. It was shown that regulatory volume decrease is mainly provided by significant release of osmolytes from the cell and decrease of the plasma membrane water permeability. Using our model, we calculated the membrane water permeability and found it to decrease from 2 · 10⁻¹ to 2 · 10⁻² cm/s. We conclude that for effective RVD to occur, a dramatic increase in the membrane permeability to K⁺, Cl⁻ and organic anions is necessary.     

Use of non-radioactive biotin-labelled probes for detecting hepatitis A virus]

The biotin-labeled DNA probes were constructed on the basis of the hybrid bacteriophage M13nip 9 single-stranded DNA containing the fragments of the hepatitis A viral cDNA. The probes were biotin treated by chemical modification of the DNA by the peraminating reagent or photochemically. The labeled DNA probes were used in molecular hybridization experiments with the nuclear acids fixed on the nitrocellulose filters. The biotin treated DNA was determined by the avidin-gold colloid conjugate with the subsequent physical silver amplification or by the streptavidin-alkaline phosphatase conjugate. The sensitivity of both probes was identical and permitted the determination of 5 x 10(-11)-5 x 10(-12) g of the control DNA and 10(-9) g of the hepatitis A virus. The developed test systems were used for detection of the viral RNA in blood from patients.     

Effect of dDAVP on basolateral cell surface water permeability in the outer medullary collecting duct

We report a novel approach for assessing the volume of living cells which allows quantitative, high-resolution characterization of dynamic changes in cell volume while retaining the cell functionality. The aim of this study was to evaluate the short-term effect of vasopressin on basolateral cell surface water permeability in the outer medullary collecting duct (OMCD). The permeability of the basolateral cell membrane was determined in the tubules where the apical membrane was blocked with oil injected into the lumen. The apparent coefficient of water permeability (P _f) was evaluated by measuring the cell swelling after the step from hypertonic to isotonic medium (600 mosm to 300 mosm). Desmopressin (dDAVP) induced an increase of the basolateral P _f from 113.7±8.5 μm/s in control cells to 186.6±11.4 μm/s in micro-dissected fragments of the OMCD incubated in vitro (10⁻⁷ M dDAVP, 30 min at 37 °C) (P<0.05). Mercury caused pronounced inhibition of basolateral water permeability (26.0±6.9 μm/s; P<0.05). The effect of mercury (1.0 mM HgCl₂) was reversible: after washing the fragments with PBS for 20 min, P _f values were restored to the control levels (125.0±9.5 μm/s). The results of the study indicate the existence of a mechanism controlling the osmotic water permeability of the basolateral cell membrane in the OMCD epithelium.     

Water permeability of the OMCD and IMCD cells' basolateral membrane under the conditions of dehydration and dDAVP action

Water permeability of the basolateral membrane was estimated in isolated fragments of OMCD or IMCD in the Wistar rats. Apical surface of the fragments was blocked with oil injected into the lumen. Apparent water permeability coefficient (Pf) was measured by the rate of epithelium swelling following transition from hypertonic to isotonic medium (600 mOsm to 300 mOsm). Water deprivation caused significant increase in the Pf value in OMCD and IMCD fragments. Desmopressin (10(-8) M) increased water permeability in hydrated rats both in OMCD and IMCD. Mercury chloride decreased the Pf and abolished the effect of desmopressin in reversible manner. Estimation of aquaporins 2, 3, 4 mRNA content in the renal medulla was performed by semi-quantitative RT-PCR. Content of AQP4 and AQP2 mRNA in dehydrated animals was significantly higher than in hydrated ones both in outer medulla and inner medulla. Expression of AQP3 increased during dehydration only in the inner medulla. The findings reveal that water permeability of OMCD and IMCD can be increased by physiological stimuli, e.g. water deprivation. The activation of gene expression of the key elements of vasopressin signal system seems to contribute to this reaction.     

The humoral immunity against diphtheria

Results of the conducted study showed that naturally acquired antibacterial and postvaccinal antitoxic antibodies against diphtheria were found in human blood sera. Challenge of ADT-M toxoid to adults resulted in production of antitoxic as well as antibacterial antibodies in high concentrations. In response to challenge of ADT-M toxoid simultaneously with bacterial vaccine against diphtheria Codivac both antibacterial and antitoxic antibodies were synthesized in blood on optimal physiologic levels. This study revealed dynamics of some specific characteristics of humoral immune response after challenge of two different vaccines against diphtheria--ADT-M toxoid and Codivac vaccine.     

Study of the mechanism of mutagenesis directed by phosphotriester analogs of oligonucleotides. The role of repair in mutagenesis

The mutation system has been suggested in an effort to test insertion and deletion mutants by changing the Lac-phenotype of bacterial colonies transformed by mutant DNA. This system also makes possible to determine heterozygotes and homozygotes among the mutants. The yield of mutants in shown to depend on the structure of the DNA heteroduplex region. The yield of deletion mutants is greater than that of insertion mutants. Heterozygotes prevail in mutant colonies (greater than 90%).     

Mutagenesis, directed by artificial oligonucleotide analogs. I. Participation of ribonucleotide fragments in DNA replication and repair

The mutation system has been developed to study the mutagenic properties of modified oligonucleotide analogs. The mutagenic properties of oligonucleotides containing one ribonucleotide have been examined. The presence of a ribonucleotide is shown not to induce any mutations. But when the oligonucleotide induces two marker deletions detached by 6 nucleotides they may be repaired separately, in this case the deletion bordering with the ribonucleotide is predominantly repaired.     

Variability of Composition of Microbiota of Gastrointestinal Tract of Perch Perca fluviatilis and Prussian Carp Carassius gibelio During the Vegetative Season

Journal of Ichthyology - The composition of the microbiota of the digestive tract of two fish species differing in feeding habits—perch Perca fluviatilis and Prussian carp Carassius gibelio...