GABA representation in hypoxia sensing: a ventilatory study in the rat

Phenibut, a nonspecific GABA derivative, is clinically used as an anxiolytic and tranquilizer in psychosomatic conditions. A GABA-ergic inhibitory pathway is engaged in respiratory control at both central and peripheral levels. However, the potential of phenibut to affect the O2-related chemoreflexes has not yet been studied. In this study we seek to determine the ventilatory responses to changes in inspired O2 content in anesthetized, spontaneously-breathing rats. Steady-state 5-min responses to 10% O2 in N2 and 100% O2 were taken in each animal before and 1 h after phenibut administration in a dose 450 mg/kg, i.p. Minute ventilation and its frequency and tidal components were obtained from the respiratory flow signal. We found that after a period of irregular extension of the respiratory cycle, phenibut stabilized resting ventilation at a lower level [20.0±3.3 (SD) vs 31.1±5.2 ml/min before phenibut; P<0.01]. The ventilatory depressant effect of phenibut was not reflected in the hypoxic response. In relative terms, this response was actually accentuated after phenibut; the peak hypoxic ventilation increased by 164% from baseline vs the 100% increase before phenibut. Regarding hyperoxia, its inhibitory effect on breathing was more expressed after phenibut. In conclusion, the GABA-mimetic phenibut did not curtail hypoxic ventilatory responsiveness, despite the presence of GABA-ergic pathways in both central and peripheral, carotid body mechanisms mediating the hypoxic chemoreflex. Thus, GABA-mediated synaptic inhibition may be elaborated in a way to sustain the primarily defensive ventilatory chemoreflex.     

Role of protein kinases of human red cell membrane in deformability and aggregation changes

The proteomic analysis has shown that the red cell membrane contains several kinases and phosphatases. Therefore the aim of this study was to investigate the role of protein kinases of human red cell membrane in deformability and aggregation alterations. The exposure of red blood cells (RBCs) to some chemical compounds has led to a change in the RBC microrheological properties. When forskolin (10 μM), an adenylyl cyclase (AC) and a protein kinase A (PKA) stimulator were added to RBC suspension, the RBC deformability (RBCD) was increased by 20% (p<0.05). Somewhat more significant deformability rise appeared after RBC incubation with dB-AMP (by 26%; p<0.01). The red cell aggregation (RBCA) was significantly decreased under these conditions (p<0.01). Markedly less changes of deformability were found after RBC incubation with protein kinase stimulator C (PKC)—phorbol 12-myristate 13-acetate (PMA). This drug reduced the red cell aggregation only slightly. The red cell tyrosine phosphotase activity was changed by N-vanadat and a significant RBCD rise and RBCA lowering were obtained. The similar effect was found when the cells were incubated with cisplatin as a tyrosine protein kinase (TPK) activator. It is important to note that a selective TPK inhibitor—lavendustin eliminated the above mentioned effects.     

Detection of annexin IV in bovine retinal rods

The fraction of proteins capable of binding to photoreceptor membranes in a Ca²⁺-dependent manner was isolated from bovine rod outer segments. One of these proteins with apparent molecular mass of 32 kD (p32) was purified to homogeneity and identified as annexin IV (endonexin) by MALDI-TOF mass-spectrometry. In immunoblot, annexin IV purified from bovine rod outer segments cross-reacted with antibodies against annexin IV from bovine liver. This is the first detection of annexin IV in vertebrate retina.     

Effect of Azospirillum brasilense lectin on the kinetics of lymph nodes cell populations and cytokine status in experimental animals

The complex study of the influence of A. brasilense Sp 7 lectin with carbohydrate specificity to L-fucose and D-galactose on the dynamics of cell populations in different structural functional zones of the white mice mesentery, as well as on the capacity of immunocompetent cells of mesenterial lymph nodes for synthesizing cytokines (interleukin-1, interleukin-6 and tumor necrosis factor), was carried out. A single oral administration of bacterial lectin in a dose of 4.5 micrograms produced a pronounced immunostimulating effect.     

Recoverin and rhodopsin kinase activity in detergent-resistant membrane rafts from rod outer segments

Cholesterol-rich membranes or detergent-resistant membranes (DRMs) have recently been isolated from bovine rod outer segments and were shown to contain several signaling proteins such as, for example, transducin and its effector, cGMP-phosphodiesterase PDE6. Here we report the presence of rhodopsin kinase and recoverin in DRMs that were isolated in either light or dark conditions at high and low Ca2+ concentrations. Inhibition of rhodopsin kinase activity by recoverin was more effective in DRMs than in the initial rod outer segment membranes. Furthermore, the Ca2+ sensitivity of rhodopsin kinase inhibition in DRMs was shifted to lower free Ca2+ concentration in comparison with the initial rod outer segment membranes (IC50=0.76 microm in DRMs and 1.91 microm in rod outer segments). We relate this effect to the high cholesterol content of DRMs because manipulating the cholesterol content of rod outer segment membranes by methyl-beta-cyclodextrin yielded a similar shift of the Ca2+-dependent dose-response curve of rhodopsin kinase inhibition. Furthermore, a high cholesterol content in the membranes also increased the ratio of the membrane-bound form of recoverin to its cytoplasmic free form. These data suggest that the Ca2+-dependent feedback loop that involves recoverin is spatially heterogeneous in the rod cell.     

Prevalence of widespread BRCA1 gene mutations in patients with familial breast cancer from St. Petersburg

Ten variants different from the canonical nucleotide sequence (GenBank, U14680) has been identified when studying the mutation spectrum in gene BRCA1. Six of them (5382insC, 2963del10, 3819de15, 3875del4, 2274insA, and R1203X) cause premature termination of protein synthesis, thus predisposing to breast cancer. A missense mutation E1250K is presumed to be a factor of predisposition to cancer. We classified three variants of nucleotide sequence found in some patients as DNA polymorphisms S694S, L771L, and E1038G. The 5382insC and 3819de15 mutations have been detected in four and two families, respectively. Five of the mutations detected have not been found in Russia before. However, all mutations except for 2963del10 have been found in other populations of the world, which indicates their long evolutionary history. Two mutations found in patients from St. Petersburg (5382insC and 3875de14) have also been found in oncological patients from other regions of the Russian Federation.     

Probing hydration of monovalent cations condensed around polymeric nucleic acids

We report the relative molar sound velocity increments, [U], partial molar volumes, V(o), and partial molar adiabatic compressibilities, K(S)(o), of the Li(+), Na(+), K(+), Rb(+), Cs(+), NH(4)(+), and N(CH(3))(4)(+) salts of poly(dAdT)poly(dAdT), poly(dGdC)poly(dGdC), poly(dIdC)poly(dIdC), poly(rA)poly(rU), poly(rG)poly(rC), poly(rI)poly(rC), and poly(rU) at 25 degrees C. When analyzing these data, we take into account the Donnan membrane equilibrium effect. Comparison between the values of [U], V(o), and K(S)(o) exhibited by the nucleic acid salts and respective chlorides (LiCl, NaCl, KCl, RbCl, CsCl, NH(4)Cl, and N(CH(3))(4)Cl) yields information about the state of counterion hydration in the vicinity of each nucleic acid structure studied here. Our analysis reveals that the poly(dGdC)poly(dGdC), poly(dIdC)poly(dIdC), and poly(rI)poly(rC) duplexes and single-stranded poly(rU) do not significantly influence the hydration properties of their condensed counterions. In the vicinity of these polymers, counterions retain their full hydration shells (within +/-15%). By contrast, counterions condensed around the poly(dAdT)poly(dAdT), poly(rA)poly(rU), and poly(rG)poly(rC) duplexes are significantly dehydrated and retain, respectively, only 65(+/-18)%, 34(+/-21)%, and 33(+/-9)% of their original hydration shells. Taken together, the volumetric data reported here provide important new information that ultimately may help us understand the central role that hydration and counterions play in modulating the conformational preferences of nucleic acids and the energetics of DNA recognition events.     

Milk ultrafiltrate as a promising source of angiogenin

The use of membrane technologies in the production of soft cheese (children's food) is associated with the appearance of up to 80% of angiogenin in the ultrafiltrate. An electrophoretically homogeneous preparation of angiogenin (MW approximately 17 kDa) was obtained from milk ultrafiltrate by two-stage ion-exchange chromatography. The yield of the angiogenin was approximately 60%, which corresponds to a 586-fold purification of the raw material. The obtained preparation retained stability in the course of lyophilization and could be stored at 4 degrees C for a long time without decomposition.     

Milk Ultrafiltrate as a Promising Source of Angiogenin

The use of membrane technologies in the production of curd (soft cheese for children) is associated with the appearance of up to 80% of angiogenin in the ultrafiltrate. An electrophoretically homogeneous preparation of angiogenin (MW 17 kDa) was obtained from milk ultrafiltrate by two-stage ion-exchange chromatography. The yield of the angiogenin was 60%, which corresponds to a 586-fold purification of the raw material. The obtained preparation retained stability in the course of lyophilization and could be stored at 4°C for a long time without decomposition.     

Comparative analysis of the effects of synthetic derivatives of batrachotoxin on sodium currents in frog node of Ranvier

1. In voltage-clamp experiments on frog myelinated nerve fibers, the effects of nine synthetic derivatives of batrachotoxin (BTX) obtained from 7,8-dihydrobatrachotoxinin A (DBTX-A) on Na+ currents (INa) have been investigated. 2. Both of 20 alpha-esters of DBTX-A with 2,4,5-trimethylpyrrol-3-carboxylic acid (DBTX-P) and benzoic acid (DBTX) at a 10(-5) M concentration caused modification of INa qualitatively similar to that induced by BTX. 3. The quaternary derivative of DBTX (QDBTX) produced such changes in INa only at a 5.10(-4) M concentration, apparently due to its much lower lipid solubility. 4. Replacement of a -CH2- by a -C = O. group in the homomorpholine ring near the tertiary nitrogen atom abolished the DBTX activity, strongly suggesting the necessity of tertiary nitrogen protonation for the toxin interaction with the channel receptor. 5. Transfer of an 11-hydroxygroup from the alpha- to the beta-position in the DBTX molecule did not decrease its activity in spite of the fact that in the beta-position this group is sterically very hindered. The activity of 11 beta-DBTX is at variance with the prediction of Codding's (1983) "oxygen triad" hypothesis. 6. DBTX-A and compounds obtained from DBTX by oxidation of the 11 alpha-hydroxygroup (K-DBTX), acetylation (Ac-DBTX), or reduction of the hemiketal moiety (H2DBTX) even at a concentration as high as 10(-3) M were able to modify only a very small fraction of the Na channels. However, a clear-cut reversible blocking action on both normal and modified Na channels was observed. 7. These results led us to conclude that BTX modifies the Na channels only in the charged form and hemiketal and 20 alpha-ester moieties provide adequate disposition of toxin on the receptor surface. The inability of H2DBTX, DBTX-A, and K-DBTX and Ac-DBTX to modify most of the Na channels can be explained by a low "probability of correct disposition" of these ligands on the receptor surface.