[The functional tests in clinical diagnostic laboratory: the detection of magnesium deficiency in the loading test].

The article deals with the value and role of functional tests in practice of clinical diagnostic laboratories. The possibilities of evaluation of biological function of homeostasis according the changes of magnesium ions or calcium concentration in urine or blood hence reflecting the deficiency of these ions in vivo. The magnesium tolerant test is described It is demonstrated that it can be applied both in curative preventive institutions and ambulatories. In the examined group of patients, 78% had physiologic parameters of magnesium concentration, 17% suffered from hypermagnesiumuria and 5%--from hypermagnesiumuria. The magnesium deficiency of different degree was detected in 87% of patients. In the most part of patients with magnesium deficiency normomagnesiumuria was detected. Only in one case with normomagnesiumuria the magnesium deficiency was absent. In 30% of patients with magnesium deficiency the concentration of cation in day urine decreased up to 2.2 times after load dose. In absence of deficiency the monotony of cation's excretion was noted. Under the magnesium deficiency the character of process changed but velocity of excretion of magnesium after load probe slightly decreased relative to values before the load. The impact of alcohol under established magnesium deficiency results in increasing of velocity of excretion of this analyte. In patient with diabetes mellitus type II six months before the diagnosis of this disease the hidden deficiency of magnesium was detected. The magnesium deficiency was not detected after the antidiabetic treatment was applied The results permit to postulate the possibility of application oral load test with magnesium to assess the impact of various stress, physical, emotional and psychological factors. The detection of magnesium deficiency permit to broad the complex treatment, to accelerate and to enhance the results of treatment of diseases. Besides, the evaluation of patient's condition according the reaction of the organism to the probe with magnesium load is an essential element of personalized medicine.

[Adenylate kinase and GDP-kinase activity of rod outer segments in the frog retina. Possible functional role of the T beta subunit of transducin]. / Adenilatkinaznaia i GDP-kinaznaia aktivnost' preparatov naruzhnykh segmentov palochek setchatki liagushki. Vozmozhnaia funktsional'naia rol' sub''edinitsy T beta transdutsina.

Pure frog retina rod outer segments (ROS) preparations (A280/A500 = 2,1-2,3) catalyze the synthesis of ATP from ADP in the presence of Mg2+. Adenylate kinase (AK) (ATP:AMP phosphotransferase, EC 2.7.4.3) specific activities for ROS preparations are within the range 2-4 mumole per hour for mg protein. The enzymatic activity of investigated preparations is due to intact, but not destroyed ROS. The component which possesses AK is found in water-soluble, but not in membranous ROS fractions and seems to be a part of the predominant ROS plasma protein--GTP-binding complex of transducin. It has been shown, that this component is the T beta subunit of transducin and its enzymatic activity is controlled by other subunits of the transducin complex. The obtained results indicate that GDP kinase (ATP:GDP phosphotransferase, EC 2.7.4.6) activity of transducin depends on the work of both of T beta and T alpha subunits. It has been shown that in the ROS preparations synthesis of the ATP from ADP and GDP phosphorylation are stimulated by a lowering of Ca2+ concentration (less than 10(-5)-10(-7) M). T beta component is suggested to play the role of phosphotransferase which phosphorylates GDP associated with the T alpha subunits and it leads to formation of a complex T alpha X GTP which is an activator of vertebrate retina ROS phosphodiesterase.

[Guanosine triphosphate complex in rod outer segments of the frog retina]. / Guanizin-trifosfatnyi kompleks v naruzhnykh segmentakh palochek setchatki liagushki.

It is shown that nearly 70% water--soluble protein of the frog retina outer segments (ROS) consist of three polypeptides with molecular weights 39 000, 36 000 and less than 15 000 daltons. These proteins are present in equal proportions and are, apparently, the subunits of a tightly bound protein complex. The subunit of 39 000 daltons is responsible for guanyl nucleotides binding. Parameters of the investigated GTP-binding complex are similar to transducyn which transmits excitation from bleached rhodopsin to PDE molecules in the bovine retina ROS. The thermodynamic state of GTP-binding protein in frog retina ROS depends on the functional state of the photoreceptor membrane, as shown by microcalorimetric method.

[Interaction of guanine nucleotides with photoreceptor membranes of rod outer segments of frog retina]. / Vzaimodeistvie guanilovykh nukleotidov s fotoretseptornymi membranami naruzhnykh segmentov palochek setchatki liagushki.

Rod outer segments (ROS) of the frog retina are shown to contain high affinity binding sites to guanylic nucleotides. Concentration of the binding sites comprises several per cent of rhodopsin concentration in our ROS preparations. These sites possess high affinity to GDP (Kd less than 10(-6) M) in dark-adapted preparations, and in the presence of bleached rhodopsin they effectively bind the non-hydrolizable analog of GTP--GPP (NH) P (Kd less than 10(-6) M). It is shown that one bleached rhodopsin molecule can induce the binding of up to 100 molecules of GPP (NH) P at low rhodopsin photolysis. Qur experimental results raise serious doubts as to the applicability of nucleotide exchange scheme by Fung and Stryer (1980).

Molecular mechanisms of photoreception. IV. Ca2+-inhibited GTPase of rod outer segments of the frog retina.

Ca2+-dependent GTPase activity is found to be present in the rod outer segments of frog retina. GTPase localization in rod outer segments is shown by fractionating the rod outer segment preparation in the sucrose density gradient. The enzyme is readily washed out of cells with isotonic NaCl solution. The Km is 0.6 mM for GTP. The activity is inhibited by 78 +/- 12% with the increase in Ca2+ concentration from 10(-9) to 10(-7) M. GTP hydrolysis is inhibited by the same concentrations of Ca2+ which block the sodium conductivity of the rod outer segment cytoplasmic membrane.