[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.

[Adenylate kinase and GDP-kinase activity of rod outer segments in the frog retina. Possible functional role of the T beta subunit of transducin].

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.

[Guanosine triphosphate complex in rod outer segments of the frog retina].

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.

[Interaction of guanine nucleotides with photoreceptor membranes of rod outer segments of frog retina].

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).

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.