[Distribution of 3H-labeled acetyl-HEMA monomer in rats]. / Distribuce 3H znaceného monomeru acetyl-HEMA u potkanu.

Original method of tritiation of acetyl-HEMA and its hydrogenated product was developed. Distribution and excretion of both compounds was examined in rat for up to 70 hrs. While the distribution in the tissues examined (liver, spleen, kidney, lung, muscle, heart, and skin) was nearly uniform, the excretion of acetyl-HEMA and its hydrogenated form differed: acetyl-HEMA in the 24. hour is excreted preferably into urine, the hydrogenated form in faeces. In addition to it the later form was absorbed from the application point (muscle) more rapidly. Distinct cumulation of activity (original compound or/and its metabolites) was observed in all tissues.

Hormesis in effect of low uranium doses on organisms.

Uranium nitrate applied daily in small amounts per os (0.5-17 mg/l in drinking water) or per cuttim (0.2-0.8 g/kg) exerts positive effect on metabolism of phosphate ions by red blood cells in vitro. This positive effect changes to the negative one with increasing dose or exposure time. It may be assumed that most other cells in the organism are affected in the same way as erythrocytes and that similar effect might be observed with other harmful agents or substances.

Specific inhibition by antityrosinase antibodies of tyrosinase-mediated melanogenesis.

Polyclonal antibodies to hamster melanoma tyrosinase were raised in rabbits, and series of immunoinhibition experiments with a purified enzyme and specific immunoglobulins were carried out. Tyrosinase activity was determined by a set of radiochemical and spectrophotometric methods utilizing tyrosine, dopa, dopamine, or dihydroxyindole (DHI) as substrates. The quantitative data obtained indicated that the complexing of tyrosinase with its specific antibody inhibited melanogenesis in a specific manner: dopachrome formation from dopa and dopamine conversion to melanin were not affected and all other enzyme activities comprising the DHI oxidation step were inhibited to various degrees. Additionally, tyrosine hydroxylation was also slightly inhibited. The data obtained implied that melanogenesis was restricted at the point of DHI oxidation. From observations on the immunoinhibition of a DHI oxidation at varying dopa-cofactor concentrations, we propose that dopa-cofactor may be bound at separate site than DHI and thus may act as a positive allosteric effector for DHI oxidation by tyrosinase. Study of tyrosinase immunoinhibition by the antibodies against the enzyme thus seems to provide a valuable system for investigating the tyrosinase-mediated melanogenesis.

[Effect of X-radiation on the metabolism of rat erythrocytes]. / Vliv X zárení na metabolismus erytrocytu krys

Rats and rabbits were whole-body irradiated with X-rays in the dose of 100 to 750 R. At daily intervals samples of blood were collected and kept in heparin. After addition 32P phosphate they were incubated for 35 minutes at 37 degrees C in vitro. Incorporation in the erythrocytes was decreased significantly from the dose of 250 to 500 R. The maximum response was obtained between the 6th and 14th day. The method can be applied for the examination of the state of the organism irradiated with the dose higher than 250 R of X-radiation. The specificity of the method is discussed.

[Effect of cyclophosphamide on themetabolism of erythrocytes]. / Vliv cyklofosamidu na metabolismus erytrocytu

Cyclophosphamide was applied i.p. in the dose of 100 mg kg-1 to rats. After one, two, three, and seven days the animals were killed and in the collected heparinized blood the incorporation of o-phosphate 32P in erythrocytes was determined in vitro at 37 degrees C and in 35 minutes. Decreased incorporation in animals with Cyclophosphamide indicated, compared with the control, disturbed metabolism of phosphate. The method can be applied as a criterion of secondary toxic effects in the treatment of cancerostatics of alkylation type.