Comparison of Direct Counts and Conductometric Measurements on a Hematology Analyzer Abacus Junior 5 Vet Myelokaryocyte Content in the Red Bone Marrow of Mice.

We studied the possibility of conductometric measurement of myelokaryocyte content in the red bone marrow of mice using a hematological Abacus Junior 5 Vet analyzer (Diatron). Statistical, correlation, and regression analyses were performed to assess of the results of myelokaryocyte counting in the suspensions of mouse red bone marrow by a direct method in cytometers and by using Abacus Junior 5 Vet analyzer. It was shown that in both intact mice and animals with modelled red bone marrow hypoplasia, irrespectively of the state of hematopoiesis in representative samples, conductometric measurements of myelokaryocyte content on the Abacus analyzer with high confidence reproduced direct counting results (in different tests p=0.64-0.82, p=0.83-0.98). This indicates that myelokaryocyte counting on the Abacus Junior 5 Vet analyzer can be an acceptable alternative to counting chamber measurements in mouse samplings. However, the variability of single measurements with the Abacus Junior 5 Vet in red bone marrow suspensions is high (5%) and this has to be considered in small samples.

Comparison of Antitumor Effects of Combined and Separate Treatment with NO Synthase Inhibitor T1023 and PDK1 Inhibitor Dichloroacetate.

Combined chronic treatment of Ehrlich solid carcinoma (EC) with an NOS inhibitor 1-isobutanoyl-2-isopropylisothiourea hydrobromide (T1023) and a PDK1 inhibitor dichloroacetate was accompanied by statistically significant synergetic antitumor effects manifested in a significant and stable suppression of neoplasm growth (by 55-65%). Separate treatment with T1023 and dichloroacetate induced moderate short-term inhibition of tumor growth (by 30-35%) followed by weakening of tumor sensitivity to these substances. These results attest to synergetic antitumor effects NOS inhibitor T1023 and PDK1 inhibitor dichloroacetate producing antiangiogenic and hypoxia-targeted cytotoxic effects, during their combined administration, which allows overcoming the adaptive potential of the tumors.

[Radioprotective Properties of NO-Synthase Inhibitor T1023: I. Indicators of Radioprotective Activity and Interaction with Other Radioprotectors].

The study of radioprotective activity of NO-synthase inhibitor, N-S-isothiourea derivative T1023 showed that this compound has a significant therapeutic range of radioprotective activity (5.5-6.0) and its optimal radioprotective dose is 1/4 LD16. The value of its Radiation Dose-Reduction Factor totaled 1.4-1.8. We have demonstrated a pronounced pharmacodynamic interaction of T1023 with some known radioprotectors. The character of the interaction was determined by its vasoactive properties. Combined use of T1023 and cystamine, which causes a decrease in vascular tone, was accompanied by a statistically significant weakening of the radioprotective effect. But, the combined use of T1023 with serotonergic and adrenergic radioprotectors having a pressor action caused a statistically significant increase in the radioprotective effect. Moreover, T1023 combined with such radioprotectors caused the synergistic radioprotective effect even when used at small doses that do not have any radioprotective effect alone. The findings suggest that NOS inhibitors can be effective radioprotectors and are able to create new opportunities for the development of safer radioprotective agents. The very same compound T1023, according to current criteria of pharmacological screening, is certainly promising for further investigations.

[Radioprotective Properties of NO-synthase Inhibitor T1023: II. The Ability for Selective Protection of Normal Tissues During Radiotherapy of Tumors].

We studied the effect of T1023, NO-synthase inhibitor, N-acyl-S-alkyl-isothiourea in a single administration at a dose of 75 mg/kg on the growth of transplantable rat sarcoma M-1 and the development of acute skin reactions after the local impact of γ-radiation at the doses of 32 and 36 Gy. The results showed that the T1023 at a single dose had no effect on the growth of sarcoma, and did not modify the radiosensitivity of the tumor and anti-tumor efficacy of γ-rays. However, at both doses T1023 significantly reduced the severity of acute radiation skin reactions. NOS inhibitor did not change the duration of the inflammatory and regenerative processes, but significantly limited the degree of radiation alteration of the deep layers of the skin and underlying tissues. The findings suggest that the hypoxic mechanism of antitumor action allows T1023 to selectively protect the non-malignant tissue during radiation therapy of solid tumors. Therefore, this compound may be regarded as a promising basis for the development of pharmacological prevention of radiotherapy complications.

[On the mechanism of radioprotective effect of NO-synthase inhibitors].

We studied the influence on hemodynamics and radioprotective activity of two inhibitors of NO-synthase (NOS)--isothiourea derivatives with different NOS isoform selectivity: T1023--a selective inhibitor of endothelial and inducible NOS; and NTT2--a highly selective inhibitor of neuronal NOS. Both compounds at a dose of 1/7 LD50/15 caused a vasopressive effect and baroreflex response in normal Wistar rats. However, the nature of hemodynamic changes was qualitatively different. T1023 caused a prolonged elevation of vascular tone and reflex shift resulted in a significant and lasting reduction in the systemic blood flow (35-45%), which created conditions for the development of circulatory hypoxia. The use of NTT2 caused a reflex change in hemodynamics accompanied by vasodilation; and systemic blood flow was maintained at the initial level. T1023 effectively protected mice subjected to 10 Gy γ-irradiation and their bone marrow stem cells irradiated with 6 Gy, not yielding to the radioprotective effect of cystamine. NTT2 at these doses did not show any radioprotective effect. The obtained results support the leading mechanism of the radioprotective effect of NOS inhibitors is the induction of hypoxia. With this mechanism of action a significant radioprotective activity can be expected for the inhibitors which effectively suppress primarily endothelial NOS.

[Effect of mesenchymal stem cells and entero-absorbent on cardiac function in rats following local irradiation of the chest].

Cardiac function in Wistar male rats was assessed by ECG records for 28 days following exposure of the chest to γ-rays at a dose of 6 Gy, dose rate 4 Gy/min. The exposed rats experienced a moderate cardiac ischemia and a certain increase in the load on the atria. The use of clay of Kaluga deposit and mesenchymal stem cells reduced the adverse radiation effects.

[Radioprotective properties of isothiourea derivatives with NO-inhibitory mechanism of action].

The study of the radioprotective activity of S-[2-alkyl (aryl) sulfonyl]-S-ethyl derivatives of (vinyl)-isothiourea in (he model of the survival of mice exposed to gamma-radiation at a dose of 10 Gy has shown that the incorporation of additional sulfur-containing groups does not increase the radioprotective properties of compounds. In contrast to aminoalkil thiols, the effectiveness of the radiation protection action of the isothiourea (ITU) derivatives studied clearly correlates with the NO-inhibitory activity. This fact allowed us to assume that the radioprotective effect of S-substituted ITU caused inhibition of the endogenous synthesis of NO, which promotes the development of circulatory hypoxia, and that a further search for the radioprotective agents in this class of chemicals should be considered as the search for effective inhibitors of NO-synthase (NOS). The theoretical analysis of the conformity of molecular structures to the composition and topology of the active center of NOS-inhibitors allowed us to prognosticate a number of new ITU derivatives with the potential NOS-inhibiting ability. As a result of further theoretical and experimental studies, four S,N-disubstituted ITU derivatives - active non-selective NOS-inhibitors, were first identified and synthesized. These compounds exhibited a pronounced and prolonged vasopressive effects at doses of 0.01-0.05 LD50/15 in the models of severe hemorrhagic and endotoxic shock, and provided 65-100% 30-day survival at doses of 0.2-0.3 LD50/15 in the mice irradiated by gamma-rays at a dose of 10 Gy (LD98/30).The findings suggest the pronounced radioprotective effect of NOS-inhibitors among the ITU-derivatives.