Isolation of cells most actively synthesizing DNA from hematopoietic organs by fractionation in an albumin density gradient

Fractionation of suspensions of rat bone marrow or spleen cells yielded fractions in which activity of DNA-dependent DNA-polymerase and aspartate-carbamoyl transferase and incorporation of¹⁴C-thymidine were two or three times greater than in the initial suspension. Depending on the osmotic concentration of the original 35% solution of bovine serum albumin, the cells synthesizing DNA most actively were concentrated in fractions Nos. 5–6 (370 milliosmoles) or Nos. 2–3 (380 milliosmoles).(Presented by Academician of the Academy of Medical Sciences of the USSR P. D. Gorizontov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 11, pp. 1339–1341, November, 1976.     

Carbon monoxide is a rapid modulator of recombinant and native P2X2 ligand-gated ion channels

Background and purpose:

Carbon monoxide (CO) is a potent modulator of a wide variety of physiological processes, including sensory signal transduction. Many afferent sensory pathways are dependent upon purinergic neurotransmission, but direct modulation of the P2X purinoceptors by this important, endogenously produced gas has never been investigated.

Experimental approach:

Whole-cell patch-clamp experiments were used to measure ATP-elicited currents in human embryonic kidney 293 cells heterologously expressing P2X₂, P2X₃, P2X_2/3 and P2X₄ receptors and in rat pheochromocytoma (PC12) cells known to express native P2X₂ receptors. Modulation was investigated using solutions containing CO gas and the CO donor molecule, tricarbonyldichlororuthenium (II) dimer (CORM-2).

Key results:

CO was a potent and selective modulator of native P2X₂ receptors, and these effects were mimicked by a CO donor (CORM-2). Neither pre-incubation with 8-bromoguanosine-3′,5′-cyclomonophosphate nor 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (a potent blocker of soluble guanylyl cyclase) affected the ability of the CO donor to enhance the ATP-evoked P2X₂ currents. The CO donor caused a small, but significant inhibition of currents evoked by P2X_2/3 and P2X₄ receptors, but was without effect on P2X₃ receptors.

Conclusions and implications:

These data provided an explanation for how CO might regulate sensory neuronal traffic in physiological reflexes such as systemic oxygen sensing but also showed that CO could be used as a selective pharmacological tool to assess the involvement of homomeric P2X₂ receptors in physiological systems.