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The present study aimed to explore modulation of ATP-activated currents (I(ATP)) by met-Enk in rat DRG neurons. I(ATP) was recorded using the whole-cell patch clamp technique. The majority of the neurons examined responded to ATP (90.0 percent;, 45/50) with inward currents. In the 45 ATP sensitive neurons three kinds of responses to application of met-Enk were distinguished: (l) inward currents (29/45), (2) outward currents (9/45), and (3) no effect (7/45). Pretreatment with met-Enk (10(-9)~10(-5) mol/L) suppressed I(ATP) (10(-4) mol/L) in 29 neurons responding to met-Enk with inward currents. The inhibition by met-Enk of I(ATP) could be blocked by naloxone (10(-7) mol/L) in a concentration-dependent manner. Met-Enk of 10(-9), 10(-8), 10(-7), 10(-6) and 10(-5) mol/L suppressed I(ATP) by l3.2+/-5.4 percent; (n=5); 39.2+/-8.6 percent; (n=8), 54.l+/-8.6 percent; (n=8),43.3+/-7.9 percent; (n=7) and 43.l+/-7.9 percent; (n=7) (mean+/-MSE), respectively. A comparison of concentration - response relations of ATP with and without preapplication of met-Enk indicated that after pretreatment with met-Enk (10(-7) mol/L) the curve shifted downward markedly with a decrease of 25 percent; of the maximum value of I(ATP) and unchanged K(d) value. The suppression of I(ATP) by met-Enk was reversed as evidenced by intracellular dialysis of H-9 by using the repatch technique. Taken together, it is suggested that the inhibition by met-Enk of I(ATP) is caused by activation of opiate receptor, which eventually results in phosphorylation of ATP receptor, mediated by modulation of G protein coupling and intracellular signal transduction.

It was demonstrated that biologically active ALR could be expressed from its cDNA in transient expression experiments in cos-7 cells. The results showed that the cytosolic fraction from the transfected cells with constructed plasmids DNA stimulated of DNA synthesis of in vitro HTC cells in a dose dependent manner. This finding suggests that the HTC hepatoma cell line may be used as a target for bioassay of human ALR in vitro.

Augmenter of liver regeneration (ALR) is a novel hepatic stimulator. After 70% of the rat liver was removed, ALR-like activity in the remnant liver began to increase within 24 h. In parallel with the activity, the ALR mRNA level in the remnant liver increased 12 h after the operation and reached a maximum in 24 h. These findings indicate that the liver itself produces ALR, which may be a hepatotropic factor acting as a trigger for liver regeneration.

Our previous work showed the existence of low molecular weight tumor suppressors in human fetal tissues. In this paper, two tumor cell suppressors were isolated and purified from methanol extract of human fetal liver by C18 reversed-phase medium pressure chromatography, gel filtration on Sephadex LH-20, and high-performance liquid chromatography, directed by suppression of growth of HL-60 cells. The structures of the suppressors were identified to be 7-ketocholesterol and 7-beta-hydroxycholesterol. Under the condition of in vitro agar plate culture, 7-ketocholesterol and 7-beta-hydroxycholesterol showed preferentially inhibitory effects on the growth of both human and murine leukemic cell lines including human HL-60 and murine S-180 cells, but less effective on the growth of normal human and murine bone marrow granulocyte-macrophage progenitors (CFU-GM).

By using Y chromosome specific sex-determining region (Sry) as a new cytogenetic marker and PCR technique, the characteristics of proliferation and differentiation of hematopoietic stem cells in mice were studied. Bone marrow cells from male mice were injected into lethally-irradiated female mice, PCR results indicated that all of the CFU-S were originated from donor. It was found that CFU-S was able to proliferate and differentiate into various hematopoietic cells in vivo during its transplantation. Whereas the fibroblasts within donor CFU-S and the fibroblasts from bone marrow in recipient mouse reestablished by donor CFU-S were shown to be originated from the recipient. The above data demonstrated that CFC-S from bone marrow in mice possessed the characteristics of hematopoietic stem cells but was not prone to differentiate into fibroblasts.

CD34+ cells were isolated from human umbilical cord blood by using a high-gradient magnetic cell sorting system with anti-CD34 monoclonal antibody coated with microbeads, and then inoculated onto a pre-formed irradiated bone marrow stroma to evaluate the grafting efficiency of CD34+ cells with rhGM-CSF or IL-3, alone or in combination. The results showed that only 36% CD34+ cells in the control, and 68 - 89.6% in the groups with growth factors treatment seeded to the stroma. A short incubation of CD34+ cells with growth factors could rapidly reconstitute a long-term hemopoiesis in the long-term liquid culture system. This demonstrates that a brief treatment of CD34+ cells with GM-CSF or IL-3 can improve the grafting efficiency of transplanted umbilical cord blood cells.