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OBJECTIVE: To explore the effects of large dose of Astragalus membranaceus (Astragalus) on the dentritic cell (DC) induction in vitro and augumentation by peripheral mononuclear cell (MNC) and on antigen presenting ability of DC in children with acute leukemia. METHODS: Forty-four children with acute leukemia in complete remission stage were divided into two groups. Twenty patients in the Astragalus (90 g daily) group were treated with large dose of Astragalus (90 g daily) based on conventional chemotherapy for one month, while 24 patients in the control group received chemotherapy alone. MNC were extracted from peripheral blood by wall-sticking method and cultured with such cell factors as interleukin-4, gramulocyte macrophage colony stimulating factor, tumor necrosis factor-alpha for 7-8 days. Phenotype of DC was assayed by flow cytometry and antigen presenting ability of them was assayed by mixed lymphocyte reaction. RESULTS: There was no morphological difference in MNC induced DC between the two groups. The average number of DC in Astragalus group and control group was 4.4 x 10(6) / 2.5 x 10(6) MNC and 2.6 x 10(6) / 2.5 x 10(6) MNC, respectively, showing significant difference (P < 0.001). DC in Astragalus group could stimulate the proliferation of allogeneic lymphocytes strongly, showing significant difference when compared with that in the control group (P < 0.001). Conclusion Large dose of Astragalus could increase the DC induction of MNC and enhance the antigen presenting ability of DC in acute leukemia patients.
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DC derived from rat pseudo-afferent lymph (L-DC) vary in CD4, CD11b/c, Thy1, and OX41 expression. CD4 and OX41 are expressed by the same subpopulation (50-60%) of L-DC. CD4+/OX41+ L-DC express short fine processes and low nonspecific esterase, whereas CD4- DC/OX41- express long pseudopodia, high nonspecific esterase, and many cytoplasmic inclusions. These differences are stable in culture. Both populations express similar amounts of MHC class II, ICAM-1, CD11b/c and OX62. Most CD4-/OX41- L-DC are strongly positive for B7, but CD4+ L-DC express less B7, and some may be negative. Both populations express invariant chain, but both the absolute numbers and levels of expression were higher for CD4- DC. Surprisingly, CD4+ L-DC are more potent APC than CD4- cells in MLRs, for sensitized T cells in vitro and for naive T cells in vivo. Cultured CD4+/OX41+ DC can still process and present native Ag. Cultured CD4-/OX41- cells cannot present native Ag but can stimulate strong MLRs. CD4- DC invariant chain expression decreases in culture, whereas expression by CD4+ DC is stable for 48 h. CD4+ and CD4- L-DC have similar turnover times in vivo, suggesting that one population is not the precursor of the other. Thus, two separate DC populations that differ functionally and phenotypically migrate from intestine to mesenteric nodes. This may reflect distinct DC lineages or differentiation modulated by different microenvironmental stimuli.
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1. We examined the propagation of action potentials in the dendrites of ventrally located presumed motoneurons of organotypic rat spinal cord cultures. Simultaneous patch electrode recordings were made from the dendrites and somata of individual cells. In other experiments we visualized the membrane voltage over all the proximal dendrites simultaneously using a voltage-sensitive dye and an array of photodiodes. Calcium imaging was used to measure the dendritic rise in Ca2+ accompanying the propagating action potentials. 2. Spontaneous and evoked action potentials were recorded using high-resistance patch electrodes with separations of 30-423 microm between the somatic and dendritic electrodes. 3. Action potentials recorded in the dendrites varied considerably in amplitude but were larger than would be expected if the dendrites were to behave as passive cables (sometimes little or no decrement was seen for distances of > 100 microm). Because the amplitude of the action potentials in different dendrites was not a simple function of distance from the soma, we suggest that the conductance responsible for the boosting of the action potential amplitude varied in density from dendrite to dendrite and possibly along each dendrite. 4. The dendritic action potentials were usually smaller and broader and arrived later at the dendritic electrode than at the somatic electrode irrespective of whether stimulation occurred at the dendrite or soma or as a result of spontaneous synaptic activity. This is clear evidence that the action potential is initiated at or near the soma and spreads out into the dendrites. The conduction velocity of the propagating action potential was estimated to be 0.5 m/s. 5. The voltage time courses of previously recorded action potentials were generated at the soma using voltage clamp before and after applying 1 microM tetrodotoxin (TTX) over the soma and dendrites. TTX reduced the amplitude of the action potential at the dendritic electrode to a value in the range expected for dendrites that behave as passive cables. This indicates that the conductance responsible for the actively propagating action potentials is a Na+ conductance. 6. The amplitude of the dendritic action potential could also be initially reduced more than the somatic action potential using 1-10 mM QX-314 (an intracellular sodium channel blocker) in the dendritic electrode as the drug diffused from the dendritic electrode toward the soma. Furthermore, in some cases the action potential elicited by current injection into the dendrite had two components. The first component was blocked by QX-314 in the first few seconds of the diffusion of the blocker. 7. In some cells, an afterdepolarizing potential (ADP) was more prominent in the dendrite than in the soma. This ADP could be reversibly blocked by 1 mM Ni2+ or by perfusion of a nominally Ca2+-free solution over the soma and dendrites. This suggests that the back-propagating action potential caused an influx of Ca2+ predominantly in the dendrites. 8. With the use of a voltage-sensitive dye (di-8-ANEPPS) and an array of photodiodes, the action potential was tracked along all the proximal dendrites simultaneously. The results confirmed that the action potential propagated actively, in contrast to similarly measured hyperpolarizing pulses that spread passively. There were also indications that the action potential was not uniformly propagated in all the dendrites, suggesting the possibility that the distribution of Na+ channels over the dendritic membrane is not uniform. 9. Calcium imaging with the Ca2+ fluorescent indicator Fluo-3 showed a larger percentage change in fluorescence in the dendrites than in the soma. Both bursts and single action potentials elicited sharp rises in fluorescence in the proximal dendrites, suggesting that the back-propagating action potential causes a concomitant rise in intracellular calcium concentration...
1. Bitufted interneurons in layer 2/3 of the rat (P14) somatosensory cortex have elongated apical and basal dendritic arbors that can span the entire depth of the cortex. Simultaneous dendritic and somatic whole-cell voltage recordings combined with Ca2+ fluorescence measurements were made to quantify voltage and Ca2+ signalling in dendritic arbors of bitufted neurons. 2. Action potentials (APs) initiated close to the soma by brief current injection back-propagated into the apical and basal dendritic arbors and evoked a transient increase in volume-averaged dendritic Ca2+ concentration (Delta[Ca(2+)](i)) of about 140 nM peak amplitude per AP. The AP evoked Ca2+ signal decayed with a time constant of about 200 ms. 3. A relatively high endogenous Ca(2+) binding ratio of approximately 285 determines the comparatively small rise in [Ca(2+)](i) of bitufted cell dendrites evoked by a back-propagating AP. 4. The [Ca(2+)](i) transient evoked by back-propagating dendritic APs decreased with distance (< or = 50 microm) from the soma in some neurons. At distances greater than 50 microm transients did not show a spatial gradient between the proximal and distal dendritic branches. 5. During trains of APs the mean amplitude of the steady-state increase in dendritic [Ca(2+)](i) encoded the AP frequency linearly up to 40 Hz with a slope of 20 nM Hz(-1). 6. The results suggest that APs initiated in the axon of bitufted neurons back-propagate and 'copy' the pattern of the axon's electrical activity also to the dendritic arbor. The AP pattern is transduced into a transient rise of dendritic [Ca(2+)](i) which, presumably, can regulate the receptive properties of the dendritic arbor for synaptic input. 7. Bitufted interneurons in layer 2/3 of the rat (P14) somatosensory cortex have elongated apical and basal dendritic arbors that can span the entire depth of the cortex. Simultaneous dendritic and somatic whole-cell voltage recordings combined with Ca2+ fluorescence measurements were made to quantify voltage and Ca2+ signalling in dendritic arbors of bitufted neurons. 8. Action potentials (APs) initiated close to the soma by brief current injection back-propagated into the apical and basal dendritic arbors and evoked a transient increase in volume-averaged dendritic Ca2+ concentration (Delta[Ca(2+)](i)) of about 140 nM peak amplitude per AP. The AP evoked Ca2+ signal decayed with a time constant of about 200 ms. 9. A relatively high endogenous Ca2+ binding ratio of approximately 285 determines the comparatively small rise in [Ca(2+)](i) of bitufted cell dendrites evoked by a back-propagating AP. 10. The [Ca(2+)](i) transient evoked by back-propagating dendritic APs decreased with distance (< or = 50 microm) from the soma in some neurons. At distances greater than 50 microm transients did not show a spatial gradient between the proximal and distal dendritic branches. 11. During trains of APs the mean amplitude of the steady-state increase in dendritic [Ca(2+)](i) encoded the AP frequency linearly up to 40 Hz with a slope of 20 nM Hz(-1). 12. The results suggest that APs initiated in the axon of bitufted neurons back-propagate and also 'copy' the pattern of the axon's electrical activity to the dendritic arbor. The AP pattern is transduced into a transient rise of dendritic [Ca(2+)](i) which, presumably, can regulate the receptive properties of the dendritic arbor for synaptic input.