RESUMO
Tropical tree fodder is harvested by frequent prunings, and resprouting depends on nonstructural carbohydrate reserves in the remaining tree parts. We studied the effects of three pruning intensities (removal of all leaves and branches leaving 1 m of stem once a year (T-12), or every 6 months (T-6), and about 50% pruning every 2 months (P-2)) on regrowth and the dynamics of soluble sugars and starch in the legume tree Gliricidia sepium (Jacq.) Walp. growing under humid tropical conditions in Guadeloupe, Lesser Antilles. Carbohydrates were sampled in roots, stems and branches. Among pruned trees, trees in the T-6 harvest regime had the highest leaf fodder yield (0.73 kg tree(-1) year(-1)). High litter loss reduced leaf yield of T-12 trees, but compared with the other treatments, T-12 trees produced the most branch biomass (3.43 kg tree(-1)). Among treatments, P-2 trees had an intermediate leaf fodder yield and the lowest branch production. Sucrose, glucose and fructose were the most common sugars in all biomass compartments. Mannose, pinitol and an unidentified cyclitol were relatively abundant in branches. Root sugar and starch concentrations were unaffected by harvest regime. There was a significant interactive effect of harvest intensity and regrowth time on stem sugar concentration. Stem starch concentration was highest in T-12 trees. After a year of fodder harvesting, whole-tree reserves of nonstructural carbohydrates were highest in T-12 trees; however, a larger proportion of reserves were located in roots and stems of T-6 and P-2 trees. These reserves, which were not lost in pruning and contributed to regrowth of G. sepium after pruning, may explain the relatively small effects of harvesting regime on soluble sugar and starch concentrations.
Assuntos
Fabaceae/fisiologia , Árvores/fisiologia , Biomassa , Carboidratos/fisiologia , Guadalupe , Raízes de Plantas/fisiologia , Caules de Planta/fisiologia , Amido/fisiologiaRESUMO
Thirteen human lung cancer cell lines, 7 representing small cell lung cancer (SCLC) and 6 different types of non-SCLC, were tested for sensitivity to tumour necrosis factor alpha (TNF-alpha) and interferon alpha and gamma (IFN-alpha and gamma) using an automated fluorometric microculture cytotoxicity assay (FMCA). One SCLC line (H-82) was found to be sensitive to IFN-alpha in short-term (72 h) culture, whereas after prolonged (5 days) culture two additional SCLC cell lines responded to IFN-gamma. TNF-alpha inhibited the growth of one large cell carcinoma cell line (H-157), whereas all SCLC lines were found to be insensitive. The combination of IFN-gamma and TNF-alpha produced no further response compared with the single agents used alone. By continuous cultivation of the IFN-alpha-sensitive cell line H-82 in the presence of increasing concentrations of IFN-alpha, an IFN-alpha-resistant subline (H-82) was established. This line displayed a high degree of resistance ( > 100 fold) to IFN-alpha and cross-resistance to IFN-gamma. There was no alteration in the number of IFN binding sites, in the growth rate, the expression of selected surface markers for SCLC or the expression of multidrug resistance markers in the H-82R subline compared with the parental H-82 cell line. The results demonstrate a heterogeneous response of SCLC cell lines to IFN-alpha and gamma and TNF-alpha with only a minority of the cell lines responding to these agents by growth inhibition. The IFN-alpha and gamma H-82R subline may serve as a valuable tool in future studies on the mechanisms of IFN antitumour activity.