Transitions between community complexes: a case study analysing gradients through mountain ridges in South Hungary

The study of boundaries is a recurring theme in ecology. However, boundaries have been examined mainly on fine scales (between communities) and on coarse scales (between biomes), while boundaries of intermediate scales (e.g. between community complexes) are quite neglected. In this study, we analysed boundaries between mesic and xeric community complexes in a sub- mediterranean karst area of South Hungary. We applied the moving split window (MSW) technique for boundary analysis. First, since the behaviour of MSW concerning complex vegetation patterns is not fully understood, we prepared artificial datasets (simulated communities) to test its capacities. Second, we established north-south oriented belt transects across mountain ridges of the Villány Mts, and investigated the transition between the community complexes of differently exposed slopes. Using MSW, we were able clearly to distinguish between transitional zones and zones that do not represent real transitions: peaks in the Z-score profile of MSW merge only in the case of transitional zones. Moreover, we found that peaks merge depending on the independence (distinctness) of the transitional zone: when it is distinct, peaks merge only at the largest window widths. In the Villány Mts, transitions seem to occur mostly in the grasslands north of the ridges. We demonstrated that these grasslands can be regarded as boundaries between mesic and xeric complexes or as zones in their own right, with their own two boundaries. Interpretation depends upon the scale of observation

Fermented wheat germ extract inhibits glycolysis/pentose cycle enzymes and induces apoptosis through poly(ADP-ribose) polymerase activation in Jurkat T-cell leukemia tumor cells

7 pages, 6 figures, 2 tables.-- PMID: 12351627 [PubMed].The fermented extract of wheat germ, trade name Avemar, is a complex mixture of biologically active molecules with potent anti-metastatic activities in various human malignancies. Here we report the effect of Avemar on Jurkat leukemia cell viability, proliferation, cell cycle distribution, apoptosis, and the activity of key glycolytic/pentose cycle enzymes that control carbon flow for nucleic acid synthesis. The cytotoxic IC(50) concentration of Avemar for Jurkat tumor cells is 0.2 mg/ml, and increasing doses of the crude powder inhibit Jurkat cell proliferation in a dose-dependent fashion. At concentrations higher than 0.2 mg/ml, Avemar inhibits cell growth by more than 50% (72 h of incubation), which is preceded by the appearance of a sub-G(1) peak on flow histograms at 48 h. Laser scanning cytometry of propidium iodide- and annexin V-stained cells indicated that the growth-inhibiting effect of Avemar was consistent with a strong induction of apoptosis. Inhibition by benzyloxycarbonyl-Val-Ala-Asp fluoromethyl ketone of apoptosis but increased proteolysis of poly(ADP-ribose) indicate caspases mediate the cellular effects of Avemar. Activities of glucose-6-phosphate dehydrogenase and transketolase were inhibited in a dose-dependent fashion, which correlated with decreased (13)C incorporation and pentose cycle substrate flow into RNA ribose. This decrease in pentose cycle enzyme activities and carbon flow toward nucleic acid precursor synthesis provide the mechanistic understanding of the cell growth-controlling and apoptosis-inducing effects of fermented wheat germ. Avemar exhibits about a 50-fold higher IC(50) (10.02 mg/ml) for peripheral blood lymphocytes to induce a biological response, which provides the broad therapeutic window for this supplemental cancer treatment modality with no toxic effects.This work was supported by Grants PPQ 2000-0688-CO5-03 and PPQ 2000-0688-C05-04 from the Spanish government, by NATO Collaborative Grant LST.CLG.976283, by Grant PHS M01-RR00425 from the General Clinical Research Unit, and by Grant P01-CA42710 of the UCLA Clinical Nutrition Research Unit Stable Isotope Core.Peer reviewe