Alterations in carbon and nitrogen metabolism induced by water deficit in the stems and leaves of Lupinus albus L

Water deficit (WD) in Lupinus albus L. brings about tissue-specific responses that are dependent on stress intensity. Carbohydrate metabolism is very sensitive to changes in plant water status. Six days from withholding water (DAW), sucrose, glucose and fructose levels of the leaf blade had already increased over 5-fold, and the activities of SS and INV(A) had increased c. 1.5-2 times. From 9 DAW on, when stress intensity was more pronounced, these effects were reversed with fructose and glucose concentrations as well as INV(A) activity dropping in parallel. The stem (specifically the stele) responded to the stress intensification with striking increases in the concentration of sugars, N and S, and in the induction of thaumatin-like-protein and an increase in chitinase and peroxidase. At 13 DAW, the plants lost most of the leaves but on rewatering they fully recovered. Thus, the observed changes appear to contribute to a general mechanism of survival under drought, the stem playing a key role in that process.

Photosynthetic light acclimation in peach leaves: importance of changes in mass:area ratio, nitrogen concentration, and leaf nitrogen partitioning

Photosynthetic light acclimation of leaves can result from (i) changes in mass-based leaf nitrogen concentration, Nm, (ii) changes in leaf mass:area ratio, Ma, and (iii) partitioning of total leaf nitrogen among different pools of the photosynthetic machinery. We studied variations in Nm and Ma within the crowns of two peach (Prunus persica L. Batsch) trees grown in an orchard in Portugal, and one peach tree grown in an orchard in France. Each crown was digitized and a 3-D radiation transfer model was used to quantify the intra-crown variations in time-integrated leaf irradiance, <PARi>. Nitrogen concentration, leaf mass:area ratio, chlorophyll concentration, and photosynthetic capacity were also measured on leaves sampled on five additional peach trees in the orchard in Portugal. The data were used to compute the coefficients of leaf nitrogen partitioning among carboxylation, bioenergetics, and light harvesting pools. Leaf mass:area ratio and area-based leaf nitrogen concentration, Na, were nonlinearly related to <PARi>, and photosynthetic capacity was linearly related to Na. Photosynthetic light acclimation resulted mainly from changes in Ma and leaf nitrogen partitioning, and to a lesser extent from changes in Nm. This behavior contrasts with photosynthetic light acclimation observed in other tree species like walnut (Juglans regia L.) in which acclimation results primarily from changes in Ma.

Comparative study on the effect of cyclic nucleotides related to the function of Biomphalaria glabrata hemocytes and human granulocytes

The biochemical processes linked up to cyclic nucleotides related to the phenomenon of phagocytosis in Biomphalaria glabrata hemocytes were studied. In hemocytes the results suggest the presence of a phagocytic capacity similar to that observed in human cells related to regulation by cyclic adenylate monophosphate (cAMP), but not by cyclic guanylate monophosphate (cGMP). This similarity and differences in the metabolic process of phagocytary capacity between human phagocytary cells and hemocytes could represent an interesting model aimed at studying the phylogenetic evolution of enzymatic complexes.

Host defenses in the aged: evaluation of the balance between oxidizing species generation and reducing power in phagocyting human granulocytes

The respiratory burst reaction has been studied in human granulocytes from normal subjects divided in four age groups: (I) 20-29, (II) 30-39, (III) 40-49, and (IV) 50-59 years old. Zimosan opsonized particles (OZ) were used to evaluate, simultaneously, the reducing power and the oxidizing species generation. Our results showed a strong parallelism and a direct correlation between oxidizing species generation and reducing power in the groups (I) and (II), in presence or in the absence of opsonized zimosan. However, the age groups (III) and (IV) showed an increase in the free radicals generation and a significant decrease in the cellular reducing power. This inverse correlation observed between oxidizing/reducing power in the (III) and (IV) age groups may suggest a metabolic cellular disequilibrium.

Quantification of the population and phagocytary activity of hemocytes of resistant and susceptible strains of Biomphalaria glabrata and Biomphalaria tenagophila infected with Schistosoma mansoni

Among the determinant factors in the resistance and susceptibility of Biomphalaria to Schistosoma mansoni, hemocytes play an important role. Aiming at studying S. mansoni/Biomphalaria interactions related to hemocytes, the first step is certainly connected with the standardization of this cell population in uninfected Biomphalaria. In this way, quantification of this cell population in hemolymph, as well as its phagocitary capacity, have been determined for the first time. Furthermore, using susceptible and resistant strains of B. glabrata and B. tenagophila, the hemocytegram and phagocytary capacity of hemocytes after infection with S. mansoni were determined too. Resistant and susceptible strains of B. glabrata (BA and BH, respectively), as well as resistant and susceptible strains of B. tenagophila (TAIM and CF, respectively) were infected with 10 miracidia of the LE and SJ strains of S. mansoni, respectively. These infected snails and respective uninfected controls were assessed in relation to the number of circulating hemocytes and alteration in the phagocytary capacity, by using Zymozan and MTT. Reading was taken by means of a spectrophotometer at 5 hours and 1, 2, 5, 10, 20 and 30 days after infection. The results showed a decrease in population of the circulating phagocytary cells, 5 hours after infection. One day post-infection, the circulating cells of the susceptible snails showed an increased metabolic activity, but the same event could not be observed in the resistant strains. In the subsequent observation periods, significant differences among the strains studied could not be observed until the end of the experiment.

Effect of gamma interferon and interleukin 10 on phosphoinositol turnover by human neutrophils in vitro

We evaluated the levels of inositolmono-(IP1), di(IP2), tri-(IP3) and tetraphosphates (IP4) in human neutrophils (N) stimulated with gamma interferon (IFN-gamma) (200 microliters from a pool of cell culture supernatant obtained from 1 x 10(7) PHA-primed peripheral blood mononuclear cells (30-60 min at 37 degrees C, 5% CO2)) in the presence of in the absence of interleukin 10 (IL-10) (10 micrograms/10 microliters). The results, reported as mean +/- SEM cpm, showed that IFN-gamma induced a significant increase only in the IP3 level (N + medium = 1,413 +/- 172 and N + IFN-gamma = 8,875 +/- 832). However, this activation mediated by IFN-gamma was blocked partially in the presence of IL-10 (N + IFN-gamma + IL-10 = 2,430 +/- 239) (P < 0.05). Interleukin 10 alone did not induce significant alterations in the content of IP1 (1,203 +/- 123), IP2 (1,880 +/- 163), IP3 (938 +/- 102) or IP4 (2,403 +/- 345) when compared to the respective controls in the absence of IL-10 (IP1 = 1,625 +/- 132; IP2 = 1,343 +/- 149; P3 = 1,413 +/- 172 and IP4 = 3,281 +/- 234). We also demonstrated the inhibitory effect of IL-10 of chemoluminescence generation by human neutrophils during phagocytosis of opsonized particles (OZ). Chemoluminescence generation was enhanced by IFN-gamma (N = OZ = 42.8 +/- 3.9 and N + OZ + IFN-gamma = 66.5 +/- 4.3) and this effect was reduced by IL-10 (N + OZ + IFN-gamma + IL-10 = 37.6 +/- 5.1). These data suggest that IL-10 modulates the neutrophil response and may be important for the development of new treatments of inflammatory injury.

Effect in vitro of gamma interferon and interleukin-10 on generation of oxidizing species by human granulocytes

We examined the effect of interleukin-10 (IL-10), gamma interferon (IFN-gamma), phorbol ester (PDB), opsonized zymosan (OZ) and aminophylline (a cAMP phosphodiesterase inhibitor) on the reducing power and oxidizing species generation by human neutrophils, using MTT dye reduction and luminol-dependent chemiluminescence assays, respectively. Gamma interferon (IFN-gamma), phorbol ester (PDB) and opsonized zymosan (OZ) were activators while interleukin-10 (IL-10) and aminophylline were inhibitors. A strong parallelism was observed between oxidizing species generation and cellular reducing power in both activation and inhibition experiments. Our results also demonstrate for the first time the effect of IL-10 on free radical generation by neutrophils. The consequence of these activating and inhibiting effects on the inflammatory process are discussed.

Photosynthetic capacity of leaves of Eucalyptus globulus (Labill.) growing in the field with different nutrient and water supplies

The effects of water and nutrient availability on photosynthetic capacity of juvenile and adult leaves of Eucalyptus globulus Labill. seedlings were evaluated by measuring oxygen evolution at light and CO(2) saturation. Seedlings supplied with near optimal amounts of water and nutrients had higher growth rates than non-irrigated, unfertilized control seedlings, but photosynthetic capacity was similar in both treatments. Differences in foliar nitrogen concentrations between the two treatments were minor, which largely explains why the growth response to near optimal nutrition was not associated with an increase in photosynthetic capacity per unit leaf area. Nevertheless, the photosynthetic capacity of juvenile leaves decreased from distal to proximal positions in the mid-crown and was positively correlated with leaf nitrogen concentration expressed on a leaf surface area basis. During the dry season, non-irrigated, unfertilized seedlings fixed carbon at lower rates than irrigated seedlings supplied with near optimal nutrition because of stomatal closure even though photosynthetic capacity was unaffected by water deficits. In both treatments, there were differences between the photosynthetic capacity of adult and juvenile leaves that were largely explained by the low specific leaf area of adult leaves.

Modulation of sheep erythrocyte receptor expression by anti-CD4, anti-CD8, and anti-HLA antibodies

The modulation of E receptors on T cells by anti-CD4 and/or anti-CD8 is reported. The percentage of E rosette-forming cells (RFC) was decreased when sheep erythrocyte and mononuclear cells were incubated in the presence of monoclonal antibodies anti-CD4 and/or anti-CD8. This inhibition was not due to shedding of the E receptor and it was reversed by 8-Br.-3',5' cyclic guanosine monophosphate (cGMP). In contrast, anti-HLA antibodies induced an enhancement of sheep erythrocyte receptor expression evaluated by RFC.