Effects of phosphorus and nitrogen enrichment on the phytoplankton in a tropical reservoir (Lobo Reservoir,Brazil)

The effects of enrichment with phosphate (0–500 µg. 1^–1) and forms of nitrogen (nitrate, nitrite, ammonia an and urea) (0–3500 µgg. ^–1) on the phytoplankton growth of Lobo Reservoir (Brazil) were studied in July, 1979. Suspended matter, chlorophyll a, cell concentrations and the carotenoid:cchlorophyll ratio were estimated following 14 days of in situ incubation. Phosphate alone caused no significant effects, but enrichment with nitrogen caused a substantial increase on the growth of phytoplankton. Comparison between the different forms of nitrogen showed insignificant effects after their additions with 350 µg. ^–1 and in combination with phosphate. However, when nitrogen was added in large quantities (3 500 µg. ^–1), significant differences between the nitrogeneous forms were found, with urea causing the strongest effect. In July, nitrogen is mhe main limiting nutrient to phytoplankton growth of Lobo Reservoir.Supported by CNPq and FAPESP.     

Metabolism of glucose, glutamine, long-chain fatty acids and ketone bodies by murine macrophages.

Maximum activities of some key enzymes of metabolism were studied in elicited (inflammatory) macrophages of the mouse and lymph-node lymphocytes of the rat. The activity of hexokinase in the macrophage is very high, as high as that in any other major tissue of the body, and higher than that of phosphorylase or 6-phosphofructokinase, suggesting that glucose is a more important fuel than glycogen and that the pentose phosphate pathway is also important in these cells. The latter suggestion is supported by the high activities of both glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. However, the rate of glucose utilization by 'resting' macrophages incubated in vitro is less than the 10% of the activity of 6-phosphofructokinase: this suggests that the rate of glycolysis is increased dramatically during phagocytosis or increased secretory activity. The macrophages possess higher activities of citrate synthase and oxoglutarate dehydrogenase than do lymphocytes, suggesting that the tricarboxylic acid cycle may be important in energy generation in these cells. The activity of 3-oxoacid CoA-transferase is higher in the macrophage, but that of 3-hydroxybutyrate dehydrogenase is very much lower than those in the lymphocytes. The activity of carnitine palmitoyltransferase is higher in macrophages, suggesting that fatty acids as well as acetoacetate could provide acetyl-CoA as substrate for the tricarboxylic acid cycle. No detectable rate of acetoacetate or 3-hydroxybutyrate utilization was observed during incubation of resting macrophages, but that of oleate was 1.0 nmol/h per mg of protein or about 2.2% of the activity of palmitoyltransferase. The activity of glutaminase is about 4-fold higher in macrophages than in lymphocytes, which suggests that the rate of glutamine utilization could be very high. The rate of utilization of glutamine by resting incubated macrophages was similar to that reported for rat lymphocytes, but was considerably lower than the activity of glutaminase.     

Polyunsaturated and saturated fatty acids-rich diets and immune tissues. 1. Fresh weight, DNA content, percentage of lipids and rate of lipogenesis from 3H2O in thymus, spleen and mesenteric lymph nodes

It has been widely reported that polyunsaturated fatty acids-rich diets (PUFA n-6) cause immunodeficiency. In this study, fresh weight, DNA and lipid content and rate of lipogenesis from 3H2O of thymus, spleen, mesenteric lymph nodes and liver were assessed in rats fed polyunsaturated (UC) or saturated (SC) fatty acids-rich chows. The results obtained indicate that both types of fatty acids caused similar increment of lipid content in the immune tissues. The rate of lipogenesis was decreased only in the thymus of (UC) rats and liver of both experimental groups as compared to control rats. The results of fresh weight and DNA content was decreased only by (UC) diet.     

Fish oil supplementation for two generations increases insulin sensitivity in rats

We investigated the effect of fish oil supplementation for two consecutive generations on insulin sensitivity in rats. After the nursing period (21 days), female rats from the same prole were divided into two groups: (a) control group and (b) fish oil group. Female rats were supplemented with water (control) or fish oil at 1 g/kg body weight as a single bolus for 3 months. After this period, female rats were mated with male Wistar rats fed on a balanced chow diet (not supplemented). Female rats continued to receive supplementation throughout gestation and lactation periods. The same treatment was performed for the next two generations (G1 and G2). At 75 days of age, male offspring from G1 and G2 generations from both groups were used in the experiments. G1 rats did not present any difference with control rats. However, G2 rats presented reduction in glycemia and lipidemia and improvement in in vivo insulin sensitivity (model assessment of insulin resistance, insulin tolerance test) as well as in vitro insulin sensitivity in soleus muscle (glucose uptake and metabolism). This effect was associated with increased insulin-stimulated p38 MAP kinase phosphorylation and lower n-6/n-3 fatty acid ratio, but not with activation of proteins from insulin signaling (IR, IRS-1 and Akt). Global DNA methylation was decreased in liver but not in soleus muscle. These results suggest that long-term fish oil supplementation improves insulin sensitivity in association with increased insulin-stimulated p38 activation and decreased n-6:n-3 ratio in skeletal muscle and decreased global DNA methylation in liver.     

Protein Malnutrition Induces Bone Marrow Mesenchymal Stem Cells Commitment to Adipogenic Differentiation Leading to Hematopoietic Failure

Protein malnutrition (PM) results in pathological changes that are associated with peripheral leukopenia, bone marrow (BM) hypoplasia and alterations in the BM microenvironment leading to hematopoietic failure; however, the mechanisms involved are poorly understood. In this context, the BM mesenchymal stem cells (MSCs) are cells intimately related to the formation of the BM microenvironment, and their differentiation into adipocytes is important because adipocytes are cells that have the capability to negatively modulate hematopoiesis. Two-month-old male Balb/c mice were subjected to protein-energy malnutrition with a low-protein diet containing 2% protein, whereas control animals were fed a diet containing 12% protein. The hematopoietic parameters and the expression of CD45 and CD117 positive cells in the BM were evaluated. MSCs were isolated from BM, and their capability to produce SCF, IL-3, G-CSF and GM-CSF were analyzed. The expression of PPAR-γ and C/EBP-α as well as the expression of PPAR-γ and SREBP mRNAs were evaluated in MSCs together with their capability to differentiate into adipocytes in vitro. The malnourished animals had anemia and leukopenia as well as spleen and bone marrow hypoplasia and a reduction in the expression of CD45 and CD117 positive cells from BM. The MSCs of the malnourished mice presented an increased capability to produce SCF and reduced production of G-CSF and GM-CSF. The MSCs from the malnourished animals showed increased expression of PPAR-γ protein and PPAR-γ mRNA associated with an increased capability to differentiate into adipocytes. The alterations found in the malnourished animals allowed us to conclude that malnutrition committed MSC differentiation leading to adipocyte decision and compromised their capacity for cytokine production, contributing to an impaired hematopoietic microenvironment and inducing the bone marrow failure commonly observed in protein malnutrition states.     

Testosterone suppresses oxidative stress in human neutrophils

The in vitro effect of testosterone on human neutrophil function was investigated. Blood neutrophils from healthy male subjects were isolated and treated with 10 nM, 0.1 and 10 µM testosterone for 24 h. As compared with untreated cells, the testosterone treatment produced a significant decrease of superoxide production as indicated by the measurement of extra‐ and intracellular superoxide content. An increment in the production of nitric oxide was observed at 0.1 and 10 µM testosterone concentrations, whereas no effect was found for 10 nM. Intracellular calcium mobilization was significantly increased at 10 nM, whereas it was reduced at 10 µM testosterone. There was an increase in phagocytic capacity at 10 nM and a decrease of microbicidal activity in neutrophils treated with testosterone at 10 µM. Glutathione reductase activity was increased by testosterone treatment, whereas no effect was observed in other antioxidant enzyme activities. An increase in the content of thiol groups was observed at all testosterone concentrations. Lipid peroxidation in neutrophils evaluated by levels of TBARS was decreased at 10 nM and 0.1 µM testosterone. These results indicate the antioxidant properties of testosterone in neutrophils as suggested by reduction of superoxide anion production, and lipid peroxidation, and by the increase in nitric oxide production, glutathione reductase activity and the content of thiol groups. Therefore, the plasma levels of testosterone are important regulators of neutrophil function and so of the inflammatory response. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparative effects of fish oil given by gavage and fish oil-enriched diet on leukocytes

The comparative effects of fish oil given by gavage and fish oil enriched diet on metabolism and function of lymphocytes and macrophages were investigated. For this purpose, the following parameters were examined: 1) phagocytosis capacity, production of superoxide (O2*-) and hydrogen peroxide (H2O2) by macrophages, 2) lymphocytes proliferation capacity, 3) antioxidant enzyme activities in the mesenteric lymph nodes (MEN) and liver, 4) Thiobarbituric Acid Reactive Substances (TBARS) content in MLN, liver, and plasma, 5) total antioxidant capacity of the plasma, and 6) fatty acid composition of macrophages, MLN, liver and plasma. Both FO treatments did not affect phagocytosis capacity but increased hydrogen peroxide production by macrophages in the presence of PMA. FO given by gavage markedly increased lymphocytes proliferation both in the absence (5.8-fold) and in the presence (16.7-fold) of Con A, whereas FO-rich diet showed an increase in the presence of Con A only (53.3%). FO given by gavage raised the proliferation index by 2.9-fold and FO-rich diet increased by 29% only as compared to controls. Concomitantly, FO given by gavage was more effective to increase TBARS content in plasma. The proportion of some fatty acids in the tissues and cells was also differently changed depending on the way FO was administered to rats: in particular: myristic, arachidonic, and eicosapentaenoic acids. This fact may partially explain the differences between both FO treatments.     

Glutamine metabolism by lymphocytes, macrophages, and neutrophils: its importance in health and disease

Many aspects of the cell biology of lymphocytes, macrophages, and neutrophils have been studied extensively. Our recent work on these cells has investigated how fuel metabolism, especially glutamine metabolism, is related to the specific function of these cells in the inflammatory response. The high rate of glutamine utilization and its metabolism in such immune cells has raised the question of why glutamine is responsible for these functions. The macrophage has access to a variety of metabolic fuels both in vivo and in vitro. The quantitatively important role of glutamine in the processes of free radical and cytokine production has been established in our laboratories. Our current understanding of the rate of utilization and the pathway of metabolism of glutamine by cells of the immune system raises some intriguing questions concerning therapeutic manipulation of utilization of this amino acid, specifically the phagocytic and secretory capacities of cells of the defense system can be beneficially altered.     

Superoxide dismutase, catalase and glutathione peroxidase activities in the lymphoid organs and skeletal muscles of rats treated with dexamethasone

The effect of dexamethasone (a synthetic glucocorticoid) on the activity of antioxidant enzymes (superoxide dismutase (SOD), catalase and glutathione peroxidase) of the lymphoid organs (mesenteric lymph nodes (MLN), spleen and thymus) was investigated. For comparison with non-immune tissues, skeletal muscles (soleus and gastrocnemius (GC) were also studied. As an indication of the occurrence of lipid peroxidation, the content of thiobarbituric acid reactant substances (TBARs) was also determined. Dexamethasone treatment decreased the TBARs content of the lymphoid organs and raised it in the GC and soleus muscles. The activity of Cu/Zn-SOD was reduced in all tissues. However, the activity of Mn-SOD was decreased in the MLN and soleus muscle only. The activity of catalase was reduced in the MLN and thymus and raised in the spleen and GC and soleus muscles. The imposed treatment raised the activity of GPX in the MLN, thymus and spleen and reduced it in GC and soleus muscles. These data led us to postulate that the mechanism for the therapeutic effect of glucocorticoids as antiinflammatory and immunosuppressive agents might include modification of antioxidant enzyme activities.