Hypobaria and hypoxia affects phytochemical production, gas exchange, and growth of lettuce

Hypobaria (low total atmospheric pressure) is essential in sustainable, energy-efficient plant production systems for long-term space exploration and human habitation on the Moon and Mars. There are also critical engineering, safety, and materials handling advantages of growing plants under hypobaria, including reduced atmospheric leakage from extraterrestrial base environments. The potential for producing crops under hypobaria and manipulating hypoxia (low oxygen stress) to increase health-promoting bioactive compounds is not well characterized. Here we showed that hypobaric-grown lettuce plants (25 kPa ≈ 25% of normal pressure) exposed to hypoxia (6 kPa pO₂ ≈ 29% of normal pO₂) during the final 3 d of the production cycle had enhanced antioxidant activity, increased synthesis of anthocyananins, phenolics, and carotenoids without reduction of photosynthesis or plant biomass. Net photosynthetic rate (P _N) was not affected by total pressure. However, 10 d of hypoxia reduced P _N, dark respiration rate (R _D), P _N/R _D ratio, and plant biomass. Growing plants under hypobaria and manipulating hypoxia during crop production to enhance health-promoting bioactive compounds is important for the health and well-being of astronauts exposed to space radiation and other stresses during long-term habitation.     

Effects of oxygen fraction in inspired air on force production and electromyogram activity during ergometer rowing

Six male rowers rowed maximally for 2500 m in ergometer tests during normoxia (fractional concentration of oxygen in inspired air, F _IO₂ 0.209), in hyperoxia (F _IO₂ 0.622) and in hypoxia (F _IO₂ 0.158) in a randomized single-blind fashion. Oxygen consumption (V˙O₂), force production of strokes as well as integrated electromyographs (iEMG) and mean power frequency (MPF) from seven muscles were measured in 500-m intervals. The iEMG signals from individual muscles were summed to represent overall electrical activity of these muscles (sum-iEMG). Maximal force of a stroke (F _max) decreased from the 100% pre-exercise maximal value to 67 (SD 12)%, 63 (SD 15)% and 76 (SD 13)% (P<0.05 to normoxia, ANOVA) and impulse to 78 (SD 4)%, 75 (SD 14)% and 84 (SD 7)% (P<0.05) in normoxia, hypoxia and hyperoxia, respectively. A strong correlation between F _max and V˙O₂ was found in normoxia but not in hypoxia and hyperoxia. The mean sum-iEMG tended to be lower (P<0.05) in hypoxia than in normoxia but hyperoxia had no significant effect on it. In general, F _IO₂ did not affect MPF of individual muscles. In conclusion, it was found that force output during ergometer rowing was impaired during hypoxia and improved during hyperoxia when compared with normoxia. Moreover, the changes in force output were only partly accompanied by changes in muscle electrical activity as sum-iEMG was affected by hypoxic but not by hyperoxic gas. The lack of a significant correlation between F _max and V˙O₂ during hypoxia and hyperoxia may suggest a partial uncoupling of these processes and the existence of other limiting factors in addition to V˙O₂. Accepted: 2 June 1997     

Interleukin-1-mediated H2O2 production by hepatic sinusoidal endothelium in response to B16 melanoma cell adhesion

We have examined H₂O₂ production by in vitro enriched hepatic sinusoidal endothelium (HSE) during interleukin-1β (IL-1β) stimulation and B16 melanoma cell adhesion. Production of H₂O₂ was quantified by flow cytometry and multiwell plate-scanning fluorimetry of intracellular 2′, 7′-dichlorofluorescein (DCFH) oxidation in HSE. Under IL-1β treatment there was a 6-fold increase in endothelial cells producing H₂O₂ (67%) and a 4-fold augmentation in the Kupffer cell population (86%). The average H₂O₂ content per cell size unit significantly (P < 0.01) increased in endothelial cells (2.6-fold) and Kupffer cells (1.7-fold). In contrast to the homogeneity of Kupffer cells, H₂O₂ production intensity was largely heterogeneous in IL-1β-activated HSE. Enhancement of H₂O₂ production by IL-β-treated HSE started at the 4th h and peaked 2–3 h later. The addition of increasing concentrations of IL-1β to HSE for 4 h caused the progressive activation of H₂O₂ production by treated cells. The addition of 80 M excess of IL-1 receptor antagonist (IL-1Ra) 10 min before IL-1β treatment abrogated IL-1β-mediated enhancement of H₂O₂. From the 2nd h of B16 melanoma adhesion to HSE there was a significant (P < 0.05) enhancement of H₂O₂ content in HSE. This activation increased 2.25-fold by the 3rd h of coculture and had reduced again by the 5th h. IL-1Ra (80 ng/ml) given to HSE 10 min before melanoma cells abrogated the HSE response to melanoma cells. The addition of 1% paraformaldehyde (PFA)-fixed B16 melanoma cells to HSE did not affect H₂O₂ production response, indicating that HSE-activating agents were on the melanoma cell surface. Preincubation of B16 melanoma cells in the presence of 5 μg/ml anti-mouse IL-1β neutralizing antibody reduced the melanoma cell-induced HSE production of H₂O₂ by 80%. On the contrary, B16 melanoma cell-conditioned medium did not vary HSE production of H₂O₂ compared to control HSE. Western blot analysis of cytosolic and membrane sediments from B16 melanoma cells confirmed the presence of IL-1β (17.4 kDa) in both cell compartments. Thus, HSE responded to melanoma cell contact with a rapid production of H₂O₂. HSE activation was IL-1-dependent. This cytokine was directly provided to HSE by the cell surface of adhered melanoma cells. © 1996 Wiley-Liss, Inc.     

Effects of fish oil on lymphocyte proliferation,cytokine production and intracellular signalling in weanling pigs

It has been widely documented that fish oil attenuates inflammatory responses partially via down-regulation of T-lymphocyte function. To determine the anti-inflammatory role of fish oil in weanling pigs, we investigated the effects of fish oil and its functional constituents on peripheral blood lymphocyte proliferation, cytokine production and subsequent intracellular signalling in inflammatory-challenged weanling pigs and in in vitro cultured lymphocytes. Fish oil (7%) or corn oil (7%) was supplemented to 72 crossbred pigs (7.6 ± 0.3 kg BW and 28 ± 3 days of age) in a 2 × 2 factorial experiment that included an Escherichia coli lipopolysaccharide (LPS) challenge (challenged or not challenged). On day 14 and 28 of the experiment, 200 μg/kg BW of LPS or an equivalent amount of sterile saline was administered to the pigs by intraperitoneal injection. Blood samples were collected on days 15 and 29 to determine peripheral blood lymphocyte proliferation, interleukin-1β (IL-1β) and interleukin-2 (IL-2) production. The results showed that inflammatory challenge decreased average daily gain (P < 0.05) and average daily feed intake (P < 0.05) during days 15 - 28. Fish oil supplementation had no effect on growth performance. Inflammatory challenge increased lymphocyte proliferative response to concanavalin A (Con A) (P < 0.05) following each challenge. Fish oil tended to suppress (P < 0.1) the proliferation following the first challenge. Similarly, fish oil tended to reduce IL-1β production (P < 0.1) following the second challenge and IL-2 (P < 0.1) production following the first challenge in both challenged and unchallenged pigs compared with corn oil. In parallel in vitro experiments, peripheral blood lymphocytes of weanling pigs were incubated with various concentrations of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) or linoleic acid (LA) (0, 20, 40, 60, 80, 100 μg/ml). EPA, DHA and high levels of LA predominantly suppressed IL-1β (P < 0.05), IL-2 (P < 0.05) production and subsequent lymphocyte proliferation (P < 0.05). Low levels of LA increased (P < 0.05) IL-2 production. Compared with LA, EPA resulted in a stronger inhibition of lymphocyte proliferation (P < 0.05) and IL-2 (P < 0.01), and DHA resulted in a stronger inhibition of IL-1β (P < 0.05) and IL-2 (P < 0.01). To elucidate the mechanism(s) by which fish oil and its functional constituents suppressed lymphocyte function, the kinetics of intracellular [Ca^{2 +}]_i and protein kinase C activity were determined in in vitro experiments. EPA, DHA and LA exerted very similar dose-dependent stimulatory effects on intracellular Ca^{2 +}. EPA and DHA inhibited protein kinase C activity (P < 0.05), while LA had no significant effect (P > 0.05). These results suggest that fish oil and its functional constituents (EPA and DHA) exerted an anti-inflammatory effect by down-regulation of lymphocyte activation in weanling pigs, possibly by manipulation of intracellular signalling.     

Membrane-bound/soluble IL-2 receptor (IL-2R) and levels of IL-1α, IL-2, and IL-6 in the serum and in the PBMC culture supernatants from 17 patients with hematological malignancies

The present study investigated the peripheral blood mononuclear cells (PBMC) blastic responses to PHA, PHA plus recombinant IL-2 (rIL-2) and rIL-2 alone; the expression of membrane-bound IL-2R on PHA-stimulated PBMC; and the levels of IL-1α, IL-2, IL-6, and sIL-2R in serum and in culture supernatants from PHA-stimulated PBMC in 17 patients with hematological malignancies (mean age 58.5 yr, range 22–82): 6 with non-Hodgkin’s lymphoma (NHL), 4 with Hodgkin’s lymphoma (HL), 5 with Hairy cell leukemia, 1 with chronic myelogenous leukemia, and 1 with chronic lymphocytic leukemia. The patients with HL and NHL with active disease (AD) were separated from those in clinical remission. The patients with AD were studied at diagnosis (obviously before therapy) and the patients in clinical remission were out of therapy since at least 6 mo. The lymphocyte blastogenic response to PHA was significantly lower in patients with HL and NHL with AD than in the control group. The response to rIL-2 alone was in the same range in the control group and in HL and NHL AD patients. By adding rIL-2 to PHA there was an increase of the blastogenic response of the same patients. The percentage of CD25 expressed on PHA-stimulated lymphocytes from patients with HL and NHL AD and from normal subjects is in the same range. Serum levels of IL-2, IL-6, and sIL-2R were significantly higher in HL and NHL AD patients than in controls as well as in all other hematological malignancies. Supernatants derived from PHA-stimulated PBMC were assessed for the presence of cytokines and sIL-2R by ELISA. The levels of IL-2, IL-6, and sIL-2R were significantly lower in HL and NHL AD patients than in controls as well as in all other hematological malignancies.     

Effects of hyaluronan treatment on lipopolysaccharide-challenged fibroblast-like synovial cells

Numerous investigations have reported the efficacy of exogenous hyaluronan (HA) in modulating acute and chronic inflammation. The current study was performed to determine the in vitro effects of lower and higher molecular weight HA on lipopolysaccharide (LPS)-challenged fibroblast-like synovial cells. Normal synovial fibroblasts were cultured in triplicate to one of four groups: group 1, unchallenged; group 2, LPS-challenged (20 ng/ml); group 3, LPS-challenged following preteatment and sustained treatment with lower molecular weight HA; and group 4, LPS-challenged following pretreatment and sustained treatment with higher molecular weight HA. The response to LPS challenge and the influence of HA were compared among the four groups using cellular morphology scoring, cell number, cell viability, prostaglandin E₂ (PGE₂) production, IL-6 production, matrix metalloproteinase 3 (MMP3) production, and gene expression microarray analysis. As expected, our results demonstrated that LPS challenge induced a loss of characteristic fibroblast-like synovial cell culture morphology (P < 0.05), decreased the cell number (P < 0.05), increased PGE₂ production 1,000-fold (P < 0.05), increased IL-6 production 15-fold (P < 0.05), increased MMP3 production threefold (P < 0.05), and generated a profile of gene expression changes typical of LPS (P < 0.005). Importantly, LPS exposure at this concentration did not alter the cell viability. Higher molecular weight HA decreased the morphologic change (P < 0.05) associated with LPS exposure. Both lower and higher molecular weight HA significantly altered a similar set of 21 probe sets (P < 0.005), which represented decreased expression of inflammatory genes (PGE₂, IL-6) and catabolic genes (MMP3) and represented increased expression of anti-inflammatory and anabolic genes. The molecular weight of the HA product did not affect the cell number, the cell viability or the PGE₂, IL-6, or MMP3 production. Taken together, the anti-inflammatory and anticatabolic gene expression profiles of fibroblast-like synovial cells treated with HA and subsequently challenged with LPS support the pharmacologic benefits of treatment with HA regardless of molecular weight. The higher molecular weight HA product provided a cellular protective effect not seen with the lower molecular weight HA product.     

Hypoxia modulates cyclin and cytokine expression and inhibits peripheral mononuclear cell proliferation.

Previously, we found that hypoxia can deeply affect the production of cytokines in human peripheral mononuclear cells (PBMC). Here, we demonstrated that the cycle progression of hypoxic PBMC, cultured in the presence or not of a specific T cell activator such as phytohaemagglutinin (PHA), was delayed when compared with aerobic cultures. This delay was accompanied by a decrease of the expression of specific cyclins associated to cell cycle progression phases. Ribonuclease Protection Assay (RPA) studies reveal a decrease in the expression of cyclin A and B in PHA-stimulated PBMC kept for 40 hr under hypoxic condition (2% O(2)), when compared with aerobic cultures (20% O(2)). In concomitance, a decrease of cyclin D2 expression was present after 16 hr of hypoxic treatment. However, the decrease was transient and disappeared after 40 hr of hypoxic treatment. Furthermore, cyclin C expression was not affected by hypoxia. Hypoxia-induced cyclin modulation was accompanied by an increased synthesis of interleukin (IL)-2 and IL-4, analyzed by ELISA. By evaluating these results, it appears that hypoxia induces a growth suppressive state in mitogen-activated PBMC by inhibiting the synthesis of mitotic cyclins A and B. However hypoxic PBMC maintain their viability and capability of producing stimulatory cytokines, after mitogen treatment. This should be important in local hypoxia, usually associated with necrotic areas, in inflammation, and infections, where T lymphocyte capability of producing stimulatory cytokines is desirable.     

Low oxygen tension potentiates proliferation and stemness but not multilineage differentiation of caprine male germline stem cells

The milieu of male germline stem cells (mGSCs) is characterized as a low-oxygen (O₂) environment, whereas, their in-vitro expansion is typically performed under normoxia (20–21% O₂). The comparative information about the effects of low and normal O₂ levels on the growth and differentiation of caprine mGSCs (cmGSCs) is lacking. Thus, we aimed to investigate the functional and multilineage differentiation characteristics of enriched cmGSCs, when grown under hypoxia and normoxia. After enrichment of cmGSCs through multiple methods (differential platting and Percoll-density gradient centrifugation), the growth characteristics of cells [population-doubling time (PDT), viability, proliferation, and senescence], and expression of key-markers of adhesion (β-integrin and E-Cadherin) and stemness (OCT-4, THY-1 and UCHL-1) were evaluated under hypoxia (5% O₂) and normoxia (21% O₂). Furthermore, the extent of multilineage differentiation (neurogenic, adipogenic, and chondrogenic differentiation) under different culture conditions was assessed. The survival, viability, and proliferation were significantly (p?<?0.05) improved, thus, yielding a significantly (p?<?0.05) higher number of viable cells with larger colonies under hypoxia. Furthermore, the expression of stemness and adhesion markers were distinctly upregulated under lowered O₂ conditions. Conversely, the differentiated regions and expression of differentiation-specific genes [C/EBPα (adipogenic), nestin and β-tubulin (neurogenic), and COL2A1 (chondrogenic)] were significantly (p?<?0.05) reduced under hypoxia. Overall, the results demonstrate that culturing cmGSCs under hypoxia augments the growth characteristics and stemness but not the multilineage differentiation of cmGSCs, as compared with normoxia. These data are important to develop robust methodologies for ex-vivo expansion and lineage-committed differentiation of cmGSCs for clinical applications.

     

The influence of hypoxia on the blood regulation of the brackish water shrimp Palaemonetes varians Leach

During periods of hypoxia in hypotonic media, Palaemonetes varians Leach showed an unimpaired regulation of blood chloride until some minutes before death. Heart rate showed no clear dependence on the water oxygen tension (P_wO₂) and postbranchial haemolymph oxygen tensions slowly decreased during progressive hypopoxia from a normoxic level of ≈ 30 mm Hg until the animals turned opaque some minutes before they died. Blood pH increased in hypoxia, from 7.6 in normoxia to > 8 in P_wO₂ 10 mm Hg. Taken together, these data have been taken to indicate that the oxygen consumption rate at the critical point (MO₂ P_cr) of this species is very low (P_wO₂ = < 10 mm Hg) compared with other brackish water natantians studied. The ecological significance of this to the species is considered.     

Survival and function of mesenchymal stem cells (MSCs) depend on glucose to overcome exposure to long‐term,severe and continuous hypoxia

Use of mesenchymal stem cells (MSCs) has emerged as a potential new treatment for various diseases but has generated marginally successful results. A consistent finding of most studies is massive death of transplanted cells. The present study examined the respective roles of glucose and continuous severe hypoxia on MSC viability and function with respect to bone tissue engineering. We hereby demonstrate for the first time that MSCs survive exposure to long‐term (12 days), severe (pO₂ < 1.5 mmHg) hypoxia, provided glucose is available. To this end, an in vitro model that mimics the hypoxic environment and cell‐driven metabolic changes encountered by grafted sheep cells was established. In this model, the hallmarks of hypoxia (low pO₂, hypoxia inducible factor‐1α expression and anaerobic metabolism) were present. When conditions switched from hypoxic (low pO₂) to ischemic (low pO₂ and glucose depletion), MSCs exhibited shrinking, decreased cell viability and ATP content due to complete exhaustion of glucose at day 6; these results provided evidence that ischemia led to the observed massive cell death. Moreover, MSCs exposed to severe, continuous hypoxia, but without any glucose shortage, remained viable and maintained both their in vitro proliferative ability after simulation with blood reperfusion at day 12 and their in vivo osteogenic ability. These findings challenge the traditional view according to which severe hypoxia per se is responsible for the massive MSC death observed upon transplantation of these cells and provide evidence that MSCs are able to withstand exposure to severe, continuous hypoxia provided that a glucose supply is available.     

Production of Interferon in Mice: Effect of Altered Gaseous Environments

Effects of altered gaseous environments (parabarosis) on interferon production in mice were studied, with Newcastle disease virus (NDV) as the inducer. Increased levels of interferon in lung tissue were observed when mice were exposed to 11% O₂ in N₂ for 3 days before and after, or only after, injection of NDV. However, serum interferon levels remained unchanged. Exposure of mice to 77% O₂ for up to 7 days did not affect the response to interferon induction as assayed in lungs or sera. Interferon levels were significantly depressed in mice exposed to a simulated depth of 213 ft in seawater [with normal partial pressure of O₂ (pO₂) in N₂] for 2 or 4 weeks. Whereas definite depression of interferon was also observed in mice maintained at a simulated altitude of 37,000 ft (with normal pO₂) for 2 weeks, those maintained at the same condition for 4 weeks showed a normal level of interferon. The results obtained with hypoxia are compatible with other reports on the influence of O₂ tension on viral infection. The factors responsible for alterations observed in interferon level in mice kept in normal pO₂, but under altered pressure, have not yet been identified.     

Glucose uptake in mouse brain regions under hypoxic hypoxia

Glucose uptake of individual structures within the brain was studied by dry-autoradiography with 2-deoxy-D-[¹⁴C(U)]glucose under mild hypoxic hypoxia (12% O₂88% N₂ or 9% O₂91% N₂ for 1 hr). Glucose consumption in the whole brain was estimated by combined gas chromatography-mass spectrometry (GC-MS). Mild hypoxia increased the optical density of the autoradiograph in all regions. The deuterated G-6-P (Glucose-6-phosphate) synthesized from deuterated glucose decreased significantly with 9% O₂ hypoxia (P<0.05). The ratio of the deuterated G-6-P to deuterated glucose, a more appropriate indicator of glucose utilization than the concentration of deuterated G-6-P, decreased significantly with 12% O₂ hypoxia (P<0.01). The hippocampus, white matter, colliculus superior, and corpus geniculatum laterale appeared to be particulary sensitive to hypoxia.     

Optimal oxygen tension for human lymphocytes in culture

Human lymphocytes stimulated with phytohaemagglutinin in vitro show maximal ¹⁴C-thymidine incorporation when the gas phase of the cultures contains 20% O₂. The rate of DNA synthesis is more affected by hyperoxic conditions than by hypoxia. Cell viability, defined by dye exclusion, is considerably less dependent on pO₂ than is cellular replication.     

An increased carbon dioxide production in transient hypoxia in healthy subjects at rest

Indices of pulmonary gas exchange and heart rate (HR) have been measured in 24 healthy subjects not adapted to hypoxia after hypoxic aerial mixture (HAM) (17, 15, 13 vol % of oxygen) respiration for 15 min. Using group data analysis, it has been shown that hypoxia under the conditions of inhalation of 17 and 15 vol % of O₂ caused no significant changes. Hypoxia under the conditions of 13 vol % of O₂ inhalation is a threshold one, when ventilation (SpO₂) drops below 85%. A significant increase in the lung ventilation (Ve) (10–14%, p < 0.05) and HR (11–15%, p < 0.05) have been observed in this case. Hyperpnea was accompanied by an increase in the oxygen uptake rate by 10% and carbon dioxide release rate (10–18%, p < 0.05). On the contrary, individual data analysis showed changes in the pulmonary gas exchange indices in 90% of subjects in the case of inhalation of 17 vol % of O₂ HAM. Four response types have been found: ventilation (increase in lung ventilation), hypoxic hypometabolism (decrease in oxygen consumption rate), and mobilization response (increase in oxygen utilization in the lungs), and anaerobic response, which is expressed in an increase in the carbon dioxide release rate along with an increase in the respiratory quotient. All these responses are of an individual type, but the ventilation response is developed in response to hypoxia caused by inhalation of 13 vol % of O₂ HAM and a decrease in SpO₂ below 85% in more than 60% of cases.     

Bone marrow niche-inspired,multiphase expansion of megakaryocytic progenitors with high polyploidization potential

Background aimsMegakaryopoiesis encompasses hematopoietic stem and progenitor cell (HSPC) commitment to the megakaryocytic cell (Mk) lineage, expansion of Mk progenitors and mature Mks, polyploidization and platelet release. pH and pO₂ increase from the endosteum to sinuses, and different cytokines are important for various stages of differentiation. We hypothesized that mimicking the changing conditions during Mk differentiation in the bone marrow would facilitate expansion of progenitors that could generate many high-ploidy Mks.MethodsCD34⁺ HSPCs were cultured at pH 7.2 and 5% O₂ with stem cell factor (SCF), thrombopoietin (Tpo) and all combinations of Interleukin (IL)-3, IL-6, IL-11 and Flt-3 ligand to promote Mk progenitor expansion. Cells cultured with selected cytokines were shifted to pH 7.4 and 20% O₂ to generate mature Mks, and treated with nicotinamide (NIC) to enhance polyploidization.ResultsUsing Tpo + SCF + IL-3 + IL-11, we obtained 3.5 CD34⁺ CD41⁺ Mk progenitors per input HSPC, while increasing purity from 1% to 17%. Cytokine cocktails with IL-3 yielded more progenitors and mature Mks, although the purities were lower. Mk production was much greater at higher pH and pO₂. Although fewer progenitors were present, shifting to 20% O₂/pH 7.4 at day 5 (versus days 7 or 9) yielded the greatest mature Mk production, 14 per input HSPC. NIC more than doubled the percentage of high-ploidy Mks to 40%.ConclusionsWe obtained extensive Mk progenitor expansion, while ensuring that the progenitors could produce high-ploidy Mks. We anticipate that subsequent optimization of cytokines for mature Mk production and delayed NIC addition will greatly increase high-ploidy Mk production.     

Severe hypoxia decreases oxygen uptake relative to intensity during submaximal graded exercise

The effect of severe acute hypoxia (fractional concentration of inspired oxygen equalled 0.104) was studied in nine male subjects performing an incremental exercise test. For power outputs over 125 W, all the subjects in a state of hypoxia showed a decrease in oxygen consumption ( O₂) relative to exercise intensity compared with normoxia (P < 0.05). This would suggest an increased anaerobic metabolism as an energy source during hypoxic exercise. During submaximal exercise, for a given O₂, higher blood lactate concentrations were found in hypoxia than in normoxia (P < 0.05). In consequence, the onset of blood lactate accumulation (OBLA) was shifted to a lower O₂ ( O₂ 1.77 l·min^–1 in hypoxia vs 3.10 l·min^–1 in normoxia). Lactate concentration increases relative to minute ventilation ( _E) responses were significantly higher during hypoxia than in normoxia (P < 0.05). At OBLA, _E during hypoxia was 25% lower than in the normoxic test. This study would suggest that in hypoxia subjects are able to use an increased anaerobic metabolism to maintain exercise performance.     

Interleukin 10 production in patients undergoing cardiopulmonary bypass: evidence of inhibition of Th-1-type responses

The cardiopulmonary bypass (CPB) procedure has long been associated with a generalized immunosuppression. To understand further the cytokine-mediated regulation of the complex physiological and immunological changes induced by CPB, the authors decided to investigate whether CPB affects the release of interleukin (IL)-10, as well as other cytokines, in correlation to the inhibition of T cell responses. Using phytohaemagglutinin (PHA) as mitogen and peripheral blood mononuclear cells (PBMC) isolated from patients undergoing CPB, we investigated whether this procedure has an effect on the secretion of different patterns of cytokines (Th1- and Th2-type) and PBMC proliferation. In all patients, CPB significantly enhances IL-10 and IL-6 production in resting and PHA-stimulated PBMC. On the other hand, IL-2 production, in response to PHA, was significantly diminished. Reduced IL-2 and enhanced IL-10 production were associated with a significant decrease in PBMC proliferation. Immunosuppression was also associated to lymphopenia, while neutrophil counts were significantly enhanced. These results show that after CPB there is a transient but clear unbalanced immune response demonstrated by a differentiated production of Th1- and Th2-type cytokines. The release of different patterns of cytokines observed after CPB may be helpful in understanding and preventing the development of infectious and immune complications in surgical procedure employing CPB.     

Effect of oxygen pressure on synthesis and export of nitrogenous solutes by nodules of cowpea

Nodules of cowpea plants (Vigna unguiculata (L.) Walp. cv. Vita 3 :Bradyrhizobium CB756) cultured for periods of 23 d with their root systems maintained in atmospheres containing a range of partial pressures of O₂ (pO₂; 1–80%, v/v, in N₂) formed and exported ureides (allantoin and allantoic acid) as the major products of fixation at all pO₂ tested. In sub-ambient pO₂ (1 and 2.5%) nodules contained specific activities of uricase (urate: O₂ oxidoreductase; EC 1.7.3.3) and allantoinase (allantoin hydrolyase; EC 3.5.2.5) as much as sevenfold higher than in those from air. On a cell basis, uninfected cells in nodules from 1% O₂ contained around five times the level of uricase. Except for NAD: glutamate synthase (EC 1.4.1.14), which was reduced in sub-ambient O₂, the activities of other enzymes of ureide synthesis were relatively unaffected by pO₂. Short-term effects of pO₂ on assimilation of fixed nitrogen were measured in nodules of air-grown plants exposed to subambient pO₂ (1, 2.5 or 5%, v/v in N₂) and¹⁵N₂. Despite a fall in total¹⁵N₂ fixation, ureide synthesis and export was maintained at a high level except in 1% O₂ where formation was halved. The data indicate that in addition to the structural and diffusional adaptations of cowpea nodules which allow the balance between O₂ supply and demand to be maintained over a wide range of pO₂, nodules also show evidence of biochemical adaptations which maintain and enhance normal pathways for the assimilation of fixed nitrogen. This work was supported by a grant from the Australian Research Council (to C.A.A.) and an Australian Development Assistance Bureau postgraduate fellowship (to F.D.D.).