Photosynthesis in response to salinity and submergence in two Rhizophoraceae mangroves adapted to different tidal elevations.

Mangrove ecosystems are vulnerable to rising sea levels. When the sea level rises, the plants are exposed to increased salinity and tidal submergence. In Taiwan, the mangrove species Kandelia obovata and Rhizophora stylosa grow in different habitats and at different elevations. To understand the response of photosynthesis to salinity and submergence in mangroves adapted to different tidal elevations, gas exchange and chlorophyll fluorescence parameters were measured in K. obovata and R. stylosa under different salinity (20 and 40‰) and submergence treatments. The period of light induction of photosynthesis for the two mangrove species was >60 min. In the induction process, the increase in photosystem efficiency was faster than the increase in stomatal opening, but CO2 fixation efficiency was restricted by stomatal conductance. The constraint of stomatal opening speed is related to the conservative water-use strategy developed in response to mangrove environments. Submergence increased the photosynthetic rate of K. obovata, but not that of R. stylosa. Although R. stylosa was more salt tolerant than K. obovata, R. stylosa was not submergence tolerant in a high-salinity environment, which may be the reason for the higher intertidal elevations observed for R. stylosa in comparison with K. obovata. The photosynthetic rate and energy-dependent quenching (qE) of the two mangroves presented a negative relationship with photoinhibition, and high-salt treatment simultaneously reduced photosynthetic rate and qE. A decrease in the photosynthetic rate increased excess energy, whereas a decrease in qE decreased photoprotection; both increased photoinhibition. As the degree of photoinhibition can be easily measured in the field, it is a useful ecological monitoring index that provides a suitable reference for mangrove restoration, habitat construction and ecological monitoring.

Seasonality and disturbance: annual pattern and response of the bacterial and microbial eukaryotic assemblages in a freshwater ecosystem.

High-throughput pyrosequencing of SSU rDNA genes was used to obtain monthly snapshots of eukaryotic and bacterial diversity and community structure at two locations in Lake Texoma, a low salinity lake in the south central United States, over 1 year. The lake experienced two disturbance events (i) a localized bloom of Prymnesium parvum restricted to one of the locations that lasted from January to April, and (ii) a large (17 cm), global rain event in the beginning of May, overlaid onto seasonal environmental change. Eukaryotic species richness as well as both eukaryotic and bacterial community similarity exhibited seasonal patterns, including distinct responses to the rain event. The P. parvum bloom created a natural experiment in which to directly explore the effects of an Ecosystem Disruptive Algal Bloom (EDAB) on the microbial community separated from seasonal changes. Microbial species richness was unaffected by the bloom, however, the eukaryotic community structure (evenness) and the patterns of both eukaryotic and bacterial community similarity at bloom and non-bloom sites were statistically distinct during the 4 months of the bloom. These results indicate that physical and biological disturbances as well as seasonal environmental forces contribute to the structure of both the eukaryotic and bacterial communities.

An efficient genetic screen in Drosophila to identify nuclear-encoded genes with mitochondrial function.

We conducted a screen for glossy-eye flies that fail to incorporate BrdU in the third larval instar eye disc but exhibit normal neuronal differentiation and isolated 23 complementation groups of mutants. These same phenotypes were previously seen in mutants for cytochrome c oxidase subunit Va. We have molecularly characterized six complementation groups and, surprisingly, each encodes a mitochondrial protein. Therefore, we believe our screen to be an efficient method for identifying genes with mitochondrial function.

Preoperative diagnosis and localization of aldosterone-producing adenoma by adrenal venous sampling after administration of metoclopramide.

BACKGROUND AND PURPOSE: Adrenal venous sampling is the most reliable test to distinguish aldosterone-producing adenoma (APA) from idiopathic hyperaldosteronism (IHA). The diagnostic accuracy can be improved by administration of adrenocorticotropin to minimize pulsatile secretion of aldosterone. Metoclopramide (MCP), a dopamine antagonist, can increase aldosterone secretion promptly without affecting cortisol secretion. This study investigated the diagnostic accuracy of adrenal venous sampling after MCP injection for the preoperative diagnosis and localization of APA. METHODS: Prospective diagnosis and adrenalectomy was based on adrenal venous sampling in 23 patients with a diagnosis of primary aldosteronism. Plasma aldosterone concentrations from adrenal veins and the inferior vena cava were measured before and 30 minutes after intravenous administration of 10 mg MCP. The ratio of bilateral adrenal venous aldosterone concentrations after MCP was used for diagnosis as follows: a ratio greater than 5 indicated APA, less than 3 indicated IHA, and 3-5 indicated an intermediate diagnosis. RESULTS: Catheterization of the right adrenal vein was unsuccessful in three patients. Twelve of 13 patients with an aldosterone ratio greater than 5 after MCP underwent unilateral adrenalectomy, and APA was confirmed in 11 of these patients. One patient with an intermediate diagnosis also had surgically confirmed APA. Six patients had a ratio less than 3. Before MCP administration, 10 of 13 patients with APA had a ratio greater than 5, and three patients had a ratio between 3 and 5; one patient with IHA had a ratio greater than 5. MCP improved the diagnosis of APA to an accuracy of 92% (12/13). Correct diagnosis of APA based on computerized tomography (CT) was 85% (11/13). There was discordance between the findings of adrenal venous sampling and CT in four of 20 patients. CONCLUSIONS: Administration of MCP to stimulate aldosterone secretion during adrenal venous sampling can improve the accuracy of differential diagnosis between APA and IHA.

The modular nature of histone deacetylase HDAC4 confers phosphorylation-dependent intracellular trafficking.

In C2C12 myoblasts, endogenous histone deacetylase HDAC4 shuttles between cytoplasmic and nuclear compartments, supporting the hypothesis that its subcellular localization is dynamically regulated. However, upon differentiation, this dynamic equilibrium is disturbed and we find that HDAC4 accumulates in the nuclei of myotubes, suggesting a positive role of nuclear HDAC4 in muscle differentiation. Consistent with the notion of regulation of HDAC4 intracellular trafficking, we reveal that HDAC4 contains a modular structure consisting of a C-terminal autonomous nuclear export domain, which, in conjunction with an internal regulatory domain responsive to calcium/calmodulin-dependent protein kinase IV (CaMKIV), determines its subcellular localization. CaMKIV phosphorylates HDAC4 in vitro and promotes its nuclear-cytoplasmic shuttling in vivo. However, although 14-3-3 binding of HDAC4 has been proposed to be important for its cytoplasmic retention, we find this interaction to be independent of CaMKIV. Rather, the HDAC4.14-3-3 complex exists in the nucleus and is required to confer CaMKIV responsiveness. Our results suggest that the subcellular localization of HDAC4 is regulated by sequential phosphorylation events. The first event is catalyzed by a yet to be identified protein kinase that promotes 14-3-3 binding, and the second event, involving protein kinases such as CaMKIV, leads to efficient nuclear export of the HDAC4.14-3-3 complex.

The detection of the HLA-B27 antigen by immunomagnetic separation and enzyme-linked immunosorbent assay-comparison with a flow cytometric procedure.

The HLA-B27 antigen is an important genetic marker in ankylosing spondylitis (AS). Methods for the detection of B27 include the microlymphocytotoxicity test and, more recently, flowcytometry (FC). Here, we describe a new method, IMS-ELISA, for measuring the B27-antigen. It combines immunomagnetic separation (IMS), to obtain B27-positive cells from whole blood samples, with an enzyme-linked immunosorbent assay (ELISA) as a read-out. IMS-ELISA was tested on 367 samples obtained from five different hospitals in Taiwan. The sensitivity, specificity and accuracy of the method were compared with FC. Any conflicting data between IMS-ELISA and FC was confirmed by HLA-DNA typing via PCR-SSP (polymerase chain reaction-sequence specific primers). Overall, the results for sensitivity, specificity and accuracy obtained by IMS-ELISA and FC did not show any significant difference (p>0.05). However, when considering laboratory time, cost, ease of operation and the screening of large samples for HLA-B27, the IMS-ELISA was superior to the FC method. We conclude that IMS-ELISA may be used as a fast screening method for HLA B27 detection.

Prostaglandin E2 suppresses the expression and release of beta 2-microglobulin from mitogen-activated normal human mononuclear cells.

BACKGROUND: Prostaglandin E2 (PGE2) is a feedback suppressor of immune response. Beta 2-Microglobulin (beta 2M) is part of HLA class I molecule that mediates viral antigen presentation to cytotoxic T lymphocytes as well as graft rejection. It has been known that beta 2M can be synthesized by both stimulated and unstimulated lymphocytes, but it is unknown whether beta 2M can be modulated by PGE2. This investigation aimed to clarify this point. METHODS: Normal human mononuclear cells (MNC) were isolated, stimulated by phytohemagglutinin (PHA), and cultured for 3 days in the presence or absence of PGE2. The culture supernatants were collected and detected for beta 2M concentration by enzyme linked immunosorbent assays (ELISA). The cell pellets were stained indirectly with immunofluorescence for HLA-class I antigen and beta 2M expression on the surface membranes. In addition, the membrane potential of stimulated or unstimulated cells was measured by flow cytometry to evaluate the effect exerted by PGE2. RESULTS: PGE2 at a concentration of more than 1 x 10(-8)M markedly suppressed the expression and release of beta 2M from PHA-stimulated MNC in a dose-dependent manner. Expression of HLA-class I molecule on PHA-stimulated MNC was also suppressed by PGE2. Kinetic study demonstrated that PGE2 began to suppress beta 2M synthesis of PHA-stimulated MNC from the 3rd day of culture. It also inhibited beta 2M release from lymphocytes in mixed lymphocyte reaction. This inhibitory effect was not due to cell death as confirmed by trypan blue exclusion. PGE2 per se exerts negligible effect on membrane potential of MNC but can normalize the depolarized state of the membrane induced by PHA as demonstrated by 3,3'-dihexyloxacarbocyanine iodide stain. CONCLUSIONS: PGE2 down-regulates the production of HLA-class I antigens and beta 2M molecules. This effect is associated with the suppression of cytotoxic T cell function by PGE2 and may be relevant to the underlying mechanism of PGE2 on this population of cells.

Interleukin 8 modulates interleukin-1 beta, interleukin-6 and tumor necrosis factor-alpha release from normal human mononuclear cells.

Recombinant human interleukin 8 (IL-8) enhanced the release of inflammatory cytokines including interleukin 1 beta (IL-1 beta), interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) from normal human mononuclear cells in a dose-related manner (from 1 ng/ml to 10 ng/ml with a maximal effect at 5 ng/ml) when the cells incubated with IL-8 for 24 h. This cytokine-releasing activity of IL-8 is temperature-dependent and required protein synthesis since low temperature (4 degrees C) and cycloheximide (100 micrograms/ml) minimized the cytokine release from MNC. However, when IL-8 concentration was greater than 20 ng/ml, the cytokine release was suppressed. For further investigating the subcellular mechanism of the adverse effect of high dose IL-8 (20 ng/ml) in cytokine synthesis, human mononuclear cells (1 x 10(6)/ml) were stimulated with PHA (1 microgram/ml) in the presence of 20 ng/ml IL-8 for 3 days. We found not only [3H]thymidine incorporation of MNC was tremendously inhibited but DNA fragmentation appeared. Subsequently, the cell cycle of PHA-stimulated MNC retarded in the phase of G0/G1. These results suggest that in low concentration (5-10 ng/ml) IL-8 not only activated neutrophil phagocytosis but facilitated the release of inflammatory cytokines from mononuclear cells. Higher dose of IL-8 (more than 20 ng/ml) conversely suppressed these cytokine release from damaged cells by its cytotoxic effect. This newly found cytokine-releasing activity of IL-8 may play a role in the modulation of inflammation.

Tamm-Horsfall urinary glycoprotein enhances monokine release and augments lymphocyte proliferation.

Tamm-Horsfall glycoprotein (THG) purified from pregnancy urine was found to stimulate normal human mononuclear cell (MNC) proliferation at a concentration greater than 10 micrograms/ml. This stimulation was non-specific because the percentage of B and T cell subpopulations including CD20, CD3, CD4, CD8 and CD4/CD8 ratio was not changed by THG. THG not only bound to human mononuclear cells but depolarized the membrane potential, increased 22Na+ uptake and enhanced the expression of IL-2R and HLA-class II antigens on these cells. The concentrations of sIL-2R, sCD4 and sCD8 in the THG-stimulated MNC culture supernatants were significantly increased compared with control supernatants. In addition, overnight incubation of THG (5-50 micrograms/ml) with MNC dose-responsively enhanced the syntheses of IL-1 beta, IL-6 and TNF-alpha by monocytes, with a maximal effect at 25 micrograms/ml. This monokine releasing activity of THG could be neutralized by a specific antibody against THG. When monocytes/macrophages were depleted from mononuclear cells by incubating with lysosomotropic methyl ester of L-leucine, THG retained the capability of stimulating lymphocytes proliferation but to a lesser degree. These results suggest that urinary THG activates monocytes to synthesize large amount of monokines through its membrane effect. The released monokines subsequently stimulate lymphocytes expressing IL-2R and HLA-class II antigens and finally lead to cell proliferation.

Prostaglandin E2 suppresses phytohemagglutinin-induced immune responses of normal human mononuclear cells by decreasing intracellular glutathione generation, but not due to increased DNA strand breaks or apoptosis.

Prostaglandin E2 (PGE2) at concentrations more than 1 x 10(-8) M markedly suppressed the cell proliferation and release of soluble molecules of interleukin-2 receptor (sIL-2R), CD4 (sCD4) and CD8 (sCD8) from phytohemagglutinin (PHA)-stimulated normal human mononuclear cells (MNC) in a dose-related manner. To further elucidate the subcellular mechanism of the inhibitory effect of PGE2 on PHA-stimulated MNC, intracellular concentration of glutathione (GSH) in PHA-stimulated MNC was sequentially measured from day 1 to day 3 by enzymic method. Furthermore, the effect of PGE2 on nuclear DNA including DNA strand breaks in alkali treatment and DNA fragmentation (apoptosis) of PHA-stimulated MNC were also measured. We found intracellular GSH levels were significantly decreased in the early stage of lymphocyte activation (day 1), but no evidence of increased DNA strand breaks or apoptotic process appeared in 3-day culture. In addition, butathione sulfoximine (a specific GSH inhibitor) and dibutyryl cyclic AMP also exhibited both proliferation inhibition and GSH-decreasing effects on PHA-stimulated MNC as well as PGE2. These results suggest that the immunosuppressive effect of PGE2 is mediated by the decreased generation of intracellular GSH, but not by the increased DNA strand breaks or apoptotic mechanism in the cells.

Polyclonal IgG anti-dsDNA antibodies exert cytotoxic effect on cultured rat mesangial cells by binding to cell membrane and augmenting apoptosis.

IgG anti-double stranded DNA antibodies (anti-dsDNA) purified from serum of patients with active systemic lupus erythematosus (SLE), have been found to be cytotoxic to the cultured rat mesangial cells (MC). In the present study, by use of immunofluorescent staining, immunoblotting, radioimmunoprecipitation, and cell cycle analysis, we showed that IgG anti-dsDNA could bind to the membrane of MC. The bound epitope was a 28 kDa protein, which would disappear if the cells were treated in advance with proteinase K (100 micrograms/ml). In addition, binding of MC by 20 micrograms/ml of anti-dsDNA IgG F(ab')2 activated plasma membrane (equivalent to 80 IU/ml of calf thymus double-stranded DNA binding activity) resulted in release of much more 3H-arachidonic acid than binding by 20 micrograms/ml of human IgG F(ab')2 (26.71 +/- 3.75% in the case of anti-dsDNA vs. 4.73 +/- 2.86% in the case of IgG). To understand further the cytotoxic mechanism of anti-dsDNA, we incubated MC with anti-dsDNA, for a variety of periods (from 10 minutes to 24 hours). After incubation, the cells were fixed and stained with hematoxylin-eosin for morphologic observation. Simultaneously, the genomic DNA was extracted and analyzed in 1.8% agarose gel electrophoresis. We found that cell death caused anti-dsDNA followed a process of apoptosis rather than necrosis. These results suggest that binding of anti-dsDNA with MC membrane may activate endonuclease which will fracture the DNA and lead to programmed cell death.

Tamm-Horsfall glycoprotein (THG) purified from normal human pregnancy urine increases phagocytosis, complement receptor expressions and arachidonic acid metabolism of polymorphonuclear neutrophils.

Tamm-Horsfall glycoprotein (THG) purified from normal human pregnancy urine was found to increase polymorphonuclear neutrophil (PMN) phagocytosis (46.57 +/- 3.54% in the medium versus 75.85 +/- 5.37% in the presence of 25 micrograms/ml THG) after 30 min preincubation. The phagocytosis-enhancing activity of THG was dose-dependent (5-50 micrograms/ml) and was possibly mediated by the increased expressions of complement receptor type 1 (CR1) and type 3 (CR3) on the neutrophils. The release of [3H]arachidonic acid and prostaglandin E2 (PGE2), but not thromboxane B2 (TXB2), from neutrophils were also significantly enhanced by THG. Using 3,3'-dihexyloxacarbocyanine iodide as indicator, THG (25 micrograms/ml) depolarized the membrane potential of PMN after 30 min preincubation. In addition, THG exhibited a specific membranotropic effect with PMN. It is conceivable that THG binds to the cell surface and depolarizes the membrane potential of PMN which subsequently enhances the release of arachidonic acid metabolites and the translocation of the complement receptors to the membrane. These biochemical events lead to the increment of PMN phagocytosis and suggests that THG may play an important role in the defense mechanisms of the urinary tract in that a large amount of THG is usually present.

Increased spontaneous release of cytidine deaminase by polymorphonuclear neutrophils of patients with active systemic lupus erythematosus.

Cytidine deaminase activity (CD) in the neutrophil culture supernatants (PMN SUP) of 27 patients with systemic lupus erythematosus (SLE) was measured using a spectrophotometric method. Compared with the controls (5.449 +/- 1.358 U/5 x 10(6) PMN), the CD activity in the spontaneous culture supernatants of PMN was significantly increased in active (10.003 +/- 2.637 U/5 x 10(6) PMN) but not in inactive (5.358 +/- 1.624 U/5 x 10(6) PMN) SLE. However, after stimulation with N-formyl-methionyl-leucyl-phenylalanine (FMLP, 1 x 10(-7) M), the ratio of enzyme activity between stimulated and spontaneous PMN supernatants was decreased in active SLE (0.794 +/- 0.178) compared with normal controls (1.300 +/- 0.225). In contrast, the enzyme activity in the cytoplasm of either stimulated or non-stimulated PMN was not different among these three groups. These results suggest that CD of PMN is releasable and can be enhanced by chemotactic factor stimulation in normal PMN. The increased spontaneous release of CD by active SLE PMN is one of the indicators for the disease activity in these patients.

Inhibition of astrocyte proliferation and binding to brain tissue of anticardiolipin antibodies purified from lupus serum.

Polyclonal anticardiolipin antibodies purified from pooled serum samples of patients with systemic lupus erythematosus were shown to have inhibitory effects on cultured normal rat brain astrocytes (RBA-1 cells). Anticardiolipin antibodies at concentrations from 50 to 200 micrograms/ml inhibited the [3H]thymidine incorporation of RBA-1 cells in a dose dependent manner after three days of culture. A kinetic study showed that anticardiolipin antibodies (100 micrograms/ml) maximally inhibit the proliferation of RBA-1 cells (20.6 (5.1)% of the control value) after incubation for one day. In contrast, human gamma globulin (100 micrograms/ml) had no effect on these cells. In the presence of anticardiolipin antibodies (100 micrograms/ml), the RBA-1 cells attached to the bottom of wells became spherical and the expression of glial fibrillary acidic protein in the cytoplasm was slightly reduced. Using 3,3'-dihexyloxacarbocyanine iodide as an indicator, anticardiolipin antibodies depolarised the membrane potential of RBA-1 cells after one day of culture. In addition, the percentage binding of RBA-1 cells with anticardiolipin antibodies was greater than with gamma globulin as determined by flow cytometric analysis. Immunofluorescence staining of brain tissue from BALB/c mice with anticardiolipin antibodies was noted in the corpus callosum, the cellular zone near the corpus callosum, and cells scattered in brain tissue. These results suggest that anticardiolipin antibodies have an inhibitory effect on brain cells and elicit thrombus formation in brain vessels, which plays a part in neuropsychiatric lupus.

Defective expression of neutrophil C3b receptors and impaired lymphocyte Na(+)-K(+)-ATPase activity in patients with systemic lupus erythematosus.

In our previous report, we demonstrated that the functions of phagocytes and lymphocytes were defective in patients with systemic lupus erythematosus (SLE). In an attempt to further clarify the defective mechanisms of these cells, 25 active SLE, 10 bronchial asthma patients (BA) on corticosteroids and 25 age and sex-matched normal individuals were investigated for the expression of membraneous C3b receptors, ionophore-induced 45Ca(2+)-uptake, mitochondrial potentials and phagocytic activity of neutrophils. We found decreased expression of C3b receptors on SLE PMN in both resting (37.2 +/- 3.7% of the normal controls) and FMLP-stimulated (68.3 +/- 7.1% of the normal controls) conditions, whereas the C3b receptor expression on BA-PMN receiving long-term steroid treatment was not different from normal controls. This suggests that the defective phagocytosis of SLE PMN is in the recognition, but not in the ingestion phase because of the normal function of Ca(2+)-influx and mitochondrial activity in SLE PMN. On the other hand, hyporesponsiveness to PHA stimulation (stimulation index: 127.4 +/- 46.3 in SLE vs. 311.2 +/- 30.4 in normals, p = 0.0077) was a distinct cell-mediated immune abnormality in our SLE patients. We measured the membrane potential of individual cells using 3,3'-dihexyloxacarbocyanin and found hyperpolarization in resting SLE lymphocytes. However, the membrane polarization of SLE lymphocytes became lower than that of normal cells after PHA stimulation for 3 days. A similar tendency was also found in Na(+)-K(+)-dependent ATPase activity in SLE lymphocytes.(ABSTRACT TRUNCATED AT 250 WORDS)