Leaf anatomy and subgeneric affiliations of C3 and C4 species of Suaeda (Chenopodiaceae) in North America

The halophytic genus Suaeda (Chenopodiaceae) includes species with the C3 and C4 photosynthetic pathways. North American species of this genus were investigated to determine whether C3 and C4 leaf anatomy are consistent within the two sections of Suaeda, Chenopodina and Limbogermen, present on this continent. All species from section Chenopodina were found to possess C3 anatomy, whereas all species from section Limbogermen were found to be C4 species. Characteristics of leaf anatomy and chloroplast ultrastructure are similar to those reported from C3 and C4 species, respectively, from the Eastern Hemisphere. All species from section Limbogermen have the suaedoid type of leaf anatomy, characterized by differentiation of the mesophyll into palisade parenchyma and a chlorenchymatous sheath surrounding central water-storage tissue, as well as leaf carbon isotope ratios (_13C) of above -20. All species from section Chenopodina have austrobassioid leaf anatomy without a chlorenchymatous sheath and _13C values of below -20. According to our literature review, the photosynthetic pathway has now been reported for about half (44) of the Suaeda species worldwide. The C3 and C4 photosynthetic syndromes are with few exceptions distributed along sectional or subsectional lines. These findings throw new light on the infrageneric taxonomy of this genus.

Pharmacodynamic modelling of the analgesic effects of piritramide in postoperative patients

BACKGROUND

The concentration-effect relationship of piritramide, a synthetic opioid analgesic predominantly used for postoperative analgesia and analgosedation, has not been reported so far.

METHODS

Twenty-four patients of both genders aged 58.1 (11.7) yr (mean (SD)) received inhalational anaesthesia for abdominal surgery. Postoperative pain was assessed with a visual analogue scale (VAS). Analgesia was provided with piritramide, infused at a rate of 7 micrograms.kg-1.min-1 until analgesia was considered sufficient (VAS < 25) or up to a maximum dose of 0.2 mg/kg. The plasma concentrations of piritramide were determined by gas chromatography. An inhibitory fractional sigmoid Emax-model was used to describe the relation between effect site concentration and perceived pain.

RESULTS

The equilibration half-life between plasma and effect site concentrations (T1/2 (keo)) was 16.8 min (median; range: 4.4-41.6 min). The steady-state plasma concentration required to produce 50% of maximum analgesia (EC50) was 12.1 ng/ml (range: 2.9-29.8 ng/ml) and correlated with initial pain intensity. The slope factor gamma was 1.9 (range: 0.5-6.1) and increased with age. Clinically relevant respiratory depression did not occur. Due to the relatively large equilibration half-life of the effect compartment, the context-sensitive half-time of the effect site concentrations after short-time administration (< 2 h) clearly exceeded those of alfentanil, sufentanil, and fentanyl.

CONCLUSIONS

The analgesic effect of piritramide was adequately described by an inhibitory fractional Emax-model. In order to overcome the pronounced hysteresis, piritramide should initially be administered as an intravenous bolus of at least 5 mg.

Thioredoxin as a potent costimulus of cytokine expression

Reduction/oxidation (redox) processes have been implicated in various biologic processes, including signal transduction, gene expression, and cell proliferation. Thioredoxin is one of the major redox-regulatory molecules which because of its dithiol/disulfide exchange activity determines the oxidation state of protein thiols. In this study, we report that treatment of several cell types with thioredoxin strongly enhances the expression of various cytokines. In monocytic Mono Mac6 cells stimulated with the phorbolester tetradecanoyl phorbolacetate (TPA), thioredoxin was found to augment the expression of TNF at the protein and mRNA levels. In this and other cell lines, such as fibrosarcoma and endothelial cells, thioredoxin also dose-dependently increased the synthesis of IL-6. Treatment of TPA-stimulated Mono Mac6 cells resulted in a strong potentiation of secreted IL-1 bioactivity and expression of IL-1 alpha and IL-8 mRNA. In addition, in TPA-activated Molt-4 T cells, an increased expression of IL-2 and IL-2-specific transcripts was detected. These data demonstrate that cytokine synthesis may be tightly controlled by redox-dependent processes. As thioredoxin is readily secreted and taken up by cells, it may play an important role as a costimulatory molecule involved in immune processes.

Thioredoxin as a potent costimulus of cytokine expression

Reduction/oxidation (redox) processes have been implicated in various biologic processes, including signal transduction, gene expression, and cell proliferation. Thioredoxin is one of the major redox-regulatory molecules which because of its dithiol/disulfide exchange activity determines the oxidation state of protein thiols. In this study, we report that treatment of several cell types with thioredoxin strongly enhances the expression of various cytokines. In monocytic Mono Mac6 cells stimulated with the phorbolester tetradecanoyl phorbolacetate (TPA), thioredoxin was found to augment the expression of TNF at the protein and mRNA levels. In this and other cell lines, such as fibrosarcoma and endothelial cells, thioredoxin also dose-dependently increased the synthesis of IL-6. Treatment of TPA-stimulated Mono Mac6 cells resulted in a strong potentiation of secreted IL-1 bioactivity and expression of IL-1 alpha and IL-8 mRNA. In addition, in TPA-activated Molt-4 T cells, an increased expression of IL-2 and IL-2-specific transcripts was detected. These data demonstrate that cytokine synthesis may be tightly controlled by redox-dependent processes. As thioredoxin is readily secreted and taken up by cells, it may play an important role as a costimulatory molecule involved in immune processes.

IL-2 gene expression and NF-kappa B activation through CD28 requires reactive oxygen production by 5-lipoxygenase

Activation of the CD28 surface receptor provides a major costimulatory signal for T cell activation resulting in enhanced production of interleukin-2 (IL-2) and cell proliferation. In primary T lymphocytes we show that CD28 ligation leads to the rapid intracellular formation of reactive oxygen intermediates (ROIs) which are required for CD28-mediated activation of the NF-kappa B/CD28-responsive complex and IL-2 expression. Delineation of the CD28 signaling cascade was found to involve protein tyrosine kinase activity, followed by the activation of phospholipase A2 and 5-lipoxygenase. Our data suggest that lipoxygenase metabolites activate ROI formation which then induce IL-2 expression via NF-kappa B activation. These findings should be useful for therapeutic strategies and the development of immunosuppressants targeting the CD28 costimulatory pathway.

Requirement of an ICE/CED-3 protease for Fas/APO-1-mediated apoptosis

The Fas/APO-1 receptor is one of the major regulators of apoptosis. We report here that Fas/APO-1-mediated apoptosis requires the activation of a new class of cysteine proteases, including interleukin-1 beta-converting enzyme (ICE), which are homologous to the product of the Caenorhabditis elegans cell-death gene ced-3 (refs 11, 12). Triggering of Fas/APO-1 rapidly stimulated the proteolytic activity of ICE. Overexpression of ICE, achieved by electroporation and microinjection, strongly potentiated Fas/APO-1-mediated cell death. In addition, inhibition of ICE activity by protease inhibitors, as well as by transient expression of the pox virus-derived serpin inhibitor CrmA or an antisense ICE construct, substantially suppressed Fas/APO-1-triggered cell death. We conclude that activation of ICE or an ICE-related protease is a critical event in Fas/APO-1-mediated cell death.