Involvement of plasma membrane calcium influx in bacterial induction of the k/h and hypersensitive responses in tobacco

An early event in the hypersensitive response of tobacco to Pseudomonas syringae pv syringae is the initiation of a K⁺/H⁺ response characterized by specific plasma membrane K⁺ efflux, extracellular alkalinization, and intracellular acidification. We investigated the role of calcium in induction of these host responses. Suspension-cultured tobacco cells exhibited a baseline Ca²⁺ influx of 0.02 to 0.06 micromole per gram per hour as determined from ⁴⁵Ca²⁺ uptake. Following bacterial inoculation, uptake rates began to increase coincidently with onset of the K⁺/H⁺ response. Rates increased steadily for 2 to 3 hours, reaching 0.5 to 1 micromole per gram per hour. This increased Ca²⁺ influx was prevented by EGTA and calcium channel blockers such as La³⁺, Co²⁺, and Cd²⁺ but not by verapamil and nifedipine. Lanthanum, cobalt, cadmium, and EGTA inhibited the K⁺/H⁺ response in both suspension-cultured cells and leaf discs and prevented hypersensitive cell death in leaf discs. We conclude that increased plasmalemma Ca²⁺ influx is required for the K⁺/H⁺ and hypersensitive responses in tobacco.     

Sediment and interstitial water chemistry of the Orbeteflo lagoon (Grosseto,Italy); nutrient diffusion across the water-sediment interface

The Orbetello lagoon is now highly eutrophic and has experienced increasing incidence of anoxia causing serious economic damage. A multidisciplinary study was commenced in March 1987 to investigate the part played by the lagoon sediments and interstitial water in recycling nutrients and contributing to the observed anoxia. Eleven undisturbed cores were collected and sub-sampled at 2 cm intervals. Interstitial water was obtained by centrifugation and analyzed for pH, Eh, nutrients, major and some minor elements. Differential fluxes from the sediments of 0.2–10 g cm^–2 day^–1 of ammonia and 0.02–0.7 g cm^–2 day^–1 of orthophosphate were obtained depending on the season, temperature of the sediments and the sampling location. A highly significant linear correlation (r ² = 0.86) was found between bicarbonate and ammonia concentrations in the interstitial waters, due to the release of these compounds during the degradation organic matter. A diagenetic model was developed to predict the alkalinity of interstitial water from the theoretical reactions involved in the decomposition of organic matter. The predicted values for bicarbonate and ammonia agreed well with the experimental results.     

Diel modulation of Hsp70 and Hsp60 in corals living in a shallow reef

Coral Reefs - In corals, different biological processes are associated with the daily variation of temperature and light, which in shallow reefs can vary widely and regularly reach extreme levels....     

Prostacyclin (PGI2) Synthase Is a Constitutively Expressed Enzyme in Human Endothelial Cells

Biogenesis of prostanoids is under the control of some polypeptide growth factors. Cytosolic phospholipase A₂, a form specific for arachidonic acid containing phospholipids, is activated by a translocation mechanism regulated by growth factors, while prostaglandin H synthase isoforms are induced de novo in several cell types. No information is available as far as PGI₂ synthase is concerned. Human umbilical vein endothelial cells were cultured under conditions favoring proliferation or differentiation or capillary-like network formation in the presence of collagen gels. Basic fibroblast growth factor (bFGF 0.5-4 ng/ml) was used as a mitogen, interleukin-1α (IL-1α 10-60 UI/ml) as a differentiating agent, and prostacyclin (PGI₂) biosynthesis was evaluated. Under the first condition, basal PGI₂ production was unaffected while, in the presence of IL-1α, a marked stimulation of PGI₂ synthesis was observed. It is known that IL-1α is a potent inducer of PGH synthase, while it is not known whether PGI₂ synthase is also induced. Two lines of evidence indicate that PGI₂ synthase is a constitutively expressed not inducible enzyme: (a) proliferating nonproducing cells when added with PGH₂ produce an amount of PGI₂ not different from the amount produced by cells stimulated with IL-1α; (b) under this condition PGI₂ synthase was immunodetectable either by immunofluorescence detected by confocal microscopy or by ELISA and, on microsomes isolated from endothelial cells, by Western blotting. It is concluded that the limiting step in the conversion arachidonate-PGI₂ is represented solely by the level of PGH synthase. These results strongly suggest, but do not prove, the constitutive nature of the enzyme. The final demonstration requires the availability of a probe to detect mRNA level, a trial we are carrying out at the moment.     

Elemental Analysis of Histological Specimens: A Method to Unmask Nano Asbestos Fibers

There is an increasing amount of evidence that nanoparticles may enhance toxicological potential in comparison to the same material in the bulk form. The aim of this study was to develop a new method to unmask asbestos nanofibers from Formalin-Fixed Paraffin-Embedded (FFPE) tissue. For the first time, in this study we applied Energy Dispersive X-ray (EDX) microanalysis through transmission electron microscopy to demonstrate the presence of asbestos nanofibers in histological specimens of patients with possible occupational exposure to asbestos. The diagnostic protocol was applied to 10 randomly selected lung cancer patients with no history of previous asbestos exposure. We detected asbestos nanofibers in close contact with lung cancer cells in two lung cancer patients with previous possible occupational exposure to asbestos. We were also able to identify the specific asbestos iso-type, which in one of the cases was the same rare variety used in the workplace of the affected patient. By contrast, asbestos nanofibers were not detected in lung cancer patients with no history of occupational asbestos exposure.The proposed technique can represent a potential useful tool for linking the disease to previous workplace exposure in uncertain cases. Furthermore, Formalin-Fixed Paraffin-Embedded (FFPE) tissues stored in the pathology departments might be re-evaluated for possible etiological attribution to asbestos in the case of plausible exposure. Since diseases acquired through occupational exposure to asbestos are generally covered by workers’ insurance in most countries, the application of the protocol used in this study may have also relevant social and economic implications.Key words: Asbestos fibers, nanofibers, EDX microanalysis, Transmission Electron Microscopy, lung cancer, occupational exposure     

Prostaglandin and thromboxane biosynthesis in isolated platelet-free human monocytes. III. The induction of cycloxygenase by colony stimulating factor-1

Previous observations showing the presence in the serum of a component capable of regulating prostanoid biosynthesis in human cultured monocytes, have led us to suspect its presence in human platelets. We have purified this serum monocytotropic factor (SMF) and have shown its identity with a component of platelet membranes. Surprisingly its structure appeared to be very similar to that of a polypeptide growth factor never before identified in platelets: the colony stimulating factor-1 (CSF-1 or M-CSF). Here we show that SMF and CSF-1 have very similar biological properties. Thus, CSF-1 when released from human platelets is capable of triggering the differentiation pathway leading from blood monocytes to resident macrophages. It is likely that cycloxygenase induction plays a pivotal role in these events.