BVDV and innate immunity.

Infection with bovine viral diarrhea virus (BVDV) is prevalent in the cattle population worldwide. The virus exists in two biotypes, cytopathic and non-cytopathic, depending on the effect of the viruses on cultured cells. BVDV may cause transient and persistent infections which differ fundamentally in the host's antiviral immune response. Transient infection may be due to both cytopathic and non-cytopathic biotypes of BVDV and leads to a specific immune response. In contrast, only non-cytopathic BVD viruses can establish persistent infection as a result of infection of the embryo early in its development. Persistent infection is characterized by immunotolerance specific for the infecting viral strain. In this paper we discuss the role of innate immune responses in the two types of infection. In general, both transient and persistent infections are associated with an increased frequency of secondary infections. Associated with the increased risk of such infections are, among others, impaired bacteria killing and decreased chemotaxis. Interestingly, non-cytopathic BVDV fails to induce interferon type I in cultured bovine macrophages whereas cytopathic biotypes readily trigger this response. Cells infected with non-cytopathic BVDV are also resistant to induction of interferon by double stranded RNA, a potent interferon inducer signalling the presence of viral replication in the cell. Thus, non-cytopathic BVDV may dispose of a mechanism suppressing a key element of the antiviral defence of the innate immune system. Since interferon is also important in the activation of the adaptive immune response, suppression of this signal may be essential for the establishment of persistent infection and immunotolerance.     

Airway contractility and smooth muscle Ca(2+) signaling in lung slices from different mouse strains.

To investigate the hypothesis that altered Ca2+ signaling in airway smooth muscle cells (SMCs) is responsible for airway hyperreactivity, we compared, with the use of confocal and phase-contrast microscopy, the airway contractility and Ca2+ changes in SMCs induced by acetylcholine (ACh) in lung slices from different mouse strains (A/J, Balb/C, and C3H/ HeJ). The airways from each mouse strain displayed a concentration-dependent contraction to ACh. The contractile response of the airways of the C3H/HeJ mice was found, in contrast to earlier studies, to be much greater and faster than that of A/J and Balb/C mice. This difference in airway reactivity can be, in part, attributable to halothane, a volatile anesthetic that was previously used during in vivo measurements of airway reactivity but found here to significantly alter the ACh contractile response of airways in lung slices. The ACh-induced Ca2+ response of the airway SMCs in all of the various mouse strains was also concentration dependent. The magnitude of the initial Ca2+ increase and the frequency of the subsequent Ca2+ oscillations induced by ACh increased with ACh concentration. However, no differences in the Ca2+ responses to ACh could be distinguished between the mouse strains. These results suggest that the mechanism responsible for airway hyperreactivity in different mouse strains resides with the Ca2+ sensitivity of the contractile apparatus of the SMCs rather than with the Ca2+ signaling itself.     

Tumor necrosis factors in 1996

The 6th International Congress on Tumor Necrosis Factors and Related Molecules was held in Faliraki, Island of Rhodes, Greece, 8–12 May, 1996. This review summarizes the topics addressed and highlights some of the major advances presented during the meeting.     

Protonation,alkylation, addition and redox reactions of 16, 17 and 18 valence electron [Mo(L)(NO)('S4')] complexes [L = SPh,PMe3, NO; 'S4'2– = 1,2-Bis-(2-mercaptophenylthio)ethane(2-)]

In the quest for complexes modelling functional characteristics of metal sulfur oxidoreductases, a series of molybdenum nitrosyl complexes with sulfur-dominated coordination sphere was synthesized. Treatment of the 16, 17 and 18 valence electron (VE) complexes [Mo(L)(NO)('S₄')] (1–3) [L?=?SPh (1), PMe₃ (2), NO (3), 'S₄'^2–?=?1,2-bis-(2-mercaptophenylthio) ethane(2-)] with the Brönsted acid HBF₄ resulted in formation of different types of products. 1 and 3 were reversibly protonated at one thiolate atom of the 'S₄'^2– ligand;2, however, yielded the phosphonium salt [HPMe₃]BF₄ and the dinuclear [Mo(NO)('S₄')]₂. Alkylation of 1, 2 and 3 by Me₃OBF₄ or Et₃OBF₄ uniformly resulted in high yields of [Mo(L)(NO)(R-'S₄')]BF₄ complexes [L?=?SPh: R?=?Me (5), Et (6); L?=?PMe₃: R?=?Me (7); L?=?NO: R?=?Me (8), Et (9)] in which one thiolate atom of the 'S₄'^2– ligand had become alkylated; the NMR spectra of 5, 6, 8 and 9 indicated that only one out of four theoretically possible diastereoisomers had formed. 5 and 6 were characterized also by single-crystal X-ray structure analyses. A comparison of ν(NO) bands and redox potentials (cyclic voltammetry) of parent complexes and alkylated derivatives showed that alkylation leads to a decrease in electron density at the molybdenum center and to a positive shift in redox potentials. The 16 VE complex 1 could be reduced, also chemically, to give the corresponding 17 VE anion [1]^–, and inserted elemental sulfur into the Mo-SPh bond, forming the 18 VE phenylperthio complex [Mo(η²–SSPh)(NO)('S₄')] (11) which, upon reaction with PPh₃, gave SPPh₃ and regenerated the parent complex 1. These results are discussed with regard to the sequence of proton and electron transfer steps occurring in substrate conversions catalyzed by metal sulfur oxidoreductases.     

A comparative study of the effects of iloprost and PGE1 on pulmonary arterial pressure and edema formation in the isolated perfused rat lung model

Isolated lungs from male Wistar rats (250–350 g) were perfused at a constant flow rate (10 ml/min, non -recirculating) with Krebs-Ringerbicarbonate buffer containing 4.5 % bovine serum albumin, and were ventilated at a positive pressure (60 breaths/min). Pulmonary arterial pressure and lung weight (as a measure of edema formation) were recorded continuously. After an equilibration period of 20 minutes the various test compounds were added to the perfusion fluid and experimental recording was continued for another 60 minutes.The effects of the stable PGI₂-mimetic, iloprost, of PGE₁, and of the biologically active PGE₁-metabolite, 13,14-dihydro-PGE,, were evaluated in this model (n=6). Iloprost showed slight, but not significant vasodilation; however, lung weight remained unchanged. PGE₁ and 13,14-dihydro-PGE₁ also caused slight vasodilation, but in contrast to iloprost these compounds induced distinct pulmonary edema. The lung weight gain was discernible at concentrations of 2.8 × 10^-6 mol/1 (significant at 2.8 × 10^-5 mol/l; p 0.05) and was accompanied by increases in the wet-weight to dry-weight ratios. These findings were duplicated in a second set of experiments (n = 6) from which the same results were obtained.The results indicate that at high concentrations PGE, (and 13,14-dihydro-PGE₁), but not iloprost, can induce pulmonary edema in rats probably by increasing the permeability of the pulmonary vasculature.     

Global vegetation models: incorporating transient changes to structure and composition

Abstract. We describe an approach for developing a Dynamic Global Vegetation Model (DGVM) that accounts for transient changes in vegetation distribution over a decadal time scale. The DGVM structure is based on a linkage between an equilibrium global vegetation model and smaller scale ecosystem dynamics modules that simulate the rate of vegetation change. Vegetation change is classified into four basic types, based largely on the projected change in above-ground biomass of the vegetation. These four types of change are: (1) dieback of forest, shrubland or grassland; (2) successional replacement within forest, shrubland or grassland; (3) invasion of forest, shrubland or grassland; (4) change in tree/grass ratio. We then propose an approach in which the appropriate ecosystem dynamics module for each type of change is applied and the grid cells of the global model updated accordingly. An approach for accounting for fire, as an example of a disturbance which may strongly influence the rate and spatial pattern of forest dieback, is incorporated. We also discuss data needs for the development, calibration and validation of the model.     

The effect of post-hypoxia on roots inSenecio andMyosotis species related to the glutathione system

This paper shows the effect of re-aeration following hypoxic pretreatment on the glutathione system in plants with different flooding tolerance. Re-aeration of hypoxically pretreated roots led to an increase of TBA-rm content indicating an accelerated lipid peroxidation (post-anoxic injury). Re-admission of oxygen resulted in a clear increase in the content of total glutathione in both flooding-intolerant speciesMyosotis arvensis andSenecio jacobaea. Simultaneously, the high ratio between reduced (GSH) and oxidized (GSSG) glutathione decreased in these species upon the onset of re-aeration, while the tolerantMyosotis palustris andSenecio aquaticus showed only little changes in contents of GSH and GSSG. An imbalance in GSH/GSSG ratio reflects oxidative stress. The glutathione reductase (GR) reacted very differently in the investigated genera. The metabolic response to varying oxygen pressure is much stronger in the flooding-intolerant species compared to species naturally growing in wetlands. The present results suggest that glutathione system is an important component in overcoming oxidative stress.     

Qualitative mathematical discussion of different evolutionary states in water transport systems of plants

We shall present several qualitative mathematical models to describe the early evolution of water transport systems in plants. To perform this in a systematic way we apply methods which have been developed in phenomenological synergetics. These methods rest on the fact that it becomes possible to describe the macroscopic behavior of a complex system by a set of control and order parameters when they are suitably identified. Our presentation is addressed to community with interdisciplinary interests.