Activated platelets express IL-1 activity

Suspensions of washed human platelets express IL-1 activity after activation with agents such as thrombin, collagen, ADP, or epinephrine as judged by the ability of the platelet suspensions to support the growth of a T cell line, D10.G4.1, which exhibits a growth requirement for IL-1. Unactivated platelets express little IL-1 activity. The IL-1 activity expressed by activated platelets appears to be entirely associated with the platelet surface. No IL-1 activity was detected in supernatants derived from suspensions of activated platelets. A mAb specific for IL-1 beta inhibited 90% of the activity expressed by thrombin-activated platelets, whereas a mAb specific for IL-1 alpha inhibited approximately 20% of the activity. A control mAb was without an effect. These results indicate that activated platelets express surface-associated IL-1 activity. Platelet surface IL-1 may provide a mechanism for altering in an extremely localized and rapid manner the properties of IL-1 responsive cells with which platelets come in direct contact during processes of inflammation and vessel wall damage.     

Stopped-flow mechanistic study of bromide substitution by an organonitrile at an iron(II) phosphinic centre; a π-electron driven process

The kinetics of the displacement reactions of the bromide ligands of trans-[FeBr₂(depe)₂] (depe = Et₂PCH₂CH₂PEt₂) by the organonitrile NCCH₂C₆H₄OMe-4, in tetrahydrofuran (either in the absence or in the presence of added Br⁻), to give the corresponding mono- and dinitrile complexes trans-[FeBr(NCCH₂C₆H₄OMe-4)(depe)₂]⁺ and trans-[Fe(NCCH₂C₆H₄OMe-4)₂(depe)₂]²⁺, have been investigated by stopped-flow spectrophotometry. The substitution reaction occurs by a mechanism involving rate-limiting dissociation of bromo ligands to form the unsaturated intermediates [FeBr(depe)₂]⁺ (k₁ = 1.52 ± 0.02 s⁻¹) and [Fe(NCR)(depe)₂]²⁺ (k₃ = 0.063 ± 0.008 s⁻¹) which add the nitrile ligand to form those nitrile complexes. The competition between the nitrile and Br⁻ for such metal centres has also been investigated and a stronger inhibiting effect of added Br⁻ is observed for the substitution of the second bromo ligand relative to the first one. The kinetic data are rationalized in terms of π-electronic effects of these unsaturated metal centres and of the bromide and nitrile ligands.     

Effects of brain ischemia on intermediate filaments of rat hippocampus

Neurofilaments subunits (NF-H, NF-M, NF-L) and glial fibrillary acidic protein (GFAP) were investigated in the hippocampus of rats after distinct periods of reperfusion (1 to 15 days) following 20 min of transient global forebrain ischemia in the rat. In vitro [¹⁴Ca]leucine incorporation was not altered until 48 h after the ischemic insult, however concentration of intermediate filament subunits significantly decreased in this period. Three days after the insult, leucine incorporation significantly increased while the concentration NF-H, NF-M, and NF-L were still diminished after 15 days of reperfusion. In vitro incorporation of³²P into NF-M and NF-L suffered immediately after ischemia, but returned to control values after two days of reperfusion. GFAP levels decreased immediately after ischemia but quickly recovered and significantly peaked from 7 to 10 days after the insult. These results suggest that transient ischemia followed by reperfusion causes proteolysis of intermediate filaments in the hippocampus, and that proteolysis could be facilitated by diminished phosphorylation levels of NF-M and NF-L.     

Mixed-ligand complexes of technetium XIII. A new and facile synthesis, structure and electrochemical behaviour of trans-[Tc(dppe)2(buNC)2](PF6)· ethanol (dppe = bis(diphenylphosphino)ethane, buNC= tert-butylisocyanide)

The Tc(I) mixed-ligand complex, trans-[Tc(dppe)₂(bu^tNC)₂](PF₆) (dppe=bis(diphenylphosphino)ethane, bu^tNC=tert-butyl-isocyanide) has been prepared from [Tc(tu−S)₆³⁺ (tu-S=thiourea) and a mixture of both ligands. The compound crystallizes triclinic in the space group

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). The technetium atom has a slightly distorted octahedral coordination sphere with the isocyanide ligands in trans-position to each other. By cyclic voltammetry, at a Pt electrode, trans-[Tc(dppe)₂(bu^tNC)₂](PF₆) undergoes a single electron reversible oxidation at E_1/2^ox=0.91 V versus SCE.     

Analysis of active nucleolus organizing regions in Capsicum (Solanaceae) by silver staining

Nucleolar activity of 22 samples belonging to nine diploid species of Capsicum was analyzed in somatic metaphases and interphase nuclei. They are: C, chacoënse, C. parvifolium, C. frutescens, C. chinense, C. annuum var. annuum, C. baccatum var. pendulum, C. pubescens, all with 2n = 24, and C. mirabile var. mirabile and C. campylopodium with 2n = 26. Silver staining was applied for the first time in Capsicum, providing useful markers for chromosome identification in combination with other banding techniques already employed in the genus. From two to eight AgNORs (silver-stained nucleolus organizing regions) were found in the diploid complement of the taxa studied. Nucleolar organizers are located at secondary constrictions of chromosomes which are conventionally stained or banded (C-banding or fluorochrome banding). Polymorphism of AgNORs and attached satellites often occurs. Nucleoli are usually fused to a variable extent. Number and position of active rDNA loci are variable not only between but also within species and populations. Homologies in position of NORs between species were established. The data obtained are related to previous conclusions on phylogenetic relationships in Capsicum. Possible trends of karyotype evolution concerning nucleolar organizers are discussed, and four NORs in the diploid complement (on chromosome pairs #1 [m] and #12 [st]) are regarded as the plesiomorphic condition.