Isolation and characterization of a membrane-bound, low-potential c-type cytochrome from purple photosynthetic bacteria, with special reference to Rhodospirillum rubrum.

Other investigators have isolated soluble, low-potential, c-type cytochromes (cytochrome c3) from a few photosynthetic procaryotes, i.e., a cyanobacterium and two species of purple nonsulfur bacteria. However, such cytochromes appeared to be absent from other purple bacteria, including Rhodospirillum rubrum and Chromatium vinosum. We now report evidence for the presence of low-potential c-type cytochromes in these two species, in which they were found to be bound to the photosynthetic membranes. Evidence for a membrane-bound, low-potential c-type cytochrome was also found in Rhodopseudomonas sphaeoides. The low-potential c-type cytochrome of R. rubrum was solubilized by a Triton X-100 treatment of chromatophores and was partly purified. It was found to have a molecular weight of about 17,000, a midpoint oxidation-reduction potential of -192 mV, and an alpha-absorption peak at 552 nm. It appears that low-potential c-type cytochromes may be present in all purple photosynthetic bacteria, of both the sulfur and the nonsulfur types.     

Low stimulated IL-4 secretion in PBMC from patients with chronic idiopathic urticaria

An imbalance between the Th1 and Th2 arms of the cellular immune system has been reported in several autoimmune diseases but not in chronic idiopathic urticaria (CIU). Peak, total secretion and secretory pattern of the Th1 cytokines (IFNgamma and IL-2) and Th2 cytokines (IL-4 and IL-10) were determined in resting and stimulated peripheral blood mononuclear cells (PBMC) from nineteen CIU patients, six acute urticaria patients and twelve controls. Stimulated IL-4 secretion was significantly reduced in CIU patients as indicated by their five- and three-fold lower peak levels and total IL-4 secretion, respectively. The IL-4 secretory pattern overtime was also markedly different in patients and controls. The late secretion of IFNgamma at 144 h was also reduced in CIU patients. These aberrations were not detectable in AU patients. Secretion of IL-2 was lower in CIU and AU patients as compared to controls while IL-10 secretion was comparable in the three groups. Our data demonstrate for the first time a predominantly reduced IL-4 secretion in CIU patients. This is associated with reduced secretion of both IL-2 and IFNgamma. These findings indicate a generalized down-regulation of both Th1 and Th2 cytokines' secretion in CIU.     

Carcinoembryonic antigen (CEA) inhibits NK killing via interaction with CEA-related cell adhesion molecule 1

The NK killing activity is regulated by activating and inhibitory NK receptors. All of the activating ligands identified so far are either viral or stress-induced proteins. The class I MHC proteins are the ligands for most of the inhibitory NK receptors. However, in the past few years, several receptors have been identified that are able to inhibit NK killing independently of class I MHC recognition. We have previously demonstrated the existence of a novel inhibitory mechanism of NK cell cytotoxicity mediated by the homophilic carcinoembryonic Ag (CEA)-related cell adhesion molecule 1 (CEACAM1) interactions. In this study, we demonstrate that CEACAM1 also interacts heterophilically with the CEA protein. Importantly, we show that these heterophilic interactions of CEA and CEACAM1 inhibit the killing by NK cells. Because CEA is expressed on a wide range of carcinomas and commonly used as tumor marker, these results represent a novel role for the CEA protein enabling the escape of tumor cells from NK-mediated killing. We further characterize, for the first time, the CEACAM1-CEA interactions. Using functional and binding assays, we demonstrate that the N domains of CEACAM1 and CEA are crucial but not sufficient for both the CEACAM1-CEACAM1 homophilic and CEACAM1-CEA heterophilic interactions. Finally, we suggest that the involvement of additional domains beside the N domain in the heterophilic and homophilic interactions is important for regulating the balance between cis and trans interactions.     

Ecto- and exo-protein kinases in Schistosoma mansoni: regulation of surface phosphorylation by acetylcholine and identification of the alpha subunit of CKII as a major secreted protein kinase

The Schistosoma mansoni parasite life cycle involves complex developmental processes that enable it to cause severe hepatic damage. Protein phosphorylation has previously been implicated in the transformation of cercariae to schistosomula of S. mansoni. Here, we studied the possible involvement of surface (ecto) and shed (exo) protein kinases (PKs) in this developmental process. We found that ecto-PKs are indeed located on the surface of the schistosomula and can phosphorylate up to 5 distinct proteins at this location. Surface phosphorylation was sensitive to acetylcholine, which increased phosphorylation of 3 proteins and reduced phosphorylation of the other 2. The ecto-PKs can be shed from the surface into the incubation medium during parasite differentiation. The main exo-PK is CKII, as concluded from the substrate specificity of the PK, its inhibition by heparin, activation by spermin, and recognition by antibody directed to the anti--alpha-subunit of CKII in the incubation medium of the schistosomula. In spite of its similarity to the ecto-PKs, the activity of the exo-PK is not affected by addition of acetylcholine. These results indicate that ecto- and exo-PKs could be involved in the parasite's development or host-parasite interactions.     

Detection of carp interstitial nephritis and gill necrosis virus in fish droppings

Carp interstitial nephritis and gill necrosis virus (CNGV) is an unclassified large DNA virus that morphologically resembles members of the Herpesviridae but contains a large (ca. approximately 280-kbp) linear double-stranded DNA. This virus has also been named koi herpesvirus, koi herpes-like virus, and cyprinid herpesvirus 3. CNGV is the cause of a lethal disease that afflicts common carp and koi. By using immunohistochemistry, molecular analysis, and electron microscopy we previously demonstrated that this virus is present mainly in the intestine and kidney of infected fish. Based on these observations, we postulated that viruses and/or viral components may appear in droppings of infected carp. Here we report that (i) by using PCR we demonstrated that fish droppings contain viral DNA, (ii) fish droppings contain viral antigens which are useful for CNGV diagnosis, and (iii) fish droppings contain active virus which can infect cultured common carp brain cells and induce the disease in na?ve fish following inoculation. Thus, our findings show that CNGV can be identified by using droppings without taking biopsies or killing fish and that infectious CNGV is present in the stools of sick fish. The possibility that fish droppings preserve viable CNGV during the nonpermissive seasons is discussed.     

The CD85J/leukocyte inhibitory receptor-1 distinguishes between conformed and beta 2-microglobulin-free HLA-G molecules

For a proper development of the placenta, maternal NK cells should not attack the fetal extravillous cytotrophoblast cells. This inhibition of maternal NK cells is partially mediated via the nonclassical MHC class I molecule HLA-G. Recently, we demonstrated that HLA-G forms disulfide-linked high molecular complexes on the surface of transfected cells. In the present study, we demonstrate that HLA-G must associate with beta(2)m for its interaction with CD85J/leukocyte Ig-like receptor-1 (LIR-1). Although HLA-G free H chain complexes are expressed on the surface, they are not recognized and possibly interfere with CD85J/LIR-1 and HLA-G interaction. The formation of these complexes on the cell surface might represent a novel mechanism developed specifically by the HLA-G protein aimed to control the efficiency of the CD85J/LIR-1-mediated inhibition. We also show that endogenous HLA-G complexes are expressed on the cell surface. These findings provide novel insights into the delicate interaction between extravillous cytotrophoblast cells and NK cells in the decidua.     

Subcuticular microstructure of the hornet's gaster: Its possible function in thermoregulation

The present study set out to elucidate the structure and function of the large subcuticular air sacs encountered in the gaster of the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae). Gastral segments I, II, III, together with the anterior portion of segment IV, comprise the greater volume of the gaster, and inside them, beneath the cuticle, are contained not only structures that extend throughout their entire length, like the alimentary canal, and the nerve cord with its paired abdominal ganglia, situated near the cuticle in the ventral side, but also the heart, which is actually a muscular and dorsally located blood vessel that pumps blood anteriorly, toward the head of the hornet. The mentioned structures take up only a small volume of the gaster, while the rest is occupied by air sacs and tracheal ducts that also extend longitudinally. Interposed between the two air sacs, there is a hard partition and above it, at the center – a paired tracheal duct that extends the entire length of the air sacs. The endothelium of the air sacs is very anfractuous, thereby enlarging and strengthening the surface area. In each gastral segment there is an aperture for the entry of air, namely, a spiracle. Additionally, in each segment, in the antero-lateral aspect of its tergum and situated between two successive segments, there is an intersegmental conjunctive bearing parallel slits of 1–2 microM in width and 10–30 microM in length. The latter are arranged concentrically around bundles of tracheae that traverse the cuticle from segment to segment. From the upper rims of the slits are suspended downward fringe-like structures or "shutters" ranging between 3–10 microM in length. We discuss the possibility that the Oriental hornet resorts to internal circulation of air, along with a thermoelectric heat pump mechanism, in order to achieve cooling and thermoregulation of its body.     

Relative hydrophobicity of organic compounds measured by partitioning in aqueous two-phase systems

Partitioning of a variety of organic compounds, the majority of which represent therapeutic drugs, was examined in an aqueous dextran–polyethylene glycol (Dex–PEG) two-phase system containing 0.15 M NaCl in 0.01 M sodium phosphate buffer at pH 7.3 and in an octanol–buffer (0.15 M NaCl in 0.01 M sodium phosphate buffer, pH 7.3) system. The possibility of introducing compounds to be partitioned in an aqueous two-phase system with dimethyl sulfoxide, and the effect of this solvent on the solute partitioning was explored. Relative hydrophobicity of the compounds was estimated and expressed in equivalent numbers of methylene units. Comparison of the results obtained for several subsets of compounds in the octanol–buffer and in aqueous Dex–PEG two-phase systems clearly demonstrates the advantage of aqueous two-phase partitioning for the hydrophobicity measurements over partitioning in octanol–buffer system.     

Photoreduction of ferredoxin-NADP in the presence and absence of ferredoxin-reducing substance (FRS)

Preparations of ferredoxin-reducing substance (FRS) were obtained from spinach chloroplasts within the elution volume range and with the spectral characteristics described by Yocum and San Pietro (8). However, no support was found for the view that FRS is the primary electron acceptor of Photosystem I. The FRS-depleted chloroplast fragments retained their Photosystem I activity, which was not enhanced by the addition of FRS. No evidence was found for a prior photoreduction of FRS by chloroplasts followed by a dark reduction of ferredoxin and NADP by reduced FRS. The FRS-depleted chloroplast fragments were found to retain and to photoreduce bound ferredoxin upon illumination by Photosystem I light at 25°K. These results suggest that the role of a primary electron acceptor of Photosystem I ascribed to FRS may belong to bound ferredoxin.