Role of thromboxane A2 in airway microvascular leakage induced by inhaled platelet-activating factor.

We studied the effects of OKY-046 (1, 10, and 30 mg/kg iv), a selective thromboxane synthase inhibitor, and of ICI 192605 (0.5 mg/kg), a selective thromboxane A2 receptor antagonist, on airflow obstruction and airway microvascular leakage induced by inhaled platelet-activating factor (PAF). Extravasated Evans blue dye content was measured as a reflection of airway microvascular leakage. In control animals, PAF caused a significantly higher increase in extravasation of dye and significantly less increase in lung resistance (RL) than histamine. OKY-046 significantly inhibited both changes in RL and airway microvascular leakage after PAF in a dose-dependent manner, whereas it inhibited histamine-induced airway microvascular leakage only at main bronchi, without any significant effect on RL. ICI 192605 significantly inhibited both RL and airway microvascular leakage induced by PAF, but not after histamine. After both PAF and histamine, changes in RL correlated significantly with the degree of microvascular leakage. Airway microvascular leakage and airflow obstruction after PAF, but not after histamine, may be dependent on thromboxane A2 generation.     

Properties,synthesis, and accumulation of storage proteins in Pieris rapae L.

Two kinds of storage proteins (SP-1, SP-2) were confirmed in hemolymph and fat body of Pieris rapae during metamorphosis. Both proteins were present in high concentrations in the hemolymph during the last larval instar. Hemolymph concentrations of SP-1 and SP-2 dropped after pupation as the proteins were being deposited in fat bodies. SP-2 is present in a larger amount than SP-1. Detailed studies on storage proteins determined their properties, mode of synthesis, and accumulation in the fat body. SP-1 has a molecular weight of 500,000 and consists of one type of subunit (M_r 77,000), while SP-2 has a molecular weight of 460,000 and is composed of two types of subunits (M_r 80,000 and 69,000). The pl values of SP-1 and SP-2 were determined to be 6.97 and 7.06, respectively. Fat body cells from 1-day-old fifth instar larvae synthesized storage proteins in large amounts, whereas those from late prepupae exhibited high protein sequestration. Proteins taken up in fat body accumulated in dense granules during the pupal stage but sharply decreased at the adult stage. Morphological changes in the fat body tissues were observed during the larval-pupal transformation; the nuclei of fat body cells became irregularly shaped, and the boundaries between cells seemed to be obscure. Synthesis, storage, or degradation of storage proteins in fat body during development is closely associated with morphological changes in the tissues.     

The pig as an intermediate host for Taiwan Taenia infection

Eggs (1000-100,000/animal) of Taiwan Taenia were inoculated per os into 14 Small-Ear-Miniature (SEM), 19 Landrace-Small-Ear-Miniature (L-SEM), and 5 Duroc-Yorkshire-Landrace (DYL) pigs. These animals were sacrificed 7-107 days after infection. Thirty-four pigs were found to be infected with Taiwan Taenia cysticerci and the infection rates of SEM, L-SEM, and DYL were 86%, 89% and 100% respectively. The cysticerci recovery rates of SEM, L-SEM and DYL pigs were 27.2%, 1.7% and 0.27% respectively. Cysticerci were recovered only from the livers and none were found in muscles, viscera or other parts of the carcasses. More cysticerci were located in the liver parenchyma (71%) than on the liver surface (29%). Taiwan Taenia cysticerci were smaller than those of classical T. saginata or T. solium. Moreover, Taiwan Taenia cysticerci had 2 rows of rudimentary hooklets on the scolex. The results of this study indicate that young pigs are good intermediate hosts for Taiwan Taenia and that the SEM pig is a satisfactory host for experimental studies with this tapeworm. These results were similar to other studies with different geographic strains of the T. saginata-like tapeworm in the Far East. These strains appear to be the same and possibly a new species.     

Rapid modulation of homing receptors (gp90MEL-14) induced by activators of protein kinase C. Receptor shedding due to accelerated proteolytic cleavage at the cell surface

Lymphocyte entry into lymph nodes and Peyer's patches is initiated by the adhesion of the lymphocytes to specialized postcapillary high endothelial venules (HEV). The binding of lymphocytes to lymph node HEV is mediated by the cell surface receptor gp90MEL-14 (gp90). Previous work has shown that gp90 is down-regulated over a period of days after mitogenic or mixed lymphocyte reaction stimulation of T lymphocytes. In our study, it is shown that stimulation of lymphocytes with activators of protein kinase C (PKC), such as PMA or 1-oleoyl 2-acetyl-glycerol, results in the nearly complete loss of surface expression of gp90 within 1 h. Pretreatment of the cells with H-7 or staurosporine, PKC inhibitors, but not HA1004, a general protein kinase inhibitor, prevents the loss of gp90MEL-14. Within 15 min of stimulation of PKC, a novel form of gp90 can be immunoprecipitated from the supernatant of stimulated cells. Upon deglycosylation, this soluble gp90 polypeptide is shown to be 12 kDa smaller than the cell surface protein. Peptide mapping showed identical patterns for surface and soluble receptor, confirming that the soluble Ag is related to the cell membrane protein. Together, these experiments suggest that activation of PKC results in the proteolytic cleavage of gp90MEL-14, resulting in receptor shedding and the inability of the lymphocytes to adhere to HEV endothelium. Furthermore, because supernatant from unstimulated, normal lymphocytes also contains a small amount of the low Mr form of gp90, cell surface proteolysis may be part of the normal turnover of this receptor glycoprotein. These experiments suggest that PKC may play a role in the regulation of lymphocyte traffic to lymphoid tissues.     

Mapping of B-cell epitopes of the human hepatitis B virus X protein.

The immune response to the X protein of human hepatitis B virus (HBV) was studied by epitope mapping by using a set of MS2-HBx fusion proteins and synthetic peptides. Antibodies in sera of patients with acute and chronic HBV infection showed a multispecific immune response. Each serum contained antibodies to a different set of epitopes, which taken together cover most of the HBx sequence. Some of the epitopes were detectable only by immunoblotting with fusion proteins; others were detectable only by an enzyme-linked immunosorbent assay (ELISA) with synthetic peptides. The carboxy-terminal half of the HBx protein was preferentially recognized by antibodies from patients with chronic hepatitis and contained a short immunodominant antigenic region with at least two major nonoverlapping epitopes. Anti-HBx antibody titers as revealed by peptide ELISAs were highest and most frequent in patients with chronic hepatitis and usually low in acutely infected patients and asymptomatic carriers. The data demonstrate a remarkable qualitative and quantitative heterogeneity of the humoral HBx immune response which can be monitored by HBx-specific peptide ELISAs. Such tests may become useful diagnostic tools.     

Polyamines and Ca2+ Mediate Hyperosmolal Opening of the Blood-Brain Barrier: In Vitro Studies in Isolated Rat Cerebral Capillaries

We recently presented evidence that the reversible opening of the blood-brain barrier (BBB) by the infusion of 1.6 M mannitol into the rat internal carotid artery is mediated by a rapid stimulation of ornithine decarboxylase (ODC) activity and putrescine synthesis in cerebral capillaries. We have now investigated this hypothesis further, using isolated rat cerebral capillaries as an in vitro model of the BBB. The ODC activity of cerebral capillary preparations was enriched up to 15-fold over that of the cerebral homogenate. Hyperosmolal mannitol in physiological buffer evoked a rapid (less than 15 s), concentration- and time-dependent increase in capillary ODC activity and an accumulation of putrescine and spermidine which was blocked by the specific ODC inhibitor, alpha-difluoromethylornithine (DFMO, 10 mM). Mannitol (1 M), as well as 2 M urea, evoked a two- to fivefold increase in the temperature-sensitive influx of 45Ca2+ and uptake of horseradish peroxidase (HRP) and 2-deoxy-D-[1-3H]glucose (DG), but not alpha-[1-14C]aminoisobutyrate, during a 2-min incubation. DFMO (10 mM) abolished 1 M mannitol-mediated stimulation of 45Ca2+ influx and uptake of HRP and DG, whereas 1 mM putrescine replenished capillary polyamines and reversed the DFMO effects. Mannitol (1 M)-induced stimulation of ODC activity and membrane transport processes was Ca2+-dependent and verapamil- and nisoldipine-sensitive. Phorbol myristate acetate (PMA, 10 nM), a protein kinase C activator, also evoked a two- to threefold stimulation of 45Ca2+ transport and HRP and DG uptake. This PMA effect was abolished by DFMO, suggesting involvement of rapid, ODC-controlled polyamine synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Structural gene isolation and prepeptide sequence of gallidermin, a new lanthionine containing antibiotic

Peptide antibiotics containing lanthionine and 3-methyllanthionine bridges, named lantibiotics are of increasing interest. A new lantibiotic, gallidermin, has been isolated from Staphyloccus gallinarum. Here we report the isolation of its structural gene which we name gdmA. In all lantibiotics so far studied genetically, three peptides can be formally distinguished: (i) the primary translation product, which we call the prepeptide; (ii) the propeptide lacking the leader sequence and (iii) the mature lantibiotic. Unlike the plasmid-coded epidermin, gdmA is located on the chromosome. The gdmA locus codes for a 52 amino acid residue prepeptide, consisting of an alpha-helical leader sequence of hydrophilic character, which is separated from the C-terminus (propeptide) by a characteristic proteolytic processing site (Pro-2 Arg-1 Ile1). Although pro-gallidermin differs from pro-epidermin (a recently isolated lantibiotic) only by a single amino acid residue exchange. Leu instead of Ile, the N-terminus of the prepeptide differs by an additional two exchanges.