Production and testing of Schistosoma japonicum candidate vaccine antigens in the natural ovine host.

The objectives of this work were to clone and express Chinese strain Schistosoma japonicum antigens and evaluate their immunogenicity and protective efficacy in the natural ovine host in China. Recombinant antigens selected for testing were: isoforms of glutathione S-transferase Sj28GST and Sj26GST; the large hydrophilic domain of Sj23, the homologue of the protective S. mansoni membrane antigen Sm23; and a 3' fragment of S. japonicum paramyosin. In addition, Chinese strain S. japonicum native paramyosin and GST were purified and used for vaccination. Antigens were co-administered with Freund's adjuvants or BCG. We also examined the effects of co-administration of native unfractionated GSTs with keyhole limpet haemocyanin (KLH), which shares a cross-reactive protective epitope with schistosomes. These are the first side-by-side comparisons of candidate defined-antigen schistosomiasis vaccines in a natural host. Significant partial protection was obtained with each of the antigens tested. Less protection was obtained with a recombinant fragment of S. japonicum paramyosin compared with native paramyosin. Co-administration of native GST and KLH was no more effective than vaccination with either antigen alone. Although encouraging levels of protection against S. japonicum were demonstrated using each of these antigens, further work is needed to optimise vaccine delivery and vaccination schedules.

Psychosocial stress can induce chronic hypertension in normotensive strains of rats.

We report on five 6-month experiments during which five colonies of four male and four female rats were exposed to psychosocial stress. Monthly blood pressure measurements by a tail-cuff method showed a modest (10 mm Hg) increase in two studies using Sprague-Dawley rats. In two further studies using the more aggressive Long-Evans strain, terminal direct carotid arterial pressures were taken as well, and in one study the differences exceeded 20 mm Hg. A fifth study used the Wistar-Kyoto, hyperactive (WKHA) strain developed by Hendley, and no differences were observed. Heart and adrenal weights; adrenal catecholamine synthetic enzymes; and heart, aortic, and kidney histology were measured and showed significant changes, which for the most part paralleled blood pressure changes. Social instability and the associated blood pressure changes were made more severe by periodic mixing of males from different colonies. This had no effect on the peaceable WKHA rats, some effect on the Sprague-Dawley rats, and a severe effect on the Long-Evans rats. The WKHA rats failed to show blood pressure changes despite stress-induced increases in heart and adrenal weights. Thus, different types of psychosocial stress and different genetics combine to induce a variety of neuroendocrine changes, not all of which necessarily lead to increased blood pressure.

Biosynthesis of choline plasmalogens in neonatal rat myocytes.

The alk-1-enyl bond in plasmenylethanolamine is formed from plasmanylethanolamine by the action of a microsomal cytochrome b5-dependent desaturase. However, the origin of the alk-1-enyl linkage in plasmenylcholine, a significant subclass of phospholipids in heart tissues of certain animal species, is not yet known. We have used neonatal rat myocytes as a model to study the biosynthesis of plasmenylcholine in the present studies since they have a phospholipid composition and subclasses of 1,2-diradyl-sn-glycero-3-phosphocholine (-GPC) similar to those of neonatal rat hearts. When equal concentrations of [3H]hexadecyllyso-GPC or [3H]hexadecyllyso-sn-glycero-3-phosphoethanolamine (-GPE) are incubated under identical conditions with myocytes for 4, 12, and 24 h, the rate of plasmenylcholine formation is faster from [3H]hexadecyllyso-GPE than from [3H]hexadecyllyso-GPC. Also, when [3H]alkyllyso-GPC and alkyllyso-[N-methyl-14C]GPC are incubated with rat myocytes for various times up to 24 h, the 3H/14C ratio in the diacyl-GPC plus alkylacyl-GPC fraction and alkyllyso-GPC remains relatively constant (3H/14C = 2.7), whereas the 3H/14C of plasmenylcholine increases from 0.3 at 2 h to 1.7 after 24 h. Finally, when the rat myocytes are prelabeled with [3H]alkyllyso-GPE for 4 h and then reincubated with either [14C]choline or [14C]methionine for 1 or 3 h, both [14C]choline and [14C]methionine are incorporated into plasmenylcholine, except the 14C/3H is much higher (5- to 15-fold) in the [14C]choline-labeled plasmenylcholine than in the [14C]methionine-labeled plasmenylcholine. Collectively, our data show plasmenylcholine is not directly derived from plasmanylcholine or lysoplasmanylcholine, but instead is formed from plasmenylethanolamine via some type of hydrolytic exchange mechanism, and the contribution of plasmenylethanolamine through methylation to the synthesis of plasmenylcholine is of limited capacity.

The efficacy of triclabendazole (Fasinex) against immature and adult Fasciola hepatica in experimentally infected cattle.

Eighteen Chinese cattle were experimentally infected with metacercariae of Fasciola hepatica and randomly assigned to 6 groups. Five groups of cattle were treated with a single oral dose of triclabendazole at a dose rate of 12 mg kg-1. At necropsy, the reduction in fluke burden compared with the untreated group was 85, 99.6, 99.8, 100 and 100% for cattle treated 2, 6, 8, 12 and 16 weeks after infection, respectively. Data are also presented on body weight changes during the experimental period and on serum gamma-GT activity in cattle from selected groups. Triclabendazole is considered to be safer and more efficacious than currently available fasciolicides in China.

Metabolism of platelet activating factor (PAF) and related ether lipids by neonatal rat myocytes.

Suspensions of neonatal rat myocytes were used to investigate the metabolism of [3H]PAF (1-alkyl-2-acetyl-(sn-glycero-3-phosphocholine) (GPC] and [3H]alkyllyso-GPC. [3H]Alkylacyl-GPC consisting of molecular species with four or more double bonds (87%) was the major metabolite formed when either [3H]PAF (4 x 10(-6) - 4 x 10(-9) M) or [3H]alkyllyso-GPC (2 x 10(-7) M) was the precursor. However, substantial amounts of [3H]alkyllyso-GPC (mostly in the media) were also generated from [3H]PAF during the early periods of the incubations. At 2 x 10(-7) M or higher concentrations of either [3H]PAF or [3H]alkyllyso-GPC, [3H]alkylglycerols were also formed (4-12% of the total radioactivity). The [3H]alkylglycerols appear to be produced from [3H]alkyllyso-GPC through the combined actions of lysophospholipase D and a phosphatase. Pretreatment of neonatal rat myocytes with phenylmethylsulfonyl fluoride partially blocked the deacetylation of [3H]PAF and decreased both the formation and subsequent acylation of [3H]alkyllyso-GPC in intact cells. Phenylmethylsulfonyl fluoride also significantly inhibited the activity of cytosolic acetylhydrolase, but it had no direct effect on the microsomal transacylase in vitro. Our data demonstrate that the metabolism of PAF and alkyllyso-GPC by neonatal rat myocytes is qualitatively, but not quantitatively, similar to what occurs in other cell types. In addition, when [3H]alkylacetylglycerol was the precursor, 75% of the label appeared as alkylglycerols in the neonatal rat myocytes, but [3H]PAF was not detected. Therefore, it appears that the de novo pathway via the dithiothreitol-insensitive cholinephosphotransferase step does not contribute to the biosynthesis of PAF in neonatal rat myocytes.