Analysis of lipid transfer activity between model nascent HDL particles and plasma lipoproteins: implications for current concepts of nascent HDL maturation and genesis

The specifics of nascent HDL remodeling within the plasma compartment remain poorly understood. We developed an in vitro assay to monitor the lipid transfer between model nascent HDL (LpA-I) and plasma lipoproteins. Incubation of α-¹²⁵I-LpA-I with plasma resulted in association of LpA-I with existing plasma HDL, whereas incubation with TD plasma or LDL resulted in conversion of α-¹²⁵I-LpA-I to preβ-HDL. To further investigate the dynamics of lipid transfer, nascent LpA-I were labeled with cell-derived [³H]cholesterol (UC) or [³H]phosphatidylcholine (PC) and incubated with plasma at 37°C. The majority of UC and PC were rapidly transferred to apolipoprotein B (apoB). Subsequently, UC was redistributed to HDL for esterification before being returned to apoB. The presence of a phospholipid transfer protein (PLTP) stimulator or purified PLTP promoted PC transfer to apoB. Conversely, PC transfer was abolished in plasma from PLTP^−/− mice. Injection of ¹²⁵I-LpA-I into rabbits resulted in a rapid size redistribution of ¹²⁵I-LpA-I. The majority of [³H]UC from labeled r(HDL) was esterified in vivo within HDL, whereas a minority was found in LDL. These data suggest that apoB plays a major role in nascent HDL remodeling by accepting their lipids and donating UC to the LCAT reaction. The finding that nascent particles were depleted of their lipids and remodeled in the presence of plasma lipoproteins raises questions about their stability and subsequent interaction with LCAT.     

Down-regulation of the<Emphasis Type="Italic"> AtCCR1</Emphasis> gene in<Emphasis Type="Italic"> Arabidopsis thaliana</Emphasis>: effects on phenotype,lignins and cell wall degradability

Cinnamoyl CoA reductase (CCR; EC 1.2.1.44) is the first enzyme specific to the biosynthetic pathway leading to monolignols. Arabidopsis thaliana (L.) Heynh. plants transformed with a vector containing a full-length AtCCR1 cDNA in an antisense orientation were obtained and characterized. The most severely down-regulated homozygous plants showed drastic alterations to their phenotypical features. These plants had a 50% decrease in lignin content accompanied by changes in lignin composition and structure, with incorporation of ferulic acid into the cell wall. Microscopic analyses coupled with immunolabelling revealed a decrease in lignin deposition in normally lignified tissues and a dramatic loosening of the secondary cell wall of interfascicular fibers and vessels. Evaluation of in vitro digestibility demonstrated an increase in the enzymatic degradability of these transgenic lines. In addition, culture conditions were shown to play a substantial role in lignin level and structure in the wild type and in the effects of AtCCR1 repression efficiency.     

Block of outward current in cardiac purkinje fibers by injection of quaternary ammonium ions

We have studied the effects of iontophoretic injection of the quaternary ammonium compounds tetraethylammonium (TEA) and tetrabutylammonium (TBA) in cardiac purkinje fibers. We find that TBA(+) is a more effective blocker than TEA(+), but injection of either compound reduces the time-dependent outward plateau currents, transient outward current (I(to)), and the delayed rectifier (I(x)). Our findings provide evidence that these outward cardiac currents are carried by channels that in some respects are pharmacologically similar to squid axon potassium channels. We demonstrate that this procedure is a new tool that can be useful in the analysis of membrane currents in the heart.     

New class of biphenylene dibenzazocinones as potent ligands for the human EP1 prostanoid receptor.

A new class of potent and selective ligands for the human EP1 prostanoid receptor is described. SAR studies reported herein allowed the identification of several potent dibenzazocinones bearing an acylsulfonamide side chain. The binding affinity of these compounds on all eight human prostanoid receptors is reported.     

First record of lily thrips, Liothrips vaneeckei Priesner, in Australia (Thysanoptera: Phlaeothripidae)

The first Australian record of the lily thrips, Liothrips vaneeckei Priesner, is reported from a bulb farm in Warragul South, Victoria. It is an occasional pest of Lilium bulbs, both in the field and in storage, particularly in the USA and several European countries, and is also infrequently found in considerable numbers on the corms of orchids.