HDL regulates the displacement of hepatic lipase from cell surface proteoglycans and the hydrolysis of VLDL triacylglycerol

We have previously shown that hepatic lipase (HL) is inactive when bound to purified heparan sulfate proteoglycans and can be liberated by HDL and apolipoprotein A-I (apoA-I), but not by LDL or VLDL. In this study, we show that HDL is also able to displace HL directly from the surface of the hepatoma cell line, HepG2, and Chinese hamster ovary cells stably overexpressing human HL. ApoA-I is more efficient at displacing cell surface HL than is HDL, and different HDL classes vary in their ability to displace HL from the cell surface. HDL2s have a greater capacity to remove HL from the cell surface and intracellular compartments, as compared with the smaller HDL particles. The different HDL subclasses also uniquely affect the activity of the enzyme. HDL2 stimulates HL-mediated hydrolysis of VLDL-triacylglycerol, while HDL3 is inhibitory. Inhibition of VLDL hydrolysis appears to result from a decreased interlipoprotein shuttling of HL between VLDL and the smaller, more dense HDL particles. This study suggests that high HDL2 levels are positively related to efficient triacylglycerol hydrolysis by their ability to enhance the liberation of HL into the plasma compartment and by a direct stimulation of VLDL-triacylglycerol hydrolysis.     

Lysophosphatidic acid is a bioactive mediator in ovarian cancer

Lysophosphatidic acid (LPA) is a naturally occurring phospholipid that exhibits pleiotrophic biological activities, ranging from rapid morphological changes to long-term cellular effects such as induction of gene expression and stimulation of cell proliferation and survival on a wide spectrum of cell types. LPA binds and activates distinct members of the Edg/LP subfamily of G protein-coupled receptors that link to multiple G proteins including Gi, Gq and G12/13 to elicit cellular responses. LPA plays a critical role as a general growth, survival and pro-angiogenic factor, in the regulation of physiological and pathophysiological processes in vivo and in vitro. Our previous work indicates that abnormalities in LPA metabolism and function in ovarian cancer patients may contribute to the initiation and progression of the disease. Thus, LPA could be a potential target for cancer therapy. This review summarizes evidence that implicates LPA in the pathophysiology of human ovarian cancer and likely other types of human malignancies.     

Interleukin-18 promotes sleep in rabbits and rats

Interleukin (IL)-1beta is involved in physiological sleep regulation. IL-18 is a member of the IL-1 family, and its signal-transduction mechanism is similar to that of IL-1. Therefore, we hypothesized that IL-18 might also be involved in sleep regulation. Three doses of IL-18 (10, 100, and 500 ng) were injected intracerebroventricularly (icv) into rabbits at the onset of the dark period. The two higher doses of IL-18 markedly increased non-rapid eye movement sleep (NREMS), accompanied by increases in brain temperature (Tbr). These effects were lost after the heat inactivation of IL-18. The 500 ng of IL-18 injection during the light period also increased NREMS and Tbr. Similar results were obtained after icv injection of 100 ng of IL-18 into rats. Furthermore, intraperitoneal injection of 30 microg/kg of IL-18 slightly, but significantly, increased NREMS, whereas it significantly decreased electroencephalogram slow-wave activity in rats. Intraperitoneal IL-18 failed to induce fever. An anti-human IL-18 antibody had little effect on spontaneous sleep in rabbits, although the anti-IL-18 antibody significantly attenuated muramyl dipeptide-induced sleep. These data suggest that IL-18 is involved in mechanisms of sleep responses to infection.     

Identification and characterization of a novel benzo[a]pyrene-derived DNA adduct

The aim of this study was to generate and identify a novel benzo[a]pyrene (BP)-derived DNA adduct found both in vitro and in vivo. To date, the majority of studies have focused on N(2)-[10 beta(7 beta,8a,9a-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene)yl]-deoxyguanosine (anti-BPDE-dG), the major adduct generated following bioactivation of BP. However, a second adduct is also formed following bioactivation of BP which has been speculated to result from further metabolism of 9-OH-BP. In order to identify this second reaction pathway, the ultimate DNA binding species, and the DNA base involved, we have synthesized and characterized a dG-derived DNA adduct arising from further bioactivation of 9-OH-BP in the presence of rat liver microsomes. Analysis of the adducted nucleotides was conducted using both the (32)P-postlabeling assay and capillary electrophoresis-mass spectrometry (CE-MS).     

Frogs without polliwogs: evolution of anuran direct development

Direct development is the assumption of the adult morphology without progression through an intervening, morphologically distinct, free-living larval phase. We discuss the ecological factors contributing to the evolution of this derived life-history strategy in frogs, and the developmental modifications that facilitate such an unusual mode of embryogenesis. Studies on the Puerto Rican tree frog, Eleutherodactylus coqui, have identified several such modifications, including developmental adaptations for dealing with increased egg size, and loss of tadpole structures. Surprisingly, this direct developer still undergoes a thyroid hormone-dependent metamorphosis, which occurs before hatching. We suggest how the ancestral biphasic developmental pattern may have been rearranged during the evolution of direct development.     

(+)-Calocedrin,a lignan dihydroanhydride from Calocedrus formosana

A novel lignan dihydroanhydride, (+)-calocedrin, was isolated from the wood of Calocedrus formosana. Its structure was determined to be trans-α-(3,4-methylenedioxybenzylidene)-β-(3,4-methylenedioxybenzyl)-γ-hydroxybutanolide by spectroscopic methods. Reduction of (+)-calocedrin resulted in an optically inactive lignan lactone, (±)-hibalactone.     

Plasticity in Skeletal, Cardiac, and Smooth Muscle: Selected Contribution: Mechanisms underlying increased force generation by rat diaphragm muscle fibers during development

It has beenfound that maximum specific force (F_max; force percross-sectional area) of rat diaphragm muscle doubles from birth to 84 days (adult). We hypothesize that this developmental change inF_max reflects an increase in myosin heavy chain (MHC) content per half-sarcomere (an estimate of the number of cross bridgesin parallel) and/or a greater force per cross bridge in fibersexpressing fast MHC isoforms compared with slow and neonatal MHCisoforms (MHC_slow and MHC_neo, respectively).Single Triton 100-X-permeabilized fibers were activated at a pCa of4.0. MHC isoform expression was determined by SDS-PAGE. MHC content per half-sarcomere was determined by densitometric analysis and comparison to a standard curve of known MHC concentrations. MHC content per half-sarcomere progressively increased during early postnatal development. When normalized for MHC content per half-sarcomere, fibersexpressing MHC_slow and coexpressing MHC_neoproduced less force than fibers expressing fast MHC isoforms. Weconclude that lower force per cross bridge in fibers expressingMHC_slow and MHC_neo contributes to the lowerF_max seen in early postnatal development.

     

Characterization of methanotrophic bacteria on the basis of intact phospholipid profiles

The intact phospholipid profiles (IPPs) of seven species of methanotrophs from all three physiological groups, type I, II and X, were determined using liquid chromatography/electrospray ionization/mass spectrometry. In these methanotrophs, two major classes of phospholipids were found, phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) as well as its derivatives phosphatidylmethylethanolamine (PME) and phosphatidyldimethylethanolamine (PDME). Specifically, the type I methanotrophs, Methylomonas methanica, Methylomonas rubra and Methylomicrobium album BG8 were characterized by PE and PG phospholipids with predominantly C16:1 fatty acids. The type II methanotrophs, Methylosinus trichosporium OB3b and CSC1 were characterized by phospholipids of PG, PME and PDME with predominantly C18:1 fatty acids. Methylococcus capsulatus Bath, a representative of type X methanotrophs, contained mostly PE (89% of the total phospholipids). Finally, the IPPs of a recently isolated acidophilic methanotroph, Methylocella palustris, showed it had a preponderance of PME phospholipids with 18:1 fatty acids (94% of total). Principal component analysis showed these methanotrophs could be clearly distinguished based on phospholipid profiles. Results from this study suggest that IPP can be very useful in bacterial chemotaxonomy.