Hepatic endothelial lipase activity in neonatal rat liver

Hepatic endothelial lipase (HEL) activity is as high in the neonatal (1-day old) rat liver as in adults. Most of the HEL activity is located at the capillaries since 75% of the total activity is released by heparin or collagenase perfusion. The residual activity (non-releasable) is located in hepatocytes and not in hemopoietic cells, which are the major cell type in neonatal liver. Per mg of protein, the HEL activity is 50% higher in neonatal than in adult hepatocytes. We suggest that neonatal hepatocytes have an increased capacity to synthesize and secrete HEL activity, so maintaining a high activity in the whole organ. it might contribute to the hepatic uptake of cholesterol from circulating lipoproteins, in a period in which endogenous cholesterol synthesis is known to be inhibited in the liver.     

Developmental Changes in the Differential Expression of Two Serotonin 5-HT3 Receptor Splice Variants in the Rat

Abstract: PCR was used to isolate identical partial cDNA clones encoding a serotonin 5-HT₃ receptor subunit from rat nodose and superior cervical ganglia. The amino acid sequence predicted from these clones, extending from the putative transmembrane domain I to the stop codon, demonstrated a 93% homology with the 5-HT₃ receptor A (R-A) subunit cloned from NCB 20 hybridoma mouse neuroblastoma/Chinese hamster embryonic brain cells. Comparison of the sequences of the rat gene and cDNA encoding this subunit revealed a five amino acid deletion, GSLLP, located within the putative second intracellular loop of the receptor subunit. This deletion was shown to occur at an intron/exon junction. Therefore, alternative splicing was probably responsible for the presence of short (5-HT₃ R-A_S) and long (5-HT₃ R-A_L) forms of 5-HT₃ R-A mRNA in these ganglia. PCR experiments, with specific primers located upstream and downstream of the GSLLP deletion, were used to detect reverse transcribed 5-HT₃ R-A mRNAs. A short fragment (92 bp), corresponding to the deleted form, and a long fragment (107 bp), corresponding to the nondeleted form, were amplified from various regions of the CNS and peripheral ganglia of the rat, as well as from NG108-15 hybridoma cells. In the adult rat, the ratio of the two forms varied very little from one tissue to another, the long form corresponding to only ～10% of the total 5-HT₃ R-A mRNA. Study of their respective distributions during ontogeny demonstrated a differential expression of the short and long forms in some tissues during late embryonic development, at embryonic day 17 (E17) or E20. In particular, the long form amounted to about one-third of the total 5-HT₃ R-A mRNA in the cerebral cortex and hippocampus at E17, and this proportion reached 50 and 75% in the superior cervical ganglion and nodose ganglion, respectively, at E20. These data indicate that alternative splicing of the 5-HT₃ R-A mRNA is regulated in the CNS and PNS during development in the rat.     

Annual Zooplankton Succession in Coastal NW Mediterranean Waters: The Importance of the Smaller Size Fractions

Zooplankton abundance, biomass (biovolume) and taxonomic compositionwere studied within an annual cycle (August 1995–October1996) in the Bay of Blanes (northwest Mediterranean). Weeklyzooplankton sampling included oblique tows made with a 200 µmJuday–Bogorov net, and vertical tows made with a 53 µmnet, to adequately sample both mesoplankton and the smallerzooplankton fractions. Total zooplankton abundance showed highvariability, lacking any clear seasonal pattern. However, thedifferent species within the zooplankton community displayeda clear succession throughout the year. In general, cyclopoidcopepods (Oithona spp.) and cladocerans (Peniliaavirostris)dominated the summer and autumn communities, whereas in winterand spring, calanoid copepods (Clausocalanus spp., Paracalanussp. and Centropages typicus) were predominant. The zooplanktonannual cycle in the Bay of Blanes does not resemble those ofother Mediterraneanlittoral areas, probably due to the inherentparticularity and variability associated with open coastal environments.On average, the abundance of organisms estimated with a traditional200 µm Juday–Bogorov net was 8.1 times lower thanthe values obtained with a 53 µm net. Even if only organisms>200 µm collected in the 53 µm tows were considered,the total abundance within the 53 µm net was still 4.4times higher than the estimates from the Juday–Bogorovnet. These results suggest the need for accurate samplings ofthe entire zooplankton assemblage when characterizing the structureand dynamics of zooplanktonic communities.     

Mitochondrial DNA and TLR9 drive muscle inflammation upon Opa1 deficiency

Opa1 participates in inner mitochondrial membrane fusion and cristae morphogenesis. Here, we show that muscle‐specific Opa1 ablation causes reduced muscle fiber size, dysfunctional mitochondria, enhanced Fgf21, and muscle inflammation characterized by NF‐κB activation, and enhanced expression of pro‐inflammatory genes. Chronic sodium salicylate treatment ameliorated muscle alterations and reduced the muscle expression of Fgf21. Muscle inflammation was an early event during the progression of the disease and occurred before macrophage infiltration, indicating that it is a primary response to Opa1 deficiency. Moreover, Opa1 repression in muscle cells also resulted in NF‐κB activation and inflammation in the absence of necrosis and/or apoptosis, thereby revealing that the activation is a cell‐autonomous process and independent of cell death. The effects of Opa1 deficiency on the expression NF‐κB target genes and inflammation were absent upon mitochondrial DNA depletion. Under Opa1 deficiency, blockage or repression of TLR9 prevented NF‐κB activation and inflammation. Taken together, our results reveal that Opa1 deficiency in muscle causes initial mitochondrial alterations that lead to TLR9 activation, and inflammation, which contributes to enhanced Fgf21 expression and to growth impairment.     

Chasing ghosts: the phylogeny of Amaurobioidinae ghost spiders (Araneae,Anyphaenidae)

The family Anyphaenidae, also known as ghost spiders, includes a diverse array of nocturnal cursorial spiders that actively hunt on vegetation. The family is mostly distributed in the Americas and has been traditionally divided into three subfamilies. The mostly tropical and North American Anyphaeninae and the Amaurobioidinae, primarily distributed in southern South America, hold the bulk of the diversity, while the Malenellininae includes a single Chilean species. Here, we use a combined morphological and molecular approach to infer the relationships of the subfamily Amaurobioidinae and examine the delimitation of contentious genera. The morphological characters include both genitalic and somatic morphology, whereas molecular data include four markers, two mitochondrial (COI, 16S) and two nuclear (28S, H3). All our analyses agree on the monophyly of Amaurobioidinae, Amaurobioidini, Gayennini, the genera Negayan, Amaurobioides, Josa, Araiya, Arachosia and Monapia, as well as the paraphyly of Anyphaeninae. The total evidence analysis supports the novel placement of Josa as the sister group of both tribes Amaurobioidini and Gayennini, most of the previously known intergeneric relationships within Gayennini, and a clade of Amaurobioidini with a projecting ocular area, including Aysenoides, Axyracrus, Amaurobioides and Aysenia. The sequence data solve the puzzling placement of Philisca puconensis, here transferred to Tomopisthes, and Tasata chiloensis, transferred to Oxysoma. The advantages of the total evidence phylogenetic approach and the evolution of the male copulatory organ are discussed.     

Ocean acidification increases fatty acids levels of larval fish

Rising levels of anthropogenic carbon dioxide in the atmosphere are acidifying the oceans and producing diverse and important effects on marine ecosystems, including the production of fatty acids (FAs) by primary producers and their transfer through food webs. FAs, particularly essential FAs, are necessary for normal structure and function in animals and influence composition and trophic structure of marine food webs. To test the effect of ocean acidification (OA) on the FA composition of fish, we conducted a replicated experiment in which larvae of the marine fish red drum (Sciaenops ocellatus) were reared under a climate change scenario of elevated CO₂ levels (2100 µatm) and under current control levels (400 µatm). We found significantly higher whole-body levels of FAs, including nine of the 11 essential FAs, and altered relative proportions of FAs in the larvae reared under higher levels of CO₂. Consequences of this effect of OA could include alterations in performance and survival of fish larvae and transfer of FAs through food webs.     

The effect of substances from different zooplankton species and fish on the induction of defensive morphology in the green alga Scenedesmus obliquus

The common green alga Scenedesmus obliquus may respond morphologicallyto the presence of natural enemies. Exposure to water-bornecues from the herbivorous zooplankton Ceriodaphnia reticulata,Daphnia galeata x hyalina, Daphnia magna and Daphnia pulicariastimulated the formation of protective colonies in S. obliquus.This response seemed strongly related to the amount of algaegrazed upon, because a highly significant correlation betweenthe amount of S. obliquus consumed and the induced colony formationwas found. However, when exposed to medium that had been inhabitedby the carnivorous zooplankton Bythotrephes longimanus and Leptodorakindtii, no colony formation occurred. A similar result wasobtained in two different experiments when S. obliquus was exposedto filtrate from cultures of the freshwater fish ide (Leuciscusidus) and perch (Perca fluviatilis). These results support thehypothesis that S. obliquus responds to a herbivorous zooplanktonchemical cue, rather than to a more general animal excretoryproduct. No support was obtained for the hypothesis that cuesfrom the enemy of their enemy could serve as signals to thealgae: despite the presence of filtrate from fish culture, filtratefrom Daphnia cultures induced the formation of colonies in S.obliquus. The biological activity seems to be linked to thealga–grazer interaction, which ensures a reliable cuethat evokes the morphological response of S. obliquus only whennecessary. The grazer-induced colony formation can be viewedas an adaptive reaction in habitats with variable grazing pressurefrom an assemblage of many different herbivores to pare downmortality through grazing.