THE METABOLISM OF CHYLOMICRON CHOLESTERYL ESTER IN RAT LIVER : A Combined Radioautographic-Electron Microscopic and Biochemical Study

Chylomicrons containing labeled cholesterol, mainly (70%) present as cholesteryl ester, were injected intravenously into intact rats, and samples of liver were obtained 27–210 min later. Most (58–75%) of the injected label was recovered in the liver after 27–75 min. Hepatic uptake occurred without hydrolysis of the labeled cholesteryl ester. In separate experiments, in vitro perfusion of livers of similarly treated rats for 30–35 min washed out only 3–9% of the labeled sterol. Samples of liver and small intestine were prepared for electron microscopy with Aquon as the dehydrating agent. Good retention (70% or more) of labeled cholesterol and satisfactory preservation of ultrastructure were obtained. After 30 min, the radioautographic reaction was localized mainly over the region of the cell boundary of the parenchymal liver cells, with fewer grains being present over intracellular organelles. At later time intervals, when considerable hydrolysis of the labeled cholesteryl ester had occurred, the radioautographic reaction was more evenly distributed. Phagocytosed labeled lipid was seen in Kupffer cells after the larger lipid load; phagocytosis by parenchymal cells was not seen. In other experiments, cholesteryl ester hydrolase activity was found in all subcellular fractions, the microsome and plasma membrane fractions showing the highest activity per mg protein. The mechanism of cholesteryl ester transport into the liver cell may involve: (1) hydrolysis at the cell surface; or (2) slow entry of intact molecules followed by intracellular hydrolysis of the ester bond.     

Lisofylline prevents leak, but not neutrophil accumulation, in lungs of rats given IL-1 intratracheally

Hybertson, Brooks M., Stuart L. Bursten, Jonathan A. Leff,Young M. Lee, Eric K. Jepson, Chris R. Dewitt, John Zagorski, Hyun G. Cho, and John E. Repine. Lisofylline prevents leak, but not neutrophil accumulation, in lungs of rats given IL-1intratracheally. J. Appl. Physiol.82(1): 226-232, 1997.Interleukin-1 (IL-1) is increased in lunglavages from patients with the acute respiratory distress syndrome, andadministering IL-1 intratracheally causes neutrophil accumulation and aneutrophil-dependent oxidative leak in lungs of rats. In the presentstudy, we found that rats pretreated intraperitoneally with lisofylline[(R)-1-(5-hydroxyhexyl)-3,7-dimethylxanthine (LSF)], an inhibitor of lysophosphatidic acid acyl transferase, which reduces the production of unsaturated phosphatidic acid species,did not develop the lung leak or the related ultrastructural abnormalities that occur after intratracheal administration of IL-1.However, rats pretreated with LSF and then given IL-1 intratracheally did develop the same elevations of lung lavage cytokine-induced neutrophil chemoattractant (CINC) levels and the same increased numbersof lung lavage neutrophils as rats given IL-1 intratracheally. Lungs ofrats given IL-1 intratracheally also had increased unsaturated phosphatidic acid and free acyl (linoleate, linolenate) concentrations compared with untreated rats, and these lipid responses were prevented by pretreatment with LSF. Our results reveal that LSF decreases lungleak and lung lipid alterations without decreasing neutrophil accumulation or lung lavage CINC increases in rats given IL-1 intratracheally.

     

Production of Epoxides from alpha,beta-Halohydrins by Flavobacterium sp

The relative activity of Flavobacterium whole cells on the enzymatic synthesis of epoxides from alpha,beta-chlorohydrins, -bromohydrins, and -iodohydrins is described.     

Bacteriological activity in unfiltered calf sera collected for tissue culture use

Summary Bacteriological tests were made on 24 lots of unfiltered calf serum collected for subsequent use as a component of tissue culture media. The examination included the isolation and identification of bacteria, assay of phages, and demonstration of endotoxin material. Only Gram-positive bacteria were isolated and 96% of the sera were contaminated with bacteria. The prevalent strains of bacteria found wereBacillus species and streptococci and 63% of the sera coagulatedLimulus amebocyte lysate. More than 90% of the lots contained phages demonstrable with the C-3000 strain ofEscherichia coli. Only one lot of the serum was found to be free from bacteria, phages, and endotoxin by the tests used.     

Trophoblast–endothelium signaling involves angiogenesis and apoptosis in a dynamic bioprinted placenta model

Trophoblast invasion and remodeling of the maternal spiral arteries are required for pregnancy success. Aberrant endothelium–trophoblast crosstalk may lead to preeclampsia, a pregnancy complication that has serious effects on both the mother and the baby. However, our understanding of the mechanisms involved in this pathology remains elementary because the current in vitro models cannot describe trophoblast–endothelium interactions under dynamic culture. In this study, we developed a dynamic three-dimensional (3D) placenta model by bioprinting trophoblasts and an endothelialized lumen in a perfusion bioreactor. We found the 3D printed perfusion bioreactor system significantly augmented responses of endothelial cells by encouraging network formations and expressions of angiogenic markers, cluster of differentiation 31 (CD31), matrix metalloproteinase-2 (MMP2), matrix metalloproteinase-9 (MMP9), and vascular endothelial growth factor A (VEGFA). Bioprinting favored colocalization of trophoblasts with endothelial cells, similar to in vivo observations. Additional analysis revealed that trophoblasts reduced the angiogenic responses by reducing network formation and motility rates while inducing apoptosis of endothelial cells. Moreover, the presence of endothelial cells appeared to inhibit trophoblast invasion rates. These results clearly demonstrated the utility and potential of bioprinting and perfusion bioreactor system to model trophoblast–endothelium interactions in vitro. Our bioprinted placenta model represents a crucial step to develop advanced research approach that will expand our understanding and treatment options of preeclampsia and other pregnancy-related pathologies.     

Costs and limits of phenotypic plasticity

The costs and limits of phenotypic plasticity are thought to have important ecological and evolutionary consequences, yet they are not as well understood as the benefits of plasticity. At least nine ideas exist regarding how plasticity may be costly or limited, but these have rarely been discussed together. The most commonly discussed cost is that of maintaining the sensory and regulatory machinery needed for plasticity, which may require energy and material expenses. A frequently considered limit to the benefit of plasticity is that the environmental cues guiding plastic development can be unreliable. Such costs and limits have recently been included in theoretical models and, perhaps more importantly, relevant empirical studies now have emerged. Despite the current interest in costs and limits of plasticity, several lines of reasoning suggest that they might be difficult to demonstrate.     

Ironing out the wrinkles of neutrophil phagocytosis

Though phagocytosis of microbes by professional phagocytes such as neutrophils is crucial for the survival of the host, it is still unclear how the apparent 'stretching' of the plasma membrane is achieved. Microscopically, pseudopod extension, particulate engulfment and phagosome closure all require seemingly large expansions of the cell surface area. Although actual membrane stretching can be ruled out on the basis of physical properties of lipid bilayers, the addition of new membrane from within the cell, either by exocytosis or phagosomal fusion with endoplasmic reticulum membrane, might provide an explanation. However, these events do not seem to have major roles during phagocytosis by neutrophils. Instead, neutrophils might use a more primitive mechanism, that is, the unfolding of surface membrane wrinkles, to provide the additional membrane for phagocytosis. Here, we briefly discuss why membrane unwrinkling provides a feasible hypothesis for membrane expansion during neutrophil phagocytosis, and suggest a potential molecular mechanism for neutrophil control over membrane surface wrinkles, and the potential signalling route.     

Phylogenetic relationships of Malvatheca (Bombacoideae and Malvoideae; Malvaceae sensu lato) as inferred from plastid DNA sequences

Previous molecular phylogenetic analyses have revealed that elements of the former families Malvaceae sensu stricto and Bombacaceae together form a well-supported clade that has been named Malvatheca. Within Malvatheca, two major lineages have been observed; one, Bombacoideae, corresponds approximately to the palmate-leaved Bombacaceae, and the other, Malvoideae, includes the traditional Malvaceae (the mallows or Eumalvoideae). However, the composition of these two groups and their relationships to other elements of Malvatheca remain a source of uncertainty. Sequence data from two plastid regions, ndhF and trnK/matK, from 34 exemplars of Malvatheca and six outgroups were analyzed. Parsimony, likelihood, and Bayesian analyses of the sequence data provided a well-resolved phylogeny except that relationships among five lineages at the base of Malvatheca are poorly resolved. Nonetheless, a 6-bp insertion in matK suggests that Fremontodendreae is sister to the remainder of Malvatheca. Our results suggest that the Malvoideae originated in the Neotropics and that a mangrove taxon dispersed across the Pacific from South America to Australasia and later radiated out of Australasia to give rise to the ca. 1700 living species of Eumalvoideae. Local clock analyses imply that the plastid genome underwent accelerated molecular evolution coincident with the dispersal out of the Americas and again with the radiation into the three major clades of Eumalvoideae.