Dissociation of intracellular lysosomal rupture from the cell death caused by silica

The relationship between intracellular lysosomal rupture and cell death caused by silica was studied in P388d(1) macrophages. After 3 h of exposure to 150 μg silica in medium containing 1.8 mM Ca(2+), 60 percent of the cells were unable to exclude trypan blue. In the absence of extracellular Ca(2+), however, all of the cells remained viable. Phagocytosis of silica particles occurred to the same extent in the presence or absence of Ca(2+). The percentage of P388D(1) cells killed by silica depended on the dose and the concentration of Ca(2+) in the medium. Intracellular lyosomal rupture after exposure to silica was measured by acridine orange fluorescence or histochemical assay of horseradish peroxidase. With either assay, 60 percent of the cells exposed to 150 μg silica for 3 h in the presence of Ca(2+) showed intracellular lysosomal rupture, was not associated with measureable degradation of total DNA, RNA, protein, or phospholipids or accelerated turnover of exogenous horseradish peroxidase. Pretreatment with promethazine (20 μg/ml) protected 80 percent of P388D(1) macrophages against silica toxicity although lysosomal rupture occurred in 60-70 percent of the cells. Intracellular lysosomal rupture was prevented in 80 percent of the cells by pretreatment with indomethacin (5 x 10(-5)M), yet 40-50 percent of the cells died after 3 h of exposure to 150 μg silica in 1.8 mM extracellular Ca(2+). The calcium ionophore A23187 also caused intracellular lysosomal rupture in 90-98 percent of the cells treated for 1 h in either the presence or absence of extracellular Ca(2+). With the addition of 1.8 mM Ca(2+), 80 percent of the cells was killed after 3 h, whereas all of the cells remained viable in the absence of Ca(2+). These experiments suggest that intracellular lysosomal rupture is not causally related to the cell death cause by silica or {"type":"entrez-nucleotide","attrs":{"text":"A23187","term_id":"833253","term_text":"A23187"}}A23187. Cell death is dependent on extracellular Ca(2+) and may be mediated by an influx of these ions across the plasma membrane permeability barrier damaged directly by exposure to these toxins.     

Rearrangements within human spliceosomes captured after exon ligation

In spliceosomes, dynamic RNA/RNA and RNA/protein interactions position the pre-mRNA substrate for the two chemical steps of splicing. Not all of these interactions have been characterized, in part because it has not been possible to arrest the complex at clearly defined states relative to chemistry. Previously, it was shown in yeast that the DEAD/H-box protein Prp22 requires an extended 3′ exon to promote mRNA release from the spliceosome following second-step chemistry. In line with that observation, we find that shortening the 3′ exon blocks cleaved lariat intron and mRNA release in human splicing extracts, which allowed us to stall human spliceosomes in a new post-catalytic complex (P complex). In comparison to C complex, which is blocked at a point following first-step chemistry, we detect specific differences in RNA substrate interactions near the splice sites. These differences include extended protection across the exon junction and changes in protein crosslinks to specific sites in the 5′ and 3′ exons. Using selective reaction monitoring (SRM) mass spectrometry, we quantitatively compared P and C complex proteins and observed enrichment of SF3b components and loss of the putative RNA-dependent ATPase DHX35. Electron microscopy revealed similar structural features for both complexes. Notably, additional density is present when complexes are chemically fixed, which reconciles our results with previously reported C complex structures. Our ability to compare human spliceosomes before and after second-step chemistry has opened a new window to rearrangements near the active site of spliceosomes, which may play roles in exon ligation and mRNA release.     

Copper transport to mammary gland and milk during lactation in rats

The delivery of copper to mammary gland and milk and the effects of lactation were examined in rats. Traces of (67)Cu/(64)Cu(II) were injected intraperitoneally or intravenously into virgin rats or lactating rats (2-5 days postpartum), and incorporation into blood, milk, and tissues was monitored. In virgin rats, most of the isotope first entered the liver and kidney. In lactating rats, almost 60% went directly to the mammary gland. Uptake rates and copper contents of the mammary gland were 20-fold higher in lactation. (67)Cu/(64)Cu appeared in milk and milk ceruloplasmin as rapidly as in mammary tissue and when there was no (67)Cu/(64)Cu-ceruloplasmin in the maternal plasma. Plasma (125)I-labeled albumin entered milk much more slowly. Milk ceruloplasmin (10 mg/l) had 25% of the (67)Cu/(64)Cu. Milk copper was 3.3 mg/l. Thus lactation markedly enhances the avidity of the mammary gland for copper, diverting most of it from liver and kidney to that tissue. Also, the primary source of milk ceruloplasmin is the mammary gland and not the maternal plasma.     

Paracrine effects of oocyte secreted factors and stem cell factor on porcine granulosa and theca cells <Emphasis Type="Italic">in vitro</Emphasis>

Oocyte control of granulosa and theca cell function may be mediated by several growth factors via a local feedback loop(s) between these cell types. This study examined both the role of oocyte-secreted factors on granulosa and thecal cells, cultured independently and in co-culture, and the effect of stem cell factor (SCF); a granulosa cell derived peptide that appears to have multiple roles in follicle development. Granulosa and theca cells were isolated from 2–6 mm healthy follicles of mature porcine ovaries and cultured under serum-free conditions, supplemented with: 100 ng/ml LR3 IGF-1, 10 ng/ml insulin, 100 ng/ml testosterone, 0–10 ng/ml SCF, 1 ng/ml FSH (granulosa), 0.01 ng/ml LH (theca) or 1 ng/ml FSH and 0.01 ng/ml LH (co-culture) and with/without oocyte conditioned medium (OCM) or 5 oocytes. Cells were cultured in 96 well plates for 144 h, after which viable cell numbers were determined. Medium was replaced every 48 h and spent medium analysed for steroids.     

Nodal signaling is required for closure of the anterior neural tube in zebrafish

Background  

Nodals are secreted signaling proteins with many roles in vertebrate development. Here, we identify a new role for Nodal signaling in regulating closure of the rostral neural tube of zebrafish.     

Determination of the period for establishment of a liver network echogenic pattern in Schistosoma japonicum infection

Schistosomiasis is caused by infection with Schistosoma haematobium, S. mansoni, S. japonicum, or S. mekongi. S. japonicum infection results in liver cirrhosis at the final stage. A "network" (NW) echogenic pattern on hepatic ultrasonography appears to be specific to S. japonicum infection. The principal aim of the present study was to determine the exact year(s) or even month(s) required for the establishment of the liver NW echogenic pattern from the initial infection in young patients with schistosomiasis japonica since there are few data on this important point. We conducted yearly ultrasonographic, serologic, coprologic, and physical examinations of schistosomiasis patients in the Philippines from 1996 up to the present. During that period, the total number of patients examined was approximately 2,000, among whom we selected 2 patients for determination of the duration required for NW establishment, when they were 10 years old. Although the exact time of initial exposure to schistosomes cannot be determined, the duration for the establishment of NW was definitively confirmed in patient no. 1 to be between 19-24 months based on the results of serologic and coprologic examinations. For patient no. 2, the circumstantial evidence suggested that the establishment of a NW might require 5 to 6 years at maximum. To the best of our knowledge, this is the first evidence-based report on the determination of the period required for the establishment of a liver NW echogenic pattern in S. japonicum infection in the Philippines.     

Phylogenetic analysis of the tenascin gene family: evidence of origin early in the chordate lineage

Background  

Tenascins are a family of glycoproteins found primarily in the extracellular matrix of embryos where they help to regulate cell proliferation, adhesion and migration. In order to learn more about their origins and relationships to each other, as well as to clarify the nomenclature used to describe them, the tenascin genes of the urochordate Ciona intestinalis, the pufferfish Tetraodon nigroviridis and Takifugu rubripes and the frog Xenopus tropicalis were identified and their gene organization and predicted protein products compared with the previously characterized tenascins of amniotes.     

Differences in a conformational equilibrium distinguish catalysis by the endothelial and neuronal nitric-oxide synthase flavoproteins

Nitric oxide (NO) is a physiological mediator synthesized by NO synthases (NOS). Despite their structural similarity, endothelial NOS (eNOS) has a 6-fold lower NO synthesis activity and 6-16-fold lower cytochrome c reductase activity than neuronal NOS (nNOS), implying significantly different electron transfer capacities. We utilized purified reductase domain constructs of either enzyme (bovine eNOSr and rat nNOSr) to investigate the following three mechanisms that may control their electron transfer: (i) the set point and control of a two-state conformational equilibrium of their FMN subdomains; (ii) the flavin midpoint reduction potentials; and (iii) the kinetics of NOSr-NADP+ interactions. Although eNOSr and nNOSr differed in their NADP(H) interaction and flavin thermodynamics, the differences were minor and unlikely to explain their distinct electron transfer activities. In contrast, calmodulin (CaM)-free eNOSr favored the FMN-shielded (electron-accepting) conformation over the FMN-deshielded (electron-donating) conformation to a much greater extent than did CaM-free nNOSr when the bound FMN cofactor was poised in each of its three possible oxidation states. NADPH binding only stabilized the FMN-shielded conformation of nNOSr, whereas CaM shifted both enzymes toward the FMN-deshielded conformation. Analysis of cytochrome c reduction rates measured within the first catalytic turnover revealed that the rate of conformational change to the FMN-deshielded state differed between eNOSr and nNOSr and was rate-limiting for either CaM-free enzyme. We conclude that the set point and regulation of the FMN conformational equilibrium differ markedly in eNOSr and nNOSr and can explain the lower electron transfer activity of eNOSr.