Friend spleen focus-forming virus induces factor independence in an erythropoietin-dependent erythroleukemia cell line

Erythroid cells from mice infected with the polycythemia-inducing strain of Friend spleen focus-forming virus (SFFVP), unlike normal erythroid cells, can proliferate and differentiate in apparent absence of the erythroid hormone erythropoietin (Epo). The unique envelope glycoprotein encoded by SFFV has been shown to be responsible for this biological effect. The recent isolation of an Epo-dependent erythroleukemia cell line, HCD-57, derived from a mouse infected at birth with Friend murine leukemia virus, afforded us the opportunity to study the direct effect of SFFVP on a homogeneous population of factor-dependent cells. The introduction of SFFVP in complex with various helper viruses into these Epo-dependent cells efficiently and reproducibly gave rise to lines which expressed high levels of SFFV and were factor independent. SFFV appears to be unique in its ability to abrogate the factor dependence of Epo-dependent HCD-57 cells, since infection of these cells with retroviruses carrying a variety of different oncogenes had no effect. The induction of Epo independence by SFFV does not appear to involve a classical autocrine mechanism, since there is no evidence that the factor-independent cells synthesize or secrete Epo or depend on it for their growth. However, the SFFV-infected, factor-independent cells had significantly fewer receptors available for binding Epo than their factor-dependent counterparts had, raising the possibility that the induction of factor independence by the virus may be due to the interaction of an SFFV-encoded protein with the Epo receptor.     

Lectin histochemistry for detecting cadmium-induced changes in the glycosylation pattern of rat placenta

Cadmium (Cd) is an industrial and environmental pollutant that produces toxic effects on gametogenesis, pre- and post-implantation embryos, and the placenta. Because the effects of acute Cd intoxication on the placenta are not well understood, we investigated changes in its glycosylated components in Cd treated dams at days 4, 7, 10 and 15 of gestation using lectin histochemistry. CdCl₂ was administered to pregnant rats; control animals received sterile normal saline. Placentas were processed for DBA, Con A, SBA, PNA, UEA-I, RCA-I and WGA lectin histochemistry to evaluate changes in the carbohydrate pattern of the placenta that might modify cell interactions and contribute to embryonic alterations. Lectin binding was analyzed in the yolk sac; trophoblast giant cells; trophoblast I, II and III; spongiotrophoblast cells and endovascular trophoblast cells in the chorioallantoic placenta. Our lectin binding patterns showed that Cd caused alteration of SBA and DBA labeling of trophoblast-derived cells, which suggested increased expressions of α and β GalNAc. Cd also caused decreased UEA-1 binding affinity, which indicated fewer α-L-Fuc residues in placentas of Cd treated dams. The nonreactivity in trophoblast I of the control placentas incubated with Con-A contrasted with the labeling in placentas of experimental dams, which indicated increased expression of terminal α-D-Man, and α-D-Glc residues. We found that Cd altered the reactivity of placenta to several lectins, which indicated modification of the glycotype presented by the fetal component of the placenta. We report that Cd exerts a deleterious effect on the glycosylation pattern of the placenta.     

Heavy metal concentrations in,and human health risk assessment of,three commercially valuable fish species in the lower Niger River,Nigeria

The concentrations of Fe, Mn, Ni, Pb and V in water, sediment and the gill, liver and muscle tissues of Synodontis resupinatus, Heterotis niloticus and Clarias gariepinus, all commercially important fish species of the lower Niger River, were investigated in 2015. Water, sediment and fish samples were collected for six months and heavy metals were determined using an Atomic Absorption Spectrometer. Fe ranked highest in water and sediment, with concentrations of 2.74 mg l^?1 and 61.60 mg kg^?1, respectively. Metals followed the magnitude of Fe > Mn > Ni > V > Pb in the water and Fe > Mn > V > Ni > Pb in the sediments. Metal concentrations were higher in the tissues of S. resupinatus compared with H. niloticus and C. gariepinus. Fe was also highest in the gills, liver and muscle of the three fish species. Its highest concentration of 132.97 mg kg^?1 dry weight was recorded in the gills of S. resupinatus. Bioconcentration factors of metals ranged from 8.79 for Mn in H. niloticus muscle to 67.99 for Ni in S. resupinatus gills. The fish species studied pose no health risk for all metals studied, because the target hazard quotient was less than 1 and the estimated daily intakes of the metals were below the reference doses.     

Function of the conserved S1 and KH domains in polynucleotide phosphorylase

We have examined the roles of the conserved S1 and KH RNA binding motifs in the widely dispersed prokaryotic exoribonuclease polynucleotide phosphorylase (PNPase). These domains can be released from the enzyme by mild proteolysis or by truncation of the gene. Using purified recombinant enzymes, we have assessed the effects of specific deletions on RNA binding, on activity against a synthetic substrate under multiple-turnover conditions, and on the ability of truncated forms of PNPase to form a minimal RNA degradosome with RNase E and RhlB. Deletion of the S1 domain reduces the apparent activity of the enzyme by almost 70-fold under low-ionic-strength conditions and limits the enzyme to digest a single substrate molecule. Activity and product release are substantially regained at higher ionic strengths. This deletion also reduces the affinity of the enzyme for RNA, without affecting the enzyme's ability to bind to RNase E. Deletion of the KH domain produces similar, but less severe, effects, while deletion of both the S1 and KH domains accentuates the loss of activity, product release, and RNA binding but has no effect on binding to RNase E. We propose that the S1 domain, possibly arrayed with the KH domain, forms an RNA binding surface that facilitates substrate recognition and thus indirectly potentiates product release. The present data as well as prior observations can be rationalized by a two-step model for substrate binding.     

Vertebrate ancient opsin photopigment spectra and the avian photoperiodic response

In mammals, photoreception is restricted to cones, rods and a subset of retinal ganglion cells. By contrast, non-mammalian vertebrates possess many extraocular photoreceptors but in many cases the role of these photoreceptors and their underlying photopigments is unknown. In birds, deep brain photoreceptors have been shown to sense photic changes in daylength (photoperiod) and mediate seasonal reproduction. Nonetheless, the specific identity of the opsin photopigment 'sensor' involved has remained elusive. Previously, we showed that vertebrate ancient (VA) opsin is expressed in avian hypothalamic neurons and forms a photosensitive molecule. However, a direct functional link between VA opsin and the regulation of seasonal biology was absent. Here, we report the in vivo and in vitro absorption spectra (λ(max) = ~490 nm) for chicken VA photopigments. Furthermore, the spectral sensitivity of these photopigments match the peak absorbance of the avian photoperiodic response (λ(max) = 492 nm) and permits maximum photon capture within the restricted light environment of the hypothalamus. Such a correspondence argues strongly that VA opsin plays a key role in regulating seasonal reproduction in birds.     

Streptococcus pneumoniae Translocates into the Myocardium and Forms Unique Microlesions That Disrupt Cardiac Function

Hospitalization of the elderly for invasive pneumococcal disease is frequently accompanied by the occurrence of an adverse cardiac event; these are primarily new or worsened heart failure and cardiac arrhythmia. Herein, we describe previously unrecognized microscopic lesions (microlesions) formed within the myocardium of mice, rhesus macaques, and humans during bacteremic Streptococcus pneumoniae infection. In mice, invasive pneumococcal disease (IPD) severity correlated with levels of serum troponin, a marker for cardiac damage, the development of aberrant cardiac electrophysiology, and the number and size of cardiac microlesions. Microlesions were prominent in the ventricles, vacuolar in appearance with extracellular pneumococci, and remarkable due to the absence of infiltrating immune cells. The pore-forming toxin pneumolysin was required for microlesion formation but Interleukin-1β was not detected at the microlesion site ruling out pneumolysin-mediated pyroptosis as a cause of cell death. Antibiotic treatment resulted in maturing of the lesions over one week with robust immune cell infiltration and collagen deposition suggestive of long-term cardiac scarring. Bacterial translocation into the heart tissue required the pneumococcal adhesin CbpA and the host ligands Laminin receptor (LR) and Platelet-activating factor receptor. Immunization of mice with a fusion construct of CbpA or the LR binding domain of CbpA with the pneumolysin toxoid L460D protected against microlesion formation. We conclude that microlesion formation may contribute to the acute and long-term adverse cardiac events seen in humans with IPD.     

Melanopsin-dependent photoreception provides earliest light detection in the mammalian retina

BACKGROUND: The visual system is now known to be composed of image-forming and non-image-forming pathways. Photoreception for the image-forming pathway begins at the rods and cones, whereas that for the non-image-forming pathway also involves intrinsically photosensitive retinal ganglion cells (ipRGCs), which express the photopigment melanopsin. In the mouse retina, the rod and cone photoreceptors become light responsive from postnatal day 10 (P10); however, the development of photosensitivity of the ipRGCs remains largely unexplored. RESULTS: Here, we provide direct physiological evidence that the ipRGCs are light responsive from birth (P0) and that this photosensitivity requires melanopsin expression. Interestingly, the number of ipRGCs at P0 is over five times that in the adult retina, reflecting an initial overproduction of melanopsin-expressing cells during development. Even at P0, the ipRGCs form functional connections with the suprachiasmatic nucleus, as assessed by light-induced Fos expression. CONCLUSIONS: The findings suggest that the non-image-forming pathway is functional long before the mainstream image-forming pathway during development.     

Viral diseases of fish: first report of carp pox in golden ide (Leuciscus idus) in North America

Carp pox, a putative viral disease exotic to North America, occurred in golden ide 1 yr after the fish were imported into the United States from the Federal Republic of Germany. The raised, white, plaque-like lesions, which occurred on about 5% of the fish, healed spontaneously and caused no mortality. Electron micrographs showed herpesvirus-like particles associated with lesion specimens; however, no infectious viruses were detected in tests with seven warmwater fish cell lines.