Multiple mechanisms for hereditary sideroblastic anemia.

Hereditary sideroblastic anemia (HSA) is a heterogeneous group of inherited anemic disorders which is characterized by the presence of ringed sideroblasts in the bone marrow, microcytic hypochromic anemia and typically its X-linked inheritance in patients. It has been shown that a deficiency of the erythroid-specific delta-aminolevulinate synthase (ALAS-E) activity is responsible for pyridoxine-responsive HSA in many patients, however, the pathogenesis of other types of HSA remains still unknown. In this article, recent evidence suggesting multiple causes for HSA is summarized and discussed.     

Dissociation of Large and Small Bovine Casein Micelles by Dialysis

The effects of dietary fat types on the thermogenic activity of brown adipocytes isolated from rat were examined. When beef tallow (saturated fatty acids + oleic) and safflower oil (linoleic) were the dietary fats, the respiration rates of brown adipocytes activated either by norepinephrine or an uncoupler of mitochondrial respiration (carbonylcyanide-m-chlorophenylhydrazone) were both slightly higher in rats fed the polyunsaturated fat. When the effects of safflower oil and evening primrose oil (linoleīc + γ-linolenic) were compared, the activated respiration rate tended to be higher in the latter. The respiratory responses to varying concentrations of norepinephrine were apparently dependent on the dietary fat types. Triglyceride stored in interscapular brown adipose tissue appeared to be modified by dietary fat types. Dietary fat also characteristically modified the fatty acid compositions of interscapular brown and epididymal white adipose tissues. Thus, the type of dietary fat caused an alteration to the thermogenesis of brown adipose tissue at the cellular level.     

Quantum Yields of Decomposition and Homo-Dimerization of Solid <Emphasis Type="SmallCaps">L</Emphasis>-Alanine Induced by 7.2 eV Vacuum Ultraviolet Light Irradiation: An Estimate of the Half-Life of <Emphasis Type="SmallCaps">L</Emphasis>-Alanine on the Surface of Space Objects

One of the leading hypotheses regarding the origin of prebiotic molecules on primitive Earth is that they formed from inorganic molecules in extraterrestrial environments and were delivered by meteorites, space dust and comets. To evaluate the availability of extraterrestrial amino acids, it is necessary to examine their decomposition and oligomerization rates as induced by extraterrestrial energy sources, such as vacuum ultraviolet (VUV) and X-ray photons and high energy particles. This paper reports the quantum yields of decomposition ((8.2 ± 0.7) × 10⁻² photon⁻¹) and homo-dimerization ((1.2 ± 0.3) × 10⁻³ photon⁻¹) and decomposition of the dimer (0.24 ± 0.06 photon⁻¹) of solid l-alanine (Ala) induced by VUV light with an energy of 7.2 eV. Using these quantum yields, the half-life of l-Ala on the surface of a space object in the present earth orbit was estimated to be about 52 days, even when only photons with an energy of 7.2 eV emitted from the present Sun were considered. The actual half-life of solid l-Ala on the surface of a space object orbit around the present day Earth would certainly be much shorter than our estimate, because of the added effect of photons and particles of other energies. Thus, we propose that l-Ala needs to be shielded from solar VUV in protected environments, such as the interior of a meteorite, within a time scale of days after synthesis to ensure its arrival on the primitive Earth.     

Locomotion is not a privilege after birth: Ultrasound images of viviparous shark embryos swimming from one uterus to the other

Underwater ultrasound, a new tool for observing the internal body parts of aquatic animals by scuba divers, allowed us long‐term and frequent observations of the embryos of captive aquatic vertebrates. New ultrasound data of captive tawny nurse sharks (Nebrius ferrugineus) revealed that their embryos frequently migrate between the right and left uteri during gestation. This report is the first reliable evidence of active embryonic locomotion in live‐bearing vertebrates and is contradictory to the concept of “sedentary embryo” which has mainly arisen from studies of mammals. The tawny nurse shark is unique among orectolobiform sharks, in which the embryo develops by feeding on sibling eggs in utero. Thus, we hypothesized that swimming aids in an efficient search and capture of these eggs in the uterine environment.     

Bacterial Neuraminidase Rescues Influenza Virus Replication from Inhibition by a Neuraminidase Inhibitor

Influenza virus neuraminidase (NA) cleaves terminal sialic acid residues on oligosaccharide chains that are receptors for virus binding, thus playing an important role in the release of virions from infected cells to promote the spread of cell-to-cell infection. In addition, NA plays a role at the initial stage of viral infection in the respiratory tract by degrading hemagglutination inhibitors in body fluid which competitively inhibit receptor binding of the virus. Current first line anti-influenza drugs are viral NA-specific inhibitors, which do not inhibit bacterial neuraminidases. Since neuraminidase producing bacteria have been isolated from oral and upper respiratory commensal bacterial flora, we posited that bacterial neuraminidases could decrease the antiviral effectiveness of NA inhibitor drugs in respiratory organs when viral NA is inhibited. Using in vitro models of infection, we aimed to clarify the effects of bacterial neuraminidases on influenza virus infection in the presence of the NA inhibitor drug zanamivir. We found that zanamivir reduced progeny virus yield to less than 2% of that in its absence, however the yield was restored almost entirely by the exogenous addition of bacterial neuraminidase from Streptococcus pneumoniae. Furthermore, cell-to-cell infection was severely inhibited by zanamivir but restored by the addition of bacterial neuraminidase. Next we examined the effects of bacterial neuraminidase on hemagglutination inhibition and infectivity neutralization activities of human saliva in the presence of zanamivir. We found that the drug enhanced both inhibitory activities of saliva, while the addition of bacterial neuraminidase diminished this enhancement. Altogether, our results showed that bacterial neuraminidases functioned as the predominant NA when viral NA was inhibited to promote the spread of infection and to inactivate the neutralization activity of saliva. We propose that neuraminidase from bacterial flora in patients may reduce the efficacy of NA inhibitor drugs during influenza virus infection. (295 words).     

B cell response pathways regulated by IL-5 and IL-2. Secretory microH chain-mRNA and J chain mRNA expression are separately controlled events

We have examined the effect of IL-5 and/or IL-2 on the expression of the secretory form of microH chain (microsecond) and J chain mRNA in a homogeneous neoplastic B cell clone, in which proliferation, IL-2R up-regulation and entry into the IgM secretory state are separately controlled events. The IL-5 signal triggers a partial induction of CL-3 cells into the IgM secretory state, characterized by a striking increase of microsecond mRNA expression and an increase in the ratio of the secretory to membrane forms of microH chain mRNA, with a modest increase of J chain mRNA. In contrast, amplification of J chain mRNA is accomplished by the late-acting B cell differentiation stimulus, IL-2, acting on IL-5-pretreated CL-3 cells or acting simultaneously with IL-5 on CL-3 cells. Such dually stimulated cells now are fully induced into IgM secreting cells. These results define the relative roles of IL-5 and IL-2 in B cell differentiation by showing important regulatory effects at the mRNA level. In addition, these results substantiate that appearance of mRNA for J chain, a molecule key to the formation of pentameric IgM, is a limiting factor for high level IgM secretion. The separate control of microsecond and J chain mRNA found in CL-3 cells stimulated with IL-5 and IL-2 elucidates a molecular mechanism by which these two lymphokines synergize in the development of CL-3 cells into IgM secreting cells.     

Ca2+/calmodulin-dependent protein phosphatase in bovine parotid gland: purification and characterization

Calmodulin-dependent protein phosphatase (CaM-PPase) was isolated from bovine parotid gland by sequential application of DEAE-52, Affi-gel blue and calmodulin-affinity chromatography followed by gel filtration and high performance liquid chromatography. The enzyme was activated in the simultaneous presence of Ni2+ or Mn2+ and Ca2+ plus calmodulin. Ca2+/calmodulin-dependent activation of CaM-PPase was antagonized by inhibitors of calmodulin action, such as W-7 and trifluoperazine. Tryptophan fluorescence was quenched in the presence of Ni2+. CaM-PPase was a heterodimer. The molecular weights of large subunits which bound calmodulin (CaM) were 68 kD and 58 kD - the 68 kD subunit was predominant. Polyclonal antibodies against bovine calcineurin cross-reacted with both types of larger subunits. Using polyclonal antibodies against bovine calcineurin or the monoclonal antibody against subunit B of bovine calcineurin, the smaller molecular weight subunit (19 kD) was found to be immunologically identical to subunit B of bovine calcineurin. In bovine parotid gland, CaM-PPase was found both in acinar and duct cells.     

Infectious Cell Entry Mechanism of Influenza Virus

Interaction between influenza virus WSN strain and MDCK cells was studied by using spin-labeled phospholipids and electron microscopy. Envelope fusion was negligibly small at neutral pH but greatly activated in acidic media in a narrow pH range around 5.0. The half-time was less than 1 min at 37°C at pH 5.0. Virus binding was almost independent of the pH. Endocytosis occurred with a half-time of about 7 min at 37°C at neutral pH, and about 50% of the initially bound virus was internalized after 1 h. Electron micrographs showed binding of virus particles in coated pits in the microvillous surface of plasma membrane and endocytosis into coated vesicles. Chloroquine inhibited virus replication. The inhibition occurred when the drug was added not later than 10 min after inoculation. Chloroquine caused an increase in the lysosomal pH 4.9 to 6.1. The drug did not affect virus binding, endocytosis, or envelope fusion at pH 5.0. Electron micrographs showed many virus particles remaining trapped inside vacuoles even after 30 min at 37°C in the presence of drug, in contrast to only a few particles after 10 min in vacuoles and secondary lysosomes in its absence. Virus replication in an artificial condition, i.e., brief exposure of the inoculum to acidic medium followed by incubation in neutral pH in the presence of chloroquine, was also observed. These results are discussed to provide a strong support for the infection mechanism of influenza virus proposed previously: virus uptake by endocytosis, fusion of the endocytosed vesicles with lysosome, and fusion of the virus envelope with the surrounding vesicle membrane in the secondary lysosome because of the low pH. This allows the viral genome to enter the target cell cytoplasm.     

Virus-induced fusion of human erythrocyte ghosts I. Effects of macromolecules on the final stages of the fusion reaction

Human erythrocyte ghosts prepared by hypotonic hemolysis can be fused by Sendai virus, provided that certain macromolecules (bovine serum albumin, dextran and others) are sequestered in the ghosts. Since fusion of the ghosts is dependent on intactness of the F(fusion)-glycoprotein of the virion, and since the other requirements for this reaction are also similar to those for the Sendai virus-induced fusion of intact erythrocytes, this system can be used as a model for the Sendai virus-induced cell fusion reaction. Sequestered macromolecules seem to be required for rounding of locally fused ghosts. Under low osmotic swelling conditions, such as use of ghosts sealed without macromolecules or using bovine serum albumin-loaded ghosts sealed in the presence of external macromolecules, no apparently complete cell fusion (large spherical polyghost formation) could be observed. Even under these conditions, however, occurence of local cell fusion could be demonstrated either by transfer of fluorescent-labeled albumin from one ghost to an other, or by observation of polyghost formation after osmotic swelling in the cold. Thus, final stages of the fusion reaction can be divided into local cell-cell fusion which could not be observed by phase-contrast microscopy, and rounding (i.e. formation of spherical polyghost). For the observation of fusion of ghosts, the last step seems to be important.