Internalization of iron-transferrin complex by murine L1210 leukemia cells and rat reticulocytes demonstrated by a minibead probe

To determine if the cellular uptake of iron is associated with internalization of iron-transferrin (TF) complex by the cell, we synthesized a visual probe in which TF is covalently bound to amide-modified latex minibead, submicrometer in size (0.345 micron). Incubation of the probe with L1210 leukemia cells and rat reticulocytes led to the binding of the probe to the cell surface visualized and semiquantified by scanning and transmission electron microscopy. The binding was inhibited by preincubation with nonderivatized iron-TF complex. Internalization of the probe occurred through clathrin-coated pits and vesicles. Minibeads derivatized by nontransport proteins or glycine as well as nonderivatized minibeads did not appreciably bind to the cells and were not internalized. Ethylamine, an inhibitor of receptor-mediated endocytosis abolished the internalization but not the binding of the probe which, then, accumulated on the cell surface. These findings provide direct evidence for internalization of TF during the iron uptake.     

Cytoskeletal organization of a cloned hemopoietic stromal cell line during attachment and spreading

The cell membrane of a cloned murine bone marrow stromal cell line D2XRII was extracted in situ using Triton X-100 detergent and the cytoskeletal structure studied during the process of adherence and spreading. During this process, three zones can be identified in the cytoplasm: the perinuclear zone, which was the fixed part of the cell; the peripheral mixed filamentous zone, which formed the core of long cytoplasmic projections; and an outer zone, which formed the boundary of cytoplasmic projections and contained only intermediate filaments. The process of spreading appeared to originate from very long strips of microfilaments emanating from the second zone, crossing the width of the outer zone, and extending beyond for a long distance. The second and third zones then appeared to "stream out" around the axis of this strip, and in this fashion the cytoplasm spreads over the substratum.     

Relationship of the glycan structure of glycoproteins to the desialylation process by rat liver endothelium

To investigate the variations in desialylation of glycoproteins by liver endothelium, we compared endothelial desialylation for 3 glycoproteins, human ceruloplasmin, human and rat transferrin. Radiolabeled glycoproteins were chased through purified rat liver endothelium and then fractionated by lectin affinity chromatography. Endothelium processed glycoproteins were fractionated by RCA120 chromatography into sialylated and desialylated components. The latter was then studied by Con A chromatography. Desialylation occurred only when the molecule contained at least a single triantennary chain of glycan. Desialylation was minimal in the case of human transferrin which contains mostly biantennary branching pattern. Thus, it appears that a single triantennary glycan chain is necessary and sufficient to trigger desialylation of glycoproteins by liver endothelium and this process is an all-or-none phenomenon.     

Isolation of some new sulphur bacteria from activated sludge

E mtiazi , G., H abibi , M.H. & S etareh , M. 1990. Isolation of some new sulphur bacteria from activated sludge. Journal of Applied Bacteriology 69 , 864–870.
During studies on bulking of activated sludge some new sulphur micro-organisms, which were able to grow aerobically and anaerobically on reduced sulphur compounds, were isolated on thiosulphate agar. These were capable of autotrophic and heterotrophic growth on a wide range of substrates. In view of their ability to oxidize reduced sulphur compounds, and because one of them was an oxidase- and catalase-positive, Gram-negative, motile coccus (0.36–0.48 μm) it was named Thiosphaera persica . The second one was an oxidase- and catalase-positive, Gram-negative, motile rod (1.32–1.80 μm) and was named Thiobacillus persica . The third one was oxidase-negative, catalase-positive, motile, Gram-negative and polymorphic and was named Sulphobacter polymorpha .     

Comparison of desialylation of rat transferrin by cellular and non-cellular methods.

We have previously shown that the liver endothelium can desialylate the glycoprotein transferrin (Tf). In the present work we provide evidence that asialotransferrin obtained by this means behaves differently on Ricinus communis agglutinin (RCA120) lectin affinity chromatography from asialotransferrin obtained by either neuraminidase treatment or acid hydrolysis. Purified rat transferrin was radiolabelled either with 125I (protein moiety) or with 3H (sialyl residues), and subsequently saturated with iron. It was then passed through an RCA120-agarose column to isolate the fully sialylated component. Sialylated Tf was then desialylated either by incubation with purified rat liver endothelium or, in vitro, by neuraminidase treatment or by acid hydrolysis. The protein was again subjected to RCA120 column chromatography. Although both neuraminidase treatment and acid hydrolysis almost completely desialylated the glycoprotein (as evidenced by near absence of 3H label), the glycoprotein was not retained by the RCA120-agarose column. By contrast, liver endothelium partially desialylated the glycoprotein, but this desialylated fraction was retained by the RCA120-agarose column. These results suggest that desialylation with neuraminidase or acid hydrolysis may be inadequate for functional studies of asialotransferrin.     

Modulation of WGA binding sites on marrow sinus endothelium in state of stimulated erythropoiesis: a possible mechanism regulating the rate of cell egress

To study the regulation of cellular and molecular traffic across the marrow-blood barrier, rat marrow endothelial surface was incubated with ferritin-conjugated concanavalin A, wheat germ agglutinin (WGA), recinus communis agglutinin I, and phytohemagglutinin. Normal animals were compared with those after erythropoietic stimulation (phenylhydrazine-induced hemolysis, phlebotomy). A selective and significant reduction in the density of WGA receptors, but not other lectins was noted congruent to the degree of reticulocytosis. Neuraminidase treatment also reduced WGA binding sites and the surface negative charge as detected by polycationic ferritin (PCF). Thus, the reduction in WGA binding sites, may reflect a decrease in the density of membrane sialic acid, rendering the endothelial surface charge less negative and providing an electrostatic attraction for the negatively charged surface of reticulocytes. The findings may also be explained by an increase in the frequency of WGA-excluding fenestrae in the endothelium. These areas, lacking sialic acid, may provide unstable areas in the membrane suitable for the passage of cells and molecules in both directions. It is concluded that, by modulating the density of sialic acid residues, the endothelium may regulate the traffic of cells and molecules across the marrow-blood barrier.     

Titanium oxide nanoparticles fabrication,hemoglobin interaction,white blood cells cytotoxicity,and antibacterial studies

This study is focused on the fabrication and characterization of titanium oxide (TiO₂) NPs. Afterwards; the interaction of TiO₂ NPs with human hemoglobin (Hb) was investigated by FTIR spectroscopy, fluorescence spectroscopy, and molecular docking studies. Also, the cytotoxic effect of fabricated TiO₂ NPs against human white blood cells (WBCs) was considered by MTT assay. The antibacterial effect of synthesized NPs was examined on Pseudomonas aeruginosa (ATCC 27853); Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923). TEM and DLS investigations showed that the synthesized TiO₂ NPs have a narrow nano-sized distribution. XRD pattern of the fabricated NPs exhibited that the TiO₂ NPs contain anatase phase. Similarity in amide I and II signal intensities showed that secondary structure of the adsorbed Hb is preserved. The intrinsic fluorescence study revealed that the fluorescence quenching of Hb was done by complex formation between Hb and TiO₂ NPs trough the hydrogen bond and van der Waals interactions. Synchronous fluorescence spectroscopy determined that interaction of TiO₂ NPs with Hb did not unfold the Hb structure in the vicinity of the Tyr and Trp residues. Molecular docking study depicted that Glu-95, Thr-134 and Tyr-140 are involved in the formation of hydrophilic bonds. MTT data and antibacterial assays indicated that TiO₂ NPs endow distinguished antibacterial activities against Gram-negative and Gram positive strains at safe concentrations. This study may reveal that fabricated TiO₂ NP can be used as a safe and potent antibacterial agent.

Communicated by Ramaswamy H. Sarma     

Survey of Flea Infestation in Dogs in Different Geographical Regions of Iran

Medically important arthropods, including fleas, play an important role in causing clinical disorders and disease in man and domestic animals. This study was conducted to determine the seasonal flea infestations for domestic dogs from different geographic regions of Iran. A total of 407 fleas, belonging to 5 different species, were recovered from 83 domestic dogs from 3 regions. There was a distinctive pattern of species distribution and infestations with the highest infestation rates observed in a temperate climate and higher rainfall. Additionally, fleas were observed over all seasons, except February and March, with the highest infestation rate observed in August (24.7%) and the lowest rate in January (1.7%). They also parasitize dogs with a different spectrum of species. The cat flea, Ctenocephalides felis (67.5%), exhibited the highest prevalence among all flea species found on dogs. Thus, climatic conditions and seasonal patterns impact on flea infestation and must be considered in developing control programs.