Effect of 17 beta-estradiol on partition behavior of human erythrocytes in dextran-poly(ethylene glycol) aqueous phases

Preincubation with 1 nM 17 beta-estradiol changes the partition behaviour of human erythrocytes in dextran-poly(ethylene glycol) aqueous phases. Erythrocyte partition decreases reaching a minimum after 5 min of incubation, then slowly increases returning to starting values after 30 min. The effect is specifically induced by the isomer of estradiol, whereas the alpha isomer and other steroid hormones (progesterone, testosterone and 5 alpha-dihydrotestosterone) are uneffective. The effect of the hormone can be suppressed by treatment of erythrocytes with either N-ethyl maleimide, sodium vanadate, or ouabain, or carrying out incubations in potassium-free buffer. These data suggest that the effect of estradiol on phase partition of erythrocytes is mediated by the (Na,K)-ATPase.     

Na-NMR Studies of the Intracellular Sodium Ion Concentration in the Halotolerant Alga Dunaliella salina

The Intracellular Na⁺ concentration in the halotolerant alga Dunaliella salina was measured in intact cells by ²³Na-NMR spectroscopy, utilizing the dysprosium tripolyphosphate complex as a sodium shift reagent, and was found to be 88 ± 28 millimolar. Intracellular sodium ion content and intracellular volume were the same, within the experimental error, in cells adapted to grow in media containing between 0.1 and 4.0 molar NaCl. These values assume extracellular and intracellular NMR visibilities of the ²³Na nuclei of 100 and 40%, respectively. The relaxation rate of intracellular sodium was enhanced with increasing salinity of the growth medium, in parallel to the intracellular osmosity due to the presence of glycerol, indicating that Na⁺ ions and glycerol are codistribbuted within the cell volume.     

Urea tolerance and osmoregulation in Bufo viridis and Rana ridibunda

1. The tolerance and adaptation to urea solutions by terrestrial green toads (Bufo viridis) and semi-aquatic frogs (Rana Ridibunda) were studied. 2. the green toad showed tolerance to urea solution of 800 mM and the frogs showed tolerance only to about 400 mM urea solution. 3. The plasma concentrations of both species was hyperosmotic to the external medium in all the different urea solutions. 4. Blood osmolality, urea, Na+ and Cl- concentrations of B. viridis were always higher than in R. ridibunda. 5. The urea concentration in muscle of R. ridibunda was higher than the urea concentration in muscle of B. viridis. 6. The muscle tissue weight loss of B. viridis was significantly lower than R. ridibunda.     

Effect of 17β-estradiol on calcium response to phytohaemagglutinin in human lymphocytes

Pre-treatment of human lymphocytes with 17-estradiol diminishes the increase in concentration of cytosolic free calcium after stimulation with phytohaemagglutinin. The effect is dependent on 17-estradiol concentration and on the preincubation time. The effect is not due to an interaction between 17-estradiol and phytohaemagglutinin, but appears to be a consequence of the binding of the hormone to the cell surface. The effect is specific for 17-estradiol, since the isomer and other steroid hormones (progesterone, testosterone, diethylstilbestrol and 5-androstan), have no effect. Since the effect of the 17-estradiol can be suppressed by treatment of lymphocytes with ouabain, it appears that the effect of estradiol on the rise of cytosolic calcium induced by phytohaemagglutinin is mediated by the (Na, K)-ATPase.     

Metabolic studies with NMR spectroscopy of the alga Dunaliella salina trapped within agarose beads

A technique for the entrapment of the unicellular algae Dunaliella salina in agarose beads and their perfusion during NMR measurements is presented. The trapped cells maintained their ability to proliferate under normal growth conditions, and remained viable and stable under steady-state conditions for long periods during NMR measurements. Following osmotic shock in the dark, prominent changes were observed in the intracellular level of ATP and polyphosphates, but little to no changes in the intracellular pH or orthoposphate content. When cells were subjected to hyperosmotic shock, the ATP level decreased. The content of NMR-visible polyphosphates decreased as well, presumably due to the production of longer, NMR-invisible structures. Following hypoosmotic shock, the ATP content increased and longer polyphosphates were broken down to shorter, more mobile polymers.     

Myelin basic protein inhibits formyl-peptide induced chemotaxis in human neutrophils

Myelin basic protein, one of the major membrane protein component of the central nervous system, was used to probe the molecular mechanism of cellular activation. Pre-treatment of human neutrophils with myelin basic protein selectively inhibits the formyl-peptide-induced chemotaxis, without affecting chemotaxis evoked by casein and activated serum. Furthermore, both the degranulation and superoxide anion production stimulated by the chemotactic peptide are not modified by the prior treatment of the neutrophils with myelin basic protein.     

Taxol-induced apoptosis in human SKOV3 ovarian and MCF7 breast carcinoma cells is caspase-3 and caspase-9 independent

Taxol is used in chemotherapy regimens against breast and ovarian cancer. Treatment of tumor model cell lines with taxol induces apoptosis, but exact mechanism is not sufficiently understood. Our results demonstrate that in response to taxol, various cell types differentially utilize distinct apoptotic pathways. Using MCF7 breast carcinoma cells transfected with caspase-3 gene, we showed that taxol-induced apoptosis occurred in the absence of caspase-3 and caspase-9 activation. Similar results were obtained with ovarian SKOV3 carcinoma cells, expressing high level of endogenous caspase-3. In contrast, staurosporine-induced apoptosis in these cells was accompanied by proteolytic cleavage of pro-caspase-3 and induction of caspase-3 enzymatic activity. The effect of taxol appears to be cell type-specific, since taxol-induced apoptosis in leukemia U937 cells involved caspase-3 activation step. We conclude that a unique caspase-3 and caspase-9 independent pathway is elicited by taxol to induce apoptosis in human ovarian and breast cancinoma cells.     

Alignment free identification of clones in B cell receptor repertoires

Following antigenic challenge, activated B cells rapidly expand and undergo somatic hypermutation, yielding groups of clonally related B cells with diversified immunoglobulin receptors. Inference of clonal relationships based on the receptor sequence is an essential step in many adaptive immune receptor repertoire sequencing studies. These relationships are typically identified by a multi-step process that involves: (i) grouping sequences based on shared V and J gene assignments, and junction lengths and (ii) clustering these sequences using a junction-based distance. However, this approach is sensitive to the initial gene assignments, which are error-prone, and fails to identify clonal relatives whose junction length has changed through accumulation of indels. Through defining a translation-invariant feature space in which we cluster the sequences, we develop an alignment free clonal identification method that does not require gene assignments and is not restricted to a fixed junction length. This alignment free approach has higher sensitivity compared to a typical junction-based distance method without loss of specificity and PPV. While the alignment free procedure identifies clones that are broadly consistent with the junction-based distance method, it also identifies clones with characteristics (multiple V or J gene assignments or junction lengths) that are not detectable with the junction-based distance method.