Determination of liposome size distribution by flow cytometry

BACKGROUND: An essential parameter that describes the quality of liposome suspensions is the mean size, respectively the size distribution. Currently several analytical methods including laser light scattering techniques (LLST) are being employed. METHODS: Here we present an alternative technique using flow cytometry (FCM) to characterize uni- and polydisperse suspensions. As model liposomes preparations containing dipalmitoylphosphatidylcholine (DPPC) were used. A constant number of particles (1,500/s) in the fluid stream and a representative number of 10,000 particles of each sample was measured. Fluorescence-labeled latex beads were measured identically, and their side scatter signals were calibrated and correlated to the results obtained with liposome vesicles. RESULTS: Evaluation of the measurement and validation of the FCM results in comparison to LLST confirm the reliability of results obtained with our method. Latex beads in the range of 100-1000 nm were used for calibration to classify liposomes. Although measurement characteristics and calculation in both methods are basically different, very good agreement of the results was achieved. CONCLUSIONS: Demonstration of stability, reproducibility, and reliability of results make the employment of this method acceptable for an adequate routine analysis technique.     

High density microcarrier culture with a new device which allows oxygenation and perfusion of microcarrier cultures

A novel system useful for aeration and cell retention in continuous perfused microcarrier cultures is described. The system is based on a vibrating cage that separates cells and microcarriers from the oxygenation chamber and allows gas bubble free oxygen transfer. In the cultivation of monkey kidney cells (VERO) on gelatin coated microcarriers, using different concentrations (5, 10 and 15 g Cytodex 3/liter) cell densities up to 10⁷ cells per ml were obtained. The described system is scaleable.     

Intensification of agriculture in southwestern Germany between the Bronze Age and Medieval period,based on archaeobotanical data from Baden-Württemberg

Vegetation History and Archaeobotany - A system of farming with an alternation of land use between being cultivated or left fallow as grassland (Feldgraswirtschaft) developed in southwestern...     

“Silenced” polydendrocytes: a new cell type within the oligodendrocyte progenitor cell population?

Oligodendrocyte progenitor cells (OPCs) were first described more than two decades ago. Novel labeling techniques have shown them to be cells with more than just progenitor functions, with their classification as a fourth glial cell type in addition to astrocytes, oligodendrocytes, and microglial cells. Another term used for this cell type is polydendrocytes, owing to both their morphology and to the evolving knowledge about their diverse functions. Recently, an exclusive hallmark of neurons—the generation of action potentials—became debatable, because a subset of polydendrocytes was reported to generate action potentials in response to adequate stimuli. The new technique of inducible reporter gene expression has brought new insights into the fate and function of polydendrocytes. In recent studies, so-called “silenced” OPCs were detected in cortical tissue, and which underwent proliferation with subsequent cell cycle exit, but without any signs of differentiation. Within this review, we focus on the identification of this new subset of polydendrocytes and their possible functions within cortical networks.     

Effect of Non-Volatile Constituents of Elsholtzia ciliata (Thunb.) Hyl. from Southern Vietnam on Reactive Oxygen Species and Nitric Oxide Release in Macrophages

The extract of Elsholtzia ciliata aerial parts was subjected to bio-guided isolation using the intercellular ROS reduction in J774A.1 macrophages to monitor the anti-oxidative activity. Fifteen compounds were isolated from the active fractions including eleven flavonoids (vitexin, pedalin, luteolin-7-O-β-d -glucopyranoside, apigenin-5-O-β-d -glucopyranoside, apigenin-7-O-β-d -glucopyranoside, chrysoeriol-7-O-β-d -glucopyranoside, 7,3′-dimethoxyluteolin-6-O-β-d -glucopyranoside, luteolin, 5,6,4′-trihydroxy-7,3′-dimethoxyflavone, 5-hydroxy-6,7-dimethoxyflavone (compound 13 ), 5-hydroxy-7,8-dimethoxyflavone); three hydroxycinnamic acid derivatives (caffeic acid, 4-(E)-caffeoyl-l -threonic acid, 4-O-(E)-p-coumaroyl-l -threonic acid) and one fatty acid (α-linolenic acid). The biological evaluation of these compounds (10–2.5 μm ) indicated that all of them exerted good antioxidant and anti-inflammatory activities, in particular compound 13 .     

Neurogenesis drives stimulus decorrelation in a model of the olfactory bulb

The reshaping and decorrelation of similar activity patterns by neuronal networks can enhance their discriminability, storage, and retrieval. How can such networks learn to decorrelate new complex patterns, as they arise in the olfactory system? Using a computational network model for the dominant neural populations of the olfactory bulb we show that fundamental aspects of the adult neurogenesis observed in the olfactory bulb – the persistent addition of new inhibitory granule cells to the network, their activity-dependent survival, and the reciprocal character of their synapses with the principal mitral cells – are sufficient to restructure the network and to alter its encoding of odor stimuli adaptively so as to reduce the correlations between the bulbar representations of similar stimuli. The decorrelation is quite robust with respect to various types of perturbations of the reciprocity. The model parsimoniously captures the experimentally observed role of neurogenesis in perceptual learning and the enhanced response of young granule cells to novel stimuli. Moreover, it makes specific predictions for the type of odor enrichment that should be effective in enhancing the ability of animals to discriminate similar odor mixtures.     

Cellular immunity elicited by human immunodeficiency virus type 1/ simian immunodeficiency virus DNA vaccination does not augment the sterile protection afforded by passive infusion of neutralizing antibodies

High levels of infused anti-human immunodeficiency virus type 1 (HIV-1) neutralizing monoclonal antibodies (MAbs) can completely protect macaque monkeys against mucosal chimeric simian-human immunodeficiency virus (SHIV) infection. Antibody levels below the protective threshold do not prevent infection but can substantially reduce plasma viremia. To assess if HIV-1/SIV-specific cellular immunity could combine with antibodies to produce sterile protection, we studied the effect of a suboptimal infusion of anti-HIV-1 neutralizing antibodies in macaques with active cellular immunity induced by interleukin-2 (IL-2)-adjuvanted DNA immunization. Twenty female macaques were divided into four groups: (i). DNA immunization plus irrelevant antibody, (ii). DNA immunization plus infusion of neutralizing MAbs 2F5 and 2G12, (iii). sham DNA plus 2F5 and 2G12, and (iv). sham DNA plus irrelevant antibody. DNA-immunized monkeys developed CD4 and CD8 T-cell responses as measured by epitope-specific tetramer staining and by pooled peptide ELISPOT assays for gamma interferon-secreting cells. After vaginal challenge, DNA-immunized animals that received irrelevant antibody became SHIV infected but displayed lower plasma viremia than control animals. Complete protection against SHIV challenge occurred in three animals that received sham DNA plus MAbs 2F5 and 2G12 and in two animals that received the DNA vaccine plus MAbs 2F5 and 2G12. Thus, although DNA immunization produced robust HIV-specific T-cell responses, we were unable to demonstrate that these responses contributed to the sterile protection mediated by passive infusion of neutralizing antibodies. These data suggest that although effector T cells can limit viral replication, they are not able to assist humoral immunity to prevent the establishment of initial infection.     

Modulation of O-glycans and N-glycans on murine CD8 T cells fails to alter annexin V ligand induction by galectin 1

Thymic negative selection and contraction of responding T cell oligoclones after infection represent important cell ablation processes required for maintaining T cell homeostasis. It has been proposed that galectin 1 contributes to these processes through interaction with lactosyl sequences principally on cell surface glycoproteins bearing core 2 (C2GnT1)-branched O-glycans. According to this model, specific T cell surface proteins cross-linked by galectin 1 induce signaling, ligand redistribution, and apoptosis in both immature thymocytes and activated T cells. The influence of lactosyl residues contained in branched O-glycans or complex N-glycans on galectin 1 binding and induction of annexin V ligand in murine CD8 T cells was assessed. Neither galectin binding nor galectin-induced expression of annexin V ligand was perturbed under conditions in which: 1) C2GnT1 activity was differentially induced by CD8 T cell activation/culture with IL-2 vs IL-4; 2) activated CD8(+) T cells lacked C2GnT1 expression; or 3) complex N-glycan formation was blocked by swainsonine. The maintenance of galectin 1 binding and induced annexin V expression under conditions that alter lactosamine abundance on O- or complex N-glycans suggest that galectin 1-mediated apoptosis is neither a simple function of fluctuating C2GnT1 activity nor a general C2GnT1-dependent mechanism underlying contraction of CD8 T cells subsequent to activation.     

Statistical estimators of frontal sinus cross section ontogeny from very noisy data

Cross-sectional areas of human frontal sinuses in the occipitofrontal projection are a good surrogate for frontal sinus volumes. This study looks at these areas in a dataset of some 200 children and 100 adults of both sexes. As measured by planimetry of roentgenograms, the areas are extremely variable ("noisy" in a statistical sense). In fact, they appear to be distributed log-normally with quite high variance. The mean of the distribution is evidently a function of age and the variances differ by sex. After logarithmic transformation, the data are adequately fitted by one sigmoid curve for each sex. Our discussion highlights implications of this finding for the biological aspects of frontal sinuses and methodological issues in ontogenetic analysis of data so noisy.