Quantification of Intracellular Polyhydroxyalkanoates by Virtue of Personalized Flow Cytometry Protocol

Polyhydroxyalkanoates (PHAs) are natural polyesters produced by microbes, a potential alternative to synthetic plastics. Various methods ranging from gravimetry to spectrophotometry are routinely used for qualitative analysis of extracted PHA. There is a great need for accurate quantification of intracellular PHA during bioprocess. Hence, the present study aims to improvise the existing Nile red-based flow cytometry protocol. It was achieved using respective cells in a non-PHA accumulating state as gating control to minimize non-specific staining. The optimal Nile red concentration required for PHA staining is 5?×?10³?pg?mL^?1, which is ~10³-fold less than that of earlier reports. Further, it was inferred that flow-based quantification was more accurate than the gravimetric method. The intracellular PHA content was highest in Pseudomonas sp. MNNG-S (52.06?%) among the Pseudomonas strains tested by the flow-based method. Both gravimetric and flow-based cell cycle analyses revealed that DNA synthesis (S phase) and PHA production (log phase) are synchronous at 24–48?h of culture. This study supports flow-based PHA quantification for real time online measurement of intracellular PHA for bioreactor monitoring, control and optimization enduing industrial applications.     

Estimation of Immune Cell Densities in Immune Cell Conglomerates: An Approach for High-Throughput Quantification

Background

Determining the correct number of positive immune cells in immunohistological sections of colorectal cancer and other tumor entities is emerging as an important clinical predictor and therapy selector for an individual patient. This task is usually obstructed by cell conglomerates of various sizes. We here show that at least in colorectal cancer the inclusion of immune cell conglomerates is indispensable for estimating reliable patient cell counts. Integrating virtual microscopy and image processing principally allows the high-throughput evaluation of complete tissue slides.

Methodology/Principal findings

For such large-scale systems we demonstrate a robust quantitative image processing algorithm for the reproducible quantification of cell conglomerates on CD3 positive T cells in colorectal cancer. While isolated cells (28 to 80 µm²) are counted directly, the number of cells contained in a conglomerate is estimated by dividing the area of the conglomerate in thin tissues sections (≤6 µm) by the median area covered by an isolated T cell which we determined as 58 µm². We applied our algorithm to large numbers of CD3 positive T cell conglomerates and compared the results to cell counts obtained manually by two independent observers. While especially for high cell counts, the manual counting showed a deviation of up to 400 cells/mm² (41% variation), algorithm-determined T cell numbers generally lay in between the manually observed cell numbers but with perfect reproducibility.

Conclusion

In summary, we recommend our approach as an objective and robust strategy for quantifying immune cell densities in immunohistological sections which can be directly implemented into automated full slide image processing systems.     

Plasma Membrane-Located Purine Nucleotide Transport Proteins Are Key Components for Host Exploitation by Microsporidian Intracellular Parasites

Microsporidia are obligate intracellular parasites of most animal groups including humans, but despite their significant economic and medical importance there are major gaps in our understanding of how they exploit infected host cells. We have investigated the evolution, cellular locations and substrate specificities of a family of nucleotide transport (NTT) proteins from Trachipleistophora hominis, a microsporidian isolated from an HIV/AIDS patient. Transport proteins are critical to microsporidian success because they compensate for the dramatic loss of metabolic pathways that is a hallmark of the group. Our data demonstrate that the use of plasma membrane-located nucleotide transport proteins (NTT) is a key strategy adopted by microsporidians to exploit host cells. Acquisition of an ancestral transporter gene at the base of the microsporidian radiation was followed by lineage-specific events of gene duplication, which in the case of T. hominis has generated four paralogous NTT transporters. All four T. hominis NTT proteins are located predominantly to the plasma membrane of replicating intracellular cells where they can mediate transport at the host-parasite interface. In contrast to published data for Encephalitozoon cuniculi, we found no evidence for the location for any of the T. hominis NTT transporters to its minimal mitochondria (mitosomes), consistent with lineage-specific differences in transporter and mitosome evolution. All of the T. hominis NTTs transported radiolabelled purine nucleotides (ATP, ADP, GTP and GDP) when expressed in Escherichia coli, but did not transport radiolabelled pyrimidine nucleotides. Genome analysis suggests that imported purine nucleotides could be used by T. hominis to make all of the critical purine-based building-blocks for DNA and RNA biosynthesis during parasite intracellular replication, as well as providing essential energy for parasite cellular metabolism and protein synthesis.     

An Annotated List of Protozoan Parasites,Hyperparasites, and Commensals of Decapod Crustacea*

SYNOPSIS. An approximately complete list of the known protozoan associates (exclusive of a few aberrant forms like Amallocystis) of decapods is presented. A few taxonomic changes are suggested. Host, site of infection and geographic location are mentioned. Some comments on pathogenicity are made.     

PfVPS45 Is Required for Host Cell Cytosol Uptake by Malaria Blood Stage Parasites

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Quantification and Characterization of Phagocytosis in the Soil Amoeba Acanthamoeba castellanii by Flow Cytometry

Phagocytosis in the common grazing soil amoeba Acanthamoeba castellanii was characterized by flow cytometry. Uptake of fluorescently labelled latex microbeads by cells was quantified by appropriate setting of thresholds on light scatter channels and, subsequently, on fluorescence histograms. Confocal laser scanning microscopy was used to verify the effectiveness of sodium azide as a control for distinguishing between cell surface binding and internalization of beads. It was found that binding of beads at the cell surface was complete within 5 min and 80% of cells had beads associated with them after 10 min. However, the total number of phagocytosed beads continued to rise up to 2 h. The prolonged increase in numbers of beads phagocytosed was due to cell populations containing increasing numbers of beads peaking at increasing time intervals from the onset of phagocytosis. Fine adjustment of thresholds on light scatter channels was used to fractionate cells according to cell volume (cell cycle stage). Phagocytotic activity was approximately threefold higher in the largest (oldest) than in the smallest (newly divided) cells of A. castellanii and showed some evidence of periodicity. At no stage in the cell cycle did phagocytosis cease. Binding and phagocytosis of beads were also markedly influenced by culture age and rate of rotary agitation of cell suspensions. Saturation of phagocytosis (per cell) at increasing bead or decreasing cell concentrations occurred at bead/cell ratios exceeding 10:1. This was probably a result of a limitation of the vacuolar uptake system of A. castellanii, as no saturation of bead binding was evident. The advantages of flow cytometry for characterization of phagocytosis at the single-cell level in heterogeneous protozoal populations and the significance of the present results are discussed.     

An Electron Microscope-Cytochemical Method for Differentiating Membranes of Host Red Cells and Malaria Parasites*

Limiting membranes of malaria parasites and host red cells stain differently when exposed to positively charged iron colloid. Negatively charged red cell membranes avidly bind colloid, whereas parasite membranes do not. This selectivity in colloidal iron uptake by the 2 types of membranes can be utilized as an aid in discerning the amounts of contaminating host cell membranes in “free” malaria parasite preparations and in related cell-free membrane extracts.     

Chlamydia trachomatis-Induced Alterations in the Host Cell Proteome Are Required for Intracellular Growth

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PIMD:An Integrative Approach for Drug Repositioning Using Multiple Characterization Fusion

The accumulation of various types of drug informatics data and computational approaches for drug repositioning can accelerate pharmaceutical research and development. However, the integration of multi-dimensional drug data for precision repositioning remains a pressing challenge. Here, we propose a systematic framework named PIMD to predict drug therapeutic properties by integrating multi-dimensional data for drug repositioning. In PIMD, drug similarity networks (DSNs) based on chemical, pharmacological, and clinical data are fused into an integrated DSN (iDSN) composed of many clusters. Rather than simple fusion, PIMD offers a systematic way to annotate clusters. Unexpected drugs within clusters and drug pairs with a high iDSN similarity score are therefore identified to predict novel therapeutic uses. PIMD provides new insights into the universality, individuality, and complementarity of different drug properties by evaluating the contribution of each property data. To test the performance of PIMD, we use chemical, pharmacological, and clinical properties to generate an iDSN. Analyses of the contributions of each drug property indicate that this iDSN was driven by all data types and performs better than other DSNs. Within the top 20 recommended drug pairs, 7 drugs have been reported to be repurposed. The source code for PIMD is available at https://github.com/Sepstar/PIMD/.     

Tissue-Dwelling Intracellular Parasites: Infection and Immune Responses in the Mammalian Host to Toxoplasma, Sarcocystis and Trichinella

The cycles, pathogenicity and immune processes observed in 3intracellular infections, with the protozoa Toxoplasma gondii,several Sarcocystis species, and the nematode Trichinella spirahsare described. All three organisms have cycles that have co-existedwith their hosts for an evolutionarily long period. Naturalhosts of the protozoa generally are able to develop immunityafter primary infection in a timely manner. However infectionis often fatal in certain unusual hosts not naturally exposedto Toxoplasma and Sarcocystis. It is suggested that whereashosts may have selected strains of intermediate pathogenicity,the two protozoa may have selected for hosts that can developtimely immune responses and survive with chronic persistentinfection. Stability of cycle is maintained by co-evolutionin the definitive host through which the cycle must pass almostregularly. Toxoplasmosis and sarcosporidiosis join malaria andAfrican trypanosomiasis as infections that co-evolved with theirhosts, selecting for immunocompetency and intermediate to lowpathogenicity (Allison, 1982). The plea is made to considerthe probable evolutionary experience of experimental hosts whenstudying their specific immune mechanisms and before possiblygeneralizing from such studies, because the immune responseis dependent on evolutionary experience. In respect to infectionwith Trichinella spiralis one might consider carnivores to havebeen selected and pure herbivores unselected. However, infectionoccurs in a wide variety of hosts, with carnivorous, scavengingand accidental transmission, some of which are of recent modificationby man. Because infection is of low prevalence, and involvesa wide variety of hosts, and pathogenicity is more related tothe degree of hypersensitivity, than to frequency of transmissionand worm load, no uniform effects of selection are apparent.Trichinella infected athymic mice have a high worm load withlittle pathogenic effect. Immunologic processes, while restrictingthe number of worms, are much more important in making the hostsick. In all three intracellular infections both protectiveimmunity and delayed type hypersensitivity are operative. Inbalance, these immune responses are protective in Toxoplasmaand Sarcocystis infection, but are pathogenic in trichinellosis,often causing the death of the infected host.     

Selection of Aptamers for Mature White Adipocytes by Cell SELEX Using Flow Cytometry

Background

Adipose tissue, mainly composed of adipocytes, plays an important role in metabolism by regulating energy homeostasis. Obesity is primarily caused by an abundance of adipose tissue. Therefore, specific targeting of adipose tissue is critical during the treatment of obesity, and plays a major role in overcoming it. However, the knowledge of cell-surface markers specific to adipocytes is limited.

Methods and Results

We applied the CELL SELEX (Systematic Evolution of Ligands by EXponential enrichment) method using flow cytometry to isolate molecular probes for specific recognition of adipocytes. The aptamer library, a mixture of FITC-tagged single-stranded random DNAs, is used as a source for acquiring molecular probes. With the increasing number of selection cycles, there was a steady increase in the fluorescence intensity toward mature adipocytes. Through 12 rounds of SELEX, enriched aptamers showing specific recognition toward mature 3T3-L1 adipocyte cells were isolated. Among these, two aptamers (MA-33 and 91) were able to selectively bind to mature adipocytes with an equilibrium dissociation constant (Kd) in the nanomolar range. These aptamers did not bind to preadipocytes or other cell lines (such as HeLa, HEK-293, or C2C12 cells). Additionally, it was confirmed that MA-33 and 91 can distinguish between mature primary white and primary brown adipocytes.

Conclusions

These selected aptamers have the potential to be applied as markers for detecting mature white adipocytes and monitoring adipogenesis, and could emerge as an important tool in the treatment of obesity.     

A Novel Method for Assessment of Natural Killer Cell Cytotoxicity Using Image Cytometry

Natural killer (NK) cells belong to the innate arm of the immune system and though activated NK cells can modulate immune responses through the secretion of cytokines, their primary effector function is through target cell lysis. Accordingly, cytotoxicity assays are central to studying NK cell function. The ⁵¹Chromium release assay, is the “gold standard” for cytotoxicity assay, however, due to concerns over toxicity associated with the use and disposal of radioactive compounds there is a significant interest in non-radioactive methods. We have previously used the calcein release assay as a non-radioactive alternative for studying NK cell cytotoxicity. In this study, we show that the calcein release assay varies in its dynamic range for different tumor targets, and that the entrapped calcein could remain unreleased within apoptotic bodies of lysed tumor targets or incompletely released resulting in underestimation of percent specific lysis. To overcome these limitations, we developed a novel cytotoxicity assay using the Cellometer Vision Image Cytometer and compared this method to standard calcein release assay for measuring NK cell cytotoxicity. Using tumor lines K562, 721.221, and Jurkat, we demonstrate here that image cytometry shows significantly higher percent specific lysis of the target cells compared to the standard calcein release assay within the same experimental setup. Image cytometry is able to accurately analyze live target cells by excluding dimmer cells and smaller apoptotic bodies from viable target cell counts. The image cytometry-based cytotoxicity assay is a simple, direct and sensitive method and is an appealing option for routine cytotoxicity assay.